CA1313026C - Process and apparatus for the adsorption/chemisorption of gaseous components - Google Patents
Process and apparatus for the adsorption/chemisorption of gaseous componentsInfo
- Publication number
- CA1313026C CA1313026C CA000588665A CA588665A CA1313026C CA 1313026 C CA1313026 C CA 1313026C CA 000588665 A CA000588665 A CA 000588665A CA 588665 A CA588665 A CA 588665A CA 1313026 C CA1313026 C CA 1313026C
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- Canada
- Prior art keywords
- gas
- dust
- adsorbent
- nozzle
- process according
- Prior art date
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/06—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with moving adsorbents, e.g. rotating beds
- B01D53/10—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with moving adsorbents, e.g. rotating beds with dispersed adsorbents
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Analytical Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Health & Medical Sciences (AREA)
- Biomedical Technology (AREA)
- Dispersion Chemistry (AREA)
- Separation Of Gases By Adsorption (AREA)
- Filtering Of Dispersed Particles In Gases (AREA)
- Treating Waste Gases (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The invention relates to a process and an apparatus for the adsorption or chemisorption of gaseous materials from a raw gas stream. The raw gas mixed with the adsorbent is led to a cloth filter in the centre of which is a trap tube and dust-guiding plates located laterally and under the trap tube. The raw gas is injected by a nozzle from below into the trap tube. Gas and separated dust recirculates around the trap tube.
This creates an internal dust-gas-recirculation around the trap tube. Moisture can be added to the raw gas and/or the adsorbent and/or the mixture of both, the moisture preferably being steam.
The invention relates to a process and an apparatus for the adsorption or chemisorption of gaseous materials from a raw gas stream. The raw gas mixed with the adsorbent is led to a cloth filter in the centre of which is a trap tube and dust-guiding plates located laterally and under the trap tube. The raw gas is injected by a nozzle from below into the trap tube. Gas and separated dust recirculates around the trap tube.
This creates an internal dust-gas-recirculation around the trap tube. Moisture can be added to the raw gas and/or the adsorbent and/or the mixture of both, the moisture preferably being steam.
Description
- ~31302~
PPcOCESS AND APPARATlJS FOR THE ADSORPTION,/CElEl~ISOR~rION
OF GASEOUS COMPONENTS _OF A~ GAS STREAM
This invention relates to a process and an apparatus for the adsorption or chemisorption of gaseous materials from a raw gas stream through the addition of essentially dry adsorbents, possibly with the characteristics of adsorbents which enter into a chemical reaction with the adsorbed gaseous components in which the reacted adsorbent together with the adsorbent that has not been reacted are separatsd out in a cloth filter and partly carried back to the adsorption process.
In the past a number of processes, mostly in connection with the protection of the environment, have been known, all of which have as their object the adsorption of harmful gas components from a pollution-laden gas stream, by the addition of finely divided adsorbents. In most cases there is additionally a chemical reaction with the adsorbent, in which the harmful gas components are combined permanently with the adsorbent. In this case there is a combination o~
adsorption and chemical reaction, the so-called chemisorption. Often in these cas~s it is essential either to have steam in the gas, or to have a particular degree of dampness in the adsorbent, especially when the chemical reaction of the harmful material with the adsorbent has, as a prerequisite, the preliminary dissolution of the adsorbed component in water.
By contrast with the wet process (for example flue gas washing by the use of slaked slime or susp~nded lime-stone) or the semi-dry process (for example absorption processes in spray dryers with tha addition of an alkali suspension, however with a dry endproduct), these drying processes have the disadvantage that, because of the slow rate of reaction, a long contact time between the adsorbent and the gas to be cleaned is '~
~ . :
13~31~2~
required. If the dwel:L time is not long enough, a large part of the adsorbent, having not taken part in this reaction, is expelled from the process unused together with the endproduct, and is thus lost. From an economic point o~ view, this loss is acceptable only within certain limits.
The degree to which the adsorbent is used is normally expressed in terms of the "molar ratio". A
; molar ratio of 1.0 signifies the complete utilization of the adsorbent, whereas a higher molar ratio indicates the loss of unreacted adsorbent in terms of the extent to which the number exits unity.
In the drying-chemi~orption processes tor adsorption processes) here considered, the molar ratios of the typical process combinations are at least 2.5.
However it is also known that this number can substantially exceed ~Ø From an economic point of view the costs associated with such processes are not ; acceptable. Moreover, high storage costs are created.
All known processes attempt to increass the utilization of the adsorbent by ensuring that the separated-out dust which has only partially been reacted is to a greater or lesser degree recirculated back to the raw stream. Recirculation factors of 5 - lO times, relative to the added fresh adsorbent, are normal, but even so a molar ratio of less than 2.5 is not known.
Apparatus for recycling the partly utilized adsorbent represents a substantial portion of the investment costs, gives rise to additisnal expenditures for measuring and control devices, and generally requires substantial space.
While some o~ these processes simply use the feed conduits to khe dust separator as the reaction space, other processes use an additional reaction chamber of considerable size, in order to increase the contact time hetween the adsor~ent and the gas. In this case the '~
.
.
1313~26 recirculated material is sent to the reaction chamber.
However with this installation as well, only a limited r~circulation quantity can be attained at justifiable expenditures, so that even in this case no satisfactory utilization of the adsorbent is possible.
It is an object of one aspect of the invention to greatly increase the degree of utilization o~ the adsorbent in a dry process, with the smallest possible investment expenditure, and-in such a way as to avoid complicated and costly apparatus for recycling dust.
