DE102010063839A1 - Method for operating a furnace in a metalworking plant and metalworking plant - Google Patents

Abstract

The invention relates to a method for operating a furnace (1) in a metal processing installation, in particular in a continuous casting installation, in which exhaust gas (A) is passed from the furnace (1) along a flow path (S) through at least one recuperator (2) , Fresh air (F) for the furnace (1) being preheated in the recuperator (2) by means of the thermal energy contained in the exhaust gas (A) and the heated air being fed to the furnace (1) and the exhaust gas (A) downstream of the recuperator in the flow direction (2) is passed into a fireplace (3). In order to achieve an improved use of energy, the invention provides that a heat exchanger (4) is arranged in the flow path (S) or parallel to the flow path (S '), supplied to the water (W) and in which the water is heated, the heated water or steam being used to operate a power generation plant (5) or to be supplied to a consumer of warm water. Furthermore, the invention relates to a plant for metal processing, in particular a continuous casting plant.

Description

The invention relates to a method for operating a furnace in a plant for metal processing, in particular in a continuous casting, wherein the exhaust gas from the furnace along a flow path is passed through at least one recuperator, wherein preheated in the recuperator means of the heat energy contained in the exhaust gas fresh air for the furnace and the heated air is supplied to the furnace and wherein the exhaust gas is passed in the flow direction behind the recuperator in a chimney. Furthermore, the invention relates to a plant for metal processing, in particular a continuous casting plant.

The generic method is used in particular in continuous casting, which can be designed as so-called. CSP plants (Compact Strip Production). Such systems require at least one furnace, in which hot air is to be entered, which is heated by burners. Through the oven, the continuously cast slab is passed to be heated to a desired or required temperature.

In order to reduce the energy required for heating the furnace air, it is known to use recuperators, wherein in a preferred embodiment of the plant three recuperators per oven are used. In the recuperator energy recovery takes place from the hot exhaust gas of the furnace, d. H. In the recuperator heat is removed from the exhaust gas and used to preheat the furnace air.

In the normal case, the combustion air to be supplied to the furnace is heated in the recuperator from the hall temperature (about 30 ° C.) to about 450 ° C. As a result, the exhaust gas is cooled from about 900 ° C to about 700 ° C.

In 1 such a system is shown. You can see the stove first 1 a continuous casting plant (CSP furnace), through which the continuously cast metal strand is passed for heating. From the furnace hot exhaust gas A is discharged and a flow path S a recuperator 2 fed. Through the recuperator 2 also performs another flow path S '' for fresh air F, by means of a fan 10 is conveyed as burner air. Over the further course of the flow path S '' enters the fresh air F in the oven 1 , In this case, the fresh air F is heated in a known manner by means of a burner (not shown) to the required temperature. However, it takes place in the recuperator 2 a preheating of the fresh air F by a heat transfer between the exhaust A and the fresh air F takes place.

It is necessary in this case, the recuperator 2 and to protect the burner (not shown) from excessive temperature of the exhaust gas A. There are two mechanisms that can be used for this purpose 1 are sketched.

About the supply of cooling air K (at ambient temperature) by a fan 11 is conveyed, cold air can be added to the exhaust gas A. The control of this process by means of a switchable valve 12 , Said cooling takes place, if the exhaust gas A a certain temperature, for. B. 900 ° C exceeds. As a result, the temperature of the recuperator 2 reaching exhaust A reduced and the recuperator 2 so protected or protected.

In order to protect the burners from too high a temperature (the air to be supplied to the burner should not be warmer than approx. 450 ° C), it can have a hot air outlet 13 Preheated combustion air escape into the environment. This is done via a controlled valve 14 , By discharging combustion air through the hot air outlet 13 the pressure p drops in the flow path S ". However, the pressure p is maintained at a desired level by means of regulation, which is achieved by controlling the fan 10 he follows. If the pressure p thus decreases, more fresh air F from the fan 10 encouraged and therefore more cold air in the recuperator 2 pumped. As a result, the temperature drops in the recuperator 2 ,

In the prior art, this procedure of heat exchange by means of a recuperator for heating the furnace air are adequately described and corresponding devices known. It is exemplified on the WO 20091018476 A1 , on the EP 0 078 446 A1 and on the DE 697 12 009 T2 pointed.

