CN113148961B - System and process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum - Google Patents
System and process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum Download PDFInfo
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- CN113148961B CN113148961B CN202110348614.9A CN202110348614A CN113148961B CN 113148961 B CN113148961 B CN 113148961B CN 202110348614 A CN202110348614 A CN 202110348614A CN 113148961 B CN113148961 B CN 113148961B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/501—Preparation of sulfur dioxide by reduction of sulfur compounds
- C01B17/506—Preparation of sulfur dioxide by reduction of sulfur compounds of calcium sulfates
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/48—Sulfur dioxide; Sulfurous acid
- C01B17/50—Preparation of sulfur dioxide
- C01B17/56—Separation; Purification
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/69—Sulfur trioxide; Sulfuric acid
- C01B17/74—Preparation
- C01B17/76—Preparation by contact processes
- C01B17/80—Apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
- F23C10/04—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone
- F23C10/08—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed the particles being circulated to a section, e.g. a heat-exchange section or a return duct, at least partially shielded from the combustion zone, before being reintroduced into the combustion zone characterised by the arrangement of separation apparatus, e.g. cyclones, for separating particles from the flue gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/18—Details; Accessories
- F23C10/22—Fuel feeders specially adapted for fluidised bed combustion apparatus
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23J—REMOVAL OR TREATMENT OF COMBUSTION PRODUCTS OR COMBUSTION RESIDUES; FLUES
- F23J15/00—Arrangements of devices for treating smoke or fumes
- F23J15/06—Arrangements of devices for treating smoke or fumes of coolers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
- F23L15/00—Heating of air supplied for combustion
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E20/00—Combustion technologies with mitigation potential
- Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/10—Process efficiency
- Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines
Abstract
The invention discloses a system and a process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum, and relates to the technical field of phosphogypsum resource utilization. The fine control of the ratio of calcium sulfide to calcium sulfate in the first-stage reduction product is realized through phosphogypsum, coal-fired proportioning and returning control. The first stage of reduction adopts dry purification, namely limestone (or calcium oxide) powder and urea are used for fixing and removing SO generated by coal combustion or phosphogypsum roasting 2 、H 2 S、NO x 、SO 3 Harmful components such as acid mist and fluorine. The two-stage oxidizing roasting is no longer added with fire coal, and the heat balance and the reaction temperature of the system can be maintained only by the system heat such as self-oxidizing heat release of calcium sulfide, SO as to improve SO 2 The purpose of flue gas purity and concentration omits the wet water washing or acid washing purification procedure of the two-stage oxidizing roasting flue gas and the one-stage circulating reduction tail gas, meets the air inlet requirement or the tail gas emission requirement of a flue gas decomposition phosphorus ore pulp or sulfuric acid preparation converter, greatly shortens the flow, and reduces the investment, the energy consumption and the production cost.
Description
Technical Field
The invention relates to the technical field of phosphogypsum resource utilization, in particular to a system and a process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum.
Background
Phosphogypsum is a byproduct of wet-process phosphoric acid production, and 1 ton of phosphoric acid (P) is produced by adopting a dihydrate process 2 O 5 Calculated by weight), the byproduct of 4-5 tons of phosphogypsum dihydrate, the main component of which is calcium sulfate dihydrate. At present, most phosphogypsum is used as general solid waste to be piled up in a special slag yard, the construction of the slag yard occupies a large area, the seepage-proofing requirement is high, the investment is high, the operation cost is high, and the environment-friendly risk exists. In recent years, a series of policies on phosphogypsum utilization are put on the way in China and places, and the demand for the phosphogypsum utilization rate is increasing. In order to realize the continuous healthy development of the phosphorus compound fertilizer industry, phosphogypsum can be used for preparing high-concentration sulfur dioxide gas for producing sulfuric acid and wet-process phosphoric acid, and meanwhile, the byproduct of cinder is produced. Wherein, sulfuric acid is recycled for producing phosphoric acid and phosphorus compound fertilizer; the byproduct cinder can be used as an active cementing material, chemical raw materials and the like, and can be used in industries of cement, building materials, chemical industry and the like, thereby realizing the recycling and efficient utilization of sulfur and calcium resources in phosphogypsum, and having practical value and important significance.
The above-mentioned process can be implemented by a one-stage method or a two-stage method. The one-stage technology is to complete two main processes of reducing decomposition of coal to phosphogypsum and oxidizing roasting of the reduction product in the same kiln and furnace. CN11377625a discloses a comprehensive utilization process and device for phosphogypsum by reduction roasting in a circulating fluidized bed, wherein coal and phosphogypsum are added at the lower part of a dense phase zone of the fluidized bed, reduction reaction is carried out under the action of primary air, secondary air enters from the upper part of the dense phase zone, and the reduced materials are oxidized, but the following problems exist: (1) In the same equipment, the oxidizing atmosphere and the reducing atmosphere are difficult to be simultaneously considered and controlled, the reduction of phosphogypsum decomposition rate caused by partial oxidizing atmosphere and incomplete combustion of coal in partial reducing atmosphere are easy to occur, and more carbon monoxide and sublimated sulfur gas can be generated to enter a post-system to cause the problems of process and safety; (2) In the production process, a large amount of harmful impurity components such as carbon dioxide, water and the like and fluorides and the like generated by phosphogypsum roasting are generated by coal combustion, and the concentration of sulfur dioxide in kiln and furnace flue gas is obviously diluted, so that the strict requirements of a sulfuric acid device conversion process on the aspects of flue gas purity, sulfur dioxide concentration and the like are difficult to meet, a roasting flue gas purification process with a complex flow is required to be arranged in a single-stage process, the flue gas is subjected to water washing or acid washing purification, and after purification, the flue gas is subjected to drying, the flue gas can enter a sulfuric acid device conversion system to produce sulfuric acid, and the process flow is complex, the investment is large, the energy consumption and the production cost are high, and the washing liquid generated by water washing and acid washing purification is easy to bring new environmental protection problems.
