The main pollution produced in the production process of automobile aluminum wheel hub projects are exhaust gas, wastewater, solid waste, and noise. This paper studies the prevention and control measures of exhaust gas pollutants in such projects and analyzes the feasibility of these measures. The exhaust gas produced by this type of project is mainly the melting flue gas generated when the aluminum ingot is melted, the dust generated during the shot blasting process, the dust generated during the electrostatic spraying process, the paint mist generated during the paint spraying, leveling process, curing and baking, and the second Toluene organic waste gas. After taking relevant pollution prevention and control measures, the project's waste gas can meet the requirements of the air pollutant emission standard, effectively reducing the impact of waste gas on the environment.
The production process of automobile aluminum wheel hub production projects includes aluminum alloy casting, X-ray non-destructive testing, thermal processing and heat treatment, processing of various mechanical equipment, air tightness seal testing, pre-treatment of coating rust, anti-rust coating, There are nine work sections including finished product packaging and storage, and the pollutants generated in the production process are exhaust gas, wastewater, solid waste, etc.[1]. The feasibility of pollution prevention measures is now taken as an example of waste gas produced in the production process. 1 Exhaust gas, various pollution sources, exhaust gas is mainly the fumes of aluminum ingot casting melting, dust generated during shot blasting, dust generated during spray production, paint mist generated during paint coating, and paint generated during leveling baking and curing. Fog and C8H10 (xylene) organic waste gas.
1.1 Melting flue gas When the aluminum ingot is put into the furnace to melt, there will be smoke and dust, and its main component is alumina.
1.2 Dust generated during shot blasting The shot blasting dust of the shot blasting room, and the dust generated during the production process is processed by the dust removal system matching the shot blasting room.
1.3 The electrostatic powder spraying process is carried out in the powder spraying room, during which dust will be generated. The exhaust fan of the equipment will be collected by the bag filter, and the collected dust will be recycled for production and utilization.
1.4 The paint mist and organic waste gas electrostatic spraying powder process is carried out in the powder spraying room, during which dust will be generated. The equipment has its own exhaust fan to collect it and collect it through a bag filter. The collected dust is recycled and reused.
2 Effective prevention and control measures for waste gas pollution
2.1 Dust pollution treatment equipment There are many types of equipment for treatment of dust produced in the production process. Commonly used are gravity sedimentation, inertial dust removal, cyclone dust removal, gas washing, and bag dust removal. Usually, people make selections based on its unique properties (such as aggregation, adhesion, electrostatic charge, etc.), the degree of dispersion of particulate matter, the temperature of the exhaust gas, the humidity of the gas, and the requirements for dust control.
2.1.1 Multi-tube cyclone dust collector Multi-tube dust collector uses dust-laden gas cyclone motion and uses centrifugal force to remove dust. This kind of dust collector has super large centrifugal force, the diameter of the removed particles is not limited, and the removal effect is better than that of the sedimentation chamber, and the area occupied by the same amount of waste gas is smaller than that of the sedimentation chamber. This kind of dust collector is simple in structure, small in area, cheap in price, and does not need to spend too much time on maintenance. The dust removal efficiency can reach 90%, and it is widely used by related enterprises [2].
2.1.2 Bag-type dust collector The bag-type dust collector adopts a filtering method to remove dust, and uses the gap between the filter material fibers to filter out dust particles. These particles adhere to the surface of the filter material and are separated from the gas. The dust removal efficiency of the bag filter is higher than that of the general dust collector, which can reach 99.9%. The disadvantage is that as the collected dust increases, the resistance of the entire system becomes larger, and the filter material must be cleaned regularly.
2.2 Dust-containing waste gas measures
2.2.1 The fumes produced by melting will produce fumes and fumes containing metal oxides when they are melted. The fumes enter the multi-tube cyclone dust collector and are discharged from the 15 m high exhaust chimney after being purified by the dust collector. Table 1 shows the treatment of melting fume and dust.
2.2.2 Shot blasting machine Dust shot blasting machine's own airtight exhaust hood absorbs and collects, and is rectified and treated by a bag filter, and the treated gas is discharged through a 15 m high exhaust cylinder. The dust-containing waste gas treatment in the shot blasting process is shown in Table 2. Table 1 Melting flue gas smoke dust treatment effect Pollutant median particle size (mm) Produced pollutant concentration (mg/m3) Discharged pollutant concentration (mg/m3) Discharged pollutant standard (mg/m3) Treatment efficiency (%) Smoke (powder) dust 0.1 158 15.8 150 90 Table 2 Process waste gas treatment effect of shot blasting The median particle size of pollutants (mm) The concentration of pollutants produced (mg/m3) The concentration of pollutants discharged (mg/m3) Pollutant emission standards (mg/m3) Treatment efficiency (%) Dust 0.1 1 059 10.59 120 99
2.2.3 Dust generated during powder spraying The semi-finished product of the wheel hub is sprayed with high-voltage electrostatic electric field. The dust generated by high-voltage electrostatic field spraying is collected and processed by a bag filter, and the treated gas is discharged through a 15 m high exhaust cylinder. Table 3 shows the treatment of dust generated by powder spraying. Dust treatment effect produced by powder spraying Median particle size of pollutants (mm) Concentration of pollutants produced (mg/m3) Concentration of pollutants discharged (mg/m3) Standards for pollutant discharge (mg/m3) Treatment efficiency (%) Dust 0.1 499 4.9 120 99 The dust removal equipment has a better governance effect under normal and stable operation. Dust will be generated when powder is sprayed, and its final emission concentration is lower than the emission standard, which can maintain long-term and stable compliance. 2.3 Paint mist and organic waste gas 2.3.1 Analysis of the effect of paint mist treatment When the spray painting process is used, the water formed by the paint mist and water in the spray booth.
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