CA2194556A1 - Regenerative process for the removal and recovery of volatile organic compounds from effluent gases - Google Patents
Regenerative process for the removal and recovery of volatile organic compounds from effluent gasesInfo
- Publication number
- CA2194556A1 CA2194556A1 CA 2194556 CA2194556A CA2194556A1 CA 2194556 A1 CA2194556 A1 CA 2194556A1 CA 2194556 CA2194556 CA 2194556 CA 2194556 A CA2194556 A CA 2194556A CA 2194556 A1 CA2194556 A1 CA 2194556A1
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- Prior art keywords
- voc
- gas stream
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- solvent
- absorbing
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Classifications
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- 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
- B01D53/14—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 absorption
- B01D53/1406—Multiple stage absorption
-
- 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
- B01D53/14—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 absorption
- B01D53/1487—Removing organic compounds
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- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Gas Separation By Absorption (AREA)
- Treating Waste Gases (AREA)
Abstract
A regenerative process for volatile organic compound (VOC's) abatement from various sources of effluent gases containing the same involves contacting a gas stream containing the VOC's with a fine spray of a suitable solvent in which the VOC's are selectively absorbed followed by a recovery operation whereby the organic solvent is regenerated for recycle to the absorbing step and the VOC's are recovered in the liquid form. The process enables VOC's to be efficiently removed from gas streams in a procedure which does not produce any waste by-product.
Description
WO 96/01678 PCT/CA95iO0109 TITLE OF INVENTION
REGENERATIVE PROCESS FOR THE REMOVAL AND
RECOVERY OF VOLATILE ORGANIC COMPOUNDS FROM
EFFLUENT GASES
5FIE~D OF INVENTION
The present invention relates to the removal of volatile organic compounds (VOC's) from gas streams containing the same and recovery of the removed VOC's in liquid form.
Emissions of VOC's have been identified in various industries, including the automobile paint spraying, printing and publishing, wood product fabrications, pulp and paper, pharmaceuticals, adhesives and electronics industry.
The principal problem with such materials is that many VOC's are hydrocarbons which are photo-chemically active and thereby create urban smog and ozone or ozone precursors. Many VoC's are.unpleasantly odorous as well as present health hazards. Regulations exist in many countries to regulate such emissions, in waste water or soils and in air emissions.
To date, many abatement technologies have been introduced to control VOC emissions. Such technologies include:
~ absorption and/or adsorption processes ~ condensation and membrane separation ~ thermal and catalytic incineration ~ biological pro~csQs All the aforesaid abatement processes can be used to control VOC's in gaseous effluents to achieve various degrees of VOC removal. Except for thermal incineration, the above mentioned processes produce some form of waste which requires further expensive treatments. While producing no such waste, thermal incineration involves the generation of undesirable green-house gases, such as carbon dioxide.
SUBSTITUTE SHEET (RULE 26) WO96101678 PCT/CAg5~00~09 SUMMARY OF INVENTlON
The present invention relates to a regenerative process for VoC abatement from various sources of effluent gases containing the same. In the prevent invention, the effluent gas stream containing the VoC's is contacted with a spray of fine liquid droplets of a suitable solvent for the VOC's and the VOC's thereby are absorbed into the solvent droplets and removed from the gas stream. The absorbing operation may be carried out at ambient temperature of about 20 to 25 C or a below ambient temperature.
VoC's may comprise alcohols, esters, ketones and aromatics of various types or other organic compounds and a solvent or solvents from which the spray is formed is chosen to suit the material comprising the VOC's. The VOC's include condensible and non-condensible VOC's, odorous and non-odorous VOC's and differing boiling point VOC's. The fine spray of liguid solvent droplets is formed in a flowing gas stream containing the VOC's in any convenient manner, such as by using dual-fluid spray nozzles.
The liquid droplets having absorbed VoC's can be coalesced to form a ~olution of the VOC's. Such solution may be regenerated and the VOC's recovered therefrom as a concentrated liquid. Such regeneration may be effected in any convenient manner, usually by employing a higher temperature than the absorbing step to drive the VOC's out of the absorbing medium. A regeneration temperature close to the boiling point of the VOC in question is particularly convenient. A combination of gas sparging and steam heating may be utilized to effect a highly efficient stripping of the VoC's, which then may be recovered by condensation as liquids for re-use or for sale. This removal and recovery procedure, therefore, enables low concentrations of VoC's contained in the gas stream to be concentrated and recovered in liquid form.
WO 96/01678 PCI/CA9SiO0~109 The sorbent or combination of sorbents used as the scrubbing medium recovered from the stripper is cooled and recycled to the absorber via the spray nozzles. The overall simplicity of the process results in a decrease in capital and operating costs while retaining high voC
removal efficiencies. As described earlier and shown in the Examples below, the regenerative process of the present invention is broadly applicable to a wide range of VOC's using suitable organic sorbents.
The innovation of the present invention resides with its ability to control VOC's from effluent gases with a sorption process from which no waste is produced. VoC's are removed from the gas stream by a suitable solvent, which then is regenerated and recycled within a closed S loop, while the VOC's are provided in a more concentrated liquid form. The cyclic procedure for removal and recovery of VOC's described herein possesses several advantages over known prior art for VOC removal or disposal. With respect to the prior art incineration process, the p~ocedure of the invention has the advantages of:
- lower operating and capital costs - lower energy consumption - a non-corroding environment resulting from ambient temperature operation - longer operating life - ease of operation - very low maintenance requirement - environmentally friendly process Compared to activated carbon absorption, the procedure of the present invention has the advantages of:
- competitive capital and operating costs - competitive energy consumption - ineP~eitivity to poisoning, blinding or plugging - does not require sorbent replacement - stripping of sorbent conducted at relatively low tPmr~atures (as compared to high temperature WO 96/016~8 PcTlcA9sloo~1o9 stripping of loaded activated carbon and the normal destruction of same by incineration) - handling of a liquid sorbent is much easier than handling a solid sorbent - very low maintenance requirement environmentally-friendly process.
