CN110975564A - Comprehensive recovery process for pollutants in high-aluminum coal flue gas purification - Google Patents

Comprehensive recovery process for pollutants in high-aluminum coal flue gas purification Download PDF

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CN110975564A
CN110975564A CN201910279746.3A CN201910279746A CN110975564A CN 110975564 A CN110975564 A CN 110975564A CN 201910279746 A CN201910279746 A CN 201910279746A CN 110975564 A CN110975564 A CN 110975564A
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flue gas
aluminum
purification
adsorption
liquid
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贺海涛
崔怀奇
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    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
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    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
    • B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
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    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/46—Removing components of defined structure
    • B01D53/54—Nitrogen compounds
    • B01D53/56—Nitrogen oxides
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/20—Silicates
    • C01B33/32—Alkali metal silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/34—Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
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    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/66—Nitrates, with or without other cations besides aluminium
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    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/68—Aluminium compounds containing sulfur
    • C01F7/74—Sulfates
    • C01F7/743—Preparation from silicoaluminious materials, e.g. clays or bauxite
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    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G49/00—Compounds of iron
    • C—CHEMISTRY; METALLURGY
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    • C01G49/00—Compounds of iron
    • C01G49/0009—Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange
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    • C01G49/00—Compounds of iron
    • C01G49/14—Sulfates
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B21/00—Obtaining aluminium
    • C22B21/0015—Obtaining aluminium by wet processes
    • C22B21/0023—Obtaining aluminium by wet processes from waste materials
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/006—Wet processes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/02—Working-up flue dust
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
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    • B01D2258/0283—Flue gases
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2259/00—Type of treatment
    • B01D2259/40—Further details for adsorption processes and devices
    • B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
    • B01D2259/40088—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating
    • B01D2259/40092—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating using hot liquid
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Abstract

A comprehensive recycling process of pollutants in high-aluminum coal flue gas purification adopts a physical adsorption method and a chemical adsorption method to remove SO2 in flue gas; removing NOx in the flue gas by adopting an oxidation and adsorption method; desorbing the two adsorbents by a water-soluble impregnation method; the desorption liquid is mixed with the flue gas to convert and absorb AL2O3\ Fe2O3 in the smoke dust and convert the smoke dust into AL2(SO4)2\ AL (NO3)3\ Fe (NO3)3\ AL (NO3) 3; separating aluminum sulfate and ferric sulfate by adopting a fractional crystallization method according to the difference of the solubility of each component; decomposing aluminum sulfate and aluminum nitrate into aluminum hydroxide, ammonium sulfate and ammonium nitrate by an ammonification double decomposition method; and absorbing and converting the impurities discharged after extracting aluminum and iron in the high-speed stirring reaction kettle again by a sodium hydroxide liquid phase fusion method, so that silicon dioxide in the impurities is fused with the impurities and converted into sodium metasilicate, and the maximum recycling of the fly ash is completed.

Description

Comprehensive recovery process for pollutants in high-aluminum coal flue gas purification
Technical Field
The invention relates to the field of atmospheric environment treatment, in particular to an industrial flue gas purification technology for comprehensively treating gaseous pollutants, liquid pollutants and solid pollutants generated by combustion of high-alumina coal in a coal-fired boiler.
Background
The annual emission amount of the high-alumina fly ash in China is about 2500 million tons, the accumulated stockpiling exceeds 1 hundred million tons, the high-alumina fly ash is stockpiled in large quantity to cause serious pollution to atmosphere, water and soil, the reason for forming the high-alumina coal in geological age is complex, the content of sulfur components in the coal is relatively high, sulfur dioxide generated in the combustion process is discharged into the atmosphere along with flue gas, is absorbed by rain and snow to form acid rain, falls on the ground, and harms are caused to human health, surface plants and soil. The special coal structure seriously damages human health and ecological environment by gaseous pollution and solid pollution formed by combustion, so that the comprehensive treatment of pollutants generated by combusting high-alumina coal is a circulating system technology to be developed.
The conventional technology adopts an efficient combustion method to fully combust the high-alumina coal, and converts and removes sulfur dioxide generated in the combustion process of the high-alumina coal by an alkaline method, a calcium method or other methods; collecting and piling high-alumina fly ash, and extracting AL from the high-alumina fly ash by a Bayer extraction method, a one-step hydrothermal method and a two-step hydrothermal method2O3. The methods are operated step by step, so that the treatment difficulty is increased, the treatment cost is greatly increased, secondary pollutants generated after the high-alumina coal is used are increased, and the resource utilization of the high-alumina coal is seriously influenced.
China is a country with extremely poor aluminum ore resources, high-grade bauxite has high external dependence, and the development of the technology for extracting alumina from high-alumina fly ash can not only effectively relieve the problem of environmental pollution caused by stockpiling of high-alumina fly ash, but also reduce the external dependence of China on the high-grade bauxite.
