The following report gives a brief look at the history and theory of gasification. Specifically it deals with the design of the stratified downdraft gasifier as published by the Federal Emergency Management Agency (FEMA) in 1989, and some potential methods to remedy the reported large amounts of tar that it produces in normal operation.
The first part of this report explains the basics of gasification theory. Next the relevance of gasification is addressed through a short explanation of the viability of gasification technology as an alternative energy source for power generation – especially in the field of transportation. Australia’s vulnerable position as a heavy relier on imported oil makes alternative fuel for transportation a particularly pertinent topic. This fact is highlighted. A short comparison with Sweden follows - Sweden being a country which has planned contingency measures to remediate the effects that any potential fuel shortage would have on that country. Next, an outline is made of some of the historical developments and a number of the milestones that have taken place within the area of gasification. The experience during the Second World War is important in showing the vital role that gasification technology can play in providing an alternative source of energy to oil.
Brief mention is made of the fuel crises of the 1970’s which led to the publication of a number of papers by large not-for-profit organisations in the 80’s and early 90’s. One such paper, by FEMA details the design of a new type of ‘stratified downdraft gasifier’ suitable for emergency fabrication and use in a fuel crisis. This design, though possibly okay for short term use, is anecdotally reported to produce high amounts of tar – always a serious problem if the intent is for the long term operation of internal combustion engines. Some ways of modifying the FEMA system to improve its tar performance are then looked into.
Specifically, two methods are focused on and ultimately tested. They are: the insulation of the firetube, and the use of air nozzles. Experimental testing showed apparent performance gains by the use of these two features; with both causing a noticeable drop in the amount of tar produced.