Page 179 - New Trends In Coal Conversion

142 New Trends in Coal Conversion

6.1 Introduction

Coal is the world’s most abundant and widely distributed fossil fuel source and is an
essential fuel in many countries. Coal contributes to 23% of the share of primary en-
ergy production and 39% of the electricity generated worldwide. In addition, about
70% of the world’s steel production depends on coal feedstock. To promote the use
of coal in an environmentally and economically feasible way, a continuous develop-
ment in clean coal technology (CCT) is necessary to reduce the impact of its use on
the environment and human health. The greatest challenge consists of bringing the
CCT cost down to achieve near-zero emissions for baseload coal-fired power genera-
tion (IEA, 2017).
New trends in clean coal combustion technology are strongly influenced by the
need to reduce greenhouse gas (GHG) emissions. Conventional techniques for flue
gas treatment derived from fossil fuel combustion in coal combustion power plants
(PCCs) are focused on the abatement of criteria pollutants such as the particulate mat-
ter, NO x , and SO x . Further improvements have been made in these techniques in terms
of pollutant removal and energy efficiency not only because environmental legislation
has become more restrictive but also because of stricter requirements regarding trace
pollutant content caused by the tail-end CO 2 capture processes.
Integrated gasification combined cycle (IGCC) is the coal-fired power plant tech-
nology that provides the greatest potential for minimizing emissions associated with
using coal to produce electricity. IGCC power plants turn solid fuel into syngas. Before
syngas is burned to produce electricity, impurities can be removed from the fuel more
effectively and efficiently than can be accomplished in PCC where postcombustion
cleanup is required. This capacity for the precombustion cleanup of pollutants is
one of the technology’s primary advantages over conventional coal combustion ap-
proaches. Lower cost and more effective removal of currently regulated pollutants,
including the particulates, sulfur and mercury (Hg), is made possible with IGCC.
This technology also allows for lower cost separation and capture of CO 2 and hence
is advantageous to PCC in terms of efficiency, environmental performance, and effi-
ciency penalty for the application of carbon capture and storage (CCS) (Lim et al.,
2017; Wolfwersdorf and Meyer, 2017). In this sense, IGCC is a promising power gen-
eration technology for use as an alternative to conventional Pulverized Coal Power
Plant (PCPP) (Ju and Lee, 2017). Although operative IGCC plants have existed since
the 1990s, there are no standardized systems available, and the integration of basic
units, including gas cleaning, is still challenging (Wolfwersdorf and Meyer, 2017).
IGCC technology is not currently commercially competitive due to the high costs of
building an IGCC plant and the additional risk in investing in technology without
an operational history (Campbell et al., 2000; EPRI, 2005; NETL, 2002).

6.2 Gas cleaning technology in PCC

Clean coal technology comprises a variety of pollutant abatement techniques, which
have emerged in recent decades in response to the environmental problems derived