March 8, 2022

Methods of Controlling Dust

Dust refers to solid particles suspended in the air. It is customary to have many names for dust, such as dust, smoke, mineral dust, sand dust, powder, etc. These terms have no clear boundaries. The International Organization for Standardization stipulates that suspended solids with a particle size of less than 75 μm are defined as dust. The presence of dust in the atmosphere is one of the main reasons for keeping Earth’s temperature, and too much or too little dust in the atmosphere would have a catastrophic effect on the environment. But in life and work, productive dust is the natural enemy of human health and the main cause of many diseases.

Methods of removing dust
Gravity Settlement Method
The gravity of the dust is used to make the dust settle and separate from the air. (Capture efficiency: 40% ~ 70%. Advantages: simple, low investment, easy maintenance. Disadvantages: large area, low potential collection efficiency. Application: suitable for collecting dust with large diameter and specific gravity .)

Inertial capture method
By suddenly changing the flow direction of the dust-laden airflow, or making it collide with some obstacle, the movement trajectory of the dust particles deviates from the gas streamline to achieve separation. (Capture efficiency: 50% to 70%. Advantages: simple, low investment, easy maintenance. Disadvantages: large area, need multi-cascade use, low capture efficiency. Application: d≥20μm non-fibrous dust.)

Cyclone capture method
When the dust-laden airflow enters the collector, it rotates, and the dust particles in the airflow move to the outer wall under the action of centrifugal force, reach the wall, and fall into the ash hopper along the wall under the action of airflow and gravity to achieve the purpose of separation. (Capture efficiency: 85% to 95%. Advantages: simple, low investment, easy maintenance, high capture efficiency. Disadvantages: changes in parameters such as processing air volume, air temperature (gas viscosity), dust density, etc., all affect the capture efficiency .Application: 3~100μm dust.)

Wet capture method
When the dust particles are in contact with water, they are directly captured by the water or the cohesion of the dust particles increases under the action of water, so that the dust is separated from the air. (Capture efficiency: 90% ~ 99% Advantages: It can capture dust and remove harmful gases at the same time. Simple structure, low cost, can handle dusty gas with high humidity and high temperature. Slurry handling issues. Application: Hydrophilic dust.)

filter capture method
It mainly relies on the primary dust layer and the dust collecting layer formed on the surface of the filter material to filter the dust in the air. (Collection efficiency: 85% ~ 99.9% Advantages: High collection efficiency Disadvantages: easy to block, easy to break, need to repeatedly clean the filter equipment, the cost is high. Application: 0.1 ~ 20μm dust.)

Static trapping
A high-voltage electric field is formed between the positive and negative electrodes to ionize the air. When the dust-containing gas passes through the electric field, the dust is charged, so that the dust particles move to the dust-collecting electrode and deposit on the dust-collecting electrode, so that the gas is purified. (Advantages: It can capture dust with special properties. Disadvantages: Due to the limitations of dust properties, such as resistance, dust concentration, wind speed, etc., it is only used in individual scenarios. Application: 0.05 ~ 20μm dust.)

How to control dust?
1. Reduce the generation of dust
The source of dust can be eliminated through the selection of processes and materials, which can greatly reduce the generation of dust. For example, in woodworking, when cutting boards, you can use a dust-free cutting machine.

2. Factory dustproof measures
Dustproof in wet operation, such as water grinding quartz in stone powder factory, raw material water grinding and wet mixing in ceramic factory and glass factory, hydraulic sand cleaning and water blast cleaning in machinery manufacturing industry. For dry production, a closed, ventilated, and dust-removing system is adopted, which consists of closed equipment, dust hoods, ventilation pipes, and dust collectors.

3. Dustproof underground
Take comprehensive dust-proof measures with wet operation and enhanced ventilation as the main content, such as: wet rock drilling; wet operation during ore transportation; 24-hour continuous operation of the mine, the main fan runs continuously, and the single-head operating face is provided with local ventilation equipment; auxiliary Dust-proof measures are adopted, such as setting up water curtains in the air inlet and return air passages to purify the air source and the air polluted by dust; flushing the walls and ventilators of the roadway to prevent secondary dust; workers in underground dust wearing dust masks.

4. Dustproof in open pit mine
Control dust sources. For example, wet drilling or dry dust collection can be used for drilling operations, and airtight, ventilation and dust removal methods can be used for crushing operations; pay attention to strengthening the dust protection of the driver’s cab and dust protection during transportation.