A comprehensive pollutant recovery process for high-aluminum coal flue gas purification

Abstract

A comprehensive recycling and utilization process for pollutants in high-aluminum coal flue gas purification, which adopts physical adsorption and chemical adsorption methods to remove SO2 from the flue gas; adopts oxidation + adsorption method to remove NOx from the flue gas; adopts water-soluble impregnation method to desorb two adsorbents; absorbs AL2O3\Fe2O3 in the smoke dust by mixing the desorption liquid with the flue gas and converts it into AL2(SO4)2\AL(NO3)3\Fe(NO3)3\AL(NO3)3; adopts step-by-step crystallization method to separate aluminum sulfate and ferric sulfate according to the difference in solubility of each component; decomposes aluminum sulfate and aluminum nitrate into aluminum hydroxide, ammonium sulfate and ammonium nitrate by ammonia double decomposition method; and re-absorbs and converts impurities discharged after extracting aluminum and iron in a high-speed stirring reactor by sodium hydroxide liquid phase fusion method, so that the silicon dioxide in the impurities is fused with the impurities and converted into sodium metasilicate, thereby completing the maximum recycling and utilization of fly ash.

Description

Technical Field

[0001] The present invention relates to the field of atmospheric environmental governance, and in particular to an industrial flue gas purification technology for comprehensively controlling gaseous pollutants, liquid pollutants and solid pollutants generated by the combustion of high-aluminum coal in coal-fired boilers. Background Art

[0002] my country's annual high-alumina fly ash emissions are approximately 25 million tons, with accumulated stockpiles exceeding 100 million tons. This large-scale storage of high-alumina fly ash has led to severe air, water, and soil pollution. Due to the complex geological formation of high-alumina coal, the coal contains a relatively high sulfur content. The sulfur dioxide produced during combustion is released into the atmosphere with the flue gas and absorbed by rain and snow, forming acid rain that falls to the ground, posing a threat to human health, as well as surface plants and soil. This unique coal structure, through combustion, creates gaseous and solid pollution that seriously harms human health and the ecological environment. Therefore, the comprehensive management of pollutants generated by burning high-alumina coal is a recycling system technology that is under development.

[0003] Conventional technology uses high-efficiency combustion methods to fully burn high-aluminum coal. The sulfur dioxide produced during the combustion process is then converted and removed through alkaline, calcium, or other methods. The high-aluminum fly ash is then collected and stored, and then Al₂O₃ is extracted from the fly ash using Bayer extraction, one-step hydrothermal, and two-step hydrothermal methods. These separate methods not only increase the difficulty and cost of processing, but also significantly increase the amount of secondary pollutants produced by the high-aluminum coal after use, seriously hindering its resource utilization.

[0004] my country is a country with extremely scarce aluminum ore resources and a high degree of dependence on foreign high-grade bauxite. The development of alumina technology from high-aluminum fly ash can not only effectively alleviate the environmental pollution problems caused by the storage of high-aluminum fly ash, but also reduce my country's dependence on foreign high-grade bauxite.

[0005] The Jungar, Tuyou, and Zhuozishan regions of Inner Mongolia are uniquely rich in high-aluminum coal resources in my country. Proven reserves of co-existing coal and aluminum exceed 50 billion tons. The coal contains 10%-13% alumina, while the fly ash contains 40%-55% alumina. Potential high-aluminum fly ash resources amount to 15 billion tons, far exceeding my country's total proven bauxite reserves. The Jungar coalfield produces 100 million tons of high-aluminum coal annually, generating 30 million tons of high-aluminum fly ash, which can be extracted into 12 million tons of alumina, equivalent to 25 million tons of bauxite, equivalent to annual imports. The proven reserves of Jungar's high-aluminum coal, equivalent to high-aluminum fly ash, amount to 7 billion tons. Extracting all of this Al2O3 could extend my country's aluminum resource security by 50-60 years. Summary of the Invention

