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CN110813046A - Double-circulation desulfurization device and desulfurization process - Google Patents

Double-circulation desulfurization device and desulfurization process Download PDF

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CN110813046A
CN110813046A CN201911196760.3A CN201911196760A CN110813046A CN 110813046 A CN110813046 A CN 110813046A CN 201911196760 A CN201911196760 A CN 201911196760A CN 110813046 A CN110813046 A CN 110813046A
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desulfurization
primary
tank
circulation
slurry
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杨昆
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/46Removing components of defined structure
    • B01D53/48Sulfur compounds
    • B01D53/50Sulfur oxides
    • B01D53/501Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound
    • B01D53/504Sulfur oxides by treating the gases with a solution or a suspension of an alkali or earth-alkali or ammonium compound characterised by a specific device
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/74General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/75Multi-step processes
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D53/00Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34Chemical or biological purification of waste gases
    • B01D53/74General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/80Semi-solid phase processes, i.e. by using slurries
    • CCHEMISTRY; METALLURGY
    • C01INORGANIC CHEMISTRY
    • C01FCOMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F11/00Compounds of calcium, strontium, or barium
    • C01F11/46Sulfates
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2251/00Reactants
    • B01D2251/40Alkaline earth metal or magnesium compounds
    • B01D2251/404Alkaline earth metal or magnesium compounds of calcium
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2251/00Reactants
    • B01D2251/60Inorganic bases or salts
    • B01D2251/606Carbonates
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D2258/00Sources of waste gases
    • B01D2258/02Other waste gases
    • B01D2258/0283Flue gases

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Abstract

The invention discloses a dual-cycle desulfurization device and a desulfurization process, and relates to the technical field of gas desulfurization. The apparatus of the present invention comprises: the primary desulfurizing tower, the secondary desulfurizing tower and the chimney are communicated in sequence; the primary desulfurization tower, the primary circulation tank and the first circulation pump are sequentially communicated end to form primary desulfurization liquid circulation; the secondary desulfurization tower, the secondary circulation tank and the second circulation pump are sequentially communicated end to form secondary desulfurization liquid circulation; the oxidation fan is communicated with the primary circulation tank; a pressure filtrate outlet of the primary circulation tank is communicated with a pressure filter through a pressure filter pump; the pulping tank is communicated with the second-stage circulating tank, and the second-stage circulating tank is communicated with the first-stage circulating tank through an overflow pipe. The process comprises the steps of respectively carrying out two times of desulfurization treatment on sulfur-containing flue gas, and maintaining the weak acidity of a primary circulating pool for carrying out calcium sulfite slurry oxidation. The invention has good flue gas desulfurization effect, can fully convert the calcium sulfite slurry into the gypsum, improves the conversion rate and the quality of the gypsum, and can effectively reduce the scaling and blocking phenomena of the sulfite.

Description

Double-circulation desulfurization device and desulfurization process
Technical Field
The invention relates to the technical field of gas desulfurization, in particular to a dual-cycle desulfurization device and a desulfurization process.
Background
The flue gas discharged from the coal-fired boiler is sulfur-containing flue gas, and the sulfur-containing flue gas needs to be desulfurized and then discharged. Common desulfurization methods include lime-gypsum method, alkaline method, ammonia method, and the like. Because of large lime output in China, the lime is widely applied to the metallurgy and building industries and is cheap and easy to obtain. Therefore, in many places, the lime-gypsum method is adopted for desulfurization treatment.
The main principle of the lime-gypsum method is as follows: lime is dissolved in water to generate calcium hydroxide, and sulfur dioxide is dissolved in water to form sulfurous acid. Sulfurous acid reacts with calcium hydroxide to produce calcium sulfite and water. Then the calcium sulfite is oxidized by oxygen to generate gypsum (CaSO) as a byproduct4·2H2O) crystals.
If the calcium sulfite is not oxidized into gypsum, the calcium sulfite filter cake after filter pressing basically has no utilization value and can only be used for landfill. And the calcium sulfite can be used as a cement retarder and building gypsum for sale after being oxidized into gypsum, and the sale price is 50-100 yuan/ton. One ton of lime can produce three tons of gypsum, and the cost of lime serving as a desulfurizing agent can be reduced by 300 yuan per ton, so that the method has considerable economic benefit.
