US2423794A - Production of ammonium sulphate - Google Patents

Description

July 8, 1947.v c. OTTO PRODUCTION OF AMMONIUM SULPHA'I 'E Filed'Aug. 25, 1945 3 Sheets-Sheet l Che; 0772; Y 5

' 'ATTORNEY July 8, 1947.

- c. OTTO PRODUCTION AMMONIUM SULPHATE Filed Aug. 25, 1945 5 sheets-sheet 2 INVENTOR Cmez 07'7'0 ATTORNEY July 8, 1947. c. o'r-To- I PRODUCTION OF AMMONIUM SULPHATE Filed Aug. 25, 1943 3 Sheets-Sheet 3 INVENTOR C421. Orzo ATTORNEY Patented July 8, 1947 PRODUCTION OF I AMMONIUM 'SULPHATE Carl Otto, Manhas'set, N. Y., assigno'r to Fuel Refining Corporation, New York, N. Y., a corporation of Delaware Application August 25, 1943,"Serial No. 499,986

3 Claims. (Cl. 23-119) i 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 coke 'oven gas, into ammonium sulphate by passing the gas into a so-called saturator containing a bath ofweak sulphuric acid with which the gas is brought into scrubbing contact so that the ammonia elements in the gas and the sulphuric acid elements in the bath combine to form sulphate of ammonia. The later subsequently crystallizes out of the bath liquor. Ordinarily, the sulphate crystals thus formed, accumulate in the lower portion of the bath and are withdrawn from the saturator in a carrying stream of bath liquor by a discharge pump or ejector.

Various forms of saturators of the general character described have long been, and now are in general use in this country usually by product coke oven plants. As a result of plant expansions, and economies to be obtained by their use, there is now a substantial need for saturator units of larger individual operative capacity than has been customary heretofore.

A major object of the present invention is to provide a novel method of and means for bringing the gas into scrubbing contact with the bath liquor which are efficient and well adapted for practical use in saturator units of larger capacity than have been heretofore customary. The invention is not restricted to use in and in connection with saturators originally devised and adapted for such use, as existing saturators of various types may be made more efficient and may have their operative capacities greatly increased by relatively inexpensive modifications which adapt them for use in accordance with the present invention.

Another major object Of the invention is to effect adequate and efficient scrubbing contact of the gas and bath liquor with a substantially smaller expenditure of potential energy, or gas pressure drop, in the saturator than is required in the normal operation of saturators heretofore in use. The reduction in the saturator gas pressure drop made possible by the use of the present invention results in a worthwhile saving of gas pumping energy and expense.

The present invention is primarily characterized by the movement of the gas in a generally horizontal direction through a scrubbing zone gas space maintained between an upper wall surface and a lower bath liquor surface depressed by the pressure of the flowing gas. 'At the outlet end of widgets space its roof is several inches below the upper surface of the bath liquor surrounding the scrubbing zone and into which the gas passes from the gas space. The latter is of sufficient extent in the direction of gas flow and is suiiiciently restricted in the transverse direction, to maintain liquor and gas flow conditions which result in the conversion into ammonia sulphate of much of the ammonia content of the ga while the latter is passing through saidgas space. I believe that the demonstrated practical merit of the invention is due in substantial part, at least, to the fact that the stream of gas flowing rapidly through the relatively shallow horizontal gas space, subjects the liquid forming the bottom wall of said space to ripple creating and atomizing actions. The local circulation of the bath liquid incident to the formation of ripples and the dispersion of the atomized liquid in the gas stream, each contribute to the rapid conversion of the free ammonia elements of the gas into ammonium sulphate by providing opportunity for contact of the ammonium elements in the gas with bath liquor acid elements not previously converted into ammonium sulphate. 7

While it is essential to the full attainment of the advantages of the invention that the direction of gas flow through the free gas space of the scrubbing zone should be approximately horizontal, I have found it practically desirable to incline the wall surface forming the roof of said gas space at a small angle to the horizontal with the lower edge of said wall surface at the gas discharge edge of said space. Said angle which may vary from a minimum of four or five degrees to a maximum not greater than fifteen degrees. Unless the wall forming the roof of the free gas space is so inclined, ga flow conditions and bath liquor surging actions may occur which will materially interfere with the efliciency of the scrubbing action, and which tend to cause objectionable deposits of sulphate of ammonia crystal or salt, on said wall.

