US2428885A

US2428885A - Method of ventilation including the removal of solvent vapor by adsorption

Info

Publication number: US2428885A
Application number: US492217A
Authority: US
Inventors: Enrique L Luaces
Original assignee: CHEMICAL DEVELOPMENTS CORP
Current assignee: CHEMICAL DEVELOPMENTS Corp
Priority date: 1943-06-25
Filing date: 1943-06-25
Publication date: 1947-10-14
Anticipated expiration: 1964-10-14

Description

Oct. 14, 1947.

E. L. LUACES METHOD OF VENTILATION INCLUDING THE REMOVAL OF SOLVENT VAPOR BY ABSORPTION Filed June 25, 1945 6 Sheets-Sheet 1 iNVENTOR ENRIQUE L. LUACES ATTORN EYS BY Q Ma nuq Oct. 14, 1947. E. L. LUACES METHOD OF VENTILATION INCLUDING THE REMOVAL OF SOLVENT VAPOR BY ADSORPTION Filed June 25, 1945 6 Sheets-Sheet 2 INVENTOR ENRIQ UE L. LUACE eseoaoieooeeee 000 0000000000000 ATTORNEYS Oct. 14, 1947. E. 1.. LUACES a 2,428,885

METHOD OF VENTILATION INCLUDINGTHE REMOVAL OF SOLVENT VAPOR BY ADSORPTION Filed June 25, 1943 6 Sheets-Sheet I5 ATTORN EYS whim it w "5 c ,Q. a, a

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I 1 INVENTOR ENRIQUE L. LUACES' E. LuAcEs METHOD OF VENTILATION INCLUDING THE REMOVAL OF SOLVENT VAPOR BY ADSORPTION Filed June 25, 1945 6 Sheets-Sheet 5 INVENTOR EN RIQUE L. LUACE BY JW ATTORNEYS Oct. '14, 1947. LUACES 2,428,885

METHOD OF VENTILATION INCLUDING THE REMOVAL OF SOLVENT VAPOR BY ABSORPTION Filed June 25, 1943 6 Sheets-Sheet '6 bu municmod Patented Got. 14, 1947 METHOD OF VENTILATION INCLUDING THE REMOVAL OF SOLV SORPTION ENT VAPOR BY AD- Enrique L. Luaces, Dayton, Ohio, assignor, by mesne assignments, to Chemical Developments Corporation, Dayton, Ohio, a corporation of Ohio Application June 25, 1943, Serial No. 492,217

4 Claims. 01. 98-33 This invention relates to method and apparatus for treating air, and more particularly deals with adsorption apparatus and method which may be used advantageously for conditioning air in workrooms and the like by removing therefrom vapors resulting from manufacturing operations and by controlling the humidity of the atmosphere according to the requirements in each case.

In the printing of webs of Cellophane paper and the like at high speeds, and particularly Where multicolor printing is being done, it is of utmost importance that the humidity of the atmosphere in the workroom and the moisture content of the material being printed be controlled within close limits. Itis also necessary that the printing presses or apparatus, which are generally of the gravure type, be open rather than enclosed in order to facilitate the keeping of the successive impressions in proper register by the operator. In other words, it is requisite that the operator have free access at all times to the mechanism controlling the register of the successive printing units, as otherwise the resulting multicolor print will be off-register and unsalable. This feature is of particular importance in the 2 humidity of the air in the workrooms at all times and to maintain the atmosphere in the workrooms substantially free from solvent vapors in a concentration which would prove unhealthful, or which would create a fire or explosion hazard.

The present invention will be fully understood from the following description taken in connection with the annexed drawings, wherein:

printing of continuous webs of material such as Cellophane and paper, since the removal of a portion of the printed web from the finished roll of material due to ofi-register is a costly operation, wasteful of time, labor and material.

