INDUSTRIAL A N D ENGINEERING CHEMISTRY
874
Vol. 19, No. 8
The Place of the Diesel Engine in Chemical Industry' By Edgar J. Kates2 203 WEST 1 3 r ~ ST., NEWYORK,N. Y. DIESELS FOR PRIMARY POWER
I
S CHOOSIXG a locat'ion for a chemical plant a number
of factors must be considered. D. H. Killeffer3 has succinctly indicated these factors in the following words :
The ideal chemical plant location would be directly a t the supply of raw materials, close to markets, immediately in the center of an area from which plenty of cheap, intelligent labor might be drawn, close to sources of power, bountifully supplied with water, far enough from habitations and near enough t o sewage facilities t o prevent undue expense from nuisance disposal, and finally in intimate contact with both raw materials and markets through adequate transportation facilities.
The primary reason for locating close to sources of power is, of course, to obtain cheap power. This is true Ivhether the power source is coal, transported either by railroad or \rater, or central station electricity carried upon wires. The importance of cheap power as compared with the other factors of cheap labor, raw niat'erial, and the like, depends upon the amount of power consumed per dollar's worth .of product. I n such industries as the electrolytic manufacture of aluminum, the grinding of logs into paper pulp, or the manufacture of ferromanganese, the power required is so great with respect to the value of the product t'hat thcse industries, in order t'o be commercially successful, must locate where they can obtain power a t minimum cost-close t o favorable hydroelectric developments, such as at Siagara Falls and in parts of Canada and Sori%-ay. In many chemical industries, however, the amount of power relative to the value of t'he product is not enough to doniinate the other factors. Such plants will be located Tvith more reference to raw materials or markets. Xevertheless, even ill such industries the item of power is by no means insignificant, and any savings that can be made in power costs will be clearly reflected in the net earnings. For instance, a concern may have annual sales equal to its capitalization .and be paying an 8 per cent dividend. Even though its power cost is only 10 per cent of the value of the product, a saving of but 20 per cent in the power item will permit the payment of 25 per cent more money in the form of dividends. It therefore behooves such industries to keep informed regarding the advances continually being made in the field of power production and to take advantage of the economies possible by utilizing modern Diesel engines. Freedom of Location
There is one characteristic of Diesel engine power which commends it particularly to the chemical industry. This is the fact that a plant generating its own power by means of Diesel engines may be located practically anywhere and still have cheap power. Full advantage can therefore be taken of proximity to raw materials, to markets, t o cheap labor, or whatever other considerat'ions are influential in that particular branch of the industry. Thus the use of Diesel power results in a double saving-on the one hand a reduction in material-handling, labor costs, nuisance disposal and t,he like, and on the other, a decrease in the cost of power itself. The first-mentioned class of saviiigs mill in some cases far exceed the second. Received April 19, 1927. Chairman Oil and Gas Power Division, American Society of M e chanical Engineers. a THISJ O U R N A L , is, 253 (1926). 1
2
Super-power Possibilities Overrated
Super-power and giant-power projects have received so much attention, particularly in the political arena, that many have come bo believe that it is only a question of a few years before electric power from falling water or from immense efficient steam stations will be available almost everywhere in our land, a t a cost next t'o nothing. It is true t'hat such power can be generated cheaply; the modern steam central station produces a kilowatt-hour for only 7 mills, including the fixed charges on the power house. Some hydroelectric projects favored with low construction costs and steady flow of water do still better. But the cost of delivering this power to the consumer is of a magnitude not generally appreciated. As a country-wide total, the investment in public utility transmission lines, distributing systems, and other things out'side the power house itself is considerably more than the amount invested in producing the