To ensure the desulfurization effect, the pH is required to be highly alkaline, usually 8 to 12. The highly alkaline reaction environment, although ensuring good desulfurization, is not conducive to the oxidation of the calcium sulfite slurry. The optimal pH condition for the oxidation of the calcium sulfite slurry is 5-5.5. In a high alkalinity environment, the calcium sulfite slurry is difficult to oxidize sufficiently, resulting in low conversion and poor quality of the gypsum byproduct. On the other hand, when the content of the sulfite is too high, the scaling phenomenon can be generated, so that the pipeline is blocked, and the desulfurization system can not normally operate.
In summary, in order to ensure the desulfurization effect, an environment with high alkalinity is required, and the high alkalinity environment affects the oxidation process of the calcium sulfite slurry. Therefore, how to ensure the desulfurization effect and smoothly carry out the conversion process of the calcium sulfite slurry to produce qualified gypsum is a significant problem in the high-sulfur field.
Disclosure of Invention
In order to solve the problems of the prior art, the invention provides a two-cycle desulfurization device, and provides a desulfurization process based on the desulfurization device. The invention has good flue gas desulfurization effect, can fully convert the calcium sulfite slurry into the gypsum, improves the conversion rate and the quality of the gypsum, and can effectively reduce the scaling and blocking phenomena of the sulfite.
The invention relates to a double-circulation desulfurization device, which comprises a primary desulfurization tower, a secondary desulfurization tower, a primary circulation tank, a secondary circulation tank, a first circulation pump, a second circulation pump, a pulping tank, a filter press, an oxidation fan and a chimney, wherein the primary desulfurization tower is arranged above the secondary desulfurization tower;
the gas inlet of the primary desulfurization tower is used for introducing sulfur-containing flue gas, the gas outlet of the primary desulfurization tower is communicated with the gas inlet of the secondary desulfurization tower, and the gas outlet of the secondary desulfurization tower is communicated with the chimney;
the primary desulfurization tower, the primary circulation tank and the first circulation pump are sequentially communicated end to form primary desulfurization liquid circulation;
the secondary desulfurization tower, the secondary circulation tank and the second circulation pump are sequentially communicated end to form secondary desulfurization liquid circulation;
an air outlet of the oxidation fan is communicated with the primary circulating tank; the primary circulation tank is provided with a filter pressing liquid outlet which is communicated with the filter press through a filter press pump;
the pulping tank is communicated with the secondary circulating tank, and the secondary circulating tank is communicated with the primary circulating tank through an overflow pipe.
Preferably, the supernatant outlet of the filter press is communicated with the pulping tank.
Preferably, the dual cycle desulphurization unit further comprises a shunt tube, the outlet of the second circulating pump is communicated with the first-stage circulating tank through the shunt tube, and a shunt tube valve is arranged on the shunt tube.
Preferably, a stirrer is arranged in the primary circulating pool.
Preferably, an aerator pipe is arranged at the bottom of the primary circulation tank, and an air outlet of the oxidation fan is communicated with the aerator pipe.
Preferably, a pH meter is arranged in the first-stage circulating pool.
A desulfurization process based on the double-circulation desulfurization device comprises the following steps:
s01, preparing lime slurry serving as desulfurization liquid, and introducing the obtained lime slurry into a primary desulfurization tower and a secondary desulfurization tower respectively;
s02, introducing the sulfur-containing flue gas into a primary desulfurization tower, and reacting with the lime slurry to perform primary desulfurization to obtain primary desulfurized flue gas and calcium sulfite slurry;
s03, maintaining the pH value in the secondary desulfurization tower at 7-9, introducing the obtained primary desulfurization flue gas into the secondary desulfurization tower to react with the lime slurry for secondary desulfurization, and discharging the flue gas through a chimney after the secondary desulfurization is finished; introducing the obtained calcium sulfite slurry into a primary circulation tank, introducing oxygen into the primary circulation tank, maintaining the pH value in the primary circulation tank at 5-5.5, and obtaining calcium sulfate slurry after the calcium sulfite slurry is oxidized;
and S04, introducing the obtained calcium sulfate slurry into a filter press to filter under pressure to obtain gypsum.
Preferably, in step S03, the solid content of the calcium sulfite slurry is 8% to 10%.
Preferably, in step S03, the reaction temperature of the calcium sulfite slurry during oxidation is 30-50 ℃, and the reaction time is more than or equal to 2 hours.
Preferably, step S04 is specifically: and introducing the obtained calcium sulfate slurry into a filter press, performing filter pressing to obtain separated gypsum and supernatant, and introducing the obtained supernatant into a pulping tank for preparing lime slurry.