Inks used in gravure printing are generally large in volatile solvents. These solvents include water immiscible solvents such as coal tar and petroleum fractions and also water miscible solvents such as ethers, ketones, alcohols and esters. Since it is requisite that the printing presses be open and readily accessible to the operator, it is necessary to remove large volumes of air carrying solvent vapors from the workroom. Since it is also necessary that humidity conditions be maintained within close limits in the workroom and in the storage rooms wherein the material to be printed is stored, the exhausting of such large volumes of air from the workroom in order to maintain proper working conditions and avoid fire and explosion hazards is extremely costlyand wasteful unless it is possible to remove from the air exhausted from the workrooms the solvent vapors contained therein and to return the denuded air to the workrooms free from solvent vapors and at substantially the same temperature and humidity as When exhausted therefrom.

According to the present invention, a system of operation has been developed which makes it possible eifectively to control the temperature. and

Fig. 1 is a diagrammatic view of a system for circulating air through a workroom and for maintaining the air at predetermined temperature, humidity and solvent vapor concentration;

Fig. 2 is an elevational view, partly broken away, of an adsorber which may be employed in the system of Fig. 1;

Fig. 3 is an elevational View, partly broken away, illustrating a second type of adsorber which may be employed in the system of Fig. 1;

Fig. 4 is an elevationalview, partly bro-ken away, of a third type of adsorber which may be employed in the system illustrated in Fig. 1;

Fig. 5 is an elevational view, partly broken away, of a fourth type of adsorber which may be used in the system illustrated in Fig. 1; and

Fig. 6 diagrammatically illustrates an operating scheme such as may be employed in the operation of the system illustrated in Fig. 1 using any of the several types of adsorber illustrated in Figs. 2, 3, 4 and 5.

Referring to the drawings in detail, in Fig. 1, I0 is a workroom such as may be employed for printing Cellophane or paper in multicolor gravure presses at high speeds. II is a filter and flame arrestor adapted to remove dust, lint, scrap, and the like, from the air exhausted from the workroom Ill and to prevent the propagation of fire which might originate accidentally in the workroom. I2 is an exhaust fan for removing air from the workroom III. I 3a, I31), I30, and I3d are adsorbers provided with a plurality of beds of adsorbent I4 such as activated carbon and connected through conduits I5a, I522, I50, and I5d, and valves Ilia, I 6b, I60, and I6d to the distributing headers I111, I11), I10, and "(Z on the adsorbers I3a, I3b, I30, and H11, and the duct I 8 which carries the air exhausted from the workroom II] by the exhaust fan I2.

Air exhausted from the workroom In by the exhaust fan I2 enters the adsorbers I3a, I3b, I30, and I3d through the headers Ila, I11), I10, and H12, respectively, and is discharged from the adsorbers I 3a, I 3b, I 30, and I 3d through the exhaust lines I9a, I91), I90, and I9d, respectively, which are connected through conduuits 20a, 20b, 2Ib, ZIc, and Zld 3 to the duct 22 connected with a pressure blower 23 which discharges into a humidity and temperature control chamber 24 and thence to the workroom II].

A pressure blower 25 discharges fresh air at ambient temperature through a heat exchanger 26 and duct 21 into adsorbers l3a, I31), I30, and

I3d, respectively, through valve-s 28a, 28b, 280, I50, and I501, and

and 28d, conduits Ia, I55, headers Ha, I'Ib, I10, and "ti, the latter being connected, respectively, to adsorbers Isa, I31), I30, and Hill. Air discharged by pressure blower 25 and entering the adsorbers I311; I31), I30, and I3d is discharged, respectively, through valves 29a, 29b, 29c, and 29d.

Steam from a source not shown is' admitted into adsorbers I3a, I31), I30, and I311 through valves 39a, 30b, 30c, and 3501, respectively, and distillate from the adsorbersv I3a, I31), I30, and Hal is removed through valvestla, 3Ib, 3Ic, and 3Id conduits 32a, 32b, 32c, and 3211, respectively, and caused to flow into conduit 33, and thence into thecondenser 34'. Water enters the condenser 34 through line 35 and valve 36 and leaves through line 31. Condensate flows out of the condenser through line 38 into decanter 39 from which water immiscible liquid is removed through line 40 and water miscible liquid and condensate through line 4| provided with a gooseneck 42.

