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Technologies for control of sulfur and nitrogen compounds and particulates 161

collection surface. An ESP can be installed at one of two locations. Most ESPs are
installed downstream of the air heater, where the temperature of the flue gas is between

130 and 180 C. An ESP installed downstream of the air heater is known as a “cold-
side” ESP. An ESP installed upstream of the air heater, where flue gas temperatures are
significantly higher, is known as a “hot-side” ESP.
The effectiveness of an ESP depends in part on the electrical resistivity of the par-
ticles in the flue gas. Coal with a moderate to high amount of sulfur produces particles
that are more readily controlled. Low sulfur coal produces a highly resistant fly ash that
is more difficult to control. The effectiveness of an ESP also varies depending on par-
ticle size. An ESP can capture greater than 99% of the total PM, while capturing 80 to
95% of PM 2.5 .
Fabric filters. Fabric filtration gets high efficiency collection of particulates, is a
well-established technology, and is the main alternative to electrostatic precipitation
for large combustion plants. The large size of electrostatic precipitators required and
operational problems to collect high resistivity fly ash has made FFs economically
competitive for large combustion plants. FFs are high-efficiency collectors and, unlike
ESPs, much less sensitive to particulate loading and fly ash characteristics. Design ef-
ficiencies are usually better than 99.5%. Overall collection efficiencies of
99.7%e99.9% and fine particulate collection efficiencies >99% are common.
An FF consists of a large surface area of fabric, which collects dust particles from
the flue gas passing through it. As the dust passes through the filter, a dust cake builds
up on the fabric surface. This cake participates in the collection process. Located
downstream of the air preheater, FFs usually operate in the temperature range
120e180 C. An FF consists of a number of individual compartments: each compart-

ment commonly contains between 100 and 400 tube-shaped bags or FFs. Outside-in
filter bags are supported by wire cages to prevent the bags from collapsing. When
the residual dust cake on the bag surface builds up to unacceptable levels in terms
of pressure drop, or after a certain time period, the bags are cleaned (Nicol, 2013).

6.2.3.4 Technological challenges

The integration of Carbon Capture and Storage (CCS) in a conventional coal-fired
based power plant involves a high energy requirement (Atsonios et al., 2016). To miti-
gate the overall efficiency reduction due to CCS, some new concepts for CPP have
been proposed in the literature. This section describes the role of the particle removal
technology in the promotion of these new concepts to reach a commercial status.
Oxy-fuel CPP. Oxy-fuel CPP combustion employing a cryogenic air separation unit
(ASU) for the capture of pure oxygen production has been proven at demonstration
scale in different projects (Maas et al., 2016). In this concept, most of the energy
requirement is due to the power consumption at the ASU (Atsonios et al., 2016).
The implementation of ion transport membranes (ITMs) for oxygen production in
Oxy-fuel PCPP, as an alternative to traditional cryogenic ASU, could significantly
reduce both energy consumption and the CAPEX of this technology (Atsonios

et al., 2016). ITM works at temperatures around 850 C to obtain high permeability.
As the oxygen production via ITM is still in its developmental phase, the thermal