It has been found that despite the preheating of the furnace air by means of the kiln exhaust gas in the recuperator energy consumption is still too high. For most operating points, the exhaust gas still has a temperature of about 700 ° C even after the recuperator. For a specific example, it was determined that the energy of the exhaust gas before the recuperator is up to 18.5 MW. Of this, 4.2 MW are used to heat the combustion air. The remaining 14.3 MW thermal energy, which has the exhaust after the recuperators still are not used. Furthermore, in some operating points (for example in the simulation with empty CSP furnace) to protect the burner hot combustion air is discharged behind the recuperator (as already explained above). This also causes heat energy to be lost.

The invention is in the light of the task of proposing a method for operating a furnace in a plant for metal processing and such a system, with or with improved energy efficiency can be achieved. So it should be achieved an improved use of energy.

The solution of this problem by the invention according to the method is characterized in that in the flow path for the exhaust gas from the furnace or parallel to the flow path, a heat exchanger is arranged, fed to the water and in which the water is heated, wherein the heated water or steam generated to operate a power plant or to be supplied to a consumer for hot water.

A first preferred embodiment of the invention provides that in the flow path of the exhaust gas, the recuperator and the heat exchanger are arranged in series, wherein the exhaust gas is first passed through the recuperator and then through the heat exchanger.

Alternatively, it is also possible that again in the flow path of the exhaust gas, the recuperator and the heat exchanger are arranged in series, but then the exhaust gas is first passed through the heat exchanger and then through the recuperator.

A further alternative embodiment of the proposed idea is based on the fact that the heat exchanger is arranged in a second flow path parallel to the flow path, wherein exhaust gas is at least temporarily passed through the flow path and through the second flow path simultaneously.

In the exhaust gas controlled cooling air can be added in all cases before reaching the recuperator and the heat exchanger.

From the flow path of the preheated air for the furnace can also be controlled or regulated hot air to be discharged to the environment.

The air pressure in the flow path of the preheated air for the furnace can be controlled or maintained at a predetermined value, wherein for controlling or regulating the air pressure, the volume flow of fresh air is influenced, which is supplied to the recuperator.

The proposed plant for metal processing, in particular the continuous casting plant, according to the invention is characterized in that a heat exchanger is arranged in the flow path or parallel to the flow path, wherein means for supplying water in an inlet of the heat exchanger are present, wherein a plant for power generation or means for Zuleiten of hot water to a consumer are present, which are connected to a drain of the heat exchanger.

The plant for power generation includes in particular a steam turbine.

Furthermore, it can be provided that a second flow path is arranged parallel to the flow path, wherein the heat exchanger is arranged in the second flow path and wherein at a branch point in which the second flow path branches off from the flow path, a controllable valve is arranged, which is formed, the exhaust gas with a predetermined amount in the two flow paths to guide. The exhaust gas is thus divided by the controllable valve in two flow paths.

With the proposed method and the corresponding device, it is possible to use the residual energy of the furnace exhaust gas much better. This results in an improved energy balance. The waste heat of the kiln exhaust gas can be converted directly into electricity but also provided to the hot water supply of a consumer.

The invention makes it possible to lower the temperature of the combustion air advantageously by passing hot exhaust gases through an additional valve through a second recuperator. As a result, components can be protected and the energy of the hot exhaust gases can still be used. In addition, this can preferably be dispensed with the reduction of the combustion air temperature. The system thus runs more stable overall.

In the drawings, embodiments of the invention are shown.

Show it:

1 1 schematically shows a plant scheme for the operation of a furnace of a continuous casting plant, which is carried out according to the prior art,

2 1 schematically shows a plant scheme for the furnace, which operates according to a first embodiment of the invention,

3 schematically a plant scheme for the furnace, which operates according to a second embodiment of the invention, and

4 schematically a plant scheme for the furnace, which operates according to a third embodiment of the invention.

