Biogas can serve as a substitute for natural fuel, but its use is associated with a number of features associated with the difference in its composition from natural gas. Landfill gas generated in the body of MSW landfills is characterized by a significant change in composition. The purpose of the work was a theoretical study of the effect of changing the composition of biogas and the coefficient of excess air on the parameters of the combustion process - gas and air consumption, combustion temperature and on the volume of combustion products. The influence of the ratio of CO2 and N2 contained in biogas on the main combustion characteristics was also evaluated. It is concluded that the combustion of biogas of variable composition, subject to ensuring the specified heat output of the furnace or boiler, does not require a change in air flow, but only a change in the flow of biogas depending on the content of methane in it. Reducing the content of methane leads to an increase in the volume of exhaust gases and a decrease in their temperature. Therefore, a decrease in the methane content in biogas can lead to a decrease in the intensity of heat exchange and a decrease in the efficiency of the unit. The ratio of CO2 and N2 practically does not affect the thermal parameters of combustion. The results of the study are necessary when designing equipment and determining the operating mode of equipment that burns biogas that is formed in natural conditions, for example, landfill gas generated at HSW landfill.

The goal of this paper was the study flame lengths dependence on biogas composition to decide if the boiler`s furnaces using natural gas need reconstruction for biogas usage or it is possible to use the already existing equipment. The analytical one-dimensional model of a diffusion straight-flow flame in unrestricted and restricted space and the numerical three-dimensional model of a turbulent flame in a swirled airflow have been applied in this research. The research has analyzed the flame length for methane content of 20 to 100% in biogas. It has been concluded that by changing the methane content in biogas the heating plant1s operating mode can be stable on the condition that the biogas flow rate is controlled to ensure constant heat production during its combustion and turbulent flame with a swirled airflow. Combustion, in this case, can be done by using the same burner and without changing the size of the furnace.