[0006] The invention is an improvement to the coal-fired flue gas purification technology, especially an innovation in the technology for the treatment and comprehensive utilization of pollutants generated by the combustion of high-aluminum coal. The invention adopts physical adsorption and chemical adsorption to remove sulfur dioxide in flue gas; adopts oxidation + adsorption to remove nitrogen oxides in flue gas; adopts water-soluble impregnation desorption to remove two adsorbents separately; adopts desorption liquid and flue gas mist mixed convection absorption method to absorb aluminum oxide and ferric oxide in smoke dust and convert them into aluminum sulfate, aluminum nitrate and ferric sulfate and ferric nitrate; adopts step-by-step crystallization method to separate aluminum sulfate and ferric sulfate according to the difference in solubility of each component; adopts ammonia double decomposition method to decompose aluminum sulfate and aluminum nitrate into aluminum hydroxide, ammonium sulfate and ammonium nitrate; adopts recycling method to repeatedly use ammonia, sulfuric acid and nitric acid to make them turnover carriers for continuous aluminum extraction in this process, so that the extraction of aluminum components in fly ash can be easily achieved; adopts sodium hydroxide liquid phase fusion method to absorb and convert impurities discharged after extracting aluminum and iron again in a high-speed stirred reactor, so that silicon dioxide in the impurities is fused with them and converted into sodium metasilicate, thereby completing the maximum recycling of fly ash. The present invention realizes a comprehensive pollutant recovery process in high-aluminum coal flue gas purification. While treating flue gas pollutants, the gaseous pollutants, liquid pollutants and solid pollutants are combined through various technologies to make them coexist, decompose and purify in a mutual generation and restraint process, ultimately achieving the purpose of treating waste with waste.

[0007] According to one embodiment of the present invention, the boiler flue gas first passes through the hot air device of the indirect heat exchanger to convert natural wind into hot air, and then passes through the evaporation system of the indirect heat exchanger. In the evaporation system, it first passes through the first evaporation system to concentrate the desorption liquid, passes through the second evaporation system to concentrate the synthetic liquid, and passes through the third evaporation system to evaporate and concentrate the mixed solution after the ammonia double decomposition and drive out the ammonia molecules therein.

[0008] According to one embodiment of the present invention, activated carbon modified with ion loading is used as an adsorbent carrier. This carrier is then constructed into a series-wound adsorption purification carrier, ensuring maximum contact area and duration for flue gas with minimal wind resistance. The adsorption carriers are then strategically arranged to form a staggered flue gas purification system. In this system, flue gas continuously contacts the adsorbent through a reciprocating series of windings. Due to their high boiling point and strong activity, sulfur dioxide molecules in the flue gas are rapidly adsorbed during this contact, completing the desulfurization process through adsorption purification.

[0009] According to one embodiment of the present invention, open-pore foam glass is made into a catalytic carrier of a certain specification, and the carrier is installed in the oxidation section of the purification system to form a composite purification structure with the series-wound adsorption purification section; the oxidant is poured by spraying, so that the oxidant becomes a liquid film on the foam glass ball wall during flow, and when the flue gas passes through the catalytic carrier, the nitric oxide in the flue gas contacts the oxidant on the ball wall, quickly absorbs the oxygen atoms therein and is oxidized into nitrogen dioxide. The nitrogen dioxide is adsorbed by the adsorbent when passing through the series-wound adsorption system, thereby completing the denitrification of the oxidation + adsorption system.

[0010] According to one embodiment of the present invention, when the adsorption system reaches saturation during adsorption purification operation, the adsorbate in the adsorbent carrier is dissolved and desorbed by water vapor dissolution desorption method and / or hot water dissolution desorption method, so that the adsorbate molecules (SO2, NO X ) reacts with water to form dilute sulfuric acid and dilute nitric acid.

[0011] According to one embodiment of the present invention, the desorption liquid is concentrated and then atomized separately in an aerosol convection conversion purification system, so that the dilute sulfuric acid mist liquid is brought into convection contact with the flue gas to absorb the aluminum oxide in the smoke and convert it into aluminum sulfate, and absorb the ferric oxide and convert it into ferric sulfate; the dilute nitric acid mist liquid is brought into convection contact with the flue gas to absorb the aluminum oxide in the smoke and convert it into aluminum nitrate, and absorb the ferric oxide and convert it into ferric nitrate; the mixed liquid is clarified to precipitate the unconverted impurities in the smoke, and the silicon dioxide in the impurities is dehydrated and then fused with sodium hydroxide in a high-speed stirring reactor to form sodium aluminate; the clear liquid is concentrated and then separated from the aluminum sulfate and ferric sulfate by cooling crystallization, and further crystallized to form aluminum sulfate, ferric sulfate, aluminum nitrate, and ferric nitrate products; or the aluminum sulfate elemental solution or the mixed solution of aluminum nitrate and ferric nitrate after the ferric sulfate is separated is concentrated to become the mother liquor for subsequent treatment.

