Sulfate radical removal system based on calcium chloride

Abstract

The utility model belongs to the technical field of sulfate radical removal equipment, and particularly relates to a calcium chloride-based sulfate radical removal system which comprises a reaction tank, a saltpeter, a first delivery pump, a centrifugal machine, a second delivery pump, a filtrate tank and a third delivery pump which are connected in sequence, a liquid accumulation box, a collecting pipe, a first packing layer, a circulating liquid circular coil pipe and a second packing layer are sequentially arranged in the cylindrical cavity from top to bottom, and a center barrel is further arranged in the cylindrical cavity. In the whole removal system, various parameters of the saline water can be continuously monitored and controlled by adopting some existing detection control units, so that the stable operation of the system is ensured. According to the principle that calcium chloride reacts with sulfate radicals to generate calcium sulfate precipitates, sulfate ions in saline water are efficiently removed by combining washing operation of the centrifugal machine, meanwhile, the purity of calcium sulfate and the resource utilization rate are improved, and double benefits of economy and environmental protection are achieved.

Description

A calcium chloride-based sulfate removal system Technical Field

[0001] This invention belongs to the field of sulfate removal technology, specifically relating to a sulfate removal system based on calcium chloride. Background Technology

[0002] The chlor-alkali industry refers to the industry that uses raw salt as raw material to produce basic chemical raw materials such as industrial alkali and chlorine. The sources of raw salt include sea salt, well salt, and lake salt. Among these, natural well salt contains associated mineral impurities such as sodium sulfate. In the production of caustic soda using an ion-exchange membrane unit, the continuous accumulation of Na2SO4, as well as the accumulation of Na2SO4 in the brine of lake salt, will form precipitates on the surface of the electrolytic cell electrodes, increasing energy consumption and even raising the voltage, thus shortening the service life of the electrodes and chloride ion exchange membranes.

[0003] Currently, low-pressure nanofiltration membranes are commonly used in chlor-alkali production to concentrate sodium sulfate solution to 45-60 g / L under 18-25 kg pressure, which is then frozen at low temperature to produce sodium sulfate. However, the sodium sulfate produced by this process contains water of crystallization, which limits its application range, makes it difficult to sell, results in low industrial utilization value, and leads to serious resource waste.

[0004] With the development of nanofiltration membrane technology, nanofiltration membrane products and membrane concentration technologies with different pressure resistances have emerged, such as super-concentration membrane (high-pressure membrane concentration), which can produce 150-160 g / L high-concentration sodium sulfate solution under pressure of 5.5-6.0 MPa. The membrane concentration process commonly employs two routes: one is a closed-loop circulation + anti-crystallization process, and the other is a high-pressure concentration + high-pressure pure water process. The "closed-loop circulation + anti-crystallization" route refers to using a closed-loop circulation mode and adding anti-crystallization measures, which leads to operational complexity and secondary pollution. The "high-pressure concentration + high-pressure pure water" route is mostly used in factories using brine as raw material; excess water affects brine usage, resulting in poor economic efficiency. Furthermore, both super-concentration processes directly perform high-pressure concentration on low-pressure nanofiltration water, requiring high-pressure pumps and circulation pumps (water addition pumps) with high flow rates and heads, which is not energy-efficient. Moreover, the concentration unit uses a high-pressure design and is equipped with a high-pressure nanofiltration membrane, significantly increasing investment costs. Summary of the Invention

[0005] The purpose of this invention is to provide a sulfate removal system based on calcium chloride. It utilizes the principle that calcium chloride reacts with sulfate to form calcium sulfate precipitate, and combines a reaction tank, a nitrifier, and a centrifuge washing operation to efficiently remove sulfate ions from brine, while improving the purity and resource utilization rate of calcium sulfate, thus achieving both economic and environmental benefits.

[0006] To achieve the above objectives, this utility model is implemented through the following technical solution:

[0007] In a first aspect, embodiments of this utility model provide a sulfate removal system based on calcium chloride, comprising a reaction tank, a nitrifier, a first transfer pump, a centrifuge, a second transfer pump, a filtrate tank, and a third transfer pump connected in sequence; wherein, the nitrifier includes a cylindrical cavity, and the cylindrical cavity is provided with a slurry tank, a collecting pipe, a first packing layer, a circulating liquid circular coil, and a second packing layer in sequence from top to bottom; the cylindrical cavity is also provided with a central barrel, which passes through the slurry tank, the collecting pipe, the first packing layer, the circulating liquid circular coil, and the second packing layer in sequence from top to bottom; the central axis of the central barrel coincides with the central axis of the cylindrical cavity, and the bottom of the central barrel is kept on the same horizontal plane as the bottom of the cavity structure of the cylinder.

[0008] This calcium chloride-based sulfate removal system, through a specially designed reaction tank structure, precisely controls the amount of calcium chloride added, allowing for thorough mixing and reaction between calcium chloride and sulfate ions to rapidly generate easily separable brine containing calcium sulfate precipitate. Optimized precipitator structure enables highly efficient precipitation of the calcium sulfate-containing brine, improving precipitation separation efficiency. The centrifuge employs continuous operation and precise water washing control, enabling rapid solid-liquid separation and effective removal of impurities, increasing calcium sulfate purity and further enhancing sulfate removal efficiency. This significantly reduces the sulfate ion concentration in the brine, meeting environmental emission standards.

