Summary of Commissioning for Saltwater Production Position

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This post was last edited by sunjl1981 on 2013-1-6 20:46. 1. Overview: Caustic soda is a basic chemical raw material that is widely used in industries such as petroleum, chemical fibers, pharmaceuticals, light industry, papermaking, and non-ferrous metal smelting. It is closely linked to the development of the national economy and plays a significant role in promoting the economic growth of the regions where it is used. The brine processing stage is the first step in caustic soda production, and the quality of this process directly affects the proper functioning of the entire caustic soda production process. In our company’s technical upgrade project for caustic soda, we also carried out technical improvements to the brine production process, ensuring that the output and quality of brine meet the requirements of ion-exchange membrane processes that use less caustic soda. In this caustic soda technical upgrade project, the production process for brine uses a new generation of Gore membrane filters, representing a significant improvement over traditional brine production methods. The brine production unit is responsible for using the fresh brine, recycled water, and other miscellaneous waters from electrolysis and distillation processes to dissolve raw salt. After removing inorganic impurities such as Ca2+, Mg2+, and SO42- as well as mechanical impurities from the crude brine, a concentrated brine that meets the process requirements is obtained, which is then sent to the electrolysis process for use. Preparations for testing: Form a testing team, train the testing staff, develop a testing plan, and approve the testing scheme. 2. Production Process 2.1 Salt Dissolution: Since the saltwater production method used here is the (ZF membrane process) that does not involve sulfate removal, one-quarter of the ion exchange membrane brackish water is exchanged with the brine recovered through diaphragm evaporation, in order to prevent the accumulation of sulfates. Various types of wastewater, such as ion-exchange membrane brackish water, saltwater recovered through diaphragm evaporation, filtrate from plate and frame filter presses, industrial water, and saltwater recovered by regeneration systems, all enter the water distribution tank for distribution. After the water from the various sections mentioned above is mixed in the water distribution tank, it serves as brine and is pumped by the water distribution pump. After heat exchange in the preheater, it is sent to the brine tank at around 60°C; there the water dissolves the raw salt, resulting in saturated crude brine ； The concentration of the brine is then adjusted to between 305 and 310 g/L by adding river water. Before it enters the reaction tank, the refining agents sodium hydroxide and sodium hypochlorite are added in the pre-baffle tank according to the process requirements, in order to adjust the pH value to 10.5–11.5; the excess amount of NaOH is kept at 0.3–0.6 g/L, while the residual amount of NaClO in the brine remains at 4–8 mg/L. Subsequent thorough mixing in the pre-reaction tank enables the magnesium ions present in the brine to react with sodium hydroxide to form magnesium hydroxide, while organic substances such as bacteria, algae, and humic acid are oxidized and broken down into smaller organic molecules by sodium hypochlorite. 2.2 Saltwater purification: The crude saltwater, in which the reaction has been completed, is pumped from the crude saltwater tank to a crude saltwater storage tank. From there, it is pumped under pressure into a gas-water mixer, where it mixes with air before entering a pressurized dissolved air tank. After being depressurized by a pressure valve, the mixture is released into the pretreater, and at the inlet of the pretreater, ferric chloride solution is added via a Venturi mixer. As a flocculant, ferric trichloride is used; when the brine enters the pre-treater, the pressure drops suddenly, causing air in the brine to come out and form numerous tiny bubbles. These bubbles attach to the particles formed by the combination of the flocculant and Mg(OH)2, resulting in the mechanical impurities in the brine having a lower specific gravity than the brine itself and thus floating to the surface of the pre-treater. This sludge is then discharged through the upper sludge outlet. Some of the heavier particles sink to form sediment, which is discharged through the lower sludge outlet, while the clear liquid flows out through the outlet. The brine coming out of the preprocessor still contains a small amount of mechanical impurities as well as trace amounts of magnesium hydroxide and large amounts of calcium ions; in the subsequent reaction tank A, a sodium carbonate solution is added as a refining agent, with an excess amount of sodium carbonate of 0.3–0.6 g/L. The calcium ions in the brine are completely reacted with sodium carbonate in reaction tanks A and B to produce calcium carbonate precipitate. Sodium sulfite solution is added simultaneously to completely remove free chlorine from the brine. The crude brine after full reaction flows into the intermediate tank. To ensure the formation of an excellent filter aid layer on the surface of the filtration membrane, with rigid calcium carbonate as its main component, and to keep the filtration flux, backwashing cycle, and acid washing cycle of the ZF membrane within relatively ideal ranges, it is necessary to maintain a total magnesium content in the brine at the output of the pretreatment stage of ≤5 ppm, and a total calcium content of 150–500 