[0012] According to one embodiment of the present invention, the mother liquor containing aluminum sulfate or aluminum nitrate generated in the previous method is mixed with ammonia water for double decomposition. According to the principle of chemical reaction, in an acidic environment, the ammonia molecules dissolved in water ionize to produce ammonium ions and hydroxide ions, the weakly alkaline ammonium ions combine with the strongly acidic sulfate ions or nitrate ions to produce ammonium sulfate or ammonium nitrate, and the hydroxide ions combine with aluminum ions to produce aluminum hydroxide; the mixed solution is cooled in a condenser to separate the low-solubility aluminum hydroxide from the ammonium sulfate or ammonium nitrate solution by sedimentation separation, and the aluminum hydroxide is dehydrated and dried to produce a finished product; the ammonium sulfate and ammonium nitrate solutions are heated and decomposed to drive out ammonia molecules, and the clear liquid containing sulfuric acid or nitric acid repeats the previous method to absorb aluminum oxide and iron oxide in the smoke; the ammonia molecules are dissolved in the mixed solution and continuously double decomposed, and this cycle is repeated to achieve the extraction of aluminum oxide and iron oxide in fly ash.

[0013] Modes for Carrying Out the Invention

[0014] According to one embodiment of the present invention, the purpose of the present invention is achieved by the following methods:

[0015] 1. Produce hot air and concentrate the desorption liquid through an indirect heat exchange system.

[0016] Boiler flue gas aggregates and is fed into a gas-liquid indirect heat exchanger under the push force of the front-end fan or the suction force of the rear-end induced draft fan. The heat exchanger is divided into two units: the first unit is the gas-gas indirect heat exchanger, and the second unit is the liquid-gas indirect heat exchanger. Within the first heat exchanger, the air ducts are arranged horizontally. Natural air flows through the ducts under the blowing force of the fan or the force of gravity. The hot flue gas passes horizontally through the gaps between the tubes, exchanging heat with the natural air inside the tubes. The natural air absorbs heat from the flue gas through heat transfer through the tube walls and winds through the heat exchanger in an S-shape. After repeated heating, the temperature reaches the required standard and is then blown into the drying system by the fan. In the second unit, the pipes are arranged vertically. The desorption liquid and decomposition liquid absorb heat from the flue gas through heat transfer through the tube walls. The high-temperature flue gas cuts into the tubes horizontally and dissipates heat. The desorption liquid and decomposition liquid evaporate and concentrate due to the heat exchange. According to the process requirements, the unit is divided into a two-stage ammonia distillation system and a two-stage evaporation system. The two-stage ammonia distillation system includes ammonia distillation from the desorption liquid and ammonia distillation from the double decomposition liquid. The expelled ammonia gas enters the adsorption system or the ammonia addition double decomposition system through the ammonia escape channel; the two-stage evaporation system is divided into the desorption liquid evaporation section after ammonia distillation and the double decomposition liquid evaporation section after ammonia distillation. The water vapor generated in the evaporation process is used to desorb the adsorbate in the adsorption process through the steam pipeline, and the concentrated liquid is intermittently discharged from the bottom discharge port to enter the next process.

[0017] 2. First, smoke, sulfur oxides and nitrogen oxides are removed through a dry-wet mixed desulfurization and denitrification device.

[0018] 1. Use desorption liquid to remove dust and absorb aluminum oxide and iron oxide in smoke.

