environmental protection is so strict, industrial and mining enterprises commonly use dust removal equipment to understand?!
, for industrial and mining enterprises, dust pollution is one of the main environmental protection problems at present. Many enterprises have been rectified by environmental supervision due to the dust problem. If they have money or not, they must go to dust removal equipment.
today, Qingdao Hanchang will come to share with you what dust source industrial and mining enterprises have? What are the common dust removal equipment? What are the characteristics of each? How to select? In order to help industrial and mining enterprises choose more suitable dust removal equipment.
01
industrial and mining enterprises?
industrial and mining enterprises is basically productive dust, mainly from crushing and grinding systems, transfer systems and secondary dust.
(1) Dust generation from crushing and grinding system
crushing and grinding system is the key dust source in industrial and mining enterprises, with high dust production intensity and fine dust particle size. The dust production mechanism mainly includes the following four aspects:
① Falling mineral dust is dusted by air shear. The greater the falling height, the higher the velocity of ore particles, the more serious the dusting;
② When the material moves, it drives the air around it to flow, resulting in induced dusting;
③ During the screening process, the material vibrates rapidly with the vibrating screen in the direction perpendicular to the screen surface, so that the ore particles are mixed with the air to form dust;
④ In the process of crushing and grinding, the air in the ore gap is squeezed out violently, resulting in shear compression, and the dust is discharged from the feeding port under high-speed movement, resulting in pollution.
(2) Dust generation of transfer system
transfer system is mainly in the receiving point, unloading point and transportation process of the belt conveyor. The dust generation mechanism at both the receiving point and the unloading point is due to the dust caused by the air shear when the material falls due to the height difference. During transportation, the belt in the middle section will vibrate up and down and swing left and right, resulting in intermittent instantaneous extrusion of the material, and the air in the material gap carries dust to be squeezed out. When the belt joint passes the idler, it is also easy to raise dust due to vibration. In addition, the materials adhered to the belt will also be scattered and dust will be generated during the return journey of the belt.
(3) Secondary dust emission
secondary dust may be produced by rolling up the mineral dust settled on the ground by wet spraying due to liquid evaporation during ventilation or personnel walking, or may be produced by vibrating dust removal of dust collector or back mixing of ash hopper.
02
Industrial and Mining Enterprises Commonly Used Dust Removal Equipment and Performance Characteristics
According to the dust removal mechanism, the dust collector can be divided into mechanical dust collector, filter type dust collector, wet dust collector and electric dust collector. However, in the actual selection, due to the need for additional wet dust collector with water and diversion facilities, and other dust collector design is different, it can also be divided into dry dust collector and wet dust collector according to whether the use of liquid dust or dust.
industrial and mining enterprises mainly include "bag filter, dry electric dust collector and cyclone dust collector, and wet dust collector mainly includes spray wet dust collector, impact dust collector, Venturi wet dust collector, etc 」.
(1) Bag filter
bag filter is a widely used dry dust removal equipment. In this kind of dust collector, the dust-containing gas passes through the filter cloth in one direction, and the dust particles are trapped by the filter material on the intake side, so that the clean gas flows out from the other side of the filter material, and the dust particles on the filter material are removed by natural or mechanical methods.
bag filter has high dust removal efficiency, strong adaptability to dust collection of different properties, flexible air volume, simple structure and stable work, so it is often used as the preferred dust removal equipment for industrial and mining enterprises. However, in the production process, the actual air volume exceeds the design air volume, which leads to increased filtration resistance, or mechanical wear and improper operation, which will greatly reduce the filtration efficiency and service life of the bag filter.
In terms of production practice, bag filters are widely used in dust suppression points of various dust sources in industrial and mining enterprises:
In the raw ore bin, powder ore bin, can be used to seat bin type bag filter, combined with meet the requirements of the fan gas collection, can achieve better dust suppression effect;
crushing system adopts a bag filter, a semi-closed collection device can be used in the dust source, and a reasonable configuration of the airflow conveying pipe network system, so that the dust-containing gas emission concentration reaches the national standard;
A dust collecting cover is arranged in the fine crushing equipment, and the dust-containing gas is collected by a fan and transported to a bag filter for dust removal. It can also be combined with a screening workshop and closed, and the treatment effect can also reach the standard. When the dust particles produced in the crushing process have recycling value, the ash cleaning port of the bag filter can be connected with the feeding bin of the previous process through the belt, so as to reduce dust emission and improve economic benefits.
