Flue gas cleaning arrangement

Abstract

Flue gas cleaning arrangement (100), comprising: - at least two cleaning cells (1a-1f) arranged in parallel, wherein - each of the parallel cleaning cells (1a, 1b, 1c) comprises: - an inlet flap (2), - an outlet flap (3), - a filter hose chamber (4), and - a unit (6) for selective catalytic reduction (SCR unit), wherein the SCR unit (6) is arranged in the cleaning cell (1a, 1b, 1c) between the filter bag chamber (4) and the outlet flap (3), - wherein the flue gas cleaning arrangement (100) further comprises an ammonia injection unit (5), characterized in that - the ammonia injection unit (5) and the units (6) for selective catalytic reduction are arranged on the same support structure (9) as the bag filter cells (4), and that - the ammonia injection unit (5) and the selective catalytic reduction (SCR) units (6) are arranged at least partially above the upper horizontal plane (U) of the bag filter cells (4).

Description

BACKGROUNDThe invention relates to a flue gas purification arrangement.Tubular filters or fabric filters are usually used for purifying flue gases from various power plants, reactors, boilers etc. Typically, for tubular filters, long, cylindrical tubes made of woven fabric or felt structure are used as filter medium. Dust laden flue gas enters the bag filter and flows through the hoses, either on the inside or the outside, depending on the cleaning process. A dust layer collects on the filter medium surface and causes an increasing pressure drop. When a sufficient pressure drop or preset time interval is reached, a cleaning process begins. The cleaning process can be based, for example, on mechanical vibrations, a reverse gas flow or high-pressure air pulses.BRIEF DESCRIPTIONViewed from a first aspect, there may be provided a flue gas purification arrangement comprising at least two purification cells arranged in parallel, each of the purification cells arranged in parallel comprising an inlet flap, an outlet flap, a filter tube chamber and a selective catalytic reduction (SCR) unit, the SCR unit being arranged in the purification cell between the filter tube chamber and the outlet flap.Thereby, a flue gas cleaning arrangement can be achieved which requires less foundation work and has lower investment costs. Further, it is possible that a smaller footprint is required. Moreover, the structure of the assembly is based on modularity, which can simplify its production. This is particularly advantageous in the production of arrays which vary in their cleaning capacity, since the capacity can be varied by selecting the number of cleaning cells. Furthermore, the use time of the catalyst or of catalyst elements in the SCR unit can be extended and these can be used up without jeopardizing the cleaning process, since one cleaning cell can be replaced in each case without problems while the operation of the flue gas cleaning arrangement runs over the rest of the cleaning cells.The arrangement is characterized by what is set forth in the independent claims. Some further embodiments are characterized by what is set forth in the other claims. Embodiments according to the invention are also disclosed in the specification and drawings of this patent application. The content of the patent application according to the invention can also be defined in a different manner than defined in the following claims. The inventive content can also be formed by a plurality of separate inventions, in particular if the invention is tested in the light of explicit or implicit sub tasks or in the light of achieved advantages or groups of advantages. It is possible that then some of the definitions contained in the following claims are not necessary in view of the separate inventive ideas. Features of the various embodiments of the invention may be applied to other embodiments within the scope of the basic inventive concept.Various embodiments of the first aspect may include at least one feature from the following sections:In one embodiment, ammonia injection unit is disposed in the cleaning cell between the filter tube chamber and the selective catalytic reduction (SCR) unit.An advantage is that because the reagent is supplied to the flue gas immediately before the SCR unit, a percentage of the reagent entering the SCR unit and thus participating in reactions taking place therein can be maximized. Furthermore, it is not necessary to model or simulate flow characteristics of the reagent in the assembly, as the flow path of the reagent towards the SCR unit may be very simple.In one embodiment, the ammonia