DE4300192A1 - Operating at least two waste heat processes working in conjunction with each other - Google Patents

Abstract

The saturated steam is superheated in a HP superheater (2) in the second waste heat process (B). Following an expansion of the steam in the high pressure part (HD) of the steam turbine (DT). The steam is heated in a LP superheater (3) of the second waste heat process (B). At least with low load or the standstill of the first waste heat process (A), prodn. of saturated steam results, from LP steam emanating from the LP superheater (3).With low load or idling of the second waste heat process (B), a part of the saturated steam produced in the first waste heat process (A) is condensed. The heat resulting from this condensation is used for the superheating of the LP steam taken from the HP part (HD) of the steam turbine (DT).

Description

The invention relates to a method according to the preamble of claim 1 and a steam generating plant for through implementation of the method according to the preamble of the claim 4th

To understand the invention, there are two types defined by waste heat processes. A first heat-down process is an industrial waste heat process with the following characteristics len:

• - The waste heat supply is fluctuating and is from industrial processes.
• - When generating steam to drive one after switched steam turbine will be the one for the optimal use of steam energy required Parameters, in particular the fresh steam temperature, not or not always achieved.

Such waste heat processes are characteristic of waste incineration plants, hazardous waste incineration plants and Industries in which process gases at relatively high Temperatures are condensed.

A second waste heat process is a waste heat process in which the exhaust gases for the overheating of the for the steam turbine Required live steam are suitable, such as z. B. can be generated by an upstream gas turbine.

If one uses a waste heat process of the first kind to generate supply of electrical energy using a conventional Steam process, this results in comparison to one coal or gas powered power plant a very low efficiency because of the special conditions the incineration of waste is a limitation of the process pa parameters. In industrialized countries, the Garbage increasing amounts of plastic, e.g. B. PVC. While The combustion of this material creates hydrochloride acid (HCL), which are not sufficiently neutralized can and on the boilers, especially on the superheater causes severe corrosion damage. Even with one relatively reduced steam temperature results here due to short downtimes and high maintenance costs fertilize.

From "IR. TED Wiekmeÿer, Improvements in Incinerators by Means of Gas Turbine Based Cogen Systems, Gas Turbine and Aeroengine Congress amd Exhibition, June 11-14, 1990 Brussels, Belgium "it is known to indu strial heat processes of the first kind by linking with a waste heat process of the second type ser. The industrial waste heat process is used for Production of saturated steam, which is then carried out using the Heat-up process of an upstream gas turbine in an egg a superheater is superheated to live steam.  

It is essential that none in the gas turbine heat-down process risk of corrosion comparable to waste incineration consists. However, the high expenditure on equipment is disruptive the well-known steam generator and the difficult speed, even with strong fluctuations in the heat recovery process generated saturated steam amount to a favorable efficiency achieve.

Corresponding to those generated in the industrial waste heat process The amount of saturated steam fluctuates in the heat requirement of the excess steam decomposed A balance of the energy required here can ent neither by installing additional firing before Superheater or through to steam production matched load of the gas turbine can be brought about. Both measures are not suitable, an optimal we to achieve efficiency, since the efficiency of an additive firing is basically bad and Load changes of the gas turbine to adjust the waste heat to the amount of saturated steam generated, of course, unimportant are desired.

The object of the invention is a method according to the Preamble of claim 1 and a steam generator able to carry out the procedure by an improvement in efficiency is achieved and even strong load fluctuations in one of the two Heat recovery processes using the other heat recovery process can be compensated without additional firing.

This object is achieved by the in each of claims 1 to 6 each identified features solved. Appropriate Refinements and developments of the invention counter stands are mentioned in the subclaims.  