The double-circulation desulfurization device and the desulfurization process have the advantages that: the invention adopts a double-desulfurizing tower structure and is provided with two-stage desulfurizing liquid circulation; the sulfur-containing flue gas is desulfurized sequentially through the primary desulfurizing tower and the secondary desulfurizing tower, most of sulfur in the sulfur-containing flue gas is absorbed by lime slurry in the primary desulfurizing tower and is converted into calcium sulfite slurry, and the pH value in the slurry is rapidly reduced to acidity. And then, the flue gas after primary desulfurization enters a secondary desulfurization tower for secondary desulfurization, the PH value in the secondary desulfurization tower is kept higher, and the flue gas after primary desulfurization is discharged from a chimney after full desulfurization in the secondary desulfurization tower. Therefore, the sulfur-containing flue gas can be fully desulfurized in the environment with high PH value. And in the first-stage desulfurizing tower, the product after primary desulfurizationThe acidic calcium sulfite slurry is introduced into a first-stage circulation tank to maintain the pH value of the first-stage circulation tank at 5-5.5, oxygen is introduced, and CaSO is added in an acidic environment3Will be fully oxidized to generate CaSO4·2H2O crystals, i.e. gypsum by-product. In an acidic environment, CaSO3Can be fully oxidized, fully reacts at the reaction temperature of 30-50 ℃, and CaSO3The oxidation rate of the catalyst can reach over 96 percent. The invention can fully desulfurize the sulfur-containing flue gas, fully oxidize the calcium sulfite slurry in an acid environment, improve the conversion rate and quality of gypsum byproducts and reduce the phenomenon that the pipeline is blocked by the scale of sulfite.
Drawings
FIG. 1 is a schematic view of a two-cycle desulfurization apparatus according to the present invention.
Description of reference numerals: 11-a first-stage desulfurizing tower, 12-a first-stage circulating tank, 121-an aeration pipe, 13-a first circulating pump, 21-a second-stage desulfurizing tower, 22-a second-stage circulating tank, 23-a second circulating pump, 24-an overflow pipe, 25-a shunt pipe, 3-a chimney, 4-an oxidation fan, 5-a filter press, 6-a pulping tank, 61-a slurry feeding pump, 7-a filter pressing pump, 8-an induced draft fan, a-sulfur-containing flue gas, b-lime slurry, c-calcium sulfate slurry, d-gypsum and e-supernatant.
Detailed Description
As shown in fig. 1, the dual-cycle desulfurization device of the present invention can be divided into four modules, namely a flue gas module, a desulfurization solution circulation module, a gypsum treatment module, and a pulping module. The flue gas module comprises an induced draft fan 8, a primary desulfurizing tower 11, a secondary desulfurizing tower 21, a chimney 3, a first smoke pipe, a second smoke pipe and a third smoke pipe. One end of the first smoke pipe is communicated with an outlet of the induced draft fan 8, and the other end of the first smoke pipe is communicated with an air inlet of the primary desulfurizing tower 11. One end of the second smoke pipe is communicated with the gas outlet of the first-stage desulfurizing tower 11, and the other end is communicated with the gas inlet of the second-stage desulfurizing tower 21. One end of the third smoke pipe is communicated with the gas outlet of the secondary desulfurizing tower 21, and the other end is communicated with the chimney 3. The entry of draught fan 8 is used for the intercommunication to contain the sulphur flue gas, and under the twitch of draught fan 8, contains during the sulphur flue gas gets into one-level desulfurizing tower 11 through first tobacco pipe.
Specifically, the setting position of the induced draft fan 8 may be set at the front end of the first-stage desulfurizing tower 11, or may be set at the rear end of the first-stage desulfurizing tower 11. When draught fan 8 is located the front end of one-level desulfurizing tower 11, draught fan 8 is 11 malleation induced drafts of one-level desulfurizing tower, and when draught fan 8 was located the rear end of one-level desulfurizing tower 11, draught fan 8 was 11 negative pressure induced drafts of one-level desulfurizing tower. Positive pressure induced air and negative pressure induced air can both effectively let in the one-level desulfurizing tower 11 with the flue gas that contains sulphur, and can not exert an influence to the desulfurization process and the gypsum manufacture process of the flue gas that contains sulphur, can set up according to the actual place.
