JP2013052370A - Ammonia separation device and ammonia separation method - Google Patents

Abstract

An object of the present invention is to efficiently secure the thermal energy required in a distillation column to save energy and reduce costs, and at the same time, to transport ammonia-containing vapor with an increased proportion of ammonia vapor to ammonia oxidation treatment means. Provided is an ammonia separation device capable of
An ammonia separation apparatus according to the present invention includes a distillation column to which an aqueous ammonia solution having an ammonia concentration of 3% by weight or less and steam are supplied, and at least one vapor compression disposed on the downstream side of the top of the distillation column. Machine, steam generating heat exchanger, gas-liquid separator, cooling / condenser for introducing and cooling and condensing gas separated in the gas-liquid separator, and gas from the cooling / condenser in the next step It has a conveyance line for conveying to the ammonia treatment means, and a circulation line and a discharge line arranged on the downstream side of the bottom of the distillation column.
[Selection] Figure 1

Description

  The present invention relates to an ammonia separation apparatus and an ammonia separation method for separating ammonia from an aqueous ammonia solution having an ammonia concentration of 3% by weight or less and discharging a low-concentration aqueous ammonia solution in which the ammonia concentration is reduced to a predetermined value or less.

  Wastewater discharged from various factories such as semiconductor manufacturing factories and chemical factories contains toxic substances such as ammonia, so there are strict discharge standards for wastewater to prevent water pollution in water areas such as rivers and harbors. It has been established. For this reason, for example, in a factory that discharges wastewater containing ammonia (ammonia wastewater), measures for nitrogen regulation of wastewater are taken.

  Usually, the ammonia concentration of ammonia waste water discharged from factories related to the electronics industry is 3% by weight or less, and in particular, most of the ammonia waste water shows an ammonia concentration of about 0.05 to 1% by weight. However, in order to satisfy the ammonia emission standards as described above, it is necessary to reduce the ammonia concentration to a lower concentration, for example, 50 ppm or less, and flow it to a river or the like.

  Conventionally, a method of distilling an aqueous ammonia solution is known when the ammonia concentration is reduced to a predetermined value or less so as to satisfy the emission standard. In this distillation method, an aqueous ammonia solution and water vapor are supplied to a distillation column, and ammonia is evaporated from the aqueous ammonia solution inside the distillation column, whereby a low-concentration aqueous ammonia solution whose ammonia concentration is reduced to 50 ppm or less is obtained from the bottom of the column. While being removed, ammonia vapor (ammonia gas) and water vapor are distilled from the top of the tower. Further, the ammonia vapor distilled from the top of the distillation column is then concentrated and recovered, or decomposed into nitrogen gas or the like.

  For example, when recovering ammonia from ammonia vapor, the ammonia vapor is absorbed by water in an absorption tower, and this is distilled in a distillation tower to increase the ammonia concentration, and high-concentration ammonia vapor distilled from the top of the distillation tower is removed. By condensing and recovering as an aqueous ammonia solution of about 25%, the aqueous ammonia solution can be reused.

  However, for example, ammonia wastewater discharged from factories related to the electronics industry contains trace amounts of various impurities in addition to ammonia. Therefore, when reusing an aqueous ammonia solution, it is necessary to remove these impurities. However, the ammonia separation method using the distillation tower as described above has a problem that it is difficult to recover a pure ammonia aqueous solution by separating a small amount of impurities. Furthermore, when the collected aqueous ammonia solution is sold, there is a risk that it may become impossible to dispose of the collected aqueous ammonia solution because there are cases in which the destination of collection is lost due to market conditions.

  In addition, the ammonia concentration in the ammonia wastewater discharged from factories related to the electronics industry is 3% by weight or less as described above, so the absolute amount of ammonia contained in the ammonia wastewater is small, and the aqueous ammonia solution is recovered and reused. Therefore, the cost is increased, and the operation in the ammonia separation / recovery process may become unstable. For this reason, when treating ammonia wastewater discharged from factories related to electronics industry, it is more advantageous from the viewpoint of cost and stable operation to decompose ammonia and make it harmless than to recover and reuse the aqueous ammonia solution. There was a serious aspect.

When ammonia is decomposed, the aqueous ammonia solution is supplied to the distillation tower as described above, and the ammonia vapor distilled from the top of the distillation tower and the water vapor accompanying the ammonia vapor are conveyed to the ammonia treatment means. To do. In this ammonia treatment means, ammonia is burned by direct combustion method or catalytic combustion method, whereby ammonia is oxidized and decomposed into nitrogen gas and rendered harmless.

  A treatment method for supplying ammonia aqueous solution to a distillation column and burning ammonia vapor distilled from the top of the distillation column by a direct combustion method to oxidatively decompose ammonia is disclosed in, for example, Japanese Patent No. 3684538 (Patent No. Document 1).

The method for treating ammonia waste water described in Patent Document 1 has three steps of a first step to a third step.
First, in the first step, ammonia waste water and water vapor are supplied to the distillation tower, ammonia vapor and water vapor are distilled from the top of the distillation tower and introduced into the partial condenser, and the ammonia concentration is introduced from the bottom of the distillation tower. Waste water with reduced to below a predetermined value is discharged.

  In the partial condenser, the ammonia vapor and water vapor are cooled to a predetermined temperature to condense a part of the ammonia vapor and water vapor, and the condensed condensate is returned to the distillation column, and uncondensed ammonia vapor and The water vapor is separated from the condensate and sent to the second step. Thereby, the mixed vapor | steam of ammonia vapor | steam and water vapor | steam which the density | concentration (ratio) of ammonia vapor | steam increased from the time of distillation from a distillation tower can be sent to a 2nd process.

  In the second step, the ammonia vapor and water vapor sent from the first step together with air are directly burned by an ammonia burner in a neutral or weakly reducing atmosphere and at a theoretical flame temperature of 1100 ° C. or higher. Then, oxidative decomposition of ammonia generates oxidative decomposition exhaust gas. In this case, the high-temperature gas generated by the oxidative decomposition of ammonia is sent to the gas heat exchanger and used for preheating the air supplied to the ammonia burner.

  Thereafter, in the third step, the oxidative decomposition exhaust gas generated in the second step is blown into the bottom of the water absorption tower, and the absorption water is introduced into the top of the tower, thereby containing undecomposed ammonia contained in the oxidative decomposition exhaust gas. The water-soluble component is absorbed by water and the heat of the oxidative decomposition exhaust gas is transmitted to the absorbed water, and then the exhaust gas is discharged from the top of the water absorption tower. The absorbed water that has absorbed heat from the oxidative decomposition exhaust gas is sent as recovered hot water from the bottom of the water absorption tower to the distillation tower in the first step.

  Furthermore, in Patent Document 1, the partial condenser in the first step is replaced with a heat pump type evaporator using a vapor compressor, thereby condensing ammonia vapor and water vapor distilled from the top of the distillation column. The amount of heat can be applied to the recovered hot water sent from the water absorption tower to the distillation tower to evaporate it, and this steam can be compressed and heated by a steam compressor and sent to the distillation tower.

  According to such a method of Patent Document 1, the ammonia vapor is separated from the ammonia waste water in the distillation tower, the ammonia vapor is oxidatively decomposed, and the undecomposed ammonia is absorbed into the absorption water to be again put into the distillation tower. Since it returns and processes, it can prevent that ammonia is discharge | released in air | atmosphere. Moreover, in patent document 1, it is supposed that the remarkable energy saving effect can be given to a large-scale waste water treatment.

Japanese Patent No. 3684538

  As in the above-mentioned Patent Document 1, ammonia waste water is supplied to the distillation tower, and a low concentration aqueous ammonia solution is taken out from the bottom of the distillation tower, and ammonia vapor is distilled from the top of the distillation tower. In a treatment method in which ammonia vapor is burned by a direct combustion method and ammonia is oxidatively decomposed, or in a treatment method in which ammonia vapor distilled from the top of a distillation column is burned by a catalytic combustion method to oxidatively decompose ammonia, There were the following problems.

  That is, as in Patent Document 1, when ammonia vapor and water vapor distilled from the top of a distillation column are cooled to a predetermined temperature by a condenser (partial condenser) and condensed, the cooling temperature is lowered. The concentration of ammonia vapor in the vapor separated from the condensate can be increased to efficiently perform the oxidative decomposition treatment of ammonia. However, since the condensate obtained in the condenser is refluxed to the distillation column, lowering the cooling temperature in the condenser increases the amount of heat required for heating in the distillation column, which increases costs and saves energy. There was also a problem from a point.

  If the ammonia vapor is excessively cooled by the condenser, the concentration of ammonia vapor increases, but the absolute amount of ammonia vapor decreases. As a result, the ammonia separated from the aqueous ammonia solution cannot be efficiently sent from the system in the first step where distillation is performed to the second step where oxidative decomposition of ammonia is performed.

  Furthermore, in Patent Document 1, when the partial condenser in the first step is replaced with a heat pump type evaporator using a vapor compressor, the recovered hot water sent from the water absorption tower to the distillation tower is evaporated as described above. In this case, if the condensation temperature of ammonia vapor in the evaporator is low (for example, if the partial condensation temperature is set to 60 ° C. as in case 1 in Table 1 of Patent Document 1, ) In order to compress and heat the recovered hot water to a predetermined temperature required when it is introduced into the distillation column, a multistage steam compressor is required. As a result, there is a problem that the installation cost of the steam compressor becomes high and the operating power cost of the steam compressor increases.

