Silica removal method for slurry cracking wastewater treatment

Abstract

The invention discloses a silicon removal method for slurry cracking wastewater treatment, which comprises the following steps: S1, mixing slurry cracking wastewater and a silicon removal agent through a static mixer, so that the silicon removal agent and silicon in the wastewater are subjected to precipitation reaction; s2, sequentially adding a coagulant and a flocculating agent into the wastewater treated in the S1, and meanwhile, enabling precipitated sludge to flow back to the reaction area through a sludge circulating pump; s3, mechanically stirring the wastewater in the step S2, so that precipitates generated by the silicon removal reaction are in full contact with return sludge, a coagulant and a flocculating agent to form flocs; s4, feeding the wastewater treated in S3 into a high-density sedimentation tank for solid-liquid separation, feeding supernate into a subsequent membrane treatment system, and discharging precipitated sludge from the bottom; and S5, detecting water quality parameters of effluent after the step S1 and the step S4 through an online monitoring device, and adjusting the dosage of the silicon removal agent in the step S1 according to monitoring data. The high-silicon wastewater is efficiently removed, and pollutants such as hardness and alkalinity are synchronously reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wastewater desilication, and more particularly relates to a desilication method for slag slurry cracking wastewater treatment. BACKGROUND

[0002] With the increasing requirements of industrial wastewater resource utilization, the treatment of high-silicon wastewater has become one of the key bottlenecks restricting the popularization and application of membrane reuse technology. The total silicon content in slag slurry cracking wastewater generated in the fields of metallurgy, chemical industry, coal chemical industry, etc. is usually high, generally greater than 100 ppm, including two forms of dissolved silicon and colloidal silicon. These silicon compounds are easy to form a layer of insoluble silicate scale on the membrane surface such as a reverse osmosis membrane, which seriously affects the membrane flux and service life, resulting in low wastewater reuse rate and high operation cost.

[0003] In the related art, the commonly used desilication methods mainly include chemical precipitation method, ion exchange method, adsorption method and membrane separation method. Among them, the chemical precipitation method is widely used in the pretreatment stage due to its relatively low cost and relatively simple operation. The typical process is to add magnesium salt or aluminum salt reagent to make silicon generate insoluble silicate precipitate which is removed by precipitation or filtration. For example, a method of using magnesium hydroxide and polyaluminum chloride for desilication promotes the co-precipitation of silicon by adjusting the pH to above 10.5. However, the related art has strong pH dependence, and most desilication agents need to adjust the pH of the wastewater to above 10.5 to achieve the best effect, which not only increases the consumption of acid and alkali and the complexity of operation, but also may affect the subsequent treatment process. And the degree of automation is low, the dosing system is mostly manual or simple timing control, which cannot dynamically adjust the dosage according to water quality fluctuations, easily causing waste of reagent or substandard treatment, and is difficult to ensure long-term stable operation of the system.

[0004] Therefore, how to develop an efficient desilication technology that can adapt to a wide pH range, realize precise dosing and automatic control, efficiently remove high-silicon wastewater without adjusting the pH, simultaneously reduce pollutants such as hardness and alkalinity, reduce the risk of fouling of the subsequent membrane system, improve the wastewater reuse rate, and reduce the overall operation cost is the focus of the technical personnel in the field. SUMMARY

[0005] The purpose of the present application is to provide a desilication method for slag slurry cracking wastewater treatment, so as to efficiently remove high-silicon wastewater without adjusting the pH, simultaneously reduce pollutants such as hardness and alkalinity, reduce the risk of fouling of the subsequent membrane system, improve the wastewater reuse rate, and reduce the overall operation cost.

[0006] In view of the above defects or improvement needs of the prior art, the present application provides a desilication method for slag slurry cracking wastewater treatment, comprising: S1, the slag slurry cracking wastewater and desilication agent are mixed through a static mixer to make the desilication agent react with silicon in the wastewater to precipitate; S2, a coagulant and a flocculant are sequentially added to the wastewater treated in the S1, and the precipitated sludge is backflowed to the reaction zone through a sludge circulating pump; S3, the wastewater in the S2 is mechanically stirred to make the precipitate generated by the desilication reaction fully contact with the backflowed sludge, the coagulant and the flocculant to form flocs; S4, the wastewater treated in the S3 is sent to a high-density sedimentation tank for solid-liquid separation, the supernatant is sent to a subsequent membrane treatment system, and the precipitated sludge is discharged from the bottom; S5, water quality parameters of the wastewater after the S1 and the S4 are detected through an online monitoring device, and the addition amount of the desilication agent is adjusted according to the monitoring data.

