CN114436551A - System and method for producing high-purity beta semi-hydrated gypsum or II type anhydrous gypsum by using industrial byproduct gypsum - Google Patents

Abstract

The invention belongs to the technical field of energy-saving industrial gypsum production and recycling, and discloses a system for producing high-purity beta semi-hydrated gypsum or II-type anhydrous gypsum by using industrial byproduct gypsum, which comprises a pretreatment subsystem, a calcination subsystem, a cooling subsystem, a water circulation treatment subsystem and a flue gas treatment subsystem: the pretreatment subsystem carries out washing impurity removal on industrial byproduct gypsum to obtain a pretreatment material; the calcining subsystem preheats and calcines the obtained pretreatment material to obtain high-purity gypsum and high-temperature flue gas, the high-temperature flue gas returns to the preheated pretreatment material, and the high-purity gypsum enters the cooling subsystem to be cooled and discharged to obtain a high-purity gypsum product; the flue gas treatment subsystem returns clean ash, and the water circulation treatment subsystem returns materials and water. The system for producing high-purity gypsum can accurately convert industrial by-product gypsum into beta semi-hydrated gypsum or II type anhydrous gypsum, has the characteristics of impurity removal, high raw material utilization rate, energy conservation, environmental protection, low cost and the like, and enlarges the application approaches of the industrial by-product gypsum.

Description

A system and method for producing high-purity beta hemihydrate gypsum or type II anhydrite by utilizing industrial by-product gypsum

technical field

The invention belongs to the technical field of energy-saving industrial gypsum production and reuse, in particular to a system and method for producing high-purity beta hemihydrate gypsum or type II anhydrite by utilizing industrial by-product gypsum.

Background technique

Industrial by-product gypsum refers to the solid waste generated in the industrial production of phosphate fertilizer, thermal power and titanium dioxide for the treatment of waste acid and waste gas, mainly including phosphogypsum, desulfurization gypsum and titanium gypsum. At present, there are nearly 8,000 gypsum emission enterprises in China, with an annual emission of 200 million tons. For the treatment of industrial by-product gypsum, nearby burial or open-air stacking is often used, but this extensive disposal method not only occupies valuable land resources, but also easily causes secondary pollution to the environment. At present, most of the industrial by-product gypsum in my country has not been effectively utilized, and the comprehensive utilization rate is less than 50%. As China's environmental protection efforts continue to increase. How to turn the industrial by-product gypsum into treasure and realize the comprehensive utilization of its resources is extremely urgent.

At present, the existing states of gypsum (calcium sulfate) include dihydrate gypsum, hemihydrate gypsum, type III anhydrite, type II anhydrite, and type I anhydrite (also known as α type anhydrite). The industrial by-product gypsum exists in the form of calcium sulfate dihydrate. When the dihydrate gypsum is heated to a certain temperature, it is easy to lose part or all of the crystal water and become hemihydrate gypsum or anhydrite. This process is called calcination of gypsum. At present, most of the existing large-scale gypsum product enterprises in China use rotary kilns with internal and external firing, intermittent or continuous frying pans, boiling furnaces, etc., which are small in scale, incomplete in supporting facilities, unstable in product quality and high in energy consumption. At the same time, because there are many types of industrial by-product gypsum, different process operating conditions and raw material sources result in different components and unstable quality of industrial by-product gypsum. In addition, due to the many and complex harmful impurities contained in it, as well as many problems such as acid and fluorine, it is difficult to realize a process that can solve all the problems of industrial by-product gypsum, resulting in slow progress in its research and comprehensive application.

SUMMARY OF THE INVENTION

In view of the problems and deficiencies in the prior art, the purpose of the present invention is to provide a system and method for producing high-purity beta hemihydrate gypsum or type II anhydrite by utilizing industrial by-product gypsum.

Based on the above object, the present invention adopts the following technical solutions:

A first aspect of the present invention provides a system for producing high-purity beta hemihydrate gypsum or type II anhydrite by utilizing industrial by-product gypsum, the system includes a pretreatment subsystem, a calcination subsystem, a cooling subsystem and a flue gas treatment subsystem; the pretreatment subsystem is used for washing the industrial by-product gypsum and removing impurities to obtain pretreated material; the calcining subsystem includes a preheating device and a calcining device, and the preheating device is used for The pretreated material is directly mixed with the high temperature flue gas for preheating treatment. The calcining device is used for calcining the pretreated material processed by the preheating device to burn off impurities and crystal water to obtain high-purity gypsum and high-temperature flue gas. Wherein, the high-purity gypsum enters the cooling subsystem for processing in the next process, and the high-temperature flue gas is returned to the preheating device to preheat the pre-treated material, and then is purified by the flue gas processing subsystem and then emptied; The system is used for directly mixing the calcined high-temperature and high-purity gypsum with combustion-supporting air for cooling treatment, and discharging after cooling to obtain a high-purity gypsum product.

Preferably, the preheating device includes a primary preheater and a secondary preheater, and the calcining device includes a main calcining furnace and a main separation furnace; the primary preheater and the secondary preheater are respectively provided with There are material inlet, material outlet, gas inlet and gas outlet, the main calciner is provided with material inlet, gas inlet and material gas outlet, and the main separation furnace is provided with material gas inlet, gas outlet and material outlet;

The material inlet of the primary preheater is communicated with the material outlet of the pretreatment subsystem, the material outlet of the primary preheater is communicated with the material inlet of the secondary preheater, and the material outlet of the secondary preheater is communicated with the main calciner The material inlet of the furnace is connected, the material gas outlet of the main calciner is connected with the material gas inlet of the main separation furnace, and the material outlet of the main separation furnace is connected with the material inlet of the cooling subsystem;

The gas outlet of the main separation furnace is communicated with the gas inlet of the secondary preheater, the gas outlet of the secondary preheater is communicated with the gas inlet of the primary preheater, and the gas outlet of the primary preheater is communicated with the flue gas treatment Subsystems are connected.

