CN114772559A

CN114772559A - Separated dual system and production method for preparing sulfuric acid and co-producing cement from phosphogypsum

Info

Publication number: CN114772559A
Application number: CN202210575286.0A
Authority: CN
Inventors: 赵青林; 周尚群; 李福洲; 龙泉名; 周明凯
Original assignee: Wuhan University of Technology WUT
Current assignee: Wuhan University of Technology WUT
Priority date: 2022-05-25
Filing date: 2022-05-25
Publication date: 2022-07-22

Abstract

The invention discloses a separated dual system for preparing sulfuric acid and co-producing cement by using phosphogypsum and a production method. The separated double systems comprise an ardealite pyrolysis acid preparation system and a cement clinker calcining system. The invention adopts a separated phosphogypsum pyrolysis device, separates a phosphogypsum pyrolysis sulfuric acid preparation system from a cement clinker calcining system, ensures that an operator can adjust the working condition at any time according to different pyrolysis environments required by phosphogypsum and other cement raw materials, avoids the risk of skinning and blocking of a decomposing furnace caused by a large amount of liquid phase generated by overhigh pyrolysis temperature required by the phosphogypsum, and ensures the quality of the cement clinker while improving the decomposition rate of the phosphogypsum; meanwhile, the universality of the phosphogypsum is improved, and SO in the obtained acid making flue gas₂The concentration is not less than 8%.

Description

Separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum and production method

Technical Field

The invention relates to the technical field of preparation of sulfuric acid and co-production of cement by using phosphogypsum, in particular to a separated dual system and a production method for preparing sulfuric acid and co-production of cement by using phosphogypsum.

Background

The phosphogypsum is industrial waste residue generated in the process of preparing phosphoric acid by using sulfuric acid, and the total storage amount of the phosphogypsum rapidly rises in recent years due to the increase of the demand on phosphate fertilizer along with the development of economy in China. The complex impurities in the phosphogypsum cause serious limitation on resource utilization, a large amount of stockpiling not only occupies land resources, but also directly threatens the environmental safety of surrounding water areas by the contained water-soluble phosphorus pentoxide and water-soluble fluorine, and promotes the large-scale development and utilization of the phosphogypsum.

Because the phosphogypsum contains rich calcium and sulfur resources, the technology for preparing sulfuric acid and co-producing cement by decomposing the phosphogypsum can fully utilize the calcium and sulfur resources, does not discharge solid waste residues in the production process, provides sulfuric acid as a production raw material for phosphate fertilizer enterprises, and has good economic benefit and environmental benefit. However, the decomposition characteristics of the phosphogypsum and limestone are greatly different, the decomposition temperature of the phosphogypsum is high, the decomposition atmosphere control difficulty is high, the decomposition difficulty is far higher than that of the limestone, and the traditional method for preparing sulfuric acid by decomposing the phosphogypsum in a hollow kiln has a plurality of problems. From the perspective of energy conservation and emission reduction, the application of the fluidized decomposition technology to the preparation of sulfuric acid and the co-production of cement by the phosphogypsum pyrolysis is a development direction of the technology.

As early as 1997, the technique adopted by the Lubei group aims to amplify the '3, 4 and 6' PSC project by 10 times, and reaches the production capacity of 30 ten thousand tons of ammonium phosphate and 40 ten thousand tons of sulfuric acid with 60 ten thousand tons of cement produced annually. However, the decomposing furnace at the tail of the firing kiln is easy to form crust and block in the operation process of the system, and the adopted decomposing process outside the kiln finally fails to reach the original design capability. The prior art for preparing acid and cement by decomposing outside a kiln has the following problems: 1) most phosphorite in China belongs to medium and low grade, and correspondingly, the content of impurities in the phosphogypsum is high. According to incomplete statistics, phosphogypsum SiO of our country₂The average content is about 10 percent, P₂O₅The average content is about 1.15%, and the average content of F is about 0.40%. Therefore, most of the phosphogypsum in China cannot be directly used for preparing acid and co-producing cement. 2) Complete combustion of coalThe formation of the high-quality clinker and the burning requires an oxidizing atmosphere, and the decomposition of the phosphogypsum requires a reducing atmosphere, which is a pair of contradictions that are difficult to reconcile, and the production control difficulty is high, thus causing the quality fluctuation of the cement clinker to be large. 3) Since phosphogypsum is the main component of gypsum (pure CaSO)₄) The decomposition temperature of the phosphorus is higher than that of the phosphogypsum raw material (except CaSO)₄In addition, it also contains SiO₂、Fe₂O₃Etc.) and the decomposition of phosphogypsum in the inner layer part of the stacking state which is not completely decomposed stops because of being wrapped by liquid phase which appears earlier in the raw meal, thus reducing the quality of cement. 4) SO in flue gas for acid making₂The gas concentration generally requires more than 8 percent, and because the decomposition of the phosphogypsum and the calcination of the cement clinker are carried out in one device, the calcination temperature of the cement clinker reaches 1300-1450 ℃, and the gas demand of a system is large, the SO of the tail gas discharged from the kiln under normal conditions₂The concentration is generally only about 6%, which brings difficulty to acid preparation.

Disclosure of Invention

The invention aims to overcome the technical defects, provides a separate double system and a production method for preparing sulfuric acid and co-producing cement by using phosphogypsum, and solves the problems of poor universality of phosphogypsum, high production control difficulty and SO (SO) flue gas generated in the process of preparing acid and co-producing cement by decomposing phosphogypsum outside a kiln in the prior art₂Low content of the active component.

The invention provides a separated dual system for preparing sulfuric acid and co-producing cement by using phosphogypsum, which comprises: an acid preparation system by ardealite pyrolysis and a cement clinker calcining system; wherein,

the phosphogypsum pyrolysis acid-making system comprises: the device comprises a phosphogypsum preheating device, a phosphogypsum pyrolysis device, a high-temperature gas-solid separator and an acid making device; a solid phase outlet of the phosphogypsum preheating device is connected with a solid phase inlet of the phosphogypsum pyrolysis device, a material outlet of the phosphogypsum pyrolysis device is connected with a material inlet of the high-temperature gas-solid separator, a gas phase outlet of the high-temperature gas-solid separator is connected with a gas phase inlet of the phosphogypsum preheating device, and a gas phase outlet of the phosphogypsum preheating device is connected with a gas phase inlet of the acid making device;

the cement clinker calcining system comprises a raw material preheating device, an enlarged gas-solid separator, a mixing device and a rotary kiln; the solid phase inlet of the mixing device is respectively connected with the solid phase outlet of the raw material preheating device and the solid phase outlet of the high-temperature gas-solid separator, the material outlet of the mixing device is connected with the material inlet of the expanded gas-solid separator, and the solid phase outlet of the expanded gas-solid separator is connected with the material inlet of the rotary kiln.

