As the main source of industrial waste water, compared with domestic sewage, sewage treatment is difficult and the sewage treatment process is complicated, resulting in serious water pollution. With the rapid development of industry, the type and quantity of wastewater have rapidly increased, and the pollution of water bodies has become increasingly widespread and serious, threatening the health and safety of human beings. This article will explain one of industrial wastewater treatment of coal washing wastewater treatment methods and principles for your reference.

A coal washing wastewater generated

Wet coal preparation requires a lot of water to jigging coal washing, for example, each selected 1t raw coal about 3-5m3 circulating water, the need to add some water. The water after the washing process contains a large number of small particles, usually containing the particle size of less than 1mm suspended particles of coal washing water called slime, also known as coal washing wastewater.

Coal washing wastewater can be divided into two categories, one is coal washing wastewater generated when the coal quality is better, and the other is coal washing generated when the geologic age is shorter, the ash content and impurity content are higher, Wastewater. The former type of wastewater contains larger particle size, lower concentration, the treatment is relatively easy. This kind of coal washing waste water is treated effectively by the physical method of concentrated precipitation, and the separated water can be reused for coal washing. The latter type of coal washing wastewater contains a large amount of slime particles, which not only has small particle size and high concentration, but also has strong negative charges on the surface of the particles, which is a stable colloidal system. Therefore, this type of coal washing wastewater long life is not heavy, difficult to handle. This kind of coal washing wastewater treatment is generally used coagulation sedimentation method.

Two coal washing wastewater main pollutants

The main pollutants in slime wastewater are: suspended solids, oils and organic chemicals.

1, suspended solids

Wastewater from coal preparation contains a large amount of suspended solids, which is a major pollutant. The pollutant of the coal preparation waste water is composed of fine mineral particles such as kaolin and pulverized coal. As the organic matter in coal is dominated by black, and has a special discoloration, resulting in changes in water color, and poor light transmission.

2, oil substances

Large quantities of flotation reagents such as light diesel oil and kerosene, as well as equipment leaking oil and cleaning residues on coal, have caused various amounts of oil to be washed in the coal washing process.

3, organic agents

Usually in the process of coal washing, will be filtered, dehydration, concentration and flotation and other closed-loop treatment of slime water, the link will add inhibitors, flocculants, foaming agents and other agents, and in the cleaning process Residual coal washing wastewater, resulting in water pollution.

In view of the slime water pollutants mentioned above, the suspended matters, pH and the like in the coal washing wastewater can be selected as the main pollutants and the corresponding control indexes to be treated. In the coal washing water may contain manganese, iron, etc., therefore, our country will both pollutants into coal washing water into the limits of indicators.

  Wastewater Treatment Status of Coal Preparation Plant at Home and Abroad

The goal of coal washing waste water treatment is to separate the muddy water, that is, not only to be clean, water suitable for coal washing standards, to achieve closed loop washing coal water, but also to get low moisture content, easy to dehydration slime. With the enhancement of environmental awareness and environmental protection requirements in recent years, departments and coal preparation enterprises at all levels have also demanded that the coal washing wastewater must reach a closed-circuit cycle. However, due to the difficulty of coal washing wastewater treatment over the years, energy and chemical experts and environmental experts from all over the world have always made the special study on the treatment and reuse of coal washing waste water as one of the key contents of industrial wastewater treatment.

1, foreign coal washing wastewater treatment status quo

At present, some coal-producing countries in the world, such as Russia, the United States, Germany, Britain, Australia, Ukraine, South Africa and Poland, have basically realized zero discharge of coal washing waste water and slime separation has been effectively utilized. The reason is that these countries slime separation equipment performance is good, the coal quality of the selected raw coal is generally good, resulting in a low concentration of coal washing wastewater, and less ash content, so the treatment effect is better, basically closed loop. However, there is little research on the treatment technology of high-concentration coal washing wastewater in these countries and there is no very mature experience. The coacervation agent used in coal washing wastewater treatment is rather single, mainly organic polymer flocculant. However, due to the price of the flocculant Higher, the cost of processing alone is also larger. Therefore, the domestic treatment of coal washing wastewater can not copy the experience of foreign countries should be combined with the actual situation in our country, research and development of efficient and low consumption of processing technology to meet the current booming coal chemical production needs.

2, domestic coal washing wastewater treatment status quo

In recent years, although the coal washing wastewater treatment system of the coal preparation plant has been transformed in our country, there are still many problems in the treatment of coal washing wastewater because of the large amount of raw coal in our country and the imperfect coal preparation process. At present, adding coagulant and flocculant to treat coal washing waste water is a kind of common treatment method in our country. The used medicaments mainly include inorganic salt coagulant, organic polymer flocculant and inorganic polymer flocculant. Commonly used inorganic salts coagulant mainly aluminum salt, iron salt and so on. Inorganic salt coagulant dosing alone is generally difficult to ensure the treatment effect of coal washing wastewater. Commonly used organic polymer flocculant mainly polyacrylamide or derivatives of polymers or copolymers. The actual project is often used inorganic salt coagulant and organic polymer flocculant with or use of polymeric ferric sulfate, polyaluminum chloride, polysilicate, polyaluminum chloride and other inorganic polymer flocculant treatment of coal washing wastewater .

Li Ruiqin In order to investigate the sedimentation effect of three different flocculants, lime, basic aluminum chloride and polyaluminium chloride, on the slime water of the coal preparation plant, comparative experiments were made on the sedimentation of slime water with the same dosage of three agents. The experimental results showed that under the same conditions, the slurry of PACF added with PACF precipitated fastest and the concentration of supernatant was the lowest.

Baizhizi use of ferrous sulfate as raw material, developed by the solid-phase chemical reaction of a new type of iron-based inorganic polymer water purification agent polyoxyl sulfate and polyacrylamide (PAM) combined use of coal washing wastewater treatment, Particle agglomeration effect is good, settling rapidly, the water quality is relatively clear after treatment, the light transmittance of 83%, can be recycled; slime by-product, but also can be used to produce briquette, saving adhesives and additives.

Li Ya-feng and others carried out carbide slag-polyacrylamide (PAM) treatment of coal washing wastewater experimental study. Experimental results and practical engineering application show that the use of calcium carbide slag with polyacrylamide, coal washing wastewater has better coagulation effect. When the polyacrylamide dosage reached 20mL, the water separation rate reached 40%, the specific resistance of the sludge dropped to 1.8 × 1010m / kg, and after treatment, the indicators of coal slime water can meet the national emission standards, and can Meet the water requirements of coal washing process. The experiment also found that polyacrylamide alone did not flocculation of coal washing wastewater, but with the use of carbide slag has flocculation, which shows that carbide slag in the washing of coal water coagulation plays a very important role.

Li Chunxiao et al. Studied a kind of natural modified plant cationic flocculant which takes plant wood flour as raw material and is grafted and copolymerized with etherifying agent to easily degrade and produce no secondary pollution. The results show that turbidity, CODCr and solid suspended solids removal rate of coal washing wastewater can reach respectively at pH = 6-8, the dosage of the flocculant and polyaluminum are 10mg / L and 5mg / L respectively 96.8%, 69.3%, 97.9%.

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