The inner Mongolia Junger, Earth right and Zhuozi mountain areas are special high-aluminum coal resource enrichment areas in China, and the coal resource reserves of coal and aluminum coexisting are more than 500 hundred million tons, the content of aluminum oxide in coal is 10 to 13 percent, the content of aluminum oxide in fly ash is up to 40 to 55 percent, the potential high-aluminum fly ash resource amount is 150 hundred million tons, and the potential high-aluminum fly ash resource amount is far higher than the total reserve of bauxite resources explored in China. 1 million tons of high-alumina coal can be produced in the quasi-Geer coal field every year, 3000 million tons of high-alumina fly ash can be produced, 1200 million tons of alumina can be extracted, the quantity of the alumina is 2500 million tons, which is equivalent to the quantity of the bauxite imported in one year, the proven quasi-Geer high-alumina coal is converted into the high-alumina fly ash, the storage capacity is up to 70 million tons, and the AL in the quasi-Geer high-alumina coal is used2O3The whole extraction process can prolong the guarantee period of the aluminum resources in China by 50-60 years.
Disclosure of Invention
The invention provides an improvement on coal smoke purification technology, in particular to innovation on pollutant treatment and comprehensive utilization technology generated by high-alumina coal combustion. The sulfur dioxide in the flue gas is absorbed and removed by adopting a physical absorption method and a chemical absorption method; removing nitrogen oxides in the flue gas by adopting an oxidation and adsorption method; respectively removing the two adsorbates by a water-soluble impregnation desorption method; aluminum oxide and ferric oxide in the smoke dust are absorbed and converted into aluminum sulfate, aluminum nitrate, ferric sulfate and ferric nitrate by a desorption liquid and smoke gas-fog mixed convection absorption method; separating aluminum sulfate and ferric sulfate by adopting a fractional crystallization method according to the difference of the solubility of each component; decomposing aluminum sulfate and aluminum nitrate into aluminum hydroxide, ammonium sulfate and ammonium nitrate by an ammonification double decomposition method; ammonia, sulfuric acid and nitric acid are repeatedly used by a recycling method to form a turnover carrier for continuously extracting aluminum in the process, so that the extraction of aluminum components in the fly ash is easily realized; and absorbing and converting the impurities discharged after extracting aluminum and iron in the high-speed stirring reaction kettle again by a sodium hydroxide liquid phase fusion method, so that silicon dioxide in the impurities is fused with the impurities and converted into sodium metasilicate, and the maximum recycling of the fly ash is completed. The comprehensive recovery process of pollutants in high-alumina coal flue gas purification, which is realized by the invention, can treat the flue gas pollutants and simultaneously combine gaseous pollutants, liquid pollutants and solid pollutants in a coherent medium through various technologies to mutually store, decompose and purify the gaseous pollutants, the liquid pollutants and the solid pollutants, thereby finally realizing the purpose of treating wastes with wastes.
According to one embodiment of the invention, the boiler flue gas firstly passes through a hot air device of an indirect heat exchanger to make natural air into hot air, then passes through an evaporation system of the indirect heat exchanger, and in the evaporation system, the desorption solution is firstly concentrated through a first evaporation system, the synthetic solution is concentrated through a second evaporation system, and the mixed solution after ammonia double decomposition is evaporated and concentrated through a third evaporation system to drive out ammonia molecules.
According to one embodiment of the invention, the adsorbent carrier is made of the activated carbon modified by the loaded ions, the carrier is made into a series winding type adsorption purification carrier which can keep the maximum area and contact with the flue gas for the longest time under the minimum wind resistance, and the adsorption carriers are reasonably arranged to form the flue gas purification system with a staggered structure. In the system, the flue gas is continuously contacted with the adsorbent through reciprocating series winding, and sulfur dioxide molecules in the flue gas are quickly adsorbed in the contact due to high boiling point and strong activity of the sulfur dioxide molecules, so that the desulfurization in the adsorption and purification process is completed.
According to one embodiment of the invention, open-cell foam glass is made into a catalytic carrier with a certain specification, the catalytic carrier is arranged on an oxidation section of a purification system, and the catalytic carrier and a series-wound adsorption purification section form a composite purification structure; and (2) pouring an oxidant in a spraying mode, so that the oxidant becomes a liquid film of a foam glass ball wall in the flowing process, when the flue gas passes through the catalytic carrier, nitric oxide in the flue gas is contacted with the oxidant of the ball wall, oxygen atoms in the flue gas are quickly absorbed and oxidized into nitrogen dioxide, and the nitrogen dioxide is adsorbed by the adsorbent when passing through the series-wound adsorption system, so that the denitration of the oxidation and adsorption system is completed.
According to one embodiment of the invention, the adsorption is carried out whileWhen the system reaches saturation degree during adsorption and purification operation, the adsorbate in the adsorbent carrier is dissolved and desorbed by a water vapor dissolving and desorbing method and/or a hot water dissolving and desorbing method, SO that adsorbate molecules (SO)2、NOX) And hydration to synthesize dilute sulfuric acid and dilute nitric acid.
