System and method for preparing sulfuric acid and co-producing cement clinker from ardealite

Abstract

The invention discloses a system and a method for preparing sulfuric acid and co-producing cement clinker from ardealite. The system comprises a preheater, a decomposing furnace, a rotary kiln and a grate cooler, the preheater comprises a kiln row and a furnace row which are used for material heat exchange, each of the kiln row and the furnace row comprises multiple stages of cyclones, the penultimate stage of cyclone in the kiln row is communicated with a smoke chamber uptake flue, and the last stage of cyclone is communicated with the decomposing furnace; the penultimate-stage cyclone cylinder in the furnace row is communicated with the decomposing furnace, the last-stage cyclone cylinder is communicated with the smoke chamber, materials are collected and enter the rotary kiln through the smoke chamber, and waste gas discharged by the furnace row is conveyed to the SO2 sulfuric acid preparation process through a furnace row high-temperature fan; the decomposing furnace is connected with a plurality of combustors; the decomposing furnace and the rotary kiln are both connected with the grate cooler, the grate cooler cools clinker and discharges the clinker out of the system, generated secondary air is introduced into the rotary kiln, and generated tertiary air is introduced into the decomposing furnace. The coal consumption indexes of multiple stages can be reduced, the SO2 concentration of exhaust gas discharged by the preheater is improved, and the power consumption index for preparing sulfuric acid through flue gas treatment SO2 is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cement production and processing, and particularly to a system and method for co-producing sulfuric acid and cement clinker from phosphogypsum. Background Art

[0002] Phosphogypsum is a by-product in the production of wet-process phosphoric acid, which is generated by the reaction of sulfuric acid with phosphate rock to produce phosphoric acid and phosphogypsum. Approximately 4-5 tons of phosphogypsum are produced for every 1 ton of phosphoric acid produced. According to relevant research and statistical data, the cumulative amount of global phosphogypsum is estimated to have exceeded 7 billion tons and is still increasing at a rate of hundreds of millions of tons per year.

[0003] Under the background of the energy structure adjustment in the "dual carbon" strategy, the global development of new energy projects has been vigorously promoted, and lithium iron phosphate / iron phosphate has developed rapidly. Industry enterprises have invested in the construction of production plants and supporting facilities one after another. The demand for phosphoric acid is about 2 million t / a, and nearly 10 million tons of phosphogypsum will be added annually.

[0004] Up to now, waste phosphogypsum has mainly been recycled through methods such as cement retarders, building gypsum, fiber gypsum boards, ecological restoration, mine filling agents, sulfur production co-producing cement clinker, and road construction materials. However, the resource utilization rate is only 40% - 50%, and the comprehensive utilization rate is still relatively low. The production of sulfuric acid co-producing cement clinker from phosphogypsum is dehydrated and dried phosphogypsum, adding appropriate proportions of CaO, SiO2, Al2O3, and Fe2O3, as well as carbon, clay, sand, etc., and feeding them into a rotary kiln for calcination. Through the sulfur dioxide and calcium oxide substances generated by the high-temperature decomposition of phosphogypsum inside the kiln, the generated calcium oxide reacts with other siliceous-aluminous components of the materials to form cement clinker, and the generated sulfur dioxide gas is converted and absorbed to produce sulfuric acid. The production of sulfuric acid co-producing cement clinker from phosphogypsum makes full use of the calcium and sulfur raw materials in phosphogypsum. Producing 1t of sulfuric acid and cement clinker consumes 2 - 3t of phosphogypsum, which is currently the best way to achieve large-scale utilization of phosphogypsum.