BRI~F D~CRIPTION OF DRAWINGS
FIGURE 1 is a schematic representation of the regenerative process for VOC control in accordance with one embodiment of this invention;
FIGURE 2 is a schematic representation of the nozzle arrangement in two stages in the absorber used in the emboAiment of Figure 1:
FIGURE 3 is a schematic representation of an apparatus used as a prescrubber in the embodiment of Figure l;
FIGURE 4 is a graphical representation of the variation of scrubbing efficiency with time for four VoC's used to represent the paint VOC emission;
FIGURE 5 is a graphic representation of the variation of regeneration efficiency of VoC stripping for one embodiment of this invention;
FIGURE 6 is a graphic representation of the variation of stripping efficiency of four paint VOC's at 140-C using a batch operation as described in Example 3 below: and FIGURE 7 is a graphical representation of the variation of stripping efficiency of four paint VOC's at 140-C using a continuous operation as described in Example 3 below.
G~RA~ DF~CRIPTION OF lNv~llON
The process of the present invention is applicable to the removal and recovery of a variety of classes of volatile organic compounds, with the sorbent being chosen to correspond to the VoC present in the gas stream. Such classes of volatile organic compounds include condensible and non-condensible, odorous and non-odorous VOC's and WO 96~01678 PCr/CA9SiO0409 different boiling point VOC's. Gas streams treated in accordance with the invention may contain a number of different VOC's in which a mixture of sorbents may be used, if required, as the sorbent material.
In general, the sorbents employed in the present invention are medium to high boiling stable organic compounds or mixtures of such compounds. The selective absorbent materials have very low vapour pressures, even at the temper~ture~ that may be employed in the stripping step, for example, in the region of about 100 to 150-C.
As an example, water soluble VOC's, such as alcohols, may be absorbed by contact with an aqueous solution of polyethylene glycol or simply water. Other suitable sorbent materials may be used for other VoC
materials.
Such suitable so~Le..~ materials are usually regenera~le or le_overable simply by applying heat to remove the absorbed VOC's.
The sorbent materials are usually used as a spraying medium to generate finely atomized spray droplets by a unique two-phase, atomizing spray nozzle design that has precise gas-liguid mixture control. Such nozzle allows for the flexibility required to control size and number of droplets neC~cc~ry for efficient removal of solute gases such as VOC's. The two-phase spray nozzle designs are described in U.S. Patent No. 4,893,752 and in published International Patent Application No.
WO92/04127, assigned to the assignee hereof and the disclosure of which is incorporated herein by reference.
The spray zones generated by such nozzles may be achieved in a horizontal or vertical duct, or in spray towers or packed columns, or in any housing.
D~CRTPTTON OF ~ KKED ~BODI~TS
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which Figure 1 is a schematic flowsheet of wos6iol678 2 1 9 4 5 5 6 PcTicA9s/oo4o9 a regenerative procedure for the removal of VOC~s from gas streams, in accordance with one embodiment of the invention.
As seen therein, a gas stream 10 containing VOC's may first be passed through a prescrubber 12 to remove particulate materials 14 from the gas stream while cooling the gas stream to its adiabatic dewpoint temperature and then is pACSe~ through an absorber 16 in which the gas stream is contacted with very fine droplet sprays of a suitable absorbing solvent for the VOC's, to remove the VOC's from the gas stream and provide a clean gas stream 18 which is sent to a discharge stack.
One or more sprays may be formed in the absorber 16 by employing dual-fluid sprays in which very fine liquid lS droplet sprays of the solvent are formed by an atomizing gas countercurrent or cocurrent to the flow of the gas stream through the absorber 16. The fine liquid droplets, which may have a droplet size in the range of about 5 to about 200 microns, preferably about 30 to about 200 microns, provide a surface area for absorption up to about 100 times, usually about 30 to S0 times, that of a conventional packed tower. Such fine liquid droplets may be provided by employing an atomizing gas, such as air, at a pressure of about 10 to about 90 psig.
2S The absorber 16, in effect, is an open-ended duct in which one or more dual-fluid spray nozzles produce a spray pattern which is designed to completely fill the duct while minimizing wall effects. Depending on the kinetics of the sorption process, duct velocities of up to about 40 to 50 fps can be employed with a very low pressure drop through the duct, which compares to a m of about 10 fps gas velocities for a packed bed contactor conventionally used to remove VOC's.
The gas stream flowing through the absorber 16 contacts fine liquid sprays, which causes rapid mass transfer of fine VOC's contained in the flowing gas stream to the liquid droplets to be absorbed therein, WO 9610 16'78 PCI iCA9~100409 thereby providing efficient removal of the VOC's from the flowing gas stream.
While le~s efficient than the spray-contact procedure, there ~ay be employed, as the absorber 16, open spray towers of other constructions, packed bed contactors, tray columns or other conventional gas-liquid contactors. The gas stream leaving the absorber 16 passes through a mist eliminator to coalesce and remove droplets of liquid sorbent from the gas stream before the gas stream passes to the stack 18. The loaded sorbent 20 is passed to a stripper or VoC desorber 22 for recovery of VoC's and regeneration of sorbent.
The loaded sorbent first passes through a heat exchanger 24 wherein it is heated by hot stripped sorbent lg 26 from the VOC desorber 22. In the VOC desorber 22, the loaded sorbent is contacted with a heated stripping gas stream 30 in such a manner that the VOC's are removed from the solvent into the gaseous phase. Such stripping may be effected by any convenient gas-liquid contact device, such as a packed column.
The stripped solvent 26 exiting the VoC desorber 22 is recycled through the heat P~ch~ger 24 and a cooler 32 to the absorber 16 for reuse in contacting the VOC-containing gas stream. The VOC-containing stripping gas stream 34 is r~-e~ through a cooler 36 to a condenser 38, wherein the VOC's are con~Pnsed from the stripping gas stream as a liquid product 40, with the clean gas stream 42 being vented to the stack. Alternatively, where the stripping gas is steam, this may be co-condensed, and the VOC product is then decanted. Theliquid product 40 is a valuable commodity and ~ay be sold.
