KR800001159B1 - Process of separating substantially pure nh3 and substantially pure co2 from a composition containing nh3 and co2 - Google Patents

Abstract

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Description

How to separate ammonia and carbon dioxide from a mixture containing ammonia and carbon dioxide

1 is a system diagram of the present invention in which an ammonia separator and a carbon dioxide separator are operated at approximately the same pressure so that ammonia is suitable for separating carbon dioxide from a mixture having an azeotropic ammonia rich composition.

2 is a system diagram of the present invention in which the ammonia separator and the carbon dioxide separator are adapted to operate at different pressures in the system diagram shown in FIG.

3 is a system diagram of the invention arranged to separate a mixture of ammonia and carbon dioxide and water in an azeotropic carbon dioxide rich composition.

4 is a system diagram of the present invention, adapted to separate ammonia and carbon dioxide from a solution diluted by the method of the present invention.

5 is a schematic diagram of a method for producing urine using the method of the present invention.

The present invention relates to a method for separating almost pure ammonia and carbon dioxide from a composite material containing ammonia and carbon dioxide.

“Composite containing ammonia and carbon dioxide” means a binary mixture of ammonia and carbon dioxide, a gas mixture consisting of ammonia, carbon dioxide and water vapor, or containing ammonium carbamate and / or ammonium carbonate in an aqueous solution. Refers to an aqueous solution of ammonia and carbon dioxide that may be present.

Among chemical reactions, gas mixtures of ammonia and carbon dioxide and often moisture are obtained as by-products of the reaction process.

For example, when melamine is synthesized from urine, a mixture of melamine and ammonia and carbon dioxide is produced at 1.7 tons per melamine ton. To separate ammonia and carbon dioxide from melamine and to reuse them in cases such as urine synthesis, it is necessary to treat these gases at high pressure.

Compressing this mixture requires special measures to prevent condensation of ammonia and carbon dioxide and to prevent precipitation of the ammonium carbamate formed thereby, so that the gas mixture is usually well absorbed by water or aqueous solutions. In order to increase the concentration, desorption under high pressure and repeated absorption treatment are necessary for the production of ammonium carbamate to be added to the urine synthesis process.

The drawback of this method is that the water reintroduced with ammonia and carbon dioxide has an adverse effect on the production of urine from ammonia and carbon dioxide.

If no special measures are taken as mentioned above, all ammonia from the mixture is azeotropic because the binary substances of ammonia and carbon dioxide and the tertiary substances containing water are azeotropic. It is impossible to separate carbon dioxide from carbon dioxide. Various methods have been sought to avoid the re-introduction of residual water with ammonia re-introduced during the urine synthesis process, all of which have separated the mixture of ammonia and carbon dioxide into individual components. These methods are those which selectively absorb one component or another component in an aqueous solution. Thus, one of these methods is the absorption of ammonia into an aqueous solution of a strong acid (eg NH ₄ NO ₃ ) under elevated pressure. Another known method is to mix the mixed gas with an aqueous alkanolamine solution such as monoethanolamine. There is a method of selectively absorbing carbon dioxide while washing, but these methods have a drawback that the absorbed component must be purified after separation from the absorbent. Also, a method of distilling most of ammonia from a mixture of ammonia, carbon dioxide and water in the first stage and distilling carbon dioxide in a second stage with a mixture of ammonia, carbon dioxide and moisture under high pressure has been sought.

Such methods are shown in US Pat. No. 3,112,177 and UK Pat. No. 1,129,939.

The method described in the US patent is carried out using the system pressure of 1 to 5 absolute atmospheric pressure (1-5 atm. Abs.) In the first process, and in the second process when the ammonia content is relatively low, that is, azeotropic ammonia and carbon dioxide. Less ammonia separates carbon dioxide from a mixture of ammonia, carbon dioxide and water.

The resulting bottom solution is stripped with a stripping gas, such as methane, with the system pressure at about one absolute atmosphere. As a result, the system pressure is lowered and ammonia and some carbon dioxide are released, resulting in a mixture of methane, ammonia and carbon dioxide with an overall pressure of about 1 atmosphere. The carbon dioxide is absorbed by the liquefied ammonia by condensing part of the mixture to remove the carbon dioxide remaining in the gas mixture.

A similar method is described in British Patent No. 1,129,939, which suggests that a gas mixture of carbon dioxide and ammonia containing a higher proportion of ammonia than the azeotrope is absorbed in water or an aqueous solution, and at a low pressure from the aqueous solution. Ammonia is distilled off. After distilling ammonia, the remaining aqueous solution is partially distilled while heating to remove carbon dioxide at a pressure of about 5-20 atm.

The two methods described above focus on changing the pressure of the mixture of ammonia and carbon dioxide and the fractions so that ammonia can be separated at low pressure and carbon dioxide at high pressure.

The pressure ratio, that is, the ratio of the partial pressure of ammonia and carbon dioxide and water in the step of removing ammonia and the pressure in the step of removing carbon dioxide should be 1: 5 to 1:20 in the above two methods. .

The following defects are found in these methods. That is, when the treated mixture is put under pressure above one absolute pressure, the mixture first reaches a pressure of one absolute pressure. Moreover, the ammonia gas is then discharged with a maximum pressure of one absolute pressure and there is a possibility that a large amount of other gas exists. If this ammonia is needed for subsequent processing such as urinary synthesis, higher pressures are needed.

Compression energy for this purpose is considerable and it is necessary to lower the concentration of carbon dioxide in the ammonia to avoid the formation of solid ammonium carbamate in high pressure systems and compressors. In addition, to liquefy gas ammonia, it is necessary to cool the ammonia to a considerable degree while increasing the ammonia to the desired pressure, which also requires energy.