According to one embodiment of the invention, the desorption solution is concentrated and then atomized in the gas-fog convection conversion purification system, so that the dilute sulfuric acid fog solution is in convection contact with the flue gas to absorb aluminum oxide in the flue gas and convert the aluminum oxide into aluminum sulfate, and the absorbed ferric oxide is converted into ferric sulfate; enabling the dilute nitric acid mist liquid to be in convection contact with flue gas to absorb aluminum oxide in the smoke dust and convert the aluminum oxide into aluminum nitrate, and absorbing ferric oxide and converting the ferric oxide into ferric nitrate; clarifying and precipitating the mixed solution to obtain unconverted impurities in the smoke dust, dehydrating silicon dioxide in the impurities, and then fusing the silicon dioxide and sodium hydroxide in a high-speed stirring reaction kettle to prepare sodium metaaluminate; concentrating the clear liquid, separating aluminum sulfate from ferric sulfate through cooling crystallization, and further crystallizing respectively to prepare finished products of aluminum sulfate, ferric sulfate, aluminum nitrate and ferric nitrate; or concentrating the separated ferric sulfate aluminum sulfate simple substance solution or the mixed solution of aluminum nitrate and ferric nitrate to obtain the mother solution for subsequent treatment.
According to one embodiment of the present invention, the mother liquor containing aluminum sulfate or aluminum nitrate produced in the previous embodiment is mixed with ammonia water for double decomposition, according to the chemical reaction principle, in an acidic environment, ammonia molecules dissolved in water ionize ammonium ions and hydroxide ions, weakly basic ammonium ions combine with strongly acidic sulfate ions or nitrate ions to produce ammonium sulfate or ammonium nitrate, and hydroxide ions combine with aluminum ions to produce aluminum hydroxide; cooling the mixed solution in a condenser, separating the low-solubility aluminum hydroxide from the ammonium sulfate or ammonium nitrate solution by a settling separation method, and dehydrating and drying the aluminum hydroxide to obtain a finished product; heating ammonium sulfate and ammonium nitrate solution to decompose and drive out ammonia molecules, and repeatedly carrying out the previous mode on the clear liquid containing sulfuric acid or nitric acid to absorb aluminum oxide and ferric oxide in the smoke dust; dissolving ammonia molecules in the mixed solution for continuous double decomposition, and circulating the solution in turn to realize the extraction of the aluminum oxide and the ferric oxide in the fly ash.
Modes for carrying out the invention
According to one embodiment of the invention, the object is achieved by:
firstly, producing hot air through an indirect heat exchange system and concentrating desorption liquid.
Boiler flue gas is polymerized and sent into the gas-liquid indirect heat exchanger under the action of the pushing force of a front-end fan or the suction force of a rear-end draught fan, the heat exchanger is divided into two units, the first unit is a gas-gas indirect heat exchanger, the second unit is a liquid-gas indirect heat exchanger, air pipes are transversely arranged in the first heat exchanger, natural wind flows in the air pipes under the action of the blowing force or the suction force of the fan, hot flue gas transversely penetrates through gaps between the pipes and exchanges heat with natural wind in the pipes while penetrating, the natural wind absorbs the heat of the flue gas through the heat transfer effect of the pipe walls and winds in an S shape in the heat exchanger, the temperature reaches the required standard after being repeatedly heated for many times, and the flue gas enters a drying system under the action of blowing. In the second unit, the pipelines are longitudinally arranged, the desorption liquid and the decomposition liquid are transferred to the smoke gas through the pipe wall in the pipe to absorb heat, the high-temperature smoke gas is transversely cut into the pipe to dissipate the heat, and the desorption liquid and the decomposition liquid are evaporated and concentrated under the action of heat exchange. According to the process requirement, the unit is divided into a two-section ammonia distillation system and a two-section evaporation system, wherein the two-section ammonia distillation system comprises desorption liquid ammonia distillation and double decomposition liquid ammonia distillation, and the expelled ammonia enters an adsorption system or an ammonia-adding double decomposition system through an ammonia escape channel; the two-section evaporation system is divided into a desorption liquid evaporation section after ammonia evaporation and a complex decomposition liquid evaporation section after ammonia evaporation, water vapor generated in the evaporation process is used for desorption of adsorbate in the adsorption process through a vapor pipeline, and concentrated liquid is discharged from a bottom discharge port discontinuously and enters the next process.
And secondly, firstly removing the smoke dust, the sulfur oxides and the nitrogen oxides by using a dry-wet mixed desulfurization and denitrification device.
1. And dedusting and absorbing aluminum oxide and ferric oxide in the smoke dust by using the desorption liquid.
The flue gas after heat exchange is blown into a gas gathering bin under the action of a front end fan for gathering, and the air pressure is enabled to go upwards in a balanced manner under the distribution of a flue gas distributorIn the first-stage water mist dust removal section, desorption liquid generated in the subsequent process is atomized by a high-pressure nozzle and is in convective contact with rising smoke, smoke is dissolved in the desorption liquid and flows downstream to a liquid collection area, and dilute sulfuric acid or dilute nitric acid in the desorption liquid absorbs aluminum oxide and ferric oxide in the smoke in the convective contact of the smoke and the atomized desorption liquid to generate the following chemical reaction: 3H2SO4+AL2O3＝AL2(SO4)3+3H2O；2AL2O3+12HNO3＝4AL(NO3)3+6H2O；3H2SO4+Fe2O3＝Fe2(SO4)3+3H2O；Fe2O3+6HNO3＝2Fe(NO3)3+3H2And O, removing the smoke dust by a sedimentation method, and determining the number of sections of the water mist dust removal section according to the removal efficiency.
