DE102010046858B4 - Boiler and solid fuel heat supply system and a process for burning solid fuels - Google Patents

Abstract

A heating boiler with a combustion chamber for combustion of solid fuels and with a flue gas duct for outflow of flue gas produced during combustion, comprising a catalyst and at least one, in the flow direction of the flue gas first flue gas train, which is formed from at least one heat exchanger channel of a water-bearing heat exchanger, characterized in that the first flue gas duct (14) is arranged immediately downstream of the combustion chamber (2) in the flow direction of the flue gas (12), wherein the catalyst (24, 25) within the first flue gas duct (14), preferably in an inflow region of the flue gas (12) in the first flue gas duct (14) is arranged.

Description

The invention relates to a heating boiler with a combustion chamber for combustion of solid fuels and with a flue gas duct for outflow of the resulting during combustion flue gas, which has a catalyst and at least one, in the flow direction of the flue gas first flue, which is formed from at least one heat exchanger channel of a water-bearing heat exchanger ,

The invention also relates to a heat supply system with a boiler of the aforementioned type and a method for burning solid fuels in a boiler mentioned above.

A boiler of the above type is a firing device using solid fuels such as virgin firewood, pellets, wood chips, lignite briquettes or other combustible particulate biomass as the heat source. The combustion of these solid fuels takes place in a combustion chamber, which can be charged manually or via an automatic charging device, depending on the type of solid fuel. To remove the flue gas generated during combustion in the combustion chamber, this is followed by a flue gas guide, which predefines the flow direction of the flue gas.

The boiler is primarily used for hot water or heating water in a sanitary or heating system for heat supply of buildings. For this purpose, the generated flue gas is passed along the flue gas duct via a heat exchanger. Usually, the heat exchanger incorporated in the flue gas duct has one or more successive flue gas passages, through which the flue gas flows successively and substantially rectilinearly and with low turbulence.

Each of the flues may be formed from a heat exchanger channel or from a plurality of parallel heat exchanger channels, in the latter case, the flue gas stream is divided into the corresponding flue gas partial streams.

To optimize space, the flue gas passages following one another in the flow direction of the flue gas are usually arranged adjacent to one another along the flue gas duct and are connected to one another via deflecting chambers.

A solid fuel boiler of the aforementioned type is known from the document EP 1 962 033 A1 known.

It is also known that the emission of pollutants occurring in the combustion of solid fuels in such boilers can be reduced by the use of catalysts. The catalysts used in the combustion of solid fuels consist of a high temperature resistant substrate with a noble metal coating which causes oxidation of the toxic carbon monoxide to carbon dioxide. The optimum operating temperature of these catalysts is about 250 ° C to 600 ° C.

This operating temperature of the catalyst is achieved in conventional boilers only after a long heating phase of the boiler. The Anheizphase is particularly pronounced in the generic boilers with solid fuel-loaded combustion chambers and water-guided heat exchangers and often associated with very uneven heating quality, which is why the catalysts used in these boilers have achieved an unsatisfactory effectiveness. The pronounced heating phase results in particular from the relatively low calorific value of the solid fuels and the water mass of the heat exchanger. In addition, due to the different quality of the solid fuels and their discontinuous feed into the combustion chamber inconsistent combustion parameters, and not only in the Anheizphase. Thus, in such boilers, the catalyst can easily clog with unburned smoke particles and disrupt the flue gas flow lasting. To avoid this problem, according to various embodiments of the prior art, a manually or automatically controlled Anheiz- or bypass damper can be provided with the flue gases in the manner of a two-way valve temporarily passes via a second, parallel flue gas duct past the catalyst into the atmosphere until the catalyst has reached the desired operating temperature. Only then are the flue gases passed through the flue gas duct with the catalyst.

Such a catalytic unit with automatic bypass valve for solid fuel fired combustion systems is from the document AT 503 815 A4 known. The catalyst unit consists of a catalyst and an integrated, temperature-controlled bypass flap. This ensures that flue gas, which falls below a certain temperature, is not or only in small quantities passed through the catalyst, but is guided along a parallel path through the open bypass flap.

