METHOD AND DEVICE FOR SEPARATING MERCURY VAPOUR IN CONNECTION WITH CREMATION

Abstract: The invention relates to a method and a device for during cremation separating mercury vapors formed by an amalgam disintegration from the created combustion gases. This is according to the invention achieved in that a cover (9) is arranged directly on top of the existing mercury vapor forming source, the cover being connected to an evacuation device (18) by means of a purification device (16, 17) especially provided for a mercury separation. Thus, the mercury vapors are directly taken care of when formed with a possibly small contamination of combustion gases, thereby preventinn spreading in the oven chamber (1) and mixing with the combustion gases.

Description: METHOD AND DEVICE FOR SEPARATING MERCURY VAPOUR IN CONNECTION WITH CREMATION The present invention relates to a method to separate mercury vapors during cremation from the combustion gases. The mercury vapors created during cremation originate from with amalgam performed teeth repairs. Swedens about 70 crematories are inspite of environmental ventures in this field during several years the largest mercury pollution source in the country. Purification plants have been installed in several larger crematories possibly achieving a purification effect of 90 . The costs, however, are high and it is considered unreasonable to provide also smaller crematories with purification plants of this kind inspite of that the pollution from these will increase. The measurments carried out have shown that during a combustion of a known quantity of mercury only about 35 % of the mercury are possibly separated from the combustion gases, inspite of that the purification had been perfect. Explanations have involved that the mercury vapors had to a large extent diffused through the oven walls to the walls outside. Similar phenomena have been observed in zink ovens, where the zink vapors had passed through a 40 cm thick oven wall and had condensated on its outside. Furthermore, it has been stated that the low measurement values could be due to that the mercury during the measurements during 4 to 5 hours each time could have been fixed to the oven walls to be blown out through the chimney later on, when no measurements were performed. The object of the present invention is to provide a method and a device of the kind mentioned in the beginning achieving a better and a safer purification of the flue gases with costs for the necessary equipment being lower than for said conventional equipment, thereby enabling installations even in smaller cremation ovens, alternatively in smaller crematories. According to the invention this has been achieved in that a possibly local evacuation of essentially only the mercury vapors is provided directly on top of the source of a possible mercury vapor formation, these being thereafter separately purified. Thus, the flue gases without any mercury vapors can be purified in a usual way without any larger complications, in spite of a comparatively large flow. Whereas the mercury vapors together with a smaller amount of flue gases provide a minor flow during only a short period, being separately evacuated, and possibly being purified very effiviently by means of a process especially adapted for separating the mercury vapors. A device for performing the method of the invention with a cremation taking place in an oven provided with a channel for conveying the flue gases to a purification device for these is characterized in that a cover of a heat resistent material is arranged directly on top of the source of a possible mercury vapor formation, the cover being by means of a channel connected to an evacuating device to convey the mercury vapors and an accompanying, possibly little amount of the flue gases to a purificating device especially designed for separating mercury vapors. This device is very little stressed as the flow is limited and the evacuating device only needs to perform when any mercury vapors are formed, which normally occurs only each five to twelve minutes during a combustion period of about 60 minutes. It is then also essential that the mercury vapors are taken care of directly when they are formed, thus preventing any spreading in the oven chamber and they thereby cannot create the above mentioned inconveniences. The flue gases from an outlet from the purificating device especially designed for separating the mercury vapors may contain other impurities provoking damages when evacuated into the air, the outlet thus preferably being connected to the channel for conveying the oven flue gases so that a complete purification is achieved in the ordinary oven purificating device. The flue gases from this outlet may still contain some mercury vapor residues not possibly being eliminated, some portion of the flue gases from this outlet therefore being preferably recirculated in that the outlet is also connected to the channel for evacuating the mercury vapors from the cover. For achieving a possibly maximum evacuation of the mercury vapors and for minimizing the other flue gas portion not containing any mercury vapors the cover is according to a preferred embodiment riseably and hingedly suspended and controlled to a lowered position only during some part of the initial cremating period when the mercury vapors are formed. Then, a concentrated evacuation is preferably achieved in that the cover has double walls with the space between the walls connected to the cover evacuation channel and with its lower part provided with an annular evacuation gap. A special complication consists in that some larger soot flakes are formed from the coffin outer layer during ignition when normally designed coffins are burned, the layer consisting of a wood imitation of paper glued onto a particle board material. For preventing these to fasten onto the cover and being sucked into the evacuating gap and further evacuation ports a fine grating in form of bent fingers is arranged to extend from the lower edge of the double-walled cover