ppm. An online pH detector and a manual saltwater density measurement point are installed on the coarse salt water pipeline at the outlet of the pressure pump. By measuring the pH value and density of the reacted coarse salt water, it is possible to promptly contact the salt production process to adjust the amounts of sodium hydroxide solution and steam condensate added. For the level control of the pressurized dissolved air tank, an automatic control system is used in which the speed of the motor driving the pressure pump is controlled based on the level of the pressurized dissolved air tank, thereby achieving stable level control of the tank. The pressure control of the pressurized dissolved air tank is achieved using a pneumatic component, namely a pressure reducing valve, to regulate the air pressure in the air buffer tank and thus maintain a stable pressure in the dissolved air tank (0.2–0.25 MPa). An electromagnetic flow meter and a pneumatic control valve are used to measure and control the flow rate of brine entering the pretreater. A manual free chlorine detection point is installed at the outlet of the pretreater; by measuring the free chlorine content in the brine at this outlet, the flow rate of the sodium hypochlorite flow meter in the salt treatment process can be adjusted. 2.3 Saltwater filtration: The brine in the intermediate tank is pressurized by a filter feed pump and then sent to the ZF membrane filter. The clear liquid overflows from the upper chamber of the ZF membrane filter. After filtering for a certain period of time, once the filter cake reaches a certain thickness, the system automatically enters reverse flushing mode, causing the filter cake to detach from the membrane and settle at the conical bottom of the filter. The system then returns to filtering mode. When the residue at the bottom reaches a certain thickness, the system automatically opens the residue discharge valve, allowing the residue to be discharged into the sludge tank. The filtered and qualified brine flows by gravity into the brine tank, and is then pumped under pressure by a brine pump to the electrolysis process. A flow meter and a control valve are installed at the inlet of the ZF membrane filter to regulate the flow rate for each filter. A redox potential meter adjusts the flow rate of the sodium sulfite solution by measuring the free chlorine content in the turbid salt water after the reaction. After operating for a certain period of time, in order to maintain high filtration efficiency and low filtration pressure, the filter membranes are regularly cleaned chemically online using 10-15% hydrochloric acid. Conditions for chemical cleaning with hydrochloric acid: operate the filter for 20–30 days, with a filtration pressure difference of ≥0.05 Mpa. Chemical cleaning is required if either of the two conditions is met. 2.4 The sludge discharged from the ZF membrane filter during filtration is sent to the salt-sludge circulation tank, where it is pumped by a salt-sludge circulation pump into reaction tank A, which is primarily composed of CaCO3, for use in the salt-sludge circulation process. The excess CaCO3 slurry overflows from the slurry circulation tank to the slag pool. The salt sludge in the sedimentation tank is washed to remove water through pressure filtration and then dried with compressed air to produce a filter cake with a moisture content of less than 50% by weight; this filter cake is transported out of the area using a trailer, while the filtrate flows into the filtrate tank and is pumped to the water distribution tank. Process flow diagram with control points (see attached figure) 3. Equipment requiring commissioning Serial No. Equipment Name Specification Model Unit Quantity Main Material Equipment Location 1 Venturi mixer φ159×1300 Set 1 Ti D0104 2 Air-water mixer φ426×1180 Set 1 CS+Ti D0105 3 Post-reaction tank A φ3500×6000, with stirrer motor N=4kW Set 1 CS+epoxy ethylene resin D0107A 3 Post-reaction tank B φ3500×5500, with stirrer motor N=4kW Set 1 CS+epoxy ethylene resin D0107B 4 ZF membrane filter φ1916×5802, F=86.4 m2 Set 2 Assembly D0108A/B 6 Water distribution tank φ7000×9000, V=330m3 Unit 2 Low-calcium-magnesium fiberglass + epoxy resin V0101A/B 7 Pre-treatment tank φ8000×14730, V=827.8m3 Set 1 CS+glass flake V0105 8 Brine storage tank φ4500×5000, V=70m3 Unit 1 Low-calcium-magnesium fiberglass + epoxy resin V0107 9 Salt sludge circulation tank φ3000×3000, V=21m3 Unit 1 CS+epoxy ethylene resin V0108 10 Na2CO3 preparation tank φ3000×3000, V=21m3 Unit 1 CS V0109 11 Pressurized air dissolution tank φ1600×4500, V=9m3 Set 1 CS+epoxy ethylene resin V0112 12 Air buffer tank φ412×1825, V=0.15m3 Set 1 CS V0113 13 FeCl3 storage tank φ2500×2500, V=12m3 Unit 1 UPVC V0114 14 Na2CO3 receiving tank φ3000×3000, V=21m3 Unit 1 CS V0115 15 Intermediate tank φ5000×5000, V=90m3 Unit 1 Low-calcium-magnesium fiberglass + epoxy resin V0116 16 Sludge tank φ3000×3500, V=24m3 Unit 1 Concrete + glass flake V0117 17 Filtrate tank φ2500×3000, V=14.7m3 Unit 1 CS+epoxy ethylene resin V0118 18 Pickling solution storage tank φ2500×2500, V=12m3 Unit 1 UPVC V0119 19 Concentrated brine storage tank φ7000×9000, V=330m3 Unit 2 Low-calcium-magnesium fiberglass + epoxy resin V0120A/B 20 Na2SO3 sump tank φ1400×1506, V=2.3m3 Unit 1 304 V0121 21 Hydrochloric acid water seal tank φ450×900, V=0.14m3 Unit 1 UPVC V0131 22 Air distribution panel φ159×1450, V=0.0237m3 Set 1 CS V0132 23 Backwash tank φ912×2183, V=1.27m3 Set 2 CS+low-calcium-magnesium adhesive 24 Brine heat exchanger 50m2 Set 1 Ti E0101 25 Plate and frame filter press XMZ60/1000-00-01 Set 2 Assembly L0101A/B 26 Water intake tank