May,
1911
T H E J O U R N A L OF I N D U S T R I A L A,YD ENGINEERIATG C H E M I S T R Y .
Generally speaking the cheaper the sugar the greater the consumption. The northern people consume more sugar than in the southern climes, richer nations more than poorer, and in prosperous business years the consumption increases and decreases in bad years. The per capita consumption increases constantly in all countries of the world. COMPARArlVE COST
O F PRODUCTION I N
Cane. Cane produced a t $2.00 per ton, required for one ton csf sugar, 10 tons. Cost of cane per one ton of sugar., , , . , , . . , . . . , . , . . . . $20.00 Fuel only for starting and after interruptions. . . . . . . . $ 1 .oO Other expenses. . . . . . . , . . . . . $10.00 $31 .OO
I
CANE
AKD
BEET
Beet Beet produced a t $3.50 per ton, required for one ton of beet. i tons. Cost of beet per one ton of sugar. , . , , . . . . . . . . . . . . 8 2 4 . 5 0 Fuel one ton. . , , . . . . . . . . $ 4 .OO
.
Other expenses
.. . . . .
.. .
OTHEK CONSIDERATION S O T EXACTLY CALCULABLE. Lenglh of Campaign. Cane. Beet. 150-180 days. 80-100 dal-s. Characier of S o d . -4lmost any rich soil. A special light, rich and deep soil. Sioring. No storage, worked directly X u s t be carefully stored. from field. TT'lzen Leit in the Field b y linpossibiliiy o i Haulino. Cane will grow t h a t much larger. Beet is a total loss. Labor. Often insufficient in quantity Mostly excellent and suffiand quality. cient. Government. Mostly reliable
I n far alTay countries. L-nsatisfactory.
510.00
$38.50
Mostly stable. Mnrkels. Close at hand-home Covzmuiiuation Excellent as a rule.
The use of superheated steam for economizing steam and fuel has only become general within the past few years. I t s value has now been proved and i t is now being utilized t o a n ever-increasing extent for a great many purposes. Its use may be divided into two distinct classes of work: first, for increasing the economy of engines, turbines and pumps in connection with the generation of steam power, and second, its use in various industrial processes where heat is required for boiling, cooking, distilling, drying or similar operations. The value of superheated steam for irxreasing the economy of steam engines has been known for a great many years and i t was taken advantage of in the early days in connection with the simple engine then in use operating on low steam pressures. As steam pressures were increased lubrication difficulties were experienced, due t o the fact t h a t the lubricants used in those days were not suited t o high temperatures, and this was, also true in regard to the earlier forms of piston rod packing, gaskets and the free use of babbit metal then in vogue Some of the general features of engine design for low pressure steam conditions, such as valve design, also acted t o retard the use of superheated steam. L4tthe present time, however, all these difficulties have been overcome. Good cheap mineral oils are easily obtained as well as suitable packing, gaskets, etc., and as a result superheated steam is rapidly coming into general use in the power plant. I n these days the average manufacturer or central power station operator is tremendously interested in any apparatus t h a t will reduce fuel bills and superheated steam will effect a considerable saving even in the most economical plant. Generally speaking, superheated steam in the power plant will effect a saving in three ways: b y the doing away with condensation in pipe lines, b y eliminating cylinder condensation in engine cylinders, and by the
consumption
Canefres.
Humcanes, earthquakes and other incalculable draivbarks.
PLANTS AND MACHINERY SUPERHEATED STEAM I N INDUSTRIAL PLANTS. ny ROBERTH. WYLD
339
None.
I
reduction of friction of the steam in the ports while entering and leaving the engine cylinder. The percentage of saving depends upon the design of the piping and whether the distance ',he steam has to travel is long or short, and also upon the economy of the engine or pump in which it is t o be used. If it is found necesary to carry steam long distances, superheated steam is of especial value, as absolutely dry and superheated steam can be delivered a t the end of very long lines. Its value is even greater in such cases if the steam lines are especially designed for its use. When superheated steam is used much smaller piping can be installed than would be possible with saturated steam, as the steam can be carried through the pipe a t a much higher velocity without increasing the drop in pressure due t o decreased friction losses in the line. Loss of pressure in a pipe is csused by condensation and b y friction and with superheated steam the condensation loss is entirely eliminated and the friction loss is greatly reduced. I n existing long lines i t will be found t h a t the steam pressure obtained a t the end of the pipe will be considerably higher when superheat is in use. An interesting illustration of this is found a t one of the plants of the U. S. Steel Corporation where nine pounds higher pressure is obtained a t the end of a twelve-hundred-foot line of pipe when the steam is superheated. Another case reported by a large Canadian concern is that after the installation of superheaters in their plant the pressure a t the end of an eight-hundred-foot line of piping was found t o be eighty pouni?? instead of sixty as formerly with saturated steam. The average steam saving obtained by eliminating cylinder condensation in engines and pumps is about as follows: In triple expansion engines the saving will amount to about twelve per cent., in compound engines 14 per cent. and in simple engines 18 per cent. or more. In the case of slow-speed simple engines and direct-acting steam pumps the steam saving is often remarkably large, sometimes as much as forty per cent.
