Power plants – Combustion products used as motive fluid
Reexamination Certificate
1999-06-03
2001-11-13
Thorpe, Timothy S. (Department: 3746)
Power plants
Combustion products used as motive fluid
C060S039120, C060S039182
Reexamination Certificate
active
06314715
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to gas turbines in general, and to integrated coal gasification combined cycle systems in particular.
Integrated gasification combined cycle systems provide flexible operating systems which burn coal in an environmentally acceptable manner. Such systems typically incorporate air blown or oxygen blown gasifiers. For oxygen blown gasifiers, the gasifier optimum pressure is much higher than the fuel pressure required by the gas turbine. In the case of air blown gasifiers, when the power is provided by a motor to compress air for the gasifier, the power requirement lowers the overall plant power output. In the case of oxygen blown gasifiers, power is recovered by installing a power recovery turbine, or turbo expander, in the fuel gas stream and increasing the inlet temperature indirectly using heat exchangers. In accordance with this invention, additional power is recovered by adding a combustor to the expander, and letting the pressure down through the expander and using the power output of the expander to drive a generator or other load.
More specifically, effluent gas from the gasifier is either cooled in a two train syngas cooler (a radiant cooler followed by a convention cooler) or in a quench cooler where water is injected into the cooler. The fuel gas is further treated to remove particulate material. A turbo expander is included to reduce the gas pressure to gas turbine operating pressure, and to recover useful power. Typically, the temperature before the expander needs to be elevated above the cooled temperature for particulate removal and useful heat removal. This has been accomplished in the past by use of heat exchangers and to some extent by including a shift reactor to raise the temperature.
BRIEF SUMMARY OF THE INVENTION
In this invention, a combustor is added upstream of the turbo expander, and a small amount of oxygen is added to the combustor in order to increase the power output of the expander, thereby increasing the amount of useful work, but not adding significantly to the complexity of the system. The reduced pressure fuel gas is then cooled and passed through a sulfur removal system, heated and then supplied to the gas turbine.
Accordingly, in its broader aspects, the present invention is incorporated in a power generating plant including a gas turbine which utilizes fuel gas from an oxygen blown gasifier for combustion at a predetermined pressure to drive a primary load, and where the fuel gas is supplied from the gasifier at a pressure higher than the predetermined pressure, and specifically includes an arrangement to decrease the pressure of the fuel gas to a lower pressure required by the gas turbine comprising a combustor and an expander downstream of the combustor, the combustor and the expander located between the gasifier and the gas turbine.
In another aspect, the invention relates to a method for reducing pressure in fuel gas generated by an oxygen blown gasifier prior to combustion of the fuel gas in a gas turbine, comprising: a) supplying the fuel gas at a pressure higher than required by the gas turbine to a combustor and an expander downstream of the gasifier to thereby reduce the fuel gas pressure; b) removing sulfur from the fuel gas downstream of the expander; c) heating the fuel gas to a predetermined inlet temperature; and d) supplying the fuel gas to the gas turbine at a pressure required by the gas turbine.
REFERENCES:
patent: 2675672 (1954-04-01), Schorner
patent: 4549396 (1985-10-01), Garwood et al.
patent: 4999993 (1991-03-01), Rao
patent: 5753198 (1998-05-01), Ayala et al.
patent: 5901547 (1999-05-01), Smith et al.
patent: 0 934 904 A2 (1999-08-01), None
patent: 2 191 215 (1987-12-01), None
patent: WO 97/39235 (1997-10-01), None
patent: WO 99/14473 (1999-03-01), None
General Electric Co.
Hayes E D
Nixon & Vanderhye
Thorpe Timothy S.
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