A Prototype Downdraft Gasifier Design with Mechanical Stirrer for Rice Straw Gasification and Comparative Performance Evaluation for Two Different Airflow Paths

In this research, a prototype downdraft throatless gasifier was designed with a mechanical stirrer. The gasifier was designed for gasification of rice straw pellets. The diameter of the reactor was 350 mm and a nominal value for the heat power of biomass input was 70 kW. Rice straws which were collected from Thrace Region of Turkey gasified for determination of the designed gasifier performance in Namik Kemal University Biosystem Engineering Laboratories. The effects of airflow path and stirring process on the gasification efficiency during the gasification process were investigated. Temperatures and airflow rates observed and adjusted by controlling the air flow rate in the automation system constantly. Pellets were gasified using two different airflow paths with the same equivalence ratio of 0.2 and these were compared. Air inlet from the top showed better results than air inlet from tuyeres. For the air inlet from the top, the higher heating value of producer gas was determined as 5.047 MJ Nm(-3) and cold gas efficiency was calculated as 65.4%. H-2/CO ratio was found as 1.385 which was higher than the air inlet from tuyeres.