Farmer, E. H., J. Chem. SOC.,1943, pp 119,122,541. Feuell, A. J., Skellon, J. H., ibid., 1954, p 3414. Heaton, F. W., Uri, N., J. Sci. Food Agr., 9,781 (1958). Kline, G. M., “High Polymers,” Vol 12, “Analytical Chemistry of Polymers,” Part 1, p 127, Interscience, New York, N.Y.,
Skellon, J. H., J. Sor. Chem. Ind., 50,382T (1931). Wagner, G., J. Russ. Chem.Sor., 27,219 (1895). Wiberg, K. B., Saegebarth, K. A., J. Amer. Chem. Soc., 79, 2822 (1957).
19.59.
Kljne,-G. M., ibid.,Part 3, pp 84,89,1962. ‘Singh, E. J., Gershbein, L. L., J. Chem. Educ., 43,29 (1966).
RECEIVED for review July 31, 1972 ACCEPTED December 1, 1972
Evaporation Control on Water Reservoirs Russell G. Dressier*' Trinity University, San Antonio, Tex. 78111
E. Guinat Shamtan Lubricants and Chemicals, L.T.D., Tel-Aviv, Israe
Equipment design and procedure are described for use in the full-scale application of monomolecular films by use of the suspension process on two lakes of 200-700 acres in Israel. Objectives were to determine general feasibility of method, critical wind speeds, and other factors. A high degree of film coverage was maintained for long periods. Quantitative data were collected from five fully controlled tests lasting 10 days each. On a lake of 700 acres, the critical wind speed was 15.5 mph. The dispensing system method was capable of longrange application.
S i n c e Mansfield’s (1955) first outdoor trials in 1953, scientists have been seeking a practical method for applying monomolecular films to reservoirs. One method suggested is the suspension process (Dressler, 1959), described and illustrated progressively in various publications (Dressler and Johnson, 1958; Dressler, 1964). Briefly, the Dressler patent discloses the application of ClrCzo fatty alcohols on reservoir surfaces in the form of aqueous suspension or emulsions, with or without emulsifying or suspending agents. Suspensions of 50-200 mesh fatty alcohol powders in water up to 50% concentrations can be pumped and effectively solve bhe problem of coritinuous addition to reservoir surfaces a t spaced intervals. We found early in the experimentation period that dispensing the suspension from regularly spaced points (say a t 50-ft apart) a t the rate of about 0.7-2.0 oz of alcohol/ hrloutlet can maintain a n integral film. KO pollution results from such treatment. Much has been written about wind effects and its role in disrupting a continuous film cover. Film drift is also import’aiit, and film drift rate dictates film application rate. Vines (1962) reports a film drift of 1/30 of the wind speed; t’his has been confirmed by others. Meinke and Waldrip (1964) have shown with the suspension process that consumption of alcohol is 0.5 lb/100 ft of shoreline/mile of wind velocitylday. This is equivalent’t o 1.8 oz/hr a t 50-ft intervals wit’h wind speeds of 10 mph and corresponds with the Dressler findings. The present paper is concerned with the suspension process for applying films, its equipment development, small and large-scale trials in t’he U S . , and finally, the demonstratioil trials in Israel. Present address, 204 Carolwood Drive, San Ant,onio, Tex. 78213. 80
Ind. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1 , 1973
Early Trials in U.S.
