Integrated treatment method for desulfurization and decarbonization of cement kiln flue gas and mineralization of solid waste gypsum

Abstract

The invention belongs to the technical field of environmental protection, and particularly relates to a cement kiln flue gas desulfurization and decarburization and mineralization solid waste gypsum integrated treatment method, an adopted treatment system comprises a reaction tower, and the reaction tower is sequentially divided into a desulfurization area, a decarburization area, a mineralization reaction area II and a mineralization reaction area I through partition plates from bottom to top; a washing area is further arranged above the first mineralization reaction area, raw flue gas of the cement kiln is input from the bottom and discharged after being sequentially treated by all the areas, and solid waste gypsum slurry prepared by a solid waste gypsum slurry preparation tank is sprayed downwards from the upper portion of the first mineralization reaction area. Solid waste gypsum slurry accumulated at the bottom of the first mineralization reaction area is input into a second filter to be filtered, then the filtered solid part is evenly sprayed downwards from the upper portion of the second mineralization reaction area, filtrate output by the second filter is subjected to evaporative crystallization, and an ammonium sulfate product is obtained. According to the method, the technical problem of insufficient reaction caused by difficult realization of removal of reaction raw materials and enrichment of reaction products is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and specifically relates to an integrated treatment method for cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum. Background Art

[0002] Solid waste gypsum mineralization CO 2 High capacity, theoretical carbon fixation ≥ 0.25 tons CO 2 / ton gypsum is an ideal CO 2 Mineralized raw materials. Solid waste gypsum and carbon dioxide in flue gas can be used to react with ammonia water to generate calcium carbonate and ammonium sulfate, achieving the goal of "treating waste with waste and turning waste into treasure".

[0003] In the existing cement plant technology, there is only a desulfurization device. If it is required by the state, a decarbonization device needs to be further added to achieve desulfurization and decarbonization of cement kiln flue gas, which increases the floor space and system complexity, and will further increase investment. In view of the shortcomings of the existing technology, the present invention utilizes the existing desulfurization tower for transformation, aiming to propose a new device integrating desulfurization, decarbonization and mineralization and its operation method, which not only solves the problem of expanded floor space and complicated system, but also effectively controls the additional expenses.

[0004] However, in the prior art, considering that sufficient removal of sulfur-containing pollutants and effective reduction of carbon-containing waste gas in flue gas require sufficient reaction in the reaction vessel, the corresponding reaction raw materials, such as desulfurizers and carbon absorbents, are often excessive, which presents various difficulties in designing and transforming a new treatment method that integrates desulfurization, decarbonization and mineralization. Because the removal of reaction raw materials and the enrichment of reaction products are difficult to achieve, and the continuity of the reaction is also difficult to ensure, there are still technical difficulties in achieving the above-mentioned desulfurization, decarbonization and mineralization through an integrated device. Summary of the invention

[0005] The purpose of the present invention is to provide an integrated treatment method for cement kiln flue gas desulfurization, decarbonization and mineralization of solid waste gypsum, which is used to solve the technical problem that the new device based on desulfurization, decarbonization and mineralization in the prior art is difficult to achieve sufficient desulfurization and decarbonization of flue gas and mineralization and reuse of solid waste gypsum as much as possible.

[0006] The described method for integrated treatment of cement kiln flue gas desulfurization, decarbonization and mineralized solid waste gypsum adopts a treatment system including a reaction tower, which is divided into a desulfurization zone, a decarbonization zone, a mineralization reaction zone 2 and a mineralization reaction zone 1 from bottom to top by partitions, and a washing zone is also provided above the mineralization reaction zone 1. The top of the reaction tower is a flue gas outlet, and the described treatment method includes: inputting the original flue gas of the cement kiln from the bottom to the desulfurization zone, spraying ammonia water downward from the upper part of the desulfurization zone for desulfurization, inputting the treated flue gas from the desulfurization zone to the bottom of the decarbonization zone through a pipeline, spraying ammonia water downward from the upper part of the decarbonization zone for decarbonization, inputting the treated flue gas from the decarbonization zone to the bottom of the mineralization reaction zone 2 through a pipeline, and at the same time, introducing the ammonium carbonate mother liquor accumulated at the bottom of the decarbonization zone into the mineralization reaction zone 2. The flue gas in the mineralization reaction zone 2 is transported from the bottom to the bottom of the mineralization reaction zone 1, and the solid waste gypsum slurry prepared by the solid waste gypsum slurry making tank is sprayed downward from the upper part of the mineralization reaction zone 1. The solid waste gypsum slurry accumulated at the bottom of the mineralization reaction zone 1 is input to the filter 2 for filtration, and then the filtered solid part is evenly sprayed downward from the upper part of the mineralization reaction zone 2, and the filtrate output by the filter 2 is evaporated and crystallized to obtain an ammonium sulfate product, and the reaction liquid accumulated at the bottom of the mineralization reaction zone 2 is transported to the filter 1, and the filter 1 is filtered to obtain calcium carbonate solid and dried, and the filtrate obtained by filtration by the filter 1 is recovered and input into the solid waste gypsum slurry making tank for slurrying, and the flue gas treated in the mineralization reaction zone 1 is washed in the washing zone and then discharged.

