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CARBON DIOXIDE MANAGEMENTPART 1: TECHNIQUE FOR CARBON DIOXIDE ABSORBER EVALUATION

JOHN P. ALLEN, Ph.D.

TECHNICAL DOCUMENTARY REPORT No, FDL TDR 64-67, PART I

JUNE 1964

AF FLIGHT DYNAMICS LABORATORYRESEARCH AND TECHNOLOGY DIVISION

AIR FORCE SYSTEMS COMMANDWRIGHT-PATTERSON AIR FORCE BASE, OHIO

Project 6146, Task 611611

NOTICES

When Government drawings, specifications, or other data are used forany purpose other than in connection with a definitely related Governmentprocurement operation, the United States Government thereby incurs noresponsibility nor any obligation whatsoever; and the fact that the Govern-

ment may have formulated furnished, or in any way supplied the said draw-ings, specifications, or other data, is not to be regarded by implication orotherwise as in any manner licensing the holder or any other person orcorporation, or conveying any rights or permission to manufacture, use,or sell any patented invention that may in any way be related thereto.

Qualified requesters may obtain copies of this report from the DefenseDocumentation Center (DDC), (formerly ASTIA), Cameron Station, Bldg. 5,5010 Duke Street, Alexandria, Virginia, 22314.

This report hao been released to the Office of Technical Services, U.S.Department of Commerce, Washington 25, D. C., in stock quantities forsale to the general public.

Copies of this report should not be returned to the Research and Tech-nology Division, Wright-Patterson Air Force Base, Ohio, unless returnis required by security considerations, contractual obligations, or noticeon a specific document.

200 - August 1964 - "S8-3,-68

FDL TDR 64-67Part I

FOREWORD

This report was prepared in the Flight Dynamics Laboratory, Research and TechnologyDivision, Wright-Patterson AFB, Oh.o, under Project 6146, Task 614611, entitled "CarbonDioxide and Water Vapor Control Techniques." This document summarizes the investiga-tions and results of wrk performed in the Atmospheric Regeneration and CO, ControlLaboratories. Dr. John P. Allen is the project engineer for this work, which, begun in July1963, is of a continuing nature, and will be reviewed in this and in future repo,-ts.

In this report problems of carbon dioxide management in a closed system are discussed,followed by a description of a technique for evaluating some materials and/orr methods forits control. Included in this report are performance figures resulting from the investigationwhich will provide a basis of comparison of other materials performances in similar in-vestigations.

FDL. I'DR 64-67Part I

A BSTR A C7T

A laboratory device was assembled for a closed air loop analysis of carbon dioxideremoval agents. Lithium hydroxide, potassium hydroxide, soda lime, and molecular sieve5A were used for establishing the adaptability and capability of this device for evaluationof other carbon dioxide removal agents. Carbon dioxide absorption curves from I percentand/or 5 percent carbon dioxide in laboratory air were obtained. Borax solution and aminesolutions or solids showed some carbon dioxide removal capacity which will be furtherinvestigated for quantitative data on the removal process.

This technical documentary report has been reviewed and is approved.

Asst. for Research and TechnologyVehicle Equipment DivisionAF Flight Dynamics Laboratory

Jiii

FDL FDR 64-67Part I

TABLE OF CONTENTS

SECTION PAC E

INTRODUCTION I

BACKGROUND INFORMATION I

Scope of the Investigation I

Techniqtes for Rermval of CO2 2

Theoretical Considerations 3

DEFINITION OF THE PROBLEM AREA 4

EXPERIMENTAL PROCEDURE 5

EXPERIMENTAL TESTS AND RESULTS 7

Apparatus Volume 7

Leakage 7

Time Period of CO2 Absorption 7

Solid CO, Absorbers 7

Liquid C0 2 Absorbers 9

Discussion of Tests and Results 11

SUMMARY AND CONCLUSION 15

REFERENCES 16

BIBLIOGRAPHY 17

iv

FDL TDR 64-67Part I

ILLUSTRATIONS

FIGURE PAGE

1. Closed Air Loop For CO2 Absorber Evaluation 18

2. Volume Calibration with 1033 cc Flask on 0 to 5%0 Range 19

3. Volume Calibration with 2033 cc Flask on 0 to 1% Range 19

4. Volume Calibration with 1033 cc F[ask on the 0 to 1%7 Range 20

5. CO2 Absorption by Soda Lime Canister 20

6. CO. Absorption by Soda Lime Bulb 21

7. CO2 Absorption by Soda Lime Bulb, Sequent to Figure 6 21

8. CO2 Absorption by LiOH-H20 22

9. CO Absorption by LiOH Anhydrous 22

10. CO2 Absorption by Molecular Sieve, 5A 23

11. CO2 Absorption by Na2 CO3, Granular 23

12. C02 Absorption by Amberlite IRA-401S Resin 24

13. C0, Absorption by Borax, Anhydrous 24

14. CO2 Absorption by o-Phenyle-e Diamine 25

15. CO Absorption by Rexyn RG-6 (OH) Resin 25

16. C02 Absorption by Cellulose Acetate, Granuklr 26

17. C02 Absorption by KOH Solution 26

18. C0, Absorption by Distilled Water 27

19. C(2 Absorption by Dilute Pyruvic Acid 27

20. CO, Dilution Effect by 1 x 8 Inch Test Tube 28

21. CO Absorption by Aqueous Suspension of AmberliteIRA-401S Resin, 2.28 Grams 28

22. C02 Absorption by Aqueous Suspension of AmberliteIRA-401S Resin, 2 cc 29

23. C02 Absorption by KCI, 0.1 Molar 29

FDL TDR 64-67Part I

ILLUSTRATIONS (CONTVD)

FIGURE PAGE

24. CO8 Absorption by TRIS Solution 30

25. CO. Absorption by KH 2 PO., .06 Molar 30

26. GOz2 Absorption by K1 HPO,, 0.013 Molar 31

27. CO 2 Absorption by Na2 HPO,, .06 Molar 31

28. CO, Absorption by EDTA, 5% Solution 32

29. CO2 Absorption by Urea, 4% Solution 32

30. C02 Absorption by Ethylene Diamine, 1% Solution 33

31. CO2 Absorption by Ethylene Diamine, 1% Solution,Sequent to Figure 30 33

32. CO2 Absorption by Ethylene Diamine, 1% Solution,Regenerated by Boiling 34

33. CO2 Absorption by Saturated Borax Solution 34

34. CO. Absorption by Borax Solution, 0.1 Molar 35

TABLES

PAGE

1. Man's CGO, Production Every 24 Hours 2

2. Molecular Sieve CO2 Absorption at 1% CO. in a 1655-mc System 8

3. CC2 Removal by Solid Absorbers 12

4. CO Removal by Liquid Absorbers 13

5. CO, Absorption by Solid Absorbers 14

vi

FDL TDR 64-67Part I

INTRODUCTION

The control of carbon dioxide (CO.) in at.ýrospace cabi-i atmospheres has been the themeof many investigations having as their aijr the presentation of data for incorporation intothe design of environmental control systems. The investigations have ranged from simpleabsorption systems to complex processes of absorption in which catalyti, reduction (f C0 2with hydrogen was used to ultimately recover the oxygen from the CO,. Many factors inthe COM absorption process are limiting and controlling in the overall process of CO, re-moval. To attempt to evaluate the many factors significant to CO, control systems wouldbe a herculean undertaking, but the investigation of specific factors having significant ap-plication to and a limiting effect on an engineering design would provide a great return forthe effort expended. it is intended in this work to devise a laboratory technique to _nvesti-gate some of the many facets of the CO. ccntrol processes by the absorption, adsorption,or persorption process and to evaluate some of the effects which are presenting difficultyin the engineering application of the data obtained.