power. Furthermore, the cost of operating the distribution agencies, such as the upkeep of t,he wire systems and substations, and the loss of energy during transmission (averaging 19 per cent), are graT7-e items of expense that must be paid out of the final price of the power to the consumer. Even with the present extent of transmission systems these expenses are so burdensome that the average price of electricity, obtained by dividing the gross revenue of the nat'ion's electric public utilities by the number of kilowatt-hours sold, is 2.8 cents. With longer transmission systems the unit cost of didribution will increase, so that little, if any, of the economy a t the power-generating end will reach the final consumer. This is one of the reasons why central station energy in a great' many cases cannot compete with a private power plant. Remote Locations Favor Diesels
I n locations where transmitted electric power is not to be considered, either because, though available, it is too expensive and unreliable, or because the place is too remote to justify the cost of building a transmission line, the type of private power plant to be chosen will depend upon the nature of the processes involved. If much low-temperature heat and little power are required, and if the heat and the power are needed a t the same time, coal is usually the cheapest fuel to produce the heat in the form of steam while the power is developed as a by-product in steam engines or turbines acting as reducing valves. Frequently, however, the required amount of power cannot be developed simply by taking advantage of a pressure drop in the steam used in processing. The power may be required a t a different time than the process steam, or the ponTer demand may be so large that much of it cannot be developed from the process steam. In such cases the power is not a by-product of the heat and becomes much more expensive. Such conditions are ideal for Diesel engine power. Kot only is Diesel power cheap, but a Diesel power plant may be used anpvhere. The undertaking can therefore be located quite independently of power considerations. A 1000-kilowatt Diesel power plant, using oil a t 4 cents per gallon, and serving an industry operating on a 24 hour per day schedule, will produce power a t a cost, including overhead charges on the investment, of 0.85 cent per kilowatt-hour. As a result of the high thermal efficiency, the fuel consumption is
IXDUSTRIAL A N D ENGINEERING CHEMISTRY
August, 1927
low and the fuel cost is only 0.35 cent per kilowatt-hour. If, because of extreme inaccessibility or remoteness of the plant, transportation charges double the price of the fuel to 8 cents per gallon, the total cost of power becomes 1.20 cents per kilowatt-hour, by no means a n excessive figure. A steam turbine plant of corresponding size will use about 2.7 pounds of coal per net kilowatt-hour, which with coal a t $5.00 per ton gires a fuel cost of 0.70 cent per kilowatthour and a total cost of 1.35 cents per kilowatt-hour. If the cost of coal is doubled because of extra transportation expense (and under the same conditions coal transportation is much more expensive than oil), the total cost of power in the steam plant rises to 2.05 cents per kilowatt-hour. The relatire independence of the Diesel plant as regards variations in the cost of fuel is obvious. Water Scarcity
I n localities where water is scarce or expensive the Diesel engine has the advantage of a low water consumption. The water circulated through the jackets is about 9 gallons per kilowatt-hour, and as it is a simple matter to recool it and use it again, the water consumption can readily be limited to less than 0.5 gallon per kilowatt-hour. This is but a small fraction of the water required by a steam plant. I n fact, the Diesel plant uses so little water that this oonsideiation does not enter into the question, whereas with a steam plant it is paramount. Diesel Reliability
The reliability of Diesel engines is today hardly questioned. Records of numerous plants running under various conditions have uniformly testified to a remarkably low percentage of time out for repairs. Table I shows a typical month’s record of a n oil pipe line installation comprising three p u m p ing stations each containing three Diesel-driven pumps. The engines are required to be under heavy load continuouslyi. e., 24 hours a day every day of the month. There are no spare units. The performance shown, 99.70 per cent, has been accomplished month after month with little variation.
