The photo is sourced from lignite.com
Coal is the most carbon-intensive type of feedstock for power generation. The Intergovernmental Panel on Climate Change (IPCC) estimates that greenhouse gas emissions total 820 grams of CO2-equivalent per 1 kilowatt-hour (kWh) of electricity for coal-fired power generation and only 490 grams of CO2-equivalent for gas-fired power generation, whereas biomass-based power generation produces 230 grams of CO2-equivalent per 1 KWh of electricity. Emissions can be partly reduced through combined use of fossil fuels and renewable energy sources: the IPCC estimates that the combustion of an 80% coal and 20% biomass mixture makes it possible to reduce the specific volume of greenhouse gas emissions to 740 grams of CO2-equivalent per 1 kWh of electricity.
Scientists from SFU and TPU have analysed a fuel mixture of another type where one or two grades of brown coal are used with a carbonizate, which is a product of coal gasification (solid fuel conversion to a combustible gas with the use of oxygen). In order to compare the efficiency of two-component and three-component mixtures, the researchers used thermogravimetric analysis to track changes in the weight of substances depending on temperature. The scientists heated two different mixtures by 20 degrees Celsius per minute and recorded their key characteristics: oxygen index (minimum percentage of oxygen required for combustion), temperature during combustion, and the volumes of thermal energy generated and absorbed at different stages of combustion.
The authors of the study have concluded that three-component mixtures where two different grades of brown coal are used with a carbonizate produce the best results in terms of efficiency. These mixtures combust faster and start generating heat quicker than two-component mixtures. The share of carbonizate in the mixture must not exceed 30%, as the latter’s energy characteristics deteriorate otherwise.
“The implementation of carbonised coal with high calorific value is a promising area of thermal power generation. However, it would be economically unsound to transition to pure carbonizate combustion due to costs, which is why we propose keeping carbonizate at no more than 30% to raise the calorific value of the fuel mixture,” Andrey Zhuikov, head of laboratory at the SFU Department of Thermal Engineering and Fluid Dynamics, is quoted as saying by the Russian Education Ministry.