The flue gas gathering bin is a triangular annular bin, wherein the upper half part of an inverted cone at the bottom of the device is provided with air inlets uniformly distributed on the periphery of the inner part of the inverted cone through a partition, and flue gas enters the device from a lower air inlet and then enters the device through the periphery air inlets.
The smoke distributor is a plurality of mushroom cap air distributors distributed at the bottom of the water mist dust removal section according to a certain proportion, smoke at the lower part enters the mushroom caps from the central pipe and is discharged from the air outlet pipes at the periphery, and the smoke distributor has the functions of uniformly distributing the smoke on one hand and preventing spray liquid at the upper part from flowing into a lower device on the other hand.
2. And finishing preliminary desulfurization and denitrification in a staggered form adsorption purification mode.
The flue gas after being dedusted by a plurality of water-saving fog enters a staggered grid type series winding adsorption purification section, passes through the adsorbent in the interlayer through the central cylinder through the densely distributed purifiers and diffuses outwards, and when the flue gas passes through the adsorbent (specially prepared active carbon surface) to perform series winding movement, water molecules in the flue gas and an active layer on the active carbon surface generate complex ionization reaction to generate hydroxyl functional groups (-OH), namely: h2O→-OH*+H+(indicates an adsorption state, -OH indicates a hydroxyl functional group), and oxygen molecules in the smoke are activatedThe activation energy of the carbon surface is catalytically decomposed into oxygen atoms, i.e. O2→2O*. The generation of hydroxyl functional groups and oxygen atoms generates a multi-site active complex for the active center of the surface of the activated carbon, namely: -OH*、O*The nitric oxide molecules in the smoke gas rapidly obtain oxygen atoms under the action of the multi-site active complex to generate nitrogen dioxide, namely: NO + O*→NO2. Because of the high boiling point of nitrogen dioxide and sulfur dioxide molecules (NO)2The adsorbent in the purification system is special activated carbon with surface modification and surface adsorption sites of basic functional groups, SO that when flue gas passes through an adsorption layer and contacts with an adsorbent carrier, acid-base affinity is generated on the surface of the adsorbent to be quickly adsorbed, and after the adsorbent adsorbs acid molecules, the acid functional groups are generated on the surface of the adsorbent to generate affinity for the basic molecules, SO that the embodiment intakes the basic molecules through an ammonia distillation system: NH (NH)3→-NH2 *+H+(-NH2Representing an amino function). Heating and decomposing ammonia water in an ammonia still: NH (NH)3H2O→NH3+H2And O, ammonia molecules enter the purification system along with the flue gas, and are quickly adsorbed by the adsorbent under the action of the affinity force of the acidic functional groups when passing through the adsorption purification layer: -OH*+M++X-＝-OM*+H++X-The basic molecules cover the acidic molecules in the adsorption holes, so that basic functional groups are generated on the surface of the adsorbent carrier, the basic functional groups generate affinity to the acidic molecules, and the acidic molecules are quickly adsorbed under the action of the affinity: -NH2 *+H++X-＝-NH3X*The purification of the system forms the overlapping adsorption purification of acid and alkali molecules by repeating the steps, so that the rapid removal of the nitrogen oxides and the sulfur oxides is realized.
The flue gas passes through the device body section by section from bottom to top according to a first section of series winding mode, the purification cylinders in the upper section and the lower section are distributed in a staggered manner, the same series winding type adsorption is carried out through densely distributed purifiers in the passing process, and SO in the flue gas2Due to higher polarity, boiling point and activity than othersMolecules are preferentially adsorbed, and partial NO is oxidized into NO under the action of active complex on the surface of the adsorption layer2The flue gas is purified by a plurality of sections of superposed purification layers to achieve the purpose of first-stage purification.
3. The maximum removal of nitrogen oxides is achieved by reoxidation + reabsorption.
After the flue gas passes through the first-stage purification process, most harmful components in the flue gas are removed, and because the removal of nitrogen oxides is a complex process, nitrogen monoxide is oxidized into nitrogen dioxide, and a small part of the nitrogen dioxide is reduced into nitrogen monoxide when contacting with water or an adsorbent, the nitrogen oxides are completely removed by adopting reoxidation and reabsorption. The reoxidation is to introduce the flue gas into an oxidation box, a catalytic carrier made of open-cell foam glass is arranged in the oxidation box according to a certain specification, and a composite purification structure is formed by an oxidation section and a series winding type adsorption purification section. And (3) pouring an oxidant into the catalytic carrier in a spraying mode in the oxidation section, wherein the oxidant is selected from sodium hypochlorite, sodium chlorite and the like. The oxidant flows in the catalytic carrier to form a liquid film on the spherical wall of the foam glass, when the flue gas passes through the catalytic carrier, nitric oxide in the flue gas is contacted with the oxidant on the spherical wall, oxygen atoms in the nitric oxide are quickly absorbed and oxidized into nitrogen dioxide, and the nitrogen dioxide is adsorbed by the adsorbent when passing through the series-wound adsorption system, so that the maximum denitration of the process is completed.
