Desulfurized gypsum dechlorination and upgrading process system

Abstract

The application discloses a desulfurization gypsum dechlorination and quality improvement process system and belongs to the technical field of alpha hemihydrate gypsum production. In the material step-by-step drying system of the process, the material outlet of a reaction device is communicated with the material inlet of a high-pressure slurry separation and dehydration device, the material outlet of the high-pressure slurry separation and dehydration device is communicated with the material inlet of a flash device, the material outlet of the flash device is communicated with the material inlet of a high-temperature drying device, and the separation steam outlet of the flash device is communicated with the steam inlet of a solid-liquid mixing device. The separation water outlet of the high-pressure slurry separation and dehydration device is communicated with the high-pressure inlet of a multi-stage water circulation system, the separation water outlet of the flash device is communicated with the steam inlet of a raw material reaction system, and the separation water outlet of the high-temperature drying device is communicated with the low-pressure inlet of the multi-stage water circulation system. The process reduces system energy consumption through a step-by-step drying method, effectively utilizes drying water with different pressures through a multi-stage water circulation system, and reduces system heat loss through heat recovery.

Description

Technical Field

[0001] This invention relates to the field of α-hemihydrate gypsum production technology, specifically to a desulfurized gypsum dechlorination and upgrading process system. Background Technology

[0002] Desulfurized gypsum is a byproduct of boiler combustion system exhaust gas treatment. Its main component is dihydrate gypsum (CaSO4·2H2O). As a solid waste, it is harmful to the environment, especially since it contains chloride ions, which negatively impact groundwater and soil. Traditional methods for treating desulfurized gypsum primarily involve green landfill, but this method is inefficient, requires large land areas, is costly, and prone to leakage. The most common way to utilize desulfurized gypsum is to process it into β-hemihydrate gypsum (β-CaSO4·0.5H2O) for use as building gypsum, but this has low added value, and its market application is limited by the development of the construction industry. Compared to β-hemihydrate gypsum, α-hemihydrate gypsum (α-CaSO4·0.5H2O, also known as high-strength gypsum) has excellent workability, mechanical properties, thermal stability, biocompatibility, environmental performance, and chemical corrosion resistance. It can be used in many fields such as precision casting, high-end building materials, arts and crafts, medical, aviation, and shipbuilding. It can also be used in high-end fireproof building materials and is an important raw material in high-end manufacturing.

[0003] Traditional production processes for α-hemihydrate gypsum primarily employ autoclaving, which is ineffective at removing chloride ions, requires high-quality raw materials, and cannot operate continuously, resulting in high production costs. When desulfurized gypsum is used as a raw material, excessive chloride ion content easily leads to a low yield of the finished α-hemihydrate gypsum, with strength, whiteness, and water absorption failing to meet practical application requirements. However, hydrothermal treatment of desulfurized gypsum effectively removes chloride ions, and the resulting α-hemihydrate gypsum meets practical application standards. The hydrothermal method involves placing desulfurized gypsum slurry in a high-temperature, high-pressure water environment for reaction. During the reaction, desulfurized gypsum crystals dissolve in the high-temperature, high-pressure water and then recrystallize into α-hemihydrate gypsum. The resulting crystals are fully developed and stable, and the chloride ions in the crystal lattice dissolve into the high-temperature, high-pressure water, achieving excellent dechlorination and quality improvement. However, the finished gypsum after the hydrothermal reaction undergoes a reverse reaction with water at room temperature, regenerating dihydrate gypsum, which reduces the yield of the finished product. Therefore, the slurry after the reaction needs to be dried at a high temperature. However, the drying process usually uses direct or indirect drying devices such as drum dryers, which has low drying efficiency and consumes a lot of heat, resulting in high energy consumption. Summary of the Invention

[0004] To address the above problems, this invention provides a dechlorination and upgrading process system for desulfurized gypsum, effectively solving the technical issues of intermittent production and high energy consumption in the preparation of α-hemihydrate gypsum from desulfurized gypsum. This process can effectively reduce energy consumption during the drying of gypsum slurry through a stepped drying system during continuous α-hemihydrate gypsum production. Simultaneously, it saves water resources by treating drying water at different pressures through a multi-stage water circulation system, and reduces system heat loss through heat recovery, thereby lowering the processing cost of desulfurized gypsum and the production cost of α-hemihydrate gypsum, and increasing the system's economic efficiency.

