INDUSTRIAL AND ENGINEERING CHE;MISTRY
January, 1928
The temperature of the driers a t the inletting end is kept a t 1000" C. and at the outlet, 500" C. The dried material is screened and the coarser portions are then passed through a pulverator. The very fine portions are returned for mixing with the incoming wet sludge from the filters. The remainder is conveyed to a storage house with a capacity of 18,000 tons, or the normal production for about 4 t o 5 months. The interior of the storage house is shown in Figure 10. The sludge has a very high fertiliser value and is much in demand. It is known as Milorganite (Milwaukee organic nitrogen). It will be descrihed by Victor H. Kadish in a subsequent paper. Research and Economy
Because of the large amount of research work required to make this plant possible, it is natural that it should contain well-appointed research laboratories. It is too much to expect that a big plant working on previously untried principles should operate at the highest efficiency as soon as completed. Our knowledge of the best conditions required for aeration, settling, and filtering is still incomplete. The plant is now working very satisfactorily, but it is believed that very great savings are going to result from research work now in progress. The plant, without the sewage, cost about ten million dollars and it costs about one million dollars per year to operate. The return from the sale of fertilizer is about one-half million dollars per year and it is hoped
Milorganite-A
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to reduce the cost of operation by one-half, making the actual cost of operation nil, exclusive of capital charges. This is not a wild dream. The research department possesses a battery of four experimental systems, each one fivethousandth the size of the entire big plant. The four systems operate independently and each has its own aeration tanks, settling tanks, chemical treatment tanks, and filters. (Figures 12 and 13) Here it is possible t o study the effect of variable factors, by operating all four systems exactly alike except for the variation of a single factor. The results to date indicate that the air in the aeration tanks need be supplied only in such quantity as may be necessary to keep the water saturated with oxygen and to keep the sludge sufficiently well agitated. With constancy of oxygen concentration, the action proceeds in direct proportion to the product of the concentration of polluting material and the exposed surface of the activated sludge, bacteria playing no part as such. The types of pumps used have an important bearing upon the filtering condition of the sludge delivered and the method of inletting the mixed liquor into the clarifiers has much to do with the purity of the effluent and with the capacity of the entire system. If the results of operation of the small plants can be duplicated in the big plant, we shall need only one-half of the aeration tanks and clarifiers to handle all of the sewage. The savings, including the possible saving in cost of chemical treatment, would be more than half the present net cost of operation, and the research work is only in its early stages.
New Fertilizer Material' Victor H. Kadish
SEWGRACE COMMISSION O F THE CITY
OR the first time in the history of sanitation plant
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food from sewage and trade wastes is being converted into a valuable and commercially marketable fertilizer material. This is now being accomplished on a large scale a t Milwaukee's Activated Sludge Sewage Disposal Plant. The product is being marketed under the trade name "Milorganite," which was chosen as the result of a nation-wide contest among fertilizer people. This name ties up the material with Milwaukee and emphasizes its most valuable ingredient -organic nitrogen. Nature and Composition
Milorganite is an organic product, uniform chemically and physically, and free from bacteria and weed seeds of all kinds. I n appearance it looks not unlike dried coffee grounds. It is finely and evenly ground-95 per cent or more passing a IO-mesh sieve and being retained on a 48-mesh sieve-and contains 5 per cent or less moisture. A composite sample representing 145 carloads shipped between February l and September l, 1927, showed the following analysis : Moisture Total nitroren - .~ ~ _ ~ . . . .o._. Equivalent t o ammonia Water-soluble organic nitrogen Water-insoluble organic nitrogen Nitrogen insoluble in neutral permanganate Availability of water-insoluble organic nitrogen by neutral permanganate method Active nitrogen by alkaline permanganate method Availability of water-insoluble organic nitrogen by alkaline permanganate method Total phosphoric acid Insoluble phosphoric acid Available phosphoric acid 1
Received h-ovember 25, 1927.