φ716×1000, V=0.35m3 Set 1 CS V0103 27 Water intake tank φ716×1000, V=0.35m3 Set 1 CS V0102A 28 Water supply pump IHF125-100-400 Set 2 Fluoroplastic alloy P0101A/B 29 Brine pump Model: XCA125-100-315-L Set 2 Titanium P0102A/B 30 Pressure pump XZA150-100-500-L Set 2 Titanium P0103A/B 31 Na2CO3 transfer pump IH50-32-200 Set 1 0Cr18Ni19 P0105 32 Filter feed pump IFH125-100-315 Set 2 Fluoroplastic alloy P0106A/B 33 Salt sludge pump 40ZGJ-00 Set 2 Cr26 P0107A/B 34 Filtrate pump IHF50-32-250 Set 2 Fluoroplastic alloy P0108A/B 35 Pickling solution feed pump CQB65-50-160 Set 1 Fluoroplastic alloy P0109 36 Concentrated brine pump IJ150-125-400 Set 2 Titanium P0110A/B 37 Salt sludge circulation pump 25ZDJ-00 Set 2 Cr26 P0111A/B 38 FeCl3 metering pump JZ1000/0.3B-0.75-808S Set 2 PTFE P0114A/B 39 Na2CO3 metering pump JD2000/0.3A-2.2-1004P Set 2 304 P0115A/B 4 Preparations before commissioning 4.1 Equipment inspection: Check whether the equipment foundation and installation meet the design requirements, and whether levelness, verticality, and concentricity have been adjusted according to technical specifications ； Check whether the power connections of all motors meet the electrical design requirements. Check whether the motor coupling has been aligned, and rotate the shaft 2–3 turns to verify that the connection is secure and the rotation is smooth; also check if the motor coupling is equipped with a protective cover. Check and confirm that the reduction gears of all pump units have been properly filled with oil and that individual unit testing has been completed. Check and confirm that pressure vessels such as the air distribution panel, pressurized dissolved air tank, and air buffer tank have all passed pressure testing and are equipped with complete safety accessories. Check whether the container is calibrated and has a scale. 4.2 Check whether the process piping meets the design requirements, and whether the pipes have been purged with air, washed with steam, and cleaned with water in accordance with the technical specifications. 4.3 Check whether the instrument installation meets the process requirements, and whether the instrument has been calibrated and is equipped with a valid certification label. 4.4 Check whether all equipment installations and pipeline installations have been approved upon inspection. 4.5 Check whether the automatic control system of the ZF membrane filter operates within the set parameters, and whether it functions accurately during 48 hours of continuous simulated operation. 4.6 Check whether the employees have completed their safety education and technical training and passed the examinations. 4.7 Check and confirm that the safety facilities at the test site are complete, the surrounding roads are unobstructed, and the personal protective equipment is available in sufficient quantity. 4.8 Clean the production site and check whether the entire system meets safety production requirements. 4.9 The aforementioned work processes and contents are all meticulously and completely recorded by designated personnel. 4.10 Relevant commissioning work permits must be obtained for equipment and pipeline purging, replacing materials with water, and trial operation with feed materials, and these permits must be strictly followed. 5 Purging and cleaning of equipment and pipelines 5.1 Equipment and pipelines must be purged or cleaned (referred to as purging and cleaning) after passing the pressure test. 5.2 Sequence of purging: The equipment is purged in the order of the process flow, while the pipes are purged sequentially as main pipes, branch pipes, and drain pipes; any dirt removed during purging must not enter the pipes (equipment) that have already been deemed qualified. 5.3 Before purging, the automatic control valves, flow meters, and instruments on the relevant pipelines should be removed to prevent blockages and malfunctions caused by debris. 5.4 Cleaning of equipment: 5.4.1 Use compressed air to purge and test for leaks in the pressurized dissolved air tank, air buffer tank, air distribution unit, and air pipelines (the pressure used for leak testing and purging shall not exceed the design pressure of the containers and pipelines). For air purging, visually check that no smoke or dust is emitted; a white cloth should be placed at the exhaust outlet to verify that there is no rust, dust, moisture, or other debris within five minutes, which indicates success. 5.4.2 Cleaning of liquid material storage tanks (vessels): Connect a clean water hose nearby or open the clean water inlet valve of the tank, and use clean water for cleaning. Open the drain flange or valve of the storage tank, and rinse it repeatedly with clean water—drain—rinse—drain, until the color and transparency of the drained water are visually identical to those of the inlet water, indicating that it is satisfactory; then drain any remaining water. For equipment with manholes, it is also necessary to enter the tank to remove debris and drain any remaining water. When working inside the tank, attention should be paid to ventilation, and the required permits for such work must be obtained. 