The second aspect of the invention provides a process for preparing sulfuric acid and co-producing cement by using phosphogypsum, which comprises the following steps:

preparing acid by ardealite pyrolysis: gas-solid two-phase heat exchange is carried out on the phosphogypsum in a phosphogypsum preheating device, the phosphogypsum enters a phosphogypsum pyrolysis device for pyrolysis reaction after being preheated to more than 800 ℃, gas-solid separation is carried out on the phosphogypsum after the reaction is completed and the generated thermal-state new calcium enters a mixing device and contains high-concentration SO₂The waste gas is collected by a phosphogypsum preheating device, and sulfuric acid is obtained by an acid making device; the internal temperature of the phosphogypsum pyrolysis device is 1000-1250 ℃; in the process of preparing acid by pyrolyzing phosphogypsum, the used coal powder is at least one of bituminous coal, anthracite and lignite, and the heat value range is 4000-; the coal powder input amount is calculated according to the carbon-sulfur ratio of 1.1-2.0;

calcining cement clinker: the raw materials are subjected to heat exchange by a raw material preheating device, then are uniformly mixed with thermal state new calcium obtained by ardealite pyrolysis in a mixing device, after gas-solid separation of the mixed materials is realized by an expanded gas-solid separator, solid-phase materials enter a rotary kiln for calcination, and cement clinker is obtained;

compared with the prior art, the invention has the beneficial effects that:

(1) a separated phosphogypsum pyrolysis device is adopted, and a system for producing sulfuric acid by pyrolyzing the phosphogypsum is separated from a cement clinker calcining system, so that an operator can adjust the working condition at any time according to different pyrolysis environments required by the phosphogypsum and other cement raw materials, the risk of skinning and blocking of a decomposing furnace caused by a large amount of liquid phase generated by overhigh pyrolysis temperature required by the phosphogypsum is avoided, and the quality of the cement clinker is ensured while the decomposition rate of the phosphogypsum is improved;

(2) compared with the traditional ardealite kiln decomposition technology, after the ardealite is pyrolyzed, the ardealite contains high-concentration SO₂The waste gas is discharged and collected along with a phosphogypsum preheating device of a system for preparing sulfuric acid by pyrolyzing phosphogypsum, and SO is collected at two waste gas outlets in the traditional technology₂Compared with the prior art, the method has better advantages, and experiments show that SO in the flue gas is₂The concentration is not less than 8%;

(3) the universality of the phosphogypsum is improved, aiming at the difference of the content of impurities of the phosphogypsum, the problems can be solved by adjusting parameters such as raw material formula, carbon-sulfur ratio in a phosphogypsum pyrolysis device and the like, and the clinker meeting the quality requirement is finally obtained.

Drawings

FIG. 1 is a schematic structural diagram of an embodiment of a split dual system for producing sulfuric acid and co-producing cement from phosphogypsum according to the present invention;

FIG. 2 is a schematic structural diagram of an original 2500t/d novel dry-process cement clinker production line; wherein the decomposing furnace is a decomposing furnace with a precombustion furnace;

FIG. 3 is a schematic structural diagram of an original 2000t/d novel dry cement clinker production line; wherein the decomposing furnace is a spurting decomposing furnace;

FIG. 4 is a schematic structural diagram of an original 5000t/d novel dry-process cement clinker production line; wherein the decomposing furnace is a spray-spinning combined decomposing furnace.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the description of the present invention, it is to be noted that the terms "connected" and "coupled" are to be construed broadly unless otherwise explicitly specified or limited. For example, the connection may be fixed, detachable, or integrated; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

Referring to fig. 1, a first aspect of the present invention provides a separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum, comprising: an acid preparation system 1 by phosphogypsum pyrolysis and a cement clinker calcining system 2. Wherein, ardealite pyrolysis system acid system 1 includes: the device comprises a phosphogypsum preheating device 11, a phosphogypsum pyrolysis device 12, a high-temperature gas-solid separator 13 and an acid making device 14, wherein a solid phase outlet of the phosphogypsum preheating device 11 is connected with a solid phase inlet of the phosphogypsum pyrolysis device 12, a material outlet of the phosphogypsum pyrolysis device 12 is connected with a material inlet of the high-temperature gas-solid separator 13, a gas phase outlet of the high-temperature gas-solid separator 13 is connected with a gas phase inlet of the phosphogypsum preheating device 11, and a gas phase outlet of the phosphogypsum preheating device 11 is connected with a gas phase inlet of the acid making device 14; the cement clinker calcining system 2 comprises a raw material preheating device 21, an expanded gas-solid separator 22, a mixing device 23 and a rotary kiln 24, wherein a solid phase inlet of the mixing device 23 is respectively connected with a solid phase outlet of the raw material preheating device 21 and a solid phase outlet of the high-temperature gas-solid separator 13, a material outlet of the mixing device 23 is connected with a material inlet of the expanded gas-solid separator 22, and a solid phase outlet of the expanded gas-solid separator 22 is connected with a material inlet of the rotary kiln 24.

The main work flow of the system comprises the following steps: because the phosphogypsum is easy to react with carbon to generate CaS at 500-800 ℃, the CaS and CaSO₄Compared with the prior art, the method is difficult to pyrolyze and desulfurize, SO that the desulfurization rate of the phosphogypsum is improved by reducing heat consumption, gas-solid two-phase heat exchange is carried out on the phosphogypsum in a phosphogypsum preheating device 11, the phosphogypsum enters a phosphogypsum pyrolysis device 12 for pyrolysis reaction after being preheated to be more than 800 ℃, the temperature of the phosphogypsum pyrolysis device 12 is controlled to be 1000-1250 ℃, the phosphogypsum enters a high-temperature gas-solid separator 13 along with hot gas flow for gas-solid separation after complete reaction, a solid-phase product (hereinafter, referred to as thermal state new calcium) after the phosphogypsum pyrolysis enters a mixing device 23, and the solid-phase product (hereinafter, referred to as thermal state new calcium) containing high-concentration SO enters a mixing device 23₂The waste gas enters a phosphogypsum preheating device 11, and high-concentration SO is obtained after heat exchange₂The waste gas (the temperature is 300-400 ℃) enters the acid making device 14 to obtain sulfuric acid; the raw meal exchanges heat in a raw meal preheating device 21 and then is uniformly mixed with thermal state new calcium powder obtained by ardealite pyrolysis in a mixing device 23. The mixed material is subjected to gas-solid separation in an expanded gas-solid separator 22, the solid material enters a rotary kiln 24 for calcination, and cement is obtainedAnd (3) clinker aggregate. Due to the adoption of the phosphogypsum pyrolysis device 12, the phosphogypsum is changed from the traditional stacking state decomposition into the fluidized state decomposition, so that the decomposition efficiency is greatly improved, and the purpose of reducing the heat consumption of the whole sintering system is finally achieved. The invention breaks through the technical bottleneck brought by using the fluidization pyrolysis technology to realize the co-production of the sulfuric acid and the cement clinker by the phosphogypsum, provides technical support for large-scale phosphogypsum resource utilization, and realizes the purposes of greatly dissolving the phosphogypsum and reducing carbon and improving the efficiency of the cement.

Preferably, the gas phase outlet of the enlarged gas-solid separator 22 is connected to the gas phase inlet of the raw meal preheating device 21.

Preferably, the flue gas outlet of the rotary kiln 24 is connected with the gas phase inlet of the mixing device 23, so that the flue gas generated by the rotary kiln 24 directly enters the mixing device 23 and is discharged from the raw meal preheating device 21, and the flue gas is strictly forbidden to enter the acid making system.

Preferably, a tertiary air outlet of a kiln head cover of the rotary kiln 24 is connected with a hot air inlet of the phosphogypsum pyrolysis device 12, so that air required by the phosphogypsum pyrolysis reaction is provided by the tertiary air of the kiln head.

Furthermore, hot air inlets of the phosphogypsum pyrolysis device 12 are arranged at the bottom and the lateral conical part of the phosphogypsum pyrolysis device 12, so that tertiary air introduced by the kiln head cover can respectively enter the phosphogypsum pyrolysis device 12 from the bottom and the lateral conical part of the phosphogypsum pyrolysis device 12 to form high-speed vortex airflow in the pyrolysis furnace, and the retention time of the phosphogypsum in the furnace is prolonged.

Furthermore, a valve is arranged on a communication pipeline between a tertiary air outlet of the kiln hood of the rotary kiln 24 and a hot air inlet of the phosphogypsum pyrolysis device 12, so that the air quantity is controlled by the valve.