BACKGROUND INFORMATION

SCOPE OF THE INVESTX-ATION

The carbon dioxide control problem in man-med aerospace closed systems is determinedby the metabolic limits of the spaceman and the extent of his activity. Some specific fig-ures that can be used in discussing CO, control quantitatil ely are the amount of CO, pro-duced per day and the concentrations of CAD0 to be tolerated. Values given for man's CO.production range from 0,8 to 1.2 cubic feet per hour, with an average daily CO. productionof 2.0 to 2.4 pounds (Reference 1). The amount of CO0 prod.,ced vTaries according to thediet, activity, psychological situation, temperature, and physical well-being; but a figureof 0. 1 pound per hour is an afceptable value for use in this investigation. This selectionis justified when one considers the tolerances and efficiences assumed in various CO.treatment processes. The basic tenet is that the quantity of CO . used as the basis for cal-culation be on the plus side since CO, buildup is definitely to be avoided. A CO. cnen-tration of 1 percent in the aerospace vehicle cabin atmosphere has been designated themaximum concentration allowable (Reference 1).

From this basic figure of 0. 1 pound of CO. per hour, calculations and conversions revealthe following information. When the molecular weight of CO. i; taken as 44 and its molec-ular volume 22.267 liters as given by Quinn and Jones (Reference 2), the production ofCO. per hour is:

0.1 lbs.45.359 grams22.9127 liters

.819 cu. ft.

.R87 cu. ft. (at 14.7 psi 800F)

Manuscript released by the author 21 April 1964 for publication as an RTD Technical Docu-

mentary Report.

1

FDL TDR 64-67Part IEven these .,,ures are not directly applicable to CO2 control processes because the re-moval processes are based on 10-, 15-, 20-, and 30-minute cycles. Upon conversion ofthe above production figures to shorter time intervals, the quantity of CO2 production,based on 2.4 pounds every 24 hours, changes to the values given in Table 1.

TABLE 1

Man's CO. Production Every 24 Hours

1 min. 10 min. 15 min. 20 min. 30 min.

.0016 lbs. .016 lbs. .024 lbs. .032 lbs. .05 lbs.

.756 grai 7.56 grams 11.34 grams 15.12 grams 22.68 grams

.382 liters 3.82 liters 5.73 liters 7.64 liters 11.46 liters

.0134 L d. ft. .13 cu. ft. .20 cu. ft. .268 cu. ft. .40 cu. ft.

The tabulated data indicates directly the quantity of CO2 in weight and volume to be removedand/or transferred. These values must necessarily be corrected for pressure differentialbecause the aerospace cabin might be at either 5, 7.5, 10.0, or 14.7 dsia. The lower pres-sures will alter the CO2 weight and volume relationship since, at reduced pressures, therespiratory quotient is raised even though the oxygen consumption is about the same, andthe quantity of CO. in the blood is decreased because of the release of more CO2, and theincrease in rate and volume of breathing (Reference 3).

TECHNIQUES FOR REMOVAL OF CO2

The proposed techniques for removing CO2 from aerospace vehicle cabin atmospheresare many, and may be classed generally as chemical, physical, or electro-chemical inp.Inclple. The chemical techniques range from a simple base-plus-CO2 reaction to thoseinvolving oxygen evolution from superoxides. The latter are reactions of CO2 with potassi-um superoxide and silver superoxide (References 4 and 5). The principle of physically re-moving CO2 involves adsorption (Reference 6), solution concepts (Reference 7), and isfurther extended into membrane- and resin-separation of CO (Reference 8). The electro-chemical concept of CO2 separation involves the formation of electrically transported ionsthrough an anionic membrane after which the CO2 is released as a gas (Reference 8).

The summary and conclusions of various reports on techniques of CO. removal and con-trol include both favorable and unfavorable comments on the capabilities of the respectivetechniques. The lithium hydroxide (LiOH) technique was successfully used in the Mercurycapsules and is being used in biomedical space capsules. But, because this technique isnot a regenerative one, its use is necessarily limited to missions of short duration. Anevaluation of this technique (Reference 9) revealed some problems with irritation fromLiOH dust. However, when LiOH was used with CO2 and water its reaction was consistentwith theoretical discussions of this concept.

In several reports (References 10, 11, 12, 14, and 15), the adsorption of CO2 on molecularsieves, silica gel, activated carbon, and alumina is discussed and the capacities of each aregraphically presented along with supporting data which provides a basis for design andoperation of a CO. removal technique for regenerating the CO2 absorber. Graphs are also

2

FDL TDR 64-67Part Iincluded to show the minimum and maximum quantities of adsorbent for various partialpressures of CO2 .

Other removal techniques are the freeze-out method by which the CO2 air mixture iscooled to below its frost point (Reference 12), and the absorption-by-solution (into sprayor packed towers) method. Both techniques appear at first to be beset with difficultieswhen they are applied to the prescribed conditions for manned atmospheres. For example,in the freeze-out technique, special consideration must :e given to the power requirementsfor maintaining the proper cooling temperatures, for providing high enough air flows inthe short recirculation time of the air, and for fulfilling the factors involved in handlinglow quantity (less than 1 percent) of CO2 in the air. Then, the spray-tower technique, ofcourse, would have no place in a zero-gravity environment.

But, a solution-absorption technique employing the more recen: microporous membraneliquid-gas separators reveal great potential for modifications of current CO% adsorptionon molecular sieves (as indicated by proposed low-temperature molecular sieve CO2 re-moval systems, Reference 12). An,, reiatedly, intermediate temperatures offer a goodarea for investigation of loading capacities and controlling characteristics.

Endeavors, to date, with liquid-gas separation by microporous membranes support theemphasis on its potential and the subsequent need for development of this approach to so-lution-absorption of CO2 from the air stream. A photosynthetic gas exchanger as designedby the General Electric Company (Reference 13) uses a microporous membrane for ex-change of both 02 and CO. in the solution of salts. Here, the problem was physical block-age of gas-exchange membrane by algal cells, but still the gas passage and quantities wereconsidered adequate for this use. The photosynthetic gas-exchanger report recommendedfurther work to evaluate a class of membranes of silicon rubber for diffusing and removingCO. from the air into a solution; the toxicity of this material to algal cells was a significantfact.

THEORETICAL CONSIDERATIONS

Carbon dioxide removal techniques have evolved to a stage such that the capacities andefficiences of the techniques have been defined sufficiently for exploratory application tosimulated manned-sized space capsules. The direct application of experimental data toengineering designs results in the discovery of certain hidden "facts" which may involvechanges in the capacities, efficiencies, time rates of change, etc. One of these facts is thetoxic or poisoning effect of water vapor on the molecular sieve adsorption capacity forCO 2 . This is essentially the preferential absorption of water over that of CO2 such thatthe desired CO2 absorption is nullified. This effect in experimental models of sieve systemsfor CO. removal is controlled either by freeze-out of water or by drying agents. One en-gineering design (Reference 10) thus provided for some preferential water vapor absorptionby increasing the amount of sieve available for the process, and in one estimate providedup to 9.3 pounds of molecular sieve per man. This manner of handling the problem appearsunjustified in view of the experimental data obtained in laboratory runs on CO. absorptioncapacities of the molecular sieve. Experimentally, for a molecular sieve process at 15 psiand 7.6 mm Hg CO, 2.1 pounds of sieve material would absorb up to 8.5 percent of itsweight of CO. at 77"F. This amounts to almost 4 times the rate of production for longerthan a 30-minute period, or 8 times the production rate over 15 minutes.

