FI122905B - Method and apparatus for condensing flue gases - Google Patents

Description

Method and apparatus for condensing flue gases

FIELD OF THE INVENTION The invention relates to a method for condensing flue gases according to the preamble of claim 1. The invention also relates to an apparatus for carrying out the above method according to the preamble of claim 13.

Background of the Invention

Combustion boilers that burn solid fuel produce flue gases that contain a significant amount of thermal energy, the recovery of which increases the efficiency of the incinerator. Flue gases also contain impurities such as particulate solids and gaseous impurities such as sulfur and nitrogen oxides and / or hydrogen chloride, which must be removed from the flue gases before being discharged from the plant pipe.

It is known to recover the heat from the flue gases by condensing them. The purpose of condensers is to recover the heat energy contained in the flue gases into district heat and steam, while the flue gases are cleared of impurities. Much of the energy contained in the flue gases is so called. latent heat, which is the energy contained in the water vapor produced as a combustion product. Particularly with wet fuels, such as biofuels, the proportion of latent heat is considerable. This energy can be recovered in a condenser condenser,

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9 where the water vapor condenses and releases the amount of energy required for evaporation.

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Nowadays condensers transfer heat from the flue gases to both the water circulating in the district heating plant and the combustion air in the boiler.

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£ There are known solutions that first transfer heat from the flue gases to the water circulating in the district heating plant by means of heat exchangers.

35 Then, before the flue gases are introduced into the chimney, they are led into a so-called flue gas. a rotary luvo-type combustion air humidifier where the heat contained in the 2 flue gases is transferred directly from the flue gases to the combustion air.

A solution is also known in which flue gases are condensed in a two-stage condenser. The flue gases are cooled and moistened with water as they enter the condenser. The condenser contains two indirect heat exchangers, of which the first heat exchanger transfers heat from the flue gases to the district heating network. Thereafter, the flue gases are cooled and further condensed by means of another heat exchanger 10, the cooling water of which is circulated in the heat exchange cycle for condensing the combustion air used in the boiler. Such a solution is disclosed, for example, in Finnish Patent Publication 82767, corresponding to U.S. Patent 4,799,941.

The problem with the solution according to Fl 82767 is that when the flue gases are cooled in the condenser, the impurities contained therein, in particular the sulfur-chlorine and ammonium compounds, form corrosive compounds. These compounds corrode condenser materials. For this reason, special materials are required for the corrosion-resistant parts of the condenser, which increases the purchase price of the condenser. In addition, the condensate on the bottom of the condenser must be cleaned before it can be reused. This is because not only does the condensate contain sulfur and chlorine compounds that are harmful to the materials, it also accumulates solids in the flue gases. In addition, the amount of condensate to be treated is remarkably large, since both heat exchangers are housed within the same condenser, whereby condensation condensed by both of the gentler heat exchangers accumulates at the bottom of condenser 9. Purifying the condensate is difficult and expensive for the above reasons.

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In addition, the solution of Fl 82767 has the problem of using 5 as the wetting water used to humidify the combustion air.

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£ softened or deionized water or purified condensate for which preparation / purification of S requires separate installations. The investment and operating costs of such equipment are high.

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Description of the Invention Ivhvt

It is an object of the present invention to provide a novel solution for the condensation of flue gases which avoids the problems described above and by which the condensation of the flue gases can be enhanced and the handling and utilization of condensates generated during the condensation can be facilitated.

To accomplish this, the method according to the invention is essentially characterized in what is set forth in the characterizing part of independent claim 1.

The apparatus according to the invention, in turn, is mainly characterized by what is stated in the character part of the independent claim 13.

Other dependent claims disclose some preferred embodiments of the invention.

The invention is based on the idea that the flue gases from the power boiler are condensed by at least two indirect heat exchangers arranged in at least two condensers such that each condenser has a single heat exchanger. The condensate formed at the bottom of each condenser can be collected in the Erik-25 and used for various purposes.

