US2439547A - Apparatus for production of ammonium sulphate - Google Patents

Description

C. OTTO lApril 13, 1948.

APPARATUS FOR PRODUCTION OF AMMONIUM SULPHATE Filed MalcrhV 8, 1944 2 Sheets-Sheet 2 f/////h IIL lNvENToR CHR/ 07m TTORNEY Patented pr. 13, 1948 APPARATUS FOR PRODUCTION OF AMMONIUM `SULPHATE Carl Otto, Manhasset, N. Y., assigner to uelRening Corporation, New York, N. Y., alcorporation of Delaware Application March 8, 1944, Serial No. 525,543

1 Claim. (Cl. 23e-273) The general object of the present invention is to provide an improved method of, and improved apparatus for converting the ammonia content of distillation gas, and particularly of coke oven gas, into ammonia sulphate by passing the gas through a so-called saturator containing a bath of weak sulphuric acid with which l the gas is brought into scrubbing contact, so that ammonia elements in the gas and sulphuric acid elements in the bath liquor combine to form sulphate of ammonia which subsequently crystallizes out of the bath liquor.

A saturator of the -character described, comprises a tank which ordinarily has a hopper bottom and the lower portion of which serves as a container for the sulphuric acid bath. The

upper portion of the tank space serves as a gas space receiving the'gas treated after the latter has been injected into and has risen -to and escaped from the upper surface of the bath. Ammonia saturators present special problems rising out of, or increased in importance by, the considerable bulk and gas treating capacity of the saturators. `At the level of the topof the bath therein the internal horizontal cross section of such a saturator tank space is usually not less than about eighty square feet and it may be more than three hundred square feet. Ordinarily, the volume of bath liquor in thesaturater is in excess of three thousand gallons, and it may be as great as twelve' thousand gallons. The volume of distillation gas passing in a twenty-four hour day through a saturator of relatively small size may be as much as twenty million cubic feet, and the daily volume of gas passing through a relatively large saturator may be more than one hundred million cubic feet.

While the bulk of its initial tar content is customarily separated from the' gas before the latter is passed into an ammonia saturator, t'ar is invariably separated from the gas in the saturator at a rate high enough to objectionably aiect the saturator operation if the tar is allowed teaccumulate in the saturator. The tar accumulation in a saturator can .be kept desiralbly small by providing the saturator with a bath liquor overflow connection and passing bath liquor into the saturator tank more or less continuously so that tar oating on the top of the bath will be carried out of the saturator by the overowing bath liquor. One object of the present invention is to provide a saturator with animproved overflow connection characterized by the inclusion, in a simple and compact structure, of Windows, a cut-off valve, and Washing means.

In the normal operation of an ammonia saturator, there is invariably a tendency to the deposit on, and rigid adherence to the internal surfaces of the saturator, of dense crystallized ammonia sulphate massesof such physical character that they are commonly referred to as rock salt. In usual practice the sulphuric acid content ofthe bath liquor Varies from a minimum of three or four per cent up to a maximum of about seven `per cent. The tendency to the formation of rock salt deposits is greater `when the acidity of the bath liquor is relatively l-ow, asr it' may `be in `Athe production of `large ammonia sulphate crystals, than when the acidity is higher, as it customarily is in the production of relatively" small crystals. While the rapidity with which rock salt deposits are formed varies with conditions of saturator operation, and may be minimized by washing and other special provisions. it is practically essential in the operation'of every saturator to periodically free the saturator from rock salt deposits by the operation commonly known as killing the bath. l V

The bath killing operation consists in' re placing the" so-called "mother liquor of which the :saturator bath is composed in normal operation, by a mixture of sulphuric acid and water. Tliefresh bath liquor formed by said mixture differs from mother liquor in that it does not have the ammonia sulphate content of mother liquor. Normally, the mother liquor holds in solution more than'forty per cent by Weight of sulphate of ammonia, and in normal operation, mother liquor holds in suspension about thirty per cent by volume of ammonia sulphate crystals. In consequence of their composition differences `the density of mother liquor is much greater than that of fresh bath liquor. Thus the density -of mother `liquor may be aboutl 33 Baum While the density of the `fresh bath liquor may be as low `as 22 Baum.

