System for co-producing ammonium sulfate and calcium carbonate by using ardealite mineralized flue gas carbon dioxide

Abstract

The invention discloses a system for co-producing ammonium sulfate and calcium carbonate from ardealite mineralized flue gas carbon dioxide. The system comprises a reactor, a circulating pump, a cyclone separator, a three-stage cooler, an absorption tower and a three-stage heat pump system, the reactor is used for introducing ardealite slurry, ammonia gas and CO2-containing flue gas to form mixed slurry, the circulating pump is used for inputting the mixed slurry into the cyclone separator, the cyclone separator is used for dividing the mixed slurry into a fluid I overflowing upwards and a fluid II swirling downwards, and the fluid II is communicated with the circulating pump. The three-stage cooler is used for cooling the first fluid from 60-65 DEG C to 18-20 DEG C in a staged mode, the absorption tower is used for absorbing CO2 in CO2-containing flue gas, and the three-stage heat pump system is used for conducting heat exchange on the three-stage cooler and inputting heat after heat exchange into the reactor, so that the temperature of the reactor is kept at 60-65 DEG C. The invention can solve the technical problems that the ardealite conversion reaction needs high temperature and CO2 absorption needs low temperature in the ardealite one-step mineralization technology.

Description

Technical Field

[0001] The invention relates to the technical field of phosphogypsum solid waste treatment and industrial flue gas CO2 source emission reduction, and in particular to a system for mineralizing flue gas carbon dioxide to co-produce ammonium sulfate and calcium carbonate. Background Art

[0002] Industrial production processes emit a large amount of flue gas CO2, which will cause greenhouse effects and air pollution. CO2 capture, storage and utilization (CCSU) can achieve source emission reduction. Various methods for implementing CCSU all take flue gas CO2 capture as an independent link. Although the existing chemical absorption method has high capture efficiency, problems such as energy consumption, absorbent consumption and secondary pollution of tail gas need to be solved.

[0003] The prior art CN103861446A discloses a three-phase fluidized mineralization method of flue gas CO2 and phosphogypsum slurry, which can utilize the one-step phosphogypsum mineralization technology to convert flue gas CO2 and phosphogypsum into ammonium sulfate and calcium carbonate. However, this technology has the technical pain points that the phosphogypsum conversion reaction requires high temperature and the CO2 absorption requires low temperature. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a system for mineralizing flue gas carbon dioxide from phosphogypsum to co-produce ammonium sulfate and calcium carbonate.

[0005] The technical solution of the present invention is as follows:

[0006] A system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide by mineralizing phosphogypsum, comprising a reactor, a circulation pump, a cyclone separator, a three-stage cooler, an absorption tower, and a three-stage heat pump system;

[0007] The reactor is respectively connected to the circulation pump, the cyclone separator and the absorption tower, the circulation pump is connected to the cyclone separator, the three-stage cooler is respectively connected to the cyclone separator and the absorption tower, and the three-stage heat pump system is respectively connected to the three-stage cooler and the reactor;

[0008] The reactor is used to introduce phosphogypsum slurry, ammonia and CO2-containing flue gas, which form a mixed slurry in the reactor. The circulating pump is used to input the mixed slurry into the cyclone separator, and the cyclone separator is used to separate the mixed slurry into fluid one overflowing upward and fluid two swirling downward. The tertiary cooler is used to cool the fluid one from 60-65°C to 18-20°C in stages. The absorption tower is used to absorb CO2 in the CO2-containing flue gas. The three-stage heat pump system is used to exchange heat with the three-stage cooler and input the heat after heat exchange into the reactor to keep the temperature of the reactor at 60-65°C.

[0009] Preferably, the reactor is a cone-bottom reactor.

[0010] Preferably, the circulation pump is a screw circulation pump.

[0011] Preferably, the volume flow ratio of the fluid one to the fluid two is 1:2.

