Page 376 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

12.3 General Approaches to Reducing GHG Emissions 355

so on. It is estimated that in the residential-commercial sector in USA, by the year
2010, carbon emissions could be reduced by 10.5 % below 1990 levels with
cost-effective conservation measures.
The follow sections focus on CCS.

12.4 Carbon Capture Processes

CCS refers to a number of technologies that capture CO 2 at some stage from
processes such as combustion (most for power generation), gasification, cement
manufacture, iron and steel making, and natural gas treatment. We introduce CCS
in a generic way using combustion as main examples. Similar approaches can be
taken for other industrial processes as well.
Like approaches to other air emission control, carbon capture can be achieved by
pre-, in-, and post-combustion gas separation. The following topics are introduced
in the section that follows.
• Pre-combustion carbon capture

– Gasification and IGCC
• In-combustion carbon capture
– Oxyfuel combustion
– Chemical-looping combustion
• Post-combustion carbon capture
– CO 2 capture from flue gas
– CO 2 capture from atmosphere

12.4.1 Pre-combustion Carbon Capture

Pre-combustion carbon capture process is associated with the integrated gasification
combined cycle (IGCC) [49]. Figure 12.1 shows the simplified process of IGCC
with pre-combustion CO 2 capture. It is achieved by converting primary fossil fuels
into hydrogen fuel. Hydrogen can be produced by partial oxidation of primary fuel
for syngas followed by water shift and syngas purification, where CO 2 and other
impurities are removed.

12.4.1.1 Syngas Production

Partial oxidation of aprimary fuel is ahighlyfuelrich combustion process as described
in Eq. (12.5). Since the process aims at the conversion of solid fuels into gaseous