[0007] Preferably, in the desulfurization zone, the cement kiln flue gas enters the desulfurization zone from the bottom of the tower, and the amount of ammonia water sprayed is adjusted according to the concentration of sulfur dioxide in the flue gas; when setting the ammonia water spray amount, the ammonia water spray amount is excessive relative to the desulfurization demand.

[0008] Preferably, the desulfurization zone supplements oxygen through an oxidation fan while desulfurization is taking place, and the ammonium sulfite generated by the reaction of oxygen with sulfur dioxide and ammonia water is oxidized to become ammonium sulfate; the substances generated in the desulfurization zone are mainly ammonium sulfate and supplemented by ammonium carbonate, and the solution of the obtained substances is transported to the solid waste gypsum slurry tank through a recovery pipeline for slurrying.

[0009] Preferably, in the decarbonization zone, the flue gas coming out of the desulfurization zone enters the decarbonization zone, and ammonia water is used to react with the carbon dioxide in the flue gas to generate a high concentration of ammonium carbonate solution, which is used for the subsequent mineralization of the solid waste gypsum. The amount of ammonia water used needs to allow the ammonia content to form a molar ratio of 2:1 with the phosphogypsum added in the solid waste gypsum slurry tank.

[0010] Preferably, in the mineralization reaction zone 2, the ammonium carbonate solution with a higher concentration generated in the decarbonization zone is pumped into the mineralization reaction zone 2 through a circulation pump; at the same time, the incompletely reacted solid portion obtained through liquid-solid separation in the filter 2 outside the reaction tower is also evenly sprayed into the mineralization reaction zone 2, and reacts with the pumped-in higher concentration ammonium carbonate solution to generate ammonium sulfate and calcium carbonate; the incompletely reacted solid portion includes calcium sulfate and calcium carbonate, and the solid waste gypsum input into the reaction tower undergoes a mineralization reaction in the mineralization reaction zone 1, and the calcium sulfate content of the obtained incompletely reacted solid portion is reduced, so that the concentration difference between ammonium carbonate and calcium sulfate in the mineralization reaction zone 2 is relatively high, and the excess ammonium carbonate allows the calcium sulfate to react completely to obtain a higher purity calcium carbonate solid.

[0011] Preferably, in the mineralization reaction zone two, the low-concentration ammonium sulfate mother liquor generated by the reaction and the low-concentration ammonium carbonate mother liquor that has not been completely reacted all enter the filter one. After liquid-solid separation, the low-concentration ammonium sulfate mother liquor and the ammonium carbonate mother liquor enter the solid waste gypsum slurrying tank for slurrying with the solid waste gypsum; the obtained calcium carbonate product is used as cement raw material after drying.

[0012] Preferably, in the mineralization reaction zone one, in the solid waste gypsum slurry tank, the solid waste gypsum slurry and the low concentration of ammonium sulfate and the low concentration of ammonium carbonate mother liquor are mixed and transported to the upper part of the mineralization reaction zone one and sprayed downward, and then reacted in the mineralization reaction zone one. Since the liquid phase here has undergone a mineralization reaction, the ammonium carbonate content in the area is reduced, resulting in a high concentration difference between ammonium carbonate and calcium sulfate. The excess calcium sulfate allows the ammonium carbonate to react completely. After the reaction, a high concentration of ammonium sulfate mother liquor and an incompletely reacted solid portion are obtained; the filtered ammonium sulfate mother liquor is evaporated and crystallized by waste heat to become ammonium sulfate fertilizer.