The CO, removal concept is thus in need of a technique for obtaining a water-free gasstream or of a CO. absorber or adsorber technique that is unaffected by the presence of

3

FDL TDR 64-67Part Iwater or possibly enhanced by the presence of water. Hydrophobic membranes permeableto gases and possibly differentially permeable to gases would provide one answer. Workis progressing along this vein. Also the CO. absorption by ion exchange resins (References7 and 16) and membranes of ion exchange resin provide for CO. diffusion unaffected by thepresence of water. The characterization of materials that could act in this capacity coL'dprovide an impetus to their application to CO. control in the range required for atmosphericcontrol.

DEFINITION OF THE PROBLEM AREA

From the ioregoing discussion it becomes evident that the CO2 removal from an airstream by means of a regenerable absorber or adsorber, is directly related to the processof water vapor removal. The presence of water vapor limits severely the quantitative re-moval of CO2 by molecular sieve materials. A "water-proof" molecular sieve would seemto solve the problem but this idea has not as yet been investigated.

Another concept would be to use an absorption principle in which the presence of wateris required for CO absorption This type of CO2 absorption occurs with the organic amines.This concept is discussed in Reference 15 but the data presented is limited in scope. Anextension of this type of CO. absorption investigation appears merited.

The absorption of CO2 from a low-percentage CO2 content in air constitutes a realproblem when no more than 1 percent (or more desirably, considerably less than 1 per-cent) must be maintained in the air. To maintain a 1-percent CO, content means that toremove 1 volume of C0 2 , 99 volumes of air must have passed through the removal device.With this requirement must also be considered the efficiency of the process and the capac-ity or degree to which the absorber can be loaded. In solid absorber systems, to maintainan air passage great enough to result in an air mixture containing less than the 1 percentmaximum CO., the air must be continually processed at a high mass flow, but must alwayscontain the low percentage of CO 2 .

The absorption process must necessarily have an efficiency of less than 100 percent toattain the required CO2 air mixture control and will range downward to zero percenz ac-cording to how close to saturation the absorber is. The most effective portion of t'e ab-sorption process would be that portion above the value where removal of CO2 would equalCO2 production by the source; this production source value, as noted earlier, is establishedby man's physiology to be 0.1 pound of CO, per hour. The data given in Table I establishesbasic figures for the removal process. From these figures, for a cycling process, with a10-minute cycle, the removal process must remove at least 7.56 grams of CO2 or 3.818liters. On a percentage basis, 381.8 liters of a CO2 air mixture at I-percent CO2 must beprocessed every 10 minutes with a 100-percent CO2 removal efficiency; otherwise, theCO, percentage in the air will rise. For a 20-minute cycle, 763.6 liters of CO. air mixturewith 1-percent CO2 must be processed under the same requirements, to just balance theCO. production. If a .5-percent CO2 level is the maximum CO. limit, then the amount ofair or 763.6 liters would be processed every 10 minutes with 100-percent removal efficien-cy.

From this discussion, it is evident that direct CO2 absorption from air requires a highair flow and high mass velocity to achieve such a complete removal with high efficiency.Flow-through absorbers are effective, but will apparently require high power inputs to at-tain the mass air flows needed to operate a CO2 removal unit of dimensions commensurate

4

FDL TDR 64-67Part Iwith the volume requirements for an atmosphere-control device. From the literature(Reference 10), an absorber with 28 pounds of molecular sieve for a 3-man crew appearsan excessive amount of absorber even though intended for both water and CC, removal.Emphasis in the work on CO2 absorbers has been on high margins of safety by oversizingabsorber beds and flow-through rates. Marginal operational modes in exploratory phasescould more realistically define the limiting factors, and more fully evaluate the designdata.

EXPERIMENT'AL PROCEDURE1

To evaluate some of the experimental and engineering data on CO, removal techniques,an apparatus providing for a closed air loop was assembled. The closed air loop (Figure1) consisted of a recirculating vacuum-blower pump with a bypass valve to provide for an

air-flow control. With valving and flowmeters, various CO, concentrations could be ob-tained in a completely closed air loop. An infrared CO, analyzer monitored the CO. con-centration. A U-shaped tube containing soda lime provided the means for changing the CO2concentration to the desired percentages of I to 5 percent. Drierite was used to dry theair and CO. so that water would not interfere with the analyzer. Through the use of a gasdispersion tube, a plastic cell for gas dispersion, or gas absorption bulbs, liquids andsolids were evaluated as to CO. absorption. During the evaluation of the solutions, an icebath served to condense the water from the air loop before the drierite drying.

The components of the closed air loop apparatus are as follows.,

1. Air-circulating pump, DynaVac Pump, Model 3, Cole-Parmer Instrument andEquipment Company.

2. Flow meter, Model 622BBV, Tube No. 603, Matheson Company.

3. Filter unit, glass wool, 60 cc, brass container.

4. CO, L/b infrared analyzer and amplifier, Model 15A, range 0 to 5 percent,Beckman Company.

5. Angus recorder, Model AW, 0 tc, 50 ua, Etsterline Company.

6. Flow meter, Tube No. 2-85A, 0 tc 2 cfh, Brooks Rotameter Company.

7. Flow meter, FB Model 10A3135A, 0 to 100 percent.

8. Stainless steel spherical tank, volume, 10 liters.

9. U-tubes, with soda lime or Drierite, volume, 90 cc.

10. Drierite tank, 350 cc (approx.) with screen cone.

11. Test tube (I inch x 8 inch), with sintered-glass gas diffuser, extra coarse,volume 76 cc.

12. Absorption bulb, internal volume, 60 cc, Flern:ng-Martin.5

FDL TDR 64-67Part I

13. Phosphorous anhydride tube, inter-nal volume, 60 cc.

14. Valves, 2-way, three ports.

15. Needle valve.

16. Flow meter, 0 to 2.0 cfh, FP Tube No. 04-38A.

17. Ice bath, thermos bottle No. 8640, te-st tube (1 x 8 inch).

18. Air-loop tubing No. 44-P, 1/4 inch, Imperial "Poly-Flo".

The air-circulating pump in the air loop produced a flow of .4 to 2 cfh or 58.6 liters perhour, and could be controlled with the bypass valve to flows of .2 ci"h. This value in flowsper minute is .003 cfm or 97 cc per minute. Ordinarily, evaluar;ons % ere made at 0.8, 1.0,or 1.6 cfh, or respectively, 377.5, 471.8, and 755.0 cc of air per minute.

Measurements of CO. content were accomplished with the Beckman infrared analyzer,which had a 0 to 5 percent range. Water-pumped nitrogen, after it passed through a silicagel cartridge, was the zero gas, and 5-percent CO. in nitrogen was the calibration gas.A range selector was used in conjunction with the Esterline Angus recorder so that tworecording ranges, 0 to 5 percent and 0 to 1 percent full-scale deflection, were available.

The flow meters and a manometer served to monitor the air flow throughout the air loop.Glass wool in a 60-cc-volume filter unit provided for ample air filtration. The a'r loop tub-ing with its 2-way brass valves allowed adequate control of the various system components.Temperature and pressure control we-e not attempted and were at ambient, 25*5°C and740± 10 mm Hg. The pressure drops throughout the loop were not given consideration at thistime.

The air in t',e loop was composed of CO. in laboratory air. Oxygen was not given anyconsideratizjn in this phase of the work. The CO, was adrr'-ted to the air loop from the CO.supply and the air plus CO, were allowed to recirculate until the CO. analyzer indicateda constant trace on the recorder at the percentage required. Leakage was definitely a prob-lem with so many connections. The rate of leakage was significant over hourly periods oftime but over the 10 to 15 minute intervals during which the measurement of the CO. ab-sorption was recorded, the leakage was slight.