  On the other hand, when condensing ammonia vapor and water vapor with the condenser as high as possible, the concentration of ammonia vapor separated from the condensate is low and the concentration of water vapor accompanying the ammonia vapor is high. In particular, when the ammonia concentration of the aqueous ammonia solution that is the raw water is as low as 3% by weight or less, such as waste water discharged from a factory related to the electronics industry, the concentration of water vapor accompanying the ammonia vapor is significantly increased when the condensation temperature is increased. .

  Usually, when ammonia vapor is oxidatively decomposed by an ammonia treatment means, ammonia vapor and water vapor are generally 350 ° C. or higher and 550 ° C. before the oxidative decomposition treatment, regardless of whether the direct combustion method or the catalytic combustion method is used. Preheating to the following preheating temperature is required.

  However, since the specific heat of water vapor is high, if the concentration of water vapor accompanying ammonia vapor increases, the thermal energy necessary to preheat ammonia vapor and water vapor to a predetermined temperature becomes excessive, and the equipment cost of the preheating device However, there is a problem in that the running cost increases because the burden on the heating means increases.

  In general, when ammonia vapor is oxidatively decomposed by direct combustion or catalytic combustion, the heat energy of the gas (nitrogen gas, etc.) generated after oxidative decomposition of ammonia is used to convert ammonia vapor and water vapor before oxidative decomposition treatment. Energy saving is achieved by preheating.

However, when the concentration of water vapor accompanying ammonia vapor is high as described above, the temperature of exhaust gas generated after oxidative decomposition of ammonia does not increase. For this reason, it was difficult to heat ammonia vapor and water vapor to a temperature of 350 ° C. or higher and 550 ° C. or lower using the exhaust gas, and there was a disadvantage that the energy saving effect was low.

  Further, when the ammonia vapor is oxidatively decomposed by the direct combustion method, if the ratio of water vapor to ammonia vapor is increased as described above, the oxidation combustion furnace is increased in size and the fuel cost for combustion is increased.

  On the other hand, when ammonia vapor is oxidatively decomposed by a catalytic combustion method, ammonia is introduced into the catalytic reaction layer to perform catalytic oxidation, and therefore it is necessary to contact ammonia with the catalyst for a predetermined time in the catalytic reaction layer. However, when the ratio of water vapor to ammonia vapor increases, the time for ammonia to contact the catalyst is shortened by the increase in the volume of water vapor. For this reason, it is necessary to enlarge the area | region of a catalyst reaction layer, and the whole apparatus must be enlarged.

  The present invention has been made in view of the above-described conventional problems, and a specific purpose thereof is to efficiently secure the thermal energy required in the distillation tower and simultaneously save energy and reduce costs. Ammonia separation apparatus and ammonia separation method capable of efficiently oxidizing and decomposing ammonia and reducing the size of the oxidative decomposition apparatus by increasing the ammonia concentration in the ammonia-containing steam conveyed to the ammonia oxidation treatment means as the next step Is to provide.

  In order to achieve the above object, an ammonia separation device provided by the present invention is arranged in a distillation column to which an aqueous ammonia solution having an ammonia concentration of 3% by weight or less and steam are supplied, and on the downstream side of the top of the distillation column. At least one steam compressor, a steam generating heat exchanger, a gas-liquid separator, a cooling / condenser that cools and condenses the gas separated by the gas-liquid separator, and the cooling / condenser From the bottom of the distillation tower, a circulation pipe and a discharge pipe arranged on the downstream side of the bottom of the distillation tower, and the top of the distillation tower is A vapor distillation part for distilling ammonia vapor evaporated from the aqueous ammonia solution together with the water vapor inside the tower is provided, and the bottom of the tower is a front of a low-concentration aqueous ammonia solution whose ammonia concentration is reduced to a predetermined value or less. A liquid can outlet that circulates to the distillation column via a circulation line and discharges to the outside via the discharge line; and the vapor compressor includes the ammonia vapor distilled from the top of the column and the A compression heating unit that directly compresses and heats the steam, and the steam generating heat exchanger includes the ammonia steam and the steam that are compressed and heated by the steam compressor, and the distillation column via the circulation line. Heat exchange is performed with the low-concentration ammonia aqueous solution to be circulated to condense a part of the ammonia vapor and the water vapor, and a heat exchange unit that generates water vapor by heating the low-concentration ammonia aqueous solution, The gas-liquid separator includes a gas-liquid separator that separates the ammonia vapor and the water vapor accompanying the ammonia vapor from the condensate condensed in the steam generating heat exchanger. The cooling / condenser has a cooling / condensing unit that cools and condenses the ammonia vapor and the water vapor separated by the gas-liquid separator to a predetermined temperature. It is.

In the ammonia separation apparatus according to the present invention, the steam generating heat exchanger is constituted by a falling steam generating heat exchanger, and the flowing steam generating heat exchanger introduces the compressed and heated ammonia steam and the steam. A compressed steam introducing section, a first deriving section for deriving the condensed liquid condensed in the heat exchange section, the uncondensed ammonia vapor and the water vapor toward the gas-liquid separator, the ammonia vapor and the A second derivation unit for direct deriving water vapor toward the cooling / condenser, the first derivation unit being disposed below the compressed steam introduction unit, and the second derivation unit comprising the compression unit It is preferable that it is disposed above the steam inlet.
In this case, it is particularly preferable that a flow rate adjusting valve is arranged on a pipe line that communicates the second lead-out portion of the flow-down steam generating heat exchanger with the cooling / condenser.

Further, in the present invention, a suction device that sucks the ammonia vapor and the water vapor and sends the ammonia vapor and the water vapor to the ammonia treatment means is disposed on the conveyance pipe line, and a pressure adjusting valve is provided between the cooling / condenser and the suction device. It is preferable that it is arranged.

Furthermore, in the present invention, a reflux line for refluxing the condensate separated by the gas-liquid separator to the distillation column is disposed, and a reflux pump, a flow meter, and a flow rate adjusting valve are disposed on the reflux line. Preferably it is.
In this case, it is particularly preferable that a reflux condenser is disposed on the reflux line.

  In such an ammonia separation apparatus of the present invention, it is preferable that two or more of the steam compressors are arranged in series, and two or more of the steam compressors are arranged in parallel. It is preferable.

  Next, in the ammonia separation method provided by the present invention, an ammonia aqueous solution having an ammonia concentration of 3% by weight or less and water vapor are supplied to a distillation tower, and the ammonia vapor evaporated from the ammonia aqueous solution inside the distillation tower is removed. Distilling from the top of the tower together with the water vapor, allowing the low-concentration aqueous ammonia solution whose ammonia concentration has been reduced to a predetermined value or less to be taken out from the bottom of the tower, the ammonia vapor distilled from the top of the tower and the water vapor at least Direct compression heating with a single steam compressor and sending it to a steam generating heat exchanger, and a low-concentration aqueous ammonia solution taken out from the bottom of the tower is circulated to the distillation tower via a circulation line and discharged. Discharging to the outside through a pipe line, the ammonia vapor and the water vapor compressed and heated by the steam generating heat exchanger Heat exchange with the low-concentration aqueous ammonia solution circulated in the distillation column to condense a part of the ammonia vapor and the water vapor, and heat the low-concentration aqueous ammonia solution to generate water vapor; The ammonia vapor and the water vapor accompanying the ammonia vapor are separated from the condensate condensed in the steam generating heat exchanger by a gas-liquid separator, and the separated ammonia vapor and the water vapor are cooled / condensed. And cooling and condensing the ammonia vapor and the water vapor that have been cooled and condensed from the cooling / condenser to the ammonia treatment means in the next step via a conveyance pipeline. The main feature is that it contains.

  Such an ammonia separation method of the present invention uses a falling steam generating heat exchanger as the steam generating heat exchanger, introduces the compressed and heated ammonia vapor and the water vapor from a compressed steam introducing section, and In the downflow-type steam generating heat exchanger, a condensate obtained by condensing the ammonia vapor and a part of the water vapor and the uncondensed ammonia vapor and the water vapor are disposed below the compressed steam introduction part. The ammonia vapor and the water vapor are led out from the second lead-out portion disposed above the compressed steam introduction portion, and the cooling / condenser is led out from the first lead-out portion toward the gas-liquid separator. It is preferable to include direct introduction into

  In this case, the ammonia separation method of the present invention includes controlling the flow rates of the ammonia vapor and the water vapor directly introduced from the steam generation heat exchanger to the cooling / condenser by a flow rate adjusting valve. Particularly preferred.

  In the ammonia separation method of the present invention, the ammonia vapor and the water vapor are sucked and sent to the ammonia treatment means by the suction device arranged on the transport pipe, and the cooling / condenser and the suction are drawn. Preferably, the method includes adjusting the pressure in the cooling / condenser by a pressure adjusting valve disposed between the apparatus and the apparatus.

Further, in the ammonia separation method of the present invention, the condensate separated by the gas-liquid separator is refluxed to the distillation column via a reflux pipe, and the flow rate of the condensate to be refluxed to the distillation column. Is preferably controlled by a flow regulating valve.
In this case, it is particularly preferable to include cooling the condensate to be refluxed to the distillation column with a reflux condenser.

