Symposium on the Design, Construction, and Operation of' Reaction Equipment Presented before t h e Diviaion of Induatriai arid Engineering Chemistry at the 84th Meeting 01 the Amo~ioao Chemical Sooiety, Danver. Colo.. A U 6 U B t 22 t o 20, 1932.
Carbon. Neglected Material of Construction for Reaction Equipment C. L. MANTISLL, Pratt Institute, Brooklyn, N. Y or pressed and baked to carbonIndastriully, fabricakd forms of amorphous or coke this binder, i t can ize search for more r e s i s t a n t carbon and graphite, because of thpir unusual be readily appreciated that the materials of construction resistance to chemical attack and corrosive inparticles of carbonized binder for chemical engineering equip jwnces, deserve greater consideration as a form the weakest portion of the nrent, various forms of mannmaterial of construction for reaction equipment shape as far as chemical attack is factured carbon have received concerned. Carbon is not imconsiderable attention and have than they have received to date. New applications mune to destruction by oxidizing found n o t a b l e applications in will be made when the tnluable properties of agents such as nitric acid, failure service. I n its commercial fabricated forms of carbon are more widely occurring because of oxidation oi forms, carbon articles may vary appreciated. The rnuterial has shown exceptional the bonding material. Of the in hardness from those of soft performance in connection with acid manuentiregroupof common reagents, e l e c t r i c - f u r n a c e graphite to only nascent oxygen, oxygen a t amorphous materials showing facture, paper making, the electrocheinical int e m p e r a t u r e s above 625" F. hardnesses comparable to those dustries, petroleum industries, combustion equip(329" C.), and strong nitric and of the m e t a l s . C a r b o n can ment, and us parts of machinery operating irr chromic acids attack carbon. readily he fabricated and nmchemical ulantn under severe condilioru. A satisfactory m a t e r i a l of chined into i n t r i c a t e shams. conbtruction must have good s i m p l e f o r m s of which i r e plaks, tubes, blocks, rods, and molded parts. From these, physical properties. Those for cohe-base carLon (the most complicated structures can be built up with greater ease common form of the manufactured carbon materials) BS deterthan is possible with ceramic materials or chemical stone- mined by the Xational Carbon Company are as follows: ware. ?.003.10 Real density 01 ap. gr. Manufactured carbon shapes show high compressive Appsient 1.53-1.04 donsity Appzon. 26 strengths and good physical properties. Carbon has high Poroalty, % A p ~ r o x .100 (45 41 Weight per cu. it. Ib. (kp.) .kpiIror. 000 (42.2) elcctrieal conductivity and :m extremely low coefficient of Tensile strength ib i s q . ( k d w om.)
N RECEliT years in the
I
Cruahingstrenaib 1b.h in (ka/a em) Transverseatreoqh lb.?&.ln. (kx.9&. im.) Thermal conduetiviiy eal./cm./e C. Coefficientof thermslkrpansion per' C. Sp. heat =am eal.igram/" 6.st 28-282' e. Sp. eleo&d ieeistanee per xn. cube (per om.cube)
-
voIat.iliration point. Ash 70 5ta;t ai onida!ion.
I.'iouitc
1. PILEOF C.mnox Tuims
FOH
Ilse
IN Corrmr.~PBECIPITATORS Tubes are 10 inohes i. d.. 13 indiea 0. d., and 7 ? inches ions.
thermal expansion. I t shows almost uriirersal resistance to cliemicai action, having found particular application in conneetion with the higJ!ly corrosivc fiimes of sulfuric, hydrofluoric, and phosphoric acids. Carbon is susceptible to attack by oxygen a t temperatures exceeding 6-00" P. (315.6" C.) and by carbon dioxide and water vapor a t coniparatively high temperatures. Because of the iact that commercial forms are made up of ground material held together hy a binder, the whole mass afterwards being formed
F. (" C.)
x'. (' C.)