5.5 Process air and instrument air systems: 5.5.1 Open the relevant valves and conduct pressure testing and leak detection on the pipelines connected to the pressurized dissolved air tank and the air buffer tank; if any leaks are found, repair them. 5.5.3 Perform intermittent purging on each branch of the air distribution panel in sequence (first removing the flange at the far end before the equipment), until satisfactory results are achieved ； 5.5.4 Remove the blind flange at the end of the instrument air pipe next to the filter control box on the 3rd floor; connect a hose from the discharge outlet of the air distribution panel to the discharge outlet of the instrument air pipe beside the gantry. Open the discharge valve of the air distribution panel and perform intermittent purging until satisfactory results are achieved, after which reinstall the blind flange ； 5.6 Steam system: The steam pipes should be purged one by one. Before purging, in addition to following the procedures in sections 2.2 and 2.3, the drain valve assemblies should be removed and the pipes warmed up first; water should then be drained promptly. Thereafter, the amount of steam used for purging should be increased gradually in intervals until no rust or debris is left on the wooden target at the steam outlet. At that point, the steam valve should be closed, the drain valve assemblies reinstalled, the steam valve opened again to continue purging with steam, and the system adjusted to the control pressure for leak testing. If any leaks are detected, they should be repaired. 5.7 ZF membrane filter system: To be carried out under the guidance of PALL’s technical personnel. 5.8 Liquid material pipelines (water distribution system, mixing system, brine system, pickling system): Flush with clean water; it is considered satisfactory if the color and transparency of the discharged water are visually consistent with those of the inlet water, and no debris is discharged. 5.8.1 Cleaning of clean water pipes and pure water pipelines: Proceed sequentially from the main pipes to the branch pipes. Remove the blind flanges at the ends of the pipes for cleaning, as well as the flanges or fittings at the ends of the pipes before they connect to the equipment (such as the pump cooling water inlet hoses). Open the water inlet valve and use clean water to flush each pipe until it meets the required standards; then reinstall the flanges and fittings. 5.8.2 Cleaning of pipes before and after the pump: Fill the tank before the pump (or water intake tank) with clean water to half capacity, remove the short pipe (elbow) or valve located before the pump (the valve before removing the filter from the desalination tank feed pump), open the outlet valve of the tank, and use clean water to flush the pipes before the pump; once this is done successfully, connect the pump inlet ； Disconnect the pump outlet pipe to the inlet flange or fitting of the next device in order to prevent dirty water from entering the equipment. Open the tank outlet valve and the pump inlet valve, as well as the pump cooling water valve. Use the clean water in the tank to manually rotate the pump before starting it; then flush each branch pipe at the pump outlet one by one until they are clean, drain any remaining water, and reinstall the pipes and fittings. 5.8.3 Cleaning of gravity-fed pipelines with pressure difference: Remove the low-position fittings or flanges at the end of the pipeline to be cleaned (before the inlet of the next device), and then use the appropriate material pump or open the water inlet valve to fill the relevant high-position containers with water until it overflows (through the overflow pipe) ； Alternatively, open the discharge valve (discharge pipe) and the return valve (return pipe) of the upper-level container, and use clean water to flush each pipe one by one until it meets the requirements and all remaining water is removed; then reinstall the pipes and fittings. 5.8.4 Pipeline from brine storage tank to brine pump: Loosen the flange at the junction of the rubber-lined steel pipe and the steel-plastic composite pipe at the outlet of the brine pump, use clean water to flush the pipeline from the brine storage tank in the direction of the brine pump until it is satisfactory and all remaining water is removed, then reinstall the pipe. 6. Water operation: After the equipment and pipelines have been cleaned, a trial run is carried out using water in place of the actual material, in accordance with the startup procedures outlined in the \"Trial Operating Procedures for Brine Production using ZF Membrane Technology\" (hereinafter referred to as the operating procedures). Solutions in the water distribution tank are made up of brine, with water being used as a substitute for additives such as FeCl3, Na2SO3, and NaClO. The precautions, requirements, and objectives for water operation are as follows: 6.1 Establish the process flow and become familiar with the startup procedures. 6.2 Tune the process and instrument air systems to ensure that the operating pressure remains stable and that the pressure control system functions properly. 6.3 Perform individual testing on the ZF membrane filter system (this must be carried out under the guidance of PALL company technicians). 6.4 During water operation, no membrane is installed in the filter; the inlet valve of the brine tank is closed, and the water that enters the filter flows back to the brine storage tank through the return pipe, thus enabling a cyclic operation. 6.5 Verify that each refined product can be fed properly, and that the rotameter (or metering pump) can be adjusted freely. 6.6 Calibrate the remote level measurement instruments and on-site instruments for the levels of the brine storage tank, pressurized dissolved air tank, etc., and adjust the automatic control systems for these levels until they operate stably. 6.7 Further adjust the levelness of the key components of the main equipment, such as the levelness of the sludge discharge nozzle of the pretreater and the clear liquid overflow pipe outlet, as well as the height difference between the upper edge of the sludge discharge nozzle and the clear water overflow outlet, until it is approved by Poulson’s technical staff. 