In a preferred practical form of the present invention, the roof wall of the scrubbing zone.

gas space is formed by the lip portion of an outwardly flared, downwardly opening mouthpiece of a cracker pipe through which the gas is passed downward into contact with the bath liquor into which said mouthpiece extends, but said roof wall may take other forms.

The present invention may be used with substantial advantage in saturators operated to produce sulphate crystals of the relatively small size usually produced heretofore, and may be used with even greater advantage in saturators operated to produce so-called large ammonium sulphate crystals. One well known grade of such large crystals comprise crystals of which 40% are too large to pass a 35 mesh screen and only are small enough to pass a 70 mesh screen; whereas of the small crystal sulphate constituting the bulk of the ammonium sulphate and specific objectives attained with its use reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described the preferred embodiments of the invention. I

. Fig. .1 is an elevation partly broken away and in section;

Fig. 2 is a plan view of the saturator shown in Fig. 1;

Fig. 2A is a section on the line ZA-ZA of Fig. 2;

Fig. 3 is a plan view of a portion of the cracker pipe mouthpiece shown in Figs. 1 and 4;

Fig. 4 is a reproduction on a larger scale of the cracker pipe mouthpiece section shown in Fig, 1;

Fig. 5 is a plan view of a portion of a modified form of the mouthpiece shown in Figs. 1-4;

Fig. 6 is a diagrammatic sectional elevation of a portion'of a saturator difiering in form from k that shown in Fig. 1;

Fig. 7 is a diagrammatic sectional elevation of a portion of another modification of the saturator shown in Fig.- 1;

Fig. 8 is a chart illustrating test apparatus results obtained with difierent rates of gas flow and with different roof inclinations;

Fig. 9 is a sectional plan of a third saturator form;

Fig. 10 is a partial section on the line |2-l2 of Fig. 9;

Fig. 11 is a sectional plan of a fourth form of saturator; and, a r

Fig. mm a section on the line I l-l4 of Fig. 11.

In Figs. 1-4, I have illustrated an ammonia saturator comprising a tank A which holds a body of bath liquor B in its lower portion and is of a type and form long in use in thiscountry, and in which I have replaced the means originally employed to pass the gas into contact with the bath liquor by a vertically disposed cracker pipe C having a mouthpiece D at its'lower end which is.

shaped and disposed in accordance with the principles of the present invention.

The tank A illustrated comp-rises a body portion which in horizontal cross section is in the form of an ellipse with flattened sides; a rounded upper portion A which may be described as an elongated dome; and a bottom portion which is formed with two depressions or wells A each serving as a receiver for crystals settling to the bottom of the saturator. The upper tank portion A is formed at its top with two openings surrounded by external flanged pipe connections A of the tank structure. The two flanged pipe connections A are displaced in opposite directions from the vertical tank axis. has its upper end secured in the opening surrounded by one of the flanged pipe connections A to which the gas supply pipe or main E is attached. The saturator gas discharge pipe Fis The cracker pipe C secured to the second flanged pipe connection A and receives gas from the saturator gas space surrounding the cracker pipe C. The cracker pipe mouthpiece D has its axis coincident with the vertical tank axis, the body portion of the cracker pipe being correspondingly inclined to said axis. To prevent movement of the lower endof the cracker pipe and its mouthpiece away from the tank axis under the action of gravity, the lower end of the cracker pipe is connected to the upper tank portion A by one or more suitably disposed stay bolts or tension rods C.

The discharge pipe F passes gas into a so-called acid catcher G which collects bath liquor entrained in the gas passing out of the saturator through the pipe F; the gas passing away from the acid catcher G through piping not shown. Sulphate crystals and carrying bath liquor are withdrawn from the wells A through separate suction pipes H. The suction pipes I-I pass out of the saturator through wall openings surrounded by external nozzle portions A of the tank structure through which the pipes H are connected to pumping or exhausting apparatus (not shown) but serving in a known manner to pass the crystals and liquor mixture to the usual crystal and liquor separating apparatus from which bath liquor separated from the crystals may be returned to the saturator. As shown, a horizontal spray ring I located in each well A discharges upwardly directed jets of air or gas supplied under a suitable pressure through corresponding pipes I which extend through saturator wall openings surrounded by external nozzle portions A through which the pipes I are connected to means supplying air or gas under suitable pressure. The jets discharged by the spray pipe rings I agitate the bath liquor and tend to retard the movement of very fine sulphate crystals to the inlet ends of the suction pipes H.