[0012] Preferably, the three-stage cooler comprises a cooler 1, a cooler 2 and a cooler 3 which are arranged in series, and the three-stage heat pump system comprises a compressor 1, a compressor 2, a compressor 3, a valve 1, a valve 2, a valve 3, a heat exchange medium and a regenerator, and the heat exchange medium is arranged in the cooler 1, the cooler 2 and the cooler 3 for evaporating and absorbing heat in each cooler;

[0013] The input ends of the compressor 1, compressor 2 and compressor 3 are connected to the cooler 1, cooler 2 and cooler 3 respectively, and are used to compress the working fluid steam after absorbing heat to increase the target temperature and target pressure;

[0014] The regenerator is connected to the reactor and is used to condense the working fluid steam after absorbing heat and release heat, so that the temperature of the reactor is maintained at 60-65°C;

[0015] The input ends of valve one, valve two and valve three are respectively connected to the regenerator, and the output ends are respectively connected to cooler one, cooler two and cooler three, so as to input the condensed heat exchange medium into each cooler for circulation.

[0016] Preferably, the valve one, valve two and valve three are all expansion throttle valves.

[0017] Preferably, the heat exchange medium is R134a.

[0018] Preferably, the volume ratio of CO2 in the CO2-containing flue gas is 15-20%.

[0019] Preferably, the temperature of the CO2-containing flue gas is 50-100°C.

[0020] The beneficial effects of the present invention are:

[0021] The present invention can cool the high-temperature slurry step by step by arranging a three-stage cooler, recover heat by arranging a three-stage heat pump system, and realize the coupling of low-temperature absorption and high-temperature reaction based on the three-stage recycling of heat. On the premise that the comprehensive energy efficiency of refrigeration and heating is greater than 3, CO2 can be absorbed at a low temperature of 18-20°C and phosphogypsum can be converted at a high temperature of 60-65°C. The technical pain points of the one-step mineralization technology of phosphogypsum, that the phosphogypsum conversion reaction requires high temperature, and the CO2 absorption requires low temperature, are solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 This is a schematic diagram of the structure of the system for mineralizing flue gas carbon dioxide to co-produce ammonium sulfate and calcium carbonate according to the present invention.

[0024] Numbers in the figure: 1-reactor, 2-circulation pump, 3-regenerator, 4-cyclone separator, 5-cooler one, 6-cooler two, 7-cooler three, 8-absorption tower, 9-compressor three, 10-valve three, 11-compressor two 12-valve two, 13-compressor one, 14-valve one. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0026] like Figure 1 As shown, the present invention provides a system for the co-production of ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization, comprising a reactor 1, a circulation pump 2, a cyclone separator 4, a three-stage cooler, an absorption tower 8, and a three-stage heat pump system;

[0027] The reactor 1 is respectively connected to the circulation pump 2, the cyclone separator 4, and the absorption tower 8, the circulation pump 2 is connected to the cyclone separator 4, the tertiary cooler is respectively connected to the cyclone separator 4 and the absorption tower 8, and the three-stage heat pump system is respectively connected to the tertiary cooler and the reactor 1;

[0028] The reactor 1 is used for introducing phosphogypsum slurry, ammonia and CO2-containing flue gas, which form a mixed slurry in the reactor 1. The circulating pump 2 is used for inputting the mixed slurry into the cyclone separator 4. The cyclone separator 4 is used for dividing the mixed slurry into fluid one overflowing upward and fluid two swirling downward. The tertiary cooler is used for cooling the fluid one from 60-65°C to 18-20°C in stages. The absorption tower 8 is used for absorbing CO2 in the CO2-containing flue gas. The three-stage heat pump system is used for exchanging heat with the three-stage cooler and inputting the heat after heat exchange into the reactor 1 to keep the temperature of the reactor 1 at 60-65°C.

