US2440311A - Process of treating coal tar containing a small amount of ammonium chloride - Google Patents

Description

W. TIDDY PROCESS OF TREATING COAL TAR CONTAINING A SMALL AMOUNT OF AMMONIUM CHLORIDE F1156 July 24, 1946 W azaa 24min N I mumwworm W mmhmi Om I. I N. m Q LW n k m 7% QT umww w Q mw mo$ I; (if II. Q mu 552 m mmA mm w N... \.N@ 1 w P a W mm mwjom zou JL m4? my KUJJOEPZOU mmnwmwml mmjomhzou NKDFdEUQ-INF QN INVENTOR Wiilz'am Eddy v 7BY 9p ATTORNEY Patented Apr. 27, 1948 UNITED STATES NIUM CHLORIDE *Willia'm =Tiddy,- Maiihasset, *assignor i120 Allied Chemical: Dye

ration of -N ewYork Corporation, a-"corpm ApplicationfJuly 24, 1946;-Serial No; 685,957 3 Claims. (01. 1961-146) The present invention relates to thesubstantially complete removal from coke oven tar'of the small amountof water soluble salts chiefly ammonium chloride present therein.

'Coke oven tars'produced in coke oven' batte'riesby the customary procedure involving cooling and washing coke oven gas usually withan aqueous medium, when distilled to-produce--'desired tar distillates, such, for example; as creosote oil, naphthalene, tar-acid and light'oil fractions, invariably result in corrosion of the 'distillation equipment and plugging, due-toafmmonium chloride deposits, of the condensers asso'ciated with the distillation equipment. 'Thesedifficulties are chiefly attributable tothe small amount of ammonium chloride 'invariably present in coke oven tar. 'Various' proposals have been advanced for eliminating the small amount, usually' of the orderof L2-% -by--weight, of ammonium chloride present in coke oven tar to minimizejcorrosion of the'distillation equipment and plugging up of the condensers when the tar is distilled Of these proposals the one" which has found widest commercial application'is the washing of the tar with'water frequentlyby'pumping a,

the tar into the top of a storage'tank containing a layer of water under atmospheric pressure and temperature, the tar 'desoending through the water layer and forming a tar layer underlying the water layer. After introduction of the desired batch of tar into the water layer, the-tar and the water containing the dissolved salt are separately removed from the tank. Th'isprocedure is objectionable for 1 numerous reasons, among which may be mentioned (1)it'is relatively costly to carry out since it involves the use of one or more large storage tanksfor' the water layer through which the taris-passed and hence is capable of handling, per unit of time only a limited amount of tar; in order to handle the large volume of tar subjected to distillation in a tar distillation plant, a number of'such' tar washing units are required involving substantial plant investment, and (2') the procedure ire-'- quently results in a tar having a high water content, in excess or the water content'of the tar originally processed, which tar, prior to distillation, requires a dehydration treatment materially increasing the cost of treating the tar.

It is-an object of this invention to provide a process for removing substantially completely the small amount of ammonium'chloride-present in coke oven tar, which process is efiicient'in-operation in that it effects substantially complete removal of the-ammonium chloride; at "least to an extent-seas to g' r'eatlyminimi'zeyif not completely eliminate corrosion of thedistillation equipmentand theplugg ingg 'idu to'animonium chloride-deposits; of the'conden sers'when the tar is distilled; which process-is capable ofhandling economicalfly,ilarge lquafitifies bf. tar 'to effect substantially complete removal of the small amount of amm'oniu'm chloridecontained therein; which process' requires' relatively simple and inexpensive equipment for itspractice and-which process results irra *tar;-product'-low in iwater, usually less than- 2 by weight 'so ithat-it can be distilled directly as it comes from' ithe ammonium chloride removal process and does-notre'quire arseparate dehydrationtreatment.

other objectstand 'advantages of this inventionwill appear from-.the fOIlOWing detailed description-thereof, V