In fig. 1, the primary desulfurization tower 11 and the secondary desulfurization tower 21 are pneumatic emulsification cyclone type desulfurization towers having the same structure. Each comprises a gas homogenizing chamber and a cyclone cylinder which are communicated in sequence; one-stage or multi-stage emulsion layers are arranged in the cyclone cylinder, and a demister used for water-gas separation is arranged at the position of the desulfurizing tower close to the gas outlet. This kind of desulfurizing tower is commonly used in wet desulfurizing process, so it is also possible for those skilled in the art to select other desulfurizing towers commonly used in wet desulfurizing process, such as empty tower spray tower, cyclone plate tower, multi-stage reaction tower, bubble tower, dynamic wave, granite water film tower, etc.
In addition, the number of the first-stage desulfurizing tower 11 and the second-stage desulfurizing tower 21 is not fixed, and the first-stage desulfurizing liquid circulation system can comprise a plurality of first-stage desulfurizing towers 11 which are sequentially communicated, and a corresponding number of first-stage circulation tanks 12 are arranged. The more the quantity of one-level desulfurizing tower 11, the higher the treatment effeciency that also contains the sulphur flue gas, can set up according to actual demand.
Similarly, the secondary desulfurization solution circulation may also include a plurality of secondary desulfurization towers 21 sequentially connected to each other, and a corresponding number of secondary circulation tanks 22. The larger the number of the secondary desulfurization towers 21, the better the desulfurization effect.
For example, two primary desulfurization towers 11 and primary circulation tanks 12, one secondary desulfurization tower 21 and a secondary circulation tank 22, which are sequentially connected, may be provided, that is, three desulfurization towers are provided, the first two are the primary desulfurization towers 11, and the third is the secondary desulfurization tower 21. Or a primary desulfurizing tower 11 and a primary circulating pool 12 are arranged, and a secondary desulfurizing tower 21 and a secondary circulating pool 22 are sequentially communicated. By analogy, the number of the first-stage desulfurizing tower 11 and the second-stage desulfurizing tower 21 can be set by those skilled in the art according to actual requirements.
The operation principle of the flue gas module is as follows, under the action of the induced draft fan 8, the sulfur-containing flue gas enters the primary desulfurizing tower 11 from the gas equalizing chamber of the primary desulfurizing tower 11. The cyclone cylinder contains lime slurry (namely, desulfurization solution); the sulfur-containing flue gas enters a cyclone cylinder of a first-stage desulfurizing tower 11, contacts with lime slurry and reacts as follows:
CaCO3+SO2+1/2H2O→CaSO3·1/2H2O+CO2
after the reaction, a slurry containing calcium sulfite (hereinafter referred to as calcium sulfite slurry) is produced. Meanwhile, most of sulfur in the sulfur-containing flue gas is absorbed and removed by the lime slurry, and primary desulfurized flue gas is obtained. At the moment, the primary desulfurized flue gas and the calcium sulfite slurry are mixed in the cyclone cylinder. And (3) introducing the primary desulfurization flue gas and the calcium sulfite slurry in the cyclone cylinder into a demister for water-gas separation, and separating the primary desulfurization flue gas from the calcium sulfite slurry, wherein the primary desulfurization flue gas is introduced into a secondary desulfurization tower 21 for secondary desulfurization, and the calcium sulfite slurry is introduced into a primary circulating tank 12 for oxidation.
During one-level desulfurization flue gas lets in second grade desulfurizing tower 21 through the second tobacco pipe, pass through the gas homogenizing chamber of second grade desulfurizing tower 21 in proper order, whirl section of thick bamboo and defroster, the process is the same in one-level desulfurizing tower 11, one-level desulfurization flue gas fully reacts with lime thick liquid in second grade desulfurizing tower 21 and carries out the secondary desulfurization, surplus few part sulphur fully absorbs in the lime thick liquid one-level desulfurization flue gas in the secondary desulfurizing tower gets rid of, behind the desulfurization of second grade desulfurizing tower 21, the sulphur in the flue gas is basically got rid of completely, can discharge in the atmosphere through chimney 3.