[0019] The flue gas after heat exchange is blown into the gas collection bin under the action of the front-end fan and gathered. Under the distribution of the flue gas distributor, the air pressure is balanced and it ascends to the first-stage water mist dust removal section. The desorption liquid generated in the subsequent process is atomized by a high-pressure nozzle and produces convection contact with the rising flue gas. The smoke dust dissolves in the desorption liquid and flows downstream to the liquid collection area. During the convection contact between the flue gas and the atomized desorption liquid, the dilute sulfuric acid or dilute nitric acid in the desorption liquid absorbs aluminum oxide and iron oxide in the smoke dust, producing the following chemical reactions: 3H2SO4+Al2O3=Al2(SO4)3+3H2O; 2Al2O3+12HNO3=4Al(NO3)3+6H2O; 3H2SO4+Fe2O3=Fe2(SO4)3+3H2O; Fe2O3+6HNO3=2Fe(NO3)3+3H2O. The smoke dust is removed by sedimentation method, and the number of water mist dust removal sections is determined according to the removal efficiency.

[0020] The smoke gathering chamber described in this embodiment is a triangular ring-shaped air chamber with air inlets evenly distributed around the inner circumference of the upper half of the inverted cone at the bottom of the device through a partition and closed. The smoke enters from the lower air inlet and then enters the device through the circumferential air inlet.

[0021] The flue gas distributor described in this embodiment is a number of mushroom cap air distributors distributed in a certain proportion at the bottom of the water mist dust removal section. The flue gas at the bottom enters the mushroom cap from the central pipe and is then discharged from the peripheral air outlet pipe. Its function is to evenly distribute the flue gas on the one hand, and to prevent the upper spray liquid from flowing into the lower device on the other hand.

[0022] 2. Complete preliminary desulfurization and denitrification through staggered adsorption purification.

[0023] After several water-saving mist dust removals, the flue gas enters the staggered series adsorption purification section, passes through the densely distributed purifiers, and diffuses outward through the adsorbent in the interlayer through the central tube. When the flue gas moves in series through the adsorbent (special activated carbon surface), the water molecules in the flue gas produce a complex ionization reaction with the active layer on the surface of the activated carbon to generate hydroxyl functional groups (-OH), that is: H2O→-OH*+H + , (* indicates adsorption, -OH represents hydroxyl functional groups). Simultaneously, the oxygen molecules in the flue gas are catalytically decomposed into oxygen atoms by the activation energy of the activated carbon surface, i.e., O2 → 2O*. The generation of hydroxyl functional groups and oxygen atoms creates multi-site reactive complexes at the active centers on the activated carbon surface, i.e., -OH* and O*. Under the action of these multi-site reactive complexes, the nitric oxide molecules in the flue gas rapidly acquire oxygen atoms, generating nitrogen dioxide, i.e., NO + O* → NO2. Since nitrogen dioxide and sulfur dioxide molecules have high boiling points (NO2 = 21.1 ° C, SO2 = -10 ° C), strong polarity, and are acidic molecules, and since the adsorbent in the purification system is a special activated carbon that has been surface-modified and has alkaline functional groups on the surface adsorption sites, when the flue gas passes through the adsorption layer and contacts the adsorbent carrier, both sides generate acid-base affinity and are rapidly adsorbed. After the adsorbent adsorbs the acidic molecules, acidic functional groups are generated on the adsorbent surface, which in turn generate affinity for alkaline molecules. Therefore, this embodiment absorbs alkaline molecules through the ammonia evaporation system: NH3→-NH2*+H + (-NH2 represents amino functional group). Ammonia water is decomposed by heat in the ammonia still: NH3H2O→NH3+H2O. Ammonia molecules enter the purification system along with the flue gas and are rapidly adsorbed by the adsorbent due to the affinity of the acidic functional group when passing through the adsorption purification layer: -OH*+M + +X - =-OM*+H + +X -The alkaline molecules cover the acidic molecules in the adsorption pores, generating alkaline functional groups on the surface of the adsorbent carrier. The alkaline functional groups have affinity for the acidic molecules and quickly adsorb the acidic molecules under the action of affinity: -NH2*+H + +X - =-NH3X*, and this process is repeated, so that the purification of the system forms an overlapping adsorption purification of acid and base molecules, thereby achieving the rapid removal of nitrogen oxides and sulfur oxides.