[0005] In the prior art, the production of sulfuric acid co-producing cement clinker from phosphogypsum mainly uses hollow kilns and preheater kilns. The rotary kiln has a large load, low production capacity, and high energy consumption indicators, especially in the aspects of phosphogypsum pretreatment, calcination, and gas purification, resulting in an increase in production costs. At the same time, the composition of phosphogypsum is affected by the source of phosphate rock and the phosphoric acid production process, and the content of impurities (such as phosphorus, fluorine, organic matter, etc.) fluctuates greatly. Moreover, the calcination intensity of the rotary kiln is limited, and the material state inside the kiln has a great influence on the decomposition of phosphogypsum. The material ratio is restricted, and it is difficult to produce qualified cement clinker in most cases. Summary of the Invention

[0006] The object of the present invention is to overcome the problems existing in the prior art that the rotary kiln for producing sulfuric acid by phosphogypsum and co-producing cement clinker has a large load, low production capacity, high energy consumption and it is difficult to burn qualified cement clinker. A system and a method for producing sulfuric acid by phosphogypsum and co-producing cement clinker are provided. The system and method for producing sulfuric acid by phosphogypsum and co-producing cement clinker can reduce the coal consumption index in the stages of phosphogypsum pretreatment, clinker calcination and clinker cooling. At the same time, the SO2 concentration of the exhaust gas discharged from the preheater is increased, and the power consumption index of the process for treating flue gas SO2 to produce sulfuric acid is reduced.

[0007] In order to achieve the above object, on the one hand, the present invention provides a system for producing sulfuric acid by phosphogypsum and co-producing cement clinker. The system for producing sulfuric acid by phosphogypsum and co-producing cement clinker includes a preheater, a decomposition furnace, a rotary kiln and a grate cooler. The preheater includes a kiln train and a furnace train that are respectively connected to a phosphogypsum raw material homogenization silo for heat exchange of materials. Both the kiln train and the furnace train include multiple cyclones arranged and connected in sequence. Among them,

[0008] The penultimate cyclone in the kiln train is communicated with the rising flue of the smoke chamber, and the last cyclone is communicated with the decomposition furnace. The exhaust gas discharged from the kiln train is transported to the raw material place through a kiln train high-temperature fan for drying the raw materials;

[0009] The penultimate cyclone in the furnace train is communicated with the decomposition furnace, and the last cyclone is communicated with the smoke chamber and is arranged to be able to collect the materials decomposed by the decomposition furnace and enter the rotary kiln through the smoke chamber. The exhaust gas discharged from the furnace train is transported to the SO2 sulfuric acid production process through a furnace train high-temperature fan;

[0010] A plurality of burners are connected to the decomposition furnace for introducing combustible gas;

[0011] Both the decomposition furnace and the rotary kiln are connected to the grate cooler. The grate cooler is arranged to be able to cool the clinker output from the rotary kiln and discharge it from the system, and to introduce the secondary air generated into the rotary kiln and the tertiary air generated into the decomposition furnace.

[0012] Preferably, the system for producing sulfuric acid by phosphogypsum and co-producing cement clinker further includes a sedimentation chamber connected to the grate cooler, and an AQC boiler is connected to the sedimentation chamber. The AQC boiler is used for waste heat power generation.

[0013] Preferably, a dust collector is connected to the AQC boiler. The dust collector is used for dust collection and exhaust gas discharge.

[0014] The second aspect of the present invention provides a method for co-producing sulfuric acid from phosphogypsum and cement clinker. This method for co-producing sulfuric acid from phosphogypsum and cement clinker uses the system for co-producing sulfuric acid from phosphogypsum and cement clinker as described above for production, including: first feeding raw materials into a preheater, and performing multi-stage heat exchange through a kiln train and a furnace train respectively; then, using a smoke chamber and a decomposition furnace to perform secondary decomposition on the materials and then entering the rotary kiln through the smoke chamber, and forming clinker through high-temperature calcination in the rotary kiln; finally, cooling the clinker with a grate cooler and then discharging it from the system; meanwhile, transporting the waste gas discharged from the furnace train to the sulfuric acid production process through a high-temperature fan of the furnace train, and preparing sulfuric acid through flue gas purification and conversion absorption; using a high-temperature fan of the kiln train to transport the waste gas discharged from the kiln train to the raw material location for drying the raw materials.