[0007] Optionally, in the S1, the desilication agent is a composite desilication agent, the addition amount is 0.1-1 mL / L, and the mass concentration is 0.145-1.45 g / L; the pH of the slag slurry cracking wastewater ranges from 8 to 10, and the temperature is 15-20℃, without the need of adjusting the pH.

[0008] Optionally, in the S1, the length of the static mixer is 5-8 m, the number of blades is 5-8, and the mixing time is 17-28 seconds; the reaction time of the desilication agent mixed with the wastewater is 5-10 minutes.

[0009] Optionally, in the S2, the coagulant is polyaluminum chloride (PAC) with an addition amount of 50-150 mg / L, the flocculant is polyacrylamide (PAM) with an addition amount of 1-3 mg / L, and the sludge circulation ratio is 0.03-0.05, i.e. the sludge circulation amount is 3%-5% of the total treated water amount.

[0010] Optionally, in the S3, the linear velocity of the impeller of the mechanical stirring is 1.5 m / s, and the water circulation amount in the stirring zone is 10.8 times of the designed water treatment amount; the total reaction time of the S1 to the S3 is within 15 minutes.

[0011] Optionally, in the S5, the water quality parameters monitored by the online monitoring device include pH, total dissolved solids, turbidity and silicon content; a response curve of the addition amount and the silicon content of the effluent is established by a programmable logic controller according to the monitored silicon content data, the addition amount of the desilication agent is dynamically adjusted, and the silicon content of the effluent is controlled to be below 50 mg / L.

[0012] Optionally, in the S4, the precipitated sludge is transported to a sludge thickening tank of a high-salinity wastewater treatment system through a single-screw pump, the sludge concentration is controlled to be about 2%, the flow rate of the sludge transportation pipeline is greater than or equal to 1 m / s, and the pipeline backwashing is performed once every 8 hours.

[0013] Optionally, in the S1, the silicon removal agent is added by an electromagnetic diaphragm metering pump, the flow range of the metering pump is 20-110 L / h, the addition accuracy is ±2%, and the control mode is receiving a 4-20 mA analog signal and being linked with a programmable logic controller; the metering pump automatically executes a backwashing program once every 8 hours of operation, and the backwashing duration is 5 minutes, so as to prevent the crystallization of the medicament from blocking.

[0014] Optionally, in the S4, a DN100 specification UPVC or fluorine-lining carbon steel pipe material is used for the conveying pipeline of the sediment sludge, and the curvature radius of the pipeline elbow is greater than or equal to 1.5 times the pipeline diameter; an online turbidity instrument and a pH probe are arranged on the conveying pipeline, so as to monitor the sludge conveying state in real time and upload the data to the central control system.

[0015] Optionally, the total silicon concentration of the slag slurry cracking wastewater is less than or equal to 100 ppm, in which the dissolved silicon accounts for 45% and the colloidal silicon accounts for 55%; and the hydraulic retention time of the sedimentation zone of the high-density sedimentation tank is greater than or equal to 15 minutes, so as to ensure that the silicon removal reaction product is fully settled.

[0016] The silicon removal method for slag slurry cracking wastewater treatment provided in the application comprises the following steps: S1, mixing slag slurry cracking wastewater and a silicon removal agent through a static mixer, so that the silicon removal agent reacts with silicon in the wastewater; S2, sequentially adding a coagulant and a flocculant to the wastewater treated in the S1, and simultaneously returning the sediment sludge to the reaction zone through a sludge circulating pump; S3, mechanically stirring the wastewater in the S2, so that the sediment generated by the silicon removal reaction fully contacts with the returned sludge, the coagulant and the flocculant to form a floc; S4, sending the wastewater treated in the S3 into a high-density sedimentation tank for solid-liquid separation, and sending the supernatant into a subsequent membrane treatment system, and discharging the sediment sludge from the bottom; and S5, detecting the water quality parameters of the wastewater after the S1 and the S4 through an online monitoring device, and adjusting the addition amount of the silicon removal agent in the S1 according to the monitoring data.

