Page 375 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

354 12 Carbon Capture and Storage

Reorganizing the equations leads to
1
8
>
> x ¼
>
> 1 y
> 1 þ 0:6935
y
<
s ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1 x 3 þ x þ y
>
>
> 11
> ¼ 6:046 10
x 22:04 þ x þ y
>
:
Solving these equations with the assistance of software we can get
x y 1; 1 x ¼ 1:32 10 10 ; 1 y ¼ 1:91 10 10
The extremely low CO and H 2 concentration is a result of stoichiometric
combustion at high temperature. Anyway, for each mole of CH 4 , there is about
1 mol of CO 2 produced. At 1 atm and 25 °C, one mole of gas corresponds to
3
0.248 m /mol. Thus, the CH 4 feeding rate is 4032.26 mol/h. As a result, the CO 2
production rate is the same as 4032.26 mol/h, or
kg kmole
¼ 44 4:032 ¼ 177:42 kg/h
_ m CO 2
kmol h
12.3 General Approaches to Reducing GHG Emissions

Enhanced global warming effects can be reduced by reducing the emission of CO 2
and other GHGs. Emission reductions of CO 2 can be accomplished by a combi-
nation of several of the following approaches:
• Improved energy conversion efficiency in stationary and mobile combustion
processes.
• Supply and end-use efficiency improvement and conservation.
• Shift to alternative energy sources, which have been introduced in Chap. 8.
They are effective in air pollution control as well as carbon emission reduction.
• Carbon capture and storage (CCS).
Carbon emissions of CO 2 are inevitable as long as hydrocarbon fuels are used
for energy conversion. However, more efficient combustion processes may produce
less CO 2 per unit power generated. The CO 2 emissions per kWh power generated
from a low efficiency coal-fired boiler may be 4 times that from a natural gas-fired
gas turbine combined cycle plant (NGCC).
End-use efficiency improvements and energy conservation are the simplest and
most cost-effective approaches to reduce carbon emissions and other air pollutants.
For example, in the residential and commercial sectors, it can be achieved by
reducing heating and air conditioning consumptions, better insulations, lowering
hot water consumption, replacement of incandescent with fluorescent lighting, and