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March 13, 1951 J. E. SEEBOLD 2,545,314 HYDROCHLORIC RECOVERY Filed Feb. 12, 1943 2 Sheets-Sheet

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March 13, 195 J. E. SEEBOLD 2,545,314 RECOVERY Filed Feb. 12, 1943 2 Sheets-Sheet 2

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Patented Mar. 13, 1951 2,545,314

UNITED STATES PATENT OFFICE 2,545,314 HYDROCH LORIC ACEO RECOVERY - James Edward seebold, Chicago, Ill., assignor to Hercules Powder Company, Wilmington, Del, a corporation of Delaware Application February 12, 1943, serial No. 475,624 2 Claims. (CI. 23-154) 2 This invention relates to the manufacture of the absorption tower, the heat of absorption of hydrochloric acid and more particularly to the the gas causes the formation of steam, which manufacture of hydrochloric acid by absorption formation in turn reduces the temperature of from waste gases containing chloride. the rest of the liquid so that the high concentra * In one inethod for the manufacture of hydro 5 tion of hydrochloric acid is formed. chloric acid, is first formed in Having now indicated in a general way the any suitable manner as by the reaction between nature and purpose of the invention, there foll sodium chloride and or it may re lows a more detailed description of the preferred sult as a by-product in the manufacture of embodiments thereof With reference to the ac organic chlorinated materials as, for example, companying drawings in which: chlorinated rubber. The hydrogen chloride is Figure 1 is a perspective view of an absorption then absorbed in water or dilute acid. tower for use with the present process; * Hydrogen chloride is absorbed in water when Figure 2 is a graph showing an observed rela its partial pressure in the gaseous phase is great tionship between the temperature of the liquid er than that in the liquid phase and absorption at the bottom of the tower and the ; continues until the partial pressure in the gas and eous phase is equal to the vapor pressure of the Figure 3 is a graph showing an observed rela gas in solution. To have this difference in par tionship between the percentage of hydrogen tial pressures, at high acid concentrations, either chloride left in the tail gas and the strength of the gases must have a high hydrogen chloride 20 the acid produced. concentration or the liquid must have a low tem perature or both. Where the hydrogen chloride In Figure 1 is shown an elongated cylindrical content of the gas is low, the gas-liquid equilibri tower 9, which is preferably made of iron, and um point is reached at a low acid concentration lined with glass. The tower is packed substan and means for removing the heat of solution, tially its full length with Raschig rings or the like which for the absorption of hydrogen chloride . At the top of the tower is the steam ejector in water is very large, must be provided in order 2, which may be used as needed, through which to obtain further absorption. steam is passed out of the steam jet 3, thereby Modern practice involves the use of packed ab Creating a partial vacuum in the line 4. The sorption towers provided with suitable cooling steam from the ejector 2 together with the tail means and wherein a gas containing hydrogen 30 gaS9s may be passed through a condenser not chloride is brought into countercurrent contact shown, or allowed to escape. Also, at the top of with the absorbent acid solution or With Water. the tower is the water supply 6 controlled by One or more absorbers may be used suitably con valve and having a spray head 8. nected to give the desired result. The tower In the bottom of the tower is the gas inlet packing must be kept wet either by the introduc 3. 5 connection 20 controlled by valve 2 and the acid tion of water or by recirculating some of the acid recovery pipe 22, which leads to the hydrometer effluent back to the absorber or both. float box 23, wherein the hydrometer 24 is used Equipment now in use for the absorption of to check the quality of the acid. The hydrometer hydrogen chloride is, however, subject to the dis float box is provided with outlet 25 for the re advantage that the provision of cooling means 40 moval of any material which may separate, such is quite expensive since the cost of Suitable ma as carbon tetrachloride, and outlet 26 for the re terials is high. Furthermore, provision for cool moval of the acid to carboys or other storage. ing complicates the construction and mainten This product acid may be cooled in a suitable ance of the equipment, thus adding to the cost. external cooler if desired. If cooling is to be effected in the absorption tower 45 Substantially pure hydrogen chloride may be itself, it is necessary to construct the tower of used but the invention contemplates the use also materials having a high heat conductivity, such of by-products of the chlorination of organic as the more expensive acid resisting metals. materials, such as chlorinated rubber, which con ... New in accordance with the present invention, 50 tain substantial amounts of hydrogen chloride gases rich in hydrogen chloride may be passed and preferably more than 60% in order to obtain through an absorption tower without external a hydrochloric acid of about 20 Baumé (about cooling means of such size, velocity and tempera 32% HCl). Cold water is used for absorbing the ture that 20° Baumé hydrochloric acid is pro gas, but the heat absorption will cause the vapori duced. No external cooling means is used. In zation of a part of the Water at one point in the 2,545,814 4. 