Apparatus for cleaning pollutant-laden waste gas

Information

  • Patent Grant
  • 6274097
  • Patent Number
    6,274,097
  • Date Filed
    Thursday, October 29, 1998
    26 years ago
  • Date Issued
    Tuesday, August 14, 2001
    23 years ago
Abstract
An apparatus for cleaning pollutant-laden waste gas by regenerative thermal afterburning has two towers (1, 2) each divided into three heat-retaining chambers (14 to 16 and 17 to 19) by vertical partitions (10 to 13). Two opposite heat-retaining chambers (14 to 16 and 17 to 19) of the towers (1, 2) are connected by one switching chamber (26, 27, 28) in each case, said chambers being disposed between a loaded gas supply channel (29) and a clean gas removal channel (23). For alternately supplying loaded gas to two opposite heat-retaining chambers of the towers and removing clean gas from two other opposite heat-retaining chambers of the towers, each switching chamber (26, 27, 28) is adapted to be connected alternatively with the loaded gas supply channel (29) and the clean gas removal channel (23) by shut-off devices (50, 52, 53) operated with a control unit.
Description




This invention relates to an apparatus for cleaning pollutant-laden waste gas by regenerative thermal after burning.




Such plants for cleaning in particular waste air containing organic compounds such as solvents are known (cf. EP 0 472 605 B1). Each tower forms a chamber, the organic compounds in the waste air being burned in the combustion space connecting the upper ends of the two chambers. When waste air is supplied to the chamber in the first tower, it is preheated by the heated heat-retaining packing thereof, the organic compounds in the preheated waste air are burned in the combustion space, and the heat-retaining packing in the chamber in the second tower is heated by hot cleaned waste air. Then the supply of waste air is switched to the chamber in the second tower, while cleaned waste air is drawn off from the chamber of the first tower.




In the known apparatus, two pipes with a large diameter corresponding to the high throughput of such a cleaning apparatus and connected via connection pieces to a prechamber below each tower extend in practice in the longitudinal direction under the side-by-side towers for supplying waste air to be cleaned or loaded gas and for removing cleaned waste air or clean gas. The openings of the two connection pieces into the prechamber are provided with shut-off devices each operated by a control unit formed by a piston/cylinder unit disposed below the large pipe




Due to the prechamber disposed under each tower and necessarily having a suitable height for ensuring the function of the shut-off devices, and due to the control units disposed under the pipes, the known apparatus has a considerable height and thus corresponding weight. Also, a shaft or the like must be provided under each control unit for removal thereof and the fixed equipment thereof. Further, the prechambers for operating the shut-off devices under the towers form a dead volume which reduces the cleaning effect.




The problem of the invention is therefore to improve the cleaning power of the known regenerative thermal after burning apparatus while reducing dimensions, weight and costs.




Due to the division of the towers into a plurality of heat-retaining chambers and due to the switching chambers connecting two opposite heat-retaining chambers of the two towers in each case, the channels for supplying loaded gas and removing clean gas are combined together with the switching chambers into a compact unit in the inventive apparatus, so that the apparatus has a much smaller overall volume and weight than known waste gas cleaning apparatuses with regenerative thermal after burning.




The overall volume and weight of the inventive apparatus are reduced further if the two channels for supplying loaded gas with the intermediate switching chambers are disposed one above the other.




Furthermore, one achieves a substantial additional reduction of overall volume and weight of the inventive apparatus if the two towers are disposed at a distance apart so as to form a space and at least part of the unit consisting of the two channels with the intermediate switching chambers is disposed in this space. Moreover, the overall volume is considerably reduced if the control units for the shut-off devices are disposed in the space between the two towers.




Compared to a conventional waste gas cleaning apparatus with regenerative thermal afterburning, the weight and height of the apparatus can thus be reduced according to the invention by more than one third, and the ground plan thereof by about one sixth. This accordingly reduces production costs. It also permits the inventive apparatus to be set up e.g. inside buildings or on a roof.