[0015] Preferably, the secondary decomposition includes:

[0016] Using the penultimate-stage cyclone in the kiln train to send the materials into the rising flue of the smoke chamber for pre-decomposition, using the last-stage cyclone in the kiln train and the penultimate-stage cyclone in the furnace train to send the collected materials into the decomposition furnace for re-decomposition together, and after the decomposition furnace decomposes, using the last-stage cyclone in the furnace train to send the decomposed materials into the smoke chamber.

[0017] Preferably, before feeding into the preheater, the raw materials are proportioned, pulverized, dried and homogenized in sequence, and the ratio of the materials fed into the kiln train and the furnace train is 3:7 - 4:6.

[0018] Preferably, the decomposition furnace is fed with combustible gases through multiple burners, including CO, H2 and CH4.

[0019] Preferably, the decomposition furnace is in a reducing atmosphere state, the partial pressure of CO or H2 accounts for 20% - 40% of the partial pressure of CO2, and during the decomposition process, the residence time of the materials is guaranteed to be more than 20 s, and the residence time of the gas is more than 10 s.

[0020] Preferably, this method for co-producing sulfuric acid from phosphogypsum and cement clinker further includes:

[0021] Discharging the dried waste gas after desulfurization and dust removal;

[0022] Discharging the waste gas remaining after preparing sulfuric acid after desulfurization and dust removal;

[0023] Introducing the secondary air generated after the grate cooler cools the clinker into the rotary kiln for the pulverized coal combustion in the rotary kiln, introducing the tertiary air generated into the decomposition furnace for the combustion of the combustible waste gas in the decomposition furnace, and discharging the remaining waste gas after power generation by the surplus air and dust collection.

[0024] According to the above technical solution, the waste gas at the tail of the kiln is discharged through the preheater systems of the furnace row and the kiln row. The waste gas discharged from the kiln row is used for drying raw materials, saving the coal consumption for material drying. The waste gas after raw material drying is discharged after desulfurization and dust removal. The SO2 concentration of the waste gas discharged from the furnace row is above 20%. It is used to prepare sulfuric acid through flue gas purification, conversion and absorption, improving the efficiency of sulfuric acid preparation. The remaining waste gas is discharged after desulfurization and dust removal. The cooler at the head of the kiln supplies cold air to cool the clinker. The secondary air generated is used for the coal powder combustion in the rotary kiln, and the tertiary air is used for the combustion of combustible waste gas in the decomposition furnace. The remaining waste gas is discharged after power generation by the surplus air and dust collection. At the same time, the decomposition technology outside the kiln is adopted to reduce the load of the rotary kiln, meet the normal modulus batching of cement clinker, greatly increase the output of clinker, reduce the equipment specification of the rotary kiln, and reduce the firing heat consumption by more than 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic structural diagram of a system for producing sulfuric acid from phosphogypsum and co-producing cement clinker according to the present invention;

[0026] Figure 2 is a working flow chart of a system for producing sulfuric acid from phosphogypsum and co-producing cement clinker according to the present invention;

[0027] Figure 3 is a flow chart of a method for producing sulfuric acid from phosphogypsum and co-producing cement clinker according to the present invention.

[0028] DESCRIPTION OF THE REFERENCE NUMERALS

[0029] 1 - decomposition furnace 2 - rotary kiln

[0030] 3 - cooler 4 - kiln row

[0031] 5 - furnace row 6 - cyclone

[0032] 7 - smoke chamber 8 - settling chamber

[0033] [[ID=3,2]]9 - AQC boiler 10 - dust collector

[0034] 11 - high-temperature fan of furnace row 12 - high-temperature fan of kiln row DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustration and explanation of the present invention, and are not intended to limit the present invention.