outside wall and at a distance from the evacuation gap a small distance into the cover up to the cover inside wall. In this way larger soot flakes are kept away from evacuation gaps and the soot flakes adhering to the grating are disintegrated by the quickly augmenting temperature and fall down from the grating, and only a minor portion can in form of small particles be sucked through the evacuation ports without possibly obstructing them. As a further precaution a blower device can be connected to the channel from the cover for a momentary purification of the evacuation ports when initiating the cover evacuation device. This may be performed before the amalgam has started to disintegrate and before any mercury vapors are formed, any interference of the mercury vapor evacuation then not occuring. The invention will be explained more in detail in the following in connection with the attached drawing showing an execution example of a device according to the invention and in which figure 1 is a schematic side view of the various device components with a combustion oven shown in section, figure 2 is a side view, partly in section of a evacuation cover, figure 3 is a partial section along line A-A in figure 2 and figure 4 is a partial section of a detail B in figure 2. Figure 1 shows a combustion oven 1 of a conventional design with a channel 2 for flue gas evacuation from the oven and for conveying these to an after-burner 3 with nozzles 4 for secondary air injection and an eventually required additional fuel admission. A flue gas channel 5 leads from the after-burner 3 to a conventional flue-gas purification device 6 with a blower, a cooler and filters, and from there to a chimney 7. In the oven 1 a coffin 8 is placed and at its head end a cover 9 is suspended riseably and hingedly in a vertical, with the cover connected part of a evacuation channel 10 displaceably suspended in a vertical, with a sealing provided port in the cover roof. The evacuation channel 10 is bent into a horisontal portion 11 provided with a suspensding device 12 with a driving unit 14 equipped with a control unit 13. The evacuation channel portionll is connected with one end of a compensating bellows 15, with its other end connected to the inlet of a fixed cooler 16. Its outlet is connected to a purification device 17, especially designed for separating mercury both in form of particles and vapors. Thereto a circulation blower 18 is connected evacuating the gases cleaned in the device 17 by means of a channel 19 and conveying them to the previously mentioned after-burner 3. The flue-gases emanating from the purification device 17 are additionally cleaned in the after-burner 3 and in the normal oven purification device 6 before they are emitted to the atmosphere by means of a chimney 7. However, some mercury might still remain and for minimizing this portion it might be convenient to arrange a channel 20 from the channel 19 to the evacuation channel 10, preferably to the inlet of the cooler 16 for recirculating some of the gases in the channel 19 through the purification devices 16, 17 for a renewed gas purification. For cooling the evacuation channel 10 nearest to the oven 1 this part of the channel 10 is suπxuϊ3ed by a water cooled primary cooler 21. Furthermore, this part of the channel 10 is connected to a pressure chamber 22 supplied from a pressurized air source by means of a valve 23 arranged in the channel 10. The valve 23 is controlled by the control unit 13 and can briefly close the channel to the evacuation cover 9 from the channel portion 11 and connect the pressurized air source 22 to the cover 9, its evacuation edge and other evacuation ports being cleaned by means of a pressurized air pulse. Thereafter, the valve 23 is reset, thereby disconnecting the pressurized air chamber 22 for a renewed charging, instead connecting the channel portion 11 with the evacuation cover 9. The various operations are controlled by a control unit 13, which before any initiation of the combustion is actuating the driving device 14 to lift the cover 9. The coffin with its contents has normally a temperature of about 4 * C, any amalgam disintegration therefore not occuring only minutes later. After 3 to 4 minutes the control unit 13 resets the valve 23 during a few seconds to clean the ports of the cover 9. After resetting the valve 23 the control unit 13 initiates the driving device 14 and the circulation blower 18. The cover setting in a vertical direction has been programmed for various cases and when the combustion has lasted sufficiently long for eliminating all the amalgam, i.e. after about 12 minutes, the control unit 13 initiates the driving device 14 to lift the cover 9 and the control unit 13 stops the blower 14, the mercury separating device then not longer be needed. The cover 9 is in accordance with figures 2 to 4 provided with an outside wall 30 and an inside wall 31. The outside wall 30 has on top a port 32, to the edges of which the evacuation channel 10 is sealingly connected. The inside wall 31 is provided with small evacuation holes 33. The two wall lower edges form an annular evacuation gap 34, covered by a fine grating in form of bent fingers 35 fastened to the outside wall lower edge and bent over and with some distance from the gap 34 to the inside of the inside wall 31, where they are fixed at some distance in from the lower edge. The evacuation gap achieves an effective mercury vapor evacuation, the vapors being with a correct lowering of the cover prevented to pass the evacuation gap 34. The previously mentioned large soot flakes,possibly formed when initiating the combustion, are caught by the fingers 35, simultaneously acting as a connecting device between the two walls. The invention is of course not restricted to the illustrated and described execution example, but can instead be modified in various ways within the scope of the inventive idea as it is defined in the claims. This refers especially to the operational program and the device 17 especially designed for separating mercury.