Preferably, the cooling subsystem includes a primary cooler, a secondary cooler, a tertiary cooler and a finished product cooler; the primary cooler, the secondary cooler and the tertiary cooler are all provided with material inlets respectively , material outlet, gas inlet and gas outlet; the finished product cooler is provided with a material inlet and a material outlet;

The material inlet of the primary cooler is communicated with the material outlet of the main separation furnace, the material outlet of the primary cooler is communicated with the material inlet of the secondary cooler, and the material outlet of the secondary cooler is communicated with the material inlet of the tertiary cooler Connected, the material outlet of the tertiary cooler is communicated with the material inlet of the finished product cooler;

The gas inlet of the tertiary cooler is used to introduce combustion-supporting air into the tertiary cooler, the gas outlet of the tertiary cooler is communicated with the gas inlet of the secondary cooler, and the gas outlet of the secondary cooler is connected with the primary cooling. The gas inlet of the primary cooler is communicated with the gas inlet of the main calciner, and the gas outlet of the primary cooler is communicated with the gas inlet of the main calciner.

Preferably, the pretreatment subsystem includes a primary water washing device, a secondary water washing device and a crushing device, the primary water washing device and the secondary water washing device are used for washing and removing impurities from the industrial by-product gypsum, and the crushing device is used for The material after the secondary water washing is crushed to obtain the pretreated material; the primary water washing device, the secondary water washing device and the crushing device are respectively provided with a material inlet and a material outlet, wherein the primary water washing device and the secondary water washing device are also There are water inlet and water outlet respectively;

The material inlet of the primary water washing device is the raw material inlet, the material outlet of the primary water washing device is communicated with the material inlet of the secondary water washing device, the material outlet of the secondary water washing device is communicated with the material inlet of the crushing device, and the material outlet of the crushing device is connected with the preheater. The material inlet of the thermal device is communicated.

More preferably, the primary water washing device in the pretreatment subsystem includes a water washing stirring tank and a water washing sedimentation tank, the water washing stirring tank is provided with a material inlet, a water inlet and a material liquid outlet, and the water washing sedimentation tank is provided with a material liquid inlet, water outlet and material outlet. The outlet, the material liquid outlet of the water washing and stirring tank is connected with the material liquid inlet of the water washing settling tank; the secondary water washing device includes a horizontal disc filter; the crushing device includes a crusher and a crusher; the pretreatment subsystem also A conveying device is included, and the conveying device includes a screw conveyor.

More preferably, the horizontal disc filter is equipped with a vacuum filtration system for filtration operation to realize the separation of material and water.

Preferably, the system for producing high-purity gypsum further includes a water circulation treatment subsystem; the water circulation treatment subsystem includes a neutralization stirring tank and a neutralization settling tank, and the flue gas treatment subsystem includes an indirect heat exchanger, which is an indirect heat exchanger. The heater is used to cool the high-temperature flue gas discharged from the gas outlet of the primary preheater, and the flue gas after the cooling treatment is evacuated after dust collection;

The neutralization and stirring tank is provided with a material inlet, a water inlet and a material liquid outlet, and the neutralization settling tank is provided with a material liquid inlet, a material outlet and a water outlet; the water inlet of the neutralization and stirring tank is connected with the pretreatment subsystem. The water outlet is connected, the material liquid outlet of the neutralization stirring tank is connected with the material liquid inlet of the neutralization settling tank, the material outlet of the neutralization settling tank is connected with the raw material inlet of the primary water washing device, and the water outlet of the neutralization settling tank is respectively connected with the primary water washing The device is connected with the water inlet of the secondary water washing device; the water outlet of the neutralization settling tank is provided with two branch pipes, one of which is connected with the cooling water inlet of the finished product cooler, and the cooling water outlet of the finished product cooler is respectively connected with the pipe through the pipe. The water inlets of the primary water washing device and the secondary water washing device are connected, and the other branch pipe is connected to the cooling water inlet of the indirect heat exchanger. The water ports are connected; and cooling water pipes are arranged in the finished product cooler and the indirect heat exchanger.

More preferably, the flue gas treatment subsystem further includes a bag filter, an external exhaust fan, a pneumatic lift pump, and a Roots blower, and the indirect heat exchanger and the bag filter are all provided with a gas inlet and a gas outlet, The bag filter is also provided with a dust collection outlet; the gas inlet of the indirect heat exchanger is communicated with the gas outlet of the primary preheater in the preheating device, and the gas outlet of the indirect heat exchanger is connected with the gas of the bag filter The inlet is communicated, the gas outlet of the bag filter is communicated with the outside world through the external exhaust fan, and the dust outlet of the bag filter is communicated with the gas inlet of the calcining subsystem through a pneumatic lift pump; the pneumatic lift pump is communicated with the Roots blower, Used to re-feed the clean ash recovered by the baghouse to the calcining subsystem.

More preferably, the primary preheater, secondary preheater, main calciner, main separation furnace and primary cooler, secondary cooler and tertiary cooler in the cooling subsystem in the calcination subsystem There are pressure gauges and thermometers at the top and bottom of the furnace to check and control the internal conditions of the device; the main separation furnace is also equipped with a sampling port for sampling and testing to confirm the quality of the product.

More preferably, in order to ensure the same velocity of flue gas flowing in the calcining subsystem and cooling subsystem, the diameter of each gas outlet pipe in the calcining subsystem and cooling subsystem is designed according to the internal temperature of the equipment and the air volume of the external exhaust fan.

The second aspect of the present invention provides a method for producing high-purity beta hemihydrate gypsum or type II anhydrite using the system for producing high-purity gypsum described in the first aspect, comprising the following steps:

(1) Add the industrial by-product gypsum to the raw material inlet of the system for producing high-purity gypsum, and enter the pretreatment subsystem of the system to carry out water washing and impurity removal treatment to obtain pretreated materials and washing wastewater;

(2) The pretreated material enters the calcination subsystem for preheating and calcination to obtain high-temperature flue gas and high-purity gypsum; wherein, the high-temperature flue gas returns to the preheating device to directly mix the pre-treated material for preheating, and then enter the flue gas treatment After the subsystem is cooled, it is dedusted to obtain clean ash and purified gas, and the clean ash is returned to the calcining subsystem; the high-purity gypsum enters the cooling subsystem and is cooled and discharged to obtain a high-purity gypsum product; during the cooling process of the high-purity gypsum, Combustion-supporting air enters the cooling subsystem and is directly mixed with high-purity gypsum for heat exchange, and then enters the calcining device in the calcining subsystem;

(3) The washing wastewater obtained in step (1) is returned to the pretreatment subsystem for recycling after neutralization and sedimentation treatment.