[0005] This invention provides a desulfurized gypsum dechlorination and upgrading process system, including a raw material reaction system, a material cascade drying system, a multi-stage water circulation system, a material post-processing system, and a steam heating system.

[0006] The material cascade drying system includes a high-pressure slurry separation and dewatering device, a flash evaporation device, and a high-temperature drying device connected in series.

[0007] The material outlet of the raw material reaction system is connected to the material inlet of the high-pressure slurry separation and dewatering device, the material outlet of the high-pressure slurry separation and dewatering device is connected to the material inlet of the flash evaporation device, and the material outlet of the flash evaporation device is connected to the material inlet of the high-temperature drying device.

[0008] The separation water outlet of the high-pressure slurry separation and dewatering device is connected to the high-pressure inlet of the multi-stage water circulation system, the separation steam outlet of the flash evaporation device is connected to the steam inlet of the raw material reaction system, and the separation water outlet of the high-temperature drying device is connected to the low-pressure inlet of the multi-stage water circulation system.

[0009] The high-temperature drying device is connected to the material post-processing system; the steam heating system is connected to both the raw material reaction system and the high-temperature drying device.

[0010] In a preferred embodiment of the present invention, the multi-stage water circulation system includes a first heat exchanger, a second heat exchanger, a back pressure valve, and a tailwater treatment device.

[0011] The hot-side inlet of the first heat exchanger is the low-pressure inlet of the multi-stage water circulation system. The hot-side inlet of the first heat exchanger is connected to the separation water outlet of the high-temperature drying device. The cold-side inlet of the first heat exchanger is connected to the industrial water inlet.

[0012] The hot-side inlet of the second heat exchanger is the high-pressure inlet of the multi-stage water circulation system, and the hot-side inlet of the second heat exchanger is connected to the separation water outlet of the high-pressure slurry separation and dewatering device.

[0013] The inlet of the back pressure valve is connected to the outlet of the second heat exchanger, and the hot side outlet of the first heat exchanger is connected to the outlet of the back pressure valve through a circulating water collection pipeline.

[0014] The circulating water collection pipeline includes a first separation pipeline and a second separation pipeline. The first separation pipeline is connected to the water inlet of the solid-liquid mixing device, and the second separation pipeline is connected to the inlet of the tailwater treatment device.

[0015] In a preferred embodiment of the present invention, the high-pressure slurry separation and dewatering device includes a solid-liquid self-separation device and a pressure energy utilization type solid phase depressurization dewatering module.

[0016] In a preferred embodiment of the present invention, the raw material reaction system includes a material pretreatment system and a hydrothermal reaction system.

[0017] The material pretreatment system includes a raw material storage device, a crystallizer tank, and a solid-liquid mixing device. The outlet of the raw material storage device is connected to the material inlet of the solid-liquid mixing device, the outlet of the crystallizer tank is connected to the crystallizer inlet of the solid-liquid mixing device, and the solid-liquid mixing device is connected to the hydrothermal reaction system via a slurry pump.

[0018] In a preferred embodiment of the present invention, the hydrothermal reaction system includes a reaction device, the inlet of which is connected to the slurry outlet of the solid-liquid mixing device; and the outlet of the reaction device is connected to the inlet of the high-pressure slurry separation and dewatering device.

[0019] The reaction apparatus is heated by steam supplied by the steam heating system.

[0020] In a preferred embodiment of the present invention, the first outlet of the steam heating system is connected to the steam heating inlet in the reaction device, and the second outlet of the steam heating system is connected to the high-temperature steam inlet of the high-temperature drying device.

[0021] In a preferred embodiment of the present invention, the material post-processing system includes a ball mill, a finished material storage device, and a finished material packaging device connected in series.

[0022] The inlet of the ball mill is connected to the material outlet of the high-temperature drying device.

[0023] In a preferred embodiment of the present invention, the pressure value of the back pressure valve, the pressure value of the reaction device, and the pressure value of the high-pressure slurry separation and dewatering device are the same.

