October 26, 2020

Dressing plant tailings facility design

Beneficiation plant tailings facility design (mill tailings disposal design) to very low levels or content concentrator beneficiation process, while high output and temporarily unable to recover the valuable minerals transport, engineering design process. The main content of the design is the process and facility design.
The design principles mainly include: (1) Must comply with relevant national guidelines, policies and laws. Tailings shall not be discharged into rivers, lakes and seas. If they cannot be comprehensively used, they should be properly stored; (2) Layout according to local conditions and reasonable layout. The tailings pond should be as close as possible to the concentrating plant. The total effective storage capacity of each tailings pond should meet the requirements for the amount of tailings to be piled up within the production period of the concentrator; (3) the use of wasteland and barren land, which does not occupy, occupy and occupy the farmland, and Consider the possibility and rationality of reclamation after sealing; (4) The tailings water should be reused as much as possible for beneficiation, and the discharged wastewater must meet the discharge standards stipulated by the state and relevant departments.
The tailings discharged from the concentrator should be concentrated and transported into the tailings pond. The overflow water discharged from the concentration process is reused by the concentrator, and the clarified water discharged from the tailings pond is treated for beneficiation production or discharge. Whether the concentration process is required, usually according to the amount of tailings discharged from the ore dressing plant, tailings concentration and grain size, the distance between the concentrator and the tailings pond, the height difference and the topographical geology, etc., are determined by technical and economic comparison. If the concentration process can reduce the tailings flow to the tailings pond, the overflow water will be reused, but the construction cost of the concentration tank will increase. Iron ore concentrator disposed generally more concentration step. Due to the development of the theory and technology of high-concentration solid material hydraulic conveying, long-distance tailings tend to adopt high-concentration transportation. The setting of the tailings pumping station and the returning pumping station can be set according to the distance between the concentrator and the tailings pond, the height difference and the terrain along the line. Two or more seats can be set. When the coarse tailings are used as the filling material for the underground mine, a tailings classification system is added to the facility. The coarse tailings classified by the hydrocyclone are transported to the underground for filling, and the fine tailings are sent to the tailings storage. The facility design includes five components including tailings concentration tank, tailings conveying system, tailings pond, tailings water treatment and return water system.
The concentration tank is designed according to the sedimentation speed and concentration characteristics of the tailings, so that the clarified overflow water of the concentration tank reaches the water quality requirement of the ore dressing water, and the discharge concentration reaches the requirements of tailings transportation or tailings dam. The sedimentation velocity and concentration characteristics of the tailings are determined by experiments or determined by reference to the actual operating parameters of similar tailings concentration tanks. Usually, the concentrator is selected according to the calculation result. In order to achieve high concentration (usually 40% to 60% by weight), a high-efficiency concentrator is specially designed, and a flocculant is added before the tailings enter the concentration tank. Generally, there is no concentration tank for equipment. The conveyor system consists of tailings ducts, tanks, tailings pumping stations and accident tailings facilities. There are two kinds of transport: self-flow and pressure transport. When the terrain allows, use self-flow conveying as much as possible. The pipe and groove sections are determined by hydraulic calculation. The design flow generally has a fluctuation of about 10%. The front pipe, trough section and hydraulic gradient before the tailings concentration tank meet the requirements of not exceeding the critical flow rate at low flow rates and passing at high flow rates. In addition to the anti-freeze requirements, the flow cell is generally set up, not the equipment slot. Reinforced concrete rectangular grooves are often used, and the grooves are lined with shale-resistant materials such as cast stone when needed. The pipeline can be set up, semi-exposed or buried, and the latter is used in cold areas. Cast iron pipes and steel pipes are commonly used in pipes, and plastic pipes can also be used. In order to improve the anti-wear ability, steel pipes or other wear-resistant pipes of lining stone are used. Usually a spare pipe is set up, but long-distance, high-concentration tailings transport, no equipment is used, and the rheological characteristics of the tailings are controlled before the tailings enter the pipeline, limiting the laying slope of the tailings pipe and taking other necessary Safety measures to ensure that the pipeline works properly. The tailings pumping station includes the slurry pump and its ancillary facilities and pipelines.