[0013] Preferably, the desulfurized and decarbonized flue gas coming out of the mineralization reaction zone 2 enters the bottom of the mineralization reaction zone 1, and also enters the bottom of the mineralization reaction zone 1 by means of injection. Since there are solid waste gypsum slurry, ammonium sulfate and ammonium carbonate mother liquor from the solid waste gypsum slurry tank at the bottom, and the solid waste gypsum is in excess here, the ammonium carbonate is completely reacted; the ammonium sulfate mother liquor obtained by the filter 1 is again slurried in the slurry tank, solid waste gypsum is added, and reacts in the mineralization reaction zone 1 to generate ammonium sulfate and other cyclic reactions, the ammonium sulfate mother liquor undergoes multiple enrichment cycles in the system, and the concentration gradually increases.

[0014] Preferably, in the mineralization reaction zone two, the desulfurization and decarbonization gas from the decarbonization zone enters into the bottom of the mineralization reaction zone two through gas injection, and there is ammonium sulfate mother liquor at the bottom of the mineralization reaction zone two to wash and absorb the escaped ammonia entrained in the desulfurization and decarbonization flue gas; in the mineralization reaction zone one, the bottom liquid of the mineralization reaction zone one is used to further wash the small amount of escaped ammonia entrained in the desulfurization and decarbonization flue gas; in the washing zone, a water spraying device is provided for spraying water to remove the escaped ammonia and aerosol particles in the flue gas, and a demister is added at the top of the washing zone to remove droplets in the flue gas.

[0015] Preferably, before entering the reaction tower, the cement kiln flue gas is heat exchanged to obtain flue gas with a temperature lower than the decomposition temperature of the ammonium carbonate solution, and the heat absorbed by the heat exchange medium is used to dry the separated calcium carbonate product and evaporate and crystallize the generated ammonium sulfate solution.

[0016] The advantages of the present invention are:

[0017] 1. The present invention divides a reaction tower from top to bottom into several areas by setting a partition, a spraying device and a pipeline in a reaction tower, and the area includes a desulfurization area, a decarbonization area and at least two mineralization reaction areas. During the reaction process, a high content of calcium sulfate in phosphogypsum is subjected to a mineralization reaction with a low concentration of ammonium carbonate in the mineralization reaction area 1, and a low content of calcium sulfate is reacted with a high concentration of ammonium carbonate in the mineralization reaction area 2. The problem of low conversion rate of calcium sulfate to calcium carbonate is solved by a countercurrent step-by-step reaction, and the conditions for solid waste gypsum to be converted into calcium carbonate as raw material for entering the kiln are met. Excessive ammonia water is introduced into the desulfurization area and the decarbonization area to achieve sufficient desulfurization and decarbonization, and the surplus ammonia water is converted into ammonium sulfate as much as possible by the mineralization reaction, and the flue gas is washed with solid waste gypsum slurry and reaction solution many times during the process to avoid ammonia leakage. Therefore, the present invention overcomes the technical problem that it is difficult to fully desulfurize and decarbonize flue gas and to mineralize solid waste gypsum as much as possible in an integrated desulfurization and decarbonization mineralization device because the removal of reaction raw materials and the enrichment of reaction products are difficult to achieve.

[0018] 2. In the present invention, during the reaction process, the ammonium sulfate mother liquor generated at different stages is continuously enriched, and the finally obtained ammonium sulfate mother liquor has a high concentration, which can reduce the energy consumption of evaporation and crystallization in the evaporation and crystallization stage.

[0019] 3. The present invention can be modified based on the existing reaction tower structure such as the desulfurization tower, and the reaction tower can be separated by partitions, which can make full use of the existing desulfurization tower and effectively reduce investment.

[0020] 4. The present invention can also perform heat exchange on the cement kiln flue gas and utilize the waste heat of the flue gas to evaporate and crystallize the subsequent ammonium sulfate mother liquor and dry the filtered calcium carbonate product, thereby saving energy and reducing the flue gas temperature to below the decomposition temperature of ammonium carbonate, thus killing two birds with one stone.

[0021] 5. Synergistic desulfurization: the ammonium sulfite just generated is oxidized to generate ammonium sulfate, which is also the target product, by supplementing oxygen through an oxidation blower in the present invention. This achieves that the desulfurization product can be recovered and converted into ammonium sulfate, the target product, for reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of an integrated treatment method for cement kiln flue gas desulfurization, decarbonization and mineralized solid waste gypsum in the present invention.