  In the ammonia separation apparatus according to the present invention, as described above, the steam compressor, the steam generating heat exchanger, and the gas-liquid separator are arranged on the downstream side of the top of the distillation tower. The ammonia vapor and water vapor distilled from the top of the column are directly compressed and heated. In addition, the steam generating heat exchanger arranged downstream of the steam compressor is composed of the compressed and heated ammonia vapor and water vapor, and low-concentration ammonia that is circulated from the bottom of the distillation tower to the distillation tower via a circulation line. Heat exchange is performed with the aqueous solution to condense a part of the ammonia vapor and water vapor, and heat the low concentration aqueous ammonia solution to generate water vapor.

  Thus, in the present invention, the temperature of the ammonia vapor and water vapor distilled from the top of the distillation column is raised by the vapor compressor, and further, the thermal energy of the ammonia vapor and water vapor is transferred to the steam generating heat exchanger. Thus, the low-concentration ammonia aqueous solution which is taken out from the bottom of the distillation tower and circulated is reliably evaporated, and the generated water vapor is introduced into the distillation tower.

  That is, in the ammonia separation apparatus of the present invention, since the steam supplied to the distillation tower is generated efficiently using the thermal energy in the apparatus, the thermal efficiency of the entire apparatus is increased and an energy saving effect is obtained. The cost required for the treatment of ammonia can be greatly reduced as compared with the prior art.

  In the present invention, the ammonia vapor and water vapor separated by the gas-liquid separator are cooled and condensed to a predetermined temperature by a cooling / condenser, thereby increasing the ammonia vapor concentration and lowering the water vapor concentration. Then, it is conveyed to the ammonia treatment means in the next step through the conveyance pipeline.

  Thus, by reducing the concentration of water vapor with high specific heat accompanying the ammonia vapor, the amount of heat required for preheating ammonia vapor and water vapor in the ammonia treatment means can be reduced. Costs and running costs can be reduced.

  In this case, since the temperature of the gas (nitrogen gas, etc.) generated by the oxidative decomposition of the ammonia vapor is increased by lowering the concentration of the water vapor, the ammonia vapor before the oxidative decomposition treatment and the thermal energy of the gas are used. Steam can be efficiently preheated, and further energy saving can be achieved.

  Moreover, when ammonia vapor is oxidatively decomposed by catalytic combustion, ammonia can be efficiently brought into contact with the catalyst in the catalytic reaction layer by reducing the ratio of water vapor to ammonia vapor as described above. By reducing the area of the catalytic reaction layer, the entire catalytic combustion apparatus can be easily downsized.

  In such an ammonia separation apparatus of the present invention, the steam generating heat exchanger is constituted by a falling steam generating heat exchanger. In addition, the downflow type steam generating heat exchanger gas-liquid-separates the compressed steam introducing part for introducing compressed and heated ammonia vapor and water vapor, and the condensed liquid and uncondensed ammonia vapor and water vapor condensed in the heat exchanging part. And a second derivation unit for deriving ammonia vapor and water vapor directly to the cooling / condenser, the first derivation unit being more than the compressed steam introduction unit. The second derivation unit is disposed below the compressed steam introduction unit. As a result, when uncondensed ammonia vapor stays in the upper part of the downflow-type steam generating heat exchanger, the uncondensed ammonia vapor can be smoothly sent from the second outlet to the cooling / condenser. It is possible to effectively prevent the condensation of water vapor from being hindered by uncondensed ammonia vapor staying in the steam generating heat exchanger.

  In this case, the flow rate adjusting valve is arranged on the pipe connecting the second derivation section of the flow-down type steam generation heat exchanger and the cooling / condenser, so that the cooling / condensation is performed from the flow-down type steam generation heat exchanger. The flow rate of ammonia vapor sent to the condenser can be easily controlled, and it is possible to select whether or not to flow uncondensed ammonia vapor to the cooling / condenser according to the situation of the falling steam generating heat exchanger .

  Further, in the ammonia separation device of the present invention, a suction device for sucking ammonia vapor and water vapor and sending it to the ammonia treatment means is disposed on the transport pipe, and a pressure regulating valve is provided between the cooling / condenser and the suction device. It is arranged. This makes it possible to easily control the total pressure of ammonia vapor and water vapor in the cooling / condenser. For example, the cooling / condenser can be operated with the internal pressure being less than atmospheric pressure, or the internal pressure It is also possible to operate in a state where the pressure exceeds atmospheric pressure. In particular, by operating the cooling / condenser under a pressure lower than atmospheric pressure, the equipment cost of the apparatus can be reduced at a low cost.

  Furthermore, in the ammonia separation apparatus of the present invention, a reflux line for refluxing the condensate separated by the gas-liquid separator to the distillation column is arranged between the gas-liquid separator and the distillation column, and the reflux A reflux pump, a flow meter, and a flow rate adjustment valve are sequentially arranged on the pipeline. Thereby, it is made to recirculate | reflux to a distillation column, controlling the flow volume of the condensate which condensed ammonia vapor | steam and water vapor | steam, and the condensate can be used effectively in a distillation column. In addition, the pressure of the condensate on the outlet side of the reflux pump can be easily maintained high.

  In particular, in the present invention, since the cooling / condenser for cooling ammonia vapor and water vapor is arranged on the downstream side of the gas-liquid separator, the condensate separated in the gas-liquid separator is excessively cooled. And return to the distillation column. For this reason, even if the condensate is refluxed to the distillation column, it is possible to prevent an increase in cost required for heating the distillation column and to obtain an energy saving effect.

  In this case, by further providing a reflux condenser on the reflux line, the condensate (reflux) that is separated by the gas-liquid separator and refluxed to the distillation column is higher than the temperature at the top of the distillation column. Can be prevented. For example, when the reflux liquid refluxed from the gas-liquid separator to the distillation tower is higher than the temperature at the top of the distillation tower, adiabatic expansion (so-called boiling) occurs on the outlet side of the reflux pump arranged on the reflux pipe, and the difference is different. There is a risk of causing noise and vibration of piping. On the other hand, in the present invention, by setting the reflux condenser as described above, the temperature of the reflux liquid refluxed to the distillation column can be cooled below the temperature at the top of the distillation column, so the flow rate adjustment Combined with the fact that the pressure of the reflux liquid at the outlet side of the reflux pump can be kept high by the valve, it prevents adiabatic expansion (boiling) from occurring at the outlet side of the reflux pump and prevents the generation of abnormal noise and piping vibration. be able to.

  Furthermore, in the ammonia separation apparatus of the present invention, two or more steam compressors can be arranged in series. Thereby, the temperature of the ammonia vapor | steam and water vapor | steam distilled from the tower top part of the distillation tower can be continuously compression-heated with the some steam compressor arrange | positioned in series. For this reason, it is possible to easily compress and heat ammonia vapor and water vapor to a higher temperature. Further, even when ammonia vapor and water vapor are compressed and heated to a predetermined temperature, the ammonia vapor and water vapor can be stably raised to a predetermined temperature.

  In the present invention, two or more steam compressors can be arranged in parallel. As a result, even if a large amount of ammonia vapor is distilled off from the top of the distillation column, the ammonia vapor can be distributed to the respective vapor compressors for efficient compression heating. For this reason, it becomes possible to increase the throughput per unit time in the ammonia separator.

Next, in the ammonia separation method according to the present invention, as described above, the temperature of the ammonia vapor and water vapor distilled from the top of the distillation column is raised by a vapor compressor, and the ammonia vapor and water vapor The heat energy is effectively used in the steam generating heat exchanger, and the low-concentration ammonia aqueous solution that is taken out from the bottom of the distillation tower and circulated is reliably evaporated, and the generated water vapor is introduced into the distillation tower. .

  In the present invention, since the steam supplied to the distillation column is generated by efficiently using the thermal energy in this way, the thermal efficiency of the entire apparatus is increased, an energy saving effect is obtained, and the cost required for the treatment of ammonia. Can be greatly reduced compared to the conventional case.

  In the ammonia separation method of the present invention, the ammonia vapor and water vapor separated by the gas-liquid separator are cooled and condensed to a predetermined temperature by a cooling / condenser, thereby increasing the concentration of ammonia vapor and reducing the concentration of water vapor. After being lowered, it is transported to the ammonia treatment means in the next step via the transport pipeline.

  Thereby, since the calorie | heat amount required in order to preheat ammonia vapor | steam and water vapor | steam in an ammonia process means can be decreased, the installation expense and running cost of a preheating apparatus can be reduced. Further, since ammonia can be efficiently brought into contact with the catalyst in the catalyst reaction layer, the area of the catalyst reaction layer can be reduced and the entire catalytic combustion apparatus can be easily downsized.

  Furthermore, in this case, since the temperature of the gas generated by the oxidative decomposition of ammonia vapor can be increased, the ammonia vapor and water vapor before the oxidative decomposition treatment can be efficiently preheated using the thermal energy of the gas, thereby further saving energy. Can be planned.