i2S a r e s u l t of the chemical inertness of carbon, combined with its high strength, new uses in chcniical apparatus are developing as rapidly as manufacturers can perfect methods for the production of intricate slrapes needed for chemical p l a n t s . A large v a r i e t y of sizes and shapcs are a t present ava.ilable for application in chemical apparatus under difficult condit.ions. At the present time carbon has shown its suitability in equipment employed in five d i f f e r e n t fields: ( I ) acid
6000-9000(122-633) 32W4000(225-4221
0.00786 0.0000072
0.2")
o.no4~-0.0017 (due metrio SSUi".) Appro=. 0300 (34821 1.00-1.20
025 (328)
F t c u n ~2. Cannori SupponTISG
Coi.Lnns
Noverrrber, 1952
I N D U S T R I A L A N D E N G 1 N E E K I N G C H E M I S T 1%Y
It is common practice to use bricks approximately 9 X 7 X 21,12 inches (22.8 X 17.8 X 6.4 cm.) with i t slightly curved face for the lininl: of the cylindrical portion of n pulp digester, while various wedge and spccid shaped hrirks tire omployed in the dome and conical bottom sections. It is xmihle to produce carbon in theso shapes, fiut the expense of d e s a n d molding equipment is a considerable item, and it has been demonstratcd that erfect carbon linin@ can be installed by using straight-side$ 9 X 411. x 21/$ inch or 9 X 7 X 2 l I 2 inch (22.8 X 11.4 X 6.4 cm. or 22.8 X 17.8 X 6.4 cm.) brick, making whatever cuttings are necessary in the field. A t the present time, liuwever, t,he carbon manufacturers are prepared to furnish the r:urved bricks in a 9 X 7 X Z1/% inch size necessary for tlie cylindrical shell of the digester. reoiiircd fur nrakiw the They have eomideted tlic eauimient, .. spe& siiapes 2 brictis for tlie donre s~iipedtop ani1 conical bottom of the digester cll. Pulp uianufaoturers can now be supplied rvith thesp I shapes which have born heretofore believed necessary for lining the digester. The labur iieeded to do the job is considerably reduced. Some of the plants in the paper industry, because at the Ijresent time \-cry costly equipment is used where constant rcplacement w e d s to be iriade, are experimenting with carbon tubes for heat interchangers tu compete in one case with expensive tantalum. To date, the experiment has heen a successful one. A new developnier~tis the production of impervious chemical carbon pipe which will be impervious to liquids and gases within practical pressure limits as established by industry at present. Tests of this material exteoding over a two-year period hare iiidicated the resistance of the new material to corrosion mid to thermal shock. Fittings for this substance are at present lreing developed. The next few montlis will see this material offered to the chemical industry as a solution for their pipe corrosion problems. Manufactured carbon lumber for building the sides of buildings where corrosive conditions are particularly severe is now produced. Carbon beams and carbon roof materials of slabs are also available. In this connection, carbon can successfully compete with wood wlien all the cconomic factom of the situation are considored.
1257
FIGURE 5. CANSON TUBESWITH Tiimms
the mass afterward being baked. This is the typical construction in an alumiuum cell, which consists of 8 steel pot or box lined with carbon. Amorplrous carbon and graphite electrodes are essentials for the reaction equipment in which electric steel, ferro-alloys, calcium carbide, cyanamide, silicon carbides, fused alumina, graphite; aluminum, magnesium, calcium, and sodium metals; phosphorus, phosphoric acid, carbon disulfide; chlorine, caustic soda, and chlorates are produced (4). From the viewpoint of tlie raw materials used, the methods of mauufacture, and their applications, the electrodes may be subd i v i d e d i n t o amorphous carbon electric-furnace electrodes, amorphous carbon electrodes for aluminum, graphite furnace electrodes, USE 1K ~ I , ~ : L . T I ~ ~ J ~ l ~ ~ . \ t l ~ : h r , and graphite sbapesfor elecIADUSTRIES trolytic work. Electrodes for e l e c t r o ID the electrochemical inthermic work serve as the dustries, carbon in either an refractory conductors of the a m o r p b o u s o r graphitic electric current and do not form bas long been either cnter into the reactions takstandard or the only availing place in the furnace or able possible material. The ot,her apparatus in which use of graphite as an anode they arc used. KO other in chlorine and chlorate cells s a t i s f a c t o r y material is for the electrolysis of sodium available. I n many cases chloride and the production t.he impurities of the elecof chlorine and caustic, and trode either do riot cnter the in the fused electrolyte proproduct of the furnace or, if duction of magnesium, is they do, make no apprewell known. In a similar ciable difference. Thus a way, the exiensivo employsatisfactory electrode for ment of carbon elcctrodea iir electrothermic p u r p o s e s aluminum cells and i n ehxmay have an appreciable tricfurnaces is familiar. In ash content and ,show B a number of important fused comparatively high resiselec t r 01 y t e processes, the tivity. The raw materials only available cathode cona r e low-ash anthracite, struction material found to which after calcination is date is carbon, generally g r o u n d so t h a t B highr a m m e d i n place in the strength aggregate may he form of a plastic mass of the CARBON-LINED PULP D I G E S ~IN ~ RPAPER F Z G U6.~ SMALL obtained. MILL ground carbon with a binder,
