Manufacturing

Technologically Proven

Coal is converted to gas that can be used in manufacturing applications using a “gasifier.” According to the U.S. Department of Energy, a gasifier converts hydrocarbon feedstock into gaseous components by applying heat under pressure in the presence of steam.  

A gasifier differs from a combustor in that the amount of air or oxygen available inside the gasifier is carefully controlled so that only a relatively small portion of the fuel burns completely. This “partial oxidation” process provides the heat. Rather than burning, most of the carbon-containing feedstock is chemically broken apart by the gasifier’s heat and pressure, setting into motion chemical reactions that produce “syngas.” Syngas is primarily hydrogen and carbon monoxide, but can include other gaseous constituents; the composition of which can vary depending upon the conditions in the gasifier and the type of feedstock.

Minerals components in the fuel, which don’t gasify like carbon-based constituents leave the gasifier either as an inert glass-like slag or in a form useful to marketable solid products. A small fraction of the mineral matter is blown out of the gasifier as fly ash and requires removal downstream.

Sulfur impurities in the feedstock are converted to hydrogen sulfide and carbonyl sulfide, from which sulfur can be easily extracted, typically as elemental sulfur or sulfuric acid, both valuable byproducts. Nitrogen oxides, another potential pollutant, are not formed in the oxygen-deficient (reducing) environment of the gasifier; instead, ammonia is created by nitrogen-hydrogen reactions. The ammonia can be easily stripped out of the gas stream.

Another advantage of gasification-based energy systems is that when oxygen is used in the gasifier (rather than air), the carbon dioxide produced by the process is in a concentrated gas stream, making it easier and less expensive to separate and capture. Once the carbon dioxide is captured, it can be sequestered – that is, prevented from escaping to the atmosphere.