  In such an ammonia separation method of the present invention, a falling steam generating heat exchanger is used as the steam generating heat exchanger, the compressed and heated ammonia vapor and steam are introduced from the compressed steam introducing section, and further, the ammonia vapor and The condensate obtained by condensing a part of the water vapor and uncondensed ammonia vapor and water vapor are led out from the first lead-out part arranged below the compressed steam introduction part toward the gas-liquid separator, and the ammonia vapor and The water vapor can be led out from the second lead-out portion disposed above the compressed steam introduction portion and directly introduced into the cooling / condenser. As a result, when uncondensed ammonia vapor stays in the upper part of the flow-down type steam generating heat exchanger, the uncondensed ammonia vapor can be smoothly sent from the second outlet to the cooling / condenser. For this reason, it is possible to effectively prevent the condensation of water vapor from being hindered by uncondensed ammonia vapor staying in the flow-down type steam generating heat exchanger.

  In this case, the flow rate of ammonia vapor and water vapor introduced directly from the steam generating heat exchanger to the cooling / condenser can be controlled by the flow rate adjusting valve, and depending on the situation of the downflow type steam generating heat exchanger. It is possible to select whether or not to flow uncondensed ammonia vapor to the cooling / condenser.

  Further, in the ammonia separation method of the present invention, ammonia vapor and water vapor are sucked and sent to the ammonia treatment means by the suction device arranged on the conveying pipe, and are arranged between the cooling / condenser and the suction device. The total pressure of ammonia vapor and water vapor in the cooling / condenser can be easily adjusted by the pressure regulating valve. Thereby, for example, the cooling / condenser can be operated in a state where the internal pressure is less than atmospheric pressure, or can be operated in a state where the internal pressure exceeds atmospheric pressure. In particular, by operating the cooling / condenser under a pressure lower than atmospheric pressure, the equipment cost of the apparatus can be reduced at a low cost.

Furthermore, in the ammonia separation method of the present invention, the condensate separated by the gas-liquid separator is refluxed to the distillation column via the reflux line, and the flow rate of the condensate to be refluxed to the distillation column is controlled by a flow rate adjusting valve. Can be controlled. Thereby, it is made to recirculate | reflux to a distillation column, controlling the flow volume of the condensate which condensed ammonia vapor | steam and water vapor | steam, and the condensate can be used effectively in a distillation column. In addition, the pressure of the condensate on the outlet side of the reflux pump can be easily maintained high.

  In particular, in the present invention, since the cooling / condenser for cooling ammonia vapor and water vapor is arranged on the downstream side of the gas-liquid separator, the condensate separated in the gas-liquid separator is excessively cooled. And return to the distillation column. For this reason, even if the condensate is refluxed to the distillation column, it is possible to prevent an increase in cost required for heating the distillation column and to obtain an energy saving effect.

  In this case, in the present invention, the condensate to be refluxed to the distillation column can be cooled by a reflux condenser so that the temperature of the condensate can be made equal to or lower than the temperature at the top of the distillation column. This prevents the adiabatic expansion (boiling) from occurring on the outlet side of the reflux pump in combination with the fact that the flow rate adjustment valve can maintain the pressure of the reflux liquid at the outlet side of the reflux pump to be high. Generation of vibration can be prevented.

It is a flowchart explaining the ammonia separation apparatus which concerns on this invention. It is a flowchart explaining the ammonia separation apparatus which concerns on the modification of this invention. It is a flowchart explaining the ammonia separation apparatus which concerns on another modification of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below, and various modifications can be made as long as it has substantially the same configuration as the present invention and has the same effects. Is possible.

  The ammonia separation apparatus 1 according to the present embodiment shown in FIG. 1 is configured by evaporating and separating ammonia from an aqueous ammonia solution (ammonia wastewater) having an ammonia concentration of 3% by weight or less used in an electronics industry factory or the like. The apparatus discharges a low-concentration aqueous ammonia solution and transports the separated ammonia vapor to the ammonia treatment means in the next step.

  The ammonia separation device 1 of the present embodiment includes, as main components, a distillation column 2 to which an aqueous ammonia solution and water vapor are supplied, a vapor compressor 3 disposed on the downstream side of the top of the distillation column 2, and vapor compression. A steam generating heat exchanger 4 disposed on the downstream side of the machine 3, a gas / liquid separator 5 that separates the condensed liquid condensed by the steam generating heat exchanger 4 from uncondensed ammonia vapor and water vapor, It has a cooling / condenser (cooling condenser) 6 for introducing and cooling and condensing ammonia vapor and water vapor separated by the separator 5.

Hereinafter, these components will be described in detail.
The distillation column 2 can be operated in a range from a negative pressure (for example, the internal pressure of the column is 60 kPa) to a positive pressure (for example, the internal pressure of the column is 130 kPa) where the equipment cost is low. In addition, it has a cylindrical shape, and a packing for gas-liquid contact or a plurality of shelves (tray) are arranged inside the tower.

  In the vicinity of the top of the distillation column 2, a raw water supply unit for supplying an aqueous ammonia solution (raw water) containing ammonia at a concentration of 3% by weight or less to the inside of the column is arranged, and water vapor is separately provided at the bottom of the column. The 1st and 2nd steam supply parts supplied to are arranged. In this case, the raw water supply unit is disposed so as to be able to supply an aqueous ammonia solution as raw water to the top of the distillation tower 2 for the purpose of raising the top temperature of the distillation tower 2. The temperature of ammonia vapor and water vapor distilled from the top of the column and introduced into the vapor compressor 3 can be increased, and further, the temperature of ammonia vapor and water vapor heated by the vapor compressor 3 can be increased more efficiently. can do.

  The raw water supply pipe 31 is connected to the raw water supply section of the distillation tower 2, and the preheat heat exchanger 7 is arranged in the raw water supply pipe 31. The preheating heat exchanger 7 performs heat exchange between the raw water and a low-concentration aqueous ammonia solution (treatment liquid) discharged to the outside through a discharge pipe 33 described later, so that the raw water is heated to a predetermined temperature. Can be preheated.

  Further, a vapor distilling portion for distilling ammonia vapor evaporated from the aqueous ammonia solution inside the tower together with water vapor is disposed at the top of the distillation column 2, and the vapor distilling portion is connected to the first connecting pipe 21. Is directly connected to the steam compressor 3. In addition, the water supply unit 8 is connected to the first connection pipeline 21. The water supply unit 8 is configured to be replenished by injecting water into the first connection pipeline 21, and it is also possible to adjust the replenishment amount of water to be replenished into the first connection pipeline 21. It is.

  The bottom of the distillation column 2 is provided with a liquid can outlet for discharging a low-concentration aqueous ammonia solution whose ammonia concentration has been reduced to a predetermined value or lower by distillation. A circulation line 32 is connected to circulate the low-concentration aqueous ammonia solution discharged from the water to the distillation column 2 through the steam generating heat exchanger 4.

  A circulation pump 9 for circulating a low-concentration aqueous ammonia solution to the circulation line 32 is disposed on the circulation line 32, and between the circulation pump 9 and the steam generating heat exchanger 4, A discharge pipe 33 for discharging the low concentration aqueous ammonia solution to the outside is connected.

  Further, on the discharge pipe 33, a first flow meter 11 a that measures the flow rate of the low-concentration aqueous ammonia solution flowing through the discharge pipe 33 and a first flow meter that adjusts the flow rate of the low-concentration aqueous ammonia solution flowing through the discharge pipe 33. 1 flow rate adjustment valve 11b is arranged. The opening and closing of the first flow rate adjusting valve 11b is controlled based on the measured value of a liquid level sensor (not shown) that measures the liquid level of the distillation column 2 and the measured value of the first flow meter 11a. By adjusting the first flow rate adjusting valve 11b and controlling the flow rate of the low-concentration aqueous ammonia solution flowing through the discharge pipe 33, the liquid level management for keeping the liquid level of the distillation column 2 constant is performed.

  In this case, the first flow rate adjustment valve 11b may be configured as a manual type adjustment valve or an automatic adjustment valve. For example, the measurement value and the first flow rate of the above-described liquid level sensor are used. It is preferable to be configured as an automatic adjustment valve interlocked with the measured value of the total 11a.

  The circulation line 32 is connected to a first water vapor supply unit disposed in the distillation column 2 in order to introduce the low-concentration aqueous ammonia solution and the water vapor generated in the steam generation heat exchanger 4 into the distillation column 2. Yes. Further, the second water vapor supply unit disposed in the distillation column 2 is supplied with a water vapor replenishment unit 10 so that water vapor can be directly blown into the liquid at the bottom of the distillation column 2 at an unsteady time such as at the start of operation. Is connected.

  The vapor compressor 3 has a compression heating unit that sucks ammonia vapor and water vapor distilled from the top of the distillation column 2 and compresses and heats them, and discharges the compressed and heated ammonia vapor and water vapor.

  When the distillation column 2 is configured to be operable in a range from a negative pressure state to a positive pressure state as described above, the vapor compressor 3 includes ammonia vapor and water vapor, including an overheated state. The compression heating is performed in the range of 93 ° C. to 113 ° C., preferably in the range of 96 ° C. to 111 ° C. Designing and operating the vapor compressor 3 so as to compress and heat ammonia vapor and water vapor within such a range is efficient and advantageous in terms of capital investment and running cost.