[0023] The reference numerals in the figure include: 1. reaction tower, 2. solid waste gypsum slurry tank, 3. ammonia water storage tank, 4. filter one, 5. filter two, 6. circulation pump, 7. oxidation fan, 8. desulfurization zone, 9. decarbonization zone, 10. mineralization reaction zone two, 11. mineralization reaction zone one, 12. washing zone, 13. demister. DETAILED DESCRIPTION

[0024] The specific implementation modes of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0025] like Figure 1As shown, the present invention provides an integrated treatment method for cement kiln flue gas desulfurization, decarbonization and mineralization of solid waste gypsum, adopting a treatment system integrating desulfurization, decarbonization and mineralization, the treatment system used includes a reaction tower 1, the reaction tower 1 is sequentially divided into a desulfurization zone 8, a decarbonization zone 9, a mineralization reaction zone 10 and a mineralization reaction zone 11 by partitions from bottom to top, and a washing zone 12 is also arranged above the mineralization reaction zone 11, and the top of the reaction tower 1 is a flue gas outlet, the treatment method includes: inputting the original flue gas of the cement kiln from the bottom to the desulfurization zone 8, spraying ammonia water downward from the upper part of the desulfurization zone 8 for desulfurization, inputting the flue gas treated in the desulfurization zone 8 to the bottom of the decarbonization zone 9 through a pipeline, spraying ammonia water downward from the upper part of the decarbonization zone 9 for decarbonization, inputting the flue gas treated in the decarbonization zone 9 to the bottom of the mineralization reaction zone 10 through a pipeline, and at the same time, transporting the ammonium carbonate mother liquor accumulated at the bottom of the decarbonization zone 9 to the bottom of the mineralization reaction zone 10, and The flue gas inside the mineralization reaction zone 10 is input to the bottom of the mineralization reaction zone 11, and the solid waste gypsum slurry prepared by the solid waste gypsum slurry tank 2 is sprayed downward from the upper part of the mineralization reaction zone 11. The solid waste gypsum slurry accumulated at the bottom of the mineralization reaction zone 11 is input to the filter 25 for filtration, and then the filtered solid part is evenly sprayed downward from the upper part of the mineralization reaction zone 10, and the filtrate output by the filter 25 is evaporated and crystallized to obtain an ammonium sulfate product, and the reaction liquid accumulated at the bottom of the mineralization reaction zone 10 is transported to the filter 4, and the filter 4 is filtered to obtain solid calcium carbonate, which is dried by the waste heat of the flue gas. The filtrate obtained by filtering the filter 4 is recovered and input to the solid waste gypsum slurry tank 2 for slurrying, and the flue gas treated by the mineralization reaction zone 11 passes through the water spraying device of the washing zone 12 to remove the escaped ammonia and aerosol particles, and finally passes through the demister 13 to remove droplets in the flue gas and the treated flue gas is discharged.

[0026] For the reaction tower 1, the above-mentioned treatment method allows the flue gas to enter the reaction tower 1 from the bottom, first pass through the desulfurization zone 8 for desulfurization, then pass through the decarbonization zone 9 for decarbonization, and then pass through the mineralization reaction zone 2 10 and the mineralization reaction zone 1 11 for mineralization reaction. In the mineralization reaction zone, on the one hand, the ammonium carbonate is reacted completely through a large amount of phosphogypsum to reduce the ammonia partial pressure in the gas phase, and on the other hand, the escaped ammonia entrained in the flue gas is removed through full contact with the reaction slurry. Finally, the flue gas is washed through the washing zone 12 to further remove sulfides and escaped ammonia in the flue gas to ensure that the flue gas meets the emission standards.

[0027] Among them, because the cement kiln flue gas with a temperature of about 130°C needs to undergo heat exchange before entering the desulfurization zone 8 to reduce its temperature to about 50°C, the flue gas after heat exchange is used to generate ammonium carbonate in the subsequent generation. Here, the flue gas temperature needs to be controlled because the ammonium carbonate solution begins to decompose at about 70°C. If heat exchange is not performed, the generated ammonium carbonate solution will decompose due to the high temperature, resulting in the inability to carry out the subsequent mineralization reaction. On the other hand, not exchanging heat will cause a waste of heat. After heat exchange, the heat absorbed by the heat exchange medium can be used for subsequent drying of the separated calcium carbonate product, and can also be used for evaporation and crystallization of the generated ammonium sulfate solution, saving evaporation energy consumption.