Centrifugal slurry pumps are commonly used for slurry transportation; high-lift, long-distance lifts use oil-isolated mud pumps , piston pumps, plunger pumps or water-isolated pumps. In order to adapt to the fluctuation of tailings volume and meet the requirements for the increase of the slurry pump lift due to the continuous increase of the tailings dam, the slurry pump speed control device can be used to change the pump speed. Slurry pumps are generally equipped with spare pumps. Accident tailings facilities include accident tailings ponds and their cleaning facilities. The accident tailings pond is generally located near the lowest point of the tailings pumping station and the “U” shaped pipe section of the conveying pipe to accommodate the tailings discharged when the slurry pump fails, so as not to pollute the environment. The accident tank volume of the tailings pumping station usually adopts the normal pulp volume of 10-20 min, the sum of the pulp volume of the empty pipe section and the emptying volume of the pulp pond; the volume of the accident tank of the U-shaped section of the tailings conveying pipe, and the emptying pipe in the pool The calculation is determined by 2 to 3 times the volume of the segment. The accident pool is preferably hydraulically cleaned. If using a shipping machine or manual cleaning, the accident pool must be divided into at least two compartments and the volume should be appropriately increased. The tailings pond tailings volume is determined according to the design scale and service life of the concentrator. Generally, small and medium-sized concentrators consider a tailings pond, and its storage capacity should accommodate all tailings within the service life of the concentrator. If the concentrating plant has a large design scale, long service life, or local terrain conditions, it can be divided into several Tailings warehouse, built in phases to reduce initial investment.
Tailings dams generally consist of initial dams (basic dams) and stacked dams. In the initial dam, dam types such as earth dams, rockfill dams or earth-rock dams are used. Stacking dams generally use tailings dams. When the tailings are too fine to be piled up, the earth and rock materials are used to raise the dam downstream, or the initial dam is built to the final dam height. The tailings accumulation dam has three modes: upstream, neutral and downstream. In the United States, the former Soviet Union, and China, upstream dams are used; in Canada, downstream and mid-line are used. The storage capacity of the dam height in different periods of use shall meet the following conditions: (1) storage design tailings, the initial dam generally adopts not less than the tailings amount after half a year of production; (2) the amount of flood storage; (3) freezing The area accommodates the ice and the volume of the ice under the frozen period; (4) the requirement to clarify the tailings water. The design of the tailings dam shall be based on the specification of the minimum safety super-high and minimum beach length, seepage and stability calculation of the sedimentation beach, and meet the structural requirements. Drainage structures usually use drainage wells (or chutes)-drainage pipes (or tunnels), and spillways can be used when conditions permit, and flood drainage measures such as upstream dams or surrounding flood trenches can be built. The size of the structure is determined according to the flood control calculation and hydraulic calculation. The reinforced concrete structure is mostly used, and the section is designed according to the specifications. The backwater facility consists of a return pump house, a pipeline and a return pool. The designed backwater volume is determined according to the maximum amount of water returned by the beneficiation process and the possible backwater volume calculated from the balance of the tailings pond water. The design of the tailings pond backwater needs to fully consider the potential energy of the water in the reservoir to save energy. Usually, after the clarification distance of the tailings in the warehouse, the shipbuilding or cable car type return pump house will be built. If the pump room outside the dam is used, a fixed pump room shall be provided near the exit of the tailings reservoir drainage structure.
Tailings water treatment tailings water contains residual ore dressing agents, soluble harmful substances contained in ore and tailings particles, which need to be treated before they can be discharged or reused. The tailings pond has the functions of “self-cleaning” such as clarification, oxidation and biochemistry. The tailings water of many concentrators can meet the emission standards or reuse requirements after passing through the tailings pond. High pH, containing a large number of particles or colloidal dispersion containing S, F and heavy metal ions tailings water can be adding an appropriate amount of pH adjusting agent, flocculant or other chemical agents before entering the tailings processing tailings. Agents used are sulfuric acid, lime, aluminum salts, iron salts, such as bleaching powder supplemented by high-molecular flocculant. The cyanide lean liquid of the gold smelting plant usually adopts the process of acidification aeration and sodium hydroxide absorption, first recovers sodium cyanide, and then further treatment with liquid chlorine, bleaching powder and sodium hypochlorite to reach the discharge standard. The United States, Canada, China and other countries also use SO 2 or air to treat cyanide-containing tailings water.

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