Preferably, the phosphogypsum pyrolysis device 12 is a phosphogypsum rotational flow-suspension state separation type pyrolysis furnace, and the phosphogypsum pyrolysis device 12 is also provided with a coal powder inlet so as to be convenient for adding coal powder. The number and the position of the pulverized coal inlets are not limited, and the pulverized coal inlets can be set by a person skilled in the art according to actual requirements.

Preferably, the phosphogypsum preheating device 11 is a multistage preheating device connected with multistage suspension preheaters, in some embodiments of the present invention, the number of the preheaters is generally 4 (the final stage is determined according to the heat exchange effect desired by an enterprise), and the preheaters are sequentially connected, and each single-stage preheater and the high-temperature gas-solid separator 13 of the phosphogypsum preheating device 11 are low-pressure loss preheaters, such as a cyclone preheater, a straight-tube preheater, etc.

Preferably, the phosphogypsum pyrolysis acid-making system 1 further comprises: the device comprises an ardealite grinding and drying device 15, an ardealite dry powder bin 16 and a dust collector 17; wherein, the solid phase outlet of the phosphogypsum grinding and drying device 15 is connected with a phosphogypsum dry powder bin 16, so that the ground and dried phosphogypsum is sent into the phosphogypsum dry powder bin 16; a gas phase inlet of the phosphogypsum grinding and drying device 15 is connected with a gas phase outlet of the raw material preheating device 21, a part of waste gas of the cement clinker calcining system 2 is led into the phosphogypsum grinding and drying device 15 through a pipeline, and powder selection is carried out while drying; a gas phase outlet of the phosphogypsum grinding and drying device 15 is connected with a gas phase inlet of a dust collector 17, and a solid phase outlet of the dust collector 17 is connected with a phosphogypsum dry powder bin 16, so that dust-containing particles in the gas are collected by the dust collector 17 and then are sent into the phosphogypsum dry powder bin 16; the solid phase outlet of the phosphogypsum dry powder bin 16 is connected with the phosphogypsum preheating device 11 so as to send the phosphogypsum into the phosphogypsum preheating device 11.

Further, a solid phase inlet of the gypsum grinding and drying device 15 is connected with a first belt conveyor, so that the phosphogypsum which is fully dried and homogenized in the yard or is filtered and properly broken is conveyed into the gypsum grinding and drying device 15 through the first belt conveyor for grinding and drying, and the phosphogypsum loses free water and crystal water to become semi-hydrated gypsum in the process. Furthermore, an iron remover is also arranged on the first belt conveyor to prevent iron materials from damaging the grinding and drying machine 15.

Further, a second belt conveyor is connected between a solid-phase outlet of the gypsum grinding and drying device 15 and the phosphogypsum dry powder bin 16, so that the phosphogypsum is ground, dried and selected by the gypsum grinding and drying device 15 and then is conveyed to the dry powder bin 16 through the second belt conveyor for storage.

Furthermore, a first metering scale is arranged between the second belt conveyor and the phosphogypsum dry powder bin 16, a second metering scale is arranged between the dust collector 17 and the phosphogypsum dry powder bin 16, and materials are respectively weighed by the first metering scale and the second metering scale and then enter the phosphogypsum dry powder bin 16.

Furthermore, a third metering scale, a third belt conveyor and a lifter 18 are sequentially arranged between the phosphogypsum dry powder bin 16 and the phosphogypsum preheating device 11, and the discharged material of the phosphogypsum dry powder bin 16 is metered by the third metering scale, then discharged to the third belt conveyor and then enters an ascending pipeline of the phosphogypsum preheating device 11 through the lifter 18.

Further, the phosphogypsum grinding and drying device 15 is one of a hammer type dryer, a vertical mill dryer, a vertical roller mill dryer, a disc mill dryer or a DMC mill dryer.

Preferably, a heat exchange cooling tower 19 is further connected between the phosphogypsum preheating device 11 and the acid making device 14 to ensure that the phosphogypsum contains high-concentration SO₂The waste gas is collected in the phosphogypsum preheating device 11 and then enters the heat exchange cooling tower 19, and the sulfuric acid is obtained in the acid making device after cooling.

Furthermore, the heat exchange cooling tower 19 has the functions of heat exchange and continuous cooling of the gas, a small amount of dilute sulfuric acid can be sprayed in the tower, and the ore dust and impurities in the gas are washed away by using the dilute sulfuric acid.

Preferably, the raw meal preheater unit 21 is a multistage preheater unit in which a plurality of suspension preheaters are connected, and in some embodiments of the present invention, the number of preheaters is generally 4 (the final stage is determined according to the heat exchange effect desired by the enterprise), and the individual single-stage preheaters of the raw meal preheater unit 21 and the expanded gas-solid separator 22 are connected in series, and each single-stage preheater and the expanded gas-solid separator 22 is a low-pressure loss type preheater, such as a cyclone preheater, a straight-tube preheater, and the like.

Preferably, the mixing device 23 is newly added by design calculation according to the condition of the production line. For example, the decomposing furnace of the original production line is modified into a pyrolyzing furnace for pyrolyzing the phosphogypsum, and a mixing device is additionally arranged for mixing hot raw materials supplied by each system. The corresponding mixing device can be a furnace type structure of a pipe type, a spouting type or a combined spouting and spinning type.

Preferably, the mixing device 23 is retrofitted to existing clinker production line decomposers. For example, the device can be formed by reforming a DD type, a DD-I type, a DD-II type, a TDF type, a TSD type, an NFC type, an MFC type decomposing furnace and the like, wherein the temperature in the furnace is 860 ℃ to 920 ℃; during modification, the positions and angles of the pulverized coal and the raw materials (including the thermal state new calcium powder) entering the mixing device 23 of the decomposing furnace can be properly adjusted, the tertiary air pipe is omitted, and the flue gas path of the smoke chamber (uptake flue) is unchanged.

In some embodiments of the invention, the cement clinker calcination system 2 is retrofitted from an existing clinker firing system comprising: a raw material preheating device, a decomposing furnace and a rotary kiln; the improvement comprises the following steps: the tertiary air is not directly fed into a decomposing furnace of an original clinker firing system, so that the tertiary air is connected with a hot air inlet of the phosphogypsum pyrolysis device 12; meanwhile, the flue gas and the materials which are discharged from the decomposing furnace are separated in the expanded gas-solid separator 22 with stronger capacity; the flue gas generated by the rotary kiln 24 directly enters the mixing device 23 and is discharged from the raw meal preheating device 21 of the cement clinker calcining system 2, and the flue gas is strictly forbidden to enter the phosphogypsum pyrolysis acid-making system 1. The invention directly utilizes the existing or stopped cement production line to carry out rapid reconstruction, and carries out large-scale resource utilization on the phosphogypsum in the shortest time. The carbon reduction amplitude of the clinker preparation system is not less than 12% after the double-series or single-series kiln system is modified. And the single-series kiln line is transformed into the double-series kiln line, so that the yield of the cement production line can be greatly improved to be twice as high as that of the original cement production line, and the process method has the advantages of small environmental pollution, low investment, low production cost, good economic benefit and the like.

In some more specific embodiments of the present invention, the mixing device 23 is modified from a decomposing furnace with a precombustor in an existing clinker firing system, and the raw meal preheating device in the existing clinker firing system comprises a C1-C5 preheater. During modification: the raw material preheating device 21 utilizes a C1-C4 preheater of the raw material preheating device in the original clinker firing system, a C5 preheater is changed into an expanded gas-solid separator 22, a newly-heated newly-generated calcium inlet of the pre-combustion furnace 31 and an original tertiary air duct are connected with the phosphogypsum pyrolysis device 12 in a diversion mode. The thermal state new calcium obtained by the improved phosphogypsum pyrolysis acid making system 1 is introduced into the precombustion furnace 31 through a thermal state new calcium inlet, and enters the precombustion furnace 31 together with the original C4 supplied materials, the mixed hot raw materials enter the original decomposition furnace main furnace 32 from the precombustion furnace 31, enter the enlarged gas-solid separator 22 for gas-solid separation after being discharged from the decomposition furnace main furnace 32, and the separated powder enters the rotary kiln 24 for calcination.