[0009] As a further technical solution, the central tank has a vertical cylindrical structure, with a feed inlet at the top and a discharge outlet at the bottom. The top feed inlet of the central tank is used to continuously receive the brine containing calcium sulfate precipitate generated in the reaction tank, and the bottom discharge outlet of the central tank is used to discharge the brine containing calcium sulfate precipitate. The main function of the central tank is to guide the feed flow to the settling zone, control the fluid flow rate to ensure effective crystal settling, and isolate feed disturbances to maintain the stability of the upper clarification zone of the precipitator. It is the core flow guiding component for achieving efficient solid-liquid separation.

[0010] As a further technical solution, the slurry collection tank includes a tank body and a supernatant outlet pipe located at the bottom of the tank body. The outlet of the supernatant outlet pipe is located outside the nitrifier. The tank body is a cylindrical cavity, and the diameter of the tank body is larger than the diameter of the central tank. The slurry collection tank is used to store the supernatant, and the supernatant outlet pipe is used to discharge the supernatant from the slurry collection tank to the outside of the nitrifier. To facilitate control of the opening and closing of the supernatant outlet pipe, a valve is also provided on the supernatant outlet pipe. In some cases, the supernatant outlet pipe can also be connected by a pipeline to return the supernatant discharged from the supernatant outlet pipe to the reaction vessel or to other subsequent processing.

[0011] As a further technical solution, a plurality of collecting pipes are circumferentially arranged at the bottom of the liquid accumulation tank, and a plurality of openings are provided on the pipe wall of the collecting pipe; one end of the collecting pipe is connected to the bottom of the liquid accumulation tank, and the other end of the collecting pipe is fixed on the side wall of the cylindrical cavity in the nitrate precipitation device. The collecting pipe is used to collect the supernatant after sedimentation separation, converge and guide the supernatant into the liquid accumulation tank. The distance between adjacent openings in the horizontal direction on the pipe wall of the collecting pipe is 100-130 mm, and the aperture is 20-30 mm. The openings on the pipe wall of the collecting pipe are used to collect the supernatant after sedimentation separation, and then converge and guide it to the liquid accumulation tank through the main pipe of the collecting pipe.

[0012] As a further technical solution, the first packing layer is arranged above the second packing layer, and there is a distance between the second packing layer and the bottom of the cylindrical cavity of the nitrate precipitation device;

[0013] Packing layer supports are arranged at the bottoms of the first packing layer and the second packing layer, and the packing layer supports are fixed on the cylindrical cavity of the nitrate precipitation device;

[0014] There is a distance between the first packing layer and the second packing layer, and the first packing layer and the second packing layer are honeycomb packings.

[0015] The nitrate precipitation device adopts two layers of honeycomb packings, uses the porous structure of the packings to guide the water flow to rise evenly, reduces turbulence, and at the same time provides an attachment surface for particle coalescence, improving the sedimentation efficiency higher than that of the conventional deflector plate. Moreover, the distance between the packing layers and the aperture can be adjusted according to the brine treatment volume. The circulating liquid outlet in the middle of the packing layer can lead out part of the supernatant, or can be refluxed to the nitrate precipitation device by a circulating pump to form an internal circulating flow, enhancing the probability of particle collision and promoting floc growth. The packing layer support can be made of strip-shaped grids made of metal or plastic and cross-welded or assembled. The packing layer support is used to bear the weight of the packing layer, ensure uniform fluid distribution at the same time, and prevent the packing from falling or blocking.

[0016] As a further technical solution, a circular circulating liquid coil is also arranged between the first packing layer and the second packing layer. The circular circulating liquid coil includes an annular pipe and a cylindrical pipe, and a plurality of openings are provided on the pipe wall of the annular pipe; one end of the cylindrical pipe is connected to the annular pipe, and the other end of the cylindrical pipe is arranged outside the cylindrical cavity of the nitrate precipitation device; a circular circulating liquid coil support is arranged at the bottom of the circular circulating liquid coil, and the circular circulating liquid coil support is fixed on the cylindrical cavity of the nitrate precipitation device. The circular circulating liquid coil is used to collect the circulating liquid in the clarification area, converge the liquid in the area between the first packing layer and the second packing layer in the nitrate precipitation device through the circulating liquid outlet on the circular circulating liquid coil, and is used for subsequent transportation to the circulating system supporting the nitrate precipitation device by a liquid adding pump.

[0017] As a further technical solution, the nitrate settling tank also includes a conical cavity, which is located at the lower part of the cylindrical cavity. The cone angle of the conical cavity structure is 30°-60°. A flushing port is provided on one side of the bottom of the conical cavity, and a sludge outlet is provided at the bottom of the conical cavity. The flushing port is located above the sludge outlet and inclined at 30°-45° towards the sludge outlet. The flushing liquid for the flushing port comes from the residual liquid discharged from the centrifuge, preventing calcium sulfate from accumulating and clogging the sludge outlet. The flushing port is used to prevent calcium sulfate precipitate from accumulating and clogging the sludge outlet. The sludge outlet is used to discharge the calcium sulfate precipitate from the conical cavity out of the nitrate settling tank. To increase the residence time of the brine containing calcium sulfate precipitate in the nitrate settling tank, a valve can also be provided on the sludge outlet, which is closed when the amount of liquid being processed is small, thereby increasing the residence time of the liquid in the nitrate settling tank.

