Application of Polyaluminum Chloride

Application of Polyaluminum Chloride

With the development of industry, the discharge of industrial wastewater and sewage is increasing day by day, and the pollution caused by it seriously threatens people's health. Oily wastewater is a common wastewater. Oily wastewater mainly comes from refinery wastewater, oilfield wastewater, and mechanical processing industry wastewater. With the increase in oilfield extraction and crude oil processing depth in my country, the quality of oily wastewater continues to deteriorate. Reasonable treatment and utilization of oily wastewater can not only protect the environment, but also recover crude oil and improve the reuse rate of water. The most commonly used and most effective method for oily wastewater treatment is chemical method, that is, adding coagulant to water for coagulation treatment. Inorganic polymer coagulants are widely used in the treatment of industrial wastewater, domestic sewage and drinking water because of their excellent performance and low price.

At present, the treatment of oily wastewater generally adopts "oil separation and air flotation, coagulation and sedimentation, and aeration biochemical method". Among them, the coagulation process, as a key link to remove emulsified oil and suspended solids in water, plays an extremely important role in the normal operation of the entire wastewater treatment process, especially the subsequent biochemical treatment process. It determines the operating conditions of the subsequent process, and ultimately determines the water quality and cost. Polymer inorganic coagulants are effective agents in this process.

[Application] 

Polyaluminum chloride is a new type of inorganic polymer coagulant, the most widely used variety, with mature industrial production technology, and has become the mainstream product in the polymer aluminum coagulant market. Japan was the first to produce and apply it, and it was officially put into industrial production and application in the late 1960s. China also began production and application in the early 1970s. The application range of basic aluminum chloride is getting wider and wider, and it can be used in water purification, industrial wastewater, domestic sewage, sludge, etc. It is the most widely used coagulant in domestic water supply and industrial water supply treatment. It can also be used in papermaking glue, refractory material binder, textile industry mordant, medicine, foundry, machinery, leather, cosmetics, etc. Because basic aluminum chloride has the advantages of less dosage, simple process, convenient operation and high purification degree. With high efficiency and wide source of raw materials, it has developed rapidly at home and abroad in the past 20 years.

This product is a cationic inorganic polymer coagulant, which can provide multi-nuclear complex ions when put into water, and continuously hydrolyze and polycondense to finally generate aluminum hydroxide. Therefore, polyaluminum chloride can provide high-valent polymer ions after hydrolysis, the flocs form quickly, the particles are large and heavy, the sedimentation performance is good, and the flocculation effect is better than that of ordinary aluminum salts such as aluminum sulfate. The applicable pH range is wider than that of traditional aluminum salts (pH 5-9), and the pH and alkalinity of the treated water drop less. When the water temperature is low, it can still maintain a stable flocculation effect, and its alkalization degree is higher than other aluminum salts and iron salts, so the corrosion effect of the liquid medicine on the equipment is small. At the same time, it can also be used to remove iron, manganese, chromium, lead and other heavy metals contained in water, as well as fluoride and oil in water, so it can be used to treat various industrial wastewater. The effective dosage of this product is 20-50mg/L. Liquid products can be directly metered. The solid product needs to be prepared into a 10% to 15% solution in a dissolving tank, and then added according to the required concentration. The product is highly corrosive, and the feeding equipment needs anti-corrosion treatment. Need to be equipped with labor protection facilities.

When coagulation is used to treat petrochemical wastewater, polyaluminum chloride has better flocculation performance than traditional flocculants such as aluminum sulfate or even polyferric sulfate, especially high-efficiency polyaluminium chloride. When the turbidity of the effluent reaches the same level, its cast The amount added is only 1/5 of that of polyferric sulfate. In this way, less sludge is produced, which is beneficial to subsequent treatment, and has a high turbidity removal rate, which has little effect on the pH value of raw water, and can be used as a flocculant for petrochemical sewage reuse treatment. Polyaluminum chloride was used to treat industrial membrane silver-containing wastewater, and the factors affecting the treatment effect, such as PAC dosage, solution pH value, temperature and PAC alkalinity, were studied. The results show that under proper conditions, PAC has a good coagulation effect on metallic silver in film industrial wastewater, and the silver concentration in the treated wastewater is generally 0.003-0.005mg/L, which meets the national discharge standards.

Papermaking industry has a large amount of wastewater discharge, of which the middle section water accounts for a large proportion. Moreover, the black liquor of many papermaking enterprises is also pretreated (anaerobic, strong acid treatment, cellulose separation, neutralization, etc.) and then mixed into the middle water for treatment. At present, the easiest way to treat mid-section water is chemical coagulation. The coagulant used is single-agent polyaluminum chloride or double-agent polyaluminum chloride-polyacrylamide. Although the dual-medicine treatment is fast and effective, it is cumbersome to operate in actual production, especially when the water quality is unstable.

Polyaluminum chloride has strong adaptability to water treatment, especially for high turbidity water treatment. For example, in urban and industrial water supply treatment, it is suitable for any water source water quality treatment and its circulation purification treatment process, especially for the treatment of various raw water with serious micro-pollution, pure water pretreatment, water pretreatment, etc. Circular purification treatment in thermal power plants. When the water temperature is low, the coagulation and turbidity removal efficiency of traditional coagulants such as aluminum sulfate will be significantly reduced, which may lead to deterioration of effluent water quality. The use of PAC can obtain better coagulation and turbidity removal effect whether it is low temperature or low turbidity water, and can also be used to remove medium metals such as manganese, iron, chromium, lead, etc., as well as fluoride and oil in water contained in water. wait. In addition, when polyaluminum chloride is used, there will be problems of uneven mixing, which can be diluted before adding. Polyaluminum chloride can also be used for sludge conditioning in combination with weak cationic polyacrylamide, aluminum sulfate or ferric chloride.