Per cen 4.08
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-R . 4 2
6.58 0.30 5.12 0.71 86.13 3.22 62.89 3.08 0.65 2.43
OF
MILWAUKEE, WISCONSIN
This analysis, representing approximately 5000 tons, shows that the insoluble organic nitrogen is in a highly available form. While nitrogen is the most valuable constituent of Milorganite, it also contains some available phosphoric acid which is just as available as the phosphoric acid in acid phosphate. The finished product runs very uniform chemically day in and out, despite variations in the raw material, because the many tanks, conduits, channels, etc., comprise a huge reservoir containing I500 to 2000 tons of dry solids, of which approximately only 5 per cent are withdrawn daily. In other words, the suspended solids removed constitute a very small percentage of the quantity on hand and are balanced against the incoming solids in the raw sewage. Investigations into Fertilizing Value
It was early recognized that the ultimate economic success of the project depended upon the successful marketing of the dried product. In order to determine the fertilizing value of Milorganite compared with other materials in common use, the Sewerage Commission in 1923 established a fellowship in the College of Agriculture, University of Wisconsin, with Mr. 0. J. Noer as Fellow under the direction of Prof. E. Truog, of the Department of Soils. For nearly four years intensive research was conducted in the laboratory, greenhouse, and field. Analyses in the laboratory and pot-culture experiments showed conclusively that the nitrogen in Milorganite was readily available and compared favorably with such standard organic materials as dried blood, tankage, fish scrap, and cottonseed meal.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
10
During a period of three years in excess of one hundred plots were established in Wisconsin on a variety of crops such as corn, potatoes, tobacco, vegetables, small grains, etc., in which Milorganite as a source of nitrogen was compared with other materials. For this purpose ten mixtures of similar analysis were prepared at a middle-western fertilizer plant under actual manufacturing conditions, which obviated the possible criticism that experimental mixtures were not comparable with commercial mixtures. The results secured in the field bore out the preliminary work in the laboratory and greenhouse; in fact, in some instances mixtures containing Milorganite produced greater yields and better quality than those mixtures in which nitrogen was supplied from other sources. Early indications pointed to Milorganite as being an ideal material for turf fertilization. Consequently, liberal samples were furnished to many golf clubs in all parts of the country for use on greens and fairways. Results were uniformly gratifying and demands for the material for this purpose came in long before production got under way. Production and Marketing Results During 1926 production was intermittent during the first half of the year, and up to July 1 only 500 tons were pro-
Vol. 20, No. 1
duced. From July 1 to December 31, inclusive, production was approximately 5000 tons, or 27 tons daily average. Shipments for the year amounted to 2200 tons, of which about 80 per cent went to fertilizer manufacturers and the remaining 20 per cent to special markets such as golf clubs and florists. For the period January 1 to November 15, 1927, production was 16,600 tons (daily average 50 tons). During the same period shipments were 19,700 tons, of which 3000 tons went to special markets and the remainder to fertilizer manufacturers. Orders on hand for delivery up to May 1 amount to 13,000 tons, which will absorb the estimated production to that date. The average return has been about $15.00 per ton f. 0. b. Milwaukee. While the price fluctuates with market conditions, the average return over a period of years should not fall below this figure. In the event of future operating economies the return from, sales of Milorganite should offset a portion of the cost of purifying the sewage. At the present time, with an average of 80,000,000 gallons of sewage treated daily, the monthly production of Milorganite is about 2500 tons. For the year 1928 it is estimated the output will run between 30,000 and 35,000 tons. The successful marketing of Milorganite is no longer problematical and every ton produced should be readily placed.
Synthesis of Methane from Water Gas'" Frank W. Hightower and Alfred H. White DEPARTMENT OF CAEMICAL ENGINEERING, UNIVERSITY OB MICHIGAN, ANNARBOR,MICH.
This paper presents the results of a study of the conversion of mixtures of C02,CO, and Hz,to CH4 and other products a t temperatures of 280-370' C. while a t atmospheric pressure and in presence of a nickel catalyst. The results are in general agreement with other investigators in showing the formation of large proportions of methane from gases containing CO, Hz, COa, and H20 within fairly wide limits of composition. The decomposition of CO according to the equation 2 c o = c co* appeared to a small degree a t 300-370' C., but was somewhat erratic in quantity. I t is suggested that the decomposition may be autocatalytic since the decomposition appeared to be less with new catalysts. The path of the reaction as between the three equations usually written CO 3H2 = CHI H . 0 (1) COz 4Hz = CHa 2H20 (2) 2CO 2H2 = CHI COz (3)
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depends upon a number of conditions. Reaction (2) appears to be uncomplicated. The question as t o whether (1) or (3) dominates is largely a function of the water vapor present. Water vapor represses (1) to a marked extent. If conditions are arranged so that t h e water vapor is removed a t intervals during the conversion, reaction (1) predominates. The equilibrium constants obtained from this experimental work are compared with those calculated from published data on the reactions. CO Hz0 = Con Hz C 2Hz = CH, 2co = c coz The most probable values calculated in this way for log, K of the combined reactions vary from 19.4 t o 22.24 a t 350" C. The highest value we have obtained experimentallf is 19.6 and the experimental results are in general below the theoretical.
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A
LL efforts to synthesize methane from carbon monoxide or carbon dioxide and hydrogen reacting in
the gas phase failed until Sabatier and Senderens',* took up this problem in 1896 in the course of studies of the catalytic effects of finely divided metals on gas reactions. They soon determined that, the conditions of preparation being equal, catalysts of nickel had a more pronounced effect than catalysts of other metals. The possibilities of industrial 1 Presented before the Division of Gas and Fuel Chemistry a t the 74th Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 1 This paper forms a part of the dissertation submitted by Mr. Hightower in partial fulfilment of t h e requirements for the Ph.D. degree a t the University of Michigan. Numbers in text refer to bibliography a t end of article.
*
utilization of such hydrocarbon syntheses were recognized and numerous records in the patent literature attest to attempts to carry out the synthesis of methane on an industrial scale. As this provides a method of converting a non-combustible gas (COz), as well as a gas of low-heating value (CO), into a hydrocarbon gas of high-heating value, the processes were naturally first applied to the various forms of artificial consumers' gas, such as illuminating gas and water gas. Within a few years of the publication of Sabatier and Senderens' first work' other investigators had turned from the commercial applications of the synthesis to the chemical principles underlying the reactions, Attempts were made to follow the course of the reactions, determine the conditions for optimum production of methane, and formulate the en-
