Coal and coal properties

Coal is used a lot in industries such as textiles, food processing, power generation... Identifying whether the quality of coal is good or bad plays a decisive role in the output of goods of businesses.

In fact, understanding the properties of coal is a basic knowledge for each manager, before importing coal, from a certain supplier. Therefore, in the following article, we invite you to join Thuan Hai to learn the properties of coal, from there, distinguish the good and bad quality of this fossil fuel.

Cách thức nhận biết than đá tốtHow to recognize good coal

First, when learning about coal's properties, we need to identify the chemical composition of this fuel.

1. Chemical composition in coal fuel


Carbon is the main burning component in solid fuels, the emitted heat of 1 kg of carbon is called calorific value. So the more carbon in the fuel, the higher the fuel's calorific value. The older the fuel formation age, the higher the carbon content, but then the greater the bond of coal, the more difficult the coal to burn.


Hydrogen (also known as hydrogen) is an important burning component of solid fuels, emitting heat of 144,500 kj / kg when burned. But the amount of hydrogen in nature is very little.


Sulfur is the burning ingredient in fuels. Sulfur coal exists in three forms: organic bond Shc , mineral Sk, sulfate bond Ss.

Organic sulfur and minerals that can participate in combustion are called burning sulfur Sc.

Meanwhile,  sulfur sulphate is usually in the form of CaSO4, MgSO4, FeSO4... These bonds do not participate in the burning process but turn into ash of the fuel. They melt into the glue, this is also the cause of the slag formation. Therefore, if we want coal without coagulation, we have to choose coal with low sulfur content, usually coal in the mines of Cao Son, Nui Beo, Deo Nai,  Thong Nhat , with very high calorific value and low sulfur content.

The calorific value of sulfur is about one-third that of carbon. When sulfur burns, it produces SO2  or SO3 gas  . When encountering water vapor,  easily soluble SO3 creates H2SO4 acid,  causing metal corrosion. The  released SO2 gas has an unpleasant odor and is a dangerous toxic gas. Therefore, just visually can tell us whether coal has more or less sulfur content.

Oxygen và Nitrogen

Oxygen and Nitrogen are inert substances in solid and liquid fuels. The presence of oxygen and nitrogen reduces the burning composition of the fuel, causing the fuel's calorific value to decrease. The younger the fuel, the more oxygen. When the fuel is burned, nitrogen does not participate in the combustion process, transforming into the free form in the smoke. We are commonly found in Indo coal (high volatility, low heat, high smoke).

Các loại khí là thành phần trong than đáGases are the constituent of coal

Ash, slag (A)

Are the ingredient left over after the coal has been burned.

2. The properties of coal

Humidity (%)

The moisture content of coal is the water content contained in the fuel. Humidity full of coal is determined by drying the fuel in the oven at a temperature of 1050 o C until the weight of the fuel is no longer changed. The lost weight is called fuel moisture.

Indeed, at a temperature of 1050OC is not enough to completely exhaust from fuel moisture. Usually it must be at a temperature of 5000 - 8000OC to fly out.

Nhận biết độ ẩm của than đáKnow the moisture content of the coal

Ash level is also known as coal slag (%)

The mineral matter in coal turns into ash when burned. Their presence reduces the burning constituent meaning that they reduce the calorific value of the coal.

The percentage of ash in coal greatly affects the burning properties of coal such as: reducing the heat value of coal, causing abrasion on the surface of the heat absorption pipe, and dirt, reducing the heat transfer coefficient through the pipe wall. Ash also affects furnace operation. Even bad coal as ash pulls the slag on the boiler burn surface. This means that the furnace must force the fan to increase enough heat for the combustion chamber, leading to an increase in electricity costs.

The ash of the fuel is determined by taking the fuel sample to burn to 800 - 8500 O C for solid fuel, 5000 O C for liquid fuel until the remaining weight does not change. That constant weight in a percentage is what is called the ash of the fuel. The ash of madut is about 0.2 - 0.3%, of wood about 0.5 - 1%, of anthracite can be up to 15-30% or more.

Volatile matter (%)

When the fuel is heated in the absence of oxygen, the bonds of organic molecules are broken down. That process is called thermal decomposition. Products of thermal decomposition are gases known as "volatile" and denoted by Vk.%.

The thermally decomposed gases include Hydrogen, Cacbuahydro, Carbonoxide, and Carbonic. We imagine this process like when cooking wood, shavings are compared to volatile. In coal that is more volatile, the more coal is consumed.

The oxygen-rich bonds are less stable bonds, easily broken at high temperatures. Therefore, the younger the age of the coal, the more volatile it becomes. Specifically, we have the following volatile ratio: peat (V = 70%), coal (V = 10-45)%.

When temperature begins, the volatile matter depends on the age of the coal. The younger the coal is, the lower the temperature of volatilization will start. The amount of volatile matter also depends on the time of thermal decomposition.

Calorific value (Q (Cal / g))

The calorific value of  coal  is the heat emitted when completely burned 1 kg of coal, denoted by the letter Q (Kj / kg). The calorific value of coal is classified into high calorific value and low calorific value. 

Nhận biết than đá tốt qua trực quanGood coal identification visually

3. Identify good coal visually

Not all of us have the expertise to assess coal. Through the visual properties below, however, you can somewhat assess the quality of the coal.

Specifically, the characteristics are as follows:

About touch: Holding coal up to see lightly, feeling the oil clinging to hands, difficult to wash.
Smell: Burning coal does not have an unpleasant odor, coal has a little sulfur content.
Visual: Seeing coal black, with luster.

If your company is looking for a quality coal supplier with competitive price, please contact:

Thuan Hai - The optimal energy solution:

Address: Thuan Hai Building, Lot Vb.20a2, Street 24, Tan Thuan Export Processing Zone, Tan Thuan Dong Ward, District 7, City. Ho Chi Minh City, Vietnam.

Hotline: 1900 1766



>>> Read more: Coal and electricity industry