  Moreover, this steam compressor 3 adjusts the rotation speed of the steam compressor 3, and adjusts the supply amount (injection amount) of the water injected from the water supply part 8 in the upstream of the steam compressor 3. The compression heating temperature and vapor pressure of ammonia vapor and water vapor can be arbitrarily set. Ammonia vapor and water vapor compressed and heated by the vapor compressor 3 are sent to the vapor generation heat exchanger 4 through a second connection line 22 that connects the vapor compressor 3 and the vapor generation heat exchanger 4. .

  The steam generating heat exchanger 4 is configured as a vertical downflow steam generating heat exchanger, and the ammonia vapor and steam compressed and heated by the steam compressor 3 and the distillation column 2 through the circulation line 32. A heat exchanging unit is provided that exchanges heat with a low-concentration ammonia aqueous solution to be circulated to condense a part of the ammonia vapor and water vapor, and heats the low-concentration aqueous ammonia solution to generate water vapor.

  In particular, the steam generating heat exchanger 4 is preferably configured as a multi-pipe heat exchanger with a flow-down method. By using such a down flow type multi-tube heat exchanger, the circulation amount of the low-concentration ammonia aqueous solution to be circulated in the distillation column 2 can be reduced, so that the power of the circulation pump 9 can be small and energy saving. In the present invention, the configuration of the steam generating heat exchanger 4 is not particularly limited. For example, the structure of the steam generating heat exchanger can be a horizontal type, and the forced circulation type heat exchange is also possible. It is also possible to use a vessel.

  In this case, the temperature of the condensate on the cylinder side in the downflow-type steam generating heat exchanger 4 is the same as that of the compressed and heated ammonia vapor and water vapor, and is 93 ° C or higher and 113 ° C or lower, preferably 96 ° C or higher and 111 ° C or lower. It is set as follows.

  The steam generating heat exchanger 4 includes a compressed steam introducing unit that introduces ammonia vapor and water vapor compressed and heated by the vapor compressor 3, a condensed liquid condensed in the heat exchange unit, uncondensed ammonia vapor and water vapor, The first deriving unit for deriving the gas toward the gas-liquid separator 5, and when the uncondensed ammonia vapor stays above the heat exchange unit, the uncondensed ammonia vapor and the accompanying water vapor are cooled and condensed by the condenser 6 And a second derivation unit that derives toward.

  In particular, in the steam generating heat exchanger 4 of the present embodiment, compressed steam is introduced in order to efficiently condense and heat the compressed and heated ammonia vapor and water vapor from the upper side to the lower side of the heat exchange unit. The part is arranged at the upper part of the steam generating heat exchanger 4, and the first derivation part is arranged at the lower part of the steam generating heat exchanger 4. The second lead-out part is arranged above the compressed steam introduction part in order to lead out ammonia vapor staying above the heat exchange part and smoothly send it to the cooling / condenser 6.

  Connected to the first derivation section of the steam generating heat exchanger 4 is a third connection line 23 that communicates the steam generating heat exchanger 4 and the gas-liquid separator 5. The condensed condensate and uncondensed ammonia vapor and water vapor can be sent directly to the gas-liquid separator 5.

  In this case, the third connection pipe 23 is not condensed in the steam generation heat exchanger 4 when the inside of the third connection pipe 23 is filled with, for example, a condensate condensed in the steam generation heat exchanger 4. It is conceivable that ammonia vapor and water vapor cannot be smoothly sent to the gas-liquid separator 5 and the operation of the steam generating heat exchanger 4 becomes unstable. Further, when ammonia vapor and water vapor are introduced into the gas-liquid separator 5, pulsation (ripple) is generated in the condensate on the outlet side of the third connection line 23, and the introduction of ammonia vapor and water vapor is irregular. Therefore, it is conceivable that mist is easily generated in the gas-liquid separator 5.

In order to prevent the occurrence of such a problem, in the present embodiment, the third connection pipe line 23 smoothly circulates the condensate, uncondensed ammonia vapor, and water vapor without being full of condensate. It has an aperture size that can be adjusted.

  For example, in the third connection line 23 of the present embodiment, ammonia vapor and water vapor introduced from the steam compressor 3 to the steam generating heat exchanger 4 are all condensed, and the condensed condensate is the third connection line 23. In the upper part of the liquid level of the condensate flowing in the third connection pipe 23, a space part of 5% or more with respect to the total cross-sectional area of the third connection pipe 23, preferably 15 It is preferable that the aperture size is such that a space having a margin of at least% is formed.

  Further, a fourth connection pipe 24 that connects the steam generation heat exchanger 4 and the cooling / condenser 6 is connected to the second lead-out portion of the steam generation heat exchanger 4, and this fourth connection pipe 24, a second flow meter 12a for measuring the flow rate of ammonia vapor and water vapor flowing from the steam generating heat exchanger 4 to the cooling / condenser 6, and a second flow rate adjusting valve for adjusting the flow rate of the ammonia vapor and water vapor. 12b.

  By providing the second flow rate adjusting valve 12b, whether ammonia vapor and water vapor are allowed to flow to the cooling / condenser 6 via the fourth connection line 24 depending on the situation of the steam generating heat exchanger 4. It is possible to select whether or not.

  In this case, the second flow rate adjustment valve 12b may be configured as a manual adjustment valve or an automatic adjustment valve. For example, ammonia derived from the deriving unit of the cooling / condenser 6 may be used. It is preferably configured as an automatic adjustment valve linked with the temperature of the steam and the measured value of the second flow meter 12a.

  Further, the steam generating heat exchanger 4 includes a liquid introduction part for introducing a low-concentration aqueous ammonia solution extracted from the bottom of the distillation column 2 into the inside, and a low-concentration aqueous ammonia solution and a heat exchange part that have passed through the heat exchange part. And a third derivation unit for deriving the water vapor generated toward the distillation column 2.

  The gas-liquid separator 5 includes a gas-liquid separator that separates ammonia vapor and water vapor not condensed in the steam generating heat exchanger 4 from the condensate condensed in the steam generating heat exchanger 4. In this gas-liquid separator 5, the reflux line 34 for refluxing the condensate separated in the gas-liquid separator to the distillation column 2, and the ammonia vapor and water vapor separated in the gas-liquid separator 5 are supplied to the cooling / condenser 6. The fifth connecting pipe 25 to be sent is connected.

  On the reflux line 34, a reflux pump 13 for sending the condensate to the distillation column 2 and a condensate (reflux) that is arranged downstream of the reflux pump 13 and returns to the distillation column 2 through the reflux line 34. A third flow meter 16a for measuring the flow rate of the liquid) and a third flow rate adjusting valve 16b for adjusting the flow rate of the condensate (reflux liquid) are arranged.

  The opening and closing of the third flow rate adjustment valve 16b is controlled based on the measured value of a liquid level sensor (not shown) that measures the liquid level in the gas-liquid separator 5 and the measured value of the third flow meter 16a. By adjusting the third flow rate adjusting valve 16b to control the flow rate of the reflux liquid, the liquid level in the gas-liquid separator 5 can be controlled, and the pressure on the outlet side of the reflux pump 13 is kept high. Thus, boiling of the reflux liquid can be prevented.

  In this case, the third flow rate adjustment valve 16b may be configured as a manual type adjustment valve or an automatic adjustment valve. For example, the liquid level in the gas-liquid separator 5 described above is set. It is preferably configured as an automatic adjustment valve that is linked to the measured value of the liquid level sensor to be measured and the measured value of the third flow meter 16a.

  Further, in the present embodiment, a reflux cooler 17 for cooling the reflux liquid is disposed between the reflux pump 13 on the reflux line 34 and the third flow meter 16a. The reflux cooler 17 may be a multi-tube type or a plate type. The reflux cooler 17 includes a refrigerant introduction unit that introduces a refrigerant, a refrigerant extraction unit that derives the refrigerant, and a flow rate adjustment valve (not shown) that is arranged in the refrigerant introduction unit and adjusts the introduction amount of the refrigerant. . In this case, a flow rate adjustment valve (not shown) for adjusting the amount of refrigerant introduced may be configured as a manual adjustment valve or an automatic adjustment valve. The refrigerant is not particularly limited, and cold water or cold air can be used.

  The reflux cooler 17 includes a reflux liquid thermometer (not shown) that is disposed on the outlet side of the reflux cooler 17 and measures the temperature of the reflux liquid, and a temperature of the top of the distillation column 2 that is not shown. A tower top thermometer is connected. Thereby, the reflux cooler 17 compares the temperature of the reflux liquid measured by both thermometers with the temperature at the top of the tower, and determines whether or not the reflux liquid is cooled by the reflux cooler 17. When the temperature of the reflux liquid returned to the distillation column 2 is higher than a predetermined temperature, the temperature of the reflux liquid is a predetermined temperature (specifically, about 2 to 5 ° C.) than the temperature at the top of the distillation column 2. The amount of refrigerant introduced is adjusted by a flow rate adjustment valve (not shown) so that the reflux liquid is cooled to a predetermined temperature.

  Note that the reflux liquid thermometer for measuring the temperature of the reflux liquid returned to the distillation column 2 may be arranged on the inlet side of the reflux condenser 17 instead of the outlet side of the reflux condenser 17. Furthermore, in this embodiment, it is possible to omit the installation of the reflux cooler 17 itself. Depending on the concentration of the aqueous ammonia solution supplied to the distillation tower, the operation method of the ammonia separation device 1, etc., the reflux cooler 17 It can be arbitrarily selected whether or not to install.

