A system for mineralizing flue gas carbon dioxide with phosphogypsum co-producing ammonium sulfate and calcium carbonate

Abstract

This invention discloses a system for the co-production of ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide. The system includes a reactor, a circulating pump, a hydrocyclone separator, a three-stage cooler, an absorption tower, and a three-stage heat pump system. The reactor is used to introduce phosphogypsum slurry, ammonia, and CO2-containing flue gas to form a mixed slurry. The circulating pump is used to input the mixed slurry into the hydrocyclone separator, which separates the mixed slurry into an upward overflowing fluid and a downward swirling fluid. The three-stage cooler is used to cool the first fluid from 60-65°C to 18-20°C in stages. The absorption tower is used to absorb CO2 from 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 exchanged heat into the reactor, maintaining the reactor temperature at 60-65°C. This invention solves the technical pain points of the one-step phosphogypsum mineralization technology, which requires high temperatures for the phosphogypsum conversion reaction and low temperatures for CO2 absorption.

Description

Technical Field

[0001] This invention relates to the fields of phosphogypsum solid waste treatment and industrial flue gas CO2 source reduction technology, and particularly to a system for the co-production of ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas carbon dioxide. Background Technology

[0002] Industrial production processes emit large amounts of CO2 in flue gas, contributing to the greenhouse effect and air pollution. CO2 capture, storage, and utilization (CCSU) can achieve source reduction. Various CCSU implementation methods treat flue gas CO2 capture as an independent step. While existing chemical absorption methods offer high capture efficiency, issues such as energy consumption, absorbent consumption, and secondary pollution of exhaust gases remain to be addressed.

[0003] The prior art CN103861446A discloses a three-phase fluidized mineralization method for flue gas CO2 and phosphogypsum slurry membrane, which can convert flue gas CO2 and phosphogypsum into ammonium sulfate and calcium carbonate using a one-step mineralization technology for phosphogypsum. However, this technology has the technical drawbacks of requiring high temperature for the phosphogypsum conversion reaction and low temperature for CO2 absorption. Summary of the Invention

[0004] To address the aforementioned problems, this invention aims to provide a system for the co-production of ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide.

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

[0006] A system for the co-production of ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide includes a reactor, a circulating pump, a hydrocyclone separator, a three-stage cooler, an absorption tower, and a three-stage heat pump system.

[0007] The reactor is connected to the circulating pump, the hydrocyclone separator, and the absorption tower respectively. The circulating pump is connected to the hydrocyclone separator. The three-stage cooler is connected to the hydrocyclone separator and the absorption tower respectively. The three-stage heat pump system is connected to the three-stage cooler and the reactor respectively.

[0008] The reactor is used to introduce phosphogypsum slurry, ammonia, and CO2-containing flue gas. The phosphogypsum slurry, ammonia, and CO2-containing flue gas form a mixed slurry in the reactor. The circulating pump is used to input the mixed slurry into the hydrocyclone separator, which is used to separate the mixed slurry into an upward overflowing fluid one and a downward swirling fluid two. The three-stage cooler is used to cool the fluid one from 60-65℃ to 18-20℃ in stages. The absorption tower is used to absorb CO2 from 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 exchanged into the reactor to maintain the temperature of the reactor at 60-65℃.

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

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

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

[0012] Preferably, the three-stage cooler includes a cooler I, a cooler II, and a cooler III arranged in series, and the three-stage heat pump system includes a compressor I, a compressor II, a compressor III, a valve I, a valve II, a valve III, a heat exchange medium, and a regenerator. The heat exchange medium is disposed in the cooler I, cooler II, and cooler III for evaporation and heat absorption in each cooler.

[0013] The input terminals of compressor one, compressor two, and compressor three are respectively connected to cooler one, cooler two, and cooler three, and are used to compress the working fluid vapor after heat absorption to increase it to the target temperature and target pressure.

[0014] The regenerator is connected to the reactor and is used to condense and release heat from the heat-absorbing working fluid vapor, so as to maintain the temperature of the reactor at 60-65℃.

[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, for feeding the condensed heat exchange medium into each cooler for circulation.

[0016] Preferably, 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℃.