Preferably, when producing high-purity hemihydrate beta gypsum, the calcination temperature in step (2) is 300-400°C.

Preferably, when producing high-purity type II anhydrite, the calcination temperature in step (2) is 600-700°C.

More preferably, in step (2), the specific steps of entering the pretreated material into the calcination subsystem for processing are: after the pretreated material is preheated by the primary preheater and the secondary preheater in sequence, it enters the main calciner Calcination and decomposition are carried out to obtain high-purity gypsum and high-temperature flue gas, and then all enter the main separation furnace for separation; the high-purity gypsum enters the cooling subsystem from the main separation furnace, and the high-temperature flue gas returns to the secondary preheater from the main separation furnace in turn. And the first-stage preheater to exchange heat with the pretreated material in the preheating device.

Preferably, in step (2), the specific step of entering the high-purity gypsum into the cooling subsystem for cooling treatment is as follows: the high-purity gypsum is graded through the primary cooler, the secondary cooler, the tertiary cooler and the finished product cooler in sequence. After cooling, the material is discharged to obtain a high-purity gypsum product; at the same time, the combustion-supporting air enters the cooling subsystem, and then enters the tertiary cooler, the secondary cooler and the primary cooler in turn, and exchanges heat with the high-purity gypsum in the cooler. Finally, it enters the main calciner.

Preferably, the specific step of entering the industrial by-product gypsum into the pretreatment subsystem for processing in step (1) is as follows: the industrial by-product gypsum is washed by a primary water washing device and a secondary water washing device to remove impurities and then separated from solid and liquid to obtain Concentrated material and washing wastewater; wherein, the concentrated material enters the crushing device for crushing and dispersing to obtain pretreated material, and the two washing wastewater enters the water circulation treatment subsystem for recycling.

Preferably, the specific steps of recycling the washing waste water in step (3) are: after the washing waste water enters the neutralization stirring tank, adding alkaline oxides to stir and react to obtain a reacted mixture, and then sending the mixture to neutralization The sedimentation tank conducts precipitation and separation to obtain the precipitation material and the supernatant water; wherein, the precipitation material is incorporated into the raw material into the raw material feed port and re-enters the pretreatment subsystem, and the supernatant water is divided into two parts for indirect heat exchange of smoke and material respectively, and one part Enter the finished product cooler for finished product cooling, the other part enters the indirect heat exchanger to cool the high temperature flue gas, and finally returns to the primary water washing device and the secondary water washing device to participate in the next round of water washing.

More preferably, the specific steps of cooling and dedusting the high-temperature flue gas in step (2) are as follows: the flue gas discharged from the preheating device enters the indirect heat exchanger and the cooling water pipeline inside the indirect heat exchanger for indirect heat exchange, and then Enter the bag filter for filtration and purification to obtain filtered and purified gas and clean ash. The filtered and purified gas is blown into the chimney by the external exhaust fan and discharged, and the filtered clean ash is blown into the pneumatic lift pump by the Roots blower. The gas is re-introduced to the gas inlet of the calcination subsystem.

More preferably, in step (1), the material is uniformly crushed and dispersed to a particle size of 100-1000 μm.

More preferably, the wind speed of the flue gas in the calcining subsystem and the cooling subsystem is 15-20 m/s.

Compared with the prior art, the beneficial effects of the present invention are as follows:

(1) The system for producing high-purity gypsum of the present invention combines the five subsystems of the pretreatment subsystem, the calcination subsystem (including the preheating device), the cooling subsystem, the water circulation processing subsystem and the flue gas processing subsystem. By-product gypsum resource utilization, by controlling the temperature in the main calcining furnace in the calcining system, high-purity beta hemihydrate gypsum or type II anhydrite is accurately produced. In one embodiment, the purity of the prepared high-purity gypsum product reaches More than 92%, it can effectively remove the soluble impurities (potassium oxide, sodium oxide, potassium fluoride, sodium fluoride, soluble phosphorus, etc.) in the industrial by-product gypsum, and at the same time prepare high value-added gypsum products.

(2) The system for producing high-purity gypsum of the present invention is washed twice by circulating water in the pretreatment subsystem to reduce the soluble impurities in the industrial by-product gypsum; the preheating of the material is realized by the multi-stage preheating device in the calcination subsystem, which is convenient for the material Fully calcining and energy saving and consumption reduction in the calcining process; the multi-stage cooling device in the cooling subsystem realizes the preheating of the combustion air and the cooling of the finished materials, which can not only reduce the fuel consumption after the heated combustion air enters the main calciner, It can also reduce the temperature of the finished material to meet the transportation temperature requirements of the finished material; return the clean ash through the flue gas treatment subsystem to continue calcination, and reduce the temperature of the exhaust flue gas through the indirect heat exchange process of smoke and water, thereby reducing the exhaust fan. Operating power; the material and water returned through the water circulation treatment subsystem continue to be used as raw materials and flushing water, wherein the flushing water indirectly heats up during the process of passing through the cooling subsystem and the calcining subsystem, which can promote the flushing of materials. Soluble impurities dissolve rapidly.

(3) The present invention combines the processes of cooling, waste heat recovery, water circulation, and ash return with the main process, improves the comprehensive utilization efficiency of industrial by-product gypsum, and maximizes the utilization of industrial by-product gypsum; the whole process has no external pollutants. It has the advantages of continuous operation, high thermal efficiency, low energy consumption, high output, low cost, stable operation, high operation rate, convenient operation, safety and reliability, and is suitable for large-scale production, with good economic and environmental benefits.