340
T H E J O C R S A L OF I - Y D C S T R I A L
The fuel saving is not always in theoretical proportion to the steam saving and is usually somewhat less, in most cases amounting to about 6 per cent. in the case of triple expansion engines, up t o sometimes as high as 2 5 or even 30 per cent. in the case of plants containing only simple engines and direct-acting pumps. I n many cases, however, the equipping of a boiler plant with superheaters will increase the efficiency of the boiler as a complete unit, including furnace and superheater, and this increase of efficiency may be enough to compensate for the extra heat demanded to do the superheating or may even do more than this so as to make the fuel saving even greater than the steam saving. Results of this kind have been published as the results obtained by actual tests. Superheated steam is of especial value in connection with steam turbines, for in this case not only a considerable steam and fuel saving is obtained, but
Small direct fired superhearn
absolutely dry steam is of advantage, due to the fact t h a t water friction on the turbine blading is done away with and the life and capacity of the turbine thereby increased. In connection with the above estimated savings it may be stated that these are figured on the basis of a moderate amount of superheat, with a final temperature of not more than 5 0 0 ° F. a t the engines, corresponding t o from 100’ to 1 5 0 O of superheat a t the pressures generally carried. I n American practice, higher temperatures are seldom employed, as such would require specially designed engines. With these moderate temperatures, however, very considerable economies can be obtained in the average plant and superheated steam in this way can be used in a plant already in operation without any material change in equipment, and i t may be said t h a t many such existing plants offer the greatest field for such economies. Viewed from another standpoint, the use of super-
heated steam in such existing plants may be of great value. Instead of effecting a saving in fuel and steam a superheater installation may be made to increase the capacity of an existing boiler plant for work and it has been found that in an average plant, six boilers, equipped with superheaters will do the same work as seven without. Where boiler plants are overloaded and it is a difficult matter to add additional boilers, either due to restricted space or some other reason, the installation of superheaters will effect the same result and without any increase to the fuel consumption. Some of the most interesting applications of superheated steam have been those where i t has been used for industrial processes and new uses are continually being found for it. I t may be used to advantage in almost any process where heat is required either for boiling, cooking, distilling, drying or similar work. Its substitution where the use of an open fire has been
Superheater in horizontal water tube boiler
found necessary in order to obtain temperatures not obtainable by the use of saturated steam a t ordinary pressures is a very interesting application. The fact that by superheating any reasonable temperature can be obtained regardless of pressure makes i t possible t o utilize i t in ways where a direct fire was the only way to obtain the necessary results before its introduction. Superheaters are in successful operation supplying steam a t temperatures as high as I Z O O O F. a t the present time. Of course, in such cases the superheater has to be especially designed t o withstand the heat, and superheaters constructed of bare pipe or tubing will not last under such severe usage. Mention of these special uses of superheated steam might be made. G L Y C E R I N E STILLS.
One interesting application is in soap works where i t is desired to obtain high temperatures in glycerine stills. I n one plant this result is reached by super-
May, 1911
T I 1 6 J 0 C R . Y L 4 L OF I N D C S T R I , I L A4AVDE.l-GI,VEERING CHE.WISTKI'.
Superheater in horizontal water tube boiler
Portable superheater, casing removed.