injection unit is disposed in the cleaning cell between the inlet flap and the filter tube chamber.An advantage is that the reagent has ample time to mix with the flue gas before reactions take place in the SCR unit, which can intensify the reactions and the purification of the flue gas.In one embodiment, the ammonia injection unit is disposed in front of the inlet flap.An advantage is that the reagent has ample time to mix with the flue gas before reactions take place in the SCR unit, which can intensify the reactions and the purification of the flue gas.In one embodiment, the cleaning cell comprises a heat exchanger arranged downstream of the filter hose chamber and upstream of the ammonia injection unit.An advantage is that an optimum temperature can be achieved for the reactions taking place in the SCR unit and consequently the cleaning of the flue gas can be enhanced or optimized.In one embodiment, the arrangement comprises a second heat exchanger arranged after the outlet flap.An advantage is that thermal energy of the flue gas can be recovered and consequently the ecological and economic efficiency of the arrangement can be increased.In one embodiment, the second heat exchanger is configured to receive the flue gas from at least two cleaning cells arranged in parallel, optionally from all of the cleaning cells arranged in parallel in the arrangement.An advantage is that the number of second heat exchangers and consequently the investment costs associated therewith can be reduced.In one embodiment, the ammonia injection units and the SCR units are arranged on the same support structure as the tubular filter cells.An advantage is that compared to solutions in which the bag filter cells are arranged on a support structure separate from the ammonia injection units and the SCR units, a smaller footprint of the plant may be required.In one embodiment, the ammonia injection units and the SCR units are at least partially disposed above the upper horizontal plane of the bag filter cells.An advantage is that the footprint of the arrangement can be reduced.In one embodiment, the ammonia injection units and the SCR units are at least partially disposed below the upper horizontal plane of the bag filter cells.An advantage is that the space utilization of the support structure can be improved.In one embodiment, the ammonia injection units and the SCR units are at least partially disposed below the bottom horizontal plane of the bag filter cells.An advantage is that the footprint of the arrangement can be reduced.In one embodiment, the bag filter cells are grouped into at least two filter bag chamber groups, and the ammonia injection units and the SCR units are at least partially disposed between the bag filter bag chamber groups.An advantage is that the space utilization of the support structure can be improved.In one embodiment, the inlet flap is a flap flap, for example a single flap.An advantage is that the butterfly valve has a simple structure and can provide improved flow properties.In one embodiment, the outlet flap is a plate flap, for example an individual plate flap.An advantage is that an outlet flap with a long life cycle and robust construction can be achieved.Based on the above, it should be noted that various embodiments mentioned in the above paragraphs may be combined in any possible suitable manner to implement the present invention.BRIEF DESCRIPTION OF THE FIGURESSome embodiments illustrating the present disclosure are described in more detail in the accompanying drawings, in which FIG. 1 illustrates a flue gas cleaning arrangement, FIG. 2 illustrates a further flue gas purification arrangement, FIG. 3 illustrates a third flue gas purification arrangement, and FIG. 4 is a schematic view of a flue gas cleaning arrangement in a partial cross section.Some embodiments are shown in simplified form in the figures for reasons of clarity. In the figures, like parts are denoted by the same reference numerals.DETAILED DESCRIPTIONFIG. 