[0036] In the present invention, unless otherwise specified, the directional terms included in the terms only represent the direction of the terms in the normal use state, or the common name understood by those skilled in the art, and should not be regarded as a limitation of the terms.[[ID=,44]]

[0037] See Figure 1, on the one hand, the present invention provides a system for co-producing sulfuric acid and cement clinker from phosphogypsum. The system for co-producing sulfuric acid and cement clinker from phosphogypsum includes a preheater, a decomposition furnace 1, a rotary kiln 2, and a grate cooler 3. The preheater includes a kiln train 4 and a furnace train 5 that are respectively connected to a phosphogypsum raw material homogenization silo for heat exchange of materials. Both the kiln train 4 and the furnace train 5 include a plurality of cyclones 6 arranged and connected in sequence. Among them,

[0038] The second-to-last cyclone 6 in the kiln train 4 is connected to the riser of the smoke chamber 7, and the last cyclone 6 is connected to the decomposition furnace 1. The waste gas discharged from the kiln train 4 is transported to the raw material area through the high-temperature fan 12 of the kiln train for drying the raw materials;

[0039] The second-to-last cyclone 6 in the furnace train 5 is connected to the decomposition furnace 1, and the last cyclone 6 is connected to the smoke chamber 7 and is configured to collect the materials decomposed by the decomposition furnace 1 and enter the rotary kiln 2 through the smoke chamber 7. The waste gas discharged from the furnace train 5 is transported to the sulfuric acid production process from SO2 through the high-temperature fan 11 of the furnace train;

[0040] A plurality of burners are connected to the decomposition furnace 1 for introducing combustible gas;

[0041] Both the decomposition furnace 1 and the rotary kiln 2 are connected to the grate cooler 3. The grate cooler 3 is configured to cool the clinker output from the rotary kiln 2 and discharge it from the system, and to introduce the secondary air generated into the rotary kiln 2 and the tertiary air generated into the decomposition furnace 1.

[0042] Through the above technical solutions, the waste gas at the kiln tail is discharged through the preheater systems of the furnace train 5 and the kiln train 4. The waste gas discharged from the kiln train 4 is used for drying the raw materials, saving the coal consumption for material drying. The waste gas after raw material drying is discharged after desulfurization and dust removal; the SO2 concentration in the waste gas discharged from the furnace train 5 is above 20%. After flue gas purification and conversion absorption, sulfuric acid is prepared, improving the sulfuric acid production efficiency. The remaining waste gas is discharged after desulfurization and dust removal. The grate cooler 3 at the kiln head supplies cold air to cool the clinker. The secondary air generated is used for coal powder combustion in the rotary kiln 2, and the tertiary air generated is used for combustible waste gas combustion in the decomposition furnace 1. The remaining waste gas is discharged after power generation by the surplus air and dust collection. At the same time, the out-of-kiln decomposition technology is adopted to reduce the load of the rotary kiln 2, meet the normal modulus batching of cement clinker, greatly increase the clinker output, reduce the equipment specification of the rotary kiln 2, and reduce the firing heat consumption by more than 40%.

[0043] When specifically set, such as Figure 1As shown, where the dashed arrows indicate the material flow direction and the solid arrows indicate the gas flow direction. In the kiln row 4, the material flow between the multi-stage cyclones 6 is set to flow from the phosphogypsum raw material homogenization silo towards the decomposition furnace 1, while the gas flow is in the opposite direction to the material flow, set to flow from the smoke chamber 7 towards the first-stage cyclone 6; in the furnace row 5, the material flow between the multi-stage cyclones 6 is set to flow from the phosphogypsum raw material homogenization silo towards the decomposition furnace 1 and the smoke chamber 7 respectively, and the gas flow is also in the opposite direction to the material flow, set to flow from the decomposition furnace 1 towards the first-stage cyclone 6.