The inventive apparatus can be delivered as one whole operable unit. The assembly of the apparatus including all electric supply and measuring devices and optionally also the flush gas pipework can thus be done exclusively in the factory, where tests and preliminary operation can also be performed. This shortens erection time on the building site by almost two thirds.




The whole plant can at the same time be supported on the frame bearing the two towers. The whole system need merely be placed on four concrete foundations. One can thus dispense with the elaborate steel substructure required by the known apparatus. Due to the low height of the inventive plant, one can also do without an elaborate stage and stair construction providing access to the combustion chamber. A simple ladder suffices.




The control units for operating the shut-off devices connecting the switching chambers alternately with the loaded gas supply channel and clean gas removal channel, and the flush device are tempered by being arranged in the space between the towers, so that they also work reliably at a cold ambient temperature, for example in the winter.




Due to the arrangement of the clean gas supply channel above the switching chambers and the loaded gas channel therebelow, all lifting rods for moving the By closing bodies up and down and their bearings are located in an area which is not reached by loaded gas- This substantially extends the life of the lifting rods and their bearings in particular when corrosive or dust-laden waste gases are to be cleaned. Suspended installation of the relatively heavy closing bodies on the lifting rods furthermore eliminates the danger of the lifting rods tilting. Also, the inventive apparatus is extremely easy to maintain. Work on the control units and shut-off devices can be done easily and safely because personnel need not go into the apparatus. The same applies to cleaning the lower area of the heat-retaining packings.




Moreover, only small pressure loss differences occur when the direction of gas flow is changed. Longer gas paths on the average result in the combustion space than hitherto although the volume thereof has remained the same, which has a positive effect on cleaning power. Due to the possibility of mounting the burner in the floor rather than on a side wall of the combustion space, and the resulting flame symmetry, there is no necessity to install costly metallic heat-resistant gas turbulators, in particular when the partitions dividing the heat-retaining chambers extend into the combustion space.




The burner can also be disposed on the ceiling of the combustion space, but it saves more space to position it on the floor thereof. Also, a plurality of burners can be provided. The burner or burners can likewise be replaced by other burning devices, for example electric heating elements.




While the lower area of the reactor must generally be insulated from the outside in known waste gas cleaning apparatuses with regenerative thermal afterburning, the surface to be insulated can be reduced by more than two thirds in the inventive apparatus.




The two towers are preferably divided in the inventive apparatus into three heat-retaining chambers by the partitions extending from the bottom to the top, two opposite heat-retaining chambers of the two towers being connected with one joint switching chamber and each of the three switching chambers being adapted to be connected with a flush gas pipe. This embodiment of the inventive apparatus with altogether six heat-retaining chambers achieves a cleaning power of 99.5%. If one control unit or shut-off device fails, the apparatus can be operated as a four-heat-retaining-chamber system instead of a six-heat-retaining-chamber system, still having a cleaning power of 98%. The necessary maintenance work on the failed control unit or shut-off device can be done during four-heat-retaining-chamber operation.




The switching chambers are preferably separated from the loaded gas supply channel and clean gas removal channel by lower and upper partitions, the two partitions of each switching chamber being provided with an opening to be closed by the closing body of the shut-off device.




The two openings of each switching chamber are preferably flush with each other, the two closing bodies for the two openings being displaceable between two stops and spring-loaded away from each other jointly on one lifting rod. The two stops are disposed at a distance apart such that both closing bodies on the lifting rod come to lie simultaneously against the inner side of the two openings of the particular switching chamber, on the one hand, while only one closing body lies against one or the other opening in one or the other partition, on the other hand. This embodiment cuts in half the number of control units, the corresponding periphery and the failure probability. The control units are preferably formed by double-acting pneumatic piston/cylinder units.




If a fan is inserted between the waste gas source and the waste gas cleaning plant for conveying loaded gas into the waste gas cleaning plant, a buffer tank is preferably provided as a pressure fluctuation flattener between the fan and the waste gas cleaning plant.