[0024] In a preferred embodiment of the present invention, an industrial circulating water switch regulating valve is provided on the pipeline connecting the industrial water inlet to the first heat exchanger.

[0025] In a preferred embodiment of the present invention, an external drainage switch regulating valve is provided on the pipeline connecting the circulating water collection pipeline and the tailwater treatment device.

[0026] In a preferred embodiment of the present invention, a circulating water switch regulating valve and a chloride ion content detection instrument are provided on the pipeline connecting the circulating water collection pipeline and the solid-liquid mixing device.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention achieves wet separation, flash separation and high-temperature drying separation of water in the α-hemihydrate gypsum slurry after the reaction is completed through a material cascade drying system, thereby reducing the drying energy consumption of the system; at the same time, the material cascade drying system always maintains a high temperature, avoiding phase reversal of α-hemihydrate gypsum during the drying process and ensuring the product qualification rate.

[0029] (2) Based on the characteristics of the water separation device in the material cascade drying system, the present invention fully recovers the heat in the drying and separation water through a multi-stage water circulation system, and recovers the pressure energy of the high-pressure slurry, which has a good energy-saving effect; at the same time, new industrial water is only needed when the chlorine content of the circulating water exceeds the limit value, which reduces the water consumption of the process system and effectively improves the system economy.

[0030] (3) The crystal control agent provided by the crystal control agent tank can be used in both the crystal phase transformation process and the dechlorination process, which improves the reusability of the crystal control agent tank and enhances the economy of the system.

[0031] (4) This invention achieves efficient and clean conversion of desulfurized gypsum to α-hemihydrate gypsum through a series of processes including blending, hydrothermal reaction treatment, drying, grinding and packaging. Under the premise of realizing the resource utilization of desulfurized gypsum and efficient dechlorination, it solves the problems of continuous production, high energy consumption and water consumption of the process system, thereby improving the economic efficiency of the system and promoting the industrial-scale application of this process. Attached Figure Description

[0032] Figure 1 A flow chart of a desulfurized gypsum dechlorination and upgrading process system provided by the present invention.

[0033] Figure reference numerals: 1-Raw material storage device; 2-Solid-liquid mixing device; 3-Slurry pump; 4-Reaction device; 5-High-pressure slurry separation and dewatering device; 6-Flash evaporation device; 7-High-temperature drying device; 8-Finished material packaging device; 9-Finished material storage device; 10-Ball mill device; 11-First heat exchanger; 12-Second heat exchanger; 13-Dechlorination device; 14-Back pressure valve; 15-Crystallization control agent tank; 16-Tailwater treatment device; V01-Industrial water switch regulating valve; V02-External drainage switch regulating valve; V03-Circulating water switch regulating valve; Cl01-Chloride ion content detection instrument; R1-Desulfurized gypsum; R2-Saturated steam; R3-Industrial water; R4-Calcium hydroxide inlet. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of the embodiments of the present invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0036] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0038] Desulfurized gypsum, primarily composed of dihydrate gypsum (CaSO4·2H2O), is a solid waste requiring harmless treatment and resource utilization. The presence of chloride ions in desulfurized gypsum affects the water absorption and strength of the resulting hemihydrate gypsum (CaSO4·0.5H2O) after resource utilization. Traditional methods for treating chloride ions mainly involve water washing, but this technology consumes a large amount of water, has high drying energy consumption, and is economically inefficient. Therefore, a more economical method for the resource utilization of desulfurized gypsum is needed.

[0039] The most common way to utilize desulfurized gypsum is to process it into β-hemihydrate gypsum (β-CaSO4·0.5H2O) for use as building gypsum, but its added value is low. Compared to β-hemihydrate gypsum, α-hemihydrate gypsum (α-CaSO4·0.5H2O) has better performance and economic value, and is the development direction for the resource utilization of desulfurized gypsum. Traditional α-hemihydrate gypsum production processes are mostly autoclaving, which requires high-quality raw materials, cannot operate continuously, and has high production costs. In contrast, the hydrothermal method for preparing α-hemihydrate gypsum has lower requirements for raw materials, can use desulfurized gypsum as a raw material, and can effectively reduce chloride ions in the finished product, showing good development prospects. However, the high energy consumption of its drying process urgently needs to be addressed.

