Simulation Study of an Oxy-Biomass-Based Boiler for Nearly Zero Emission Using Aspen Plus

Bioenergy integrated CO 2 capture is considered to be one of the viable options to reduce the carbon footprint in the atmosphere, as well as to lower dependability on the usage of fossil fuels. The present simulation-based study comprises the oxy bio-CCS technique with the objective of bringing about cleaner thermal energy production with nearly zero emissions, CO 2 capture and purification, and with the ability to remove NO x and SO 2 from the flue gas and to generate valuable byproducts, i.e., HNO 3 and H 2 SO 4 . In the present work, a simulation on utilization of biomass resources by applying the oxy combustion technique was carried out, and CO 2 sequestration through pressurized reactive distillation column (PRDC) was integrated into the boiler. Based on our proposed laboratory scale bio-CCS plant with oxy combustion technique, the designed thermal load was kept at 20 kW th using maize stalk as primary fuel. With the objective of achieving cleaner production with near zero emissions, CO 2 rich flue gas and moisture generated during oxy combustion were hauled in PRDC for NO x and SO 2 absorption and CO 2 purification. The oxy combustion technique is unique due to its characteristic low output of NO sourced by fuel inherent nitrogen. The respective mechanisms of fuel inherent nitrogen conversion to NO x , and later, the conversion of NO x and SO 2 to HNO 3 and H 2 SO 4 respectively, involve complex chemistry with the involvement of N–S intermediate species. Based on the flue gas composition generated by oxy biomass combustion, the focus was given to the fuel NO x , whereby different rates of NO formation from fuel inherent nitrogen were studied to investigate the optimum rates of conversion of NO x during conversion reactions. The rate of conversion of NO x and SO 2 were studied under fixed temperature and pressure. The factors affecting the rate of conversion were optimized through sensitivity analysiês to get the best possible operational parameters. These variable factors include ratios of liquid to gas feed flow, vapor-liquid holdups and bottom recycling. The results obtained through optimizing the various factors of the proposed system have shown great potential in terms of maximizing productivity. Around 88.91% of the 20 kW th boiler’s efficiency was obtained. The rate of conversion of NO x and SO 2 were recorded at 98.05% and 87.42% respectively under parameters of 30 °C temperature, 3 MPa pressure, 10% feed stream holdup, liquid/gaseous feed stream ratio of 0.04 and a recycling rate of the bottom product of 20%. During the simulation process, production of around four kilograms per hour of CO 2 with 94.13% purity was achieved.