At present, the existing two-stage technology is to separate the reduction decomposition of coal to phosphogypsum to prepare a mixture of calcium sulfide and calcium sulfate and the oxidizing roasting process of the mixture, so that the problem (1) existing in the one-stage technology is solved, but coal is added again during the oxidizing roasting of the mixture in the second stage, more carbon dioxide, water and the like are produced during combustion, and the problems of more harmful impurity components in flue gas, obvious concentration of sulfur dioxide in the flue gas and the like exist, so that the existing two-stage technology also needs to be provided with a water washing or acid washing purification process with a long flow, firstly, the flue gas in the reduction stage can be purified and then can reach the standard and be discharged, secondly, the flue gas in the roasting stage can be purified and then enter a sulfuric acid device conversion system to produce sulfuric acid after being dried, the technology has long flow, large investment, high energy consumption and production cost, and the washing liquid produced by water washing and acid washing purification is easy to bring new environmental protection problems.
It can be seen that the problems and defects in the prior art are serious limitations of the phosphogypsum to prepare high-concentration and high-purity sulfur dioxide flue gas, and further development and application of sulfuric acid preparation technology become important problems to be solved urgently.
Disclosure of Invention
The aim of the invention is achieved by the following technical scheme. Unless otherwise indicated, percentages of the various gas components referred to herein are by volume and percentages of the various solid components are by mass.
The invention aims to provide a system and a process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum, which solve the problems that in the prior art, the reducing and oxidizing atmosphere is difficult to control, the sulfur dioxide concentration and purity of roasting flue gas are low, the requirement of the air intake of a sulfuric acid device conversion system is difficult to meet, special washing or pickling purification procedures with complex flow are required, firstly, the flue gas of a roasting section is purified to remove acid mist, fluorine and other harmful impurities, and then the flue gas is dried and then enters the sulfuric acid device conversion system to produce sulfuric acid, and secondly, the flue gas of a reduction section is washed or pickled to remove SO 2 、H 2 S、SO 3 The acid mist and fluorine harmful impurities can be discharged after reaching the standard, so that the whole process flow is complex and long, the investment is large, the energy consumption and the production and operation cost are high, the production cost is high, and the washing liquid produced by water washing and acid washing purification is easy to bring new environmental protection problems and the like.
In order to solve the technical problems, the invention adopts the following technical scheme: a system for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum is characterized in that: the device comprises a circulating fluidized bed, a first cyclone separator, a second cyclone separator, a first combustion device, a first air preheater, a first bag-type dust remover and a first fan which are sequentially connected, wherein a discharge hole of the circulating fluidized bed is sequentially connected with a buffer bin and a bubbling fluidized bed, an exhaust hole of the bubbling fluidized bed is sequentially connected with a third cyclone separator, a second combustion device, a second air preheater, a second bag-type dust remover and a second fan, and a discharge hole of the bubbling fluidized bed is connected with a roller slag cooler and a rollerA cinder storage bin is connected with a discharge hole of the cinder cooler; the second bag-type dust collector discharge port is connected with the cinder storage bin, and the first cyclone separator, the second cyclone separator and the first bag-type dust collector discharge port are all connected with the buffer bin; the hot air outlet of the first air preheater is respectively connected with the first combustion device and the air inlet of the circulating fluidized bed; and the hot air outlet of the second air preheater is respectively connected with the second combustion device and the air inlet of the bubbling fluidized bed. Limestone (or calcium oxide) powder is added into a circulating fluidized bed to fix and remove SO generated by burning coal and small amount of phosphogypsum decomposition 2 、H 2 S、SO 3 Harmful impurities such as fluorine.
The further technical scheme is that the buffer bin is a hollow bin body, and a flow control valve is arranged at a discharge hole.
The further technical scheme is that the discharge port of the first cyclone separator is connected with the feed port of the circulating fluidized bed, so that the accurate control of the material returning quantity and the proportion of calcium sulfide to calcium sulfate in the discharge of the circulating fluidized bed is realized.
The further technical scheme is that the first combustion device is hollow and cylindrical, and the waste heat recovery water pipe is arranged on the outer side wall of the first combustion device. Urea is added to the first combustion device to remove Nitrogen Oxides (NO) produced by the combustion of the coal x ) And the like.
The further technical scheme is that the second combustion device is hollow and cylindrical, and the waste heat recovery water pipe is arranged on the outer side wall of the second combustion device.
A further technical proposal is that no coal is added into the bubbling fluidized bed.
The invention also discloses a process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum, which is characterized by comprising the following steps:
s1, phosphogypsum, fire coal and limestone (or calcium oxide) powder are added into a circulating fluidized bed, preheated air is introduced, the reaction temperature is kept at 805-950 ℃, and CaSO is controlled 4 The reduction rate is 55-75% (corresponding to the ratio of calcium sulfide to calcium sulfate in the reaction material), the obtained reaction material is fed into buffer bin, and the flue gas is separated by first cyclone separator and second cyclone separatorAfter solid phase particles are separated, the flue gas enters the first combustion device to burn out, and urea solution is sprayed into the first combustion device to remove NO x The method comprises the steps of carrying out a first treatment on the surface of the The burnt flue gas exchanges heat with air in the first air preheater, and is discharged through a first fan after being dedusted by a first bag-type dust remover;
s2, materials in the buffer bin enter a bubbling fluidized bed through a flow control valve, preheated air is introduced, the operation temperature is controlled to be 1100-1250 ℃, mixed gas of the cinder and sulfur dioxide after reaction is obtained, and the cinder enters a cinder storage bin for storage after being cooled by a roller cinder cooler; after solid phase particles of the sulfur dioxide mixed gas are separated by a third cyclone separator, the sulfur dioxide mixed gas enters into the combustion ashes in the second combustion device, after the burnt sulfur dioxide mixed gas exchanges heat with air in the second air preheater, the sulfur dioxide mixed gas enters into SO after being dedusted by a second cloth bag deduster 2 A phosphorite decomposing device or a sulfuric acid device conversion system.