1 N U U S T 1 1 I A I,
A N D E N G I N E E 1%1 N G C I 1 E M I S T I L
Y
Vul. 24. No. 11
be formed by a nronolithic lining (S). 7'11: blocks, being prefomred and baked, are denscr than tlic esrlmi paste and uffer greater resistance to oxidation. I3locks are manufactored in xlractically all square e l e c h d e Fizes. Tiicy arc set up in the furnace like ordinary rcfraetnry bricks with tht: exception that the bond used is carbon paste instead uf refractory cerncnt. A number of standard sliapcs of t,lie same dimensions as refractory bricks are marketed. Th( (12.8
x
(22.8
x
CY2.8 (22.8
x x x
ca2.s x (22.8 (?2.8
x
These bricks and lrloc.ks are made of groiind calcined coal or coke, bounded with tar and pitch, and haked to a t,eniperaLure high enough to completely colw t l i c liiiidcr. hizcs otlier t.lian those listed are special, but i~ractically:my shapc or size can be obtained. The use of carbon refractories nlioil-~tlie possibility of furnace linings being rthlc bo resist temperatures at wiiiclr ordinary refractories u;ould either melt, spall, or lose bheir valuable properties. Other tl,an carbon, commercially we have no refractories useful above approximately 2700" C. Furnace linings and slag Boors in high-pressure boiler furnaces where pulverized coal is oserl, represent two other recent developments. Figure 8 is of a sectiolr of a carbon Boor in the slag pit of a powdered-coal burning furnace. This material has stood up remarkably well in this mrvice, and no iron precipitate on the surface of the carbon, due to tlio release of carbon dioxide gas, has been noted after some three years of operation. The carbon is only slightiy attacked, and the floor which was built of 8 inch (20.3 cm.) thick slabs appears to have an indefinite life. Electrodes for fuseddalt electrolysis, sucli as the prodmlion of aluminum, must he low in impurities in that these are transmitted t o the metal produced in the furnace. The raw material for these is petroleum coke, a pure low-ash hyprodiict of petroleum oil refining. The purity and resistivity uf the electrodes (anodes) are importatit, because of tile low voltages at which the furnaces operate. lJsE
IN
COMBUSPION EQUIPMENT
C:arlmir hiis a nielting point assunred to be around 440JOO (:. i t sublimes or volatilizes a t approximately 3500" C. Inasiniu:Ii as its nielting point is considerably above tlioso of the normal nietal oxides irsed for furnace Iiiiiri~sexcept io oxidizing atmospheres, carbon is a good refractory. It begins to
oxidize bctmen 500' and 600' C. In a reducing at.mosp1iere it is better tiran any of t,heusual refractories. For certain t,ypes of furniiccs a current-carrying button1 is required. Tlie matcrial largely used for this purpose is a mixture of around carbonaceous materials with a binder like tar or pitch. The mms is tamped into place and baked, xiving a hard product. Surnc electrode manufacturers produce carbon paste as a ~:riinnrercialproduct. This is made of crushed calcined nia& rials screened t o a certain predeterniined size and niixed xvitir a proper amount of binding material. The binding niaterial is varied according to the use to wliich the product is t,o be put.. This niat,erial is sold in small lots, bagged for shipment, or in carload quantities. Before use, it is lieated to make it plastic. Carlion blocks are generally used for furnace linings and furnace bottoms, particularly in large open furnaces or in places where greater structural strength is dehired than would
FIGURE 8.
SEClTIUN UF CAIIllON lTr.oUlr
IN SLAG PIT OF FURNACE ~ U ~ N I N U
POWDERED COAL
Electric furnace graphite is unique among refractories because of its purity, low linear cspansion, and nonfusibilityail of which permit it to retairi its shape, size, structure, aid physical properties nnder conditions of extremely high temperature. USE IN
MACHXKERY ~I'EJ1.ATIX.G USI>&R CoBROSlVE Cowrnoss
I n chemical machinery, particularly in pumps carrying corrosive liquids, carbon or graphite impellers have been quite successful in experimental work to date. Graphite or carbon bearings under extremely corrosive conditions iiavc functioned satisfactorily. Bushings, gaskets, and packings can be made to nithstand almost any conditions under idrich metals or other materials sooner or later fail. Among the new developments has been the manufacture of carbon pipe which will stand liquids under appreciable hydrostatic head. It is
R’ovember, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
expected that this new form will find increasing application where other materials fail. Industrially, fabricated forms of amorphous carbon and graphite, because of their unusual resistance to chemical attack and corrosive influences, deserve greater consideration as a material of construction for reaction equipment than they have received to date. New applications will be made when the valuable properties of fabricated forms of carbon are more widely appreciated. The material has shown exceptional performance in connection with acid manufacture, paper making, the electrochemical industries, petroleum industries, combustion equipment, and as parts of machinery operating in chemical plants under severe conditions.