Claims: Claims 1. A method for during cremation separating mercury vapors formed by an amalgam disintegration from the created flue gases, characterized in that a local evacuation of mainly only the mercury vapors is achieved directly on top of the existing mercury vapor forming source, the mercury vapors thereafter being cleaned. 2. A device for performing the method according to claim 1, for a cremation performed in an oven (1) provided with a channel (2) for conveying the flue gases to a device (3, 6) for their purification, characterized in that a cover (9) of a heat resistant material is provided directly on top of the existing mercury vapor forming source, the cover (9) being by means of a channel (10) connected with a evacuation device (18) for conveying the mercury vapors and an accompanying, preferably small amount of flue gases to a purification device (16, 17) especially designed for separating the mercury. 3. A device according to claim 2, characterized in that an outlet from the purification device (17) especially designed for separating the mercury also communicates with the evacuation channel (2) for discharging the oven flue gases. 4. A device according to claim 2, characterized in that an outlet from the purification device (17) especially designed for separating the mercury also communicates with the evacuation channel (10) for the mercury vapors from the cover (9). 5. A device according to any of the claims 1-4, characterized in that the cover (9) is riseably and hingedly suspended and controlled to a lowered position only during some part of the initial cremating period when the mercury vapors are formed. 6. A device according to any of the claims 2-5, characterized in that the cover (9) has double walls, the space between the walls (30, 31) being connected to the cover evacuation channel (10) and at its lower part provided with an annular evacuation gap (34). 7. A device according to claim 6, characterized in that a fine grating in form of bent fingers (35) is arranged to extend from the lower edge of the cover outside wall (30) and at some distance from the evacuation gap (34) some distance into the cover up to the cover inside wall (31). 8. A device according to claim 6 or 7, characterized in that the cover inside wall (31) is perforated (33). 9. A device according to any of the claims 2-8, characterized in that a blower device (22) for a momentary purification of the cover evacuation gap (34) and the perforations (33) is connected to the channel (10) from the cover (9) and arranged to momentarily perform immediately before each initiation of the cover evacuation device (18). AMENDED CLAIMS [received by the International Bureau on 06 July 1996 (06.07.96); original claims 1,2,6 and 9 amended; remaining claims unchanged (2 pages)] 1. A method for during cremation separation mercury vapors formed by an amalgam disintegration from the created flue gases, characterized in that a local evacuation of mainly only the mercury vapors is achieved directly on top of the existing mercury vapor forming source, i.e. right above the head end of a coffin or corresponding object, the mercury vapors thereafter being cleaned. 2. A device for performing the method according to claim 1, for a cremation performed in an oven (1) provided with a channel (2) for conveying the flue gases to a device (3,6) for their purification, characterized in that a cover (9) of a heat resistant material is provided directly on top of the existing mercury vapor forming source, i.e. right above the head end of a coffin (8) or corresponding object, the cover (9) being by means of a separate channel (10) connected with an evacuation device (18) for conveying the mercury vapors and an accompanying, preferably small amount of flue gases to a purification device (16,17) especially designed for separating the mercury. 3. A device according to claim 2, characterized in that an outlet frcm the purification device (17) especially designed for separating the mercury, also communicates with the evacuation channel (2) for discharging the oven flue gases. 4. A device according to claim 2, characterized in that an outlet from the purification device (17) especially designed for separating the mercury also cαranunicates with the evacuation channel (10) for the mercury vapors from the cover (9) . 5. A device according to any of the claims 1-4, characterized in that the cover (9) is riseably and hingedly suspended and controlled to a lowered position only during some part of the initial cremating period when the mercury vapors are formed. 6. A device according to any of claims 2-5, characterized in that the cover (9) has double walls, the space between the walls (30,31) being connected to the special cover evacuation channel (10) and its lower part provided with an annular evacuation gap (34). 7. A device according to claim 6, characterized in that a fine grating in form of bent fingers (35) is arranged to extent from the lower edge of the cover outside wall (30) and at some distance from the evacuation gap (34) some distance into the cover up to the cover inside wall (31). 8. A device according to claim 6 or 7,characterized in that the cover inside wall (31) is perforated. 9. A device according to any of claims 2-8, characterized in that a blower device (22) for a momentary purification of the cover evacuation gap (34) and the perforations (33) is connected to the special channel (10) from the cover (9) and arranged to momentarily perform immediately before each initiation of the cover evacuation device (18).

Inventors: ERICSSON FOLKE, ERICSSON, FOLKE
Applicants: ERICSSON FOLKE, FOLKE ERICSSON ING FA, ERICSSON, FOLKE, ING. FIRMA FOLKE ERICSSON
Application year: 1996
Main classification: C22B43
IPC codes: C22B43, F23G1, F23J15