KR20180119080A - Method and device for cleaning and reheating flue gas - Google Patents

Abstract

Provided are a method and an apparatus for cleaning and reheating flue gas. At this time, the hot flue gas is delivered to a flue gas heat exchanger (2), and then to a flue gas scrubber (6). Subsequently, the heat exchanger (2) is subjected to perfusion through heat absorption and then to a chimney (15), wherein the flue gas flows through a liquid separator (9) after the flue gas scrubber (6) and before the heat exchanger (2) in the flow direction (S).

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method and apparatus for cleaning and reheating flue gas,

The present invention relates to a method for cleaning and reheating a flue gas wherein the hot flue gas is passed through a heat exchanger, then a flue gas scrubber, followed by a heat exchanger And is then passed on to the chimney. The present invention also relates to a device for cleaning and reheating flue gas flowing in the flow direction with a heat exchanger housing which is perfused by said gas for reheating and having heat exchanger elements.

This kind of method and apparatus of this kind are used for the flushing of flue gases, for example coal or oil power plants (hereinafter simply referred to as "power plants").

It is an object of the present invention to prevent the heat exchanger from being contaminated with hard and hard cakings. This rigid caking can increase the pressure loss in the heat exchanger, result in large cleaning costs, and even in the worst case, force a short-term and undesired shutdown of the plant.

To carry the flue gas, the residual sulfuric acid contained therein and the fine dust as high as possible into the atmosphere, the plants are equipped with a device for reheating the flue gas regularly downstream of the flue gas scrubber. Without this reheating, the condensate will already form regularly in the chimney. These condensates usually occur at the chimney wall or near the chimney wall, then aggregate together and form large droplets. Also, large washing droplets resulting from the cleaning of the droplet separator of the flue gas scrubber are likewise flushed with the flue gas into the chimney and then out of the chimney. If the flue gases were reheated they would have vaporized in the heat exchanger. These droplets - large condensate drops and large wash droplets - are then discharged from the chimney, and are brought close to and closer to the periphery.

These so-called chimney ratios are acidic (sulfuric acid as a component), severe damage (lacquer damage and corrosion) in vehicles through corrosion, severe damage to buildings (melting concrete and building materials), (industrial and personal) Resulting in severe damage to facilities, and damage to plants and gardens (acid rain). This, of course, must be avoided indefinitely, especially in areas where people live. Will lead to incessant conflicts with residents who must see how their private cars, homes, commercial establishments, etc. are destroyed by the acid rain.

The reheating of the flue gas prevents these problems by preventing condensate formation, vaporizing the droplets through reheating, and condensing outside of the flue. Because the flue gas is heated, he ascends, the condensates first stay small and then vaporize in ambient air before reaching the bottom.

For this reheating, a so-called Yungstrom heat exchanger - a rotating regenerative heat exchanger - has been used for decades. The heat exchanger surfaces first absorb heat (and cool the flue gas) in the hot flue gas stream in front of the flue gas scrubber, and then cool the flue gas in half the revolution Back heat to the flue gas coming from the flue gas scrubber again. The heat exchanger surfaces absorb heat from the hot flue gas stream, store it, and then continue to rotate into the backwash and then release the stored heat back to it.

These regenerative heat exchangers have, among other things, the following disadvantages:

During heating in the raw gas, the heat exchanger also absorbs dust components in addition to heat. Also, the regenerative heat exchanger is not hermetic - there is a leak, through which the hot biogas can leak into a clean, cool, clean gas stream. Through these two effects, a large number of dust parts to be separated in the flue gas scrubber are brought into the clean gas stream, which increases the amount of dust that the clean gas still has after the flue gas scrubber.

This is undesirable, of course, and dust emissions from power plants must be minimized. This contamination of the clean gas with fine dust through leaks in the regenerative heat exchanger is therefore not desired.

For this reason, the idea of a leak-free heat exchanger has been developed. Such a heat exchanger may be formed as a gas / gas heat exchanger. He may include a tube system, which is perfused internally by the raw gas and externally by the clean gas. But he can also be formed as a gas / liquid heat exchanger. In doing so, both gas flows are separated through a liquid circulation which conveys heat from the raw gas to the clean gas. The flue gas flows through the heat exchanger in the form of a tubular or plate with the liquid on the one hand and the carrier liquid on the other. The hot biogas releases its heat to the cooling liquid. The liquid is then directed to the clean gas side, where heat in a similar tube heat exchanger or plate heat exchanger is returned to the clean gas.

