US2471013A - Ammonia recovery in soda ash production - Google Patents

Description

J.. R. TAYLOR AMMONIA RECOVERY IN SODA 'ASH RODUCTION Filed Jun 17; 1944- /nuen'rs J RJ12/7 I d@ fil-borne?.

May 24, 1949.

`column, say .80

Patented May 24, 1949 'AMMONIA .RECOVERY IN iSLODA-ASH PRODUCTION John Ross Taylor, Westmount, Quebec, Canada, assignor .to `Richard Kellogg 'Wurtcle,odericlx Ontario, Canada Application J une 17, 1944, SerialfNo. ,540,184

-in Canada Juney 24, 1943 l Claim. i1 This invention relates ,to kthe vproduction of soda ash 'and .',Darticijilarly directed to -that portion "DI .the mdtlfiillnfd apparatus in which ammonia is 'recovered from ,the carbonated liquor from which Asodium bicazbonate has been removed,

vwhich constitutes one stage :in the well known Production of soda'osh Ammonialis a relatively `expensive reagent in the production of ,soda ash. Its eihcient recovery is thus ,an important consideration. In standard practice the ammoniastill or distiller is a tall f eet .h igh, consisting of a series oicast iron Qsectionsi'to feet in diameter. Heat is introducediatthebottomof the column. Scale formation :creates a ,problem necessitating periodical .cleaningof the column. To reduce sedimentation -and scale formation, sand traps are usually employed .tolclnove larger solid particles from theprelimed'liquor. Installation and operating costs arehigh.

The object ofthe present invention is to reiduce greatly the installation and operating costs of the ammonia recovery system. More particularly the object-is to provide a :method and apparatus for the recovery of ammonia which is more economical in installation as lwell as operating costs, and which substantially eliminates sedimentation fand scale vformation, thus permitting more continuity and-eiciency of operation.

lOther kobjects -will appear from the following descriptlonuwith reference L-to the accompanying dr-awingfinffwhich Figure 1 is a ksideelevatinm, partly in section of the distiller unit, and

Figure 2 is an end elevation, also partly in section, of the unit.

In the drawing, I is a chamber having lirebrick or other walls 2. Horizontally disposed within the chamber is a plurality of closed tubular members 3 connected in series and preferably one below the other for gravity flow. Within each tubular member an agitator 4 of the screw conveyor type extends from the inlet end to the discharge outlet and is driven by any suitable means 5. At the discharge end of the tube the blades of the screw conveyor are attened longitudinally to provide a discharging portion 4. The discharge outlet consists of an opening B in the wall of the tube so arranged that the screw conveyor discharges the liquor over its lower lip 1 into a conduit 8 through which the liquor falls directly into the inlet end of the next tube of the series without substantial contact with the wall thereof to prevent scale formation therein. The conduit 8 discharges directly into a zone of the preliming .chamber no succeeding' .cylinder-'of the screw conveyor. Therme t ,sh

wh; iohe is used., or from .other source ;of11'.1te.1,`liui1or and lime, and iisoharees liouor irri. the "initial ,cylinder of :the uhu. .Ammonia and water vapour 'liberated in each tubular ,member are .Withdrawn through pipe 11:0 and maybe ioohveyedzthroueh'smaniiold Il to the normal reugtower, ,.notfshown. 4l2 .is Ya dischargeoutlet @from ,the'last tube of the series. The ,chamber 'i .is preferably 'hesiod vby waste heat irom-`boiler 'orgcalciner wflue gases, vbut may ,he heatedloy .direct foil, ,ses or rooal irihg es desired, and e "substantially .Constant temperature is maintained .about Leash of the progressive ammonia distiilihs Leibes Jin the 'unit-V '.In operetiohthe:usuel'pielimed'iidiior,.or liquor and lime, Vis mfed 'into'thei initial 'jtube of the series andis continuously Y conveyed under constant iagitation 'through "the shooeisisive "tubes 'to liberate progressively' 'ammonia .unidertheinfhlenoe of the heatto which each'tube is subjected. The consieht eeitetionby"ih espirel :Conveyors eliminates sedimentation and ,makes :sshd :traps or the .like unnecessary. "It also. Levoiiisssoaleiiormetionand thus .eliminates the A,heeessiiv for the :frequent cleaning -operations: reqiiire'd in y'the usual system.

ine of 'theisendtr-aesrin standard practice- The agitation .constantly 'ehposeshew siiiieees .of {liouor tothe :heetedwells Lof the tubes and `Causes more rapid 'liberation "of ammonia. Since each distillation tube is heated, rapid elimination of ammonia is effected inthe initial tubes and little ammonia is left for liberation in the nal tube of the series. This eliminates loss of ammonia in the effluent discharged through pipe I2. It will be observed that because of the location of the discharge outlet S and lip 1 each heated distiller tube contains a substantial body of liquor to absorb heat from the surrounding chamber. Thus an effective distillation temperature is maintained during the passage of the liquor through each tube.

