AU701881B2

AU701881B2 - Process and arrangement for operating a dryer fed by heating steam

Info

Publication number: AU701881B2
Application number: AU48781/96A
Authority: AU
Inventors: Franz Bauer; Andrea Hausler; Hartmut Hohne
Original assignee: VEAG Vereinigte Energiewerke AG
Current assignee: Vattenfall Europe Generation AG and Co KG
Priority date: 1995-02-20
Filing date: 1996-02-19
Publication date: 1999-02-11
Anticipated expiration: 2016-02-19
Also published as: GR3035709T3; EP0811142A1; EP0811142B1; AU4878196A; ATE198665T1; WO1996026404A1; ES2155930T3

Abstract

The invention pertains to a process and arrangement for operating a dryer fed by heating steam, in particular a coal dryer (4), in a power plant. The aim of the invention is to integrate the energy of the exhaust vapors into the power generating process with the greatest possible degree of efficiency. This is achieved by superheating the saturated steam (21) with hot steam (15) and feeding the resulting superheated steam (22) into the low-pressure section of the steam turbine or into another steam turbine. To accomplish this the invention provides that the saturated steam line (12) is connected to a steam-steam heat exchanger (2) in the superheated steam line (1) and the steam line (13) of the steam-steam heat exchanger (2) is connected to the low pressure section of the steam turbine or another steam turbine.

Description

1 The invention concerns a method and an arrangement to operate a dryer, particularly a coal dryer, charged with heating steam, in a power plant.

As heating steam for the drying of coal, cooled superheated steam tapped from a steam turbine is fed to the heat exchanger provided in the coal dryer and the wet brown coal situated in the coal dryer is dried by this DE 29 01 723, 37 31 720, DD 141 344). The vapours expelled from the wet coal are fed as vapour steam to a steam converter. The condensate, obtained due :to the drying of the wet coal with the superheated steam, is also fed to this steam converter. While the vapour condensate is removed, the generated saturated steam is used for energy DE 29 01 723). A use of the vapour steam for energy is achieved also by that it is superheated by compression (DE 36 40 610). It is also feasible to use the vapour steam for recirculation in the dryer (DE 41 15 781, DE 40 20 994).

of a special furnace, to feed a portion directly for recirculation to the dryer and the other portion to a turbine (DE 37 31 720, DD 141 344). However, it has been established that with this use of the vapour steam in this manner the degree of efficiency of the total installation is not at its optimum.

At least preferred embodiments of the invention integrate the vapour steam used for energy in the process of the power plant with an as high as possible degree of efficiency.

In accordance with a first aspect of the present invention there is provided a method to operate a dryer charged with a heating steam, wherein a superheated steam S: 17950-N 2 from a steam turbine is supplied as the heating steam indirectly to the dryer, and wherein a condensate of the superheated steam is converted into a saturated steam by means of a vapour steam from the dryer, the method comprising the steps of superheating the saturated steam by means of the superheated steam from the steam turbine, and supplying the superheated saturated steam to a low-pressure part of the steam turbine or of another turbine.

In accordance with a second aspect of the present invention there is provided a steam supply apparatus for a dryer charged with heating steam, the dryer comprising an internal heat exchanger, a vapour steam pipeline, and a condensate pipeline, the steam supply apparatus comprising a steam turbine, a superheated steam pipeline from a highpressure part of the steam turbine to the dryer, wherein the superheated steam pipeline is connected to the internal heat exchanger of the dryer, a steam converter connected to the vapour steam pipeline and the condensate pipeline of the dryer, the steam converter comprising a saturated steam pipeline and a vapour condensate pipeline, and a .".steam/steam heat exchanger being integrated in the superheated steam pipeline and being connected to the :saturated steam pipeline from the steam converter and comprising a steam pipeline which is connected to a lowpressure part of the steam turbine or of another turbine.

At least preferred embodiments of the invention can ensure that the superheated steam is cooled by the saturated steam to the temperature suitable for the dryer and thus the saturated steam is superheated to be used for energy.

The invention is explained in detail on an embodiment based on a coal dryer, by way of example only. The drawing shows in: S: 17950-N 2a Fig.l the diagram of the plant for coal drying within a power plant operated by brown coal, Fig.2 the media parameters when drying coal from a 53 to 12 water content.

The coal dryer 4 has the coal supply 5 for the wet raw brown coal 14 and the coal discharge 6 for the dry brown coal 17 (Fig.l). Inside of the coal dryer 4 the heat exchanger 7 is provided and it is connected with the superheated steam pipeline 3. The condensate pipeline 8 of the heat exchanger 7 is connected with the steam converter 10 via the expander 23.

