Salt lake old brine raw water filtering system and process

Abstract

The invention discloses a salt lake old brine raw water filtering system and process, and the salt lake old brine raw water filtering process comprises the following steps: S1, filtering: pumping salt lake old brine raw water into a membrane pool of the filtering system through a raw water pump, submerging a membrane group in the membrane pool, and pumping produced water through negative pressure of a produced water pump; s2, backwashing: backwashing the membrane group in the membrane pool to recover the water production flux of the membrane; and S3, clean water flushing and chemical cleaning are conducted regularly, and long-term temperature operation of the system is guaranteed. In the filtering process of the salt lake old brine, suspended matters and the like in the salt lake old brine raw water are removed, so that a subsequent lithium extraction process is facilitated, and the utilization rate of resources is increased.

Description

Technical Field

[0001] The present application relates to the field of environmental protection technology, and in particular to a filtering system and process for raw brine from salt lakes. Background Art

[0002] The tail liquid of potassium extraction from salt lake brine (hereinafter referred to as old brine) contains a small amount of lithium ions (about 300PPM). As a carrier of lithium resources, old brine is an important resource for lithium extraction from salt lakes in my country. However, as the residual liquid precipitated after potassium extraction from salt lake brine, old brine contains residual flotation agents, chloride ions, etc., with high mineralization, weak acidity, high specific gravity, natural organic matter, etc. The region where the salt lake is located has a continental climate, drought, little rain, high altitude, large temperature difference and wind and sand, so the old brine SS (Suspended Solids, the content of suspended solids in the liquid) content is high and volatile, high viscosity, and easy to crystallize. In order to ensure the long-term stable operation of the lithium extraction process, slow down the fouling of the adsorption tower, and reduce the backwash regeneration cycle, the old brine needs to be pretreated. Summary of the invention

[0003] The purpose of the present invention is to provide a filtering process for salt lake old brine to solve the above technical problems.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] The present application embodiment discloses a filtering process for salt lake brine, which is characterized by the following specific steps:

[0006] S1, Filtration: Pump the salt lake brine into the membrane pool of the filtration system through the raw water pump, immerse the membrane group in the membrane pool, and use the negative pressure of the water production pump to suck the brine;

[0007] S2, backwash: The membrane pool stops producing water and reversely flushes the membrane group in the membrane pool.

[0008] Furthermore, in the above-mentioned filtration process of salt lake brine, during the negative pressure suction process of the water production pump, the water level of the salt lake brine in the membrane pool is maintained to immerse the membrane group.

[0009] Furthermore, in the above-mentioned filtering process of salt lake old brine, the backwashing comprises the following steps:

[0010] S31, brine backwashing: after a single water production cycle, the membrane group is backwashed with filtered brine;

[0011] S32, CEB cleaning: After multiple water production cycles, use clean water or hydrochloric acid or oxidant to clean the membrane group;

[0012] S33, CIP chemical cleaning: After brine backwashing and CEB cleaning, when the water production drops more than the set value or the transmembrane pressure difference is higher than the set value, the membrane group is soaked and cleaned by CIP chemical.

[0013] Furthermore, in the above-mentioned filtration process of salt lake old brine, the brine is aerated before backwashing and the aeration continues until the backwashing of the brine is completed.

[0014] Furthermore, in the above-mentioned filtering process of salt lake old brine, the CEB cleaning comprises the following steps:

[0015] S321: CEB clean water cleaning: use clean water to backwash the membrane group;

[0016] S322: CEB acid cleaning: After a certain period of CEB water cleaning, the membrane group is backwashed with acid cleaning solution;

[0017] S323: CEB oxidant cleaning: After a certain period of CEB acid cleaning, the membrane group is backwashed with an oxidant cleaning solution.

[0018] Furthermore, in the above-mentioned filtration process of salt lake brine, the CIP chemical immersion time of the membrane group is greater than 30 minutes.

[0019] Furthermore, in the above-mentioned filtration process of salt lake brine, before the CEB cleaning and CIP chemical cleaning, the membrane pool needs to be aerated and emptied, and the aeration continues until the emptying is completed, and it is emptied again after backwashing and spraying with clean water.

[0020] Furthermore, in the above-mentioned filtration process of salt lake brine, after the CEB cleaning and CIP chemical cleaning, clean water backwashing and spray rinsing are required.

