WO2012038109A2

WO2012038109A2 - Method and installation for generating steam

Info

Publication number: WO2012038109A2
Application number: PCT/EP2011/061380
Authority: WO
Inventors: Bernd Gericke; Stephan KÖBERLE; Jürgen Müller
Original assignee: Thyssenkrupp Xervon Energy Gmbh
Priority date: 2010-09-20
Filing date: 2011-07-06
Publication date: 2012-03-29
Also published as: WO2012038109A3; DE102010037657A1

Abstract

The invention relates to a method for generating steam, in which sand, as an energy storage medium, circulates in a closed loop. The sand is heated in said closed loop by a hot gaseous heat carrier (3) in a contact apparatus (2) and yields the stored heat to heat exchanger elements (5) of at least one evaporator and at least one superheater in a fluid bed cooler (4). The sand is returned from the fluid bed cooler (4) to a sand store (1) and from there is fed again to the contact apparatus (2) for renewed heating. According to the invention the sand cooled in the fluid bed cooler (4) is fed to a turbulence chamber (6), in which a circulating fluidised bed is generated by admission of air. The sand conveyed upwards by the circulating fluidised bed is deposited in a solids separator (7) and fed to the sand store (1) arranged below the solids separator. The sand from the sand store (1) then passes due to gravity from the sand store (1) into the contact apparatus (2) that is arranged below the sand store (1).

Description

Process and plant for steam generation

Description:

The invention relates to a method for generating steam, in particular for the production of high-pressure steam, and a system for carrying out the method. The generated steam is overheated and can have a pressure greater than 40 bar as high-pressure steam. The steam can be used in many ways, eg. B. to operate a power plant turbine or as production steam in chemical plants.

In the process from which the invention proceeds, sand is fed as an energy storage medium in a closed circuit. The sand is heated in this circuit by a hot gaseous heat carrier in a contact apparatus and releases the stored heat in a fluidized bed cooler to heat exchanger elements of at least one evaporator and at least one superheater. From the fluidized bed cooler, the sand is placed in a sand storage and fed from there to the contact apparatus for re-heating. As a gaseous heat carrier, hot combustion gases or air heated by solar energy can be used. In particular, the method may be operated in conjunction with a solar tower power plant that concentrates the incident solar radiation onto a solar receiver that heats ingested ambient air to a temperature greater than 550 ° C. Hot air temperatures of 1000 ° C and more can be achieved.

From DE 1 01 49 806 C2 a method with the features described above is known. The contact apparatus for heating the sand and the fluidized bed cooler are arranged one above the other within a tower, on which a radiation receiver for solar energy use is arranged. The sand is returned from the fluidized bed cooler to a cold storage tank outside the

Tower is arranged approximately at ground level. By a riser the sand from the sand storage must be supplied to the arranged above the hot storage contact apparatus. In the riser a conveyor for conveying the sand by means of air is included.

Based on this prior art, the present invention seeks to provide an effective sand / circulation concept, which can be easily operated and requires no elaborate delivery units. It should work safely and be easy to maintain.

The object of the invention and solution of this problem is a method according to claim 1. According to the invention, the sand cooled in the fluidized-bed cooler is fed to a vortex chamber in which a circulating fluidized bed is produced by supplying air. The sand conveyed upwards with the circulating fluidized bed is separated off in a solids separator and fed to the sand accumulator arranged below the solid accumulator. The sand storage is often referred to as cold storage, as it absorbs the cooled in the fluid bed cooler sand. From the sand storage, the sand then passes by gravity into the contact apparatus, which is arranged below the sand storage. In the method according to the invention, the sand accumulator or cold accumulator is arranged above the contact apparatus. It is accepted that to promote the sand from the fluidized bed cooler in the sand storage a greater height must be overcome. The circulating fluidized beds have hitherto been used in combustion plants, in particular furnaces with dry desulphurisation. According to the circulating fluidized bed is used in the present method as a conveyor for a sand cycle. It is exploited that by the generation of a circulating fluidized bed in

a swirl chamber large delivery heights of 30 m and more can be bridged.