The present invention devises a method for the simple and economic separation of pure ammonia and carbon dioxide through each separation process from a mixture of ammonia and carbon dioxide and the water present therein.

Surprisingly, it was found that ammonia and carbon dioxide can be recovered separately from the mixture without the above-mentioned problems if the mixture supplied in the process of separating carbon dioxide is made white in water but the weight ratio of the supplied water is 0.2: 1 to 6: 1. .

The present invention devises a method for separating pure ammonia and pure carbon dioxide from a mixture consisting of ammonia and carbon dioxide. The above-mentioned separation is carried out in the ammonia separation zone and the carbon dioxide separation zone by heat, and in particular, the separation of carbon dioxide is performed by adding 0.2 to 6 times the weight of feed material supplied to the carbon dioxide separation zone.

By introducing 0.2 to 2.5 times the weight of the feed material supplied to the carbon dioxide separator into the carbon dioxide separator, it is possible to obtain the best efficiency in the separation operation.

Below the water input range described above, the required re-feed amount increases and the separation becomes more and more difficult, and below 0.2 times, the separation efficiency is unacceptably lowered.

At 2.5 times or more, the temperature at which carbon dioxide is separated increases and there is a risk of corrosion, and more than 6 times more than the feed, the amount of energy required to remove the input water is unacceptable. Becomes loud.

It should be noted that the amount of water added to the carbon dioxide separator according to the present invention is an amount added to the water contained in the feed material consisting of ammonia, carbon dioxide and water actually supplied to the carbon dioxide separator.

The process of the present invention can also be applied to ammonia rich or carbon dioxide rich initials.

"Ammonia-rich" means that the ammonia-carbon dioxide ratio of the starting material is in a state where the ammonia is disturbed first when the starting material is heated. The term "carbon-rich" means that the ammonia-carbon dioxide ratio heats the starting material. At the time it means that carbon dioxide is in a disturbing state first.

Therefore, one of the devices of the present invention is a method in which ammonia-rich material is used as a starting material as described above.

First, the starting material is passed through an ammonia separator in which gaseous ammonia is obtained as an upper stream overhead and boiling aqueous solutions of ammonia and carbon dioxide are obtained as bottoms.

Secondly, the reservoir obtained here is passed as a feed through a carbon dioxide separator having carbon dioxide as an upstream and a boiling aqueous solution of ammonia and carbon dioxide as a reservoir and with water present according to the process of the invention.

Another device is a method in which the carbon dioxide-rich material described above is used as a starting material, and in this method,

Firstly, the starting material is passed through a carbon dioxide separator where water is present according to the method of the present invention and carbon dioxide is obtained as a supernatant stream and an aqueous solution of ammonia and carbon dioxide is obtained as a reservoir. And a gas mixture containing carbon dioxide and water vapor, passed through a desorption band to remove from the desorption zone.

Thirdly, the obtained gas mixture is passed through the ammonia separation section described above in which ammonia is obtained in an upper stream and an aqueous solution of boiling ammonia and carbon dioxide is obtained in a reservoir.

The addition of moles to the carbon dioxide secretion zone in the process of the present invention may be partially added to the feed material at one or several points in the carbon dioxide separation zone at the same time or before the feed is supplied to the carbon dioxide separation zone. The added water may itself be a dilute solution of ammonia and carbon dioxide, that is, 90% or more in terms of water weight. However, this ratio depends on the pressure of the material.

At lower pressures, higher water concentrations are required.

The ammonia separator has a bottom temperature ranging from 60 ° C to 170 ° C, and an upper temperature range from -35 ° C to 66 ° C. The bottom temperature of the carbon dioxide separator described above is 75 ° C. The upper temperature up to 200 ° is operated in the range of 0 ° to 100 ° C so that the temperatures at the top are lower than the temperatures at the bottom.

The optimum temperature at the bottom of the ammonia separator depends on the pressure and the composition of the incoming material entering the ammonia separator.

However, when ammonia, carbon dioxide, and water react to produce a solid product, or when the inflow material entering the carbon dioxide separation zone is in such a state that carbon dioxide cannot be separated to the maximum, the temperature of 60 ° C or less Used.

In most cases, the bottom temperature in the ammonia separator does not exceed 170 ° C. to maintain the ammonia separator and the temperature in the carbon dioxide separator, which is always slightly higher than the ammonia separator, is higher than the temperature that will cause unacceptable corrosion. Should be low. For the same reason, the bottom temperature of the carbon dioxide separator should not exceed 200 ° C in particular. The upper temperature of the ammonia separator is mainly determined by the pressure used.

The upper temperature of the carbon dioxide separator is determined by the final purity of the carbon dioxide obtained. Generally, when the upper temperature reaches about 100 degrees Celsius, the ammonia obtained is less than 100 pM.

The upper temperature in these two separators is determined by the amount of ammonia re-introduced and the amount and temperature of dilution and washing water used, respectively. The pressure of the carbon dioxide separator is preferably less than twice the pressure of the ammonia separator and the best condition is that the pressures of the two separators are the same. Although this pressure ratio may be carried out at 2 or more, in this case, the pressure to separate the ammonia is lowered, which requires a huge investment cost to liquefy the ammonia and accordingly consumes enormous energy. For this reason, it is preferable not to exceed the above-mentioned maximum pressure ratio.

According to the method according to the invention it can be operated at the same pressure in the ammonia separator and carbon dioxide separator. It is also an advantageous method to change the pressure ratio little by little. As an example, the pressure ratio is slightly changed depending on the size of the heat transmitting area required and the economical efficiency of heat in recovering ammonia and carbon dioxide. You can also adjust.