This, however, the boiler is operated for a long time without emission protection, before the flue gas flow is conducted over the catalyst for pollutant removal.

The design effort for the design of a second flue gas duct with bypass flap control is very high compared to the effect achieved.

In addition, operating errors with manually operated bypass flaps or faults in electrically operated flap controls can lead to the period in which the flue gases pass untreated into the environment, additionally and unnecessarily extended.

The invention is therefore based on the object to provide a boiler for solid fuels, in which the flue gases are cleaned reliably and efficiently with simple structural means.

The object is achieved in that the first flue is arranged in the flow direction of the flue gas immediately downstream of the combustion chamber, wherein the catalyst is disposed within the first flue, preferably in an inflow region of the flue gas in the first flue.

It is essential here that the catalyst is assigned to the first flue gas pass in the manner described above. The first flue means the flue gas duct along the flue gas duct, or in the presence of a plurality of flues, the smoke flue which the flue gas flowing out of the combustion chamber along the flue gas duct first reaches. In the inflow region of the flue gas into the first flue, the flue gas generated in the combustion chamber concentrates for the first time and it gradually forms a low-turbulence, stable flue gas flow, which is promoted by the first flue. The invention defines the inflow region, in which a stable flue gas flow is formed, into approximately half of the conveying path of the flue gas through the first flue gas pass.

With the arrangement according to the invention it is achieved that the generated flue gas hits the catalyst completely and in the shortest path from the combustion chamber directly, namely before the flue gas in the flue gas duct is deprived of lost or useful heat.

Due to the proximity of the first flue gas to Brenngut in the combustion chamber, the flue gas can be supplied to the catalyst with the highest possible temperature and the shortest path, so that the operating temperature reached in no time and thus the catalytic combustion of the pollutants of the flue gas is initiated as soon as possible.

It has surprisingly been found that with such a design of the boiler, the operating temperature of the catalyst can be achieved rather than in conventional boilers with bypass control.

The rapid achievement of the operating temperature of the catalyst makes it possible to dispense with a conventional flue gas guide with bypass excitation. Apart from the structural simplification of the technical equipment of the boiler are omitted by eliminating the bypass excitation the path of the flue gas and its catalytic combustion is not affected by external control intervention.

With the given continuous path of the flue gases through the flue gas guide according to the invention, the catalytic combustion of the pollutants can be done more reliably, as early as possible and as far as possible completely. As a result, an efficient pollutant reduction is achieved from the flue gas.

The initially incurred in the heating phase of the catalyst flue gas particles are burned again by the prevailing high temperature in the vicinity of the combustion chamber in a short time, so that only temporary deposits arise that produce no such flow resistance that could hinder the flue gas flow.

As a result, a simple and safe operation of the boiler is guaranteed at the same time low environmental impact.

Advantageous embodiments and further developments of the boiler according to the invention will become apparent from the dependent claims 2 to 12, the following description and the accompanying drawings.

In an advantageous embodiment, the flue gas duct is arranged with the first flue gas duct in the combustion chamber. Thus, the water content and the heat exchanger channel of the water-guided heat exchanger is heated during startup of the boiler directly through the combustion material located in the combustion chamber, which supports the early tempering of the catalyst due to the heat conduction through the walls of the heat exchanger.

If the catalyst is arranged in the heat exchanger channel of the first flue, a subsequent installation of the catalyst in the flue of an existing boiler is simple and space-saving.

It is particularly advantageous if the catalyst is arranged in a position near an inflow opening of the flue gas into the heat exchanger channel. After an initial flow calming the incoming flue gas flow, the catalyst is applied in this spaced position to the inlet largely uniform and low resistance with the flue gas, which favors the effectiveness of the catalyst. In addition, such positioning protects the catalyst from direct contact with the flame impact in the combustion chamber.

If the inflow cross-section of the catalytic converter is substantially congruent with the flow cross-section of the heat exchanger duct, the inflow cross-section of the catalytic converter, which is formed perpendicular to the intended inflow direction of the flue gas, completely takes up the flow cross-section of the heat exchanger duct, so that no flue gas flow can flow past the catalyst untreated. Thus, the catalytic combustion can be further improved.