  The cooling / condenser 6 includes a cooling / condensing unit that cools and condenses ammonia vapor and water vapor separated by the gas-liquid separator 5 to a predetermined temperature. In the present embodiment, the cooling / condenser 6 is configured by a tubular heat exchanger having a refrigerant introduction portion 6a for introducing a refrigerant and a refrigerant derivation portion 6b for deriving the refrigerant. In the refrigerant introduction portion 6a, A fourth flow rate adjustment valve 6c that adjusts the amount of refrigerant introduced is provided.

  In this case, the tube heat exchanger may be a vertical type or a horizontal type, and ammonia vapor may be cooled on the barrel side or inside the tube. Furthermore, the medium of the refrigerant is not particularly limited, and cold water or cold air can be used. The cooling / condensing unit is configured as an alternative to the cooling / condensing unit 6 by, for example, securing a large space in the upper portion of the gas-liquid separator 5 and arranging a cooling / condensing tube in the space. May be.

  The cooling / condenser 6 includes a transport line 35 for transporting ammonia vapor cooled in the cooling / condensing unit and water vapor accompanying the ammonia vapor to the ammonia processing means in the next process, and ammonia in the cooling / condensing unit. A sixth connection pipe 26 is connected to return the condensate produced by the condensation of steam and water vapor to the gas-liquid separator 5.

  Furthermore, a suction device 14 that sucks ammonia vapor and water vapor accompanying the ammonia vapor and sends it to the ammonia treatment means on the transport line 35, and a pressure adjustment valve 15 disposed between the cooling / condenser 6 and the suction device 14. And are arranged.

As described above, the suction device 14 and the pressure regulating valve 15 are arranged on the downstream side of the cooling / condenser 6, so that the ammonia vapor cooled by the cooling / condenser 6 can be reliably supplied to the ammonia treatment means in the next step. Can send. Further, the total pressure of ammonia vapor and water vapor in the cooling / condenser 6 can be easily controlled. For example, the cooling / condenser 6 is operated not only at an internal pressure but also at atmospheric pressure. It is also possible to operate in a state of less than or to operate in a state where the internal pressure exceeds atmospheric pressure.

  In the present embodiment, the suction device 14 is operated and the cooling / condenser 6 is operated under a pressure equal to or lower than atmospheric pressure in order to keep the equipment cost of the ammonia decomposing apparatus low. In the case where the cooling / condenser 6 is operated under normal pressure, the installation of the pressure regulating valve 15 can be omitted.

  In the ammonia separation device 1 of the present embodiment, the cooling / condenser 6 is arranged on the downstream side of the gas-liquid separator 5 in this way, and the ammonia vapor separated from the condensate by the gas-liquid separator 5 has a predetermined temperature. Therefore, the proportion of ammonia vapor in the gas (ammonia-containing vapor) conveyed to the ammonia treatment means in the next process via the conveyance pipeline 35 can be reliably increased (in other words, the proportion of water vapor is decreased). can do).

  In this case, as will be described later, the cooling / condenser 6 is sent from the gas-liquid separator 5 so that the molar fraction of ammonia vapor to the whole ammonia-containing vapor conveyed to the ammonia treatment means is 50% or more. It is preferable to cool the ammonia vapor and water vapor to 83 ° C. or lower when the outlet of the cooling / condenser 6 is at atmospheric pressure, for example.

  Next, ammonia is evaporated from an aqueous ammonia solution having an ammonia concentration of 3 wt% or less in the distillation tower 2 using the ammonia separation device 1 of the present embodiment having the above-described configuration, and then the discharge pipe 33 is connected. A method for discharging a low-concentration aqueous ammonia solution and conveying ammonia vapor to the ammonia treatment means in the next step through the conveyance pipe 35 will be described.

  The ammonia separation method according to this embodiment is an ammonia separation method that is advantageous in terms of capital investment and running cost when the ammonia concentration in an ammonia aqueous solution (raw water) containing ammonia is 3% by weight or less. Since the absolute amount of NO is small, it is preferably used when the detoxification treatment by the oxidation treatment is more advantageous in terms of cost and stable operation than the recovery of ammonia for the purpose of recycling.

  In addition, the separation method according to the present embodiment is suitably applied to the case of separating substances having a large difference in vapor pressure at the same temperature, such as ammonia and water. In this case, the mixed stock solution of the substances to be separated may be an aqueous solution or a solvent liquid.

  In the ammonia separation method according to this embodiment, first, an aqueous ammonia solution (raw water) having a concentration of ammonia of 3% by weight or less (for example, about 0.05 to 1% by weight) discharged from a factory or the like is used as a heat exchanger for preheating. After preheating at 7, the raw water is supplied to the inside of the distillation column 2 from the raw water supply unit arranged near the top of the distillation column 2. At the same time, water vapor is supplied to the bottom of the distillation column 2 through the circulation line 32.

  The supply of water vapor to the bottom of the column is performed directly from the water vapor replenishment unit 10 into the liquid at the bottom of the distillation column 2 at an unsteady time such as at the start of operation. In a steady state, the low-concentration aqueous ammonia solution taken out from the bottom of the distillation column 2 is sent to the steam generating heat exchanger 4 through the circulation line 32 without using the steam replenishing unit 10, By heating the low-concentration aqueous ammonia solution in the exchanger 4 to generate water vapor, and circulating the generated water vapor together with the low-concentration aqueous ammonia solution through the circulation line 32 to the bottom of the distillation column 2, Water vapor is supplied to the bottom.

In the distillation column 2 to which an aqueous ammonia solution (raw water) and water vapor are supplied, the raw water flowing down from the top of the column and the reflux liquid flowing in from the reflux line 34 and the water vapor rising from the bottom of the column come into countercurrent contact. As a result, the ammonia is evaporated, and the ammonia vapor is distilled together with the water vapor from the vapor distillation portion at the top of the tower to the first connecting pipe 21. Further, by evaporating the ammonia, the ammonia concentration of the aqueous ammonia solution is reduced to a predetermined allowable drainage concentration (for example, 50 ppm or less), and the low-concentration aqueous ammonia solution is transferred from the liquid outlet at the bottom of the tower to the circulation line 32. Take out.

  At this time, in the distillation column 2 of the present embodiment, the supply amount of raw water and steam is controlled, and the internal temperature at the top of the column is 85 ° C. or higher and 104 ° C. or lower, preferably 90 ° C. or higher and lower than 100 ° C. In this way, ammonia is evaporated. Further, the ammonia concentration in the mixed vapor of ammonia vapor and water vapor (ammonia-containing vapor) distilled from the top of the distillation column 2 is 1 mol% or more and 33 mol% or less.

  In this case, the internal temperature at the bottom of the column must be higher than the internal temperature at the top of the column due to the pressure loss of the packing or tray inserted between the column top and the bottom of the column. The temperature is preferably controlled to 91 ° C. or higher and 105 ° C. or lower.

  Further, the ammonia aqueous solution having an allowable drainage concentration removed from the bottom of the distillation column 2 is sent to the steam generating heat exchanger 4 through the circulation line 32 as described above, and the liquid level of the distillation column 2 is also measured. By controlling the opening / closing amount of the first flow rate adjustment valve 11b in accordance with the liquid level of the distillation column 2 so as to keep the level constant, a part of the ammonia aqueous solution is externally passed through the discharge pipe 33. Discharged. Note that the low-concentration aqueous ammonia solution passing through the discharge pipe 33 is introduced into the preheating heat exchanger 7 before being discharged to the outside and used for preheating raw water.

  On the other hand, the ammonia vapor distilled from the top of the distillation column 2 to the first connection pipe 21 and the water vapor accompanying the ammonia vapor are directly introduced into the vapor compressor 3 and compressed and heated. At this time, the steam compressor 3 adjusts the rotation speed of the steam compressor 3 or adjusts the supply amount of water to be injected on the upstream side of the steam compressor 3. Is heated to 93 ° C to 113 ° C, preferably 96 ° C to 111 ° C.

  By performing the compression heating in this way, the ratio of water vapor in the mixed vapor of ammonia vapor and water vapor (ammonia-containing vapor) is the same as that when distilling from the distillation column 2, but the subsequent steam generating heat exchanger 4 Thus, the mixed vapor of ammonia vapor and water vapor is condensed at a temperature higher than the temperature at the top of the distillation column 2. When ammonia vapor and water vapor are condensed at a high temperature thus compressed and heated, the water vapor mainly condenses, so the ammonia concentration in the condensate is lowered and most of the ammonia exists as ammonia vapor, thereby Thereafter, the mixed vapor is cooled by the subsequent cooling / condenser 6 to mainly condense the water vapor, leaving a considerable amount of ammonia vapor as the vapor, thereby separating the high-concentration ammonia from the condensate. It becomes possible.

  The ammonia-containing steam compressed and heated by the steam compressor 3 is sent to the flow-down steam generating heat exchanger 4 through the second connection pipe 22. In the steam generating heat exchanger 4, heat exchange is performed between the ammonia-containing steam compressed and heated by the steam compressor 3 and the low-concentration aqueous ammonia solution circulated to the distillation tower 2 through the circulation line 32. While condensing a part of the ammonia-containing vapor, the low-concentration aqueous ammonia solution is heated as described above to generate water vapor. At this time, the temperature of the condensate condensed in the steam generating heat exchanger 4 is substantially the same as that of the ammonia-containing steam in a compressed and heated state (that is, 93 ° C to 113 ° C, preferably 96 ° C to 111 ° C). The following.