[0018] The settling principle of the nitrate settling tank is as follows: The central cylinder continuously transports brine containing calcium sulfate precipitate to the nitrate settling tank. Due to the large volume of the nitrate settling tank, the brine containing calcium sulfate precipitate discharged from the bottom outlet of the central cylinder gradually aggregates and settles in the nitrate settling tank. When it reaches the sludge removal port, a large amount of flocculent mixture has been generated in the lower settling zone of the nitrate settling tank. Due to the density difference, the light components in the flocculent mixture slowly diffuse into the packing layers set on both sides of the central cylinder. The light components flow evenly from bottom to top, avoiding the turbulent impact and liquid surface fluctuation caused by direct feeding from the top of the nitrate settling tank. This allows the calcium sulfate particles sufficient time to aggregate and settle, prolonging the residence time of the material in the packing layer, promoting the collision and adsorption of particles with the packing surface, forming larger flocs, thereby achieving efficient separation of sedimentation and stable clarification of the supernatant.

[0019] As a further technical solution, the reaction vessel is a cylindrical tank. The top of the reaction vessel is equipped with a baffle channel and a sample inlet connected in sequence. The baffle channel is connected to the calcium chloride dosing device and the concentrated crude brine pipe, respectively. A stirrer is installed inside the reaction vessel, and a discharge port is located at the bottom. The baffle channel is used to initially mix the calcium chloride solution with the concentrated crude brine before it enters the reaction vessel for full reaction. The stirrer is used to thoroughly mix the calcium chloride with the sulfate-containing brine. Simultaneously, the stirring time is determined based on factors such as the properties of the brine and the reaction temperature, generally 15-60 minutes, to ensure the reaction reaches the expected conversion rate. The discharge port is used to discharge the brine containing calcium sulfate precipitate generated in the reaction vessel. The discharge port is connected to the inlet of the nitrate precipitator via a pipe.

[0020] As a further technical solution, the baffle is a pipe structure with a rectangular or circular cross-section. The baffle includes a tank body, with an inlet at the top and an outlet at the bottom. The inlet is connected to a concentrated crude brine pipe, and the outlet is connected to the feed inlet of the reaction tank.

[0021] As a further technical solution, the tank is equipped with baffles, in multiple sets, with an adjacent baffle spacing of 0.3-0.5m, and the adjacent baffles are arranged in an alternating pattern to form an "S"-shaped flow channel. This structure helps to increase the uniformity of the initial mixing of calcium chloride solution and concentrated crude brine.

[0022] The baffles can be vertical or inclined. Vertical baffles are perpendicular to the water flow direction, with a height equal to 2 / 3 of the tank height, and a 1 / 3 empty space at the bottom to form a flow channel. Inclined baffles are at an angle of 60°-75° to the water flow direction. This structure helps increase the uniformity of the initial mixing of the calcium chloride solution and the concentrated crude brine.

[0023] The beneficial effects of the above-described embodiments of this utility model are as follows:

[0024] (1) The calcium chloride-based sulfate removal system provided by this utility model, through the specific structure design of the reaction tank, precisely controls the amount of calcium chloride added, so that calcium chloride and sulfate ions are fully mixed and reacted to quickly generate brine containing calcium sulfate precipitate that is easy to separate; by optimizing the specific structure of the precipitator, the brine containing calcium sulfate precipitate is efficiently precipitated, and the precipitation separation efficiency is improved; the centrifuge adopts continuous operation and precise water washing control, which can quickly achieve solid-liquid separation and effectively remove impurities, improve the purity of calcium sulfate, further improve the sulfate removal efficiency, and significantly reduce the concentration of sulfate ions in the brine to meet environmental emission standards.

[0025] (2) The calcium chloride used in this invention is a common chemical raw material, readily available and inexpensive, reducing the cost of sulfate removal and offering significant economic advantages compared to traditional methods. The nitrification chamber uses two layers of honeycomb packing, utilizing the porous structure of the packing to guide the water flow upwards uniformly, reducing turbulence and providing an attachment surface for particle aggregation, thus improving sedimentation efficiency. This is higher than that of conventional guide plates. Furthermore, the spacing and pore size of the packing layers can be adjusted according to the brine treatment volume. The circulating liquid outlet in the middle of the packing layer can lead out some supernatant, or it can be pumped back to the nitrification chamber to form an internal circulation flow, increasing the probability of particle collision and promoting floc growth. The supernatant collected in the collection tank can be recycled back to the reaction tank for reuse, improving resource utilization. The flushing port at the bottom of the nitrification chamber is located above the discharge port and tilted at 30° to 45° towards the discharge port. The flushing liquid at the flushing port comes from the residual liquid discharged from the centrifuge, preventing calcium sulfate accumulation and blockage.

[0026] (3) The calcium sulfate produced by this invention can be used as an industrial raw material to produce building materials, chemical products, food additives, etc., thereby realizing resource recycling, reducing waste emissions, and having good environmental and social benefits.

[0027] (4) The sulfate removal system provided by this utility model has a simple structure, is easy to operate, and is easy to automate. The automated design of the precipitator and centrifuge reduces manual intervention, lowers the technical requirements for operators, and facilitates its application in industrial production. Attached Figure Description

[0028] The accompanying drawings, which form part of this specification, are used to provide a further understanding of this utility model. The illustrative embodiments of this utility model and their descriptions are used to explain this utility model and do not constitute an improper limitation of this utility model.