In general, the absolute value of the pressure at which the separation takes place is determined by the pressure at which the recovered ammonia is used.

Typically, the absolute pressure of 1 to 50 is adopted, but in the ammonia separation zone and the pressure of 5 to 25 absolute atmospheric pressure are preferable, and 15 to 22 absolute atmospheric pressure is particularly preferable.

It is an advantageous method to avoid the costly compression process by implementing the process of the present invention at a pressure at which gas ammonia can be agitated by the cooling water so that ammonia is obtained. According to the method described in British Patent No. 1,129,939, carbon dioxide is washed with water in a wash tower to remove traces of ammonia in order to prevent precipitation, which is not good for this process. Has no effect.

In order to discharge carbon dioxide, a solution of ammonia is formed in water that is introduced into a distillation tower.

The amount of water used in this method is very small and insufficient to achieve the same effect as the present invention.

As described above, ammonia and carbon dioxide are separated according to the mole ratio of ammonia and carbon dioxide of the material to be treated in the first step.

However, if the material treated by the method of the present invention is present in a state in which ammonia and carbon dioxide are diluted in water, a gas mixture is obtained and the gas mixture formed therefrom is separated into ammonia and carbon dioxide according to the method of the present invention. It is desirable to first remove most of the ammonia and carbon dioxide from all or part of it.

The present invention is particularly effective for separating a gas mixture mainly composed of ammonia, carbon dioxide and water obtained by decomposing ammonium carbamate undiverted at an absolute pressure of 1 to 25 kg / cm ² in the process for producing urine from ammonia and carbon dioxide. It can be applied in a way that has advantages.

At this time, the separation process is performed in the following order.

First, the gas mixture is passed through the CO ₂ separation Ciolumn, which has a temperature gradient from the bottom to the top, to the weight of water at one or several points of the CO ₂ separation tube. In order to form an aqueous solution containing 65 to 96% of carbon dioxide and ammonia, an appropriate amount of water or aqueous solution is supplied, so that the gas flow of carbon dioxide does not include ammonia and water, Remove the gas flow of carbon dioxide from above

Second, the aqueous solution of ammonia and carbon dioxide described above is desorbed to generate a stream of an aqueous solution containing mainly ammonia and carbon dioxide and a secondary gas stream formed of ammonia and carbon dioxide residues and water. It enters and passes through a desorption zone that is desorbed.

Thirdly, the secondary gas flow generated is passed through an ammonia separator where carbon dioxide and water are separated in the outflow of the aqueous solution, and the ammonia is also removed as a separate gas stream in the ammonia separator to directly or indirectly synthesize the above-described synthesis process. Reinsert into

First, second and third steps are carried out in the absolute pressure range of 1 to 25 kg / cm ² .

The method of the present invention will be described in detail with reference to the drawings.

According to FIG. 1,

A mixture of ammonia-rich ammonia, carbon dioxide and a portion, which is an aqueous solution or a gas mixture, is introduced into ammonia separator 3 in the form of a rectification column by system 1 and pump 2. Gas ammonia is discharged along opening 4 in rectifier 3, condensed by cooling in condenser 5, and the gas mixture of ammonia and other gases that are not condensed is discharged from condenser 5 as an upstream layer.

濟, passivating agent)로써 본장치에 공급되는 공기, 산소 또는 산소방출제(oxygen releasing agent)로 부터 발생한 것이다. 방청기체(防

氣體, passivating gas)의 일부는 압축기 6과 계통 7 및 계통 8을 경유하여 정류관 3에 유입되고 다른 일부는 계통 9를 따라 탈흡기(脫吸器, desorber) 10에 유입된다. 응축기 5에서 배출된 상층류는 계통 36을 따라 세척기(洗滌器, washer) 11에 유입되고 여기에서 계통 34를 따라 유입된 물에 의하여 세척됨으로써 암모니아는 스트립(Strip)되어 암모니아의 수용액을 형성하고 이 암모니아 수용액은 펌프 12에 의하여 재순환냉각기(recirculation cooler) 13에 유입되어서 이들중 일부는 계통 14를 따라 세척기 11에 재유입되고 다른 일부는 필요할 경우 압력을 감소시켜서 계통 15를 통하여 정류관에 재유입된다.The other gases mentioned above are anti-corrosive agents in order to prevent unacceptable corrosion of the materials constituting the apparatus.

I) from the air, oxygen or oxygen releasing agent supplied to the unit as a passivating agent. Antirust gas

Part of the passivating gas enters rectifier tube 3 via compressors 6 and 7 and 8 and the other part enters desorber 10 along system 9. The supernatant discharged from condenser 5 enters washer 11 along system 36 where it is washed by water entering system 34, whereby ammonia is stripped to form an aqueous solution of ammonia. The aqueous solution enters the recirculation cooler 13 by pump 12, some of which are reintroduced into scrubber 11 along system 14 and some of which are reintroduced through the system 15 by reducing the pressure if necessary.

The other gases separated in the scrubber 11 are discharged along the system 16 and, if necessary, outflow through the system 19, in whole or in part, or simultaneously supplied to the carbon dioxide rectifying tube 18 along the system 17. Some of the ammonia liquefied in condenser 5 is resupplied to ammonia rectifier 3 along system 20 as a refeed. The remaining liquefied ammonia flows out along line 37. The heat required for rectification is supplied by a steam coil 35 mounted at the bottom of the rectifier tube.

At the bottom of the ammonia rectifier 3, an aqueous solution of ammonia and carbon dioxide is discharged along the system 21 and introduced into the carbon dioxide rectifier 18.