The vapour steam pipeline 9 of the coal dryer 4 is also connected with the steam converter 10. The steam converter has the vapour condensate pipeline 11 and the saturated steam pipeline 12, which is connected with the steam/steam heat exchanger 2. The steam/steam heat exchanger 2 is connected with the superheated steam pipeline 1, which is coming from the steam turbine (not illustrated). The steam pipeline 13 of the steam/steam heat exchanger 2 is connected with the low-pressure part (not illustrated) of a steam turbine within the coal- C operated power plant.

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oeC S:17950-N 3 The modus operandi is as follows: The superheated steam 15 from the steam turbine proceeds via the superheated steam pipeline 1 to the steam/steam heat exchanger 2 and is cooled by the saturated steam 21. The superheated steam 16 cooled thus for the coal dryer 4 is supplied to the heat exchanger 7 in the coal dryer 4. Through the coal supply 5 the wet raw brown coal 14 is introduced into the coal dryer 4 and it is dried by the cooled superheated steam 16 by means of the heat exchanger 7. The dry brown coal 17 is removed through the coal discharge 6. The moisture expelled from the wet raw brown coal by means of the drying process results in the vapour steam 19, which is introduced into the steam converter 10 via the vapour steam pipeline 9. In this conjunction the coal dryer 4 is operated under a pressure of 5 bar (Fig.2).

e S" The condensate 18 obtained from the drying process is conveyed via the condensate pipeline 8 to the steam converter 10. On this occasion the pressure of the condensate 18 is reduced in the expander 23 so far that it will be below the pressure of the vapour steam 19. During the steam conversion in the steam e converter 10 the saturated steam 21 and the vapour condensate are produced. The vapour condensate 20 is used for the purpose of heating the feed water within the power plant. The saturated steam 21 is conveyed via the saturated steam pipeline 12 to the steam/steam heat exchanger 2. As a result of the cooling of the superheated steam 15 in the steam/steam heat exchanger 2 the saturated steam 12 is superheated and thus the superheated steam 22 is produced, which via the steam pipeline 13 is supplied to the low-pressure part of the steam turbine.

The thus superheated steam 22 makes a better energy utilisation possible and thus leads to a higher degree of efficiency of the power plant.

The superheated steam 22 can be supplied to another steam turbine also with similar advantages.

7U The invention can be used for all dryers heated indirectly by steam with or without fluidised bed and with or without recirculating medium, e.g. for the drying of sludge, biomasses and foodstuff.

The invention is particularly applicable for the drying of moist combustible materials.

The invention can be used for dryers operating both under atmospheric conditions and under pressure, while the latter mode of operation is preferred.

List of reference numerals used 1 Superheated steam pipeline 2 Steam/steam heat exchanger 3 Superheated steam pipeline 4 Coal dryer Coal supply 6 Coal discharge 7 Heat exchanger 8 Condensate pipeline 9 Vapour steam pipeline Steam converter 11 Vapour condensate pipeline 12 Saturated steam pipeline 13 Steam pipeline 14 Raw brown coal Superheated steam 16 Cooled superheated steam 17 Dry coal 18 Condensate 19 Vapour steam Vapour condensate 21 Saturated steam 22 Superheated steam 23 Expander

Claims

1. A method to operate a dryer charged with a heating steam, wherein a superheated steam from a steam turbine is supplied as the heating steam indirectly to the dryer, and wherein a condensate of the superheated steam is converted into a saturated steam by means of a vapour steam from the dryer, the method comprising the steps of: superheating the saturated steam by means of the superheated steam from the steam turbine; and supplying the superheated saturated steam to a low-pressure part of the steam turbine or of another turbine.

2. A method as claimed in claim 1 wherein the dryer charged with heating steam is a coal dryer. 15

3. A steam supply apparatus for a dryer charged with heating steam, the dryer comprising an internal heat exchanger, a vapour steam pipeline, and a condensate pipeline, the steam supply apparatus comprising: a steam turbine; a superheated steam pipeline from a high-pressure part of the steam turbine to the dryer, wherein the superheated steam pipeline is connected to the internal heat exchanger of the dryer; a steam converter connected to the vapour steam pipeline and the condensate pipeline of the dryer, the steam converter comprising a saturated steam pipeline and a vapour condensate pipeline; and a steam/steam heat exchanger being integrated in the superheated steam pipeline and being connected to the saturated steam pipeline from the steam converter and comprising a steam pipeline which is connected to a low- pressure part of the steam turbine or of another turbine.

4. A method of operating a dryer substantially as herein described with reference to the accompanying drawings. S: 17950-N -7- A steam supply substantially as herein described with reference to the accompanying drawings. Dated this 1st day of December 1998 VEAG Vereinigte Energiewerke AG By their Patent Attorneys GRIFFITH HACK *.e o f S:17950-N