[0020] The beneficial effects of this invention are:

[0021] This invention achieves step-by-step cooling of high-temperature slurry by setting up a three-stage cooler and recovering heat by setting up a three-stage heat pump system. Based on the three-stage recycling of heat, it realizes the coupling of low-temperature absorption and high-temperature reaction. Under the premise that the comprehensive energy efficiency of cooling and heating is greater than 3, it can absorb CO2 at a low temperature of 18-20℃ and convert phosphogypsum at a high temperature of 60-65℃. It solves the technical pain point of the one-step mineralization technology of phosphogypsum, which requires high temperature for phosphogypsum conversion reaction and low temperature for CO2 absorption. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0024] The numbers in the diagram are: 1-reactor, 2-circulating 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 Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following 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 phosphogypsum mineralization flue gas and carbon dioxide, comprising a reactor 1, a circulating pump 2, a hydrocyclone separator 4, a three-stage cooler, an absorption tower 8, and a three-stage heat pump system.

[0027] The reactor 1 is connected to the circulating pump 2, the hydrocyclone 4, and the absorption tower 8 respectively. The circulating pump 2 is connected to the hydrocyclone 4. The three-stage cooler is connected to the hydrocyclone 4 and the absorption tower 8 respectively. The three-stage heat pump system is connected to the three-stage cooler and the reactor 1 respectively.

[0028] The reactor 1 is used to introduce phosphogypsum slurry, ammonia, and CO2-containing flue gas. The phosphogypsum slurry, ammonia, and CO2-containing flue gas form a mixed slurry in the reactor 1. The circulating pump 2 is used to input the mixed slurry into the hydrocyclone 4. The hydrocyclone 4 is used to separate the mixed slurry into an upward overflowing fluid one and a downward swirling fluid two. The three-stage cooler is used to cool the fluid one from 60-65℃ to 18-20℃ in stages. The absorption tower 8 is used to absorb CO2 from 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 exchanged into the reactor 1 to maintain the temperature of the reactor 1 at 60-65℃.

[0029] When using this invention, phosphogypsum slurry is added to reactor 1, ammonia is added from the side, and flue gas containing CO2 enters from below. The resulting mixed slurry enters hydrocyclone 4 from circulation pump 2. The hydrocyclone 4 classifies the particles in the slurry. Larger particles mainly return to reactor 1 with the downward swirling of the slurry. The slurry containing smaller particles overflows from the top of the hydrocyclone into a three-stage cooler, where it is cooled from 60-65°C to 18-20°C before entering absorption tower 8 to absorb CO2 from the flue gas. The slurry in absorption tower 8 is heated by the flue gas, from a temperature of 18-20°C at the top of the tower to a temperature of 23-25°C at the bottom of the tower. Flue gas with a flow rate of 0.1–0.5 m / s flows upwards and comes into countercurrent contact with a solids-containing slurry with a flow rate of 0.01–0.02 m / s sprayed from the top of the tower, transferring heat and mass. 80–85% of the CO2 in the flue gas is absorbed by the ammonia-rich slurry and converted into liquid ammonium carbonate. This reacts with calcium sulfate dihydrate, the main component of phosphogypsum in the liquid phase, to produce calcium carbonate and ammonium sulfate. After the slurry in absorber 8 has absorbed all the CO2, it flows back to reactor 1. The residence time of 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 ammonia escaping in the tail gas is less than 5–10%.

[0030] In one specific embodiment, reactor 1 is a cone-bottom reactor, and circulating pump 2 is a screw circulating pump. It should be noted that the structural selection in this embodiment is merely a preferred structure of the present invention; other reactors and circulating pumps in the prior art can also be applied to the present invention.

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

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

[0033] The input ends of compressor 13, compressor 21, and compressor 39 are respectively connected to cooler 15, cooler 26, and cooler 37, and are used to compress the working fluid vapor after heat absorption to increase it to the target temperature and target pressure.

[0034] The regenerator 3 is connected to the reactor 1 and is used to condense and release heat from the heat-absorbing working fluid vapor, so as to maintain the temperature of the reactor 1 at 60-65℃.

[0035] The input ends of valve 14, valve 212, and valve 310 are respectively connected to the regenerator 3, and the output ends are respectively connected to cooler 15, cooler 26, and cooler 37, for inputting the condensed heat exchange medium into each cooler for circulation.