[0028] The reaction process of each area is as follows:

[0029] 1. Desulfurization zone 8: After heat exchange, the flue gas from the cement kiln enters the desulfurization zone 8 from the bottom of the tower. According to the concentration of sulfur dioxide in the flue gas, the system automatically calculates and adjusts the spraying amount of ammonia water. Experiments have shown that ammonia water will first react with sulfur dioxide and then with carbon dioxide. Therefore, when setting the spraying amount of ammonia water, the spraying amount of ammonia water is excessive relative to the desulfurization demand to ensure that all sulfur dioxide in the flue gas is removed or meets the environmental emission standards. In addition, after reacting with sulfur dioxide, the remaining ammonia water will also react with carbon dioxide in the flue gas to generate ammonium carbonate solution required for the mineralization reaction. At the same time, the desulfurization zone 8 supplements oxygen through the oxidation fan 7, and the ammonium sulfite generated by the reaction of oxygen with sulfur dioxide and ammonia water is oxidized to become ammonium sulfate. The ammonium sulfate and a small amount of ammonium carbonate generated are pumped into the phosphogypsum slurry tank through the circulating pump 6 for phosphogypsum slurrying. The reactions occurring in the desulfurization zone 8 are as follows:

[0030] 2NH 3 +H 2 O+SO 2 →(NH 4 )SO 3 ;

[0031] (NH 4 )SO 3 +SO 2 +H 2 O→2(NH 4 )H SO 3 ;

[0032] (NH 4 )H SO 3 +NH 3 →(NH 4 )SO 3 ;

[0033] 2(NH 4 ) 2 SO 3 +O 2 →2(NH4 ) 2 SO 4 ;

[0034] NH 3 +H 2 O+CO 2 →NH 4 HCO 3 ;

[0035] Among them, the substances finally generated are mainly ammonium sulfate, supplemented by ammonium carbonate, which is slightly excessive relative to the ammonia required for desulfurization, but the excess ammonia will not react significantly with carbon dioxide.

[0036] 2. Decarbonization Zone 9: The flue gas from the desulfurization zone 8 enters the decarbonization zone 9, and uses ammonia water to react with the carbon dioxide in the flue gas to generate a high concentration of ammonium carbonate solution, which is used for the subsequent mineralization of solid waste gypsum. The main reactions occurring in the decarbonization zone 9 are as follows: NH 3 +H 2 O+CO 2 →(NH 4 ) 2 CO 3 . A large amount of ammonia water is used here to achieve full absorption of carbon dioxide. In addition, in order to ensure that the absorbed carbon dioxide is converted into the target product calcium carbonate as much as possible, the amount of ammonia water needs to allow the ammonia content to form a certain molar ratio with the phosphogypsum added in the solid waste gypsum slurry tank, which is approximately 2:1, so as to achieve complete conversion of the phosphogypsum. The ammonia water input into the decarbonization zone 9 and the desulfurization zone 8 can come from the same ammonia water storage tank 3, as in the present embodiment, or from different ammonia water storage tanks 3.

[0037] 3. Mineralization reaction zone 2 10: The high concentration ammonium carbonate solution generated in the decarbonization zone 9 is pumped into the mineralization reaction zone 2 10 through the circulation pump 6. At the same time, the unreacted solid part (mainly calcium sulfate and calcium carbonate) obtained through liquid-solid separation in the filter 2 5 outside the reaction tower 1 is also evenly sprayed into the mineralization reaction zone 2 10, and reacts with the high concentration ammonium carbonate solution pumped in as follows: (NH 4 ) 2 CO 3 +CaSO 4 →CaCO 3 +(NH 4 ) 2 SO 4 .