Direct fired superheater, before placing of brickwork.
n
Portable superheater. "Cross sectional \.iew of return bend element and connecting hmders used in the construction of superheaters ''
342
THE J O U R N A L OF I i V D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R I '
heating steam in one of the boilers up to a temperature of somewhat over 600 O F. The pressure maintained in this boiler is somewhat higher than in the others in the plant. The steam from this high pressure boiler is then passed'through the coils of the glycerine still, leaving the coils in a still superheated condition and passing into the boilers a t the lower pressure where it mixes with the rest of the steam. In this manner a temperature of 500' to 550' F. is easily maintained in the still. I n the lower pressure boilers the steam is again superheated and used for boiling soap and for power purposes. I n the soap-boiling process it is found t o decrease materially the time required to cook a batch of soap. ASPHALT R E F I N I W G .
Another use is found in asphalt refining where superheated steam in coils has taken the place of direct fires under the kettles. The danger of disastrous fires is avoided and the work is done in quick time. It is found t h a t low pressure steam superheated will do as much work as saturated steam a t a high pressure. Another process of a similar nature using superheated steam is t h a t of pipe dipping. It is found t h a t when the tank is maintained a t a high temperature the coating applied to the pipe is not only smoother and more perfect, but also that less of the coating material is needed. S U P E R H E A T I N G LOW-PRESSURE
STEAM.
In connection with the superheating Of low-presmany manufacturers are just finding the superheating Of exhaust from their engines for process work a very proposition. An interesting case of this kind is found in a large knitting mill where steam is first initially superheated for power uses, and after passing through the engines exhaust is again superheated and in pipe 'Oils for drying purposes, and leaving these 40° feet to a dye ' k h t l y superheated house where the latent heat is utilized for boiling dyes. P A P E R A N D P U L P MILLS.
Many advantages have been found in the use of superheated steam in the paper mill. General practice in such a plant now is t o superheat the steam initially in the boilers using this steam in the engines, thereby saving 15 t o 2 0 per cent. by the elimination of cylinder condensation and thus obtaining exhaust steam practically dry and free from moisture instead of containing from I O t o 1 5 per cent. of water. This dry steam although of less weight will do more work on the paper driers a n d it has been found that bleeding enough live superheated steam into this exhaust so t h a t the steam on arriving a t the ports of the paper drier contains 5 t o 10' of superheat will give the highest efficiency. I n some mills the available exhaust steam is insufficient t o do the drying and in such cases the bleeding of sufficient live steam superheated into the exhaust not only gives the desired heat but b y thoroughly drying and slightly superheating i t makes it more efficient in the rolls. A distinct advantage has been found in the use of superheated steam in digesters in pulp mills. Recent
May,
1911
tests in a large sulphite mill have I own that the time taken t o reach the cooking poir.; In the digesters was reduced from three hours, using saturated steam to two hours and to two hours and a quarter using steam superheated. Naturally this saving of time and reduction of water from condensed steam resulted in a less diluted acid solution a t this point in the process and further saving in time during the rest of the process. This saving in time practically amounts t o the same thing as a saving in fuel, or viewed from another standpoint the capacity of the digester for work is increased without an increase of fuel consumption. Another result also has been the possibility of obtaining the best of pulp from even very wet chips, which are sometimes difficult to use on account of dilution of the acid b y this excess moisture. COTTON O I L A K D LARO R E F I N E R I E S .
Superheated steam is now very generally used in cotton oil and lard refineries for the purpose of deodorizing cotton seed oil. Also for similar work in linseed oil plants. This use for superheat has been especially successful. W A T E R GAS P L A N T S .
Still another interesting application is t h a t in connection with water gas generators. Numerous installations of this character have been made and b y blowing highly superheated steam through the incandescent bed of fuel it is possible t o continue the blow for a longer period of time, due to the cooling effect of s u p r h e a t e d steam being less than occurs with saturated steam and consequently a greater quantity of gas can be made per blow, I n such Cases superheated is also generally used throughout the who]e plant, as the saving on the average engines and pumps used in such plants is large. The results are especially good in such cases, due t o the fact that the pumps and exhausters do not run a t the Same time as the generators are in use and thus there is a practically continuous demand for EVAPORATION PROCESSES.
Superheated steam has found a distinct field where steam is used for evaporating purposes, especially in such plants where considerable power is also required and exhaust steam used for the evaporating work. Obtaining thoroughly dry exhaust steam for such purposes has been proved a decided advantage. A very successful application has been found in salt manufacturing plants where large quantities of exhaust steam are used for evaporation of brine. SUGAR B E E T P U L P DRIERS.
