Manufacture of f-l ard Rubber Dust HARRY
MCCORVACK, 33rd and Federal Streets, Chicago, Ill. production of R finished molded article. The rubber in the c o m p o u n d (Para sheets and reclaim) was necessary as a b i n d e r fur the rem a i n i n g components of the stock, as t h e old i u n e r t u b e s liad lost almost c o m p l e t e l y tlieir elasticity and plasticity.
FACTORY producing a v a r i e t y of hard rubber articles frequently tiuds it desirable, i n compoundiugastock for the hard rubber, to have an appreciable a m o u n t of b a r d rubber dust in tlie compound. T h i s method of operation has several advantages: It offers an outlet for the hard rubber scrap, coming f r o m t h e fa+ tory's manufacturing operations, by converting the hard r u b b e r s c r a p to dust; it a s s i s t s in securing complete and rapid vulcanization of the hard rubber article and produces a rubber stock which is easier to form.
A
NE\\ h X ! Z S s
A brief study of t hese operations, together with their c o s t , led t o t h e definite conclusion that a better process for making rubber dust had to process is descr&d for Illiring rub&r with be evolved; otherwise the factory could not afford to make and sulfur arid uccornplishirig vulcanizulion ul the use the A series of same lime. Tlle resulting product is in granuexperiments, u s i n g OLDPROCESS OF MANUFACTUEX: laled form ready for fine grinding. Slandurd rubber and sulfur in the eauiurnerit, designed is thqed iri mixture, gave indications that, A factorv. in COD., oneratine . . . " for . other .Durpo.se.s, . under proper conditions of operaf o r m i t y with the description carrying oht the proce.s.7. tion, a satisfactory vulcanisajust given, was u t i l i z i n g old tion could be secured. These inner tubes as a cheap source and as the chief source of rubber entering into tlie p-oduction experiments demonstrated that one of the essentials for a of hard rubber dust. The process employed in making the satisfactory process would lie tlie mixing of the sulfur with tlie dust at the inception of the investigation herewith described rubber when both liad been raised to a temperature at which they would be plastic. involved the following operations: A further study of the operatiou indicated the selection of a 1. Disintegration of the old inner tubes by milling on rubber mixer and vulcanizer in which the material could be heated rolls. wit,h fairly close temperature control, and where the material 2. Breakinadown washed Para sheets wonld be continuously stirred while being heated; it was also found that operating under a vacuum was desirable. An investigation of the equipment on hand in the factory, whicli 6. Vulcanising in tray8 in n pressure vulcauiaer for 14 hours. might be found to function satisfacturily, disclosed 8 vacuum 7. Vulcanized slabs broken u with a hammer by hand. rotary drier (made by the Buffalo Foundry and Machinery 8. Pieces broken down on rolK to pass a No. 12 screen. 9. Soreeninga ground in a Raymond impact mill to approxi- Company) which was not then in use. This equipment mately 100 mesh, olassification by air sevsration acoomvanvina seemed to possess tlie characteristics desired, and it was the grinding operation. decided to attempt to use it as the mixer and vulcanizer. The machine was sine R3, 3 feet in diameter by 10 feet The ground classified product was then ready for iisc after long; i t could be operated satisfactorily with a charge of nine operations from raw materials to finislied product. 2000 pounds of disintegrated tuhcs together with the required The stock used in making dust was: amount of sulfur. Maintaining a dernperature of 340' F., satisfactory vulGround tubs& 880 caniaation could be secured from 4.5 to 6 hours. The vulSu1Iur 420 canizer was kept under a vacuum of approximately 22 inches B map oil 120 Para sheeta 120 for the major portion of the time. It was noted, however, Reolaim rubber 1W that after vulcanizing about 3 to 3.5 hours, there was a Total 1500 marked rise in temperature of the material being vulcanized The systom of vulcanizing used a t that time iiecesiitated and, accompanying this, a copious evolution of hydrogen sulthe milling of this stock in the sanie inanmer as would he re- fide. The rise in temperature, along with the gas evolved, quired for the inilling of a rnhher Ptock intended for the completely destroyed the vacuum a t times. ~~~~~
~
1108
1109
The operations in this systcni of proccdnre werc:
11r;cnvcu July 7 . 1988. IEXO
o v SrMi.o"i"M1
Pumps
E