One object of thepresent invention is to :provide an` improved method of, and means `for periodically withdrawing mother liquor from the saturator and passing into the saturator sulphuric acid and Water, in such manner as to elect the bath killing operation with desirable rapidity and without interfering with the continuous and eilicient recovery of ammonia from the distillation gas and so as to minimize the periodduring which the separation of sulphate of ammonia crystals from the bath liquor at the normal rate is interrupted. A further `object of the invention is to effect the bath killing operadjuncts;

3 ation without requiring an increase in loath liquor level height signicantly increasing the gas pressure drop in the saturator.

For the attainment of the above mentioned objects, I have provided simple and effective means for storing mother liquor withdrawn from the saturator during the ibath zkilling operation, and for returning lthe mother liquor to the saturator during a subsequent regular operation period, so that its acid and crystal contents are not wasted. In some cases, more or less of the mother liquor withdrawn during the bath killing operation may be returned to the saturator'before the sulphate content of-the.: bath liquorvin the saturator has built up to! its normal-opera tion value. This permits some reduction in the period required to restore normal operating conditions. In the preferred form of the invention sulphate crystals are separated from the mother liquor withdrawn from the saturator during 'the bathk-illing operation prior tol the passage ci* the mothern liquor into theV storage receptacle in ywhich it-isheld during the subsequent portionof the bat-h killing operation.

My improved overflow construction-contributes to the attainmentl of my improved bath killing results.A Thev windows which I provide -in the overflow-connection permit of -easy visualr-exami" nation of operating conditions in' the saturator sor that the-bath killing operations'need'not be eiected withunnecessary frequency, but may be -eectedV whenever' necessary. .The cut-off valve which I includeinmyoverilow' connection Vforms a simpleand eifective-meansfor temporarily interrupting'the bath liquor overflow from the bath whenever this may be desirable.v Such interruption is some `times desirable tiopermitfthe bath levelV in thehsaturator tank to be temporarily raised duringfa brief portion of'the, bath killing operation; for thepurposeiof rapidly removing rocksalt deposits onthe inner wall of the saturator i tank' immediatelyabove the normal bath level.' Ordinarily, however, with my invention the `entire bath killing and restoring operation may be effected `without thesignicant increase in'saturatorbath level heightwhich hasl customarily attended and characterizedthe bath killing operation practice heretofore followed.` Such in'- crease in bath'develfheightvobjectionably im creases the saturatorqgas pressure dropand the required gas` pumping energy. y

The various features-of novelty which characterizemy invention are pointed outwith particu'- drawing andcdescriptive matter vin whichnI have illustrated` andi described preferred Vembodiments lof the invention.

Of the drawings:

4? gas is passed into the saturator through an axially disposed cracker pipe B which receives gas at its upper end from a gas main C through an inlet chamber C above the saturator. rEhe cracker pipe B comprises a lower end section B forming an outwardly flared discharge mouth below the normal Ylevel'A of the bath liquor which lls the lower portion of the `saturator-and in which the discharge end B of the cracker pipe is submerged. The bath level A is normally maintained approximately constant by the n-ormally open overflow connection t0 the saturator including the novel overflow element D herein- Fig. llis a. diagrammaticelevation, Lpar-tly in v section.. of ari-.ammonia saturator and' associated Fig. 2 is an' enlarged elevationthrougn the saturatorioverfiow connection; 1

Fig.: 3 is an invertediplan section on the line 3 3 of Fig. 2; and

'Fig 4 is'an elevation -fof'Y apparatus shown in Fig. 1. Y f Y Thel apparatus shown diagrammatically in Fig.

1, comprises al saturator tank,A of conventional type vhavingha cylindrical body, a hopper bottom portion A andan-upper gas-outletA2. Coke oven after described.

Bath..liquor passing away from the saturator through the overilow element D, passes through a drain pipe El intothe receiving or seal chamber F of atar separator F, The latter is in the form of .a'tank open at its upper end to permit tar to be skimmed ofi the bath liquor in the separator. The latter includes a vertical partition or Weir F2 separating therlower portion ofthe chamber F froma chamber F3 which receives liquor flowing over the Weir F2 from the chamber F. .An overflow outlet' F4 from the chamber F3 discharges into a mother liquor reservoir G.