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According to an embodiment of the invention, the apparatus has two condensers. First in the flue gas flow direction? in the first condenser, 30 flushes of my wash are sprayed onto the flue gases. As a result of washing, most of the solids and harmful gaseous components contained in the flue gases are removed in one step. At the same time, by means of the first heat exchanger £ in the first condenser, the water vapor in the flue gases can be condensed. The spent washing solution and the condensate condensed by the heat exchanger 35 accumulate at the bottom of the first condenser. The first heat exchanger 4 in the first condenser conveys the thermal energy contained in the flue gases to the district heating.

The purified flue gas is led to the second, the last condenser 5, where the water vapor contained in the flue gases condenses into a condensate which is collected at the bottom of the last condenser. In addition, the heat energy contained in the flue gases is transferred to the heat transfer medium circulating in the heat exchanger by means of a final heat exchanger located in the last condenser. From the last condenser 10, the flue gases are discharged, for example through a chimney.

In another embodiment of the invention, it is possible to remove a plurality of gaseous components contained in the flue gases in the different stages of the condensation in connection with condensation of the flue gases. In this case, the equipment has its own condensers for removing the various components. According to one embodiment of the invention, the apparatus has three condensers, whereby two different gaseous components, e.g. ammonium compounds and sulfur and chlorine compounds, can be removed from the flue gases in two separate steps.

In this embodiment, the apparatus first arranged in the flue gas flow direction is flushed with an acidic wash solution to remove most of the ammonium compounds contained in the flue gases. Naturally, part of the solids contained in the flue gases is also removed at this stage 25.

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The flue gas purified from the ammonium compounds is introduced into a second condenser, where they are sprayed with a basic washing solution. As a result of washing, most of the chlorine and sulfur compounds contained in the flue gases and the rest of the solids can be removed. Both the first and second condensers include a heat exchanger for condensing the water vapor in the flue gas into a condensate which is collected together with the washing solution used in the flue gas scrubbing at the bottom of the condensers 35. By means of heat exchangers in the first and second condensers, the thermal energy contained in the flue gases is transferred to the district heating.

The purified flue gas from the second condenser is supplied to the third condenser, i.e. the last condenser. In the final condenser, the water vapor contained in the flue gases is condensed into the condensate and the thermal energy contained in the flue gases is recovered.

The combustion air used in the power boiler is humidified and heated in a combustion air humidifier separate from the condensers. Here, a wetting solution containing the condensate formed in the final condenser and the spent wetting solution accumulating in the bottom of the humidifier is sprayed with the combustion air introduced into the boiler. The wetting solution used is also used in the heat-15 exchanger of the last condenser as a heat transfer medium.

The invention brings several advantages. Because the heat exchangers are housed in a plurality of separate condensers where the downstream condenser (s) located downstream of the final condenser are flushed, the corrosive constituents remain in the condensers of these condensers. Thus, when entering the final condenser, the flue gases are cleaner and cause less corrosion in the final condenser. The corrosion resistance of the plant is thus improved. If desired, the last condenser can be made from cheaper materials, which reduces the investment cost of the plant. Further, since the flue gases entering the final condenser are purified, the condensate formed by the flue gases in the final condenser is also pure, i.e. it does not contain corrosive sulfur and chlorine compounds, so that it can be used in a direct flue gas humidifier. irrigation solution. This eliminates the need to use any softened water or deionized water for flue gas humidification, which also results in economic savings.

In addition, the invention makes the operation of the last heat exchanger more efficient. The spent humidifying water 6 from the combustion air humidifier, which is fed to the second condenser as a heat transfer medium, is cold and thus effectively cools the flue gases.

In addition, the water treatment plant used to purify the condensate from the condenser (s) located before the last condenser can be constructed much smaller than the prior art solution because of the smaller amount of condensate formed in the upstream condenser (s). This also reduces the investment costs of the plant. Similarly, the operating costs of plant 10 are lower because the amount of solution to be treated is smaller.

Furthermore, according to one embodiment of the invention, the various gaseous impurities present in the flue gases can be removed separately in the different condensers and thus the flue gases can be better purified.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be explained in more detail with reference to the accompanying drawings, in which: Figure 1 schematically illustrates an apparatus for condensing flue gas and humidifying air for combustion air; schematically represents a flue gas condenser.