ARLY chemical and inetalliirgiaal tmgincering practice avoided wherever possible tlie w e of iiinnp~:of whatever "type, sex, color, or previous ~:onditionof servitude." Even today, in spite of the vonderful ileveloprnent in corrosion-resisting rnatrrials, pumps are to bc avoirled because they are usually secondary to tlic dmnicd pro even the best are likely sources of troulA=and expciisc; may be sources of contamination; they are an additional cost for power in the Row slieet: and they are sornetirnes not so corrosion-resisting as the rnaniifaetorer would lend us to believe. COB~U~ION-RESISTI XG hf.ITEl1IAI.R Therc is no all-purpose corrosion-resisting material. Acidproof stoneware, porcelain, and glass come perhaps nearer than any, but stoneware is heavy and easily broken because of its high coefficient of expansion, and glass has not so far come into commercial use. Porcelain, stoneware, and glasstined pumps are on the market, but their high cost has limited tlicni to very special uses. Next oii the list as a fairly universal corrosion-resistant material ii; Cturiron, a liigh-silicon iron. It is, however, very hard and brittle, has high tliernial expansion, and can be ground but not machined. Lead is much used because of its re ncc to sulfuric a d solutions. Its principa.1disadvantnres are its softness arid Imv elastic limit. Very excel l e n t lead-lined equipment is now on the innrket, but can be recommended mly for certain types of pumps, arid its uses a r c l i m i t e d by the solubility of lead in many reagents. E qu i prnen t may also bo l i n e d nrith rubber. h new vulc a n i z i n g process b o n d s this material very satisfactorily to steel. Its use, with t h e except,ion of hard rubber, has been limited almost wholly to centrifugal pumps.
Coppcr and copper-base alloys are used extensively, chiefly because of their cheapness and excellent machinability. The iron-base materials, such as alloys of chromium and nickel, are also conring to the fore. Many of these are readily miichiiial~le,are v e r y hard, and have high tensile strength. Their largest use, however, is in tiiermal equipment because of their resistance to corrosioii at high temperature. Monel metal, a nickel-base alloy containing about 60 per cent nickel and 30 per cent copper, finds considerable use because of its strength, its workability, and its resistance to uiaiiy solutions. Tin, ah~minum,aluminum-base alloys, inagnesium alloys, hard rubber, Bakelite, and vulcanite may be mentioned, but this by no means completes Lhe list. 1;Si:S
Ox' PUMPS
Tlie tieverdl iises of pumps and kindred devices may be cliissified ns iollww 1. The simple transfer of gmes, liquids, colloid solubSons, or solids suspended in either liquids or gases, from one point t o another, usually with comparatively small changes in pressure.
This is b far the largest use.
2. d e r e such transfer is incident to or combined with a marked chenge in prossure or "head," the latter being thc main object. 3. For the purpme of produring high-pressure or highvacuum phenomena in
or chemiezl chin&
In discussing the first g r o u p i n g y t h e simple t r a n s f e r of gases, l i q u i d s , etc., with nominal changes in pressure-the use of a p n m p in t h e s e cases has t h e same justification as the use of elevators and belts in t h e t r a n s f e r of s o l i d s - t h a t is, the additional expense of so arranging the Bow sheet in order to take advmt.ageof the force
1110
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 ill I S T A Y
Vol. 24, No. 10
of gravity is greater TYPESOF EQUIPMENT than that of the cost With such background, we may now examine the different of t h e p u m p p l u s i t s o p e r a t i n g ex- types of pumping equipment and determine in a general way pense over a period their adaptability to special chemical processes. If we broaden the definition to include all devices designed of from ten to twenty to lift fluids against the force of gravity, pumping devices years. The side-hill con- may be classified as follows: centrating and flota- 1. Those devices having no moving parts, usually not classed as tion mills of the West Pumps Siphons are good e x a m p l e s Acid eggs, monte-jus, blow cases of such gravity flow Barometric legs FIGURE1. ACIDEGGOR BLOWCASE to avoid the use of Air lifts Ejectors, injectors, aspirators pumps. I n case of gases, the directional flow is of course reversed. We still 2. Reciprocating devices, with valve action and positive displacement build high chimneys for steam plants and smelters instead Piston pumps of using suction fans and blowers. There is an additional Hun er pumps reason for doing so in that we wish to discharge the obnoxDiapfragm pumps ious gases as high into the air 3. Centrifugal devices, one moving part, no vdves, relative displacement as possible. Volute centrifugal umps It goes w i t h o u t s a y i n g , Turbine centrifugJpurnps also, t h a t in such simple Blowers transfers, the less c h a n g e in Fans p r e s s u r e o r head, the more 4. Rotary devices, usually b u t two efficient the o p e r a t i o n , just moving parts, no valves, more or . I A less positive displacement as in t h e t r a n s f e r of solids Rotary pumps, cycloidal blowers the level or slightly inclined 'c Screw umps conveyor belt is more effii1 Speciafdesign 'c' cient than the vertical elevaI tor. SIPHON.The siphon has applicaI n t h e c h e m i c a l plant the tion wherever the level of the receivposition of the pump in the ing vessel is lower than that of the disflow sheet is usually very imcharging-that k, wherever the sum portant. In a simple leaching total of the lift is less than the drop, process, the logical place for the provided always that the lift does not pump is a t the head