The body portion of the saturator is formed with an opening surrounded by an external nozzle A through which bath liquor may overflow into an external tar separator J of known form. As shown, the saturator J comprises a tank in which there is a seal pot or chamber J closed-at its lower end and open at its upper end, into which liquor overflowing from the saturator is passed through a vertical pipe J having its open lower end adjacent the lower end of the seal pot J and having its upper end connected to an overflow box K secured to the end of the nozzle A. As shown, the overflow box K is in the form of a lead linedpipe fitting having one open side in register with the nozzle A The member K has a lower nozzle end portion K which is mechanically connected to the upper'end of the discharge pipe or spout J and has an upper-nozzle end portion closed by a head K The latter is formed with a central passage through which a longitudinally adjustable rod or stem K3 extends into connection with the upper end of a vertically disposed tubular sleeve or weir member K The latter is fitted snugly in, and is longitudinally.

adjustable in thelower nozzle portion K of the member K. The level of the upper end of said sleeve K corresponds to and determines the saturator bath liquor level B, and the bath level B.

may be vertically adjusted by adjusting the rod K relative to the head K As shown, the rod K may be secured in any of different positions by a' pet J, overflows from the latter through a weir notch J- into the tank J. The tar separating frm the gas passingtlirough the saturator, floats at the top of the saturator bath and is carried out of the saturator by the bath liquor overflowing through the nozzle A into the tank J from which the tar may be manually skimmed oii or otherwise eliminated. A' baffle J prevents the tar'enterin'g the tank from reaching the liquor outlet J o'fthe tank. The continuous and relatively expeditious removal of tar from the saturator thus effected, contributes to the production of sulphate crystals much freer from tar contamination and tar discoloration than is possible when "no such tar elimination is effected.

The bath liquor withdrawn from the saturator through the crystal discharge pipes H, and that carried into the acid catcher by the gas passing away from the saturator, and the bath liquor passing out of the saturator through the overnew opening surrounded by the nozzle A in the tar'separator J, may all be returned to the saturator. 'All or a substantial portion of such bath liquor may be returned to the saturator through pipes L extending into the saturator through wall openings surrounded by external nozzles A As shown in Figs. 1 and 2, the discharge ends of the return pipes L extend in the same generally tangential relation to the vertical axis of the saturator so that the return liquor discharged by the pipes tends to maintain a bath circulation in the counter-clockwise direction about the vertical tank axis. This circulation contributes to a suitably rapid and complete combination of ammonia in the gas with the acid in the bath liquor and also contributes to a movement of the tar floating at the top of the bath, toward and into the overflow connection leading to the tar separator J.

As those skilled in the art will understand, all pipe and tank surfaces, etc. exposed to contact with the bath liquor should be formed of or provided with a protective coating of material such as lead or Monel metal which is-immune to the corrosive action of the bath liquor.

To eliminate -or minimize salt deposits, a washing liquid, ordinarily hot water, may be sprayed into the saturator through suitable spray pipes suchas the spray pipe M entering the saturator through the upper tank part A, and spray pipes M which enter the .s'aturator tank through lateral openings surrounded by external nozzles A and spray pipes M may well serve to atomize'the water which they :spray into the saturator, all as described and claimed in my prior application for patent Serial No. 473,949, filed January 29, 1943. I have-found, however, that in the operation of a saturator at the high capacity rate made possible by the use of the present invention, the relatively large amount of bath liquor splashed onto the saturator internal walls above the bath liquor level '3' greatly eliminates or greatly reduces the liability of objectionable salt deposits on those walls.