The desulfurization solution circulation module in this embodiment will be described below, and the desulfurization solution in this embodiment refers to lime slurry. The desulfurization liquid circulating module comprises a primary circulating tank 12, a secondary circulating tank 22, a first circulating pump 13, a second circulating pump 23 and a plurality of communicating pipelines. Wherein, the first-stage desulfurizing tower 11, the first-stage circulating pool 12 and the first circulating pump 13 are sequentially communicated end to form first-stage desulfurizing liquid circulation. Specifically, the bottom of the first-stage desulfurizing tower 11 is provided with a liquid outlet, and the side wall of the middle part is provided with a liquid inlet. The liquid outlet of the first-stage desulfurizing tower 11 is communicated with a first-stage circulating pool 12 through a communicating pipeline. The bottom of the first-stage circulation tank 12 is provided with a liquid outlet, the liquid outlet of the first-stage circulation tank 12 is communicated with the inlet of the first circulation pump 13, and the outlet of the first circulation pump 13 is communicated with the liquid inlet of the first-stage desulfurizing tower 11. Under the driving action of the first circulating pump 13, the first-stage desulfurizing tower 11, the first-stage circulating tank 12 and the first circulating pump 13 form a first-stage desulfurizing liquid circulation. The secondary desulfurization tower 21, the secondary circulation tank 22 and the second circulation pump 23 are also sequentially communicated end to form secondary desulfurization liquid circulation, and the specific structure of the secondary desulfurization tower is the same as that of the primary desulfurization liquid circulation, which is not described again.
The gypsum processing module consists essentially of: an oxidation fan 4, a filter press pump 7 and a filter press 5. The filter press 5 can be a plate and frame filter press or a vacuum belt dehydrator. The side wall of the primary circulation tank 12 is provided with a pressure filtrate outlet which is communicated with the inlet of the pressure filtration pump 7, and the outlet of the pressure filtration pump 7 is communicated with the inlet of the pressure filter 5. The filter press 5 is provided with a solids outlet and a liquid outlet. The calcium sulfite slurry generated by the reaction in the first-stage desulfurizing tower 11 enters a first-stage circulation tank 12, and the following oxidation reaction occurs in the environment where the oxidation fan 4 is introduced with oxygen and maintains a low PH value:
2CaSO3·1/2H2O+O2+3H2O→2CaSO4·2H2O
the calcium sulfite slurry in the primary circulation tank 12 is fully oxidized to generate slurry containing calcium sulfate (hereinafter referred to as calcium sulfate slurry), the calcium sulfate slurry is pumped into a filter press 5 to be subjected to solid-liquid separation under the action of a filter press pump 7, and supernatant and filter cake which are separated from each other are generated, the supernatant is gypsum filtrate, and the filter cake is gypsum (CaSO)4·2H2O) crystals.
The pulping module comprises a pulping tank 6, a pulping tank stirrer, a pulp feeding pump 61 and a feeding machine. The feeding machine is communicated into the pulping pool 6 through a feeding pipe, and the pulping pool 6 is communicated into the secondary circulating pool 22 through a feeding pump 61. An overflow pipe 24 is arranged at the upper part of the secondary circulating tank 22, one end of the overflow pipe 24 is communicated with the secondary circulating tank 22, and the other end is communicated with the primary circulating tank 12. A shunt pipe 25 can be communicated with the pipeline between the second circulating pump 23 and the second-stage desulfurizing tower 21, one end of the shunt pipe 25 is communicated with the outlet of the second circulating pump 23, and the other end is communicated with the inside of the first-stage circulating pool 12. Correspondingly, valves for controlling the opening and closing of the pipelines are arranged at the overflow pipe 24 and the shunt pipe 25. The feeder is used for introducing lime raw materials into the pulping tank 6, simultaneously adding process water or filtrate into the pulping tank 6 according to a common proportion, uniformly stirring the mixture by a pulping tank stirrer to form lime slurry, and then feeding the lime slurry into the secondary circulating tank 22 under the action of a slurry feeding pump 61. The slurry in the secondary circulation tank 22 may overflow into the primary circulation tank 12 through an overflow pipe 24. Meanwhile, when the primary desulfurization solution circulation and the secondary desulfurization solution circulation operate, part of the slurry in the secondary desulfurization solution circulation is shunted to enter the primary desulfurization tank by opening the shunt pipe 25, the slurry is supplemented for the primary desulfurization solution circulation, and the opening and closing of the overflow pipe 24 and the shunt pipe 25 can be controlled according to the actual operation condition so as to control the slurry supplementing process of the primary desulfurization solution circulation. In addition, due to the above structure, when the dual-cycle desulfurization apparatus normally operates, the slurry with high PH in the secondary circulation tank 22 enters the primary circulation tank 12 in an overflow or diversion manner, the inflow amount is small, so that the primary circulation tank 12 can maintain a low PH state, and the inflow amount can be controlled by a valve, so that the low PH environment in the primary circulation tank 12 is not damaged during slurry replenishment.
