Page 218 - Advanced Gas Turbine Cycles

I80 Advanced gas turbine cycles
production to 35th. Gases leave the exhaust stack at 138°C under maximum load
conditions.
For the first operating condition (HRSG unfired) the heat load is estimated at 7.5 MW.
For the second condition (HRSG fired) when 35 t/h of saturated steam is raised, the heat
load is 23 MW. The values of heat to work ratios (AD) are thus

7.5 )
(=) = 2.34, and ($ = 7.19, respectively.

Other parameters for the plant operating condition-f HRSG unfired (WHR) and
HRSG fired (WHB)-are as follows:

Alternator power output 3.2 MW
Airmass flow rate 20.45 kg/s
Pressure ratio 7: 1
Maximum temperature 890°C
Thermal efficiency 0.23
Heat recovery steam generator
Unfired Steam (saturated) mass flow rate 12 t/h
Steam pressure 13 bar
Fired Steam (saturated) mass flow rate 35 t/h
Steam pressure 13 bar
WHR WHB ($= 1.34)
A 2.34 7.19
EUF 0.77 0.85
FESR 0.147 O.O75(7C = 0.4, VB = 0.9)
A full description of this plant is given in Ref. [l].

9.6.2. The Liverpool University CHP plant

A gas turbine CHP scheme which operates at Liverpool University, UK, consists of a
Centrax 4 MW (nominal) gas turbine with an overall efficiency of about 0.27, exhausting
to a WHB. The plant meets a major part of the University’s heat load of about 7 MW on a
mild winter’s day. Supplementary firing of the WHB (to about 15 MW) is possible on a
cold day. Provision is also made for by-passing the WHB when the heat load is light, in
spring and autumn, so that the plant can operate very flexibly, in three modes viz., power
only, recuperative and supplementary firing.
The major performance parameters at design operating conditions are as follows:

Electrical power output 3.8 MW
Heat output (normal load) 6.6 MW
(with supplementary firing) 15.0 MW
Gas fuel energy supply 14.95 MW
Thermal efficiency 0.27