THE CHEMICAL WORLD THIS WEEK
There is no incentive for research and development if the increased production that follows is taken away by taxes, C. L. Kirkbride told the engineers. He received the annual Professional Progress Award from Thomas Clifton, AIChE president C & E N REPORTS:
American Institute of Chemical Engineers, Annual
Meeting
ChE's Turn to Basic Principles as Knowledge of Operations Increases Metallic fluids prove effectiveness as heat transfer media . . . N e w costs of gas from coal presented ATLANTIC CITY.-More than 500 of the 1500 chemical engineers who traveled here for the 44th annual meeting of their so ciety arrived a day early for a special session to discuss the reorientation of the fundamental precepts of their science. Their discussion reflected a feeling that the "unit operation," long standing huilding block of their theoretical considera tions, was being fragmented into basic areas of applied physics and chemistry and was no longer a suitable basis for organi zation of either teaching or research. Many speakers advocated the reorgani zation of the science in terms of the basic concepts of heat transfer, mass transfer, applied mathematics, and others. Howe\ er, no desire was expressed to crystal lize the organization during the present "transitional period." The opinion seemed to favor a fluid approach which would avoid the strict categories of "unit op erations" and "unit processes." The teachers seemed particularly enthusiastic about such a revision in approach. Sev eral of them said tbat the old system of organization has made it extremely diffi 5344
cult to present knowledge now available in a rational fashion. They too, however, expressed a resistance to any attempt to set the pattern of chemical engineering science for the indefinite future at this time. During the meeting it was announced that William I. Burt, vice ρ resident in charge of manufacturing for B. F . Good rich Chemical Co., was elected president of AIChE for 1952. William T. Nichols, director of the general engineering depart ment of Monsanto Chemical Co. was elected vice president.
The W e e k ' s Events C a l i f o r n i a Section Awards G o t o Pauling, Li Emil O f t Receives A I C Honor Scroll Radioisotopes G a i n i n g Ground in Thorapy and Diaqnosis . . . . Kaiser Aluminum Dedicates New Orleans Plant Chemîcals-in-Foods Investigators Visit Stauffer Labs
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C H E M I C A L
Further evidence of a feeling of need for new techniques was apparent in the organization of the symposium on heat transfer which was presented in a form new to the AIChE. Although previous meetings have included discussion panels and extended question periods this session was the first one in which all papers were presented in preprint form and the meeting itself was devoted entirely to questions and discussion. In each of the two half-day sessions, the presiding officers, Donald L. Katz and Alan Foust, devoted a half hour to abstracting eight of the symposium papers. The remainder of the time was then devoted to written and oral questions from the floor. Some of the voluntary discussions included slides and were obviously prepared in advance. Others were extemporaneous. However, in all cases the exchange was animated and a firm hand was required to keep the meetings within a reasonable time schedule. From the obvious success of this experimental session it may be assumed that other symposia in the future will follow this pattern. The most lively discussion was stimulated by a series of papers devoted to the use of liquid metals as heat transfer media, a subject of special significance in the utilization of nuclear energy for power genI. Burt eration. Systems involving lead, bismuth, mercury, sodium, potassium, and various alloys of these metals were used in the various studies reported. Such systems make good heat transfer fluids under any conditions where high temperatures are encountered according to R. A. Tidball of Mine Safety Appliances. Working witfi a sodiumpotassium eutectic mixture, at temperatures up to 1000° F. W. T. Nichols he found that the metals, being elemental, had almost no tendency to foul the equipment and gave heat transfer coefficients that varied less than 4 % over a 70-week period. The purity of the fluid was protected by a blanket of purified argon at 10 pounds per square inch gage over the expansion chamber. Heat transfer coefficents were five to seven times as great as those for conventional transfer media. However, even though no fouling factors need be used to predict the performance of the fluid metals in heat exchangers, AND
ENGINEERING
NEWS
Tidball found that conventional theory was not adequate, and he said that much more experimental work must be done before the complete heat transfer mechanism in these fluids will be understood. He submitted that one cause of the deviations from conventional theory is the exceptionally high thennal conductivity of the metals, which has less and less effect on the over-all transfer as turbulence in the exchanger increases. Cost of Gas from Coal The ever popular subject of making fluid fuel from coal received a new economic treatment in a study reported by H. R. Jones of Blaw-Knox. Jones predicted that within less than 10 years all of the natural gas produced will be committed to existing transcontinental pipelines and communities that are not located on those lines at that time will continue to look for a gaseous fuel from other sources. He suggested that the gasification techniques evolved in connection with the Fischer-Tropsch synthesis may provide a cheaper source at that time than the conventional gas-producing sets. To investigate this possibility from an economic point of view he postulated a 100 million standard cubic feet per day unit employing a Lurgi-type pressure gasifier charged with noncaking coal and a medium pressure catalytic converter. Sulfur compounds and carbon dioxide would be removed from the stream between the gasifier and the converter and the product gas would