Term of Award

Spring 2024

Degree Name

Master of Science, Mechanical Engineering

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Mechanical Engineering

Committee Chair

Prakash Bhoi

Committee Member 1

Sevki Cesmeci

Committee Member 2

David Calamas

Abstract

With rapidly growing global economies and world population, fossil fuel continues to play a major role in meeting current energy demands. Carbon capture and storage (CCS) technologies have, hence, been implemented to reduce CO2 emissions in the atmosphere. With the implementation of CCS technologies comes the need to utilize the captured CO2. This research, therefore, proposes CO2 gasification of biochar as a viable carbon utilization pathway. With captured CO2 coming at various concentrations, there is a need to understand how CO2 concentration affects biochar conversion to useful products. This study, therefore, evaluates the effects of CO2 concentration on carbon conversion and product yield and performs kinetic analysis, using the volume reaction model, to determine important parameters such as activation energy and pre-exponential factor. The operating conditions utilized in this study include gasification temperatures of 700, 800, and 900 , inlet CO2 concentrations of 15, 30, 45, and 60 % by volume (N2 balance), and an inlet CO2 flow rate of 5 L/min. Biochar was gasified with CO2 in a fixed bed reactor and the concentration of the output gas was analyzed. An increase in temperature and inlet CO2 concentration both resulted in an increase in carbon conversion with a maximum carbon conversion of 57.1% occurring at 900 and 60% inlet CO2 concentration. Results also showed that CO2 conversion increased against temperature but decreased with increasing inlet CO2 concentration. The maximum CO2 conversion reported, in this study, was 76%, occurring at 900 and 15% inlet CO2 concentration. An activation energy in the range of 109 to 117 kJ/mol and pre-exponential factor in the range of 63 to 253 s-1 were determined in this study. This research explains that while carbon (biochar) conversion increases with increasing inlet CO2 concentration, CO2 conversion decreases as inlet CO2 concentration increases. Flue gases captured at low concentrations can, therefore, be utilized for gasification, with only impurities needing to be removed, as opposed to carbon sequestration. Overall, this study describes how captured CO2 improves carbon conversion efficiency and suggests that CO2 gasification of biochar is a potential carbon utilization pathway for greenhouse gas emission reduction.

OCLC Number

1437797854

Research Data and Supplementary Material

No

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