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1. Ventilation and dust removal design of crushing and screening workshop
Metal ore, in particular non-ferrous metal mines, which are mostly metallic mineral dust mixed dust, free silica content is generally more than 10%, some as high as 90%. In particular, some gold mines are mostly produced in quartz veins, and the free silica content is generally above 60%. According to this situation, according to the requirements of national emission standards, the emission concentration of the ventilation and dust removal system should not exceed 100 mg / m 3 (the allowable concentration of dust emission of free silica content less than 10% is 150 mg / m 3).
The concentration of dust in the air and the dispersion of dust are important factors in measuring the harm of dust to the human body. According to the hygienic regulations, the maximum allowable concentration of dust containing 10% or more of free silica in the working dust is 2 mg/m3 in the working zone of the workshop, and contains less than 10% of free = silica dust. The maximum allowable concentration is 10 Mg/m3.
According to relevant information, most of the dust particles deposited in the lung cells are 0.2 to 2 microns in diameter. Therefore, it is generally believed that dust less than 5 microns is the most harmful to the human body. The dust and dispersion generated by the crushing and screening workshops in the plant are not necessarily the same at each dust production point.
1) Humidification of material humidification materials is an important measure for dust prevention. If production permits, the ore should be humidified as much as possible. The method of humidifying the material is generally humidified by a nozzle.
The Wu'an-4 sprayer produced by Wuhan Plastics 12 Factory is better and can be selected according to its performance. Nebulizer portion disposed generally provided above the belt conveyor into the crusher before and after crushing, should be higher than mine blocking plate. The number varies depending on the width of the belt, one belt of less than 800 mm wide is provided, and two belts of 1000 to 1400 mm width are provided. In addition, the spray direction of the nozzle should be paid attention to during installation. The nozzle is placed behind the dust cover to prevent the water mist from being sucked into the dust cover.
2) Equipment sealing and ventilation (mechanical dust removal) The dust-tight point sealing is a very necessary measure to suppress dust diffusion. Although a mechanical dust-discharging system is sometimes designed, the sealing effect is not strict and the desired effect is not achieved. Of course, it is only sealed and cannot cause a certain negative pressure in the sealing cover, and a good effect cannot be achieved.
The airtight part is partially sealed, the whole is sealed, and the large volume is sealed (or called a chamber type closed). The airtight cover should be smart and rigorous and easy to operate to maintain its vitality. There must be sufficient volume in the hood to buffer the positive pressure created by the disturbance of the airflow. The wind speed of the dust cover of the airtight cover should not be too large, otherwise a large amount of dust will be brought to the dust removal system to increase the burden of the purification equipment.
Generally, it is selected according to the following data: the fine dust of the screen is v=0.4~0.6 m/s, that is, the dry and fine materials are meters/second. Crushed or ground fine powder v2 m / s, that is, medium and finely divided materials 1-2 m / s. The coarse material is v3 m/s, ie 2 to 3 m/s. The shrinkage angle of the cover should be 600. The position of the cover on the tape conveyor should be from the bottom of the material chute to the center of the exhaust hood equal to 1.5 (B+6), B is the width of the tape, and b is the length of the side of the exhaust hood along the length of the tape. Beneficiation plant equipment exhaust amount can be professionally designed manual calculations.
3) Mechanical dust removal design
The vertical and inclined tubes of the wind speed in the A dust removal duct are 8 to 15 m/s; the horizontal tubes are 18 to 25 m/s.
B. Dust removal duct position The dust removal duct should not be in the horizontal position as much as possible, but should be inclined at not less than 60°. If necessary, a sweeping port should be provided on the pipeline.
C duct selection According to the size of the pipe diameter, the thickness of the duct can be selected between 1.5 and -3 mm.
D Dust purification equipment selection The initial concentration of dust produced by the concentrator is about 500-1000 mg/m3, which needs to be purified to reach the national allowable discharge concentration before it can be discharged. The efficiency of the purification equipment required by the country's permitted emission concentration is listed in Table 31.5.2.
Dust removal and purification equipment has developed rapidly in recent years and has many types. The cyclone dust separator separated by centrifugation is generally 60-80% because it is not efficient. It is rarely used alone. It is used only when the concentration of dust is large and the level of dust removal does not reach the discharge effect. Dust removal. Such dust collectors include CLP/A, CLP/B, CLT, diffusion, multi-tube dust collectors, and the like.
Filter bag dust collector, high dust collection efficiency, generally 95 to 99%, commonly used pulse bag filter, this type of dust collector organic control and electronic control, according to the national standard map produced by such dust collector, its The pressure of the pulse valve requires compressed air of 5.88lO5~6.86lO5pa, which can be achieved by air compressor stations in general factories.