The invention is based on the surprising finding that the catalysts normally used for solid fuel boilers do not produce such a pressure loss even when completely exposed to the flue gases produced in the heating phase of the boiler, which could impair the flue gas flow.

In a particularly advantageous embodiment, a second catalyst is arranged in the first flue gas, which is arranged downstream of the first catalyst in the flow direction of the flue gas.

In this case, the invention takes advantage of the idea that heat is automatically generated in a catalytic combustion. Thus, the heat generated in the first catalyst can be used in addition for the heating of the subsequent in the flow direction of the second catalyst, which nachreinigt the flue gas in a second catalytic combustion stage. As a result, the pollutants in the flue gases are reduced even more. From the invention is included with the same advantageous effect to arrange further catalysts in a row within the first flue. Thus, each of the preceding catalyst protects and heats the catalyst following it.

If the successive catalysts are arranged at a distance from each other, a mixing zone can be provided in which a renewed mixing of the flue gases takes place. The invention is based on the recognition that the catalytic combustion in the outer edge zones of the flow cross-section of the catalyst is less effective than in the center of the flow cross-section. In the mixing zone, the non-uniformly pre-cleaned flue gas can be homogenized, whereby the effect of post-combustion in the second catalyst increases and the pollutant reduction is further improved.

If the flue gas duct has a turbulator, then according to the invention it is arranged downstream of the flue gas duct in the flow direction of the flue gas. The turbulator consists of one or more baffles, which are introduced in the flue gas guide. By means of the turbulator, the boiler or chimney resistance can be adjusted as desired, and thus the residence time and the temperature of the flue gases can be influenced. The swirling of the flue gas generated at the turbulator can in any case not have a temperature-reducing effect on the catalyst in this preferred arrangement.

If the turbulator is designed to be adjustable, the boiler or chimney resistance can be varied and, inter alia, the initial pressure loss in the cold state of the boiler can be optimally adjusted, whereby the flue gas flow through the catalyst in the start-up phase of the boiler can be better supported.

Preferably, the catalyst or catalysts are releasably connected to the heat transfer channel. Assuming that the catalyst is subject to wear, since the applied on the substrate noble metal coating expended over time, it is advantageous that a fixing or fixing of the catalyst on the longer-lasting heat transfer channel can be solved without destruction, so that the catalyst the corresponding consumption Intervals can be easily replaced.

The catalyst is very practically revisable and accessible for exchange when a deflection chamber arranged downstream of the first flue gas duct has a closable access opening. Apart from the fact that the catalyst can be accessible from the front via the inlet opening in the heat exchanger channel, it may be favorable depending on the construction of the boiler and the mounting of the catalyst, the catalyst also on the back of the heat exchanger channel, namely accessible via the access opening in the deflection chamber do.

Of great advantage is that the inspection opening is arranged such that it can be operated via a filling opening of the combustion chamber. Thus, the catalyst over the manual feed of the combustion chamber with fuels anyway existing opening can be reached and replaced. The replacement of the catalyst can be done so on the one hand with little effort. On the other hand, therefore, an additional closable opening in the boiler housing to achieve the catalyst is structurally unnecessary.

In a favorable embodiment, the inspection opening can be closed by means of an adjustable closure flap. This adjustability of the closure flap allows the provision of a different sized opening cross-section of the inspection opening. Although the invention normally allows operation of the boiler without bypass function for the catalyst, in particularly exceptional situations, such. B. in very unfavorable weather conditions, the required boiler train (flue gas pressure difference) in the start-up phase to be low. In this case, the adjustable flap of the inspection opening allows simple means an emergency operation via a second flue gas duct, which briefly bypasses the flue gas on the first flue with the catalyst and thus reduces the flow resistance in the boiler until the necessary boiler draft has set.

The object is also achieved by a heat supply system containing the boiler according to the invention, wherein the water-guided heat exchanger and / or a water jacket of the boiler is connected to a Heizwasserkreislauf having a bypass circuit for return temperature increase.

