US1672878A - Process of chlorination - Google Patents

Description

June 12, 1928.

5. BROWN PROCESS OF CHLORINATION 3 Sheets-Sheet l vwmtoz 5 0 nW/ abbohmw Original Filed Jan. 13, 1921 June 12, 1928.

I 5. BROWN PROCESS OF CHLORINATION Original Filed Jan". 13, 1921 3 sham-sheet 2 3 Q m 0 O Wv Q g June 12. 1928.

- 1,672,878 s. BROWN PROCESS OF CHLORINATION Original Filed Jan. 13, 1921 3 Sheets-Sheet 3 Patented June 12, 1928.

UNITED STATES PATENT OFFICE.

SANDFORD BROWN, 01 MONTCLAIR, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO HALOWAX CORPORATION, OF NEW YORK, N. Y., A CORPORATION 01 new xoax. v

PROCESS OF CHLORINATION.

Original application filed January 13, 1821, Serial No. 437,010. Divided and this application filed January 5, 1924.

The invention relates to a process of chlorinating naphthalene and recovering hydrochloric acid evolved during the chlorination process and more particularly to such a process in which the naphthalene is maintained in moltencondition during the chlorination, and the operations are carried out under a partial vacuum. This application is a division of my application improvements in chlorination apparatus, Serial No. 437,010, filed January 13, 1921, Patent 1,564,044, issued December 1, 1925.

Naphthalene may be chlorinated by maintaining bodies of the same in molten condition in a series of pots or chlorinating vessels through which chlorine gas is successivel assed. In all the prior'practices with whic 1 am familiar, in which molten naphthalene is to be chlorinated, it has been deemed neces- 2 sary or highly advantageous to maintain the naphthalene under pressure, and to force the chlorine gas through the materiah It has been stated that the rapidity of absorption of the chlorine by naphthalene will be increased when the temperature is raised above 212 F., and the pressure is raised above atmospheric pressure.

It is highly desirable to maintain the naphthalene in molten condition, and revent it from volatilizing, so far as possl le, since naphthalene vapor, if present in the chlorinating apparatus, is liable to cool sufficiently to solidify and clog up gas lines, valves, and other parts of the system. It

has heretofore been believed, by those skilled in the art, that positive pressure in the chlorinating apparatus is necessary to prevent the naphthalene from excessively vaporizing, and that if negative pressure is employed the naphthalene will vaporize faster than it can be chlorinated.

I havefound, on the contrary, that the chlorination proceeds as effectively when a partial vacuum is maintained in the chlorinating chamber, that is, a pressure less than atmospheric, the chlorine gas being drawn through the chlorinating chambers by suction instead of being forced through the same, the chlorinating chambers being heat-.

' ed, when necessary, in the usual way, as by means of steam jackets. Also, that I can pre vent the molten naphthalene from vaporizing even more effectively, by sucking the chlorine rate of chlorination increases.

Serial No. 684,478.

gas through the apparatus, than was accomplished in the prior practice with which I am familiar in which the chlorine gas was forced through the system under positive pressure. I have found that m'y'novel process makes this possible because it permits the adjustment of the rate of chlorination and the temperature of the reaction in a manner which was notpossible in the former pressure system, so far as I am aware.

In accordance with my method a vacuum pump is used at the end of the system to draw the chlorine gas throu h the molten naphthalene, and the evolve hydrochloric acid gas through the acid absorbing vessels. Such a pump is usually a rotary pump, but is sometimes a reciprocatin pump. In either case it ismuch more exible, in its conditions of use, than the rotar or reciprocating pumps previously used or forcing the chlorine gas, under pressure, through the naphthalene. In the use of the vacuum pump, in my process, for producing suction at the rear end of the system, no gas passesthrough it, except a slight air leakage, it merely maintaining a static balance at the end of the system. The chlorinating reaction is an exothermic one, and the temperav ture-in the chlorinating vessels rises as the With the vacuum pump used as described the rate of naphthalene at the partial vacuum existing,

so that consequentlythe naphthalene does not vaporize to any harmful extent even under the partial vacuum used.

