Assessing the Current Status of Air Pollution Sources in the Coal Industry

Chapter III

RESEARCH RESULTS

3.1. Assess the current status of air pollution sources in the coal industry

Dust is created in almost all stages of mining technology. Dust affects the external environment mainly during the stages of coal transportation, screening, processing and consumption. Among technological stages, coal transportation is the stage that creates the largest dust and has the widest scope of influence. Next is the screening and consumption stages. The dust composition in Quang Ninh coal region has unique characteristics compared to other places. According to the investigation results, the silica content contained in 1m3 of dust in the mine area is as follows: in dust

coal: 8.5  3mg accounting for 3.6  13.5% of total dust; in stone dust: 20  2mg accounts for 12 

26 % of total dust [8].

Table 3.1 introduces some dust measurement results when machines work as well as at some working positions in open pit mines.

Table 3.1. Dust generation level of coal mining activities [3]

Active form

Forms of activity

Dust concentration (mg/m 3 )

Loading and unloading

- When the EKG-5A excavator operates with a capacity of 175 m3/h.

- When the EKG-5A excavator does not work.

205.0

18.5

Exploding mines

- With 200 kg of explosives (measured at a distance of 30 - 40m), create a cloud 200m high.

- 1 ton of soil and rock creates 27 - 170g of dust.

800-5,000

Transport by car

- When a car passes by.

- When the frequency of cars is highest

120

2,257

Dispose of waste

- When a car dumps waste.

- When the spread has stabilized

1,340

Coal screening

- In Cua Ong coal processing factory.

- When the area surrounds the factory.

108.7

90 - 127

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(Source Mining Experimental Center)

3.1.1. Peeling soil and rock, blasting

According to statistics, when mining 1,000 tons of coal in an underground mine, it creates 11-12 kg of dust, while in an open-pit mine this level is twice as high. In open pit mines, the dust concentration around the excavator when working is up to 400 mg/m 3. When blasting 1 m 3 of soil and rock with explosives, 0.027-0.17 kg of dust is generated.

The total volume of soil and rock dumped from open-pit coal mines by region and by period from 2010 to 2015 is very large, as listed in table 3.2 below:

Table 3.2. Total volume of soil and rock dumped from open-pit coal mines [25]

Area name

Volume of waste soil and rock
	total	2010	2011-2015
total	4,337,799	602,523	829,589
Cam Pha	3,947,970	537,873	515,200
Hon Gai	389,829	64,650	314,389

Source: [25]

The entire volume of dumped soil and rock above is being and will be dumped at waste dumps in the Left Bank Coc Sau area, Bang Nau construction site, Quang Loi, Khe Cham, (Cam Pha area); Ha Tu mine, Nui Beo, Ha Lam, 917 mine, Ha Rang mine and Tan Lap mine (Ha Long city area).

Table 3.3. Statistics on the amount of waste rock and soil due to blasting activities at some mines

Mine name	Location	Area of soil and rock that must be excavated (km 2 )	Amount of explosives used (Tons/year)	Amount of soil and rock released by blasting (10 3 m 3 )	Amount of dust generated (ton/year)
first	Cao Son mine	Cam Pha	6	135,285 – 185,259	406,090	46314.75
2	Coc Sau Mine	Cam Pha	4	130,500 – 170,298	656,028	42574.5
3	Fat Mountain Mine	Cam Pha	6.7	98,823 – 138,620	107,255	34655

(Source: Investigation by student Vu Xuan Lich)

The dust load generated during the blasting and coal mining stages per year is quite large, however the dust generated by blasting is only instantaneously high, then spreads into the air, reaching a height of 100 - 150m. This spread depends more or less on wind intensity and terrain where blasting is carried out, but most of it subsides after half an hour. Therefore, the impact of dust on the surrounding air environment is only immediate and has a narrow, neighboring area within the construction site, within a radius of 150-300m. Residential areas near the construction site will be affected by dust generated by blasting if the blasting area is located on high terrain, facing north or northeast winds in winter.