In iao'cordanceiwiththis invention substantially all of:the small amouht,usuallyof the order of .2 :by weight of" ammonium chloride present in coke oven-tars :is removedwby' continuously flowing -a stream" ofrthe coke oven .tar; continuously adding 5130 this 7 stream hot water or water and steam; introducing this-mixture at -a temperature Within the range :of about 200:toabout350" F5:and underxsupei'atmospheric pressure, preferably within the range" 'of about 50 to about pounds per square inch gauge into a; settling'and separation -zone, continuously flowing. this-mixture-underthe temperature and superatmospher- -io'- pressure conditions stated through the separation and': settling zone where the ammonium chloride solution sproduoed "separates from the tar; forming-ta super natant ammonium chloride solutionresting' -on ea tar :layer; continuously removing the -c:ike'oveni-tarsubstantially free of ammonium' 1 chloride from 1 this zone and separately removing the ammonium chloride solution from the zone. Preferably the ammonium chloride-solution as well-as the tar substantially free of ammonium chloride are removed continuously -from':th'isiseparation 'and settling zone maintainedunder superatmospheric pressure and at the: elevated atemperature above indicated; if desired, however; the-ammonium chloride solution may be're'moved from the separationand settling zone intermittently,- i.le.,-- at-Apredetermined 'intervals;

Qperating in' accordance "with the process of this invention lt hasibeen round the ammonium chloride content of coke oven" tar has been reduced from .2%"by' weig ht' to '.0l'5%' by weight and that the tar removed from the separation and settIing-ZOne contalns less than 2 water.

water, for example, of the order of 2%, the process of this invention will not necessarily result in a reduction of the water content of the tar as compared with its water content prior to treatment, but will invariably produce a tar which contains no more water than the amount of water present in the tar originally subjected to treatment.

The amount of water mixed with the tar will depend on the capacity of the equipment in which the process is carried out, the ammonium chloride content of the tar, and the temperature and pressure conditions runder which the settling and separation is effected. An amount in excess of that required to dissolve all of the ammonium chloride present in the tar should be employed. In general from 1 to 19 volumes of tar may be mixed with each volume of water, preferably about 4 volumes of tar are employed per volume of water. The rates of flow of the tar, water and steam are not critical factors and will depend upon the specific equipment inflwhich the process is carried out and are so chosen as to subject the tar and aqueous medium to a time of treatment in the settling and separationgzone hereinafter disclosed.

The time of treatment of the tar. in the separation and settling zone will depend on the extent of this zone, the rate at which the tar and aqueous medium are introduced thereinto and the rate at which the tar and: ammonium chloride solution are withdrawn therefrom. These factors should be so correlated that the time of treatment falls within therange of about 3 to about 12 hours, i. .e.,' a time interval falling within the range of about 3 to about.12 hours elapses between the time a particle offitar and'aqueous medium mixture enters thiszone and the time the tar portion of this particle mixture is withdrawn therefrom. Preferably thesefactors are so correlated that the tar and aqueous medium mixture require about 8 hours to pass through this zone. Operating under theconditions above noted substantially complete removal of the ammonium chloride from the tar as the mixture flows through this zone is effected.

The invention will be further described in connection with the accompanying drawing which is a flow sheet of the process and shows diagrammatically apparatus suitable for carrying out the process.

Crude coke oven tar from supply tank I. is drawn through line 2 by pump 3, preferably a steam pump. A line 4 leads from this pump to a heat exchanger 5, passes through this exchanger and communicates with a line 6 which leads into a separation and settling tank 1. Water flows through a line 8 having a manually operable valve 9 therein into a mixer ID of any conventional type. Steam flows from a supply line H having a valve 12 therein into the mixer II), the steam preheating the water to a desired temperature which is determined by the temperature control device l3 in the line l4 leading from the mixer It to the tar line..2. The. temperature controller I3 is connected with the valve 12 to control the amount of steam supplied to the mixer l to preheat the water to any desired temperature depending upon the setting of the temperature controller [3.

A meter l in the by-pass line communicating with line N indicates the amount of water admixed with the tar; this amount being controlled lb the valve 9. r

Pump 3 is operated by steam supplied through line I6 leading from supply line H and having a valve l1 therein. Valve I1 is actuated by a pressure controller l3 located in line 6 at or near the inlet totank I; this pressure controller may be of anywell known type and, is set to maintain the tar water mixture entering the settling and'separation tank I at a constant superatmospheric pressure, preferably within the range of 50 to 150 pounds per square inch gauge.