[0029] When using the present invention, phosphogypsum slurry is added to the reactor 1, ammonia is added from the side, flue gas containing CO2 enters from the bottom, and the formed mixed slurry enters the cyclone separator 4 from the circulation pump 2. The particles in the slurry are classified through the cyclone separator 4, and particles with larger particle sizes mainly swirl downward with the slurry back to the reactor 1. The slurry containing particles with smaller particle sizes overflows from the upper part of the cyclone separator into the three-stage cooler to be cooled from 60-65°C to 18-20°C, and then enters the absorption tower 8 to absorb CO2 in the flue gas. The slurry in the absorption tower 8 is heated by the flue gas, and is heated from the top temperature of 18-20°C to the bottom temperature of 23-25°C. The flue gas with a flow rate of 0.1-0.5 m / s moves from bottom to top, and in the tower, it countercurrently contacts the solid-containing slurry with a flow rate of 0.01-0.02 m / s sprayed down from the top of the tower for heat and mass transfer. After 80-85% of the CO2 in the flue gas is absorbed by the ammonia-rich slurry, it is converted into liquid ammonium carbonate, and then reacts with calcium sulfate dihydrate, the main component of the phosphogypsum in the liquid phase, to generate calcium carbonate and ammonium sulfate. After the slurry in the absorption tower 8 absorbs CO2, it flows back to the reactor 1. The residence time of the phosphogypsum particles in the reaction system is greater than 8 hours, the conversion rate of calcium sulfate is greater than 95%, and the volume fraction of escaped ammonia in the tail gas is less than 5-10%.

[0030] In a specific embodiment, the reactor 1 is a cone bottom reactor, and the circulating pump 2 is a screw circulating pump. It should be noted that the structure of this embodiment is only a preferred structure of the present invention, and other reactors and circulating pumps in the prior art may also be applicable to the present invention.

[0031] In a specific embodiment, the volume flow ratio of the fluid 1 to the fluid 2 is 1: 2. It should be noted that the volume flow ratio of this embodiment is only a preferred volume flow ratio of the present invention, and other volume flow ratios may also be used when using the present invention.

[0032] In a specific embodiment, the three-stage cooler includes a cooler 1 5, a cooler 2 6 and a cooler 3 7 arranged in series, and the three-stage heat pump system includes a compressor 1 13, a compressor 2 11, a compressor 3 9, a valve 1 14, a valve 2 12, a valve 3 10, a heat exchange medium and a regenerator 3, and the heat exchange medium is arranged in the cooler 1 5, the cooler 2 6 and the cooler 3 7 for evaporation and heat absorption in each cooler;

[0033] The input ends of the compressor 1 13, the compressor 2 11, and the compressor 3 9 are respectively connected to the cooler 1 5, the cooler 2 6, and the cooler 3 7, and are used to compress the working fluid steam after absorbing heat to increase the target temperature and target pressure;

[0034] The regenerator 3 is connected to the reactor 1 and is used to condense the working fluid steam after absorbing heat and release heat, so that the temperature of the reactor 1 is maintained at 60-65°C;

[0035] The input ends of the valve 1 14, valve 2 12 and valve 3 10 are respectively connected to the regenerator 3, and the output ends are respectively connected to the cooler 1 5, cooler 2 6 and cooler 3 7, so as to input the condensed heat exchange medium into each cooler for circulation.

[0036] In a specific embodiment, the valve 1 14, the valve 2 12 and the valve 3 10 are all expansion throttle valves, and the heat exchange medium is R134a. It should be noted that the valves and heat exchange medium of this embodiment are only the preferred valves and heat exchange medium of the present invention, and other valves and heat exchange mediums in the prior art may also be applicable to the present invention.

[0037] In a specific embodiment, the volume ratio of CO2 in the CO2-containing flue gas is 15-20%, and the temperature of the CO2-containing flue gas is 50-100°C.

[0038] In a specific embodiment, the system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide by mineralizing phosphogypsum of the present invention is used to co-produce ammonium sulfate and calcium carbonate from flue gas carbon dioxide by mineralizing phosphogypsum, which specifically includes the following steps:

[0039] Prepare logistics: flue gas with CO2 volume concentration of 18% (dry basis) 50000Nm 3 / h, temperature 50℃, pressure 125kPa (absolute); NH3 gas 550kmol / h, pressure 150kPa (absolute); phosphogypsum 50000kg / h (dry basis), CaSO4·2H2O content not less than 92% (dry basis); process water, 48800kg / h. Except for the specified temperature, the above logistics are at room temperature.