In the normal-operation, however, the liquor level in the separator F is kept too low vto permit overflow through the outlet Fir-by a pumpVI-I which withdraws liquor from the-bottom ofY the chamber F3 through a pipe connection H to the inlet of said pump. The pump H has a second inlet pipe yconnection H2 through which the pump may` draw liquor `from the reservoir G. VFlow through the pump inlet connections Il and H2 may be cut ofi or throttled by corresponding valves I and I. As shown, the pump H has its outlet connected through la heater J to a pipe J which discharges into a return pot orchamber K. through a valve The return pot Khas a drainpipe or-bottom discharge connection K' through which'bath liquor passes to the -saturator. The drain pipe K1 extends throughthe saturator wall and has its lower end extending down into the bath liquor'for a few inches.

Y Crystals formed'l and settling in the saturator vare `withdrawn from the bottom of the saturator in an entraining or carrying stream of bath liquor through ,a crystal outlet passage A3. The latter is connected, by a pipe L to the inlet of a pump VL which discharges the carrying liquor andentrained crystals through a pipe L2 into aV feed tank or receiving chamber M from which most of the larger crystals and a smallporton of the carrying liquor pass toa centrifuge N. The bulkfofrthe carrying liquor thus freed from more or less of its crystal content overflows in lthe tank.M` through a pipe lVI., The latter has a discharge branch including a cut-oil valve IG j leadingA to the separatori, a second discharge branch including a cut-oil? valve IK leading to the return pot K. LiquorV passing with crystals from the feedtank M to the centrifuge N, drains from `thelatter into the return pot K through f a drain pipe connection N. Hot water may be passed into the return pot K through a pipe O suitable washing liquid against the internal walls of the saturator, such as are disclosed and claimed in my application Serial Nog-173,949, filed January 29, 1943, now abandoned. .As shown in Fig. 1, a pipe R supplies saturator washing liquid which may come from the hot water source P through a valve I4, or through avalve I from the liquor return pipe J Ordinarily, Iconsider it advantageous to return some of the bath liquor to the saturator in such manner as to maintain a crystal separation zone immediately above the crystal outlet A3 which serves to minimize or prevent the movement of unduly small crystals to said outlet. The liquor so returned to the saturator may include bath liquor returned from the feed tank M through the pipe M1, bath liquor which has overflowed from the saturator into the tar separator F, or a mixture of bath liquor from the feed tank and tar separator. Means for maintaining said separation zone are disclosed and claimed in my application Serial No; 492,265, led June 25, 1943, now Patent No. 2,424,206, issued July 15, 1947.

As such means form no part of the present invention and are not necessary toits use, they need not be illustrated or further referred to herein.

As shown, the novel overflow`element D, comprises a box-like body serving' as a pipe elbow. The flanged inlet end D' of said body is bolted or otherwise rigidly secured to the flanged outer end of a nozzle portion A5 of the saturator tank structure. The depending outlet end portion D2 of said body is bolted or otherwise rigidly secured through a valve body S to theupper end of the drain pipe E extending down into the tar separat-or F. The valve body S as shown is an annulus, the central opening S of which is in register with the bore of the pipe lil` and withthe opening in the outlet end D2 of the element D. A butterily valve member S3 is mounted on a horizontal shaft S3 which extends diametrically across the opening S and has itsends journalled in diametrically opposed portions of the annular member S. Normally, the valve S2 occupies its open position shown in full lines in Fig. 2. When rotated into its horizontal position, it prevents signicant ow from the saturator through the element D into the'drain Apipe S3. For its intended use, such small leakage past the valve disc S2 as may occur when the latter is in its closed position, is inconsequential.

The element D has vertical side wallseach formed with a circular window opening T in i which a plate glass disc T is secured by inner and outer clamping rings T2 which are anchored in place by clamping bolts T3. The element D has a vertical wall remote from the saturator tank A and formed with a window opening t closed by a glass window disc 5t'. The latter as shown is slightly smaller in diameter than the window glasses 'I'. The window glass t' is secured in place by clamping rings T2 and clamping bolts T3 similar to those employed to secure the window glasses T in place.

