US2984078A - Process for condensing chlorine gas - Google Patents

Description

May 16, 1961 H. SCHMIDT ETAL 2,984,078 PROCESS FOR CONDENSING CHLORINE GAS Filed Sept. 12, 1958 CHLOR/NE CONSUMERS 1 I T T CHLORINE MAIN LINE 9 I I RES/DUAL GAS I W I 5 ATMOSPHERE Y ABS OLUTE r 2 & INERTGAS 6 2 v o .coou/ve 5 -50 C 4- |APPARATU5 CONDENSER 2.5m ---l STORAGE TANK T Lieu/0 CHLOR/NE INVENTORS HEINZ SCHMIDT PAUL RE/NSHAGE/V WALDEMAR ZIEMER FRANZ HOLZl/VGER 2,984,078 I l PROCESS FOR CONDENSING CHLORINE GAS Heinz Schmidt, Paul Reinshagen, Waldemar Ziemer, and Franz Holzinger, all of Frankfurt am Main, Germany, assignors to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Bruning, Frankfurt am Germany, a corporation of Germany Filed Sept. 12, 1958, Ser. No. 760,538 Claims priority, application Germany Sept. 14, 1957 3 Claims. (Cl. 62-9) The present invention relates to a process for condensing chlorine gas.

. Chlorine condensers often have the function of buffering installations which, together with various electrolytic chlorine discharge devices, balance the produc tion and consumption of chlorine so that a constant pres sure is maintained in the chlorine distributing pipe system.

Low temperature cooling apparatus when subjected to stronger load variation cannot fulfill the aforesaid buffering function in a sufficiently elastic manner, since the condenser spaces are filled with residual gas and do not permit an instantaneous increase or reduction of the condensation capacity without a variation of the gas pressure being involved. The amount of gas that undergoes condensation is often regulated by means of shutofi devices which, however, because of the necessary pressure gradient, cannot be installed without a disadvantage being involved, especially into installations which are operated only under a slight superatmospheric pressure.

The object of this invention is to overcome the above difliculties by means of an adjustable inert gas cushion which regulates the admission of chlorine to the cooling surfaces of the condenser.

The process .for condensing chlorine gas according to this invention comprises varying the amount of condensing chlorine at a constant condensation pressure and temperature by means of an inert gas cushion produced by introducing or withdrawing inert gas.

As inert gases there may be used all gases uncondensable under the conditions prevailing in the chlorine condensation, such as nitrogen, air, gaseous carbonic acid and the noble gases, for example argon. When it is desired to produce especially pure gaseous chlorine, it is advantageous to use nitrogen as inert gas.

According to a modification of the above process the admission or the removal of inert gas is regulated automatically by the pressure prevailing in the chlorine supply pipe so that the pressure remains constant.

The process may also be modified so that the temperature at which the chlorine undergoes condensation is automatically kept constant. In the case where a multiple stage apparatus is concerned, the inert gas may be admitted in the first stage while it is withdrawn in the last stage.

In using the process of this invention in industry uncondensable dry inert gas is injected into the condenser to reduce the condensation capacity, the amount of inert gas injected being controlled automatically by the pressure prevailing in the chlorine distributing pipe. In case it is necessary to increase the condensation capacity, the partial pressure of the inert gas is reduced by means of a blow-through valve that opens automatically, whereby a portion of the inert gas added and the residual condensing chlorine gas are caused to flow off. It is accordingly possible to increase or reduce the amount of condensing substance within reasonable time by means of an automatic regulator at a constant pressure of chlotime and at a constant condensation temperature. When a multiple stage process is concerned, the inert gas is advantageously injected in the first stage, that is when the chlorine undergoes condensation, while the inert gas is withdrawn in the second or last stage of the process. A better understanding of the invention can be had by reference to the accompanying drawing, which shows schematically the process and apparatus of the invention. Chlorine obtained by electrolysis or chlorine of other origin of 98.8% purity and containing altogether 1.2% of uncondensable gases, such as nitrogen, is compressed to 2.5 atmospheres absolute and transported to a series of chlorine consumers by means of a conduit system 1. To maintain the pressure prevailing in this system of conduits at'a constantlevel, the latter are connected by shunt conduit means 2 with condenser 3, whose cooling surfaces are kept at a constant temperature of 30 C.

