CN109704292B - Fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate - Google Patents
Fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate Download PDFInfo
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- CN109704292B CN109704292B CN201910117113.2A CN201910117113A CN109704292B CN 109704292 B CN109704292 B CN 109704292B CN 201910117113 A CN201910117113 A CN 201910117113A CN 109704292 B CN109704292 B CN 109704292B
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- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 title claims abstract description 112
- 238000010438 heat treatment Methods 0.000 title claims abstract description 70
- 238000001354 calcination Methods 0.000 title claims abstract description 26
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 title abstract description 49
- 239000007789 gas Substances 0.000 claims abstract description 98
- 239000000463 material Substances 0.000 claims abstract description 55
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 51
- 239000003546 flue gas Substances 0.000 claims abstract description 51
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 26
- 230000009471 action Effects 0.000 claims abstract description 20
- 238000005243 fluidization Methods 0.000 claims abstract description 19
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 48
- 229910052717 sulfur Inorganic materials 0.000 claims description 48
- 239000011593 sulfur Substances 0.000 claims description 48
- 239000003575 carbonaceous material Substances 0.000 claims description 31
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 11
- 238000002485 combustion reaction Methods 0.000 claims description 10
- 238000000197 pyrolysis Methods 0.000 claims description 10
- 229910002091 carbon monoxide Inorganic materials 0.000 claims description 8
- 230000009467 reduction Effects 0.000 claims description 6
- 239000005539 carbonized material Substances 0.000 claims description 4
- 239000000571 coke Substances 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 239000002817 coal dust Substances 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims description 3
- 238000007599 discharging Methods 0.000 claims description 3
- 230000000087 stabilizing effect Effects 0.000 claims description 3
- -1 activated semicoke Substances 0.000 claims description 2
- 238000005192 partition Methods 0.000 claims 1
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 10
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 9
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000010440 gypsum Substances 0.000 description 7
- 229910052602 gypsum Inorganic materials 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000005507 spraying Methods 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 3
- 239000000292 calcium oxide Substances 0.000 description 3
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000006477 desulfuration reaction Methods 0.000 description 3
- 230000023556 desulfurization Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 230000005465 channeling Effects 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000012265 solid product Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 239000003034 coal gas Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000003673 groundwater Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000002686 phosphate fertilizer Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- Treating Waste Gases (AREA)
Abstract
The present disclosure provides a fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate, comprising a heating furnace body, a burner and a heat exchanger, wherein the calcium sulfate/calcium nitrate is added from the top of the furnace body, is in a fluid-like microfluidization state in the fluidized bed under the action of bottom fluidization gas, and is then heated to a decomposition temperature under the heating action of high-temperature flue gas at the other side. The high-temperature flue gas and the gas decomposition products can be effectively separated, the purity of the gas decomposition products is greatly improved, the high-temperature flue gas and the materials in the high-temperature flue gas and gas decomposition products are subjected to inverse heat exchange integrally, and the fluidization device is additionally arranged at the bottom of the furnace to enable the materials to be in a microfluidization state, so that disturbance in the bed can be enhanced, and the heat exchange coefficient in the furnace is increased.
Description
Technical Field
The disclosure relates to the field of industrial solid waste resource utilization, in particular to a fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate.
Background
Along with the rapid development of high-concentration phosphate fertilizer and phosphoric acid industry in China, the yield of byproduct phosphogypsum is increased sharply, and the main component of phosphogypsum is CaSO 4·2H2 O and also contains a small amount of other metal ion sulfate. At present, the annual emission of phosphogypsum in China is nearly one hundred million tons, and the accumulated accumulation amount is nearly 5 hundred million tons. At present, although the phosphogypsum in China has a certain utilization way, certain problems exist, the treatment capacity is small, and the pollution situation of the phosphogypsum in China can not be relieved. Phosphogypsum contains acidic and harmful substances, and has to be stacked specially, so that the phosphogypsum occupies land and wastes resources, and the phosphogypsum can pollute groundwater after being stacked for a long time.