The operating pressure of the carbon dioxide rectifying tube 18 is approximately equal to the operating pressure of the ammonia rectifying tube 3. The material collected at the bottom of the deaerator 10 is discharged along the pump 22 and the system 23 and introduced into the carbon dioxide separator 18 as a diluent. In order to improve heat distribution efficiency, this liquid stream is first dissipated from the rectifier tube 18 and then from the cooler 26 again. In the rectifier tube 18, the remaining heat required for rectification is supplied by a heating coil 24, such as with steam.

Part of the liquid flow from system 23 enters chiller 27 along system 25, cools with water and exits system 28. The stream of wash water being fed to the carbon dioxide rectifier along system 29 is supplied to remove the largest possible ammonia from the carbon dioxide.

The upper stream discharged from the carbon dioxide rectifier tube 18 through the system 30 is a gas composed of carbon dioxide and the other gas described above containing almost no ammonia.

The low laminar flow discharged from the carbon dioxide rectifying tube 10 to the inhaler 10 through the system 31 is a solution in which ammonia and carbon dioxide are diluted in water and is heated by heat as in the example of steam supplied through the heating coil 32 in the deaerator 10. Almost all ammonia and carbon dioxide are emitted. Almost all carbon dioxide and ammonia-free solutions enter the carbon dioxide rectifier tube 18 along system 23, and a gaseous mixture of ammonia, carbon dioxide, and water formed in the deaerator 10 enters the ammonia rectifier tube 3 via system 33.

In Fig. 2, the same parts as in Fig. 1 are indicated by the same numbers as in Fig. 1,

CO2 rectifiers operate at higher pressures than ammonia rectifiers. In order to increase the pressure of the gas flow and the liquid flow, a compressor (A) was installed in the system 17 and a pump (B) was installed in the system 21. Furthermore, system 31 was equipped with a damping valve (C) to reduce the pressure of the stratum flow in the carbon dioxide rectifying tube 18.

Deaerator 10 operates at a system pressure approximately equal to the system pressure of the ammonia rectifier. Another form of suitable practice is to perform desorption at a pressure equal to the system pressure of the carbon dioxide rectifying tube.

The same part as in FIG. 1 is shown in FIG. 3 with the same number as in FIG.

A mixture of carbon dioxide-rich ammonia, carbon dioxide and water is introduced into the carbon dioxide rectifying tube 18 along the system 41 and the pump 42. This apparatus of the present invention makes it possible to separate almost pure carbon dioxide and almost pure ammonia from a mixture consisting of an azeotropic carbon dioxide rich composition. Except for this initial supply system, Figure 3 is identical to Figure 1.

In Fig. 4, the same parts as in Fig. 1 are indicated by the same numbers as in Fig. 1,

Dilute aqueous solution of ammonia and carbon dioxide enters the deaerator 10 via system 51 and pump 52. Except for these different initial supply systems, FIG. 4 is the same as FIG.

According to Figure 5,

In the urine synthesis reactor 101, the urine synthesis solution is produced at a pressure of 110 to 250 kg / cm ² and a temperature of 165 to 220 degrees Celsius. This solution is fed through strip 102 to stripper 103 which is operated at a synthesis pressure or lower and is brought into reverse contact with fresh carbon dioxide and solution supplied along grid 104 in the presence of heat. The gas mixture consisting of water and carbon dioxide and ammonia discharged from stripper 103 enters condenser 106 via system 105. The condenser is preferably operated at the same pressure as the synthesis pressure, and the solution formed in the tributary layer of the urine synthesis reactor 101 is discharged to raise the condensation temperature so that the heat of condensation is released at the highest possible temperature. 109 is supplied to the condenser via system 108 and system 109.

The heat generated here produces steam with an absolute pressure of 1 to 6 kg / cm ² , which can be used in other processes of the process of the invention. Spinner 109 is driven by ammonia supplied from storage tank 111 via pump 110 and fresh ammonia is supplied along system 112. In the condenser 106, total or partial condensation and absorption of the gas mixture introduced along the system 105 is effected. The carbamic acid solution thus obtained and the residues of the gas mixture which may be present are dissolved along the system 113, ammonia, carbon dioxide and moisture from the gas mixture discharged through the system 114 from the top of the urine synthesis reactor 101. It was obtained and introduced into the urine synthesis reactor 101 together with the carbamic acid solution containing fresh carbon dioxide and ammonia and inert components supplied by usable air or oxygen, which were used for forming the corrosion-resistant thin film of the apparatus and system. This condensation process takes place in a gas purifying condenser 115 connected to system 113 or to the bottom of urinary reactor 101 by system 116.

Gas that has not condensed in the gas purification condenser may be introduced through system 117 into a desorber, not shown in the figure, operating at any pressure to recover the ammonia still present. However, it is also possible to supply the solution obtained in the gas purifying condenser to the condenser 106 via the radiator 109.

The stripped urine synthesis solution is discharged from stripper 103 and the pressure is attenuated to 2-5 kg / cm ² in damping valve 118 and then introduced into carbamic acid digester 120 along line 119. In the carbamic acid cracker, carbamate, which still exists, is substantially decomposed by heat. The gas mixture, which is out of the heating point of the carbamic acid decomposer 120 together with the urine solution, is separated from the urine solution in the decomposer 121 and then introduced into the separator of ammonia, carbon dioxide, and water, which will be described later.

The aqueous solution of urine obtained in the separator 121 of the carbamic acid decomposer 120 is diffused in the expansion vessel 122 to reach atmospheric pressure, where more undissolved ammonia and water vapor are discharged along the system 123. do.

The aqueous solution of urine is introduced via system 124 into the device shown as the preliminary device 125 where the concentration of urine solution is increased by evaporation, crystallization or other known means. The final product is discharged through system 126.