Description of drawings

1 is a flow chart of a system for producing high-purity gypsum in an embodiment of the present invention, wherein 1 is a pretreatment subsystem, 11 is a water washing agitation tank, 12 is a water washing sedimentation tank, 13 is a horizontal disc filter, and 14 is a spiral Conveyor, 15 is the crusher; 2 is the calcining subsystem, 21 is the primary preheater, 22 is the secondary preheater, 23 is the main calciner, and 24 is the main separation furnace; 3 is the cooling subsystem, 31 is a primary cooler, 32 is a secondary cooler, 33 is a tertiary cooler, 34 is a finished product cooler; 4 is a flue gas treatment subsystem, 41 is an indirect heat exchanger, 42 is a bag filter, 43 It is an external exhaust fan, 44 is a pneumatic lift pump, 45 is a Roots blower; 5 is a water circulation treatment subsystem, 51 is a neutralization stirring tank, and 52 is a neutralization sedimentation tank.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below through embodiments combined with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

Example 1

An embodiment of the present invention provides a system for producing high-purity gypsum by using industrial by-product gypsum, as shown in FIG. 1 , including a pretreatment subsystem 1, a calcination subsystem 2, a cooling subsystem 3, a flue gas treatment subsystem 4 and a water circulation Processing subsystem 5; the pretreatment subsystem 1 includes a water washing and stirring tank 11, a water washing sedimentation tank 12, a horizontal disc filter 13, a screw conveyor 14, and a crushing machine 15; the calcining subsystem 2 includes a first stage Preheater 21, secondary preheater 22, main calciner 23, main separation furnace 24; the cooling subsystem 3 includes a primary cooler 31, a secondary cooler 32, a tertiary cooler 33, and a finished product cooler 34; the flue gas treatment subsystem 4 includes an indirect heat exchanger 41, a bag filter 42, an external exhaust fan 43, a pneumatic lift pump 44 and a roots blower 45; the water circulation treatment subsystem 5 includes a neutralization stirring tank 51 and neutralization settling tank 52.

In the pretreatment subsystem 1, the water washing and stirring tank 11, the water washing sedimentation tank 12, the horizontal disc filter 13, and the crushing and dispersing machine 15 are respectively provided with a material inlet and a material outlet, wherein the water washing and stirring tank 11 is also provided with The water inlet, the water washing sedimentation tank 12 is also provided with a water outlet, and the horizontal disc filter 13 is also provided with a water inlet and a water outlet; The material inlet of the sedimentation tank 12 is connected, the material outlet of the washing sedimentation tank 12 is connected with the material inlet of the horizontal disc filter 13, and the material outlet of the horizontal disc filter 13 is connected with the material inlet of the crusher 15 through the screw conveyor 14. Communication, the material outlet of the crusher 15 is communicated with the material inlet of the calcining subsystem 2 .

In the calcination subsystem 2, the primary preheater 21 and the secondary preheater 22 are respectively provided with a material inlet, a material outlet, a gas inlet and a gas outlet, and the main calciner 23 is provided with a material inlet and a gas inlet , the material gas outlet, the main separation furnace 24 is provided with a material gas inlet, a gas outlet and a material outlet; the material inlet of the primary preheater 21 is communicated with the material outlet of the pretreatment subsystem 1, and the primary preheater 21 The material outlet of the secondary preheater 22 is communicated with the material inlet of the secondary preheater 22, the material outlet of the secondary preheater 22 is communicated with the material inlet of the main calciner 23, and the feed gas outlet of the main calciner 23 is connected with the feed gas of the main separation furnace 24. The inlet is communicated, and the material outlet of the main separation furnace 24 is communicated with the material inlet of the cooling subsystem 3; the gas outlet of the main separation furnace 24 is communicated with the gas inlet of the secondary preheater 22, and the gas outlet of the secondary preheater 22 It communicates with the gas inlet of the primary preheater 21 , and the gas outlet of the primary preheater 21 communicates with the gas inlet of the indirect heat exchanger 41 in the flue gas treatment subsystem 4 .

In the cooling subsystem 3, the primary cooler 31, the secondary cooler 32, and the tertiary cooler 33 are respectively provided with material inlet, material outlet, gas inlet and gas outlet, and the finished product cooler 34 is provided with material Inlet and material outlet; the material inlet of the primary cooler 31 is communicated with the material outlet of the calcination subsystem 2, the material outlet of the primary cooler 31 is communicated with the material inlet of the secondary cooler 32, and the The material outlet is communicated with the material inlet of the tertiary cooler 33, the material outlet of the tertiary cooler 33 is communicated with the material inlet of the finished product cooler 34, and the material outlet of the finished product cooler 34 is discharged; the gas of the tertiary cooler 33 The inlet is used to introduce combustion-supporting air into the tertiary cooler 33, the gas outlet of the tertiary cooler 33 is communicated with the gas inlet of the secondary cooler 32, and the gas outlet of the secondary cooler 32 is connected with the gas of the primary cooler 31. The inlet is communicated, and the gas outlet of the primary cooler 31 is communicated with the gas inlet of the main calciner 23 .

In the flue gas treatment subsystem 4, the indirect heat exchanger 41 and the bag filter 42 are provided with a gas inlet and a gas outlet, and the bag filter 42 is also provided with a dust outlet; The gas inlet is communicated with the gas outlet of the primary preheater 21 in the preheating device, the gas outlet of the indirect heat exchanger 41 is communicated with the gas inlet of the bag filter 42, and the gas outlet of the bag filter 42 passes through the external exhaust fan 43 is communicated with the outside world, and the dust collection outlet of the bag filter 42 is communicated with the gas inlet of the secondary preheater 22 in the preheating device through a pneumatic lift pump 44; the pneumatic lift pump 44 is communicated with the Roots blower 45 for The clean ash recovered by the bag filter 42 is sent to the calcining subsystem 2 again.