Sulfur dioxide, one of the major pollutants, has raised serious environmental concerns, raising government intense attention; the national institutes of government has first required that the pollutant emission level of the newly built coal-fired unit reaches the gas turbine unit and the emission level of sulfur dioxide reaches 35mg/m < 3 >. At present, 95% of the generator sets in China adopt a limestone-gypsum wet desulfurization technology, the technology has the advantages of simple system, high desulfurization efficiency, stable operation and the like, but a large amount of limestone is required to be mined, so that mountain damage and ecological environment threat are caused, the method is a sulfur fixation and carbon removal process, and 2.15 hundred million tons of inferior gypsum are produced as a byproduct each year. Inferior gypsum has poor properties and contains more harmful substances such as heavy metals, so that the inferior gypsum is difficult to utilize, and the ecological environment is seriously damaged by accumulation of a large amount of desulfurized gypsum.
The low-grade gypsum is recycled to regenerate the desulfurizing agent (calcium oxide) for recycling, and the SO 2 gas with high concentration can be produced and can be used as the raw material gas for producing sulfuric acid and sulfur. The sulfur resource shortage type sulfur production process is a sulfur resource shortage type country, sulfur import and consumption amount in the world are in the forefront each year, the external dependence is high, and the sulfur is used as one of important chemical raw materials, so that the market value and the application value of the sulfur are both greater than those of the sulfuric acid.
Therefore, the realization of the regeneration of the flue gas desulfurization agent calcium oxide and the recycling of sulfur dioxide which are widely used at present is an effective measure for solving the environmental protection problem and reducing the external dependence. However, to the best of the inventors' knowledge, chain grate furnaces and rotary kiln converters are widely used in existing calciners and incinerators, and the reaction is accomplished mainly by burning coal and natural gas to heat the material to a calcination and decomposition temperature. However, the high temperature flue gas generated by combustion is mixed with SO 2 generated by calcium sulfate to reduce the purity of SO 2, SO that the conventional calciner is unfavorable for recovering the gaseous product SO 2 of the calcined calcium sulfate.
Disclosure of Invention
In order to solve the deficiencies of the prior art, the present disclosure provides a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate,
In order to achieve the above object, the technical scheme of the present disclosure is as follows:
The fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate comprises a heating furnace body, wherein a heating furnace upper gas space is arranged at the upper part of the heating furnace body, a material inlet and a decomposed gas outlet are arranged in the heating furnace upper gas space, a groove type heat exchanger is arranged in the heating furnace body, a material channel and a high-temperature flue gas channel in the groove type heat exchanger are longitudinally staggered, the bottom of the material channel is communicated with a micro-fluidized bed heating furnace bellows, and the micro-fluidized bed heating furnace bellows is used for providing fluidizing gas for fluidizing the material;
After the calcium sulfate/calcium nitrate enters a material passage in the heat exchanger from the material inlet, the calcium sulfate/calcium nitrate is in a microfluidization state under the action of bottom fluidization gas, and then is subjected to pyrolysis under the action of high-temperature flue gas.
Furthermore, a fluidization hood is arranged at the communication part between the micro-fluidized bed heating furnace bellows and the bottom of the material pavement, and the fluidization hood is used for stabilizing fluidization gas.
Further, when calcium sulfate is calcined, the fluidization gas is sulfur-containing exhaust gas, a carbon material is added in the material pavement, the calcium sulfate, the carbon material and the sulfur-containing exhaust gas are mixed according to a set proportion and then are subjected to pyrolysis under the action of high-temperature flue gas, and the carbon material and the sulfur-containing exhaust gas are used for reducing the decomposition temperature of the calcium sulfate; when calcium nitrate calcination is performed, the fluidizing gas is air or nitrogen.
Further, one end of the high-temperature flue gas passage is communicated with the outlet of the combustion chamber, the other end of the high-temperature flue gas passage is communicated with a high-temperature flue gas outlet arranged on the side part of the heating furnace body, and the temperature of the high-temperature flue gas is 1100-1300 ℃.
The fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate comprises a heating furnace body, wherein a tube bundle type heat exchanger is arranged in the heating furnace body and comprises a plurality of heat exchange tubes, a high-temperature flue gas flow passage is arranged in each heat exchange tube, a material flow passage is arranged outside each heat exchange tube, and a fluidized bed spraying tube is arranged at the bottom end of each material flow passage and used for spraying fluidized gas;
After the calcium sulfate/calcium nitrate enters the material flow channel, the material flow channel is in a microfluidization state under the action of bottom fluidization gas, and then pyrolysis is carried out under the action of high-temperature flue gas.
Further, when calcium sulfate is calcined, the fluidization gas is sulfur-containing exhaust gas, a carbon material is added in the material flow channel, the calcium sulfate is mixed with the carbon material and the sulfur-containing exhaust gas according to a set proportion and then subjected to pyrolysis under the action of high-temperature flue gas, and the carbon material and the sulfur-containing exhaust gas are used for reducing the decomposition temperature of the calcium sulfate; when calcium nitrate calcination is performed, the fluidizing gas is air or nitrogen.
Further, the top end of the heat exchange tube is communicated with a high-temperature flue gas outlet, the bottom end of the heat exchange tube is communicated with a combustion chamber, and the temperature of the high-temperature flue gas is 1100-1300 ℃.
Further, the particle size of the carbon material is 60 μm-3mm, and the carbon material includes, but is not limited to, pulverized coal, activated coke, activated semicoke, activated carbon, carbonized material and graphite.
Further, the sulfur-containing exhaust gas is from tail exhaust gas of the carbothermic reduction system, the temperature of the sulfur-containing exhaust gas is 800-1200 ℃, and the components of the sulfur-containing exhaust gas comprise N 2, S steam, CO and CO 2.
Further, a solid decomposition product outlet is arranged at the bottom of the heating furnace body.
Compared with the prior art, the beneficial effects of the present disclosure are:
The present disclosure proposes a fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate, and proposes two arrangement modes under the same action, and aims at the problem that high temperature flue gas of a chain grate furnace and a rotary kiln converter in the existing calcining heating furnace is mixed with decomposed gas generated by material decomposition, and the fluidized bed indirect heating furnace can be utilized to realize separation of the high temperature flue gas and the high concentration SO 2 decomposed gas generated by calcium sulfate decomposition, SO that the purity of SO 2 atmosphere is greatly improved, and the purity of sulfur and sulfuric acid prepared is indirectly improved; in addition, the high-temperature flue gas and the materials in the method are subjected to inverse heat exchange integrally, and the fluidization device is additionally arranged at the bottom of the furnace to enable the materials to be in a microfluidization state, so that the disturbance in the bed can be enhanced, the heat exchange coefficient in the furnace can be increased, and the method has a wide application prospect.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.
FIG. 1 is a schematic front view of an embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
FIG. 2 is a schematic left-hand view of an embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
FIG. 3 is a schematic top view of an embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
FIG. 4 is a schematic front view of another embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
FIG. 5 is a schematic diagram of a left side view of another embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
FIG. 6 is a schematic top view of another embodiment of a fluidized bed indirect heating furnace for calcining calcium sulfate/nitrate of the present disclosure;
In the figure: 1. heating a furnace body; 2. an upper gas space of the heating furnace; 3. a microfluidization bed heating furnace bellows; 4. a combustion chamber; 5. a burner; 6. high temperature flue gas walkways; 7. a material walkway; 8. a fluidization hood; 9. a heat exchange tube; 10. a spray pipe; 11. and a hot smoke collecting box.
Detailed Description
The disclosure is further described below with reference to the drawings and specific examples.
It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the present application. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.
In the present disclosure, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, are merely relational terms determined for convenience in describing structural relationships of the various components or elements of the present disclosure, and do not denote any one of the components or elements of the present disclosure, and are not to be construed as limiting the present disclosure.
In the present disclosure, terms such as "fixedly coupled," "connected," and the like are to be construed broadly and refer to either a fixed connection or an integral or removable connection; can be directly connected or indirectly connected through an intermediate medium. The specific meaning of the terms in the disclosure may be determined according to circumstances, and should not be interpreted as limiting the disclosure, for relevant scientific research or a person skilled in the art.