In some more specific embodiments of the present invention, the mixing device 23 is modified from a spurt-type calciner of an existing clinker firing system, wherein the raw meal preheating device of the existing clinker firing system comprises a C1-C5 preheater. During modification: the raw material preheating device 21 utilizes a C1-C4 preheater of the raw material preheating device in the original clinker firing system, changes a C5 preheater into an expanded gas-solid separator 22, a newly-added thermal state new calcium generation thermal state inlet of a decomposing furnace 41 and an original tertiary air pipe which are connected with the phosphogypsum pyrolysis device 12 in a diversion way. The thermal state new calcium obtained by the modified phosphogypsum pyrolysis acid making system 1 is directly introduced into the decomposing furnace 41 (the existing mixing device 23) through the thermal state inlet of the thermal state new calcium, the incoming material of C4 enters through the raw material inlet of the original clinker system, namely, the thermal state new calcium pyrolyzed by the phosphogypsum and the incoming material of C4 enter into the decomposing furnace 41 (the existing mixing device 23) together, the thermal state new calcium and the incoming material of the original C4 enter into the expanding gas-solid separator 22 for gas-solid separation after leaving the decomposing furnace 41 (the existing mixing device 23), and the separated powder enters into the rotary kiln 24 for calcination.

In some more specific embodiments of the present invention, the mixing device 23 is modified from a combined spray-rotary type decomposing furnace in the original clinker firing system, in which the raw meal preheating device comprises a C1A-C5A preheater and a C1B-C5B preheater. During modification: the phosphogypsum preheating device 11 utilizes a B series C1B-C4B preheater in the original clinker firing system, wherein the original C5B preheater is upgraded and modified into a high-temperature gas-solid separator 13, hot new calcium coming out of the high-temperature gas-solid separator 13 directly enters a cone part of a mixing device 23 which is upgraded by the original decomposing furnace in the original clinker firing system, and materials at a feed opening of the original B series C4B enter an added phosphogypsum pyrolyzing device 12; the raw material preheating device 21 utilizes a C1A-C4A preheater in the original clinker firing system to change a series A C5A preheater in the clinker firing system into an expanded gas-solid separator 22, and an original tertiary air duct is connected with a hot air inlet of the phosphogypsum pyrolysis device 12 in a diversion way. The thermal state new calcium obtained by the phosphogypsum pyrolysis acid making system 1 after the B series transformation and the original A series C4A coming material enter the mixing device 23 transformed and upgraded by the original decomposing furnace together, the new calcium enters the expanded gas-solid separator 22 after being discharged from the mixing device 23, and the separated powder enters the rotary kiln for calcination and is cooled by the grate cooler to prepare the clinker.

Preferably, the cement clinker calcination system 2 further comprises a grate cooler 25, and a solid phase inlet of the grate cooler 25 is connected with a solid phase outlet of the rotary kiln 24 so as to cool the calcined clinker.

As a preferred technical scheme of the invention, the separated dual system for preparing sulfuric acid and co-producing cement by using the phosphogypsum comprises: an acid preparation system 1 by ardealite pyrolysis and a cement clinker calcining system 2. Wherein,

the phosphogypsum pyrolysis acid-making system 1 comprises: a phosphogypsum preheating device 11, a phosphogypsum pyrolysis device 12, a high-temperature gas-solid separator 13, an acid making device 14, a phosphogypsum grinding and drying device 15, a phosphogypsum dry powder bin 16 and a dust collector 17, a solid phase outlet of the phosphogypsum grinding and drying device 15 is connected with a phosphogypsum dry powder bin 16, a gas phase outlet of the phosphogypsum grinding and drying device 15 is connected with a gas phase inlet of a dust collector 17, a solid phase outlet of the dust collector 17 is connected with the phosphogypsum dry powder bin 16, a solid phase outlet of the phosphogypsum dry powder bin 16 is connected with a phosphogypsum preheating device 11, a solid phase outlet of the phosphogypsum preheating device 11 is connected with a solid phase inlet of a phosphogypsum pyrolysis device 12, a material outlet of the phosphogypsum pyrolysis device 12 is connected with a material inlet of a high-temperature gas-solid separator 13, a gas phase outlet of the high-temperature gas-solid separator 13 is connected with a gas phase inlet of the phosphogypsum preheating device 11, and a gas phase outlet of the phosphogypsum preheating device 11 is connected with a gas phase inlet of an acid making device 14;

the cement clinker calcining system 2 comprises a raw material preheating device 21 and an expanded gas-solid separator 22, the device comprises a mixing device 23, a rotary kiln 24 and a grate cooler 25, wherein a solid phase inlet of the mixing device 23 is respectively connected with a solid phase outlet of a raw material preheating device 21 and a solid phase outlet of a high-temperature gas-solid separator 13, a material outlet of the mixing device 23 is connected with a material inlet of an enlarged gas-solid separator 22, a gas phase outlet of the enlarged gas-solid separator 22 is connected with a gas phase inlet of the raw material preheating device 21, a solid phase outlet of the enlarged gas-solid separator 22 is connected with a material inlet of the rotary kiln 24, a solid phase outlet of the rotary kiln 24 is connected with a solid phase inlet of the grate cooler 25, a flue gas outlet of the rotary kiln 24 is connected with a gas phase inlet of the mixing device 23, a tertiary air outlet of a kiln hood of the rotary kiln 24 is connected with a hot air inlet of a phosphogypsum pyrolysis device 12, and a gas phase outlet of the raw material preheating device 21 is connected with a gas phase inlet of a phosphogypsum grinding and drying device 15.

In the invention, each gas connecting pipeline can be provided with a fan according to the requirement.

preparing acid by ardealite pyrolysis: gas-solid two-phase heat exchange is carried out on the phosphogypsum in a phosphogypsum preheating device 11, the phosphogypsum enters a phosphogypsum pyrolysis device 12 for pyrolysis reaction after being preheated to more than 800 ℃, the phosphogypsum enters a high-temperature gas-solid separator 13 for gas-solid separation after complete reaction, the generated thermal-state new calcium enters a mixing device 23 and contains high-concentration SO₂The waste gas is collected by a phosphogypsum preheating device 11, and sulfuric acid is obtained by an acid making device;

calcining cement clinker: the raw materials are subjected to heat exchange through a raw material preheating device 21, then are uniformly mixed with thermal state new calcium obtained by ardealite pyrolysis in a mixing device 23, the mixed materials are subjected to gas-solid separation in an enlarged gas-solid separator 22, and then the solid materials enter a rotary kiln 24 for calcination to obtain cement clinker.

The specific composition of phosphogypsum is not limited by the invention, and includes dihydrate, semi-hydrate and anhydrous phosphogypsum produced by wet-process phosphoric acid industrial production methods (dihydrate method, semi-hydrate method and anhydrous method) and pretreated phosphogypsum, and can be selected by a person skilled in the art according to actual conditions. In some embodiments of the invention, the chemical composition of the selected phosphogypsum is: CaO 26% -36%, SO₃ 36％-50％、SiO ₂ 2％-10％、P₂O₅ 0.01％-2.5％、F 0％-3％、K₂O 0％-0.7％、Na₂O0％-0.5％、Al₂O₃ 0％-1.4％、Fe₂O₃0-0.6 percent of MgO, 0-0.35 percent of MgO and 20-24 percent of others.