Leakage of the biogas and thus fine dust particles to the clean gas side are not possible in the two configurations of the heat exchanger.

However, according to experience with working with these leak-free heat exchangers, they can become dirty during operation. A caking is formed on the surfaces of the heat exchanger that are flushed with flue gas. These cakes consist of calcium sulfate, limestone, fine dust, and other components of the flue gas, or rather the remaining droplets in the flue gas. They are in most cases very strongly connected to the surface of the heat exchanger and have a rigid and partly even crystalline structure. The caking takes place especially where the surfaces of the heat exchanger receive flue gas flow.

The result of this caking is increased pressure loss and reduced heat exchange performance.

The caking becomes thicker over time and grows into the path of the flue gas through the tubes or plates of the heat exchanger. This narrows the passage space for the flue gas, increases the speed, and increases the pressure loss. The rate of contamination - that is, the generation of caking - increases even more with increasing caking thickness. The caking results in vortices in the free passage between the heat exchanger surfaces, thus allowing much more liquid to hit the heat exchanger surfaces and deposit there. The increase in pressure loss can be so severe that the boiler must be downshifted or completely switched off. And, of course, a large increase in pressure loss results in greater operating costs. The flue gas blowers must operate against this pressure loss and consume much more current than under normal and clean conditions. This self-consumption reduces the amount of power that must be distributed, thereby reducing the metabolism and benefits of the plant.

Heat exchange performance decreases over time, and reheating no longer works. The caking generally does not conduct very well thermally, but acts as an insulating layer between the flue gas and the surface of the heat exchanger.

In addition, corrosion frequently occurs with respect to the caking. Exposed and relatively clean surfaces of the heat exchanger exhibit less or no corrosion, while under the caking there is a high rate of corrosion. The caking acts as a substantially protective layer, below which corrosive liquids can act on the heat exchanger surface and corrode it.

The cleaning of the contaminated heat exchangers results in regular difficulties. The cakes are not only very tightly connected but also tightly connected to the surfaces of the heat exchanger elements. The connection must be released by mechanical force, and the caking must be separated by a high pressure cleaning method. This results in very high work effort as well as damage to the heat exchanger material because the abrasive force of the high pressure washer not only polishes and removes the caking but also removes the surface of the heat exchanger entirely. This reduces the lifetime of this relatively expensive heat exchanger.

The cleaning is also very time-intensive and takes much longer than just a few hours. Generally, short stall conditions are not sufficient to clean the heat exchanger. That is, if a large increase in pressure loss and an associated disturbance of thermal heating occur before the end of the operating cycle, longer operating failures can not be avoided.

The cleaning is also very expensive. The elements of the heat exchanger, such as tube bundles or plate bundles, which are to be cleaned, are practically inaccessible and must often be lifted out of their position for cleaning. For this, a crane with a large lifting force is needed. The clean bundles already have a very large weight, and the bundles are heavier when progressive contamination occurs. Thereafter, the above cleaning on a special place requires considerable time and manpower depending on the type and thickness of the caking.

Unfortunately, it is mostly not possible to remove all caching. Regarding this, there is not enough time and sufficient manpower in ordinary inspection. Also, the internal heat exchanger surfaces are reachable only to a very limited extent. The remaining caking in the heat exchanger then acts to accelerate to create a new caking. In addition, cleaning with a high-pressure scrubber roughens the surface of the heat exchanger, which also accelerates the creation of new cakes. Rough surfaces and residual caking act to accelerate or accelerate caking. The new cakes can be deposited on these rough surfaces or caking residues faster than on clean, clean surfaces.

In addition, the cleaning measures result in progressive damage of the heat exchangers. On the one hand, removal and damage to the heat exchanger surfaces can occur, while disassembly and re-installation can lead to other damages in the structure of the heat exchanger. The life of the heat exchanger is shortened. Experience has shown that one wash has the effect of significantly reducing life span over 12 months of operation.

With these experiences, I was able to ponder about the cleaning devices and install them. The purpose of these cleaning devices is to prevent or slow down the pollution, thereby, on the one hand, to secure the operation of the power plant during the operating cycle and, on the other hand, to reduce operating costs and cleaning costs.

First, these cleaning devices were mounted only in front of the heat exchanger bundles when viewed in the direction of the flue gas flow. Experience has shown that the strongest generation of caking has occurred here. First it was worked out with compressed air and steam, but it was quickly confirmed that this would not have the effect of increasing the desired duration of operation. Thereafter, it was washed with high-pressure water.