[0024] The flue gas passes through the main body of the device from bottom to top in accordance with the first-section series winding method. The purification cylinders in the upper and lower sections are staggered. During the passage, the flue gas undergoes the same series winding adsorption through densely distributed purifiers. SO2 in the flue gas is preferentially adsorbed due to its higher polarity, boiling point and activity than other molecules. Part of NO is oxidized into NO2 under the action of the active complex on the surface of the adsorption layer. The flue gas reaches the first-level purification purpose through the purification of several stacked purification layers.

[0025] 3. Maximize the removal of nitrogen oxides through reoxidation + re-adsorption.

[0026] After the flue gas passes through the first-stage purification process, most of the harmful components are removed. Since the removal of nitrogen oxides is a complex process, nitrogen monoxide is oxidized to nitrogen dioxide, and a small part of nitrogen dioxide is reduced to nitrogen monoxide when it comes into contact with water or adsorbent. Therefore, reoxidation and re-adsorption are required to completely remove the nitrogen oxides. The method is to pass the exhaust gas after the first-stage purification through the segmented series-wound adsorption purification system of the peripheral branch purifier for re-purification. The process is achieved through reoxidation and re-adsorption. The reoxidation is to pass the flue gas into an oxidation box. The oxidation box is installed with a catalytic carrier made of open-pore foam glass according to certain specifications. The oxidation section and the series-wound adsorption purification section form a composite purification structure. In the oxidation section, an oxidant is poured onto the catalytic carrier by spraying. The oxidant can be sodium hypochlorite, sodium chlorite, etc. The oxidant flows inside the catalytic carrier and forms a liquid film on the wall of the foam glass ball. When the flue gas passes through the catalytic carrier, the nitric oxide in the flue gas comes into contact with the oxidant on the wall of the ball, quickly absorbing the oxygen atoms therein and being oxidized into nitrogen dioxide. The nitrogen dioxide is adsorbed by the adsorbent when passing through the series-wound adsorption system, thereby completing the maximum denitrification of the process.

[0027] When the adsorbent has adsorbed a sufficient amount of molecules, the adsorption efficiency begins to decline, the adsorption gradually enters a saturated state, and the desorption process needs to be started.

[0028] 4. Complete the desorption of the adsorbate through water dissolution method.

[0029] This process employs two desorption methods: one is to dissolve the adsorbate in the branch purification system through the penetration of gaseous water molecules, and the other is to dissolve the adsorbate in the main stacked purification system through the flushing of liquid water molecules. Water vapor is alternately introduced into the branch purifier through a steam distributor. Under the influence of its diffusion force, it penetrates the adsorption pores of the activated carbon, dissolving and transforming with the adsorbate. The newly formed molecules, under the influence of the expansion force generated during the formation process, push themselves out of the adsorption pores and dissolve in the water molecules, i.e., SO2* + O* = SO3*, H2O + SO3* = H2SO4, H2SO4 + 2NH3 = NH4)2SO4, 2NH3 + 2NO2 + H2O → NH4NO3 + NH4NO2, and NH4NO2 → N2 + 2H2O. This achieves desorption and generates nitrsulfuryl ammonium salts. Alternatively, liquid water is pumped into each purification layer of the main body through a high-pressure water pipe and sprayed into the corresponding purification unit through the spray holes of the desorption loop pipe, desorbing the adsorbate according to the above principle.

[0030] 3. Separate ferric sulfate and ferric nitrate from the mixed solution.

[0031] Through segmented aerosol convection mixed absorption conversion (dilute sulfuric acid and dilute nitric acid are carried out separately in different aerosol convection absorption sections), the dilute sulfuric acid in the mist liquid absorbs aluminum oxide and iron oxide to convert them into aluminum sulfate and iron sulfate, and the dilute nitric acid absorbs aluminum oxide and iron oxide to convert them into aluminum nitrate and iron nitrate. In order to maximize the purity of the regenerated product, the present invention adopts a solubility difference separation method to separate iron sulfate from the mixed solution of iron sulfate and aluminum sulfate. This method separates the two components by cooling the mixed solution to about 25°C (according to the solubility of aluminum sulfate and iron sulfate solutions at 25°C: AL2(SO4)3: 38.5g / 100ml, Fe2(SO4)3: 20g / 100ml). When the solution When the temperature is maintained at 25°C, the solubility difference between the two components is greater than 18.5g / 100ml. When the temperature is greater than 25°C, the solubility of the two components gradually decreases with increasing temperature; when the temperature is less than 25°C, the solubility of the two components gradually decreases with decreasing temperature. Therefore, the method of the present invention adopts the method of maintaining the temperature of the mixed solution at 10°C-55°C, preferably 20°C-30°C, and maintaining the solution concentration at 20g / 100ml-30g / 100ml to separate ferric sulfate from the mixed solution, and further crystallizes them into finished aluminum sulfate, aluminum nitrate, ferric sulfate, and ferric nitrate products, or uses the aluminum sulfate solution and the mixed solution of aluminum nitrate and ferric nitrate after the ferric sulfate is separated as mother liquor for subsequent treatment.

