High-pressure pyrolysis in a drop-tube reactor: Effect of the pressure and temperature on the resulting products and kinetics

Description

Thermochemical conversion processes, in particular pyrolysis, play a major role for the energetic and non-energetic utilization of secondary carbon resources. For many industrial applications of conversion technologies, great potential is foreseen in the transition to higher pressures. Higher pressures and temperatures are expected to cause an increase in the resulting species of liquid and solid products, hydrogen, and aromatic compounds [1,2]. In the case of pyrolysis, a few studies are performed at pressures up to 30-40 bar [1,2], while experimental data at higher pressure conditions up to 100 bar required for the design of the next generation of reactors are lacking.
The present study is focused on the effect of pressure and temperature on the pyrolysis kinetics and product yields. For this purpose, the pressure varies in the range between 5 and 100 bar and the temperature covers values from 600 to 800 °C. All experiments are carried out in a high-pressure drop-tube reactor with continuous feeding, which leads to high particle heating rates. The pyrolysis behavior of two samples of sewage sludge and coal as well as their blend are investigated. Particle and gas residence times are held constant in the experiments by the adjustment of the carrier gas flow rate. A comprehensive characterization of all pyrolysis products in the gaseous, liquid (tar/oil and water), and solid phase (char) is performed to systematically study the impact of process conditions on their respective yields. The reaction products have demonstrated the expected relationships, which indicate that the obtained kinetic data are reliable. Kinetic parameters of activation energy and frequency factor for the gas evolution of the main components (H2, CO, CO2, and CH4) – as a reference case – are determined to contribute to a comprehensive database for process modelling and further model development and validation.

References:
[1] Sekar, M., Mathimani, T., Alagumalai, A., Chi, N.T.L., Duc, P.A., Bhatia, S.K., Brindhadevi, K. Pugazhendhi, A. 2021. A review on the pyrolysis of algal biomass for biochar and bio-oil – Bottlenecks and scope. Fuel, 283, pp. 119190
[2] Matamba, T., Tahmasebi, A., Rish, S.K., Yu, J. 2020. Promotion effects of pressure on polycyclic aromatic hydrocarbons and H2 formation during flash pyrolysis of palm kernel shell. Energy Fuels, 34, pp. 3346-3356

Period	26 Sept 2023
Event title	11th International Freiberg Conference on Circular Carbon Economy: Towards Net-Zero Carbon Economy
Event type	Conference
Location	Rotterdam, NetherlandsShow on map
Degree of Recognition	International