of the exceed 34 feet for water and correoperation where it feeds only sponding heights for other liquids. For c l e a r m a t e r , the rest of the m e r c u r y the theoretical lift cannot system being under pressure. exceed 29 inches, in practice somewhat In other operations it may be less. best to place it a t the end. F 1 ~ ~ ~ * w ~ ~ ~ ~ ~ The siphon is the usual method of In the manufacture of sulfuric TOR emptying the cast-iron melting pot a c i d , t h e b l o w e r o r fan is in a lead refinery. The main reason logically placed in the middle of the operation just before for using a siphon instead of a valve the converters and after the sulfur dioxide has been puricast into the bottom is because of the fied, for obvious reasons. In the coke plant the compressors high thermal expansion of cast iron. are placed after the ammonia extractors so that the system Shaped like a huge evaporating dish, it up to that point is under slight suction, and after that point, x expands uniformly, whereas a heavier under pressure. portion for the valve would cause The first important point to be decided is the position of 3. AIRLIFT strains, uneven expansion, and perhaps the pump or pumps in the flow sheet. This position often FIGURE cracking a t the h s t firing. A siDhon dictates the kind of material of which it is to be fabricated. The chemical engineer will not only find a great variety of must be filled with the liquid before it begins to operate.- To pumps on the market, but each pump will be suitable for fill it in this case, the workman immerses the whole pipe into a variety of purposes. It is often possible to standardize t.he molten lead, then closes a valve a t one end and carefully on a single type and size throughout the plant. The ex- withdraws it, always keeping the open end below the level perienced operator will appreciate what this means in every- of the liquid. day plant operation. As a rule the pumping cost is a minor item in the chemical process. The chemical engineer is not so much interested, therefore, in rated efficiency as in materials of construction and the trouble the pump is likely to give owing to corrosion X or other failure. After determining the proper location of the pump in the flow sheet, the second consideration must be to choose the material from which the pump must be constructed. This leads to the second point-that the kind of material from A d j u s t i n g Vents 1 which the pump must be made often limits the type of pump FIGURE4. EJECTOR which can be used.
i
I
~
October. 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
If the siphon is stationary, it can be "primed" by pressure applied on the discharging vessel, or suction upon the receiving vessel. ACID EGG. If we close the lead vat as in Figure 1 and apply pressure a t B , we have an acid egg, monte-jus, or blow case. Inserting float C and inlet and check valves D and D' makes the acid egg automatic. The flow is intermittent and irregular. The height that the liquid can be lifted depends on the air X pressure. The advantages are that it can be constructed of almost any noncorroding material, it is inexpensive, and causes little trouble. Its efficiency is low and capacity small. BAROMETRIC LEG. A modification of the siphon principle is the barometric leg illustrated in Figure 2. I n this, evaporator A is kept under partial vacuum by the liquid column in the b a r o m e t r i c leg, B, which theoretically must be slightly longer than 34 feet for water. The vapor continually condenses a t C. I n practice, as nitrogen and oxygen are soluble in practically all solutions, air tends to trap a t the highest part of the leg and the efficiency drops unless this is removed by a suction pump or aspirator connected a t D. If the condensate is valuable, it should have a by-pass to B, or it may be made to operate interC' mittently by a float or mercoid switch FIGURE5. SIMPLE a t E. WELLPUMP SHOWAIR LIFT. The air l i f t s h o w n in ING ESSENTIALS OF 3 is a somewhat more efficient R E C I P R O C A T I NFigure G PUMPS method of utilizing compressed air in lifting liquids. It necessitates a considerable submergence of the legin the liquid to be elevated. It is evident that the total lift (lift plus submergence) cannot in theory be more than the equivalent of air and water mixture equal in weight to the water column of the leg-that is, the weight of the water-air mixture AX is equivalent to a similar column of water alone of the height BX. In practice 80 per cent of this figure is hardly reached. The ratio lift : (lift plus submergence) decreases with increased lift (AB). For a lift of 20 feet ( A B ) ,this ratio equals 0.64 to 0.66-thatJ is, B X , the leg, equals 10 to 11 feet. For 500 feet this ratio decreases to about 0.40, or B X , the submergence, must be more than 700 feet. The air lift is simple in mechanical construction, but no definite mathematical formula has been advanced for its action. It may, without confusion, be considered a sort of inverted siphon where the
---3=a
Y
I
HEANVELOC~TYIN PIPELINE
1111 CEMERFSTROKE
_ _ _ ~ _
DOUBLE-ACTING DUPLEX PUMP
Courtesg Goulds Pumps, Inc.