[0017] The method has the following beneficial effects: The rapid and uniform mixing of the desilication agent and wastewater is realized by a static mixer, so that the silicon starts to form nano-sized precipitated particles in the pipeline, avoiding the problems of local high concentration or uneven mixing existing in the traditional stirring mixing mode. Through the sludge circulation reflux technology, the precipitated sludge at the bottom of the high-density sedimentation tank is introduced into the reaction zone as a crystal nucleus, promoting the rapid aggregation and growth of the small precipitates generated by the desilication reaction, significantly shortening the reaction time and improving the precipitation efficiency. The mechanical stirring strengthens the flocculation process, so that the desilication precipitates fully contact with the coagulant and flocculant to form dense large particle flocs, improving the subsequent sedimentation separation effect. Through the online monitoring device, the water quality parameters are detected in real time, and a dynamic response mechanism is established combined with the programmable logic controller, so that the desilication agent dosage is automatically adjusted according to the actual water quality fluctuation, realizing precise dosing and automatic control, avoiding the problems of reagent waste or substandard treatment caused by the traditional manual or timed control mode. The entire process can efficiently remove silicon under the pH condition of raw water, without the need for additional pH adjustment, simplifying the operation process, reducing acid and alkali consumption, reducing the operation cost, while ensuring the stability of the effluent water quality, prolonging the service life of the subsequent membrane system. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and those skilled in the art can obtain other drawings according to the provided drawings without creative labor.

[0019] Figure 1 A flow chart of a desilication method for slag slurry cracking wastewater treatment provided by the embodiments of the present application. DETAILED DESCRIPTION

[0020] The purpose of the present application is to provide a desilication method for slag slurry cracking wastewater treatment, so as to realize efficient removal of high-silicon wastewater without adjusting pH, simultaneously reduce pollutants such as hardness and alkalinity, reduce the risk of fouling of the subsequent membrane system, improve the wastewater reuse rate, and reduce the overall operation cost.

[0021] In order to make the purpose, technical solutions and advantages of the present application more clear, the following will further describe the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application. In addition, the technical features involved in each embodiment of the present application described below can be combined with each other as long as they do not conflict with each other.

[0022] The following describes a desilication method for slag slurry cracking wastewater treatment provided by the present application through an embodiment.

[0023] Reference is made to Figure 1 , Figure 1 A flow chart of a method for removing silicon from slag slurry cracking wastewater treatment provided by the embodiments of the present application.

[0024] The embodiments provide a method for removing silicon from slag slurry cracking wastewater treatment, which is applied to a slag slurry cracking wastewater treatment system generated in a polysilicon production process. The system includes a static mixer, a reaction zone, a stirring device, a high-density sedimentation tank, an online monitoring device, and a programmable logic controller, and the like.

[0025] In the embodiments, the method can include: S1, mixing slag slurry cracking wastewater and a silicon removal agent through a static mixer to make the silicon removal agent react with silicon in the wastewater; The raw water is 807 slag slurry cracking wastewater, and the water quality parameters are: total silicon concentration of 100 ppm (dissolved silicon of 45 ppm and colloidal silicon of 55 ppm), pH of 8.5, temperature of 18℃, hardness of 50 mg / L, and alkalinity of 150 mg / L.

[0026] Eugene KH-828 type composite silicon removal agent is used, and is added by a SEKO AKS803 type electromagnetic diaphragm metering pump. The flow range of the metering pump is 20-110 L / h, the addition accuracy is ±2%, and the control mode is receiving a 4-20 mA analog signal and PLC system linkage. The silicon removal agent addition amount is set to 0.5 mL / L (mass concentration of about 0.725 g / L).