A CO. absorption determination consisted of obtaining a percent of CO2 in the air loop,and then valving it into the CO. absorbing device. The CO, removal from the air streamwas recorded against a time interval so that rate of removal could be observed and theinitial and final CO. concentrations recorded. The weight change of the absorber was re-corded in some instances. These weights were not significant for lithium hydroxide andsoda lime since the water liberated in the reaction was removed from the absorber andabsorbed in the drierite tubes. A comparison of the curves provided a basis for qualifyingthe absorbing materials as to their CO. removal capacities.

6

FiX TI)R 64-67Part I

IXP!_RIMENTAL TESTS %IND RLSUJ'IJ

APPARATUS VOLUME

The internal volume of th.e air loop was measured by a dilution effect of a certain con-centration of CO,, in the loop. A volumetric flask was introduced into the air loop so thata volume of laboratory a:r diluted the original CO. concentration 'I 1-liter flask Aith, aninternal volume of 1033 cc when valved into the air loop reduced the CO. percentage from3.60 to 1.80 percent (Figure 2). A 2-liter flask with an internal volume of 2030 cc reducedthe CO, percentage from 0.PAs to 0.30 percent (Figure 3). A duplicate test with the 1-literflask changed the CO, percentage from 0.60 to 0.31 percent (Figure 4). This would calcu-late to a figure of approximately 1040 cc for the internal volume of the air loop. A surgetank with an internal volume of 615 cc was used in initial runs so that the volume was 1655cc in initial evaluations. Thus, the volume changed as modifications were made to the airloop as to tubing lengths and the drierite containers. However, in view of the leakage dis-cussed below these volume values of 1040 and 1655 cc were considered reasonably accurate.

LEAKAGE

The air loop revealed some leakage of the contained gases. With CO, in the air loop, theCO. leakage rate was higher at the higher percentages of CO.. It was found that, with 3.20percent of CO2 in the system, after 1 hour, the CO2 concentration was 2.95 percent- after2 hours, 2.70 percent; 3 hours, 2.45 percent. These values indicate a leakage of 0.25 pe--cent per hour. Other values indicated leakage rates either more or less than 0.25 percentper hour; however, the leakage was a small factor in the overall process. At a concentrationof 1 percent of CO. in the air loop, the leakage was less than the 0.25 percent per hour rateindicated by the various test runs in which the CO. absorption was low, and a graph of thisCO. concentration remained within 0.02 percent of the initial CO2 concentration over the10-minute interval for the absorption process.

TIME PERIOD OF CO, ABSORPTION

As the CO. air mixture was passed through the absorber, the time interval over whichthe CO percentage was recorded w:as arbitrarily limited to 10 minutes. However, lessertime intervals were considered valid when the curve indicated a removal rate comparableto that of an arbitrary standard absorber.

,uLID CO. ABSORBERS

Soda lime in either a canister or a U-tube revealed a good CO. absorption. Figure 5shows almost complete absorption of CO2 by soda lime in a canister from a 5-percentCO. air mixture in 10 minutes. The end point at zero was at the first unit on the graphand corresponded to the zero gas trace. The soda lime was used to adjust the COC, per-centages in the air loop and to remove all CO2 from the loop when this removal was re-quired. Since some water is released in the reaction, weight measurements of the amountof C0 2 absorbed by the soda lime were not obtained. The soda lime used was 8 to 14 mesh,indicator grade (Fisher reagent), and had a 30 percent by weight CO2 absorption capacity,Figures 6 and 7 show CO, removal curves in qnorter time intervals with I-percent CO2in the air loop.

Lithium hydroxide monohydrate was also used in CO. absorption tests and the graphs7

FDL TDR 64-67Part Iobtained indicated over short time periods complete and rapid C0 2 removal from a I-per-cent CO2 concentration in air (Figure 8). Weight measurements of the phosphorous anhy-dride tube coma ining the LiOH revealed that the water formed in the absorption processwas being evolved from the reaction mixture. In one absorption run a weight loss of 7milligrams was measured even though the infrared CO2 analyzer indicated a complete re-moval of CO. from the air stream.

Baking the LiOH monohydrate at 225"C to drive off the water of crystallization producedanhydrous LiOH which revealed a greater weight increase when used for COC absorpion(Figure 9). This weight increase, however, did not correspond to the weight of CO2 c lcu-lated in the air loop; instead, a weight increLae of 17 mg was measured. This correspondsto 8.59 cc of CO2, but at a starting percentage of 0.95-percent 0O, in the air loop, thiswould correspond to 9.88 cc of CO, in the air (or 19.52 mg of C00). This fact was signifi-cant in the use of LiOH only as an "absorber qualifier" and not as a standard of measure-ment when making CO 2 absorption comparisons.

Molecular sieve, No. 5A, as 1/8-inch pellets in a weighed absorption bulb, was used inthis series of tests as a standard for the total absorption of CO2 in the air loop. The mo-lecular sieve (without the bulb) weighed 36.834 grams, and was sufficient to absorb 1.84grams of CO. at a 5-percent ",oading capacity. This molecular sieve capacity was alsosufficient to make eventual saturation with CO a remote possibility in these absorptionruns.

The absorption of C02 by the molecular sieve was complete and rapid in the time periodof 10 minutes (Figure 10); the weight increase was .138 grams when a 4.9-percent CO2air mixture was used. And, at a 4.9-percent C02 concentration and air mixture volume_ of1655 cc, this would give 81.09 cc of C02, corresponding to 0. 160 grams of CO understandard conditions. The difference in weight is explained by leakage in the air loop, whichwas greater at tne higher percentages.

Other runs, with I-percent CA, as the maximum CO2 concentration, provided weightadditions of 30, 28, 29, and 33 milligrams. Table 2 indicates these weight to volume rela-tiionships; the various weights given show the different molecular sieve adsorptions ofCO in the several tests, and also represent some water absorption from the air. And,since 1 percent of the 1655 cc internal volume equals 16.55 cc of C00, from the table, aweight of 30 milligrams would indicate 15.17 cc (17.103 cc at 27"r( and 740 mm) if the en-tire weight increase were all CO2 . (These evaluations were made during a series of rimsin which solutions were also being evaluated so that some water vapor was present in theair loop and on the desiccant materials in various percentages of saturation.)

TABLE 2

Molecular Sieve CO Absorption at 1% CO2 in a 1655-cc System

Weight Diff. Equiv. Volume Voluhme at 27TC, 740 mm(mg) (cc) (cc)

28 14.364 16.188

29 14.870 16.758

30 15.176 17.103

33 16.694 18.8148

FI)L TDR 64-67Part I

Other solid materials evaluated for WJO, adsorption were sodium carbonate 32.17grams), sodium bicarbkriate plus sodium carbonate, Amberlite IRA-401S ion exchangeresin (21.170 grams), borax (5 to 10 mesh), o-phenylene diamine, Rexvyr •C' f" " .'rm ionexchange resin, and cellulose acetate. Noe of these solids compared closely with the mo-lecular sieve or the soda lime in CO2 absorption capacity. Related curves are given inFigures I 1 to 16.

Some solid materials that were tried but with which much difficulty of air passage wasexperienced were tlh Wilson No. 43 gas mask mix, sodium bicarbonate, and asparagine.No absorption curves were obtained.

