Chemistry: fischer-tropsch processes; or purification or recover – With preliminary reaction to form hydrogen or a carbon oxide – Gaseous oxygen utilized in the preliminary reaction
Reexamination Certificate
2000-06-15
2001-07-24
Richter, Johann (Department: 1621)
Chemistry: fischer-tropsch processes; or purification or recover
With preliminary reaction to form hydrogen or a carbon oxide
Gaseous oxygen utilized in the preliminary reaction
C518S700000, C518S702000, C518S704000, C518S705000
Reexamination Certificate
active
06265453
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to hydrocarbon conversion systems, and more particularly to a Fischer-Tropsch-based system with an enhanced turbine combustor.
BACKGROUND OF THE INVENTION
Gas turbines are used in many applications including gas-turbine-driven powerplants. The gas turbine exhaust has been used to improve the overall powerplant performance by taking the high temperature turbine exhaust and recovering the heat. It is normally recovered by conventional steam generating techniques, e.g., boiler, and routed to a steam turbine. The condensed steam may be recycled to the boiler. This arrangement is typically called a combined cycle powerplant. “Cogeneration” refers generally to the simultaneous on-site generation of electric energy and process steam or heat from the same plant. As described further below, as an aspect of the present invention, a cogeneration system is novelly incorporated into a Fischer-Tropsch-based system.
The synthetic production of hydrocarbons by the catalytic reaction of carbon monoxide and hydrogen is well known and is generally referred to as the Fischer-Tropsch reaction. The Fischer-Tropsch process was developed in early part of the 20
th
century in Germany. It was practiced commercially in Germany during World War II and has been practiced in South Africa for some time. An ongoing quest has existed, however, to improve the economics of the process.
The Fischer-Tropsch-based conversion process may first involving converting light hydrocarbons (such as methane) into synthesis gas (primarily CO and H
2
) and then converting the synthesis gas to heavier hydrocarbons through the Fischer-Tropsch reaction. The hydrocarbon products derived from the Fischer-Tropsch reaction range from some methane to high molecular weight paraffinic waxes containing more than 50 carbon atoms, but primarily includes C5+.
Numerous Fischer-Tropsch catalysts, such as iron and cobalt catalysts, have been used in carrying out the reaction, and both saturated and unsaturated hydrocarbons can be produced. Numerous types of systems and reactors have been used for carrying out the Fischer-Tropsch reaction. See, for example, U.S. Pat. Nos. 4,883,170 and 4,973,453, which are incorporated herein by reference for all purposes.
It has been a quest for some time to improve the economics of hydrocarbon conversion systems, particularly those utilizing the Fischer-Tropsch reaction. Improved economics will allow wide-scale adoption of the process in numerous sites and for numerous applications. These efforts are reflected in U.S. Pat. Nos. 5,733,941 and 5,861,441, which are incorporated herein by reference for all purposes.
One particular challenge to improved performance is related to the thermal limitations of gas turbines that are included in some embodiments of Fischer-Tropsch systems. The turbine blades can only withstand a certain level of heat. This in turn limits the throughput since the oxygen-containing gas supplied to the turbine expander must be limited to control the temperature.
SUMMARY OF THE INVENTION
Therefore, a need has arisen for an improved hydrocarbon conversion system that addresses shortcoming of previous conversion systems. According to an aspect of the present invention, a method for converting light hydrocarbons into heavier hydrocarbons includes the steps of: compressing air in a compressor section of a gas turbine; delivering a portion of the compressed air to a combustor of the gas turbine; delivering a portion of the compressed air to a Fischer-Tropsch hydrocarbon conversion unit; extracting thermal energy from the combustor and delivering it to the Fischer-Tropsch hydrocarbon conversion unit; converting light hydrocarbons into heavier hydrocarbons in the Fischer-Tropsch hydrocarbon conversion unit; and delivering combustion gases from the combustor to an expansion section of the gas turbine. According to another aspect of the present invention a heat recovery steam generator (HRSG) may be used to harness waste heat from the expansion section of the turbine.
According to another aspect of the present invention, a Fischer-Tropsch-based system for converting light hydrocarbons into heavier hydrocarbons includes a gas turbine having a compressor section, combustor, and expander section, and having a compressed air conduit; a Fischer-Tropsch hydrocarbon conversion subsystem for converting light hydrocarbons into heavier hydrocarbons; a heat removal subsystem associated with the combustor for thermally coupling the hydrocarbon conversion subsystem to the combustor to deliver thermal energy from the combustor to the hydrocarbon conversion subsystem; and a process air conduit fluidly coupled between the compressed air conduit and the Fischer-Tropsch hydrocarbon conversion subsytem, the process air conduit for delivering a portion of the compressed air developed by the compressor section to the Fischer-Tropsch hydrocarbon conversion subsystem. According to another aspect of the present invention, a HRSG is included to recover energy from the expansion section exhaust.
A technical advantage of the present invention is that it allows for more thorough combustion (and thus more efficiency) by the combustor, e.g., the O
2
content of the turbine exhaust may go from 10-14% to as low as 2%. Other technical advantages exist.
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“PFBC clean-coal technology. A new generation of combined-cycle plants to meet the growing world need for clean and cost effective power.” ABB Carbon Marketing Department, S-612 82 Finspong, Approximately Feb. 1998.
PCT International Search Report (PCT Article 18 and Rules 43 and 44) dated Oct. 11, 2000 re International Application PCT/US 00/17701 filed Jun. 27, 2000 (Applicant's ref. 062754.0221).
Baker & Botts L.L.P.
Parsa J.
Richter Johann
Syntroleum Corporation
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