With this bypass circuit, the water temperature of the inflowing into the heat exchanger return water can be increased in a short time in the heating phase of the boiler. The dew point temperature of the flue gas in the combustion chamber, which is expected to be around 54 ° C, can thus be overcome quickly. Also, the temperature of the gas flames of the fuel increase more quickly. As a result, almost no condensate is deposited on the surface of the heat exchanger channel, which ensures the functioning of the catalyst and avoids damage to the catalyst.

In addition, the limited by the heat exchanger walls of the combustion chamber are tempered faster by the return temperature increase, which improves the burning of solid fuels and accelerated. This additionally increases the efficiency of the catalyst in the heating phase of the boiler.

According to an advantageous embodiment of the heat supply system is connected to the Heizwasserkreislauf a known buffer memory. As a result, the boiler permanently emit its heat generated to the buffer memory and thus operated as far as possible in full load operation, whereby a uniform combustion can be done with a constant high flue gas temperature, which always ensures the operation of the catalyst in the favorable operating temperature range.

The object is also achieved by a method according to claim 15, wherein the combustion is ignited in the boiler according to the invention in the upper region of the introduced in the combustion chamber solid fuels and the combustion of solid fuels takes place via an upper burnup.

In this procedure, very pure gas flames are generated with low water vapor content from the beginning of the combustion, which has a particularly advantageous effect on the early achievement of the operating temperature of the catalyst. The invention takes into account that otherwise arise in the start-up phase of the boiler in significant amounts of water-containing flue gases, which reduce the temperature of the flue gas as a result of evaporation.

These and other features arising from the patent claims, the description of the embodiment and the drawings can be implemented individually or in combination as advantageous embodiments of the invention, for which protection is claimed here.

The boiler according to the invention will be explained in more detail using an exemplary embodiment. The accompanying drawing after 1 shows a schematic sectional view through such a boiler 1 ,

The boiler 1 comprises in a boiler body a closed combustion chamber 2 partially from a water-led heating mantle 3 and additionally of a heat insulation 4 is surrounded. About one in the upper part of the combustion chamber 2 provided filling opening 5 by means of a filling door 6 is closable, the combustion chamber 2 with firewood 7 palpated. The boiler 1 can also work with other solid fuels 7 , like lignite briquettes, are charged. The filled logs 7 lie during the combustion process as a fuel in a lower region of the combustion chamber 2 on a Einlegerost 8th on. About a removal opening 9 in the lower part of the combustion chamber, by means of a removal door 10 can be closed, ashes and remains of spent fuel 7 be removed.

In the upper part of the combustion chamber 2 is a flue gas duct 11 provided that the Outflow of the flue gas generated during combustion 12 from the combustion chamber 2 serves and the way of the flue gas as a flue gas stream 2 pretends. The flue gas duct 11 sits down over a smoke pipe connection 13 up to a chimney connection, not shown. The flue gas duct 11 has in a, integrated into the combustion chamber part, a first and second flue 14 . 15 on. Each of the flues 14 . 15 along the flue gas duct 11 is made of water-carrying heating bags 16 a heat exchanger 17 surround the respective heat exchanger channel 18 . 19 of the flue 14 . 15 form. The heat exchanger 17 and the heating jacket 3 are connected to each other on the water side and via a supply pipe connection 20 and a return line nozzle 21 connected to a Heizwasserkreislauf a heating system, not shown.

Flue gas side are the first and the second flue 14 . 15 in the direction of flow of the flue gas shown by arrows in the drawing 12 arranged consecutively and via a deflection chamber 22 fluidically interconnected, so that the flue gas flow 12 always both flues 14 . 15 happens in succession. In the heat exchanger channel 18 the first flue gas train 14 , slightly set back to an inlet opening 9 of the heat transfer channel 18 , is a first catalyst 24 arranged. In this inflow has the flue gas flow 12 largely stabilized and meets low resistance to the first catalyst 24 in the slightly recessed position in the heat transfer channel 18 is protected from direct flame contact.