It should be understood that the invention comprises drawing the chlorine gas by suction through the molten naphthalene as stated, with such adjustment or regulation of the suction, and consequent re lation of the rate of chlorination, that vo atilization of the naphthalene will be largely prevented, as stated. Cooling water may of course 'be circulated through the jackets surrounding the chlorinating chambers, during the chlorinating reaction, as is customary, aiding in keeping the temperature down. No partlcular degree of suction applied and partial vacuum produced thereby need be specified, preferre operation, however, beingto so operate the suction ump that only a slight air leak will pass tlirough it, as stated. Similarly, as to the temperatures to be maintained within the chlorinating chambers as the result of operatin in the manner specified, it need only be said that temperatures between the melting point and boiling point of the naphthalene, at the existing partial vacuum, at which there will be slight volatilization of the naphthalene, need be maintained. Optimum conditions for the best results will readily be ascertained.

Another important advantage of this rocedure is that there can be no leakage rom the chlorinating apparatus into the atmosphere surrounding the same. In the previous practice, in which pressures up to fifty pounds per square inch were used in the chlorinating vessels, leakage from the system was frequent and this was highly dangerous and costly as both chlorine and hydrochloric acid (which is produced in the course of the process) escape and affect the workmen and surrounding property; this is particularly true of the hydrochloric acid gas which combiningwith the moisture of the atmosphere to form hydrochloric acid solution is very destructive of apparatus, piping, rooting, etc. Accordingly, it was customary to carry out. the reaction out of doors. VV'th my present method there can be no leakage outward from either the chlorinating vessel or the hydrochloric recovery vessels; the latter are usually located outdoors because of leakage: in fact, a usual part of the system is a large and costly tower ventilated to the open air.

It is essential that the chlorinating vessels be installed inside of the building for efiicient and convenient operation, to prevent radiation losses and to permit easy handling of the product, and it is very advantageous also for it to be possible to operate the hydrochloric vessels within the building, thus preventing damage by freezing. M system makes the operation of both the c lorinating and acid vessels indoors quite practical, as the leaks are always of air into the system and not of deleterious gases out of the system, and these leaks may be readily detected by hissing sounds at the point (f leak age or by the pressure difference on the gauges.

When leaks arise in the chlorinating vessels, as ordinarily operated, the operation must be stopped immediately until repairs are made, whereas in my system, the leaks may be detected and easily repaired without stopping the operation.

A further and important advantage of the suction and vacuum method referred to relates to the method of acid absorption which may be utilized. In the prior practice, chlorine gas being positively pum ed through the ehlorinating vessels, the ydrochlorie acid gas evolved was progressed under slight pressure through a series of absorbing vessels containing Water known as tourills, and the usual absorption towers. With this system the hydrochloric acid gas was passed over the surface of the water in the tourills and was absorbed thereby. The passage of gas through the absorption system was apparently induced to a large extent by the atlinity which the water has for the gas. \Vhen stone-ware apparatus is used in bydrochloric acid recovery it is impracticable to make use of suflicient pressure to force the acid gas through the whole absorbing system, the positive pressure in the absorption system of the prior installations being actually very slight. When, however, for any reason contact between the gas and the surface of the water was interrupted, as by the appearance of a film of oil on the surface of the water, the flow of the gas through the system was impeded and the absorption of the gas by the water decreased.

In order to obtain maximum absorption, a large number of absorbers is necessary. The area of the aqueous absorbing surface for each unit of volume of gas passing over it, must be very large, necessitating a large volume of liquid.

This (lifliculty is overcome by my method whereby the entire system is maintained under a partial vacuum, the chlorine gas be-, ing'sucked through the chlorinating vessels and the hydrochloric acid gas being sucked through the absorption system, in a continuous process. Because of this lnm'lilication of the process, it is possible to introduce hydrochloric acid gas near the bottom of each tourill and have the same bubble up through the entire body of water in each tourill, the suction being suflicient to permit the use of this method. Because of this procedure the acid is absorbed much more eflectively and economically than in the previous method, the number of tourills required being only a small fraction of the number required in the previous system, and no large absorbing towers being required. There is accordingly a considerable saving of floor space and of expense for plant, with added efiicieney of absorption, greater safety and other desirable features. In my system. all the gas comes into positive contact with the absorbing medium, the velocity of the gas may be relatively high and the volume of water per unit of volume of gas may be relatively small.

