Glass-Lined Steel Equipment in Chemical Industry P.
S. BAHNES,T h e
Pfaudler Company, 89 East Aye., Rochester, N.
G
LASS-LIXEI) steel and cast-iron process and storage
Y.
The steel shell is fabricated from low-carbon open-hearth equipment has recently passed its fiftieth anniversary. plate, free from laminations and slag spots, the thickness The first glass-lined tanks wereintended solely for the usually ranging between and '/z inch, depending upon Iiulk storage of malt beverages and were constructed of size and required pressure. cylindrical, flanged ring sections, bolted togethcr and built up Butt welds are always employed, since the tank must cool to any desired length or height. Their advantages gradually a t a uniform rat.e while annealing the glass. Only oxyled to adoption by other industries, particularly for chemi- acetylene welds are possible, since satisfactory adliesion of the cals and food products of all kinds. This, in torn, required glass is not obtainable by other methods. the development of added features of design such as jackets After fabrication of the sliell, all inside welds are ground for heating and cooling, agitators, and iniscellaneous ac- smooth. Next, the surface of the metal (cast iron or steel) cessories, maiiy of which were rendered feasible hy the advent is sand-blasted so as to rcmove mill scale and afford aii added uf oxy-acetylene welding. The greatest diversification of bond for the ground coat of glass enamel. It is highly probdesign and usage is to be found in the cliemical and allied able that an actual reaction occurs between this ground coat and the metal itself, thus affording ~naximum adhesion. industries, to whicli this paper is confined. The terms "glass-lined" and "glass~namel-lineri" are used After. applying the ground coat, two or more finishing coats interchangeably and rofer to complex borosilicates, frequently are added. pigmented vith cobalt or other metals and fusing a t temperaThe euameling furnaces are of several types, either open or tures averaging about 1800" F. The predominant raw muffled, and fired by gas, oil, or coke. Revolving tables are materials are silica and borax. Them glass enamels are often included so as to equalize temperatures. Existing iiiglily resistant toward all acids (excepting hydrofluoric) furnaces will accommodate one-piece closed tanks up to 9000 regardless of temperature or concentration, but must he used gallons capacity. Smaller furnaces are usually available so as to permit economical processing of special items, sucli as with caution against caustic alkalies. agitators, pipe and fittings, etc. MANUFACTURE OF GLASSLINED EQUIPMENT Two methods of application are in vogue-namely, hot Preparation is by smelting in the electric furnace, followed dust and wet spray. The choice depends upon several factors, sucli as size, design, and severity of operating service. by grinding to an extremely fine frit. IIot-dust enamels are applied manually to steel or cast-iron It is not a particularly difficult matter to compound a glass enamel solely from the standpoint of high resistance to acid, shapes after vithdrawal from the furnace a t a temperature but years oi research underlie the development of enamels approximating 1850" F. This method permits the applicawhich cornbine with acid resistance the properties essential to tion of glass enamels oimasirnum resist.ivity but is necessarily proper adhesion and perfect coverage over a relatively large confined to open-type tanks, not too large to allow coating area of steel. Adding to tliis the development of the ac- before l i a ~ i n gcooled below the fusion point. At present the companying technic in welding and in furnace operation, maximum size is 500 gallons. Closed-tank designs with hotglass-enameling may well be classified as an art rather than a dust enamels are obtained by enameling the covers separately and then clamping or bolting them to open shells. cut-and-dried manufacturing operation. 1080
Wet-spray i:namels arc applied cold, prior to cutering the marneliiig famace, and can readily he used on closed tanks hy \wrkinp tlirougli tlie manhole. This method perniit,ii fabricatirip large one-piece units, limited orily by the size of the eoaineling furnace anti tlie niaximmn size wliieh can 1,e slrippcd by commoii carrier. IIowever, it is not usual to wpply estremely large individual units for use against se\.idcorrosive ? liquids, since tlie area of enamel must be kept within a liinit that will insure absolutely perfect coverage. Where acid conditions arc iuvulverl, the fiuislred surface iii(iuldtest free of even microscopic defects, a spark test being the method most commonly employed. A brush with copgcr h i d e r is used, grounding one lead of a low-voltage current on the shell; a defect then appears as an arc and occasion8 rcjectioii of the piece. Vracture from tliermal slrock, tinder conditions involviiig t l i e application of lieat from a steam or oil jacket, is eliminated hy adjusting the cnarnel formula whereby its coefficient of
tanks, pressures u p to 76 mid 100 pounds per aquare inch are ieadily obtainable from welded-on steel jacketa, tlirough wliich are carried flanged glass-lined outlet connections with suitable stuffing boxes. Above tlie temperature range obtainable witlr steam, oil can be used safely u p til ai,proxilllatcly ROO" I*.
cspansioii approximates that of the metal itself. The following general considerations have occasioned tlie estensive use of glass-lined equipment Ly the chemical and sllied industries:
-
Protect,ion of the oauinmeirt itself aeitinst acid action and .. rapid depreci2iiion. Protection of the product against eontarninabion and turbidity iTsiiltirig from dissolved metallic salts. Eiuo in cleaning and sterilization. Inrprovcd yield by eliminating side reactions that, w e catalyzed ily metal.