This object is attained by carrying out the recycling of the dust within a cloth filter, the process being adjustable within wide limits, and such that simultaneously a recirculation o~ gas takes place in order to increase the mixing of adsorbent and gas, this being substantially independent oP the recycled quantity of dust and also being adjustable within wide limits.
In a particular form of the invention, the raw gas and the fresh adsorbent are fed to a cloth filter which is constructed as a bag filter. There a portion o~ the gas is maintained in circulation by means o~ a trap tube in combination with a nozzle, wherein separated dust takes part in the circulation after separation~
By this means, the recirculation of dust takes place within the bag filter which serves as a dust separator, virtually without requiring additional space.
By virtue of the geometric formation o~ the inner space, a flow condition is reached which promotes an intensive mixing of the recirculated dust with the polluted gas.
In accordan~e with the invention, the raw gas with the fresh adsorbent is led to the trap tube through an adjustable nozzle section. Further, the raw yas with the adsorbent and the separated dust is led to the trap tube through an adjustable gap during the inner recycling. In this manner the raw gas with the adsorbent, and the circulating gas with the dust 2 ~
components, are brought together and mixed before entering the trap tube.
It is important to the invention that the cross-section of the nozzle and of the gap be adjustable in such a way that the pressure recovery in the trap tube compensates the loss of recirculation of the gas-dust-mixture outside of the trap tube.
The inner space of the bag filter is so arranged that not only does the already separated dust circulate within wide limits, but also a multiple of the entering raw gas stream is recirculated, adjustable by alteration of the geometric form. The process offers dust recirculation without additional expense (for transportation elements and storage facilitie~), simultaneously with a contact time of adsorbent with gas which is adjustable within wide limits.
The process in accordance with the invention therefore combines the process steps of dust recirculation~ gas recirculation and dust separation in a single apparatus in which the recirculated quantity of dust and the recirculated quantity of gas can be adjusted independently of each other and within wide limits.
The internal racirculation of dust influences the degree of utilization ~the molar ratio) of the adsorbent, and also the degree of separation, whereas the recycled quantity of gas contributes to an intensification of the mixture of gas and dust~
A~cordingly, the process and apparatus offer not only a better utilization of the adsorbent, but also the attainment of a greater degree of separation for the pollutants to be adsorbed. The essence of the invention resides in that both the recirculatèd gas quantity and the recycled dust quantity are so adjusted with respect to each other (through an appropriate combination of nozzle cross-saction and gap) that the degree of - .
.
13~3~2~
utilization and the cleanness of ~he yas correspond to the requiremsnts set forth.
Further it is proposed that the raw gas and/or the adsorbent and/or the mixture of raw gas and adsorbent S be moistened, such that the temperatures are re~ulated in such a way that the gas does not ~all below its dew point. In this way, the fresh adsorbent can be added to the gas stream in its most finely divided ~orm. The moisture can be provided by water, by a corresponding solution, or by steam. Depending upon the operating sequence of the process, the moisture and/or steam can be added to the raw gas stream, to the fresh adsorbent, or to the recirculating gas stream. It is also conceivable to add the moisture during the fine grinding of the adsorbent.
More particularly, this invention provides a process ~or the adsorption or chemisorption of gaseous materials from a raw gas str~-am utilizing the addition of essentially dry adsorbent, possibly with characteristics of adsorbents which have a chemical reaction with the adsorbed gas components, whereby the reacted adsorbent, together with the unreacted adsorbent, are separated in a cloth filter in the form of dust, whereupon they are led back to the adsorption process, charactsrized in that the dust recycling takes place within a cloth ~lter and is adjustable witAin wide limits, in which simultaneously a recycling o~ the gas takes place in order to intensify the mixing of the adsorbent and gas, the gas recycling being largely independent of the recycled guantity of dust, and also being adjustable within wide limits.
An example embodiment of the invention is illustrated in the drawings, and will be described more fully below. In the drawings:
;~
~.
~3~3~26 5a Figure 1 is a section through an apparatus in accordance with the invention;
Figure 2 is a view, to a larger scale, of the entry region of the trap tube;
Figure 3 is a view of a portion of Figure 2, to a larger scale;
Figure 3a shows a variant of one portion of the structure seen in Figure 3; and Figure 4 illustrates a further embodiment of the invention.
Figure 1 shows a cloth filter illustrated as a bag filter 1 of the standard construction. A large number of such bag filters can be provided within a separator installation. In this example embodiment, the bag filter consists of a rectanguIar housing 2 with an upper bulkhead 3, in which the ~ilter bags 8 are suspended. Within a total filter installation, the housings 2 are also described as chambers. Above the bulkhead 3 is a :
;~
`~
:~ 3 ~ 6 clean gas chamber 4 provided with a clean gas conduit 5 through which the clean gas exists. At the lower end there is a dust collecting bunker 6 provided with an outlet valve 7. The filter bags 8 are disposed around a central free space 20 in which a rectangular trap tube 9 is located. The latter has its upper end 10 located at a predetermined distance from the upper ~ilter bulkhead 3. The lower end 11 of the trap tube 9, which extends further downwardly than the filter bags, has an outer lo rounded portion 21, thus defining a chamber in which dust 22 collects (Fig. 3). Fig. 3a shows a further shock losæ reducing shape 21a for the lower end 11 of the trap tube 9. Spaced from the lower end 11 of the trap tube 9 are angulated dust-directing plates 12, which are attached to the housing 2 of the filt~r at hinges 13. They are so arranged as to define an inner opening 23 on the one hand, and on the other to define, with the lower edge 11 of the trap tube 9, a gap 24. By changing the slope angle alpha of the dust directing plates 12, the gap 24 can be changed. Below the opening 23 there i5 provided a nozzle 15 in which the nozzle cross-section can be changed by adjusting the upper nozzle walls 16. To this end the nozzle walls 16 are provided with hinges 17. At the lower portion of the nozzle 15 is connected a raw gas conduit 1~ into which the absorbant can be introduced along a conduit 19 in a fineIy divided condition.
