Heat value is the amount of heat generated per unit volume of a material when completely burned. The unit of heat value is Joules per kilogram (J/Kg) or Joules per cubic meter (MJ/m3). The heatc value is mostly used to determine CNG’s efficiency. The heat value of compressed natural gas (CNG) depends on its components such as the proportions of Methane, Ethane, Propane, etc., and factors like pressure, temperature, etc., at the time of sampling. In the following content, Gas South will address prevalent questions regarding the heat value of CNG.
1. What is the heat value of CNG?
Compressed natural gas (CNG) is a clean fuel widely used around the world, primarily composed of Methane (CH4) which accounts for approximately 85-95% of its content. The remaining small portion includes Ethane, Propane, and other substances. CNG is natural gas compressed at high pressure (ranging from 200 to 250 barg) and stored in specialized tanks for transportation to the consumption points. CNG is currently a popular alternative fuel replacing coal, gasoline, and diesel in various industrial manufacturing sectors and public transportation. It offers competitive pricing, optimized efficiency, and longer equipment lifespan while reducing emissions that contribute to environmental pollution.
As mentioned earlier, the heat value of CNG depends on the composition of gasses (%CH4, %C2H6, etc.) along with factors such as temperature and pressure at the time of sampling. Moreover, the heat value of natural gas may vary in different countries.
The commonly used unit for CNG's heat value is 1 MJ/kg, which indicates the amount of energy (measured in megajoules) released when burning 1 kilogram of natural gas. Additionally, there are other units used for measuring the heat value, such as MJ/Sm3, MJ/Nm3, mmBTU/Sm3, KCal/Sm3, and KJ/Sm3. Specifically, the heat value of CNG falls within the range of 50-56 MJ/kg, which is higher than other fossil fuels like diesel oil (DO) and mazut (FO).
2. How to calculate the heat value of CNG?
Currently, the method to calculate the heat value of CNG (Compressed Natural Gas) is not specified. To obtain the heat value of CNG, CNG businesses often employ various manual techniques and different tools to measure the heat value.
3. The heat value of CNG compared to LNG, LPG, and other fossil fuels
Both CNG and LNG are forms of natural gas that undergo processing for the purpose of convenient storage and cost-effective transportation. LNG is in a liquid form, which makes it easy to transport in large quantities in specialized tanks or containers to the point of consumption, ensuring safety and economic efficiency. Upon arrival at the point of consumption, LNG is easily converted back to its gaseous state through a LNG skid.
THE TABLE OF TECHNICAL CHARACTERISTICS OF BURNING FUEL (*)
Similar to CNG, the heat value of LNG also depends on the composition of the gas and several other factors (pressure, temperature, production processes, etc.). Specifically, the heat value of LNG is approximately 55 MJ/kg. Liquefied Petroleum Gas (LPG), with its main components being Propane (C3H8) and Butane (C4H10), has a heat value of around 49.5 MJ/kg.
Currently, natural gas is considered a leading alternative fuel with economic, performance, and environmental benefits. Determining the heat value of CNG helps us understand the energy produced per specific unit of mass or volume, thereby assessing the quality of the fuel. With a higher heat value compared to LPG, diesel oil (DO), and fuel oil (FO), it is evident that CNG is a highly efficient choice in terms of thermal energy compared to the mentioned fuels.