The condensate condensed in the steam generating heat exchanger 4 and the uncondensed ammonia-containing steam that has not been condensed in the steam generating heat exchanger 4 are supplied to the gas-liquid separator 5 via the third connection line 23. Sent. At this time, since the third connecting pipe 23 has a predetermined size as described above, the condensate and the ammonia-containing vapor are not filled with the condensate in the third connecting pipe 23. Can be smoothly circulated toward the gas-liquid separator 5.

  In the present embodiment, for example, when heat exchange is performed in the steam generation heat exchanger 4, when the uncondensed ammonia vapor stays in the upper part of the vapor compressor 3 because the molecular weight of the ammonia vapor is smaller than that of the water vapor, There exists a possibility that the operation | movement of the steam generation heat exchanger 4 may become unstable. Therefore, when uncondensed ammonia vapor stays in the upper part of the steam compressor 3, the second flow rate adjustment valve 12b arranged on the fourth connection pipe 24 is opened, and the staying uncondensed uncondensed water is opened. The ammonia vapor and the water vapor accompanying the ammonia vapor are circulated to the cooling / condenser 6 via the fourth connection pipe 24. When ammonia vapor does not stay in the upper part of the vapor compressor 3, the second flow rate adjustment valve 12b may be closed to stop the flow of ammonia vapor from the vapor compressor 3 to the cooling / condenser 6. .

  Next, in the gas-liquid separator 5 into which the condensate and the ammonia-containing vapor are introduced, the condensate and the ammonia-containing vapor are separated, and the separated ammonia-containing vapor is cooled via the fifth connection line 25.・ Distribute to the condenser 6.

  At the same time, the separated condensate is led out to the reflux line 34 and is refluxed by the reflux pump 13 to the top of the distillation column 2 via the reflux cooler 17 and the third flow rate adjusting valve 16b. In this case, since the gas-liquid separator 5 is arranged upstream of the cooling / condenser 6, the condensate to be refluxed to the distillation column 2 receives only a part of the cooling by the cooling / condenser 6. Have high thermal energy. For this reason, even if the condensate separated by the gas-liquid separator 5 is refluxed to the distillation column 2, the internal temperature of the distillation column 2 can be prevented from decreasing and energy saving can be achieved.

  In this embodiment, the condensate (reflux) to be refluxed from the gas-liquid separator 5 to the distillation column 2 is condensed by the steam generating heat exchanger 4 and separated by the gas-liquid separator 5. In addition to the condensate condensed in the cooling / condenser 6 as described later, the temperature of the reflux liquid may be slightly higher than the temperature at the top of the distillation column 2. In this way, when the temperature of the reflux liquid flowing through the reflux pipe 34 is higher than the temperature at the top of the distillation column 2, adiabatic expansion (boiling) occurs on the outlet side of the reflux pump 13, and an abnormal noise called rattling is generated. And there is a risk of pipe vibration.

  However, as in the present embodiment, the reflux condenser 17 and the third flow rate adjustment valve 16b are installed on the reflux pipe 34 on the downstream side of the reflux pump 13, and the reflux liquid is supplied to the distillation tower 2 by the reflux condenser 17. While cooling to a temperature lower than the temperature at the top of the tower, the flow rate of the reflux liquid is adjusted by the third flow rate adjusting valve 16b to increase the pressure on the outlet side of the reflux pump 13, thereby bringing the outlet side of the reflux pump 13 to the outlet side. Therefore, the reflux liquid can be smoothly refluxed to the top of the distillation column 2 without causing abnormal noise or piping vibration. In particular, in this embodiment, in order to safely operate the ammonia separation apparatus, the reflux liquid is cooled to a temperature lower by about 2 to 5 ° C. than the temperature at the top of the distillation column 2 by the reflux cooler 17. .

  In the cooling / condenser 6 to which ammonia vapor and water vapor are sent from the gas-liquid separator 5 and ammonia vapor and water vapor are also sent from the steam generating heat exchanger 4, these ammonia vapor and water vapor are supplied to a predetermined temperature. For example, it is cooled to 83 ° C. or lower and condensed. Thereby, the amount of water vapor accompanying the ammonia vapor can be reduced, and the ammonia concentration of the ammonia-containing vapor conveyed to the ammonia treatment means in the next process via the conveyance pipeline 35 can be increased.

In this case, the temperature of ammonia vapor and water vapor introduced from the gas-liquid separator 5 and the steam generating heat exchanger 4 to the cooling / condenser 6 is 93 ° C. or higher, which is the temperature compressed and heated by the vapor compressor 3. For example, the water vapor accompanying the ammonia vapor at 93 ° C. or higher becomes a large amount of about 75 mol% or more of the entire mixed vapor.

  On the other hand, in the present embodiment, the ammonia vapor and the water vapor are cooled to 83 ° C. or lower by the cooling / condenser 6 as described above, so that the water vapor is actively condensed. Therefore, the cooled ammonia vapor and the ammonia vapor are cooled. In the mixed steam with water vapor accompanying the water vapor, the proportion of ammonia vapor can be increased to 50 mol% or more.

  In addition, although the amount of water vapor accompanying the ammonia vapor after cooling can be reduced as the ammonia vapor is cooled to a lower temperature by the cooling / condenser 6, if the ammonia vapor is cooled excessively, the next step is performed. Since the absolute amount of the ammonia vapor to be carried out decreases and ammonia may not be efficiently taken out of the system of the ammonia separation device 1, the cooling temperature cooled by the cooling / condenser 6 is set to a predetermined value. It is preferable to set it above the temperature (for example, above 70 ° C.).

  The ammonia vapor cooled by the cooling / condenser 6 is sucked by the suction device 14 disposed on the transport pipe 35 and is transported toward the ammonia processing means together with water vapor accompanying the ammonia vapor. The At this time, by controlling the pressure regulating valve 15 installed between the cooling / condenser 6 and the suction device 14, the inside of the cooling / condenser 6 is easily maintained at a predetermined pressure state, for example, lower than atmospheric pressure. can do.

  On the other hand, the condensate condensed in the cooling / condenser 6 is returned to the gas-liquid separator 5 via the sixth connection pipe 26. In this case, the cooling / condenser 6 cools and condenses the ammonia vapor and water vapor separated from the condensate in the gas-liquid separator 5, and therefore the amount of condensate condensed in the cooling / condenser 6. Is less than the condensate separated by the gas-liquid separator 5. For this reason, even if the condensate condensed in the cooling / condenser 6 is returned to the gas-liquid separator 5, the temperature of the condensate in the gas-liquid separator 5 is not greatly reduced.

  Then, the ammonia vapor transported from the cooling / condenser 6 to the ammonia processing means via the transport pipeline 35 is oxidized and decomposed into nitrogen gas or the like by the ammonia processing means and exhausted to the outside. In the present embodiment, the ammonia treatment means is not particularly limited. For example, ammonia can be suitably oxidatively decomposed by using a catalytic combustion method or a direct combustion method.

  When ammonia is oxidatively decomposed using the catalytic combustion method, the ammonia concentration of the ammonia vapor conveyed from the ammonia separator 1 and the water vapor accompanying the ammonia vapor is 25% or less of the lower explosion limit concentration. Then, the diluted ammonia vapor is heated to a temperature of 350 ° C. to 550 ° C. by an electric heater.

  Thereafter, heated ammonia vapor is introduced into the catalytic reaction layer and brought into contact with the catalyst, whereby the ammonia is subjected to catalytic oxidation. In this case, the high-temperature gas generated by catalytic oxidation is used for preheating performed before the heating of the ammonia vapor by the electric heater before being exhausted to the outside.

  On the other hand, when ammonia is oxidatively decomposed using the direct combustion method, it is often diluted with air so that the ammonia concentration becomes 25% or less of the lower explosion limit concentration, as in the catalytic combustion method. When the direct combustion method is used, ammonia combustion treatment is performed at a high temperature of 1000 ° C. or higher as a countermeasure against NOx.

The catalytic combustion method, for example, is easier to operate than the direct combustion method when there is no catalyst poison in the ammonia vapor line to be processed, and the amount of NOx generated is small, and the processing temperature is also low. Therefore, it is advantageous in terms of safety. Furthermore, the catalytic combustion method has the advantage that the equipment cost, running cost, and equipment installation area of the apparatus can be reduced as compared with the direct combustion method.

  As described above, according to the ammonia separation method of the present embodiment, the ammonia vapor and water vapor distilled from the top of the distillation column 2 are compressed and heated by the vapor compressor 3 and then the compressed and heated ammonia vapor. And the low-concentration aqueous ammonia solution taken out from the bottom of the distillation column 2 is evaporated using the heat of the water vapor and circulated through the distillation column 2 again.

  In this way, ammonia can be separated from the aqueous ammonia solution (raw water) by evaporating and separating it from the aqueous ammonia solution (raw water) in the distillation tower 2 while efficiently using the heat energy in the entire ammonia separation device 1. Costs required (running costs, etc.) can be greatly reduced compared to the prior art.