The raw gas, along with the adsorbent which it contains, passes through the nozzle 15 and the trap tube g to reach the upper region of the filter bags 8. The gas is passed through the filter bags, and is substantially freed of dust.- In this manner, a dust layer of increasing thickness forms on the outer surface of the bags 8. According to known methods the dust layer is removed at preset time intervals, this being done automatically utilizing differential pressure. The -\ ~3~ 3~26 clean gas, largely freed from dust and impurities, leaves the. filter 1 through the clean gas chamber 4 and the clean gas pipe 5. In the example embodiment, the quantity o~ fresh absorbant required for the process is mixed with the raw gas stream by appropriate apparatus immediately before the entry into the ~ilter chamber.
It is conceivable to introduce the adsorbent also at other appropriate locations in the system, for example downstream of the nozzle 15~ From the raw gas conduit 18, which can taper in the direction of the stream, the dust-laden gas exists upwardly through a slot of width 25, and is formed into a directed jet by the lateral limit walls 16. By virtue of the hinges 17, the walls 16 can be changed in angulation, as is shown in broXen lines in Figure 3, so that (for example under partial load) the gas outlet from the nozzle 15 can be changed from the origin21 width 25 to the narrower width 26. By this means the impulse of the existing gas stream can be increased, so that, even under partial load, the below-described recirculation can be maintained to the desiredextent.
The spacing of the nozzle 15 from the lower end 11 of the trap tube 9 is determined in accordance with generally known methods. The spacing 27 between the walls of the trap tube 9 is greater than the spacing 25 of the walls of the nozzle 15. In this region the gas stream exiting from the nozzle 15 widens and at the same tim~ is mixed with dust-laden gas in the region of the gap 24, the latter gas being drawn in laterally due to the lower pressure at the nozzle exit. In this manner there is created an overlapping gas stream circulating around the trap tube 9. This brings about an intense mixing of gas and recycled dust, and in this mannPr gives rise to a better material transport factor. By changing the angle alpha and thereby altering the slope of the dust-directing plates 12, the size of the gap 24 ~3~L3~6 for the recycled gas stream can be selected, whereby the quantity of recycled gas can ba changed. The adjustment of the angle alpha can be done during operation by appropriate apparatus.
The dust which falls downwardly during cleaning of the bags is partly taken into the recycled gas stream, and partly removed from the inner recycle system by adjustable openings or slits 28 in the dust-directing plates 12, whereupon it collects in the bunker 6 of the Eilter 1 and is withdrawn through the valve 7.
A further portion of the separated dust runs along the dust-directing plates 12, falling over the forward edges thereof into the gas stxeam exiting from the nozzle 15, the gas stream recycling this portion of the dust into the system due to mixing with the gas. The dust-directing plates 12 consist of two parts which are provided at their ends with slotted holes. After adjustment the plates are fixed with the help of a threaded fastener 1~. By altering the length 29, an additional portion of the dust (i~ the length is shortened) can be removed from the recirculation system and passed into the bunker 6.
Using the appropriate gap 2~, any desired recycling condition Por gas and dust can be set, provided that the impulse o~ the gas exiting from the nozzle lS is sufficient to accelerate the dust and recycled gas up to the exit velocity at the top end of the widening of the stream inside the trap apparatus (having regard to the total exit pressure-loss). When the dust-directing plates 12 hang vertically (angle alpha = 0), only an extremely small amount of dust is recycled, while the recycled gas quantity reaches its maximum, assuming an unchanging exit impulse from the nozzle 15, because the pressure loss in the gap 24 reaches its smallest value.
Conversely the recycled gas can go to zero if the angle alpha is selected to be large enough that the gap 24 is .
~ 3~3~2~
only sufficient to allow the collected dust to pass through. At the same time this constitutes the condition in which the largest possible dust recirculation is achieved, assuming an appropriate selection of the length 29 of the dust-directing plates 12.
Since the quantity of recirculated gas and the quantity of recirculated dust exhibit opposing tendencies when adjustments are made, the concentration of dust in the upwardly flowing gas stream can be selected within wide limits, can be altered, and is restricted only in terms of the impulse or energy balance-of the system. An additional degree of freedom consists in the adjustment of the exit impulse by altering the opening 26 of the nozzle 15, so long as allowance is made for the associated pressure loss.
The degree of separation, apart from other parameters, is dependent upon the sur~ace area which the adsor~ent offers per unit vslume of gas. Since, with a specific granular size, the sum of the surface of all particles is proportional to the dust loading of the gas stream, the separated amount per unit time, in each volume element of the system, is proportional to the solids content of the gas~ The degree of separation is also proportionately influenced by the adsorbent content of the ga~ stream and the recirculated quantity of dust per unit volume.
The influence of the recirculating quantity of gas arises virtually exclusively from the effe~t of an increase of the mixing of gas and dust, and leads to advantageous material transfer conditions in the system.
