GLASS CHLORINATION
EQUIPMENT T.J. THOMPSON AND CAMPBELL RUTLEDGE, JR. Corning Glass Worb, Corning, N. Y.
ROGRESS III commercial apphcahon of chlonnation prooases has been substantially contingent upon d e velopment of slutable materiala of constructaon to withstand the mvere corrosion of such operations. Among the many materiala of coustruction which have attained commercial impxtmce, g l m has proved ta be particuhly servicesble for handling of chlorine, bromine, and their many compunds. Bororrilicate glans with its low thermal expansion and marked chemical Ability provides a material uniquely resistant over a wide temperature range to the destructive
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&e& of powerful oxidking agents, hydrochloric acid, and hydrobromic acid. In the form of flanged piping, socket piping, heat exchanger tubing, fractionating columns, and centrifugal pump of standard design, such ghmware lends iteelf well to fabrication of highly useful equipment and accesaorieS for chlorine and bmmine prooessing. Glass equipment has proved to he d e p d a b l e and economical in the following applications:
Manufacture of Halogens. Glsas piping and tubing are being used for conveying hot salt brinea to and from electrolytic caustic cells pmducing chlorine. Reanltant (Uppa left) “PYFSX’’Cwom COOLEB~; (upper rzght) “T”’ elimination of metallic precipitates in the cell and PIPINGA-EMBLY; (below) ASSEMBLYVIEW OF NME G~naa inanlation of pipe linea against stray current corP- w m Drnnm-Commso D m o MOTOR meion are noted. Moist chlorine gas m y be conducted away from the cells to succeeding coolers, dehydrators, and compressors. In the manufaotura of bromine and bromides, glsss piping and accessory equipment are ideal for handling the very corrosive vapors and liquids without impairment of their purity.
Gas Cooling. Althongh the t h d condnctivity of glsss IS relatidy low compared to metala, the o v d heat transfer r a t a obtained with glass in many instances are of substantial magnitude and compare well with materisls having much greater conductivity h a u s e the principal resistances to heat flow are the 6lme bordering each side of the pipe wall. Flanged glw piping assembled with metal water jackets and return bends is a popular typ8 of cooler construction employd for handling wet bromine and chlorine gases. Another method of ut2bing glssa tubing employs “ c d e ” &ect with cooling water pouring down over a bank of parallel tubes from a weir box. Still a third type is the usual tnbe-sheet cooler employing stotlewsre headers.
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-onveyin Liquid cooling, a: borosilicate glsss IB m u n e to at&
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Although by the halogen derivatives (except hydmflnorio acid), as~ b l ofy piping and fittings is by mema of wmpression joints, and this newsSitatea use of Suitsble gasket material to resist the wide variety of wmbinations of acids and solvents. Deaign of the pipe joint is such that very little of the &et maW is exposed to attack, and for almost all commercial mixtnrea of acids and halogen compounds, M e t i n g materials are available which ensure entiefactory joints over wide temperature ran? veying and cooling of hot acid-solvent rmxtures 10 glsss equipment have comquently pmved to he widely applicable. 156
IS7 Rasehig M g s using a glass oentrifugal pump to Circulate the absorbing acid through glass heat exchangers and back over the tower packing.
Initial heat t r a d e r rates obtainable with glass heat exohangers are not usudy diminished greatly over long operating periods. This is partly because of immunity to pitting and scaling by corrosive action; but unique and somewhat inexplicable is the notable absence of substantial scale deposition from cooling water. Specillc uses of glass linea for transporting hydrochloric acid range from air lifts for the old style tourills to &eted pipe linea conveying cold acid from storage tanks via glw pump through heat exchanger to steel pickling baths. The attachment of glass piping to other materials &em no partioular problem.
Fractionation. Glasa bubble plate columns complete with glass bubble caps, bolts, and nuts &ord means for continuom separation and recovery of hot atrong hydrochloric snd hydrobromic acid solutions from the by-product wastee of halogenating reactions In addition to bubble-cap towers, e5cient fractionation can be carried out in psckea glass columns which use a shell similar to the plate columns or one construated from large socket pipe. Glass Rascbig rings are available in a range of sires. Reflux condensers constructed from Btsndsrdglass heat exchanger piping are useful adjuncts to the fractionating columns. Abso”lJtion* FLetnrn-bend piping srranged for counter or parallel flow of &as and liquid is often applicable for scrubbing out midual aci& from chlorinated solvents. To absorb hydrogen Chloride or bromide vapors, thinner wall water-jaoketed heat exchanger tubing facilitatee economid absorption and cooling in one operation. Absorption columns are generally constructed aa packed type towers, similsr to fractionating towers. An exsmple is conthuous recovery of nitrogen dioxide (NOJ vapors to form high-purity nitric acid in a glass column packed with
H d ~ e M t i o n . Equipment used for chlorinating or brominating a substance varies $dely according to the Mof the reaction involved and the means required to carry it forward. Glass windows for transmitting ultraviolet ligbt lrom arc Lamps to reactants have been devised for certain chlorinationswhich require actinic light activation and whiab must be carried out in large veesels. In liquid-phase chlorinations which produce hydrochloric acid as a by-product of the reaction, use of glass pipes for introducing chlorine into the Bolution eliminates one source of contaminstion. To break up a chlorine stream into very h e bubbles in a liquid being gsssed, reaort has been made to h e m e a b soreens. The availability of improved t y p of woven glsss cloth is of interest in this connection. Glans d u x condenaers may be used above chlorination or bromination tsnks to separate volatile product from valuable but corrosive by-pmduct acid gases. One of the more w e n t applications of glass equipment which bas found wide commercial usage is the cooling of sodium hypochlorite solutions when manufactured by direct injection of Liquid chlorine into strong caustic soda solutions. Control of the tamperatum is newauy to prevent chlorate and chlorite formation and thus improve yield and stability. Flanged glsss tubes having one end dosed (like a Large teat tube) are fitted with a metal head to form a “candle cooler” unit which is immersed in the solution while the coolant rapidly circulates inside the tube. Although it is generally consided that glaas has datively poor resistance to strongly alkaline solutions, long economical service life is obtained in hypoohlorite manufacture. Harmful contamination is thus minimized with resultant improvements in color and stability of the bleach solution.