(2) electrostatic precipitator
Electrostatic dust removal is the use of up to tens of thousands of volts or even hundreds of thousands of volts of high-voltage generated by the strong electric field to ionize the gas, and then the dust is charged, and the charged dust is collected and separated from the airflow.
electrostatic precipitator are:
① The dust removal efficiency is high, and it also has a good dust removal effect on the mineral dust of 0.1μm particle size;
② Large air volume;
The resistance loss is small, and the pressure drop of the gas through the electrostatic precipitator is generally 150-300MPa;
The special structure of the electrostatic precipitator can capture the strong corrosive dust particles;
⑤ Low operating costs.
disadvantages are:
① High cost of one-time investment, large steel consumption and large area;
② The scope of application is limited by the specific resistance of dust;
③ High requirements for manufacturing, installation and operation level.
Generally speaking, the scope of application of electrostatic precipitators is as follows:
① High air volume, high temperature flue gas and high dust concentration (40 g/m3) gas;
② Dust with fine particle size (less than 0.14 μm);
③ specific resistance at 104-1011Ω · cm;
④ For flue gas with high humidity or dew point temperature, heat preservation or heating measures shall be adopted;
⑤ For corrosive materials, electric precipitator with special structure and good anti-corrosion performance should be selected;
⑥ The wind speed of the electric field is generally in the range of 0.4-1.5 m/s.
electrostatic precipitator in China's industrial and mining enterprises is not very high, mainly due to the high purchase cost, and need to be equipped with experienced staff to operate, otherwise prone to failure and affect production.
(3) Cyclone dust collector
cyclone dust collector is a dust collector that makes the dust-containing gas enter the device along the tangential direction and uses centrifugal force to separate the dust particles from the gas to achieve the purpose of purification. After entering the dust collector from the inlet of the dust collector along the tangential direction, the dust-laden airflow rotates downward along the outer wall, reaches the bottom of the cone, turns upward, rotates upward along the axis, and is discharged from the exhaust pipe. Dust is thrown to the outer wall under the action of centrifugal force, and falls into the ash hopper along the wall under the combined action of downward swirling airflow and gravity.
cyclone dust collector are as follows:
① There are no moving parts inside, which is convenient for maintenance and production management;
② In the case of the same air volume, the volume is small and the price is cheap;
③ It can be installed vertically as a pre-dust collector;
④ When multiple parallel processing large air volume, the efficiency and resistance are not affected;
⑤ The valuable dust can be recovered after dry cleaning;
⑥ When special materials are used, it can handle high temperature and highly corrosive dust-containing gases.
disadvantages are:
① The leakage of ash discharge valve will seriously affect the dust removal efficiency;
② When dealing with high concentration or abrasive dust, the wear is more serious;
③ When used alone, the dust removal efficiency is not high;
④ When the simplified diameter increases, the dust removal efficiency decreases, so the air volume of a single dust collector is limited.
(4) spray dust collector
spray dust reduction technology is a simple and economical method to control open dust, and the nozzle of mist flow with good dust reduction effect is the key of spray technology.
In the process of material transportation and treatment, water spraying and humidifying materials can reduce or eliminate the generation of dust, and spraying the dust generated at the dust location can suppress the dust, so this technology is suitable for crushing, screening, belt conveyor transfer points and other occasions with fine dust and large dust. Can also use the impact of compressed air resonant cavity to generate ultrasonic, the water mist into dense fine droplets, so as to capture and condense fine dust, to achieve on-site dust suppression.
For mineral dust with a certain hydrophobicity, dust reducing agent can be added in the spray to increase the wettability of the aqueous solution to the mineral dust, so that the solid-liquid interface replaces the original solid-gas interface of the mineral dust particles, thereby improving the dust reduction efficiency.