1 illustrates a flue gas cleaning arrangement. The flue gas cleaning arrangement 100 for cleaning flue gases generated in any combustion furnace or in any industrial application is provided. The source of the flue gas may be a combustion plant, for example a coal-fired, a wood-fired, a gas-fired or an oil-fired combustion plant, a reactor, for example a fluidized bed reactor or a grate furnace, a boiler, for example a recovery boiler.The flue gas cleaning arrangement 100 comprises three cleaning cells 1 a, 1 band 1 carranged in parallel. Each of the purification cells 1 a, 1 b, 1 ccomprises an inlet door 2, an outlet door 3, a filter tube chamber 4 and a selective catalytic reduction (SCR) unit 6.The filter tube chamber 4 comprises a plurality of tubes 11 (shown in FIG. 4 ), typically 50 to 500 tubes. The length of the hose 11 is typically 6 to 10 meters and the diameter 100-200 mm.The cleaning cell 1 a, 1 b, 1 cis configured such that the SCR unit 6 is arranged between the filter tube chamber 4 and the outlet flap 3, i.e. on a clean gas side of the cleaning cell. In an embodiment, for example as shown in FIG. 1, the arrangement comprises an ammonia injection unit 5 provided between the filter tube chamber 4 and the SCR unit 6. In other words, each of the three purification cells 1 a- 1 cincludes, in the flow direction, flue gas, the inlet door 2, the filter tube chamber 4, the ammonia injection unit 5, the SCR unit 6, and the outlet door 3.It should be noted that the number of purging cells arranged in parallel may vary from two to dozens of cells, which are typically selected in a range of 3 to 10. The term "parallel cleaning cells" does not necessarily mean that the cleaning cells are physically arranged or attached next to each other, but that flue gas to be cleaned by the arrangement 100 is divided into parts and each of the parallel cleaning cells clean one of the parts.The ammonia injection unit 5 is configured to add and mix a reagent to the flue gas to be supplied to the SCR unit 6. The reagent typically comprises anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH) and / or urea (CO(NH 2)2) The reagent reacts with nitrogen oxides (NOx) of the flue gas using a catalyst in the SCR unit 6 and produces diatomic nitrogen (N 2) and water (H 2 O).In some embodiments, the ammonia injection unit 5 comprises one or more nozzles, arranged perforated lines, etc., through which the reagent is injected into the flue gas.In an embodiment, as shown for example in FIG. 1, the ammonia injection unit 5 is arranged after the filter tube chamber 4 and before the SCR unit 6.In one embodiment, a heat exchanger 7 is arranged after the filter hose chamber 4 and before the ammonia injection unit 5 in the cleaning cell 1 a, 1 b, 1 carranged in parallel. In a further embodiment, the heat exchanger 7 is arranged between the ammonia injection unit 5 and the SCR unit 6. The heat exchanger 7 is configured to heat the flue gas to a temperature which is sufficient or optimal for reactions taking place in the SCR unit 6.In one embodiment, the SCR unit 6 comprises one or more honeycomb banks of catalytic blocks through which the flue gas must flow. It should be noted, however, that other structures and shapes known in the art are also possible.In one embodiment, the arrangement 100 comprises a second heat exchanger 8 arranged after the outlet flap 3 for receiving the flue gas cleaned in the SCR unit 6. In one embodiment, each of the parallel arranged cleaning cells 1 a, 1 b, 1 ccomprises itself the second heat exchanger 8. In a further embodiment, a second heat exchanger 8 receives flue gas from at least two parallel arranged cleaning cells 1 a, 1 b, 1 c. In yet another embodiment, as shown for example in FIG. 1, a second heat exchanger 8 is configured to receive flue gas from all the cleaning cells 1 a, 1 b, 1 cof the arrangement 100 arranged in parallel.In one embodiment, the inlet flap 2 is a butterfly flap, for example a single butterfly flap, also referred to as a butterfly flap or wafer flap. However, another type of flap may be used as the inlet flap. By closing and opening the inlet flap 2, the flow of the flue gas in the corresponding cleaning cell 1 a, 1 b, 1 cmay be stopped or permitted.In one embodiment, the outlet flap 3 is a plate flap, for example an individual plate flap. However, another type of flap may be used as the outlet flap. By closing and opening the outlet flap 3, the flow of the flue gas from the corresponding cleaning cell 1 a, 1 b, 1 cmay be stopped or permitted. The cleaning cell 1a, 1b, 1c can be isolated from the rest of the assembly 100 by closing both the inlet flap 2 and the outlet flap 3. This may be useful in certain inspection and maintenance operations.In one embodiment, all the cleaning cells arranged in the flue gas cleaning arrangement have the same or at least substantially the same cleaning capacity.FIG. 2 illustrates another flue gas purification arrangement. In an embodiment, as shown in FIG. 2, for example, the ammonia injection unit 5 is provided before the filter hose chamber 4 but after the inlet flap 2 in the cleaning cell 1 a, 1 b, 1 c. Consequently, the flue gas supplied to the filter