LIQUID C02 ABSORBERS

Liquid absorbers were evaluated in either a test tube (1 x 8 inch) with a gas-dispersionsintered-glass EC tube or in a lucite cell using a plastic tube as the gas dispersion device.The test tube utilized 25 or 50 ml of the aqueous solutions of the absorbers, whereas, inthe plastic cell, 10 or 15 ml of the solutions were used. The test tube has an internal vol-ume of 76 cc; the lucite cell, 32 cc. The lucite cell was P 2-inch-diameter cylinder v ithtwo 1/4-inch NPT openings in one face of the cylinder. Te other face of the cylinder wasa polyethylene fiim, 5 mils thick. The surface of the film away from the cylinder was theflat face of another cylindrical cell having a volume of 27.6 cc and two 1/4-inch NPT open-ings which were connected with tygon tubing.

Dilute potassium hydroxide solution, 55 cc of a .99-percent solution, was used as an ab-sorption medium in the test tube. The air loop was modified so that an ice bath condensedmost of the water vapor prior to the passage of the air mixture through the drierite tubes.The curves of absorption indicate rapid and almost complete absorption of the CO. froma 4.1-percent CX)0 air mixture; Figure 17 is a typical absorption curve.

Water will dissolve CO2 from the air at quantities as referenced in Quinn and Jones(Reference 2). This solution effect was evaluated with the test-tube technique and the curvein Figure 18 reveals the absorption which took place over a 10-minute interval. A longerabsorption period (up to 110 minunes) revealed a continuing decrease in the percentage ofCO. absorbed, but this decrease is related to leakage. This absorption of CO2 into wateris a factor to be considered when buffers and other similar solutions are evaluated overlong absorption times but was found tr) have little or no significance in the comparativeevaluation of absorption or solution effects by the various solutions considered in thiswork.

Other tolutions were evaluated either in the test tube with the fritted gas-dispersiontube or in the. plastic cell. Potassium hydroxide, dilute pyruvic acid. TRIS buffer, phos-phate buffers, and ethylene diamine were evaluated as CO. absorbers. Leakage for theplastic cell air loop was less than 0.1-percent CO. in the 10-minute evaluation periodwhen 5-percent CO, was used in the air ioop tFigure 19).

Distilled water, 15 ml in the plastic cell, revealed only slight CO. absorption when com-pared to that shown by Figure 18. Acidulated water using 2 ml of 3-percent pyruvic acidto 15 ml of distilled water in the plastic cell produced a curve no different from the leak-age curve (Figure 19).

Leakage from the "bubbling test tube" absorption method was 0.2" percent for a I(.minute period (Figure 20). Therefore, significant absorption should ii. ficate a CO. -per-centage change greater than this value, Distilled water, 25 ml in the test tube, shcwed a

9

FDL TDR 64-67Par I0,550 to 0.70 percent CO2 change in 10 minutes (Figure I,..

Ion-exchange resin IRA-401S, 2.28 grams, was added -o the ti aid a;.-., pro~ductn-a suspension of the resin, and the CO, absorption from a 5-perceni C0, air mi:.ture ',A arecorded (Finres 21 and 22). From the straight par of the cur.e -n F .,u 21, e seethat an 0.40-percent CO. change was obtained in 10 minutes. Also. -here 'Aas Q drop from5-percent CO, to 3 percent, and the curve was still droop-ng after 15 minutes.

Carbon dioxide absorption evaluations using the ;est tube me-h(_o revealed that with TRIS(tris hydroxvmethyl aminomethane) buffer at pH 7.4, the Q(O, absorprion 'as less :han forJistilled "Aater. Potassium chloride at 0.1 molar was also evaluaaea for (-O, -ibsorpt.-on n-Vthis technique and showed little difference from that of ýi•iille .Aate-r Fi-Jure 23,.. Ho*-ever, TRIS bufe-" at pH 10.3 showed a good absorption curve Figure 24).

Phosphate buffers containing the potassium and sodium phospha'es showed CO_ absorp-tion roughly corresponding to their pH's. Potassium mono-basic phosphate soluti.on a, .'molar revealed at pH 4.80 the same curve as for distilled va-er at pj (- .Fure 6.1 , =•.edi-basic potassium phospha'e at pH 8.75 showed more absorpr::_.n of C-0 th-an s!d cUmJi-basic phosphate at .06 molar with a pH of Q.0, F _gures ^t and 2-1. .%bsorpti•-"; of CG•by ethylene diamino tetraacetic acid made with KOV was comparable -o tha- ._isorbed bydilute KOH TFiure 28). Urea solution at I gram per 25 ml of dJis:lle-d -a:er .evea.•ej- aCO, reduct;on of an 0.80-percent CO, in the air m-xture in '0 minutes F'cure .ylene diamine (technicl grade) was used at 5-percent solution to d4lute 5 to 20 ml of Jis-tilled water. This dilution had a pH of 11.8. The CG, absorption bv this solutio, n F, zures30 and 31) was very good and showed, upon saturation with Cco a removal rare simlarto that of distilled water. Absorption of CO, by 15 ml of 5-percent ethylene ,ia•ni,.e wi---a pH of I ] Q showed good absorption n the plastic cell. The pH of the ethylene dai IInsolution after saturation with CO, was 8.1. Further absorplion of CC- by *his solution "this pH was slight and similar to that of distilled ,rarer.

An attempt to regenerate the absorptioi capacity was made bv boiling the elbvlene diam'nesolution for 10 minutes with vigorous stirring. Upon cooling, 'his solution had a pH of 4.1,and showed furtber CO. absorption capacity, Figure 32 givee the CO. removal rate. ,nd,upon continuation of the CO. absorption, the pH of this solution was R.05. -ý second boilingfor 15 minutes with vigorous stirring produced a solution of Q,ý and a :egeneration of theCO2 absorption capacity very similar to the regeneration produced upon -he first bo.ling.

A saturated borax solution was used for CO- absorption. Quinn and Jones ,Reference 2,obtained tabuiated data on CO. absorption by salt so!ut~ons in Ahich saturated .norax 'olu-tion was inuicated to have a CO, absorption coefficient of 21.7 aF compared to that of0.98 for potassium chloride at 0.82 molar. Other inorganic salts revealed absorption coef-ficients comparable to that of KCI. Te curve of CC, absorption by n_'rax solutions revealeaa rate which compares favorably with that of dilute KOH solution F- igures 33 and 34). Re-moval of CU- from the borax solution wag not attempted.

The CO. removal rates for saturated borax solution x4ere witi, 1-percent CO. air mix-tures. With 0.•S-percent CO, a decrease in CO, percentage lo 0.37-percent was recordedin 10 minutes. In an additional 10-minute Period beyond "he first 10-minutes, *:e percent-age of reduction went to 0.17 percent. repeat run wits ,). I molar biorax solution revealedcomparable data, in that the CO. percentage reduction in a Q-minute perioa. iez nning at0. 6 7-percent CO. air mixture, was reduced to (%.37 percent.

1 0

i')L TDR 64-67Part I

A water "blank" using the bubbling test tube technique showed a 0.05-percent reductionin the C02 percentage value in a 10-minute period on the 0 to I percent range.

DISCUSSION OF TESTS AND RESULTS

The test apparatus used in this work is directly applicable to a study of solid and liquidCO, absorbers. Since one of the requirements of a regenerable CO removal system isthat the absorber "absorb and desorl'" at least 7.56 grams of CO. per 10-minute period,a quantitative relationship can be esuablished to correlate the capacity and effectivenessof this test apparatus to the requirements of a "one-man sized" system. The 1.04-literinternal volume of the absorption system must be correlated with a simulated aerospacevehicle cabin volume of approximately 500 cubic feet (1 cubic feet equals 28.316 liters)which calculates to a volume ratio of 1 to 15000. This figure may be misleading when inter-polations are made.