6.8 After the water operation is complete, drain any remaining water from the preprocessor, and apply anti-corrosion treatment to the overflow port as required. 6.9 Tune the pickling system (automatically adjusted by the ZF membrane filter system’s control unit, under the guidance of PALL Corporation’s technical staff). 6.10 Adjust the opening degree of the release valve until the rising speed of the liquid level in the pretreatment system and the bubble release meet the requirements. 6.11 Tune the brine heat exchanger to ensure proper heat exchange with steam and cooling water, that the heat transfer capacity meets the process requirements, and that the water temperature control system functions properly. 7. Contents and procedures for material commissioning 7.1 Pre-commissioning preparations: Check and review the installation records, purging records, pressure testing and leak detection records, as well as the records of individual unit and integrated system tests, to confirm that all preliminary preparations have been completed. The equipment and installation system has been tested with water and passed the tests; all residual water from the system has been removed. The job operation procedures, original record forms, and safety regulations are all in place; the operators and commissioning supervisors are familiar with the key operational points and have been confirmed to have completed successful training. Operators must complete training successfully before they can take up their posts. The process control points and a schematic diagram of the process flow have been posted on the wall. The flow direction of the pipeline materials has been marked on site; the labeling for major equipment, inspection cards, inspection routes, contents, and intervals have all been determined. The raw materials and auxiliary materials have all passed inspection and been delivered to the site. The coordination trial run scheduling meeting has been held, and the cooperation from relevant departments has been confirmed (electrical, instrumentation, safety, production, fire protection, environmental protection, labor protection, process, etc.). The control inspection methods for products and intermediates have been established, and the analysts have received training and passed the assessment. 2 Material trial run: a) Confirm that the filter has no membrane installed, and that one of the inlet valves for the brine tank is open. b) During the trial operation of the materials, the brine that enters the filter flows back to the concentrated brine storage tanks V0120A and B through the overflow pipe, and then the unqualified brine is sent back to the water distribution tank using a concentrated brine pump, thus enabling a cyclic operation. c) Prepare the NaOH solution, Na2CO3 solution, FeCl3 solution, HCl solution, Na2SO3 solution, and NaClO solution according to the procedure specific to each position, and start the pumps to feed them into their respective high-level tanks (or storage tanks) until the desired level is reached. d) The remaining operations are carried out in accordance with the startup procedure specified in the job operation manual. e) Check in accordance with the process control specifications whether the quality parameters of each intermediate control meet the requirements; if not, the operations should be adjusted promptly. f) When the brine, upon analysis, meets the conditions for membrane installation – that is, when the brine at the outlet of the intermediate tank satisfies the standards: Ca2+ > 150 ppm, there is no free chlorine in the crude brine, and there are no significant amounts of crystalline salts or mechanical impurities – the process is stopped and membrane installation is carried out under the guidance of Porex Company’s technical staff. g) Use the brine pump to send all the brine that enters the brine tank during normal operation to the distribution tank, and close the inlet to the brine tank. The unqualified filtered brine, which was used for driving the system again after film installation, entered the crude brine storage tank, while the qualified refined brine was sent to the refined brine storage tank, thereby bringing the system back to normal operation. 8 Problems encountered during the commissioning process 8.1 The motor of the pressure pump was damaged while the pump was in operation; the main reason for this was that the wiring box of the motor used in this pump was not manufactured in accordance with relevant standards, which allowed water to enter the motor. It worked normally after replacing the motor with one from another manufacturer. 8.2 Frequency conversion regulation fails to meet the control requirements, mainly due to long signal distances that cause attenuation and lead to control errors; after adjustments, the control requirements are satisfied. 8.3 The automatic control valve vibrates severely when its opening is below 50%; after contacting the manufacturer, it was determined that this was caused by a weak pneumatic actuator in the valve. The problem was resolved after the manufacturer replaced the pneumatic actuator. 8.4 The safety valve of the metering pump was leaking, but it is now functioning properly after repair. 8.5 The magnetic pump was not operating properly, with no pressure at the pump outlet. After checking the inlet and outlet pipes, no abnormalities were found; the reason was that the magnetic force necessary to drive the impeller was absent in the pump. The issue was resolved after the supplier replaced the entire magnetic pump. 8.6 Some pipes have leakage points, which shall be repaired by the installation unit. 9 List of Process Control Parameters (Technical Control Parameters) for This Position
