4.4. Effects of supplementary firing on the equipment rating and
fuel feed rate
We have also investigated the influence of supplementary firing
on the rating of the plant equipment and biomass feeding rates for
a BIGCC plant of 50MWe capacity (with electrical generator efficiency
of 99%). The GT system has been chosen with rp¼ 16 and
rt¼5. Fig. 10a shows the power generated or consumed by the
turbines and compressors of the plant at different degree of
supplementary firing. It is observed that at f¼ 0, the GT produces
58.4MW power, while 21.5MW is generated by the steam turbine.
The MC and AC require 21.2MWand 8.05MW, respectively, at this
operating condition. As f is increased, the power generated by the
steam turbine increases, and that by the GT correspondingly
decreases. The power consumed by the MC and AC also decreases at
higher f. Fig. 10b shows the variation in total air and steam flow
rates in the plant for different degree of supplementary firing. The
increase in f increases the steamgeneration rate in the plant. The air
flow rate decreases as a result of the increase in f. The decrease in
the air flow rate, at higher f, results in the lower power consumption
by the compressors. Fig.10c shows the variation in the biomass
feeding rates with the variation in f. At f¼ 0, no supplementary
firing is employed and the plant solely depends on wood gasified in
the gasifier. Under this condition the wood firing rate is found to be
24.7 tph (tonne per hour). As f increases, the feed rate of the second