菜单
关闭
|
Coalbed Methane (CBM), refers to hydrocarbon gases stored in coal seams which is mainly composed of methane, and adsorbed on the surface of coal matrix particles, and partially free in coal pore or dissolved in coal seam water. It is a mineral resource of coal-associated, and belongs to unconventional natural gas.
We distinguish between three kinds of Coalbed Methane:
1. Coalbed Methane (CBM), that is, Methane exhausted from unexplored coal beds, It is associated gas of coalbed and belongs to unconventional natural gas. The calorific value of one cubic meter pure coalbed methane is equivalent to 1.13 kg gasoline or 1.21 kg standard coal. The methane (CH₄) content of surface pumped CBM is generally greater than 95%. When the methane content is 97.8%, The Low calorific value(LCV) is 34.5964 MJ/Nm³ (about 8263 kcal/Nm³), and The High calorific value(HCV) 38.9311 MJ/Nm³ (about 9299 kcal/Nm³) at 0 ℃ and 101.325 kPa. Its calorific value is equal to that of natural gas. It can be mixed with natural gas and is an ideal fuel for power generation.
2. Coal Mine Gas (CMG), also known as colliery gas, Methane coming from active underground mining. Coal mine gas is released from seams of coal during mining activities. The calorific value of Coal mine gas is related to content of methane (CH₄). Generally, methane (CH₄) content is adjusted to 30% or below before being utilized in underground gas extraction, At 0 ℃ and 101.325 kPa, the LCV is 14.63 MJ/m³ (about 3494 kcal/Nm³) and the HCV is 16.24 MJ/m³ (about 3878 kcal/Nm³). Therefore, Coal mine gas is divided into the High concentration gas and Low concentration one, and there are differences in the selection of power generation equipment compared to CBM.
3. Abandoned Mine Methane (AMM), refers to Methane exhausted from abandoned mines. Even after the coal mine ceases operation, methane may still be slowly released from underground coal seams and rock formations. These methane mainly escape into the atmosphere through ventilation ducts, cracks, boreholes, or surface fissures in abandoned mines. The technology of recovering and utilizing methane from abandoned mines is mainly achieved through drilling and gas collection systems, which guide the methane that originally escaped into the atmosphere to the surface for utilization. This not only reduces greenhouse gas emissions but also converts it into energy resources, improving economic efficiency.
Coal mine gas includes three categories: High concentration gas (methane concentration above than 30%), Low concentration gas (methane concentration of 8% -30%), and Ultra-low concentration gas (methane concentration less than 8%). More than 60% of the colliery gas in China is Low concentration gas containing less than 30% methane. According to the requirements of coal mine safety regulations, the colliery gas whose methane concentration is below 25% can not be stored and transported.
The commonly used Coalbed Methane refers to Class 2 and Class 3 gases, namely CMG and AMM. Due to high methane content of 30 - 95 %, especially CBM, CMG and AMM are suitabl the utilization e forin gas engines, and is an ideal fuel for power generation. Our company adopts water mist conveying system for low concentration colliery gas, which has multi-level fire protection transportation, with explosion venting, explosion suppression and explosion-proof protection to ensure safety conveying of low concentration colliery gas. It is suitable for generating electricity from coalbed methane with methane concentration above 8%.
Gas requirement of Coal Mine Gas：
● Methane content (Volume) ≥ 8%; Methane concentration change rate ≤ 2 %/min.
● Methane and oxygen ≥ 26%; Oxygen (Volume) ≥ 16%.
● Gas temperature ≤ 40℃; Gas pressure 2.5-10 kPa; Pressure change rate ≤ 1 kPa/min.
● Moisture content ≤ 40 g/Nm³, no free water.
● Impurity content ≤ 30 mg/Nm³; Impurity size ≤ 5 μm.
● Sulfur content ≤ 100 mg/Nm³.