In the 2 to 4 Three different detailed concepts are presented, like a stove 1 a continuous caster can be operated to a to achieve an improved energy balance. They are all based on the idea that in addition to at least one recuperator 2 a heat exchanger 4 is available, with the residual heat from the exhaust gas A of the furnace 1 can be used to either in a plant 5 to produce electricity for electricity generation (shown in the figures) or to use the residual heat to provide hot water to a consumer (not shown).

The basic structure of the concepts is based first on that according to the state of the art as described in 1 shown and described above. From the oven 1 Hereinafter, exhaust A along a flow path S into a recuperator 2 directed. The recuperator 2 Fresh air F is supplied, along a flow path S '' through the recuperator 2 and continue in the oven 1 is directed. In the recuperator 2 There is a heat transfer from the exhaust A to the fresh air F, so that the fresh furnace air (combustion air) is preheated.

Regarding the recuperators used, reference is made to the state of the art. They each have a separate room for the two media between which heat is to be exchanged. Plate heat exchangers, in particular spiral heat exchangers, tube heat exchangers, jacket tube heat exchangers or countercurrent layer heat exchangers can be used.

According to the in 2 The solution now shown is now a heat exchanger 4 in series with the recuperator 2 switched, ie the heat exchanger 4 is arranged in the flow path S, that of the furnace 1 to the fireplace 3 leads. Here, first, the exhaust gas A through the recuperator 2 passed and then cooled already about 700 ° C exhaust gas A through the heat exchanger 4 , Also for the heat exchanger mentioned above for the recuperator configurations come into question.

The heat exchanger 4 will water W through an inlet 6 fed. In the heat exchanger 4 the water W heats up and is converted into steam, which flows through a drain 7 a plant 5 for power generation is supplied, which includes a steam turbine. The conversion of the energy in the steam into electricity is well known as such and need not be further deepened here.

As in 2 can be seen here, as in the prior art, a temperature of the exhaust gas A behind the furnace 1 done by cooling air K via a fan 11 and a switchable valve 12 is added. It can also be provided that via a switchable valve 14 a hot air outlet 13 is opened to vent heated fresh air and in order to maintain the pressure p the fan 10 to operate accordingly, so that more cold fresh air F is conveyed into the flow path S ''.

The solution according to 3 is according to 2 very similar. The difference here is that the heat exchanger 4 for heating the water W here first after the oven 1 is arranged; the recuperator 2 follows only after the heat exchanger 4 , seen in the flow direction in the flow path S. Via a valve 15 If necessary, hot exhaust gas can be added to the heat exchanger 4 around to the recuperator 2 be directed. The solution shown is also characterized by the fact that it is possible to first cool the exhaust gas A by heating water and converting it to steam and only then the recuperator 2 supply. Therefore, in 3 the preferred case outlines that on the supply of cooling air K by means of a fan 11 and switchable valve 12 is waived; the pre-cooling of the exhaust gas A thus takes place through the heat exchanger 4 , However, it should be mentioned that the arrangement in question 11 . 12 also in the solution according to 3 can be provided.

In 4 a further alternative embodiment of the inventive concept is illustrated. Here it is envisaged that the heat exchanger 4 is arranged in a flow path S parallel to the second flow path S '. "Parallel" is to be understood here as meaning that the flow paths S and S 'are supplied with exhaust gas A from the furnace and run independently of one another. The exhaust gas A is thereafter at least temporarily passed through the flow path S and through the second flow path S 'simultaneously.

As can be seen, the second flow path S 'is thus arranged parallel to the flow path S, in which the heat exchanger 4 is placed. At a branching point 8th the second flow path S 'branches off. Here is a controllable valve 9 arranged. With the valve 9 can be specified, to what extent exhaust gas to the heat exchanger 4 is directed. Is the valve 9 closed, ie exhaust gas A is passed only through the flow path S, is exactly the situation before, as it corresponds to the prior art.

For operating points in which an additional heat recovery from the exhaust gas A is not desired, so can through the valve 9 the supply of exhaust gas A to the heat exchanger 4 prevented and all exhaust A via the recuperator 2 be guided.