The dwell time of the gas in the system is strictly determined by the size of the chamber, and cannot be in~luenced - as with any other process utilizing a reaction chamber. By contrast, the contact time relative to the dust can be influenced within wide ~313~2~
limits by altering the dust concentration, and is directly proportional thereto. In this way the molar ratio tutilization factor) of the adsorbent is immediately influenced. In contrast to the systems described earlier representing the state of the art, the process according to the invention, despite lower apparatus cost (elimination of devices for transportation, storage and dosing o~ the recirculated material), allows the recirculation of 20 to 80 times the introduced fresh material. The following conditions are apparent:
The pressure recovery in the trapped tube compensates for the 105s of recirculation of the dust-gas-mixture outside the trap tube.
With a correspondingly higher speed in the nozzle 15 (from a physical poin of view the speed of sound establishes a limit here), the quantity of recirculated dust can be still further increased~ However in the practical case, the actual limit for recirculation is established in terms of the economically replaceable expenditure of energy.
This expenditure of energy is influenced in an important way by the configuration of the no2zle exit 26 and the entrance 11 to the trap tube ~. While the exit 26 from the nozzle 15 must be made as sharp-edged as possible and cannot diverge, since this would lead to a decrease of the exit impulse, the lower edge 11 of the trap ube 9 mu~t be carefully rounded, such that the angle beta must be substantially greater than 0, in order to eliminate shock losses during deflection.
Further achieved by this configuration is the fact that the downwardly falling dust, as seen in cross-hatch in Figure 3, will continue to be stored until it reaches its usual angle of repose 22. The dust which becomes hardened over the course of time leads to a practically ideal stream flow. With dust that flows well tie. with :
~ 3~ 302~
a small angle of repose), the desired stream flow can also be achieved by a corresponding configuration for the plate 21a, as illustrated in Figure 3a. In accordance with Figure 4, a mill 30 is connected to the ; S adsorbent conduit 19, the mill 30 having a delivery conduit l9a for fresh adsorbent. Steam delivery conduits are identified with the numeral 31, including a conduit 31a ~or the mill 30, a conduit 31b into the adsorbent conduit 19, a conduit 31c into the filter space under the filter bags 8, and a conduit 31d into ths raw gas conduit 18.
PPcOCESS AND APPARATlJS FOR THE ADSORPTION,/CElEl~ISOR~rION
OF GASEOUS COMPONENTS _OF A~ GAS STREAM
This invention relates to a process and an apparatus for the adsorption or chemisorption of gaseous materials from a raw gas stream through the addition of essentially dry adsorbents, possibly with the characteristics of adsorbents which enter into a chemical reaction with the adsorbed gaseous components in which the reacted adsorbent together with the adsorbent that has not been reacted are separatsd out in a cloth filter and partly carried back to the adsorption process.
In the past a number of processes, mostly in connection with the protection of the environment, have been known, all of which have as their object the adsorption of harmful gas components from a pollution-laden gas stream, by the addition of finely divided adsorbents. In most cases there is additionally a chemical reaction with the adsorbent, in which the harmful gas components are combined permanently with the adsorbent. In this case there is a combination o~
adsorption and chemical reaction, the so-called chemisorption. Often in these cas~s it is essential either to have steam in the gas, or to have a particular degree of dampness in the adsorbent, especially when the chemical reaction of the harmful material with the adsorbent has, as a prerequisite, the preliminary dissolution of the adsorbed component in water.
By contrast with the wet process (for example flue gas washing by the use of slaked slime or susp~nded lime-stone) or the semi-dry process (for example absorption processes in spray dryers with tha addition of an alkali suspension, however with a dry endproduct), these drying processes have the disadvantage that, because of the slow rate of reaction, a long contact time between the adsorbent and the gas to be cleaned is '~
~ . :
13~31~2~
required. If the dwel:L time is not long enough, a large part of the adsorbent, having not taken part in this reaction, is expelled from the process unused together with the endproduct, and is thus lost. From an economic point o~ view, this loss is acceptable only within certain limits.
The degree to which the adsorbent is used is normally expressed in terms of the "molar ratio". A
; molar ratio of 1.0 signifies the complete utilization of the adsorbent, whereas a higher molar ratio indicates the loss of unreacted adsorbent in terms of the extent to which the number exits unity.
In the drying-chemi~orption processes tor adsorption processes) here considered, the molar ratios of the typical process combinations are at least 2.5.
However it is also known that this number can substantially exceed ~Ø From an economic point of view the costs associated with such processes are not ; acceptable. Moreover, high storage costs are created.
All known processes attempt to increass the utilization of the adsorbent by ensuring that the separated-out dust which has only partially been reacted is to a greater or lesser degree recirculated back to the raw stream. Recirculation factors of 5 - lO times, relative to the added fresh adsorbent, are normal, but even so a molar ratio of less than 2.5 is not known.
Apparatus for recycling the partly utilized adsorbent represents a substantial portion of the investment costs, gives rise to additisnal expenditures for measuring and control devices, and generally requires substantial space.
While some o~ these processes simply use the feed conduits to khe dust separator as the reaction space, other processes use an additional reaction chamber of considerable size, in order to increase the contact time hetween the adsor~ent and the gas. In this case the '~
.
.
1313~26 recirculated material is sent to the reaction chamber.
However with this installation as well, only a limited r~circulation quantity can be attained at justifiable expenditures, so that even in this case no satisfactory utilization of the adsorbent is possible.
It is an object of one aspect of the invention to greatly increase the degree of utilization o~ the adsorbent in a dry process, with the smallest possible investment expenditure, and-in such a way as to avoid complicated and costly apparatus for recycling dust.