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Figures 1 to 3 use numbers corresponding to the corresponding parts, and are not explained later unless otherwise required by the specification.

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DETAILED DESCRIPTION OF THE INVENTION In the specification and claims, the term "line" refers to any pipe, unit or conduit suitable for transferring a liquid, gas or suspension.

Figure 1 illustrates a multi-stage flue gas condenser 1 having two separate flue gas condensers, the first condenser 2 and the second, i.e. the last condenser 3. In this embodiment, the gaseous impurities from the condensed flue gases are removed in a single step. Gaseous impurities can be, for example, sulfur and chlorine compounds. In addition, solid particles in the flue gases are removed. In this embodiment, the first and last condensers are spaced apart. They are connected by a line 4 through which the flue gases are transferred from the first condenser 2 to the last condenser 3. Both condensers include a heat exchanger operating by indirect heat exchange, which may be, for example, either a tubular or lamellar type heat exchanger. As is generally known, in an indirect heat-exchanger, the heat transfer medium and the medium from which heat is transferred or to which heat is transferred are separated on different sides of the walls of the heat transfer elements. In the present invention, the heat transfer medium flows inside the heat transfer elements and the flue gases that are condensed flow outside the heat transfer elements. A first heat exchanger 2 'is provided inside the first condenser 2 and a final heat exchanger 3' is provided inside the last condenser 3. The structure and function of condensers and heat transfer elements are well known to those of ordinary skill in the art and have not been explained herein. its more accurate.

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The flue gases are led from the power boiler 5 to the upper part of the first condenser 2 5 via line 6. The flue gas flow in the first £ 5 condenser is from top to bottom. The flue gases are washed in the first condenser 2 by means of a washing solution sprayed into the flue gases. Depending on the gaseous impurities to be removed from the flue gases, a reagent is added to the wash solution to facilitate the removal of the 8 impurities. The reagent may be, for example, an alkaline reagent such as sodium hydroxide for the removal of sulfur and chlorine compounds in flue gases. At the top of the first condenser 2 in the flue gas flow direction 5 prior to the heat exchanger 2 'is provided a wash solution distribution means 7 for uniformly distributing the wash solution over the cross-sectional area of the first condenser 2. sharing tools. As a result of the washing solution 10, sulfur and chlorine compounds in the flue gases form sulfate and sulfite compounds as well as chlorides and the solids in the flue gases bind to the scrubbing solution, whereby the flue gases are purified. The flue gases in the first condenser 2 continue to flow downwardly along the heat transfer surfaces of the heat exchanger 2 'causing them to cool and condense the water vapor therein into water. The condensate condensed from the water vapor contained in the flue gases and the washing water used for flue gas scrubbing form condensate A which collects on the bottom of the first condenser 2, from which it is conveyed via line 9

In the water treatment plant 10, the condensate obtained from the first condenser 2 is treated so that the impurities accumulated therein can be removed. The treated condensate A is circulated via pump 11 via line 12 to the nozzles 7 of the first condenser 7. A portion of condensate ™ A can also be led directly to line 12 without purification via line 28.

The first heat exchanger 2 'in the first condenser 2 is connected to a district heating network in which the circulating solution is led through line 13 to the first heat exchanger 2'. The heat transfer medium from the district heating plant, i.e. the water, flows through the first heat exchanger 2 'and at the same time absorbs the heat energy contained in the flue gases. From the first heat exchanger 2 ', the heat transfer medium is returned to the district heating network via line 14.

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A line 4 is provided at the lower part of the first condenser 2 through which the cooled and purified flue gases are passed to the lower part of the last condenser 3. Line 4 is arranged at such a height relative to the bottom of both condensers 5 that the condensates formed in the condensers cannot be mixed. In the last condenser 3, the flue gases flow from the bottom upwards along the heat transfer surfaces of the last heat exchanger 3 '. The flue gases are further cooled by the last heat exchanger 3 'and the water vapor contained therein condenses and forms condensate which collects on the lower part of the condenser 3. The cooled flue gases are discharged from the last condenser 3 via an array 15 arranged on the upper part thereof. The flue gases can be led from the last heat exchanger to, for example, a chimney of a power boiler (not shown in the figure) and thereby to the open air.