be passed through a carbon dioxide absorber. Theoretically such a unit would produce a fuel gas with a heat value above 900 B.t.u. Break-down of Costs Jones' cost estimates include engineering design, procurement, erection, interest on initial and working capital, raw material, labor, maintenance, and all utilities at current rates. On this basis the initial investment would be $52.5 million for a 100 million cubic foot plant. Cost of the product' would be 55 cents per thousand standard cubic feet if noncaking coal or char having 26 million B.t.u. per pound heat content and virtually no tarforming constituents could be obtained for $4.00 a ton. Gasification would account for three quarters of the total cost of the product, according to Jones, with the cost of the coal representing almost two thirds of the gasification cost. Additional cost apportioning shows 1 1 % for initial purification, 2 % for conversion to fuel gas, 2% for final purification, 2% for gas compression, and 8% for auxiliary operations. These estimates do not yet make the procedure economically attractive. Any substantial reduction in cost would most probably have to b e made in the gasification step of the operation. Gas Drying Costs Another techno-economic study, one on techniques for dehydrating gas streams, was reported by John Campbell of Black, Sivalls and Bryson. Available equipment V O L U M E
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was classified as dry desiccant systems, triethylene glycol absorbers, low temperature plants, and glycol injection systems. Campbell advised that no one type of system was best for all applications but that with gases other than natural fuel gas the glycol absorbers are the cheapest to install and operate. They will give gas having as little as 1.2 pounds of water per
Atomic scientists have bought us time with superior weapons, AEC Commissioner T. E. Murray told the engineers. Let us use it to think and act wisely million cubic feet at 100 pounds pressure at temperatures below 90° F. and pressures up to 1500 pounds per square inch. For more extreme service demands the dry desiccant systems will give a dryer product at temperatures up to 125° F. and pressures up to 3000 pounds and is the second choice for all applications other than those involving natural gas. The other two types of dryers both require a substantial pressure drop in the system so that if the gases are not already at high pressure, compression costs make them relatively expensive. However, in natural gas operations they have a special advantage of permitting the recovery of a hydrocarbon condensate which pay for both the installation and operation of the unit in a short time. Of these two types the glycol injection systems have the lowest operating costs and will dehydrate gas for as little as 29 cents per million cubic feet. They also have the advantage of requiring less pressure drop. However, the refrigeration systems can be used over a wider temperature range, according to Campbell. The Arosorb Process Sun Oil Co. is moving toward completion of their 60 million gallon per year aromatics recovery plant which will use their newly developed Arosorb process. Additional technical details on this proc-
DECEMBER
17,
1951
ess were presented to the meeting by James I. Harper of that company. The process involves feeding a dried hydrocarbon stream into absorbers packed with silica gel which will absorb the aromatic fractions preferentially. As the cycle continues t h e aromatics are desorbed from the bed and separated by distillation. The process is essentially a plant scale development of a familiar analytical procedure. For his presentation Harper chose to consider only the recovery of benzene and toluene. In such an operation using a I0O0-barrel-per-day feed rate, he said, the dried hydrocarbons would be passed through the absorbers for 30 minutes. Theoretically silica gel will absorb 0.026 gallon of aromatics per pound but in the plant installation about one-third excess absorbant will be used. At the end of the absorbing period a "push" stream of butane or pentane will be introduced for 10 minutes to force the heavier aliphatics out of the column. Xylene is used as a desorbant and passes through the column for 40 minutes. By careful control the various aromatics recovered could be desorbed and collected separately but Harper said that Sun had found it cheaper to desorb a mixed product and separate by distillation. Resin Catalysts I n commercial production many organic reactions, particularly esterifications, are helped along by the use of an acid catalyst usually one of the strong inorganic acids. David Saletan of the University of Michigan told the engineers that this function can be performed equally well by any of the cation exchange resins in their acid form. These materials provide an environment of equally high acidity but the hydrogen ions are trapped within the particles of resin and cannot get out to create a conosion problem or to contaminate the liquid phase. When resin catalysts are used, he said, the reaction takes place inside the resin particle. He presented rate calculations to show that the reactants must diffuse into the solid phase and the products must then diffuse out again. By these calculations he was able to correlate reaction rate data over a wide range of conditions. Saletan further submitted that these general calculations could be applied to any reaction which takes place primarily in the particles of a disperse phase. Richard H. Wilhelm, professor of chemical engineering at Princeton University, received AIChE's William H. Walker Award. The award was made "for his excellent publication record over the years and for recent outstanding contributions" to the literature of the chemical engineering field. Charles R. Wilke, associate professor of chemical engineering at the University of California, Berkeley, was chosen as this year's winner of the AIChE Junior Award. This honor is given for outstanding contributions to the literature of chemical engineering. 5345