by cooling apparatus 4 employing a boiling cooling agent, for example difluoromonochloromethane. The cooling capacity of condenser 3 and cooling apparatus 4 are so dimensioned that in the extreme case the total amount of chlorine produced can be liquefied; in the chosen example, which is carried out under a pressure of 2.5 atmospheres absolute at a temperature of 30 C. and where the chlorine contains 1.2% of uncondensable gases, about 99% of the chlorine can be condensed. By means of automatically controlled valve 5, in communication with condenser 3, the amount and partial pressure of the gases within condenser 3 is controllable so that the desired degree of liquefaction is reached and the pressure in the system is kept constant at 2.5 atmospheres absolute. At equilibrium, the equilibrium partial pressure of chlorine in condenser 3 is 1.2 atmospheres. Since the system is under a total pressure of 2.5 atmospheres, the partial pressure of non-condensable gases is 1.3 atmospheres, and the partial volumes of chlorine and non-condensable gas are 48% and 52%. If consumer demand for chlorine drawn from conduit 1 decreases, tending to increase the chlorine pressure in conduit 1, pressure regulated control means 7 activate circuit 10 opening valve 5, which permits escape of the equilibrium gas mixture from condenser 3. The system will tend to reestablish equilibrium conditions by condensation of chlorine gas and simultaneous accumulation of non-condensable gases within condenser 3. Thus, the pressure stress in conduit 1 is relieved by condensation of chlorine.

Conversely, if consumer demand tends to decrease the chlorine supply, valve 5 is closed, partially or completely, to discourage escape of the equilibrium gas mixture and to throttle further condensation of chlorine in condenser 3. However, if large variations in the chlorine demand occur, the time lag involved in building up the content of non-condensable gas in the condenser'to the value found for the gas in the equilibrium gas mixture is too lengthy to permit effective control, since only small amounts of non-condensable gas are normally found in the chlorine and are introduced into the condenser in this manner. However, according to the invention, chlorine can be quickly displaced from the condenser surfaces by increasing the partial pressure of noncondensable gases in the condenser by another means, and the process of condensation thus quickly throttled. This is done by supplying an amount of dry uncondensable gases to the condenser 3; the amount of inert gas supplied is controlled by a valve 6 which receives its impulses through circuit '9 from a pressure meter 7 inserted in the chlorine supply pipe. By means of valve 6 the amount of uncondensable inert gas is increased as the pressure falls in the chlorine supply pipe or reduced as the pressure increases; in the extreme case the valve is closed. When this valve is opened, valve 5 in communication with condenser 3 is simultaneously closed,

Patented lVlay 16, 19 61 31 and reversely. Valve. 5 in communication=- with. condenser 3 has the function of maintaining the pressure in the chlorine supply lines at a constant level by regulating the amount of the escaping -cushion of inert gas.

Dilution ofchlorine in conduit 1 by'inert gas introcluced into condenser 3 through fvalve 6zis prevented: by check valve 8 in shunt conduit means 2.

We claim:

1. In a method'for distributing gaseous chlorine'at a substantially constant pressure fronr achlorine source to achlorine sinlethrough a distributing system comprising, in communication, said source,-saidlinkrand a condenser in which chlorine in eXcessof that required to maintain said substantially'constant pressure is condensed at a substantially constant'condensation' temperature and pressure, the improvement" which comprises rapidly decreasing-the amount of chlorine condensed in saidcondenser when chlorine demand at said sink is is increased, and rapidly. increasing'the amount" of chlo-' rine condensed in-said condenser when chlorine'demand at said sink islow by withdrawing the gaseous contents 4 of said condenser, including chlorine and inert gas; whereby the partial pressure of inert gas in the condenser is decreased.

2. A method according to claim 1 wherein the admission and withdrawal of inertgas from said condenser are-regulated automatically by the pressure of chlorine gas in the distributing system exterior to said condenser.

3; A method according to claim 1 wherein, in'a distributing system comprising a'chlorine source and sink and a plurality of condensing stages, inert gas is introduced into the first of said stages and withdrawn from the last of said stages.

References Cited in the file of this patent UNITED STATES PATENTS Kogel July 2, 1957 OTHER REFERENCES Chemical'Engineers Handbook (Perry); published" by McGraw-Hill (New York), third edition 1950 (Text book Edition); pages 290 and 291 relied on.

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