When the adsorbent adsorbs enough molecules, the adsorption efficiency begins to decrease, the adsorption gradually enters a saturated state, and the desorption process needs to be started.
4. The desorption of the adsorbate is completed by a water dissolution method.
The desorption adopted by the process is divided into two modes, namely, the adsorbate of the purification system is dissolved by permeating gaseous water molecules, and the adsorbate in the main body superposed purification system is dissolved by flushing liquid water molecule groups. Introducing vapor into the branch purifier alternately via the vapor distributor, and soaking under the action of diffusion forceEntering into the adsorption hole of the active carbon, fusing and transforming with the adsorbate, so that the new molecule pushes itself out of the adsorption hole under the action of the expansion force generated in the generation process and is dissolved in the water molecule group, namely: SO (SO)2 *+O*＝SO3 *，H2O+SO3 *＝H2SO4，H2SO4+2NH3＝(NH4)2SO4，2NH3+2NO2+H2O→NH4NO3+NH4NO2，NH4NO2→N2+2H2So as to realize desorption and generate nitro sulfenyl ammonium salt; and secondly, liquid water is conveyed through a high-pressure water pipe and is respectively pumped into each section of the purification layer of the main body, the liquid water is sprayed to the corresponding purification unit through the spraying holes of the desorption ring pipe, and the adsorbate is desorbed according to the principle.
And thirdly, separating ferric sulfate and ferric nitrate from the mixed solution.
Through fractional gas-mist convection mixed absorption and conversion (dilute sulfuric acid and dilute nitric acid are respectively and independently carried out in different gas-mist convection absorption sections), dilute sulfuric acid in a mist liquid absorbs aluminum oxide and ferric oxide and converts the aluminum oxide and the ferric oxide into aluminum sulfate and ferric sulfate, dilute nitric acid absorbs aluminum oxide and ferric oxide and converts the aluminum oxide and the ferric oxide into aluminum nitrate, in order to improve the purity of a regenerated product as much as possible, the invention adopts a solubility difference separation method to separate ferric sulfate from a mixed solution of ferric sulfate and aluminum sulfate, and the method realizes separation of two components by cooling the mixed solution to about 25 ℃ (according to the observation of the solubility of aluminum sulfate and ferric sulfate solutions at 25 ℃, AL2(SO4)3：38.5g/100ml，Fe2(SO4)3: 20g/100ml), when the temperature of the solution is kept to 25 ℃, the solubility difference of the two components is more than 18.5g/100ml, and when the temperature is more than 25 ℃, the solubility of the two components is gradually reduced along with the increase of the temperature; when the temperature is less than 25 ℃, the solubility of the two components is gradually reduced along with the reduction of the temperature, so the method of the invention adopts the method of keeping the temperature of the mixed solution to be 10-55 ℃, preferably 20-30 ℃, and keeping the concentration of the solution to be 20g/100ml-30g/100ml to separate the ferric sulfate from the mixed solution, and then the ferric sulfate is separated from the mixed solutionCrystallizing in one step to obtain aluminum sulfate, aluminum nitrate, ferric sulfate and ferric nitrate, or separating ferric sulfate to obtain aluminum sulfate solution and mixed solution of aluminum nitrate and ferric nitrate to obtain mother solution for subsequent treatment.
Secondly, carrying out ammonia double decomposition on the conversion solution.
According to the chemical reaction principle, ammonia gas is introduced into the aluminum sulfate solution or the mixed solution of aluminum nitrate and ferric nitrate generated in the third embodiment for double decomposition. Under an acidic environment, ammonia molecules dissolved in water ionize ammonium ions and hydroxide ions, weakly alkaline ammonium ions are combined with strongly acidic sulfate ions or nitrate ions to generate ammonium sulfate or ammonium nitrate, and hydroxide ions are combined with aluminum ions and iron ions to generate 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)3Cooling the mixed solution in a condenser to separate the aluminum hydroxide or ferric hydroxide precipitate from the ammonium sulfate or ammonium nitrate solution, further processing the aluminum hydroxide or ferric hydroxide to obtain a finished product, heating the ammonium sulfate and ammonium nitrate solution to decompose and drive out ammonia molecules, repeatedly implementing the previous mode on the clear solution containing sulfuric acid or nitric acid to absorb the aluminum oxide and ferric oxide in the smoke dust, dissolving the ammonia molecules in the mixed solution for continuous double decomposition, and circulating the steps to realize the extraction of the aluminum oxide in the fly ash.
And fifthly, extracting silicon dioxide from the fly ash impurities after extracting aluminum and iron.