The position of the catalyst 24 in the heat exchanger channel 18 is determined by a small, not shown stop element, which is at a distance from the inlet opening 9 in the heat exchanger channel 18 is attached. Its exact positioning becomes the catalyst 24 into the heat exchanger channel 18 inserted and lies on one side and loose on the stop element. Is the heat exchanger channel 18 , as slightly inclined in the embodiment, becomes the catalyst 24 even safer in his position.

With a distance to the first catalyst 24 is below a second catalyst 25 in the heat exchanger channel 18 positioned so that there is a vortex zone between them 26 formed. The distance between the catalysts 24 . 25 is determined by a flat spacer plate, also not shown, before the introduction of the second catalyst 25 into the heat exchanger channel 18 lying flat on the lower wall of the heat exchanger channel 18 to the first catalyst 24 is created. The exact positioning of the catalyst 25 in the heat exchanger channel 18 then results from its one-sided application to the spacer plate. Is the heat exchanger channel 18 , as slightly inclined in the embodiment, is also the catalyst 25 reliably held in position.

The catalysts not shown 24 . 25 In this embodiment, each consist of a honeycomb-like support structure made of a high temperature resistant ceramic whose flow tubes with a noble metal or noble metal compounds of z. As platinum, palladium or rhodium coated.

The outer circumferential dimensions of the support structure of the catalysts 24 . 25 are suitable for the flow cross section of the heat exchanger channel 18 trained and provided only with a clearance fit, the displaceability of the catalysts 24 . 25 along the heat exchanger channel 18 guaranteed. The catalysts 24 . 25 , in this way flush with the walls of the heat exchanger duct 18 connect during boiler operation completely with the flue gas flow 12 acted upon and deliver in this embodiment each have a flow resistance of about 2 Pa. In comparison, the optimum boiler draft or the required pressure difference of the boiler is 1 in the starting state at about 15 Pa and can be adjusted by various means.

Over the filling opening 5 and the deflection chamber 22 which has a lockable inspection opening 27 can, the heat exchanger channels 18 . 19 be serviced and cleaned. Because the catalysts 24 . 25 loose with the heat exchanger channel 18 They can be connected via the lockable inspection opening 27 can be mounted and replaced without the aid of tools.

To cheer the boiler 1 Only the top pieces of the filled logs are resting 7 over the filling opening 5 ignited while the required combustion air from below via an open primary air damper 28 in the removal door 10 integrated, nachströmt. The loading door 6 is closed during the cheering. One in the door 6 integrated secondary air damper 29 is opened according to a preset preset and provides the necessary oxygen supply to the catalytic combustion of the flue gas 12 in the catalysts 24 . 25 ,

After firing takes over a conventional temperature-controlled Feuerzugregler 30 the regulation of combustion via a control of the primary air damper 28 , This is especially in the start-up phase, a burning of logs 7 realized by upper combustion, in the largely pure and low-water vapor flue gas 12 arises, which reaches a temperature of about 250 ° C in a short time, the optimum operating temperature of the catalysts 24 . 25 , which is in a temperature range of 250 to 600 ° C corresponds.

The flue gas 12 rises under turbulence in the combustion chamber 2 on, collects to the flue gas stream 12 coming directly from the combustion chamber 2 into the heat exchanger channel 18 the first flue gas train 14 flows. There, at the inlet 23 of the heat transfer channel 18 , the flue gas flow hits 12 on the first catalyst 24 on. In this catalyst 24 become in the first stage of the catalytic combustion in the flue gas 12 contained carbon monoxide oxidized to carbon dioxide with heat release. After substantially rectilinear passage of the flue gas stream 12 through the first catalyst 24 follows in the vortex zone 26 a largely thermal and stoichiometric mixing of the flue gas stream 12 before the flue gas 12 the second catalyst 15 happens and the carbon monoxide still contained are oxidized in a second stage of catalytic combustion. The flue gas stream 12 happens always and first the catalysts 24 . 25 before the flue gas 12 by the withdrawal of the useful heat along the subsequent route through the heat exchanger channels 18 . 19 the first and second flues 14 . 15 cools.