The external heating of the distiller tubes avoids dilution of the liquor as when the latter is heated by injected steam in standard practice. This gives a discharge liquor having a higher concentration of calcium chloride and the latter may be more economically recovered. The tubes may be steam jacketed and thus avoid the use of the chamber l. By thus heating the tubes the temperature of the respective tubes may be readily varied for most eilicient liberation of the am- 3 monia. The external heating of each tube at a regulated temperature permits a more rapid rate of feed of the liquor and thus increases the cap acity of the distiller.

Hot milk of lime from the hydrator and hot liquor from the reux tower may be fed directly to the distiller, thus eliminating the usual lime settling tank and prelimer with the attendant complications. This makes use of the heat of the milk of lime. Furthermore, the hydrator may be eliminated by feeding crushed quicklime directly into the distiller with the hot liquor from the reux tower to utilize fully the heat of hydration of the lime and thus reduce still further the amount of external heat supply required. The continuous agitation of the screw conveyors in the distiller tubes makes this possible.

Owing to its construction the distiller unit may be operated under an internal partial vacuum and thus further reduce the amount of heat required to distill the ammonia. The reduced pressure within the distiller unit may be produced by use of the ejectors in the absorber unit as disclosed in copending application No. 540,786, now Patent No. 2,446,442, issued August 3, 1948.

When yoperations are adjusted to most efcient conditions of temperature and rate of flow, they may be maintained constant over long periods because of the elimination of sedimentation, scale and the like which, in the usual system, require periodical shut-down for cleaning, and the maintenance of auxiliary equipment. In the standard system the distiller acts as a bubbling cap plate still with its constant refluxing and varying plate concentrations. In the present system there is no reuxing in the distiller since the ammonia vapours are removed from each distiller tube and the concentration is effected entirely in the reux tower. This insures easy recovery of the ammonia with reduced loss in the effluent and, at the same time, requires a minimum of control during continuous operation.

It will be observed that the distiller unit of the invention may be made of ordinary pipe or plate and is thus much cheaper in construction than the standard distiller unit now in use.

The method and apparatus as specifically described with reference to the recovery of ammonia from the carbonated liquor in soda ash production may also be used for purifying and concentrating the waste distiller liquor. When such liquor is passed through the distiller unit lime and sodium chloride will precipitate out 4 leaving a concentrated calcium chloride brine. The precipitated solids being carried through the distiller tubes are removed from the concentrated calcium chloride solution.

It will also be apparent that the invention may be employed in any art where concentration of solutions is required and particularly in the presence of precipitating solids. For example, in the production of salt, sugar and the like where continuous operation on large volumes of solutions is involved.

It is to be understood that various changes may be made without departing from the spirit and scope of the invention as dened in the following claim.

I claim:

In the production of soda ash, the method of recovering ammonia from filter liquor which comprises maintaining a series of separate bodies of predetermined xed depth of liquor and lime, continuously feeding a supply of fresh liquor and lime to the rst body only of said series, continuously discharging a portion of the last body in the series, continuously withdrawing by gravity flow a portion of the first and intermediate bodies and feeding each withdrawn portion to the next body in the series, separately agitating and sweeping each body to prevent sedimentation therein and to discharge solids with the liquor in each said withdrawn portion, continuously subjecting all of said bodies to a common heating medium maintained free of contact with the bodies, maintaining each of said bodies free from contact with external gases to prevent dilution therewith of the liquor and ammonia vapors arising from said bodies, and separately removing said ammonia vapors from each body as it is liberated therefrom.

JOHN ROSS TAYLOR.

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

UNITED STATES PATENTS Number Name Date 363,952 Frasch May 31, 1887 458,798 Stroh et al Sept. 1, 1891 658,723 Naef Sept. 25, 1900 689,768 Wathen Dec. 24, 1901 1,604,523 Barnhart Oct. 26, 1926 1,650,713 Hennebutte Nov. 29, 1927 2,174,008 Mow Sept. 26, 1939

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