According to a further technical scheme, one part of solid particles obtained after separation by the first cyclone separator is sent into a buffer bin, and the other part of the solid particles is returned into the circulating fluidized bed as return materials.
The further technical proposal is that the mass ratio of phosphogypsum to fire coal in the step S1 is 0.8-1.5, and the addition amount of limestone (or calcium oxide) powder is 1.0-9.0% of the mass of phosphogypsum.
A further technical proposal is that no coal is added into the bubbling fluidized bed.
A further technical proposal is that the temperature of the preheated air is 500 ℃.
Working principle:
phosphogypsum as reducing fuel and limestone (or calcium oxide) powder for removing sulfur and other impurities in the coal and furnace are metered by a feeding device and then fed into a circulating fluidized bed, the coal and the fed hot air undergo combustion gasification reaction, and CO and hydrogen (H) are generated while heat is released 2 ). The operation temperature of the circulating fluidized bed is maintained at about 850-950 ℃, and part of CaSO is in the circulating fluidized bed 4 Reducing CO and hydrogen generated by burning and gasifying fire coal to make CaSO 4 Reducing to CaS and simultaneously adding calcium oxideThe powder or the calcium oxide powder produced by calcining the added limestone powder is burnt with the sulfur contained in the fire coal to gasify the H 2 S and SO 2 And fluorine generated by phosphogypsum roasting, and the like, and react to generate CaS and CaSO 4 And CaF 2 And the reaction products carried by the flue gas in the circulating fluidized bed and residual particles such as coal enter the first cyclone separator, the separated material particles are directly shunted into the bubbling fluidized bed through the buffer bin, and part of the material particles are returned to the circulating fluidized bed as return materials by the return device and are continuously combusted, gasified and reduced. During operation, the CaSO in the discharge of the circulating fluidized bed can be controlled by the addition amount and the proportion of phosphogypsum and coal in the added reaction materials and the return amount 4 To control the reduction rate of CaS and CaSO in the bubbling fluidized bed 4 Is a ratio of (2).
The flue gas enters the combustion device after passing through the first cyclone separator and the second cyclone separator, and is mixed with hot air from the air preheater, so that the flue gas can be spontaneously combusted, a small amount of combustible gases such as CO and the like contained in the flue gas and unconverted carbon particles are burnt out, and a small amount of CaS carried by the flue gas is reoxidized into CaSO at the operating temperature 4 Recovering the heat energy and ensuring the subsequent tail gas to reach the standard. In order to control the emission concentration of nitrogen oxides (NOx) in the combustion process, urea solution is injected into a combustion device for denitration (NOx) treatment. After exchanging heat between flue gas in the combustion device and the waste heat recovery water pipe on the side wall, the flue gas enters the air preheater to exchange heat with cold air introduced by the fan, and the air respectively entering the circulating fluidized bed and the combustion device is heated to about 300-500 ℃. The cooled flue gas is discharged through a fan after being dedusted by a cloth bag. And sending the solid particles collected by bag dust removal into a buffer bin.
The main chemical reactions occurring in the circulating fluidized bed reduction process are as follows:
C+2H 2 O＝CO 2 +2H 2
C+1/2O 2 ＝CO
CO+H 2 O＝CO 2 +H 2
CaSO 4 +4CO＝CaS+4CO 2 (-171kj/mol)
CaSO 4 +4H 2 ＝CaS+4H 2 O(-17kj/mol)
CaSO 4 +2C＝CaS+CO 2 (+171kj/mol)
CaSO 4 +CO＝CaO+CO 2 +SO 2 (+219kj/mol)
CaSO 4 +H 2 ＝CaO+H 2 O+SO 2 (+260kj/mol)
CaO+H 2 S＝CaS+H 2 O
CaO+SO 2 +1/2O 2 CaSO 4
NO+CO(NH 2 ) 2 +1/2O 2 ＝2N 2 +CO 2 +H 2 O
the materials in the buffer bin are sent into the bubbling fluidized bed through a flow control valve according to the requirements, wherein a part of CaS and a small amount of carbon particles carried in together with the CaS and a proper amount of hot air preheated by a preheater are subjected to oxidation reaction to release heat, and the reaction temperature of the bubbling fluidized bed is maintained at about 1100-1250 ℃; at the same time, the unoxidized portions of CaS and CaSO 4 Reaction takes place to produce SO 2 Flue gas and roasting slag (a mixture of CaO, etc.). High concentration SO produced by bubbling fluidized bed 2 The flue gas enters the combustion device, contacts with excessive hot air from the air preheater, and spontaneous combustion occurs at high temperature, so that a small amount of S, a small amount of combustible gas and other substances existing in the flue gas are burnt out. The generated high-temperature flue gas enters an air preheater, exchanges heat with cold air sent by a fan, and the heated air is respectively sent into a bubbling fluidized bed and a combustion device, and the cooled flue gas can be directly sent into high-concentration SO after being dedusted by a cloth bag without purification and drying 2 Preparing wet-process phosphoric acid reaction slurry by a flue gas phosphorite decomposing device, and further producing wet-process phosphoric acid; since the flue gas has reached the purity of the sulfuric acid plant converter inlet air and SO 2 The process requirements such as concentration and the like can also be directly sent into a sulfuric acid device converter (catalytic oxidation unit) to produce sulfuric acid. Discharging of bubbling fluidized bed and collecting by cloth bag dust removerAnd after the obtained solid-phase particles are combined, cooling the solid-phase particles by a roller slag cooler, and conveying the solid-phase particles into a cinder storage bin.
