Device for the cleansing of flue gases from waste incineration installations

Abstract: The device is provided with a multicyclone (1) connected to the incineration installation intended for the collection of flyash, a heat exchanger (7) to which said multicyclone is connected and intended for the reduction of the temperature of the collected flue gases and the reheating of the cleaned flue gases, a gravitation chamber (20) with a rotating scraper (25) and intended for slowing the speed of the incoming flue gases and the precipitation and removal of the flyash, a cooling chamber (33) connected to said gravitation chamber and intended for the refrigeration of the incoming flue gases, where means are provided for the removal of the condensate from the refrigerated flue gases to a water treatment installation, and an outlet for the removal of the treated and cooled flue gases.

Description: The invention is for a device for the cleansing of the severely polluted flue gases which arise in waste incineration installations before these enter the atmosphere. Known cleansing installations are installations provided with electrostatic filters and means for scrubbing the polluted flue gases. A major disadvantage of these is that large quantities of water are needed for the cleansing operation, which water becomes polluted with heavy metals during the scrubbing of the flue gas and must in turn be treated before being discharged into the environment. Another disadvantage is that the cost price and maintenance costs of such installations are very high. In order to cope with these disadvantages a device in accordance with the principal characteristic of the invention has been realized as described in claim 1 of this application whereby the flyash together with the heavy metals is removed in solid form from the flue gases, the remaining part of the flue gases is cooled, the condensate of this is removed together with the heavy metals in liquid form via a water treatment installation and the remaining cleaned quantity of flue gases is expelled into the atmosphere. The US-A-4 701 212 describes the cooling of flue gas in order to separate Hg as condensate. By way of example, and without attempting to be exhaustive in any way, a more detailed description of a preferred embodiment of the device in accordance with the invention is given below. This description refers to the attached drawings, where: fig. 1 shows a vertical section through a cyclone with a heat exchanger connected to it. fig. 2 shows a vertical section through the gravitation chamber connected to the heat exchanger and the cooling chamber; fig. 3 shows a section along the line III-III in fig. 2 In fig 1 a multicyclone 1 can be seen which is provided with an insulating mantle 2 and in which emerges a pipe 3 through which the dirty flue gases from an incineration installation in which all kinds of waste are burnt enter the multicyclone. In this a large part of the flyash is removed from the flue gases and carried away via the extraction pipe 4 installed beneath the multicyclone. The partially cleansed flue gases are carried through a collector pipe 5 which leaves the multicyclone and which is connected to a pipe 5', which has a side branch 13 and an expansion bellows 6, for the removal of the recycled flue gases and leading to a heat exchanger 7 provided with an insulating mantle 8. The flue gases enter at a temperature of close to 250°C and leave the heat exchanger at a temperature of close to 55°C through a pipe 9. To this end the heat exchanger is provided with an axial duct system 10 to cool the flue gases from 250°C and with a radial duct system 11 to heat the cleansed flue gases to between 100°C and 110°C and with a second radial duct system 12 with a fan 14 to adjust the temperature of the flue gases to 55°C. The outlet of the radial duct system 11 is connected at one end to an exhaust pipe 15 leading to a chimney 16 and at the other end to a pipe 17 provided with a flue gas fan 18 as a result of which the flue gases cooled and cleansed by the device described below flow into the radial duct system 11 of the heat exchanger 7 in order to cool the flue gases coming from the multicyclone 1. The pipe 9 is connected to an annular duct 19 provided around the lowest part of a cylindrical gravitation chamber 20, equipped with an insulating mantle 21. This annular duct is connected to the gravitation chamber by means of openings 22 provided in the wall of the gravitation chamber 20. The floor 23 of this gravitation chamber is pitched towards the centre where a hollow column 24 is installed. A double-armed scraper 25 is mounted so that it can rotate around this hollow column and against the bottom 23. Each end of this scraper is provided with driving wheels 26 driven slowly by an electrical motor 27 mounted on the scraper and which run in a rail 28 mounted around the inside wall of the gravitation chamber. The solid particles are precipitated on the floor 23 of said chamber by gravity from the flue gases entering the gravitation chamber 20 through the openings 22 at a speed of virtually 3mm/sec. The insulating mantle 21 prevents the flue gases from cooling and condensing. The very slowly rotating scraper 25 transports the deposited flyash containing solid heavy metals to the centre of the floor 23 of the gravitation chamber 20 before being removed via an extraction pipe 29 provided with a rotating lock 30 to prevent the penetration of dead air. The upper section of the hollow column 24 is provided with openings 31 through which the flue gases are carried away via the column 24 downwards into a cooling chamber 33 in which they are severely cooled to a temperature of close to -1°C. At this temperature acid components, such as HCl, Hf and SO 2 , and heavy metals present in gas phase, such as Hg, condense and the condensate is collected by means of the pitched floor 34 of the cooling chamber 33 in a collection sump 35, from which the condensate is carried with the aid of an immersion pump 36 and a pipeline 37 to a water treatment installation. In order to bring about said cooling, several cooling elements 38 are installed in the upper section of the cooling chamber 33 which are supplied by cooling sets 40 installed between the gravitation chamber 20 and the cooling chamber 33 and the heat derived from which can be used for heating other spaces. In order to prevent the condensate from freezing heating elements 41 can be built into the said floor 34. The remaining cleansed flue gases are carried via the openings 42 provided in the wall of the cooling chamber 34 and which emerge into an annular duct 43 away to the pipe 17 provided for this purpose through which these cleansed gases pass into the atmosphere via the heat exchanger 7 and the chimney 16. It goes without saying that the type, the arrangement, the form and dimensions of the parts described above may differ according to the desired purpose and that the device described above could be added to with other accessories which could improve its practical functioning.