The gas mixture separated by the urine aqueous solution from the separator 121 is introduced into the system for removing ammonia, carbon dioxide and water through the system 127, which is mainly composed of a carbon dioxide separator 128, a deaerator 129 and an ammonia separator 130. These pipes actually operate at the same pressure in the absolute pressure range of 1 to 25 kg / cm ² .

If the separation system is operated in an absolute pressure range of 1 to 6 kg / cm ² , there is a particular advantage because the solution supplied to the desorption column 129 can be stripped by the steam formed in the condenser 106.

The most convenient operation of the separation system is to allow the carbamic acid decomposer 120 and the separator 121 to operate at the same pressure. At the bottom of the carbon dioxide separation tube 128, almost all ammonia and water are absorbed or condensed, and the carbon dioxide, which contains little ammonia and water, is brought into contact with an amount of water that can be raised to the top of the tube.

At the bottom, the terminal of the apparatus, water or an aqueous solution, which is a condensate of the apparatus 125, is supplied via system 131, and further, the aqueous solution obtained in the secondary separation stage is resupplied via system 132 and system 133. At the top of the CO 2 separator tube 128, the ascending gas mixture is washed by water supplied to system 134 to remove the small amount of ammonia still present in the mixture. This water, along with the absorbed ammonia, enters the bottom of the tube. The weight of the water supplied through the systems 131, 132, 133, and 134 at the bottom of the tube 128 is 5 to the weight of the gas mixture supplied through the system 127 with 65-96% of the water discharged from the bottom of the tube. The amount is enough to contain 20 times the water. In general, the optimum composition ratio of water is 20 to 95% by weight, and thus the amount of water to be added is preferably 8 to 15 times the weight of the gas mixture.

By operating the tubes according to this method, carbon dioxide and ammonia can be removed from the gas mixture separated in the separator 121 with very low energy consumption in the separation process.

The temperature at the bottom of the tubes is maintained at 70 ° to 90 ° and the temperature at the top is maintained at 30 ° to 70 °.

At the top of the tube 128, carbon dioxide is discharged and purified along the sieve system 135, which contains only a few percent water and traces of ammonia as much as possible. The material produced at the bottom of the tube 128 contains carbon dioxide and water which, if present in the gaseous mixture supplied along system 127, remained substantially indistinguishable from almost all ammonia. This solution is taken from system 136 and supplied to deaerator 129 where it is desorbed with the aid of steam which supplies virtually all ammonia and carbon dioxide to system 137.

Substances produced at the bottom of the deaerator 129 are water containing ammonia and carbon dioxide below one permissible amount of discharge pursuant to the Environmental Protection Act and discharged along a system 138 connected to a system 132 connected to a carbon dioxide separation pipe 128. .

Some of the material produced at the bottom may enter the carbon dioxide separator 128 as wash water through system 134 and the remaining residues may be discharged to system 139 and may be fed back to apparatus 125 in whole or in part.

Almost all ammonia that had been separated in separator 121, excluding carbon dioxide and water, and part of the ammonia that was circulating, generated from the top of the deaerator 129 at 105 ° C to 175 ° C. 142 is introduced into the ammonia separation tube 131, where carbon dioxide and water are removed by the water supplied through the system 143 and the ammonia liquid supplied through the system 144. The substantially pure ammonia thus obtained enters the cooling installation 146 through system 145 and condenses. The condensed ammonia liquid enters the ammonia storage tank 111 via system 147. The bottom solution consisting of ammonia, carbon dioxide and water produced in the ammonia separation tube is reintroduced into the carbon dioxide separation tube 128 through the system 133. In the above method, no water is returned from the low pressure process, i.e., after the damping valve 118 to the urine synthesis process. Accordingly, in the urine reactor, the reaction is carried out at a considerably high conversion degree so that a synthetic solution containing less carbamic acid is obtained.

Less carbates need to be decomposed in the stripper and stripping requires only a small amount of steam because the stripping action is better performed due to the lower water concentration of the synthetic solution.

Consumption of steam for separation of ammonia, carbon dioxide and water can be achieved by reducing the amount of steam in the urine synthesis process because the amount of water to be evaporated is reduced. Since only ammonia is recycled from the low pressure process, the operation of the device is simplified.

Operational reliability is further reconsidered because no vulnerable carbamate pump is needed.

The results according to the invention are shown in the following examples and all percentages from Examples 1 to 4 represent percentages by weight unless otherwise indicated.

Example 1

In the apparatus shown in FIG. 1, nearly pure ammonia carbon dioxide was separated from the mixture of ammonia and carbon dioxide and water. Aqueous solutions of ammonia and carbon dioxide, 33.4% ammonia, 18.2% carbon dioxide, and 48.4% water, were fed to the bottom of ammonia rectifier 3 at a temperature of 73 ° C. and 18 absolute atmospheric pressure. Compressor 6 was supplied with 635 kg of air per hour, of which 248 kg was supplied to the ammonia rectifier 3 and the remaining 387 kg to the deaerator 10.

A mixture of gases consisting of 50.4% ammonia, 17.7% carbon dioxide and 30.9% moisture, and up to 1.0% other gases at a temperature of 162 ° C, introduced from the deaerator 10, was also added to the ammonia rectifier at a rate of 39,304 kg per hour. Supplied.

At the top of the rectifier, a gas mixture consisting of 99.4% ammonia and 0.6% other gases was discharged at a rate of 65,217 kg per hour. Some of these gases were liquefied in condenser 5 by the cooling water. A stream of liquefied mixture reflowed at 44,630 kg per hour was sent to rectifier tube 3. A gas mixture consisting of 88.9% ammonia and 11.1% other gases was discharged from condenser 5 at a rate of 3474 kg per hour and washed in washer 11 with 4,496 kg of water per hour. Heat was removed from washer 11 by circulating cooler 13. An aqueous solution consisting of 38.7% ammonia and 61.3% water was re-injected into the ammonia rectifier at a rate of 7,335 kg per hour.