The absorption curves of Tables 3 and 4 present an initial dip in tl.e CO2 concentrationduring the first minutes of the time interval (Figure 20). This was due to the dilution proc-ess ,€hen the air flow was introduced to the absorber container. This container introduceda volume of air with little or no CO2 and it was analyzed as it was being mixed while thetotal air volume was recirculating through the loop. To mix completely, 2 to 3 minuteswere required, after which the measurements of the CO2 concentrations were consideredvalid, and the curve tracings returned to "normal." Extending the curve back to the initialstart of the drop would give a continuous CO- removal rate coupled with a dilution effect.The test tube method and the plastic cell method revealed this dip in the curve more sothan did the solid material absorption bulb method.

From the test data on the zurves and tabulations in Tables 2 and 3, the values for CO.removal by the various materials show that the molecular sieve (Figure 10) and lithiumhydroxide (Figures 8 and 9) are rapid and complete CO2 removal agents for the short-timeinterval. Comparable liquid agents are the KOH solutions (Figure 17) and the ethylenediamine solutions (Figures 30, 31, and 32). These restIts with ethylene diamine are to beexpected bes ed upon past experience with CO2 absorption by amine solutions. Mono-etha-nolamine was used by the Navy for C(20 control in submarine atmosphere control. Thereaction kinetics of the absorption and Lae regene'ation processes require further investi-gation. The stability of vie ethylene diamine during regeneration processes and the toxici-ty of such a system's components would need to be evaluated.

The ion exchange resins used in this investigation were the anionic type with aminegroupings. CO was abscrbed to some extent but here the CO, removal process was com-plicated in its interpretai ion since the higher pH's of the strong base resins were undoubt-edly an uncounted influerne in CO. absorption. The slopes of the absorption curves wereshallow and over the 10-minute period revealed little CO( removal. The results of theresin absorption using the resins suspended in water showed significant CO( absorptionbut at a low rate. Amberlite IRA-401S gave a value of 8.275 cc of CO( removed in 6 min-utes by a 2-cc quantity of resin suspended in 50 ml of distilled water (Figure 21).

The liquid C02 absorption curves indicated that some effects needed further investigation.The borax solutions, the urea solution, and the ethyle-e diamine solutions indicated CO.absorptions significantly more than that of water or the buffer solutions. Ethylene diaminesolutions were comparable to that of KOH and showed a regeneration capability. The boraxsolution was not investigated further.

The solid CO, absorber tests indicated that the resins and the o-phenylene diamine had acapacity for absorbing CO,. Further evaluations should bi conducted to reveal the significance3f the CO, removal capacities. Cellulose acetate revealed slight CO removal capac%,.11 I

FDL TDR 64-67Part I

The solid absorbers sho,* ing rapid CO. removal are compared in Table 4 on a numite-by-minute basis to show the rapid initial CO, removal from the air. This initial drop inCO) percentage in the air loop was not without a dilution effect brought about by the addedvolume of the absorber container.

TABLE 3

CO2 REMOVAL BY SOLID ABSORBERS

Agent Percentage of CO. Time (Min.)Start End Imnrval

Soda Lime, 36.227 g. 1.0 .01 51.0 .01 10

Soda Lime canister 5.0 .15 10

LiOH-H 2 0, 28.674 g. .98 0 10

LiOH (-H20O) 16.437 g. .94 0 9

Molecular Sieve, 5A, 36.834 g. 4.9 .1 104.7 .25 10

Amberlite IRA 401S 21.17 g. 5.0 4.6 9

Cellulose Acetate 9.05 g. .95 .88 10

o-Phenylene Diamine 7.0 g. .93 .88 10

Na.COs, 32.971 g. .98 .94 10

Rexyn RG-6 Resin 21.103 g. 1.0 .98 10

Borax, Anhydrous 27.512 g. 1.0 .98 6

12

FDL TDR 64-67Part I

TABLE 4

CO. REMOVAL BY LIQUID ABSORBERS

AGN ____ Percentage of CT eA G..... TimeStart 7 Removed End Interval (Mia.)

in 5 to 10_nMm. It.

Distilled Water, 2.7 .25 1.05 10

KCI, 0.1 Molar 4.6 .25 2.55 10

KHzPO, .06 Molar, pH 4.8 4.05 .25 3.Q 10

K 2 HPO,, 0.013M pH 8.75 4.80 3.40 7

Empty Test Tube 5.00 .1 4.15 10

Na-,HPO,, .06 MoLar pH 9.0 4.5 .25 2.40 10

KOH, .991"C 4.6 .05 10

4.2 .35 10

EDT ', 5- in .5T, KOH 5.0 3.Q5 7

Pyruvic Acid, Dilute 4.65 .05 4.55 10

Amberlite Resin, 2 g/50 cc Water2.28 g. per 50 cc Water 5.00 .45 3.45 10

2 cc/50 cc Water 3.40 .50 3.20 10

Borax, Saturated Sol. .q4 .IQ .37 10

Bora-:, 0.1 Molar Sol. 1.0 .14 .33 10

TRIS. .06 Molar pH 10.33 5.0 .70 2.2ý 10

Urea Sol. I g, , 25 ml 11.O 4.40 . 2.50 10

Ethylene Diam ine, 1:5 Dil. 4.8 5.

: 310

of 5, Sol. pH 11. Q

Ethylene Diamine (ds Above) 5.00 .20 7

Ethylene Diamine (Regen.) 4.,0 "94.0 10

FDL TDR 64-67Part I

TABLE 5

CO. ABSORPTION BY SOLID ABSORBERS

Percentage CO,

Time LiOH Molecular Sieve Soda LimeMin. H20 Anhyd. 1st run 2nd run F-M F-M CanisterBulb -Bulb

0 .98 .94 4.9 4.7 1.0 .96 5.0

.80 .70 3.0 2.8 0.42 .63 3.0

2 .49 .36 2.0 1.9 0.08 .33 1.8

3 .27 .15 1.3 1.3 0.02 .07 .70

4 .13 .06 0.8 0.8 0.01 .03 .45

5. .08 .02 0.5 0.6 0.01 .02 .30

6 .04 .01 0.3 0.45 .01 .20

7 .02 .01 0.2 0.35 .01 .15

8 .01 0.15 0.30 .13

9 .01 0.13

14

FDL TDR 64-67Part I

SUMMARY AND CONCLUSIONS

The apparatus which has been described in this repcrt was adequate in the evaluation ofCO, removal agenits for use in a closed air loop. Lithium hydroxide, soda lime, and molecu-lar sieve, 5A, when used as CO. removal agents showed rapid and complete (.'0, removal,as illustrated graphically. Other solids tried were cellulose acetate, borax, sodium carbon-ate, o-phenylene diamine, and two resins of the amine type, \mberlite IRA-401S and RexynRG-6 (OH) form. The amine compounds showed a significant CO, removing capacity andshould be investigated further.

Liquids used for CO, removal were solutions of buffer salts, KOtt, borax, ethylene dia-mine, urea, suspensions of the resin (IRA-401S), pyruvic acid, and Li)T.\ in KOII. The buf-fer salts were KC1, Na.fHPO 4 , KHIPO4 , K21HPO 4 , and TRIS. The curves of the C'O_ absorp-tion revealed rapid and complete removal with KOH and ethylene diamine solutions. Fhesolutions with high p1i's showed more CO2 removal than solutions with pH1's near 8 andlower. Acid phf's showed little or no absorption. Borax, TRIS, and urea solution showedCO, removal rates which would justify further investigation.

Regeneration of the CO, removal capacity was tried with ethylene Jiamine solution byboiling for 10 to 15 minutes. The CO. absorption capacity was restored but the regenerationprocess requires further investigation.