The main chemical reactions occurring in the bubbling fluidized bed oxidative roasting apparatus are as follows:
CaS+3CaSO 4 ＝4CaO+4SO 2 (-105kj/mol)
2CaS+3O 2 ＝＝2CaO+2SO 2 (+915kj/mol)
2CaSO 4 ＝2CaO+O 2 +2SO 2 (-1006kj/mol)
CaSO 4 +2C＝CaS+2CO 2 (-171kj/mol)
compared with the prior art, the invention has the beneficial effects that:
(1) The circulating fluidized bed with strong heat and mass transfer characteristics is adopted as a reduction device, and the ratio of phosphogypsum to fire coal and the reaction condition are controlled, and the control of the return material quantity ratio of the circulating fluidized bed is combined to realize the CaS and CaSO in the discharged materials 4 Fine control of the ratio; by utilizing the characteristics of a circulating fluidized bed, limestone (or CaO) powder is added for reaction fixation and H in the flue gas is removed 2 S、SO 2 Harmful components such as fluorine; combustible gases such as a small amount of CO, H2 and the like contained in the flue gas and a small amount of carbon residue are burnt out through the first combustion device, a small amount of CaS carried by the flue gas is oxidized, the heat is recovered, and the influence of the small amount of CO, H2, caS and the like on the safety and emission of the subsequent process is eliminated; meanwhile, urea solution is sprayed into the first combustion device, the temperature of the combustion chamber is controlled, the reaction is carried out, nitrogen oxides are converted into nitrogen (N2), and the concentration and the content of the nitrogen oxides in the flue gas are reduced. I.e. in the implementation of CaSO 4 And the dry purification is adopted to remove pollutants such as sulfide, oxysulfide and nitrogen oxide in the flue gas while the reduction is controlled, and a complex tail gas water washing (or acid washing) wet purification process is not required, so that the investment, the energy consumption, the production and operation costs and the production cost are reduced.
(2) By calculating the heat balance of the system, the bubbling fluidized bed is used as an oxidizing roasting device, and fuel coal is not required to be added again. Can be controlled finely by adding phosphogypsum and coal in the reaction material of the circulating fluidized bedRealize CaSO in the discharge of the circulating fluidized bed (namely bubbling fluidized bed feeding) 4 Reduction rate (corresponding to CaS and CaSO) 4 The ratio) of the catalyst to the catalyst, and the conditions of maintaining the heat balance of the system and the temperature required by the reaction can be achieved by only relying on heat such as heat release of CaS oxidation in the bubbling fluidized bed.
Introducing preheated air into bubbling fluidized bed, oxidizing part of CaS, small amount of carbon residue, etc. in the feed material at high temperature to release heat, and the rest of CaS and CaSO 4 Reacting to obtain high-concentration SO 2 Flue gas, caO and the like. By controlling the CaS and CaSO in the feed 4 At the same time, the proper oxidizing atmosphere is controlled to lead CaS to be equal to O 2 Exothermic reactions of oxidation with CaS versus CaSO take place 4 The reduction endothermic reaction of (2) is carried out simultaneously according to a certain proportion, the self-heating reaction is utilized to maintain the heat balance of the system, the reaction is continuously carried out, the addition of fuel coal in the bubbling fluidized bed oxidation roasting procedure is not needed, and the generation of a large amount of CO in the combustion of the fuel coal is avoided 2 And H 2 O, resulting in flue gas requiring wet water or acid cleaning, purification, drying and SO 2 The concentration is diluted, and the like, and obviously improves SO 2 The gas concentration ensures that the flue gas produced by the bubbling fluidized bed is dry flue gas with purity meeting the requirement of converting and air intake of the sulfuric acid device, omits a flue gas wet purification and drying system with a complex flow, greatly shortens the flow, saves investment, and reduces energy consumption, production and operation costs and production cost. Meanwhile, a small amount of S and a small amount of combustible gas existing in the flue gas are burnt out in the second combustion device, heat energy is recovered, and the influence of the small amount of S and the combustible gas on the safety and emission of the subsequent process is eliminated.
(3) The high-temperature flue gas of the circulating fluidized bed reduction device and the bubbling fluidized bed oxidizing roasting device is subjected to the processes of burning out and waste heat recovery, and the heat energy is recycled step by the roller slag cooler, SO that the heat efficiency is high, the comprehensive energy consumption and the production cost of the production device are obviously reduced, and the phosphogypsum is efficiently decomposed and prepared into high-concentration and high-purity SO (sulfur dioxide) at low cost 2 Flue gas.
(4) Decomposing the high-concentration and high-purity SO in a bubbling fluidized bed oxidizing roasting device (furnace) 2 The flue gas does not need to be purified and dried, and is savedThe complex and long water washing (or acid washing) purification and drying process is removed, and the high-concentration SO can be directly sent into 2 The wet phosphoric acid reaction slurry device is used for preparing wet phosphoric acid by decomposing phosphorus ore slurry by flue gas, so as to further produce wet phosphoric acid, or the wet phosphoric acid is directly sent to a sulfuric acid device converter to prepare sulfuric acid, and meanwhile, the byproduct of cinder is produced.
Drawings
Fig. 1 is a functional block diagram of an inventive system.
In the figure: 1-circulating fluidized bed, 2-first cyclone separator, 3-second cyclone separator, 4-first combustion device, 5-first air preheater, 6-first cloth bag dust collector, 7-first fan, 8-third cyclone separator, 9-second combustion device, 10-second air preheater, 11-second cloth bag dust collector, 12-second fan, 13-roller slag cooler, 14-buffer bin, 15-bubbling fluidized bed.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The invention will be further described with reference to the accompanying drawings and examples, which are not intended to limit the technical scope of the invention. All changes made based on the derivation of the invention are intended to fall within the scope of the invention.
A system and process for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum are specifically shown in figure 1 (10 ten thousand tons of phosphogypsum are used for preparing high-concentration SO per year) 2 Examples of industrial test devices).