However, after being sent through the pipe network, the pressure is difficult to guarantee. In order to solve this practical problem, the Ventilation Laboratory of Beijing Nonferrous Metals Design and Research Institute has developed a low-voltage pulse bag filter, which has been commissioned by the relevant factories. This type of dust collector solves the problem of reduced pressure of compressed air, which can be 1.96105～2.94. Pulse cleaning is performed at lO5 Pa.
There is also a small flat bag filter that uses mechanical vibrating to clean the ash. It is used on small mining bins and is very flexible when placed directly on the belt transfer point.
In addition, there are bag dust collectors for anti-drying, bag dust collectors for reverse blowing, and rotary backwash bag filters. There are also many types of wet dust collectors, and CLS type water film dust collectors are often used for dust removal in concentrators.
In the past few years, a gold mine has improved the use of this type of dust collector and achieved better results. That is, the tangential water spout is cancelled, a central tube is added, the sprayer is installed on the central tube, and a mist plate is installed on the upper part, which not only solves the problem that the fan brings water but also improves the dust removal effect. The hot air room of Beijing Nonferrous Metals Design and Research Institute has such improved drawings.
When the amount of air is large, the low-pressure venturi dust collector designed by the hospital can also be used. The efficiency of the dust collector can reach 95%, the air volume ranges from 5,000 to 50,000 m3/h, and the resistance loss is 1471.5 Pa (150 mm). Water column) below. The wet dust collector is mainly used in mines with sufficient water source, and the underflow mud of the dust collector can be easily discharged or concentrated. If the underflow is not processed, the operation of the precipitator is often disabled.
The dust collected by the dry dust collector should also be properly treated, such as being discharged to the belt and in the mine bin. Otherwise, the screw conveyor or the centralized wind suction system is concentrated to handle the dust. Regardless of the dry or wet dust collector, a better ash (pulp) valve should be selected. The dry double flap needs further improvement in structure, and the rotary lowering valve is also better.
The lower part of the wet scrubber currently uses a conical water seal and a simplified S-shaped water seal. Dust-proof work in the dust-proof workshop of the workshop, in addition to a good ventilation and dust removal system, management work and hydraulic cleaning are also important links. The design should be put forward to the waterway professional, and the water should be flushed with water.
2. The main building of the main plant is the grinding and floating workshop, including the powder mine, grinding, flotation and other sections.
The upper part of the powder ore warehouse needs to be ventilated, and the lower mine silo discharge port to the belt conveyor. Generally, the drop is small, and the dust emitted is not large. If it is properly sealed, there is no mechanical exhaust system. If a dust removal system is required, the flat bag dust removal unit can only be installed at the belt transfer point.
Between the grinding and flotation spans, it is preferable to have a sunroof, which can eliminate the residual heat of the ball mill motor and the smell of the medicament between the flotation spans. The agitation tank of the preparation room should be sealed and exhausted, and generally not treated, and discharged directly into the atmosphere. Some of the drug delivery rooms are located in a separate room.
In order to control the harmful gas emitted by the medicament, the drug delivery device is often arranged in the fume hood, and the air volume of the fume hood is calculated according to the open door or orifice area and the inlet wind speed. The wind speed of the harmful gas containing cyanide is v = l ~ 1.5 m / s, and other harmful gases v = 0.7 ~ 1.0 m / sec. The room of the drug delivery device should also have an overall ventilation facility, and the ventilation should be no less than 6 times/hour.
The high-voltage switch room, electrical control room, transformer and low-voltage power distribution room, instrument room, etc. in the grinding and floating plant are often arranged in the middle between grinding and flotation. The high-voltage switch room shall be provided with accidental ventilation of not less than 12 times/hour. In the electric control room, winter heating should be provided in the heating area, and appropriate cooling and ventilation facilities should be considered in the non-heating area. The instrument control room should have air conditioning facilities, and the standards can be based on process requirements.
With the development of science and technology, computer technology is gradually applied to the beneficiation process, and the air conditioning of the computer room and its corresponding precision instruments should be designed according to the process requirements. 3. The drying of the drying workshop (including the filtration section) is dry and desiccated, with rotary kiln drying and spiral drying. The rotary kiln has direct fire and indirect heating drying of flue gas.
Since the extracted flue gas contains a large amount of dust (about 15 g/m3 or more), two stages of dust collection are used: the first stage uses a dry cyclone (should be insulated), and the second level generally Use a wet dust collector (if the bag can withstand high temperatures, you can also use a bag filter). The wet dust collector should be treated with anti-corrosion treatment. Due to the relatively high temperature of the flue gas, the lead-lead water film dust collector is currently used. Some concentrates do not contain sulfur, which is easy to handle.
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