As one or more embodiments, as shown in fig. 1-3, a fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate comprises a heating furnace body 1, wherein the upper part of the heating furnace body 1 is provided with a heating furnace upper gas space 2, the heating furnace upper gas space 2 is provided with a material inlet and a decomposed gas outlet, the inside of the heating furnace body 1 is provided with a groove type heat exchanger, material walkways 7 and high-temperature flue gas walkways 6 in the groove type heat exchanger are longitudinally staggered, the bottom of the material walkways 7 is communicated with a micro-fluidized bed heating furnace bellows 3, and the micro-fluidized bed heating furnace bellows 3 is used for providing fluidized gas for fluidizing materials;
After the calcium sulfate/calcium nitrate enters the material passage 7 in the heat exchanger from the material inlet, the material is in a microfluidization state under the action of bottom fluidization gas, and pyrolysis is carried out under the action of high-temperature flue gas.
The fluidized air cap 8 is arranged at the communication part between the micro-fluidized bed heating furnace bellows 3 and the bottom of the material pavement 7, and the fluidized air cap 8 is used for stabilizing fluidizing gas.
In this embodiment, when the calcium sulfate is calcined, the fluidization gas is sulfur-containing exhaust gas, a carbon material is added in the material passage 7, and the calcium sulfate, the carbon material and the sulfur-containing exhaust gas are mixed according to a set proportion and then subjected to pyrolysis under the action of high-temperature flue gas, wherein the carbon material and the sulfur-containing exhaust gas are used for reducing the decomposition temperature of the calcium sulfate; when calcium nitrate calcination is performed, the fluidizing gas is air or nitrogen.
Calcium nitrate is not led to sulfur-containing exhaust gas and carbon materials; the decomposition of nitrate refers to the decomposition of pure salts, without other reactants, equivalent to a calciner.
The carbon material is directly added below a material level line in the furnace through a discharging pipe at the top of the furnace, so that buried pipe feeding is realized, and gas channeling is prevented.
One end of the high-temperature flue gas passage 6 is communicated with the outlet of the combustion chamber 4, and the other end is communicated with a high-temperature flue gas outlet arranged on the side part of the heating furnace body, wherein the temperature of the high-temperature flue gas is 1100-1300 ℃.
The combustion chamber 4 is arranged with a burner 5.
The decomposed gas enters other systems from the decomposed gas outlet of the upper gas space 2 of the heating furnace to be utilized, and the natural sedimentation of solid product powder can be realized through the upper gas space 2 of the heating furnace, so that the aim of purifying the high-concentration decomposed gas is fulfilled.
The material walkways 7 and the high-temperature flue gas walkways 6 are longitudinally staggered, so that the contact area of the materials and the heat exchanger can be increased, and the heat exchange effect is improved.
The material of the groove type heat exchanger is resistant to high temperature and gaseous product corrosion, and 310s or ceramic materials can be considered.
The particle size of the carbon material is 60 mu m-3mm, and the carbon material comprises, but is not limited to, coal dust, active coke, active semicoke, active carbon, carbonized material and graphite.
The sulfur-containing exhaust gas is from tail exhaust gas of the carbothermic reduction system, the temperature of the sulfur-containing exhaust gas is 800-1200 ℃, and the components of the sulfur-containing exhaust gas comprise N 2, S steam, CO and CO 2. The sulfur-containing exhaust gas generated in the carbothermic reduction process is taken as the fluidizing gas to participate in the reaction as the reducing agent, so that the reaction temperature is reduced, meanwhile, the disturbance of materials in the bed is increased, the heat exchange effect of the materials and high-temperature flue gas is increased, and the heat exchange coefficient is improved.
The bottom of the heating furnace body 1 is provided with a solid decomposition product outlet.
As one or more embodiments, as shown in fig. 4-6, a fluidized bed indirect heating furnace for calcining calcium sulfate/calcium nitrate comprises a heating furnace body 1, wherein a tube bundle type heat exchanger is arranged in the heating furnace body 1, the tube bundle type heat exchanger comprises a plurality of heat exchange tubes 9, a high-temperature flue gas flow passage is arranged in the heat exchange tubes 9, a material flow passage is arranged outside the heat exchange tubes, a fluidized bed spraying tube 10 is arranged at the bottom end of the material flow passage, and the spraying tube 10 is used for spraying fluidizing gas;
After the calcium sulfate/calcium nitrate enters the material flow channel, the material flow channel is in a microfluidization state under the action of bottom fluidization gas, and then pyrolysis is carried out under the action of high-temperature flue gas.