The top temperature of this rectifier was 40 ° Celsius. Through systems 16 and 17, other gases were sent to the carbon dioxide rectifier 18 at a rate of 635 kg per hour.

From the bottom of ammonia rectifier 3, a solution of temperature 131 ° C, consisting of 25.4% ammonia, 21.0% carbon dioxide and 53.6% water, was sent through system 21 to CO2 rectifier 18 at a rate of 78,027 kg per hour.

This 18-pressure atmospheric rectifier, along system 25, consists of traces of ammonia and carbon dioxide and water, and flows in diluents with a temperature of 206 ° C when discharged from the deaerator at a rate of 73,299 kg per hour. It became. The heat contained in this diluent is removed from the cooler 26. The solution being discharged from the deaerator 10 at a rate of 108,909 kg per hour can also be cooled and discharged from the chiller 27, which means that 108,909 kg per hour and water are discharged.

This water can be used, for example, to absorb ammonia and carbon dioxide.

Water for washing was introduced at the rate of 5,959 kg per hour in order to clean the last trace of ammonia.

The bottom temperature of the carbon dioxide rectifier tube 18 was maintained at 158 degrees Celsius by steam, and the top temperature was 35 degrees Celsius.

A gas mixture consisting of 93.7% carbon dioxide, 6.3% other gases, and ammonia below 100 P.P.M. was discharged from the rectifier at a rate of 10,094 kg per hour.

An aqueous solution consisting of 81.9% water, 13.4% ammonia and 4.7% carbon dioxide was sent to deaerator 10 at a rate of 147,826 kg per hour from the bottom of rectifier tube 18 at a temperature of 158 ° C. By steam, the solution stripped most of the ammonia and carbon dioxide from the desorber, releasing water at a rate of 108,909 kg per hour, containing only traces of ammonia and carbon dioxide.

The temperature at the top of the deaerator was 161.8 ° Celsius.

Example 2

In the apparatus shown in FIG. 2, almost pure ammonia and carbon dioxide were separated from the mixture consisting of ammonia, carbon dioxide and water.

Aqueous solutions of ammonia and carbon dioxide, consisting of 33.4% ammonia, 18.2% carbon dioxide, and 48.4% water, were supplied to the bottom of the ammonia rectifier at a temperature of 73 ° C and system pressure of 15 atm. Compressor 6 was supplied with air at a rate of 635 kg per hour, of which 248 kg per hour were fed to ammonia rectifier 3 and 387 kg per hour to deaerator 10.

In addition to ammonia rectifier 3, a gas mixture of 150 ° C and 49.1% ammonia, 15.5% carbon dioxide, 34.4% moisture, and other gases from the deaerator 10 was introduced at a rate of 37,943 kg per hour.

At the top of the rectifier, a gas mixture consisting of 99.0% ammonia and 1.0% of other gases was discharged at a rate of 60,888 kg per hour. Intense cooling caused some of this gas mixture to liquefy in condenser 5. The flow of this liquefied mixture was sent as re-entry to rectifier 3 at a rate of 40,056 kg per hour. A gas mixture consisting of 81.7% ammonia and 18.3% other gases was discharged from condenser 5 at a rate of 3474 kg per hour. Heat was removed from washer 11 by circulating cooler 13.

A solution of 36.2% ammonia and 63.8% moisture was fed back into the ammonia rectifier at a rate of 7,842 kg per hour and the temperature above the rectifier was 39 ° C. Through system 16, system 17 and compressor (A), 635 kg of inert gas per hour was introduced into the carbon dioxide rectifier tube 18 operating at 25 absolute atmospheric pressure. Through system 21 and pump (B), a solution consisting of 128 ° C, 24.1% ammonia, 19.9% carbon dioxide, and 56.0% moisture was introduced into the CO2 rectifier 18 at a rate of 77,172 kg per hour. The rectifier tube 18, with an internal pressure of 25 absolute pressure, has a temperature of 197 ° C and a trace of ammonia and carbon dioxide in water at a rate of 48,915 kg per hour when discharged from the deaerator through system 25. Inflowed. Some of the heat contained in this diluent was removed from the bottom of the CO2 rectifier tube 18 and the remaining heat was removed from the cooler 26. The solution is discharged from the desorber at the rate of 85,031 kg per hour as it is cooled in the cooler 27, which means that 36,116 kg of water is discharged per hour, which can be used for example to absorb ammonia and carbon dioxide.

The top of the CO2 rectifier was fed 5,959 kg of unmelted wash water per hour to wash out as much of the last trace of ammonia as possible. By steam, the temperature at the bottom of the carbon dioxide rectifier tube 18 was maintained at 170 ° C and the temperature at the top was 35 ° C. A gaseous mixture containing 93.7% carbon dioxide and other gases 6.3% and ammonia below 100 ppm was discharged from the top of the rectifier at a rate of 10,094 kg per hour.

At the bottom of rectifier 13, a temperature of 170 ° C, consisting of 80.0% moisture, 15.2% ammonia and 4.8% carbon dioxide, was sent to deaerator 10 after the pressure was attenuated by the damping valve (C). The ammonia and carbon dioxide in this solution were stripped by the steam to the deaerator, and water containing only traces of ammonia and carbon dioxide was discharged at a rate of 85,031 kg per hour. The temperature at the top of the deaerator was 158 ° Celsius.

Example 3

In the apparatus shown in FIG. 3, almost pure ammonia and carbon dioxide were separated from an aqueous solution of azeotropic carbon dioxide-rich ammonia and carbon dioxide.