FDL TDR 64-67Part I

REFERENCES

1. Breeze, R. K., "Space Vehicle Environmental Control Requirements Based onEquipment and Physiological Criteria," ASD-TR-61-161, Part I, C/N AF33(616)-7635, ASD, WPAFB, Dec. 1961

2. Quinn, E. L, & Jones, C. L., "Carbon Dioxide," ACS Monograph No 72, ReinholdPublishing CO., N. Y., 1936

3. WADC, "Handbook of Respiration," WADC-TR-58-352, C/N AF33(616)-3972, AML,ARDC, WPAFB, 0., Aug. 1958

4. ASD, "Atmospheric Control Systems for Space Vehicles," ASD-TDR-62-527, PartI, C/N AF33(616)-8323, ASD, WPA,7B, 0., Mar. 1963

5. ASD, "Potassium Superoxide Canister Evaluation for Manned Space Vehicles,"ASD-TDR-62-583, C/N AF33(616)-8323, ASD, WPAFB, 0., Sep. 1962

6. Mason, J. L, & Burriss, W. L., "Application of Molecular Sieve Adsorbents toAtmosphere Control Systems for Manned Spacecraft," Report No. SS-887-R,AiResearch MFG. Div., Garrett Corp., May 1963

7. Gregor, H. P., "Absorption of Carbon Dioxide by Solid State Polymeric Amines,"Contract Nonr-839(20), Project NR 266-006, May 1959

8. ASD, "Investigation of an Electro-Chemical Device for Carbon Dioxide Absorptionand Oxygen Generation," ASD-TDR-63-441, C/N 33(657)-7938, ASD, WPAFB, 0.,May 1963

9. Air Reduction CO., Inc., "Closed Circuit Respiration/Veiw-ilation System, PhaseI.," WADD-TR-60-33, C/N AF33(616)-3856, AML, ASE), WPAFB, 0., Jan. 1960

10. Willard, T. L., "Research and Development on Closed Respiratory System Acces-sories, ASD-TR-61-527, C/N AF33(616)-7270, AML, ASD, WPAFB, 0., Oct. 1961

11. Christensen, G., Adsorption-Desorption Cycling Effects on Molecular Sieves forCO. Removal, Peport No. SS-788-R, AiResearch Mfg. Div., Garrett Corp., Oct.1962

12. ASD, "Low Temperature Adsorption of Carbon Dioxide," ASD-TDR-62-560, C/NAF33(616)-8323, ASD, WPAFB, 0., Sep. 1962

13. AMRL, "Design Study of Gravity Independent Photosynthetic Gas Exchanger,"AMRL-TDR-63-59, C/N AF33(657)-7410, AMRL, WPAFB, 0., Jun. 1963

14. Roach, C. G., "Design and Development of Regenerative Carbon Dioxide SorbersAMRL-TDR-62-135, C/N AF33(616)-7909, AMRL, WPAFB, 0., Nov. 1962

15. ASD, "Analytical Methods for Space Vehicle Atmospheric Control Process,"ASD-TR-61-162, Part II, C/N AF33(616)-8322, ASD, WPAF13, 0., Nov., 1962

16

FDL TDR 64-67Part I

REFERENCES (CONT'D)

16. Robins, J., "The Absorption of Carbon Dioxide by Polymeric Amines," Disserta-tion, Polytechnic Institute of Brooklyn, N. Y., Jun. 1959

BIBLIOGRAPHY

1. Fox, W. B., "Adsorption of Carbon Dioxide by Artificial Zeolites," ASRMFD-TM-62-81, ASD, WPAFB, 0., Nov., 1962

2. "Handbook of Chemistry and Physics," 44th Edition, The Chemical Rubber Pub-lishing Co., Cleveland, 0., 1962

3. ASD, "Environmental Conrrol Systems Selection for Manned Space Vehicles,"ASD-TR-61-240, Part 71, Vol. I., C/N AF33(616)-8323, ASD, WPAFB, 0., Feb. 1963

4. "Modern Plastics, Encylu-,.kdia for 1964," Plastics Catalogue Corp., Vol. 41,No. IA, N. Y., Sep. 1963

5. Specter, W. S., "Handbook of Biological Data.," W. B. Saunders Co., Philadelphia,Pa., 1956

6. MMSCV Directorate, "Flight Test of a Gravity Independent Photosynthetic GasExchanger," A Feasibility Study, SSD-TDR-63-240, C/N AF04(647)-622, MMSCVDirectorate Space Systems Division, AFSC, Los Angeles, Calif.

17

Recorder I02SU " Flow

Meter Soda

Ampl Ferow TubeMotor

Analyzer

Valve Valve Drierite F"Tank

FlowMeter_________________ __

Motor

U, Valve

F, IterUnit

ValveB

FlowMeter

Valve

T ~Drierite ZTube e i!17Abs F-M

I' I

Tub Bulbe

Air Pur e 1 o)aJMeterm m imJi m

Tube IW I)B AIj-

a~ s tI

Sr-er mO T jibe

Figaure I Closed Ai r Loop For %(: u r"( a, II t!

VOLUME CALIBRATION

Added I liter flask V 1033 cc

0

44

0%

6 5 4 3 2 I0Ti me

Figure 2. Volume Calibration with 1033 cc Flask on 0 to 51,' R{ange

100 VOLUME CALIBRATION OF AIR LOOP

2- liter flask volume 2033 cc -

Flow 1I Gc fh Temp. 250C

I O2 fllsae Ime nev l

b7.

0

T 0m

.4gi( l m,(alb a o ih2 3 c -I., n0t

1%VOLUME CALIBRATION OF AIR LOOP

I - liter flask volume ý034 cc

Flo 1~ 6cfh Temp25C

0%

5 4 3 20Time

Vigure 4. Volurne (Calihrat ion a ith 10O3" cc !'ak hfh* 0 to I"

5%%

SOLID C02 ABSORBER

Soda lime canister

F~ow 0 8 cfh Temp 250 C

Volume of air loop 1655 cc

5% CO2 full scale I mir intervals - -- ----- -

0

10 9 8 7 6 5 4 3 2Tim e

o t i~ri - 5 ( ) ~ sorpti i~ 1,N' x~ .: (i

^0

SOLID CO2 ABSORBERSod. hirne, 36.227 g.

Flow 1 6 Cth Temp. 25 * C-

Volume of Lit loop - 1040 Cc c

1% CO full scole I Win nierwos2

.0 -- - I I j,W 4-

.0 __ _ - 1---- ,,o -- __ - - - --

- -- -i - 4- -

"-/ /zzr:if ..... /- -- /t

-... I -/ . / /"

0~

6 5 4 3 2 i 0

T mme

Figure 6. CO 2 Absorption by Soda Lime Bulb

%..

SOLID CO2 ABSORBER -

Soda lime, 8-14mesh, indicoting, 362Z7 g -

'Plow. 1.6 cfh Temp 270 C.

olume of Olf oo. 1040 cc "

1% CO full scale Imin ,ntervols2

.009

/ • ,/

0 7 6 4 3 2Ti me

Figure 7 (')- %bs(,rplion hK I, wit', P>im ;,que' !o I :,,rt

SOI OABOBRU

Lit0hdoierwooyae !64

Flw14C T.% 70w

0

T me

7=1I

9O 7 8 5 6 5 2 0T ime

Figuare .CO, -Absorption by LUNH AH2dou

5%SOLID COZ ABSORBER

Molecular seive 5A 36 834gFlow-, 0.8 cfh Temp 25*C -",.

Volume of air loop.' 1655 CC :§ - > *

5% COr full scale I mu in tervols . ....

i II------ - --. --- I--I---1- -. --

lid -- ---- ---- 4----. -,.- -_ __ __ _ _ '-•- 1.. 4..