tube chamber 4 is already mixed with the reagent. The heat exchangers 7 arranged between the BHF cells 4 and the SCR units 6 may be included in the embodiment shown in FIG. 2, but not necessarily in all embodiments.FIG. 3 illustrates a third flue gas purification arrangement. In one embodiment, the ammonia injection unit 5 is provided in front of the inlet doors 2.In one embodiment, the ammonia injection unit 5 is configured to supply and mix the reagent with the flue gas, which is then divided and supplied to at least two purification cells.In an embodiment, as shown in Fig. 3, the ammonia injection unit 5 is configured to supply and mix the reagent with the flue gas, which is then divided and supplied to all the cleaning cells 1a, 1b, 1c of the assembly. In other words, an ammonia injection unit 5 may provide the reagent needed in the flue gas cleaning process performed in the assembly 100.In one embodiment, each of the cleaning cells 1 a, 1 b, 1 cof the assembly is provided with an ammonia injection unit arranged in front of the corresponding inlet flap 2.In an embodiment, the cleaning cell 1 a, 1 b, 1 cis provided with a first ammonia injection unit 5 arranged before the filter hose chamber 4 as shown in FIGS. 2 and 3, for example, and a second ammonia injection unit 5 arranged after the filter hose chamber 4 as shown in FIG. 1.In one embodiment, the ammonia used in the flue gas purification arrangement 100 is at least partially already supplied in the source of the flue gas, i.e. before the flue gas enters the flue gas purification arrangement 100. Nevertheless, the flue gas purification arrangement 100 may comprise ammonia injection units 5 as required, as described in this specification.FIG. 4 is a schematic view of a flue gas cleaning arrangement in a partial cross section.In one embodiment, the cleaning cells arranged in parallel are arranged on the same supporting structure 9 as the filter tube chambers 4. The term "support structure" as used herein refers to arrangements and structures, for example support structures, the primary or secondary function of which is to support the filter tube chambers 4. It should be noted that in FIG. 4 only a part of the support structure 9 is shown.In some embodiments, as shown in FIGS. 1-3, for example, the bag filter cells 4 are arranged in a row. In one embodiment, the tube filter cells 4 are grouped into at least two filter tube chamber groups. In an embodiment, as shown in FIG. 4, for example, the tube filter cells 4 are grouped into two filter tube chamber groups 10 a, 10 bwhich are inverted from each other on opposite sides of an imaginary dividing plane D. The embodiment shown in FIG. 4 comprises a total of six cleaning cells 1 a- 1 f, so that each of the filter tube chamber groups 10 a, 10 bincludes three cleaning cells. It should be noted that the number of cleaning cells arranged in the filter tube chamber groups may vary depending on, e.g., capacity requirements and the space available.A central channel 14 is located between the filter tube chamber groups 10a, 10b to provide space for various components, such as the outlet flap 3. In one embodiment, the ammonia injection units 5 and the SCR units 6 are at least partially disposed between the filter tube chamber groups 10 a, 10 b, e.g., at least partially disposed in the central channel 14.In a further embodiment, the central channel 14 is located on the side of the filter tube chamber groups.In one embodiment, the ammonia injection units 5 and the SCR units 6 are at least partially disposed above the upper horizontal plane U of the bag filter cells 4. In one embodiment, the components are placed over the upper horizontal plane U.In an embodiment, the support structure 9 comprises a roof structure 12 below which a penthouse 13 is located, and the ammonia injection units 5 and the SCR units 6 are at least partially arranged in the penthouse 13.In one embodiment, the ammonia injection units 5 and the SCR units 6 are at least partially disposed below the upper horizontal plane U of the bag filter cells 4. In one embodiment, the components are placed below the upper horizontal plane U.In one embodiment, the ammonia injection units 5 and the SCR units 6 are at least partially disposed below the lower horizontal plane L of the bag filter cells 4. In one embodiment, the components are placed below the lower horizontal plane L, e.g., below the hoses 11.In the embodiment shown in Fig. 4, the ammonia injection unit 5 is arranged to supply the reagent to the flue gas F immediately after the heat exchanger 7. In an embodiment, the