The calcium sulfate slurry is separated into gypsum filtrate and a gypsum filter cake in the filter press 5, the gypsum filtrate can be used as a preparation raw material of lime slurry, and therefore the supernatant outlet of the filter press 5 is communicated with the pulping pool 6, and the gypsum filtrate can flow back to the pulping pool 6 to be used as a raw material for preparing the lime slurry when flowing out from the supernatant outlet, so that the gypsum filtrate can be recycled, and the material waste is reduced.
In order to ensure that the oxidation reaction in the primary stirring tank is sufficient, a stirrer is arranged in the primary stirring tank.
In order to increase the contact area between the oxygen and the calcium sulfite slurry and enhance the oxidation effect, an aeration pipe 121 is arranged at the bottom of the primary circulation tank 12, and an air outlet of the oxidation fan 4 is communicated with the aeration pipe 121. The aeration pipe 121 can effectively increase the contact area of the oxygen and the calcium sulfite slurry, so that the oxidation reaction is more sufficient.
The PH value in the primary circulation tank 12 is an important parameter of oxidation reaction, so the PH value in the primary circulation tank 12 needs to be monitored in real time, an electronic PH meter is arranged in the primary circulation tank 12, the PH value in the primary circulation tank 12 can be monitored in real time, and an operator can conveniently perform operation adjustment according to the monitored PH value.
Another object of this embodiment is to provide a desulfurization process based on the above-mentioned dual-cycle desulfurization apparatus, which includes the following steps.
And S01, preparing lime slurry serving as desulfurization liquid, and introducing the obtained lime slurry into the primary desulfurization tower 11 and the secondary desulfurization tower 21 respectively.
Step S01 is specifically to pour the lime raw material into the pulping tank 6 through the feeder, add the process water according to a conventional ratio, and then start the pulping tank stirrer to stir, so that the lime raw material and the process water are uniformly mixed to prepare the lime slurry. The slurry feed pump 61 is started, and the slurry feed pump 61 pumps the lime slurry in the slurry tank 6 into the secondary circulation tank 22. As the slurry pump 61 continues to operate, the slurry level in the secondary circulation tank 22 gradually rises and the lime slurry will begin to overflow into the primary circulation tank 12 as the slurry level reaches the level of the overflow pipe 24. The slurry feed pump 61 is continuously started until a sufficient amount of lime slurry is present in both the primary circulation tank 12 and the secondary circulation tank 22. And then starting the first circulating pump 13 and the second circulating pump 23, and under the pumping action of the first circulating pump 13 and the second circulating pump 23, respectively feeding the lime slurry in the first-stage circulating tank and the lime slurry in the second-stage circulating tank into the first-stage desulfurizing tower 11 and the second-stage desulfurizing tower 21.
And S02, introducing the sulfur-containing flue gas into a primary desulfurization tower 11, and reacting with the lime slurry to perform primary desulfurization to obtain primary desulfurized flue gas and calcium sulfite slurry.
Step S02 is specifically to communicate the inlet of the induced draft fan 8 to the exhaust port of the coal-fired boiler, start the induced draft fan 8, the induced draft fan 8 extracts the sulfur-containing flue gas discharged by the coal-fired boiler and enters the primary desulfurization tower 11, and react with the lime slurry in the primary desulfurization tower 11 to perform primary desulfurization, so as to obtain primary desulfurization flue gas and calcium sulfite slurry. When the sulfur-containing flue gas and the lime slurry are subjected to primary desulfurization, most of sulfur in the sulfur-containing flue gas is absorbed and removed, the lime slurry in the primary desulfurization tower 11 is converted into calcium sulfite slurry, and the pH value of the calcium sulfite slurry is rapidly reduced to weak acidity.
S03, maintaining the pH value in the secondary desulfurization tower 21 at 7-9, introducing the obtained primary desulfurization flue gas into the secondary desulfurization tower 21, reacting with the lime slurry in the secondary desulfurization tower 21 to perform secondary desulfurization, and discharging the flue gas through a chimney 3 after the secondary desulfurization is finished; and introducing the obtained calcium sulfite slurry into a primary circulation tank 12, introducing oxygen into the primary circulation tank 12, maintaining the pH value in the primary circulation tank 12 at 5-5.5, and obtaining calcium sulfate slurry after the calcium sulfite slurry is oxidized.
In step S03, the lime slurry is continuously supplied into the secondary circulation tank 22 to maintain a high PH in the secondary desulfurization solution circulation, and further maintain a high PH, specifically 7 to 9, in the secondary desulfurization tower 21. When the sulfur-containing flue gas passes through the secondary desulfurization tower 21, the sulfur-containing flue gas is fully absorbed by the lime slurry with high pH value, so that the effect of full desulfurization is achieved, and then the sulfur-containing flue gas can be discharged into the atmosphere.