Pipes MA-extending into the saturator-through the nozzles A discharge a mixture of steam with air orgas and preferably coke oven gas, into'the bath liquor adjacent the wall of the tank and a small distance below the bath liquor surface B. :"As shown the discharge ends of the pipes MA are so shaped thatsteam and gas jets into the bath liquor alongside the tank wall and are so directed that they tend to maintain a bath liquor. circulationabout the vertical .axis' of the tank. fIhe steam in, the steam-air or steam gas mixture discharged into the'bath liquor through the pipes MA locally heats the bath liquor at the top of the bath adjacent the tank wall and thus eliminates or minimizes risk of sulphate or rock salt deposits on the tank wall adjacent the bath level. The addition of air or gas to the steam avoids water hammer effects. No claim is made herein on the arrangement or use of the steamgas supply pipes MA as such pipes and their use are disclosed and claimed in my prior application-Seria1.No.475,371 filed February 10, 1943. It is to be noted however, that the pipes MA tend to maintain a bath liquor circulation about the vertical tank axis in the same direction as do the previously mentioned pipes L, and thus contribute to the rapid removal of tar through the overflow outlet nozzle A -Make-up acid is supplied to the saturator through a supply pipe N and a spray or 'distributing pipe ring N surrounding the upper inlet portion of the mouthpiece D. Except in respect to the 'form' and disposition of the means for passing the incoming gas .into scrubbing contact with the bath liquor, thespecific features of the saturator construction and arrangement hereinbefore referred form no part of the invention claimed herein.

As shown in Figs. 3 and 4, the mouthpiece D which may be formed of cast lead, comprises an upper cylindrical portion D, a lower conical lip D and an intermediate portion D outwardly curved or flared to increase in diameter at .a progressingly increasing rate as the distance from the lower end of the cylindrical portion D increases. As shown, the upper end portion of the mouthpiece D includes a flange D for bolt connection of the mouthpiece to the lower end of the cracker. pipe C.

As shown, curved ribs D depending from the underside of the mouthpiece D and extend inward from the periphery of the latter. The ribs D while not essential elements of the present invention, contribute to the proper distribution of the gas passing out of the gas space beneath the mouthpiece and bubbling up through thelbath liquor at the mouthpiece periphery. The ribs D also provide curved flow channels for the gas discharged irom the cracker pipe and for the bath liquor streams set into motion by the gas and thus supplement the action of the curved discharge ends of the return pipes L and gas injector pipes MA in creating a flow of bath liquor in the counterclockwise direction above the vertical tank axis.

In the normal contemplated use of the apparatus shown in Figs. 1-4, make-up acid is supplied to the saturator through the pipe N as required to maintain the desired bath liquor acidity. The sulphuric acid content of the bath liquor may well be about 5.5 per cent or less in the production of large crystals, and about 7 per cent or more in the production of ordinary small size crystals. The actual rate of make-up acid'supply depends, of course, upon the rate at which the ammonia containing gas is passed through the saturator and upon the ammonia content of the gas. The level regulating weir K'may be adjusted to maintain the top service level B of the bath liquor at the distance a above the lower peripheralcorner edge D of mouthpiece D which gives the best operation results under particular operating conditions.

The fact that the use of the present invention increases the operating capacity of saturator-s has been demonstrated. Thus, for example, a sawrator of the type, form and proportions illustrated inFigs. 1-4, in which-the diameter of the peripheral edge of the mouthpiece is six and a half feet, and in which the distance a is six inches, is now being regularly and successfully used to recover the free ammonia in coke oven'gas passing through the saturator at the rate of-about forty-four million cubic feet per twenty-four hour day. No prior saturator, as far as I am aware, has ever operated regularly at a higher rate, or at as high a rate per unit of saturator volume or bulk. Said saturator as originally constructed, and as regularly used for a period of years, included means for discharging gas into the bath liquor through vertically elongated ports or slots in vertical walls extending down into the bath liquor far enough so that the upper end of said ports or slots were at a level some fifteen or more inches below the top surface of the bath. While the aggregate horizontal width of said vertical wall slots originally included in the saturator was considerably greater than the circumference of the mouthpiece D, the saturator in its original form was never practically operative at a rate of more than about twenty-two million cubic feet of gas per twenty-four hour day, and its regular use was eventually abandoned because its capacity was too small in comparison with the requirements of the plant in which it was installed and also because its scrubbing performance was not good enough to recover a sufiiciently large portion of the ammonia in the gas entering the saturator. With the saturator in its present form and operating at the high rate above mentioned, the ammonia recovery is practically complete. Owing to the much greater distances below the top surface level of the bath at which the gas was discharged into the bath liquor'in the original form of the saturator, the gas pumping energy required to move the gas through the saturator was more than twice as great per cubic foot of gas moved as is required in the use of the saturator in its present condition.