Go to oneStep one, grinding the dried ardealite to obtain CaSO₄·2H₂The percentage content of O is more than 80 percent, and the residue of the sieve with the particle size of 80 mu m is controlled not to exceed 18 percent when the material is fed into a decomposing furnace.

Preferably, the internal temperature of the phosphogypsum pyrolysis apparatus 12 is 1000-1250 ℃. Air required by the pyrolysis reaction is provided by kiln head tertiary air, the tertiary air enters the phosphogypsum pyrolysis device 12 from the bottom and the lateral cone of the phosphogypsum pyrolysis device 12 respectively, high-speed vortex airflow is formed in the phosphogypsum pyrolysis device 12, the pyrolysis temperature is controlled, and the phosphogypsum can stay in the phosphogypsum pyrolysis device 12 sufficiently, so that the phosphogypsum is pyrolyzed sufficiently.

Preferably, in the process of preparing acid by pyrolyzing phosphogypsum, the used coal powder is at least one of bituminous coal, anthracite and lignite, and the calorific value range is 4000-.

Furthermore, the coal powder input amount is calculated according to the carbon-sulfur ratio of 1.1-2.0, and the decomposition rate of the phosphogypsum is more than 90% in the ratio range.

Preferably, it contains a high concentration of SO₂The waste gas is collected by a phosphogypsum preheating device 11, and is cooled by a heat exchange cooling tower 19 to obtain sulfuric acid in an acid making device 14.

Preferably, the solid-phase material enters the rotary kiln 24 to be calcined, and then is cooled by the grate cooler 25 to obtain the cement clinker.

Preferably, the cement clinker, the gypsum and the mixed material are ground to obtain qualified cement.

Example 1

The phosphogypsum raw material adopted by the embodiment 1 of the invention is CaSO from a certain company in Guizhou₄·2H₂The percentage of O was 93.75% and the main composition is shown in Table 1.

TABLE 1

Composition (A)	CaO	SO₃	SiO₂	P₂O₅	F	K₂O	Na₂O	Al₂O₃	Fe₂O₃	MgO	Loss
												Phosphogypsum	31.35	42.40	2.78	0.97	0.12	0.07	0.44	0.37	0.14	0.07	21.29

A separate type dual system for preparing sulfuric acid and co-producing cement by using phosphogypsum is shown in figure 1 and comprises: an acid preparation system 1 by ardealite pyrolysis and a cement clinker calcining system 2. The phosphogypsum pyrolysis acid-making system 1 comprises: the system comprises a phosphogypsum preheating device 11, a phosphogypsum pyrolysis device 12, a high-temperature gas-solid separator 13, an acid making device 14, a phosphogypsum grinding and drying device 15, a phosphogypsum dry powder bin 16, a dust collector 17, a hoister 18 and a heat exchange cooling tower 19. The cement clinker calcining system 2 comprises a raw meal preheating device 21, an expanded gas-solid separator 22, a mixing device 23 which is modified from an original decomposing furnace with a precombustion furnace, a rotary kiln 24 and a grate cooler 25. A solid-phase inlet of the ardealite grinding and drying device 15 is connected with a first belt conveyor, and the first belt conveyor is also provided with an iron remover; a solid phase outlet of the phosphogypsum grinding and drying device 15 is connected with a phosphogypsum dry powder bin 16 through a second belt conveyor, and a first weighing scale is arranged between the second belt conveyor and the phosphogypsum dry powder bin 16; a gas phase outlet of the phosphogypsum grinding and drying device 15 is connected with a gas phase inlet of a dust collector 17, a solid phase outlet of the dust collector 17 is connected with a phosphogypsum dry powder bin 16, and a second metering scale is arranged between the dust collector 17 and the phosphogypsum dry powder bin 16; a solid phase outlet of the phosphogypsum dry powder bin 16 is connected with a phosphogypsum preheating device 11, and a third metering scale, a third belt conveyor and a lifter 18 are sequentially arranged between the phosphogypsum dry powder bin 16 and the phosphogypsum preheating device 11; a solid phase outlet of the phosphogypsum preheating device 11 is connected with a solid phase inlet of the phosphogypsum pyrolysis device 12, a material outlet of the phosphogypsum pyrolysis device 12 is connected with a material inlet of the high-temperature gas-solid separator 13, a gas phase outlet of the high-temperature gas-solid separator 13 is connected with a gas phase inlet of the phosphogypsum preheating device 11, a gas phase outlet of the phosphogypsum preheating device 11 is connected with a gas phase inlet of the acid making device 14, and a heat exchange cooling tower 19 is also connected between the phosphogypsum preheating device 11 and the acid making device 14; a solid phase inlet of the mixing device 23 is respectively connected with a solid phase outlet of the raw material preheating device 21 and a solid phase outlet of the high-temperature gas-solid separator 13, a material outlet of the mixing device 23 is connected with a material inlet of the enlarged gas-solid separator 22, a gas phase outlet of the enlarged gas-solid separator 22 is connected with a gas phase inlet of the raw material preheating device 21, a solid phase outlet of the enlarged gas-solid separator 22 is connected with a material inlet of the rotary kiln 24, a solid phase outlet of the rotary kiln 24 is connected with a solid phase inlet of the grate cooler 25, a flue gas outlet of the rotary kiln 24 is connected with a gas phase inlet of the mixing device 23, a tertiary air outlet of a kiln head cover of the rotary kiln 24 is connected with a hot air inlet of the phosphogypsum pyrolysis device 12, hot air inlets of the phosphogypsum pyrolysis device 12 are arranged at the bottom and a side cone part of the phosphogypsum pyrolysis device 12, a valve is arranged on a communication pipeline between the tertiary air outlet of the kiln head cover of the rotary kiln 24 and the hot air inlet of the phosphogypsum pyrolysis device 12, the gas phase outlet of the raw material preheating device 21 is connected with the gas phase inlet of the phosphogypsum grinding and drying device 15.

The transformation method comprises the following steps: a2500 t/d novel dry cement clinker production line is reformed (see figure 2), a decomposing furnace is a decomposing furnace with a precombustion furnace, and the size of the decomposing furnace is phi 5.6 multiplied by 29 m. During modification: the new equipment comprises an ardealite preheating device 11, an ardealite pyrolysis device 12, a high-temperature gas-solid separator 13, an acid making device 14, an ardealite grinding and drying device 15, an ardealite dry powder bin 16, a dust collector 17, a hoister 18, a heat exchange cooling tower 19 and the like. Secondly, the original cement clinker calcining system is modified, including changing a C5 cyclone cylinder into an enlarged gas-solid separator 22, changing a new hot state new calcium inlet of a precombustion furnace 31 (namely changing the function of the original decomposing furnace with the precombustion furnace into a mixing device 23), and changing a channel of an original tertiary air pipe into a phosphogypsum pyrolysis device 12. The thermal state new calcium obtained by the modified phosphogypsum pyrolysis acid making system is introduced into the pre-combustion furnace 31 through a thermal state new calcium inlet, and enters the pre-combustion furnace 31 together with the original C4 supplied materials, the mixed hot raw materials enter the original decomposing furnace main furnace 32 from the pre-combustion furnace 31, enter the expanded gas-solid separator 22 for gas-solid separation after being discharged from the decomposing furnace main furnace 32, and the separated powder enters the rotary kiln 24 for calcination and is cooled by the grate cooler 25 to prepare the clinker.