This washing with high pressure has indeed resulted in that the contamination of the front tufts can obviously be reduced. Although caking could not be completely prevented, strong generation no longer occurred. The increase in pressure loss was prevented first, and the thermal loss was not so great.

Now, however, the experience has shown that the kings now appear in the heat exchangers, in the bundles that lie far behind them - in areas that were not first or only relatively few. Although this caking was alive with some sort of delay (a longer period of operation), this has greatly increased cleaning efforts in terms of time and cost.

Because of this, some of the power plants also have additional washing systems installed there, and no place for them was available in other power plants. For the sake of cost, in the latter plants, the channels filled with heat exchangers were assembled as small and packed as possible.

However, thereafter, it was also perceived through other cleaning devices that the caking was "just" transferred back to the other heat exchanger bundles, and the cleaning effort or heat exchanger damage continued to increase. In addition, many cleaning systems result in large investment and operating costs. Eventually, of course, each wash results in immediate cooling of the flue gas, resulting in the introduction of liquid into the chimney, and then into the environment. However, this should be prevented.

The perception that cleaning systems can not produce the desired function is inherited. On the one hand, increased investment costs and operating costs arise, on the one hand, the cleaning measures are limited enough, and even lead to an increase in cleaning costs in the off-state.

The description of this malfunction of the cleaning devices is relatively simple. When liquid droplets contaminated with solids hit a heated or even hot surface, a portion of the liquid remains on the surface and soaks it. Through continuous heat supply the liquid is then vaporized and only the solid remains. This solid is connected to the surface of the heat exchanger at the time of vaporization, penetrates into the fine crevices and into the holes in the surface, and fills them. Over time, very thick and firm cakes grow over time.

If this generation of caking is reduced through cleaning cleaning, these cleaning droplets will occur far behind the heat exchanger in the same function as the original droplets coming from the flue gas scrubber. When the last heat exchanger is cleaned, the cleaning droplets fly into the channel and the chimney, and then down as the chimney rain.

That is, the cleaning effect of the cleaning system at one site results in a contamination effect at other sites. Temporary cooling of the flue gas during flushing or temporary flushing of the flushing liquid out of the chimney recovers the action of the heating and results in disturbances in the environment which must be prevented through the original heating. In some cases, problems with supervisory authorities arise even as the preliminary standards of the authorities can not be met temporarily.

These experiences can be combined with the fact that washing of the heat exchanger should be prevented because it results in more problems and costs than benefits during operation.

As a result, the arrangement of the flue gas cleaning device in the upstream of the heat exchanger has been conceived in the other target direction. An entirely correct contemplation was that the amount and rate of pollution generation could be reduced through improved separation. As a result of this deliberation, the flue gas separator droplet separators were assembled in three stages, and in some cases even four stages, and the function of the liquid separators improved through other facility specific measures.

Through it, development has been achieved entirely. The amount of caking has decreased and the production of caking has slowed down. On the one hand, the improved droplet separator produced less droplets during operation - through an improved separation function, and on the other hand droplets were less contaminated with solids on average.

Triple or even quadruple drop separators really have better separation than double drop separators. This is evident when certainly each droplet separator only seeks between 98% and 99.9% of the larger droplets, but never 100%. More stages mean a higher degree of separation.

In this way, the amount of solids in the droplets also decreases. Most of the droplets downstream of the droplet separator consist of droplets from the last droplet separator cleaning process. If this last droplet separator is relatively heavily contaminated, the wash droplets that carry over are likewise severely contaminated with solids. On the other hand, if he was very clean and uncontaminated, the cleaning droplets were slightly dirty. That is, having a three-stage or even four-stage droplet separator with high cleaning performance, the last stage cleaning droplet is much less contaminated than the cleaning droplet from the two-stage droplet separator.

That is, through the improvement of separation, the generation of caking could be clearly reduced. This makes it possible to drive a full cycle of operation without interruption at most facilities. But there were two problems.

1) Large cleaning effort and

2) Constant generation of pressure loss.

With this method, it is recognized that the limit has been reached, and other improvements are not possible.

It is therefore an object of the present invention to provide an improved method in conjunction with the problems described above and a device suitable for carrying out the method.

To do this, a separation scheme that meets three conditions must be found:

1. High separation performance for large droplets is ensured consistently. That is, there is no reduction in separation performance due to progressive contamination.

2. Cleaning droplets should be prevented. In conventional installations, cleaning droplets responsible for 60% to 70% of the total liquid droplets are prevented, thereby doubling the cleaning performance with respect to fine dust.