875’
Range of Sizes
Diesel engines can be obtained in a wide range of sizes suitable for most industrial applications. Most of the engines regularly manufactured range from 40 to 2000 kilowatts, but engines can be had as small as 10 kilowatts and as large as 10,000 kilowatts. Small engines have practically the same fuel efficiency as large ones, which is by no means the case with steam plants. Advantage can be taken of this characteristic by building power plants containing a number of Diesel engines to run simultaneously when carrying the maximum plant load. This not only insures greater flexibility in meeting variable conditions, but also makes it possible to add engines to the plant as the power requirements increase. I n a steam plant, on the other hand, the fuel economy of large units is so much greater than that of small ones that it is common practice to put in a plant much larger than the present needs in order to secure better efficiency for the future. Such idle investment is avoided in the Diesel plant. Plant Costs
On account of improrements in design and methods of manufacture, the cost of Diesel engines has declined quite remarkably in the last five years, and prices are generally lower even than pre-war figures. The cost of a complete plant depends upon a number of variables, such as freight, foundations, and type of building. However, as a first approximation, the cost of a 500- to 1000-kilowatt Diesel generating plant, complete except for the land and building, will be about $135 per kilowatt. This compares favorably with the cost of a high-grade steam plant of equal size, including boilers, stokers, stack, turbines, condensers, piping, draft fans, coaling equipment, and the other necessary auxiliary equipment.
O u t for Repairs for Nine Diesel-Driven P u m p s in C o n t i n u o u s Operation o n Oil Pipe Line (Typical month’s record) TIMEI N SERVICE TIMEOUT FOR REPAIRS TIME DIVIDEDB Y INSTALLATIOX A N D ADJUSTMENTS IN SERVICE TIXEWANTED Houvs Houvs Per cenf Station A: 0.58 719.42 Unit 1 710.92 9.08 Unit 2 720.00 Unit 3 0.00 Table I-Time
-
Total Station B: Unit 1 Unit 2 Unit 3 Total Station C: Unit 1 Unit 2 Unit 3 Total Grand total
9.66
2150.34
4.68 1.32 0.93
715.32 718.68 719.07
6.93
2153.07
0.43 2.47 0.16
719.57 717.53 719.84
3.06 -
4-2 6460.35
-
19.68
99.55
7 Figure 1-Relative
99.68
99.86 Av. 99.70
Further evidence of the reliability of modern Diesel engines is giren by the practice of many Diesel-driven ice plants of running the engines continuously throughout the entire summer, shutting down for minor inspection only when the ice storage room is full or for some other reason independent of the engines. I n other lines of service still longer continuous runs have been made. I n 1924 a non-stop of 201 days was made in a Kansas municipal power plant, and recently in another municipal plant a different make of engine completed a non-stop run of exactly 15 months, the shutdown even then having been quite voluntary.
Size of 1000-Kilowatt S t e a m a n d Diesel P l a n t s ( S a m e Scale)
The Diesel plant occupies much less ground space than a corresponding steam plant, and the building is smaller in all dimensions. The relative size of the two types of 1000kilowatt plants is indicated in Figure 1, where they are brought to the same scale and superimposed. Examples of Diesels Delivering Primary Power
Some typical instances of chemical industries using Diesel engines for primary power are shown herewith. I n Figure 2 is illustrated a 500-kilowatt engine driving a cottonseed-oil mill in Texas. The three 300-kilowatt generating units shown in Figure 3 furnish power to a copper mine and milling plant in Cuba. A concern in Florida producing phosphates has obtained its power from a Diesel generating plant for fifteen years. The plant has grown to a capacity of 1200-kilowatts, the most recently installed unit, of 450 kilowatts, being shown
IXDUS‘TllldL A N D E
FiCliire 2- SUU-Kilowatt I X e x r i Engine l>riuing Coffoaeeed Oil Milt i t / t:igitre 4. In spite uf the age CJE most of the engines, tlio t o t d opwating cost is st.atcd by the niaiiagement to IJC 7 i i i i l l s prr kilowatt. This includes rqairs, rrncwals, furl I:il)iir. mid siipplies, but no overhead.
