Prediction of carbon capture and sequestration (CCS) technology in a 125 MW tangentially coal-fired subcritical thermal power plant for retrofitting in Bangladesh

Abstract

The main objective of this study is to assess the use of carbon capturing and sequestration (CCS) technology in the existing plant to reduce the emissions leading to retrofitting. A typical 125 MW tangentially coal-fired Barapukuria Thermal Power Plant (BTPP), Bangladesh has been scrutitinized considering air-firing (existing) and five different oxy-firing (OF) cases have been numerically investigated. For predicting the particle flow, radiative heat transfer and turbulence effects, discrete droplet method (DDM), discrete transfer radiation method (DTRM) and k–ϵ model is considered respectively. For homogeneous reaction for the devolatilization and heterogeneous reactions for the char oxidation process, a two steps reaction mechanism is considered. Model has been validated by comparing the predicted flue gas temperature against the plant data at different positions of the furnace and reasonable agreement have been observed. This study assessed the flow characteristics, thermal behavior and species generations of the selected plant under 80% fuel loading. It is predicted that with the increase of cases from air-firing, level of oxiding elements are increasing in the main combustion zone due to enriched O2 level leading to complete combustion of the particles. It is also found that for OF 31 case, level of CO2 is close to the air-firing case. it has been found that wall temperature is comparatively higher for 100% loading and comparatively lower for 50% loading for almost all similar type of air or oxy-firing conditions. For 100% load, the wall temperature has been reached around 2900 K for OF31 case. It is predicted that air operation equivalent to oxy-firing have been found at < OF 30+ % (Flame temp), at = OF 30+ % (Convec Heat transfer) and at > OF 30+ % (radiative Heat transfer) respectively.