In the water circulation treatment subsystem 5, the neutralization and stirring tank 51 is provided with a material inlet, a water inlet and a material-liquid outlet, and the neutralization and settling tank 52 is provided with a material-liquid inlet, a material outlet and a water outlet; the neutralization and stirring tank The water inlet of 51 is communicated with the water outlet of the washing settling tank 12 and the horizontal disc filter 13 in the pretreatment subsystem 1, and the feed liquid outlet of the neutralization stirring tank 51 is communicated with the feed liquid inlet of the neutralization settling tank 52. The material outlet of the sedimentation tank 52 is connected with the raw material inlet of the pretreatment subsystem 1, the water outlet of the neutralization sedimentation tank 52 is connected with the water inlet of the washing and stirring tank 11 and the horizontal disc filter 13 respectively, and the outlet of the neutralization sedimentation tank 52 is connected. The water outlet is provided with two branch pipes, one of which is communicated with the cooling water inlet of the finished product cooler 34, and the cooling water outlet of the finished product cooler 34 is communicated with the water washing and stirring tank 11 and the water inlet of the horizontal disc filter 13 respectively through the pipes. , the other branch pipe is communicated with the cooling water inlet of the indirect heat exchanger 41, and the cooling water outlet of the indirect heat exchanger 41 is communicated with the water inlet of the washing and stirring tank 11 and the horizontal disc filter 13 respectively through the pipes.

Example 2

The embodiment of the present invention provides a method for producing high-purity beta hemihydrate gypsum using the system for producing high-purity gypsum described in Embodiment 1, comprising the following steps:

(1) The industrial by-product gypsum is added to the raw material inlet of the system for producing high-purity gypsum, and enters the pretreatment subsystem 1 of the system for washing, impurity removal, crushing, and dispersing treatment to obtain pretreated materials and washing wastewater; The system for producing high-purity gypsum is the system described in Example 1, which specifically includes a pretreatment subsystem 1, a calcination subsystem 2, a cooling subsystem 3, a flue gas treatment subsystem 4, and a water circulation treatment subsystem 5.

Among them, the pretreatment subsystem 1 includes a washing and stirring tank 11, a washing settling tank 12, a horizontal disc filter 13, a screw conveyor 14, and a crushing and dispersing machine 15. The washing slurry is obtained by stirring and mixing, so that the soluble impurities in the material are fully dissolved in water and discharged. The washing slurry enters the washing sedimentation tank 12 and settles, and then solid-liquid separation is performed to separate the material from the primary washing wastewater; among which, the material enters the horizontal plate. The filter 13 is mixed with water for secondary flushing, and then filtered to obtain concentrated materials and secondary washing wastewater; The pretreated material is obtained, and on the other hand, the two washing wastewater recovered by the washing sedimentation tank 12 and the horizontal disc filter 13 is sent to the water circulation treatment subsystem 5 for recycling.

Further, the water-washing stirring tank 11 is used to mix the industrial by-product gypsum (a mixture of phosphogypsum, desulfurized gypsum, titanium gypsum, etc., the content of CaSO ₄ ·2H ₂ O is more than 90%, and the content of SiO ₂ is less than 4%) with 60～70 ℃. The hot water is stirred at a high speed for 30 minutes and fully mixed, so that 3% to 5% of the soluble impurities (potassium oxide, sodium oxide, potassium fluoride, sodium fluoride, soluble phosphorus, etc.) in the material are fully dissolved in the water and discharged, making industrial by-products The impurity content in the gypsum is reduced to about 1%; the washing sedimentation tank 12 is used to settle the washing slurry discharged from the washing stirring tank 11, and the density difference between the washing water and the material is used to achieve physical concentration and sedimentation. Under the extrusion of the upper layer material, the free water is extruded to realize the concentration and separation of the material to obtain a concentrated material with a moisture content of 40% to 50%; the horizontal disc filter 13 is equipped with a vacuum filtration system, and the horizontal disc filter 13 It is used to mix the concentrated material discharged from the washing sedimentation tank 12 with hot water at 60-70 °C, and perform secondary flushing on the material to reduce the impurity content in the industrial by-product gypsum to about 0.5%, and then realize the material and the material through the vacuum filtration system. The water is separated to obtain concentrated materials with a moisture content of 3% to 5%; the screw conveyor 14 is used to transfer the water-containing concentrated materials to the crushing and dispersing machine 15; the crushing and dispersing machine 15 is used to uniformly crush and disperse the water-containing concentrated materials To the desired particle size of 100-1000 μm, it is sent to the calcining subsystem 2 .

Further, the use of the horizontal disc filter 13 can, on the one hand, reduce the content of soluble impurities in the material during the secondary flushing, and on the other hand, can reduce the adhering water content of the material, thereby reducing the gas consumption during the calcination of the main calciner 23, so as to reduce the calcination of the main calciner 23. Low energy consumption.

(2) The pretreated material enters the calcination subsystem 2 for preheating and calcination to obtain high-purity gypsum and high-temperature flue gas; wherein, the high-temperature flue gas returns to the preheating device to preheat the pre-treated material, and then enters the flue gas treatment sub-system. The system 4 is cooled and then dedusted to obtain clean ash and purified gas, and the clean ash is returned to the calcining subsystem 2; the high-purity gypsum enters the cooling subsystem 3 and is cooled and discharged to obtain a high-purity gypsum product; in the cooling process of the high-purity gypsum , the combustion-supporting air enters the cooling subsystem 3 for direct mixing and heat exchange with high-purity gypsum, and then enters the calcining device in the calcining subsystem 2.

The calcination subsystem 2 includes a primary preheater 21, a secondary preheater 22, a main calciner 23 and a main separation furnace 24; the flue gas treatment subsystem 4 includes an indirect heat exchanger 41, a bag filter 42, External exhaust fan 43 , air lift pump 44 and Roots blower 45 . After preheating through the primary preheater 21 and the secondary preheater 22 in turn, the pretreated materials enter the main calciner 23 for calcination and decomposition to obtain high-purity gypsum and high-temperature flue gas, and then all enter the main separation furnace 24 for separation ; Among them, the high-purity gypsum enters the cooling subsystem 3 from the main separation furnace 24, and the high-temperature flue gas returns from the main separation furnace 24 to the secondary preheater 22 and the primary preheater 21 in turn, and the preheated material in the preheating device Direct mixed heat exchange is carried out. The flue gas discharged from the preheating device enters the indirect heat exchanger 41 and the cooling water pipeline inside the indirect heat exchanger 41 for indirect heat exchange, and then enters the bag filter 42 for filtration and purification to obtain filtered and purified gas and clean ash. Among them, the filtered and purified gas is blown into the chimney by the external exhaust fan 43 and discharged, and the filtered clean ash is blown into the air lift pump 44 by the roots blower 45 and sent to the secondary preheating in the calcination subsystem 2 again. The gas inlet of the device 22.