Aqueous solution of ammonia and carbon dioxide, consisting of 20% ammonia, 20% carbon dioxide and 60% water, was supplied to the carbon dioxide rectifier tube 18 at a temperature of 130 ° C and system pressure of 18 absolute atmospheres. From the bottom of ammonia rectifier 3, a temperature of 130 ° C, consisting of 26.0% ammonia, 22.1% carbon dioxide, and 51.9% moisture, was sent to the carbon dioxide rectifier tube 18 at a rate of 27,405 kg per hour through system 21. The rectifier 18 had a temperature of 206 ° C when discharged from the deaerator 10, and a diluent consisting of traces of ammonia and carbon dioxide and water was introduced at a rate of 54,990 kg per hour. Some of the heat contained in this solution was removed from the bottom of the CO2 rectifier tube 18 and the remaining heat was removed from the cooler 26.

The solution was cooled in chiller 27 and discharged at a rate of 95,278 kg per hour from desorber 10, which means that 40,288 kg of water was discharged per hour, which is used for example to absorb ammonia and carbon dioxide. 6,347 kg of washing water per hour was supplied to the top of the carbon dioxide rectifying tube to wash out the last traces of ammonia. By steam, the bottom temperature of the carbon dioxide rectifier tube 18 was maintained at 160 ° C and the temperature at the top was 35 ° C.

The gas mixture, consisting of 94.6% carbon dioxide and 5.9% other gases, contains ammonia of less than 100 ppm and was discharged from the rectifier at a rate of 10,694 kg per hour. At the bottom of rectifier 18, a temperature of 160 ° C, consisting of 82.0% water, 13.3% ammonia and 4.7% carbon dioxide, was sent to desorber 10 at a rate of 128,683 kg per hour.

By steam, the solution stripped most of the ammonia and carbon dioxide from the desorber, leaving water containing only traces of ammonia and carbon dioxide at a rate of 95,278 kg per hour. The temperature above the deaerator was 161.8 ° Celsius.

Compressor 6 was supplied with 635 kg of air per hour, of which 248 kg per hour were supplied to the ammonia rectifier and the remaining 387 kg were supplied to the deaerator 10.

A gas mixture consisting of 50.7% ammonia, 17.9% carbon dioxide, 30.4% moisture, and other gases below 1.0% from the deaerator 10 was fed to the ammonia rectifier at a rate of 33,405 kg per hour. At the top of the rectifier, a gas mixture of 99.0% ammonia and 1.0% of other gases was discharged at a rate of 62,360 kg per hour.

Part of this gas mixture was liquefied in condenser 5 by the cooling water. The liquefied mixture was reintroduced into ammonia rectifier 3 at a rate of 49,071 kg per hour. A gas mixture of 80.7% ammonia and 19.2% of other gases was discharged from condenser 5 at a rate of 3,289 kg per hour and the discharged mixture was removed from washer 11 with 4,000 kg of water per hour. Heat was removed from washer 11 by means of a circulating cooler 13. Heat was removed from washer 11 by circulating cooler 13.

A solution consisting of 60.1% water of 39.9% ammonia was fed back to the ammonia rectifier at a rate of 6654 kg per hour.

The temperature of this rectifying tube was 50 degrees Celsius. Through systems 15 and 16, other gases were sent to the carbon dioxide rectifier 18 at a rate of 635 kg per hour.

Example 4

In the apparatus shown in FIG. 4, almost pure ammonia and carbon dioxide were separated from a dilute aqueous solution of ammonia and carbon dioxide at a system pressure of 18 absolute atmospheres.

Aqueous solutions of ammonia and carbon dioxide (82.0% moisture, 4.7% carbon dioxide and 13.3 ammonia) were fed to the deaerator 10 at a rate of 50,000 kg per hour.

From the bottom of rectifier 18, a solution of 159.6 degrees Celsius and of about the same configuration was sent to deaerator 10 at a rate of 38,166 kg per hour.

Most of the ammonia and carbon dioxide are stripped from the solution in the desorber 10 by steam so that water containing only traces of ammonia and carbon dioxide is discharged from the desorber at a rate of 65,279 kg per hour. The temperature above the deaerator is 162 ° C. Compressor 6 was supplied with 635 kg of air per hour, of which 400 kg per hour was fed to ammonia rectifier 3 and 235 kg per hour to deaerator 10.

A gas mixture consisting of ammonia, 50.7%, carbon dioxide 17.9%, moisture 30.4%, and other gases of 1.0% or less from the deaerator 10 was supplied to the ammonia rectifier at a rate of 23,522 kg per hour. At the top of the rectifier, a gas mixture consisting of 98.4% ammonia and 1.6% of other gases was released at a rate of 39,099 kg per hour. Some of this gas mixture was liquefied in condenser 5 by cooling water. The liquefied mixture was fed back to rectifier 3 at a rate of 29,160 kg per hour. A gas mixture consisting of 80.7% ammonia and 19.3% of other gases was discharged from condenser 5 at a rate of 3,289 kg per hour. This gas mixture was washed in washer 11 with 4,000 kg of water per hour. Heat was removed from washer 11 by circulating cooler 13.