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In the final heat exchanger 3 ', the circulating heat transfer medium is used to humidify the combustion air supplied to the power boiler 5. In addition to humidification, the combustion air cools down. The heat transfer medium used in the final heat exchanger 3 'is led to the combustion air humidifier 16 via line 25. Provided to the upper portion 16 of the combustion air humidifier is a humidifying solution dispensing means 17 which uniformly distributes a humidifying solution across the cross-sectional area of the humidifier 6. Below the wetting solution distribution means 17 is provided a filler layer 18, the purpose of which is to provide a sufficient contact area for the wetting solution and the combustion air. The humidified combustion air 9 is conveyed to the humidifier 16 via a line 19 arranged at its lower part, and the humidified combustion air 30 is discharged from the humidifier g 30 through a line 20 arranged at its upper part. Line 20 is connected to power boiler 5.

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δ £ Part of the wetting solution evaporates in the humidifier. The remainder of the humidifying solution, C, accumulates at the bottom of the humidifier 16. From there it is circulated via pump 35 21 through line 22 back to the heat exchanger 3 'of the last condenser 3 as a heat transfer medium. The condensate B obtained from the last condenser 3 10 is also introduced into the heat transfer medium passing in line 22, i.e. the wetting solution C. Condenser B is conveyed through line 23 in connection with line 22 and pump 24 is used to move it, since condensate B formed in the final condenser 3 does not contain high levels of chlorine and sulfur, it can be added to the combustion air humidifier without further purification. Condensation B is formed in the final condenser 3 in such a way that it is sufficient to completely replace the amount of wetting solution evaporated in the humidifier, without the need to add any other water, for example raw water or deionized water, to the wetting solution. The humidifier 16 and its components can also be made of inexpensive materials which do not require very high corrosion resistance. Part of the wetting solution C is discharged to the water treatment plant 10 via line 29 connected to line 22.

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Figure 2 shows a multi-stage flue gas condenser 1 having three separate flue gas condensers, a first condenser 2a, a second condenser 2b and a third, i.e. the last condenser 3. In this embodiment, the gaseous components are removed from the flue gases to be condensed in two stages. The system has three condensers, whereby, for example, ammonium compounds and sulfur and chlorine compounds can be removed separately. In addition, solid particles in the flue gases are removed at the same time.

In this embodiment, the first, second and last condensers are spaced apart. All condensers include a heat exchanger operated by indirect heat exchange. A first heat exchanger is provided inside the first condenser 2a? 2a ', a second heat exchanger g 30 2b' is provided inside the second condenser 2b and a final heat exchanger 3 'is arranged inside the last condenser 3.

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The flue gases are led from the power boiler 5 to the upper part of the first condenser 2a ° via line 6. The flue gas flow direction in the first condenser 2a is from top to bottom. The flue gases are washed in the first condenser 2a by means of an acidic wash solution 11 sprayed onto the flue gases which is capable of reacting with gaseous ammonium compounds such as ammonia in the flue gases. The acidic wash solution in this embodiment contains an acidic reagent such as an acid, for example hydrochloric or sulfuric acid.

Provided in the upper part of the first condenser 2a above the heat exchanger 2a 'is a distribution solution 7 for distributing the washing solution evenly distributing the washing solution over the cross-sectional area of the first condenser 2a, and the gaseous ammonium compounds in the flue gases and solids in the flue gases The reactions of the gaseous ammonium compounds with the wash solution depend on the reagent added to the wash solution. For example, if sulfuric acid is added to the scrubbing solution, the ammonium compounds in the flue gases will produce ammonium sulfate and / or sulfite compounds as a result of the scrubbing solution. On the other hand, if hydrochloric acid is added to the washing solution, the ammonium compounds in the flue gases will form ammonium chlorides under the influence of the washing solution.

