1 Present situation of mine water treatment technology
(1) coagulant and mixed form.
Aluminum salt or iron salt coagulant is usually used to purify mine water containing suspended solids. At present, polyaluminum chloride is commonly used, and polyaluminum iron is also useful. The flocculant mainly uses polyacrylamide.
Coagulant mixing methods in mine water treatment usually adopt water pump mixing, pipeline mixer mixing and mechanical mixing, among which water pump mixing is more commonly used. ?
(2) precipitation and clarification.
Mine water purification treatment adopts sedimentation tank or clarifier as the main treatment unit. The sedimentation tank adopts horizontal sedimentation and inclined tube (plate) sedimentation, which has low energy consumption, but there are some shortcomings such as large area of treatment facilities, easy blockage of precipitated sludge and poor sludge discharge. Mechanical accelerated clarifier and hydraulic circulating clarifier are both water treatment facilities integrating coagulation and sedimentation. Hydraulic circulating clarifier has the advantages of low energy consumption, strong load impact resistance, simple facility maintenance and convenient operation. Mechanical accelerated clarifier occupies a small area, but it consumes a lot of energy and equipment maintenance, and its treatment effect is not as good as that of hydraulic circulating clarifier in practical application. Air flotation tanks are also used, but they are rarely used. ?
(3) filtering.
The commonly used filtration facilities for mine water treatment include fast filter and gravity valveless filter. The pipeline and valve system of the fast filter is complicated, and the backwashing operation is complicated; Gravity valveless filter can automatically backwash, with simple operation and convenient management and maintenance. Filters usually use double-layer filter material, which does not contain bituminous coal and quartz sand. ? Add the safety engineer website to your favorites.
(4) disinfection.
Mine water must be disinfected like domestic water after purification. Chlorine dioxide is generally used for disinfection, and sodium hypochlorite and liquid chlorine are used less. ?
(5) Mine water mainly contains suspended solids dominated by coal dust, which has the characteristics of black color, loose alum flower structure formed after dosing and slow settlement. After many mine water treatment projects containing suspended substances are put into production, the designed water quantity and quality can not meet the design requirements, mainly because of insufficient reaction of advection or inclined tube sedimentation tanks and large surface load. On the other hand, the lift pump, water supply pump, dosing equipment, disinfection equipment, control system and ancillary buildings are all designed according to the designed water treatment capacity, which will cause great waste of engineering investment. ?
(6) The concentration of suspended solids in mine water of different coal mines is quite different, which determines that the types and quantities of coagulants added are also different. Due to improper selection and addition of coagulant, some coal mines can not achieve the expected effect after water treatment. Because it is impossible to monitor the water quality, treatment flow, dosage and pool position in time, many mine water treatment projects only have pumps and simple dosing devices, and the water quantity and quality after mine water treatment cannot be guaranteed. ?
(7) The mining machinery used in underground coal mine production needs emulsified oil and engine oil, and the oil substances enter the mine water. Conventional coagulation, inclined tube sedimentation and filtration technology can not effectively remove oil substances from mine water. ?
2 Yaoqiao coal mine water purification treatment process
The design treatment capacity of Yaoqiao coal mine water treatment project is 9000t/d, and the treated water is used as production and bathing water, and the mixed reaction, clarification, filtration and disinfection processes are adopted. The process is shown in figure 1. ?
Figure 1 Mine Water Treatment Process
Mine water is lifted by the underground drainage pump to the pre-sedimentation regulating tank, flows into the suction well by gravity, and then enters the hydraulic circulation clarifier by the lifting pump. Coagulant is added before the pump and flocculant is added after the pump. The effluent from the hydraulic circulating clarifier flows into the gravity valveless filter, and the effluent from the filter flows into the clear water tank by gravity. Chlorine dioxide is added in front of the clean water pool for disinfection. The backwashing water in valveless filter flows into the water collection tank by itself, and is lifted by the submersible sewage pump to the pre-sedimentation regulating tank, so as to improve the utilization rate of mine water resources. The slime water in the mud bucket in the hydraulic circulating clarifier is regularly discharged to the slime concentration tank, and after concentration, it is lifted to the filter press system by the slurry pump for treatment. ?
Characteristics of well water treatment technology in No.3 mine
According to the characteristics of mine water quality, the technical parameters of mine water treatment project in Yaoqiao Coal Mine are determined, which are lifted to the hydraulic circulating clarifier once, and then enter the subsequent treatment structures by gravity. The effluent quality is stable and reliable, with less power equipment and low energy consumption.