LIST OF REFERENCE NUMBERS

1

oven

2

recuperator

3

fireplace

4

heat exchangers

5

Plant for power generation

6

Intake

7

procedure

8th

branching point

9

Valve

10

fan

11

fan

12

switchable valve

13

hot air outlet

14

switchable valve

15

Valve

A

exhaust

F

fresh air

W

water

K

cooling air

p

air pressure

S

flow

S '

second flow path

S ''

Flow path of preheated air for the oven

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 20091018476 A1 [0009]
• EP 0078446 A1 [0009]
• DE 69712009 T2 [0009]

Claims (10)

Method for operating a furnace ( 1 ) in an apparatus for metalworking, in particular in a continuous casting plant, wherein the exhaust gas (A) from the furnace ( 1 ) along a flow path (S) through at least one recuperator ( 2 ), wherein in the recuperator ( 2 ) by means of the heat energy fresh air (F) for the furnace contained in the exhaust gas (A) ( 1 ) preheated and the heated air the oven ( 1 ) and wherein the exhaust gas (A) in the flow direction behind the recuperator ( 2 ) in a fireplace ( 3 ), characterized in that in the flow path (S) or parallel to the flow path (S ') at least one heat exchanger ( 4 ) is supplied to the water (W) and in which the water is heated, wherein the heated water or the generated steam is used to a plant for power generation ( 5 ) or to be supplied to a consumer for warm water. A method according to claim 1, characterized in that in the flow path (S) of the exhaust gas (A) of the recuperator ( 2 ) and the heat exchanger ( 4 ) are arranged in series, wherein the exhaust gas (A) first by the recuperator ( 2 ) and then through the heat exchanger ( 4 ). A method according to claim 1, characterized in that in the flow path (S) of the exhaust gas (A) of the recuperator ( 2 ) and the heat exchanger ( 4 ) are arranged in series, wherein the exhaust gas (A) first through the heat exchanger ( 4 ) and then through the recuperator ( 2 ). Method according to claim 1, characterized in that the heat exchanger ( 4 ) is arranged in a flow path (S) parallel to the second flow path (S '), wherein exhaust gas (A) at least temporarily simultaneously through the flow path (S) and through the second flow path (S') is passed. Method according to one of claims 1 to 4, characterized in that in the exhaust gas (A) before it reaches the recuperator ( 2 ) and the heat exchanger ( 4 ) controlled or regulated cooling air (K) is added. Method according to one of claims 1 to 5, characterized in that from the flow path (S '') of the preheated air for the furnace ( 1 ) controlled or regulated hot air is discharged to the environment. Method according to one of claims 1 to 6, characterized in that the air pressure (p) in the flow path (S '') of the preheated air for the furnace ( 1 ) is maintained or regulated at a predetermined value, wherein for controlling or regulating the air pressure (p), the volume flow fresh air (F) is influenced, the recuperator ( 2 ) is supplied. Metal processing plant, in particular a continuous casting plant, comprising a furnace ( 1 ) of the exhaust gas (A) along a flow path (S) by at least one recuperator ( 2 ) is conductible, wherein in the recuperator ( 2 ) by means of the heat energy fresh air (F) for the furnace contained in the exhaust gas (A) ( 1 ) is heated and the heated air the furnace ( 1 ) can be supplied, wherein the exhaust gas (A) in the flow direction behind the recuperator ( 2 ) in a fireplace ( 3 ), in particular for carrying out the method according to one of claims 1 to 7, characterized in that in the flow path (S) or parallel to the flow path (S '), a heat exchanger ( 4 ), wherein means for supplying water into an inlet ( 6 ) of the heat exchanger ( 4 ), whereby a power generation plant ( 5 ) or means for supplying hot water to a consumer, which are provided with a drain ( 7 ) of the heat exchanger ( 4 ) are connected. Plant according to claim 8, characterized in that the plant ( 5 ) comprises a steam turbine for generating electricity. Plant according to claim 8 or 9, characterized in that parallel to the flow path (S) a second flow path (S ') is arranged, wherein in the second flow path (S') of the heat exchanger ( 4 ) and wherein at a branching point ( 8th ), in which the second flow path (S ') branches off from the flow path (S), a controllable valve ( 9 ) is arranged, which is designed to conduct the exhaust gas (A) with a predetermined amount in the two flow paths (S, S ').

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