[0040] Based on this, in order to solve the problem of high energy consumption in the current desulfurized gypsum resource utilization drying process, this invention provides a dechlorination and upgrading process system for desulfurized gypsum. The system reduces drying energy consumption through cascade drying and improves the reuse level of water and heat through a multi-stage water recycling system, thereby achieving continuous production of desulfurized gypsum and a significant reduction in its cost.

[0041] like Figure 1 This invention provides a desulfurization and dechlorination upgrading process system for gypsum, comprising a material pretreatment system, a hydrothermal reaction system, a material cascade drying system, a material post-treatment system, a multi-stage water circulation system, and a steam heating system. It should be noted that... Figure 1 The dashed lines in the diagram represent the paths of water and steam, while the solid lines represent the paths of the slurry.

[0042] The material cascade drying system includes a high-pressure slurry separation and dehydration device 5, a flash evaporation device 6, and a high-temperature drying device 7 connected in series. The outlet of the hydrothermal reaction system is connected to the material inlet of the high-pressure slurry separation and dehydration device 5 via a pipeline. The material outlet of the high-pressure slurry separation and dehydration device 5 is connected to the material inlet of the flash evaporation device 6. The separated water outlet of the high-pressure slurry separation and dehydration device 5 is connected to the high-pressure inlet of the multi-stage water circulation system. The material outlet of the flash evaporation device 6 is connected to the material inlet of the high-temperature drying device 7. The separated steam outlet of the flash evaporation device 6 is connected to the steam inlet of the solid-liquid mixing device 2. The separated water outlet of the high-temperature drying device 7 is connected to the low-pressure inlet of the multi-stage water circulation system.

[0043] When the material after the reaction is completed is dried, it first enters the high-pressure slurry separation and dehydration device 5 for wet separation, and high-pressure water and high-pressure dehydrated slurry are separated. The high-pressure dehydrated slurry is transported to the flash evaporation device 6 through the material outlet of the high-pressure slurry separation and dehydration device 5, and flash evaporation is carried out under low pressure. After flash evaporation, low-pressure dehydrated slurry and low-pressure water are obtained. The low-pressure dehydrated slurry enters the high-temperature drying device 7 through the material outlet of the flash evaporation device 6 for high-temperature drying, and the dried finished product α hemihydrate gypsum is obtained.

[0044] The material cascade drying system is equipped with a high-pressure slurry separation and dehydration device 5, a flash evaporation device 6, and a high-temperature drying device 7. Since some moisture has been removed by wet separation and flash evaporation before high-temperature drying, and these two processes make full use of the static principle and pressure energy, the amount of dehydration required in the high-temperature drying stage is reduced, thus reducing the drying energy consumption.

[0045] The high-pressure slurry separation and dewatering device 5 includes a solid-liquid self-separation device and a pressure energy utilization type solid-phase depressurization dewatering component. The pressure energy utilization type solid-phase depressurization dewatering component utilizes the pressure difference when the high-pressure slurry is converted to low pressure for energy recovery. Dewatering is carried out through the solid-liquid separation device and depressurization centrifugation. The high-pressure slurry separation and dewatering device 5 set by the present invention can achieve the dual purpose of energy recovery and dewatering.

[0046] The high-temperature drying device 7 adopts a partitioned heating method, such as a partitioned heater, with high-temperature steam as the heat source. The high-temperature steam inlet is connected to the outlet of the steam heating system. The heat source side outlet of the high-temperature drying device 7, such as the heat side outlet of the partitioned heater, is recycled or discharged according to the form of steam source.

[0047] The multi-stage water circulation system includes a first heat exchanger 11, a second heat exchanger 12, a back pressure valve 14, and a tailwater treatment device 16. The hot side inlet of the first heat exchanger 11 is the low-pressure inlet of the multi-stage water circulation system. The hot side inlet of the first heat exchanger 11 is connected to the separated water outlet of the high-temperature drying device 7. The cold side inlet of the first heat exchanger 11 is connected to the industrial water inlet.