A further advantageous embodiment of the method according to the invention provides that at least a portion of the sand heated in the contact apparatus is intermediately stored in a buffer memory, which is arranged below the contact apparatus. The buffer is often referred to as hot storage, since it contains the heated sand. Depending on the amount of steam to be generated, a controlled mass flow of the hot sand from the buffer store and / or the contact apparatus is fed to the fluid bed cooler, which in turn is arranged below the contact apparatus and the buffer store. According to a preferred embodiment of the invention, the sand accumulator, the contact apparatus for heating the sand, and the buffer memory are arranged one above the other and above the fluidized bed cooler. As a result, expensive delivery units can be avoided. The transport of the sand from the sand storage to the contact, from there to the buffer and finally to the fluidized bed cooler according to the invention by gravity, wherein for guiding the sand stream z. As downpipes, slides, chutes and similar devices can be used. Mechanical conveyors, which are maintenance-intensive, eliminated.

As a solids separator, a cyclone can be used. In the cyclone, a high degree of separation can be achieved because an air / sand mixture is generated in the vortex chamber, which is continuously fed to the cyclone and has an approximately homogeneous flow profile when entering the cyclone. In contrast to a pneumatic conveying or a bubble-forming fluidized bed, the circulating fluidized bed is distinguished by the fact that the solids density in the air flow at the outlet cross-section of the vortex

chamber - at a constant steam generation - equal and thus evenly distributed over the cross-sectional area at the entrance of the cyclone.

The air flow from the Feststoffabscheider is fed to a filter system. At least part of the filter residue can be returned to the vortex chamber. The filter system works as a dedusting filter.

The circulating fluidized bed is operated with sand, which was previously cooled in a fluidized bed cooler. In the circulating fluidized bed, a temperature of less than 250 ° C sets. The temperature is so low that dedusting filters, which are connected downstream of the solids separator, can be operated with filter cloths.

The sand in the fluidized bed cooler passes through several chambers separated by weirs, wherein the chambers of the fluidized bed cooler successively form a first evaporator stage, at least one superheater stage, a second evaporator stage and a stage for feedwater preheating in the direction of flow of the sand. In the chambers of the fluidized bed cooler fluidized beds are formed by supplying a gaseous fluidizing agent, for example, stationary or expanding fluidized beds can be flowed through. For fluidization, air is preferably used.

As evaporator circulation evaporator, preferably natural circulation evaporator, are used, which are integrated into a common water and steam cycle. The water-steam mixture produced in the two evaporator stages is fed to a drum, where the steam is separated from the water via separation devices and the saturated steam is supplied to the superheater stages. Between the two evaporator stages are preferred

example provided two superheater stages, the heat exchanger elements are successively flowed through by the steam to be overheated.

To further increase the efficiency, there are intermediate heat exchanger heat exchanger elements, which are fed with the steam of the outlet of the high-pressure steam turbine stage. These heat exchanger elements can be installed in the same or a parallel fluidized bed cooler.

The sand cooled in the fluid bed cooler can be fed to the vortex chamber by means of mechanical conveyors. According to a preferred embodiment of the invention, the transport of the cooled sand to the vortex chamber takes place by means of a gaseous transport medium.

For heating the sand, a gaseous heat carrier is used according to a preferred embodiment of the invention, which has been heated by solar energy to a temperature of more than 550 ° C.

The invention is also a plant according to claim 12 for carrying out the method described. Advantageous embodiments of this system are described in the subordinate claims 13 to 16 and explained below with reference to an embodiment. They show schematically:

1 shows a plant for steam generation,

Fig. 2 is an illustration of the vapor and liquid streams of the system.

The plant shown in FIG. 1 comprises: at least one sand store 1; a contact apparatus 2 for heating up from the sand accumulator 1

led sand by heat exchange with a hot heat carrier 3; a fluid bed cooler 4 equipped with heat exchanger elements 5 of at least one evaporator and at least one superheater. The sand is fed as an energy storage medium in a closed circuit. In this cycle, the sand in the contact apparatus 2 is heated by a hot gaseous heat carrier. The heated sand then releases the stored heat in the fluidized bed cooler 4 to the heat exchanger elements 5 of at least one evaporator and at least one superheater. The sand is returned from the fluidized bed cooler 4 in the sand storage 1 and fed from there to the contactor 2 for re-heating. As a heat carrier for heating the sand in particular air can be used, which has been heated by solar energy to a temperature of more than 550 ° C. The cooled in the fluidized bed cooler 4 sand is fed to a vortex chamber 6, in which by supplying air, a circulating fluidized bed is generated. The sand conveyed upwards with the circulating fluidized bed is separated in a solids separator 7 and fed to the sand accumulator 1 arranged below the solids separator 7. The sand passes from the sand accumulator 1 by gravity into the contact apparatus 2, which is arranged below the sand accumulator 1.