, As is Well known, saturator surfaces exposed to contact with bath liquor must be formed of or covered by material `immune to attack by dilute sulphuric acid. Customarily, the saturator tank is lead lined and the overflow connection may also be lead lined. Ordinarily, however, the element D may well be formed of -hard lead, Monel metal or of some other alloy suitably resistant to attack by sulphuric acid. Advantageously and as shown, means are provided for spraying wash liquid into the overflow element D to prevent 'e l deposits of rocksalt in the element and to keep the glass window discs T- and t' suitably transparent. The means shown for this purpose comprise pipes U and UA extending into the element D through its upper side. As shown, the pipe U is connected to a spray head V within the element D. The spray head has three outlets V so arranged that each outlet discharges a jet of Washing liquid directly against a corresponding one of the window discs T and t'. Wash liquor is supplied to the pipes U and UA through a supply pipe UC which may receive hot Water from the source P through a valve I6, or may receive Warm bath liquor from the pipe J through a valve I". In the contemplated operation of the saturator shown in Fig. 1, gas passes continuously through the saturator and in scrubbing Contact with the bath liquor therein, so that at all times substantially all of the ammonia elements of the gas are converted into sulphate of ammonia which is dissolved in the bath liquor. While the saturator operation is continuous in respect to the formation of ammonia sulphate,A it is intermittent in respect to the composition of the bath liquor, comprising regular operation periods alternatin with bath killing and restoring periods.

During each regular operation period, the bath consists of mother liquor. The latter is a dilute solution of sulphuric acid in water and is saturated with dissolved sulphate of ammonia, and holds in suspension a substantial volume of ammonia sulphate crystals of varying sizes. In each regular operation period, bath liquor is returned to the saturator continuously through pipes J' and M and return pot K at substantially the same rate at which bath liquor is withdrawn from the saturator `through the overflow connection and crystal outlet A3. In each regular operation period the composition of the mother liquor will customarily be approximately constant though it may vary slightly, however, if sulphuric acid is not fed through the pipe Q at a rate suitably proportional to the rate at which gas carries ammonia into the saturator. The mother liquor composition may vary also as the saturator temperature changes and thereby increases or decreases the water content of the bath by varying the dew point of the water Vapor in the gas.

Each bath killing operation is initiated by valve adjustments required for the passage of mother liquor withdrawn from the bottom of the saturator through the outlet A3 into the storage reservoir G, instead of back into the saturator through the pot K, and for the passage of water into the upper portion of the saturator to replace the mother liquor Withdrawn. The valve adjustments then effected in the apparatus shown include the opening of the valves I4 and IG, and the closure of the valves I and I if the latter were previously open. Usually, also the valves I2 and I3 should both be then closed. The rate at which water is then passed into the saturator ordinarily should at least equal the rate at which bath liquor is withdrawn from the saturator through the crystal outlet A3. Usually the rate at which water is thensuppled to the saturator should be high enough to maintain a small tar eliminating overflow through the o-utlet A3. In some cases, also, during a brief portion of a bath killing period, the overflow outlet valve S3 may be closed and the rate at which water is passed into the saturator made sufciently higher than the rate at which bath liquor .is withdrawn from the saturator to the outlet A3 so that the bath liquor level in the saturator may be raised.

During the bath killing operation, effected as described, the composition of the mother liquor passing out of the saturator to the outlet A3 tends to remain approximately constant since th'e mother liquor density so greatly exceeds the density of the water passing to the saturator from the heater P that the mother liquor and the water above it do not mix rapidly. Th'e fresh bath liquor formed by the warm water and acid then passing into the saturator, is a good solvent for crystallized ammonia sulphate and rapidly dissolves rock salt deposits on the internal surfaces of the saturator. Y

The above mentioned increase in the height of bath level in the saturator during the bath killing operation, if and when effected, insures the rapid dissolving of rock salt deposits which may have formed on the saturator wall surface portions adjacent but slightly above the normal bath level. Such deposits may result from the bath liquor turbulence produced by the gas as it is injected into and bubbles up out of the bath liquor and are ordinarily augmented by bath' liquor agitating fand recirculating provisions. During the bath killing operation, the acidity of the bath may or may not be increased, as conditions make desirable.

After the introduction of suincient water into the bathto subject the rock salt deposits to a suitable dissolving action, valve adjustments are effected to interrupt the passage of liquor out of the saturator through' its outlet and to reduce the rate at which water is supplied to the saturator and to pass bath liquor overflowing into the tar 'separator into the return pot K instead of into the reservoir G. The inlet valve I may be opened then or later so th'at the pump I-I will gradually pass back into the saturator the mother liquor which accumulated in the reservoir G during the period in which the overflow from the feed tank M passed to said reservoir. Operation in the manner just ydescribed is adapted to rapidly effect the bath killing operation 4and the restoration of the normal ammonia sulphate content of the bath, so that within a few hours following the initiation of the bath' killing operation, the normal mother liquor composition of the bath is restored and a new regular operation period is thereby initiated. During the bath killing operation as in regular operation the rate at which make up acid is supplied may be regulated by adjustment of th'e valve Q' in the acid supply pipe U.