[0021] An embodiment of the present application also discloses a filtration system for salt lake brine, comprising a plurality of membrane pools and a raw water pump, a produced water pump, an aeration fan, a clean water backwash pump, a clean water spray pump and a produced water backwash pump connected to the membrane pools, wherein a plurality of membrane groups are arranged in the membrane pools, and the membrane groups include a plurality of silicon carbide flat membranes.

[0022] Compared with the prior art, the advantages of the present invention are: the filtering process of the salt lake old brine adopts negative pressure immersion suction and overall low-pressure operation to reduce energy consumption; the membrane group adopts modular design to reduce the footprint; and the silicon carbide diaphragm can withstand strong acids, strong alkalis and strong oxidants; through CEB cleaning and CIP chemical cleaning, its large flux can be quickly restored to improve the filtration efficiency; at the same time, the inorganic silicon carbide diaphragm is less affected by temperature and is suitable for environments with large temperature differences; before and after CEB cleaning and CIP chemical cleaning, clean water backwashing and clean water spraying are performed to ensure that there is no agent residue during the agent cleaning process, and the old brine and the produced brine will not be polluted; in addition, the agent does not react with the old brine and the produced brine during the agent cleaning process, and the cleaned agent can be recovered and recycled to reduce the amount of agent used and secondary pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 Shown is a schematic structural diagram of a filtering system for salt lake brine in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described by the following examples: The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0026] Combination Figure 1 As shown, a system for old brine from a salt lake includes several membrane pools and a raw water pump, a produced water pump, an aeration fan, a clean water backwash pump, a clean water spray pump and a produced water backwash pump connected to the membrane pools. Several membrane groups are arranged in the membrane pools, and the membrane groups include several silicon carbide diaphragms.

[0027] In this technical solution, the clean water can be conventional tap water, etc., and the silicon carbide diaphragm and membrane group can utilize the existing structure. A plurality of membrane groups 1 form a membrane tower structure and are placed in a membrane pool 2. The bottom of the membrane pool 2 adopts a conventional cone bottom structure to improve the pollution holding capacity of the membrane pool and reduce the concentrated water discharge, thereby improving the water production efficiency. A plurality of aeration heads 5 connected to the aeration fan 4 through an aeration pipeline 3 (arrows indicate the flow direction of the medium, the same below) are arranged at the bottom of the membrane pool, and a plurality of spray heads 8 connected to the clean water spray pump 7 through a spray pipeline connection 6 are arranged at the top of the membrane pool. The raw water pump 9 is connected to the membrane pool through the raw water pipeline 10 to pump the salt lake brine to the membrane pool. The water production pump 11 pumps the brine to the water production tank 13 through the water production pipeline 12. The water production tank 13 is also connected to the membrane group 1 through the water production backwash pump 14 and the water production backwash pipeline 15 to realize the backwashing of the brine. , the clean water backwash pump 16 is connected to the membrane group through the clean water backwash pipeline 17, wherein the production water pipeline 12, the production water backwash pipeline 15 and the clean water backwash pipeline 17 share part of the pipeline connected to the membrane group (the part indicated by the double-headed arrow), and the flow direction is controlled by conventional valves, etc., the clean water backwash pipeline 17 is provided with a conventional pipeline mixer 18, and the metering pumps 19 of the reagents are respectively connected to the pipeline mixer 18, and the clean water backwash pipeline is used to realize CEB acid backwashing, the membrane pool and the clean water tank are also connected to the clean water replenishment pipeline 20 to ensure that the membrane group is always in an immersed state during operation and to replenish clean water in time, and backwashing, spraying and membrane pool emptying are through a separate discharge pipeline 21; each pipeline is also provided with conventional valves, pressure sensors, temperature sensors, etc. (not shown) for controlling the flow direction of the liquid in the pipeline and real-time monitoring of the operation status, etc.

