Svnthesis and Recovery of J
J
Hydrogen Chloride Gas C. C. BRUMBAUGH, A. B. TILL3IAN, AND R. C. SUTTER Diumond '4lkali Company, Puinesrille, Ohio
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?'lie gabcs leahe the coole~'it T h e theory and operation of a commercial plant for the HE conventional procabout 100 'F., the resistaricr production of 99.5 +YO anhydrous hydrogen chloride gas ess for obtaining arito Wow through the roolcr under 20-pound gage pressure at point of delivery are dehydrous hydrogen chloride tieing overcome by a steam scribed. The gas is derived from the burning of relatit el? gas from chlorine and hyevacuator on the absorber impure raw materials or as a by-product of chlorination drogen includes the burnvent. Condensate from the cooler is drained to a rubbering of previouslj- purified reactions. The anhydrous hydrogen chloride gas is isolined storage trap in the lated from water and other impurities by the stripping of h \ drogen and re-evaporated amount of about 50 galstrong acid under pressure, followed by refrigeration to chlorine. .In excellent delons of strong acid per 24give final drying. srription of a process and hour day and is pumped equipment for obtaining anperiodirally to the 3670 acid storage tank. hydrous hydrogen chloride The cooled synthesis gsses, iricluding hydrogen and other nongas from evaporated liquid chlorine has been given by Maude (3). condensables, pass to the top of a ro-current falling film type of Reference also is made to Maude's paper for an historical review of absorber (1, d ) , and thence to a packed Karbate tower, where the synthesis of liydrogen chloride gas and discussion of alternate vent gases are scrubbed by 207, recycle hydrogen chloride gas, synthesis routes. As it is necessary to have the anhj-drous hydrcthe noncondensables are renioved by the evacuator at the top of the scrubber. T h e quantity of 20% recycle acid is regulated t o gen chloride gas uridFr pressure in order to overcome the resistmaintain a n acid strength of 367, a t the bottom of the absorller. ance of the drying apparatus, and t o transfer the gas to the procT h e total pressure drop through the K a h a t e gas cooler arid :a\)ess using the anhydrous hydrogen chloride gas, one of the followsorber is in the range of 6 to 8 inches of watrr. ing alternates heretofore has been chosen. either operating t h r The 36Y0 acid leaves the absorber at, a temperature i n the rangu of 80' t o 90' F. and is pumped to rubber-lined storage and surge furnace under pressure, or compressing the gas after it leaves the tanks. Considerable tonnage of anhydrous hydrogen chloridt. gas drying equipment. equivalent can be stored in the tank-, giving flexibility betiwen Pressure operation of a chlorine-hydrogen furnace is rathei the rate of burning chlorine and hydrogen, and the generation of difficult, and it is also objectionable t o place an anhydrous or n anhydrous hydrogen chloride gas. ;Is a n alternate to thc furnace route, hydrogen chloride gas whydrogen chloriderich g s sy tern under less than atmospheric sulting from organic chlorination or salt cake furnaces may be erripressure. The operation of a blo\Ter with a suctiori of less than ployed. By either route the gas niiy be suitably fed to thc abatmospheric pressure involves maintenance difficulties n-ith the sorber in 2OyOsolution and the 36y0acid after removal of residiial blower and particularly with the packing glaiids to avoid air organic by activated carbon sent to the 367, storagc tank. From storage, the 36% acid is pumped to a packed Karbate leakage., which ivould reduce the quality of the anhydrous gas. t o w r stripper having a Karbate tube reboiler, heated with 50In accordance with the present process, raw electrolytic cell pound per square inch gage steam, the stripper Ixing operated a t hJ.drogen and chlorine are burned in an excess of hydrogpn, t h e 20-pound gagc pressure. T h e hydrogen chloride enrichcd gmev leave the top of the stripper a t a temperature in t!le rangc of 160' resultant synthesis gas being absorbed in a conventional abto 170' F., and the 20% stripped acid from the bottom of the sorber to n.i:rke 3670 acid. This acid is then sii,ipped under superstripper is a t the boiling point a t 20 pounds per aqatiri: inch gageatmospheric prcssure, and the overhead ga-: is reit iyerated and i.e., 270" F . T h e stripped acid passes through a Iixrbate cascade drird to yield anhydrous hydrogen chloride gad a t a (!?livery presc o ( i l t ~to a ruhber-lined nuIyc tank, the rooling thus provitliiig sure of 20 pound,