FIGURE 6 . GRAPHICCHARACTERISTICS OF RECIPROCATING PUMPS
weight of column of water BX serves to balance the weight of water-air mixture A X . Any aperture lower than A a t C or C' would therefore cause a continuous flow of water. Modifications of the air lift have a number of important industrial applications, such as lifting salt brines in the salt mines of Kansas, and sulfur in the sulfur mines of Louisiana and Texas. EJECTORS, INJECTORS, AND ASPIRATORS.Another method of moving a fluid without using moving parts is by use of the ejector, a type of which is shown in Figure 4. Fluid X under pressure expands through nozzle A . Its velocity Ball Valve3
Discharge
L
FIGURE 7. END-PACKED SINGLE-ACTION DUPLEXPLUNGER PUMP
FIGURE 8. LIQUID PISTONPUMP
1112
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 24, No. 10
It is well to remember that for every cycle of piston A the same liquid flows from suction one half the time and is discharged the other half. The flow is therefore intermittent. In order partly to smooth out this discharge, a double-action pump is used. Even then there is a variation in discharge, because a t the end of every stroke neither cylinder is discharging and there is no flow. The next step is to use two such double-action cylinders arranged with the crank pins 90 degrees apart,. This gives a double-action duplex pump. The diagrams, Figure 6, compare graphically the discharge of these several types. The importance of reciprocating pumps should be emphasized. They are still standard in many operations. Where steam is to be used for process heating-and there are many such possibilities in the chemical plant-the steam-driven reciprocating pump fits in admirably. The pump may be regarded as a reducing valve and its comparative efficiency to other types of pumps be disregarded. FIGURE9. SIMPLE DIIPHRAGM PUMP The reciprocating pump is essentially a slow-speed machine. Its main moving part is a piston or plunger traveling with a head is increased with a corresponding decrease in pressure to-and-fro motion past a tight packing. The fluid to be head. When the pressure head becomes less than that of pumped follows. The undirectional flow of this fluid is acthe second fluid, Y,in contact with it, the second fluid is complished by valves of which there must. be a t least two. sucked along with it. The The head delivered is posisimple ejector develops only tive. A t each stroke a volume equal to the displace a small head, its efficiency is ment of the plunger is forced low, and it dilutes the maout through the d i s c h a r g e terial being t r a n s p o r t e d . valves, and the pressure deThe injector is c o m m o n l y veloped will be sufficient to used in boilers and locomotives to inject the feed water PELLER do this. If the discharge pipe INES is choked or a valve closed, b y m e a n s of a s t e a m jet. the pressure will continue to These have been developed increase until the pipe bursts SUCT,OH to such a degree that they or some other part gives way. will inject quite warm water It is therefore necessary to into the boiler against the full s t e a m pressure. Operated have a relief or by-pass valve in the line, which o p e n s a t by steam or compressed air, any u n d u e p r e s s u r e a n d they serve to transfer liquids allows the liquid to flow back from tank to tank. They are the basis for spray nozzles, to suction. T h e q u a n t i t y SINGLE-SUCTION VOLUTEPUMP delivered depends upon the oil burners, etc. I n modified FIGURE10. SINGLE-STAGE WITH CLOSED IMPELLER speed. Every stroke means form (aspirators) they make a definite amount of liquid. very efficient vacuum pumps. RECIPROCATING PUMPS.One of the earlier types of posi- The only way to change the discharge is to change the speed. tjve-action pumps, illustrated in Figure 5, is even today The flow is also intermittent. It is this unsteady flow which being used in shallow wells. The essentials of such a pump leads to pressure surges and often to tremendous thumps are the piston A , the piston track or cylinder B , the valves C and C’, and the actuating power X. By rearrangement of the valves and by making the piston solid, a single- or doubleaction reciprocating pump can be constructed.
FIGURE 11. TURBINE TYPECENTRIFUGAL PUMP
in the discharge line and sometimes in the suction line also. For this reason, reciprocating pumps are supplied with an air chamber on the discharge side and sometimes on the courtesy Goutas pumps,I ~ C . suction side, to even the pressure by means of an air cushion. F~~~~~ 12. G~~~~~~ c~~~~~~~~~~~~~~~ OF cENTRIPUGAL The advantages of reciprocating pumps are that the sucPUMPS Gdions
per
minute.