[0032] 2. Perform double decomposition by adding ammonia to the conversion liquid.

[0033] According to the principle of chemical reaction, ammonia gas is introduced into the aluminum sulfate solution or the aluminum nitrate and ferric nitrate mixture generated in the third embodiment for double decomposition. In an acidic environment, the ammonia molecules dissolved in water ionize into ammonium ions and hydroxide ions. The weakly alkaline ammonium ions combine with the strongly acidic sulfate ions or nitrate ions to form ammonium sulfate or ammonium nitrate. The hydroxide ions combine with the aluminum ions and iron ions to form aluminum hydroxide and iron hydroxide, namely: AL2(SO4)3+6NH3.H2O=2AL(OH)3+3(NH4)2SO4; AL(NO3)3+3NH3H2O=3NH4NO3+AL(OH)3; Fe2O3+6HNO3=2Fe(NO3 )3+3H2O; Fe(NO3)3+3NH3H2O=3NH4NO3+Fe(OH)3. The mixed solution is cooled in a condenser to separate the aluminum hydroxide or ferric hydroxide precipitate from the ammonium sulfate or ammonium nitrate solution. The aluminum hydroxide or ferric hydroxide is further processed into finished products. The ammonium sulfate or ammonium nitrate solution is heated and decomposed to drive out ammonia molecules. The clear liquid containing sulfuric acid or nitric acid repeats the above method to absorb aluminum oxide and ferric oxide in the smoke. The ammonia molecules dissolve in the mixed solution and continue to decompose. This cycle is repeated to achieve the extraction of aluminum oxide from fly ash.

[0034] 5. Extract silicon dioxide from fly ash impurities after extracting aluminum and iron.

[0035] This method achieves this by vigorously stirring and fusing a sodium hydroxide solution with silicon dioxide in a high-speed stirred reactor. According to the chemical reaction formula: 2NaOH + SlO2 = NaSlO3 + H2O, silicon dioxide and sodium hydroxide are mixed in a ratio of 1:1.33 (adjusted based on product modulus requirements). The smoke impurities precipitated from the clarified mixture are then mixed with the sodium hydroxide in a high-speed stirred reactor. The reaction is then stirred at a speed of greater than 100 rpm for 40-60 minutes. The sodium hydroxide and silicon dioxide in the reactor fuse and transform under forced contact. Because the silicon dioxide in the smoke decomposes into extremely fine powder during coal combustion, the high-speed stirring increases the frequency of contact and collision with the sodium hydroxide solution, accelerating the chemical reaction. After a chemical reaction time of less than 60 minutes, the two components are converted into sodium metaaluminate. This process achieves the recovery and utilization of more than 90% of solid pollutants.

[0036] To sum up, a comprehensive recovery and utilization process of pollutants in high-aluminum coal flue gas purification, through a dry-wet hybrid integrated flue gas purification device, combined with various processes and technologies, can remove solid pollutants, liquid pollutants, and gaseous pollutants in an integrated manner on the basis of achieving flue gas desulfurization, denitrification and dust removal, and utilize the physical and chemical properties of the pollutants to enable each component to play its advantages in mutual coexistence, decomposition and purification, and ultimately achieve the purpose of treating waste with waste.