The vortex chamber 6 has a lower inlet 8 for sand or a sand / air mixture and an upper material outlet 9 for a sand / air mixture. At the material outlet 9 of the vortex chamber 6, the solids separator 7 connects. The inlet 8 of the vortex chamber is connected by a line 10 to the fluid bed cooler 4. Through this line 10, the sand can be supplied with air as a transport medium of the vortex chamber 6. For generating the circulating fluidized bed is an air supply 1 1 with

a fan 12 is provided, which connects to the bottom side of the vortex chamber 6. The solids separator 7 is disposed above the sand accumulator 1 and by a gravity exploiting means 13 for discharging deposited sand, for. B. connected by a downpipe, a chute or a slide with this.

Below the contact apparatus 2, a buffer memory 14 for receiving heated sand is also arranged, from which a mass flow of the hot sand controlled in dependence on the quantity of steam to be generated is taken off and fed to the fluid bed cooler 4. The fluidized-bed cooler 4 is arranged below the contact apparatus 2 and the buffer memory 14. For the system according to the invention is essential that the sand storage 1, the contactor 2 for heating the sand and the buffer memory 14 are arranged one above the other and above the fluidized bed cooler 4. About slides, downpipes, dumping or similar devices, the sand passes from the sand storage 1 in the contactor 2, from there into the buffer memory 14 and can finally be fed to the fluidized bed cooler 4. The arrangement according to the invention one above the other eliminates complex delivery units. The swirl chamber 6 bridges a height of more than 30 m, measured from the lower inlet 8 for sand or a sand / air mixture to the upper material outlet. 9

The air flow 15 from the solids separator 7 is fed to a filter unit 16. The filter unit 16 can be operated with fabric filters due to the low temperature of the sand conveyed in the swirl chamber, which is less than 250 ° C. At least part of the filter residue is returned by a corresponding device 17 in the vortex chamber 6.

The fluidized-bed cooler 4 has a plurality of chambers 18 arranged next to one another and separated by weirs, to which chambers 18 air supply devices 19 for producing fluidized beds are connected. In the chambers 18 heat exchanger elements 5 of an evaporator, a superheater or a heat exchanger for feedwater preheating are arranged. In the embodiment shown in Fig. 1, the chambers 18 of the fluidized bed cooler 4 in the flow direction of the sand sequentially form a first evaporator stage 20, two superheater stages 21, 21 ', a second evaporator stage 22 and a stage 23 for feedwater preheating. FIG. 2 shows the steam and liquid flows of the plant, specifically using the example of generating a high pressure steam, which is used to drive a power plant turbine 24.

The steam generated in the two evaporator stages 20, 22 is brought together and passed through the heat exchanger elements 21, 21 'of the superheater stages. As evaporator 20, 22 circulation evaporator, preferably natural circulation evaporator, are used, which are integrated into a common water and steam cycle. The saturated steam generated in the evaporators 20, 22 flows successively through the heat exchanger tubes of the two superheater stages 21, 21 'and can then be used as superheated steam for driving the power plant turbine 24.

In the exemplary embodiment, an injection cooling 25 is provided between the two superheater stages 21, 21 '. For cooling, feed water 26, 26 'is branched off either before or preheated after the feedwater preheater.

Claims

claims:

1 . A process for generating steam, in particular for generating high-pressure steam, wherein sand is passed as Energiespeichermediunn in a closed circuit, wherein the sand is heated in this circuit by a hot gaseous heat transfer medium (3) in a contactor (2) and the stored Heat in a fluidized bed cooler (4) to heat exchanger elements (5) at least one evaporator and at least one superheater emits and wherein the sand from the fluidized bed cooler (4) returned to a sand store (1) and from there the contactor (2) for reheating is fed again, characterized in that the cooled in the fluidized bed cooler (4) sand a vortex chamber (6) is fed, in which by supplying air, a circulating fluidized bed is produced, that the upwardly conveyed with the circulating fluidized bed sand in a solids separator (7 ) and the below the Feststoffabsche iders (7) arranged sand storage (1) is supplied and that the sand from the sand storage (1) passes by gravity into the contact device (2), which is arranged below the sand memory (1).

