Page 42 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

Chapter | 1 Introduction 21

environment, gave support to large-scale development of integrated
gasification combined cycle (IGCC) power plants.
Post-2000: Global warming and political instability in some oil-producing
countries gave a fresh momentum to gasification and pyrolysis. The threat
of climate change stressed the need for moving away from carbon-rich
fossil fuels. Gasification came out as a natural choice for conversion of
renewable carbon-neutral biomass into gas and torrefied biomass as an
option for replacing coal in power plants.
The quest for energy independence and the rapid increase in crude oil
prices prompted some countries to recognize the need for development of
IGCC plants. The attractiveness of gasification for extraction of valuable
feedstock from refinery residue was rediscovered, leading to the develop-
ment of some major gasification plants in oil refineries. In fact, chemical
feedstock preparation took a larger share of the gasification market than
energy production.
A brief review of historical development of the pyrolysis process is
given in Section 5.1.1.

1.5 COMMERCIAL ATTRACTION OF GASIFICATION
Gasification is a promising and important means of biomass conversion. A
major attraction of gasification is that it can convert waste or low-priced
fuels, as well as biomass, coal, and petcoke, into high-value chemicals like
methanol. Biomass holds great appeal for industries and businesses, espe-
cially in the energy sector. For example:
1. Flue-gas cleaning downstream of a gasification plant is less expensive
than that in a coal-fired plant.
2. Polygeneration is a unique feature of a gasifier plant. It can deliver steam
for process, electricity for grid, and gas for synthesis, thereby providing a
good product mix. Additionally, a gasifier plant produces elemental sulfur
as a by-product for high-sulfur fuel.
3. For power generation, an IGCC plant can achieve a higher overall effi-
ciency (38 41%) than a combustion-based Rankin cycle plant with a
steam turbine.
4. An IGCC plant can capture and store CO 2 (CCS)atone-half ofwhatitcosts
in a traditional PC plant (www.gasification.org). Other applications of gasifi-
cation that produce transport fuel or chemicals may have even lower cost for
CCS.
5. A process plant that uses natural gas as feedstock can use locally avail-
able biomass or organic waste and gasify the instead, and thereby reduce
dependence on imported natural gas, which is known for exceptionally
high supply and price volatility.