3. No increase in pressure loss should occur. An increase in pressure loss caused by progressive generation of caking is prevented.

There are various droplet separator schemes that can separate droplets from flue gas. Prior art multilayer droplet separators in various configurations in an absorber are included.

A particularly successful concept is the so-called "roller separator". The roller separator uses tube segments as impact bodies - unlike conventional lamellar separators that use extruded and specially formed profiles.

This roller separator has proven to be highly resistant to contamination and caking during operation and yet nevertheless has acceptable separation performance relative to the separation of conventional lamella separators. However, the roller separator has traditionally been used only as a coarse separator so far, because the lamella separator is superior to the roller separator in its use as a fine separator.

The roller separator has heretofore been mainly used for disinfecting existing droplet separators. In these disinfected facilities, enough experience could have been collected in the meantime, in order to be used as a basis for use in new facilities.

It is known that especially large droplets can cause the effect of caking generation.

Small droplets never reach the surface. They have a small mass, and therefore avoid flue gas ducts or plates with flue gases and avoid them. They do not bounce off. After that, they vaporize through the supply of heat, and the solids continue to fly as fine dust.

The intermediate droplets can partially or completely avoid flow resistance along the flight path or simply touch the surface of the heat exchanger and then largely split into a number of partial droplets that continue to fly with the flue gas, It evaporates.

Only large droplets can not avoid the flow resistance of the heat exchanger tubes or plates based on their mass and fall away against the hot surface of the heat exchanger. Thereafter, short-term instability of the small surface area occurs, followed by subsequent vaporization on the surface, leaving only thin and tightly connected thin layers on the surface.

The large droplets are large condensation droplets that are split by large wash droplets that occur and break through the washing of the last separator or by ceilings, walls or other broken edges in the flue gas channel between the separator and the heat exchanger. These condensed droplets arise because the ambient temperature is much lower than the flue gas temperature, and therefore also in the good insulation of the flue gas channel, due to the considerable temperature difference. There may be occasions where a split droplet is deposited on the walls and then agitated before it is again entrained.

Condensate droplets also have a kind of solid part. Particles which are deposited in the form of dry dusts which are deposited on the walls of the flue gas channel and also on the ceiling and partly in contact with the wetted surface and which are partly in contact with the surface and also deposited there, Deposited through droplets. When the liquid from the condensation and the deposits are in close contact, the droplets are pulled back into the flue gas stream and flow toward the heat exchanger.

With conventional droplet separators it is not possible to prevent these large droplets from reaching the heat exchanger or it is not possible to remove them out of the flue gas stream in advance. Common separators have lamellas and are located inside the absorber. They have the disadvantage of creating deposits in the lamellas, which in turn produce caking up to clogging. Also, depending on the temperature condition in the surrounding, a large amount of condensate may be generated between the absorber and the heat exchanger.

In order to find a remedy in this connection, in the process according to the invention for the cleaning and reheating of flue gases, the hot flue gas is fed to the heat exchanger, then the flue gas scrubber, The flue gas is passed through the additional liquid separator after the flue gas scrubber in the flow direction and in front of the heat exchanger.

The relative proximity of the additional liquid separator to the heat exchanger thereby achieved prevents condensation droplets from forming in the heat exchanger between the liquid separator and the heat exchanger resulting in the contamination problems described above.

An embodiment of the process according to the invention is preferred in which the flue gas flows through the heat exchanger approximately horizontally under heat absorption.

In a particularly preferred improvement of the method according to the invention, the liquid separator comprises a plurality of elongate, three-dimensional collision bodies, the longitudinal extension of the collision bodies being inclined or transverse to the direction of flow of the flue gas And the expansion and arrangement of the collision bodies are formed obliquely or horizontally with respect to the longitudinal extension so that the collision bodies overlap each other in the direction of flow of the flue gas in the projection view, The liquid separator can not be perfused without changing the perfusion direction.

The present invention also relates to an apparatus for cleaning and reheating flue gas flowing in a flow direction with a heat exchanger having a heat exchanger housing wherein the heat exchanger is perfused by the gas for reheating and the heat Inside the separator housing, a liquid separator is arranged in front of the heat exchanger as viewed in the direction of flow of the flue gas. The arrangement of the liquid separator in the heat exchanger housing provides for the relative proximity of the liquid separator to the heat exchanger, which is advantageous for the implementation of the process according to the invention on the one hand. On the other hand, the rate of perfusion of the flue gas is relatively small through the heat exchanger, and hence through the rate of inflow to the liquid separator, based on the regularly relatively large volume of the heat exchanger housing, Separation performance is achieved.

