Mist Spraying Technology to Suppress Dust in Mineral Mining

Submit periodic environmental reports every 6 months to the Department of Natural Resources and Environment and the project owner.

Specialized environmental officer: the environmental officer staff is in the labor safety department, responsible for monitoring environmental quality in the project area and controlling the implementation of mitigation measures. Specialized staff are responsible for regular training on monitoring, supervision, and data management with a frequency of every 6 months for system operating units. Environmental officers are also responsible for site inspection and supervision throughout the project implementation process to ensure that the operating unit fully complies with the proposed procedures.

* Report on environmental management plan

Report content includes:

- Evaluate the success of environmental protection activities in project implementation areas compared with predictions made.

- Clearly evaluate whether the framework of the environmental management plan is complete. If not, explain the reasons and make recommendations for completing the environmental management plan framework, review the collected information, data analysis, reports and budget drafts.

- Technical reports and plans will include a series of administrative policies and contractual agreements.

b. Environmental monitoring program

Propose a program to monitor waste and non-waste-related impacts generated during preparation, construction, operation and closure (if any), such as: dismantling, closing, renovation environmental restoration and other activities that have the potential to impact the project's environment.

- Waste monitoring: must monitor the flow/total amount of waste and typical parameters for the project's waste according to Vietnam's current standards and regulations with a minimum frequency of 01 time/3 months.

- For establishments that generate large amounts of wastewater and emissions and have the potential to cause high levels of environmental pollution, automatic and continuous monitoring systems must be installed.

flow rate and typical pollution parameters in the waste for the agency approving the environmental impact assessment report to consider and decide. In all cases, it is mandatory to install automatic and continuous monitoring systems for flow and typical pollution parameters for projects that generate wastewater with a discharge flow of 5,000m3/24h or more . up and the project generates emissions with an exhaust flow of 100,000m 3 /h (not applicable to emissions generated from associated gas flares in oil and gas exploitation activities).

- Surrounding environment monitoring: only monitor project-specific pollution parameters according to Vietnam's current standards, regulations and regulations in case there are no stations in the project implementation area. General monitoring point of state agencies, with a minimum frequency of 01 time/6 months.

- Other supervision (if any, depending on each specific project):

+ Monitor factors: erosion, sliding, slumping, land subsidence; Erosion of river banks, stream banks, lake banks, and coastlines; sedimentation of river beds, stream beds, lake beds, and sea beds; changes in surface water and groundwater levels; salinization; alum intrusion; and impacts on other natural and socio-economic objects with appropriate frequencies to track the spatial and temporal changes of these factors. Monitoring points (if any) must be specifically shown on the diagram with clear annotations and coordinates according to current standards.

+ Monitor changes in rare animal and plant species in the project implementation area and are subject to negative impacts caused by the project with a minimum frequency of 01 time/year.

3.6.5. Dust treatment measures

There are currently many dust removal methods that have been widely applied in industries, especially the coal industry, but they are mainly based on 4 basic methods as follows:

- Use a water humidification system to prevent or suppress dust.

- Method of using dust containment equipment.

- Use air intake and ventilation systems to control dust dispersion.

- Combine all 3 methods above in one system.

Due to the complexity of dust generated from coal mining activities, the volume generated and the degree of dispersion is high, but the settling speed is quite fast (due to the large size of dust particles), it is recommended to Choose a method of moistening with water to prevent or suppress dust. Below are presented some methods to minimize dust arising from basic production stages of the coal industry. For drilling and blasting work

Dust and toxic gases such as CO, NO... created in this step are instantaneous and local, but the impact of this step is huge on workers. To minimize dust and gases mentioned above, the following basic measures should be applied during the production process:

1. Wet drilling technology: using water as drilling fluid to limit the possibility of dust generation. For dry drilling equipment such as rotary drilling machines, it is necessary to install funnels around the mouth of the drill hole to prevent dust from spreading into the surrounding environment, affecting workers.

2. Spray water on rock surface and blasting site (see illustration in Figure 3.8).

figure 3.8: mist spraying technology to suppress dust in mineral exploitation this method uses 1

Figure 3.8: Mist spraying technology to suppress dust in mineral exploitation

This method uses water and compressed air to create a mist to suppress dust kicked up when removing coal from the foot of the longwall to a scraper placed along the coal seam right at the foot of the longwall. This system includes:

+ Steel pipe with a diameter of 16mm carries compressed air from the mine's general compressed air pipeline.

+ 21mm diameter rubber pipe connected from 30mm long nozzle compressed air steel pipe.

+ The nozzle is specially designed to create a water-compressed air mixture.

During the process of removing coal from the longwall to the scraper trough, the nozzle operates, and when this process stops, the nozzle also stops working by closing the water and compressed air supply valves.

3. In previous years, large open-cast mines in the Cam Pha area often used explosives such as regular ANFO (loose granular form), ANFO often packed in plastic bags, water-resistant ANFO, AD1, Zecno 79/21, TX -1A, NT-13, EE-31 in fact shows that regular ANFO explosives, water-resistant ANFO and emulsion explosives are explosives that both meet the needs of exploitation scale as well as environmental protection requirements, especially for Zecno 79/21 explosives are recommended for Cao Son, Coc Sau and Deo Nai mines not to be used because they cause environmental pollution.

