Bio-methanol production from palm wastes steam gasification with application of CaO for CO2 capture: techno-economic-environmental analysis

Abstract

The gasification of biomass as a source of energy has gained much attention due to their potential in generating valuable downstream products. In this study, the production of downstream methanol using sorption enhanced steam gasification of palm oil wastes is configured through the Aspen Plus® simulator. The CO2 capture is accomplished by deploying CaO, which is an economically viable technique. For this purpose, the flowsheet configuration for methanol production is evaluated from techno-economic and environmental feasibility perspectives using built-in Aspen Plus techniques considering the impact of three key operating parameters; temperature, steam flowrate and CaO flowrate on methanol production. The results of the economic and environmental assessments demonstrate a reduction in CO2 emissions with respect to the optimum CaO case at 52.7 tonnes CO2-e/h, and in comparison with the base case (90.7 tonnes) and the case without adsorbent regeneration (53.3 tonne) for the Palm kernel shell (PKS) biomass feedstock. Whereas, the reduction in CO2 emissions for empty fruit bunches (EFB) biomass feedstock with respect to optimum CaO case is approximated at 61.8 tonne CO2-e/h, and in comparison with the base case (86.6 tonne CO2-e/h) and the case without adsorbent regeneration (62.6 tonne CO2-e/h). This reduction is also associated with an increase in the capital cost at $120.2 and $119.7 million, and the total annualised cost at $155.4 and $153.1 million of the optimum CaO case for PKS and EFB, respectively. Whereas, $119.1 and $107 million in capital costs with $146 and $139 million in annualised costs are reported for the base case and $118.9 and $117.3 capital costs with $146.7 and $142.3 million annualised costs reported for the case without adsorbent regeneration with respect to PKS and EFB feedstocks, respectively. However, it is also associated with a comparable net profit per methanol production at $201, $132 and $208 million, respectively for the three cases of PKS feedstock, and $170, $130 and $179 million respectively for the three cases of EFB feedstock. The use of CaO and regeneration slightly increases the cost, however, it significantly reduces the CO2 emissions.