Surprisingly, it has been shown that liquid separators comprising a number of impingement bodies are particularly suitable for use in the heat exchanger housing.

It is very particularly preferred if the collision bodies are elongated and formed three-dimensionally, preferably substantially tubular. These types of liquid separators are also referred to as " roller separators ". It seems that at first glance the use of such in the heat exchanger housing is contradictory, since these roller separators themselves, which have relatively poor separator performance, are known.

Nonetheless, it is now proposed to utilize a roller separator as protection for the heat exchanger. Roller separators are notoriously bad separators compared to the lamella separators. Therefore, this is a contradiction in the prevailing teaching that the last separator should have the best separation performance.

Indeed, through this invention, the prevailing teaching should be changed. That is, the predominant teachings that separation performance should be increased by one step, and that all of the droplet separators are subsequently mounted in the absorber, are in trouble. He does not take into account that from a specific separation performance, inevitable cleaning of solids in gases results in greater contamination than reduces the increase in separation performance. Also, the arrangement is a problem.

In other words: Since the increase in separation performance at the last stage results in very small gaps in the separator lamella, these droplet separators can be very well contaminated and often cleaned. Through the cleaning, a strong droplet is created which results in more emissions than the separator stage with increased cleaning performance is filtered out of the flue gas. In other words, a one-forward move forces a two-foot retreat.

Hence, the solution according to the invention goes the other way. Surprisingly, it has been recognized that the cleaning results in a greater part of the discharge from the particular separation performance of the overall system, and, in particular, in the heat exchanger, leads to unpleasant caking up to clogging.

Hence, the object of the structure according to the invention is to find a solution in which the last separation stage does not need to be cleaned at all. At this time, it is assumed that this last stage then has worse separation performance.

Within the roller separator, it has appeared to last completely clean or dirty slightly without washing even after long periods of operation. And this contamination of the rollers has little effect on the total amount of droplets from the separator system.

In addition, the roller separator has proven to be well suited for use as protection in front of the heat exchanger of reheating. A possible explanation is that the roller separator separates particularly large droplets well. However, as described above, the main function of the very last separator is to segregate and separate the entrained cleaning droplets of the previously placed separator. As is known, these cleaning droplets are rather large to very large droplets.

It has also been found that the arrangement of the roller separator in the heat exchanger housing results in a rather flue gas velocity rather on the basis of its size, thereby avoiding negative effects such as condensation between the liquid separator and the heat exchanger.

The disadvantage that the small droplets produced through the upstream separation steps are not subsequently separated can be ignored. At the amount of liquid reaching the roller separator, these small droplets have only a relatively small portion. And 90% to 99% of the amount of the liquid according to the cleaning frequency is a rate from the cleaning step of the separation step provided upstream.

The liquid separator formed as a roller separator must have at least two layers of mutually offset tubes (or impact-like impact bodies), and the tubes are formed such that they completely block the path in the flow direction, do. This makes it safe for at least the majority of the large droplets to strike the collision body.

Preferably, the roller separator comprises three or four tube layers. The third tubular layer and the fourth tubular layer are particularly meaningful when the separator is installed very close to the heat exchanger. This third layer and possibly the fourth layer then deodorizes the heat of discharge of the heat exchanger and prevents the vaporization of droplets on the impingement tubes from occurring after the first tube layer is heated.

The separator should be installed as close as possible to the heat exchanger. Generally, the flue gas velocity in the heat exchanger must be lower than usual in the channel, so that the flue gas channel in front of the heat exchanger expands. The tube separator likewise requires as low a flue gas velocity as possible for good function. Also, between the separator and the heat exchanger, condensation droplets can no longer be expected. The heat of discharge of the heat exchanger is sufficient to keep the channel dry, in other words, to prevent condensation, in an interval of up to 2.5 m in general. However, an interval of less than 0.5 m to the heat exchanger is not desired because the drying processes on the tube separator can occur, which can reduce the function of the tube separator and increase the pressure loss, Heating will result.

Therefore, the interval of the liquid separator from the heat exchanger is preferably between 0.5 m and 2.5 m, preferably between 1 m and 2 m, particularly preferably about 1.5 m.

The heat exchanger may be formed as a particularly favorable leak-free heat exchanger, especially as a gas / gas heat exchanger.