TYPESOF Ewsmmxvi, From t,iie standpoint of design, glass-lined equiiunent in standard types may be differentiated as open and closed, vertical mil Iiorizontal, and with and without jackets for heating and cooling. Unjacketed types are usually employed for storage and, when equipped wit.li suitable agitators, for various nixing problems. They i ~ r fornishetl e ill both horizoiital and vertical types, as rlictatd by available factory space. Subject to
lirriitati~iispreviously mentioned, all-welded storage tmks are available in sizes ranging from the laboratory piece up to tank cars aiid 9000-gallon plant storage units. Jacketed types are required in most manufacturing Iirocesscs within the chemical industry, to pcrmit heating by means of steam or circulated liot oil, cooling with brim or water. While jacket stay Bolts are not pmsible in enameled
I.mw T*XXSI ~ WFOR Y I h ~ o v a t .F ~ O M F u s w a c ~
Tlie majorit.y of process imits for rcaatiiuis, distillation, digestion, etc., are of the clased jacketed type, usually with cnauielerl steel agitators. These are available in standard ilesigris arid, for acid conditions of miximum severity, in sizes up to 500 gallol~s. Open jacketed eT7aporators in hemisliheriea1 s l i a i i c ~arc extensively used for purposes sucli as the preparation of c . P. chemicals and reagents. Glass-lined pipe and fit.tiriga can be obtained in sizes from I b / z i n c h upward. Condensers are available, although somewhat restricted as to size and design. Agitators are usually of the propeller or anchor type, suspended tlirougli a st,uffing box in tlie cover. Inlets and outlets are flanged and welded on, t l i e enamel being carried over the face of the flange. The net result is a complete process unit which expose8 only glass enamel to the action of tlie tank contents. Laboratory units are obtainable in sizes down to 2 gallons. quipped with jackets and agitators; high-pressure autocla with renewable enameled liners are Sirice glass enamel is tliorouglily :acids, many reactions are possihk he haiidled outside the luhoratory. Provided suitable care is cser d in its operation, glasslined equipment will gim long service under Iiiglilg corrosi\-e conditions. For example, jiieketerl kettles, used in ttir refining of rare metals, liave been in continuous service for 6 years against hot, full-strength aqua regia; others, with strong hydrochloric iicid at 400" F., for tlie preparation of dye intermediates, One large installation satisfact.orily resists wet I~roniiucand chlorine, together with concentrated k)miiide solutions, a t elevated temperatures axid pressures. Another example i.: found in tlie chlorination of organic products such as toluene. Tlie average life, before reenameling becomes rrccessary, is between 3 and 4 years, as demonstrated by an iiistallatiori conrprising t m l r c large unit,s. A battery of six tanks, w e d for gold-platiug solution?, is reported in excellent conditioii after 13 years of serricc. Jacketed kettles for acid pliot.ograpliic emul.:'IOIIS serve between 5 arid 10 years before requiring repairs. Other examples denmistrate satisfactory resistance over a period of years to hj~drobromicacid, iodine compounds, mixtures of alcohol aud hydrochloric acid, etc.