I R D U S T IS I A I. A N D E N G I N li E H I N G C t1 E M I S T R Y
O r tober. 1’132
FIGURE
13
t?TARY PUMP IN ACTiOV
tion connections may be under less than atmospheric pressure mthout “air biuding,” and unlike centnfugal p u m p they do iiot nerd priming; they are more 0exible in operation and maintain about the same efficiericyover wide variations of discharge; they are designed for higher heads than centrifugal puinps; and because they can be connected with direct steam, the utilization of the exhaust steam for process heating may be of advantage in the chernical plant. PLUNGER P a p s . In the pumps so far described, the piston tames the packing with it. When these pumps are made larger or when they must handle much suspended matter, frequent replacenient of packing becomes necessary. In the plunger type of pump, the plunger moves past stationary packing. An illustration is the end-packed mglcaction duplex pump in Figure 7. An important modification of the plunger type of pump is the “liquid piston“ pump illustrated diagrarnmatically in Figure 8, the essential feature of which is the volurnc entrapped betweeii valves, which must be a t least twice the volume of the stroke of the paston. It can readily be seen that with every cycle of the piston, the amount of liquid over and above the suction and discharge voliiirie riiiaiiis with and moves with the piston, acting as a buffer. The pumps are ubil~llyplaced vertically to avoid diffusion and flow losst~s l l i e Iiyurd pistons may be mercury or other
FIGURE15. Hoon TYPE CYCLOIDAL BLOWER
1113
noncorroding liquids. In case of hot oils or other hot liquid, i t may be the Same liquid which, of course, remains comparatively cool. The pump therefore remains cool, and only the valves are exposed to the hot liquids. DIAPHRAGM PUMPS. For handling corrosive liquids and where oil and packing niay eontammate the product, various types of diaphragm pumps have been developed. Figure 9 shows a simple and quite efficient type. For handling liquids with large quantities of suspended solids, it is very satisfactory. Instead of a piston or plunger, it has a flexible diaphragm, A , a discharge valve, B, and a suction valve, G . The stroke may be varied by an ad]ustabIe eccentric, thus controlling the discharge. Many different types are on the market, both double and single diaphragm. CENTTUFUQAL PUMPS.Pumps that depend for their action upon centrifugal force, or the variation in pressure due to rotation, are termed centrifugal pumps. The esseiitisl parts are a rotating member termed the impeller and a properly designed case surrouiiding it. Liquid entem the center of the impeller and is set in rotation, which develops a pressure at the outer dxameter of the impeller. The function of the receiver or c a e is to reduce the high velocity of the liquid as it leaves the vanes of the impeller and changes this kinetic energy to prensure, without undue friction losses.
F~UURE 14. Smew PUMP
Centnfugal pumps i ~ ~ abey classified 86 smgle-btage or multistage, open-impeller or closed-impeller, single-suction or double-suction. They axe also spoken of as volute or turbine design Figure 10 shows a sindestage, single-suction, volute pump with closed impeller. In such a single-stage pump, the liquid exerts an unbalanced hydraulic pressure which tcnds to pull the impeller
FIGURE17. VACUUM PUMP w m i E C C E N ~ROTOR C
1112
1S D U S T
H 1 A I, A N D E N G I N:!I E I*
1NG
C I1 15 M I S T R 1~
Vol. 24, No. 10
f o r m e d by a wellThe two-stage doubledesigned case of the s u c t i o n p u m p has volute type. therefore comegreatly A centrifugal pump must be filled with into favor. The open impeller liquid-that is, it consists essentially of must be primed h e a s e r i e s of c u r v e d fore starting, unless the pump has a vanes extcndiug from a c e n t r a l lrub. As flooded suction, which these vanes are not means if the p u m p elevation islower than in actual caridact with t,he casing, there is the liquid supply. always a certain Centrifugal pumps are usually rated on amount of back leaka g e which increases the hasis of head and with t h e wearing capacity at the point of m a x i m u m effiof t h e p u m p . To c i e n c y . Increasing remedy this, t h e closed impeller lras the speed usually inbeendnveloped. Tlie HvnnnuLic l b w s *OR PUMPIRG Ihrv MATERIAL TWROUO~I I h i i creases the head for vanes of the imp&?r Pnessuas A u ' r o c ~ ~ vEN ~ 8pL1WVOl. pROOUCTlOV m y given r a t e of are enclo,scd between d i s c h a r g e . As the two shcets or rings of metal. A closer fit can be maintained prinoipal operating