[0036] In one specific embodiment, valve 14, valve 2, and valve 3 10 are all expansion throttling valves, and the heat exchange medium is R134a. It should be noted that the valves and heat exchange medium in this embodiment are only preferred valves and heat exchange mediums of the present invention; other valves and heat exchange mediums in the prior art can also be applied to the present invention.

[0037] In one 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 one specific embodiment, the system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide as described in this invention includes the following steps:

[0039] Logistics preparation: 50,000 Nm³ of flue gas with a CO2 volume concentration of 18% (dry basis). 3 The flow rates are as follows: 550 kmol / h of NH3 gas at 50℃ and 125 kPa (absolute); 50,000 kg / h of phosphogypsum (dry basis) with CaSO4·2H2O content not less than 92% (dry basis); and 48,800 kg / h of process water. Unless otherwise specified, all flow rates are at ambient temperature.

[0040] A phosphogypsum slurry was prepared by mixing 50,000 kg / h of phosphogypsum granules with 48,800 kg / h of process water at a volume ratio of 3:7, and then added to a cone-bottom reactor. Ammonia gas at a pressure of 0.12 MPa and a flow rate of 550 kmol / h was introduced into the cone-bottom reactor from the side. 3 Flue gas containing 18% (dry basis) CO2 at 50℃ enters the cone-bottom reactor from below. The mixed slurry in the cone-bottom reactor (with a liquid phase mass ratio of water:ammonia:ammonium sulfate:carbon dioxide = 0.795:0.027:0.174:0.004, a solid content of 30%, and a solid phase calcium carbonate mass ratio greater than 99%) enters the circulation loop from the circulation pump 2. After passing through the hydrocyclone separator 4, the particles in the slurry are classified. The ratio of the upward overflow volume flow rate to the downward swirling volume flow rate is 1:2. Larger particles mainly return to the cone-bottom reactor with the downward swirling of the slurry. The slurry containing smaller particles overflows from the top of the hydrocyclone into the cooler 5, where it is cooled from 60°C to 46°C. Then it enters the cooler 6, where it is cooled from 46°C to 33.3°C. Then it enters the cooler 7, where it is cooled from 33°C to 20°C. Finally, it enters the absorption tower 8 to absorb CO2 from the flue gas. The slurry in the absorption tower 8 is heated by the flue gas, from a temperature of 20°C at the top of the tower to a temperature of 23°C at the bottom of the tower. The temperature inside the tower is controlled at 20–23°C to maintain high carbon dioxide absorption efficiency and low ammonia slip rate. Flue gas with a flow rate of 0.1 m / s flows upwards, countercurrently contacting the slurry sprayed from the top of the tower at a flow rate of 0.02 m / s for heat and mass transfer. 85% of the CO2 in the flue gas is absorbed by the slurry and converted into liquid ammonium carbonate, which then reacts with calcium sulfate dihydrate, the main component of phosphogypsum in the liquid phase, to produce calcium carbonate and ammonium sulfate. The slurry at the bottom of absorption tower 8 is refluxed into the cone-bottom reactor, where heat is replenished by regenerator 3 to maintain a temperature above 60°C within the cone-bottom reactor, thus maintaining a relatively fast reaction rate within the reactor. The residence time of phosphogypsum particles in the reaction system is greater than 8 hours, and the conversion rate of calcium sulfate is greater than 96%. The flue gas temperature decreases from 50°C at the bottom of the tower to 20°C at the top, with the volume fraction of ammonia slip in the tail gas being less than 5% and the volume fraction of CO2 being less than 2.7%.