In use, the system illustrated in Fig. 1 operates as follows:

The adsorbers I311, I31), I30, and lad are intended to operate in successive cycles of adsorption, steaming, and drying and cooling. Two of the adsorbers are maintained in the adsorption cycle at all times, while one of the other two adsorbers will be in the steaming cycle and the fourth will be in the drying and cooling cycle. The operation of the a dsorbers in the adsorption cycle must be regulated in such manner that one is only half saturated when the other is fully saturated.

Assuming that the system'has been in operation for some time,.the status of the four ad sorbers shown might be the following:

Adsorber I3a Half saturated Adsorber I3b Drying and cooling Adsorber I3c Steaming Adsorber I3d Fully saturated- At this point, the blower 25 is stopped and the valves 28?!) and 291) on adsorber I31) are shut off. Valves 2Ib and Ifib are then opened thus permitting air exhausted by the fan I2 from the workroom l0 and discharged through duct IB to enter the adsorber I3b through valve IBb, conduit I52), and header l'lb, thence through the beds of adsorbent I4, the outlet I 9b, the conduit 2%, and valve 2th into the duct 22 and through the pressure blower 23 and the humidity andtemperature control chamber 24 into the workroom IO. U

Immediately after opening the valves 2Ib and IBb on adsorber 13b, the valves Ifid and 2Id are shut thus stopping the flow of air through adsorber I311; At this point adsorber I3a will be half saturated, adsorber I3b will have entered the adsorption cycle, adsorber I30 will be com: pleting the steaming cycle, and adsorber I3d will be fully saturated and ready to be steamed. To this end, valves 30c and 3Ic on adsorber lBe'are shut and the valves 3Id and 3911 on adsorber I3d will be opened. This places the adsorber I30 in condition to be dried and cooled and causes the adsorber I3d to enter in the steaming cycle.

Steam flowing into adsorber I3d through valve 30d will flow downwardly through the lower bed I4 and thence outwardly through the valve 3IOZ into the line 33 and the condenser 34' carrying with it vapors of solvents removed by the lower bed of the adsorber I3d while said adsorber was in'the steaming cycle. At the same time, steam entering the adsorber I3d through the valve Sud will flow upwardly through the upper bed I l and thence through the header I'Id into the lower portion of the adsorber IM and from there through valve 3Id into the line 33 and the condenser 34.

Having placed the adsorber I3d in the steaming cycle, the next step is to place the adsorber I30 in the drying and cooling cycle. To this end, valve 290 and valve 280 are opened, steam is caused to flow through the heat interchanger 25, and the blower 25 is placed in motion. Air discharged by the blower 25 will be heated in passing throughthe heat interchanger '25 and will then flow through duct 21, valve 280, conduit I50, and header ITc into the top and bottom portions ofthe'adsorber I30. The warm air will pass downwardly through the upper bed of adsorbent and upwardly through the lower bed of adsorbent, and thence outwardly through the outlet I5c and thevalve 250 and will be discharged into the atmosphere. This condition will continue until the temperature rise in the beds of adsorbent is sharp and steady and indicates that the beds of adsorbent are fully dried. At that point the steam flowing into heat interchanger 26 is shut off and the blower 25 is continuedin movement until the temperature of the beds in the adsorber I3c has dropped to substantially room temperature. i

The cyclesof operation of the several adsorbers are so planned, that at this point, when the adsorber I30 is once again ready to enter the adsorption cycle, the adsorber [3a, will have reached saturation, the adsorber {301 will have reached the end of the steaming cycle, and the adsorber I3b will be half through the adsorption cycle. Thereupon the flowingof air to be treated is begun through adsorber I30 and ceased in adsorber I312. At the same time adsorber I3d passes from the steaming cycle into the drying and cooling cycle, and the adsorber I3a enters the steaming cycle. This general scheme of operation will be fu'rther described hereinafter in connection with Figlfi. A