[0027] The silicon removal agent is stored in a 500L PE vertical storage tank, the storage tank is equipped with a nitrogen sealing system to prevent the agent from being oxidized, and a liquid suction filter with an accuracy of 50μm is installed at the front end of the agent outlet pipeline. A 100L 316L stainless steel buffer tank is arranged in front of the metering pump to stabilize the agent supply pressure.

[0028] Before the wastewater enters the reaction and precipitation system, the Kenics KM type static mixer is used to mix the wastewater with the silicon removal agent. The static mixer is made of UPVC material, the length is 6m, the number of blades is 6, and is installed in the water inlet pipeline (pipe diameter φ200mm). Under the condition of flow rate 0.28m / s, the mixing time is about 21 seconds. After the silicon removal agent is mixed with the wastewater, the reaction continues in the pipeline, and the reaction time is 8 minutes. In this process, silicon begins to form nanoscale silicate particles, and there is no need to adjust the pH.

[0029] S2, sequentially adding a coagulant and a flocculant to the wastewater treated in S1, and simultaneously returning the sludge sediment to the reaction zone by a sludge circulating pump; The wastewater treated by step S1 enters the flocculation section of the high-density sedimentation tank, and the coagulant polyaluminum chloride PAC and the flocculant polyacrylamide PAM are added in sequence. The PAC dosage is 100 mg / L, and the PAM dosage is 2 mg / L.

[0030] At the same time, the settled sludge at the bottom of the high-density sedimentation tank is backflowed to the reaction zone by a Xinquan G50-2 single-screw sludge circulating pump. The sludge circulating pump flow rate is 0.4 m 3 / h, and the sludge circulation ratio is 0.04, i.e. the sludge circulation amount is 4% of the total treated water amount. The backflowed sludge acts as a crystal nucleus, promoting the aggregation of the small precipitates generated by the desilication reaction.

[0031] S3, the wastewater in S2 is subjected to mechanical stirring to make the precipitates generated by the desilication reaction fully contact with the backflowed sludge, coagulant and flocculant to form flocs; In the stirring zone of the high-density sedimentation tank, a mechanical stirring device with an impeller diameter of φ1400 mm is used for stirring. The impeller linear speed is controlled at 1.5 m / s, and the water body circulation amount in the stirring zone reaches 10.8 times (about 1.51 m 3 / s) of the design water treatment amount. Under the action of mechanical stirring, the precipitates generated by the desilication reaction fully contact with the backflowed sludge, PAC and PAM to form dense large particle flocs.

[0032] From step S1 to the end of step S3, the total reaction time is controlled within 13 minutes.

[0033] S4, the wastewater treated by S3 is sent to the high-density sedimentation tank for solid-liquid separation, the supernatant enters the subsequent membrane treatment system, and the settled sludge is discharged from the bottom; The wastewater treated by step S3 enters the sedimentation zone of the high-density sedimentation tank for solid-liquid separation. The sedimentation zone hydraulic retention time is 15 minutes, and the flocs settle under the action of gravity. The supernatant overflows from the top of the sedimentation tank and enters the subsequent multi-media filter, ultrafiltration and reverse osmosis membrane treatment system in sequence.

[0034] The settled sludge is discharged from the bottom of the high-density sedimentation tank, and the sludge concentration is about 2%. The sludge is transported by a Xinquan G50-2 single-screw pump to the sludge concentration tank of the high-salinity wastewater treatment system. The sludge conveying pipeline uses DN100 UPVC pipe material, the pipeline flow rate is 1.2 m / s, and the elbow curvature radius R is 150 mm. An online turbidity meter and a pH probe are arranged on the conveying pipeline to monitor the sludge conveying state in real time, and the data is uploaded to the central control system. The sludge conveying system performs pipeline backwashing every 8 hours, and the backwashing duration is 10 minutes to prevent pipeline blockage.

[0035] S5, the water quality parameters of the wastewater after S1 and the effluent of S4 are detected by an online monitoring device, and the dosage of the desilication agent in S1 is adjusted according to the monitoring data.

[0036] On-line monitoring devices were installed on the pipeline after step S1 and at the outlet of the high-density sedimentation tank. The monitoring parameters included pH, total dissolved solids (TDS), turbidity, and silicon content.