The first engineering work was done in the U.S. on a 2acre lake at San Antonio, Tex., by dispensing a suspension of octadecanol in water from &gal drip cans. A reservoir could be kept covered with film under reasonable wind speeds if applied at above the minimum rate. It also shed light on problems, such as plugging of drip orifices, settling of suspensions, and tenable wind speeds. Drip cans are inadequate for applying films to reservoirs of any size larger than a few acres. Consequently, efforts were directed toward the development of a pumping system with orifice outlets to supply the film material to the reservoir surface. First trials concerned testing the uniformity of orifice discharges from plastic hoses. Variation was within *7% (Dressler, 1962). h simple unit was built consisting of a gasoline-driven water pump with belt-driven slurry concentrate pump. To this was connected 1-in. diam plastic hoses having 1/8-in. holes on 50-ft spacings. The hoses led in two directions, lay in shallow mater, and were held a t the surface a t each orifice point by heavy wire supports imbedded in the lake bottom. The unit was operated so that the slurry concentrate was diluted about 100: 1 with fresh lake water before being pumped through the hoses. With this single unit, a 50-acre lake at Eagle Pass, Tex., was maintained covered with film a t will (Chenz.Eng. News, 1958). Others have experimented with the suspension process on small reservoirs, i.e., those under 5 surface acres, and have confirmed the feasibility of this method of application. Some of those who have experimented with the process in independent trials were Roberts (1959), Drew (1958), Crow (1961), Neinke and Waldrip (1964), and Reiser (1969). Following the successful trials on the 50-acre reservoir at Eagle Pass, Tex., trials nere conducted on a 330-acre reservoir
U.S.Geological
near Eagle Pass to emphasize the necessity for power-driven equipment. Some of the questions to be resolved during the early experimental trials were :
Survey studies and results (Langbein et al. 1951) presents the use of hydrology data to distinguish between seepage loss and evaporation loss on a n outdoor reservoir.
(1) Would there be difficulty with settling of the slurry with or without continuous stirring? (2) What spacing would be required for orifice outlets? (3) What would be the effects of wind on forward and on lateral movement of the film? (4)What would be the maximum wind velocity tolerable? (5) Would there be a, problem of caking of powdered alcohol on shipping and storage? (6) Would the orifice outlets plug? (7) Would there be a fairly uniform distribution of the film material within requirements?
Israel Equipment Design
I n the preliminary trials on land and on 2- and 50-acre lakes, Dressler obtained data sufficient to answer most of these questions. Continuous stirring was desirable but not necessary if correct suspending, emulsifying, or thickening agents were used (1). Concerning (2), 50-ft spacing or less is desirable. I n regard to (3) and (4), these are factors to be studied more thoroughly on a larger reservoir, such as in Israel. I n shelf tests powdered hexaclecanol can be stored in 100-lb fiber containers for years without caking (5). The powdered material should be well screened before slurrying, and there must be screens on the discharge of the slurry pump feeding the distribution hoses (6). I n addition, orifices must be above a minimum size, i.e., about l/s-in. diam or larger. Of course, orifice size and spacing influence slurry concentration t o be provided in the distribution lines, as well as resultant pump and line pressures required. The seventh question was answered in the preliminary tests on land, showing t h a t distribution was uniform and well within requirements. Other questions concerned the details of the system design, type of support for distribution lines, and servicing the system with raw materials in the field. Another question was the cost of saving 1000 gal of water by use of such a system. Economics of Film Treatment
The costs of treating a reservoir have been studied by various persons, and the results have been revised over the past 15 years to accoimpany the improvements in efficiencies of the process. Dressler (1964) estimated that costs of saving 1000 gal of water would normally be within the range of 1-3 cents for large reservoirs, Le., 2000-60,000 acres. Reiser (1969) confirmed these figures. These costs are based on assumed water-saving efficienclies of around 40%. Of course, better efficiencies would lowier the costs. Recently, Simko and Dressler (1969) and others (Koe and Dressler, 1967; Foulds and Dressler, 1968) investigated the effect of odd and even carbonchain fatty alcohol blends. These blends achieve up to 88% water evaporation retardation in laboratory tests as compared to 50% with siingle fatty alcohols. Although these are laboratory figures, they probably reflect some degree of improvement on outdoor reservoirs. Costs in this case would be relatively improved, especially because the cost of the alcohol is the single major expense in the operation (Dressler, 1964). I n the Lahfer pu’blication (Dressler, 1962), the chapter entitled, “Engineering Approach to Evaporation Control,” contained sufficient data to allow the design of a commercial size suspension process application unit. Methods were set forth also for measuring evaporation rates with and without film and water savings. A method that is an application of the