ammonia injection unit 5 is arranged to supply the reagent to the flue gas F immediately before the SCR unit 6, for example at or above the SCR unit, as shown by the dotted line 5 in FIG. 4.In addition to the ammonia injection units 5 and the SCR units 6, at least one / r of the inlet flaps 2, the outlet flaps 3, the heat exchangers 7 and the second heat exchanger(s) 8 may be arranged at least partially above the upper horizontal plane U, at least partially below the upper horizontal plane U and / or at least partially below the lower horizontal plane L.In one solution, the ammonia injection units 5 and the SCR units 6 are arranged in a further support structure (not shown) which is separate from the support structure 9 of the tubular filter cells 4. However, this solution is not an embodiment of the invention.The invention is not limited solely to the embodiments described above, but many variations are possible within the scope of the inventive idea defined by the following claims. Within the scope of the inventive concept, the attributes of various embodiments and applications may be used together with or replace the attributes of another embodiment or application.The drawings and the corresponding description are intended merely to illustrate the spirit of the invention. Within the scope of the inventive idea defined in the following claims, the invention may vary in detail.REFERENCE NUMERALS1 Cleaning cell 2 Inlet flap 3 Outlet flap 4 Filter hose chamber 5 Ammonia injection unit 6 SCR unit 7 Heat exchanger 8 Second heat exchanger 9 Supporting structure 10 Filter hose chamber group 11 Hose 12 Roof structure 13 Penthouse 14 Middle channel 100 Arrangement D Dividing plane F Flue gas L Lower horizontal plane U Upper horizontal plane

Claims

Flue gas purification arrangement (100) comprising: - at least two parallel arranged purification cells (1a-1f), wherein - each of the parallel arranged purification cells (1a, 1b, 1c) comprises: - an inlet flap (2), - an outlet flap (3), - a filter hose chamber (4), and - a selective catalytic reduction (SCR) unit, wherein the SCR unit (6) is arranged in the purification cell (1a, 1b, 1c) between the filter hose chamber (4) and the outlet flap (3), - wherein the flue gas purification arrangement (100) further comprises an ammonia injection unit (5), characterized in that - the ammonia injection unit (5) and the selective catalytic reduction units (6) are arranged on a same support structure (9) as the hose filter cells (4), and in that - the ammonia injection unit (5) and the selective catalytic reduction (SCR) units (6) are arranged at least partially above the upper horizontal plane (U) of the tubular filter cells (4).Arrangement according to claim 1, wherein - the ammonia injection unit (5) is arranged in the cleaning cell (1a-1f) between the filter tube chamber (4) and the selective catalytic reduction (SCR) unit (6).Arrangement according to claim 1, wherein - the ammonia injection unit (5) is arranged in the cleaning cell (1a-1f) between the inlet flap (2) and the filter tube chamber (4).Arrangement according to claim 1, wherein - the ammonia injection unit (5) is arranged in front of the inlet flap (2).Arrangement according to one of the preceding claims, wherein - the cleaning cells (1a-1f) arranged in parallel comprise a heat exchanger (7) arranged after the filter tube chamber (4) and before the ammonia injection unit (5).Arrangement according to any one of the preceding claims, comprising - a second heat exchanger (8) arranged after the outlet flap (3), optionally configured to receive flue gas from at least two cleaning cells (1a-1f) arranged in parallel.Arrangement according to one of the preceding claims, wherein - the ammonia injection units (5) and the selective catalytic reduction units (6) (SCR) are arranged at least partially below the upper horizontal plane (U) of the tubular filter cells (4), optionally at least partially below the lower horizontal plane (L) of the tubular filter cells (4).Arrangement according to any of the preceding claims, wherein - the cleaning cells (1a-1f) are grouped into at least two filter tube chamber groups (10a, 10b), and - the ammonia injection units (5) and the selective catalytic reduction units (SCR) (6) are arranged at least partially between the filter tube chamber groups (10a, 10b).Arrangement according to any of the preceding claims, wherein - the ammonia injection unit (5) is configured to add to the flue gas: - anhydrous ammonia (NH 3), aqueous ammonia (NH 4 OH), urea (CO(NH 2)2).

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