characteristic of a centrifugal pump between the outer circumference of these rings and the cas- is this relation between head and discharge at constant ing, and the clearances can be riiaiiitaiiied by reneu*able speed, manufacturers usually S U ~ I J ~with Y each pump a grapli wearing rings. of its characteristics curves similar to Figure 12. For this The advantages of centrifugal pumps arc tliat, they have particular pump the rat,ing would be 1100 gallons a t a head but one moving part and require no valves; they delivcr of 32 feet (point of maximum efficiency), the horsepowrr liquids a t uniform pressure without shock or pulsation; used about 11. But the chaxt gives much more interestvalves in the discharge line can be completely closed u7it.h- ing facts. If the head is reduced io 21 feet, 1400 gallons out appreciable injury; they can handle large qiiautities of per minute can be delivered at about the same horsepower. solids in suspension; tiicy lend tlremselvcs more readily to If, unfortunately, the pipe fitt,ershould put a few extra kinks manufacture out of corrosion-resisting materials: and their in the discharge line for the sake of beauty and symmetry, thereby increasing the head bo 45 feet, there would be 110 efficiency is comparatively liigh. TURBINE I'UYPS. The distinction between t.urbine and water at all a t that speed. volute punips is the diffusion ring A , Figure 11, containing GEARAND SCREWPUMPS. Of interest to engineers with the problem of moving heavy viscous solutions, or in fact any liquid without appreciable solids in suspension, is the positive type of rotary pump exemplified hy the gear pump, the screw pump, and various fipecial designs such as the eccenLric impeller, oval ease, etc. The gear pump is illustrated ' aud the screw pump in Figure 14. Curiously in Figure 13 enough, the cycloidal blower of the Roots type illustrated in Figure 15 wits among the first of the rotary type of blowers developed, and found application in supplying air in large quantities at comparatively low pressures for blast furnacm, etc. In Figure 13, the gears, B, entrap slugs of liquid a t D and carry them around to C, where they are forced out and u p ward because of the meshing of the gears. A modification of this is the screw pump shown in Figure 14. The liquid entrapped at the ends, A , is carried by the screw action to the center, thc meshed screws producing a positive head at B. Tile advantages of such pumps are that they have but t.wo moving parts and do uot require valves; they deliver liquids at uniform pressure without shock or pulsation; and they operate very efficiently ou highly viscous fluids such as molasses, petroleum oils, vegetable oils: etc., giving exceptionally high heads. liwv~ttuDEVICESOF SPECIALDESIGN. There have been :i great number of attempts to produce positive compressors of $herotary type c q & k of detim?riRgga:asesat high pFessure. One of the more successful is the Nash Hytor illustrated in FIGURE18. SULLIVAN TWOSTAGE COMPRESSOR WlTfl Figure 16. It has a cylindrical rotor carrying vanes with INTERCOOLER close side clearance to the elliptical casing. A quantity of passages B , wliich gradually change the direction of the liquid liquid inert to the gas to be handled is put into the casing. issuing from the tip of impeller G and discharge it iuto volute This must be sufficient to seal the impeller at points of least E with minimum friction loss. With our present knowledge end clearance, X, X, when rotated. The rotation of the of hydrodynamics, this function can be more cheaply per- impeller muses the liquid to rotate with it. This, due to away from the shaft.
October, 1932
I N D U S T R I A L A N D E N G I N E E K I N G C H E &I I S T R Y
centrifugal force, hugs the casing, as shown by the dotted lines. Gas is sucked in between the vanes at the inlet ports, A , A , and is forced out again a t the outlet ports, 13, B. The pump is simple in construction, may be made of corrosionresisting materials, and can develop pressures up to 20 pounds. One of the interesting uses is in compressing chlorine gas using concentrated sulfuric acid as the liquid. A very efficient high-vacuum pump, shown in Figure 17, has an eccentric rotor, A , with a sliding partition valve pressed constantly against its rotating circumference. The sliding partition valve serves to separate the inlet from the outlet port at all positions of the rotor, the rotation of the latter serving alternately to suck gas from the inlet port and force it out of the outlet port The pump is built with close clearances and operates with an oil seal.