Example 1
Fig. 1 shows a system for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum, which comprises a circulating fluidized bed 1, a first cyclone separator 2, a second cyclone separator 3, a first combustion device 4, a first air preheater 5, a first bag-type dust collector 6 and a first fan 7 which are sequentially connected, wherein a discharge port of the circulating fluidized bed 1 is sequentially connected with a buffer bin 14 and a bubbling fluidized bed 15, an exhaust port of the bubbling fluidized bed 15 is sequentially connected with a third cyclone separator 8, a second combustion device 9, a second air preheater 10, a second bag-type dust collector 11 and a second fan 12, a discharge port of the bubbling fluidized bed 15 is connected with a roller slag cooler 13, and a discharge port of the roller slag cooler 13 is connected with a cinder storage bin; the discharge port of the second bag-type dust collector 11 is connected with a cinder storage bin, and the discharge ports of the first cyclone separator 2, the second cyclone separator 3 and the first bag-type dust collector 6 are all connected with a buffer bin 2; the hot air outlet of the first air preheater 5 is respectively connected with the first combustion device 4 and the air inlet of the circulating fluidized bed 1; the hot air outlet of the second air preheater 10 is connected with the air inlets of the second combustion device 9 and the bubbling fluidized bed 15 respectively. The buffer bin 14 is a hollow bin body, a flow control valve is arranged at the bottom discharge hole, and the amount of materials entering the bubbling fluidized bed 15 is controlled through the flow control valve, so that the accurate control of the system is facilitated.
In order to facilitate the addition of the return materials, the discharge port of the first cyclone separator 2 is connected with the feed port of the circulating fluidized bed 1. One part of the solid particles obtained after the separation of the first cyclone separator 2 is sent into the buffer bin 14, and the other part is sent into the circulating fluidized bed 1, so that the reduction rate of phosphogypsum in the circulating fluidized bed 1 is further controlled through returning charge.
In order to fully utilize the waste heat of combustion, the first combustion device 4 and the second combustion device 9 are hollow cylinders, and waste heat recovery water pipes are arranged on the outer side walls of the cylinders. The burnt high-temperature gas transfers heat to the water in the waste heat recovery water pipe, and heats the water into high-temperature and high-pressure steam for production, so that the production energy consumption can be greatly saved.
Example 2
Phosphogypsum (component: caSO) 4 ·2H 2 O content 88.0%, siO 2 10.0% of the content) of phosphogypsum (dihydrate dry basis) is mixed with fire coal and added into the circulating fluidized bed 1, the feeding amount of the phosphogypsum (dihydrate dry basis) is 12500kg/h, the feeding amount of the fire coal is 8920kg/h, and the mass ratio of the phosphogypsum to the fire coal is 1.40:1.00; limestone powder is added into the circulating fluidized bed 1, the feeding amount is 753kg/h, and the feeding amount of the limestone powder is 6.02 percent of the feeding amount of phosphogypsum. Air with the preheating temperature of 500 ℃ is introduced into the bottom of the circulating fluidized bed 1, and the air quantity is 16735Nm 3 /h; the fire coal and the hot air are burnt and gasified, and the heat is releasedAt the same time, CO and H are produced 2 . The operation temperature of the circulating fluidized bed is maintained at 900 ℃, and a part of CaSO in the materials in the furnace is maintained 4 Is covered by C, CO, H 2 Reduction to CaS, caSO 4 The reduction rate of (2) is 58%, and CaO produced by roasting and decomposing limestone and H produced by burning sulfur-containing coal 2 S and SO 2 Reacting to form CaS and CaSO 4 The CaS amount was 2661kg/h.
After the reaction, the flue gas enters a second cyclone separator 3 for further separation after passing through a first cyclone separator 2, part of solid particles collected by the first cyclone separator 2 is returned to the circulating fluidized bed 1 as return materials, and the other part of the solid particles enter a buffer bin 14; the solid particles collected by the second cyclone separator 3 enter a surge bin 14, the flue gas at the outlet of the second cyclone separator 3 enters the first combustion device 4, excessive after-combustion air is introduced, and the total amount is 3102Nm 3 Controlling the temperature of the combustion chamber to about 900 ℃, burning a small amount of combustible gases such as CO and the like contained in the flue gas and a small amount of carbon residue, and re-oxidizing a small amount of CaS carried by the flue gas into CaSO 4 The urea solution is added to denitrate the flue gas, and the total amount of the flue gas in the first combustion device 4 is 32673Nm 3 /h，SO 2 The concentration was 28mg/Nm 3 ，NO x The concentration was 48mg/Nm 3 (reaching emission standards); after the waste heat is subjected to heat exchange and cooling to about 650 ℃ through a waste heat recovery water pipe, the waste heat enters a first air preheater 5, the air entering the circulating fluidized bed 1 is heated to about 500 ℃, the temperature of flue gas is reduced to about 160 ℃, and the flue gas is discharged after being dedusted through a first cloth bag device 6 and then is exhausted through a first fan 7, so that the exhaust reaches the standard; the first bag-type dust collector 6 is collected and enters a surge bin 14. And the boiler recovers waste heat and byproducts superheated steam.
The amount of the material fed into the bubbling fluidized bed 15 is 9137kg/h through a flow control valve of the buffer bin 14, and a part of CaS particles and a small amount of carbon residues contained in the material and the fed high-temperature drying air are subjected to oxidation combustion reaction to emit heat, so that the reaction temperature of the bubbling fluidized bed 15 is maintained at about 1200 ℃; at the same time, the remaining CaS and CaSO 4 Reaction takes place to produce CaO and SO 2 . To control the atmosphere in bubbling fluidized bed 15 to facilitate CaSO 4 The amount of the preheated air is calculated by the theoretical amount, and the air quantity is 6741Nm 3 /h，The temperature was 500 ℃.