The specific production method comprises the following steps: fully drying and homogenizing aged phosphogypsum in a storage yard, then sending the aged phosphogypsum into a grinding and drying device 15 for grinding and drying through a first belt conveyor, removing free water in the phosphogypsum, and additionally arranging an iron remover on the first belt conveyor to prevent iron materials from damaging the grinding and drying device 15; one part of the exhaust gas (the temperature is controlled to be 300-350 ℃) of a clinker sintering systemIntroducing the materials into a grinding dryer 15 through a pipeline, selecting powder while drying, controlling the granularity of the materials to be 10-80 mu m, weighing the selected phosphogypsum by a first weighing scale, then sending the weighed phosphogypsum into a phosphogypsum dry powder bin 16, collecting dust-containing particles in gas by a dust collector 17, weighing the dust-containing particles by a second weighing scale, and then sending the weighed particles into the phosphogypsum dry powder bin 16; the dry powder bin 16 is weighed and fed into a third belt conveyer through a third weigher, and then enters an ascending pipeline of a phosphogypsum preheating device 11 through a lifter 18, so that the phosphogypsum enters the phosphogypsum preheating device 11, the phosphogypsum is subjected to gas-solid two-phase heat exchange in the phosphogypsum preheating device 11 and enters a phosphogypsum cyclone-suspension state separation type pyrolysis furnace 12 after being preheated to 800 plus materials of temperature, the phosphogypsum cyclone-suspension state separation type pyrolysis furnace 12 uses tertiary air to enter the phosphogypsum cyclone-suspension state separation type pyrolysis furnace 12 from the bottom of the furnace vertically upwards and the side surface of a cone part tangentially respectively, so that a cyclone-spray combined type upwards flow field is generated in the phosphogypsum cyclone-suspension state separation type pyrolysis furnace 12, and the coal powder and the phosphogypsum powder are dispersed along with the tertiary air to complete full mixing, combustion and pyrolysis. Because the phosphogypsum pyrolysis needs a reducing atmosphere, the combustion atmosphere is controlled by controlling the air quantity and the carbon-sulfur ratio, the temperature of a high-temperature oxidation zone of the phosphogypsum pyrolysis furnace is ensured to be 1000-1250 ℃, and the phosphogypsum decomposition rate is controlled to be about 92 percent. After full pyrolysis, the solid powder enters a high-temperature gas-solid separator 13 along with hot air flow for gas-solid separation, the solid powder-thermal nascent calcium obtained after separation enters a precombustion furnace 31 (a current mixing device 23) of the original decomposing furnace, and after the solid powder-thermal nascent calcium is premixed in the precombustion furnace 31, the material passes through a main furnace 32 (the current mixing device 23) of the decomposing furnace and an expanded gas-solid separator 22 and enters a rotary kiln 24 for calcination, and the calcined clinker is cooled by a grate cooler 25 to obtain qualified clinker; containing SO₂The waste gas (the concentration is 8-11%, the temperature is 300-. The phosphogypsum rotational flow-suspension state separation type pyrolysis furnace 12 adopts fuel to select bituminous coal by pushing, the carbon-sulfur ratio is selected to be 1.25, and the calorific value is 5500kcal/kg-6000 kcal/kg. The production capacity of the transformed clinker is improved to about 4500 t/d.

Example 2

A separated dual system and a production method for preparing sulfuric acid and co-producing cement by phosphogypsum are different from those in the embodiment 1 in that:

the adopted phosphogypsum raw material is CaSO from a certain company in Guizhou₄·0.5H₂The percentage of O was 93.23%, and the main composition is shown in Table 2.

TABLE 2

Composition (A)	CaO	SO₃	SiO₂	P₂O₅	F	K₂O	Na₂O	Al₂O₃	Fe₂O₃	MgO	Loss
												Phosphogypsum	33.04	44.30	2.09	1.05	0.46	0.059	0.21	0.27	0.10	0.051	18.37

The transformation method comprises the following steps: a2000 t/d novel dry-process cement clinker production line is reconstructed (see figure 3), a decomposition furnace is a spurting type decomposition furnace, and the size of the decomposition furnace is phi 4.52 multiplied by 22.7 m. During modification: the new equipment comprises an ardealite preheating device 11, an ardealite pyrolysis device 12, a high-temperature gas-solid separator 13, an acid making device 14, an ardealite grinding and drying device 15, an ardealite dry powder bin 16, a dust collector 17, a hoister 18, a heat exchange cooling tower 19 and the like. Secondly, the original cement clinker calcining system is modified, including changing a C5 cyclone into an enlarged gas-solid separator 22, adding a new thermal state new calcium inlet to a decomposing furnace 41, and changing the original tertiary air pipe to be connected with the phosphogypsum pyrolysis device 12. The thermal state new calcium obtained by the modified phosphogypsum pyrolysis acid making system 1 is directly introduced into the decomposing furnace 41 (the existing mixing device 23) through the thermal state new calcium inlet, namely, the thermal state new calcium enters the mixing device 23 together with the original C4 incoming material, the thermal state new calcium is discharged from the mixing device 23 and enters the expanded gas-solid separator 22 for gas-solid separation, and the separated powder enters the rotary kiln 24 for calcination and is cooled through the grate cooler 25 to prepare clinker.

The specific production method comprises the following steps: the pyrolysis temperature high-temperature oxidation zone of the pyrolysis furnace is 1150-1200 ℃, the decomposition rate of the phosphogypsum is about 95 percent, the reaction is completed and then enters a high-temperature gas-solid separator 13 along with hot gas flow for gas-solid separation, solid powder obtained after separation, thermal newly generated calcium directly enters an original decomposition furnace 41 (a mixing device 23) and a cement clinker calcining system2, the incoming materials are uniformly mixed in a mixing device 23 and then enter a rotary kiln 24 for calcination through an expanded gas-solid separator 22, and the calcined clinker is cooled through a grate cooler 25 to obtain qualified clinker; containing 8-11% SO₂The waste gas (the temperature is 350-400 ℃) is collected at the waste gas outlet of the phosphogypsum preheating device 11 and enters a heat exchange cooling tower 19, and the sulfuric acid is obtained in an acid plant after the waste gas is cooled to 20-40 ℃. The ardealite rotational flow-suspension state separation type pyrolysis device 12 adopts fuel for pushing and selecting bituminous coal, the heat value is 5500kcal/kg-6000kcal/kg, and the carbon-sulfur ratio is 1.25. The production capacity of the transformed clinker is improved to about 4000t/d from the original 2000 t/d.

Example 3

the adopted phosphogypsum raw material is CaSO from a certain company in Yunnan₄·2H₂The percentage of O was 90.15%, the main composition of which is shown in Table 3.

TABLE 3

Composition (I)	CaO	SO₃	SiO₂	P₂O₅	F	K₂O	Na₂O	Al₂O₃	Fe₂O₃	MgO	Loss
												Phosphogypsum	30.13	41.70	7.78	0.06	0.02	0.07	0.04	0.12	0.04	0.03	20.01

The transformation method comprises the following steps: a5000 t/d novel dry-process cement clinker production line (see figure 4) in a certain high-altitude area is improved, a decomposition furnace of the production line is a jet-spinning combined decomposition furnace, and the size of the decomposition furnace is phi 7.5 multiplied by 33 m. During modification: adding partial equipment of an ardealite pyrolysis acid-making system, which mainly comprises an ardealite pyrolysis device 12, a high-temperature gas-solid separator 13, an acid-making device 14, an ardealite grinding and drying device 15, an ardealite dry powder bin 16, a dust collector 17, a lifter 18 and a heat exchange cooling tower 19; the phosphogypsum preheating device 11 utilizes C1B-C4B of B series of the original production line, wherein a C5B cyclone cylinder of the original B series is upgraded and modified into the high-temperature gas-solid separator 13, hot new calcium coming out of the high-temperature gas-solid separator 13 directly enters a cone part of the decomposing furnace 51 (the existing mixing device 23), and other cement raw meal enters the decomposing furnace 51 (the existing mixing device 23) through a feed opening of the original C4A. And secondly, transforming the original cement clinker calcining system, including changing the C5A cyclone cylinder of the A series into an enlarged gas-solid separator 22, and changing the original tertiary air pipe to be connected with the phosphogypsum pyrolysis device 12 of the phosphogypsum pyrolysis acid-making system. The thermal state new calcium obtained by the modified phosphogypsum pyrolysis acid making system and the original A series C4A incoming material enter a decomposing furnace 51 (the existing mixing device 23) together, the new calcium comes out of the decomposing furnace 51 (the existing mixing device 23) and then enters an expanded gas-solid separator 22, and the separated powder enters a rotary kiln 24 for calcination and is cooled by a grate cooler 25 to prepare clinker.