In the inventive apparatus a catalyst can be provided in addition to the heat-retaining packing or instead of the upper layer thereof. Catalytic regenerative thermal afterburning would then be performed.











BRIEF DESCRIPTION OF THE DRAWINGS




An embodiment of the inventive apparatus will be explained in more detail below with reference to the drawing, in which:





FIG. 1

shows a cross section through the waste gas cleaning apparatus;





FIG. 2

show a section along line II—II in

FIG. 1

;





FIG. 3

shows a longitudinal section along line III—III in

FIG. 1

;





FIG. 4

shows schematically a longitudinal section through the loaded gas supply channel and clean gas removal channel and the intermediate switching chambers with a first variant of the shut-off devices in three different switching positions;





FIGS. 5 and 6

show schematically a longitudinal section through one of the switching chambers with another variant of the shut-off devices in first and second switching positions; and





FIG. 7

shows a plan view of the switching chamber of FIGS.


5


and


6


.











According to

FIGS. 1 and 2

the regenerative thermal afterburning reactor has two towers


1


and


2


connected via combustion space


3


with burner


4


as a device for burning organic or other combustible pollutants in the loaded gas to be cleaned




Below combustion space


3


towers


1


,


2


are separated from each other by space


5


. Burner


4


is provided on floor


9


in the middle of combustion space


3


.




At their lower end towers


1


,


2


are provided with grates


6


. The total inside wall of the reactor, i.e. of towers


1


,


2


including combustion space


3


and the area with space


5


, apart from grates


6


,


7


, is lined with heat insulation


8


.




Each tower


1


,


2


is divided according to

FIGS. 2 and 3

by vertical partitions


10


,


11


,


12


, and


13


into three, substantially equally large heat-retaining chambers


14


,


15


and


16


or


17


,


18


and


19


. Partitions


10


to


13


, which are made of a ceramic material, extend up to the ceiling of the reactor and serve at the same time as heat insulation. Heat-retaining chambers


14


to


19


are disposed so that each heat-retaining chamber


14


,


15


and


16


of one tower


1


is opposite one heat-retaining chamber


17


,


18


and


19


of tower


2


on the other side of space


5


.




Heat-retaining chambers


14


to


19


are filled up to the height of combustion space


3


with heat-retaining packing


20


supported on grate


6


or


7


. The space above heat-retaining packings


20


is formed by joint combustion space


3


.




Heat-retaining packings


20


can be ceramic packing or ceramic honeycomb bodies, for example according to EP 0 472 605 B1. Grates


6


,


7


are supported on frame


21


which carries the total reactor.




In the lower area of space


5


clean gas removal channel


23


extends in the longitudinal direction of the reactor, being formed as rectangular pipe


24


and extending from one to the other face of the reactor. At one end of pipe


23


there is flange


25


to which the clean gas removal pipe (not shown) is connected.




Below clean gas removal channel


23


three switching chambers


26


,


27


and


28


are disposed in tandem, and below switching chambers


26


,


27


and


28


there is loaded gas supply channel


29


.




As evident in particular from

FIG. 4

, switching chambers


26


,


27


,


28


are separated by upper partition


30


and lower partition


31


from clean gas removal channel


23


and loaded gas supply channel


29


. Transverse walls


33


,


34


,


35


, and


36


separate switching chambers


26


,


27


,


28


from one other and close switching chambers


26


and


28


on the outer faces thereof.




Switching chambers


26


,


27


,


28


are, as shown by switching chamber


27


in

FIG. 1

, connected with two opposite heat-retaining chambers


14


and


18


or, as shown in

FIG. 1

,


15


and


18


as well as


16


and


19


of towers


1


,


2


via gas through channels


38


,


39


,


40


,


41


.




Through channels


39


to


41


are separated from one other by transverse walls


33


to


36


(

FIG. 4

) and closed thereby on the faces of the reactor. They end under grates


6


and


7


and are closed at the bottom by bottom walls


42


and


43


.