[0040] 50000kg / h phosphogypsum particles were mixed with 48800kg / h process water in a volume ratio of 3:7 to form phosphogypsum slurry, which was then added to the cone bottom reactor. 550kmol / h 0.12MPa ammonia was added to the cone bottom reactor from the side. 50000Nm 3 / h 50℃ flue gas containing 18% (dry basis) CO2 enters the cone-bottom reactor from below. The mixed slurry of the cone bottom reactor (wherein the liquid mass ratio is water: ammonia: ammonium sulfate: carbon dioxide = 0.795: 0.027: 0.174: 0.004, the solid content is 30%, and the solid phase calcium carbonate mass ratio is greater than 99%), enters the circulation loop from the circulation pump 2, and the particles in the slurry are classified through the cyclone separator 4. The ratio of the volume flow of the upward overflow to the volume flow of the downward cyclone is 1:2. The particles with larger particle sizes mainly return to the cone bottom reactor with the slurry in the downward cyclone. The slurry containing particles with smaller particle sizes overflows from the upper part of the cyclone into the cooler 1 5 and is cooled from 60°C to 46°C, and then enters the cooler 2 6 to be cooled from 46°C to 33.3°C, and then enters the cooler 3 7 to be cooled from 33°C to 20°C, and finally enters the absorption tower 8 to absorb CO2 in the flue gas. The slurry in the absorption tower 8 is heated by the flue gas from the top temperature of 20°C to the bottom temperature of 23°C. The temperature in the tower is controlled at 20-23°C to maintain a high carbon dioxide absorption efficiency and a low ammonia escape rate. The flue gas with a flow rate of 0.1m / s is countercurrently contacted with the slurry with a flow rate of 0.02m / s sprayed from the top of the tower from bottom to top in the tower for heat and mass transfer. After 85% of the CO2 in the flue gas is absorbed by the slurry, it is converted into liquid ammonium carbonate, and then reacts with the main component of calcium sulfate dihydrate in the liquid phase of phosphogypsum to produce calcium carbonate and ammonium sulfate. The slurry at the bottom of the absorption tower 8 flows back into the cone bottom reactor, and heat is supplemented by the regenerator 3 to maintain the temperature in the cone bottom reactor greater than 60°C to maintain a faster reaction rate in the reactor. The residence time of phosphogypsum particles in the reaction system is greater than 8h, and the conversion rate of calcium sulfate is greater than 96%. The flue gas temperature drops from 50°C at the bottom of the tower to 20°C at the top of the tower, and the volume fraction of escaping ammonia in the tail gas is less than 5%, and the volume fraction of CO2 is less than 2.7%.

[0041] In this embodiment, R134a is used as the heat exchange medium, and the slurry in the overflow circuit of the cyclone separator 4 is cooled from 60°C to 20°C by a three-stage cooler, and the minimum heat exchange temperature difference of the cooling heat exchanger is greater than 5°C. The heat exchange medium evaporates and absorbs heat at 1.01MPa in the cooler 15, and the R134a steam coming out of the cooler 15 is 1.01MPa, 40°C, and is compressed and increased in pressure to 2.1MPa, 70°C by the compressor 13. The heat exchange medium evaporates and absorbs heat at 0.726MPa in the cooler 26, and the working medium steam coming out of the cooler 26 is 0.726MPa, 28°C, and is compressed and increased in pressure to 2.1MPa, 70°C by the compressor 211. The heat exchange working fluid evaporates and absorbs heat at 0.504MPa in cooler three 7. The working fluid steam coming out of cooler three 7 is 0.5MPa and 16℃, and is compressed and pressurized to 2.1MPa and 70℃ by compressor three 9. The pressurized steam of the working fluid at the outlet of each compressor is combined and enters the regenerator 3 for condensation and heat release, and the temperature in the cone bottom reactor is controlled at 60℃. The condensed working fluid is divided into three equal parts and cooled and reduced in pressure by throttle valves and then enters three coolers for circulation, thereby realizing the comprehensive utilization of heat. The comprehensive energy efficiency of cooling and heating is 6.4.