Claims

1. A comprehensive process for recycling pollutants in high-aluminum coal flue gas purification, the process comprising: a. Produce hot air, evaporate and concentrate desorption liquid, and decomposition liquid by utilizing the waste heat of flue gas; b. Remove sulfur oxides and nitrogen oxides from flue gas through physical adsorption and chemical adsorption; c. Remove adsorbents through water dissolution; d. Use desorption liquid to absorb aluminum oxide and iron oxide from flue dust during aerosol convection dust removal; e. Maximizing the denitrification effect through reoxidation and re-adsorption; f. Separating aluminum sulfate and ferric sulfate by solubility differences; g. Producing aluminum hydroxide by double decomposition of aluminum sulfate and aluminum nitrate with ammonia; h. Producing sodium metasilicate by fusing sodium hydroxide with silicon dioxide in a high-speed stirred reactor; The waste heat utilization is to produce hot air and concentrate the desorption liquid through an indirect heat exchange system; The hot air produced is the hot air obtained by gas-to-gas heat exchange of boiler flue gas in the first unit; The concentrated desorption liquid is the desorption liquid and decomposition liquid concentrated by the boiler flue gas through gas-liquid heat exchange in the second unit of the heat exchanger, and the concentrated liquid is intermittently discharged from the bottom discharge port to enter the next process; Use dilute sulfuric acid or dilute nitric acid in the desorption liquid to absorb aluminum oxide and iron oxide in the smoke; Dilute sulfuric acid absorbs aluminum oxide and iron oxide and converts them into aluminum sulfate and iron sulfate. Dilute nitric acid absorbs aluminum oxide and iron oxide and converts them into aluminum nitrate and iron nitrate. Initial desulfurization and denitrification are achieved through staggered adsorption purification; When the adsorption system reaches saturation during adsorption purification operation, the adsorbate in the adsorbent carrier is dissolved and desorbed by water vapor dissolution desorption and / or hot water dissolution desorption, and the denitrification effect is maximized through reoxidation + re-adsorption; After the desorption liquid is concentrated, it is separated into mist in the aerosol convection conversion purification system. The dilute sulfuric acid mist is in contact with the flue gas through convection, absorbing the aluminum oxide in the smoke and converting it into aluminum sulfate. Iron is converted into ferric sulfate; dilute nitric acid mist is brought into convective contact with flue gas to absorb aluminum oxide in the smoke and convert it into aluminum nitrate, and absorb ferric oxide and convert it into ferric nitrate; the mixed solution is clarified to precipitate unconverted impurities in the smoke, and the silicon dioxide in the impurities is dehydrated and then fused with sodium hydroxide in a high-speed stirring reactor to produce sodium aluminate; the clear solution is concentrated and then cooled and crystallized to separate aluminum sulfate and ferric sulfate, and further crystallized to produce finished products of aluminum sulfate, ferric sulfate, aluminum nitrate, and ferric nitrate; or the aluminum sulfate solution or the mixed solution of aluminum nitrate and ferric nitrate after the ferric sulfate is separated is concentrated to become the mother liquor for subsequent treatment; Pass ammonia into aluminum sulfate solution or a mixture of aluminum nitrate and ferric nitrate for double decomposition.

2. According to the process for comprehensive pollutant recovery and utilization in high-aluminum coal flue gas purification of claim 1, the removal of sulfur oxides and nitrogen oxides from flue gas by physical adsorption and chemical adsorption is achieved in two ways. One is to feed the flue gas into a staggered series-wound adsorption purification section, where SO2 and some NO in the flue gas are adsorbed as the flue gas passes through the surface of the adsorbent, a specially prepared activated carbon. The second method is to pass the flue gas into an oxidation box, in which a catalyst carrier made of open-pore foam glass is installed. The flue gas is reoxidized by spraying an oxidant on the surface of the catalyst carrier in the oxidation box, and the reoxidized flue gas passes through the adsorption system for physical adsorption; The oxidant includes but is not limited to sodium hypochlorite, sodium chlorite, and dilute nitric acid, and its use concentration range is 5%-25%.

3. According to the comprehensive recycling and utilization process of pollutants in the purification of high-aluminum coal flue gas described in claim 1, the removal of adsorbents by water-soluble method is as follows: first, water vapor is alternately introduced into the branch purifier through a steam distributor, and is immersed in the adsorption pores of the activated carbon under the action of its diffusion force, and is dissolved and transformed with the adsorbent, so that the newly formed molecules are pushed out of the adsorption pores under the action of the expansion force generated during the generation process and then dissolved in water molecular clusters, thereby achieving desorption and generating nitrsulfuryl ammonium salts; then, liquid water is transported through a high-pressure water pipe and injected into each purification layer of the main body, and sprayed to the corresponding purification unit through the injection eye of the desorption ring tube to desorb the adsorbent.