CONCLUSIONS Referring to the classification a t the beginning of this article, we find that the chemical engineer is little concerned with classification 2, where the transfer of fluids under high pressure or head is the main object. Such objectives fall more in the realm of the mechanical engineer and find large application in water works and the transfer of oil and gas over pipe lines But in classification 3, where high-pressure or high-vacuum phenomena in conjunction with heat or cold are used to aid physical or chemical change, we find a major present-day interest and one where the pump or compressor is an important item in the flow sheet. We need mention only a few of the newer chemical engineering processes, such as synthetic ammonia, solid carbon dioxide, liquid chlorine, liquid sulfur dioxide, recovery of helium, synthetic methanol, etc. So marked has been this change that we have coined the phrase, the high-pressure industries. We note the following: that the high-pressure and highvacuum industries are chiefly concerned with the manipulation of gases; that for low pressures, fans, blowers, and rotary type compressors can be employed; that for partial vacuum effects, condensers, barometric legs, and aspirators can be used; but for high-pressure effects, the reciprocating compressor is still standard. The compressor shown in Figure 18, as differenliated from the reciprocatins pump, shows only minor modifications. Valves are lighter and clearances smaller. Khen a gas is compressed, its ~-olumedecreases. Work is done on it.
1115
This together with the friction losses appear as heat. I n blowers, fans, etc., where the pressure is low, this rise in temperature can be neglected. It must be taken care of in the high-compression engine, not only because of the effect of heat on the cylinders and packing, but for efficiency of operation. Table I gives the theoretical final temperatures a t various pressures when compression is completed, the air being taken into the cylinder a t 60" F. TABLE I. CYLINDER TEMPERATURES AT END OF PISTON STROKE AIR COMPRE0SlON
Lb. oaae 10 20 30
4n ._
50 60 70 80 90 100 110 120 130 140 150 200 250
FINALTEMPERATURH Single stage Two stage
F.
O
F
145 207 255
2n2 __-
339 375 405 432 459 485 507 529 550 570 589 072 749
188 203 214 224 234 243 250 257 265 272 279 309 331
Single-stage compressors are built both single and double action. They are used for the compression of air up to approximately 80 pounds. Multistage reciprocating compressors, wherein air is subjected to two or more compressions, are used when pressures in excess of 80 pounds are desired. I n compressors of this type, the air receives an initial compression in one cylinder, passes through an intercooler which serves to reduce the temperature, is then compressed further in a second cylinder, and so on in succession, each cylinder being also water-cooled. In a multistage compressor, each cylinder is smaller than the preceding, and in fact must be proportioned to receive exactly the compressed and properly cooled gas of the previous cylinder. Because of the more effective cooling and because clearance losses are reduced, multistage compressors are more efficient. Theoretically, therefore, the more stages the higher the efficiency, but size and cost of machinery, a4 well as friction losses, limit the number of stages to seven a t the most. I n such machines, pressures of from 1000 to 15,000 pounds are attainable. RECEIVED April 21, 1932.
The Netherland Fertilizer Industry In normal years the Xetherlands uses more artificial plant food per acre of crop and improved pasture and hay land than any other country. Kearly 40 per cent of its area of 12,640 square miles consists of pasture and 26.5 per cent of arable land The total quantity of chemical basic fertilizer materials consumed during 1930 in this small area n-as estimated a t 1,300,000tons. The manufacture of fertilizer materials for the domestic and export markets constitutes an important industry. Despite the lack of domestic supplies of phosphates and sulfur, the country is the leading world exporter of superphosphate anti since 1930 has occupied an important position in the ammonium sulfate export trade. The first synthetic nitrogen plant in the Xetherlands, located near blast furnaces at Ijmuiden, commenced operations in the autumn of 1929. In the summer of 1930 the state coal mines opened a plant at Lutterade, Limburg, a-hile the plant a t Sluiskil, Zeeland Flanders, started production in 1931. Their combined capacity for 1932 has been estimated at 122,000 metric tons of nitrogen; the normal home consumption approximates 65,000 metric tons. The annual capacity of the Lutterade plant approximates 225,000 tons of ammonium sulfate. The company also markets aqua ammonia for industrial purposes and in March, 1932, completed a new plant with an annual production capacity of
47,000 tons of ammonium nitrate, 12,000 tons of ammonium sulfate-nitrate, and a by-product yield of 2000 tons of sodium nitrate. The total output of about 55,000 metric tons of synthetic nitrogen does not include approximately 15,000 tons of ammonium sulfate obtained annually as a by-product in the coke works of the state coal mines. The plant has storage capacity for 40,000 tons of ammonium sulfate and facilities for loading either bulk or bagged products at the rate of 100 tons hourly. It produces about one-third of its sulfuric acid requirements from Spanish pyrites. The annual capacity of the Sluiskil nitrogen plant, operated by Compagnie Nderlandaise de l'Azote, formed by the Italian Montecatini, the Belgian Coppee company, and others, approximates 50,000 tons nitrogen. The Ijmuiden plant is operated by the Mij. tot Exploitatie van Kooksovengassen, a company formed by the Royal Dutch Blast Furnaces and Factories and a subsidiary of the Royal Dutch Shell petroleum organization It has an annual capacity of 17,000 tons of nitrogen. The Cnited States received approximately one-fourth of the 254,685 tons of ammonium sulfate exported in 1931. Increased further participation is evidenced by American statistics for the first half of 1932, which indicate the Netherlands as the supplier of 107,670 long tons of the all-time record receipts of 165,441 long tons.