[0038] Since the concentration of ammonium carbonate solution is high in the mineralization reaction zone 10, and the calcium sulfate in the solid waste gypsum has been partially converted into calcium carbonate after passing through the mineralization reaction zone 11, the calcium sulfate content in the solid part is reduced at this time, resulting in a high concentration difference between ammonium carbonate and calcium sulfate, which increases the driving force for the reaction, and the efficiency of the reaction will be relatively high. The excess ammonium carbonate allows the calcium sulfate to react completely to obtain a calcium carbonate solid with a higher purity. The higher here is relative to the direct use of the slurry output from the solid waste gypsum slurry tank for reaction. The calcium carbonate solid obtained with a high conversion rate after the reaction, the low-concentration ammonium sulfate mother liquor generated by the reaction and the low-concentration ammonium carbonate mother liquor that has not been completely reacted, all enter the filter 4, and after liquid-solid separation, the low-concentration ammonium sulfate mother liquor and the ammonium carbonate mother liquor enter the solid waste gypsum slurry tank 2 for slurrying with the solid waste gypsum. After the liquid-solid separation, a calcium carbonate product with a high conversion rate is obtained, which is dried using the waste heat from the flue gas heat exchange, and the dried calcium carbonate product can be used as cement raw material.

[0039] At the same time, the desulfurization and decarbonization gas from the previous unit (i.e., decarbonization zone 9) enters the bottom of the mineralization reaction zone 2 10 through gas injection. There is ammonium sulfate mother liquor at the bottom of the mineralization reaction zone 2 10, so it can wash and absorb the escaped ammonia entrained in the desulfurization and decarbonization flue gas, thereby reducing the escape of ammonia in the gas.

[0040] 4. Mineralization reaction zone 11: In the solid waste gypsum slurry tank 2, the solid waste gypsum slurry is mixed with low-concentration ammonium sulfate and low-concentration ammonium carbonate mother liquor and then transported to the upper part of the mineralization reaction zone 11 and sprayed downward. The solid waste gypsum slurry, ammonium sulfate, ammonium carbonate and other substances react in the mineralization reaction zone 11 to generate calcium carbonate and a higher concentration of ammonium sulfate mother liquor, as well as an incompletely reacted solid part. The main component of the solid waste gypsum is calcium sulfate. These reaction products are transported to the external filter 2 5 at the bottom of the mineralization reaction zone 11 for filtration, and a higher concentration of ammonium sulfate mother liquor, as well as solid substances such as calcium carbonate and calcium sulfate are obtained respectively. The solid substances such as calcium carbonate and calcium sulfate are then transported to the aforementioned mineralization reaction zone 2 10 to continue to react with a higher concentration of ammonium carbonate solution, and the incompletely reacted calcium sulfate solid is completely reacted in the mineralization reaction zone 2 10. The ammonium sulfate mother liquor obtained by filtration is evaporated and crystallized by waste heat to become ammonium sulfate fertilizer.

[0041] The desulfurized and decarbonized flue gas from the mineralization reaction zone 2 10 enters the bottom of the mineralization reaction zone 11, and also enters the bottom of the mineralization reaction zone 11 by spraying. Since there is solid waste gypsum slurry and ammonium sulfate and ammonium carbonate mother liquor from the solid waste gypsum slurry tank 2 at the bottom, and there is an excess of solid waste gypsum here, the ammonium carbonate is almost completely reacted. According to the liquid equilibrium theory, the bottom liquid of the mineralization reaction zone 11 can effectively reduce the partial pressure of ammonia in the flue gas, thereby achieving the initial washing of a small amount of escaped ammonia entrained in the desulfurized and decarbonized flue gas, reducing the escape of ammonia in the gas, and reducing the deammoniation pressure of the subsequent washing zone 12.

[0042] In the above reaction process, since the ammonium sulfate mother liquor obtained by filter 4 is again subjected to a series of cyclic reactions such as pulping in a pulping tank, adding solid waste gypsum, and reacting in a mineralization reaction zone 11 to generate ammonium sulfate, the ammonium sulfate mother liquor undergoes multiple enrichment cycles in the system, and the concentration gradually increases. Therefore, the ammonium sulfate mother liquor finally obtained by filtering through filter 25 has a higher concentration, which can effectively reduce the energy consumption of subsequent evaporation and crystallization.

[0043] 5. Scrubbing zone 12: The desulfurized and decarbonized flue gas entering the scrubbing zone 12 may also carry some escaped ammonia and aerosol particles. This solution adds a water spray device in the scrubbing zone 12 to remove the possible escaped ammonia and aerosol particles. In addition, a demister 13 is added at the top of the scrubbing zone 12 to remove droplets in the flue gas.