Loaded gas supply channel


29


extends, like clean gas removal channel


23


, from one to the other face of the reactor, is likewise formed as rectangular pipe


44


and provided at one end with flange


45


to which the loaded gas supply pipe (not shown) is connected.




The two channels


23


,


29


for removing clean gas and supplying loaded gas and intermediate switching chambers


26


,


27


,


28


thus form one unit, optionally together with through channels


38


to


41


.




For alternately supplying loaded gas to two opposite heat-retaining chambers


14


and


17


,


15


and


18


or


16


and


19


of towers


1


and


2


and for removing clean gas from two other opposite heat-retaining chambers


14


and


17


,


15


and


18


or


16


and


19


, switching chambers


26


,


27


,


28


are provided with shut-off devices for closing openings


47


,


48


in partitions


30


,


31


connecting switching chambers


26


,


27


,


28


with clean gas removal channel


23


and loaded gas supply channel


29


in each case.




The shut-off devices consist in each case of lifting rod


50


with one (

FIGS. 5

to


7


) or two (

FIG. 4

) closing bodies formed as lift valve disks


51


or


52


,


53


. The shut-off devices are operated by control units preferably formed as pneumatic double-acting piston/cylinder units


54


, the piston rod thereof being at the same time flush with lifting rod


50


. Piston/cylinder units


54


are disposed in space


5


between towers


1


,


2


.




In the embodiment of

FIG. 4

the two openings


47


,


48


are flush with each other on the top and bottom of each switching chamber


26


,


27


,


28


, i.e. they are disposed coaxially with lifting rod


50


for operating the two lift valve disks


52


,


53


of particular switching chamber


26


,


27


,


28


in this embodiment.




The two lift valve disks


52


,


53


are displaceable on lifting rod


50


between two stops


55


,


56


and loaded against each other by spring


57


.




In their closed position lift valve disks


52


,


53


lie against the inner side of switching chambers


26


,


27


,


28


, i.e. on the underside of upper partition


30


and on the upper side of lower partition


37


. Stops


55


,


56


are disposed at a distance apart such that the two lift valve disks


52


,


53


can be brought simultaneously in the closed position, as shown for the right-hand shut-off device in FIG.


4


. Piston or lifting rods


50


are mounted in each case in bearing


59


above clean gas removal channel


23


through which they extend to switching chambers


26


,


27


,


28


.




Connected to each switching chamber


26


,


27


,


28


is flush gas pipe


60


, as shown schematically in

FIG. 2

, whereby part of the clean gas can be used as the flush gas.




During operation, pollutant-laden loaded gas flows into loaded gas supply channel


29


at


45


. From the loaded gas supply channel it passes at the switching position shown in

FIG. 4

into switching chamber


26


, from which it flows in two directions, i.e. via through channel


39


and the opposite through channel into heat-retaining chamber


17


of tower


2


and into opposite heat-retaining chamber


14


of tower


1


. Loaded gas then flows from the bottom to the top through heat-retaining packing


20


in heat-retaining chambers


14


and


17


, which have been heated in the prior cycle, and takes up the heat.




The gas substreams passing out of heat-retaining packings


20


of heat-retaining chambers


14


and


17


unite in combustion space


3


, the contained combustible pollutants being burned by the flame of burner


4


, whereupon the gas stream divides again to emit its heat to heat-retaining packing


20


in the two adjacent heat-retaining chambers


15


and


18


connected via switching chamber


27


with clean gas removal channel


23


. That is, clean gas leaving the flame of burner


4


flows downward through heat-retaining packings


20


in the two heat-retaining chambers


15


and


18


and then via through channels


38


and


40


into switching chamber


27


, from where clean gas passes through opening


47


into clean gas removal channel


23


.




During this operating state, the third pair of heat-retaining chambers


16


and


19


is flushed with flush gas which is supplied to switching chamber


28


whose upper and lower openings


47


,


48


are closed by the two lift valve disks


52


,


53


. The flush gas thus passes from flush gas pipe


60


via through channel


41


and the opposite through channel to heat-retaining chambers


16


and


19


which were subjected to loaded gas in the previous operating state.