In the emho~iment shown in Fig. 2, four dual-fluid spray nozzles are illustrated as being employed to effect the spraying of the sorbent solution into the absorber 16. The dual-fluid spray nozzles 50 are arranged in two pairs separated by a demister 52, upstream of the VOC
Wo96/01678 2 ~ q 4 5 5 6 PCT/CA95~00~09 desorbing zone 54 in which two of the nozzles 50 are located and a downstream VOC-absorbing zone 56 in which the other two of the nozzles 50 are located.
In this emho~iment~ lean sorbent solution is fed in parallel by line 44 to the two nozzles 50 located in the downstream zone 56. Partially-loaded sorbent solution recovered in the demister 52 is forwarded by line 46 to be fed in parallel by lines 48 to the nozzles 50 located in the upstream zone 54.
The above-described embodiment illustrated by Fig.
2 shows a two-stage nozzle arrangement using four nozzles to effect the spraying of the sorbent solution into the absorber 16, with two stages spraying two nozzles per stage. However, any desired numher of such spray nozzles may be employed per stage and more than two stages of gas stream contact may be used, depending on the concentration and nature of the VOC's in the gas stream, the affinity and capacity of the sorbent for the VOC's in the gas stream and the degree of desired removal of VoC's from the gas stream.
In addition, a fan may be provided downstream of the conduit to draw the gas stream through the conduit and further to provide further agglomeration of any residual liquid droplets, which may be removed from a demister located downstream of the fan.
The elongate conduit is illustrated as being in a horizontal orientation. However, the elongate conduit may oriented vertically or at an angle. In one embodiment, the elongate conduit may be in a vertical orientation with the inlet end at the lower end of the conduit. The dual-fluid spray nozzles may be arranged to form spray patterns countercurrent and/or co-current to the upward flow of the gas stream through the vertical conduit.
In another embodiment shown in Fig. 3, the prescrubber 12 is further depicted with a wash ring, four nozzles and a mist eliminator to remove the particulates WO 96/Ol678 2 1 9 4 5 5 6 PC-r/CA9~100~09 and undesirable materials from the gas stream from which the VOC's are to be removed. The prescrubber also serves to cool the gas stream to its adiabatic dew point. Water is usually used as the spraying medium to the nozzles s depicted in Fig. 3. Der~n~ng on the amount of particulate and undesirable materials to be removed by the prescrubber, one or more nozzles are used.
EXAMp r~F.~
~Y~m~le 1 This Example illustrates the removal of four typical VOC's generated in a paint spraying operation, in accordance with one embodiment of this invention.
The four VOC's removed from the gas stream were 1-Butanol, Butyl Acetate, 2-Heptanone and Xylene. Three nozzles were employed in an apparatus as illustrated in Fig. 2, in three stages resulting in one spraying nozzle per stage. The duct size used in these runs was 1 ft.
O.D. TABLE 1 below presents the scrubber operating conditions and the resulting VOC removal efficiency in a series of tests. The tests were carried out at ambient tPmr~rature and pressure.
As shown in TABLE l, VOC removal efficiencies of 88%
to 100% were obtained for the four VOC's under study at a very low liquid/gas ratio of 1.2 to 3.0 US gal. per 1000 cubic ft. of gas treated.
W096/01678 21 94556 PcT/CA9Sl00~l09 TABr ~ 1 Removal of VoC's from Paint SpraYina o~eration VOC Sc~ubber ~'on~itions RUN NU~ER
Number of Serial Stages 3 3 3 Number of Nozzles 3 3 3 Nozzle ~ mpter (mm) 3 30*1 30*1 Nozzle yL~l~e (psig3 50 46 65 ~low per nozzle (Usgph) 9 48 81 Me~n Sauter DiqmetPr (microns) 47 36 36 Gas now in (~) 373 470 469 L/G (USgal/1000 ft3) 1.2 1.7 3.0 VOC GAS ~LET
Co~c~lr~lions (~y~) Butyl Acetqte 267 454 559 l-Butanol 503 305 241 2-Heptanone 258 438 525 ~ylenes 203 326 556 VOC RE!~IOVAL ~lCENCY (~Z) Butyl ~ tqte 88 87 91 l-ButaDol 93 96 94 - 2-Heptanone 98 96 98 2~ylenes 100 90 96 WO 96/01678 2 1 9 4 5 5 6 PCr/CA95/00~09 Example 2 This Example illustrates the stripping of the four VoC's absorbed in Example 1 by a regeneration operation in accordance with one embodiment o~ this invention.
In this Example, the lo~ded sorbent obtained from the absorber in Example 1 was continuously regenerated in a 4.25 inch diameter packed column. The effect of air sparging, liquid flow, temperature and increased column packing length were studied. The results presented in TABTE 2 below show that VOC removal efficiencies improve substantially with increased air sparging rate, temperature close to the boiling point of the VoC~s under study and increased packing length.
F~am~le 3 This Example illustrates the regeneration efficiency of VOC stripping in a continuous flow packed column as well as from a batch operation.
The sorbent loaded with four VOC's generated in a paint spray booth was used in both tests. Fig. 6 and 7 present the resulting VOC removal efficiency with respect to sampling time. The results indicste higher and faster stripping in the continuous flow packed column than in the batch operation at a regeneration temperature of 140-C.
From the results presented in Examples 1 to 3, it is therefore feasible to design a continuous absorption and stripping process for the removal of these four VoC's.
SUM~Y OF DISCT~SU~
In summary of thi~ disclosure, the present invention provide~ a novel method of removing and recovering VOC
components from gas streams by a regenerative solvent absorbent procedure in which the VOC components are removed and collectea as a product stream and a VOC-free gas stream is vented, while the solvent absorbent is regenerated for recycle. Modifications are possible within the scope of this invention.
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WO 96iO1678 PCTiCA9S/00409 Example 3 This Example illustrates the regeneration efficiency of VoC stripping in a continuous flow packed column as well as from a batch operation.