In the particular saturator shown in Figs. 1-4, the under-surface of the conical lip D of the mouthpiece D is inclined at an angle of thirteen degrees to the horizontal. With such inclination the maximum gas velocity in the gas space between the mouthpiece and the depressed bath liquor surface B is attained directly beneath the corner edge D The normal or average depth 1) of the portion of the gas space directly beneath the corner edge D depends upon the density of the gas, the density of the bath liquor, the length of the circumferentially extending corner edge D and the quantity rate of gas flow, and can be readily approximated by computation when those factors are known. In the above mentioned saturator operation at the rate of forty-four million cubic feet of gas per twenty-four hour day, the bath liquor density is about 1.3 that of water and the gas density is about 0.389 that of air, the gas space distance D is about two and three-tenths inches, and the average linear gas velocity directly beneath the corner edge D is about one hundred twenty-four feet per second.

In normal operation, the gas'space depth b and the linear. gas velocity directly beneath any one particular point along the length'of the'corner edge I) will vary as a result of bath liquor surging and wave movements. An annular outer portion of the surface B normally comprises wave crests l3 and alternating wave trough as-indicated in the right-hand portion of Fig.4; The wave crests B are the result of the wave or ripple create ing action of the gas moving through the gas space and the height of the wave crests B increases as the periphery of the surface 13 is approached. As is well known, only a gentle breeze, i. e., a wind velocity of a few miles an'hour, is requiredto maintain the surface of a small pond in a rippled condition. With operation at the rate mentioned above, the minimum gas velocity beneath the lip of the mouthpiece portion D is in excess of a mile a minute. Such a gas velocity is not only sufficient to maintain the subjacent portion of the surface B in a strongly rippled condition, but is sufiicient to subject the bath liquor to a substantial atomizing effect. Minute atomized acid particles or droplets swept off the ripply surface B b the high velocity gas steam will be dispersed into the gas stream in a manner insuring highly fiicient inter-action between the ammonia constituent of the gas and the acid constituent ofthe atomized bath liquor.

As a result of studies and tests made by me, I believe that the undersurface of the mouthpiece lip D or analogous gas space roof or top wall should incline downwardly toward the discharge end of the gas space generally as does the lip D As stated above, the inclination to the horizontal of the undersurface of the lip portion D shown in the drawings is thirteen degrees. I found by mypractical tests that this angle can be increased to fifteen degrees and can be decreased to four degrees without any radical effect on the general operation of the saturator. I found that above 15 the rippling and atomizing action necessary for the removal of the ammonia began to disappear; I found further by my tests that at an angle smaller than four degrees the bath liquor began to surge. This produces a pulsating gas outflow. Such flow pulsation reduces the effi- -ciency of the scrubbing action and is conducive to objectionable salt deposits on the underside of the mouthpiece lip.

While the exact form andcurvature of the intermediate portion D of the mouthpiece is not essential, I do consider it practically important that the curvature of the inner surface of the portion D should be such as to form a rounded orifice inlet along which the gas will flow smoothly instead of being displaced therefrom as a result of a vena contracta action. Such displacement increases the tendency to the formation of objectionable salt deposits on the mouthpiece.

The chart or diagram shown in Fig; 8 illustrates the results of experimental tests made by me to determine effects produced by variations in the velocity of air flow through an air space which in Vertical section, is shaped 1ike-the gas space beneath the left half of the mouthpiece D shown in Fig. 3. The. roof of the said gas space of the apparatus used in making said tests was equal in length or extent measured in the direction of air flow, to the radial extent of the lip portion of a mouthpiece shaped like the mouthpiece D shown in Fig. 3, and having internal and external diameters of three feet and six and a half feet, respectively. In said experimental tests the inclined portion of the gas space roof, corresponding to the conical lip portion .D of Fig. 3, was inclined at different angles. In Fig. 8, the abscissae indicate gas space roof wall inclinations in degrees, and the ordinates represent quantitative rates of air flow in cubic feet per minute through a section of the air space beneath the roof 'wall of the test apparatus havinga horizontal width 9 of one :inch measured in .a direction transverse to the direction of air flow.

