FI81726C - FILTER FOER RENING AV ROEKGASER. - Google Patents

Description

1 81726

Filter for cleaning flue gases

The invention relates to a filter for removing harmful substances from flue gases, the filter having 5 filter layers through which the flue gases are passed.

Due to the combustion process and fuels, the flue gases of the boilers contain various harmful substances which, when released into the atmosphere, affect the environmental conditions and e.g. detrimental to forest growth and the condition of lakes. A wide variety of solutions have been developed for the removal of these compounds, of which the removal of sulfur compounds is typically based on the supply of lime or calcareous substances to the flue gases, either as a dry or aqueous slurry. The disadvantage of these solutions is that they result in a large variety of dust and reaction results which must be disposed of in some way. In order to prevent the formation of nitrogen oxides, various combustion methods have been designed in which the combustion process itself has been influenced, as well as various different absorption methods and the use of absorption and catalyst substances to remove already formed nitrogen oxides. Combustion methods have been usefully applied to some extent, but have not been sufficient to reduce the formation of nitrogen oxides sufficiently. The use of various catalysts and absorbents, in turn, again results in the formation of harmful reaction results as well as complex equipment for recycling and purifying the catalysts.

The object of the present invention is to provide such a filter for cleaning flue gases from harmful substances, which does not have the said problems and with which the cleaning can be carried out as efficiently as possible. This is achieved according to the invention by comprising a jacket mounted around the chimney, inside which the filter layer is formed, 2 81726 - that the filter layer is formed by activated carbon, - that the filter layer is mounted inside the jacket so that part of the length of the jacket forms above the filter layer a tubular duct, - that fans are mounted above the filter layer of the jacket to blow air from the outside of the jacket obliquely upwards into the inside of the jacket.

The essential idea of the invention is that the flue gases 10 are passed through a replaceable activated carbon bed and the pressure drop caused by the bed is compensated by a vacuum created on the outlet side of the bed, whereby the filter does not slow down or inhibit the flue gas flow.

The invention will be described in more detail in the accompanying drawings, in which Figure 1 shows a filter according to the invention schematically, Figure 2 shows a second embodiment of the invention schematically and Figure 3 shows a detail of the embodiment according to Figure 2.

Figure 1 shows a filter 2 placed at the end of a chimney 1, which is formed by a layer made of granular activated carbon. Around the filter 2 there is a cylindrical jacket 3 formed by a tubular duct above the filter 2 and in the middle of the filter there is a cylindrical flue gas guide 4 with a guide cone 5 at the lower end. The jacket 3 is fitted with ducts 6 at the end. 7. The filter 2 is located substantially outside the outlet 1a of the chimney 1, the lower surface of the filter being located outside the outlet 1a. The lower surface of the filter 2 has, for example, a net 8 formed of stainless steel, the hole size of which is smaller than that of the

II

3,81726 Grain size of activated carbon. The net 8 holds the activated carbon granule layer in place, preventing the granules from falling downwards. Below the filter, outside the chimney 1, there is a funnel ring 9 comprising a plurality of separate ash hoppers 10. Each funnel 10 is associated with an ash tube 11 which leads to tanks (not shown) located at the bottom of the chimney 1. On top of the hopper ring 9 there is a brushing device 13 arranged to move on the rails 12, at the top of which a brush 10 14 brushing the support net 8 extends along the rails 12 either continuously in a circle or reciprocating so that the entire lower surface of the filter 2

When the filter is operating, the flue gas comes from the outlet 1a of the chimney 1 15 and under the influence of the guide cone 5 forms annularly towards the lower surface of the filter 2 and further flowing through the activated carbon layer of the filter 2, leaving the harmful substances 2. even burning the boiler. For this purpose, fans 7 are preferably mounted around the jacket 3 at regular intervals above the filter 2, which provide an air flow through the ducts 6 between the jacket 3 and the control cylinder 4, thus creating an ejection effect and sucking flue gas through the filter 2. In this way, the pressure drop caused by the filter 2 is compensated and the gas flow corresponds to the normal flow of the chimney. As the flue gas flows through the filter layer 2, the dusty constituents present in the flue gas 30 remain on the inlet or bottom surface of the filter 2 and could block the filter completely over time. To prevent this, there is a conical ring below the filter 2 with a plurality of discharge cones 10 for removing dust. Above the conical ring, a rotating brushing device 13 rails 1-35a 12 brushes the lower surface of the filter 2, either at regular intervals or continuously, keeping it free of dust falling into the hoppers 10 and further from the hoppers 10 through pipes 11 to one or more chimneys not shown. -5 to a coma tank from which it is either periodically or continuously removed. Since activated carbon is only effective for a certain period of time and then ceases to function, it must be periodically either replaced or otherwise regenerated by heating it under suitable conditions to such an extent that harmful substances and absorbed substances can be removed and incinerated.