[0037] The PLC control system collected the monitoring data in real time, and established a response curve of "silicon removal agent dosage-outlet silicon content" according to the outlet silicon content. When the outlet silicon content deviated from the set value (the target value was 50 mg / L or less), the PLC system automatically adjusted the stroke frequency of the metering pump to dynamically adjust the silicon removal agent dosage. For example, when the outlet silicon content rose to 55 mg / L, the system automatically increased the silicon removal agent dosage from 0.5 mL / L to 0.6 mL / L; when the outlet silicon content decreased to 40 mg / L or less, the dosage was reduced to 0.4 mL / L, achieving precise control.

[0038] In addition, the metering pump automatically performed a backwashing program every 8 hours of operation, and the backwashing lasted for 5 minutes. The backwashing pipeline was connected to a clean water source to prevent the silicon removal agent crystals from blocking the pump head and the pipeline.

[0039] After the treatment by the present embodiment, the outlet water quality of the high-density sedimentation tank was as follows: the total silicon concentration was 48 mg / L (dissolved silicon 18 mg / L, colloidal silicon 30 mg / L), the silicon removal rate was 52% (dissolved silicon removal rate 60%, colloidal silicon removal rate 45%), the hardness decreased to 14 mg / L, the removal rate was 72%, the alkalinity decreased to 55 mg / L, the removal rate was 63%, the COD removal rate was 42%, and the suspended solids removal rate was 82%. The outlet silicon content met the water inlet requirement (≤50 mg / L) of the subsequent reverse osmosis membrane system, effectively reducing the risk of membrane fouling.

[0040] In terms of operating cost, the cost of the silicon removal agent was about 1.0 yuan / m 3 of water, the sludge treatment cost was about 0.38 yuan / m 3 of water, and the total treatment cost was about 1.38 yuan / m 3 of water.

[0041] In summary, the embodiment realizes rapid and uniform mixing of the desilication agent and wastewater through a static mixer, so that silicon starts to form nano-sized precipitated particles in the pipeline, avoiding the problems of local over-concentration or uneven mixing existing in the traditional stirring and mixing method. Through the sludge circulation reflux technology, the precipitated sludge at the bottom of the high-density sedimentation tank is introduced into the reaction zone as a crystal nucleus to promote the rapid aggregation and growth of the small precipitates generated by the desilication reaction, significantly shortening the reaction time and improving the precipitation efficiency. The mechanical stirring strengthens the flocculation process, so that the desilication precipitates fully contact with the coagulant and flocculant to form dense large particle flocs, improving the subsequent sedimentation separation effect. Through the online monitoring device, the water quality parameters are detected in real time, and a dynamic response mechanism is established combined with the programmable logic controller, so that the desilication agent dosage is automatically adjusted according to the actual water quality fluctuations, realizing precise dosing and automatic control, avoiding the problems of reagent waste or substandard treatment caused by the traditional manual or timed control method. The entire process can efficiently remove silicon under the pH condition of raw water, without the need for additional pH adjustment, simplifying the operation process, reducing acid and alkali consumption, reducing operating costs, while ensuring stable effluent water quality, prolonging the service life of the subsequent membrane system.

[0042] The embodiment further illustrates the optimized operation strategy and equipment maintenance measures of the system on the basis of the previous embodiment.

[0043] The optimization of the desilication agent dosing system can include: The embodiment adopts a desilication agent dosing system with two pumps in parallel, and the flow range of the two electromagnetic diaphragm metering pumps is 20-110 L / h. During normal operation, one pump works and the other pump is in hot standby state. When the working pump fails or enters the backwashing program, the standby pump automatically starts to ensure the continuity of the desilication agent dosing.

[0044] In addition to receiving a 4-20 mA analog signal, the control mode of the metering pump is also configured with a manual adjustment function. During system maintenance or special working conditions, the operator can switch to the manual mode to directly set the dosing flow through the human-machine interface, ensuring the flexibility of system operation.

[0045] The flow state optimization of the static mixer can include: The embodiment adopts a static mixer with a length of 7 meters and 7 blades, and the mixing time is about 24 seconds. The blades of the static mixer are arranged in an alternating left and right rotation manner. After passing through each blade, the fluid is divided into two streams and rotates. The reverse rotation of adjacent blades causes the fluid to produce stronger turbulent effect, and the mixing uniformity is better than that of the single-direction rotation blade structure.