I n the early part of 1967, Tahal was commissioned to make a survey of water evaporation retardation methods. Tahal (P.O. Box 11170, Tel-Aviv) is a n official agency of the State of Israel, advising in the field of water conservation and usage. J. Frenkiel of that organization and E. Guinat headed the program to select the best method of application available and to design, install, and demonstrate commercial-size equipment on two 200-acre lakes in the Tel-Aviv area. Frenkiel was familiar with the technology of evaporation control as a result of a survey made by him in 1962 (Frankiel, 1962) and publication subsequently, of a book on the general subject (Frenkiel, 1965). One of the above-mentioned lakes (both man-made) was Kishon-Lake (at Kfar Baruch, 60 miles north of Tel-Aviv) of irregular shape with two side arms and the prevailing wind from the west or noithwest. This lake, which varied from 200 to 700 acres depending on the season, was the site of the initial trials, by use of one film application unit. I n the Israel area, the rainfall is 14 in./year, and evaporation 75 in./year. The second lake was about 40 miles south of Tel-Aviv (near Helets) and was nearly circular in shape and, therefore, better susceptible to treatment. One of the objectives was to gain the basic knowledge of the process to allow the eventual treatment of Lake Tiberias (Sea of Galilee, 6 X 15miles). The initial design for the application equipment was done in San Antonio, and the fabrication of five commercial units was accomplished in Tel-Aviv. The design was based on data taken from land-pumping trials through plastic lines with orifices and from information gained in the Eagle Pass, Tex., 50-acre lake trials. The application units consisted of a slurry make-up tank mounted above a dilute circulation tank. The drive was a diesel engine, operating two pumps and two agitators. Each unit had lines, one on each side of the pump to cover 0.4 mile of shoreline. Thus, a unit would cover 0.8 mile. The slurry lines were in the form of a loop, with 2-in. plastic lines outgoing and 1-in. lines returning. The distribution was originally through 40 orifices a t 50-ft intervals for each of the two lines. Later, these were closer spaced. The orifice holes were fitted with cone-shaped brass inserts to prevent plugging. These were of l/lc-in. minimum dimension originally. The unit was gravity-flow, 7 ft high with a 4-ft square base, and mounted on skids. The lines were secured in shallow water by heavy wire hangers driven into the lake bottom, spaced to bring the distribution line to the surface a t each orifice location. Operation and Results
I n the first day’s operation on the northern 200-acre lake, it was possible t o maintain a film over a down-wind sector of the lake with one unit (wind velocity, 12 mph) substantially covering a major portion of the lake. The material was Condea (Hamburg) spray-dried C16-c~ powdered alcohol. The slurry concentrate was 15 w t % and diluted 100-200 to 1 in the distribution pump by intake lake water. With orifices a t l/lc-in. size, some clogging was experienced, but by putting the slurry through a colloid mill, this was cirInd. Eng. Chem. Prod. Res. Develop., Vol. 12, No. 1 , 1973
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cumvented. I n the 1968 tests in some cases, coverage was maintained up t o 30 km/hr (18.6 mph). Trials were made with slurried alcohol with 10% monoethoxylated alcohol added. After the 1967 tests, the orifices had been enlarged. This required, in turn, an increase in the dilution and resultant amounts of water t o be pumped. The pumps were changed, and the pumping system was redesigned. Tahal has been studying the data and is preparing a comprehensive report. The data collected are being processed, based on energy balance and not on direct measurements of quantities. The major contributioiis thus far are as follows: .critical I wind-speed limit was established above which even double quantities of alcohol did not preserve the monolayer. During two full seasons, large-scale tests were carried out, and comprehensive data were collected as to the percentage of coverage obtained, especially a t various wind speeds which tend t o break up the film. On a lake of 3 km2 (700 acreh), a critical wind speed n a s about 25 km,’hr (15.5 mph), above which it is unfeasible to maintain the lake cover, even when using much increased quantities of alcohol. The dispersing system (suspension process) was further improved, proving it capable of long-range application, and a foolproof system for easy maintenance and operation is being worked out. Quantitative data, collected from five fully controlled test series of 10 days each, confirmed that it is feasible t o maintain a high percentage of coverage for long periods.