The specific production method comprises the following steps: the ardealite rotational flow-suspension state separation type pyrolysis device 12 adopts fuels of bituminous coal and lignite, wherein the heat value of the bituminous coal is 6000kcal/kg-6500kcal/kg, the heat value of the lignite is 4000kcal/kg-4500kcal/kg, and the mass ratio of the bituminous coal to the lignite is 7: 3, selecting the carbon-sulfur ratio to be 1.25, and feeding the mixture into the phosphogypsum pyrolysis furnace through two coal injection pipes. The lignite coal injection pipe is arranged above the tertiary air, the bituminous coal injection pipe is arranged on the opposite side of the lignite coal injection pipe, inflammable lignite can be rapidly combusted in a high-altitude area, the temperature in the initial section of the phosphogypsum pyrolysis furnace is increased, and accordingly bituminous coal can be ignited more rapidly compared with the bituminous coal which is used alone. But the rapid combustion of the lignite also consumes a large amount of oxygen in a limited space, SO that the initial combustion speed of the bituminous coal is inhibited, then the combustion speed is gradually accelerated along with the full mixing of the bituminous coal and tertiary air, the temperature distribution of the phosphogypsum pyrolysis furnace is more balanced, the temperature of a high-temperature oxidation zone of the pyrolysis furnace is 1150-₂The waste gas (the temperature is 300-400 ℃) is collected at the waste gas outlet of the phosphogypsum preheating device 11 and enters a heat exchange cooling tower 19, and the sulfuric acid is obtained in an acid plant after the waste gas is cooled to 20-40 ℃. The production capacity of the transformed clinker is improved to more than 6000 t/d.

Compared with the prior art, the invention has the beneficial effects that:

in the traditional phosphogypsum co-production cement process, a phosphogypsum calcium raw material and a limestone calcium raw material are mixed together, because the pyrolysis temperature of the phosphogypsum is too high, the limestone calcium raw material and other raw materials such as clay are too early and generate liquid phase to cause skinning, and in order to solve the problem, a separated phosphogypsum pyrolysis device is arranged to separate the phosphogypsum and other raw materials for reaction, the phosphogypsum is pyrolyzed in a pyrolysis environment of about 1200 ℃, and clinker calcination is finished in a rotary kiln according to the prior cement process, so that excessive liquid phase of raw materials is avoided.

The invention separates the phosphogypsum pyrolysis acid making process which needs to be realized under the reducing atmosphere from the cement clinker calcining process which needs to be realized under the oxidizing atmosphere (or the weak reducing atmosphere), and the acid making system generates the acid containing high-concentration SO₂After heat exchange is carried out by a phosphogypsum preheating device arranged in a phosphogypsum pyrolysis acid making system, the phosphogypsum preheating device enters an acid making device to complete acid making; the hot new calcium generated by the phosphogypsum pyrolysis acid making system enters a mixing device, is uniformly mixed with the raw material powder obtained by preheating by a raw material preheating device, and then enters a rotary kiln to finish the calcination of clinker, and the flue gas generated by the cement clinker calcination system enters waste heat power generation or a raw material mill after heat exchange by the raw material preheating device arranged in the cement clinker calcination system.

The separated dual system can be operated separately and independently and can be operated cooperatively and simultaneously; compared with the traditional phosphogypsum acid-making system, the newly added important thermal equipment is a phosphogypsum pyrolysis device and a high-temperature gas-solid separator which work under the reducing atmosphere; compared with the traditional clinker sintering system, the newly improved important thermal equipment is a mixing device (which can be improved or independently newly arranged on the basis of the original decomposing furnace) and an expanded gas-solid separator which work under an oxidizing atmosphere (or a weak reducing atmosphere); the separated double systems can realize the rapid upgrading and reconstruction of the existing novel dry-method cement production line, and increase the yield of the original production line while cooperatively treating the phosphogypsum.

The invention can quickly transform the existing cement firing system, does not influence the production of cement clinker while realizing the acid preparation by the phosphogypsum, and has the space for increasing the yield and the efficiency of a single-series old cement production line; when the technology is adopted, phosphogypsum is usedThe decomposition rate of the flue gas can reach more than 90 percent, and SO in the flue gas₂The concentration is not less than 8%, the large-scale and high-efficiency development and utilization of the phosphogypsum can be realized, and the problem of huge pollution caused by the accumulation of the phosphogypsum at present is solved.

The above-described embodiments of the present invention should not be construed as limiting the scope of the present invention. Any other corresponding changes and modifications made according to the technical idea of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A disconnect-type dual system of ardealite preparation sulphuric acid coproduction cement which characterized in that: comprises an phosphogypsum pyrolysis acid making system and a cement clinker calcining system; wherein,

the phosphogypsum pyrolysis acid-making system comprises: the device comprises a phosphogypsum preheating device, a phosphogypsum pyrolysis device, a high-temperature gas-solid separator and an acid making device; the solid phase outlet of the phosphogypsum preheating device is connected with the solid phase inlet of the phosphogypsum pyrolysis device, the material outlet of the phosphogypsum pyrolysis device is connected with the material inlet of the high-temperature gas-solid separator, the gas phase outlet of the high-temperature gas-solid separator is connected with the gas phase inlet of the phosphogypsum preheating device, and the gas phase outlet of the phosphogypsum preheating device is connected with the gas phase inlet of the acid making device;

the cement clinker calcining system comprises a raw material preheating device, an expanded gas-solid separator, a mixing device and a rotary kiln; the solid phase inlet of the mixing device is respectively connected with the solid phase outlet of the raw material preheating device and the solid phase outlet of the high-temperature gas-solid separator, the material outlet of the mixing device is connected with the material inlet of the expanded gas-solid separator, and the solid phase outlet of the expanded gas-solid separator is connected with the material inlet of the rotary kiln.

2. The separate type dual system for preparing sulfuric acid and co-producing cement from phosphogypsum as claimed in claim 1, wherein a gas phase outlet of the expanded gas-solid separator is connected with a gas phase inlet of the raw meal preheating device, a flue gas outlet of the rotary kiln is connected with a gas phase inlet of the mixing device, and a tertiary air outlet of a kiln head cover of the rotary kiln is connected with a hot air inlet of the phosphogypsum pyrolysis device.

3. The separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 2, wherein hot air inlets of the phosphogypsum pyrolysis device are arranged at the bottom and the side cone of the phosphogypsum pyrolysis device, and a valve is arranged on a communication pipeline between a tertiary air outlet of a kiln head cover of the rotary kiln and the hot air inlet of the phosphogypsum pyrolysis device.

