(691e) Simulation of CO2 Gasification of Manure-Derived Hydrochar Using Aspen Plus

Approximately 160 million tonnes of cow manure are produced every year in the US. However, high moisture content, eutrophication, greenhouse gas emissions, and excreted pathogens are some major concerns associated with livestock manure, which limit the manure application as fuel and fertilizer. Direct combustion of manure is not an efficient option due to the high moisture content (>80 %) and can produce large amounts of SO_x and NO_x. Therefore, an efficient energy conversion process is necessary to utilize this large amount of annually accumulated livestock manure for bioenergy generation.

Gasification of hydrothermally treated cow manure can be an efficient option to utilize this alternate source of energy. Gasification process will convert the hydrothermally treated feedstock into a mixture of gaseous products in presence of limited amount of oxidizing agents like oxygen (O₂), steam, air or carbon dioxide (CO₂) or a mixture of these agents. The gaseous product will consist of mainly carbon monoxide (CO) and hydrogen (H₂), known as synthetic gas or syngas which can be converted to different fuel forms as necessary. This process also reduces to amount of CO₂ produced which makes it environmental friendly.

The goal of this study was to simulate the gasification process in ASPEN plus V9 simulation software using previously determined reaction kinetics and CO₂ as the oxidizing agent to evaluate the effect of process parameters (temperature, equivalence ratio) on syngas production. Results showed that CO and H₂ concentration increased with increasing temperature and equivalence ratio. However, after a certain range the CO concentration started decreasing. These results were later validated using data from a practical gasification experiment performed in a downdraft gasifier.