[0029] Figure 1 is a schematic diagram of the overall structure of the sulfate removal system based on calcium chloride in this utility model;

[0030] Figure 2 is a front view of the nitrate settling device in this utility model;

[0031] Figure 3 is a cross-sectional view AA of Figure 2 in this utility model;

[0032] Figure 4 is a cross-sectional view of the manifold in Figure 3 of this utility model;

[0033] Figure 5 is a BB cross-sectional view of Figure 2 in this utility model;

[0034] The diagram is for illustrative purposes only.

[0035] The components include: reaction tank 1, nitrifier 2, central tank 2-1, liquid collection tank 2-2, collection pipe 2-3, supernatant outlet pipe 2-4, first packing layer 2-5-1, second packing layer 2-5-2, packing layer support 2-6, circulating liquid circular coil 2-7, flushing port 2-8, sludge outlet 2-9, first transfer pump 3, centrifuge 4, second transfer pump 5, filtrate tank 6, and third transfer pump 7. Detailed Implementation

[0036] It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0037] Example 1

[0038] As shown in Figure 1, a typical embodiment of this utility model provides a sulfate removal system based on calcium chloride, comprising a reaction tank 1, a nitrifier 2, a first transfer pump 3, a centrifuge 4, a second transfer pump 5, a filtrate tank 6, and a third transfer pump 7 connected in sequence.

[0039] The reaction vessel 1 is a cylindrical tank used to provide a place for calcium chloride and sulfate-containing brine to fully mix and react. The top of the reaction vessel 1 is equipped with a baffle channel and a sample inlet connected in sequence. The baffle channel is connected to the calcium chloride dosing device and the concentrated crude brine pipe, respectively. The baffle channel is used to initially mix the calcium chloride solution and the concentrated crude brine before entering the reaction vessel 1 for full reaction.

[0040] Specifically: The baffle is located at the front end of the feed inlet of reaction tank 1. The baffle is connected to the feed inlet by flange or welding. This connection method helps to shorten the material transmission distance and reduce energy loss. The calcium chloride dosing device is connected to the middle or upstream pipeline of the baffle via a branch pipe, and the pipeline is equipped with a check valve and pressure gauge to prevent backflow of calcium chloride solution.

[0041] The baffle tank is a rectangular or circular cross-section pipe structure made of corrosion-resistant PP or 316L stainless steel. The baffle tank includes a tank body, the dimensions of which can be 1.5-3.0m in length and 0.3-0.6m in width or diameter. The tank body dimensions can also be designed according to the flow rate of the crude brine to be treated, ensuring a residence time of 5-10 seconds within the tank. The tank body has an inlet at the top and an outlet at the bottom. The inlet connects to the concentrated crude brine pipe, and the outlet connects to the feed inlet of reaction tank 1. The diameters of the inlet and outlet pipes are consistent with the main pipeline to ensure smooth water flow. The tank body contains baffles, with 3-5 baffles selected. The spacing between adjacent baffles is 0.3-0.5m, and the staggered arrangement of adjacent baffles forms an "S" shaped flow channel, thereby increasing the uniformity of the initial mixing of the calcium chloride solution and the concentrated crude brine.

[0042] The baffles can be vertical or inclined. Vertical baffles are perpendicular to the water flow direction, with a height of 2 / 3 of the tank height and a 1 / 3 gap at the bottom to form a flow channel, which encourages the water flow to bypass the bottom or side of the baffle and enhances the turbulence. Inclined baffles are at an angle of 60°-75° to the water flow direction, guiding the water flow to form a spiral flow and enhancing the mixing effect.

[0043] The calcium chloride dosing device is used to add calcium chloride solution to reaction tank 1 in a theoretically measured quantity (molar ratio of calcium chloride to sulfate ions is 1:1). The dosage must be controlled within a reasonable range to avoid waste of calcium chloride and increased subsequent processing costs. The calcium chloride dosing device is an existing structure and can be equipped with a fully automatic intelligent control system. This dosing device mainly includes a storage tank, a metering pump, and online monitoring instruments connected in sequence. The storage tank and the metering pump are connected by a salt-corrosion-resistant UPVC or stainless steel pipe, and the pipe is equipped with valves, such as electric ball valves or solenoid valves. A control system is also included, and the valves, metering pump, and online monitoring instruments are all connected to the control system. The storage tank is a tank structure used to store the pre-prepared calcium chloride solution (concentration is usually 10%–30%, which can be adjusted according to the sulfate concentration in the brine). The storage tank is equipped with a stirrer to maintain the homogeneity of the calcium chloride solution and prevent calcium chloride crystallization and precipitation.

[0044] The metering pump adopts a high-precision electromagnetic diaphragm metering pump or plunger pump, which features corrosion resistance and stable flow. The maximum dosing flow rate of the metering pump can be set according to the solution volume and sulfate concentration range in reaction tank 1 (e.g., 0–1000 L / h). Online monitoring instruments include a sulfate ion concentration detector (e.g., ion-selective electrode method or spectrophotometer), a flow meter (for monitoring brine flow rate), and a pH meter (for assisting in judging the degree of reaction); online monitoring instruments are used to monitor key parameters of the pretreated brine in real time.

[0045] The control system can employ an automated control module based on a PLC (Programmable Logic Controller) or a DCS (Distributed Control System), and has a built-in chemical metering calculation program that can automatically adjust the metering pump and valves based on the detection data from online monitoring instruments. To facilitate the control of calcium chloride dosage, a sulfate concentration detector is installed in the upstream pipeline of the concentrated crude brine entering the baffle tank, and the sulfate concentration detector is connected to the control system, thereby achieving precise control of the calcium chloride solution dosage.