Referring now to Fig. 2, 43 is an adsorber supported on a skirt 4 and provided with an upper bed 45 and a lower' bed 46. Each of the beds issupported on an' angle iron ring 41 and comprises a foramifnous plate 48 and a wire mesh screen 49. The dome is provided with a manhole 50 through which adsorbent may be loaded to. form the top bed team the body of the adsorber is provided with a manhole 5| through which the adsorbent may be loaded to form the bottom bed 45. The manhole 52 serves to empty theupper bed and the manhole 53 serves to empty the lower bed. Asteam distributor 5 is provided intermediate the beds 45 and st and the flow of steam thereto from a source not shown is controlled by the valve 55. A header 55 connects the upper portion ofthe adsorber with the bottom portion thereofland is provided with a conduit 51 provided with a valve 58 and with a conduit 59 provided with a valve 60. On the shell of the adsorber intermediate the

beds

45 and 45 is provided a conduit 5| provided with a valve 62, and the conduit BI is provided with a branch conduit 63 provided with a valve 64. At the bottom of the adsorber there is 'a trap 65 provided with a valve 66 and a line 61 for removing distillate, and also provided with a valve 68 and a line 69 for the removal of condensate and for draining sludge from the bottom of the trap 65.

In operation, air to be treated enters the adsorber through valve 58, conduit 51, and header 56, traverses the bed 45 downwardly and the bed 46 upwardly and exits through conduit BI and valve 62. During the steaming cycle, steam enters the distributor 54 through valve 55 and flows upwardly through bed 45 and downwardly through bed 46. The steam flowing upwardly through bed 45 leaves the adsorber through header 56 and enters the bottom portion of the adsorber where it commingles with the steam flowing downwardly through bed 46. The distillate leaves the adsorber through valve 66 and distillate line 61 which are connected to the trap 65. During the drying and cooling cycle air enters the adsorber through valve 69, conduit 59, and header 56, flows downwardly through bed 45 and upwardly through bed 46, and exits through conduit 6|, branch conduit 63, and valve 64.

Fig. 3 illustrates an adsorber 19 supported on a skirt H and provided with

adsorbent beds

12, 13, and 14, each of which is supported on an angle iron ring and comprises a foraminous plate 16 and a wire mesh screen 11. The adsorber is provided with manholes 18, 19 and 89 intended for loading adsorbent to form

beds

12, 13, and 14, respectively, and is further provided with manholes 8|, 82, and 83 intended to empty the

beds

12, 13, and 14, respectively. Air to be treated enters the adsorber through valve 84, conduit 85, and header 86 and flows upwardly through bed 13 and downwardly through

beds

12 and 14. That portion of the air which flowed upwardly through bed 13 commingles with that portion of the air which flowed downwardly through bed 12 and exits through the upper connection of the header 81, and that portion of the air which flowed downwardly through bed 14 exits through the lower connection of the header 81. All of the treated air is exhausted through the valve 88.

During the steaming cycle, steam is introduced through valve 89 into the header 81 and flows upwardly through

beds

12 and 14 and downwardly through bed 13. The distillate of beds 13 and 14 commingles and exits through the lower connection of the header 86 and the distillate from bed 12 exits from the upper connection of the header 86, and the whole is exhausted through valve 99.

During the drying and cooling cycle, air enters through the valve 9| and is distributed by the header 86. It flows downwardly through bed 12 and bed 14 and upwardly through bed 83. Those portions of the air flowing upwardly through bed 13 and downwardly through bed 12 commingle and exit together through the upper connection of the header 81 and that portion of the air which flows downwardly through bed 14 exits through the lower connection of the header 81. The whole is exhausted from the adsorber through valve 92 associated with header 81.

The adsorber is provided with a trap 93'provided with a drain 94 and a valve 95.

Fig. 4 illustrates an adsorber 96 supported on a skirt 91 and provided with beds of adsorbent 98 and 99 each of which is supported on the shell I99 of the adsorber and the center riser I9I by means of the angles I92 and I93, .Each bed comported on a skirt I25 6 prises a, foraminous plate I94 and a wireimesh screen I95.

The body of the adsorber is provided with manholes I96 and I91 which serve to permit loading of the adsorbent to form the beds and with manholes I98 and I99 which serve to empty the beds. During the adsorption cycle, air to be treated enters the adsorber through valve I I9 and conduit III which connects the bottom of the adsorber and flowsin'part upwardly through bed 99 and in part upwardly through riser I9I and downwardly through bed 98 and both portions exit together through conduit I I2 and valve II3.