-re ::- C A- -.. . - . - , -- - . -. a,,•

0. -- S- 7"

S3L D 2O ABS Ofý E ESo,-r CartCrot- gr0- 32 ?7 ,

W 0 're C' a,r :'s CF r •,

1 3 8 7 4 32 2

,_- 4 . - -- 7 ", "- I•' ; •, • ." . . ' l -4

_ _ _ __IIII I 1 _ -I I-_ - - - - -- - - -

5%r

1 1n ___I

so 1--L

SOLID~~I COIBSRE

AD T __ __

Fmerigur 12. CO bopinb xbrieI401S Resi.sin7g

0%

4 0 9___5__32

Figure ~ OLI CO2O.bsrtinb AmBSOi RBER 1 RsiBoax onhyr00 ---2-----

/, FVw. 6ch Tm.2C- - Volme f ai lop: 0090

Tiom

i-2ue 13CO Bsorptioan by Borax Ah275129

Flw 1624 ~ p 7C

\iZ z~ 7urs -~r z~711 -ISO 1

k` - ---

-~~~ 9~ 0 - - --___ -~11X171 217 V Azr

C, 7

- -- --- --- ---- -A---__

IM

0

S O L I 9 O A B S O6B5R473

Four -ph4.en CO2 minepio ,y 70Peg~neDa

1% -- 02 -- full sc- - -I--zi~~ mi in- -

90 ___

___ ___ - - ~ -~--.~ r- ---

-3 -- - -0

-0 --- 7--- - - --- - - --- -- -- -- -so--

SOLI -O BSRE

if 10987

T ime

Figure 15. CO .Absorption by Rex-yn RG-6 (OH) l~esin

25

011

.0

04

SOLID CO2 ABSORBER

Cellulose acetate. gran. 9.05~. 9 __ -_____

Flow' 1.6 cfh Temp. 25"C __

Volume of air loop 1040 cc. P=7

1% CO 2 full scale I mini. intervals - - - - -- - --

10 9 8 7 6 5 4 3 2 1 0

Figure 16, CO 2 Absnrption by Cellulose Acetate, Granular

5%VTEST TUBE CO. ABSORBER

Potassium hydroxide, 55 ml. 0.99% solution

Flow *;0. 4 cth Temp. 25 0C

Volume of air loop 1655 cc,

.0%L

10 9 87 65432 0Time

Figure 17. CO, Absorption by KOH Solution

26

5%TEST TUBE C02 ABSORPTION

Distilled Water, 25 ml.Flow 0. 8 cfh Temp 25*

C. 9

Volume of' air loop 1655 Ccc

5% CO full scale I min intervals ______70________

04

020

o

V

0%0

10 9 8 7 6 5 4 3 2 I0Time

Figure 18. CO2 Absorption by Distilled Water

0 77

5%A

TEST TUBE COZ ABSORPTION

I X 8 inch test tube, leakage testFlow .08 cfh Temp. 25%.

Volume of air loop *'1655 cc,

5% CO2 full scale I min.~ inter vo - ---- ---- -s-

if 0) 9 8 7 .6 5 4 3 2Time

Figure 20. CO. Dilution Effect by 1 x 8 Inch Test Tube

5%_

0

U

Volume of oir loop . 1655 cc.

0% 5% CO2 full scale I min intervals0 09%76

Ti me

Figure 21. CO 2 Absorption by Aqueous Suspension of Amberlite [RA-401S Resin,2. 28 Grams

28

5% TEST TUBE CO2 ABSORPTION

Amberlite IRA- 401S Resin, 2 cc 'n----50 ml di~teiled water

~I'Av 08 cth Temp 25*C

Tdim

*0

0%6

Time

FigureFgur 22. CO. Absorption by Aqueou 0.pnso of AMoelaRA-0SRsn2 cc

5%

Flo .____ tT m .2 * .-

0%_

10 9 8 7 6 5 4 320Time

Figure 24. COS Absorption by ThIS Solution

03

5 % - - --... . _--.-t

- -

o-4 -

TEST TUBE CO 2 ABSORPTION

0 Potassium di basic phosphate,O. 013 molor 25 ml pH 8 75 -

Flow ' 0.8 cfh Temp. 25"C

Volume of air loop . 1655 cc.

5% CO2 full scale I min intervals

% -- /7 6 5 4 3 2 I

TimeFigure 26., CO 2 Absorption by K1 HP0 4 , 0. 013 Molar

TEST TUBE CO 2 ABSORPTION - -

Sodium di basic phosphate, 0.06 molar25 m!. pH9 0 -

Flow; 0.8 cfh Temp. 25"C. -. 0

Volume of ,ir loop 1655 cc

5% CO 2 full scale I min intervals -- 70

0 - t- I

-- 0

.0

/ / -__ -0% ---

9 8 7 6 5 4 3 2

Time

Figure 27, CO Absorption by Na2 HPO4 , .06 Molar

31

5%l

U TEST TUBE CO2 ABSORPTION

( Ethylene dinitrilo) tetraacetic ocid',EDTA 25 ml of EDTA 'in KOH, 5% EOTA in 0.5% KOH

Flow --O 8 cfh Temp. 250 CVolume of air loop :1655 zc.

0% 5% C02 full scale -I min intervals7 6 5 4 3 2 I0

Time

Figure 28. CO. Absorption by EDTA, 51/' Solution

5% TEST TUBE C0 2 ABSORPTIONAx

Ura05m Ig/5m

0

T im e

Figure 29. CO. Absorption by Urea, 41ý Solution32

5%

TEST TUBE COZ ABSORPTION

Ethylene diomine, 25 ml of I to 5diaufion of 5% solition, pti 11.9 6

Flow .8cfh Temp 25" C

0 volume of aer loop 16555 cc

0 t

U

5 4 3 2 I0

Figure 30. CO. Absorption by Ethylene Diamine, 11, Solution

TEST TUBE CC' 2 ASRTO

Ett~ylene diomine, 25mi of I to 5deoufion of 5% solution, pH 1! 8

Flow 0 8 cf h Temnp 25*C

Volume of air loop .1655cc

.0

0%6 54 3 2

T e

Figure 31. CO. Absorption by F1>hvlene lDiarnine, I S Solution. Sequent to 1-igure, 30

.33

TEST TUBE CO2 ABSORPTION

Ethylene diamine ,25 ml of I to 5 dilution of 5%solution pH 98 Regenerationi by boiling 65 min

FlowO'08 cf h Temp 25*C

Volume of Off loop' 1655 cc

5% CO2 full scale I min intervals

4

0

'a t

10 9 8 7 6 5 4 3 2Time

Figure 32, ('02 Absorption by Ethylene Diarnine, I 5 Solution, Regenerated by Boi-ling

TE ST TUBE CO2 ABSORPTION - -or-Borax, saturated solution, 25 mil -

BFlow 08 cf h Te mp 25 C7*Y 71

'dolI me of air loop: 1655 cc

1% CO 2full scale 1min intervals

/ / -

0% L 11 /

10965 4 3 21Time

Figure 33. CO. Absorption by Saturated Borax Solution

34

TEST TUBE CO2 ABSORPTION"

Boaca solutiof., 01 molor, 25 ml

Flow 0-8 cfh Temp. 32"C \ - -

Volume of air loop: 1655 cc5 % C OZ &. "1 % C

02 full SCole '

"• -

47 f_

-. . 11 " --

t/

___--- _ ______ )-*- -- - -- - - ' - -- ---1 " __ _ __

_

10 9 8 7 6 5 4 §

2

Ti me

Figure 34, CO. Absorption b% Borax, So 0or,. 0. 1 Molar

35)