Page 55 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

34 Biomass Gasification, Pyrolysis and Torrefaction

electricity, heat, and gas. This type of trigeneration system is thermodynami-
cally efficient and offers good flexibility to the operator.
Revenue from electricity and heat is often fixed by the local utility or
by government regulating agencies.

2.2.2.2 Revenue from Chemicals
One of the most important uses of gasification and pyrolysis is the produc-
tion of chemicals. The South African Synthetic Oil Limited (SASOL) has
been operating coal gasifiers for production of oil from coal since 1950s.
Here, coal is gasified to hydrogen and carbon monoxide. These gases are
synthesized into liquid hydrocarbon using Fischer Tropsch synthesis.
Nowadays, many petroleum refineries are using large-scale gasifiers to gas-
ify heavy oils into hydrogen or other gases. Of late, green chemicals are also
gaining popularity. Many chemicals, traditionally produced from petroleum
(e.g., resin), could be produced from pyrolysis of biomass as well. Activated
charcoal, for example, is an effective reaction medium for many chemical
reactions. Coke produced from biomass could be a substitute for coal-based
coke.
Revenue from chemicals could be much higher than that from electricity
or heat, but it fluctuates a great deal depending on the market condition.

2.2.2.3 Revenue from Secondary Fuel Production
A major commercially successful use of biomass has been the production
of substitute fuels. For example, for reduction in greenhouse gases from coal-
fired power plants there is a rising demand for torrefied biomass fuel. It is
also being considered in iron extraction in blast furnace for the same reason.
A large number of fermentation-based plants are in operation for production
of corn- or sugarcane-based ethanol that is to substitute for petro-derived gas-
oline. Production of diesel from waste cooking oil and fat is also done on a
commercial scale. Revenue from such transportation fuels varies with market
price of diesel or gasoline.
Carbon credit could also be an important source of revenue in some
cases. The net reduction in carbon dioxide emission from a project could
bring in additional revenue to the plant through sale of carbon credits. This
revenue could be added to that earned through the sale of the products of
biomass gasification, pyrolysis, or torrefaction.

2.3 BIOMASS CONVERSION PROCESS PLANT EQUIPMENT
AND COST
Depending upon the end use of the product, the process configuration of a
biomass plant would change, but its basic structure will remain the same.
Most of the auxiliary plant and equipment would be similar in a biomass