DI4.1: Innovation in Coal to Power (CtP) and Gas to Power (GtP):
Decarbonization of fossil fuels prior to combustion. The IGCC technology.
In a standard power plant, coal (or natural gas) burns to heat its boilers to about
540 °C to create high-pressure steam. The steam is piped to the turbines at pressures of more than 12.5 MPa.
The turbines are connected to the generators and spin them at 3 600 revolutions
per minute (rpm) to make alternating current (AC) electricity at 20 000 V. Soft
(river) water is pumped through tubes in a condenser to cool and condense the
steam coming out of the turbines.
An average plant may generate about 10 billion kWh/y, or enough electricity to
supply 700 000 homes. To meet this demand, 14 000 t of coal a day should be
burned.
A old style C(NG)tP plant has an efficiency of 28–33% in the conversion of
chemical energy into electricity.
Since 1985, the efficiency of electricity production has been increased by ca. 20%.
Coal to Power (CtP) or Natural Gas to Power(NGtP), all together C(NG)tP, modern
plants have an efficiency of 46
+ %, with an important reduction of CO 2 emission.
The improved technology works with a steam temperature of over 600 °C and a
pressure over 28 MPa. Additionally, heat exchangers recover some of the heat that
is still contained in the flue gases that is used to preheat the combustion air and the
water circulating in the water-steam circuit, thus increasing the overall efficiency of
the plant by ca. 20
+
%.
Another important improvement is represented by the innovative technology for
using lignite (very abundant in some geographical areas) instead of coal. Lignite has
a higher hydrogen content with respect to coke and a lower energy density (see
Table 1.5). Drying lignite at above 100 °C using residual heat of the power production decreases its water content (hydrogen and oxygen) and increases the carbon
content making it a better fuel. In this way, steam is produced at over 580 °C and
27.5 MPa, close to the improved coke plant, resulting in a great economic benefit
for countries which are rich of poor-quality coal.
The use of heat of flue gases for superheating steam up to 600 °C and pressurize
it at P > 28 MPa is a plus that improves the turbine work and increases the electricity production.
A further improvement on the coal to power technology is represented by the
so-called IGCC or integrated gasification combined cycle. In such technology, coal
is converted first into syngas which is improved by combining with the WGS
reaction. At the end, a mixture of H 2 and CO 2 is formed accompanied by some
other impurities (SOx, CO, and others) (Eq. 4.1).
C þ 2H 2 O ! CO 2 þ 2H 2
ð4:1Þ
56
4 Reduction of the CO 2 Production
Decarbonization of fossil fuels prior to combustion. The IGCC technology.
In a standard power plant, coal (or natural gas) burns to heat its boilers to about
540 °C to create high-pressure steam. The steam is piped to the turbines at pressures of more than 12.5 MPa.
The turbines are connected to the generators and spin them at 3 600 revolutions
per minute (rpm) to make alternating current (AC) electricity at 20 000 V. Soft
(river) water is pumped through tubes in a condenser to cool and condense the
steam coming out of the turbines.
An average plant may generate about 10 billion kWh/y, or enough electricity to
supply 700 000 homes. To meet this demand, 14 000 t of coal a day should be
burned.
A old style C(NG)tP plant has an efficiency of 28–33% in the conversion of
chemical energy into electricity.
Since 1985, the efficiency of electricity production has been increased by ca. 20%.
Coal to Power (CtP) or Natural Gas to Power(NGtP), all together C(NG)tP, modern
plants have an efficiency of 46
+ %, with an important reduction of CO 2 emission.
The improved technology works with a steam temperature of over 600 °C and a
pressure over 28 MPa. Additionally, heat exchangers recover some of the heat that
is still contained in the flue gases that is used to preheat the combustion air and the
water circulating in the water-steam circuit, thus increasing the overall efficiency of
the plant by ca. 20
+
%.
Another important improvement is represented by the innovative technology for
using lignite (very abundant in some geographical areas) instead of coal. Lignite has
a higher hydrogen content with respect to coke and a lower energy density (see
Table 1.5). Drying lignite at above 100 °C using residual heat of the power production decreases its water content (hydrogen and oxygen) and increases the carbon
content making it a better fuel. In this way, steam is produced at over 580 °C and
27.5 MPa, close to the improved coke plant, resulting in a great economic benefit
for countries which are rich of poor-quality coal.
The use of heat of flue gases for superheating steam up to 600 °C and pressurize
it at P > 28 MPa is a plus that improves the turbine work and increases the electricity production.
A further improvement on the coal to power technology is represented by the
so-called IGCC or integrated gasification combined cycle. In such technology, coal
is converted first into syngas which is improved by combining with the WGS
reaction. At the end, a mixture of H 2 and CO 2 is formed accompanied by some
other impurities (SOx, CO, and others) (Eq. 4.1).
C þ 2H 2 O ! CO 2 þ 2H 2
ð4:1Þ
56
4 Reduction of the CO 2 Production