STEAM GENERATOR

Abstract

A steam generator for a power plant sub-system, having at least one evaporator tube through which a flow medium can flow, as well as a number of heat exchanger surfaces formed by the surface of the evaporator tube, wherein at least parts of the/each heat exchanger surface are provided with a catalytically active coating for the exothermic decomposition of hydrocarbons. By means of the catalytic coating of the heat exchanger surfaces of the evaporator tubes, an increased heat requirement calculation can be carried out, without also having to accept the formation of unwanted harmful substances inside the steam generator.

Claims

1.-16. (canceled)

17. A steam generator for a power plant sub-system, comprising: at least one evaporator tube, which is part of a heat-steam cycle of a steam turbine, through which can flow a flow medium, and a number of heat exchanger surfaces which are formed by the surface of the evaporator tube, wherein the heat exchanger surface, or each heat exchanger surface, is provided at least partially with a catalytically active coating for an exothermic decomposition of hydrocarbons, wherein in the steam generator additional heat demand is covered without an auxiliary firing system.

18. The steam generator as claimed in claim 17, wherein the heat exchanger surfaces are designed for the transfer of heat released during the composition of the hydrocarbons to a flow medium which flows through the evaporator tube.

19. The steam generator as claimed in claim 17, wherein the catalytically active coating for the exothermic decomposition of hydrocarbons comprises at least one noble metal.

20. The steam generator as claimed in claim 17, wherein the catalytically active coating comprises at least one noble metal which is selected from a group which contains gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt).

21. The steam generator as claimed in claim 17, wherein the catalytically active coating is designed for the exothermic decomposition of methane.

22. The steam generator as claimed in claim 17, further comprising an injection device for the dosing of hydrocarbons.

23. The steam generator as claimed in claim 17, wherein the heat exchanger surface, or each heat exchanger surface, is provided at least partially with a bonding agent.

24. A method for operating a steam generator of a power plant sub-system, the method comprising: feeding hydrocarbons to a steam generator which comprises at least one evaporator tube, wherein the hydrocarbons are brought into contact with a number of heat exchanger surfaces which are formed by the surface of the evaporator tube and are provided at least partially with a catalytically active coating, and wherein the hydrocarbons, upon contact with the catalytically active coating, are exothermically decomposed on this, wherein the heat released during the exothermic decomposition is dissipated into the heat-steam cycle of a steam turbine, and wherein in the steam generator additional heat demand is covered without an auxiliary firing system.

24. The method as claimed in claim 24, wherein heat released during the decomposition of the hydrocarbons is transferred to a flow medium which flows through the evaporator tube.

25. The method as claimed in claim 24, wherein at least one noble metal is used as the catalytically active coating.

26. The method as claimed in claim 24, wherein use is made of a catalytically active coating which comprises at least one noble metal from a group which contains gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt).

27. The method as claimed in claim 24, wherein methane is exothermically decomposed on the catalytically active coating.

28. The method as claimed in claim 24, wherein the hydrocarbons are injected into the steam generator.

29. The method as claimed in claim 24, wherein the heat exchanger surface, or each heat exchanger surface, is provided at least partially with a bonding agent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In the following text, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In this case, in the drawing:

[0037] FIG. 1 schematically shows a steam generator in a side view, and

[0038] FIG. 2 shows a detail of the steam generator according to FIG. 1 in a plan view.

DETAILED DESCRIPTION OF INVENTION

[0039] FIG. 1 schematically shows in a side view a steam generator 1 as part of a power plant sub-system 3, in the present case a steam turbine. A gas turbine 5 is connected upstream to the steam generator 1. From the gas turbine 5, exhaust gas 7 flows into the steam generator 1. The exhaust gas 7 flows through the steam generator 3 inside an exhaust gas passage 9, which on account of the horizontal design is also referred to as a horizontal gas duct, in the direction of a chimney which is designed as an exhaust duct or vertical duct 11. In the process, the exhaust gas 7 yields by heat transfer a high proportion of the heat contained within it to the heat exchanger surfaces 13 which are arranged inside the exhaust gas passage 9 and are formed by the surfaces 15 of the evaporator tubes 17 which are arranged in the steam generator 3.

[0040] As a result of this, the flow medium 19 which flows in the evaporator tubes 17 is heated and evaporated. The largely cooled exhaust gas 7, after its heat yield to the flow medium 19, in the present case water, leaves the steam generator 1 via the chimney 11. The steam which is generated in the evaporator tubes 17 is utilized in a water-steam cycle and expanded in a conventional steam turbine process, which is not described in more detail.

[0041] In the present case, all the heat exchanger surfaces 13 are fully provided with a bonding agent 23 and a catalytically active coating 25. The catalytically active coating 25 in the present case consists of platinum and serves for the exothermic decomposition of hydrocarbons. As a result of the exothermic decomposition of hydrocarbons, heat is generated inside the steam generator 1 in a targeted manner without pollutants such nitrogen oxide and/or sulfur oxide being formed in the process.

[0042] In the present case, natural gas is injected into the steam generator 1 via an injection device 27, which is shown schematically with reference to an arrow. Natural gas contains a high proportion of hydrocarbons and especially of methane. The methane which is contained in the natural gas flow is exothermically decomposed into carbon dioxide and water on the catalytically active coating 25 of the heat exchanger surfaces 13. The energy released in the process is yielded in the form of heat via the heat exchanger surfaces 13 to the flow medium 19 which flows in the evaporator tubes 17.

[0043] The heat is dissipated into the heat-steam cycle, as a result of which the output of the steam section of a gas and steam power plant is increased. Furthermore, as a result of the heat dissipation the temperature of the catalytically active coating 25 is limited.

[0044] Shown in FIG. 2 in a plan view is a detail of the steam generator 1 according to FIG. 1. To be seen with reference to this view are the evaporator tubes 17 which are arranged in the steam generator 1 and provided with the catalytically active coating 15. The exhaust gas 7 of the gas turbine 5 flows together with the methane in the exhaust gas passage 9 through the steam generator 1. The methane is decomposed on the catalytically active coating 25, wherein the heat released in the process is transferred to the flow medium 19 which flows in the evaporator tubes 17.

[0045] To be seen with reference to the present view is that the evaporator tubes 17 or the heat exchanger surfaces 13 which are formed by the surfaces 15 of the evaporator tubes 17 are completely coated. Basically, it is naturally also possible to coat only regions of the heat exchanger surfaces 13.

[0046] Overall, it is possible, as a result of the catalytically active coating 25 of the heat exchanger surfaces 13 of the evaporator tubes 17 to increase the process heat without having to accept the forming of undesirable pollutants inside the steam generator 1. The steam generator 1 is operated with targeted heat generation free of an auxiliary firing system.