Turbine
exhaust gases have typically 13 to 15 % volume of oxygen available,which
can be utilized to fire additional fuel and thus improve the efficiency
of the system.Supplementary firing is a very efficient process and can
easily double or quadruple the steam generation compared to unfired mode at a fuel to steam efficiency of more than 100 %he
efficiency of supplementary firing is nearly 100 %;the reasons for this are discussed
at other pages of my web site.
This
article describes a furnace fired O-type boiler capable of firing up to
2300 F.It consists of a completely water cooled furnace,about 12 ft long,sized
to contain the flame,followed by a bare tube screen section,a two-stage superheater
with interstage attemperation,a convection bank with bare/finned
tubes and a horizontal gas flow economizer. Four 6 in pipes located at
the end of convection bank act as downcomers.The performance of the unit
is shown in Table below in unfired and fired modes.A Coen burmer, firing
natural gas, was used.This is located at the furnace front wall. Steam
drum and mud drum sizes are 48 and 30 in respectively.The unit is
externally insulated.In addition the main stack and a diverter valve with
bypass stack were provided.The unit is in operation at a paper
plant in Monterrey,Mexico since 1999.
item | Unfired mode | Fired mdoe |
exhaust gas flow,lb/h | 187,789 | 187,789 |
exhaust gas temperrature,F | 979 | 979 |
firing temperature,F | 979 | 1969 |
gas temperature lvg furnace,F | 970 | 1890 |
gas temperature to superheater,F | 922 | 1747 |
gas temperature to evaporator,F | 871 | 1576 |
gas temperature to economizer,F | 494 | 548 |
gas temperature lvg stack,F | 353 | 314 |
burner fuel,MM Btu/h (lhv) | 0 | 59.42 |
total gas pressure drop,in wc | 8.2 | 9.45 |
steam pressure,psig | 430 | 430 |
steam flow,lb/h | 27,600 | 80.500 |
steam temperature,F | 590 | 590 |
feed water temperature,F | 225 | 225 |
water temperature to evap,F | 446 | 364 |