Theoretical study of activated carbon production via a two-step carbonization-activation process based on Aspen Plus calculation

Using waste biomass to produce high-value activated carbon is an important way for biomass resource utilization. The energy and mass balance during carbonization and steam activation is crucial for the system operation and still not be systematically understood and calculated. In this work, a detailed model for two-step activated carbon production was established based on Aspen Plus. The effect of activation temperature, steam/bio-char ratio, and activation agent on the activation process was investigated. The results show that utilization of the heat duty of combustion of volatiles and sensible heat from flue gas could supply the necessary energy for carbonization, steam generator (boiler), and activation reactors. Steam/bio-char ratio could influence the activation process and the heat balance. The steam/bio-char ratio was controlled as 1-2, which was reasonable for activation carbon production. The increasing heat load provided the higher reaction temperature condition and the sensible heat of syngas. From the point of view of theory and practice, for the production of wooden activated carbon, the activation temperature of 800-900 degrees C is reasonable. Directly using hot flue gas of volatile combustion as activation agent was energy-saving and benefiting the production of syngas with higher heating value.

Automated summary

Using waste biomass to produce high-value activated carbon is crucial for biomass resource utilization. The energy and mass balance during carbonization and steam activation is important for the system operation. Control of activation temperature and steam/bio-char ratio is essential for the activation process.