Dry high concentration SO produced by bubbling fluidized bed 15 2 The mixed gas enters a third cyclone separator 8 for dust collection, byproduct cinder is sent into a roller cinder cooler 13, and the separated SO 2 The mixed gas enters a second combustion device 9, dry hot air is introduced by adopting graded air supply, the temperature of the combustion chamber is controlled to 1200 ℃, and a small amount of sulfur and combustible gas in the flue gas are combusted. SO in flue gas 2 The concentration is 18.5%, the flue gas is subjected to heat energy recovery through a waste heat recovery water pipe and then enters a second air preheater 10 for air preheating, the preheated dry air is sent to a bubbling fluidized bed 15 and ashes and a second combustion device 9 for oxygenizing combustion, and meanwhile, the flue gas is cooled to about 180 ℃, and then enters a second bag-type dust collector 11 for dust removal and purification (dust collection is carried out to byproduct cinder), SO that high-concentration SO is obtained 2 Gas, smoke volume 7027Nm 3 And/h, delivering the mixture to high-concentration SO through a booster fan 2 The flue gas is decomposed the phosphorite device to prepare the phosphoric acid reaction slurry device of wet process, then is used for producing phosphoric acid of wet process; because it has reached the technological requirement of preparing sulfuric acid, it can also be directly fed into catalytic oxidation unit (converter) of sulfuric acid-preparing device to produce sulfuric acid.
The bubbling fluidized bed 15 discharges the cinder and enters a roller cinder cooler 13 for heating boiler water supply, and a byproduct cinder product (the effective CaO content is 65.0 percent, siO) is obtained after cooling 2 Content 30.0%); the yield of the by-product superheated steam of the first combustion device 4 and the second combustion device 9 is 14.55t/h, and the parameters are 450 ℃ and 3.82MPa.
Example 3
Phosphogypsum (component: caSO) 4 ·2H 2 O content 91.5%, siO 2 7.5% of the content) of the phosphogypsum is mixed with the fire coal, the mixture is added into the circulating fluidized bed 1, the feeding amount of the phosphogypsum is 12500kg/h, the feeding amount of the fire coal is 9275kg/h, and the mass ratio of the phosphogypsum to the fire coal is 1.35:1.00; limestone powder is added into the circulating fluidized bed 1, the feeding amount is 783kg/h, and the adding amount of the limestone powder is 6.02% of the adding amount of phosphogypsum. Air with the preheating temperature of 500 ℃ is introduced into the bottom of the circulating fluidized bed 1, and the air quantity is 17401Nm 3 /h; the coal and hot air are burnt and gasified to generate CO and H while releasing heat 2 . The operation temperature of the circulating fluidized bed is maintained at 900 ℃, and the furnace contents areA part of CaSO in the material 4 Is covered by C, CO, H 2 Reduction to CaS, caSO 4 The reduction rate of (2) is 65%, and simultaneously CaO produced by roasting and decomposing limestone and H produced by burning sulfur-containing coal 2 S and SO 2 Reacting to form CaS and CaSO 4 The CaS amount was 2767kg/h.
After the reaction, the flue gas enters a second cyclone separator 3 for further separation after passing through a first cyclone separator 2, part of solid particles collected by the first cyclone separator 2 is returned to the circulating fluidized bed 1 as return materials, and the other part of the solid particles enter a buffer bin 14; the solid particles collected by the second cyclone separator 3 enter a surge bin 14, the flue gas at the outlet of the second cyclone separator 3 enters the first combustion device 4, excessive post-combustion air is introduced, and the total amount is 3225Nm 3 Controlling the temperature of the combustion chamber to about 900 ℃, burning a small amount of combustible gases such as CO and the like contained in the flue gas and a small amount of carbon residue, and re-oxidizing a small amount of CaS carried by the flue gas into CaSO 4， The urea solution is supplemented to denitrate the flue gas, and the total amount of the flue gas in the first combustion device 4 is 33973Nm 3 /h，SO 2 The concentration was 30mg/Nm 3 ，NO x The concentration was 50mg/Nm 3 (reaching emission standards); after the waste heat is subjected to heat exchange and cooling to about 650 ℃ through a waste heat recovery water pipe, the waste heat enters a first air preheater 5, the air entering the circulating fluidized bed 1 is heated to about 500 ℃, the temperature of flue gas is reduced to about 160 ℃, and the flue gas is discharged after being dedusted through a first cloth bag device 6 and then is exhausted through a first fan 7, so that the exhaust reaches the standard; the first bag-type dust collector 6 is collected and enters a surge bin 14. And the boiler recovers waste heat and byproducts superheated steam.
The amount of material fed into the bubbling fluidized bed 15 is 8787kg/h through a flow control valve of the buffer bin 14, and a part of CaS particles and a small amount of carbon residue contained in the material and the fed high-temperature drying air are subjected to oxidation combustion reaction to emit heat, so that the reaction temperature of the bubbling fluidized bed 15 is maintained at about 1250 ℃; at the same time, the remaining CaS and CaSO 4 Reaction takes place to produce CaO and SO 2 . To control the atmosphere in bubbling fluidized bed 15 to facilitate CaSO 4 The amount of the preheated air is calculated by the theoretical amount, and the air quantity is 7009Nm 3 And/h, a temperature of 500 ℃.
High dry consistency from bubbling fluidized bed 15Degree SO 2 The mixed gas enters a third cyclone separator 8 for dust collection, byproduct cinder is sent into a roller cinder cooler 13, and the separated SO 2 The mixed gas enters a second combustion device 9, dry hot air is introduced by adopting graded air supply, the temperature of the combustion chamber is controlled to 1200 ℃, and a small amount of sulfur and combustible gas in the flue gas are combusted. SO in flue gas 2 The concentration is 18.7%, the flue gas is subjected to heat energy recovery through a waste heat recovery water pipe and then enters a second air preheater 10 for air preheating, the preheated dry air is sent to a bubbling fluidized bed 15 and ashes and a second combustion device 9 for oxygenizing combustion, and meanwhile, the flue gas is cooled to about 180 ℃, and then enters a second bag-type dust collector 11 for dust removal and purification (dust collection is carried out to byproduct cinder), SO that high-concentration SO is obtained 2 Gas, smoke volume 7307Nm 3 And/h, delivering the mixture to high-concentration SO through a booster fan 2 The flue gas is decomposed the phosphorite device to prepare the phosphoric acid reaction slurry device of wet process, then is used for producing phosphoric acid of wet process; because it has reached the technological requirement of preparing sulfuric acid, it can also be directly fed into catalytic oxidation unit (converter) of sulfuric acid-preparing device to produce sulfuric acid.