According to "Environmental management of Russia's mining and energy industry": when exploding 1kg of explosives will create 0.043 - 0.25 kg of dust, so the amount of dust generated at Cao Son Mine is 4,817.25 - 46,314.75 kg /year, Coc Sau mine is 5,611.5 - 42,574.5 kg/year, Nui Beo mine is 4,249.39 - 34,655kg/year.

3.1.2. Coal screening

Raw coal from the mining site is transported to the raw coal warehouse at the screening areas, then screened and classified at the screening areas. The process of loading and unloading raw coal onto the screening conveyor and the dry screening process will generate a significant amount of dust. According to calculation results, the dust load generated during the screening process is 903,000 kg/year. Meanwhile, the operating area of the screening stage is smaller and where many workers gather, so the dust generated during this period will have a great impact on workers and the surrounding air environment. around the production area, affecting the vegetation in the area. On the other hand, most of the mine's coal storage areas are not covered, so dust can easily spread during dry weather and during coal loading activities.

Currently, in the key coal production area, there are two large screening clusters: Nam Cau Trang coal screening plant - Hon Gai coal screening company in Hong Ha ward - Ha Long city and Cua Ong coal screening company located in Hong Ha ward - Ha Long city. Cua Ong ward - Cam Pha city.

Table 3.4. Some coal processing plants in Ha Long and Cam Pha areas

Name

Address

Capacity (tons/year)

first

Coal processing plant

South White Bridge

Hong Ha Ward - Ha City

Long

3 million

Cua coal recruitment company

Grandfather

Cua Ong Ward – City

Cam Pha

12 – 14 million

(Source: Investigation by student Vu Xuan Lich)

Figure 3.1: Production line of Cua Ong coal plant

a. Nam Cau Trang Coal Plant

Nam Cau Trang Coal Plant - Hon Gai Coal Company belonging to Vietnam Coal and Mineral Industry Group was put into operation in 1996 in Hong Ha Ward - City. Ha Long with an initial design capacity of 2 million tons/year, since 2008, the factory's capacity has increased to 3 million tons/year. Nam Cau Trang Coal Plant is a place that generates a lot of dust in the surrounding area. Dust arises during the transportation of coal from Ha Tu and Nui Beo mines to the area

ready to recruit. Internal roads, screening areas, and coal storage areas all generate dust.

To reduce the impact of dust on the surrounding air environment, Vietnam Coal and Mineral Industry Group has taken investment measures to minimize the effects of the plant. The company installed a conveyor system to transport finished coal to the warehouse system, reducing transportation routes and reducing dust and noise in the production area. The most important thing to mention is the implementation of a comprehensive project on thoroughly treating dust pollution and flooding in residential areas around the Nam Cau Trang coal plant (unit under Decision 64) with an implementation value of nearly 7 billion VND. Implemented items include: Renew and upgrade nearly 2 km of coal transport road; Dredging and building embankments of nearly 900 m of drainage ditches in the North; Build a dust suppression mist spraying system including 5 stations with 257 dust suppression mist spraying columns for the entire internal coal transportation route.

7,000 m2 of trees, ornamental plants and 500 pigeons... create a landscape,

Attractive, friendly ecological environment... More specifically, the company has also successfully built a green belt surrounding the Nam Cau Trang Screening Factory. b. Cua Ong Coal Selection Company

Dust generated during the stages of screening, loading, transporting coal, and transporting soil and rock waste is calculated according to the pollution coefficient according to the WHO rapid assessment method and the output of coal and rock as follows:

Table 3.5. Dust emissions generated by Cua Ong Coal Processing Company

(When there is no control solution)

Sources arise	Dust load (kg/ton)
first	Dry sifting	0.21
2	Transporting and loading	0.17
3	Dispose of soil and rock	0.134
4	Fuel usage	0.28
	TOTAL	0.794

(Source: Cua Ong Coal Plant)

The dust content generated during the screening stage of coal processing plants I and II is not large. However, due to the small open surface of the area, the scope of dust's impact on air environment quality is concentrated in the screening area and directly affects the health of workers.