In a first method, the up according to the invention in case the first heat-down process stops has come or only driven under light load will be solved. For this, the steam, after its expansion in the high pressure part of the steam turbine, in a low pressure superheater of the second waste heat process overheated and by taking heat from the low pressure superheater coming low pressure steam generates saturated steam. The second, e.g. B. starting from a gas turbine waste heat process thus be continued even if from the first Ab no saturated steam is supplied. Thus, the Steam turbine without restriction even with the gas turbine and their heat recovery steam generator.

In a second method, the method according to the invention is used Task in the event that the second heat recovery process Has come to a standstill or only occurred under light load is resolved. For this purpose, part of the first generated saturated steam condenses and the heat of condensation to overheat the High pressure part of the steam turbine extracted low pressure steam used. So when using the procedure as usual, the gas turbine is no longer continuous Lich drive so that when generating electricity with high-quality fuel is not sensible (e.g. in never tariff times), the gas turbine can be switched off or is only operated under low load.

In a third method, the method according to the invention is used Task solved in the event that a combination of both of the above methods are desired together. In this method it is achieved that either a heat Exchange from the first waste heat process to the second waste heat process takes place, or the heat exchange in reverse direction. It is therefore ensured that in case of low load or standstill of the first ab  heat process a heat exchange to generate satiety steam through the never coming from the low pressure superheater the pressure steam takes place or in the case of light loads or breastfeeding heat exchange was available for the second heat recovery process Overheating of the high pressure part of the steam turbine low pressure steam by condensation of the im Most waste heat process generated saturated steam takes place.

Furthermore, the object of the invention by the Er provision of one to carry out the respective procedures suitable steam generation system solved. So he is most steam generating plant to carry out the first Procedure with a first waste heat boiler, in which he first heat process is running, and in the one High pressure evaporator for saturated steam generation is arranged and with a second waste heat boiler in which the second Waste heat process takes place and in which a high pressure superheater is arranged for fresh superheating, the saturated steam of the first evaporator is supplied. According to the invention is now in the flow direction of the exhaust gases behind the high pressure superheater is a low pressure superheater, the low pressure steam is fed to an HD steam generator that in turn by extracting heat from the low pressure steam from water generates saturated steam, which is the high pressure superheater is supplied.

A suitable one for carrying out the second method The steam generating plant is basically like the first one Steam generating plant built, but part of the saturated steam coming from the first heat recovery process in one LP steam superheater condenses and with the generated Heat the low pressure steam overheats.

To combine the first and the second procedure with each other Being able to kidney is a third according to the invention Steam generating plant proposed, resulting from the  Share the first and second steam generating plants put together. This third steam generating plant is out extremely flexible due to low load periods and breastfeeding stood in each of the two waste heat processes through each because other heat recovery processes can be intercepted.

The structure of the steam generator can thereby ver be simplified that the LP steam superheater and the HD Steam generator together to form a combination heat exchanger be quantified, the functions of both functions perceives.

In a practical development of the counterpart of the invention It is envisaged that with high-pressure saturated steam from the high pressure evaporator and / or the balancing heat high pressure superheater the superheated High pressure steam feeds a high pressure turbine that the from her steam relaxed to low pressure to the low passes on the superheater, from which it passes over the Compensation heat exchanger to a low pressure turbine reaches.

Building the second is essential Waste heat boiler, since the exhaust gases flowing into it Several heat exchangers in series pass where at it from the heat requirement of each upstream Heat exchanger depends on how much heat for the nachge switched heat exchanger remains. So it is provided behind the high pressure superheater the low pressure superheater and to arrange a low pressure evaporator behind this and that of the high pressure turbine and the low pressure ver low pressure steam coming over the low pressure to supply heat.

Furthermore, it is advisable to use it if there is excess heat, go to the first waste heat boiler  first preheater and in the second waste heat boiler behind the low pressure evaporator to install a second preheater.