The sorbent loaded with four VOC's generated in a paint spray booth ~as used in both tests. Fig. 6 and 7 present the resulting VoC removal efficiency with respect to sampling time. The results indicate higher and faster stripping in the continuous flow packed column than in the batch operation at a regeneration temperature of 140-C.
From the results presented in Examples 1 to 3, it is therefore feasible to design a continuous absorption and stripping process for the removal of these four VoC's.
su~Ma~Y OF DISCT~SU~
In summary of this disclosure, the present invention provides a novel method of removing and recovering VoC
components from gas streams by a regenerative sol~ent absorbent procedure in which the VOC components are removed and collected as a product stream and a VOC-free gas stream is vented, while the solvent absorbent is regenerated for recycle. Modifications are possible within the scope of this invention.
REGENERATIVE PROCESS FOR THE REMOVAL AND
RECOVERY OF VOLATILE ORGANIC COMPOUNDS FROM
EFFLUENT GASES
5FIE~D OF INVENTION
The present invention relates to the removal of volatile organic compounds (VOC's) from gas streams containing the same and recovery of the removed VOC's in liquid form.
Emissions of VOC's have been identified in various industries, including the automobile paint spraying, printing and publishing, wood product fabrications, pulp and paper, pharmaceuticals, adhesives and electronics industry.
The principal problem with such materials is that many VOC's are hydrocarbons which are photo-chemically active and thereby create urban smog and ozone or ozone precursors. Many VoC's are.unpleasantly odorous as well as present health hazards. Regulations exist in many countries to regulate such emissions, in waste water or soils and in air emissions.
To date, many abatement technologies have been introduced to control VOC emissions. Such technologies include:
~ absorption and/or adsorption processes ~ condensation and membrane separation ~ thermal and catalytic incineration ~ biological pro~csQs All the aforesaid abatement processes can be used to control VOC's in gaseous effluents to achieve various degrees of VOC removal. Except for thermal incineration, the above mentioned processes produce some form of waste which requires further expensive treatments. While producing no such waste, thermal incineration involves the generation of undesirable green-house gases, such as carbon dioxide.
SUBSTITUTE SHEET (RULE 26) WO96101678 PCT/CAg5~00~09 SUMMARY OF INVENTlON
The present invention relates to a regenerative process for VoC abatement from various sources of effluent gases containing the same. In the prevent invention, the effluent gas stream containing the VoC's is contacted with a spray of fine liquid droplets of a suitable solvent for the VOC's and the VOC's thereby are absorbed into the solvent droplets and removed from the gas stream. The absorbing operation may be carried out at ambient temperature of about 20 to 25 C or a below ambient temperature.
VoC's may comprise alcohols, esters, ketones and aromatics of various types or other organic compounds and a solvent or solvents from which the spray is formed is chosen to suit the material comprising the VOC's. The VOC's include condensible and non-condensible VOC's, odorous and non-odorous VOC's and differing boiling point VOC's. The fine spray of liguid solvent droplets is formed in a flowing gas stream containing the VOC's in any convenient manner, such as by using dual-fluid spray nozzles.
The liquid droplets having absorbed VoC's can be coalesced to form a ~olution of the VOC's. Such solution may be regenerated and the VOC's recovered therefrom as a concentrated liquid. Such regeneration may be effected in any convenient manner, usually by employing a higher temperature than the absorbing step to drive the VOC's out of the absorbing medium. A regeneration temperature close to the boiling point of the VOC in question is particularly convenient. A combination of gas sparging and steam heating may be utilized to effect a highly efficient stripping of the VoC's, which then may be recovered by condensation as liquids for re-use or for sale. This removal and recovery procedure, therefore, enables low concentrations of VoC's contained in the gas stream to be concentrated and recovered in liquid form.
WO 96/01678 PCI/CA9SiO0~109 The sorbent or combination of sorbents used as the scrubbing medium recovered from the stripper is cooled and recycled to the absorber via the spray nozzles. The overall simplicity of the process results in a decrease in capital and operating costs while retaining high voC
removal efficiencies. As described earlier and shown in the Examples below, the regenerative process of the present invention is broadly applicable to a wide range of VOC's using suitable organic sorbents.
The innovation of the present invention resides with its ability to control VOC's from effluent gases with a sorption process from which no waste is produced. VoC's are removed from the gas stream by a suitable solvent, which then is regenerated and recycled within a closed S loop, while the VOC's are provided in a more concentrated liquid form. The cyclic procedure for removal and recovery of VOC's described herein possesses several advantages over known prior art for VOC removal or disposal. With respect to the prior art incineration process, the p~ocedure of the invention has the advantages of:
- lower operating and capital costs - lower energy consumption - a non-corroding environment resulting from ambient temperature operation - longer operating life - ease of operation - very low maintenance requirement - environmentally friendly process Compared to activated carbon absorption, the procedure of the present invention has the advantages of:
- competitive capital and operating costs - competitive energy consumption - ineP~eitivity to poisoning, blinding or plugging - does not require sorbent replacement - stripping of sorbent conducted at relatively low tPmr~atures (as compared to high temperature WO 96/016~8 PcTlcA9sloo~1o9 stripping of loaded activated carbon and the normal destruction of same by incineration) - handling of a liquid sorbent is much easier than handling a solid sorbent - very low maintenance requirement environmentally-friendly process.
BRI~F D~CRIPTION OF DRAWINGS
FIGURE 1 is a schematic representation of the regenerative process for VOC control in accordance with one embodiment of this invention;
FIGURE 2 is a schematic representation of the nozzle arrangement in two stages in the absorber used in the emboAiment of Figure 1:
FIGURE 3 is a schematic representation of an apparatus used as a prescrubber in the embodiment of Figure l;
FIGURE 4 is a graphical representation of the variation of scrubbing efficiency with time for four VoC's used to represent the paint VOC emission;
FIGURE 5 is a graphic representation of the variation of regeneration efficiency of VoC stripping for one embodiment of this invention;
FIGURE 6 is a graphic representation of the variation of stripping efficiency of four paint VOC's at 140-C using a batch operation as described in Example 3 below: and FIGURE 7 is a graphical representation of the variation of stripping efficiency of four paint VOC's at 140-C using a continuous operation as described in Example 3 below.
