Wood gasifiers had been operated successfully to generate low-calorie gas at the beginning
of the 20th century. Then a good number of commercial gasifiers were installed in the
United States to provide electricity and street lighting to many cities. Within a few years
a large number of automotive gas producers were operating all over the world. Surprisingly,
these technologies had been almost abandoned after the 1950s (9). At present a
wide range of raw materials from agricultural residues to municipal solid wastes have
been suitably used for gasification.
of the 20th century. Then a good number of commercial gasifiers were installed in the
United States to provide electricity and street lighting to many cities. Within a few years
a large number of automotive gas producers were operating all over the world. Surprisingly,
these technologies had been almost abandoned after the 1950s (9). At present a
wide range of raw materials from agricultural residues to municipal solid wastes have
been suitably used for gasification.
It is important to note the following:
A gasifier can be used to generate low- or medium-calorie gas for direct combustion
or to produce a fuel gas for an internal combustion engine.
A gasifier has to be equipped with an effective gas cleaning system if the gas is to
be used for an internal combustion engine.
Some of the products of gasification are not only damaging to engines and burners,
but also harmful to human beings. That is why these gases cannot be used as cooking gas.
In general, the gasifiers may produce some condensable volatile product such as tar
that is not desirable. But its amount can be reduced significantly by introducing the following
three tar conversion mechanisms:
(a) thermal cracking at high temperature
(b) combustion of the tar with air, and
(c) catalytic thermochemical conversion.