It is also advantageous in many cases to operate several chlorinating and acid recovery systems in parallel, as will be more fully explained hereinafter.

The object of my invention is the provision of an improved chlorinating process in accordance with the foregoing, and as will more fully appear from the following specification and .be particularly pointed out in the appended claims.

In order that my invention may be more clearly understood, attention is ,hereb directed to the accompanying drawings orming part of this application and illustrating one manner of practicing my improved process, and one form of apparatus in which the same may be carried out. In the drawings Fig. 1 represents diagrammatically a side elevation of apparatus comprising a chlorinating and acid absorbing installation;

Fig. 2 is a diagrammatic top plan view of the same;

Fig. 3 is an enlarged vertical section taken through the adjacent portions of a pair of chlorinating pots;

Fig. 4 is a view partly in side elevation and partly in vertical section of a pair of adilacent tourills or acid absorbing vessels; an

Fig. 5 is a diagrammatic top plan view of a modified form of apparatus, embodying parallel chlorinating and acid recovery systems.

Referring to the drawings I have illustrated a series of three clilorinating pots 1, 2 and 3, it being understood that any desired number may be used. These pots are represented as being similar to those described in Patent 1,294,230 granted to Kirk Brown February 11, 1919.

These pots are suitably heated preferably by steam jacketing the same on the bottoms and about their sides as is indicated at 4 and 5. aphthalene or other material to be chlorinated is led into the system, preferably from one end until the same extends in fluid condition at a desired level in all the pots, after which chlorine gas maybe introduced into the system, at the other end. In the drawings I have diagrammatically indicated a tank 6 from which naptlialene flows through a pipe 7 provided with a valve 8 into the pot 3. At the opposite end of the series of chlorinating vessels I have indicated a pipe 9, provided with a shut-oil valve 9, through which chlorine may be introduced below the surface of the naphthalene in pot 1. These pots are kept closed during the chlorinating operation and may be provided with covers 10 secured in any desired manner. In practising the process, the naphthalene alone is first heated sufficiently to thoroughly melt the same, say, to about 212 F. After the reaction with the chlorine starts the temperature rises, as a result of the exothermic reaction, to a point between the melting point of the naphthalene and its boiling point at the degree of vacuum existing in the chlorinating vessel, within which range it is maintained.

The chlorine gas is drawn through the system by means of a pump indicated at 11.

' 24, any

The connection between each pair of chlorinating pots such as 1, 2 and 3 is preferably made in the manner described in Patent 1,294,230 referred to, my invention, however, not being limited to such an arrangement. vAs shown a pipe 12 is provided in each pot. As is shown in Fig. 3, each pipe 12 is connected by a coupling 13 with a corresponding pipe section 12 in the adjacent pot,'section 12' being connected by an elbow 14 with a vertical pipe 15 provided with a valve seat at its upper end, above the normal level of the naphthalene. A valve is provided having a part 16 to coact with this valve seat and to'control the opening in the top of the pipe 15. This valve is operated from the exterior of the pot, as by means of valve stem 17 operated by a hand wheel 18.

The pots are provided with a series of superposed pans 19 as is usual in a chlorinating apparatus. The chlorine gas which enters pot 1 through pipe 9 is drawn by the suction of pump 11 through the naphthalene in pot 1, some of the chlorine gas, together'with hydrochloric acid gas, which is evolved in the chlorination of the naphthalene passing through the valve and pipe connections to pot 2, and some ofthe chlorine gas and a greater quantity of hydrochloric acid gas passing through the valve and pipe connections in pot 2 into pot 3. When the material in pot 1 has been chlorinated to a desired stage, the supply of chlorine gas passing through pipe 9 may be stopped, the valve in pot 1 closed and the chlorinated product removed from pot 1, after which the partially chlorinated product in pots 2 and 3 may be blown over or otherwise transferred to pots 1 and 2, and pot 3 refilled with naphthalene to be-chlorinated, after which the operation may be repeated Hydrochloric acid gas evolved in the chlorination passes from pot 3 through a series of tourills, at the end of which the pump 11 is connected. In the construction shown, the hydrochloric acid gas passes from pot. 3 through a pipe connection 19 to a tourill 20. From this point the acid gas which has not been absorbed within the water in tourill 20 may pass through pipe connection 21 to a tourill 22 and thence through tourills 23.and 24 which are connected in series by connections 25 and 26. Or, the gas may pass through connection 21 to a tourill 22, and thence through tourills 23 and 24' which are similarly connected in series. Pipe connections 21 and 21 are provided with suitable valves 27, 27, so that one series or the other of tourills, or both series in parallel, may be utilized. From the last tourill of either series, 24 or acid gas which has not been absorbed will pass through connection 28 or 28' to a tourill 29 which is connected by connection 30 to the pump.