Serial Number | Controlled Area | Control Parameter | Unit | Control Limit | Control Frequency | Remarks
1 | Water distribution tank | pH value of brine | 10.5–11.5 | 1 time per tank |
2 | Brine dissolving tank | Salt layer height | m | Maintain detectability of salt layer | Frequently | No record required |
3 | Outlet of brine dissolving tank | Temperature of brine | °C | 50–60 | Frequently |
4 | Pre-reaction tank | NaCl, excess NaOH, NaClO, SO42- | g/L, g/L, mg/L, g/L | 305–310, 0.3–0.6, 4–8, ≤5 | 1 time every 2 hours, 1 time every 2 hours, 1 time every 2 hours, 2 times per shift |
5 | Coarse brine storage tank | Temperature | °C | 50–60 | Frequently |
6 | Pressurization pump | pH value of brine at pump outlet | 10.5–11.5 | Frequently |
7 | Pressurized dissolved air tank | Pressure | MPa | 0.2–0.25 | Frequently | No record required |
8 | Pre-treater | FeCl3 content in incoming brine, temperature at pre-treater outlet, NaOH at pre-treater outlet, Mg2+ (total magnesium) at pre-treater outlet, NaClO at pre-treater outlet | mg/L, °C, g/L, mg/L, mg/L | ≤30, 50–60, 0.1–0.3, 0–5, 1–3 | 2 times per shift, frequently, 1 time every 2 hours, 1 time every 2 hours, frequently | No record required, no record required |
9 | Upper floating sludge | Frequently |
10 | Lower settled sludge | Once per shift |
11 | Inlet of filter feed pump | Na2CO3 content, excess alkali amount, Ca2+ (total calcium), NaClO | g/L, mg/L, mg/L | 0.3–0.6, 150–500, 0 | 1 time every 2 hours, 1 time every 2 hours, frequently | No record required |
12 | Instrument air compressor | Air pressure | MPa | ≥0.5 | Frequently | No record required |
13 | ZF membrane filter | Filtration pressure, filtration time, filtration flow rate, slag discharge interval, backwashing time, transparency | MPa, s, m3/h, h, S | 0.015–0.05, 1200–3600, 36 (per unit), 2–4, 7–40 | Good or poor | Set value, set value, set value, set value, set value | 1 time per hour | No record required, no record required, no record required, no record required, no record required |
14 | Outlet of ZF membrane filter | NaCl, Ca2+ + Mg2+, TSS | g/L, mg/L, mg/L | 300–310, ≤1, ≤0.5 | 2 times per shift, 2 times per shift, 1 time per shift |
15 | Inlet of refined brine pump | NaCl, Ca2+ + Mg2+, NaClO, SO42-, TSS, Fe2++ Fe3+, pH value, Na2CO3, NaOH, inorganic ammonium | g/L, mg/L, mg/L, g/L, mg/L, mg/L, g/L, g/L, g/L | 305–310, ≤1, 0, ≤3, ≤0.5, ≤0.1, 10.5–11.5, 0.3–0.6, 0.1–0.3, 1 | 1 time per shift, 1 time per shift, 1 time per shift, 1 time per shift, 1 time per shift, 1 time per shift, 1 time per shift, 1 time per shift, 1 time per week |
16 | NaClO storage tank | Concentration | % | 3–7 | 1 time per tank |
17 | FeCl3 preparation tank | Concentration | % | 1 | 1 time per tank |
18 | Na2CO3 preparation tank | Concentration | g/L | 130–170 | 1 time per tank |
19 | Na2SO3 preparation tank | Concentration | % | 0.4–0.6 | 1 time per tank |
20 | Acid cleaning solution storage tank | HCl concentration | % | 8–15 | 1 time per acid cleaning | No record required |
21 | NaOH rotameter | Flow rate | L/h | ≤600 | Controlled based on brine flow rate |
22 | NaClO rotameter | Flow rate | L/h | ≤600 | Controlled based on brine flow rate |
23 | Flow rate of FeCl3 from metering pump | Flow rate | L/h | ≤1000 | Controlled based on brine flow rate |
24 | Flow rate of Na2CO3 from metering pump | Flow rate | L/h | ≤1600 | Controlled based on brine flow rate |
25 | Na2SO3 rotameter | Flow rate | L/h | ≤50 | Controlled based on brine flow rate |

10 Methods for Normal Shutdown
10.1 Upon receiving instructions, contact the relevant teams to carry out the shutdown. 10.2 Once it is confirmed from the ion exchange membrane process that the supply of brine can be stopped, close the outlet valve of the refined salt water pump and shut down the refined salt water pump. 10.3 Stop adding salt, close the valves for supplying river water or condensate water. When the salt concentration is below 305 g/L, stop the water supply pump, close the main valve for supplying water to the evaporation salt tank, and at the same time close the preheater steam valve TIC101 or the circulating water flow control valve. 10.4 Close the addition valves for the refining agents NaOH and NaClO. 10.5 The reaction tank agitator does not need to be stopped during short-term stops. 10.6 Stop the coarse salt water pump. 10.7 Stop the pressure pump. When stopping the pressure pump, it is necessary to first close the valve of the compressed air pipeline feeding into the pressure dissolving tank, then close the outlet valve of the pressure pump, and finally stop adding the iron salt pretreatment agent. Otherwise, the high-pressure brine in the pressurized dissolved air tank will flow back, damaging the equipment. 10.8 Stop adding the refining agents Na2CO3 and Na2SO3 once the overflow liquid from the preprocessor outlet ceases. If the parking duration is short, it is not necessary to stop the mixing in the front and rear reaction tanks. 10.9 When stopping the filter, first press the stop button while it is in operation; once the ZF membrane filter enters the stopped state, then stop the inflow of liquid to the filter. 10.10 After stopping the filter, fill the ZF membrane filter with pure water up to above the flange, maintaining a certain liquid level. 10.11 If the parking time is long, it is necessary to drain the brine from the pressurized dissolved air tank and to fill the overflow outlet of the pretreater with a certain amount of water to prevent salt buildup in the piping and equipment. 