Vd. 19. s o . 8 dcsir:ible :isid dniigerws c o i u i ~ c ~ i i ~t o~ be d s fumed. F‘urtherruorc, because of the higher benipernlure the speed of the , and this in turn will cause more heat (:miIutioti and rt,ill Iiiglier temperatures, finally putting the proccss eutirely out of cont,rol and causing not only a loss of material but also a ~ ~ I U ~ ~ Ist,at,e T J Uof~ affairs. For thesc rcasoiis n reserve source of power should be available for imrriedint,c use in case of iin interruption in the electric service coming into the plniit. Another instance is the distillathin of aniliite under vacuum. A still may hold 25,000 pounds (JE aniline wliiclr is heilrg evapiirated at. low tcniperatiire by keeping it nuder a ‘ I W I I I I ~ I of 29 iiielies. If a power interruption should permit a loss of vacuum tire t.enrncrature woiild rise iind tlie aniline would discolor rapidly. In t,he d i s i x w n l OS se1v:i~e .. bv” the :rciivatcd sludee inetliod. coiitiiiuous blowing of thc sludge is iiecawiry. If t,lic ;air stops, the sludge set.ties iipoti tile filtcr bed and penetrates the pores of tlie fiitros hloaks, inaking it difJicuit~.if not iiripossible, to restore them to use. In a city the size or l’:~sadenrt, Calif., the filter bed contains about thirty-five hundred filtros plat,es costing about $2.00 each. The replacement OS this filter bed, which might be the rrsult of a,n inti:rrnption iii
DIESELS FOR SECONDARY POWER
of purchased electricihy know: high-tcn,%iwj p < , w rctrried river 10iig t,ransiirissionlines is riot entirely relirrhIi>. Thistypo of power ii sihject to intcrrupt,ions caused 1 liglitniiig, wind, rlret, eurrent surges, and similar line troubl The freqiicncy and durat,ion of t,hese oiitages vary widel. The line service records of several electric utilities operating 17 t~raiisii~ission linr, tmrs in different parts of the emntry w r e recrritly published. In tire year 1925 these liiios sulfcred 337 interruptions of service tot,aling 531 hours, 55 nii~iutcs. The average per line wns 19.8 ouIages per yesr nnd tlir. arr’ragc dur:itimi of mcli out,:rge was 1 hour, 35 minutes.
Figure 4--Modern Diesel Engine i n 1200-Kilowaff Diesel Plant Producing Phoaphafea
The line having the best record reported only one outap: lasting 12.5 miiiutcs. id& the warst record was 78 outages Insting a total of 181 hours, correspoiiding to an average duration OS 2 Irours, 19 niinutea per interruption. Steady Power Required
In a iiuniber of clieniical industries any interruption iii processing is a serious matter. For example, in nitrating not only must the stirring be continuous, but the cooling water must flow constantly. I n the nitration of benzene the temperature needs to be held below 60“ C . in order to obtain a high yield of tlie desired product,. If the cooling water supply fails, the resulting rise in temperature will allow uii-
the power supply, would inrolve not only an expense of $7000 For new plates, hut also a considerable item Eor labor, as well :LS a shutdown for several days. An interruption in the power supply means great loss in :in artificial silk factory. The liquid viscose is Eorced under pressure through a platinum orifice into an acid bath which caiises it t o coagulate into a thread. Each machine, of which :i modern factory contains hundreds, holds about two hundred CIS tlicse orifice plates, called spinnerets. If a power disturbunce permits a loss in pressure of the viscose, tlie streams cc!asc to emerge and the spinnerets clog. Tliis may necessitate emptying the viscose and acid from each of tlie inachines :md removing the thousands of spinnerets in order that the orifices may be burned clean. Such repairs are cost,ly not i~nlyin themselves, but also in the great loss of production t.hat accompanies them. A serious feature of transmission line outages is that they iisuitlly occur without any warning whatever, and wlion the power is off it is frequently impossible to learn wlien it will be restored. Tliis uncertainty makes it difficult to decide whether to keep the labor force idle while waiting for the resmnption of power, or vhether to release the workers for a while. In order to cope with these conditions many chemical industries that are dependent upon transmitted electric pow’er require in the plant it,self a reserve source of power in order
X:VEEIare expected to last are not used where timber peared favorable, to conduct a research in that field. This paper is the first more than ten or twelve pears. On certain of the larger of a series describing this research.
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