  Furthermore, in this embodiment, the ammonia vapor and water vapor separated by the gas-liquid separator 5 are cooled and condensed by the cooling / condenser 6. Thereby, in the mixed vapor | steam of the ammonia vapor | steam conveyed by the ammonia treatment means and the water vapor accompanying the ammonia vapor | steam, the ratio of water vapor | steam can be reduced simultaneously with raising the ratio of ammonia vapor | steam to 50 mol% or more. Thereby, since the calorie | heat amount required in order to preheat ammonia vapor | steam and water vapor | steam in an ammonia process means can be decreased, the installation expense and running cost of a preheating apparatus can be reduced.

  In addition, when oxidizing and decomposing ammonia using the catalytic combustion method, the ammonia reaction can be efficiently brought into contact with the catalyst in the catalytic reaction layer by increasing the proportion of ammonia vapor. By reducing the area of the layer, the entire catalytic combustion apparatus can be easily downsized. Furthermore, in this case, since the temperature of the gas generated by the oxidative decomposition of ammonia vapor can be increased, the ammonia vapor and water vapor before the oxidative decomposition treatment can be efficiently preheated using the thermal energy of the gas, thereby further saving energy. Can be planned.

  In addition, in the above-mentioned embodiment, the case where the one steam compressor 3 is installed between the tower top part of the distillation column 2 and the steam generation heat exchanger 4 is demonstrated. However, in the present invention, it is also possible to install a plurality of steam compressors 3 in series and / or in parallel between the top of the distillation column 2 and the steam generating heat exchanger 4.

  For example, as shown in FIG. 2, by installing two or more steam compressors 3 in series between the top of the distillation column 2 and the steam generating heat exchanger 4, The ammonia vapor and water vapor distilled from the top of the column can be stably compressed and heated to a higher temperature.

  Further, for example, as shown in FIG. 3, by installing two or more steam compressors 3 in parallel between the top of the distillation column 2 and the steam generating heat exchanger 4, a larger amount can be obtained. Since the ammonia vapor can be compressed and heated at the same time, the throughput per unit time in the ammonia separator 1 can be increased. In addition, since it is possible to rest the vapor compressors 3 one by one during the operation of the ammonia separation device 1, maintenance of the vapor compressor 3 is facilitated.

DESCRIPTION OF SYMBOLS 1 Ammonia separation device 2 Distillation tower 3 Steam compressor 4 Steam generating heat exchanger 5 Gas-liquid separator 6 Cooling and condenser (cooling condenser)
6a Refrigerant introduction part 6b Refrigerant lead-out part 6c 4th flow regulating valve 7 Preheating heat exchanger 8 Water supply part 9 Circulating pump 10 Steam supply part 11a 1st flow meter 11b 1st flow adjustment valve 12a 2nd flow meter 12b 2nd flow rate Regulating valve 13 Reflux pump 14 Suction device 15 Pressure regulating valve 16a Third flow meter 16b Third flow regulating valve 17 Reflux cooler 21 First connecting pipe 22 Second connecting pipe 23 Third connecting pipe 24 Fourth connecting pipe Route 25 Fifth connection pipeline 26 Sixth connection pipeline 31 Raw water supply pipeline 32 Circulation pipeline 33 Discharge pipeline 34 Reflux pipeline 35 Conveyance pipeline

Claims (14)

A distillation column to which an aqueous ammonia solution having an ammonia concentration of 3% by weight or less and steam are supplied, and at least one steam compressor, a steam generating heat exchanger, and a gas-liquid separator disposed downstream of the top of the distillation column A cooling / condenser that introduces and cools / condenses the gas separated by the gas / liquid separator, a transport line that transports the gas from the cooling / condenser to the ammonia treatment means in the next step, and the distillation A circulation line and a discharge line arranged on the downstream side of the bottom of the tower,
The top of the distillation column is provided with a vapor distilling portion for distilling ammonia vapor evaporated from the aqueous ammonia solution together with the water vapor inside the tower, and the bottom of the column reduces the ammonia concentration to a predetermined value or less. A low-concentration aqueous ammonia solution is circulated to the distillation tower via the circulation line and includes a liquid can outlet for discharging to the outside via the discharge line,
The vapor compressor has a compression heating unit that directly compresses and heats the ammonia vapor and the water vapor distilled from the top of the tower,
The steam generating heat exchanger exchanges heat between the ammonia vapor and the water vapor that are compressed and heated by the vapor compressor and the low-concentration aqueous ammonia solution that is circulated to the distillation column via the circulation line. And a heat exchange unit for condensing a part of the ammonia vapor and the water vapor and generating the water vapor by heating the low concentration aqueous ammonia solution,
The gas-liquid separator includes a gas-liquid separator that separates the ammonia vapor and the water vapor accompanying the ammonia vapor from the condensate condensed in the steam generating heat exchanger,
The cooling / condensing device includes a cooling / condensing unit that cools and condenses the ammonia vapor and the water vapor separated by the gas-liquid separator to a predetermined temperature.
An ammonia separator characterized by that. The steam generating heat exchanger is constituted by a falling steam generating heat exchanger,
The downflow-type steam generating heat exchanger includes a compressed steam introduction unit that introduces the compressed and heated ammonia vapor and the water vapor, a condensate condensed in the heat exchange unit, an uncondensed ammonia vapor and the water vapor, A first deriving unit for deriving the gas toward the gas-liquid separator, and a second deriving unit for directly deriving the ammonia vapor and the water vapor toward the cooling / condenser,
The first derivation unit is disposed below the compressed steam introduction unit,
The second derivation unit is arranged above the compressed steam introduction unit,
The ammonia separator according to claim 1.   The ammonia separation device according to claim 2, wherein a flow rate adjusting valve is disposed on a pipe line that communicates the second lead-out portion of the flow-down steam generating heat exchanger with the cooling / condenser. A suction device that sucks the ammonia vapor and the water vapor and sends the ammonia vapor and the water vapor to the ammonia processing means is disposed on the conveyance pipe line,
A pressure regulating valve is disposed between the cooling / condenser and the suction device.
The ammonia separator according to any one of claims 1 to 3. A reflux pipe for refluxing the condensate separated by the gas-liquid separator to the distillation column;
A reflux pump, a flow meter, and a flow rate adjustment valve are arranged on the reflux line.
The ammonia separator according to any one of claims 1 to 4.   6. The ammonia separator according to claim 5, wherein a reflux condenser is disposed on the reflux pipe line.   The ammonia separation device according to any one of claims 1 to 6, wherein two or more steam compressors are arranged in series. The ammonia separator according to any one of claims 1 to 7, wherein two or more steam compressors are arranged in parallel. An ammonia aqueous solution having an ammonia concentration of 3% by weight or less and water vapor are supplied to the distillation tower, and the ammonia vapor evaporated from the aqueous ammonia solution is distilled from the top of the tower together with the water vapor inside the distillation tower. Taking out a low-concentration aqueous ammonia solution reduced to below the value from the bottom of the tower,
The ammonia vapor and the water vapor distilled from the top of the tower are directly compressed and heated by at least one steam compressor and sent to a steam generating heat exchanger;
Circulating the low concentration aqueous ammonia solution from the bottom of the column to the distillation column via a circulation line and discharging it to the outside via a discharge line;
Heat exchange is performed between the ammonia vapor and the water vapor compressed and heated by the steam generation heat exchanger and the low-concentration aqueous ammonia solution circulated in the distillation column, and a part of the ammonia vapor and the water vapor And condensing and heating the low-concentration aqueous ammonia solution to generate water vapor,
Separating the ammonia vapor and the water vapor accompanying the ammonia vapor from the condensate condensed in the steam generating heat exchanger by a gas-liquid separator;
Cooling and condensing the separated ammonia vapor and water vapor to a predetermined temperature by a cooling and condenser; and
A method for separating ammonia, comprising transporting the cooled and condensed ammonia vapor and the water vapor from the cooler / condenser to an ammonia treatment means in the next step through a transport pipeline. Using a falling steam generating heat exchanger as the steam generating heat exchanger, introducing the compressed and heated ammonia vapor and the water vapor from a compressed steam introducing section; and
In the downflow-type steam generating heat exchanger, a condensate obtained by condensing a part of the ammonia vapor and the water vapor and the uncondensed ammonia vapor and the water vapor are disposed below the compressed steam introduction part. Deriving from the first deriving unit toward the gas-liquid separator, and deriving the ammonia vapor and the water vapor from a second deriving unit disposed above the compressed steam introducing unit, to the cooling / condenser The ammonia separation method according to claim 9, comprising direct introduction.   The ammonia separation method according to claim 10, further comprising controlling flow rates of the ammonia vapor and the water vapor directly introduced from the steam generation heat exchanger into the cooling / condenser by a flow rate adjusting valve. Sucking the ammonia vapor and the water vapor and sending them to the ammonia treatment means by a suction device disposed on the transport pipe; and
The ammonia separation according to any one of claims 9 to 11, comprising adjusting a pressure in the cooling / condenser by a pressure regulating valve arranged between the cooling / condenser and the suction device. Method. The condensate separated by the gas-liquid separator is refluxed to the distillation column via a reflux line, and the flow rate of the condensate to be refluxed to the distillation column is controlled by a flow rate adjusting valve. The ammonia separation method according to any one of claims 9 to 12, comprising:   The ammonia separation method according to claim 13, comprising cooling the condensate refluxed to the distillation column by a reflux condenser.

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