A solution consisting of 39.9% ammonia and 60.1% moisture was re-injected into the ammonia rectifier at a rate of 6654 kg per hour. The temperature of this rectifier tube was 50.6 degrees Celsius. Through opening 15 and system 16, other gases were sent to the carbon dioxide rectifier tube 18 at a rate of 635 kg per hour. From the bottom of ammonia rectifier tube 3, it was sent to the carbon dioxide rectifier tube 18 at a rate of 20,237 kg per hour through system 21, a solution consisting of 25.1% ammonia, 20.5% carbon dioxide, and 54.4% moisture. In the rectifier tube 18, when discharged from the deaerator 10, a temperature of 206 ° C. was added at a rate of 18,801 kg per hour, consisting of traces of ammonia and carbon dioxide, and water. Part of the heat contained in the solution was removed from the bottom of the CO2 rectifier tube 18 and the remainder was transferred to the cooler 26. While cooling in the cooler 27, the solution is discharged from the desorber 10 at a rate of 65,279 kg per hour, which means 46,478 kg of water is discharged per hour, which can be used in the case of absorption of ammonia and carbon dioxide, for example. have.

The upper part of the CO2 rectifier was fed 1,491 kg of washing water per hour to wash out the last traces of ammonia. The bottom temperature of the carbon dioxide rectifier tube 18 was maintained at 159.6 degrees Celsius by steam, and the top temperature was 12 degrees Celsius.

The gas mixture, consisting of 80.4% of carbon dioxide and 19.6% of other gases, containing ammonia of less than 100 ppm, was discharged from the rectifier at a rate of 2,995 kg per hour.

Example 5

The amount given in this example is kilomoles per hour (Kmole / h).

In the apparatus shown in FIG. 5,

The system 112 was fed to a device as described above and illustrated above to produce 2,317 kilomoles of ammonia through system 112 and 1,143 kilomoles of carbon dioxide through system 104 to produce 1,019 kilomoles per hour of urine in aqueous solution.

The urine reactor 101, stripper 103, condenser 106 and purifier condenser 115 had a pressure of about 140 kg / cm ² . 2,542 kilomoles of ammonia, 551 kilomoles of carbon dioxide, and 132 kilomoles of water were discharged from the stripper 103 from the synthetic solution fed from the urine reactor 10 by heat of 215 ° C steam and fresh carbon dioxide. The gaseous mixture discharged through system 105 was partially melted in condenser 106 as a mixture of the solution from the urine reactor and fresh ammonia fed through system 108. The carbamate solution of 497 kilomol of ammonia, 169 kilomol of carbon dioxide, and 33 kilomol of moisture, produced in a mixture of the resulting gas and liquid and in a gas purifying condenser, has an average temperature of 183 degrees Celsius and 1,061 kilomol of urine. On the side, a synthetic solution containing 2,183 kilomoles of ammonia, 627 kilomoles of carbon dioxide and 1.191 kilomoles of water was synthesized in the urine reactor. Thus, the conversion of carbon dioxide reached 62.8%.

A solution consisting of 1,019 kilomoles of urine, 225 kilomoles of ammonia, 118 kilomoles of carbon dioxide and 1,019 kilomoles of water was discharged from stripper 103, diffused to 2.5 kg / cm ² and heated to 124 degrees Celsius in a carbamateizer 120. The gas mixture consisting of 151 kilomoles of ammonia and 98 kilomoles of carbon dioxide and 159 kilomoles of water is separated from the residue of urine aqueous solution, which still contains 74 kilomoles of ammonia and 20 kilomoles of carbon dioxide, in addition to 1,019 kilomoles of water and 860 kilomoles of water. Separated at 12, produced.

Most of the ammonia and carbon dioxide described above were removed in an expansion vessel 122 to obtain an aqueous solution of urine. The gas mixture separated in the separator 121 is maintained at a pressure of 2.5 kg / cm ² and supplied to the bottom of the carbon dioxide separation tube 128 containing 1,117 kilomoles of water, 5.5 kilomoles of ammonia, and 2.25 kilomoles of carbon dioxide. It is treated with condensate at 90 ° Celsius which has been introduced from. Furthermore, the separation pipe 128 contains 3,700 kilomoles of water containing ammonia traces through the system 132, 739 kilomoles of water through the system 133, 298 kilomoles of ammonia and 134 kilomoles of carbon dioxide, and 157 kilos through the system 134. Molar water is supplied respectively. The temperature of the solution fed through system 133 of system 132 was 88 ° C and 85 ° C, respectively, and the temperature of the wash water supplied through system 134 was 40 ° C.

The gas mixture discharged from the upper part of the separation pipe 128 was composed of 143 kilomoles of carbon dioxide and 3 kilomoles of water, and the bottom was composed of 106 ° C and 5,939 kilomoles of water, 461 kilomoles of ammonia and 92 kilomoles of carbon dioxide. It was sent to the deaerator 129.

At the top of the purge condenser 115 was produced and recovered and fed to the bottom of the desorber 129 a gas mixture consisting of 1,565 kilomoles of ammonia, 39.2 kilomoles of carbon dioxide, and 371 kilomoles of water and steam at 138 degrees Celsius. Moisture 6,972 kilomoles of water, and the above-mentioned portion of the material produced at the bottom of the desorber, where traces of ammonia and carbon dioxide are still present, are supplied to the carbon dioxide separation line 128 through lines 132 and 134 and Some were introduced into ammonia 130 via system 143 as wash water and the rest was used for other processes or sewage treatment.

The gas mixture discharged from the top of the deaerator 129, which is 110 ° C and consists of 618kmol of ammonia, 134kmol of carbon dioxide and 709km water, is cooled to 87 ° C in the cooler 141 and then 490 kilomoles of pure ammonia was obtained by separating by 170 kilomoles of ammonia at minus 15 degrees Celsius and 29 kilomoles of water at 40 degrees Celsius.

Claims (1)

Ammonia and carbon dioxide are separated from the ammonia separator and the carbon dioxide separator by heat, respectively, and the separation of the carbon dioxide is carried out in the presence of 0.2 to 6 times the moisture of the feed material supplied to the carbon dioxide separator. Separation of ammonia and carbon dioxide from the mixture.

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