Recent experiments in this country, following a practice already established in Germany have demonstrated the value of superheated steam in various forms of pulp driers in sugar beet refineries. I n such plants where exhaust steam is used in the driers it has been found necessary to carry very high back pressures on the engines. By passing the steam after leaving. these engines through a superheater it has been found possible t o greatly reduce this back pressure and still obtain the same results in the driers,
May, 191 I
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E S I I S T R Y .
thus making a large saving in steam, and increasing the power developed b y the engines. Numerous other cases of this character might be mentioned, but the above are typical and their chief interest lies in the fact t h a t they represent such varied uses. New ways of utilizing superheated steam are continually being discovered and doubtless the above illustrations will serve to suggest new uses to the reader who is working along similar lines t o those mentioned. As noted earlier in this article, i t is now possible to obtain superheater equipment designed to raise the temperature of the steam regardless of pressure to as high as I I O O O t o 1 2 0 0 ' F. These superheaters if properly handled will give long service. The various superheaters on the market may be divided into two classes: those installed within the settings of individual boilers and those in separate settings of their own, fired directly with any convenient fuel-either coal, oil, gas or wood. Superheaters installed within boiler settings can be designed to raise the temperature of the steam as high as 550 t o 600' F. If higher temperatures than these are desired a direct fired superheater is necessary. Such direct fired units can, of course, also be used for lower temperatures and can be designed of just the proper size for any special use. Where superheated steam is t o be used for power purposes i t might be stated t h a t care should be taken t o see t h a t the apparatus used will furnish steam a t a uniform temperature and especially in existing plants highly superheated steam is not to be recommended. As stated earlier in the article, American practice has proven that superheated steam at temperatures u p t o 500' F. can be used to advantage on almost any type of equipment provided a fairly uniform temperature is maintained, and i t may be said t h a t under these conditions practically no changes in design of piping, valves or fittings need be made over the usual construction in use for saturated steam conditions. In this way superheated steam can be utilized to advantage in a very large number of manufacturing plants, and large savings of steam and fuel obtained. At the present time it might be said that the USL of superheated steam in central power stations is more general than in manufacturing establishments, b u t a comparative study of its advantages in these two classes of plants shows t h a t there is even more reason for its adoption in the latter than the former. The three factors on which percentage of return on a n investment in superheater equipqnent depend, are first the cost of fuel, second the load factor or the hours per day run multiplied b y the average percentage of the total equipment in service, and third the - efficiency of the engine equipment. In the average manufacturing plant access to the raw material is generally the primary object and the cost of fuel a secondary consideration. Thus in many such plants the Of is high and therefore a certain percentage saved will pay a high return on a n investment to this end than be where fuel is cheap.
343
I n a large number of such manufacturing plants practically the whole boiler plant is operated and often twenty-four hours in the day, a far better condition than the central station can hope for, as they generally are called upon to furnish a heavy load for a small number of hours per day and have to, therefore, maintain a considerable portion of their equipment idle for a large part of the time, when the demand for power is light. Lastly, the average manufacturing plant cannot afford to use as highly efficient equipment as the central station where the output of power is the chief object. I t is practically true that the saving effected b y superheating is about inversely proportional to the efficiency of an engine and the saving on engines of poor economy is relatively large as compared t o one of very high efficiency. When in addition to these facts steam a t high temperatures is desired for process work, it is easy to see why superheated steam is rapidly coming into use in the manufacturing plant.
A CONVENIENT CRUCIBLE SUPPORT. B y \VILLI.~M M. THORKTON, J R . , Chemist Virginia Geological Survey
Received March 16, 1911.
The accompanying photograph shows a stand for supporting crucibles constructed of a rectangular slab of soapstone with circular holes, which is upheld b y two iron legs a t either end. The dimensions of the stone are I X 6 X 2 6 inches. The holes are 3 inches in diameter, 2r/2 inches from either end, and 3 inches apart.I The legs are made of iron bolts 3 / / , inch in
diameter and 131,'~ inches in length and threaded for 45/8 inches, a t the upper ends, The slab is held in position a t the desired level by 2 nuts on each leg, one below and one above the stone. A Bunsen burner stands in readiness beneath each opening and can be 1 The piece of stone cut a s above described wns suppliec' by the Alberene Stone Co , 223 E. 23rd S t . , N e w York.. for 80.50 f . o b . quarry a t !Alberene. Albemarie Co., Va.