In the steaming cycle, steam enters the steam distributor II4 through a steam feed line I I5 provided with a valve H6 and flows downwardly through bed 99 into the bottom portion of the adsorber and upwardly through bed 98 and then downwardly through riser I9I through which it flows to the bottom portion of the adsorber. The distillate line II1 provided with valve H8 is connected to trap II9. A drain line I29 provided with a valve I 2I is also connected to the trap H9 and serves to remove condensate and sludge from the bottom of the adsorber.

During the drying and cooling cycle air enters the adsorber through valve I22 and conduit II I and is distributed within the adsorber in the same manner as the air to be treated is distributed during the adsorption cycle. The drying and cooling air flows out of the adsorber through conduit [I2 and valve I23.

In Fig. 5 is illustrated an adsorber I24 supand provided with beds of adsorbent I26, I21, and I28. Bed I26 is supported on the shell I29 of the adsorber by an angle I39 and comprises a foraminous plate I 3| and a wire mesh screen I32. The beds I21 and I28 are each supported by angles I33 on the shell I 29 of the adsorber and by angles I34 on the riser I35.

The body of the adsorber is provided with manholes I36, I31, and I38 intended to serve for charging adsorbent to form the beds I26, I21, and I28, respectively, and the manholes I 39, I49, and MI are intended to empty the beds I26, I21, and I28, respectively.

Air to be treated enters the adsorber through valve I42 and header I43 and'flows downwardly through beds I26 and I28 and upwardly through bed I2 1. The portion flowing downwardly through bed I26 and the portion flowing upwardly through bed I 21 commingle within the space between these two beds and then flow downwardly through the riser I35 to the bottom of the adsorber. At this point the portion flowing upwardly through bed I21 and the portion flowing downwardly through bed I26 commingle with the portion flowing downwardly through bed I28 and the whole exits through conduit I44 and valve I45.

During the steaming cycle steam enters through valve I46 and flows into the adsorber through conduit I44. One-third of the steam entering the adsorber through conduit I44 will flow upwardly through bed I28 and thence into conduit I43 and two-thirds of the steam entering the adsorber through conduit I44 will flow upwardly through riser I35 into the space between the beds I26 and I21 and half of it will then flow upwardly through bed I 26 and into conduit I43 and the other half will flow downwardly through bed I21 into the conduit I43. The distillate will exit from conduit I 43 through valve I41.

During the drying and cooling cycle air will enter, through valve I48 and header I43 and will travel through the adsorber in the same manner .to the section of thepressure en a es 7 astheair to'beit'reated' travels" in the adsorption cycle. The drying and cooling air is: exhausted from the adsorber through: conduit, I44 and-valve I49- Those skilled in the art will understand; that while the flow of"dryingandfcooling air has been indicated in-eachcasettobe'in the same direction as the flow of air'to bei-treated, the apparatus'and method of the present} invention are'not limited in that sense, since the drying and: cooling air could be passedthrough the. adsorber countercurrent to the flow of air: to be treated with equal satisfaction; Likewise, those skilled. in the art will understand: that inthe case of the adsorbers"illustrated in Fig. 3and'Fig. 5, the flow of steam may befreversed without materially influencing the ultimate-results. Generally speaking; it is preferred'practice'to have the steam now in a; direction opposite to'thedirection of flow of the air to be treated; but this is'no't requisite. The direction of'fiow of each of the fluids passedthrough an adsorber i influenced primarily by local conditions and individual preference.

The operating scheme illustrated in Fig. 6 shows the relative operatin i cycle of: each of four adsorbers in a typical. system; The adsorbers are numbered I,.II, III and IV", andthecharacters .A, B, c, D, E, F, G, H, J, andK. are intended to indicate intervals of time. In'the specific instance illustrated in Fig. 6 each of the time intervals A, B, C, D, E, F, G, H, J; and K is equivalent to 20 minutes; therefore, in the case of adsorber I, for example, it will adsorb 40 minutes (A and B), it will steam'ZO' minutes (C) and it will dry and cool 20 minutes (D).