[0048] The hot-side inlet of the second heat exchanger 12 is the high-pressure inlet of the multi-stage water circulation system. The hot-side inlet of the second heat exchanger 12 is connected to the separation water outlet of the high-pressure slurry separation and dewatering device 5. Specifically, the outlet of the second heat exchanger 12 is connected to the inlet of the dechlorination device 13, and the outlet of the dechlorination device 13 is connected to the inlet of the back pressure valve 14. The outlet of the back pressure valve 14 and the hot-side outlet of the first heat exchanger 11 are both connected through a circulating water collection pipeline. Specifically, the hot-side outlet of the first heat exchanger 11 and the outlet of the back pressure valve 14 are mixed in the circulating water collection pipeline and divided into two paths, namely the first separation pipeline and the second separation pipeline. The first separation pipeline is connected to the water inlet of the solid-liquid mixing device 2, and the second separation pipeline is connected to the inlet of the tailwater treatment device 16. The pressure value of the back pressure valve 14 is the same as the pressure value of the reaction device 4 and the pressure value of the high-pressure slurry separation and dewatering device 5.

[0049] The high-pressure separated water on the hot side of the second heat exchanger 12 enters the dechlorination device 13. The dechlorination device 13 is provided with a calcium hydroxide inlet and a crystal control agent inlet. Calcium hydroxide is added through the calcium hydroxide inlet of the dechlorination device 13, and crystal control agent is added through the crystal control agent inlet of the dechlorination device 13. The crystal control agent and calcium hydroxide regulate the pH of the slurry in the dechlorination device 13 for chloride ion removal.

[0050] The crystal-controlling agent used in this invention can be organic matter, aluminum sulfate, or other compounds that can be used as crystal-controlling agents.

[0051] During the operation of the multi-stage water circulation system, the high-pressure water obtained by wet separation through the high-pressure slurry separation and dewatering device 5 enters the second heat exchanger 12 from the separation water outlet of the high-pressure slurry separation and dewatering device 5. After heat exchange, the pressure is reduced by the back pressure valve 14 to obtain the depressurized high-pressure circulating water. The depressurized high-pressure circulating water reaches the circulating water collection pipeline.

[0052] The low-pressure water obtained after flash evaporation by the flash evaporator 6 enters the first heat exchanger 11 from the low-pressure separated water outlet of the high-temperature drying device 7. After heat exchange, it reaches the circulating water collection pipeline and mixes with the depressurized high-pressure circulating water. Depending on its chloride ion content, the mixed circulating water enters the solid-liquid mixing device 2 or the tailwater treatment device 16.

[0053] In the multi-stage water circulation system, an industrial circulating water switch regulating valve V01 is installed on the pipeline connecting the industrial water inlet to the first heat exchanger 11, an external drainage switch regulating valve V02 is installed on the pipeline connecting the circulating water collection pipeline to the tailwater treatment device 16, and a circulating water switch regulating valve V03 and a chloride ion content detection instrument Cl01 are installed on the pipeline connecting the circulating water collection pipeline to the solid-liquid mixing device 2.

[0054] The multi-stage water circulation system operates under two conditions. In the first condition, the chloride ion content in the separated water reported by the chloride ion content detector Cl01 is lower than the maximum limit. At this time, the industrial circulating water switch regulating valve V01 is closed, the circulating water switch regulating valve V03 is opened, and the external drainage switch regulating valve V02 is opened. The system is adjusted to the difference between the atmospheric pressure separated water volume and the water volume required by the solid-liquid mixing device 2, in order to maintain the water volume requirement of the solid-liquid mixing device 2.

[0055] The second operating condition is that the chloride ion content value in the separated water fed back by the chloride ion content detection instrument Cl01 is higher than the maximum limit. At this time, the industrial circulating water switch regulating valve V01 is opened and adjusted to the water volume required by the solid-liquid mixing device 2, the external drain switch regulating valve V02 is closed, and the circulating water switch regulating valve V03 is closed, so as to meet the maximum limit of chloride ion removal of the hydrothermal reaction slurry.