4. Use water blasting when blasting. This method has been successfully researched and tested by the Mining Experimental Center since 2004 at a number of prepared furnace lines of Giap Khau Coal Mine and Hong Gai Coal Company. The principle of this method is to fill the mine holes with water bubbles combined with hanging water bags. This is one of the commonly used methods in the mining industry because it is simple, cheap and quite effective (reducing dust concentration by up to 85%, reducing explosive costs by 10 - 17%): Bua water is Made using a 0.2mm thick polyethylene plastic bag with a diameter equivalent to a 40mm bore diameter and a length of 400mm, one end is sealed, the other end will be tied tightly after being filled with water. into the bag. These hanging water bags are hung close to or 1-2m away from the oven mirror. When mines explode, rock and soil will be thrown and the explosion pressure will burst the water bags.

figure 3.9: prevent dust with water when blasting 1- explosives; 2- explosive primer; 3- bua; 4- 2

Figure 3.9: Prevent dust with water when blasting

1- Explosives; 2- Explosive primer; 3- Bua; 4- Exploding wire; 5, 6- Water bag

This method increases the effectiveness of dust reduction, while also reducing toxic gases in the air in the furnace mirror. Summary measurement results of environmental parameters when blasting with water blasting combined with water bags hanging in front of the furnace mirror show a clear leakage effect of this method (see table 3.24).

Table 3.24. Concentration of some gases and dust in the furnace mirror

Environmental parameters in

furnace mirror after blasting

When there is no water bubbles

and hanging water bag

When there is water and bag

hanging water

CO 2 gas



SO 2 gas



O 2 gas



NO 2 gas



CO gas



NO gas



Concentration of dust



Maybe you are interested!

(Source: Investigation and synthesis by student Vu Xuan Lich)

In addition, to reduce the amount of dust affecting workers, they can use methods to moisten the soil and rock before blasting, and can forcefully pump it with a high-pressure hose, and

free infiltration, or direct irrigation. Immediately after blasting, people also use the dust suppression method by spraying water with high-power nozzles.

5. Solution to plant trees on both sides of transportation roads and mine waste areas. For loading, unloading and transporting coal

The dust generated in this step is formed during the excavator's excavating process. The scope of impact is small and local. However, the impact of this step on workers is huge due to the longer exposure time to dust in other stages. The measure to minimize dust at this stage is to spray water to moisten the coal and rock before loading.

a. Mist spraying method with Ejector in the coal mining area at the longwall. The objective of this method is to moisten the entire amount of coal needed.

Pre-contacting the furnace mirror with a steam mist generator reduces dust in the furnace mirror, bringing very high dust reduction efficiency, dust reduction from 90.22% to 97.47%, while improving microclimate conditions. better.

The structure and operating principle of this method are described in Figure 3.10.

figure 3.10: water spray device to create mist in a longwall furnace [8] 1- bracket; 2- engine; 3 3

Figure 3.10: Water spray device to create mist in a longwall furnace [8]

1- Bracket; 2- Engine; 3 – Transmission pulley; 4 – Reciprocating pump (3 machine combinations); 5- Working pulley of the pump; 6- Ladder belt; 7- Pressure gauge; 8- Pressure regulating valve; 9- Stabilize traffic; 10- straw; 11- Water filter set; 12- return water pipe when pumping to pressure

predetermined rate; 13- Water tank; 14- water supply pipe; 15- 3-phase power supply system; 16- Rubber plastic push tube with pressure 6 – 12 – 40kg/cm 2 ; 17- Safety valve; 18- Ejector combination (nozzle and air manifold); 19- Hanger; 20- Ejector support.

The effectiveness of dust reduction when applying this equipment to the preparation furnace and in the longwall furnace is specifically introduced in tables 3.25 and 3.26.

Table 3.25. Effectively reduces dust in the preparation oven [8]


Dust measurement location

Dust concentration, mg/m 3

Dust reduction efficiency, %

Before applying

PP decreased

minimize dust

After applying reduced PP

minimize dust


For furnaces preparing along the coal seam level –25.

- When drilling, measure 2m away from the furnace mirror.

- After 30 minutes of blasting, measure 5m from the furnace mirror.

- When manually shoveling coal, stay 2m away.

- 12m away from the furnace mirror, when protected.










For furnaces preparing along the coal seam level +30.

- When drilling, measure 2m away from the furnace mirror.

- After 30 minutes of blasting, measure 5m from the furnace mirror.

- When manually shoveling coal, stay 2m away.

- 12m away from the furnace mirror, when protected.













Table 3.26. Effectively reducing dust in longwalls [8]


Dust measurement location

Dust concentration, mg/m 3

Dust reduction efficiency, %

Before applying

After applying reduced PP

minimize dust


5m from the foot of the longwall

- When not removing coal from the longwall to the scraper trough.

- When removing coal from the longwall to the scraper trough.








Away from the hearth

- 3m from the drilling location, behind the wind stream

- When transporting coal in the longwall and removing coal at the foot of the longwall.

- 30 minutes after blasting.











At the top of the longwall furnace, there is a level distance from the furnace along the coal seam

+30 is 5m.

- When drilling at the bottom.

- After blasting below for 30 minutes.

- When loading and transporting coal in the longwall and removing coal at the foot of the longwall.










( Source: Mining Experimental Center - University of Mining and Geology)

b. High-pressure water spray method to create fog at coal export ports, screening plants and on coal transport routes

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