(5) Impact dust collector
impact dust collector is a dust collector that relies on the kinetic energy of the airflow itself to impact the liquid surface and arouse water droplets and splashes.
impact dust collector:
① impact type dust collector for industrial waste gas in those high humidity, large emissions, dust content of the gas has a good purification dust;
② is especially suitable for purifying non-fibrous, non-corrosive, dust-containing gases with a temperature not higher than 300 ℃;
③ Good results can be obtained in the dust removal used in the viscous quicklime transportation system;
④ impact desulfurization dust collector installed in the induced draft fan, can extend the life of the fan;
⑤ low price, easy installation, water can be recycled, adding alkaline water in the pool, can play a desulfurization effect;
⑥ impact water bath desulfurization dust collector internal structure using Taishan granite, erosion resistance, corrosion resistance, high temperature resistance, long service life;
The dust removal efficiency is high, no secondary pollution;
⑧ Small investment, low operating cost; wide range of adaptation and strong adaptability.
(6) Venturi wet dust collector
Venturi wet dust collector is a high-efficiency wet scrubbing dust collector, which can be used for high-temperature flue gas cooling, and can also be used to purify gases containing micron and sub-micron dust particles and toxic and harmful gases that are easily absorbed by the scrubbing liquid.
Venturi dust collector are:
① dust removal efficiency up to 99%;
② has a good effect on the elimination of fine dust particles below 1μm;
③ simple structure, easy maintenance, low cost;
④ can also be used for the need to defog, cooling, absorption, evaporation and other occasions.
its shortcomings are mainly large pressure loss and more water consumption.
The dry dust collector does not need water as the dust removal medium, and has a wide range of use. The dry powder dust discharged is conducive to centralized treatment and comprehensive utilization, so it accounts for more than 90% of all dust removal systems. However, the system also has the disadvantages of being unable to remove the toxic components in the gas and easily causing secondary dust when it is not handled properly.
wet dust collector are:
Simple equipment, small footprint, low investment, reliable work;
② In the case of the same energy consumption, the efficiency is higher than that of the dry dust collector;
③ at the same time with dust, cooling, humidification effect, can handle flammable and explosive, high temperature, high humidity, high viscosity and harmful gases. At present, in the design of industrial and mining enterprises, due to the convenient maintenance of wet dust collector and the above advantages, wet dust collector will be used in non-arid areas.
But wet dust collector also has its disadvantages:
① It is necessary to treat the mud discharged from the wet dust collector;
② When the gas is corrosive, the sewage system should use anti-corrosion materials;
③ Poor purification effect on hydrophobic smoke and dust;
④ It is easy to block pipes and leaves when purifying viscous smoke and dust;
⑤ Anti-freezing measures shall be taken in severe cold areas.
03
industrial and mining enterprises
for different dust source dust removal equipment selection to explore the general dust collector selection principles are as follows:
① Select the type according to the amount of gas to be treated. When the amount of gas is large, the atmospheric dust collector is more economical than the parallel use of multiple small gas dust collectors. And the selected equipment capacity should be left with a certain margin, in order to prevent the actual situation beyond the design of ventilation.
② Selection according to the dispersion and density of dust. The cyclone dust collector is suitable for dust-containing gas with a particle size greater than 10 μm. When the particle size is less than 1 μm, a bag filter and an electric dust collector can be used.
③ Selection according to gas dust concentration. In order to ensure that the dust concentration of the outlet meets the requirements while the dust removal efficiency is high, it is necessary to understand the requirements of different types of dust collectors for the initial dust concentration.
④ Consider dust viscosity. When dust adheres to some parts of the dust collector, it is easy to cause blockage and dust accumulation.
⑤ Consider dust specific resistance. Whether the specific resistance range of dust meets the requirements should be considered when selecting an electrostatic precipitator.
⑥ Consider the temperature of dusty gas. Dry dust removal equipment must be above the dew point temperature of the dust-containing gas for dust removal, and the wet dust collector should be treated at a lower temperature as far as possible.
In the selection of equipment in industrial and mining enterprises, dust removal equipment should be selected according to the dust characteristics of different dust sources, dust control requirements and the geographical environment location characteristics of industrial and mining enterprises. In cold and arid areas, try to choose dry dust removal technology to reduce water freezing or reduce water waste. In areas with sufficient water resources or humid and hot, it is appropriate to choose wet dust removal technology to obtain better dust removal effect with lower equipment investment. There are still many factors to be considered in the equipment selection of a specific industrial and mining enterprise, such as the use of dust collection airtight cover and the arrangement of ventilation and ash transportation pipelines.