[0041] In this embodiment, R134a is used as the heat exchange medium. A three-stage cooler is used to cool the slurry in the overflow loop of the cyclone separator 4 from 60°C to 20°C, 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 1.01 MPa in cooler 5. The R134a vapor exiting cooler 5 is at 1.01 MPa and 40°C, and is compressed and pressurized to 2.1 MPa and 70°C by compressor 13. The heat exchange medium evaporates and absorbs heat at 0.726 MPa in cooler 6. The working fluid vapor exiting cooler 6 is at 0.726 MPa and 28°C, and is compressed and pressurized to 2.1 MPa and 70°C by compressor 211. The heat exchange medium evaporates and absorbs heat at 0.504 MPa in cooler 7. The working medium vapor exiting cooler 7 is 0.5 MPa and 16°C. It is then compressed and pressurized to 2.1 MPa and 70°C by compressor 9. The pressurized working medium vapors from the outlets of each compressor are combined and then enter regenerator 3 for condensation and heat release. The temperature inside the cone-bottom reactor is controlled at 60°C. The condensed working medium is divided into three equal parts and cooled and depressurized by throttling valves before entering the three coolers for circulation, thereby achieving comprehensive utilization of heat. The comprehensive energy efficiency for cooling and heating is 6.4.

[0042] In this embodiment, the final temperature of the flue gas (50°C) is 50000 Nm³. 3 CO2 (7000Nm³) in / h) 3 85% of the phosphogypsum (26,500 kg / h) is mineralized into calcium carbonate, and the conversion rate of CaSO4·2H2O in the phosphogypsum (50,000 kg / h) reaches over 96%, yielding 35,000 kg / h of ammonium sulfate. This invention, based on a three-stage heat recycling system, couples low-temperature absorption and high-temperature reaction, achieving a triple benefit of increasing CO2 absorption by 50%, improving phosphogypsum conversion by 2%, and reducing NH3 escape by 90%. The overall energy efficiency for both cooling and heating is 6.4.

[0043] In summary, this invention achieves the coupling of low-temperature absorption and high-temperature reaction, solving the technical bottleneck of the one-step phosphogypsum mineralization process, which requires high temperatures for phosphogypsum conversion and low temperatures for CO2 absorption. Compared with existing technologies, this invention represents a significant advancement.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A system for the co-production of ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide, characterized in that, Includes reactor, circulating pump, hydrocyclone separator, three-stage cooler, absorption tower, and three-stage heat pump system; The reactor is connected to the circulating pump, the hydrocyclone separator, and the absorption tower respectively. The circulating pump is connected to the hydrocyclone separator. The three-stage cooler is connected to the hydrocyclone separator and the absorption tower respectively. The three-stage heat pump system is connected to the three-stage cooler and the reactor respectively. The three-stage cooler includes cooler one, cooler two, and cooler three arranged in series. The three-stage heat pump system includes compressor one, compressor two, compressor three, valve one, valve two, valve three, heat exchange medium, and regenerator. The heat exchange medium is disposed in cooler one, cooler two, and cooler three for evaporation and heat absorption in each cooler. The input terminals of compressor one, compressor two, and compressor three are respectively connected to cooler one, cooler two, and cooler three, and are used to compress the working fluid vapor after heat absorption to increase it to the target temperature and target pressure. The regenerator is connected to the reactor and is used to condense and release heat from the heat-absorbing working fluid vapor, so as to maintain the temperature of the reactor at 60-65℃. 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, for inputting the condensed heat exchange medium into each cooler for circulation; The reactor is used to introduce phosphogypsum slurry, ammonia, and CO2-containing flue gas. The phosphogypsum slurry, ammonia, and CO2-containing flue gas form a mixed slurry in the reactor. The circulating pump is used to input the mixed slurry into the hydrocyclone separator, which is used to separate the mixed slurry into an upward overflowing fluid one and a downward swirling fluid two. The three-stage cooler is used to cool the fluid one from 60-65℃ to 18-20℃ in stages. The absorption tower is used to absorb CO2 from 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 exchanged into the reactor to maintain the temperature of the reactor at 60-65℃.

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

2.

5. The system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide according to claim 1, characterized in that, Valve 1, Valve 2, and Valve 3 are all expansion throttle valves.

6. The system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide according to claim 1, characterized in that, The heat exchange medium used is R134a.

7. The system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide according to any one of claims 1-6, characterized in that, The volume ratio of CO2 in the CO2-containing flue gas is 15-20%.

8. The system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide according to any one of claims 1-6, characterized in that, The temperature of the CO2-containing flue gas is 50-100℃.

9. The system for co-producing ammonium sulfate and calcium carbonate from phosphogypsum mineralization flue gas and carbon dioxide according to claim 7, characterized in that, The temperature of the CO2-containing flue gas is 50-100℃.

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