The bubbling fluidized bed 15 discharges the cinder and enters a roller cinder cooler 13 for heating boiler water supply, and a byproduct cinder product (the effective CaO content is 72.5 percent and SiO) is obtained after cooling 2 Content 22.5%); the yield of the by-product superheated steam of the first combustion device 4 and the second combustion device 9 is 15.13t/h, and the parameters are 450 ℃ and 3.82MPa.
Example 4
Phosphogypsum (component: caSO) 4 ·2H 2 O content 96.0%, siO 2 2.0 percent) of the phosphogypsum is mixed with fire coal, and the mixture is added into the circulating fluidized bed 1, wherein the feeding amount of the phosphogypsum is 12500kg/h, the feeding amount of the fire coal is 9730kg/h, and the mass ratio of the phosphogypsum to the fire coal is 1.28:1.00; limestone powder is added into the circulating fluidized bed 1, the feeding amount is 821kg/h, and the adding amount of the limestone powder is 6.57% of the adding amount of phosphogypsum. Air with the preheating temperature of 500 ℃ is introduced into the bottom of the circulating fluidized bed 1, and the air quantity is 18256Nm 3 /h; the coal and hot air are burnt and gasified to generate CO and H while releasing heat 2 . The operation temperature of the circulating fluidized bed is maintained at 900 ℃, and a part of CaSO in the materials in the furnace is maintained 4 Is covered by C, CO, H 2 Reduction to CaS, caSO 4 The reduction rate of (2) is 65%, and simultaneously CaO produced by roasting and decomposing limestone and H produced by burning sulfur-containing coal 2 S and SO 2 Reacting to form CaS and CaSO 4 The CaS amount was 2903kg/h.
After the reaction, the flue gas enters a second cyclone separator 3 for further separation after passing through a first cyclone separator 2, part of solid particles collected by the first cyclone separator 2 is returned to the circulating fluidized bed 1 as return materials, and the other part of the solid particles enter a buffer bin 14; the solid particles collected by the second cyclone separator 3 enter a surge bin 14, the flue gas at the outlet of the second cyclone separator 3 enters the first combustion device 4, excessive after-combustion air is introduced, and the total amount is 3383Nm 3 Controlling the temperature of the combustion chamber to about 900 ℃, burning a small amount of combustible gases such as CO and the like contained in the flue gas and a small amount of carbon residue, and re-oxidizing a small amount of CaS carried by the flue gas into CaSO 4 The urea solution is added to denitrate the flue gas, and the total amount of the flue gas in the first combustion device 4 is 35643Nm 3 /h，SO 2 The concentration was 31mg/Nm 3 ，NO x The concentration was 52mg/Nm 3 (reaching emission standards); after the waste heat is subjected to heat exchange and cooling to about 650 ℃ through a waste heat recovery water pipe, the waste heat enters a first air preheater 5, the air entering the circulating fluidized bed 1 is heated to about 500 ℃, the temperature of flue gas is reduced to about 160 ℃, and the flue gas is discharged after being dedusted through a first cloth bag device 6 and then is exhausted through a first fan 7, so that the exhaust reaches the standard; the first bag-type dust collector 6 is collected and enters a surge bin 14. And the boiler recovers waste heat and byproducts superheated steam.
The amount of the material fed into the bubbling fluidized bed 15 is 8375kg/h through a flow control valve of the buffer bin 14, and a part of CaS particles and a small amount of carbon residues contained in the material and the fed high-temperature drying air are subjected to oxidation combustion reaction to emit heat, so that the reaction temperature of the bubbling fluidized bed 15 is maintained at about 1250 ℃; at the same time, the remaining CaS and CaSO 4 Reaction takes place to produce CaO and SO 2 . To control the atmosphere in bubbling fluidized bed 15 to facilitate CaSO 4 The amount of the preheated air is calculated by the theoretical amount, and the air volume is 7353Nm 3 And/h, a temperature of 500 ℃.
Dry high concentration SO produced by bubbling fluidized bed 15 2 The mixed gas enters a third cyclone separator 8 for dust collection, and byproduct cinder is sent into a rollerBarrel slag cooler 13, SO after separation 2 The mixed gas enters a second combustion device 9, dry hot air is introduced by adopting graded air supply, the temperature of the combustion chamber is controlled to 1200 ℃, and a small amount of sulfur and combustible gas in the flue gas are combusted. SO in flue gas 2 The concentration is 18.9%, the flue gas is subjected to heat energy recovery through a waste heat recovery water pipe and then enters a second air preheater 10 for air preheating, the preheated dry air is sent to a bubbling fluidized bed 15 and ashes and a second combustion device 9 for oxygenizing combustion, and meanwhile, the flue gas is cooled to about 180 ℃, and then enters a second bag-type dust collector 11 for dust removal and purification (dust collection is carried out to byproduct cinder), SO that high-concentration SO is obtained 2 Gas, smoke volume 7665Nm 3 And/h, delivering the mixture to high-concentration SO through a booster fan 2 The flue gas is decomposed the phosphorite device to prepare the phosphoric acid reaction slurry device of wet process, then is used for producing phosphoric acid of wet process; because it has reached the technological requirement of preparing sulfuric acid, it can also be directly fed into catalytic oxidation unit (converter) of sulfuric acid-preparing device to produce sulfuric acid.