Screening plant III operates using dry screening technology, so the dust content generated in the screening area is very large. Currently, Recruitment III has been installed with mist spraying equipment to suppress dust, so the dust content dispersed in the surrounding air is significantly reduced. COD Plant III is designed near the sea, with the impact of wind and dust being widely dispersed. However, because the factory is located far from residential areas, the impact from the factory's screening area on the residential area is almost negligible, but mainly affects the health of workers working in the factory.

The process of transporting raw coal to the screening plant also causes large amounts of dust. When transported to the factory, raw coal is poured into raw coal spillways to be fed to screening houses. Activities such as removing coal and dumping coal at coal spills also generate dust, but the impact range is smaller than the transportation process. The impact of dust on the air environment of this area is local.

Coal after screening is transported to warehouses before being transported for sale. A large amount of dust is generated due to the process of dumping coal from wagons into the warehouse and loading coal from the warehouse for sale. Coal warehouses of screening plants I and II are located near roads and residential areas, so it will greatly affect the surrounding air environment and people's health, especially when strong northeast winds blow. .

The crushed stone of screening plants I and II exists in a moist state, so the possibility of dust generation is small and insignificant. The crushed stone of Coal Processing Plant III is in a dry state and is transported to the landfill mainly by dump trucks and drives along the coast, so there is no dust generated in residential areas.

3.1.3. Transporting waste rock and products

The route transporting waste rock and soil from the mining site to the waste dumps is an internal mine road with no population. Therefore, the impact of dust arises due to activity

Transport activities do not affect the population, but only increase the dust content in the air environment around the road, causing local air pollution.

The process of transporting products from mines to screening plants as well as to coal ports is a large source of dust. The routes transporting raw coal from mines to other places pass through residential areas and the transport distance is large, so the impact is large, affecting public health and causing loss of aesthetics of the area. However, the scope of impact of dust from roads depends greatly on the climatic conditions of the area. This impact will be greater in the dry season, when there are strong winds.

According to research works, the dust emission potential of coal mining auxiliary activities is calculated as follows:

Table 3.6. Dust emission potential of some activities

Activity type

Operating characteristics

Emission level (mg/m 3 )

Transport by car

+ When a car passes by

+ When it has spread stably

2257

120

Dispose of waste

+ When the car has been dumped

+ When it has spread stably

1340

(Source: Tran Yem, Doctoral thesis in Geography, Hanoi 2001)

To assess the impact of dust on coal transport routes through residential areas, I did a quick assessment by surveying 10 residential households in area 6, Hong Ha ward, Ha Long city, located on the coal transport route of Ho Chi Minh City. mines in Ha Long City area to Nam Cau Trang coal port. Through the survey, 100% of households questioned showed that the impact of coal dust on family activities is huge: houses and trees are often covered in dust and dirt, people in the area often suffer from road diseases. Respiratory diseases such as rhinitis and sinusitis. Families often have to close their doors to avoid noise and dust entering the house.

Figure 3.2: Coal loading and unloading activities

Cao Son coal mine

Figure 3.3: Coal transportation activities

Cao Son mine internal road

3.1.4. Dump waste at yards

Table 3.7. Some typical waste dumps

Name of landfill	Location	Volume of dumped soil and rock (million m 3 /year)	Time dump waste
I	Cao Son mine
first	Khe Cham III	Cam Pha	9	End year 2011
2	Seam cluster at 14 Khe Cham	Cam Pha	6	End year 2012
3	Dong Cao Son	Cam Pha	62	End year 2012
4	Bac Bang Nau	Cam Pha	673.5	Begin year 2013
5	Temporary landfill in the East area Cao Son	Cam Pha	12.5	End year 2013
No	Name of landfill	Location	Volume of dumped soil and rock (million m 3 /year)	Time dump waste

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