The flue gases in the first condenser 2a flow further downwardly along the heat transfer surfaces of the heat exchanger 2a ', whereby they are cooled and the water vapor contained therein condenses into water. The condensate condensed from the water vapor contained in the flue gases and the washing water used for flue gas scrubbing form condensate A 'which collects on the bottom of the first condenser 2a, from which it is recirculated via pump 30 to line 7 for washing solution distributing means. The condensate formed in the first condenser contains a large proportion of the corrosive ammonium compounds contained in o ™ flue gases.

't ϊ 30 In the water treatment plant 10, the condensate from the first condenser 2a is treated to remove impurities therein. The treated condensate, if desired, can be recirculated via line 12 via line 12 back to the nozzles 7 of the first condenser.

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A line 32 is provided at the lower part of the first condenser 2a, through which the cooled and purified ammonium compounds flue gases 12 pass into the lower part of the second condenser 2b. Line 32 is arranged at such a height with respect to the bottom of both condensers that the condensates formed do not condense. In the second condenser 2b, the flue gases flow from the bottom upwards along the heat transfer surfaces of the second heat exchanger 2b '5.

The flue gases are washed in the second condenser 2b by means of an alkaline scrubbing solution which is capable of reacting with the gaseous sulfur and chlorine compounds in the flue gases. The washing solution contains an alkaline reagent such as sodium hydroxide. As a result of the scrubbing solution, the gaseous sulfur and chlorine compounds in the flue gases and any remaining solids in the flue gases are bound to the scrubbing solution, whereby the flue gases are further purified. On the upper part of the second condenser 2b, 15 above the heat exchanger 2b ', there is provided a washing solution distribution means 7 which distributes the washing solution evenly over the cross-sectional area of the second condenser 2b. In the second condenser 2b, upstream, along the heat transfer surfaces of the heat exchanger 2b ', the flue gases are further cooled and the water vapor therein condensed into water. The condensate from the water vapor contained in the flue gases and the alkaline scrubbing water used in flue gas scrubbing form condensate A, which collects on the bottom of the second condenser 25 2b, from which it is circulated via pump 33 to line 34 back to the wash solution distribution means The condensate formed in the second condenser 9 contains a large proportion of the corrosive sulfur and chlorine compounds contained in the flue gases, g 30 Q_

A first heat exchanger in the first condenser 2a

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δ 2a 'and the second heat exchanger 2b' in the second condenser 2b are connected to the district heating network. The heat transfer medium, i.e. water circulating in the district heating network, is first conveyed through line 13 to the second heat exchanger 2b '. The heat transfer medium flows through the second heat exchanger 2b 'and is led through line 31 to the first heat exchanger 2a'. After flowing through the first heat exchanger 2a ', the heat transfer medium absorbed by the flue gas heat energy is returned to the district heating network via line 14.

A line 4 is provided at the top of the second condenser 2b, through which the cooled flue gases purified from the ammonium, sulfur and chlorine compounds are conveyed to the top of the last condenser 3. In the last condenser 3, the flue gases flow from the top down to the heat transfer surfaces of the last heat exchanger 3 '. The flue gases are further cooled by the last heat exchanger 3 'and the water vapor contained therein condenses and forms condensate B which collects in the lower part of the condenser 3. The cooled flue gases are discharged from the last condenser 3 via an array 15 arranged at its lower part.

In the last heat exchanger 3 ', the circulating heat transfer medium is used to humidify and cool the combustion air supplied to the power boiler 5 in the humidifier 16 as previously described. The combustion air humidifier 16 and its function are substantially the same as those described above, and are therefore not described here for more than 20 minutes.