This object is attained by carrying out the recycling of the dust within a cloth filter, the process being adjustable within wide limits, and such that simultaneously a recirculation o~ gas takes place in order to increase the mixing of adsorbent and gas, this being substantially independent oP the recycled quantity of dust and also being adjustable within wide limits.
In a particular form of the invention, the raw gas and the fresh adsorbent are fed to a cloth filter which is constructed as a bag filter. There a portion o~ the gas is maintained in circulation by means o~ a trap tube in combination with a nozzle, wherein separated dust takes part in the circulation after separation~
By this means, the recirculation of dust takes place within the bag filter which serves as a dust separator, virtually without requiring additional space.
By virtue of the geometric formation o~ the inner space, a flow condition is reached which promotes an intensive mixing of the recirculated dust with the polluted gas.
In accordan~e with the invention, the raw gas with the fresh adsorbent is led to the trap tube through an adjustable nozzle section. Further, the raw yas with the adsorbent and the separated dust is led to the trap tube through an adjustable gap during the inner recycling. In this manner the raw gas with the adsorbent, and the circulating gas with the dust 2 ~
components, are brought together and mixed before entering the trap tube.
It is important to the invention that the cross-section of the nozzle and of the gap be adjustable in such a way that the pressure recovery in the trap tube compensates the loss of recirculation of the gas-dust-mixture outside of the trap tube.
The inner space of the bag filter is so arranged that not only does the already separated dust circulate within wide limits, but also a multiple of the entering raw gas stream is recirculated, adjustable by alteration of the geometric form. The process offers dust recirculation without additional expense (for transportation elements and storage facilitie~), simultaneously with a contact time of adsorbent with gas which is adjustable within wide limits.
The process in accordance with the invention therefore combines the process steps of dust recirculation~ gas recirculation and dust separation in a single apparatus in which the recirculated quantity of dust and the recirculated quantity of gas can be adjusted independently of each other and within wide limits.
The internal racirculation of dust influences the degree of utilization ~the molar ratio) of the adsorbent, and also the degree of separation, whereas the recycled quantity of gas contributes to an intensification of the mixture of gas and dust~
A~cordingly, the process and apparatus offer not only a better utilization of the adsorbent, but also the attainment of a greater degree of separation for the pollutants to be adsorbed. The essence of the invention resides in that both the recirculatèd gas quantity and the recycled dust quantity are so adjusted with respect to each other (through an appropriate combination of nozzle cross-saction and gap) that the degree of - .
.
13~3~2~
utilization and the cleanness of ~he yas correspond to the requiremsnts set forth.
Further it is proposed that the raw gas and/or the adsorbent and/or the mixture of raw gas and adsorbent S be moistened, such that the temperatures are re~ulated in such a way that the gas does not ~all below its dew point. In this way, the fresh adsorbent can be added to the gas stream in its most finely divided ~orm. The moisture can be provided by water, by a corresponding solution, or by steam. Depending upon the operating sequence of the process, the moisture and/or steam can be added to the raw gas stream, to the fresh adsorbent, or to the recirculating gas stream. It is also conceivable to add the moisture during the fine grinding of the adsorbent.
More particularly, this invention provides a process ~or the adsorption or chemisorption of gaseous materials from a raw gas str~-am utilizing the addition of essentially dry adsorbent, possibly with characteristics of adsorbents which have a chemical reaction with the adsorbed gas components, whereby the reacted adsorbent, together with the unreacted adsorbent, are separated in a cloth filter in the form of dust, whereupon they are led back to the adsorption process, charactsrized in that the dust recycling takes place within a cloth ~lter and is adjustable witAin wide limits, in which simultaneously a recycling o~ the gas takes place in order to intensify the mixing of the adsorbent and gas, the gas recycling being largely independent of the recycled guantity of dust, and also being adjustable within wide limits.
An example embodiment of the invention is illustrated in the drawings, and will be described more fully below. In the drawings:
;~
~.
~3~3~26 5a Figure 1 is a section through an apparatus in accordance with the invention;
Figure 2 is a view, to a larger scale, of the entry region of the trap tube;
Figure 3 is a view of a portion of Figure 2, to a larger scale;
Figure 3a shows a variant of one portion of the structure seen in Figure 3; and Figure 4 illustrates a further embodiment of the invention.
Figure 1 shows a cloth filter illustrated as a bag filter 1 of the standard construction. A large number of such bag filters can be provided within a separator installation. In this example embodiment, the bag filter consists of a rectanguIar housing 2 with an upper bulkhead 3, in which the ~ilter bags 8 are suspended. Within a total filter installation, the housings 2 are also described as chambers. Above the bulkhead 3 is a :
;~
`~
:~ 3 ~ 6 clean gas chamber 4 provided with a clean gas conduit 5 through which the clean gas exists. At the lower end there is a dust collecting bunker 6 provided with an outlet valve 7. The filter bags 8 are disposed around a central free space 20 in which a rectangular trap tube 9 is located. The latter has its upper end 10 located at a predetermined distance from the upper ~ilter bulkhead 3. The lower end 11 of the trap tube 9, which extends further downwardly than the filter bags, has an outer lo rounded portion 21, thus defining a chamber in which dust 22 collects (Fig. 3). Fig. 3a shows a further shock losæ reducing shape 21a for the lower end 11 of the trap tube 9. Spaced from the lower end 11 of the trap tube 9 are angulated dust-directing plates 12, which are attached to the housing 2 of the filt~r at hinges 13. They are so arranged as to define an inner opening 23 on the one hand, and on the other to define, with the lower edge 11 of the trap tube 9, a gap 24. By changing the slope angle alpha of the dust directing plates 12, the gap 24 can be changed. Below the opening 23 there i5 provided a nozzle 15 in which the nozzle cross-section can be changed by adjusting the upper nozzle walls 16. To this end the nozzle walls 16 are provided with hinges 17. At the lower portion of the nozzle 15 is connected a raw gas conduit 1~ into which the absorbant can be introduced along a conduit 19 in a fineIy divided condition.
