Power plants – Motive fluid energized by externally applied heat – Power system involving change of state
Patent
1990-08-08
1991-09-03
Ostrager, Allen M.
Power plants
Motive fluid energized by externally applied heat
Power system involving change of state
60 39182, 60663, 60653, 60679, F01K 2100
Patent
active
050441639
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for operating a steam turbine, which has at least a medium-pressure part and a high-pressure part, with the aid of a waste heat steam generator through which hot gas flows, and to a system for performing this process, having a steam turbine of this type and a waste heat steam generator, having a high-pressure system of heating surfaces connected to the high-pressure part of the steam turbine and having intermediate superheating surfaces connected to the exhaust steam line of the high-pressure part of the steam turbine, which superheater surfaces are connected on the outlet side to the medium-pressure part of the steam turbine.
As European Patent Application 0 129 167 shows, such processes for waste heat steam generation are used primarily downstream of gas turbines, in order to usefully exploit the considerable quantities of heat contained in the gas turbine exhaust gases in order to generate steam. In combined gas and steam turbine power plants, also known as combined cycle power plants, steam turbines are driven with the thus-produced steam to additionally generate electrical energy. Waste heat steam generators are also used downstream of coal gasification systems, however, to cool the crude gas produced in them. The steam generated in the waste heat steam generator is also sometimes used as process steam or simply as heating steam. In all these fields of application, but in particular in combined gas and steam turbine power plants, care is taken to make the individual and total efficiency as high as possible, because of the large amounts of energy to be converted.
The object of the invention is to improve the efficiency in waste heat steam generation. Particularly in combined gas and steam turbine power plants, the object is to maximize the total efficiency.
This object is attained in accordance with the invention, in a process for operating a steam turbine that has at least one medium-pressure part and one high-pressure part, with the aid of a waste heat steam generator through which hot gas flows, in that superheated steam generated in a high-pressure heating surface system is supplied to the high-pressure part of the steam turbine; a smaller quantity of steam is admixed with the exhaust steam of the high-pressure part of the steam turbine, this smaller quantity of steam being produced in intermediate superheater evaporator heating surfaces in the waste heat steam generator from preheated feedwater supplied to it; the mixture of the smaller quantity of steam and the exhaust steam is superheated in intermediate superheater heating surfaces of the waste heat steam generator; and the thus-superheated steam mixture is delivered to the medium-pressure part of the steam turbine. As a result, particularly good adaptation of the feedwater temperature or steam temperature to the flue gas temperature in the waste heat steam generator, and thus the highest possible efficiency in steam production, are attained.
In a system for performing the process of claim 1, having a steam turbine having at least one medium-pressure part and one high-pressure part, having a waste heat steam generator through which hot gas flows, having a high-pressure heating surface system connected to the high-pressure part of the steam turbine, and having intermediate superheater heating surfaces connected to the exhaust steam line of the high-pressure part of the steam turbine, the intermediate superheater heating surfaces being connected on the outlet side to the medium-pressure part of the steam turbine, it is provided in accordance with the invention that the feedwater line of the waste heat steam generator leads to a branching point, from which a first segment leads into the high-pressure heating surface system and a second segment leads into intermediate superheater evaporator heating surfaces, and means for varying the distribution ratio are associated with at least one of the two segments. By means of these provisions, the greatest possible flexibility in performing the process and adaptability to
REFERENCES:
patent: 3204407 (1965-09-01), Meissenberg et al.
patent: 4693086 (1987-09-01), Hoizumi et al.
patent: 4920751 (1990-05-01), Gounder
JP-A-58-167811 (Hitachi Seisakusho K.K.) Patent Abstracts of Japan, vol. 8, No. 5 (M-267) (1442), Jan. 1984.
Bruckner Hermann
Pulec Josef
Stadie Lothar
Greenberg Laurence A.
Lerner Herbert L.
Ostrager Allen M.
Siemens Aktiengesellschaft
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