October, 1933
INDUSTRIAL
AKD EKGIKEERIKG CHEhlISTRY
CAUSESOF FAILURE OF EQUIPMENT Failures of this type of equipment, other than those resulting from normal wear over a period of years, may be classified as follows: Use of pressures in excess of those recommended by the manufacturer. Localized overheating, such as from the use of direct flame or by allowing a stream of cold liquid to impinge on a small area within a jacketed tank that has been heated to a high temperature by a previous batch. Use against chemical conditions for which the equipment was not originally specified. Glass enamels vary in resistance and the conditions should be clearly defined prior to manufacture of the equipment. Fracture from mechanical abuse, such as a heavy metal nozzle at the end of a hose. Fracture from strain at clamped or bolted flanged joints. This can readily be avoided by the use of suitable gaskets and by tightening uniformly so that the metal itself is not distorted. As a rule, it is entirely possible to recondition glass-lined steel equipment. After removal of jackets and accessories, the original coating is sand-blasted off, corrodcd steel repaired by welding, and new coats of glass-enamel applied. Methods of repairing glass enamel in the field have been given exhaustive study, and satisfactory materials are available for the majority of chemical conditions to which this equipment is subjected, provided that the area of exposed steel is comparatively small. For example, recessed gold plugs, for areas of small diameter, are extremely satisfactory
1083
and in no way shorten the service life of the adjacent glass enamel. Ceramic patch repairs are frequently employed, and with good results if care is taken in their application. One example of this is a large still and piping assembly, exposed to wet chlorine and bromine vapors, which has already been kept in service for over a year by means of ceramic patches, after a plant accident had caused damage of the glass enamel at numerous points. USES
Glass-lined equipment finds many apecific uses in the chemical and allied industries. Much of the nitration, sulfonation, and chlorinaton, as in the manufacture of dyestuffs, is done in such apparatus, which is also used in preparing dyes for use in the textile plants. Such equipment has its place in the production of synthetic I esins, pharmaceuticals, toiletries, cellulose acetate, gelatin, lacquers, rubber accelerators, and in the refining of precious metals, to mention a partial list. Kumerous industries specify glass-lined equipment for mixing and storage purposes. Glass-lined steel tank cars, for the bulk transportation of various liquids, constitute an extremely interesting development of the past few years. They were designed primarily for fluid milk, and several hundred 6000- and 8000-gallon cars are now in daily operation for this purpose. Their use is gradually broadening into other fields such as grape juiw, tomato pulp, mineral waters, laundry bleach, etc. RECEIVED February 1, 1933.
Studies in the Friedel and Crafts Reaction Effect of Size of Aluminum Chloride Particles in the Preparation of Some Keto Acids P. H. GROGGINSAND R. H. NAGEL, Bureau of Chemistry and Soils, Washington, D. C.
I
The effect of the size of the aluminum chloride the material was of the dimenparticles in carryingout !he Friedel and sions given, but in all cases a Friedel and Crafts reaction, small quantity of the p o w d e r p r a c t i c a1 considerations synthesis of 4'-chloro-2-benzoylbenzoic acid is w o u l d recommend t h e u s e of TI;aspresent. aluminum &loride in the form closely related to the eficiency of the agitation proThe first s e r i e s of e x p e r i of granules or small lumps. As vided. With, better agitation, particles u p to the ments was conducted in Niter, size of a pa have been used with Success in three-necked, r o u n d - b o t t o m compared with powdered material, these would be less hythe preparation the keto acid. ~~~~~~l of the flasks. The procedure employed g r o s c o p i c in s t o r a g e and in is described in previous publicaliberated hydrogen chloride gas from the reaction handling and less troublesome in tions (s). In t h i s s e r i e s the chamber increases the yield* The solubility of delivering to the reactor ( 2 ); small glass stirrer (the size being finally, the l a r g e r p a r t i c l e s 4'-chloro-2-banzoylbenzoic acid in water at varil i m i t e d to 1.5 inches, or 3.8 cm., bv the neck of the flask) would not react a s r e a d i l y , ous temDeratures has been determined. T o avoid solubility losses, the keto acid should be rotiting at 150 r. p. in. was inthus contributing to a better regulated initial reaction. On a d e q u a t e to provide a homoJiltered at room temperature and washed with the o t h e r h a n d , t h e u s e of geneous r e a c t i o n mass, powdered a l u m i n u m chloride cold water. data in Table I reflect this condii s frequently specified i n t h e tion. The finer particles of alumipublished literature. The purpose of this investigation was num chloride contributed to a more homogeneous reaction to determine the effect of the size of the aluminum chloride mass and hence to better yields. An increase in the reaction particles upon the yield of keto acids. time under similar conditions did not effect any improvement. With the object of providing more adequate agitation, the EFFECT OF TYPE OF AGITATIOX next series of condensations was carried out in an enamelThe preparation of 4'-chloro-2-benzoylbenzoic acid was lined, round-bottom vessel of 8 liters capacity. The reactor employed as a vehicle for determining the influence of the was fitted with an anchor type stirrer rotating a t 25 r. p. in,, size of the aluminum chloride particles. Four sizes were in- to which was attached a sheet-iron blade that practically vestigated, lump (approximately 15 to 20 mm. diameter), scraped the bottom portion of the vessel. The data in Table pea (approximately 4 mm. diameter), sea sand (approxim:itely I1 show that a slight increase in yield was obtained under 0.5 to 1 mm. diameter), and powdered. The greater part of these conditions. S C A R R Y I N G out the
crafts
"
&