The raw gas, along with the adsorbent which it contains, passes through the nozzle 15 and the trap tube g to reach the upper region of the filter bags 8. The gas is passed through the filter bags, and is substantially freed of dust.- In this manner, a dust layer of increasing thickness forms on the outer surface of the bags 8. According to known methods the dust layer is removed at preset time intervals, this being done automatically utilizing differential pressure. The -\ ~3~ 3~26 clean gas, largely freed from dust and impurities, leaves the. filter 1 through the clean gas chamber 4 and the clean gas pipe 5. In the example embodiment, the quantity o~ fresh absorbant required for the process is mixed with the raw gas stream by appropriate apparatus immediately before the entry into the ~ilter chamber.
It is conceivable to introduce the adsorbent also at other appropriate locations in the system, for example downstream of the nozzle 15~ From the raw gas conduit 18, which can taper in the direction of the stream, the dust-laden gas exists upwardly through a slot of width 25, and is formed into a directed jet by the lateral limit walls 16. By virtue of the hinges 17, the walls 16 can be changed in angulation, as is shown in broXen lines in Figure 3, so that (for example under partial load) the gas outlet from the nozzle 15 can be changed from the origin21 width 25 to the narrower width 26. By this means the impulse of the existing gas stream can be increased, so that, even under partial load, the below-described recirculation can be maintained to the desiredextent.
The spacing of the nozzle 15 from the lower end 11 of the trap tube 9 is determined in accordance with generally known methods. The spacing 27 between the walls of the trap tube 9 is greater than the spacing 25 of the walls of the nozzle 15. In this region the gas stream exiting from the nozzle 15 widens and at the same tim~ is mixed with dust-laden gas in the region of the gap 24, the latter gas being drawn in laterally due to the lower pressure at the nozzle exit. In this manner there is created an overlapping gas stream circulating around the trap tube 9. This brings about an intense mixing of gas and recycled dust, and in this mannPr gives rise to a better material transport factor. By changing the angle alpha and thereby altering the slope of the dust-directing plates 12, the size of the gap 24 ~3~L3~6 for the recycled gas stream can be selected, whereby the quantity of recycled gas can ba changed. The adjustment of the angle alpha can be done during operation by appropriate apparatus.
The dust which falls downwardly during cleaning of the bags is partly taken into the recycled gas stream, and partly removed from the inner recycle system by adjustable openings or slits 28 in the dust-directing plates 12, whereupon it collects in the bunker 6 of the Eilter 1 and is withdrawn through the valve 7.
A further portion of the separated dust runs along the dust-directing plates 12, falling over the forward edges thereof into the gas stxeam exiting from the nozzle 15, the gas stream recycling this portion of the dust into the system due to mixing with the gas. The dust-directing plates 12 consist of two parts which are provided at their ends with slotted holes. After adjustment the plates are fixed with the help of a threaded fastener 1~. By altering the length 29, an additional portion of the dust (i~ the length is shortened) can be removed from the recirculation system and passed into the bunker 6.
Using the appropriate gap 2~, any desired recycling condition Por gas and dust can be set, provided that the impulse o~ the gas exiting from the nozzle lS is sufficient to accelerate the dust and recycled gas up to the exit velocity at the top end of the widening of the stream inside the trap apparatus (having regard to the total exit pressure-loss). When the dust-directing plates 12 hang vertically (angle alpha = 0), only an extremely small amount of dust is recycled, while the recycled gas quantity reaches its maximum, assuming an unchanging exit impulse from the nozzle 15, because the pressure loss in the gap 24 reaches its smallest value.
Conversely the recycled gas can go to zero if the angle alpha is selected to be large enough that the gap 24 is .
~ 3~3~2~
only sufficient to allow the collected dust to pass through. At the same time this constitutes the condition in which the largest possible dust recirculation is achieved, assuming an appropriate selection of the length 29 of the dust-directing plates 12.
Since the quantity of recirculated gas and the quantity of recirculated dust exhibit opposing tendencies when adjustments are made, the concentration of dust in the upwardly flowing gas stream can be selected within wide limits, can be altered, and is restricted only in terms of the impulse or energy balance-of the system. An additional degree of freedom consists in the adjustment of the exit impulse by altering the opening 26 of the nozzle 15, so long as allowance is made for the associated pressure loss.
The degree of separation, apart from other parameters, is dependent upon the sur~ace area which the adsor~ent offers per unit vslume of gas. Since, with a specific granular size, the sum of the surface of all particles is proportional to the dust loading of the gas stream, the separated amount per unit time, in each volume element of the system, is proportional to the solids content of the gas~ The degree of separation is also proportionately influenced by the adsorbent content of the ga~ stream and the recirculated quantity of dust per unit volume.
The influence of the recirculating quantity of gas arises virtually exclusively from the effe~t of an increase of the mixing of gas and dust, and leads to advantageous material transfer conditions in the system.