The acid absorbing vessels are preferably stoneware tourills as shown which are filled to a suitable level with water. The gas entering any one of the same, such as the tourill 20, passes downwardly therein through a perforated pipe 31 from which the gas passes within the water and bubbles up through the same, a part of the gas being absorbed. Any gas which passes over will pass in like manner through the various tourills of the series until the same is all absorbed. When the acid solution is to be removed from one series of tourills such as 22, 23 and 24, valve 27 may be closed and valve 27 opened so that the gas will then pass through the other serles. The tourills are kept closed during the operation-of the system and may be provided with valved openings 32 through which the same may be filled with fresh water when required, the acid solution being drawn oil at the bottom through openings 33. The chlorinated material may be drawn oil or removed from any of the pots 1, 2 or 3 in any desired manner as by drawing the same off through connection 33.

The last tourill 29 which is directly connected with the pump may be used as an indicator. In the normal operation of the system no gas should come over into this tourill, but all of the same should beabsorbed within the preceding tourills.

It will be seen that in the operation of the system the pump 11 exerts a continuous suction upon all of the chlorinating pots and the acid absorbing vessels which are connected therewith in series and produces .a partial vacuum in all of the same.

At various points of the gas passage throughout the system safety valves should be located to prevent the liquids from backing over into the preceding vessels in the event of stoppage of the pump or a serious break in the vacuum. These safety valves are so desi ed that the vacuum will be released on t e inlet to the vessels before the liquids can back up through the ioutlet. This effect is obtained by bringing the liquids to a state of hydrostatic balance.

Asafety valve is indicated in Fig. 1 in the inlet pipe 9, in which plate 34 covers outlet 35 of the pipe, plate 34 being mounted on a bell-crank 36 pivoted at 37 to the strap 38. A counterweight 39 is carried by the horizontal arm of bell-crank 36. A similar valve is located between the acid recovery and chlorinatingunits, on the downwardly extending portion 40 of connection 19, the plate 34' bein mounted in the same manner as plate 34 escribed above. If a. break in the line occurs at any point between valve 9 and pump 11 the safety valves will open, thus preventing the liquids in the systerln from backing over into the preceding vesse s.

An arrangement of both chlorinating and acid absorbing vessels in parallel trains 15 indicated in Fig. 5, in which entrance pipe 9 for the chlorine connects through pipe 41 to a train of chlorinating vessels 1, 2, 3 or through pipe 42 to chlorinating vessels 1', 2", and 3", these being similar in all respects to the'vesscls 1, 2, 3, and their connections, previously described. Connection may be made for the acid gas to pass from vessel 3" to the tourills 22, 23" and 24, and from vessel 3 to tourills 22", 23 and 24", connection being made from vessels 24 and 24 respectively through pipes 28" and 28 tothe pump 11. v

Since the resistance offered to the passa e of the gas through the system varies irectly as the sum of the hydrostatic heads of the liquid in the various vessels, it is obvious that any number of chlorinating and absorbing units may be operated in parallel simultaneously by one pump without increasing the resistance. When operating in parallel, the flow of gas through the various units will adjust itself automatically and progressively, thereby equalizing and reducing the rate of temperature rise throughout the entire system. The reason the flow of gas will adjust itself automatically, is that it will flow first through the train of units in which there is the least resistance' As the chlorination proceeds,'the liquids will increasein specific gravity and consequently in hydrostatic resistance, and then the gas will flow through the other train of units in parallel; thus the two trains of units in parallel will be balancing each other.

By operating several systems in parallel, the production process is greatly facilitated, for when the contents of any one unit have reached the desired degree of concentration, the unit may be cut out of the system, the contents withdrawn, and the unit recharged without stopping the operation of the balance of the system.