G~RA~ DF~CRIPTION OF lNv~llON
The process of the present invention is applicable to the removal and recovery of a variety of classes of volatile organic compounds, with the sorbent being chosen to correspond to the VoC present in the gas stream. Such classes of volatile organic compounds include condensible and non-condensible, odorous and non-odorous VOC's and WO 96~01678 PCr/CA9SiO0409 different boiling point VOC's. Gas streams treated in accordance with the invention may contain a number of different VOC's in which a mixture of sorbents may be used, if required, as the sorbent material.
In general, the sorbents employed in the present invention are medium to high boiling stable organic compounds or mixtures of such compounds. The selective absorbent materials have very low vapour pressures, even at the temper~ture~ that may be employed in the stripping step, for example, in the region of about 100 to 150-C.
As an example, water soluble VOC's, such as alcohols, may be absorbed by contact with an aqueous solution of polyethylene glycol or simply water. Other suitable sorbent materials may be used for other VoC
materials.
Such suitable so~Le..~ materials are usually regenera~le or le_overable simply by applying heat to remove the absorbed VOC's.
The sorbent materials are usually used as a spraying medium to generate finely atomized spray droplets by a unique two-phase, atomizing spray nozzle design that has precise gas-liguid mixture control. Such nozzle allows for the flexibility required to control size and number of droplets neC~cc~ry for efficient removal of solute gases such as VOC's. The two-phase spray nozzle designs are described in U.S. Patent No. 4,893,752 and in published International Patent Application No.
WO92/04127, assigned to the assignee hereof and the disclosure of which is incorporated herein by reference.
The spray zones generated by such nozzles may be achieved in a horizontal or vertical duct, or in spray towers or packed columns, or in any housing.
D~CRTPTTON OF ~ KKED ~BODI~TS
The invention is described further, by way of illustration, with reference to the accompanying drawings, in which Figure 1 is a schematic flowsheet of wos6iol678 2 1 9 4 5 5 6 PcTicA9s/oo4o9 a regenerative procedure for the removal of VOC~s from gas streams, in accordance with one embodiment of the invention.
As seen therein, a gas stream 10 containing VOC's may first be passed through a prescrubber 12 to remove particulate materials 14 from the gas stream while cooling the gas stream to its adiabatic dewpoint temperature and then is pACSe~ through an absorber 16 in which the gas stream is contacted with very fine droplet sprays of a suitable absorbing solvent for the VOC's, to remove the VOC's from the gas stream and provide a clean gas stream 18 which is sent to a discharge stack.
One or more sprays may be formed in the absorber 16 by employing dual-fluid sprays in which very fine liquid lS droplet sprays of the solvent are formed by an atomizing gas countercurrent or cocurrent to the flow of the gas stream through the absorber 16. The fine liquid droplets, which may have a droplet size in the range of about 5 to about 200 microns, preferably about 30 to about 200 microns, provide a surface area for absorption up to about 100 times, usually about 30 to S0 times, that of a conventional packed tower. Such fine liquid droplets may be provided by employing an atomizing gas, such as air, at a pressure of about 10 to about 90 psig.
2S The absorber 16, in effect, is an open-ended duct in which one or more dual-fluid spray nozzles produce a spray pattern which is designed to completely fill the duct while minimizing wall effects. Depending on the kinetics of the sorption process, duct velocities of up to about 40 to 50 fps can be employed with a very low pressure drop through the duct, which compares to a m of about 10 fps gas velocities for a packed bed contactor conventionally used to remove VOC's.
The gas stream flowing through the absorber 16 contacts fine liquid sprays, which causes rapid mass transfer of fine VOC's contained in the flowing gas stream to the liquid droplets to be absorbed therein, WO 9610 16'78 PCI iCA9~100409 thereby providing efficient removal of the VOC's from the flowing gas stream.
While le~s efficient than the spray-contact procedure, there ~ay be employed, as the absorber 16, open spray towers of other constructions, packed bed contactors, tray columns or other conventional gas-liquid contactors. The gas stream leaving the absorber 16 passes through a mist eliminator to coalesce and remove droplets of liquid sorbent from the gas stream before the gas stream passes to the stack 18. The loaded sorbent 20 is passed to a stripper or VoC desorber 22 for recovery of VoC's and regeneration of sorbent.
The loaded sorbent first passes through a heat exchanger 24 wherein it is heated by hot stripped sorbent lg 26 from the VOC desorber 22. In the VOC desorber 22, the loaded sorbent is contacted with a heated stripping gas stream 30 in such a manner that the VOC's are removed from the solvent into the gaseous phase. Such stripping may be effected by any convenient gas-liquid contact device, such as a packed column.
The stripped solvent 26 exiting the VoC desorber 22 is recycled through the heat P~ch~ger 24 and a cooler 32 to the absorber 16 for reuse in contacting the VOC-containing gas stream. The VOC-containing stripping gas stream 34 is r~-e~ through a cooler 36 to a condenser 38, wherein the VOC's are con~Pnsed from the stripping gas stream as a liquid product 40, with the clean gas stream 42 being vented to the stack. Alternatively, where the stripping gas is steam, this may be co-condensed, and the VOC product is then decanted. Theliquid product 40 is a valuable commodity and ~ay be sold.
In the emho~iment shown in Fig. 2, four dual-fluid spray nozzles are illustrated as being employed to effect the spraying of the sorbent solution into the absorber 16. The dual-fluid spray nozzles 50 are arranged in two pairs separated by a demister 52, upstream of the VOC
Wo96/01678 2 ~ q 4 5 5 6 PCT/CA95~00~09 desorbing zone 54 in which two of the nozzles 50 are located and a downstream VOC-absorbing zone 56 in which the other two of the nozzles 50 are located.
In this emho~iment~ lean sorbent solution is fed in parallel by line 44 to the two nozzles 50 located in the downstream zone 56. Partially-loaded sorbent solution recovered in the demister 52 is forwarded by line 46 to be fed in parallel by lines 48 to the nozzles 50 located in the upstream zone 54.