In the case of a combination heat exchanger that has a bidirec tional heat exchange between the two waste heat processes enables, it is appropriate to vorzu a level controller see that depending on the temperature of the low pressure level the water level by control a first valve for a condensate drain and through Control of a second valve for a memory water inlet regulates. The combination heat exchanger will expediently always the second waste heat process arrange, regardless of whether a combination heat rope or two specific to their respective task fitted heat exchangers can be used.

To avoid an unwanted drop in temperature in the High pressure part of the steam turbine in the event of hot gas failure supply, the high pressure and low pressure section be coupled with an overrunning clutch. Should z. B. the gas turbine will go into short circuit, the two will Parts automatically decoupled and the high pressure part of the Steam turbine shuts down even during one bypass controlled by the pressure the high pressure steam in feeds the low pressure rail.

An embodiment of the invention is in the drawing voltage and is described in more detail below. Show it:

Fig. 1 is a schematic of the two interconnected Abhitzeprozesse to generate steam for a steam turbine,

Fig. 2 shows the second Abhitzeprozeß with additional details,

Fig. 3 shows the second Abhitzeprozeß with an LP steam superheater and a high-definition steam generator,

Fig. 4 shows a T / Q diagram of a combined gungs- Dampferzeu / Dampfüberhitzungaanlage at design for normal load,

Fig. 5 is a diagram corresponding to FIG. 3 at low load of the gas turbine,

Fig. 6 is a diagram corresponding to FIG. 3 at shutdown of the gas turbine,

Fig. 7 is a diagram corresponding to FIG. 3 at low load of the first Abhitzeprozesses,

Fig. 8 is a diagram corresponding to Fig. 3 in the event of failure of the first heat recovery process.

How can see the pattern of FIG. 1, get hot exhaust gases of an industrial W1 Abhitzeprozesses A, z. B. a waste incineration plant, to a high pressure evaporator fer 1 , to which they partially or completely give up their heat potential and continue to flow as a correspondingly cooled, possibly condensed medium W2 in the waste heat boiler C. The saturated steam generated in the high-pressure evaporator 1 is fed to the second heat recovery process B, which is formed as a combined steam generation / steam superheating system. A waste heat boiler D assigned to this plant is normally treated with hot exhaust gases W3, e.g. B. from the gases from a gas turbine GT, heated. In the direction of flow of the exhaust gases W3 there is a high pressure superheater 2 in which the saturated steam of the high pressure evaporator 1 overheats and is then fed to the high pressure part of a steam turbine DT / HD.

After its relaxation in the high-pressure part of the steam turbine DT / HD, the low-pressure steam is now superheated in a low-pressure superheater 3 , which is arranged behind the high-pressure superheater 2 . The so overheated low pressure steam flows through a compensating heat exchanger 5 to the low pressure part of a steam turbine DT / ND, in which it is up to the evaporation pressure, for. B. the condensation pressure, ent.

In the second waste heat boiler D behind the low-pressure heater 3 there is also a low-pressure evaporator 4 which generates low-pressure steam, provided that the steam from the first heat-down process A does not have the entire heat potential between the inlet temperature of the exhaust gas W3 and the saturation temperature of the low-pressure steam in the superheater 2 and 3 can accommodate. The low-pressure steam generated by the low-pressure evaporator 4 passes together with the low-pressure steam coming from the high-pressure part of the steam turbine DT / HD to the low-pressure superheater 3 .

Both the exhaust gas W2 flowing out of the first heat recovery process A and the exhaust gas W4 flowing out of the second heat recovery process B can be used for heating further apparatus, e.g. B. an economizer, if there is still usable heat potential. These are options that are sufficiently well known and therefore do not require any further description. In the variant indicated in FIG. 1, a first preheater 7 is provided in the first Abhit boiler C and a second preheater 8 is provided in the second waste heat boiler D. The two preheaters 7 , 8 are supplied with water by an economizer 9 via pumps 16 , 17 . On the input side, the eco nomizer 9 is fed via a pump 15 with condensate from a condenser 10 lying at the outlet of the low-pressure part of the steam turbine DT / ND.