[0044] VI. Solid waste gypsum slurry tank 2: The solid waste gypsum slurry tank 2 outside the reaction tower 1 is a device for fully mixing the solid waste gypsum with the filtrate from the filter 4 to generate slurry; and the filtrate of the filter 4 includes low-concentration ammonium sulfate mother liquor and low-concentration ammonium carbonate mother liquor, and the mixed slurry is input as a raw material into the aforementioned mineralization reaction zone 11 for mineralization reaction. The reason for such operation is that after multiple cycles of the ammonium sulfate mother liquor, the ammonium sulfate mother liquor finally separated from the filter 2 5 can achieve ammonium sulfate concentration enrichment, thereby reducing the subsequent evaporation and crystallization energy consumption of the ammonium sulfate mother liquor; at the same time, the reaction also reduces the concentration of ammonium carbonate in the slurry, so that the ammonium carbonate is basically reacted with the added solid waste gypsum, reducing the volatilization of ammonia and the waste of raw materials.

[0045] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the inventive concept and technical solution of the present invention, or the inventive concept and technical solution are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum, characterized in that: The treatment system adopted comprises a reaction tower (1), wherein the reaction tower (1) is divided into a desulfurization zone (8), a decarbonization zone (9), a second mineralization reaction zone (10) and a first mineralization reaction zone (11) in sequence from bottom to top by partitions, and a washing zone (12) is further arranged above the first mineralization reaction zone (11). The top of the reaction tower (1) is a flue gas outlet. The treatment method comprises: inputting the raw flue gas of the cement kiln into the desulfurization zone (8) from the bottom, and the desulfurization zone (8) is discharged from the desulfurization zone (9). 8) spraying ammonia water downward from the top to desulfurize, the flue gas treated in the desulfurization zone (8) is input to the bottom of the decarbonization zone (9) through a pipeline, the decarbonization zone (9) spraying ammonia water downward from the top to decarbonize, the flue gas treated in the decarbonization zone (9) is input to the bottom of the mineralization reaction zone II (10) through a pipeline, and at the same time, the ammonium carbonate mother liquor accumulated at the bottom of the decarbonization zone (9) is transported to the bottom of the mineralization reaction zone II (10), and the mineralization reaction The flue gas inside the second reaction zone (10) is input into the bottom of the first mineralization reaction zone (11), the upper part of the first mineralization reaction zone (11) sprays downward the solid waste gypsum slurry produced by the solid waste gypsum slurry tank (2), the solid waste gypsum slurry accumulated at the bottom of the first mineralization reaction zone (11) is input into the second filter (5) for filtration, then the filtered solid part is sprayed downward evenly from the upper part of the second mineralization reaction zone (10), and the filtrate output from the second filter (5) is evaporated and crystallized to obtain an ammonium sulfate product, the reaction liquid accumulated at the bottom of the second mineralization reaction zone (10) is transported to the first filter (4), the first filter (4) is filtered to obtain calcium carbonate solid and dried, the filtrate obtained by filtering the first filter (4) is recovered and input into the solid waste gypsum slurry tank (2) for slurrying, and the flue gas treated by the first mineralization reaction zone (11) is washed by the washing zone (12) and then discharged.

2. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: In the desulfurization zone (8), cement kiln flue gas enters the desulfurization zone (8) from the bottom of the tower, and the amount of ammonia water sprayed is adjusted according to the concentration of sulfur dioxide in the flue gas; when setting the ammonia water spray amount, the ammonia water spray amount is excessive relative to the desulfurization demand.

3. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 2, characterized in that: The desulfurization zone (8) is supplemented with oxygen through the oxidation blower (7) while desulfurization is being carried out. The ammonium sulfite generated by the reaction of oxygen with sulfur dioxide and ammonia water is oxidized to become ammonium sulfate. The substances generated in the desulfurization zone (8) are mainly ammonium sulfate and supplemented with ammonium carbonate. The solution of the obtained substances is transported to the solid waste gypsum pulping tank (2) through a recovery pipeline for pulping.

4. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: In the decarbonization zone (9), the flue gas from the desulfurization zone (8) enters the decarbonization zone (9), and ammonia water is used to react with carbon dioxide in the flue gas to generate a high concentration of ammonium carbonate solution for subsequent mineralization of solid waste gypsum. The amount of ammonia water used needs to form a molar ratio of 2:1 between the ammonia content and the phosphogypsum added in the solid waste gypsum slurry tank.

5. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: In the second mineralization reaction zone (10), the ammonium carbonate solution with a high concentration generated in the decarbonization zone (9) is pumped into the second mineralization reaction zone (10) through the circulation pump (6); at the same time, the incompletely reacted solid part obtained through liquid-solid separation in the second filter (5) outside the reaction tower (1) is also uniformly sprayed into the second mineralization reaction zone (10) to react with the pumped-in ammonium carbonate solution with a high concentration to generate ammonium sulfate and calcium carbonate; the incompletely reacted solid part includes calcium sulfate and calcium carbonate. The solid waste gypsum input into the reaction tower (1) undergoes a mineralization reaction in the first mineralization reaction zone (11), and the calcium sulfate content of the obtained incompletely reacted solid part is reduced, so that the concentration difference between ammonium carbonate and calcium sulfate in the second mineralization reaction zone (10) is relatively high, and the excess ammonium carbonate allows the calcium sulfate to react completely to obtain a calcium carbonate solid with a relatively high purity.

6. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 5, characterized in that: In the mineralization reaction zone 2 (10), the low-concentration ammonium sulfate mother liquor generated by the reaction and the low-concentration ammonium carbonate mother liquor that has not been completely reacted all enter the filter 1 (4). After liquid-solid separation, the low-concentration ammonium sulfate mother liquor and the ammonium carbonate mother liquor enter the solid waste gypsum slurry tank (2) for slurrying with solid waste gypsum; the obtained calcium carbonate product is used as cement raw material after drying.

7. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: In the mineralization reaction zone 1 (11), in the solid waste gypsum slurry tank (2), the solid waste gypsum slurry is mixed with low-concentration ammonium sulfate and low-concentration ammonium carbonate mother liquor and then transported to the upper part of the mineralization reaction zone 1 (11) and sprayed downward, and then reacted in the mineralization reaction zone 1 (11). Since the liquid phase here has undergone a mineralization reaction, the ammonium carbonate content in the area is reduced, resulting in a high concentration difference between ammonium carbonate and calcium sulfate. The excess calcium sulfate allows the ammonium carbonate to react completely. After the reaction, a high-concentration ammonium sulfate mother liquor and an incompletely reacted solid portion are obtained; the reaction products of the mineralization reaction zone 1 (11) are transported together to the external filter 2 (5) for filtration, respectively obtaining a high-concentration ammonium sulfate mother liquor and an incompletely reacted solid portion; the filtered ammonium sulfate mother liquor is evaporated and crystallized by waste heat to become ammonium sulfate fertilizer.

8. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: The desulfurized and decarbonized flue gas from the second mineralization reaction zone (10) enters the bottom of the first mineralization reaction zone (11), and also enters the bottom of the first mineralization reaction zone (11) by means of injection. Since there is solid waste gypsum slurry, ammonium sulfate and ammonium carbonate mother liquor from the solid waste gypsum slurry tank (2) at the bottom, and the solid waste gypsum is excessive here, the ammonium carbonate is completely reacted; the ammonium sulfate mother liquor obtained from the filter one (4) is again slurried in the slurry tank, solid waste gypsum is added, and reacts in the first mineralization reaction zone (11) to generate ammonium sulfate, etc., and a series of cyclic reactions are carried out, so that the ammonium sulfate mother liquor undergoes multiple enrichment cycles in the system, and the concentration gradually increases.

9. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: In the mineralization reaction zone 2 (10), the desulfurization and decarbonization gas from the decarbonization zone (9) enters the bottom of the mineralization reaction zone 2 (10) through gas injection. There is ammonium sulfate mother liquor at the bottom of the mineralization reaction zone 2 (10) to wash and absorb the escaped ammonia entrained in the desulfurization and decarbonization flue gas; in the mineralization reaction zone 1 (11), the bottom liquid of the mineralization reaction zone 1 (11) is used to further wash a small amount of escaped ammonia entrained in the desulfurization and decarbonization flue gas; in the washing zone (12), a water spraying device is provided for spraying water to remove the escaped ammonia and aerosol particles in the flue gas, and a demister (13) is added at the top of the washing zone (12) to remove droplets in the flue gas.

10. The method for integrated treatment of cement kiln flue gas desulfurization and decarbonization and mineralized solid waste gypsum according to claim 1, characterized in that: Before entering the reaction tower (1), the cement kiln flue gas is heat exchanged to obtain flue gas with a temperature lower than the decomposition temperature of the ammonium carbonate solution. The heat absorbed by the heat exchange medium is used to dry the separated calcium carbonate product and to evaporate and crystallize the generated ammonium sulfate solution.

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