The method is realized by stirring and fusing a sodium hydroxide solution and silicon dioxide in a high-speed stirring reaction kettle. According to the chemical reaction formula: 2NaOH + SlO2＝NaSlO3+H2The chemical reaction principle of O is that silicon dioxide and sodium hydroxide are proportioned according to the proportion of 1: 1.33 (according to the modulus of the product)Different requirements are additionally adjusted), the smoke dust impurities precipitated after the mixed solution is clarified are mixed with sodium hydroxide in a high-speed stirring reaction kettle, the stirring speed is kept at the rotating speed of more than 100r/sim for 40-60 minutes through a stirring mode, the sodium hydroxide and the silicon dioxide in the kettle are fused and converted in a forced contact environment, the silicon dioxide in the smoke dust is decomposed into micro powder with extremely fine granularity in the coal combustion process, the contact collision frequency with the sodium hydroxide solution is improved in the high-speed stirring state, the combination reaction speed is accelerated, the two components are converted into sodium metaaluminate through the combination time of less than 60 minutes, and the process finishes the recycling of more than 90 percent of solid pollutants.
In conclusion, the comprehensive recycling process of pollutants in high-aluminum coal flue gas purification is characterized in that a dry-wet mixed integrated flue gas purification device is combined with various processes and technologies, solid pollutants, liquid pollutants and gaseous pollutants are removed integrally on the basis of realizing the desulfurization, denitrification and dedusting of flue gas, and the physicochemical properties of the pollutants in mutual inhibition are utilized to enable the components to play advantages in mutual existence, decomposition and purification, so that the purpose of treating waste with waste is finally realized.

Claims (10)

1. A comprehensive recycling process of pollutants in high-aluminum coal flue gas purification comprises the following steps: a. producing hot air, evaporating, concentrating and desorbing liquid and decomposing liquid by utilizing the waste heat of the flue gas; b. removing sulfur oxides and nitrogen oxides in the flue gas by physical adsorption and chemical adsorption; c. removing adsorbate by a water dissolving method; d. absorbing alumina and ferric oxide in the smoke dust in the process of aerosol convection type dust removal through desorption liquid; e. the denitration effect is maximized through reoxidation and reabsorption; f. separating aluminum sulfate from ferric sulfate by solubility difference; g. preparing aluminum hydroxide by carrying out double decomposition on aluminum sulfate and aluminum nitrate by adding ammonia; h. sodium metasilicate is prepared by fusing sodium hydroxide and silicon dioxide in a high-speed stirring reaction kettle; the process is also suitable for purifying the flue gas generated by any coal combustion.
2. The process for comprehensively recycling pollutants in high-aluminum coal flue gas purification according to claim 1, wherein the waste heat utilization is to produce hot air and concentrate desorption liquid through an indirect heat exchange system;
the hot air is produced by carrying out gas-gas heat exchange on boiler flue gas in a first unit; the method is characterized in that: in the gas-gas heat exchanger, the air pipes are transversely arranged, natural wind flows in the air pipes under the action of blowing force or attraction of a fan, hot flue gas transversely passes through gaps between the pipes and exchanges heat with the natural wind in the pipes while passing through, the natural wind absorbs the heat of the flue gas through the heat transfer action of the pipe walls and moves in an S shape in the heat exchanger in a winding manner, and the temperature reaches the required standard after being repeatedly heated for many times;
the concentrated desorption liquid is the desorption liquid and the decomposition liquid concentrated by gas-liquid heat exchange of the boiler flue gas in the second unit of the heat exchanger; the method is characterized in that pipelines in the gas-liquid heat exchanger are longitudinally arranged, desorption liquid and decomposition liquid are transferred to smoke gas to absorb heat in the pipelines, high-temperature smoke gas is transversely cut into the pipelines to dissipate heat, and the desorption liquid and the decomposition liquid are evaporated and concentrated under the action of heat exchange; and water vapor or ammonia gas generated in the evaporation process is introduced into a desorption or decomposition system of adsorbate in the adsorption process through a corresponding pipeline, and concentrated solution is discharged from a bottom discharge hole intermittently and enters the next process.
