ENGINEERING, DESIGN, AND PROCESS DEVELOPMENT tion, a temperature rise through the first tower was noted. It was postulated that the fresh, unfouled material was acting as a catalyst for a small amount of methane synthesis with liberation of heat. Accordingly, the iron oxide and carbon towers were by-passed, and gas from the Girbotol unit was passed into the soda-iron towers without heating in order to sulfide the iron oxide and decrease its activity as a synthesis catalyst. When operations were resumed, it mas found that the temperature rise no longer occurred but that the sulfur content of the gas leaving the soda-iron was higher than that entering. After a few days operation in this manner, temperatures in the first tower began to rise again and reached a point where the furnace was shut off and the reaction was entirely self-sustaining. Shortly thereafter, local oveiheating resulted in a small failure of the vessel wall. The unit was shut d o m without further damage. Analyses of gas samples in and out of the tower taken shortly before the failure occurred indicated that heat liberation was due to reaction of residual oxygen with hydrogen and carbon monoxide in the gas and to methanation reactions. It seemed obvious that, under p r e m r e , control of these reactions and disqipation of the heat would require special provisions and probably continuous attention. Since the operations to date had demonstrated that the carbon toivers alone were sufficient to produce gas of the required purity, it was decided to eliminate the soda iron from the system entirely. The undamaged vessel of this pair of units was piped to permit its use as a spare active carbon tower. During the operation in December 1952 and January 1953, !vhich lasted 7 weeks, the purification was off stream for 1 hour because of a broken amine sample line. Other than this, there Tvas no time in which the unit was not operating normally, producing gas of the required quantity and well beyond the required purity. It is believed that this is evidence of the feasibility of continuous operation of the unit and of the completely satisfactory purification of a gas of this type. Suggested Future Work
I n the laboratory investigations of the removal of organic sulfur by active carbon, reported by Sands, LT‘ainwright, and Egleson ( 6 ) , it was found that the capacity of the active carbon for organic sulfur was a linear function of the inlet sulfur concentration over the range studied ( 5 to 40 grains per 100 cubic feet). iiccording t o thelaboratoryresults, it should have been possible to clean about 400 cubic feet of gas per pound af carbon before regeneration was
necessary. The work on the plant scale showed that, on a normal cycle, about twice this amount of gas \vas cleaned without any measurable amount of organic sulfur in t’he outlet’ and, on one special test, ten times this amount was cleaned before the effluent gas sholved 0.1 grain of sulfur per 100 cubic feet. The plant operat’ions viere made with a gas lower in sulfur content (0.3 to 1.0 grain per 100 cubic feet) and in a deeper and larger diameter bed. Any or all of these factors may have contribut,ed to the difference in results. The effect of all thrce on the absorption efficiency should be determined t’o make possiible the reliable and precise design of plant’ equipment and it’s sucimsful operation. The possibility of continuously regenerating iron oxidc in situ under pressure with very small quantities of oxygen in the gas should be explored, and the total capacity of t,he oxide under these conditions should be determined. The plant purification of ga:: i’mm coal v,-as the ult,imato aim of this work-the purificatioii de ibed in this paper w-as t o be preliminary. However, it is to be expected that litt,le difference, except for a higher initial sulfur content, will exist in the purificntion of coal gas. One operation period of 8 days was achieved on synthesis gas from coal ( 3 h y 1953), rvhich indicated that, with minor revisions, coal gas purification could be satislactorily accomplished in a plant of thip type. Honever, further opwat,ions of this kind to develop final procedures and to tlete1,miiie performance would be desirable. Literature Cited (1) Batohelder, H, R., Dressier, 11. G.. Tenney, R. F., Kruger, It. E., and Segur, R. D., presented a t the .-lnnual Convention of the American Gas Assoc., Atlantic City, PI’. J., October 1950. (2) Dressier, R. G., Batchelder, H. R., Tenney, R. P., Wetieell, L. P., Jr., and Hirst, L. L., U. 9. Bur. M n e s , Rept. Inzest.
5038 (June 1953). (3) Kastens, IU.L., Hirst, L. L., and Dressler, R. G., IXD.ENG. CHEM.,44, 450-66 (1952). (4) “Petroleum and Synthetic Oil Industry of Germany,” B.I.O.&‘. Ouer-all Rept., 1, 83, 92, London, His Majesty’s Stationery
Office (1947). (5) Resen, F. L., Oil Gas J . , 50, S o . 4, 59 (May 31, 1951). (6) Sands, A. E., Wainwright, H. W., and Egleson, G . C., C. AIines, R e p t . Invest. 4699 (July 1950)
S.Bur.
R E C E I V Efor D seview October 26, 1953. ACCEPTED February 16, 1934. Presented as part of the Symposium on I’roperties and Reactions of Carbon before the Division of Gas and Fuel Chemistry at the 124th Meeting of the .4>IERIC.