Figure 3 shows a two-stage flue gas condenser 1 with two separate flue gas condensers. The flue gas condensers are mounted to each other such that the wall 26 between them is one to 25 for each condenser. If the condensers are housed within the same outer shell, the wall 26 acts as a divider between the two condensers. The wall 26 extends over the entire height 9 of the condensers as a continuous wall. The wall 26 thus also separates the lower parts of the condensers containing the condenser, so that the condensates formed in the condensers cannot mix with each other. Like

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the structure is technically easy to implement and such a compact structure o takes up little space in the plant, m N- o

Figure 3 uses the parts and reference numerals 35 shown in Figure 1, whereby the two-stage flue gas condenser of Figure 3 replaces the first condenser 2 and the last condenser 3 shown in Figure 1. The corresponding two-phase condenser can also be applied in the embodiment of Figure 2. In this case, the two-stage condenser of Figure 3 replaces the second condenser 2b and the last condenser 3.

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The first and last condensers 2 and 3 are mounted to each other so that the wall 26 therebetween is common to both condensers and acts as a divider between the two condensers. The wall 26 also separates the lower portions of the condensers 2 and 3 containing condensate, whereby the condensate A formed in the first condenser 2 and the condensate B formed in the last condenser 3 are not allowed to mix. The lower part of the wall 26 has an opening 27, from which the washed and cooled flue gases in the first condenser 2 can flow to the last condenser 3. The opening 27 is positioned so that it is above both condensate water surfaces in the first and last condensers 2 and 3. among themselves. Otherwise, the operation of the first and last condensers and their parts are identical to those described in connection with Figure 1, and therefore will not be described here again.

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The invention is not intended to be limited to the exemplary embodiments set forth above, but is intended to be extensively applied within the scope of the inventive idea defined in the claims defined below. The flue gas flow directions in the condenser-25 where 2, 2a, 2b and 3 may also be in the opposite direction to those described above.

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Claims (25)