The above-described embodiment illustrated by Fig.
2 shows a two-stage nozzle arrangement using four nozzles to effect the spraying of the sorbent solution into the absorber 16, with two stages spraying two nozzles per stage. However, any desired numher of such spray nozzles may be employed per stage and more than two stages of gas stream contact may be used, depending on the concentration and nature of the VOC's in the gas stream, the affinity and capacity of the sorbent for the VOC's in the gas stream and the degree of desired removal of VoC's from the gas stream.
In addition, a fan may be provided downstream of the conduit to draw the gas stream through the conduit and further to provide further agglomeration of any residual liquid droplets, which may be removed from a demister located downstream of the fan.
The elongate conduit is illustrated as being in a horizontal orientation. However, the elongate conduit may oriented vertically or at an angle. In one embodiment, the elongate conduit may be in a vertical orientation with the inlet end at the lower end of the conduit. The dual-fluid spray nozzles may be arranged to form spray patterns countercurrent and/or co-current to the upward flow of the gas stream through the vertical conduit.
In another embodiment shown in Fig. 3, the prescrubber 12 is further depicted with a wash ring, four nozzles and a mist eliminator to remove the particulates WO 96/Ol678 2 1 9 4 5 5 6 PC-r/CA9~100~09 and undesirable materials from the gas stream from which the VOC's are to be removed. The prescrubber also serves to cool the gas stream to its adiabatic dew point. Water is usually used as the spraying medium to the nozzles s depicted in Fig. 3. Der~n~ng on the amount of particulate and undesirable materials to be removed by the prescrubber, one or more nozzles are used.
EXAMp r~F.~
~Y~m~le 1 This Example illustrates the removal of four typical VOC's generated in a paint spraying operation, in accordance with one embodiment of this invention.
The four VOC's removed from the gas stream were 1-Butanol, Butyl Acetate, 2-Heptanone and Xylene. Three nozzles were employed in an apparatus as illustrated in Fig. 2, in three stages resulting in one spraying nozzle per stage. The duct size used in these runs was 1 ft.
O.D. TABLE 1 below presents the scrubber operating conditions and the resulting VOC removal efficiency in a series of tests. The tests were carried out at ambient tPmr~rature and pressure.
As shown in TABLE l, VOC removal efficiencies of 88%
to 100% were obtained for the four VOC's under study at a very low liquid/gas ratio of 1.2 to 3.0 US gal. per 1000 cubic ft. of gas treated.
W096/01678 21 94556 PcT/CA9Sl00~l09 TABr ~ 1 Removal of VoC's from Paint SpraYina o~eration VOC Sc~ubber ~'on~itions RUN NU~ER
Number of Serial Stages 3 3 3 Number of Nozzles 3 3 3 Nozzle ~ mpter (mm) 3 30*1 30*1 Nozzle yL~l~e (psig3 50 46 65 ~low per nozzle (Usgph) 9 48 81 Me~n Sauter DiqmetPr (microns) 47 36 36 Gas now in (~) 373 470 469 L/G (USgal/1000 ft3) 1.2 1.7 3.0 VOC GAS ~LET
Co~c~lr~lions (~y~) Butyl Acetqte 267 454 559 l-Butanol 503 305 241 2-Heptanone 258 438 525 ~ylenes 203 326 556 VOC RE!~IOVAL ~lCENCY (~Z) Butyl ~ tqte 88 87 91 l-ButaDol 93 96 94 - 2-Heptanone 98 96 98 2~ylenes 100 90 96 WO 96/01678 2 1 9 4 5 5 6 PCr/CA95/00~09 Example 2 This Example illustrates the stripping of the four VoC's absorbed in Example 1 by a regeneration operation in accordance with one embodiment o~ this invention.
In this Example, the lo~ded sorbent obtained from the absorber in Example 1 was continuously regenerated in a 4.25 inch diameter packed column. The effect of air sparging, liquid flow, temperature and increased column packing length were studied. The results presented in TABTE 2 below show that VOC removal efficiencies improve substantially with increased air sparging rate, temperature close to the boiling point of the VoC~s under study and increased packing length.
F~am~le 3 This Example illustrates the regeneration efficiency of VOC stripping in a continuous flow packed column as well as from a batch operation.
The sorbent loaded with four VOC's generated in a paint spray booth was used in both tests. Fig. 6 and 7 present the resulting VOC removal efficiency with respect to sampling time. The results indicste higher and faster stripping in the continuous flow packed column than in the batch operation at a regeneration temperature of 140-C.
From the results presented in Examples 1 to 3, it is therefore feasible to design a continuous absorption and stripping process for the removal of these four VoC's.
SUM~Y OF DISCT~SU~
In summary of thi~ disclosure, the present invention provide~ a novel method of removing and recovering VOC
components from gas streams by a regenerative solvent absorbent procedure in which the VOC components are removed and collectea as a product stream and a VOC-free gas stream is vented, while the solvent absorbent is regenerated for recycle. Modifications are possible within the scope of this invention.
WO 96/01678 2 ! 9 4 5 5 6 PCT/C~9SiO0409 o o ~ ~ ~ ~ o ~ ~
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~-- o ~ ~'I ~ O 0 5 _~ O O O C
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~,C~ E ~, ~~ E o oo ~ ~ '~ ,s: E o '~ ~ ~ '~
WO 96101678 13 PCr/CA9S/00~109 ~ O oo ~ O ,~
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_ O o ~ ~ o ~ 0~ O
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WO 96iO1678 PCTiCA9S/00409 Example 3 This Example illustrates the regeneration efficiency of VoC stripping in a continuous flow packed column as well as from a batch operation.
The sorbent loaded with four VOC's generated in a paint spray booth ~as used in both tests. Fig. 6 and 7 present the resulting VoC removal efficiency with respect to sampling time. The results indicate higher and faster stripping in the continuous flow packed column than in the batch operation at a regeneration temperature of 140-C.