10.12 Enter the reason and time for parking on the report. 11 Emergency shutdown: In the event of a sudden power outage while saltwater is being processed, the pump stop button should be pressed immediately, and the on-duty dispatcher must be informed. At the same time, the outlet valves of all pumps, the outlet valve of the pressurized dissolved air tank, the valve for FeCl3, the valve for the compressed air supply to the pressurized dissolved air tank, and the valves for other purification agents should all be closed. The inlet valve of the filter should also be closed once the instrumented pressure drops to 0.3 MPa. 12 Operations at Other Control Points 12.1 Preprocessor Operations – Sludge Discharge: The outlet for the supernatant fluid in the preprocessor is closed, which raises the liquid level inside the preprocessor; as a result, the floating sludge enters the sludge discharge nozzle and then flows through pipes to the slag tank. After sludge removal, open the supernatant outlet for normal clear water discharge. Lower sludge discharge operation: After the upper sludge discharge is completed, open the lower sludge discharge valve. Observe the color of the sludge at the lower discharge outlet through the sight glass; when the color of the sludge changes from dark to light, close the lower sludge discharge valve. 12.2 Pickling operation a) Prepare an 8–15% HCl solution in the pickling tank. b) The filter is in shutdown mode. Manually operate on the control panel to open the exhaust valve (valve #7). c) Manually open the drain valve (port g, manual diaphragm valve) to return the filtrate from the upper part of the filter back to the intermediate tank. Once the filtrate is below the tube sheet, open several covers on the filter tube sheet to allow observation. Once the liquid level is below the drain port, close the drain valve (port g, manual diaphragm valve). e) Manually open valve 6#, and after the filter effluent has been drained, close valve 6#. Open the pure water valve and pour pure water into the filter to rinse the filter bags once. Fill with water to about 10 centimeters below the ceiling, then open the manual compressed air valve at the bottom of the filter and use compressed air to stir and rinse. It is most appropriate for the water level to rise to the level of the exhaust port during aeration and stirring; if the water level is too low, more pure water can be added until it reaches the exhaust port. After rinsing is complete, close the manual compressed air valve at the bottom of the filter and open flexible valve No. 6 to drain the wastewater. f) After closing valve 6#, use a pump to feed the pickling solution into the filter; the liquid level should be controlled in the same way as during rinsing. g) Open the manual compressed air valve at the bottom of the filter, and use compressed air to stir the mixture for 1 hour. h) Return the cleaning fluid inside the filter to the cleaning fluid tank. i) After draining the cleaning solution, rinse the filter bag once with pure water. j) Please immediately introduce the filtrate after the filter cleaning is complete. k) When the concentration of HCl solution in the pickling tank is below 8%, start the pickling solution pump to send a portion of the HCl solution into the water distribution tank. Add more of the new 32% HCl solution to restore the HCl concentration in the pickling tank to 15%. 12.3 Procedure for adding FeCl3 solution: Adjust the piston stroke of the metering pump, and calculate the required amount of FeCl3 solution to be added using the following formula: Q1(L/h) = 3Q2 (based on a concentration of 10 mg/L). Here, Q1 represents the amount of FeCl3 solution added, in L/h, while Q2 represents the volume of crude salt water being treated, in m3/h.

12.4 Procedure for adding NaClO solution: Adjust the settings of the rotameter, and calculate the required amount of NaClO solution to be added using the following formula: Q1(L/h) = 0.17Q2 (based on a concentration of 10 mg/L). Here, Q1 represents the amount of NaClO solution added, in L/h, while Q2 represents the volume of crude salt water being treated, in m3/h. While adding NaClO solution, it is necessary to monitor the free chlorine concentration in the crude salt water at the outlet of the pre-treatment unit; an ideal concentration is between 1 and 3 mg/L. The amount of NaClO solution added should be adjusted accordingly. 12.5 Reaction operation with NaOH: Estimate the amount of NaOH to be added, and after determining that the concentration of NaOH in the brine is within the acceptable range, adjust the rotor; generally, an electrolyte concentration of around 10% is used for NaOH. Measure the pH of the saline in the reaction tank before testing, and keep it between 10.5 and 12. Ensure that the crude brine output from the preprocessor contains 0.1–0.3 g/L of NaOH. 12.6 Procedures for preparing a Na2CO3 solution: 125 kg of solid Na2CO3 is mixed with water to produce 1 m3 of solution, with a Na2CO3 concentration of 12.5%. Weight of Na2CO3 (kg) = 125 / V, where V is the volume of the Na2CO3 preparation tank, in m3. The amount of Na2CO3 to be added is estimated through reaction calculations; after determining that the concentration of Na2CO3 in the brine is within the desired range, the piston stroke of the metering pump is adjusted to add Na2CO3 to the subsequent reaction tank. It is ensured that the concentration of Na2CO3 in the brine entering the filter pump is between 0.3 and 0.6 g/L. 12.7 Procedure for adding Na2SO3: Adjust the rotameter knob according to the amount of free chlorine in the brine, and calculate the required amount of Na2SO3 solution using the following formula: Q1 (L/h) = 1 × Q2 (based on 5 mg/l). Where: Q1 – Amount of Na2SO3 solution to be added, (L/h); Q2 – Volume of brine to be treated, (m3/h). 