And (3) introducing the calcium sulfite slurry into the primary circulation tank 12 from a liquid outlet of the primary desulfurization tower 11, starting the oxidation fan 4, and introducing oxygen into the primary circulation tank 12, wherein the pH value in the primary circulation tank 12 is maintained at 5-5.5 because the calcium sulfite slurry obtained in the step S02 is weakly acidic, and the calcium sulfite slurry can be fully oxidized to form calcium sulfate slurry under the pH condition. And because the pulp supplementing mode adopts an overflow or shunt mode, the environment with low PH value can be continuously kept in the first-stage circulating pool 12, which is beneficial to the oxidation process of the calcium sulfite. Specifically, the solid content of the calcium sulfite slurry introduced into the primary circulation tank 12 is preferably 8% -10%, and the solid content of the calcium sulfite slurry is beneficial to the oxidation process. The oxidation rate of the calcium sulfite slurry can be influenced by the reaction temperature and the reaction time of the calcium sulfite slurry, and through a plurality of experiments of an applicant, the oxidation rate of the calcium sulfite can reach more than 96% after the calcium sulfite slurry continuously reacts for at least two hours when the pH value is 5-5.5 and the reaction temperature is 30-50 ℃, most of the calcium sulfite is oxidized to generate gypsum, and the oxidation rate of the calcium sulfite is greatly improved.
S04, introducing the obtained calcium sulfate slurry into a filter press 5, and carrying out pressure filtration to obtain gypsum.
Step S04 is specifically to introduce the calcium sulfate slurry into the filter press 5 through the filter press pump 7, and to realize solid-liquid separation in the filter press 5, thereby forming a gypsum filtrate and a gypsum filter cake, where the gypsum filter cake is a gypsum byproduct. The gypsum filtrate can flow back to the pulping tank 6 for recycling, and the gypsum filter cake can be sold as a cement retarder or a building material.
The invention adopts a double-desulfurizing tower structure and is provided with two-stage desulfurizing liquid circulation; the sulfur-containing flue gas is desulfurized sequentially through the primary desulfurizing tower 11 and the secondary desulfurizing tower 21, in the primary desulfurizing tower 11, most of sulfur in the sulfur-containing flue gas is absorbed by the lime slurry in the primary desulfurizing tower 11 and is converted into calcium sulfite slurry, and the pH value in the slurry is rapidly reduced to acidity. And then, the flue gas after primary desulfurization enters a secondary desulfurization tower 21 for secondary desulfurization, the PH value in the secondary desulfurization tower 21 is kept high, and the flue gas after primary desulfurization is discharged from a chimney 3 after being sufficiently desulfurized in the secondary desulfurization tower 21. Therefore, the sulfur-containing flue gas can be fully desulfurized in the environment with high PH value. In the first-stage desulfurizing tower 11, the acidic calcium sulfite slurry generated after the first desulfurization is introduced into the first-stage circulating tank 12 to maintain the pH value in the first-stage circulating tank 12 at 5-5.5, and oxygen is introduced, wherein in an acidic environment, CaSO is generated3Will be fully oxidized to generate CaSO4·2H2O crystals, i.e. gypsum by-product. In an acidic environment, CaSO3Can be fully oxidized, fully reacts at the reaction temperature of 30-50 ℃, and CaSO3The oxidation rate of the catalyst can reach over 96 percent. The invention can fully desulfurize the sulfur-containing flue gas, fully oxidize the calcium sulfite slurry in an acid environment, improve the conversion rate and quality of gypsum byproducts and reduce the phenomenon that the pipeline is blocked by the scale of sulfite.
In the description of the present application, it is to be understood that the orientation or positional relationship indicated by the directional terms such as "front, rear, upper, lower, left, right", "lateral, vertical, horizontal" and "top, bottom", etc., are generally based on the orientation or positional relationship shown in the drawings, and are used for convenience of description and simplicity of description only, and in the case of not making a reverse explanation, these directional terms do not indicate and imply that the device or element being referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore, should not be considered as limiting the scope of the present application.
Spatially relative terms, such as "above … …," "above … …," "above … …," "above," and the like, may be used herein for ease of description to describe one device or feature's spatial relationship to another device or feature as illustrated in the figures, and it is to be understood that spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is turned over, devices described as "above" or "on" other devices or configurations would then be oriented "below" or "under" the other devices or configurations. Thus, the exemplary term "above … …" can include both orientations of "above … …" and "below … …". The device may be otherwise variously oriented (rotated 90 or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
It should be noted that the terms "first", "second", and the like are used to define the components, and are only used for convenience of distinguishing the corresponding components, and the terms have no special meanings unless otherwise stated, and therefore, the scope of protection of the present application is not to be construed as being limited.