[0042] In this embodiment, the final (50°C) flue gas (50000Nm 3 / h) in CO2 (7000Nm 3 / h) is mineralized into calcium carbonate products (26500kg / h), the conversion rate of CaSO4·2H2O in phosphogypsum (50000kg / h) reaches more than 96%, and 35000kg / h of ammonium sulfate products are obtained. The present invention is based on the three-stage recycling of heat, realizes the coupling of low-temperature absorption and high-temperature reaction, and achieves the triple beneficial effects of increasing CO2 absorption rate by 50%, increasing phosphogypsum conversion rate by 2%, and reducing NH3 escape rate by 90%, and the comprehensive energy efficiency of cooling and heating is 6.4.

[0043] In summary, the present invention can achieve the coupling of low-temperature absorption and high-temperature reaction, and solve the technical pain points of the one-step mineralization technology of phosphogypsum, that is, the phosphogypsum conversion reaction requires high temperature, and the CO2 absorption requires low temperature. Compared with the prior art, the present invention has significant progress.

[0044] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A system for mineralizing flue gas carbon dioxide to produce ammonium sulfate and calcium carbonate, characterized in that: It includes reactor, circulation pump, cyclone separator, three-stage cooler, absorption tower and three-stage heat pump system; The reactor is respectively connected to the circulation pump, the cyclone separator and the absorption tower, the circulation pump is connected to the cyclone separator, the three-stage cooler is respectively connected to the cyclone separator and the absorption tower, and the three-stage heat pump system is respectively connected to the three-stage cooler and the reactor; The reactor is used to introduce phosphogypsum slurry, ammonia and CO2-containing flue gas, which form a mixed slurry in the reactor. The circulating pump is used to input the mixed slurry into the cyclone separator, and the cyclone separator is used to separate the mixed slurry into fluid one overflowing upward and fluid two swirling downward. The tertiary cooler is used to cool the fluid one from 60-65°C to 18-20°C in stages. The absorption tower is used to absorb CO2 in the CO2-containing flue gas. The three-stage heat pump system is used to exchange heat with the three-stage cooler and input the heat after heat exchange into the reactor to keep the temperature of the reactor at 60-65°C.

2. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 1, characterized in that: The reactor is a cone bottom reactor.

3. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 1, characterized in that: The circulating pump is a screw circulating pump.

4. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 1, characterized in that: The volume flow ratio of the fluid 1 to the fluid 2 is 1:

2.

5. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 1, characterized in that: The three-stage cooler includes a cooler 1, a cooler 2 and a cooler 3 which are arranged in series, and the three-stage heat pump system includes a compressor 1, a compressor 2, a compressor 3, a valve 1, a valve 2, a valve 3, a heat exchange medium and a regenerator, and the heat exchange medium is arranged in the cooler 1, the cooler 2 and the cooler 3 for evaporating and absorbing heat in each cooler; The input ends of the compressor 1, compressor 2 and compressor 3 are connected to the cooler 1, cooler 2 and cooler 3 respectively, and are used to compress the working fluid steam after absorbing heat to increase the target temperature and target pressure; The regenerator is connected to the reactor and is used to condense the working fluid steam after absorbing heat and release heat, so that the temperature of the reactor is maintained at 60-65°C; The input ends of valve one, valve two and valve three are respectively connected to the regenerator, and the output ends are respectively connected to cooler one, cooler two and cooler three, so as to input the condensed heat exchange medium into each cooler for circulation.

6. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 5, characterized in that: The valve one, valve two and valve three are all expansion throttle valves.

7. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 5, characterized in that: The heat exchange medium is R134a.

8. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to any one of claims 1 to 7, characterized in that: The volume ratio of CO2 in the CO2-containing flue gas is 15-20%.

9. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to any one of claims 1 to 7, characterized in that: The temperature of the CO2-containing flue gas is 50-100°C.

10. The system for co-producing ammonium sulfate and calcium carbonate from flue gas carbon dioxide from phosphogypsum mineralization according to claim 8, characterized in that: The temperature of the CO2-containing flue gas is 50-100°C.

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