[0046] The reaction vessel 1 is equipped with a stirrer connected to a power unit. The stirrer is used to thoroughly mix calcium chloride with sulfate-containing brine. The stirring time is determined based on factors such as the properties of the brine and the reaction temperature, generally ranging from 15 to 60 minutes, to ensure the reaction reaches the expected conversion rate. A discharge port is located at the bottom of the reaction vessel 1 to drain the brine containing calcium sulfate precipitate generated during the reaction. The discharge port is connected to the inlet of the nitrate precipitator 2 via a pipe.

[0047] The settling tank 2 receives the brine containing calcium sulfate precipitate discharged from the reaction tank 1, achieving efficient sedimentation and separation of the calcium sulfate precipitate, separating the supernatant and calcium sulfate precipitate. The supernatant can be refluxed, while the calcium sulfate precipitate is discharged to the settling tank 2 and enters the centrifuge for further separation and cleaning. The centrifuge 4 uses an existing centrifuge with a spray device, such as the P-series two-stage piston pusher centrifuge from Zhejiang Light Machinery Centrifuge Manufacturing Co., Ltd., or the HR horizontal two-stage piston pusher centrifuge from Xiangtan Centrifuge Co., Ltd. The centrifuge 4, by controlling the rotation speed, centrifugation time, and spray device, thoroughly separates and cleans the calcium sulfate precipitate to obtain a high-purity calcium sulfate product, meeting the requirements for use as a raw material in other industries. The filtrate produced by the centrifuge is transported to the filtrate tank 6 by the second transfer pump 5. The filtrate tank 6 is used to collect and store the filtrate produced during centrifugation. When the filtrate in the filtrate tank 6 is discharged from the boundary area by the third transfer pump 7.

[0048] As shown in Figure 2, the nitrate settling tank 2 includes a cylindrical cavity and a conical cavity. The cylindrical cavity is located on top of the conical cavity, and its bottom is fixedly connected to the top of the conical cavity. The cylindrical cavity serves as a clarification zone for solution clarification, while the conical cavity serves as a settling zone for calcium sulfate crystallization and precipitation. The cone angle of the conical cavity structure is 30°-60°. A flushing port 2-8 is provided on one side of the bottom of the conical cavity, and a sludge outlet 2-9 is provided at the bottom of the conical cavity. The flushing port 2-8 is located above the sludge outlet 2-9 and is inclined at 30°-45° towards it. The flushing liquid for the flushing port 2-8 comes from the residual liquid discharged from the centrifuge or the supernatant in the nitrate settling tank 2. The flushing port 2-8 is used to prevent calcium sulfate precipitate from accumulating and clogging the sludge outlet 2-9. The sludge outlet 2-9 is used to discharge the calcium sulfate precipitate from the conical cavity out of the nitrate settling tank 2.

[0049] Within the cylindrical cavity of the pre-nitrification tank 2, from top to bottom, are arranged a liquid collection tank 2-2, a collecting pipe 2-3, a first packing layer 2-5-1, a packing layer support 2-6, a circulating liquid circular coil 2-7, and a second packing layer 2-5-2. A central barrel 2-1 is also provided, which sequentially passes through the liquid collection tank 2-2, the collecting pipe 2-3, the first packing layer 2-5-1, the packing layer support 2-6, the circulating liquid circular coil 2-7, and the second packing layer 2-5-2. The central axis of the central barrel 2-1 coincides with the central axis of the cylindrical cavity structure, and the bottom of the central barrel 2-1 is at the same horizontal plane as the bottom of the cylindrical cavity structure. The central barrel 2-1 has a vertical cylindrical structure. A feed inlet is located at the top of the central barrel 2-1, and for ease of feeding, the height of the feed inlet at the top of the central barrel 2-1 can be higher than the height of the cylindrical cavity in the pre-nitrification tank 2. A discharge outlet is located at the bottom of the central barrel 2-1. The top inlet of the central tank 2-1 is used to continuously receive the brine containing calcium sulfate precipitate generated in the reaction tank 1, while the bottom outlet of the central tank 2-1 is used to discharge the brine containing calcium sulfate precipitate. To further enhance the mixing effect, a stirrer can also be installed inside the central tank 2-1. The main functions of the central tank 2-1 are to guide the feed flow to the settling zone, control the fluid velocity to ensure effective crystal settling, and isolate feed disturbances to maintain the stability of the upper clarification zone of the nitrifier 2. It is the core flow guiding component for achieving efficient solid-liquid separation.

[0050] As shown in Figure 3, the slurry collection tank 2-2 includes a tank body and a supernatant outlet pipe 2-4 located on the outer side of the bottom of the tank body. The opening of the supernatant outlet pipe 2-4 is located outside the nitrifier 2. The tank body of the slurry collection tank 2-2 is a cylindrical cavity, and the diameter of the tank body is larger than the diameter of the central tank 2-1. The supernatant outlet pipe 2-4 is a common cylindrical pipe. The slurry collection tank 2-2 is used to store the supernatant, and the supernatant outlet pipe 2-4 is used to discharge the supernatant from the slurry collection tank 2-2 to the outside of the nitrifier 2. To facilitate the control of the opening and closing of the supernatant outlet pipe 2-4, a valve is also provided on the supernatant outlet pipe 2-4. In some cases, the supernatant outlet pipe 2-4 can also be connected by a pipeline to return the supernatant discharged from the supernatant outlet pipe 2-4 to the reaction tank 1 or to other subsequent processing.