In-zthe "tests illustrated in Fig. 8, a noticeable surging action was produced with, .and only with,

the relatively large rates of air flow and the relatively small inclination to the horizontal of the air space roof wall indicated by .points in the chart :area at the left of the line 8 of Fig. 8. Relatively deep or strong ripples were created on the waterv surface beneath the air spaces in the test apparatus with quantity rates of air flow and air space .roof inclinations indicated by points within the area at the left of the line 9 of Fig. 8. Relatively small but definitely noticeable ripples were created and maintained at the surface of the water beneath the air space in the test apparatus with quantity rates of .air flow and airspace top wall inclinations indicated by points within the chart area between the lines 9 and ID of Fig. 8. With quantity rates of ,gas flow and ai space roof inclinations indicated by points in the area at the right of the line H) of Fig. 8, no significant defiatomized liquor particles swept off the subjacent liquor and entrained by the gas. The ammonia still held in the gas passing away from the gas space beneath the mouthpiece is eliminated from the gas as the latter bubbles up through the bath liquor in which the mouthpiece lip is submerged. The effectiveness of the bubbling contact of the gas with the bath liquor may be augmented, and other advantages obtained by providing the mouthpiece lip adjacent its periphery with perforations such as the narrow radially extending slots D shown in Fig. 5. The upflow of gas through the perforations D increases the area of contact of the liquor with the gas bubbling through it and thus contributes to the efficiency of the total scrubbing action. The flow of gas from the gas space beneath the mouthpiece through the perforations D reducing the volume and velocity of the gas passing into the bath liquor at the periphery of the mouthpiece and thus reduces the tendency of the gas to pass into and through the liquor in the form of overly large globules or masses. Such large globules increase the tendency to objectionable surging and impairs the gas and liquor contact efficiency. Furthermore, the reduction in the volume of gas flow into the bath liquor at the periphery of the mouthpiece reduces the amount of entrained bath liquor carried out of the saturator by the gas into the acid catcher. The gas liquor so entrained includes sulphate crystals and subjects the acid catcher to an erosive action desirably avoided.

When the perforations D" are adjacent the mouthpiece periphery. as shown in Fig. 5, they do not significantly modify the scrubbing conditions in the gas space beneath the mouthpiece. Moreover, the provision of such perforations may well be accompanied by some increase in the diameter of the mouthpiece. In some cases, a mouthpiece may be provided with perforations'serving the purpose of the slots D by attaching an annular perforated peripheral extension to an imperforate mouthpiece body. The distributed discharge of the make-up acid by the pipe N into the liq o above the mouthpiece .lip, contributes to the effectiveness of the scrubbing action occurring as the gas bubbles up through the bath liquor, .and minimizes any tendency of the perforations D to fill 'up With'deposited sulphate.

In Fig. 6 I have illustrated diagrammatically the general form and proportions of a saturator of a compact and desirable design constructed and operated in accordance with the present invention, and having an operative capacity in excess of ninety million cubic feet of gas per twenty-four day, which is more than double the capacity of any saturator heretofore in use, of which I have knowledge. In the saturator design illustrated in Fig. 6, the .saturator tank body A .is circular in horizontal cross section and its inside diameter is twenty feet; the inside cracker pipe diameter is nine feet; and the maximum diameter of the cracker pipe mouthpiece DB is thirteen and a half feet. While I believe that generally satisfactory operation of the 'saturator shown in Fig. 6 will be obtainable with the angle of inclination of the underside of the conical lip of the mouthpiece DB, as great as fifteen degrees or as small as four degrees, I believe that the optimum angle will be about eight degrees if the rate of operation does not vary much from the normal capacity rate of ninety million cubic feet per twenty-four hour day.

- In Fig. 7, I have illustrated diagrammatically the use of a vertically disposed tubular element D which is coaxial with and beneath the mouthpiece and surrounds a rotating pump impeller P, such as has been frequently employed in saturaters producing large sulphate. crystals to create a bath liquor circulation to facilitate and augment the growth of sulphate crystals. The element O'shown in Fig. '7 differs from the tubular elements heretofore employed in association with an impeller like the impeller P to augmentand direct bath circulation, in that its internal diameter progressively increases as its upper end is approached. The diameter of the upper edges or rim portion of the member 0 is large enough and is located at a suitable distance below the mouthpiece, so that it serves as a baffie, checking and materially minimizing the bath liquor surging tendency.