In addition, a cleaning system for cleaning the liquid separator as required may be preferably provided, in particular, to be activatable in shutdown of the apparatus.

The present invention should be described in detail based on the accompanying drawings.

1 shows a device for cleaning and reheating flue gases, purely schematically and partially cut-including a heat exchanger, a flue gas scrubber, and a special type of brick,
Fig. 2 again shows, purely schematically - an enlarged sectional view of the heat exchanger of the device according to the invention.

In the apparatus shown in Figure 1, the hot flue gas from a power plant not shown in the figure is also referred to as a " raw gas " - the feed line 1 to the heat exchanger 2 in the flow direction S .

The heat exchanger (2) comprises a heat exchanger housing (3) and heat exchanger elements (4). They are formed into a tubular shape in the illustrated embodiment and are perfused by the hot flue gas at the heat outlet.

The raw gas that is cooled at this time is then supplied to the flue gas scrubber 6 through the exhaust line 5. The flue gas scrubbing apparatus includes a plurality of droplet separator arrangements 7, wherein the droplet separator arrangements receive the cooled flow of the biogas from below to above and are thereby cleaned to become so-called clean gases. The flue gas scrubber may also include scrubbing devices for the droplet separator arrangements, but the scrubbing devices are not shown in the figures. Through the other supply line 8, the cooled clean gas is introduced into the heat exchanger housing 3. In which there is a liquid separator 9 in front of the heat exchanger elements 4 in the flow direction. He can have a plurality of tubular collision bodies 10 extending transversely with respect to the flow direction S of the gas, as can be seen in FIG.

In the embodiment shown in Fig. 2, three rows 11, 12, 13 of the collision bodies 10 are provided. The impact bodies are dimensioned and arranged such that they overlap each other in the projection view.

After seeping through the liquid separator 9, the clean gas flows around the heat exchanger elements 4 outside under heat absorption.

The reheated clean gas is then transferred to the chimney 15 through another discharge line 14.

1: supply line 2: heat exchanger
3: Heat exchanger housing 4: Heat exchanger elements
5: discharge line 6: flue gas cleaner
7: droplet separator arrangement 8: supply line
9: liquid separator 10: collision body
11, 12, 13: column 14: discharge line
15: chimney S: flow direction

Claims (10)

As a method for cleaning and reheating a flue gas,
In this method, the hot flue gas is passed through the heat exchanger (2), then the flue gas scrubber (6), then the heat exchanger (2) And then to the chimney 15,
Characterized in that the flue gas flows in the flow direction (S) after the flue gas scrubber (6) and before the heat exchanger through the liquid separator (9). The method according to claim 1,
Characterized in that the flue gas flows through the heat exchanger approximately horizontally under heat absorption. 3. The method according to claim 1 or 2,
The liquid separator includes a plurality of elongated, three-dimensional collision bodies (10), the longitudinal extensions of the collision bodies being arranged at an angle to the flow direction (S) of the flue gas, Are arranged obliquely or horizontally with respect to the longitudinal extension so that the impingement bodies 10 overlap each other in the flow direction of the flue gas flowing in the projection, Characterized in that the liquid separator (9) can not be perfused without change. An apparatus for cleaning and reheating flue gas flowing in a flow direction (S), said apparatus having a housing (3) and a heat exchanger (2) comprising heat exchanger elements provided in said housing,
Characterized in that a liquid separator (9) is arranged in front of the heat exchanger elements (4) in the flow direction (S) of the flue gas in the heat exchanger housing (3) . 5. The method of claim 4,
Characterized in that the liquid separator (9) comprises a plurality of impingement bodies (10). 6. The method of claim 5,
Characterized in that the impingement bodies (10) are elongated and three-dimensionally, preferably substantially tubular, for cleaning and reheating the flue gas. The method according to claim 6,
Characterized in that the impingement bodies (10) are formed such that the impingement bodies overlap each other in the flow direction (S) in the projection view. 8. The method according to any one of claims 4 to 7,
Characterized in that the minimum spacing of the liquid separator (9) from the heat exchanger elements (4) is 0.5 m and 2.5 m, preferably 1 m and 2 m, particularly preferably about 1.5 m. For cleaning and reheating. 9. The method according to any one of claims 4 to 8,
Characterized in that the heat exchanger (2) is formed as a leak-free gas / gas heat exchanger. 10. The method according to any one of claims 4 to 9,
Characterized in that a cleaning system for cleaning the liquid separator (9) is provided, in particular during shutdown of the apparatus, for cleaning and reheating the flue gas.

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