A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Enviro1m1ent, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 2001

The main objective of this study was development of a Multi-Stage Gasifier Unit, using pre-heated air for engine applications. A cross-flow gas-to-gas plate heat exchanger to preheat the air supplied to the gasifier by recovering heat from the exhaust of a diesel engine was designed, fabricated and tested. A two-stage gasifier was fabricated; primarily it was tested with different air supply rates, with and without preheating of air to find the temperature profile in the gasifier and the quality of producer gas. Next, the gasifier was coupled with a diesel engine. The producer gas was cleaned and cooled using a cyclone and a spray tower. The diesel engine was tested on a dual fuel mode using producer gas and diesel as well as on diesel alone mode. Dried wood and coconut shell were used separately to fuel the gasifier. The two-stage gasifier developed two high temperature zones inside it. It normally experienced occasional blockage of fuel, when air was supplied through two ports only. This was successfully prevented by addition of a part of primary air from the top of the gasifer. An introduction of 50 % primary air from the top showed better results by creating a more uniform high temperature zone favorable for producing of higher quality gas and cracking tar. A Perkins diesel engine of three cylinders was operated at a constant speed of 1500 rpm, on diesel fuel alone and on dual-fuel. A maximum value of 71 % of energy supply by producer gas was achieved for a load of 2.6 kW and gasifier air supply rate of 250 lit/min in the tested range of electrical power 0 - 10 kWe.