Saturators constructed and operated in accordance with the present invention may take forms quite different from those already described. Thus, for example, the saturator shown in Figs. 9 and 10 comprises a, tank A shaped like that shown in Figs. 1 and .2 but having a cracker pipe element DD in the form of an elon a inverted trough. The element DD extends horizontally in the direction of the major axis of the elliptical tank A away from the tank wall at one end of said axis, and terminates short of the tank. wall adjacent the opposite end of said axis. The crown or upper side of the element is shown as well above the general level of B of the bath liquor, but the rim portion DD of the element is submerged. In vertical section transverse to its lower outer edge D the rim portion DD may be proportioned and inclined to the horizontal generally as is theconical lip portion D of the mouthpiece D of Figs. 1 and 3. As shown, the cracker pipe DD receives gas at one end through a suitable inlet in the vertical wall of the tank A from an external gas supply pipe ED, and the inclined rim portion DD extends circularly about the opposite end of the cracker pipe. At the side of the tank remote from the gas supply connection' ED the tank shown in Fig. 9 is provided 11 with an overflow outlet connection K associated with a tar separator J, as in the construction shown in Figs. 2 and 2a. 7

The tank saturator shown in Figs. 11 and 12 has a tank structure comprising a lower part AE circular in horizontal cross-section and having a hopper bottom, and comprising an upper circular part AF smaller in diameter and extending down into the upper portion of the part AE and coaxial with the latter. The lower portion of the tank part AF and the upper portion of the tank part AE form the opposite side walls of a gas inlet space CE, which as shown, extends about the Vertical axis of the saturator for considerably more than 180. The space CE is closed at its ends by vertical end walls C and is closed at its upper side or edge by a top wall C The gas treated is passed into the inlet space CE through a gas supply pipe EE, and the gas passing through the saturator leaves the latter through a discharge pipe FE.

A generally horizontal wall DE extends inwardly from the lower edge of the tank portion AF at the inner side of the gas inlet space CE and forms the roof of a scrubbing zone gas space. The scrubbing zone gas space extends about the vertical axis of the saturator alongside the gas inlet space CE and is in open communication at its outer edge with the space E, and receives gas from the space CE along the full length of the latter. The saturator shown in Figs. 11 and 12 is provided with an overflow outlet K discharging into a tar separator J which may be of the type and form shown in Fig. 2A. Liquor return pipes and steam-gas injection pipes, like the pipes L and MA shown in Figs. 1 and 2, may be employed to create a bath liquor circulation in each of the tanks shown in Fig. 9 and in Figs. 11 and 12. In the operation of any of the saturators shown it is practically desirable to continuously and rapidly remove the tar separating from the gas, since any considerable accumulation at the top of the bath interferes with the scrubbing action and tends to discolor the sulphate crystals formed. The use of means such as those formed by the pipes L and MA" for effecting a circulation of bath liquor adjacent to the top of the bath tends to expedite the removal of the tar as well as to augment the efficiency of the sulphate forming process. The regulation of the bath level efiected by the vertical adjustment of the weir K permits of a desirable regulation of the character of the circulation produced by the jets discharged through the pipes L and MA.

I have discovered that when the ammonia containing gas is discharged into the bath liquor at the relatively high quantity rate made readily possible by the hereinbefore described method of passing gas into scrubbing contact with the bath liquor, the tendency to the deposit of sulphate crystals on the Wall of the gas space above the bath liquor is substantially reduced. In consequence, the amount of wash liquid used in the general manner described in my prior application Serial No. 473,949, filed January 29, 1943, to pre-' vent such deposits, may be substantially smaller than when the rate at which gas is discharged into the bath liquor is at the lower rates. Thus, for example, heretofore customarily in the operation of the above mentioned saturator con structed as shown in Figs, 1-4, I have found that when gas is passed into the saturator at the rate of about forty-four million cubic feet of gas per twenty-four hour day, objectionable deposits of crystallized sulphate on the gas spacewall m y 12 be substantially avoided without using more than a relatively small fraction of the wash liquor needed to prevent such deposits when the same saturator is operated at the rate of twenty-two million cubic feet of gas per twenty-four hour day.