Further, the concentrated material discharged from the crusher 15 in the pretreatment subsystem 1 is directly mixed and heat-exchanged with the high-speed flue gas (wind speed 16-18m/s) discharged from the top of the secondary preheater 22, on the one hand, the external smoke is reduced. On the other hand, increase the temperature of the concentrated material, reduce the adhering water on the surface of the concentrated material by 1% to 2%, and then enter the primary preheater 21 together to separate the smoke material; the flue gas at the top of the primary preheater 21 enters The indirect heat exchanger 41 then exchanges heat indirectly with the cooling water pipeline built in the indirect heat exchanger 41 and then enters the bag filter 42. The cooling water pipeline contains the supernatant water flowing out of the neutralization settling tank 52, and uses the flue gas. The sensible heat heating increases the temperature of the supernatant water while reducing the temperature of the exhaust flue gas, and reduces the exhaust volume of the flue gas, thereby reducing the operating power of the external exhaust fan 43 to save energy and reduce consumption; the indirect heat exchanger 41 discharges The filtered flue gas enters the bag filter 42 for filtration and purification, and the filtered and purified gas and clean ash are obtained. The filtered and purified gas is blown into the chimney by the external exhaust fan 43 and discharged, and the filtered clean ash is blown by the Roots blower 45. The gas fed into the air lift pump 44 is fed into the main separation furnace 24 and the pipeline connecting the secondary preheater 22, and then re-enters the calcination subsystem 2; the material discharged from the bottom of the primary preheater 21 and the flue gas discharged from the top of the main separation furnace 24 (wind speed 16-18m/s) and the clean ash returned by the bag filter 42 are directly mixed for heat exchange, and then enter the secondary preheater 22 to separate the smoke again; the material discharged from the bottom of the secondary preheater 22 enters the main The calcination and decomposition are carried out in the calciner 23, the material adhered to the water and the crystallization water are reacted, and the obtained finished material and the flue gas enter the main separation furnace 24 to separate the smoke material, and the finished material discharged from the bottom of the main separation furnace 24 enters the cooling subsystem. 3.

Further, when the materials are exchanging heat in stages in the preheating device, the temperature in the primary preheater 21 is 150-180°C, the negative pressure is about -3550Pa, the temperature in the secondary preheater 22 is 220-260°C, and the negative pressure is about -3550Pa. About -2900Pa; the calcination temperature in the main calcining furnace 23 is 300-400 °C, and the pressure is about 600 Pa. Since the residence time of the material in the main calcining furnace 23 is within 1-2s, high temperature is used for flash calcination to fully ensure crystallization The water dehydration reaction enables the material to remove 1.5 molecules of crystal water under high temperature flash calcination; the temperature in the main separation furnace 24 is 300-400°C, and the negative pressure is about -2350Pa.

The cooling subsystem 3 includes a primary cooler 31 , a secondary cooler 32 , a tertiary cooler 33 , and a finished product cooler 34 . The high-purity gypsum is successively passed through the primary cooler 31, the secondary cooler 32, the tertiary cooler 33 and the finished product cooler 34 for graded cooling and then discharged to obtain a high-purity gypsum product; Enter the cooling subsystem 3 , and then enter the secondary cooler 32 and the primary cooler 31 in turn, conduct direct mixing and heat exchange with the high-purity gypsum in the cooler, and finally enter the main calciner 23 .

Further, the finished material discharged from the main separation furnace 24 and the combustion-supporting air discharged from the top of the secondary cooler 32 are directly mixed for heat exchange, and the gas wind speed is 16-18 m/s, and then enters the primary cooler 31 together to separate the air and the material. The combustion-supporting air from the top of the primary cooler 31 enters the main calciner 23, and the finished material discharged from the bottom of the primary cooler 31 is directly mixed with the combustion-supporting air discharged from the top of the tertiary cooler 33 for heat exchange. Enter the secondary cooler 32 together to separate the air and the material again; the finished material discharged from the bottom of the secondary cooler 32 and the combustion-supporting air sucked in by the external exhaust fan 43 are directly mixed for heat exchange, and the gas wind speed is 16-18m/s, and then a And enter the tertiary cooler 33 to separate the air and the material; the finished material discharged from the bottom of the tertiary cooler 33 and the cooling water pipeline built in the finished product cooler 34 are fully indirectly heat-exchanged and then discharged from the finished product outlet. The pipeline contains the supernatant water flowing out of the neutralization settling tank 52, which is used to increase the temperature of supernatant water and reduce the temperature of the finished material discharged. This can reduce the discharge temperature of the finished material on the one hand and meet the transportation requirements of the finished product, on the other hand. Increase the temperature of the supernatant water for better washing of raw materials. The combustion-supporting air and the calcined finished material have undergone three heat exchanges in the primary cooler 31, the secondary cooler 32 and the tertiary cooler 33 to increase the temperature of the combustion-supporting air entering the main calciner 23, and the combustion-supporting air entering the main calciner 23. The higher the temperature in the main calciner 23, the smaller the amount of heat released from combustion in the combustion reaction to increase the temperature of the combustion-supporting air, thereby correspondingly reducing the consumption of gas. The whole cooling process realizes the cascade comprehensive utilization of energy.

Further, when the material is cooled in stages, the temperature in the primary cooler 31 is 260-300°C, the negative pressure is about -1750Pa, the temperature in the secondary cooler 32 is 180-220°C, the negative pressure is about -1200Pa, and the tertiary cooling is performed. The temperature in the cooler 33 is 120-160°C, the negative pressure is about -780Pa, and the discharge temperature of the finished material in the finished product cooler 34 after heat exchange is 80-100°C, to prepare a high-purity beta hemihydrate gypsum product (CaSO ₄ ·0.5H _{2 )} . O content ≥ 92%).

