Syngas is an abbreviation for synthesis gas, which is a mixture comprising of carbon monoxide, carbon dioxide, and hydrogen. The syngas is produced by gasification of a carbon containing fuel to a gaseous product that has some heating value. Some of the examples of syngas production include gasification of coal emissions, waste emissions to energy gasification, and steam reforming of coke.
The name syngas is derived from the use as an intermediate in generating synthetic natural gas and to create ammonia or methanol. It is a gas that can be used to synthesize other chemicals, hence the name synthesis gas, which was shortened to syngas. Syngas is also an intermediate in creating synthetic petroleum to use as a lubricant or fuel.
Syngas has 50% of the energy density of natural gas. It cannot be burnt directly, but is used as a fuel source. The other use is as an intermediate to produce other chemicals. The production of syngas for use as a raw material in fuel production is accomplished by the gasification of coal or municipal waste. In these reactions, carbon combines with water or oxygen to give rise to carbon dioxide, carbon monoxide, and hydrogen. Syngas is used as an intermediate in the industrial synthesis of ammonia and fertilizer. During this process, methane (from natural gas) combines with water to generate carbon monoxide and hydrogen.
The gasification process is used to convert any material that has carbon to longer hydrocarbon chains. One of the uses of this syngas is as a fuel to manufacture steam or electricity. Another use is as a basic chemical building block for many petrochemical and refining processes.
The general raw materials used for gasification (creation of syngas) are coal, petroleum based materials, or other materials that would be rejected as waste. From these materials, a feedstock is prepared. This is inserted to the gasifier in dry or slurry form. In the gasifier, this feedstock reacts in an oxygen starved environment with steam at elevated pressure and temperature. The resultant syngas is composed of 85% carbon monoxide and hydrogen and small amounts of methane and carbon dioxide.
The syngas may contain some trace elements of impurities, which are removed through further processing and either recovered or redirected to the gasifier. For example, sulfur is recovered in the elemental form or as sulfuric acid and both of these can be marketed. Syngas is a primary source of sulfuric acid. If syngas contains a considerable quantity of nitrogen, the nitrogen must be separated to avoid production of nitric oxides, which are pollutants and contribute to acid rain production. Both carbon monoxide and nitrogen have similar boiling points so recovering pure carbon monoxide requires cryogenic processing, which is very difficult.
If the syngas is to be put to use to generate electricity, then it is generally used as a fuel in an IGCC (integrated gasification combine cycle) power generation configuration. The energy is then utilized by the factor that original produce the syngas, thereby lowering operating costs. There are commercially available technologies to process syngas to generate industrial gases, fertilizers, chemicals, fuels and other products.