Gasification is a process that uses heat, pressure, and steam to convert materials directly into a gas. It has been in use for many years and involves breaking down complex organic molecules and carbon, in both liquid and solid-state, into simple gases.
Gasification is a thermal process but it is designed to produce a syn-gas as the main product, rather than the flue gas produced by a similar thermal process, combustion (i.e. incineration). The syn-gas consists largely of carbon dioxide and H2 and contains a large percentage of the inherent chemical energy of the input fuel.
Rather than treating waste in an oxygen-free environment, as is the case when waste is pyrolysed, gasification occurs in the presence of a controlled amount of air that is sufficient to allow only partial combustion of a small amount of the fuel input. The thermodynamics of the process is therefore very different from pyrolysis. Oxygen in the air aids the breakdown of the heavy organic compounds in the waste, thereby optimizing the yield of syn-gas. Most of the gases produced are flammable and are therefore generally used as fuel in processes or applications where such gases are required. When mixed with air, syn-gas can be used in gasoline or diesel engines with minimal modifications required to the engine.
Our gasification technologies differ in several technical aspects but rely on four key engineering factors:
Typical raw materials used are coal, petroleum-based materials, and organic materials. The feedstock is prepared and fed, in either dry or slurried form, into a sealed reactor chamber called a gasifier, where it is subjected to high heat, pressure, and either an oxygen-rich or oxygen-starved environment. Most commercial gasification technologies do not use oxygen, but all require an energy source to generate heat which starts the process.