[0044] In this embodiment, in order to achieve waste heat power generation, reuse resources, and avoid waste, preferably, the system for producing sulfuric acid by co-producing cement clinker from phosphogypsum further includes a sedimentation chamber 8 connected to the grate cooler 3, and an AQC boiler 9 is connected to the sedimentation chamber 8. The AQC boiler 9 is used for waste heat power generation. The AQC boiler 9 uses the high-temperature waste gas (about 300 - 400 °C) discharged from the grate cooler 3 to heat water to generate steam, and uses this steam to drive a steam turbine to generate electricity, which not only reduces energy waste, reduces carbon emissions, but also significantly reduces the energy consumption cost of cement production.

[0045] In this embodiment, in order to capture, separate, and remove dust particles in industrial waste gas to reduce air pollution and recover valuable dust, preferably, a dust collector 10 is connected to the AQC boiler 9. The dust collector 10 is used for dust collection and discharging waste gas. In this way, the dust-containing gas passes through the filter bag, the dust is intercepted on the surface of the filter bag, and the purified gas is discharged. The dust removal efficiency is high, which can greatly reduce pollution and improve the resource recovery rate.

[0046] In addition, as Figure 2 and Figure 3 shown, on the other hand, the present invention provides a method for producing sulfuric acid by co-producing cement clinker from phosphogypsum. The method for producing sulfuric acid by co-producing cement clinker from phosphogypsum uses the system for producing sulfuric acid by co-producing cement clinker from phosphogypsum as described above for production, including: first feeding the raw materials into the preheater and performing multi-stage heat exchange through the kiln row 4 and the furnace row 5 respectively; then, using the smoke chamber 7 and the decomposition furnace 1 to perform secondary decomposition on the materials and then entering the rotary kiln 2 through the smoke chamber 7, and the clinker is formed by high-temperature calcination in the rotary kiln 2; finally, the clinker is cooled by the grate cooler 3 and then discharged from the system; at the same time, the waste gas discharged from the furnace row 5 is transported to the SO2 sulfuric acid production process through the furnace row high-temperature fan 11, and sulfuric acid is prepared through flue gas purification and conversion absorption; the waste gas discharged from the kiln row 4 is transported to the raw material location for raw material drying by using the kiln row high-temperature fan 12.

[0047] The above secondary decomposition includes: using the penultimate cyclone 6 in the kiln row 4 to feed the material into the smoke chamber 7 (1050 - 1150 °C) for pre-decomposition, with the decomposition rate of phosphogypsum being about 60% and the desulfurization rate being 40% - 50%. Using the last cyclone 6 in the kiln row 4 and the penultimate cyclone 6 in the furnace row 5 to feed the collected materials into the decomposition furnace 1 for re-decomposition. Among them, the materials collected by the last cyclone 6 in the kiln row 4 are above 850 °C, and the materials collected by the penultimate cyclone 6 in the furnace row 5 are above 750 °C. After the decomposition in the decomposition furnace 1, use the last cyclone 6 in the furnace row 5 to send the decomposed materials to the smoke chamber 7.

[0048] In this embodiment, before feeding into the preheater, the raw materials are sequentially proportioned, pulverized, dried, and homogenized. And the material ratio of the materials fed into the kiln row 4 and the furnace row 5 is 3:7 - 4:6. Specifically in proportioning, when preparing cement clinker by decomposing phosphogypsum, phosphogypsum, silica sandstone, and bauxite are used for proportioning. Among them, the content of CaSO4·2H2O in phosphogypsum is 90% - 95%, and the content of calcium silicate and siliceous raw materials is ≤3%. Phosphogypsum, silica sandstone, and bauxite are proportioned in the ratio of 88 - 90:2 - 3:7 - 10.

[0049] In this embodiment, the decomposition furnace 1 is fed with combustible gases through multiple burners, including CO, H2, and CH4.

