engleski

Experimental study on the ash transformation during pressurized oxy-biomass combustion

Oxy-biomass combustion is one of the most promising technologies for negative CO2 emission. However, the first-generation oxy- combustion technologies, which operate under atmospheric pressure, suffer from a significant penalty in net generating efficiency, of over 10 percentage points. This is primarily due to the auxiliary energy consumption from the air separation unit (ASU), flue gas recirculation (FGR), and gas processing unit (GPU). By operating oxy-combustion under pressurized condition, the plant efficiency can be increased because the latent heat in the flue gas moisture can be recovered and coupled back into the steam cycle. Pressurized oxy- combustion has been regarded as the most promising technology for CO2 capture. In this study, we propose to burn biomass using pressurized oxy-combustion technology, named “Pressurized Oxy-biomass Combustion (POBC)”, which can achieve an acceptable cost for CO2 capture with a high net generating efficiency. However, the alkali metal and chlorine contents in biomass are high, resulting in severer slagging, ash deposition, and corrosion in biomass-fired furnace. What is worse, these problems can be aggravated under POBC conditions, because the significantly increased partial pressure of alkali vapor drives these vapor condensed and deposited at a much higher temperature than that under atmospheric pressure conditions. At the moment, there is no report on the mineral transformation of biomass ash during POBC process. In this study, the mineral transformation of biomass during POBC process is investigated in a pressurized fix- bed reactor. The effects of pressure (1-10 bar), temperature (500-1000 °C), atmosphere (O2/N2, O2/CO2), and aluminum-silicon additives (kaolin) on the ash mineral transformation are studied. The morphologies, elemental compositions, and mineral composition of the produced biomass ash under varied conditions are characterized using scanning electron microscopy equipped with energy dispersive X- ray spectrometry (SEM-EDS) and X-ray fluorescence (XRF), respectively.

Biomass ash ; pressurized oxy-combustion ; potassium ; chlorine.

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