Syngas evolution and energy efficiency in CO2-assisted gasification of pine bark

Abstract

Forestry residues, one of the main sources of carbon–neutral lignocellulosic biomass, are abundant to support energy sustainability and reduce carbon emissions into the atmosphere. In this paper, the characteristics of syngas from the gasification of pine bark in CO2 atmosphere are presented using a fixed-bed reactor at temperatures of 700, 800, 900 and 1000 °C. Gasification behavior at these temperatures was investigated in terms of evolved flow rate of CO, H2, CH4, total hydrocarbons (CmHn) and total syngas yield. Solid residues were analyzed for morphological characteristics. Total accumulative syngas rate and overall energy efficiency at different temperatures were also calculated and compared. Results showed that gas yields of H2, CO, and total syngas increased with increase in temperature. However, the yield of CmHn was maximum at 800 °C. Syngas with heating value of 21.0 to 23.3 MJ/kg was obtained from CO2 gasification. CO mole fraction accounted for approximately 66–80% (vol.) of the total syngas from char and CO2 gasification via Boudouard reaction and hydrocarbon reforming with CO2 at high temperatures. Gasification of each gram of pine-bark provided with the capability of converting ~0.25–1.74 g of CO2 into valuable products examined at 800 to 1000 °C. The porosity and thus specific surface area of solid char residue increased with increase in temperature. Overall energy efficiency increased with increase in temperature to values as high as 56.6% at 1000 °C, while maintaining this high efficiency over long reaction times that revealed promising pathway for harnessing of energy production and CO2 utilization.