Couilesy o/ Tezas Cult Sulphur Co
SuLFun CAROO-LOADINO IhNT,
GAl.VESTON, T E X A S
Economic Position of Sulfur A. M. TAYLOR, SO East 4lsl Street, New York, N. Y.
F
ROM time immemorial sulfur has been the backlog of
the chemical industry and, to use a trite expression, its rate of consumption lias been considered tho barometer of general trade activity. There is hardly an industry into which it. or one of its products does not enter. No other element plays such an active part in our chemical processes. Yet we ask the question: "What of the future of sulfur?" Clarke (7) has est.imated the world's resoryes a t from 56,000,000 to 121,000,000 metric tons, so that there is little immediate dansrofanyscarcity. The largest reserye8arein Italy and the United States, conservatively estimated at 25,000,000 and 40,000,000 tons, respectively. Chile is reported to have 5,500,000 tons averaging 70 to 90 per cent; Spain 500,000 to 1,750,000 tons averaging 15 to 30 per cent, and Japan several million tons of 50 per cent ore. The producing deposits of Italy and Texas have the advantage of the lomest cost of production. If Clarke is correct in his estimate of 40,000,000 metric toris being the available resources of the United States, then the supply will be exhausted in fifteen years if our consumption and exportation continue a t the present rate of 2,525,000 tons yearly. Even if our m ~ - ~ e were suflicient for fifty years, conservation of sulfur should receive our serious consideration if we are to continue to use it as a raw material in our basic induutries. SOURCES OF SIJLFuE
World produolion United SLatea SiCilY Itsly Japan
2:525'000
245:OOV 88
z;
ow
75bov 70,000
1929 LOW Ions
2.800.000 2,362,889 237,000
.....
PKoDUcTloN
1931 LO"l7 tons Cmmda GWU8"Y
Austrslis France Nethdrlsnda United Kingdom
.... .... .... ....
New Zealand
407.580
OF
Ye*=
P*"*TSe
Ton,? 1930 1929 1928
347.512 333,465 312.815
S0LP"K E Q U I V A L G N T Ton8
124 228
120:371 113,305
Tiie imports of pyrites alnounted in 1930 to 368,114 tons (equivalent to 184,000 tons of sulfur), and in 1929 to 514,336 stons (equivalent to 257,168 tous of sulfur). Of these imports in 1930 Spain furnished 325,992 tons, Canada 42,117 tons, and nussia5 tons, The shipment of sulfur direct to the consumer amounted in 1928 to 1,396,000 tons, in 1929 to 1,555,000 tons, and 1930 to 1,465,000 tons. Of the total sulfur shipped to the consumer, brimstone represented 82.7 per cent, imported pyrites 6.4, and domestic pyrites 6.9. Sulfur used in various industries in 1929 has heen estimated as follows ($6):
75,000
....
Ton8 Hesvy e i i e m i e ~ l ~ Fertilizer and inaectioides Pulp and pspcr EXplmi"e8 Dye and ooel tars
9u1.x.u~ 1930
1829
Lon" ton* 266.943 120.509 08,030 68,190 36.073 28.083
L"W ton*
18,212
37.048
593.312
OF I'YlWrES
Production of pyrites in the United States, iiicluding hyproduct pyrites and pyrrhotite concentrates from Tennessee, pyrites concentrates from New York, and partly desulfurized tailings from Wisconsin, is as follows:
10,ooo
U. 9. Exuows
Total e p o l t a
(6)
1830 Lono rona 2 900 ow
Of the sulfur produced in the linited States, 86 per cent of the total comes from the deposits of the Texas Gulf Sulfur, the Freeport Sulfur, and the Uuval Sulfur Companies located in Texas. No sulfur was produced in 1929 and 1930 in Nevada, California, or Utah, which made small contributions during preceding years.
Rubber Electroohemica1 Paints and ~ s r i n i s l m Food roduots MilCeEane0"S
2w.012 109,474 104,538 136.732 50,707
Total
43,856
47.000
43 000 23:OVO ~,OOV
.,..
136.W __
1.581.000
The production of sulfuric acid in 1929 w s as follows:
865,183
1116