From the results presented in Examples 1 to 3, it is therefore feasible to design a continuous absorption and stripping process for the removal of these four VoC's.
su~Ma~Y OF DISCT~SU~
In summary of this disclosure, the present invention provides a novel method of removing and recovering VoC
components from gas streams by a regenerative sol~ent absorbent procedure in which the VOC components are removed and collected as a product stream and a VOC-free gas stream is vented, while the solvent absorbent is regenerated for recycle. Modifications are possible within the scope of this invention.
Claims (16)
1. A method for the removal and recovery of volatile organic compounds (VOC's) from a gas stream containing the same using a solvent absorbent medium for said VOC's, which comprises:
- passing said gas stream through an elongate conduit having an inlet thereto and an outlet therefrom;
- feeding said solvent absorbent medium in stages to at least two dual-fluid spray nozzles located in and longitudinally spaced apart in said conduit and separated by a first demister which divides the conduit into an upstream VOC absorbing zone in which at least one nozzle is located and a downstream VOC absorbing zone in which at least one nozzle is located;
- injecting lean solvent absorbent medium to said at least one nozzle located in the said downstream VOC
absorbing zone by a first atomizing gas to form a spray pattern containing liquid droplets ranging in size from about 5 to about 200 microns in said downstream VOC
absorbing zone and contacting said gas stream therein;
- absorbing VOC's from said gas stream into said liquid droplets of solvent absorbent medium in said spray pattern in said downstream VOC absorbing zone;
- coalescing said liquid droplets containing absorbed VOC's in a second demister located at the downstream end of said downstream VOC absorbing zone to provide a partially-loaded solvent absorbent medium while permitting a VOC-depleted gas stream to exit said elongate conduit through the outlet therefrom;
- recovering the partially-loaded solvent absorbent medium from the said second demister;
- feeding the said partially-loaded solvent absorbent medium to the at least one spray nozzle located in the said upstream VOC absorbing zone to which a second atomizing gas is fed to form a spray pattern containing liquid droplets of partially-loaded solvent absorbing medium ranging in size from about 5 to about 200 microns in the said upstream VOC absorbing zone and contacting said gas stream therein:
- absorbing VOC's from the gas stream into said liquid droplets of partially loaded solvent absorbent medium in said spray pattern in said upstream VOC
absorbing zone;
- coalescing said liquid droplets containing absorbed VOC's in said first demister to form a fully-loaded solvent absorbent medium while permitting partially-depleted VOC-containing gas to pass to said downstream VOC absorbing zone;
- passing the fully-loaded solvent absorbing medium to a VOC desorber wherein the VOC's are stripped from the fully-loaded solvent absorbing medium in the form of vapor and to provide a VOC-depleted solvent absorbing medium for recycle to solvent absorbent medium feeding step; and - condensing said VOC vapor and recovering said VOC's in liquid form.
- passing said gas stream through an elongate conduit having an inlet thereto and an outlet therefrom;
- feeding said solvent absorbent medium in stages to at least two dual-fluid spray nozzles located in and longitudinally spaced apart in said conduit and separated by a first demister which divides the conduit into an upstream VOC absorbing zone in which at least one nozzle is located and a downstream VOC absorbing zone in which at least one nozzle is located;
- injecting lean solvent absorbent medium to said at least one nozzle located in the said downstream VOC
absorbing zone by a first atomizing gas to form a spray pattern containing liquid droplets ranging in size from about 5 to about 200 microns in said downstream VOC
absorbing zone and contacting said gas stream therein;
- absorbing VOC's from said gas stream into said liquid droplets of solvent absorbent medium in said spray pattern in said downstream VOC absorbing zone;
- coalescing said liquid droplets containing absorbed VOC's in a second demister located at the downstream end of said downstream VOC absorbing zone to provide a partially-loaded solvent absorbent medium while permitting a VOC-depleted gas stream to exit said elongate conduit through the outlet therefrom;
- recovering the partially-loaded solvent absorbent medium from the said second demister;
- feeding the said partially-loaded solvent absorbent medium to the at least one spray nozzle located in the said upstream VOC absorbing zone to which a second atomizing gas is fed to form a spray pattern containing liquid droplets of partially-loaded solvent absorbing medium ranging in size from about 5 to about 200 microns in the said upstream VOC absorbing zone and contacting said gas stream therein:
- absorbing VOC's from the gas stream into said liquid droplets of partially loaded solvent absorbent medium in said spray pattern in said upstream VOC
absorbing zone;
- coalescing said liquid droplets containing absorbed VOC's in said first demister to form a fully-loaded solvent absorbent medium while permitting partially-depleted VOC-containing gas to pass to said downstream VOC absorbing zone;
- passing the fully-loaded solvent absorbing medium to a VOC desorber wherein the VOC's are stripped from the fully-loaded solvent absorbing medium in the form of vapor and to provide a VOC-depleted solvent absorbing medium for recycle to solvent absorbent medium feeding step; and - condensing said VOC vapor and recovering said VOC's in liquid form.
2. The method of claim 1 wherein said VOC's are heat stripped from said fully-loaded solvent absorbing medium and said VOC-depleted solvent absorbing medium is cooled prior to said recycle.
3. The method of claim 1 wherein said solvent absorbent medium comprises a regenerable aqueous medium in which VOC's are absorbed to form a VOC-laden liquid stream and from which VOC's may be desorbed to regenerate said regenerable aqueous medium.
4. The method of claim 1 wherein said solvent absorbent medium comprises a regenerable organic material containing a medium to high boiling stable organic compounds or a mixture of such compounds.
5. The method of claim 4 wherein said regenerable organic materials have very low vapour pressure at the temperatures that are employed in the VOC desorber, for example, in the region of 100°C to 150°C.
6. The method as of claim 1 wherein classes of volatile organic compounds to be treated in the gas stream include condensible and non-condensible VOC's, odorous and non-odorous VOC's and different boiling point VOC's.
7. The method of claim 1 wherein more than two stages of gas stream contact are provided in the elongate conduit with each stage containing one or more dual fluid nozzles followed by a demister.