If loaded gas is to flow for example through the two heat-retaining chambers


16


and


19


, piston/cylinder unit


54


for switching chamber


28


is subjected to compressed air such that lifting rod


50


travels upward, causing lower stop


55


to draw both lift valve disks


52


,


53


including spring


57


upward so far that upper disk


52


closes opening


47


to clean gas removal channel


23


. This at the same time draws lower disk


53


upward such that lower opening


48


is opened and loaded gas thus flows from loaded gas supply channel


29


via through channel


41


and the opposite through channel into heat-retaining chambers


16


and


19


of towers


1


and


2


. When heat-retaining packings


20


in heat-retaining chambers


16


and


19


have cooled after a certain time, the next operating state is entered, i.e. switching chamber


28


and through channel


41


as well as the opposite through channel, which still contain waste gas, are flushed with flush gas from pipe


60


. For this purpose the compressed air in pneumatic piston/cylinder unit


54


is relaxed, so that spring


57


urges the two disks


52


,


53


from the inner side of switching chamber


26


against the two openings


47


,


48


(flush position), thereby tightly separating the area to be flushed from loaded gas supply channel


29


and clean gas removal channel


23


. The flush gas can then be passed from flush gas pipe


60


into switching chamber


28


, divides to the left and right into through channel


41


and the opposite through channel and flushes heat-retaining packings


20


in the two heat-retaining chambers


16


and


19


from the bottom to the top. Residual waste gas thus passes into combustion space


3


where it is cleaned by combustion. In the subsequent operating state, heat-retaining chambers


16


and


19


receive clean gas. The shut-off device, i.e. lifting rod


50


with disks


52


and


53


, assumes its third position in which piston/cylinder unit


54


is accordingly subjected to compressed air. Lifting rod


50


thus moves downward. With the aid of upper stop


55


the two disks


52


,


53


together with spring


57


are moved downward until opening


48


to loaded gas supply channel


29


is closed. Cleaned gas can thus leave heat-retaining chambers


16


and


19


at the bottom and pass into clean gas removal channel


23


.





FIGS. 5

to


7


show another variant of the shut-off devices. That is, in this variant the shut-off devices provided for each of the three switching chambers


26


to


28


are two lifting rods


50


with one lift valve disk


51


fastened thereto in each case. Openings


47


,


48


in upper partition


30


and lower partition


31


are obliquely offset from each other, as evident in particular from FIG.


7


. Disks


51


fastened rigidly to lifting rods


50


lie against the top of partition


30


or partition


31


in the closed position.




The variant of

FIGS. 5

to


7


has six lifting rods and thus six piston/cylinder units as opposed to three lifting rods


50


and three piston/cylinder units


54


in the variant of

FIG. 4

, but the variant of

FIGS. 5

to


7


can prove more robust In any case the variant of

FIGS. 5

to


7


also permits a space-saving arrangement due to offset openings


47


and


48


.




The structure and function of the reactor correspond to the embodiment of

FIGS. 1

to


4


.




On the underside of loaded gas channel


29


there are manholes


62


providing access to the particular valve system for maintenance, cleaning or repair work.




Loaded gas channel


29


is suspended below the reactor so that it can be supplied from all directions; one can thus often dispense with an elaborate loaded gas supply pipe guided around corners.

FIG. 3

shows lateral opening


63


on loaded gas channel


29


which can be used for systems supplied in the transverse direction of the reactor.