[0028] The above-mentioned salt lake brine system is used for filtration, and the specific steps are as follows:

[0029] S1. Test run: Use clean water to test run the filtration system, so that the experimental operators can be familiar with the equipment, check the operation of the equipment after power on and water supply, ensure the normal operation of the system and the operability of subsequent experiments; test the air tightness of the system to ensure the water quality of subsequent experimental water;

[0030] S2, Filtration: Pump the salt lake brine into the membrane pool of the filtration system through the raw water pump, immerse the membrane group in the membrane pool, and use the negative pressure of the water production pump to suck the brine;

[0031] S31, brine backwash: The membrane pool is backwashed every 10 to 20 minutes of water production. After the membrane pool stops producing water, aeration is turned on and continued until the backwash is completed. The brine is backwashed for 30 to 60 seconds through the water backwash pump, and the membrane pool resumes water production and circulates;

[0032] S321: CEB cleaning: The system backwashes the membrane group once every 18 to 180 water production cycles using clean water or 2000ppm hydrochloric acid (the composition and concentration of the acid cleaning solution can be determined according to the actual composition of the old brine, which is convenient for the subsequent recovery and reuse of the reagents, etc.); first, the water production pump stops running, the membrane pool stops producing water, the aeration fan is turned on for aeration and the membrane pool is emptied, and then, the clean water in the clean water tank is used for backwashing for 30 to 300 seconds through the clean water backwash pump, and then, the clean water in the clean water tank is used for spraying for 20 to 200 seconds through the spray pump to complete the cleaning of the filter cake layer on the surface of the silicon carbide flat membrane, and then the membrane pool is emptied again, and the acid metering pump is used to The membrane group is backwashed with 2000ppm hydrochloric acid in the acid metering tank for 30 to 300 seconds, and then the clean water in the clean water tank is backwashed for 30 to 300 seconds by the clean water backwash pump, followed by the clean water in the clean water tank being sprayed and rinsed for 20 to 200 seconds by the spray pump, and then the water is replenished after being emptied. In the dosing process, the acid metering pump and the backwashing pump are started to transport the mixed reagents to the membrane group through the production water pipeline to restore the flux of the membrane. The acid metering pump stops running, and the clean water backwashing pump is continuously turned on to replace the residual reagents in the production water pipeline. At the same time, the reagents remaining in the pores of the membrane are rinsed with clean water, and the spray pump is started with a delay to rinse the residual reagents on the membrane surface;

[0033] S322: CEB oxidant cleaning: After a certain period of CEB hydrochloric acid backwashing, use an oxidant (hydrogen peroxide or sodium hypochlorite) with a concentration of 1000ppm (the composition and concentration of the alkaline cleaning solution can be determined according to the actual composition of the old brine, which is convenient for the subsequent recovery and reuse of the reagents, etc.) to backwash the membrane group. The CEB oxidant cleaning process is the same as the CEB hydrochloric acid cleaning process, and the hyposodium solution in the hyposodium metering tank is pumped by the hyposodium metering pump;

[0034] S33, CIP chemical cleaning: After brine backwashing and CEB acid backwashing, when the water output drops by 20% or the transmembrane pressure difference is higher than the set value, the membrane group is cleaned by CIP chemical soaking (sodium hydroxide plus sodium hypochlorite alkaline washing or hydrochloric acid acid washing or alkaline washing first and then acid washing, etc.); first, the water production pump stops running, the membrane pool stops producing water, the aeration fan is turned on for aeration and the membrane pool is emptied, and then, the clean water in the clean water tank is used for backwashing for 30 to 300 seconds through the clean water backwash pump, and then, the clean water in the clean water tank is used for spraying for 20 to 200 seconds through the spray pump to complete the cleaning of the filter cake layer on the surface of the silicon carbide diaphragm, and the brine remaining in the water production pipeline and membrane elements is replaced to avoid magnesium hydroxide contamination during the alkaline washing process, and the membrane pool is emptied again, and the clean water in the clean water tank is used for spraying by the spray pump Replenish water to the membrane pool and add conventional alkaline agents, and let it react for 30 to 60 minutes. After the reaction is completed, use the water production pump to circulate the agent for cleaning. The water production pipeline is equipped with ORP, PH, and flow online monitoring instruments. The pressure transmitter and flow transmitter on the water production pipeline are used to automatically judge the CIP cleaning effect. When the ORP and PH values ​​change significantly, but the transmembrane pressure difference and water production flow rate have not yet recovered ideally, the agent is replenished again and the cleaning concentration of the agent is increased. When the transmembrane pressure difference or water production flow rate is restored, it means that the cleaning is restored. Then the clean water backwash pump and the spray pump are started at the same time to perform clean water backwashing and spray rinsing to rinse the residual agent on the membrane surface. After the flushing and replacement are thorough, water replenishment operation is carried out.