The technology of combining hydraulic circulating clarifier with gravity valveless filter is adopted, and the main treatment structure is reinforced concrete structure, which has the characteristics of small floor space, long service life, low engineering investment, simple technology, convenient operation and management, and low operating cost.
The floating oil in mine water is unstable after adding electrolyte coagulant, and it can be effectively removed by being intercepted and adsorbed by a large number of returning sludge in the hydraulic circulating clarifier. ?
The mine water purification treatment system in Yaoqiao Coal Mine has realized the whole process monitoring of automatic dosing, automatic sludge discharge and automatic backwashing, including electrical control system, upper monitoring system, PLC system and instrument detection system. The instrument detection system includes continuous and automatic detection of dosing flow, treatment flow, water tank level and dosing tank level, turbidity of inlet and outlet water, etc. ?
4 benefit analysis?
4. 1 Economic benefit analysis
Before the implementation of the mine water treatment project in Yaoqiao Coal Mine, the production and domestic water of the whole mine mainly depended on pumping underground deep well water. After the implementation of the mine water treatment project, the annual purified mine water volume is 3.24 million t?
(1) Groundwater pumping cost and annual pumping cost. The annual pumping capacity of deep well water is 3.24 million t; The annual pumping cost is 206 1 10,000 yuan; The pumping cost is 0.636 yuan/t.
The calculation basis is: the water resource fee is 0.23 yuan/ton; The electricity price is 0.52 yuan/kWh; Sewage charges 0.08 yuan/ton; There are 0/5 water source wells/kloc, with an investment of 280,000 yuan (including 0/50,000 yuan for drilling wells and 0/30,000 yuan for civil engineering, equipment and installation), and the service life of the water source wells is 20 years. Each water source well has a lifting pump 1 set, power 15kW, daily operation 15h and flow rate of 40t/h; 2 operators for each water source well, with the labor wage of 900 yuan/month; The annual maintenance cost of each water source well is 654.38 million yuan. ?
(2) Mine water treatment cost and annual mine water purification and utilization cost. The annual treatment capacity of mine water is 3.24 million t; The annual cost of mine water purification and utilization is 745,000 yuan; The water treatment cost is 0. 19 yuan /t (excluding water supply and electricity charges).
The calculation basis is: the project investment is 2.53 million yuan, including 940,000 yuan for civil engineering, 6.5438+0.6 million yuan for equipment engineering, 350,000 yuan for installation engineering and 6.5438+0.8 million yuan for other expenses; Civil engineering depreciation for 40 years, equipment depreciation for 20 years; The annual maintenance fee of the equipment is 2% of the equipment investment; The electricity price is 0.52 yuan/kWh, the effective power of mine water treatment is 42kW, and the effective power of water supply is 30kW；; 8 operation and management personnel, with an artificial salary of 900 yuan/month; Polyaluminum chloride (PAC)2000 yuan /t, dosage 30 mg/L; Polyacrylamide (PAM) is 20,000 yuan /t, and the dosage is 0.3 mg/L; The water treatment capacity is 9000 tons/day, and the annual effective production days are 360 days?
(3) Annual economic benefits.
Annual economic benefit = annual fee for pumping deep well water+annual fee for sewage discharge-annual fee for purifying and utilizing mine water =206. 1+25.9(0.08 yuan/t× 3.24 million t)-74.5 = 1.575 million yuan. ?
4.2 Environmental benefit analysis
After the purification treatment of mine water in Yaoqiao Coal Mine, the emission of suspended solids can be reduced by 630t per year, and the environmental benefits are obvious.
4.3 Analysis of social benefits
The purified mine water can be used as production and domestic water, which can reduce the exploitation of underground deep well water, save groundwater resources and protect the natural balance between groundwater and surface water in mining areas. It can solve the environmental problems caused by over-exploitation of underground deep well water and improve the relationship between coal mining enterprises and surrounding villages; It can solve the contradiction between the increasing water consumption and the increasing shortage of water resources in mining areas, ensure the normal production and operation of coal mining enterprises, improve the comprehensive benefits of coal mining enterprises and promote the sustainable development of mining areas. ?
5 conclusion
The annual discharge of mine water in China is about 2.2 billion tons, but the resource utilization rate of mine water is only about 20%. A large amount of untreated mine water is discharged directly, which not only pollutes the environment, but also wastes valuable mine water resources. China's coal mining enterprises are mostly distributed in arid and semi-arid areas, and water resources are relatively poor. About two-thirds of coal mines are seriously short of water, which restricts the sustainable development of coal production and mining economy to some extent. ?
The mine water purification treatment technology in Yaoqiao Coal Mine is a key technological innovation project during the Ninth Five-Year Plan period. Its application in other coal mine fields will have broad promotion prospects.