1078
INDbS’lHIAL AYI)
ENGlNEEIIlNG
ated peat, from the standpoint of tlie cheapness and abundance of tho miv materials alone. Peat, one of the raw materials entcriiig into the arnmoniated product, is lvidely distriliuted in conimercially workable deposits within short distances of the principal fertilizerusing parts of the country. E’reiglrt charges on the raw materials should be low, especially as liquid annnonia niay be shipped in tank cars to Incations convenient to the peat beds. I n certain locatims where p i t and phosphate rock occur close to each other, the prepwation of the raw material, it6 processing to the anrmoniated product, and its incorporation in a niixed fertilizer might be carried out. to admiitage a t the same location and iii juxt8posit.ion to an intensive fcrtiher-consuming area in whiclr organic nitrogen carriers are often preferred. The other material entering into tlie t,reated yrodnct is arnmouia, the most abundant and one of tire cheapest forms of nitrogen obtainable for fertilizer Inanufact,ure. Derived from nitrogen fixation processes and from by-product. coke ovens, it is shipped buth as anhydrous and aqua aninionia in tank cars. liefore treatmerit with annnonia, it. would probably he desirable to dry the peat to some degree. Possibilities of air drying and of artificial drying are presented. Tlie cost of preparing peat for fuel purposes was studied several years ago by the Iiureau of Mines ((i).The conclusions, based largely on the work of Canadian engineers on Canadian peat, indicated that the cost of peat fuel (air-dried, niacerated peat containing 30 per cent moisture) based on 100 working days of 10 tiours each is $4.48 per ton on board cars at siding.
C11ERIISIIIY
Vol. 2 5 , n o 10
On a W-liour day h i s it is estimated at $3.50 per ton, with full allowance for overhad and dcpredation. The cost of similar drying iii t,his country should not exceed this fignre and in many locations should be considerably reduced, especially in the warmer portions of the eonrdry \&ere the number of working days is greater. The process for carrying out the ammoniation involvcs a nunibcr of technical questions which >ire yet to be solved, but the possibility of its commercial production seems promising. Ilotti raw materials are abundant and clienp, and the proc~rssingrelativcly simple in principle at least. Many details connected with the properties arid production of aninioniated peat, are being investigated to obtain a definite pictnm of its usefu1nei.s.
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( L J haaui:. Ofliaiul Agr. Chein., Oificid and Teiiliitivi Metiruda of Analysis, (‘hap. 11, p. 24, pp. 3040 (1931).
( 2 ) Cam, S.. xxid Frank, A. It., French Patrnt 689,011 (Jan. 28. 1!130): 1irit.ish Patents 347,G41 (Aiidl 29. 1!1:3Ij, arid il.iD.004 15, 1%2oj. (4) Eramius, P., German Patent 514,510 (XOY.7, 1928). ( 5 ) Feustd, I. C., end Ihrrs, K. G., Dept. Agr, Tech. Bull. 214 (1933).
(6) Odeli, W.W.,and Hood. 0.P., Bur. Mines. Bull. 253, 7, 19 (1028). , (7) l’ortman, E., German Patent 618,792 (She. 8, 1928). (8) Wdton, G . P., and Gardiner, R. P., U. 8. Patent 1,858;2:10
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(Xsy IO, 11132). Rr;ir:iu~u hoiii l a , 1833. Preseoted before lie Diviiiun of Agricultursi end Food Ciiemictry a t the 85th Meeting of tlie lmeiioan Chemiosl Society, Wseiiinpion, D. C.. Maroh 26 to 31, 1933.