I believe that the operation of the saturator at the high rate mentioned minimizes or prevents sulphate crystal deposits on the gas space wall as a result of the relatively large amount of bath liquor splashed onto the gas space walls by the geyser-like stream of gas bubbling up through the bath liquor from the discharge edge of the scrubbing zone gas space. That gas flow is operative to maintain a body or mass 13 of bath liquor and gas above the discharge edge D of the cracker pipe mouthpiece DB which extends above the top level B of the unemulsified bath liquor generally as illustrated at the right-hand side of the mouthpiece DB shown in Fig. 6. The gas moving rapidly through and out of the emulsified liquor body 13, splashes liquor against the gas space wall at a rate appreciably in excess of the rate at which bath liquor adhering to the wall is evaporated by the gas flowing through the gas space. In consequence, a down moving film of bath liquor is maintained on the gas space wall which carries with it its sulphate crystal content of said film.

My observations of the operation of the above mentioned saturator shown in Figs. l-4, leads me to believe that the optimum practical advantage obtainable by splashing bath liquor onto the gas space wall in a saturator of the general types and forms illustrated, will ordinarily be obtained when the quantity rate of gas flow out of the scrubbing zone gas space and into the bath liquor, is in excess of twocubic feet, preferably about two and an eighth cubic feet, per second, per inch of length of the discharge edge of the roof above said gas space, i. e., the edge designated D in Fig. 4, D in Fig. 6, D in Figs. 9 and 10, and D in Fig. 12.

When the body B of bath liquor above the discharge edge of the scrubbing zone space is annular, as is the case when the cracker pipe mouthpiece of the forms shown in Figs. 4 and 6, for example, it tends to the maintenance of a top surface level of the non-emulsified bath liquor which is slightly higher at the outer side of the body 13* than at the inner side of said body. This variation in liquor surface levels at opposite sides of the body B of emulsified bath liquor above the discharge edge of the scrubbing zone gas space, can be substantially eliminated by suitably interrupting the continuity of the emulsified bath liquor body. Such interruption is obtained, for example with the construction shown in Figs. 11 and 12, in which bath liquor has an opportunity to flow into the space above the arc-shaped wall DE from the space between the ends DE of that wall. As will be readily apparent, the continuity of the body B shown in Fig. 7 could be similarly interrupted by thickening the outer end portions of some of the ribs D particularly if said thickened ribs be extended outward beyond the periphery of the mouthpiece lip as shown in Fig. 7.

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, it 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 13 forth in the appended claims, 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:

1. A saturator for producing ammonium sulphate comprising in combination an enclosed tank, an overflow outlet in the wall of said tank for establishing and maintaining the level of liquor therein, a crackerpipe having a lower vertical portion centrally disposed in said tank and having an outwardly downwardly flared mouth at its lower end, the rim of said flare mouth being at a level slightly below the overflow level and the flared portion having a downward slope from the crackerpipe toward the rim of from 4 130- 15 to the horizontal.

2. A saturator as claimed in claim 1 with the addition that slots are provided near the rim in the flared mouth of the crackerpipe.

3. In a process for producing ammonium sulfate which comprises passing ammonia-containing gas into contact with a bath liquor containing sulfuric acid, the improvement which consists in passing the gas beneath a surface which 14 slopes downwardly, from the point at which it is brought in, at an angle of 4 to 15 to the horizontal, the lower edge of said surface being below the normal liquid level, so that the liquid surface beneath the sloping surface is depressed and agitated by said gas, the rate of gas flow being in excess of two cubic feet per second per inch of length of the discharge edge of said surface.

CARL OTTO.

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

UNITED STATES PATENTS Number Name Date 1,986,900 Sperr Jan. 8, 1935 2,123,887 French July 19, 1938 1,012,273 Pennock et a1 Dec. 19, 1911 FOREIGN PATENTS Number Country Date 361,935 Breat Britain Nov. 23, 1931 648,540 Germany Aug. 3, 1937 272,601 Germany Apr. 4, 1914 657,439 Germany Mar, 4, 1938

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