It will be apparent to those skilled in the art that various other changes and modifications may be made in the above-described embodiments and concepts and all such changes and modifications are intended to be within the scope of the appended claims.

Claims (10)

1. A dual-circulation desulfurization device is characterized by comprising a primary desulfurization tower, a secondary desulfurization tower, a primary circulation tank, a secondary circulation tank, a first circulation pump, a second circulation pump, a pulping tank, a filter press, an oxidation fan and a chimney;
the gas inlet of the primary desulfurization tower is used for introducing sulfur-containing flue gas, the gas outlet of the primary desulfurization tower is communicated with the gas inlet of the secondary desulfurization tower, and the gas outlet of the secondary desulfurization tower is communicated with the chimney;
the primary desulfurization tower, the primary circulation tank and the first circulation pump are sequentially communicated end to form primary desulfurization liquid circulation;
the secondary desulfurization tower, the secondary circulation tank and the second circulation pump are sequentially communicated end to form secondary desulfurization liquid circulation;
an air outlet of the oxidation fan is communicated with the primary circulating tank; the primary circulation tank is provided with a filter pressing liquid outlet which is communicated with the filter press through a filter press pump;
the pulping tank is communicated with the secondary circulating tank, and the secondary circulating tank is communicated with the primary circulating tank through an overflow pipe.
2. The dual cycle desulfurization apparatus of claim 1, wherein the supernatant outlet of the filter press communicates with the slurrying tank.
3. The dual-cycle desulfurization device of claim 1, further comprising a bypass pipe, wherein the outlet of the second circulation pump is communicated with the primary circulation tank through the bypass pipe, and a bypass pipe valve is arranged on the bypass pipe.
4. The dual cycle desulfurization apparatus of claim 1, wherein an agitator is disposed within the primary circulation tank.
5. The dual-cycle desulfurization device of claim 1, wherein an aerator pipe is arranged at the bottom of the primary circulation tank, and an air outlet of the oxidation fan is communicated with the aerator pipe.
6. The dual-cycle desulfurization apparatus of claim 1, wherein a PH meter is disposed in the primary circulation tank.
7. A desulfurization process based on the double-cycle desulfurization apparatus as set forth in any one of claims 1 to 6, characterized by comprising the steps of:
s01, preparing lime slurry serving as desulfurization liquid, and introducing the obtained lime slurry into a primary desulfurization tower and a secondary desulfurization tower respectively;
s02, introducing the sulfur-containing flue gas into a primary desulfurization tower, and reacting with the lime slurry to perform primary desulfurization to obtain primary desulfurized flue gas and calcium sulfite slurry;
s03, maintaining the pH value in the secondary desulfurization tower at 7-9, introducing the obtained primary desulfurization flue gas into the secondary desulfurization tower to react with the lime slurry for secondary desulfurization, and discharging the flue gas through a chimney after the secondary desulfurization is finished; introducing the obtained calcium sulfite slurry into a primary circulation tank, introducing oxygen into the primary circulation tank, maintaining the pH value in the primary circulation tank at 5-5.5, and obtaining calcium sulfate slurry after the calcium sulfite slurry is oxidized;
and S04, introducing the obtained calcium sulfate slurry into a filter press to filter under pressure to obtain gypsum.
8. The desulfurization process of claim 7, wherein in step S03, the solid content of the calcium sulfite slurry is 8% -10%.
9. The desulfurization process of claim 7, wherein in step S03, the reaction temperature of the calcium sulfite slurry during oxidation is 30-50 ℃, and the reaction time is more than or equal to 2 hours.
10. The desulfurization process according to claim 7, wherein the step S04 is specifically: and introducing the obtained calcium sulfate slurry into a filter press, performing filter pressing to obtain separated gypsum and supernatant, and introducing the obtained supernatant into a pulping tank for preparing lime slurry.
CN201911196760.3A 2019-11-29 2019-11-29 Double-circulation desulfurization device and desulfurization process Pending CN110813046A (en)

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CN112933905A (en) * 2021-01-29 2021-06-11 乌海宝杰新能源材料有限公司 Efficient and energy-saving graphitized tail gas treatment system and treatment process thereof
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