literature Cited
Chem. Eng. Sews, 36, 44 (June 30,1958). Crow, F. R., Agr. Eng., 42,240-43 (May1961). Dressler, R. G., I$. Eng. Chem., 56, 36 (July 1964). Dressler, R. G., Retardation of Evaporation by Monolayers,” V. K. LahIer, Ed., pp 203-11, Academic Press, New York, N.Y., 1962. Dressler, R. G., U.S. Patent 2,903,330 (1959). Dressler, R. G., Johnson, A. G., Chem. Eng. Progr., 54 (I), 66-9 (1958).
Drew, H. F., Report of S. W. Evaporation Research Council, Texas Water Board, Austin, Tex., 1958. Foulds, E. L., Dressler, R. G., Ind. Eng. Chem. Prod. Res. Develop., 7 , 7 5 (1968). Frenkiel, J., “Evaluation of Evaporation Reduction in Field Trials,” lecture given at symposium on Water Evaporation Control, Poona, India, December 1962. Frenkiel,, J.., “EvaDoration Reduction,” Unesco, Paris, France, 1965.
Langbein, W. B., Hains, C. H., Culler, R. C., U.S. Geol. Survey Circ. No. 110, 1951. Mansfield, W. W., Nature, 175,247 (1955). hleinke, W. W.,. Wddrip, W. J., “Research on Evaporation in Small Reservoirs, Texas Water Comm. Bull. 6401, March 1964. Xoe. E. R.. Dressler. R. G., Ind. Ena. Chem. Prod. Res. Develov.. ., 6,‘132, (1967).
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Reiser, C. O., I n d . Eng. Chem. Proc. Design Develop., 8 , 63 (1969). Roberts, W. J., J. Geophys. Res., 64 (lo), 1605-10 (1959). Simko, A. J., Dressler, R. G., Ind. Ena. Chem. Prod. Res. Develop., _ . 8,446-50 (1969).
Vines, R. G., “Retardation of Evaporation by Monolayers,” p 137, Academic Press, New York, N.Y., 1962. RECEIVED for review December 11, 1972 ACCEPTEDDecember 15, 1972 Presented at the Division of Colloid Chemistry, 164th Meeting, ACS, New York, N.Y., August 29,1972.
Size and Shape of Asphaltene Particles in Relationship to High-Temperature Viscosity Hendrik Reerink KoninklijkelShell-Laoratorium (SheU Research B.V.), Amsterdam, T h e Netherlands
I
EDITOR‘S NOTE The manuscript for this paper was duly studied, and in the judgment of a respected reviewer, certain conclusions require qualification. T h e author countered with (in his professional judgment) appropriate explanations and interpretations. These, however, have not satisfied the reviewer’s concepts, though he recommends that the work be published. W e have here a classical instance of two competent scientists advancing a segment of technology by objective debate. Fortunately, the Signals section provides an opportunity to publish, while at the same time offering a medium for each party to submit “Correspondence” in future issues.
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82 Ind.
Eng. Chem. Prod. Res. Develop.,
Vol. 12, No. 1, 1973
Bitumens can be split by means of n-alkanes into a n extremely viscous oil (maltenes) and a solid precipitate (asphaltenes) , The rheological properties of bitumens depend strongly on the asphaltene content. This is clearly demonstrated in Figure 1, which has been constructed from data obtained by Mack (1932) in measuring the viscosity of solutions of asphaltenes in the parent maltenes. I n the books of Pfeiffer (1950) and Hoiberg (1964), the role of the asphaltenes is also stressed. That asphaltenes are of relatively high molecular weight is apparently of importance. I n a survey, Dickie and Yen (1967) quote values for the molecular weight ranging from about lo3 to above 105. The high molecular weight itself cannot explain the influence on rheology, For instance, if the asphaltene molecules solution would were spherical and nonsolvated, a 10 vol