As will be apparent, the reduction in the ammonia sulphate content of the bath occurring on the described replacement of mother liquor by a mixture of water and acid, does not diminish, but, on the contrary, tends to augment the capacity of the bath to absorb ammonia from the gas rise in bath level pumping load. The formation of ammonia sulphate crystals is interrupted, however, when the mother liquor is replaced by the water and acid mixture and is resumed only after the amount of ammonia sulphate in solution in th'e mixture has materially increased, and the rate at which such crystals are formed does not rise to its normal value until the mixture approaches its saturated solution condition, While the bath killing operation temporarily interrupts the formation of crystals, it does not reduce the total amount of sulphate crystals produced and recovered, but makes their production intermittent.

The rate at which troublesome deposits of rock salt are formed in the saturator depend to some extent on fortuitous changes in operating conditions and particularly on bath temperature conditions. In consequence,I the visual inspection of the interior of the saturator and conditions through a suitable inspection window in the saturator wall or advantageously located in the overflow outlet as are the windows T and t', permits the bath killing operations to be initiated when, and only when, such operations are needed instead of at regular and unnecessarily frequent time intervals. A

Troublesome rock salt deposits :are especially apt to occur on the cracker pipe mouthpiece B' and to prevent such deposits, steam or other heating means may be provided for maintaining said mouthpiece at a temperature higher than the average saturator bath temperature. Thus, for example, as shown in Fig. 1, the mouthpiece may be hollow so that it encloses a heating space W of annular form. A valved supply pipe W' supplies steam or other suitable heating fluid to the heating space W and Wa represents a valved outlet pipe through which water of condensation or cooled water or air may be discharged from the space W. The rate at which fluid is supplied to the space W may be regulated in accordance with the need therefor as determined by vision inspection through the windows of th'e element D. In some cases, of course, the flow of heating unit through the heat element may well bel continuous. With the apparatus shown in Fig. 11, the amount of tar carried by the mother liquor into the feed tank M and reservoir G, may be kept very small as is practically desirable. In Vusing the tar separator shown in Fig, 1, the tar accumulating in the separator F must be manually skimmed off.

In Fig. 4, however, I h'ave illustrated an overflow receptacle FA differing from the receptacle F of Fig. 1 in that it includes provisions for automatically dischargin-g Boating impurities. The receptacle FA includes compartments FAv and FA3 correspondingto the compartments F" and F3 of Fig. 1. However, the compartments FA and FA3 are shown as separated by a partition FA2 which extends upward to a level about the maximum height liquid level in either of the compartments FA and FAS. Floating impurities in the compartment FA overflow through an overflow pipe F5 into tar receiver FB. Bath liquor separating in the compartment FA' from impurities overflowing through F5 passes into the compartment through an overflow pipe Fe. The latter is open at its lower end to the chamber FA' adjacent the bottom of the latter, andv has its upper end discharging into the chamber FA3 through the partition FA2 at a level slightly lower than the level at which impurities overilow through the outlet F5.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of embodiment of my invention now known to me, lit will be apparent to those skilled in the art that changes may be made in the forms'of the apparatus disclosed without departing from the spirit of my invention as set forth Vin the appended claim, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention; what I claim as new and desire to secure by Letters Patent is:

Apparatus for producing sulphate of ammonia crystals from distillation gas comprising a saturator tank having a bath liquor overiiow outlet opening intermediate its upper and lower ends, conduit means connected to a source of supply of distillation gas land extending into the portion of said tank below the overflow outlet opening for 6 continuously passing distillation gas through' said saturator and into scrubbing contact with said bath liquor, an overow conduit comprising a pipe member to prevent sulphate crystal deposits on its walls and windows.

CARL OTTO.

10 REFERENCES CITED The following references are of `record in the le of this patent:

UNITED STATES PATENTS;

Number Name Date 2,022,813 Ruys Dec. 3, 1935 2,226,101 Ogden Dec. 24, 1940 2,232,115 Koppers Feb. 18, 1941V 1 2,313,463 Bussmann May 4, 1943 OTHER REFERENCES Lunge, Sulphuric Acid and Alkali, v01. 1, part 2, pages 701 and 702. Pub. by Gurney & Jackson,

15 London (1913)..

The Gas World for December 3, 1938, pages 15-19.

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