[0056] Before the material cascade drying system, this invention also includes a material pretreatment system. The material pretreatment system comprises a raw material storage device 1, a crystal-controlling agent tank 15, and a solid-liquid mixing device 2. The solid-liquid mixing device 2 has four inlets: a material inlet, a crystal-controlling agent inlet, a water inlet, and a steam inlet. The outlet of the raw material storage device 1 is connected to the material inlet of the solid-liquid mixing device 2. The outlet of the crystal-controlling agent tank 15 is connected to both the crystal-controlling agent inlet of the solid-liquid mixing device 2 and the crystal-controlling agent inlet of the dechlorination device 13. The solid-liquid mixing device 2 is connected to the hydrothermal reaction system via a slurry pump 3.

[0057] In the material pretreatment system, the material from the raw material storage device 1 enters the solid-liquid mixing device 2 via a screw conveyor for raw material proportioning and mixing into a slurry. Compared with manually preparing the slurry in two slurry mixing tanks separately and then supplying it to the reaction device 4 in stages, the material pretreatment system provided by the present invention has the following advantages: first, it reduces energy consumption; second, it improves the level of automation; and third, it can utilize circulating water in real time.

[0058] The raw materials in the raw material storage device 1 and the crystal control agent in the crystal control agent tank 15 are respectively transported to the solid-liquid mixing device 2 through the material inlet and the crystal control agent inlet. Water is injected through the water inlet of the solid-liquid mixing device 2, and steam is injected through the steam inlet of the solid-liquid mixing device 2 to mix the materials, crystal control agent, water and steam. The solid-liquid mixing device 2 is equipped with a stirrer inside to mix the solid and liquid. After mixing, the slurry is transported to the hydrothermal reaction system through the slurry pump.

[0059] The hydrothermal reaction system includes a reaction device 4. The internal stirring mechanism of the reaction device 4 is either a stirrer or a drum, and it employs steam injection heating. The injected steam is directly mixed with the slurry to maintain the temperature and pressure of the hydrothermal reaction. The steam source is a steam heating system. Compared to indirect and volumetric heating, this invention directly mixes the slurry and steam during the reaction process, increasing the slurry temperature. Furthermore, the reaction device 4 rotates as a whole during the reaction, effectively improving heat utilization efficiency and preventing material sedimentation within the cylinder.

[0060] After the solid-liquid mixing device 2 has completed mixing, the slurry is transported to the reaction device 4 by the slurry pump 3 for reaction. The steam required during the reaction is provided by the steam heating system. After the hydrothermal reaction is completed, the product can enter the material cascade drying system for drying.

[0061] After the hydrothermal reaction is completed and the product is dried, it can enter the material post-processing system for further processing. The material post-processing system includes a ball mill 10, a finished product storage device 9, and a finished product packaging device 8 connected in series. After drying, the material is ball-milled to the required particle size by the ball mill 10, and then stored in the finished product storage device 9. The stored material is then packaged in the finished product packaging device 8.

[0062] The steam heating system has two outlets: one is connected to the steam heating inlet of the reaction device 4, and the other is connected to the high-temperature steam inlet of the high-temperature drying device 7. The steam sources of the steam heating system include, but are not limited to, coal-fired boilers, biomass-fired boilers, gas-fired boilers, electric heating boilers, and purchased steam.