The tar water mixture from pump 3, as above indicated; flows through line 4 and then through the heat exchanger 5, or, if it is desired, through line l9 by-passing heat exchanger 5 directly into line 6 leading to tank 1'. Flow through line I9 is controlled by valve l9. A temperature controller 20 of any well known type is disposed at or near the inlet to tank 1 in line 6 and operates a valve 2| in line 22 leading from the steam supply line H to line 6. This temperature controller is set so as to maintain the tar water mixture entering the separation tank 1 at a constant temperature within the range of 200 to 350 F.

The separation tank 1 may be placed in a horizontal position, as diagrammatically shown in the drawings, or tilted from 7 to 20 from the horizontal to improve separation of'the tar and ammonium chloride solution.

As the mixture of water and tar flows longitudinally through tank I, it stratifies into two layers, the ammonium chloride solution forming the supernatant layer and the tar the lower layer. A level controlinstrument 23 of any conventional type at the discharge end of tank 1 effects actuation of pressure reducing valve 24 in line 25 through which the ammonium chloride solution is withdrawn from the tank. Tar withdrawal line 26 leads from the base of tank I and has therein a pressure reducing valve 21 which is actuated by flow controller 28 of any conventional type. Line 26 has one branch passing through the heat ex- ,changeri and leads into a line 29 which communicates with tar storage. tank 30, and. another branch 3l which by-passes heat exchanger 5. Flow through the .by-pass branch 3| is controlled by a manually operable valve 32. Bypass line 3| leads into the line 29 communicating with storage tank 30.

Controller 28 and the liquid level controller 23 are so set as to maintain an interface. mixture of approximately 50% tar and 50% ammonium chloride solution at about the point in the separation tank spaced approximately .7 of the length of the tank from the inlet thereto. Line 25 leads into a tank 33 provided with a vent 34- and having a line 35 leading to sewer or other point of disposal for the ammonium chloride solution.

It will be noted that the present'inventio'n provides a continuous process for substantially completely removing the small amount of ammonium chloride present in coke oven tar which process is simple to carry out, and has a high throughput capacity. The process of this invention treats coke oven tar continuously tic-reduce the ammonium chloride content thereof to .015% or even lower and to produce a tar containing less than 2% water, which tar can be fed continuously directly to the distillation equipment, greatly minimizing, if not completely eliminating,

corrosion and condenser plugging up diiiiculties,

due to ammonium chloride deposits, heretofore encountered in the distillation of coke oven tar.

The term water is used in the claims in its ordinary chemical sense to mean H20 and includes water in the vapor phase, 1. e., steam as well as vapor and liquid mixtures.

It is to be understood that this invention is not restricted to the present disclosure as variations may be made without departing from the scope of the invention.

What is claimed is:

l. A process of treating coal tar containing a small amount of ammonium chloride which comprises continuously flowing the tar, continuously adding water to the tar, introducing the resultant mixture under a superatmospheric pressure of at least about 50 pounds per square inch gauge and at a temperature within the range of about 200 to about 350 F. into a settling and separation zone and flowing the mixture through this zone while permitting the resulting ammonium chloride solution and tar to separate and removing tar substantially free of ammonium chloride from this zone.

2. A process of treating coke oven tar containing a small amount of ammonium chloride which comprises continuously flowing a stream of the coke oven tar, continuously adding a stream of water to the coke oven tar, introducing the resultant mixed stream under a pressure of from about 50 to about 150 pounds per square inch gauge and at a temperature of from about 200 to about 350 F. into a settling and separation zone, flowing this mixture through this zone while permitting the resulting ammonium chloride solution and tar to separate and while maintaining the tar and ammonium chloride solution' under said temperature and pressure conditions and removing tar substantially free of ammonium chloride from this zone.

3. A process of treating coke oven tar containing approximately .2% by weight of ammonium chloride which comprises continuously flowing a stream :of the coke oven tar, continuously adding to the flowing stream of coke oven tar a flowing stream of hot water, continuously introducing the resultant mixture at a temperature [of 250 to 300 F. and at a pressure of from to pounds per square inch gauge into a separation and settling zone, continuously flowing the mixture through this zone while maintaining the tar and ammonium chloride solution under said temperature and pressure to permit the tar and ammonium chloride solution to separate into two layers, the ammonium chloride solution forming the supernatant layer, continuously removing the coke oven tar substantially free of ammonium chloride from said zone and releasing the pressure thereon and continuously removing the ammonium chloride solution from said zone.

WILLIAM TIDDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number

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