[0051] Several collecting pipes 2-3 are arranged circumferentially at the bottom of the collection tank 2-2. One end of the collecting pipe 2-3 is connected to the bottom of the collection tank 2-2, and the other end of the collecting pipe 2-3 is fixed to the side wall of the cylindrical cavity in the settling tank 2. The collecting pipes 2-3 are used to collect the supernatant after sedimentation and separation, and guide the supernatant to the collection tank 2-2.

[0052] The number of collecting pipes 2-3 can be selected as eight, with eight collecting pipes 2-3 arranged around the bottom of the collection tank 2-2. To facilitate the collection of the supernatant after sedimentation and separation, the eight collecting pipes 2-3 are evenly arranged around the bottom of the collection tank 2-2. The collecting pipes 2-3 are existing structures, capable of collecting, converging, and guiding liquids. They can be cylindrical tubes with several openings on their walls. The horizontal spacing between adjacent openings on the wall of the collecting pipe 2-3 is 100-130 mm, and the diameter of the openings is 20-30 mm. The openings on the wall of the collecting pipes 2-3 are used to collect the supernatant after sedimentation and separation, which is then converged and guided to the collection tank 2-2 through the main pipe of the collecting pipe 2-3.

[0053] As shown in the cross-sectional view of the manifold in Figure 4, there are openings on both sides of the manifold 2-3. The openings can be symmetrically positioned, and the distance between adjacent openings can be 100-130mm.

[0054] The packing layer includes a first packing layer 2-5-1 and a second packing layer 2-5-2. The first packing layer 2-5-1 is disposed above the second packing layer 2-5-2. A gap is provided between the second packing layer 2-5-2 and the bottom of the cylindrical cavity of the pre-nitrification chamber 2. Optionally, the gap between the second packing layer 2-5-2 and the bottom of the cylindrical cavity of the pre-nitrification chamber 2 is 1.5-2.0 m. A packing layer support 2-6 is provided below both the first packing layer 2-5-1 and the second packing layer 2-5-2. The packing layer support 2-6 is fixedly disposed within the cylindrical cavity of the pre-nitrification chamber 2. A certain gap is provided between the first packing layer 2-5 and the second packing layer 2-5-2. Optionally, the gap between the first packing layer 2-5 and the second packing layer 2-5-2 is 1.0-1.5 m. The first packing layer 2-5 and the second packing layer 2-5-2 are honeycomb packings, which can be made of polypropylene. The pore size of the honeycomb packing can be selected as 50-80 mm. Both the first packing layer 2-5-1 and the second packing layer 2-5-2 are used to create a stable laminar flow environment, accelerating the agglomeration and sedimentation of calcium sulfate particles. The packing layer support 2-6 is an existing structure, which can be constructed by cross-welding or assembling strip grids made of metal (such as 304 stainless steel or carbon steel) or plastic (PP or PVC). The packing layer support 2-6 is used to support the weight of the packing layer while ensuring uniform fluid distribution and preventing packing from falling off or clogging. A circular coil 2-7 for circulating liquid is also provided between the first packing layer 2-5-1 and the second packing layer 2-5-2.

[0055] As shown in Figure 5, the circular coil 2-7 of the circulating liquid includes an annular pipe and a cylindrical pipe. The annular pipe is connected to one end of the cylindrical pipe, and the other end of the cylindrical pipe is arranged outside the cylindrical cavity of the nitrate settler 2. A number of openings are provided on the pipe wall of the annular pipe. The cross-sectional view of the annular pipe is similar to that of the collecting pipe in Figure 4, with the only difference being the size and spacing of the openings. The spacing between adjacent openings on the pipe wall of the annular pipe is 150 - 200 mm, and the aperture is 40 - 60 mm. The openings on the pipe wall of the annular pipe are used to collect the liquid separated by sedimentation between the packing layers and are led out to the outside of the cylindrical cavity of the nitrate settler 2 through the cylindrical pipe connected to the annular pipe.

[0056] A support for the circular coil of the circulating liquid is provided at the bottom of the circular coil 2-7 of the circulating liquid, and the support for the circular coil of the circulating liquid is fixed on the cylindrical cavity of the nitrate settler. The support for the circular coil of the circulating liquid is an existing structure. To further enhance the stability and support strength of the circular coil of the circulating liquid, the structure of the support for the circular coil of the circulating liquid that can be selected includes a central support member and rectangular channel steels arranged around the central support member. The central support member includes a "well"-shaped channel steel and an annular channel steel externally connected to the "well"-shaped channel steel. The circular coil 2-7 of the circulating liquid is used to collect the circulating liquid in the clarification zone, and the liquid in the area between the first packing layer 2-5-1 and the second packing layer 2-5-2 in the nitrate settler 2 is gathered through the circulating liquid outlet on the circular coil 2-7 of the circulating liquid, and is used to be subsequently transported to the circulating system supporting the nitrate settler 2 through a liquid addition pump, and then transported to the nitrate settler 2 or the reaction tank 1.