[0063] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0064] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A desulfurized gypsum dechlorination and upgrading process system, characterized in that, The system comprises a raw material reaction system, a material step drying system, a multi-stage water circulation system, a material post-processing system and a steam heating system. The material step drying system comprises a high-pressure slurry separation and dehydration device (5), a flash device (6) and a high-temperature drying device (7) connected in series. The material outlet of the raw material reaction system is communicated with the material inlet of the high-pressure slurry separation and dehydration device (5), the material outlet of the high-pressure slurry separation and dehydration device (5) is communicated with the material inlet of the flash device (6), the material outlet of the flash device (6) is communicated with the material inlet of the high-temperature drying device (7), and the separation steam outlet of the flash device (6) is communicated with the steam inlet of the raw material reaction system. The separation water outlet of the high-pressure slurry separation and dehydration device (5) is communicated with the high-pressure inlet of the multi-stage water circulation system, the separation water outlet of the flash device (6) is communicated with the steam inlet of the raw material reaction system, and the separation water outlet of the high-temperature drying device (7) is communicated with the low-pressure inlet of the multi-stage water circulation system. The high-temperature drying device (7) is communicated with the material post-processing system, and the steam heating system is communicated with the raw material reaction system and the high-temperature drying device (7) respectively. The raw material reaction system comprises a material pretreatment system and a hydrothermal reaction system. The material pretreatment system comprises a raw material storage device (1), a crystal control agent tank (15) and a solid-liquid mixing device (2), the outlet of the raw material storage device (1) is communicated with the material inlet of the solid-liquid mixing device (2), the outlet of the crystal control agent tank (15) is communicated with the crystal control agent inlet of the solid-liquid mixing device (2) and the crystal control agent inlet on the dechlorination device (13) respectively, and the solid-liquid mixing device (2) is communicated with the hydrothermal reaction system through a slurry pump (3). The hydrothermal reaction system comprises a reaction device (4), the inlet of the reaction device (4) is communicated with the slurry outlet of the solid-liquid mixing device (2), and the outlet of the reaction device (4) is communicated with the inlet of the high-pressure slurry separation and dehydration device (5). The heat source of the reaction device (4) is derived from the steam provided by the steam heating system. The multi-stage water circulation system comprises a first heat exchanger (11), a second heat exchanger (12), a back pressure valve (14) and a tail water treatment device (16). The hot side inlet of the first heat exchanger (11) is the low-pressure inlet of the multi-stage water circulation system, the hot side inlet of the first heat exchanger (11) is communicated with the separation water outlet of the high-temperature drying device (7), and the cold side inlet of the first heat exchanger (11) is communicated with the industrial water inlet. The hot side inlet of the second heat exchanger (12) is the high-pressure inlet of the multi-stage water circulation system, and the hot side inlet of the second heat exchanger (12) is communicated with the separation water outlet of the high-pressure slurry separation and dehydration device (5). The outlet of the second heat exchanger (12) is communicated with the inlet of the dechlorination device (13), the outlet of the dechlorination device (13) is communicated with the inlet of the back pressure valve (14), and the outlet of the back pressure valve (14) is communicated with the hot side outlet of the first heat exchanger (11) through a circulating water collecting pipeline. The dechlorination device (13) is provided with a calcium hydroxide inlet and a crystal control agent inlet. Calcium hydroxide is added through the calcium hydroxide inlet of the dechlorination device (13), and a crystal control agent is added through the crystal control agent inlet of the dechlorination device (13). The crystal control agent and the calcium hydroxide control the pH value of the slurry in the dechlorination device (13) for removing chloride ions. The circulating water collecting pipeline comprises a first separation pipeline and a second separation pipeline. The first separation pipeline is connected with the water inlet of the solid-liquid mixing device (2), and the second separation pipeline is connected with the inlet of the tail water treatment device (16).

2. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The high-pressure slurry separation and dehydration device (5) comprises a solid-liquid self-separation device and a pressure energy utilization type solid-phase pressure reduction dehydration module.

3. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The first outlet of the steam heating system is connected with the steam heating inlet in the reaction device (4), and the second outlet of the steam heating system is connected with the high-temperature steam inlet of the high-temperature drying device (7).

4. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The material post-processing system comprises a ball milling device (10), a finished material storage device (9) and a finished material packaging device (8) connected in sequence. The inlet of the ball milling device is connected with the material outlet of the high-temperature drying device (7).

5. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The pressure value of the back pressure valve (14), the pressure value of the reaction device (4) and the pressure value of the high-pressure slurry separation and dehydration device (5) are consistent.

6. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The pipeline, in which the industrial water inlet is connected with the first heat exchanger (11), is provided with an industrial circulating water on-off regulating valve (V01).

7. The process system for dechlorination and quality improvement of desulfurized gypsum according to claim 1, characterized in that, The pipeline, in which the circulating water collecting pipeline is connected with the tail water treatment device (16), is provided with an external water on-off regulating valve (V02). The pipeline, in which the circulating water collecting pipeline is connected with the solid-liquid mixing device (2), is provided with a circulating water on-off regulating valve (V03) and a chloride ion content detection instrument (Cl01).

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