4. According to the comprehensive recovery and utilization process of pollutants in the purification of high-aluminum coal flue gas described in claim 1, the absorption of aluminum oxide and iron oxide in the smoke by the desorption liquid during the aerosol convection dust removal process is achieved by a gas-liquid convection absorption method in the aerosol convection dust removal section, and the method is: the flue gas is distributed by the flue gas distributor so that the air pressure is balanced and it ascends to the first-stage aerosol convection dust removal section to produce convection contact with the desorption liquid atomized by the high-pressure nozzle, and the smoke dust dissolves in the desorption liquid and flows downstream to the liquid collection area.

5. According to the comprehensive recovery and utilization process of pollutants in the purification of high-aluminum coal flue gas described in claim 1, the aerosol convection dust removal section is a system composed of several sections in the integrated purification device for realizing wet dust removal and absorbing effective components in the smoke dust. In this system, desorption liquids of different components absorb the effective components in the smoke dust and operate separately; the structural characteristics of the device are: the top is a high-pressure atomization device, and the bottom is a flue gas distribution system, and the flue gas ascends through the flue gas distribution system at the bottom and performs convection contact movement with the atomized liquid droplets at the top; the flue gas distribution system is characterized in that: a number of mushroom cap air distributors are distributed in a certain proportion on the chassis of the aerosol convection dust removal section, and the flue gas at the bottom enters the mushroom cap from the central pipe and is discharged from the peripheral air outlet pipe.

6. A comprehensive pollutant recovery and utilization process for high-aluminum coal flue gas purification according to claim 1, wherein the separation of aluminum sulfate and ferric sulfate by solubility difference comprises: maintaining the temperature of the mixed solution at 10°C-55°C, maintaining the concentration of the mixed solution at 20g / 100ml-25g / 100ml, separating ferric sulfate from the mixed solution, and further crystallizing them into finished products of aluminum sulfate, aluminum nitrate, ferric sulfate, and ferric nitrate; or using the aluminum sulfate solution after separating ferric sulfate and the mixed solution of aluminum nitrate and ferric nitrate as the mother liquor of double decomposition treatment.

7. The process for comprehensive recovery and utilization of pollutants in high-aluminum coal flue gas purification according to claim 1, wherein the aluminum hydroxide is produced by double decomposition of aluminum sulfate and aluminum nitrate by adding ammonia: ammonia generated by the ammonia distillation system of the indirect heat exchanger is introduced into the aluminum sulfate solution or the aluminum nitrate and ferric nitrate mixture generated in the previous process for double decomposition; in an acidic environment, ammonia molecules dissolved in water ionize to produce ammonium ions and hydroxide ions, the weakly alkaline ammonium ions combine with the strongly acidic sulfate ions or nitrate ions to form ammonium sulfate or ammonium nitrate, and the hydroxide ions combine with aluminum ions and iron ions to form aluminum hydroxide and ferric hydroxide; Ammonium sulfate and ammonium nitrate solutions are heated and decomposed to drive out ammonia molecules. The clear liquid containing sulfuric acid or nitric acid is repeatedly subjected to aerosol convection to absorb aluminum oxide and iron oxide in the smoke. The ammonia molecules are dissolved in the mixed liquid and continuously decomposed. This cycle is repeated to achieve the extraction of aluminum oxide from fly ash.

8. A comprehensive pollutant recovery and utilization process for high-aluminum coal flue gas purification according to claim 1, wherein the preparation of sodium metasilicate by fusing sodium hydroxide with silicon dioxide in a high-speed stirred reactor comprises: mixing silicon dioxide and sodium hydroxide in a ratio of 1:1.33; mixing smoke impurities precipitated after clarifying the mixed solution with sodium hydroxide in a high-speed stirred reactor, and reacting the mixture for 40-60 minutes by stirring at a speed greater than 100 r / min, wherein the sodium hydroxide and silicon dioxide in the reactor are fused under a forced contact environment to convert into sodium metaaluminate.