[0046] A pressure monitoring point is arranged at the outlet of the static mixer to monitor the pressure loss of the mixer in real time. When the pressure loss exceeds the design value, the system automatically alarms to indicate that there may be blade fouling or partial blockage of the pipeline, which needs to be cleaned and maintained.

[0047] The hierarchical control of the reaction zone can include: The reaction zone is subdivided into a rapid mixing zone and a slow flocculation zone. The rapid mixing zone is located at the front section of the reaction zone, with a high stirring intensity to ensure rapid mixing of coagulants, flocculants, and return sludge. The slow flocculation zone is located at the rear section of the reaction zone, with a reduced stirring intensity to provide suitable hydraulic conditions for the growth and compaction of flocs, avoiding the destruction of formed flocs by intense stirring.

[0048] The linear velocity of the stirring impeller in the rapid mixing zone is 2.0 m / s, and the residence time is 3 minutes. The linear velocity of the stirring impeller in the slow flocculation zone is reduced to 1.2 m / s, and the residence time is 5 minutes. Through hierarchical control, the floc formation effect is significantly improved, and the settling performance is significantly improved.

[0049] The sludge layer control of the high-density sedimentation tank can include: The high-density sedimentation tank is equipped with a sludge layer level meter to monitor the sludge layer height in real time. The sludge layer height is controlled within the range of 30%-40% of the effective water depth of the sedimentation tank. When the sludge layer height exceeds 40%, the system automatically increases the sludge discharge amount; when the sludge layer height is less than 30%, the system reduces the sludge discharge amount.

[0050] By precisely controlling the sludge layer height, a stable sludge suspension layer is formed inside the sedimentation tank, which has a filtering and retaining effect on fine flocs in the upward flow, further improving the effluent water quality.

[0051] The data management of the online monitoring system can include: The online monitoring device of this embodiment collects data every 5 seconds, and the data is uploaded to the central control system through industrial Ethernet. The control system is configured with a data storage server, and all monitoring data is automatically stored and retained for one year.

[0052] The control system has data analysis functions, which can generate historical curves, statistical reports, and trend prediction graphs of various water quality parameters. The operating personnel can identify the system operation rules through historical data analysis and optimize the operation parameters. When an abnormal fluctuation occurs in a certain water quality parameter, the system automatically triggers an alarm and pushes information to the mobile terminal of the operating personnel.

[0053] The equipment maintenance strategy can include: In addition to regular backwashing of the metering pump and sludge conveying pipeline, this embodiment also establishes a complete preventive maintenance plan for the equipment. The static mixer is chemically cleaned every three months using a dilute acid solution to remove silicate scale on the blade surface. The bearings and seals of the mechanical stirrer are inspected and lubricated every six months. The online monitoring probe is calibrated every month to ensure the accuracy of the monitoring data.

[0054] Through the optimization operation and fine management of the embodiment, the system operation stability is further improved, the silicon removal effect is continuously stable, and the silicon content in the effluent is long-term stable control below 40 mg / L, which provides a reliable guarantee for the safe operation of the subsequent membrane treatment system.

[0055] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0056] The skilled person can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware, computer software or a combination of both. In order to clearly show the interchangeability of hardware and software, the composition and steps of each example have been described in the above description. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0057] The steps of the method or algorithm described in combination with the embodiments disclosed herein can be directly implemented by hardware, software modules executed by a processor, or a combination of both. The software modules can be placed in random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0058] The above provides a detailed introduction to the silicon removal method for slag slurry cracking wastewater treatment. The principles and implementation methods of the present application are described in this paper. The above embodiment is only used to help understand the method and its core idea. It should be pointed out that for ordinary skilled person in the art, without departing from the principles of the present application, some improvements and modifications can be made to the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A method for desilication for slurry cracking wastewater treatment, characterized by, The method comprises the following steps: S1, mixing the slag slurry cracking wastewater and the desilication agent through a static mixer to make the desilication agent react with the silicon in the wastewater; S2, sequentially adding a coagulant and a flocculant to the wastewater treated in the step S1, and returning the precipitated sludge to the reaction zone through a sludge circulating pump; S3, mechanically stirring the wastewater in the step S2 to make the precipitate generated in the desilication reaction fully contact with the returned sludge, the coagulant and the flocculant to form flocs; S4, sending the wastewater treated in the step S3 to a high-density sedimentation tank for solid-liquid separation, sending the supernatant to a subsequent membrane treatment system, and discharging the precipitated sludge from the bottom; S5, detecting the water quality parameters of the wastewater after the step S1 and the step S4 through an online monitoring device, and adjusting the dosage of the desilication agent in the step S1 according to the monitoring data.

