Optimal Design of Gasifier Reactor for Crop Residues Gasification Using Integrated MCDM Techniques/QFD Approach

Abstract

Gasification technology has a critical role to play in the quest to provide off and on-grid renewable energy solutions for rural agricultural communities. Optimal gasifier design is essential for sustainable energy generation and operation of gasifier systems. The aim of this study is therefore to design an optimal gasifier reactor for the gasification of crop residues using Integrated Multicriterial Decision Making (MCDM) Techniques and Quality Function Deployment (QFD) methodological approach. The MCDM/QFD framework consists of user requirement, engineering parameters and seven gasifier types. The engineering parameters were categorised under five sections and the best gasifier type under each category was determined using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The design characteristics of the best ranked gasifier type under each category was incorporated into a stratified downdraft gasifier reactor type. The characteristic of five crop residues and consideration of a 10-kW engine system for electricity generation was used to size and designed the gasifier reactor. The study revealed that updraft gasifier is the optimal gasifier that is efficient and can handle wide range of feedstock characteristics. Similarly, stratified downdraft and circulating fluidized bed gasifier are the optimal in terms gasifier operating conditions and good syngas quality respectively. A 45-kW semi-batch stratified Downdraft (SD) Gasifier with internal diameter and height of 0.36 m and 1.7 m respectively were designed based on average fuel consumption of 23 kg/hr and an airflow rate of 26.31 m³/hr. The optimal gasifier consists of a screw auger system, an extended ash collection bunker, and a gas recirculation combustion unit.