With the boiler described above 1 according to the embodiment, the catalysts reach 24 . 25 after just a short warm-up phase their optimum operating temperature and realize a long-lasting and largely complete catalytic combustion of the flue gas 12 ,

LIST OF REFERENCE NUMBERS

1

boiler

2

combustion chamber

3

heating jacket

4

thermal insulation

5

fill opening

6

loading door

7

Logs, solid fuel, kiln

8th

grid insert

9

removal opening

10

removal door

11

Exhaust gas line

12

Flue gas, flue gas flow

13

Flue pipe connection

14

first flue

15

second flue

16

heating pockets

17

Heat exchanger

18

heat exchanger duct

19

heat exchanger duct

20

Supply pipe fitting

21

Return pipe fitting

22

deflection

23

inflow

24

first catalyst

25

second catalyst

26

vortex zone

27

inspection opening

28

Primary air flap

29

Secondary air flap

30

Draft regulator

Claims (15)

A heating boiler with a combustion chamber for combustion of solid fuels and with a flue gas duct for outflow of flue gas produced during combustion, comprising a catalyst and at least one, in the flow direction of the flue gas first flue gas train, which is formed from at least one heat exchanger channel of a water-bearing heat exchanger, characterized that the first flue ( 14 ) in the flow direction of the flue gas ( 12 ) directly to the combustion chamber ( 2 ) is arranged below, wherein the catalyst ( 24 . 25 ) within the first flue ( 14 ), preferably in an inflow region of the flue gas ( 12 ) in the first flue ( 14 ) is arranged. Heating boiler according to claim 1, characterized in that the flue gas duct ( 11 ) with the first flue ( 14 ) in the combustion chamber ( 2 ) is arranged. Heating boiler according to claim 1 or 2, characterized in that the catalyst ( 24 . 25 ) in the heat exchanger channel ( 18 ), preferably in a position close to an inlet opening ( 23 ) of the flue gas ( 12 ) into the heat exchanger channel ( 18 ) is arranged. Heating boiler according to claim 3, characterized in that the flow cross-section of the catalyst ( 24 . 25 ) is substantially congruent with the flow cross-section of the heat exchanger channel ( 18 ) is trained. Heating boiler according to one of the preceding claims, characterized in that in the first flue ( 14 ) a second catalyst ( 25 ), which is the first catalyst ( 24 ) in the flow direction of the flue gas ( 12 ) is arranged below. Heating boiler according to claim 5, characterized in that the successive catalysts ( 24 . 25 ) are arranged spaced from each other. Heating boiler according to one of the preceding claims, characterized in that the Flue gas duct ( 11 ) has a turbulator in the flow direction of the flue gas ( 12 ) the first flue ( 14 ) is arranged below. Heating boiler according to claim 7, characterized in that the turbulator is adjustable Heating boiler according to one of claims 3 to 8, characterized in that the catalyst (s) ( 24 . 25 ) detachable with the heat exchanger channel ( 18 ) is / are connected. Heating boiler according to one of the preceding claims, characterized in that a first flue gas ( 14 ) subsequently arranged deflection chamber ( 22 ) a lockable inspection opening ( 27 ) having. Heating boiler according to claim 10, characterized in that the inspection opening ( 27 ) is arranged such that it via a filling opening ( 5 ) of the combustion chamber ( 2 ) is operable. Heating boiler according to claim 10 or 11, characterized in that the inspection opening ( 27 ) is closable by means of an adjustable flap. Heat supply system with a boiler according to one of claims 1 to 12, characterized in that the heat exchanger ( 17 ) and / or a water jacket ( 3 ) of the boiler ( 1 ) is connected to a Heizwasserkreislauf having a bypass circuit for return temperature increase. Heat supply system according to claim 13, characterized in that a buffer storage is connected to the Heizwasserkreislauf. Method for combustion of solid fuels in a heating boiler according to one of claims 1 to 12, characterized in that the combustion in the upper region of the in the combustion chamber ( 2 ) solid fuels ( 7 ) and the combustion of solid fuels ( 7 ) takes place via an upper burnup.

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