4. The separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 1, wherein the phosphogypsum pyrolysis acid-making system further comprises: the device comprises a phosphogypsum grinding and drying device, a phosphogypsum dry powder bin and a dust collector; wherein,

the solid-phase outlet of the phosphogypsum grinding and drying device is connected with the phosphogypsum dry powder bin, the gas-phase inlet of the phosphogypsum grinding and drying device is connected with the gas-phase outlet of the raw material preheating device, the gas-phase outlet of the phosphogypsum grinding and drying device is connected with the gas-phase inlet of the dust collector, the solid-phase outlet of the dust collector is connected with the phosphogypsum dry powder bin, and the solid-phase outlet of the phosphogypsum dry powder bin is connected with the phosphogypsum preheating device.

5. The separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 1, which is characterized in that a heat exchange cooling tower is also connected between the phosphogypsum preheating device and the acid making device; the cement clinker calcining system also comprises a grate cooler, wherein a solid-phase inlet of the grate cooler is connected with a solid-phase outlet of the rotary kiln.

6. The separate type dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 1, characterized in that the phosphogypsum pyrolysis device is a phosphogypsum rotational flow-suspension state separate type pyrolysis furnace, the phosphogypsum preheating device is a multistage preheating device connected with multistage suspension preheaters, and each single-stage preheater of the phosphogypsum preheating device and the high-temperature gas-solid separator are low-pressure-loss preheaters; the raw material preheating device is a multi-stage preheating device connected with a multi-stage suspension preheater, and each single-stage preheater and the enlarged gas-solid separator of the raw material preheating device are low-pressure loss preheaters.

7. The separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 1, wherein the cement clinker calcining system is modified from an original clinker firing system, and the original clinker firing system comprises: a raw material preheating device, a decomposing furnace and a rotary kiln; the improvement comprises the following steps: the tertiary air is not directly fed into a decomposing furnace of an original clinker firing system, so that the tertiary air is connected with a hot air inlet of the phosphogypsum pyrolysis device; and simultaneously, the flue gas and the materials out of the decomposing furnace are separated in the expanded gas-solid separator.

8. The separate type dual system for preparing sulfuric acid and co-producing cement by using phosphogypsum as claimed in claim 7, wherein the mixing device is formed by modifying a decomposing furnace with a precombustor in an original clinker firing system, and the raw meal preheating device in the original clinker firing system comprises a C1-C5 preheater; during modification: the raw material preheating device utilizes a C1-C4 preheater of the raw material preheating device in the original clinker firing system, a C5 preheater is changed into the expanded gas-solid separator, a thermal state new calcium inlet is additionally arranged in the precombustion furnace, and the original tertiary air duct is connected with the phosphogypsum pyrolysis device in a way of changing;

or the mixing device is formed by reforming a spurting type decomposing furnace in the original clinker firing system, and the raw material preheating device in the original clinker firing system comprises a C1-C5 preheater; during modification: the raw material preheating device utilizes a C1-C4 preheater of a raw material preheating device in an original clinker firing system, a C5 preheater is changed into the expanded gas-solid separator, a newly-increased thermal state new calcium thermal state inlet of a decomposing furnace, and an original tertiary air pipe is connected with the phosphogypsum pyrolysis device in a diversion way;

or the mixing device is formed by reforming a spray-rotation combined decomposing furnace in the original clinker firing system, and the raw material preheating device in the original clinker firing system comprises a C1A-C5A preheater and a C1B-C5B preheater; during modification: the phosphogypsum preheating device is characterized in that a B-series C1B-C4B preheater and an original C5B preheater in an original clinker firing system are upgraded and transformed into the high-temperature gas-solid separator, hot fresh calcium coming out of the high-temperature gas-solid separator directly enters a conical part of the mixing device upgraded by the original decomposing furnace in the original clinker firing system, and materials at a feed port of the original B-series C4B preheater enter the additionally-arranged phosphogypsum pyrolysis device; the raw material preheating device changes an A series C5A preheater in a clinker firing system into the expanded gas-solid separator and changes an original tertiary air duct into a hot air inlet which is connected with the phosphogypsum pyrolysis device by utilizing a C1A-C4A preheater in an original clinker firing system.

9. The separated dual system for preparing sulfuric acid and co-producing cement from phosphogypsum according to claim 1, which is characterized by comprising: an acid preparation system by phosphogypsum pyrolysis and a cement clinker calcining system; wherein,

the phosphogypsum pyrolysis acid-making system comprises: the device comprises a phosphogypsum preheating device, a phosphogypsum pyrolysis device, a high-temperature gas-solid separator, an acid making device, a phosphogypsum grinding and drying device, a phosphogypsum dry powder bin and a dust collector; a solid phase outlet of the phosphogypsum grinding and drying device is connected with the phosphogypsum dry powder bin, a gas phase outlet of the phosphogypsum grinding and drying device is connected with a gas phase inlet of the dust collector, a solid phase outlet of the dust collector is connected with the phosphogypsum dry powder bin, a solid phase outlet of the phosphogypsum dry powder bin is connected with the phosphogypsum preheating device, a solid phase outlet of the phosphogypsum preheating device is connected with a solid phase inlet of the phosphogypsum pyrolysis device, a material outlet of the phosphogypsum pyrolysis device is connected with a material inlet of the high-temperature gas-solid separator, a gas phase outlet of the high-temperature gas-solid separator is connected with a gas phase inlet of the phosphogypsum preheating device, and a gas phase outlet of the phosphogypsum preheating device is connected with a gas phase inlet of the acid making device;

the cement clinker calcining system comprises a raw material preheating device, an expanded gas-solid separator, a mixing device, a rotary kiln and a grate cooler, wherein a solid phase inlet of the mixing device is respectively connected with a solid phase outlet of the raw material preheating device and a solid phase outlet of the high-temperature gas-solid separator, a material outlet of the mixing device is connected with a material inlet of the expanded gas-solid separator, a gas phase outlet of the expanded gas-solid separator is connected with a gas phase inlet of the raw material preheating device, a solid phase outlet of the expanded gas-solid separator is connected with a material inlet of the rotary kiln, a solid phase outlet of the rotary kiln is connected with a solid phase inlet of the grate cooler, a smoke outlet of the rotary kiln is connected with a gas phase inlet of the mixing device, and a tertiary air outlet of a kiln hood of the rotary kiln is connected with a hot air inlet of the phosphogypsum pyrolysis device, and a gas phase outlet of the raw material preheating device is connected with a gas phase inlet of the phosphogypsum grinding and drying device.

10. The process for preparing sulfuric acid and co-producing cement by using phosphogypsum is characterized by comprising the following steps of:

preparing acid by pyrolyzing phosphogypsum: the phosphogypsum is subjected to gas-solid two-phase heat exchange in the phosphogypsum preheating device, preheated to more than 800 ℃, enters the phosphogypsum pyrolysis device for pyrolysis reaction, enters the high-temperature gas-solid separator for gas-solid separation after complete reaction, and the generated thermal-state new calcium is introduced into the mixing device and contains high-concentration SO₂The waste gas is collected by the phosphogypsum preheating device, and sulfuric acid is obtained in the acid making device; the internal temperature of the phosphogypsum pyrolysis device is 1000-1250 ℃; in the process of preparing acid by pyrolyzing the phosphogypsum, the used coal powder is at least one of bituminous coal, anthracite and lignite, and the heat value range is 4000-; the coal powder input amount is calculated according to the carbon-sulfur ratio of 1.1-2.0;

calcining cement clinker: the raw materials are subjected to heat exchange through the raw material preheating device, then are uniformly mixed with thermal state new calcium obtained by ardealite pyrolysis in the mixing device, the mixed materials are subjected to gas-solid separation in the expanded gas-solid separator, and then the solid materials enter the rotary kiln for calcination to obtain cement clinker;

the process for preparing sulfuric acid co-produced cement by using the phosphogypsum is realized by a separated dual system for preparing sulfuric acid co-produced cement by using the phosphogypsum as claimed in any one of claims 1 to 9.