As a resource-dependent building materials industry, environmentally friendly sandstone aggregates are relevant to the future development of the industry. Therefore, environmental issues must be addressed. In the environmentally friendly fine sand and gravel aggregates crushing production line, there are major pollution issues such as dust, noise and wastewater. Relevant issues were discussed to promote the green development of the fine sandstone aggregate industry.
1. Dust control
There are two main ways of dust control: dust suppression and dust removal. In the sand and gravel aggregates crushing production line, dust is mainly divided into organized dust and unorganized dust.
1) Organized dust
Organized dust is mainly generated in the process of crushing, screening and transfer, and the treatment of organized dust should be suppressed first, and the dust generation in the production process should be reduced through optimized design, so as to effectively reduce the subsequent dust treatment load, save investment and improve efficiency.
At the connection between each process, the appropriate cutting pipe and the appropriate inclination angle should be selected to reduce the drop of the cutting point and the impact on the equipment.
When the belt is transported, it should be closed to prevent dust from overflowing, and the speed of the belt conveyor should be reasonably controlled, so as to reduce the generation of dust, and at the same time, efficient exhaust dust collection devices should be installed at each unloading point.
Spray humidification of the aggregate on the screen of the vibrating screen can reduce the secondary dust pollution, so that the amount of organized dust is lower than the dust emission standard of 20mg/m³.
2) Unorganized dust
The generation of unorganized dust mainly occurs in the process of mining, storage and delivery of finished products, due to the large space area in these places, it is not suitable to use the exhaust dust removal method, so other reasonable dust removal measures should be adopted.
For the treatment of mine dust, advanced blasting technology should be used to reduce the fine ore rate and reduce the dust height, and at the same time, the spray device should be used to wet the blasting area, so as to green the mine after mining and realize a green mine in the real sense.
The storage of the stacking shed adopts the method of fully enclosed storage, and a plurality of spray humidification and dust removal devices are installed above the stacking shed to effectively reduce dust. For the dust generated in the process of finished product shipment, due to the incomplete separation of stone powder and aggregate in the production process, some stone powder will be attached to the surface of the aggregate, so that dust pollution will be produced in the transportation process, in order to avoid this situation, the finished aggregate can be screened and washed, and the wet production process can be adopted, which can not only solve the dust pollution in transportation, but also remove the stone powder and mud powder on the surface of the finished product to improve product quality.
In addition, a special car wash area is established in the factory area to clean the car body, and at the same time, the car tarpaulin is used to cover and seal during the car transportation, which can further reduce the dust generated during transportation. The roads in the factory area are comprehensively hardened, and then according to the weather conditions, artificial sprinkling is carried out to reduce dust and comprehensively control dust pollution.
In addition, the dust collected from the entire production process should be transported separately through the zipper machine and elevator for centralized storage and utilization to avoid secondary dust pollution.
2. Noise control
The noise sources in the plant area are mainly the crushing and screening workshop and dust collection fan of machine-made sand and gravel aggregates, and the noise pollution control should be mainly controlled from two aspects: sound source and propagation path.
First of all, the old equipment should be updated, and some advanced process equipment with low noise should be selected, such as replacing the metal screen with a polyurethane screen, installing a muffler, a sound insulation cover or reducing the vibration of the fan and other noise reduction measures on the fan to reduce noise from the root; Secondly, the workshop will be closed and soundproof as much as possible, and at the same time, greening will be carried out in the factory area to block the transmission of part of the noise. If employees need to enter the workshop to work, they should also take labor protection measures, and should wear earplugs, earmuffs, etc., to ensure the health of workers.
3. Wastewater treatment
There are two main types of sand and gravel aggregate production lines: dry and wet. Although there is no wastewater in dry production, dust pollution is difficult to control and it is impossible to remove stone and mud powder attached to the surface of the finished aggregate, which can affect the quality of the product. As a fine gravel aggregate production line, it is necessary to solve the problem of stone powder and mud powder adhesion on the surface of the product and improve product quality. Therefore, it is necessary to screen the product, but wastewater is also generated.
The traditional sandstone aggregate wastewater treatment is mainly natural sedimentation or flocculation sedimentation. Most of the sedimented slurry is treated by natural dewatering. This method takes a long time and depends on the weather conditions. If the sedimentation tank is not treated in time, it will cause the wastewater to overflow outside the tank and recirculate into the surrounding waters, causing pollution to the surrounding environment. As a result, new processes with a high degree of automation are required.
First of all, the wastewater is pretreated by high-efficiency cyclone dust collector and dewatering screen, and the large gravel is quickly separated and recycled, and then the pretreated wastewater is concentrated into a thickener for concentration, and then the slurry is concentrated. Concentrate to a certain concentration. Combined with radial flow sedimentation tank, belt filter press, ceramic filter and other technologies for mechanical dewatering, sedimentation sludge separation, the method is fast and efficient, high degree of automation, saving land area, and can reduce the operating cost, reduce the production of mud. The powder is easy to be processed centrally and will not cause secondary dust contamination due to natural air drying. The treated wastewater will be recycled to achieve "zero" discharge of industrial water.
Compared with the existing technology, the wastewater treatment process can improve the level of automation, shorten the dewatering time, and can carry out wastewater treatment continuously and efficiently.
Under the trend of environmental protection and high pressure, equipment manufacturers have launched intensive sand making equipment with environmental protection mechanisms. Sand and gravel enterprises should combine the current development level of production technology, choose efficient and reliable treatment schemes, and promote the healthy development of the sand and gravel aggregate industry.