The bubbling fluidized bed 15 discharges the cinder and enters a roller cinder cooler 13 for heating boiler water supply, and a byproduct cinder product (the effective CaO content is 86.5 percent, siO) is obtained after cooling 2 Content 8.5%); the yield of the by-product superheated steam of the first combustion unit 4 and the second combustion unit 9 is 15.87t/h, and the parameters are 450 ℃ and 3.82MPa.
Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the scope and spirit of the principles of this disclosure. More specifically, various modifications and improvements may be made to the component parts and/or arrangements within the scope of the disclosure, drawings and claims of this application, all of which are within the scope of the invention. In addition to variations and modifications in the component parts and/or arrangements, other similar modifications and uses will be apparent to those skilled in the art, and are intended to be within the scope of the invention.
Claims (4)
1. A system for preparing high-concentration sulfur dioxide flue gas by using phosphogypsum is characterized in that: the device comprises a circulating fluidized bed (1), a first cyclone separator (2), a second cyclone separator (3), a first combustion device (4), a first air preheater (5), a first cloth bag dust collector (6) and a first fan (7) which are sequentially connected, wherein a discharge port of the circulating fluidized bed (1) is sequentially connected with a buffer bin (14) and a bubbling fluidized bed (15), an exhaust port of the bubbling fluidized bed (15) is sequentially connected with a third cyclone separator (8), a second combustion device (9), a second air preheater (10), a second cloth bag dust collector (11) and a second fan (12), a discharge port of the bubbling fluidized bed (15) is connected with a roller slag cooler (13), and a discharge port of the roller slag cooler (13) is connected with a cinder storage bin; the discharge port of the second bag-type dust collector (11) is connected with a cinder storage bin, and the discharge ports of the first cyclone separator (2), the second cyclone separator (3) and the first bag-type dust collector (6) are connected with a buffer bin (14); the hot air outlet of the first air preheater (5) is respectively connected with the first combustion device (4) and the air inlet of the circulating fluidized bed (1); the hot air outlet of the second air preheater (10) is respectively connected with the air inlets of the second combustion device (9) and the bubbling fluidized bed (15); the buffer bin (14) is a hollow bin body, and a flow control valve is arranged at the discharge hole; the first combustion device (4) is hollow and cylindrical, and a waste heat recovery water pipe is arranged on the outer side wall of the first combustion device; the discharge port of the first cyclone separator (2) is connected with the feed port of the circulating fluidized bed (1), so that the accurate control of the material returning quantity and the proportion of calcium sulfide to calcium sulfate in the discharge of the circulating fluidized bed (1) is realized;
the process for preparing the high-concentration sulfur dioxide flue gas by using phosphogypsum by the system comprises the following steps of:
s1, phosphogypsum, fire coal and limestone or calcium oxide powder are added into a circulating fluidized bed (1), preheated air is introduced, the temperature of the preheated air is 500 ℃, the reaction temperature is kept between 805 and 950 ℃, and CaSO is controlled 4 The reduction rate is 55-75%, the obtained reaction material enters a surge bin (14), the flue gas enters a first combustion device (4) to burn out after solid phase particles are separated by a first cyclone separator (2) and a second cyclone separator (3), and the flue gas enters the first combustion device(4) Internal spraying urea solution to remove NO x The method comprises the steps of carrying out a first treatment on the surface of the The flue gas after burning out exchanges heat with the air in the first air preheater (5), and is discharged through the first fan (7) after being dedusted by the first bag-type dust remover (6);
s2, materials in the buffer bin (14) enter a bubbling fluidized bed (15) through a flow control valve, preheated air is introduced, the temperature of the preheated air is 500 ℃, the operation temperature is controlled to be 1100-1250 ℃, coal does not need to be added into the bubbling fluidized bed (15), mixed gas of cinder and sulfur dioxide after reaction is obtained, and the cinder enters a cinder storage bin for storage after being cooled by a roller cinder cooler (13); the sulfur dioxide mixed gas enters a second combustion device (9) to burn out after solid phase particles are separated by a third cyclone separator (8), and SO is obtained after the burnt sulfur dioxide mixed gas exchanges heat with air in a second air preheater (10) and is dedusted by a second cloth bag deduster (11) 2 Flue gas with the gas concentration of 18.5 percent or 18.7 percent or 18.9 percent enters SO 2 A phosphorite decomposing device or a sulfuric acid device conversion system;
one part of solid particles obtained after separation by the first cyclone separator (2) is sent into a buffer bin (14), and the other part is returned into the circulating fluidized bed (1) as return materials; in the step S1, the mass ratio of phosphogypsum to fire coal is 0.8-1.5, and the addition amount of limestone is 1.0-9.0% of the mass of phosphogypsum.
2. A system for preparing high concentration sulfur dioxide flue gas using phosphogypsum as claimed in claim 1, wherein: limestone or calcium oxide powder is added into a circulating fluidized bed, and SO generated by burning coal and small amount of phosphogypsum decomposition is fixed and removed by a dry purification method 2 、H 2 S、SO 3 And fluorine, and the emission requirement is met without special tail gas wet water washing or acid washing purification procedures.
3. A system for preparing high concentration sulfur dioxide flue gas using phosphogypsum as claimed in claim 1, wherein: urea is added into the first combustion device to remove nitrogen oxides generated by coal combustion, so as to meet the emission requirement.
4. A system for preparing high concentration sulfur dioxide flue gas using phosphogypsum as claimed in claim 1, wherein: the CaSO in the discharge of the circulating fluidized bed can be realized by finely controlling the addition proportion of phosphogypsum and coal in the reaction material added into the circulating fluidized bed and the return material quantity of the circulating fluidized bed 4 The reduction rate of the catalyst reaches the conditions that the heat balance of the system can be maintained and the temperature required by the reaction can be maintained only by means of the heat released by the oxidation of the CaS in the bubbling fluidized bed, namely, coal is not required to be added in the bubbling fluidized bed.
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