Of decisive importance for the operation of the second Abhitzeprozesses B in its function as a combinatorial ned steam / evaporated overheating facility is the effect of the combination of the heat exchanger. 5 This has the task of balancing the two waste heat processes A, B in such a way that one of the two waste heat processes A, B fails or can be operated under low load and the missing heat is generated by the other waste heat process. It can either dry the low-pressure steam as required and overheat it sufficiently, or generate high-pressure saturated steam. A first room of the combination heat exchanger 5 is connected to the first high pressure evaporator 1 , while the low pressure steam coming from the low pressure superheater 3 flows through a second room.

On the high-pressure side of the combination heat exchanger 5 there is not only steam but also condensate, the level of which is determined by the low-pressure steam temperature. Should z. B. the gas supplying the second waste heat process B, GTur bine GT are reduced or even switched off, the low-pressure steam is optionally dried by condensing saturated high-pressure steam and overheated to the extent that it can be fed to a low-pressure part of the steam turbine DT / ND, thereby replacing the low-pressure superheater 3 .

Conversely, the combination heat exchanger 5 behaves when the amount of steam coming from the first heat-up process A decreases. The inflowing exhaust gas W3 of the second Abhit zeprocesses B is now no longer cooled at the high-pressure superheater 2 so much that sufficient heat remains to overheat the low-pressure steam in the low-pressure superheater 3 above its setpoint, so that it then shears its excess heat at the combination heat exchanger 5 can deliver, which in turn generates high-pressure saturated steam. This can in turn be fed to the high-pressure superheater 2 . Of course, the Kombinati onswärmetauscher 5 can also consist of two separate functional units, one of which ensures the overheating of the low-pressure steam and the other of the high-pressure saturated steam generation.

The entire system is used to generate electricity, a he first generator G1 from the gas turbine GT and a second Generator G2 is driven by the steam turbine.

The illustration in FIG. 2 reveals further details of the two th waste heat process B of FIG. 1, the connecting lines a to g leading to the rest of the power plant process. The in the condensation of high pressure saturated steam in combination heat exchanger 5 condensate produced as well as a feed water inlet e ensure the necessary What ser which onswärmetauscher for generating high pressure steam in combination Nati 5 is needed. A first level controller N1, which specifies the water level as a function of the temperature T, ensures that excess condensate reaches the condensate drain f with the aid of a first level control valve 13 , or a feed water inlet e is made possible with the aid of a second level control valve 14 . A pressure regulator P controls a high-pressure diversion station 6 , which connects the low-pressure superheater 3 to the high-pressure superheater 2 and thus helps to avoid an undesired drop in temperature if the exhaust gas supply of the second waste heat process fails. With a two-level controller N2, the water level in a low pressure drum 11 for the low pressure evaporator 4 is controlled.

As already indicated, the combination heat exchanger 5 can also be implemented by two separate functional units. As shown in Fig. 3, this serves an LP steam superheater 5 a and an HD steam generator 5 b.

The low-pressure steam superheater 5 a receives its low-pressure steam from the low-pressure superheater 3 , which it is intended to support or to set, and passes the dried and superheated low-pressure steam on to the low-pressure steam turbine DT / ND. For heat exchange, saturated steam from the high-pressure evaporator 1 of the first waste heat process is fed to it via the connection a.

The HD steam generator 5 b is connected to the level control of a feed water inlet and a condensate drain and is heated by the condensation him from the low pressure superheater 3 supplied low pressure steamers to ge. The high pressure steam generated by it is passed on to the high pressure superheater 2 .

