Design and Testing of a Small-Scale Updraft Gasifier for Gasification of Eastern Redcedar

Abstract

Eastern redcedar is considered a nuisance by many people in Oklahoma where the plant is taking over approximately 762 acres (3.0 square km) of rangeland per day. Gasification of eastern redcedar is one alternative for providing a market by converting the trees to fuel, There were two objectives of this research: (1) Provide a detailed design of an updraft gasifier that can be used with a variety of feedstocks including eastern redcedar mulch and (2) Test the viability of eastern redcedar mulch as a feedstock for gasification The design aspect included drawing gasifier components, fabrication, testing, redesign, and retesting. Parts were fabricated in the Biosystems and Agricultural Engineering Laboratory. Operating procedures for the new design were established and used throughout the testing phase. Mulched eastern redcedar was used as the feedstock for gasification. Optimal airflow was established based on consistent gasifier operation. An updraft gasifier was designed for gasification of eastern redcedar mulch. Unique features of the design included: a simple design useful for testing feedstocks with a variety of particle sizes and moisture and ash contents, a scraper/agitator system which deters air channeling as demonstrated by a stable temperature gradient and consistent combustion zone temperatures, and a feedstock hopper and auger which allows semi-continuous feedstock feed rate. Testing with eastern redcedar mulch resulted in best operation in the ER range of 0.177 to 0.215 for the 8-inch (20 cm) diameter gasification chamber as evidenced by HHV and cold gas efficiency. Moisture and ash content and particle size are suitable for gasification in this system without pretreatment. Gasification was complete, with no noticeable tar buildup in the gasifier. The testing of this gasification system provides evidence that eastern redcedar can be utilized as a feedstock for gasification. The design is original and provides a tool for future experimentation at Oklahoma State University and future construction of gasifiers of this type.