The steam turbine in this offering/proposal is shown above without the electric generator and the exciter. The subcritical, superheated steam from the boiler enters the high pressure (HP) section of the turbine and then exits after expansion back to the reheater section of the boiler where it is superheated and then returns to the intermediate pressure (IP) section of the steam turbine where it expands and then exits directly to the low pressure (LP) section of the steam turbine where it flows in two directions and finally exhausts into the condenser. The electric generator which converts the rotational mechanical work of the steam turbine into electricity is not shown above. Steam turbine generator and auxiliaries, brand new and never installed are stored in a climate-controlled warehouse awaiting shipment to the site of a new owner.
This turbine-generator unit selection is excellent because it is centered on General Electric Company’s philosophy of long-term service reliability and efficiency. The unit comes with single reheat, and seven steam extraction points for closed feedwater heaters and deaerator, all of which ensure excellent steam cycle efficiency and overall improvement in plant heat rate performance. Many units of this type are in service in the United States and throughout the world and have had good track records in service.
Available cooling system resources at the destination site may be significantly different from the site for which the system was originally designed in the United States. Stodad Corporation is in a position to advise any purchaser of this unit on the cooling system design at the destination site which will allow close approach to the original low pressure exhaust design pressure unit rating of the turbine-generator. The cooling resources at the destination site are important consideration including proximity to the load, transmission system and other factors.
The Alstom Circulating Fluidized Bed (CFB) steam generator for this plant has been designed to burn coal with up to 30% ash and 25% moisture. This CFB steam generator can also burn wood chips, pet coke, and other types of biomass feed such as sawgrass without expensive fuel preparation which includes pulverization in conventional burner fired boilers. This provides additional fuel flexibility in operating the plant without compromising efficiency and operational reliability.
The CFB is also good for the environment. The use of sulfur-absorbing sorbents such as limestone or dolomite in the bed reduces the number of sulfur oxides (sulfur dioxide and sulfur trioxide) emitted during combustion. Over 90% of the sulfur in high-sulfur content coal can be captured during combustion in CFB. This saves the money that would otherwise be spent on scrubbers and flue gas desulfurization equipment used to control sulfur oxides pollution emission from the combustion process in other types of boilers.
Fuels are also burned at 1400 to 1700 F in CFB, a threshold below the temperature for the formation of nitrogen oxides. Production of nitrogen oxides is temperature dependent and so, less of them are produced by using CFB. Also, the ash-melting problems of high combustion temperatures are avoided or minimized.