2. The method according to claim 1, characterized in that at least a portion of the in the contact apparatus (2) heated sand in a buffer memory (14) is temporarily stored, which is arranged below the contact apparatus (2).

3. The method according to claim 1 or 2, characterized in that a regulated depending on the amount of steam to be generated mass flow of hot sand from the buffer memory (14) and / or the contactor (2) to the fluidized bed cooler (4) is supplied below the Contact apparatus (2) and the buffer memory (14) is arranged.

4. The method according to any one of claims 1 to 3, characterized in that the air flow from the solids separator (7) a filter unit (16) is supplied and that at least a portion of the filter residue is returned to the vortex chamber (6).

5. The method according to any one of claims 1 to 4, characterized in that the sand in the fluidized bed cooler (4) passes through several chambers separated by weirs (1 8), wherein the chambers (1 8) of the fluidized bed cooler (4) in the flow direction of Sand sequentially form a first evaporator stage (20), at least one superheater stage (21, 21 '), a second evaporator stage (22) and a stage (23) for feedwater preheating.

6. The method according to claim 5, characterized in that in the chambers (18) of the fluidized bed cooler (4) are formed by supplying a gaseous fluidizing means of fluidized beds.

7. The method according to claim 5 or 6, characterized in that in the evaporator stages (20, 22) generated steam is brought together and through the heat exchanger elements (5) of the superheater stage (21, 21 ') is guided.

8. The method according to any one of claims 5 to 7, characterized in that between the two evaporator stages (20, 22) two superheater stages (21, 21 ') are arranged.

9. The method according to any one of claims 1 to 8, characterized in that in the fluidized bed cooler (4) cooled sand with a gaseous transport medium of the vortex chamber (6) is supplied.

10. The method according to any one of claims 1 to 8, characterized in that the sand in the vortex chamber (6) is conveyed to a height of more than 30 m high.

1 1. Method according to one of claims 1 to 10, characterized in that for heating the sand, a gaseous heat carrier (3) is used, which has been heated by solar energy to a temperature of more than 550 ° C.

12. Plant for carrying out the method according to one of claims 1 to 1 1, comprising at least one sand store (1), a contact device (2) for heating sand from the sand reservoir (1) by heat exchange with a hot gaseous heat carrier (3) a fluid bed cooler (4) equipped with heat exchanger elements (5) of at least one evaporator and at least one superheater, and a conveyor for continuously recycling a sand mass flow cooled in the fluid bed cooler (4) into the sand accumulator (1),

characterized in that the conveyor comprises a swirl chamber (6) having an inlet (8) for sand or a sand / air mixture and an upper material outlet (8) for a sand / air mixture and a solids separator connected to the material outlet (8) (7), wherein the inlet (8) of the vortex chamber (6) is connected by a line (10) to the fluid bed cooler (4), wherein the vortex chamber (6) an air supply means (1 1) with a blower (12) is connected to produce a circulating fluidized bed within the swirl chamber (6), wherein the solids separator (7) is disposed above the sand reservoir (1) and connected thereto by means for discharging separated sand, and wherein the sand reservoir (1) is above the Contact apparatus (2) arranged and connected by a gravity-utilizing transport device with the contact device (2).

13. Plant according to claim 12, characterized in that below the contact apparatus (2) a buffer memory (14) for receiving heated sand is arranged, wherein the buffer memory (14) by a discharge and metering device with the fluidized bed cooler (4) is connected ,

14. Plant according to claim 1 2 or 13, characterized in that the fluidized bed cooler (4) a plurality of juxtaposed and separated by weirs chambers (18), wherein the chambers (18) air supply means (19) are connected for generating fluidized beds.

15. Plant according to claim 14, characterized in that arranged in the chambers (18) heat exchanger elements (5) of an evaporator, a superheater or heat exchanger for feedwater preheating.

16. Plant according to one of claims 12 to 15, characterized in that the vortex chamber (6) has a measured from the inlet (8) for sand or a sand / air mixture (9) to the material outlet height of more than 30 m.