Page 163 - Advanced Gas Turbine Cycles

132 Advanced gas turbine cycles

(i) high efficiency
(ii) low capital cost; and
(iii) a low quantity of carbon dioxide discharged to the atmosphere (either
intrinsically low production or sequestration, liquefaction, removal and disposal
of that produced by the plant).
In some of the plants proposed these objectives are attained simultaneously.

8.2. Classification of gas-fired plants using novel cycles

Against this background of the changed economics of plant performance, we consider
some of the many new gas turbine plants that have been proposed over the past few
years. In this section, we first formulate a list and classify these plants (and the ‘cycles’
on which they are based), as in Tables 8.1A-D, noting that most but not all use natural
gas as a fuel.

8.2.1. Plants (A) with addition of equipment to remove the carbon dioxide produced
in combustion

These cycles allow sequestration and disposal of C02 as a liquid, rather than
allowing it to enter the atmosphere. They involve the introduction of additional
equipment for the C02 removal but little or no modification of the basic CBT or CBTX
plant itself.
Three such plants are:
A1 An open CCGT plant with ‘end of pipe’ removal of C02;
A2 A ‘semi-closed’ CCGT plant, involving recirculation of part of the exhaust gases,
enabling the C02 to be separated more easily; and
A3 A ‘semi-closed’ CBTX plant, involving recirculation of part of the exhaust gases
downstream of the heat exchanger, which also enables the C02 to be separated
more easily.
Use of similar removal equipment in a simple CBT cycle is also possible but the
exhaust gas from the turbine would require cooling before sequestration.

Table 8.1A
Cycles A with addition of CO, equipment
Description Type Special features FueVoxidant CO, removal Comment
AI ‘End of pipe’ OpedCCGT - Natural gadair LP (chemical) Simple C02 removal,
CO, removal but large C02 plant
AZSemi&xed, SUCCGT - Natural gadair LP (chemical) Simple Cq removal,
CO, removal smaller CO, plant
A3 Recuperative, SUCBTX Recuperator Natural gaslair LP (chemical) Simple CO, removal
CO2 removal