Influence of Thermal Physical Properties of Biogas Combustion Products on the Thermal Parameters of Water Heating Boilers

Abstract

The combustion products of biogas and natural gas differ in the content of components, which affects their heat content and heat exchange in boilers. To determine the possibility of using biogas in boilers designed for burning natural gas, the work compares the thermophysical properties of the combustion products of natural gas and biogas and their influence on the results of boiler calculations. Methods were obtained for calculating the thermal conductivity and viscosity of a mixture of gases depending on their composition and temperature. The comparison showed that the calorimetric and thermophysical properties of biogas combustion products differ from the properties of natural gas combustion products by up to 4 %, and the difference from the reference properties of combustion products given in the standard method for calculating boiler units is on average 6 %. A comparison has been made of the results of verification thermal calculations of low-power hot water boilers KVMG-1.0 and KSV-1.0 using the properties of combustion products given in the standard method for calculating boiler units, and when calculating them using the proposed equations. Calculations have shown that the results of calculations based on reference data of the standard method lead to higher values of exhaust gas temperatures and fuel consumption. It can be concluded that natural gas in boilers can be replaced by biogas without the need to reconstruct the boiler, but for thermal calculations it is necessary to take into account changes in the composition and properties of fuel combustion products.