(3) The washing wastewater obtained in step (1) is returned to the pretreatment subsystem 1 for recycling after neutralization and sedimentation treatment.

The water circulation treatment subsystem 5 includes a neutralization stirring tank 51 and a neutralization settling tank 52, and the secondary washing wastewater discharged from the water washing settling tank 12 and the horizontal disc filter 13 in the pretreatment subsystem 1 all enter the neutralization stirring tank. 51, add calcium oxide to the neutralization stirring tank 51 and stir to react, obtain the mixture after the reaction, then the mixture is sent into the neutralization settling tank 52 to carry out precipitation separation, to obtain precipitation material and supernatant water; wherein, the precipitation material is incorporated into The by-product gypsum of the raw material industry is put into the raw material inlet, and the supernatant water is divided into two parts for indirect heat exchange of smoke and material, one part enters the finished product cooler 34 for finished product cooling, and the other part enters the indirect heat exchanger 41 to cool the high temperature flue gas The hot water after heat exchange is 60-70°C, and then flows into the water washing and stirring tank 11 and the horizontal disc filter 13 in the pretreatment subsystem 1 to carry out the next round of material washing to realize the repetition of the water cycle. use.

Example 3

The content of a method for producing high-purity type II anhydrite by using the system for producing high-purity gypsum described in Example 1 is basically the same as that in Example 2, except that the water washing and stirring described in step (2) The temperature of the hot water in the tank 11 is 90-100°C, and the content of soluble impurities is reduced to about 0.8% after flushing; the temperature of the hot water in the horizontal disc filter 13 is 90-100°C, and the content of soluble impurities is reduced to 0.8% after the second flushing. 0.4% or so. In the step (3), when the materials are exchanging heat in stages in the preheating device, the temperature in the primary preheater 21 is 220-300°C, the negative pressure is about -4250Pa, and the temperature in the secondary preheater 22 is 350-400°C, The negative pressure is about -3750Pa; the calcination temperature in the main calcining furnace 23 is 600-700°C, and the pressure is about 1200Pa, which can make the material remove 2 molecules of crystal water at high temperature; the temperature in the main separation furnace 24 is 600-700°C, The negative pressure is about -3050Pa. In step (4), when the material is graded and cooled, the temperature in the primary cooler 31 is 450-500°C, the negative pressure is about -2250Pa, the temperature in the secondary cooler 32 is 320-400°C, and the negative pressure is about -1550Pa, The temperature in the third-stage cooler 33 is 220-260°C, the negative pressure is about -880Pa, and the discharge temperature of the finished material in the finished product cooler 34 after heat exchange is 80-100°C, and a high-purity type II anhydrite product (CaSO ₄ ) is prepared. content ≥94%). In step (5), calcium hydroxide is added to the neutralization stirring tank 51 for stirring reaction, and the hot water after heat exchange is 90-100°C.

To sum up, the present invention effectively overcomes the deficiencies in the prior art, and has high industrial utilization value. The functions of the above embodiments are to illustrate the essential content of the present invention, but not to limit the protection scope of the present invention. Those skilled in the art should understand that the technical solutions of the present invention may be modified or equivalently replaced without departing from the spirit and protection scope of the technical solutions of the present invention.

Claims (10)