3 What I claim and desire to protect by Letters tower, which vaporization results in a cooling Patent is: of the fluid. The space velocity of the gas and 1. A process for the manufacture of hydro the temperature of the entering gas and water chloric acid which comprises supplying water at a may be so adjusted as to result in a certain ten temperature substantially below 100° C., to the perature and strength of the acid leaving the 5 upper portion of an uncooled absorption tower, bottom of the tower. An observed relationship Supplying a gas rich in hydrogen chloride to the between this temperature at the bottom of the lower portion of the absorption" tower at a tem tower, and the strength is: shown: in the . perature substantially below. 90° C., passing the graph at Figure 2. From this, graph it Will be hydrogen chloride containing gas upwardly seen that the temperature at the bottom of the O through the absorption tower countercurrent to tower can in most cases be held below about 90° the...flow, of water therethrough whereby the hy C. for most acid strengths. The acid. Strengths. drogen chloride gas is absorbed by the water, between 34 and the equilibrium point, which is controlling the rate of flow of the water, the rate about 37, are obtained with much cooler. Solut: of foWirof Said gas; and the temperatures thereof tions, but tend to result in a very great amount lis SO. aS to maintain the tennperature Within the of the hydrogen chloride being left in the tail: tower at the entrance point of the gas substan gas as is indicated in Figure 3, where an observed. tially below 90° C. and the strength of the acid relationship between this hydrogen chloride left obtained at least about 20° Bé. (about 32%) in the tail gas and the resultant acid strength are. 20 allowing the heat of absorption of the hydrogen compared. chloride.ini the Water to evaporate a portion of The; following is an example of a; method of the Waterin: the tower, applying partial vacuum carrying out the proceSS: to evaporate additional water and to withdraw Eacample an amount of Water vapor:from the upper-portion An absorption tower. Substantially of the de 25 of the towers, whichs contains as latent. heats of sign shown in Figure; 1 was set up. comprising a Vaporizations an amount of heat which is a sub glass-lined steel, pipe of 32' inside diameter and Stantial proportion of the heat of absorption lagged for its entire 10 length with 1/2; insula evolved...in: the tower, and withdrawing from the tion. The pipe was packed to a height of 9 with bottom:of the tower an acids with a concentration A' Raschig rings. A steam-ejector was used for 30. of at; least about: 32% by weight of hydrogen. drawing...the gases: upward... through the column chloride. and the absorbing water. was: allowed to... foW 2. A process: for the manufactures of strong. countercurrent to the gases... by gravity. The hydrochloric acid which comprises flowing a gas gases were admitted-at-the-bottom of the tower. containing more than 60%; by weight hydrogen and-the-acid withdrawn. Agas containing 69.2% 35 chloride; at a temperature of about 25°C; to the: hydrogen chloride at a temperature of about:25 bottom of an uncooied absorption tower; supply C. was passed into the bottom of the tower. ing water at a temperature:of about 25°C; to-the Water, at a temperature of about 253 C. Was, ad top-of the absorption tower" in flows countercurs. mitted to the top of the tower...and the gas passed rent to the said gas, allowing the:heat of absorp. upwardly through it by means, of the Steam jet 40 tion. Of the: hydrogen, chloride: in the water. to ejector: at a velocity of about 1 per Second. In evaporate: a portion of the water in-the-tower, asholt time, the liquid at the bottom of the tower applying partial vacuum-to evaporate additional had a temperature of about 70° C. The hydro Water and to withdraw.water-vapor-containing: as chloric acid withdrawn contained about 32%hy latentheates.Sentially, this heat of absorption, the drogen chloride and the tail gases contained 45 relative: rate of Water and hydrogen chlorides gas about 2.5% of hydrogen chloride. being such that the liquid leaving the bottom of Various, concentrations of hydrogen chloride the tower, has a temperatures of about 70° C., and may be used in the entering gas, but, in order to Withdrawing hydrochloric acid of about 32%, cone obtain a commercial" concentration of hydro Centration at about: 70° C. from the bottomg of chloric acid (about 32%) in a single paSS, it is 50 the tower; preferable that the-entering gas contain at least JAMES...EDWARD, SEEBOLD, . 60%The of velocity hydrogen of chloride.the gas in the-tower may be REEERENCES, CITED varied, but for thies best yields-a velocity of from Thes, following references: are of record in the about 0.5 ft/sec. to 3 ft/sec. should be used and 55 s file of this patent: preferably about 1 ft/sec. for a contact time of from about 5 to about 15 seconds; and preferably UNITED STATES PATENTS Number Naine: Date: forThe about temperature 10: Seconds, of the entering gas may also 1,831,474. Ayres.------Nov. 10, 1931. be varied from about 09: Ci to about. 50°C: , but 60 1932,954. ... Conradtly:------Gct. 31, 1933. should preferably beat about 25°C. In addition, . .2,047,611 Baxter:------July 14.1936 the: temperature...of the entering water may be 2,127.57i. Pardee------Aug. 23, 1938 varied from about 0°C..to about:100° C. but should FOREIGN PATENTS: also the preferably about 25° C. The velocity of the gas and the water late:should be; so adjusted 65 Nune Country. Date. that the temperature at the bottom of the tower 408,578. Great Britain.------Apr. 9, 1934. does not exceed about 90° C. and preferably from 503,220. Great Britain.-----...Mar:27, 1939 about:40 to about: 70° C. - OTHER REFERENCEs. This: applications is...a... continuation-in-part, of Lunge: Sulfuric Acid & Alkali, vol. 11, part:I, my application for United StatestLetters. Ratent, 70 pp. 310-312. Guerney & Jackson, London; Eng Serial No. 381,287 filed. March 1, 1941, now land. abaradoned. -