[0057] The precipitation separation process of the brine containing calcium sulfate precipitate discharged from the reaction tank 1 in the nitrate settler 2 is as follows: The brine containing calcium sulfate precipitate enters from the top of the central barrel 2-1 in the upper clarification zone of the nitrate settler. Due to the large volume of the nitrate settler 2, the brine containing calcium sulfate precipitate discharged from the bottom discharge port of the central barrel 2-1 gradually coalesces and settles in the lower settling zone of the nitrate settler 2. When reaching the mud outlet 2-9, a large amount of flocculent mixture has been generated in the lower settling zone of the nitrate settler 2. Due to the density difference, the light components in the flocculent mixture slowly diffuse into the packing layers (the first packing layer 2-5-1 and the first packing layer 2-5-2) arranged on both sides of the central barrel. In the packing layers (the first packing layer 2-5-1 and the second packing layer 2-5-2) of the brine containing calcium sulfate precipitate, the calcium sulfate particles collide and adsorb on the surface of the packing, and gradually settle to the settling zone at the lower part of the nitrate settler under the action of gravity, and are discharged through the mud outlet 2-9 at the bottom of the settling zone. And the calcium sulfate precipitate in the settling zone is washed through the flushing port 2-8 on one side of the bottom of the settling zone. The supernatant liquid at the upper end of the first packing layer 2-5-1 in the nitrate settler converges and is guided to the liquid collecting tank 2-2 through the openings on the pipe body of the collecting pipe 2-3. The SO4 in the supernatant liquid clarified by the first packing layer 2-5-1 2-The concentration is reduced to about 5 g / L and can be refluxed to the reaction tank 1 or enter the subsequent treatment as needed. The liquid between the first packing layer 2-5-1 and the second packing layer 2-5-2 converges through the circulating liquid circular coil 2-7 and the circulating liquid outlet provided thereon, and is used to be subsequently transported to the circulating system supporting the nitrate settler 2 through a liquid addition pump, and then transported to the nitrate settler 2 or the reaction tank 1.

[0058] In order to achieve the continuous operation of the nitrate settler 2, in actual operation, the liquid in the circulating liquid circular coil 2-7 is often transported to the nitrate settler 2 to keep the overall liquid level in the nitrate settler 2 at the corresponding position of the collecting pipe 2-3. Through the specific structural design of the nitrate settler 2, the light components of the mixed liquid entering the nitrate settler 2 flow uniformly from bottom to top, avoiding the turbulent impact and liquid surface fluctuation generated by directly feeding from the top of the nitrate settler 2, enabling the calcium sulfate particles to have sufficient time to coalesce and settle, prolonging the residence time of the material in the packing layer, promoting the collision and adsorption of the particles on the surface of the packing, forming larger flocs, and thus achieving efficient separation of precipitation and stable clarification of the supernatant liquid.

[0059] The calcium sulfate precipitation outlet 2-9 at the bottom of the nitrate settler 2 is connected to the feed inlet of the centrifuge 4 through the first transfer pump 3. The first transfer pump 3 is used to transport the calcium sulfate precipitation discharged from the nitrate settler to the centrifuge 4 through the transfer pump.

[0060] In addition, based on the sulfate removal system of calcium chloride, some existing detection and control units can be added to continuously monitor and control various parameters of the brine to ensure the stable operation of the system.

[0061] The principle of sulfate removal based on calcium chloride in the present utility model is as follows:

[0062] The present invention utilizes the chemical reaction between calcium chloride (CaCl2) and sulfate ions (SO4 2- ) and its reaction equation is: CaCl2 + SO4 2- →CaSO4↓ + 2Cl-. By adding an appropriate amount of calcium chloride to the brine containing sulfate ions, it promotes the combination of sulfate ions and calcium ions to form calcium sulfate precipitation, thereby achieving the separation and removal of sulfate ions from the brine.

[0063] The working process of the sulfate removal system based on calcium chloride in the present utility model is as follows:

[0064] (1) Brine pretreatment: The brine containing sulfate ions is preliminarily pretreated to remove the suspended solids, large particle impurities and other pollutants that may affect the reaction. Conventional pretreatment methods such as filtration, precipitation, and grid interception can be used to ensure that the quality of the brine entering the reaction tank 1 meets the reaction requirements and avoid blockage or damage to the subsequent reaction and equipment.

[0065] (2) Calcium chloride addition: Based on the concentration of sulfate ions in the pretreated brine, calcium chloride solution is added to reaction tank 1 in a quantitative manner according to the theoretical amount using a dosing device and the stoichiometric ratio. The amount added must be controlled within a reasonable range to avoid waste of calcium chloride and increased subsequent treatment costs.

[0066] (3) Reaction stirring: While calcium chloride is being added, the stirring device is started through the baffle tank to quickly and evenly mix the calcium chloride solution with the brine, promoting the chemical reaction between calcium ions and sulfate ions. The stirring time is determined according to the properties of the brine, reaction temperature, and other factors, and is generally 15-60 minutes to ensure that the reaction reaches the expected conversion rate.

[0067] (4) Precipitation and Separation: After the reaction, the brine containing calcium sulfate precipitate enters the precipitator 2, guiding the brine to flow along a specific path, making the precipitation process more orderly and reducing the impact of turbulence on the precipitation effect; at the same time, it provides sufficient settling time for the calcium sulfate precipitate, allowing the precipitate to be fully separated. In addition, when the calcium sulfate precipitate accumulates to a certain extent at the bottom, the flushing liquid in the flushing port 2-8 at the bottom of the precipitator is activated to flush the calcium sulfate precipitate to the sludge discharge port 2-9 for subsequent transportation. After treatment in the precipitator 2, the SO42- concentration in the supernatant is about 5 g / L. The supernatant is returned to the device for further extraction and concentration, and can be discharged or further reused after meeting the standards.

