Mine dust and dust detection safety technology

1. Dust properties and their hazards

Dust refers to solid particles that can be suspended in the air for a long time. The suspended dust is an aerosol. The dispersing medium is air, and the dispersed phase is solid particles. The flying dust is solid particles that can float in the air for a long time ( Floating dust), the length of floating dust in the air is directly related to the particle size of the dust. The dust with a particle size of 10um settles to the ground, generally takes 4~9h, and the dust with a particle size of 1um takes tens of days. Dust below 0.5um can float in the air for a long time without sedimentation.

It can be seen that the dust particle size is more than 10um. It is more consistent with the view that the ambient air 5um diameter is less dust pneumoconiosis caused major harmful dust, some of the high mineral content of free silica dust, the role of human-induced fibrosis is very strong, China's coal mine The free silica content in the dust of rock tunneling work is generally above 10%, the highest can reach 80%, and most of it is between 30~40%.

Coal dust is explosive. Most of the coal dust in coal mining face of anthracite coal mine is non-explosive coal dust except for a few cases, and the coal dust generated from coal mining face of bituminous coal and lignite coal mine is explosive dust. The lower the degree of carbonization of coal and the higher the volatile content, the stronger the explosiveness of coal dust.

The concentration of upper and lower explosives obtained under different types of coal and different test conditions is different, but in general, the lower limit concentration of coal dust explosion is 30~50g/m3, and the upper limit concentration is 1000~2000g/m3. The strongest explosive concentration is 300~500g/m3.

The detonation temperature of coal dust explosion is generally 650~990 °C. When coal dust explosion occurs, coal dust with particle size less than 1mm can participate in the explosion, but the main body of the explosion is coal dust with particle size less than 0.75mm. When it contains biogas, the concentration reaches At 3.5%, an explosion may occur when the concentration of coal dust in the air reaches 6.1 g/m3. The effect of oxygen concentration on coal dust explosion is that when the oxygen content is lower than 17%, the coal dust will not explode.

Coal dust explosion can release a lot of heat energy, the explosion flame temperature can be as high as 2000 ° C, the explosion pressure can be as high as 1.9Mpa. When coal dust explosion, the speed of shock wave propagation is greater than the speed of flame propagation. The measured flame propagation speed at home and abroad is 610~1800m/s, and the explosive shock wave can reach up to 2000m/s. The coal dust explosion gas contains a large amount of carbon monoxide and carbon dioxide, and the content of carbon monoxide in the air of the explosion zone can be as high as 8%.

Another major hazard of dust, the fine particles of dust generated in the coal production process can fly and suspend in the production environment for a long time, workers absorb the productive dust in the long-term work, and deposit in the small bronchi and alveoli of the lungs. These dusts deposited in the lungs undergo a series of physiological and pathological changes with the cells of the lung tissue, causing the lung tissue to gradually become fibrotic. When the fibrotic lesions develop to a certain extent, it can lead to obstacles in the respiratory function of the human body. This disease caused by fibrotic lesions in the lungs of workers caused by coal mine-produced dust is called coal worker's pneumoconiosis.

The excavator has long inhaled the high dust of free silica. The pneumoconiosis of these workers is called silicosis. The coal miners work in high coal dust environment for a long time. Pneumoconiosis can also occur. This kind of dust is called coal lung. .

The case of dredging workers is mainly rock dust. The total dust of the two lungs generally does not exceed 10g, of which the free silica content is about 3~4g; the coal pigs in coal mining are mainly coal dust, and the total dust of both lungs can often reach 40~50g, wherein the free silica content is only about 1g.

According to reports in recent years, the prevalence of coal mine pneumoconiosis has declined from the previous level, generally between 3 and 10%, with an average of 5%.

2, coal mine dust

80% of the coal mine dust is produced from the mining face. Under the condition of no dust prevention measures, the dust concentration of the blasting is 300~500mg/m3, and the dust concentration of the fully mechanized mining and fully mechanized caving work reaches 2500~3000 mg/m3. 1 is the dust concentration of each dust measuring point measured by a working face without dustproof measures. Table 2 shows the dust concentration of each measuring point measured under the normal use of dustproofing measures.

Table 1 Dust concentration at each measuring point of the working face

Dust category

Dust measuring point

Full dust



Falling coal



against the wind

Falling coal




Driver's office



against the wind

Driver's office







Coal mouth



Return air alley



Note: The air volume at the working surface is 900m3/min

Table 2 List of dust concentration at each measuring point

According to the dust prevention technology implemented in the mine, the dust prevention measures can be divided into the following five categories:

2.1 Reduce dust generation

There are two measures to reduce the generation of dust: First, measures to reduce the amount of dust generated in the production process, that is, reduce the amount of dust generated per ton of coal or the amount of dust produced per unit time, and reduce the concentration of dust in the dusty airflow. For example, to improve the picking and mining state of mining and excavation machinery, select the best cutting parameters with small dust production; reduce the number of blastholes and the amount of explosives under possible conditions, and secondly, adopt some kind in advance or in the production process. Measures to suppress floating dust generation (referred to as dust suppression measures). For example, the coal seam water injection or the gob irrigation water pre-wet the coal body; the wet type eye; the blasthole fill the water cannon mud; the coal wall and the rock state are washed before and after the shot; the coal and rock sprinkling water are discharged.

2.2 dust reduction measures

Dust-reducing measures are measures to reduce the dust suspended in the airflow by spraying. At present, the main dust-proof measures include purification and ventilation, inside and outside the shearer, inter-stand spray, coal injection spray, wet drilling, and water use. Gun mud, sprinkler, armor spray, etc.

2.3 dust removal measures

The dust-removing measure is a method in which the dust suspended in the airflow is discharged to the working place by a ventilation method, or the air volume is increased to dilute and reduce the dust concentration in the working place. For example, improving ventilation methods, methods, and using optimal dust removal wind speeds.

2.4 Dust removal measures

The dust removal measure is a measure that uses the dust collector to collect and remove the dust contained in the wind flow to purify the wind flow. For example, a wet or dry dust collector (dust trap) for dust removal at the working face or anchor spray, eye opening and transfer point.

2.5 individual dust prevention measures

Individual dust-proof measures are to use personal dust-proof equipment to filter the dust in the breathing air, so that the workers can inhale the purified air, or take a clean pressure method from the outside of the workplace for the workers to breathe. For example, it is equipped with a dust mask, a dust mask, a dust cap or a compressed air respirator.

3, dust detection

The average daily maximum allowable concentration of dust in the atmosphere of residential areas as stipulated in the design hygiene standards of industrial enterprises in China is 0.15mg/m3. The concentration of dust (total dust, respiratory dust) in the air in the coal mine safety regulations for people working underground and sidewalks , to meet the requirements in Table 2.

Table 2 Dust concentration standards in the workplace air

Free SiO2 content in dust (%)

Maximum allowable concentration (mg/m3)

Total dust

Respiratory dust

1 , <10


3 . 5

2 , 10~<50



3 , 50~<80


0 . 5

4 , ≥80


0 . 3

Dust detection is a scientific method for measuring, analyzing and inspecting the content of dust and its physical and chemical properties in the production environment. From the comprehensive understanding and mastery of the physical and chemical properties of dust, there are many items to be tested, such as dust shape, density, particle size distribution, solubility, concentration, chemical composition of the dust, chargeability, and explosiveness. However, from the perspective of safety and hygiene, daily dust detection projects are mainly dust concentration, free SiO2 content in dust and dispersion of dust.

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