[0050] In this embodiment, the inside of the decomposition furnace 1 is in a reducing atmosphere state, and the partial pressure of CO or H2 accounts for 20% - 40% of the partial pressure of CO2. And because the materials in the decomposition furnace are in a suspended and reducing atmosphere state, the pyrolysis temperature of phosphogypsum is 780 - 880 °C. To ensure that the decomposition rate of phosphogypsum is above 98% and the desulfurization rate reaches above 95%, during the decomposition process, ensure that the residence time of the materials is above 20 s and the residence time of the gas is above 10 s.

[0051] In addition, the method for producing sulfuric acid and co-producing cement clinker from phosphogypsum also includes:

[0052] Drying the exhaust gas and discharging it after desulfurization and dust removal;

[0053] Drying the exhaust gas remaining after producing sulfuric acid and discharging it after desulfurization and dust removal;

[0054] Introduce the secondary air generated after the cooler 3 cools the clinker into the rotary kiln 2 for the combustion of pulverized coal in the rotary kiln 2, introduce the tertiary air generated into the decomposition furnace 1 for the combustion of combustible exhaust gas in the decomposition furnace 1, and discharge the remaining exhaust gas after power generation by the surplus air and dust collection.

[0055] Through the above technical solution, the method combines off-line pre-calcination with rotary kiln technology. Specifically, the exhaust gas discharged from kiln row 4 is used for raw material drying, saving coal consumption for material drying; the SO2 content in the exhaust gas discharged from furnace row 5 is above 20%, improving the efficiency of sulfuric acid preparation; meanwhile, the out-of-kiln decomposition technology is adopted. After being decomposed by the decomposition furnace 1, it enters the rotary kiln 2 through the smoke chamber 7. After the phosphogypsum is decomposed, the remaining CaO, together with silicon, aluminum, and iron raw materials, forms clinker through high-temperature calcination. The heat of the rotary kiln 2 is provided by the pulverized coal combustion of the burner at the kiln head. The clinker is discharged from the system after being cooled by the grate cooler 3. This production method reduces the load of the rotary kiln 2, meets the normal modulus batching of cement clinker, greatly improves the clinker output, reduces the equipment specification of the rotary kiln 2, and reduces the firing heat consumption by more than 40%.

[0056] The preferred embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any suitable combination of each specific technical feature. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods. But these simple modifications and combinations should also be regarded as the content disclosed by the present invention and all fall within the protection scope of the present invention.

Claims

1. A system for producing sulfuric acid and co-producing cement clinker from phosphogypsum, characterized in that, The system for producing sulfuric acid and co-producing cement clinker from phosphogypsum includes a preheater, a decomposition furnace (1), a rotary kiln (2) and a grate cooler (3). The preheater includes a kiln train (4) and a furnace train (5) that are respectively connected to the homogenization silo of phosphogypsum raw materials for heat exchange of materials. The kiln train (4) and the furnace train (5) both include multiple cyclones (6) arranged and connected in sequence. Among them, the second-to-last cyclone (6) in the kiln train (4) is connected to the rising flue of the smoke chamber (7), and the last cyclone (6) is connected to the decomposition furnace (1). The waste gas discharged from the kiln train (4) is transported to the raw material location through the high-temperature fan (12) of the kiln train for drying the raw materials; the second-to-last cyclone (6) in the furnace train (5) is connected to the decomposition furnace (1), and the last cyclone (6) is connected to the smoke chamber (7) and is configured to collect the materials decomposed by the decomposition furnace (1) and enter the rotary kiln (2) through the smoke chamber (7). The waste gas discharged from the furnace train (5) is transported to the sulfuric acid production process from SO2 through the high-temperature fan (11) of the furnace train; a plurality of burners are connected to the decomposition furnace (1) for introducing combustible gas; both the decomposition furnace (1) and the rotary kiln (2) are connected to the grate cooler (3). The grate cooler (3) is configured to cool the clinker output from the rotary kiln (2) and discharge it from the system, and to introduce the secondary air generated into the rotary kiln (2) and the tertiary air generated into the decomposition furnace (1).