1259
ACKNOWLEDGMENT The author gratefully acknowledges the cooperation received in the form of illustrations and data from the Kational Carbon Company, Cleveland, Ohio, and the Speer Carbon Company, St. Marys, Pa. LITERATURE CITED (1) Camp, A. D., Chem. & M e t . Eng., 37, 676 (1930). (2) Camp, A. D., Paper Trade J., 94, 38 (1932). (3) Mantell, C. L., “Indwtrial Carbon,” Van Xostrand, 1928. (4) Mantell, C. L., “Industrial Electrochemistry,” McGraw-Hill, 1931. RECEIVED July 20, 1932.
Individual Tire Vulcanizers A Recent Development in Vulcanizing Equipment for the Rubber Industry L. R. KELTNER AND H. GRAY,The B. F. Goodrich Company, Akron, Ohio
A
each other in a vertical vulcanWEALTH of descriptive Individual or unit vulcanizers for pneumatic izer equipped with a hydraulic data is available dealing tires are one of the more recent developments in ram. While holding the molds in a general way with the vulcanizing equipment f o r the rubber industry. closed by hydraulic pressure, the m e t h o d s and equipment ernA description of the construction, design, and tires are formed and cured by ployed in the process of rulcanioperation of these vulcanizers i s given in conapplying air, hot water, or steam zation of rubber goods. This under pressure in the bag and process, as nearly always applied, siderable detail. I n comparison with the conheating the mold outside of the involves the combining of sulfur ventional heater press-conveyor method of vultire with steam a t a definite temwith rubber under the influence canizing tires, the individual vulcanizer i s more perature for a specified time. of heat and usually pressure, for economical in its direct labor, operating, and The time and temperature dethe purpose of improving the maintenance requirements, more flexible f r o m p h y s i c a l properties of rubber pend, of course, on the acceleration ( I ) of therubber compounds compounds. Many variations the standpoint of rubber compounds employed, e m p l o y e d a n d t h e combined in the manner of supplying the but less economical when production conditions thickness of the tire and hag. heat and pressure have been used require frequent mold changes. It i s concluded Efficient o p e r a t i o n of this and described in the literature. that the indiuidual vulcanizer i s worthy of method r e q u i r e s an elaborate There are, however, some deconsideration for future equipment requirements. s y s t e m of conveyors for revelopments in vulcanizing procmoving molds containing the ewes a n d e q u i p m e n t which merit more detailed description and analysis than has hereto- cured tires from the heaters, and ioading molds containing fore been presented. Individual or unit vulcanizers are in this the uncured tires into the heaters. Additional efficiency is class. They are mechanically unique, produce an extremely obtained by the use of mechanical mold openers, mold lid uniform product a t very low curing cost, and have been adopted lifters, devices for extracting the tires from the molds, mold quite extensively where new equipment has been required. sprays, mold closing presses, and other labor-saving devices (Figures 2 and 3). It can easily be seen that such a system WATCHCASE VULCANIZERS is dependent upon the uninterrupted operation of the entire The idea of vulcanizing or, as more frequently termed, unit or group of heaters for which the above-mentioned “curing” pneumatic tires singly is not new. The Batchcase accessory equipment operates. vulcanizer, so-called because its hinged doors operate in a The watchcase vulcanizer provides independent operation manner similar to the covers of a watch, has been used for not obtainable with the heater press-conveyor system. It curing a limited number of tire sizes since 1900. Articles by lacks, however, rapid interchangeability of mold equipment, Rossman ( 2 ) giving a brief description of the horizontal and sufficient capacity for large cross-section and small-diameter vertical types and a review of the patent literature relating tires, and adaptability to additional mechanical time savers. to watchcase vulcanizers was published in 1928. The best The necessity of overcoming these deficiencies while keeping of these vulcanizers was a vertical type in which tires were the flexibility of independent operation led to the developcured in pairs. The two hinged doors were each half of a ment of individual or unit tire vulcanizers. These are demold cavity, the other stationary halves being fastened back signed to cure sizes varying from the largest cross-section bus to back in the center (Figure 1). balloon to the smallest-diameter airplane tire. Their mechaniWith few exceptions, watchcase vulcanizers held little cal action is fully automatic. Every operat ion from the time advantage over the conventional heater press-conveyor the uncured tire is placed in the mold until the cured tire is method of curing tires. Briefly, the conventional method is removed from the lower bead-forming ring is performed withas follows: An expansible rubber bag is inserted into the out the aid of man power. In fact, the direct labor required uncured tire. The bagged tire is placed in a steel mold in for curing passenger-size tires is less than one minute of one which a tread and side-wall design has been cut. Fifteen to man’s time per tire. thirty of these molds (depending upon size) are stached upon Pertinent descriptive details of an individual tire vulcanizer