3. The process for comprehensively recycling pollutants in the purification of high-alumina coal flue gas as claimed in claim 1, wherein the removal of sulfur oxides and nitrogen oxides in the flue gas by physical adsorption and chemical adsorption is realized by two ways, one of which is to complete the preliminary desulfurization and denitrification by a staggered form adsorption purification way; the method is characterized in that flue gas is sent into a staggered form series-wound adsorption purification section, passes through an adsorbent in an interlayer through a central cylinder through a densely-distributed purifier and diffuses outwards, when the flue gas passes through the adsorbent (the surface of special active carbon) to perform series-wound motion, water molecules in the flue gas and an active layer on the surface of the active carbon generate complex ionization reaction to generate hydroxyl functional groups (-OH), namely: h2O→-OH*+H+(indicates an adsorption state, -OH indicates a hydroxyl functional group), and meanwhile, oxygen molecules in the smoke are also coated on the surface of the activated carbonIs catalytically decomposed into oxygen atoms, i.e. O2→2O*(ii) a The generation of hydroxyl functional groups and oxygen atoms generates a multi-site active complex for the active center of the surface of the activated carbon, namely: -OH*、O*The nitric oxide molecules in the smoke gas rapidly obtain oxygen atoms under the action of the multi-site active complex to generate nitrogen dioxide, namely: NO + O*→NO2(ii) a Because of the high boiling point of nitrogen dioxide and sulfur dioxide molecules (NO)2The adsorbent in the purification system is special activated carbon with surface modification and surface adsorption sites of basic functional groups, SO that when flue gas passes through an adsorption layer and contacts with an adsorbent carrier, acid-base affinity is generated on the surface of the adsorbent to be quickly adsorbed, and after the adsorbent adsorbs acid molecules, the acid functional groups are generated on the surface of the adsorbent to generate affinity for the basic molecules, SO that the embodiment intakes the basic molecules through an ammonia distillation system: NH (NH)3→-NH2 *+H+(-NH2Represents an amino functional group); heating and decomposing ammonia water in an ammonia still: NH (NH)3H2O→NH3+H2And O, ammonia molecules enter the purification system along with the flue gas, and are quickly adsorbed by the adsorbent under the action of the affinity force of the acidic functional groups when passing through the adsorption purification layer: -OH*+M++X-＝-OM*+H++X-The basic molecules cover the acidic molecules in the adsorption holes, so that basic functional groups are generated on the surface of the adsorbent carrier, the basic functional groups generate affinity to the acidic molecules, and the acidic molecules are quickly adsorbed under the action of the affinity: -NH2 *+H++X-＝-NH3X*The purification of the system forms the overlapping adsorption purification of acid and alkali molecules by repeating the steps, so that the rapid removal of the nitrogen oxide and the sulfur oxide under the chemical adsorption is realized; the flue gas passes through the device body section by section from bottom to top according to a first section of series winding mode, the purification cylinders in the upper section and the lower section are distributed in a staggered manner, the same series winding type adsorption is carried out through densely distributed purifiers in the passing process, and SO in the flue gas2Is preferentially adsorbed due to polarity, boiling point and activity higher than other moleculesPhysical adsorption), part of NO is oxidized into NO under the action of active complex on the surface of the adsorption layer2The flue gas is purified by a plurality of superposed purification layers to achieve the purpose of first-stage purification;
secondly, the maximum removal of nitrogen oxides is realized through reoxidation and reabsorption, wherein the reoxidation is to introduce the flue gas into an oxidation box, a catalytic carrier made of open-cell foam glass is installed in the oxidation box according to a certain specification, and a composite purification structure is formed by an oxidation section and a series winding type adsorption purification section;
the reoxidation is realized in the following way: pouring an oxidant into the catalytic carrier in a re-oxidation section in a spraying mode, wherein the oxidant flows in the catalytic carrier to form a liquid film of a foam glass ball wall, when the flue gas passes through the catalytic carrier, nitric oxide in the flue gas is contacted with the oxidant of the ball wall, oxygen atoms in the flue gas are rapidly absorbed and oxidized into nitrogen dioxide, and the nitrogen dioxide is adsorbed (physically adsorbed) by the adsorbent when passing through the series-wound adsorption system;
the oxidant includes but is not limited to sodium hypochlorite, sodium chlorite, dilute nitric acid, etc., and the concentration of the oxidant is 5-25%.
4. The process for comprehensive recovery and utilization of pollutants in high-alumina coal flue gas purification as claimed in claim 1, wherein the adsorbate is removed by a water-soluble method, wherein the adsorbate of the shunt purification system is dissolved by gaseous water molecule infiltration, and the adsorbate in the main body superposed purification system is dissolved by liquid water molecule group showering; the method is characterized in that: the vapor passes through the steam distributor and lets in along separate routes clarifier in turn, soaks in the adsorption hole of active carbon under the effect of its diffusion force, and it is converted with the adsorption mass fusion to make neogenetic molecule produce the effect of expansion force in the formation in-process and push out the adsorption hole with self and dissolve in the hydrone group again, promptly: SO (SO)2 *+O*＝SO3 *，H2O+SO3 *＝H2SO4，H2SO4+2NH3＝(NH4)2SO4，2NH3+2NO2+H2O→NH4NO3+NH4NO2，NH4NO2→N2+2H2O, so as to realize desorption and generate nitro sulfenyl ammonium salt; and secondly, liquid water is conveyed through a high-pressure water pipe and is respectively pumped into each section of the purification layer of the main body, the liquid water is sprayed to the corresponding purification unit through the spraying holes of the desorption ring pipe, and the adsorbate is desorbed according to the principle.
