Plasma gasification departs from typical gasification by the
addition of electricity to the combustion chamber. In plasma
gasification, fuel or waste is fed to a reactor vessel where an
electrically generated plasma at a temperature of 20,000 C° is
present. When the fuel or waste is exposed to the plasma it is
heated to a very high temperature (>2,000C°), which causes the
organic compounds in the fuel or waste to dissociate into very
simple molecules such as hydrogen, carbon monoxide, carbon dioxide,
water vapour and methane. These simple molecules, that are all
gases, are allowed to continuously flow from the reactor to gas
cooling and cleaning equipment. Ash and other inorganic material
present in the fuel or waste is melted down to a complex liquid
silicate that flows to the bottom of the reaction vessel. Metals
that are present also melt and flow to the bottom of the reactor
vessel, where they can either mix with the silicate, or if present
in a large enough quantity, float on the bottom of it as a separate
layer. The liquid melt is allowed to flow continuously from the
vessel to a water quench where the liquid silicate melt is cooled
to a non leachable, non toxic, obsidian like solid silicate. Some
metals are not melted. Instead, they vapourise and pass out of the
reactor vessel with the gases formed by the organic material.
When they enter the cooling equipment for the gases, they condense
to fine metal particulates. Halogen and sulphur compounds present
in the fuel are converted to hydrogen halides and hydrogen
sulphide, and pass out of the reactor with the other gases.
The gas from the reactor has a low to medium calorific value, and
is therefore suitable as the fuel for a gas fired power generation
unit. However, after leaving the reactor, the gas is still
contaminated with a number of undesirable compounds, such as
hydrogen chloride and metal particulates, that can cause damage to
machinery and the environment. The gas is therefore cleaned in
various process equipment. The cleaned gas, similar in quality to
natural gas, is then fed to a compressor and storage facility ready
for use. The most typical use of the gas is as fuel for power
generation, although it can also be used as a feedstock for
chemical processes. For example, the production of methanol. When
used as a fuel for power generation, more power is usually produced
than is consumed by the gasifier. Therefore, electrical power can
be exported for sale, or used for onsite purposes. For high
calorific value wastes and fuels the power exported can be four
times that consumed by the gasifier. For more information visit
safewasteandpower.com
