Comparative Analysis of Blowing Agents for Coal Gasification in Oxy-Fuel Energy Complexes

Oxy-fuel energy complexes (OFCs) offer a promising approach for carbon dioxide (CO₂) capture in coal-fired power plants, but efficient coal gasification is crucial to maintain high cycle efficiency. However, there are currently no studies on the effect of the type of blowing agent on OFCs’ efficiency. This study evaluates various blowing agents—air, oxygen, steam, CO₂, and their mixtures—for gasification of Kaakhemsky coal, focusing on optimal consumption, generator gas composition, temperature, calorific value, and efficiency. Using heat balance equations and equilibrium constants, calculations were performed under assumptions of stationary operation at 40 atm pressure, incorporating reactions like water-gas shift and methane reforming. Results indicate that air-based blasting yields high nitrogen content (up to 54%), leading to low calorific values (8.4 MJ/m³) and high NOx emissions, rendering it unsuitable. Pure CO₂ and steam blasting require excessive agent consumption (6.2–10 kg/kg coal) and external heat, producing low-quality gas with high CO₂ or H₂O fractions inhibiting combustion. Oxygen blasting provides high-quality gas (2% non-combustibles, 17.8 MJ/m³ calorific value) but demands pure oxygen and excess heat recovery at 1004°C. Mixtures of oxygen with steam or CO₂ emerge as optimal: oxygen-steam reduces oxygen consumption to 0.3 kg/kg coal, enhancing calorific value to 19.7 MJ/m³ at 187°C, while oxygen-CO₂ achieves 17.2 MJ/m³ at 260°C without steam generation needed. Both options minimize non-combustible species fraction (<7%), support stable combustion, and align with OFCs’ requirements for low emissions and high efficiency. Recommendations include cycle modeling to compare these for integrated power plant design, potentially improving CO₂ capture and thermal performance.