5. The process of claim 1, wherein the adsorption of alumina and iron oxide in flue gas is carried out by a gas-liquid convection absorption method in the gas-mist convection dust removal section, and the adsorption of alumina and iron oxide in flue gas is carried out by: the flue gas passes through the distribution of flue gas distributor and makes the balanced ascending of atmospheric pressure produce the convection current contact with the desorption liquid of high pressure nozzle atomizing in the first order aerial fog convection dust removal section, and the smoke and dust is dissolved in desorption liquid and is flowed to the collecting region down, and the flue gas is in the convection current contact with the desorption liquid that has atomized, and dilute sulphuric acid or dilute nitric acid in the desorption liquid absorb aluminium oxide and ferric oxide in the smoke and dust, produce following chemical reaction: 3H2SO4+AL2O3＝AL2(SO4)3+3H2O；2AL2O3+12HNO3＝4AL(NO3)3+6H2O；3H2SO4+Fe2O3＝Fe2(SO4)3+3H2O；3HNO3+Fe2O3＝2Fe(NO3)3+3H2O。
6. The process of claim 1, wherein the fume-convective dust-removing section is a system comprising several sections for wet dust removal and absorption of effective components in the fume in the integrated purification device, and the desorption liquid of different components is operated to absorb the effective components in the fume separately; the device is characterized in that: the top is provided with a high-pressure atomizing device, the bottom is provided with a flue gas distribution system, and flue gas ascends through the flue gas distribution system at the bottom and makes convection contact movement with atomized liquid drops at the top; the flue gas distribution system is characterized in that: a plurality of mushroom cap air distributors are distributed on a chassis of the aerosol convection dust removal section according to a certain proportion, smoke at the lower part enters the mushroom caps from the central pipe and is discharged from the peripheral air outlet pipe, and the effects of the mushroom cap air distributors are that the smoke is uniformly distributed on one hand, and spray liquid at the upper part is prevented from flowing into a lower device on the other hand.
7. The process for comprehensively recycling pollutants in the purification of high-alumina coal flue gas as claimed in claim 1, wherein the aluminum sulfate and the ferric sulfate are separated through the difference of solubility, in order to improve the purity of the regenerated products as much as possible, the ferric sulfate is separated from the mixed solution of the ferric sulfate and the aluminum sulfate by adopting a solubility difference separation method; the method realizes the separation of two components by cooling the mixed solution to 10-55 ℃, and is observed according to the solubility of aluminum sulfate and ferric sulfate solution at 25 ℃: AL2(SO4)3：38.5g/100ml，Fe2(SO4)3: 20g/100ml, the change in solubility of the two components in solution is characterized by: when the temperature of the solution is kept to 25 ℃, the solubility difference of the two components is more than 18.5g/100ml, when the temperature is more than 25 ℃, the solubility of the two components is gradually reduced along with the rise of the temperature, and when the temperature is less than 25 ℃, the solubility of the two components is gradually reduced along with the reduction of the temperature, so that the method of the invention adopts the steps of keeping the temperature of the mixed solution to 10-55 ℃, preferably 20-30 ℃, and keeping the concentration of the mixed solution to 20g/100ml-25g/ml, so as to separate ferric sulfate from the mixed solution, and further respectively crystallize to prepare the finished products of aluminum sulfate, aluminum nitrate, ferric sulfate and ferric nitrate; or the aluminum sulfate solution after separating ferric sulfate and the mixed solution of aluminum nitrate and ferric nitrate become the mother solution of double decomposition treatment.
8. The process of claim 1, wherein the aluminum hydroxide is prepared by double decomposition of aluminum sulfate and aluminum nitrate with ammonia according to the chemical reaction principle: 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(ii) a Introducing ammonia gas generated by an ammonia distillation system of an indirect heat exchanger into an aluminum sulfate solution or a mixed solution of aluminum nitrate and ferric nitrate generated in the previous process for double decomposition; under an acidic environment, ammonia molecules dissolved in water ionize ammonium ions and hydroxide ions, weakly alkaline ammonium ions are combined with strongly acidic sulfate ions or nitrate ions to generate ammonium sulfate or ammonium nitrate, and hydroxide ions are combined with aluminum ions and iron ions to generate aluminum hydroxide and iron hydroxide;
further cooling the mixed solution in a condenser to separate aluminum hydroxide or ferric hydroxide precipitate from ammonium sulfate or ammonium nitrate solution; further processing the aluminum hydroxide or the ferric hydroxide into a finished product;
heating ammonium sulfate and ammonium nitrate solution to decompose and drive out ammonia molecules, and repeatedly carrying out aerosol convection on clear liquid containing sulfuric acid or nitric acid to absorb aluminum oxide and ferric oxide in smoke dust; dissolving ammonia molecules in the mixed solution for continuous double decomposition, and circulating the solution in turn to realize the extraction of the aluminum oxide in the fly ash.
9. The process for comprehensively recycling pollutants in the purification of high-alumina coal flue gas as claimed in claim 1, wherein the preparation of sodium metasilicate by the fusion of sodium hydroxide and silica in a high-speed stirring reaction kettle is realized by the strong stirring and fusion of sodium hydroxide solution and silica in a high-speed stirring reaction kettle according to the chemical reaction formula: 2NaOH + SIO2 (NaSIO 3+ H2O); the method comprises the steps of proportioning silicon dioxide and sodium hydroxide according to the proportion of 1: 1.33, (adjusting according to different modulus requirements of products); the method comprises the steps of mixing the smoke dust impurities precipitated after the mixed solution is clarified with sodium hydroxide in a high-speed stirring reaction kettle, keeping the stirring speed at a rotating speed of more than 100r/sim for reacting for 40-60 minutes in a stirring mode, and fusing the sodium hydroxide and the silicon dioxide in the kettle in a forced contact environment to convert into sodium metaaluminate.
10. The process of claim 1, which is also suitable for the purification of any coal-fired flue gas.
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