In this embodiment, when the calcium sulfate is calcined, the fluidization gas is sulfur-containing exhaust gas, a carbon material is added in the material flow channel, the calcium sulfate, the carbon material and the sulfur-containing exhaust gas are mixed according to a set proportion and then subjected to pyrolysis under the action of high-temperature flue gas, and the carbon material and the sulfur-containing exhaust gas are used for reducing the decomposition temperature of the calcium sulfate; when calcium nitrate calcination is performed, the fluidizing gas is air or nitrogen.
Calcium nitrate is not led to sulfur-containing exhaust gas and carbon materials; the decomposition of nitrate refers to the decomposition of pure salts, without other reactants, equivalent to a calciner.
The carbon material is directly added below a material level line in the furnace through a discharging pipe at the top of the furnace, so that buried pipe feeding is realized, and gas channeling is prevented.
The spray pipe 10 can increase disturbance of materials in a bed and improve heat exchange effect.
The top end of the heat exchange tube 9 is communicated with a high-temperature flue gas outlet, the bottom end of the heat exchange tube is communicated with the combustion chamber 4, and the temperature of the high-temperature flue gas is 1100-1300 ℃.
In this embodiment, the high-temperature flue gas outlet is arranged on the hot flue gas collecting box 11, the hot flue gas collecting box 11 is arranged above the furnace body, the combustion chamber 4 is arranged below the furnace body, and the combustor 5 is arranged in the combustion chamber 4.
The tubular heat exchanger is made of a material resistant to high temperature and corrosion by gaseous products, and 310s or a ceramic material can be considered.
The particle size of the carbon material is 60 mu m-3mm, and the carbon material comprises, but is not limited to, coal dust, active coke, active semicoke, active carbon, carbonized material and graphite.
The sulfur-containing exhaust gas is from tail exhaust gas of the carbothermic reduction system, the temperature of the sulfur-containing exhaust gas is 800-1200 ℃, and the components of the sulfur-containing exhaust gas comprise N 2, S steam, CO and CO 2. The sulfur-containing exhaust gas generated in the carbothermic reduction process is taken as the fluidizing gas to participate in the reaction as the reducing agent, so that the reaction temperature is reduced, meanwhile, the disturbance of materials in the bed is increased, the heat exchange effect of the materials and high-temperature flue gas is increased, and the heat exchange coefficient is improved.
The bottom of the heating furnace body is provided with a solid decomposition product outlet.
In the two fluidized bed indirect heating furnaces, a dividing wall type heat exchange mode is adopted between the calcium sulfate and the high-temperature flue gas, SO that the analyzed SO 2 gas is not mixed with the high-temperature flue gas, the purity of the SO 2 raw material gas can be improved, and the purity of the prepared sulfuric acid and sulfur can be indirectly improved.
In the concrete implementation, calcium sulfate is added from the top of a fluidized bed heating furnace, under the action of fluidizing gas at the bottom, the calcium sulfate presents a microfluidization state similar to fluid in the bed, and after being mixed with carbon materials and sulfur-containing exhaust gas according to a certain proportion in the heating furnace, the calcium sulfate is heated to a temperature range of 800-1200 ℃ under the heating action of high-temperature flue gas at the other side, and the residence time in the furnace is 10-60 s; the solid product generated by the reaction is mainly calcium oxide crystal, and is discharged from the bottom of the heating furnace, and the whole of the calcium sulfate and the high-temperature flue gas exhibits reverse heat exchange, so that the heat exchange temperature difference can be increased, and a better heat exchange effect can be obtained; the gas phase product generated by the reaction is high-concentration SO 2 (the concentration of SO 2 in the gas is 5% -30%), the gas temperature is between 700 and 1000 ℃, and related researches and documents show that the temperature is the optimal temperature section for preparing sulfur by carbothermic reduction, SO that the purity and conversion rate of the prepared sulfur can be greatly improved by sending the sulfur into a carbothermic reduction reaction system, and the regeneration of phosphogypsum (CaSO 4·2H2 O) and desulfurized gypsum which are difficult to treat at present and the recycling of SO 2 can be realized in the technology. Meanwhile, the high-concentration SO 2 gas can also be used for preparing industrial raw material sulfuric acid.