It will be noted from Fig. 6 that during the time interval A adsorber I'and. adsorber III are in the adsorption cycle, adsorber- II is in the steaming cycle, and'adsorber IV is in the drying and cooling cycle. Likewise, in the time'interva1 B the adsorbers I and IV are in theads'o'rption cycle, the adsorber II is in the drying and cooling cycle, and the adsorber III is in the steaming cycle. It will be noted, therefore, that adsorber I is in thefirst stage 'or first lap of the adsorption cycle during the time interval A while the ad'sorber III is in the last stage or second lap of the adsorption cycle, while during the time interval B the adsorber I is in thelast stage or second lap of the adsorptioncycle while" the adsorber Kids in the initial stage or first lap of the adsorption cycle. It will be noted, in addition, that at no time in the operation of the system illustratedin Fig. 6 are more or lessthan two adso'rbers in the" adsorption cycle, nor more than one'adsorber'in the st eamingv cycle or in the drying cycle.

Referring back to Fig. 1, fresh air is'admitted blower 23- through conduit 50 provided with fiow regulator I51, and is thus mixed with process air in passingthrough said-pressureblower 23. The humidity and temperature control'chamberld' is intended for the purpose of controlling the temperature and the humidity of the air'returned tothe workroom ill by the pressure blower ZS a-fter'it has been freed of solvent vapors inpassing throughthe adsorption apparatus 'which'fo'rms part of the overall system in admixturewi'th make-up air entering through conduit I50. This is accomplished by adding moisture to'the air(as,v with a" spray of water or steam) under controlledic'onditions or by removing moisture therefrom (as by refrigeration or adsorption), and by increasing or decreasing the temperature as mightbe necessary. However, the details of-constructiona'nd. opera- 82 tion of the humidity andv chamber 24' do not form a part of; the present invention and need not be described in detail herein; It will sufilce to state that the humidityand temperature control. chamber 24 operates au'tomatically'as an integral part of the system illustrated in Fig. 1 wherein all of the individual operations are automatically controlled by suitable instruments to form a coordinated process. The method of the present invention can only operate successfully under such coordinated conditions since it is imperative that the concentration of moisture and of solvent vapor in the; atmosphere of ;the workroom, as well as the temperature of the atmosphere, be maintained in a definite predetermined relationship in order to insure proper operative conditions not only from the point of view of health, fire and explosion hazards, but also from the point of view of production, efficiency and economy as reflected by accuracy of register in high speed multicolor printing of the web of Cellophane or paper or'the like being processed in the workroom It].

It will be understood that while there have been described herein certain specific embodimerits of the present invention, it is not intended that this invention be limited to the specific details of construction, arrangement of parts, procedures, proportions, times and materials herein described or illustrated in the drawings, in View of, the fact that this invention is susceptible to modifications according to individual preference and conditions without departing from the spirit of this disclosure and the scope of the appended claims.

The structure of the adsorption units herein described is claimed in copending application Serial No. 508,518, filed November 1, 1943, as a division hereof, and the adsorption method herein described is claimed in copending application Serial No. 508,519, filed November 1, 1943, as a division hereof.

I claim:

1. The method of continuously maintaining predetermined conditions of temperature, humidity and solvent vapor content in the atmosphere of an enclosure wherein said solvent is used comprising, exhausting atmospheric air from the enclosure, removing solvent content from said air in a first adsorber of a-bank of adsorbers while simultaneously subjecting a second adsorber to steam, removing solvent from said atmosphere in athird adsorberand drying and cooling a fourth adsorber, all in a first cycle; then removing solvent content of saidair as withdrawn from said enclosure in said first adsorber, drying and cooling said second adsorber, subjecting said third adsorber to steam' and removing solvent content from said air as Withdrawn from aid enclosure in said fourth adsorber, all in a'second cycle, then subjectingsai-d'first adsorber to steam, removing solvent content from said airas withdrawn from saidenclosureinsaid second adsorber, drying and cooling said third adsorber and removing solvent content from said air as withdrawn from said enclosure in said fourth adsorber; then drying and cooling said firstadsorb-er; removingsolvent content from said air as withdrawn from said enclosure in' said second adsorber and in said third adsorber, subjectings aid fourth adsorber to steam, all in a fourth'cycle; and" continuously during each of said. cycles removing said treated air from two of saidadsorbers, establishing predetermined conditions of temperature and hutemperature control 9 midity of said treated air, and then returning said air to said enclosure.