8. The method of claim 1 wherein the said elongate conduit has a fan located downstream thereof for further agglomeration of liquid droplets from the gas stream, which may be removed from a further demister located downstream of the fan.
9. The method of claim 1 wherein said elongate conduit is provided in a vertical orientation with said inlet end at the lower end thereof and said dual-fluid spray nozzles are arranged to form said spray patterns countercurrent and /or cocurrent to the upward flow of said gas stream through said conduit.
10. The method of claim 1 wherein said elongate conduit is provided in a horizontal orientation and/or at an angle to the horizontal orientation with said inlet end.
11. The method of claim 1 wherein said liquid droplets are sized from about 30 to about 200 microns.
12. The method of claim 1 wherein said atomizing gas is applied to the dual-fluid nozzles at a pressure of about 10 to about 70 psig.
13. The method of claim 1 wherein the VOC-containing gas stream is first conditioned in a prescrubber for the removal of particulates and/or other undesirable materials and for cooling of the gas stream to its adiabatic dew point.
14. The method of claim 1 wherein the absorption operation is carried out at ambient temperature in the absorber.
15. The method of claim 9 wherein the absorption operation is carried out at a temperature lower than ambient temperature.
16. A method for the removal and recovery of volatile organic compounds (VOC's) from a gas stream containing the same using a solvent absorbent medium for said VOC's, which comprises:
contacting said gas stream with said solvent absorbing medium to remove VOC's from said gas stream to provide a purified gas stream and a spent solvent absorbing medium, stripping VOC's from said spent solvent absorbing medium to provide regenerated solvent absorbing medium and a vapor stream containing stripped VOC's, recycling regenerated solvent absorbing medium to said contacting step, condensing VOC's from said vapor stream to form a liquid VOC product stream, recovering said liquid VOC products stream, and venting said purified gas stream.
contacting said gas stream with said solvent absorbing medium to remove VOC's from said gas stream to provide a purified gas stream and a spent solvent absorbing medium, stripping VOC's from said spent solvent absorbing medium to provide regenerated solvent absorbing medium and a vapor stream containing stripped VOC's, recycling regenerated solvent absorbing medium to said contacting step, condensing VOC's from said vapor stream to form a liquid VOC product stream, recovering said liquid VOC products stream, and venting said purified gas stream.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9413714A GB9413714D0 (en) | 1994-07-07 | 1994-07-07 | Regenerative process for removal and recovery of volatile organic compounds (VOCs) from effluent gases |
| GB9413714.8 | 1994-07-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2194556A1 true CA2194556A1 (en) | 1996-01-25 |
Family
ID=10757976
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2194556 Abandoned CA2194556A1 (en) | 1994-07-07 | 1995-07-07 | Regenerative process for the removal and recovery of volatile organic compounds from effluent gases |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU2877895A (en) |
| CA (1) | CA2194556A1 (en) |
| GB (1) | GB9413714D0 (en) |
| WO (1) | WO1996001678A1 (en) |
Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5849983A (en) * | 1996-02-16 | 1998-12-15 | Shell Oil Company | Prevention of shearing of hydrocarbon droplets to aerosol sizes |
| GB9702742D0 (en) * | 1997-02-11 | 1997-04-02 | Ici Plc | Gas absorption |
| KR100321278B1 (en) * | 1999-03-15 | 2002-01-19 | 김성문 | A process for recovering volatile organic solvent |
| KR20010025359A (en) * | 2000-12-19 | 2001-04-06 | 손진목 | Treatment system for volatile organic compounds |
| US7160358B2 (en) * | 2004-04-09 | 2007-01-09 | Turbosonic Inc. | Pollution control in wood products dryer |
| CN103764293A (en) | 2011-03-28 | 2014-04-30 | 磁力技术涡轮声波公司 | Erosion-resistant conductive composite material collecting electrode for WESP |
| US11027289B2 (en) | 2011-12-09 | 2021-06-08 | Durr Systems Inc. | Wet electrostatic precipitator system components |
| AT515710B1 (en) * | 2014-05-13 | 2016-05-15 | Scheuch Gmbh | Method and device for purifying an exhaust gas stream |
| CN108926966A (en) * | 2018-07-19 | 2018-12-04 | 李田英 | A kind of exhaust gas combined treatment equipment and its treatment process containing coating cloud and VOCs |
| US20230002298A1 (en) * | 2019-12-02 | 2023-01-05 | Schlumberger Technology Corporation | Reducing energy consumption in meg reclamation |
| CN113117502A (en) * | 2019-12-31 | 2021-07-16 | 中国石油化工股份有限公司 | Method and device for treating low-concentration organic waste gas |
| CN113828114B (en) * | 2020-06-24 | 2023-04-07 | 中国石油化工股份有限公司 | Method and device for recycling dry spinning medium and spinning method and device |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3047658C2 (en) * | 1980-12-18 | 1987-05-14 | Achenbach Buschhütten GmbH, 5910 Kreuztal | Process for cleaning solvent-containing exhaust air and device for carrying out the process |
| US5198000A (en) * | 1990-09-10 | 1993-03-30 | The University Of Connecticut | Method and apparatus for removing gas phase organic contaminants |
| GB9101336D0 (en) * | 1991-01-22 | 1991-03-06 | Turbotak Inc | Stripping method and apparatus |
| JPH05293332A (en) * | 1992-04-21 | 1993-11-09 | Showa Shell Sekiyu Kk | Method for removing gas containing volatile organic compounds |
| US5277707A (en) * | 1992-07-16 | 1994-01-11 | Cool Fog Systems, Inc. | Air stream solvent vapor remover |
-
1994
- 1994-07-07 GB GB9413714A patent/GB9413714D0/en active Pending
-
1995
- 1995-07-07 WO PCT/CA1995/000409 patent/WO1996001678A1/en active Application Filing
- 1995-07-07 AU AU28778/95A patent/AU2877895A/en not_active Abandoned
- 1995-07-07 CA CA 2194556 patent/CA2194556A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1996001678A1 (en) | 1996-01-25 |
| AU2877895A (en) | 1996-02-09 |
| GB9413714D0 (en) | 1994-08-24 |
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