viously (Shulman et al., 1966a) using Type 4A molecular sieves in the same basic equipment. The effect of regeneration on mass transfer rates was tested by repeated use of the resin with regeneration in dry air a t 200°F. after each use. The observed mass transfer coefficients decreased by about 15% after the first regeneration but then remained constant for 13 additional adsorption-regeneration cycles. Conclusions
Nomenclature
D, D, G G ..-t
particle diameter column diameter mass flow rate of gas, lb./hr. sq. ft. total gas flow rate, Ib. moles/hr. JD mass transfer factor, dimensionless K$ over-all mass transfer coefficient, lb. moles/hr. lb. atm. P total pressure, atm. y = mole fraction adsorbate 2 = bed size, lb. = = = = = = =
literature Cited
Methods for improving the efficiency of a continuous countercurrent fluid-solids contactor are presented. Results for water vapor adsorption in molecular sieves show that the mass transfer coefficient characterizing the performance of the equipment can be increased by 17 to 60% when weirs are placed in the contactor column or the column is constricted. Dry Amberlyst A-21 ion exchange resins were shown to be potentially useful for SO2 removal. Weirs or constrictions in the contactor column increased the characteristic mass transfer coefficient for this system by 11 to 100%.
Chilton, T. H., Colburn, A. P., Znd. Eng. Chem. 26,1183 (1934). Colburn, A. P., Trans. A m . Znst. Chem. Engrs. 29, 174 (1 933). Cole, R., Shulman, H. L., Znd. Eng. Chem. 52,lO (1960). Linde Co., Division of Union Carbide Corp., Tonawanda, N. Y., Data Sheet No. 4A-2 (1957). Shulman, H. L., Youngquist, G. R., Allen, J. L., Ruths, D. W., Press, S., IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 5,357 (1966a). Shulman, H. L., Youngquist, G. R., Covert, J. R., IND. ENC. CHEM.PROCESS DESIGN DEVELOP. 5,257 (1966b). RECEIVED for review July 31, 1967 ACCEPTED June 6, 1968 Research sponsored by the Division of Air Pollution, Bureau of State Services, U. S. Public Health Service.
REMOVAL OF TELLURIUM HEXAFLUORIDE FROM GASEOUS SYSTEMS BY SOLID REAGENTS D O N A L D R. VISSERS A N D M A R T I N J. S T E I N D L E R
Argonne National Laboratory, 9700 South Cass Ave., Argonne, Ill. 60439 Static gas sorption studies were carried out to screen 1 3 potential reagents as sorbents for T e h . The most promising, activated alumina and BPL activated charcoal, were evaluated as sorbents for T e h in factorially designed sets of studies using an isotope dilution technique with 125mTeto evaluate the TeF6 sorption in a gas flow system. The effects of temperature (25" and 100" C.),bed height ( 1 and 2 inches), gas velocity (20 and 40 feet per minute), and tellurium hexafluoride concentration (190 to 500 p.p.m.) on the removal efficiency of tellurium hexafluoride were evaluated; bed height was found to be the most important. Activated alumina and BPL activated charcoal were found to remove TeF6 effectively (>99.9970) from airTeF6 systems (190 to 500 p.p.m. TeF6). Activated alumina also was an effective sorbent for TeFe in the presence of low concentrations of fluorine in air. The heat of sorption for TeF6 on activated alumina was 5 kcal. per mole.
Lum-bed fluoride volatility methods for reactor fuel reprocessing are currently under development a t the Argonne National Laboratory (Jonke et al., 1967). T h e volatile fluoride species of fission product tellurium represents a troublesome component in the process off-gas of these fluoride volatility processes because of the relatively high concentration of radioactive tellurium in the spent reactor fuel (Blomeke, 1955; Zysin et al., 1964), the chemically inert character of the tellurium fluorides found, and the low maximum permissible concentration for occupational exposure for a 168-hour week, MPClss, for airborne fission product tellurium (Morgan et al., 1959). The principal tellurium species in the fluoride volatility process off-gas is likely to be tellurium hexafluoride (Chilenskas, 1965; Culler, 1964; Fischer and Steunenberg, 1956). Since no quantitative information was available on the 496
I&EC P R O C E S S D E S I G N A N D DEVELOPMENT
ability of various reagents to remove tellurium hexafluoride from gas streams, a series of investigations was carried out. Batch-type sorption screening investigations were used to determine the more promising reagents for removing tellurium hexafluoride, and their ability was evaluated quantitatively as sorbents for tellurium hexafluoride utilizing radiotagged tellurium. The purpose of this study was to demonstrate that the decontamination requirements for tellurium hexafluoride in the off-gas system from a fluid-bed fluoride volatility reactor fuel processing plant could be ascertained. No attempt was made to provide design data adequate for scale-up or the performance characteristics of large beds. Heat of sorption measurements with TeF6 were carried out on the activated alumina to define the sorption phenomenon better.