Electrically Heated Steam Generators for the Process Industries S. %. O w h*, Westinghouse Electric and Manufactitring ASY of tlJe prroeess indnsbries generate their own electric energy, utilizing bled or exhaust steam for process Iiertting. The problem of balancing tire electric load and the steam load is a difficult one and often leads to ti waste of fuel. AI, electric stearn boiler located a t the point of use of stearn heat can be of material assistance in obtaining t,hat balance so necessary t o economical operat . i o n . Sucli an application also aroids the heat losses occasioned by long steam lincs to remote parts of the chemical plant. Still other p r o c e s s indiiitrirs using purchased electrical energ!: have a boiler plant for the winterofice heating load and for tire yearly process heating. Wliere the J m J C ess heating requirement8 arc small, it is often econoniical to produce steam electrically during the warm weather so that the power boiler may Re shut down. Thus the expensive o p e r a t i o n of tire power hniler is eliminated when the major portion of its capacity is not required. Although the cost of electrical energy m a y be h i g h e r t h a n tlie
Company, hlansfield, Ohio
cost of energy obtained by using gas, oil, or coal, this difference is usually overcome by savings 011 insurance, floor space, maintenance, working conditions, and labor savings. The number of rejects are also greatly reduced in many cases by using steam at the correct temperature required. The electric boiler may also be used in winter to take peak loads t,liat might exceed tlie capacity of the existing equipment. Where small amounts t ~ fprocess steam are required a t given pressures or temperaturcs, it is often economical to produce steani electrically. An illustration of this is mliere higher temperatures are required than can be obtained with the power house steam. Supposing the power liouse steam can be d e l i v e r e d where needed at 125 pounds gage p r e s s u r e (350’ P.) but for the given process a steam temperature of 375O F. is required. An electrically heated steam generator of a suitable size, generating steam at, 185 ponnds gage pressure (375” P.1. .. can he used to advantage. The only energy loss in the electric boiler, barring small electrical line losses, is the radiation loss of
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October. 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
the generator shell and pipes. With the generator shell properly insulated thermally and the short pipes covered, it is feasible to expect efficiencies of 95 per cent or higher. ADVANTAGES Electrically heated and electrically controlled steam generators may be made entirely automatic in operation; therefore, it is usually unnecessary to employ a licenbed operator. The heaters are so controlled that, if the water reaches a predetermined low level they are switched off; also. if the pressure reaches a predetermined maximum, the heaters are switched bff. The apparatus for supplying the feed water to
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I n this case the pressure of the steam generated was less than the feed water supply pressure. The automatic feed consisted of a float-operated mercury switch installed on the generator shell and a solenoid-operated valve installed in the feed water supply pipe line. When the water reached a low level, the float forced the mercury sx-itch t o the “on’, position, which in turn energized the solenoid holding the valve open, permitting the water to be fed into the generator. As soon as the water raised the float to the normal water level, the mercury switch was forced to the “off” position, the solenoid was deenergized, and a spring forced the valve closed. This is only one of several schemes that may be used. The apparatus for each application, however, must be determined after all conditions obtaining and t o be met have been considered. There are almost innumerable uses for electrically heated steam generators; a n outstanding one is in hospitals where silent, safe apparatus is needed for generating steam for sterilizing. The steam generator can be made t o meet the demand for hot water and high-pressure steam as needed, which is not always true with regular power house equipment.
IN POUNDS
FIGURE 2 . STEAM-WATER CURVE Power, 10 kw-hr.2 pressure, 100 pounds gage: feed water. 60 F.; efficiency, 95 per cent
the generator is simple and may be made automatic. These safety features, together with a relief valve or valves, and low-water and high-pressure alarms, make this apparstus almost as safe as the most energetic promoter of “Safety First” could hope t o obtain. The operation then becomes a matter of occasional inspection, with less frequent blowdowns, Tvashouts, and maintenance than may be required by any similar boiler. On an application requiring 7 5 pounds of steam per hour a t 100 pounds gage pressure, a steam generator 16 inches inside diameter, 48 inches long, with a suitable steam dome and with electrical immersion heaters, and having a total rating of 30 kw. is required (Figure 1). These, with a contactor panel, low-water and high-pressure controller, and the necessary feed water apparatus, make up the equipment. With a n inside diameter of 6 feet and a length of 6 feet, a 1500-kw. unit will deliver 4000 pounds of steam per hour at 100 pounds pressure. It often occurs that in a given process both steam and hot water are required. Such a problem is easily solved with this generator. The hot water as well as the steam can be made available where the process is carried on. The generator is compact. The accessories such as switches, contactor, and feed water apparatus can be mounted on a wall or overhead, and floor space is saved. If one desires, the complete unit may be mounted on a skid so that it becomes portable. All that need be done is to make electrical and water connections when the generator is moved to the place where it is needed. USE The owner of a small dairy purchased an 18-kw, generator, 16 inches in diameter and 48 inches long, (Figure 1) and in a short time his demand’ for steam and hot water increased. New heaters were installed, raising the rating t o 22 kw.,which met his demands. The rating could be increased to 30 kw. t o meet further needs. This generator, when first installed, was not equipped for supplying the feed water automatically. Too much lost time soon demonstrated the economy of automatic feeding apparatus which subsequently was installed.
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FIGURE 3. LOSS-PRESSURE CURVES Generator, 16 inches i. d. X 48 inches long
Figure 2 shows a curve for water us. steam that can be generated with 10 kw-hours a t 100 pounds gage pressure-for example, 5 pounds of steam per hour and 11.5 gallons of water a t the same time. If a generator rated a t 30 kw. is available, it is possible to generate 15 pounds of steam and heat 34.5 gallons of water. If hot water is not needed, 27.8 pounds of steam can be generated, using 10 kw-hours, or if no steam is needed, 13.8 gallons of water can be heated. While this curve is not exact, it is correct enough for rough checking. Figure 3 shows the losses of a steam generator such as that shown in Figure 1 at various pressures. The generator in this case is 16 inches inside diameter and 48 inches long, and has a dome 8 inches in diameter and 8 inches high. RECEIVED M a y 27, 1933.
CORRECTION.In the paper on “Improved Process for Physical Development of Plates, Films, and Lantern Slides” by A . F. Ode11 [IsD. ENG.CHEM.,2 5 , 878 (1933)], the developing formula given in the fifth paragraph of the second column calls for the use of 0.025 gram of amidol; this should read 0.25 gram.