[0035] At the same time, samples of old brine and produced brine were taken from the water inlet and water outlet of the membrane pool, and four groups were taken at random time intervals. The corresponding SS values ​​were tested by gravimetric method using G4 sand core crucible (4-7μm). The results are shown in Table 1:

[0036] Table 1 Comparison of SS values ​​before and after filtration

[0037]

[0038] From the data in Table 1, we can see that

[0039] In summary, the filtration process of the old brine of the salt lake uses negative pressure immersion suction and overall low-pressure operation to reduce energy consumption. The membrane group adopts a modular design to reduce the footprint, and the silicon carbide diaphragm can withstand strong acids, strong alkalis and strong oxidants. Through CEB cleaning and CIP chemical cleaning, its large flux can be quickly restored to improve the filtration efficiency. At the same time, the inorganic silicon carbide flat diaphragm is less affected by temperature and is suitable for environments with large temperature differences. Before and after CEB cleaning and CIP chemical cleaning, clean water backwashing and clean water spraying are used to ensure that there is no agent residue during the agent cleaning process, and the old brine and the produced brine will not be contaminated. In addition, the agent does not react with the old brine and the produced brine during the agent cleaning process. The cleaned agent can be recovered and recycled to reduce the amount of agent used and secondary pollution.

[0040] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions according to the present invention are shown in the accompanying drawings, while other details that are not closely related to the present invention are omitted.

[0041] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements that are inherent to such process, method, article, or apparatus.

Claims

1. A filtration process for salt lake brine, characterized in that: The specific steps are as follows: S1, Filtration: The raw water from the salt lake is pumped into the membrane pool of the filtration system through the raw water pump, and the membrane group in the membrane pool is not submerged, and the produced water is sucked out by the negative pressure of the produced water pump; S2, backwash: reverse flushing the membrane group in the membrane pool to restore the membrane water flux; S3. Regularly perform water flushing and chemical cleaning to ensure long-term temperature operation of the system.

2. The filtration process of salt lake old brine according to claim 1, characterized in that: During the negative pressure suction process of the water production pump, the water level of the salt lake brine in the membrane pool is kept to immerse the membrane group.

3. The filtering process of salt lake old brine according to claim 1, characterized in that: The backwashing comprises the following steps: S31, brine backwashing: after a single water production cycle, the membrane group is backwashed with filtered brine; S32, CEB cleaning: After multiple water production cycles, use clean water or hydrochloric acid or oxidant to backwash the membrane group; S33, CIP chemical cleaning: After brine backwashing and CEB cleaning, when the water production drops more than the set value or the transmembrane pressure difference is higher than the set value, the membrane group is soaked and cleaned by CIP chemical.

4. The filtering process of salt lake old brine according to claim 3 is characterized in that: Aeration is performed during the brine production and backwashing process and continues until the brine backwashing is completed.

5. The filtering process of salt lake old brine according to claim 3 is characterized in that: The CEB cleaning comprises the following steps: S321: CEB clean water cleaning: use clean water to backwash the membrane group; S322: CEB acid cleaning: After a certain period of CEB water cleaning, the membrane group is backwashed with acid cleaning solution; S323: CEB oxidant cleaning: After a certain period of CEB acid cleaning, the membrane group is backwashed with an oxidant cleaning solution.

6. The filtering process of salt lake old brine according to claim 3 is characterized in that: The CIP chemical soaking time of the membrane group is greater than 30 minutes.

7. The filtering process of salt lake old brine according to claim 3 is characterized in that: Before the CEB cleaning and CIP chemical cleaning, the membrane tank needs to be aerated and drained. The aeration continues until the draining is completed, and the tank is drained again after backwashing and spraying with clean water.

8. The filtering process of salt lake old brine according to claim 3 is characterized in that: After the CEB acid backwashing and CIP chemical cleaning, clean water backwashing and spray rinsing are required.

9. A filtering system for salt lake brine, characterized in that: It comprises several membrane pools and raw water pumps, produced water pumps, aeration fans, clean water backwash pumps, clean water spray pumps and produced water backwash pumps connected to the membrane pools. Several membrane groups are arranged in the membrane pools, and the membrane groups include several silicon carbide flat membranes.

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