Table 1.
a
Material Activated alumina BPL activated charcoal Activated charcoal (coconut) Linde molecular sieve Linde molecular sieve Magnesium fluoride Sodium fluoride Soda lime Copper metal turnings Nickel wool Tellurium metal powder Aluminum turnings Copper(I1) oxide Measured by BET method using nitrogen.
Reagents Tested for TeF6 Removal
Source
Alcoa Pittsburgh Coke and Chemical Co. Sargents Union Carbide Corp. Union Carbide Corp. Prepared at Oak Ridge National Laboratory Harshaw Chemical Co. Mallinckrodt Chemical Works Mallinckrodt Chemical Works Brillo Manufacturing Co. Sargents Argonne National Laboratory Allied Chemical Co.
Cbnlroller
---
Designation F-1, -8 $14 mesh -12 f 3 0 mesh, BPL AC-11368 '/16-inch type 13X '/16-inch type 1OX 14-18 mesh Tablets, '/8 X l/g inch 4-8 mesh Reagent Coarse grade Reagent 2S, clean Reagent
Surfact Area, Sq. M.IG.6
295 2075 1790 280 332 146 99.99y0of TeF6 while developing a TeFs surface loading of 25% in the lower 2 inches of the bed. The results of these studies clearly indicate that packed beds of activated alumina are capable of properly decontaminating the fluoride volatility process off-gas stream for TeF6 in the presence of low levels of fluorine. Based on these promising results, additional studies are needed to obtain design data adequate for bed scale-up and performance characteristics of large beds. Acknowledgment
The authors are grateful to L. Ross, who prepared the radioactively tagged tellurium metal and to G. Redding, who determined the nitrogen BET surface areas of the sorbents. literature Cited
Blomeke, J. O., “Nuclear Properties of 236U Fission Products,” U. S. Atomic Energy Commission, Rept. ORNL-1783 (1955). Box, G. E. P., Hunter, J. S., Technometrics 3 (l), 311 (1961). Chilenskas, A., Argonne National Laboratory, personal communication, 1965. Coryell, C. D., Sugarman, N., “Radiochemical Studies. The Fission Products,” National Nuclear Energy Series, Book 2, Part V, p. 1613, McGraw-Hill, New York, 1951. Cromer, S., U. S. Atomic Energy Commission, Rept. MDDC-803 (1947). Culler, F. L., U. S. Atomic Energy Commission, Rept. ORNL-3627 (1964). Fischer, J., Steunenberg, R. K., U. S. Atomic Energy Commission, Rept. ANL-5593 (June 1956). Gaunt, J., Trans. Faraday Soc. 49,1122 (1953); 51, 893 (1955). Henkel, P., Klemm, \V., Z. Anorg. Allgem. Chem. 222, 65 (1935). Holmes, J. T., Koppel, L. B., Jonke, A. A., IND.ENG.CHEM. PROCESS DESIGN DEVELOP. 6,408 (1967). Jonke, A. A., Levenson, M., Levitz, N. M., Steindler, M. J., Vogel, R. C., Nucleonics 25 (5), 58 (May 1967). Klemm, W., Henkel, P., Z. Anorg. Allgem. Chem. 207, 73 (1932). Morgan, K. Z . , et al., “Maximum Permissible Body Burdens and Maximum Permissible Concentrations of Radio-Nuclides in Air and in \Yater for Occupational Exposure,” U. S. Department of Commerce, National Bureau of Standards Handbook 69, June 5, 1959. Vissers, D. R., Steindler, M. J., U. S. Atomic Energy Commission, Rept. ANL-7142 (February 1966). Yost, D. M., Claussen, W. H., J . Am. Chem. Sod. 55, 885 (1933). Zysin, Y. A,, et al., “Fission Product Yields and Their Mass Distributions,” Consultants Bureau, New York, 1964. RECEIVED for review January 15, 1968 ACCEPTEDJune 10, 1968 Work performed under the auspices of the U. S. Atomic Energy Commission.