Claims: Device for the cleansing of flue gases from waste incineration installations, consisting of a multicyclone (1) for the collection of a large part of the flyash from the flue gases and which is connected to said incineration installation; a heat exchanger (7) to which said multicyclone (1) is connected and intended for the reduction of the temperature from the flue gases collected from the multicyclone and the reheating of the cleaned flue gases; a gravitation chamber (20) to which said heat exchanger (7) is connected and intended for reducing the speed of the incoming flue gases and for the gravitational separation and precipitation of the flyash from the flue gases; a scraper (25) installed against the bottom (23) of aforesaid gravitation chamber and intended for scraping together and removing the flyash precipitated in the gravitation chamber; driving means (26-27) for propelling said scraper; an extraction pipe (29) provided in the bottom (23) of said gravitation chamber (20) and intended for the removal of the flyash; an outlet (24) with holes (31) provided in said gravitation chamber for guiding the rising flue gases out; a cooling chamber (33) provided with cooling elements (38) connected to said gravitation chamber (20) and intended for the refrigeration of the incoming flue gases; heating elements (41) provided in the cooling chamber (33) for extracting a condensate from the frozen flue gases; a catchment sump (35) provided in the floor (34) of the cooling chamber (33) for the collection of the condensate; a pump (36) for removing the condensate in the catchment sump (35) to a water treatment installation; and an extractor (17-42) connected to the cooling chamber (33) and intended for the removal of the treated and cooled flue gases in the cooling chamber. Device according to claim 1, with the characteristic that the pipe (3) of the multicyclone (1) connected to the incineration installation emerges into the multicyclone by means of a distribution pipe, underneath the multicyclone is connected to an outlet pipe (4) for the removal of a large part of the flyash from the flue gases, at the top the multicyclone is connected to a collector pipe and a pipe (5') equipped with an expansion bellows (6) for carrying the flue gases to the heat exchanger (7) where the multicyclone is equipped with an insulating mantle (2). Device according to claim 1, with the characteristic that the heat exchanger (7) is equipped with an axial duct system (10) and a radial duct system (11) which at one end is connected to the outlet pipe (17) of the cooling chamber (33) and at the other end to the chimney (16) of the device, at the top the heat exchanger is connect to the multi-cyclone (1) and at the bottom to the gravitation chamber (20), where a second radial connection (12) provided with a fan (14) is provided in the heat exchanger. Device according to claim 1, with the characteristic that the gravitation chamber (20) is provided with an insulating mantle (21) to prevent condensation. Device according to claim 1, with the characteristic that the bottom (23) of the gravitation chamber (20) is gently pitched to the centre of same and that the outlet provided in the bottom of the gravitation chamber consists of an opening with an extraction pipe (29) provided at said central point and on which a rotating lock (30) is mounted in order to prevent the admission of dead air. Device according to claim 1, with the characteristic that the scraper (25) consists of a double arm installed so that it can rotate around a hollow column (24) provided with openings (31) which form the connection between the gravitation chamber (20) and the cooling chamber (33), the free end of each arm is provided with two driving wheels (26) driven by an electrical motor (27), which driving wheels run in a rail (28) mounted against the inner surface of the wall of the gravitation chamber (20). Device according to claim 1, with the characteristic that around the lowest part of the gravitation chamber (20) an annular duct (19) is provided which is connected to the heat exchanger (7) and provided with openings (22) passing through the wall of the gravitation chamber. Device according to claim 1, with the characteristic that the gravitation chamber (20) is situated above the cooling chamber and that between the two chambers there is a space (39) for the installation of cooling sets (40) for the cooling elements (38) in the cooling chamber (33). Device according to claim 1, with the characteristic that around the wall of the cooling chamber (33) an annular duct (43) is provided which is connected to the cooling chamber via the openings (42) provided in the wall, which duct is connected to the outlet pipe (17) for the removal of the cleansed and cooled flue gases. Device according to claim 1, with the characteristic that the floor (34) of the cooling chamber (33) is pitched towards the catchment sump (35) provided in the floor. Device according to claim 1, with the characteristic that the catchment sump (35) is provided with an immersion pump (36) for the removal of the collected condensate. Device according to claim 1, with the characteristic that the cooling elements (38) are set up in the upper part of the cooling chamber (33). Device according to claim 1, with the characteristic that the heating elements (41) are installed in the floor (34) of the cooling chamber (33).

Inventors: KEERSMAEKERS MARC, KEERSMAEKERS, MARC
Applicants: KEERSMAEKERS MARC, KEERSMAEKERS, MARC
Application year: 1995
Main classification: B01D50
IPC codes: B01D45, B01D50, F23J15, F23G7