2. The method of claim 1, wherein, In the step S1, the desilication agent is a composite desilication agent, the dosage is 0.1-1 mL / L, and the mass concentration is 0.145-1.45 g / L; the pH of the slag slurry cracking wastewater is 8-10, and the temperature is 15-20℃, without pH adjustment.

3. The method of claim 2, wherein the silicon is removed by a method selected from the group consisting of: In the step S1, the length of the static mixer is 5-8 m, the number of blades is 5-8, and the mixing time is 17-28 seconds; the reaction time of the desilication agent mixed with the wastewater is 5-10 minutes. ​ 4. The method of claim 3, wherein the silicon is removed by a method selected from the group consisting of: In the step S2, the coagulant is polyaluminum chloride, the dosage is 50-150 mg / L; the flocculant is polyacrylamide, the dosage is 1-3 mg / L; and the sludge circulation ratio is 0.03-0.05, i.e. the sludge circulation amount is 3%-5% of the total treated water amount. ​ 5. The method of claim 4, wherein the silicon is removed by a method selected from the group consisting of: In the step S3, the linear velocity of the impeller of the mechanical stirring is 1.5 m / s, and the water circulation amount in the stirring zone is 10.8 times of the designed treated water amount; and the total reaction time of the steps S1 to S3 is within 15 minutes. ​ 6. The method of claim 5, wherein the silicon is removed by a method selected from the group consisting of: In the step S5, the water quality parameters monitored by the online monitoring device include pH, total dissolved solids, turbidity and silicon content; a response curve of the dosage and the silicon content of the effluent is established according to the monitored silicon content data through a programmable logic controller, the dosage of the desilication agent is dynamically adjusted, and the silicon content of the effluent is controlled to be below 50 mg / L. ​ 7. The method of claim 6, wherein the silicon is removed by, In the step S4, the precipitated sludge is transported to a sludge thickening tank of a high-salinity wastewater treatment system through a single-screw pump, the sludge concentration is controlled to be about 2%, the flow velocity of the sludge transportation pipeline is greater than or equal to 1 m / s, and the pipeline backwashing is performed once every 8 hours.

8. The method of claim 7, wherein the silicon is removed by, In the step S1, the desilication agent is added through an electromagnetic diaphragm metering pump, the flow range of the metering pump is 20-110 L / h, the addition accuracy is ±2%, the control mode is receiving a 4-20 mA analog signal and being linked with a programmable logic controller; the metering pump automatically performs a backwashing program once every 8 hours of operation, and the backwashing duration is 5 minutes to prevent the crystallization blockage of the medicament.

9. The method of claim 8, wherein the silicon is removed by, In the step S4, the transportation pipeline of the precipitated sludge adopts a DN100 specification UPVC or lined fluorocarbon steel pipe material, the curvature radius of the pipeline elbow is greater than or equal to 1.5 times of the pipeline diameter; an online turbidity meter and a pH probe are arranged on the transportation pipeline to monitor the sludge transportation state in real time and upload the data to a central control system.

10. The method of claim 9, wherein the silicon is removed by a method selected from the group consisting of: The total silicon concentration of the slag slurry cracking wastewater is less than or equal to 100 ppm, wherein the dissolved silicon accounts for 45% and the colloidal silicon accounts for 55%; the hydraulic retention time of the sedimentation zone of the high-density sedimentation tank is greater than or equal to 15 minutes, so as to ensure that the silicon removal reaction products are fully settled. ​

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