1. a system utilizing industrial by-product gypsum to produce high-purity gypsum, is characterized in that, described system comprises pretreatment subsystem, calcination subsystem, cooling subsystem and flue gas treatment subsystem; For washing the industrial by-product gypsum and removing impurities to obtain pretreated materials; the calcining subsystem includes a preheating device and a calcining device, and the preheating device is used to directly mix the pretreated materials with high-temperature flue gas. Preheating treatment, the calcining device is used for calcining the pretreated material processed by the preheating device to burn off impurities and crystal water to obtain high-purity gypsum and high-temperature flue gas, wherein the high-purity gypsum enters the cooler The system proceeds to the next process, and the high-temperature flue gas is returned to the preheating device to preheat the pre-treated material, and then emptied after being purified by the flue gas treatment subsystem; the cooling subsystem is used for the calcined high-temperature The high-purity gypsum is directly mixed with the combustion-supporting air for cooling treatment, and the material is discharged after cooling to obtain a high-purity gypsum product. 2. The system for producing high-purity gypsum according to claim 1, wherein the preheating device comprises a primary preheater and a secondary preheater, and the calcining device comprises a main calciner and a main separation furnace ; The primary preheater and secondary preheater are respectively provided with material inlet, material outlet, gas inlet and gas outlet, and the main calciner is provided with material inlet, gas inlet and material gas outlet. The separation furnace is provided with a material gas inlet, a gas outlet and a material outlet; The material inlet of the primary preheater is communicated with the material outlet of the pretreatment subsystem, the material outlet of the primary preheater is communicated with the material inlet of the secondary preheater, and the material outlet of the secondary preheater is communicated with the main calciner The material inlet of the furnace is connected, the material gas outlet of the main calciner is connected with the material gas inlet of the main separation furnace, and the material outlet of the main separation furnace is connected with the material inlet of the cooling subsystem; The gas outlet of the main separation furnace is communicated with the gas inlet of the secondary preheater, the gas outlet of the secondary preheater is communicated with the gas inlet of the primary preheater, and the gas outlet of the primary preheater is communicated with the flue gas treatment Subsystems are connected. 3. The system for producing high-purity gypsum according to claim 2, wherein the cooling subsystem comprises a primary cooler, a secondary cooler, a tertiary cooler and a finished product cooler; the primary cooling The cooler, the secondary cooler and the tertiary cooler are respectively provided with a material inlet, a material outlet, a gas inlet and a gas outlet, and the finished product cooler is provided with a material inlet and a material outlet; The material inlet of the primary cooler is communicated with the material outlet of the main separation furnace, the material outlet of the primary cooler is communicated with the material inlet of the secondary cooler, and the material outlet of the secondary cooler is communicated with the material inlet of the tertiary cooler Connected, the material outlet of the tertiary cooler is communicated with the material inlet of the finished product cooler; The gas inlet of the tertiary cooler is used to introduce combustion-supporting air into the tertiary cooler, the gas outlet of the tertiary cooler is communicated with the gas inlet of the secondary cooler, and the gas outlet of the secondary cooler is connected with the primary cooling. The gas inlet of the primary cooler is communicated with the gas inlet of the main calciner, and the gas outlet of the primary cooler is communicated with the gas inlet of the main calciner. 4. The system for producing high-purity gypsum according to claim 3, wherein the pretreatment subsystem comprises a primary water washing device, a secondary water washing device and a crushing device, and the primary water washing device and the secondary water washing device are used for For washing and removing impurities from the industrial by-product gypsum, the crushing device is used to crush the material after the secondary water washing to obtain the pretreated material; the primary water washing device, the secondary water washing device and the crushing device are respectively equipped with Material inlet and material outlet, wherein the primary water washing device and the secondary water washing device are also provided with a water inlet and a water outlet respectively; The material inlet of the primary water washing device is the raw material inlet, the material outlet of the primary water washing device is communicated with the material inlet of the secondary water washing device, the material outlet of the secondary water washing device is communicated with the material inlet of the crushing device, and the material outlet of the crushing device is connected with the preheater. The material inlet of the thermal device is communicated. 5. The system for producing high-purity gypsum according to claim 4, characterized in that, the system for producing high-purity gypsum further comprises a water circulation treatment subsystem; the water circulation treatment subsystem comprises a neutralization stirring tank and a neutralization sedimentation The flue gas treatment subsystem includes an indirect heat exchanger, and the indirect heat exchanger is used for cooling the high-temperature flue gas discharged from the gas outlet of the primary preheater, and the flue gas after the cooling treatment is evacuated after dust collection; The neutralization and stirring tank is provided with a material inlet, a water inlet and a material liquid outlet, and the neutralization settling tank is provided with a material liquid inlet, a material outlet and a water outlet; the water inlet of the neutralization and stirring tank is connected with the pretreatment subsystem. The water outlet is connected, the material liquid outlet of the neutralization stirring tank is connected with the material liquid inlet of the neutralization settling tank, the material outlet of the neutralization settling tank is connected with the raw material inlet of the primary water washing device, and the water outlet of the neutralization settling tank is respectively connected with the primary water washing The device is connected with the water inlet of the secondary water washing device; the water outlet of the neutralization settling tank is provided with two branch pipes, one of which is connected with the cooling water inlet of the finished product cooler, and the cooling water outlet of the finished product cooler is respectively connected with the pipe through the pipe. The water inlets of the primary water washing device and the secondary water washing device are connected, and the other branch pipe is connected to the cooling water inlet of the indirect heat exchanger. The water ports are connected; and cooling water pipes are arranged in the finished product cooler and the indirect heat exchanger. 6. A method for producing high-purity beta hemihydrate gypsum or type II anhydrite using the system for producing high-purity gypsum described in any one of claims 1 to 5, characterized in that, comprising the steps: (1) Add the industrial by-product gypsum to the raw material inlet of the system for producing high-purity gypsum, and enter the pretreatment subsystem of the system to carry out water washing and impurity removal treatment to obtain pretreated materials and washing wastewater; (2) The pretreated material enters the calcination subsystem for preheating and calcination to obtain high-purity gypsum and high-temperature flue gas; wherein, the high-temperature flue gas returns to the preheating device to directly mix the pre-treated material for preheating, and then enter the flue gas treatment After the subsystem is cooled, it is dedusted to obtain clean ash and purified gas, and the clean ash is returned to the calcining subsystem; the high-purity gypsum enters the cooling subsystem and is cooled and discharged to obtain a high-purity gypsum product; during the cooling process of the high-purity gypsum, Combustion-supporting air enters the cooling subsystem and is directly mixed with high-purity gypsum for heat exchange, and then enters the calcining device in the calcining subsystem; (3) The washing wastewater obtained in step (1) is returned to the pretreatment subsystem for recycling after neutralization and sedimentation treatment. 7. The method for producing high-purity beta hemihydrate gypsum or type II anhydrite according to claim 6, wherein the calcination temperature in step (2) during the production of high-purity beta hemihydrate gypsum is 300-400°C; When producing high-purity type II anhydrite, the calcination temperature in step (2) is 600-700°C. 8 . The method for producing high-purity beta hemihydrate gypsum or type II anhydrite according to claim 7 , wherein the step (2) in which the high-purity gypsum enters the cooling subsystem for cooling treatment is as follows: 9 . : The high-purity gypsum passes through the primary cooler, the secondary cooler, the tertiary cooler and the finished product cooler for grading and cooling, and then the high-purity gypsum product is obtained; at the same time, the combustion-supporting air enters the cooling subsystem, and then enters the three The primary cooler, the secondary cooler and the primary cooler exchange heat with the high-purity gypsum in the cooler, and finally enter the main calciner. 9 . The method for producing high-purity beta hemihydrate gypsum or type II anhydrite according to claim 8 , wherein the industrial by-product gypsum described in step (1) enters the specific step of the pretreatment subsystem for processing. 10 . It is as follows: the industrial by-product gypsum is washed by the primary water washing device and the secondary water washing device to remove impurities and then separated from solid and liquid to obtain concentrated materials and washing wastewater; wherein, the concentrated materials enter the crushing device for crushing and dispersing to obtain pretreated materials, and the two are: The secondary washing wastewater enters the water circulation treatment subsystem for recycling. 10. The method for producing high-purity beta hemihydrate gypsum or type II anhydrite according to claim 9, wherein the specific step of recycling the washing waste water in step (3) is: After mixing with the stirring tank, add the alkaline oxide to stir and react to obtain the reacted mixture, and then the mixture is sent to the neutralization sedimentation tank for precipitation and separation to obtain the precipitation material and the supernatant water; wherein, the precipitation material is incorporated into the raw material and put into the raw material feed The inlet re-enters the pretreatment subsystem, the supernatant water is divided into two parts for indirect heat exchange of smoke and material respectively, one part enters the finished product cooler to cool the finished product, the other part enters the indirect heat exchanger to cool the high temperature flue gas, and finally The reflux enters the primary water washing device and the secondary water washing device to participate in the next round of water washing.

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