High recovery method of waste phosphoric acid film during electrode foil production

Abstract

The invention discloses a high recovery method of a waste phosphoric acid film during electrode foil production. The method comprises a DP1 process waste acid pipeline, a DP1 waste phosphoric acid front liquid storage tank, a DP1 waste phosphoric acid standby storage tank, a DP1 waste phosphoric acid sterilization filtration system, a primary low-pressure nanofiltration membrane system, a secondary high-pressure nanofiltration membrane system, a reverse osmosis membrane system, a reverse osmosis membrane producing water storage tank, a multiple-washing high-pressure nanofiltration system, a nanofiltration membrane producing water storage tank, a reverse osmosis membrane concentrated water storage tank, a washing system producing water storage tank, a primary nanofiltration membrane concentrated water storage tank, a secondary nanofiltration membrane concentrated water storage tank, a multistage washing front liquid storage tank and a washing system producing water storage tank. The invention provides the high recovery method of the waste phosphoric acid film during electrode foil production, an equipment utilization process adopting a domestic nanofiltration membrane to replace an imported nanofiltration membrane is completed by continuous exploring and verifying through experiments, the overall equipment domesticization is realized, and the limitation by foreign technology monopoly and a long post-service period is avoided, so that not only is the cost greatly reduced, but also the method can be continuously perfected and continuously improved.

Description

technical field [0001] The invention relates to the technical field of a high recovery method for waste phosphoric acid membranes, in particular to a high recovery method for waste phosphoric acid membranes when producing electrode foils. Background technique [0002] In the production process of electrode foil (aluminum foil), there will be a process called phosphoric acid electrochemical corrosion, hereinafter referred to as "DP1 process". In the case of direct current, it is uniformly electrochemically corroded, in which the elemental aluminum of the anode will become Enter the liquid system, in the case of PH=1.2, the chemical formula Aluminum dihydrogen phosphate exists. When the content of aluminum ions reaches a certain level, the acidity in it cannot meet the electrochemical corrosion liquid environment of aluminum foil, and it will be discharged from the DP1 process system in front of the waste liquid and become waste acid (a kind of waste acid containing 4% phos...

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Problems solved by technology

[0003] ①High equipment cost: Due to the use of acid-resistant high-pressure membranes, the more commonly used acid-resistant high-pressure membranes are American Coriolis 8040MPS-30 nanofiltration membranes, which are 8-10 times the price of ordinary high-pressure nanofiltration membranes with the same water production characteristics in China.

Therefore, based on the calculation of the treatment design of 10m³ / H, the equipment cost of the membrane alone will increase by 500,000, and the membrane is a consumable item. Calculated according to the service life of one year, the cost will increase by 500,000 per year

[0004] ② The acid and phosphoric acid content of the product is unstable: At present, the design of the domestic nanofiltration membrane system is a single-pot system, that is, the water inlet side of the membrane is two or more storage tanks, and each time a single tank is used for membrane filtration. Directly return to the storage tank on the water inlet side. Due to the continuous increase of the concentration of phosphoric acid and aluminum dihydrogen phosphate in the storage tank on the water inlet side, the membrane filtration pressure, the flow rate of the product water, and the phosphoric acid content of the product water are all changing (the greater the concentration ratio, the higher the membrane filtration pressure. The larger the product water flow rate, the smaller the phosphoric acid content of the product water), the acid content of the final product water storage tank is unstable, and the product quality (phosphoric acid content) is difficult to control

[0005] ③Low acid recovery rate: Nanofiltration membrane is used for phosphoric acid recovery, and the water production rate can reach 60%, and the remaining 40% is separated by lime for neutralization reaction residue, and the sewage is directly discharged

[0006] ④ No assembly line operation, no automatic control: due to the single-tank operation, after each storage tank is concentrated, the next tank is concentrated, and the concentrated liquid is pumped to the wastewater treatment center

[0007] ⑤ Bacterial fouling is prone to occur: the current process cannot be operated in flow water. Since the dilute phosphoric acid environment is a phosphorus-rich environment, bacteria multiply quickly. According to the theory of bacterial growth in a phosphorus-rich environment, once bacteria invade, they can reach the maximum within 24 hours. After the liquid in the tank is in contact with the air and bacteria and oxygen are introduced, the bacteria will multiply in a large area, and they will implant on the inner wall of the storage tank and multiply continuously. Membrane inner wall, causing common membrane bacterial contamination hazards

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