Figure 2 shows another embodiment of the invention, in which tubular filter cylinders 2 are used instead of a uniform granular layer of activated carbon. At the upper edge of the Oh-15 stop cylinder 5 there is a spacer 2a covered by a filter cross-section, to which cylindrical filter tubes 2 are attached. In this alternative, the flue gas flows in the chimney 1 under the control cone 5 inside the activated carbon pipes 2 from their lower end and when the upper end is closed, flows outwards through the activated carbon pipes, leaving impurities and harmful substances in the pipe walls. As in the solution according to Figure 1, a flue gas-absorbing flow is formed inside the jacket of the filter equipment by means of fans 7. The tubes 2 are interchangeable, in which case, as in the alternative using granular activated carbon according to Fig. 1, they can be regenerated in the same way as granular activated carbon can be cleaned by heating it sufficiently hot under suitable conditions. In this case, for example, one set of pipes can be replaced with a new one at regular intervals and the previous set of pipes can be taken for renewal. The filter rods according to Fig. 2 must also be cleaned because the flue gas flowing inside them brings dust when it enters, which clogs the inlet or inner surface of the filter rods. This purification can be carried out, for example, by the solution according to Figure 3, in which the purification of one filter rod is shown schematically. A brush 14 'is introduced from below or alternatively from above into the inside of the filter rod 2, which rotates in the axial direction of the cylinder tube and moves in its longitudinal direction simultaneously. In this case, the brushing removes dust accumulated on the inner surface of the tube, which can fall downwards and, according to the solution of Fig. 1, through the hoppers 10 into the outlet pipes 11. The apparatus can also be mounted above the cylinder tubes, pushing the loose dust downwards.

The invention has been described above in the description and in the drawing only by way of example and is in no way limited thereto. The structure of the cleaning devices and the direction of rotation of their brushes as well as the directions of movement can be of any kind. The operation and timing of the cleaning devices can be done in different ways. Dust hoods and dust extraction tubes may vary in shape and construction and may have either a continuous or intermittent dust extraction system.

Claims (5)

1. Filters for the removal of harmful substances from Δη flue gases, which filter has a filter layer (2) through which the flue gases are led, characterized in that there is a sheath (3) mounted around the chimney, inside of which the filter layer (2) has been formed, - that the filter layer (2) is formed of activated carbon, - that the filter layer (2) is mounted inside the manifold (3) so that part of the length of the jacket forms a tubular channel above the filter layer (2), 7) are mounted in the manhole (3) above the filter layer (2) to blow air from the outer side of the sheath (3) obliquely into the manhole (3). 2. A filter according to claim 1, characterized in that the manifold (3) is larger than the drain opening (1b) of the chimney (1), that between the manifold (3) and the chimney (1) is a ring formed by ash funnels (10), that from each ash funnel (10), a pipe leads to an ash pile located in the lower part of the chimney 20 (1), that in the middle of the sheath (3) there is a control cylinder (4) substantially the same size as the chimney (1) drain opening (1a) and provided with a guide cone (5) located at the tip downwards, that the filter layer (2) is located on top of the ash funnel ring between the manifold (3) and the control cylinder (4) and that the filter includes a cleaning device (13) for cleaning the filter layer ( 2) entrance area from dust that comes with the flue gas. 3. A filter according to claim 2, characterized in that the filter layer (2) is formed of granular activated carbon, and that the filter between the manifold (3) and the control cylinder (4) has a support network (8), on top of which the active carbon. the grains have been placed, that the cleaning apparatus (13) has been placed to move around the chimney (1) above the ash funnels (10), that the cleaning apparatus (13) has at least one brush (14) which has been placed to brush the support mesh (8) II 9 81726 lower surface. 4. A filter according to claim 2, characterized in that the filter layer (2) is formed by a plurality of active carbon cylinders (2 ') closed in one end in relation to the flow of the flue gas, into which the flue gas to be purified. , and through the surface of which the fumes flow, and that the filter includes an intermediate disk (2a), to which the active carbon cylinders (2 ') are attached at one end. 5. Filter according to claim 4, characterized in that at each active carbon cylinder (2 ') there is an ash funnel (10) and that there is a brush system for cleaning the inner surface of the cylinders (2 *) from dust.