In Figs. 4 to 8 show various T / Q-diagrams of the second Abhitzeprozesses are presented to illustrate various Dener operating cases. The amount of heat emitted by the exhaust gas is absorbed depending on the operating case with a correspondingly changing proportion of the high pressure superheater 2 , the low pressure superheater 3 or the low pressure evaporator 4 . The respective temperature of the steam c coming from the high-pressure part of the steam turbine DT / HD, of the steam d flowing to the low-pressure part of the steam turbine DT / ND, of the steam a coming from the high-pressure evaporator 1 and of the steam b flowing to the high-pressure part of the steam turbine DT / HD can also be seen .

In the normal case shown in FIG. 4, there are only very low temperature differences with an optimal design and, accordingly, a high degree of efficiency. In the low load shown in FIG. 5 in the second Abhit process, there is no excess heat for feeding the low-pressure evaporator 4 , which must be compensated for by the combination heat exchanger 5 . In the failure of the second heat recovery process shown in FIG . B. a standstill of the gas turbine GT, al linein the combination heat exchanger 5 ensures the overheating of the low-pressure steam. In the low load of the first heat recovery process shown in FIG. 7, the combination heat exchanger 5 takes heat from the second heat recovery process for high pressure steam generation, which he must do to an increased extent in the case of the failure of the first heat recovery process shown in FIG. 8.

Thus the following characteristics of the steam supply of the Steam turbine with neglect of the final predicaments are recorded:

• - The steam temperature at the inlet of the high-pressure section follows the exhaust gas inlet temperature into the high-pressure superheater 2 and is therefore subject to changes (e.g. due to the load on the gas turbine) up to the saturated steam temperature.
• - The steam temperature at the entry of the low pressure part is constant.
• - The high-pressure part is also sufficient High pressure steam supplied when the external sat Steam generation in the industrial waste heat process is broken.

It is assumed that the steam turbine the steam regulates pressure (high and low pressure) in a known manner.

Claims (14)