In regard to the system generally, it may be noted that the pumps available for forcving chlorine gas under positive pressure are very unsatisfactory, it being necessary even with the best of them, to replace the packing frequently due to the corrosion from the gas and sulphuric acid which is used in conunction with them.

In my system, the pump sufi'ers no abnormal depreciation, since it merely maintains a static balance at the end of the system, there belng nogas passed through it whatever.

By permitting the first absorption vessels or vessel, such as 20, of the acid system to remain in a completely concentrated state, and using it as a washer, a particularly fine form of acid may be procured in the balance of the absorption system.

Another advantage of the vacuum process described, in comparison with the prior positive pressure process, may be noted, namely, that when positive pressure is used, if the pump breaks down or there is any considerable diminution of the pressure,-the molten naphthalene even if it should back up the since it is at the other end of the system. In the system illustrated and described herein the safety valve located in inlet pipe 9 serves as an additional safeguard against the naphthalene backing up p1pe 9. What I claim is:

1. A chlorination process which comprises maintaining naphthalene in molten condition in a chamber, drawing chlorine as through the same by a constantly applied suction, so as to maintain the chlorinating chamber under artial vacuum, at temperatures below the oiling point of the naphthalene at the existing pressure, and recovering the resulting chlorinated naphthalene.

2. A chlorination process which comprises maintaining naphthalene in molten condition in a chamber, drawing chlorine gas through the same by a constantly applied suction, so as to maintain the chlorinating chamber under partial vacuum, at temperatures below the boiling point of the naphthalene at the existing pressure, and drawing the resulting hydrochloric acid gas by sue tion through a body of water to cause the same to be absorbed thereby, in continuous process.

3. A chlorination process which comprises maintaining naphthalene in molten condition in a series of connected naphthalene chlorinating vessels, and drawin chlorine s and the gas successively through the vesse suctlon, m cont-munaphthalene therein, by ous process, so as to maintain, the s stem under partial vacuum, at temperatures elow the boiling point of the naphthalene, at the existing pressure, and recovering the resulting chlorinated naphthalene.

4. A chlorination process which comprises maintaining naphthalene in molten condition in a. series of connected naphthalene chlorinating vessels, and drawin chlorine gas successively through the vesse s and the naphthalene therein, at temperatures below the boiling point of naphthalene at the extherein.

drawn by suction applied at the end of the system, to maintain all parts of the system under partial vacuum.

5. A chlorination process which comprises maintaining naphthalene in molten condition in a series of connected naphthalenechlorinating vessels, and water in a series of connected vessels, followin and connected with said first vessels, and drawing chlorine gas successively through the first series of vessels and the naphthalene therein, and the resulting hydrochloric acid gas through the water in the following vessels, to be absorbed thereby, all by suction, by applying a suction pump to theend of the system, and so operating the pump as to adjust the rate of chlorination of thenaphthalene and therebythe temperature of said reaction, below the boiling point of the naphthalene at the cxistin pressure, so as to substantially prevent vo tilization of the naphthalene.

6. A chlorination process which comprises, maintaining naphthalene in molten condition in a plurality of parallel trains of" normally closed na htha ene chlorinating vessels, the units 0t each train being connected together in series, connecting the first unit of each train to a supply of chlorine gas, andapplying continuoussuction equally to the rear ends of all the trains to draw the chlorine gas through the trains and molten naphthalene therein and adjusting the suction andconsequently the rate of chlorination of the naphthalene so as to maintain the temperature of the reaction below the boiling point of the naphthalene at the existing pressure, automaticall between the diiferent trains in inverse relation to the resistance encountered 7. A chlorinationprocess which comprises maintaining naphthalene in molten condition in a chamber, drawing chlorine through the same by a constantly suction, so as'to maintain the ch 0 as applied rinating chamber under partial vacuum, and adjusting the suction, and consequently the rate of chlorination of the naphthalene and the temperature of the exothermic reaction below the boiling point of the naphthalene at the existing pressure, so as to substantially prevent volatilization of the naphthalene, and {ecovering the resulting chlorinated naphthaene.

the gas flow adjusting itself In testimony whereof I have signed my name to this specification.

- SANDFORD BROWN.

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