13 Abnormal phenomena and their solutions: Sequence Number, Abnormal Phenomenon, Cause, Solution. 1: NaOH content in the brine at the outlet of the pre-treatment unit exceeds 0.6 g/L. 1) Excessive amount of NaOH was added to the acidic dechlorination brine in the ion exchange process. 2) Excessive NaOH was added to the baffle tank in the salt dissolution process. 1) Immediately notify the ion membrane process team to correct the operations. 2) Notify the saltification process to adjust the NaOH dosage. 2 The crude brine at the inlet of the filter feed pump has a Na2CO3 content of >0.6 g/L; too much Na2CO3 is being added. Adjust the amount of Na2CO3 added. 3 In brine with free chlorine >8 ppm, 1) the dechlorination effect in the dechlorination tower is not satisfactory. 2) Excessive NaClO was added to the baffle tank in the salt dissolution process. 1) Immediately notify the ion membrane process to adjust operations. Increase the dosage of Na2SO3. 2) Notify the desalination process to adjust the NaClO dosage. 4 The temperature of the brine is high. 1) The temperature of the dechlorinated fresh brine is too high. 2) The steam inflow is too high. 1) Increase the water flow rate in the brine heat exchanger circulation. 2) Control the amount of steam entering. 5 The temperature of the brine is too low. 1) The amount of steam entering is too small. 2) Fouling and blockage of the heat exchanger. 1) Increase the steam inflow. 2) Clean the heat exchanger. 6 In brackish water, the NaCl content is <300 g/L. 1) The salt layer in the testing tank is less than 2.5 meters deep. 1) Add salt in a timely manner. 7 In brine with a NaCl content of >310 g/L, the concentration solution stays in the testing tank for too long. Increase the flow rate of the saline solution. 8 The pressure in the pressurized dissolved air tank increases, causing crystalline salts and debris to block the pressure relief valve. Flush the pressure relief valve with brine to clear it. If flushing is ineffective, stop the machine and disassemble the pressure relief valve for cleaning. 9. Backmixing of brine at the pre-treater outlet; the Mg2+ (total magnesium) content in the crude brine is too high. 1) The temperature difference between the crude brine entering and leaving the pre-treater is excessive. 2) The flow rate of the brine water entering the preprocessor is unstable. 3) The amount of FeCl3 added is too low. 4) The compressed air pressure is too low. 5) Excessive or insufficient sludge discharge. 1) Adjust the temperature of the brine solution. 2) Stable flow rate. 3) Adjust the FeCl3 dosage. 4) Increase the compressed air pressure to 0.2~0.25 Mpa. 6) Determine the sludge discharge time and frequency based on the amount of salt sludge. 10 The free chlorine level at the pre-treater outlet is 0; insufficient NaClO was added to the baffled tank in the desalination process. Notify the salt-making process to adjust the amount of NaClO added. 11. At the inlet of the filter feed pump, the Ca2+ (total calcium) level is either >500 mg/L or <150 mg/L, or the Ca2+:Mg2+ ratio is <10:1. 1) Brine contains a high amount of Ca2+. ) Excessive amounts of salt sludge have accumulated in the post-reaction tank and the intermediate tank. 2) The Ca2+ content in brine is low. 1) Reduce the return flow of salt sludge. 2) Remove the salt sludge from the post-reaction tank and intermediate tank in a timely or scheduled manner. 3) Increase the return flow rate of salt sludge. 12 Error in the status of the ZF membrane filter control valve: 1) Controller signal output issue. 2) The fuse in front of the solenoid valve is damaged. 3) Poor wiring from the controller to the solenoid valve. 4) The solenoid valve does not operate smoothly. 5) Damage to the flexible valve liner. 1) Inform the instrument technician to inspect and repair the controller. 2) Inform the instrument technician to replace the fuse. 3) Inform the instrument technician to replace or rewire it. 4) Repair or replace the solenoid valve. 5) Replace the inner tank. 13 The filtration pressure of the ZF membrane filter rises too quickly. 1) The brine is acidic; the reaction between Mg2+ and NaOH occurs slowly, resulting in poor Mg2+ removal by the pre-treater. 2) The water output from the processor is turbid, with a large amount of Mg(OH)2 entering the reaction tank. 3) The rapid exhaust valve and level gauge are damaged, leading to incomplete backwashing and insufficient backwashing water volume. 4) Fatigue of the slag discharge valve’s inner liner; as a result, the valve cannot open fully during slag discharge, leading to the accumulation of salt sludge. 1) Ensure that the pH value of the brine solution remains between 10.5 and 11.5, while also controlling the amount of NaOH added to the baffled tank. 2) Adjust the operations of the preprocessor. 3) Replace the quick exhaust valve and level gauge. 4) Replace the slag discharge liner and remove the sediment at the bottom of the filter. 14 The ZF membrane suddenly stops producing water: 1) The instrument air pressure is below 0.35 Mpa; the flexible valve is fully open, and the brine is drained. 2) The solenoid valve is damaged. 1) Stop the machine immediately and restart it only after the instrument air supply is restored. 2) Notify the meter technician to carry out repairs. 15 The levels of Mg2+ and Ca2+ in the refined salt water are above the standard limits, due to poor control during the refining process. Send the substandard brine to the water distribution tank. # hcbbs