1. A method for operating at least two interlinked waste heat processes (A, B), by the steam for driving a steam turbine (DT) is generated and in which the linkage is such that in normal operation in a first waste heat process (A) saturated steam is generated and this saturated steam in a high pressure superheater ( 2 ) of a second heat recovery process (B) is superheated to the temperature required for live steam, characterized in that after expansion of the steam in the high pressure part (HD) of the steam turbine (DT), this in one Low pressure superheater ( 3 ) of the second heat recovery process (B) is overheated, and that at least when the first heat recovery process (A) is at a low load or is at a standstill by taking heat from the low pressure steam coming from the low pressure superheater ( 3 ), saturated steam is produced. 2. Method according to the preamble of claim 1, characterized in that at least at low loads or the second heat-up process (B) comes to a standstill of the saturated steam generated in the first heat recovery process (A) is condensed and the resulting heat of condensation for overheating the high pressure part (HD) of the steam door bine (DT) used low-pressure steam is used. 3. The method according to claim 1 or 2, characterized in that at least at low load or standstill of the first waste heat process (A) the generation of saturated steam by heat exchange with the low pressure steam coming from the low pressure superheater ( 3 ), and that at least at low load or standstill of the second heat recovery process (B) the overheating of the high pressure part of the steam turbine (DT) coming low pressure steam by a heat exchange in the form of a condensation of the saturated steam generated in the first heat recovery process (A). 4. Steam generation system for performing the method according to claim 1, with a first waste heat boiler (C), in which the first waste heat process (A) takes place and in which a high-pressure evaporator ( 1 ) is arranged for saturated steam generation, and with a second waste heat boiler (D) , in which the second waste heat process (B) takes place and in which a high pressure superheater ( 2 ) for fresh steam generation is arranged, the saturated steam of the high pressure evaporator ( 1 ) is supplied, characterized in that in the two th waste heat boiler (d) behind the high pressure superheater ( 2 ) a low-pressure superheater ( 3 ) is arranged, which feeds low-pressure steam to a high-pressure steam generator ( 5 b), and this, by removing heat from the low-pressure steam, generates saturated steam, which in turn is fed to the high-pressure superheater ( 2 ). 5. Steam generation system for carrying out the method according to claim 2 according to the preamble of claim 4, characterized in that in the second heat boiler (D) behind the high pressure superheater ( 2 ) a low pressure superheater ( 3 ) is arranged, the low pressure steam an LP steam superheater ( 5 a) feeds, and this condenses part of the saturated steam coming from the first heat recovery process (A) and overheats the low-pressure steam with the heat generated. 6. Steam generation system for carrying out the method according to claim 3 according to the preamble of claim 4, characterized in that a low-pressure superheater ( 3 ) is arranged in the second heat boiler (D) behind the high-pressure superheater ( 2 ), the low-pressure steam a high-pressure steam generator ( 5 b) supplies, and this water, at least when the first waste heat process (A) is at a low load or comes to a standstill, generates saturated steam by removing heat from the low pressure steam and in turn supplies this to the high pressure superheater ( 2 ), and a low pressure steam superheater ( 5 a) at least at low load or standstill of the second waste heat process (B) condenses part of the saturated steam generated in the first heat process (A) and the resulting heat of condensation serves to overheat the high pressure part (HD) of the steam turbine (DT) which is used to remove the pressure steam. 7. Steam generation system according to claim 6, characterized in that the LP steam superheater ( 5 a) and the HD steam generator ( 5 b) are combined to form a combination heat exchanger ( 5 ) which performs the function of both functional units. 8. Steam generating plant according to one of claims 4 to 7, characterized in that the high pressure saturated steam from the high pressure evaporator ( 1 ) and / or the combi nation heat exchanger ( 5 ) fed high pressure superheater ( 2 ) supplies the superheated high pressure steam to a high pressure turbine (DT / HD) , which transfers the steam released by it to low pressure to the low-pressure superheater ( 3 ), from which it reaches a low-pressure turbine (DT / ND) via the combination heat exchanger ( 5 ). 9. Steam generation system according to one of claims 4 to 8, characterized in that in the second waste heat boiler (D), in the flow direction of the exhaust gases, behind the high pressure superheater ( 2 ), the low pressure superheater ( 3 ) and behind this a low pressure evaporator ( 4 ) are net angeord and the low pressure evaporator ( 4 ) as well as the high pressure turbine (DT / HD) feeds the low pressure superheater ( 3 ) with steam. 10. Steam generation system according to one of claims 4 to 9, characterized in that in the first waste heat boiler (C) behind the high pressure evaporator ( 1 ) a first preheater ( 7 ) and in the second waste heat boiler (D) behind the low pressure evaporator ( 4 ) a second preheater mer ( 8 ) is installed and the two preheaters ( 7 , 8 ) absorb any useful heat remaining in the exhaust gases (W1, W2) in the respective waste heat process (A, B). 11. Steam generation system according to one of claims 4 to 10, characterized in that the combination heat exchanger ( 5 ) has a level controller (N1) which, depending on the temperature of the low-pressure steam, the level of its water level by controlling a first valve ( 13 ) for one Condensate drain (f) and a second valve ( 14 ) for a feed water inlet (e) controls. 12. Steam generation system according to one of claims 4 to 11, characterized in that the combination heat exchanger ( 5 ) is assigned to the second heat recovery process (B). 13. Steam generation system according to one of claims 4 to 12, characterized in that the high pressure heater ( 2 ) is connected to a low pressure superheater ( 3 ) via a pre-pressure-controlled high pressure bypass station ( 6 ). 14. Steam generation system according to one of claims 1 to 13, characterized in that the first Abhitzepro zeß (A) by exhaust gases (W1) with fluctuating, of which ever industrial processes dependent on heat emission is fed and for the optimal use of it generated steam energy required parameters, esp especially those for driving the downstream steam turbine (DT) required fresh steam temperature, not or not always achieved, and that the second heat recovery process (B) is fed by exhaust gases (W2) leading to overheating of the freshness required for the steam turbine (DT) steam are suitable.