The reason why the carbon material and the sulfur-containing exhaust gas are added in the high-temperature decomposition process of the calcium sulfate is that according to the prior related literature, the decomposition temperature of the calcium sulfate is higher, the calcium sulfate can be completely decomposed only at 1350-1400 ℃, and the higher decomposition temperature means higher energy consumption is required; however, after the reducing substances such as carbon materials, sulfur and the like are added, the decomposition temperature of the calcium sulfate is greatly reduced, the decomposition temperature is about 800-1100 ℃, the material decomposition energy consumption is greatly reduced, and the purposes of energy conservation, emission reduction and sulfur resource utilization are achieved
The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
While the specific embodiments of the present disclosure have been described above with reference to the drawings, it should be understood that the present disclosure is not limited to the embodiments, and that various modifications and changes can be made by one skilled in the art without inventive effort on the basis of the technical solutions of the present disclosure while remaining within the scope of the present disclosure.
Claims (4)
1. The fluidized bed indirect heating furnace for calcining calcium sulfate is characterized by comprising a heating furnace body, wherein a heating furnace upper gas space is arranged at the upper part of the heating furnace body, a material inlet and a decomposed gas outlet are arranged in the heating furnace upper gas space, a groove type heat exchanger is arranged in the heating furnace body, a material channel and a high-temperature flue gas channel in the groove type heat exchanger are longitudinally staggered, the bottom of the material channel is communicated with a micro-fluidized bed heating furnace bellows, and the micro-fluidized bed heating furnace bellows is used for providing fluidizing gas for fluidizing the material;
After the calcium sulfate enters a material passage in the heat exchanger from a material inlet, the calcium sulfate is in a microfluidization state under the action of bottom fluidization gas, and then is subjected to pyrolysis under the action of high-temperature flue gas;
When calcium sulfate is calcined, the fluidization gas is sulfur-containing exhaust gas, a carbon material is added in the material pavement, the calcium sulfate is mixed with the carbon material and the sulfur-containing exhaust gas according to a set proportion and then subjected to pyrolysis under the action of high-temperature flue gas, and the carbon material and the sulfur-containing exhaust gas are used for reducing the decomposition temperature of the calcium sulfate; the calcium sulfate and the high-temperature flue gas adopt a partition wall type heat exchange mode, and the resolved SO 2 gas is not mixed with the high-temperature flue gas;
The decomposed gas enters other systems from a decomposed gas outlet of the gas space at the upper part of the heating furnace to be utilized;
a fluidization hood is arranged at the communication part between the micro-fluidized bed heating furnace bellows and the bottom of the material pavement and is used for stabilizing fluidization gas;
the carbon material is directly added below a material level line in the furnace through a discharging pipe at the top of the furnace;
The sulfur-containing exhaust gas is from tail exhaust gas of the carbothermic reduction system, the temperature of the sulfur-containing exhaust gas is 800-1200 ℃, and the components of the sulfur-containing exhaust gas comprise N 2, S steam, CO and CO 2.
2. The fluidized bed indirect heating furnace for calcining calcium sulfate according to claim 1, wherein one end of the high temperature flue gas passage is communicated with the outlet of the combustion chamber, and the other end is communicated with the outlet of the high temperature flue gas arranged at the side part of the furnace body of the heating furnace, and the temperature of the high temperature flue gas is 1100 ℃ to 1300 ℃.
3. A fluidized bed indirect heating furnace for calcining calcium sulfate according to claim 1 wherein the particle size of the carbon material is 60 μm-3mm and the carbon material comprises coal dust, activated coke, activated semicoke, activated carbon, carbonized material and graphite.
4. A fluidized bed indirect heating furnace for calcining calcium sulfate according to claim 1, wherein a solid decomposition product outlet is provided at the bottom of the heating furnace body.
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