2. The method of continuously maintaining predetermined conditions of temperature, humidity and solvent vapor content in the atmosphere of an enclosure wherein said solvent is used comprising, exhausting atmospheric air from the enclosure, removing solvent content from said air in a first adsorber of a bank of adsorbers while simultaneously subjecting a second adsorber to steam, removing solvent from said atmosphere in a third adsorber and drying and cooling a fourth adsorber, all in a first cycle; then removing solvent content of said air as withdrawn from said enclosure in said first absorber, drying and cooling said second adsorber, subjecting said third adsorber to steam and removing solvent content from said air as withdrawn from said enclosure in said fourth adsorber, all in a second cycle, then subjecting said first adsorber to steam, removing solvent content from said air as withdrawn from said enclosure in said second adsorber, drying and cooling said third adsorber and removing solvent content from said air as withdrawn from said enclosure in said fourth adsorber; then drying and cooling said first adsorber, removing solvent content from said air as withdrawn from said enclosure in said second adsorber and in said third adsorber, subjecting said fourth adsorber to steam, all in a fourth cycle; and continuously during each of said cycles removing said treated air from two of said adsorbers, adding a portion of fresh air to said treated air, establishing predetermined conditions of temperature and humidity of said treated air, and then returning said air to said enclosure.

3. The method of continuously maintaining predetermined conditions of temperature, humidity and solvent vapor content in the atmosphere of an enclosure wherein said solvent is used comprising, exhausting atmospheric air from the enclosure, removing solvent content from said air in a first adsorber of a bank of adsorbers while simultaneously subjecting a second adsorber to steam, removing solvent from said atmosphere in a third adsorber and drying and cooling a fourth adsorber, all in a first cycle; then removing solvent content of said air as withdrawn from said enclosure in said first adsorber, drying and coolin said second adsorber, subjecting said third adsorber to steam and removing solvent content from said air as withdrawn from said enclosure in said fourth adsorber, all in a second cycle, then subjecting said first adsorber to steam, removing solvent content from said air as withdrawn from said enclosure in said second adsorber, drying and cooling said third adsorber and removing solvent content from said air as withdrawn from said enclosure in said fourth adsorber; then drying and cooling said first adsorber, removing solvent content from said air as withdrawn from said enclosure in said second adsorber and in said third adsorber, subjecting said fourth adsorber to steam, all in a fourth cycle; and continuously during each of said cycles removing said treated air from two of said adsorbers, adding thereto a portion of fresh air substantially less than the returned treated air and establishing predetermined conditions of temperature and humidity of said treated air, and then returning said air to said enclosure.

4. The method of continuously maintaining predetermined conditions of temperature, humidity and solvent vapor content in the atmosphere of an enclosure wherein said solvent is used and comprising, exhausting atmospheric air from the enclosure, removing solvent content from said air in an adsorber of a bank of adsorbers while simultaneously subjecting another adsorber of said bank of adsorbers to steam, removing solvent from said atmosphere in still another adsorber of said bank of adsorbers and drying and coo-ling yet another adsorber of said bank of adsorbers, all in one cycle; removing solvent content of said air as withdrawn from the enclosure in said first named adsorber, drying and cooling said second named adsorber, subjecting said third named adsorber to steam and removing solvent content from said air as withdrawn from the enclosure in said fourth named adsorber, all in another cycle; subjecting said first named adsorber to steam, removing solvent content from said air as withdrawn from the enclosure in said second named adsorber, drying and cooling said third named adsorber and removing solvent content from said air as withdrawn from the enclosure in said fourth named adsorber; then drying and cooling said first named adsorber, removing solvent contents from said air as withdrawn from the enclosure in said second named adsorber and in said third named adsorber, subjecting said fourth named adsorber to steam, all in still another cyc and continuously during each of said cycles removing said treated air from two of said adsorbers, establishing predetermined conditions of temperature and humidity of said treated air, and then returning said air to the enclosure, and starting and ending the said method in any one of the hereinbefore recited cycles.

E. L. LUACES.

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