A process for condensing flue gases in which flue gases are condensed by means of at least two heat exchangers (2 ', 2a', 2b ', 5 3'), which heat exchangers (2 ', 2a', 2b ', 3') are arranged in at least two capacitors (2, 2a, 2b, 3) in such a way that each capacitor (2, 2a, 2b, 3) is provided with a heat exchanger (2 ', 2a', 2b ', 3') and that the condensate (A, A ', B) rising in each capacitor (2, 2a, 2b, 3) are separately collected, characterized in that flue gases are first condensed in the at least first condenser (2, 2a), in which condensate condensate (A ) is conducted to a water treatment plant (10), and then the flue gases are condensed in the last capacitor (3), in which the rising condensate (B) is conducted as a humidifier (C) into combustion air. 15 Process according to Claim 1, characterized in that the condensate (A, A ', B) which rises in each capacitor (2, 2a, 2b, 3) is collected at the bottom of the respective capacitor (2, 2a, 2b, 3). Process according to claim 1, characterized in that the flue gases 20 are first condensed in the first capacitor (2a), then in the second capacitor (2b) and then in the last capacitor (3). Method according to claim 1 or 3, characterized in that, in flue gases coming from a boiler (5), a washing solution is injected through the washing solution distributor (7) into the first capacitor (2, 2a). CM δ A process according to claim 1 or 3, characterized in that the condensate (A) formed in the first capacitor (2, 2a) and purified in the water treatment plant (10) is led as a washing solution to the washing solution distributor (7). of the first capacitor (2, 2a). CL CO 5 6. A method according to claim 1 or 3, characterized in that the LO 2 condensate (A) formed in the first capacitor (2, 2a) is passed as S a washing solution into the washing solution distributor (7) of the first capacitor (2, 2a). ). 21 Process according to claim 3, characterized in that condensate (A ') formed in the second capacitor (2b) is led to the distributor (7) of the washing solution by the second capacitor (2b). 5 Method according to claim 1 or 3, characterized in that heat transfer means circulating in the last heat exchanger (3 ') arranged in the last capacitor (3) are injected as a humidifier (C) into combustion air with the humidifier's distributor (17). 10 9. A method according to claim 8, characterized in that a moisture solution (C) used in a humidifier (16) is conducted as a heat transfer agent to the heat exchanger (3 ') provided in the last capacitor (3). 15 Process according to any of the preceding claims 1 or 3, characterized in that condensate (B) formed in the last capacitor (3) is fed into the heat transfer medium circulating in the last heat exchanger (3 '). 20 Method according to claim 1, characterized in that the capacitors (2, 2a, 2b, 3) are arranged separately from each other and that the flue gases are passed through an inlet (4, 32) arranged between them from one capacitor to the other. 25 Method according to claim 1, characterized in that at least two capacitors (2, 3) are arranged side-by-side such that the O ™ capacitors have a common wall (26) and the flue gases are led through an opening (27) in the wall. (26) from one capacitor to the other. 1 30 13. A flue gas condensation device comprising at least two capacitors (2, 2a, 2b, 3) each provided with a heat exchanger (2 ', 2a', 2b ', 3') and the condensate (A, A ', and B') formed in each capacitor (2, 2a, 2b, 3) are arranged to be separately assembled, characterized in that the device comprises 22 - at least one first capacitor (2, 2a) and one the last capacitor (3), and the flue gases are arranged to be condensed first in the first capacitor (2, 2a) and then in the last capacitor (3), - means (8, 9) for conducting the condensate (A) formed in it. first condenser (2, 2a) to a water treatment plant (10), means (23, 24, 25) for passing the condensate (B) formed in the last capacitor as a humidifier (C) into combustion air. Device according to claim 13, characterized in that the capacitor 10 (A, A ', B) formed in each capacitor (2, 2a', 2b ', 3) is arranged to be collected on the bottom of said capacitor (2, 2a). ', 2b', 3). Device according to claim 13, characterized in that the device comprises a first capacitor (2a), a second capacitor (2b) and a last capacitor (3), and the flue gases are arranged to be condensed first in the first capacitor (2a). , then in the second capacitor (2b) and then in the last capacitor (3). Device according to Claim 13 or 15, characterized in that the first capacitor (2, 2a) is provided with the washing solution distributor (7) for injecting a washing solution into the flue gases coming from a boiler (5). Device according to claim 13, characterized in that the device 25 comprises means (11, 12) for conducting the condensate (A) formed in the first capacitor (2) and purified in the water treatment plant (10) as a washing solution for the washing solution. distributors (7) of the first o capacitor (2). g 30 Device according to claim 13 or 15, characterized in that the device comprises means (8, 11, 12, 28, 30) for conducting the condensate 5 (A) formed in the first capacitor (2, 2a) as a washing solution. LO 2 washing solution distributor (7) of the first capacitor (2, 2a). o C \ l Device according to claim 15, characterized in that the device comprises means (33, 34) for conducting the condensate (A ') formed in the second capacitor (2b) to the washing solution distributor (7) of the second capacitor (2b). . Device according to claim 13, characterized in that the device 5 comprises a combustion air humidifier (16) for humidifying the combustion air to be fed into the boiler (5), the combustion air humidifier (16) having a filler body layer (18). and the moisture solution distributor (17) for injecting a moisture solution into the combustion air. 10 Device according to claim 13, characterized in that the device comprises means (25) for conducting heat transfer means circulating in the last heat exchanger (3 ') arranged in the last capacitor (3) to the distributor (17) of the moisture solution. 15 Device according to claim 13, characterized in that the device comprises means (21, 22) for conducting the moisture solution (C) used in the humidifier (16) as a heat transfer agent to the heat exchanger (3 ') arranged in the last capacitor (3). ). 20 Device according to any of the preceding claims 13 or 15, characterized in that the device comprises means (23, 24) for conducting the condensate (B) formed in the last capacitor into the heat transfer medium circulating in the last heat exchanger (3 '). ). 25 Apparatus according to claim 13, characterized in that the capacitors (2, 2a, 2b, 3) are arranged separately from each other and the device comprises an inlet (4, 32) for passing flue gases from one of the capacitors to the the other one. 1 30 Device according to claim 13, characterized in that at least 5 capacitors (2, 3) are arranged side by side, such that the capacitors have a common wall (26) and that the wall (26) and comprises an opening (27) for conducting flue gases from one capacitor to the other.