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

İbrahim Savaş Dalmış,Serkan Tuğ,Türkan Aktaş,Birol Kayişoğlu,Figen Daşçı Durgut,Mehmet Recai Durgut

doi:10.15832/ankutbd.456649

Abstract

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%. H2/CO ratio was found as 1.385 which was higher than the air inlet from tuyeres.

Highlights

One of the most controversial topics in the world is global climate change caused by CO2 emissions
Biomass gasification occurs as a thermochemical process to produce gaseous fuel from carbonaceous feedstock which are included but not limited to pinewood, eucalyptus wood, wheat straw, rice straw, rice husk, corn cob, corn stalk, sugarcane bagasse, poplar, hazelnut shell, coconut shell, switch grass, olive husk and so on (Demirbas 2004; Mondal et al 2011; Nwokolo et al 2016)
A prototype gasifier system with an overhead controlled mechanical stirrer was designed for rice straw pellets gasification

Summary

Introduction

One of the most controversial topics in the world is global climate change caused by CO2 emissions. Greener energy sources have become significant alternatives to current energy resources and the number of the works being carried out on renewable energy has increased in current years. Biomass is one of the renewable energy sources which inspires interest for researchers (Anis & Zainal 2011). Fossil fuel resources are gradually decreasing causing the cost of petroleum-based products to increase. This problem imposes a need for an equipment that can produce an alternative source of fuel (Manguiat et al 2015). Producer gas consists of carbon monoxide, hydrogen, carbon dioxide, methane, traces of higher hydrocarbons, such as ethane and ethylene, water vapor, nitrogen (if air is the oxidizing agent), and various contaminants, such as small char particles, ash, tar and oil (Basu 2013)

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