The dwell time of the gas in the system is strictly determined by the size of the chamber, and cannot be in~luenced - as with any other process utilizing a reaction chamber. By contrast, the contact time relative to the dust can be influenced within wide ~313~2~
limits by altering the dust concentration, and is directly proportional thereto. In this way the molar ratio tutilization factor) of the adsorbent is immediately influenced. In contrast to the systems described earlier representing the state of the art, the process according to the invention, despite lower apparatus cost (elimination of devices for transportation, storage and dosing o~ the recirculated material), allows the recirculation of 20 to 80 times the introduced fresh material. The following conditions are apparent:
The pressure recovery in the trapped tube compensates for the 105s of recirculation of the dust-gas-mixture outside the trap tube.
With a correspondingly higher speed in the nozzle 15 (from a physical poin of view the speed of sound establishes a limit here), the quantity of recirculated dust can be still further increased~ However in the practical case, the actual limit for recirculation is established in terms of the economically replaceable expenditure of energy.
This expenditure of energy is influenced in an important way by the configuration of the no2zle exit 26 and the entrance 11 to the trap tube ~. While the exit 26 from the nozzle 15 must be made as sharp-edged as possible and cannot diverge, since this would lead to a decrease of the exit impulse, the lower edge 11 of the trap ube 9 mu~t be carefully rounded, such that the angle beta must be substantially greater than 0, in order to eliminate shock losses during deflection.
Further achieved by this configuration is the fact that the downwardly falling dust, as seen in cross-hatch in Figure 3, will continue to be stored until it reaches its usual angle of repose 22. The dust which becomes hardened over the course of time leads to a practically ideal stream flow. With dust that flows well tie. with :
~ 3~ 302~
a small angle of repose), the desired stream flow can also be achieved by a corresponding configuration for the plate 21a, as illustrated in Figure 3a. In accordance with Figure 4, a mill 30 is connected to the ; S adsorbent conduit 19, the mill 30 having a delivery conduit l9a for fresh adsorbent. Steam delivery conduits are identified with the numeral 31, including a conduit 31a ~or the mill 30, a conduit 31b into the adsorbent conduit 19, a conduit 31c into the filter space under the filter bags 8, and a conduit 31d into ths raw gas conduit 18.
Claims (23)
1. A process for the adsorption or chemisorption of gaseous materials from a raw gas stream utilizing the addition of essentially dry adsorbent, possibly with characteristics of adsorbents which have a chemical reaction with the adsorbed gas components, whereby the reacted adsorbent, together with the unreacted adsorbent, are separated in a cloth filter in the form of dust, whereupon they are led back to the adsorption process, characterized in that the dust recycling takes place within a cloth filter and is adjustable within wide limits, in which simultaneously a recycling of the gas takes place in order to intensify the mixing of the adsorbent and gas, the gas recycling being largely independent of the recycled quantity of dust, and also being adjustable within wide limits.
2. The process claimed in claim 1, characterized in that the raw gas and the fresh adsorbent are delivered to a cloth filter constructed as a bag filter, and there a part of the gas is maintained in circulation by means of a trap tube and a nozzle, whereby separated dust enters the recirculation after being separated.
3. A process according to claim 1, characterized in that the raw gas with the fresh adsorbent is fed to the trap tube from an adjustable nozzle cross-section.
4. A process according to claim 1 or claim 2, characterized in that the adsorbent, seen in the direction of the raw gas flow, is fed to a separate location behind the nozzle.
5. A process according to claim 1, claim 2 or claim 3, characterized in that the circulating gas together with a portion of the adsorbent and a part of the separated dust is directed during circulation across an adjustable gap.
6. A process according to claim 1, claim 2 or claim 3, characterized in that the raw gas with the adsorbent and the circulating gas with the dust components are brought together and mixed before entry into the trap tube.
7. A process according to claim 1, claim 2 or claim 3, characterized in that the nozzle cross-section and the gap are adjusted such that the pressure recovery in the trap tube compensate the loss in recycling of the gas-dust-mixture outside the trap tube.
8. A process according to claim 1, characterized in that the upper portion of the nozzle is adjustable by away of hinges, and the hinge axes are adjustable and fixable from outside the filter.
9. A process according to claim 8, characterized in that, in the event of interruption of the process, such as electrical failure or the like, the movable portions of the nozzle automatically move inwardly after the fixing thereof has been removed, whereby the nozzle is closed under appropriate force, such that the nozzle is protected against the entry of dust.
10. An apparatus for carrying out the process according to claim 1, characterized by a cloth filter constructed as a bag filter (1) with a plurality of filter bags (8) distributed around a central free space (20), an upper clean gas chamber (4) and a lower dust bunker (6), in which a trap tube (9) is provided within the free room at a spacing from the clean gas chamber, a nozzle (15) with an adjustable exit cross-section symmetrically arranged at a spacing from the lower end (11), an angulated bulkhead (12) with an opening (23) being provided between the nozzle (15) and the lower end (11) of the trap tube (9), the bulkhead (12) and the lower edge (11) of the trap tube (9) defining a gap (24).
11. An apparatus according to claim 10, characterized in that the bulkhead (12) is constructed in the form of dust-guiding plates.
12. An apparatus according to claim 10, characterized in that the dust-guiding plates (12) have, in cross-section, adjustable openings (28).
13. An apparatus according to claim 10, claim 11 or claim 12, characterized in that the cross-section (26) of the nozzle (15) and of the gap (24) are adjustable.
