Comprehensive Knowledge of Gas

1. What is natural gas?　

Natural gas is a combustible gas extracted directly from underground natural gas deposits or oil-natural gas deposits, primarily composed of a mixture of hydrocarbons. Natural gas is generally divided into four types: gas field gas (or pure natural gas) extracted from gas fields; associated gas extracted along with oil (also known as oil-associated gas); condensate gas field gas containing light oil fractions; and mine gas extracted from coal seams underground.

2. What are the components of natural gas? What is the main component?

The components of natural gas include methane (CH4), ethane, propane, isobutane, and n-butane, along with small amounts of hydrocarbons, nitrogen, helium, sulfur dioxide, etc. The main component of natural gas is methane, which generally accounts for over 90% of pure natural gas.

3. What are the main characteristics of natural gas?

Although natural gas has various components, they do not chemically react with each other, and the properties of natural gas are determined by the nature and content of its components. Since methane accounts for over 90% of natural gas, it is also referred to as methane gas, and we often consider the characteristics of methane gas as the characteristics of natural gas. The characteristics of methane are as follows: methane is a colorless and odorless gas, burns with a faint blue flame, is lighter than air, can become liquid under low temperature and high pressure, with a critical temperature of -82.1°C and a critical pressure of 4.64 MPa. When liquefied, its volume shrinks by 600 times, and burning 1 cubic meter of methane requires 9.52 cubic meters of air. The explosion limits of methane in air are: lower limit 5%; upper limit 15%.

4. What are the explosion limits, upper explosion limit, and lower explosion limit of combustible gases?
 

The concentration range of combustible gases mixed with air that can explode when encountering an open flame is called the explosion limit of that combustible gas. In this mixed gas, when the content of the combustible gas decreases to a level where it cannot explode, it is called the lower explosion limit of that combustible gas; when the content of the combustible gas increases to a level where it cannot explode, it is called the upper explosion limit. The mixture of gas and air must be within the explosion limit range to ignite, burn, or explode. In the natural gas-air mixture, the volume content of natural gas at 5% is the lower explosion limit, and 15% is the upper explosion limit.

5. What is the calorific value of natural gas? What is the difference between high calorific value and low calorific value?

The heat released after the complete combustion of 1 standard cubic meter of natural gas is called the calorific value of natural gas. High calorific value refers to the heat released when the exhaust gas is cooled to the original temperature after the complete combustion of 1 standard cubic meter of gas, and the water vapor is discharged in a condensed state. Low calorific value refers to the heat released when the exhaust gas is cooled to the original temperature after the complete combustion of 1 standard cubic meter of gas, while the water vapor remains in a vapor state. Generally, when we refer to the calorific value of natural gas, we are talking about the low calorific value, which is approximately 37.62 megajoules (9000 kilocalories) per standard cubic meter.

6. What is the bromine smell in the natural gas used by residents?

Natural gas is a flammable and explosive gas that is colorless, odorless, and non-toxic; the bromine smell in the natural gas used is a bromine agent added to facilitate the detection of natural gas leaks. Adding bromine to gas means introducing a scented liquid agent into the colorless and odorless gas, which, upon vaporization of the liquid agent, imparts a special smell to the gas, ensuring that it can be immediately detected by people or instruments in the event of a gas leak.