As part of our nation's program to reduce dependence on fossil fuels, various gasification technologies are being applied. These processes take renewable organic material and, through the application of heat and pressure, convert the materials into syngas for further use. Arguably, in nearly all of these processes, the most critical design aspect is the reliable and efficient removal of contaminant, particulate, gases, and unnecessary water vapor from the syngas stream. Complicating the gas cleaning equipment design is the detrimental formation of tars and scale, coupled with the need to operate at higher temperatures and pressures than those normally encountered with common 'atmospheric' gas cleaning applications. The design philosophy and unique features of some recent successful gas cleaning systems as applied to gasification are described.
In an effort to reduce our dependence on foreign oil and to preserve valuable domestic fossil fuel reserves, many firms are looking at gasification technology as a method to convert replaceable organics into end products.
Firms currently are converting cellulosic type 'wastes' and wood material - infected wood, discarded building materials, grasses, pulp mill liquors, straw, and other materials-into syngas. The syngas then can be converted to fuel gas or be further processed into materials, such as plastics, that formerly had been produced from petroleum. Often, the syngas can be used to provide the motive heat for electrical generation.
The gasification process typically involves preparation of the 'fuel,' or feedstock material, by drying and/or size reduction, followed by the application of heat, often in the form of steam - along with pressure - in a gasifier. The gasifier also may be a plasma type, wherein the feedstock is dissociated using electrical energy.
In the gasifier, feedstock is converted to syngas without the application of oxygen. The carbon in the feedstock, along with hydrogen that may be present - or be contributed by steam if it's used - is converted to primarily methane gas, the main component of the syngas. Unlike combustion, which would convert the carbon to carbon monoxide (CO) or carbon dioxide (C02) with a release of heat, the gasifier makes the conversion to methane and thus reduces the formation of C02. Reduced C02 formation can be an advantage since it's a gaseous component of global warming.