[0068] (5) Centrifugal washing and drying: The calcium sulfate precipitated at the bottom of the nitrate settling tank 2 is transported to the centrifuge 4 via the first transfer pump 3. The centrifuge 4 achieves efficient solid-liquid separation. During centrifugation, pure water is evenly sprayed onto the rotating calcium sulfate precipitate through a spray device to ensure effective cleaning. Simultaneously, the speed and centrifugation time of the centrifuge 4 can be flexibly adjusted according to the properties of the calcium sulfate precipitate to achieve optimal cleaning and separation results. The cleaned calcium sulfate is then dried to obtain a high-purity calcium sulfate product, meeting the requirements for use as a raw material in other industries.

[0069] (6) The filtrate produced by centrifuge 4 is transported to filtrate tank 6 by second transfer pump 5. Filtrate tank 6 is used to collect and store the filtrate produced during centrifugation. When the filtrate in filtrate tank 6 is sent out of the boundary area by third transfer pump 7.

[0070] In addition, during the entire removal process, some existing detection and control units can be used to continuously monitor and control various parameters of the brine to ensure stable system operation.

[0071] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A sulfate removal system based on calcium chloride, characterized in that, The system includes a reaction tank, a nitrifier, a first transfer pump, a centrifuge, a second transfer pump, a filtrate tank, and a third transfer pump connected in sequence. The nitrifier includes a cylindrical cavity, in which, from top to bottom, a slurry tank, a manifold, a first packing layer, a circulating liquid circular coil, and a second packing layer are arranged. The cylindrical cavity also includes a central barrel, which passes through the slurry tank, the manifold, the first packing layer, the circulating liquid circular coil, and the second packing layer from top to bottom. The central axis of the central barrel coincides with the central axis of the cylindrical cavity, and the bottom of the central barrel is at the same horizontal plane as the bottom of the hollow structure of the cylinder.

2. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The central barrel has a vertical cylindrical structure, with a feed inlet at the top and a discharge outlet at the bottom.

3. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The slurry collection tank includes a tank body and a supernatant outlet pipe located at the bottom of the tank body. The outlet of the supernatant outlet pipe is located outside the nitrifier. The tank body is a cylindrical cavity, and the diameter of the tank body is larger than the diameter of the central barrel.

4. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The bottom of the collection tank is provided with several collecting pipes around its circumference, and the pipe walls of the collecting pipes are provided with several openings; one end of the collecting pipe is connected to the bottom of the collection tank, and the other end of the collecting pipe is fixed to the side wall of the cylindrical cavity in the settling tank.

5. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The first packing layer is disposed above the second packing layer, and there is a gap between the second packing layer and the bottom of the cylindrical cavity of the precipitator; both the first and second packing layers are provided with packing layer supports at their bottoms, and the packing layer supports are fixed on the cylindrical cavity of the precipitator; there is a gap between the first and second packing layers, and the first and second packing layers are honeycomb packings.

6. The sulfate removal system based on calcium chloride according to claim 5, characterized in that, A circulating liquid circular coil is also provided between the first packing layer and the second packing layer. The circulating liquid circular coil includes a ring pipe and a cylindrical pipe. The ring pipe has several openings on its wall. One end of the cylindrical pipe is connected to the ring pipe, and the other end of the cylindrical pipe is located outside the cylindrical cavity of the nitrate settler. A circulating liquid circular coil support is provided at the bottom of the circulating liquid circular coil, and the circulating liquid circular coil support is fixed on the cylindrical cavity of the nitrate settler.

7. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The nitrate settling tank also includes a conical cavity, which is located at the lower part of the cylindrical cavity. The cone angle of the conical cavity is 30°-60°. A flushing port is provided on one side of the bottom of the conical cavity, and a mud outlet is provided at the bottom of the conical cavity. The flushing port is located above the mud outlet and is inclined at 30°-45° toward the mud outlet.

8. The sulfate removal system based on calcium chloride according to claim 1, characterized in that, The reaction vessel is a cylindrical tank. The top of the reaction vessel is equipped with a baffle channel and a sample inlet connected in sequence. The baffle channel is connected to the calcium chloride dosing device and the concentrated crude brine pipe, respectively. The reaction vessel is equipped with a stirrer and the bottom of the reaction vessel is equipped with a discharge port.

9. The sulfate removal system based on calcium chloride according to claim 8, characterized in that, The baffle is a pipe structure with a rectangular or circular cross-section. The baffle includes a tank body with an inlet at the top and an outlet at the bottom. The inlet is connected to a concentrated crude brine pipe, and the outlet is connected to the feed inlet of the reaction tank.

10. The calcium chloride-based sulfate removal system according to claim 9, characterized in that, The tank is equipped with baffles, and there are multiple sets of baffles. The distance between adjacent baffles is 0.3-0.5m, and the adjacent baffles are arranged in an "S" shape to form a flow channel. The baffles are vertical baffles or inclined baffles. The vertical baffles are perpendicular to the water flow direction, and the height of the baffle is 2 / 3 of the height of the tank. The bottom 1 / 3 is left open to form a flow passage. The inclined baffles are at an angle of 60°-75° to the water flow direction.

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