1. Gas combustion calculation
Combustion calculations are the basis for gas combustion applications. It provides a reliable basis for the design of industrial and civil combustion equipment
Gas combustion calculation includes three aspects:
(1) Determine the calorific value of the gas
(2) Calculate the amount of air required for combustion and the amount of flue gas produced (3) Determine the combustion temperature and draw a temperature map
1.1 Combustion and combustion reaction measurement equation
For gaseous fuels, combustion refers to the physical and chemical reaction process in which the combustible components (CmHn, H2, CO, etc.) in the gas undergo intense oxidation with oxygen under certain conditions and generate a large amount of heat and light. The combustion reaction measurement equation is carried out Basis for gas combustion calculations. It can express the quantitative proportional relationship between each combustible substance in the gas and its combustion products before and after the combustion reaction.
The combustion reaction equation of any form of hydrocarbon CmH. can be expressed by the following general formula
C.H, +(m+2)0, = mco,+一H,O+AH
In the formula AH-1mol CmH, the heat released after complete combustion
1.2 Determination of gas calorific value
---Calorific value 1 - The heat released by the complete combustion of 1m' gas is called the calorific value of the gas, and the unit is kJ/m or kJ/kg
---High calorific value - 1m'The heat released when the flue gas is cooled to the original temperature after the gas is completely burned, and the water vapor in it is discharged in the state of condensed water
---Low calorific value - the heat released when the flue gas of 1m3 gas is completely combusted and its flue gas is cooled to the original temperature, and the water vapor in it is discharged in the state of steam.
---The high calorific value of gas is numerically greater than its low calorific value, and the difference is the latent heat of vaporization of water vapor (decreases with increasing temperature)
---In industrial and civil gas application equipment, the water vapor in the flue gas is usually discharged in a gaseous state, so the low calorific value of the gas is often used in actual engineering. Sometimes in order to further utilize the heat in the flue gas, the flue gas is cooled to below its dew point temperature to condense and liquefy the water vapor. Only then is the high calorific value of the gas used.
---The gas actually used is a mixed gas containing multiple components. The calorific value of the mixed gas is generally calculated from the calorific value of each single gas according to the mixing law.