14. An apparatus according to claim 10, claim 11 or claim 12, characterized in that the dust-guiding plates (12) are movably mounted in bearings (13) and are adjustable in length (29).
15. An apparatus according to claim 11 or claim 12, characterized in that the dust-guiding plates (12) can be raised and lowered without changing their angles.
16. An apparatus according to claim 10, claim 11 or claim 12, characterized in that the lower end (11) of the trap tube (9) has a shape (21) outwardly and/or inwardly which minimizes shock losses.
17. A process according to claim l, characterized in that the raw gas and/or the adsorbent and/or the mixture of raw gas and adsorbent are treated with moisture, such that the temperature of the gas does not fall below its dew point.
18. A process according to claim 17, characterized in that the fresh adsorbent is added to the gas stream in its most finely milled form.
19. A process according to claim 17, characterized in that the moisture is added as steam to the gas or the adsorbent or the mixture of the two.
20. A process according to claim 17, claim 18 or claim 19, characterized in that the steam is introduced into the raw gas prior to entry into the nozzle.
21. A process according to claim 17, claim 18 or claim 19, characterized in that the steam in added to the fresh adsorbent inside the feed conduit.
22. A process according to claim 17, claim 18 or claim 19, characterized in that the steam is introduced into the recirculating gas stream below the filter bags.
23. A process according to claim 17, claim 18 or claim 19, characterized in that the steam is added to the adsorbent during the grinding of the same.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP3801913.2-43 | 1988-01-23 | ||
| DE19883801913 DE3801913A1 (en) | 1988-01-23 | 1988-01-23 | Process and apparatus for the adsorption or chemisorption of gaseous constituents from a gas stream |
| DEP3806863.1 | 1988-01-23 | ||
| DE19883806862 DE3806862A1 (en) | 1988-01-23 | 1988-03-03 | Process for the adsorption or chemisorption of gaseous constituents from a gas stream |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1313026C true CA1313026C (en) | 1993-01-26 |
Family
ID=25864192
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000588665A Expired - Fee Related CA1313026C (en) | 1988-01-23 | 1989-01-19 | Process and apparatus for the adsorption/chemisorption of gaseous components |
Country Status (7)
| Country | Link |
|---|---|
| AU (1) | AU606256B2 (en) |
| CA (1) | CA1313026C (en) |
| CH (1) | CH676330A5 (en) |
| DE (1) | DE3806862A1 (en) |
| FR (1) | FR2626192B1 (en) |
| NO (1) | NO890192L (en) |
| SE (1) | SE468543B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5387406A (en) * | 1990-09-17 | 1995-02-07 | Walther & Cie Ag | Method and device for the adsorption and chemisorption, respectively, of gaseous components in a gas stream |
| FR2692497B1 (en) * | 1992-06-17 | 1994-11-25 | Procedair | Device for the treatment of a gas by contact with particles of solid matter. |
| SE506249C2 (en) * | 1996-04-04 | 1997-11-24 | Flaekt Ab | Apparatus for dispensing and distributing an absorbent material in a flue gas duct |
| US6290752B1 (en) * | 1998-10-22 | 2001-09-18 | Von Roll Umwelttechnik Ag | Device and process for adsorption or chemisorption of gaseous constituents from a gas flow |
| FR2848875B1 (en) * | 2002-12-18 | 2005-02-11 | Pechiney Aluminium | METHOD AND DEVICE FOR TREATING ELECTROLYTIC CELL EFFLUENTS FOR ALUMINUM PRODUCTION |
| FR2887784B1 (en) * | 2005-07-01 | 2008-01-25 | Solios Environnement Sa | PROCESS AND DEVICE FOR TREATING GASEOUS EFFLUENTS CONTAINING PARTICULARLY FLUORHYDRIC ACID |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3992176A (en) * | 1973-10-24 | 1976-11-16 | Kaiser Aluminum & Chemical Corporation | Dry scrubbing tar and fluoride laden gases |
| DE2458171A1 (en) * | 1974-12-09 | 1976-06-10 | Tanaka Giken Nagahama Kk | Gas deodorization system - with forcible humidifier and contact tower for powdered recycled activated clay |
| CA1197074A (en) * | 1981-12-04 | 1985-11-26 | Isaias Loukos | Method and apparatus for cleaning waste gases from aluminum production facilities |
-
1988
- 1988-03-03 DE DE19883806862 patent/DE3806862A1/en active Granted
- 1988-11-24 CH CH437288A patent/CH676330A5/de not_active IP Right Cessation
- 1988-12-29 SE SE8804687A patent/SE468543B/en unknown
-
1989
- 1989-01-16 FR FR8900451A patent/FR2626192B1/en not_active Expired - Fee Related
- 1989-01-17 NO NO89890192A patent/NO890192L/en unknown
- 1989-01-19 CA CA000588665A patent/CA1313026C/en not_active Expired - Fee Related
- 1989-01-23 AU AU28718/89A patent/AU606256B2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| NO890192D0 (en) | 1989-01-17 |
| AU2871889A (en) | 1989-07-27 |
| AU606256B2 (en) | 1991-01-31 |
| SE8804687D0 (en) | 1988-12-29 |
| SE468543B (en) | 1993-02-08 |
| FR2626192A1 (en) | 1989-07-28 |
| DE3806862A1 (en) | 1989-09-14 |
| CH676330A5 (en) | 1991-01-15 |
| FR2626192B1 (en) | 1992-01-10 |
| SE8804687L (en) | 1989-07-24 |
| NO890192L (en) | 1989-07-24 |
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