2. The system for co-producing sulfuric acid and cement clinker from phosphogypsum according to claim 1, wherein The system for producing sulfuric acid and co-producing cement clinker from phosphogypsum further includes a sedimentation chamber (8) connected to the grate cooler (3). An AQC boiler (9) is connected to the sedimentation chamber (8), and the AQC boiler (9) is used for waste heat power generation.

3. The system for co-producing sulfuric acid and cement clinker from phosphogypsum according to claim 2, wherein A dust collector (10) is connected to the AQC boiler (9), and the dust collector (10) is used for dust collection and discharging waste gas.

4. A method for producing sulfuric acid and co-producing cement clinker from phosphogypsum, characterized in that, The method for producing sulfuric acid and co-producing cement clinker from phosphogypsum uses the system for producing sulfuric acid and co-producing cement clinker according to any one of claims 1-3 for production, including: first feeding the raw materials into the preheater and performing multi-stage heat exchange through the kiln train (4) and the furnace train (5) respectively; then, using the smoke chamber (7) and the decomposition furnace (1) to perform secondary decomposition on the materials and enter the rotary kiln (2) through the smoke chamber (7), and forming clinker by high-temperature calcination in the rotary kiln (2); finally, cooling the clinker with the grate cooler (3) and discharging it from the system; at the same time, transporting the waste gas discharged from the furnace train (5) to the sulfuric acid production process from SO2 through the high-temperature fan (11) of the furnace train, and preparing sulfuric acid through flue gas purification and conversion absorption; using the high-temperature fan (12) of the kiln train to transport the waste gas discharged from the kiln train (4) to the raw material location for drying the raw materials.

5. The method for producing sulfuric acid and cement clinker from phosphogypsum according to claim 4, characterized in that: The secondary decomposition includes: The penultimate - stage cyclone (6) in the kiln train (4) is used to feed materials into the up - draft flue of the smoke chamber (7) for pre - decomposition, and the last - stage cyclone (6) in the kiln train (4) and the penultimate - stage cyclone (6) in the furnace train (5) are used to feed the collected materials into the decomposition furnace (1) for re - decomposition. After the decomposition furnace (1) decomposes the materials, the last - stage cyclone (6) in the furnace train (5) is used to send the decomposed materials into the smoke chamber (7).

6. The method for co-producing sulfuric acid and cement clinker from phosphogypsum according to claim 5, characterized in that, Before feeding into the pre - heater, the raw materials are proportioned, ground, dried, and homogenized in sequence. And the material ratio of the materials fed into the kiln train (4) and the furnace train (5) is 3:7 - 4:

6.

7. The method for co-producing sulfuric acid and cement clinker from phosphogypsum according to claim 4, characterized in that The decomposition furnace (1) is fed with combustible gases, including CO, H2, and CH4, through multiple burners.

8. The method for co-producing sulfuric acid and cement clinker from phosphogypsum according to claim 7, characterized in that, The decomposition furnace (1) is in a reducing - atmosphere state, and the partial pressure of CO or H2 accounts for 20% - 40% of the partial pressure of CO2. And during the decomposition process, the residence time of the materials is guaranteed to be more than 20 s, and the residence time of the gas is more than 10 s.

9. The method for producing sulfuric acid and co-producing cement clinker from phosphogypsum according to claim 4, characterized in that, The method for producing sulfuric acid from phosphogypsum and co - producing cement clinker further includes: The dried waste gas is discharged after desulfurization and dust removal; The waste gas remaining after sulfuric acid preparation is discharged after desulfurization and dust removal; The secondary air generated after the grate cooler (3) cools the clinker is introduced into the rotary kiln (2) for the combustion of pulverized coal in the rotary kiln (2), and the tertiary air generated is introduced into the decomposition furnace (1) for the combustion of combustible waste gas in the decomposition furnace (1), and the remaining waste gas is discharged after power generation by the surplus air and dust collection.

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