Syngas is the abbreviation for Synthesis gas. This is a gas mixture that comprises of carbon monoxide, carbon dioxide and hydrogen. The syngas is produced due to the gasification of a carbon containing fuel to a gaseous product that has some heating value. Some of the examples of syngas are as follows – gasification of coal, waste to energy gasification, steam reforming of natural gas to generate hydrogen.
The name syngas is derived from the use as an intermediate in generating synthetic natural gas and to create ammonia or methanol. Syngas is also an intermediate in creating synthetic petroleum to use as a lubricant or fuel.
Syngas has 50% the energy density of natural gas. It can be burnt and is used as a fuel source. The other use is as an intermediate to produce other chemicals. The use of syngas as a fuel 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. This carbon dioxide combines with carbon to produce carbon monoxide.
Syngas is used as an intermediate in the industrial synthesis of hydrogen and ammonia. During this process, methane (from natural gas) combines with water to generate carbon monoxide and hydrogen. As a residue of energy gasification, syngas is produced and this is used as a fuel to create electricity.
If syngas consists of a considerable quantity of nitrogen, this nitrogen must be separated. Both carbon monoxide and nitrogen have similar boiling points and thus, recovering pure carbon monoxide by cryogenic processing is very difficult.
The gasification process is used to convert any material that has carbon to a syngas that is made up of carbon monoxide and hydrogen. 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 users in the petrochemical and refining industries. Gasification is a very vital process. It raises the value of low value feedstocks by transforming them to marketable products and fuels.
The general raw materials used for gasification 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 and oxygen at elevated pressure and temperature. In this way, syngas is manufactured. This syngas comprises of 85% of carbon monoxide and hydrogen and small amounts of methane and carbon dioxide.
The syngas so produced may contain some trace elements of impurities. These are removed from the syngas. Further, they are 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.
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. There are commercially available technologies to process syngas to generate industrial gases, fertilizers, chemicals, fuels and other products.