Claims
  • 1. An apparatus for cleaning pollutant-laden waste gas by regenerative thermal afterburning having two towers containing heat-retaining packing and connected at their upper ends via a combustion space, a channel (29) for supplying loaded gas to be cleaned and a channel (23) for removing clean gas which are adapted to be connected with the two towers by shut-off devices operated by control units for alternately supplying loaded gas and removing clean gas, which comprises:each tower (1, 2) being divided into at least two heat-retaining chambers (14 to 16, and 17 to 19) by partitions (10 and 11, 12 and 13) extending from the bottom to the top of the tower, the heat-retaining chamber of one tower being connected to the opposite heat-retaining chamber of the other tower by one switching chamber (26, 27, 28) in each case, the switching chambers (26, 27, 28) being disposed between the two channels (29, 23) for supplying loaded gas and removing clean gas, and each switching chamber (26, 27, 28) being adapted to be connected alternately with said loaded gas supply channel (29) and the clean gas removal channel (23) by the shut-off device operated with the control units.
  • 2. The apparatus of claim 1, wherein the two channels (29, 23) for supplying loaded gas and removing clean gas are disposed one above the other.
  • 3. The apparatus of claim 2, wherein the clean gas removal channel (23) is disposed above the loaded gas supply channel (29).
  • 4. The apparatus of claim 1, wherein the shut-off devices have lifting rods (50) adapted to move up and down, and closing bodies (50, 52, 53) fastened thereto.
  • 5. The apparatus of claim 4, wherein the control units are formed by piston/cylinder units (54) having piston rods, and the lifting rods (50) are mounted flush with the piston rods of the piston/cylinder units (54).
  • 6. The apparatus of claim 5, wherein the two towers (1, 2) are disposed at a distance apart so as to form a space (5).
  • 7. The apparatus of claim 6, wherein the piston/cylinder units (54) are disposed in the space (5).
  • 8. The apparatus of claim 1, wherein the switching chambers (26, 27, 28) are separated from the clean gas removal channel (23) by a first partition (30) and from the loaded gas supply channel (29) by a second partition (31), said shutoff devices each having a closing body, and each partition (30, 31) being provided with an opening (47, 48) to be closed by the closing body of the shutoff device for connection with the clean gas removal channel (23) and the loaded gas supply channel (29).
  • 9. The apparatus of claim 5, wherein the switching chambers (26, 27, 28) are separated from the clean gas removal channel (23) by a first partition (30) and from the loaded gas supply channel (29) by a second partition (31), said shutoff devices each having a closing body, and each partition (30, 31) being provided with an opening (47, 48) to be closed by the closing body of the shutoff device for connection with the clean gas removal channel (23) and the loaded gas supply channel (29).
  • 10. The apparatus of claim 8, wherein the two openings (47, 48) of at least one of the switching chambers (26, 27, 28) are offset.
  • 11. The apparatus of claim 9, wherein the two openings (47, 48) of at least one of the switching chambers (26, 27, 28) are mounted flush with each other, the two closing bodies (52, 53) are displaceable between two stops (55, 56) which are provided on the lifting rods (50), said closing bodies lying against one or the other inner side of the two openings (47, 48) of the switching chamber (26, 27, 28) in the closed position and being spring-loaded away from each other, the two stops (55, 56) being disposed at a distance such that the two closing bodies (52, 53) can simultaneously come to lie against the inner side of the two openings (47, 48) of the switching chamber (26, 27, 28).
  • 12. The apparatus of claim 1, wherein each tower (1, 2) is divided into three heat-retaining chambers (14 to 16, 17 to 19) by partitions (10 and 11, 12 and 13) extending from bottom to top, and the heat-retaining chambers (14 to 19) are adapted to be connected with a flush gas pipe for flushing.
  • 13. The apparatus of claim 11, wherein each tower (1, 2) is divided into three heat-retaining chambers (14 to 16, 17 to 19) by partitions (10 and 11, 12 and 13) extending from bottom to top, and the heat-retaining chambers (14 to 19) are adapted to be connected with a flush gas pipe for flushing.
  • 14. The apparatus of claim 1, wherein the combustion space has a floor (9) and a combustion device is disposed in the area of said floor (9).
Priority Claims (1)
Number Date Country Kind
197 47 905 Oct 1997 DE
US Referenced Citations (1)
Number Name Date Kind
5297954 Colagiovanni Mar 1994
Foreign Referenced Citations (1)
Number Date Country
WO 9014560 Nov 1990 WO