Polyaluminum chloride used in circulating water of sand washing ground is mainly used in the settling process of sand washing wastewater, so as to promote solid-liquid separation. Then it is sent to the pressure filter, and the clean water is recycled and recycled by the overflow of the filter press. The sludge containing wastewater is recovered by flocculation and centrifugation. In the process of filtration and centrifugation, polyaluminum chloride was added again to improve the separation efficiency. Polyaluminum chloride used in circulating water of sand washing field is a mixture of treated water and fine sand. Its main characteristics are high turbidity, fine particle size of solid, negative charge on the surface of solid particles, repulsion force between the same charges makes these particles disperse in water, and is affected by gravity and Brownian motion; due to the interaction between solid particles in sand washing water (such as adsorption, dissolution, adsorption, dissolution, etc As a result, the properties of sand washing wastewater are quite complex, which not only has the properties of suspension, but also has the properties of colloid. Due to the above reasons, it is difficult to clarify the sand washing wastewater naturally, and the supernatant of this kind of wastewater is still liquid with a large amount of suspended solids after sedimentation.
Polyaluminum chloride is used as circulating water in sand washing field. In order to make the sand washing water precipitate rapidly in the concentration tank, ensure the qualified backwater combined with circulating production and make the production run efficiently and economically, it is necessary to select appropriate flocculant to strengthen the treatment of sand washing water. Through the production practice in recent years, it has been proved that the polyaluminum chloride produced by our company has a good effect on the treatment of sand washing water, can accelerate the sedimentation of sediment in the water, and is conducive to the production of pressure filtration.
The effect of polyaluminum chloride for circulating water in sand washing field is several times better than that of general polyaluminum chloride. The effect is very obvious in sand washing and filter pressing, or in the discharged groundwater. The effect of sedimentation can be seen in about 5 seconds. Therefore, the reason why many sand washing sites choose flocculant for circulating water in sand washing field.
The problem of water insoluble substance in the process of purifying sand washing circulating water with PAC for sand washing wastewater is encountered. Compared with polyaluminum chloride used for traditional sand washing wastewater and new-type sand washing wastewater, the mineral raw materials used are generally complex in composition. The finer the grinding, the higher the alumina dissolution rate, which will cause the insoluble matter difficult to precipitate. At present, there are three ways to realize solid-liquid separation in China: natural sedimentation method, which usually takes a long time and requires a certain site to build a large sedimentation tank; plate and frame filter press filtration, but with high investment and high cost, some use horizontal spiral centrifuges, which costs a lot of investment; adding coagulant aids such as Polyacrylamide to control the dosage, the effect is good. The solid insoluble particles in the liquid can be continuously filtered and separated by polyaluminum chloride through plate and frame filter press, which does not affect the use of the solution. The plate and frame filter press can keep the low concentration of particles in degreasing solution and phosphating solution, prolong the service life of solution and prolong the cleaning cycle of spray system. The characteristic of plate and frame filter press is that it can clean the solution continuously and produce the waste residue without water. Compared with other coagulants, polyaluminum chloride has the following advantages: wide range of application and wide adaptability to water. It is easy to form large alum flower quickly and has good precipitation performance. The suitable pH value range is wide (5-9), and the pH value and alkalinity decrease little after treatment. When the water temperature is low, the stable precipitation effect can still be maintained. The alkalinity is higher than that of other aluminum salts and iron salts, and the erosion effect on equipment is small. The product is an inorganic polymer coagulant. Through the mechanism of compression double layer, adsorption electric neutralization, adsorption bridging and sediment net trapping, the fine suspended particles and colloidal ions in water are destabilized, and aggregation, flocculation, coagulation and sedimentation are achieved to achieve the purification treatment effect. The physical and chemical properties of liquid products are colorless, light yellow, light gray or tan transparent or translucent liquid, without precipitation. Solid products are white, light gray, light yellow or brown grains or powders. Alumina content: liquid product & gt; 8%, solid product 20% - 40%, alkalinity 70% - 75%. Method: the product (solid) and normal temperature water are added at 1 / 3 weight ratio while stirring. After the product is completely dissolved, water is added to dilute it to the required concentration. The raw water concentration is 100 ~ 500mg / h, and the dosage is 3 ~ 6mg / I. The water test should be carried out according to the water quality to select the best dosage and then put into use. Packaging and storage solid is 25kg bag, inner plastic film, outer plastic woven bag. The product should be stored indoors in dry, ventilated and cool place without damp. PAC is an important coagulant in the field of water purification. It has high purification effect on low temperature, low turbidity and high turbidity water. However, it is very important to ensure the purity of PAC in water purification because its monomer reacts with organic substances to produce substances harmful to human health. Safety, health and protection polyaluminum chloride product is corrosive. If it is accidentally splashed on the skin, it should be washed with water immediately. The production and use of this product should wear work clothes, masks, gloves and long rubber boots. The production equipment should be sealed and the workshop should be well ventilated.
In conclusion, PAC and PAM should be used together when the mud content of sand washing wastewater is large. If the crushed raw ore is bluestone, pebble and river sand, polyaluminum chloride xanthate is not needed, and polyacrylamide white powder can be used alone.
