US1089109A - Method of calcining alunite. - Google Patents

Description

H. F. GH'APPELL. METHOD 0F GALCINING ALUNITB.

Patented Mar. y3, 1914.

3 SHEETS-SHEET 1.

@rfi- H.' F. CHAPPELL.

METHOD 0F GALGINING ALUNITE. APPLICATION FILED MAY s, 191s.

l @BQ @9m Patented Mar. 3, 1914;.l

a' SHEETS-SHEET z.

Le W df n. I. CHAIPELL. METHOD 0I' GALGINING ALUNITE. APPLICATION FILED In 3,1913.

Patented Mar. 3

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Losanna, i

To olif 'whom tt may concern.'

Be it ltnown that Lllowsan Cuarenta, a citizen of the United Sta-tes, residing in the borough ot Manhattan, city, county, and State of New York, have'invented certainy new and useful Improvements in lllethods of Calcining Alunite; and l do hereby declare the following to be a full, clear, and. enact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

Prior to the present invention, it has been customary to calcine alunite in 'heaps in the open air, or in kilns similar to those used tor calcining lime, permitting the gases given oft1 from the alunite to mix freely with the products from the combustionot the fuel. Thus, in the kiln method of calentire mass, together with the products of combustion of the t'uel employed, aredischarged from the top of the kiln in a. state This mixed volume of gases contains not only the sulfurous and suliuric acids and their anhydride, but also the tire gases and the watery vapors incident to the driving od of the moisture and water ot composition, of the alunite. llt is extremely dilicult, under these circumstances to absorb and render innocuous the sulfur gases, and it is not practicable to recover the sul-- furie anhydrid in the form oit turning acidu Aside from these dilhculties and disadvantages attendant upon the disposition of the sulfur gases, the calcining operation itself, as heretofore practised, has been lacking in uniformity of product, `certainty as to the time factor involved, economy of t'uel, and regularity of progression.

l have discoveredthat the calcining operation can be carried on to very great advantage over the former practice, ii conducted in two stages, and also, when so divided into 'two stages, that the sulfurous and sulfuric acids and their anhydrids can be readily and economically recovered, the sulfuric anhydrid being recoverable in part by condensation and in part by absorption. The proportion of sulfurous anhydrid with respect to the sulfuric anhydrid and sul furie acid evolved from the charge is also capable ofibeing diminished, as will hereinafter more fully appear.

ln the first stage ot the calcining operation, the alunite is calcined in direct contact with the fuel gases, the fresh 'charge being Specification of Letters Patent. Application lefl Hay Si, 35913;

to be transferred is about 600 lli f ris Aand until. l :evolution of sulfur fumes.

calcining operation are drawn ed' trom the water vapor given oil from the l the hrst stage.

`tion is, 'retort or mame and by heat appliedfioni Eljatented llllar, @,illllla Serial 1t o. ?'S6,'269.

retained in the furnace area in which the tiret stage oli' the operation is proceediz. until fumes of sulfuric acid just benin 'l bei perceptible the enit L 1. time, tlieteripera ure at that part initial portion elf' the charge which is r partly calcined alunite is then' transterrcd into a retort or rnutliegwhere it is heated out et contact with the lire gases, from the temperalture o: about 600 C. with which it enters the retort to trom 900 C. to 1,000O C., such time as there 1s no further The completely calcined alunite will be found te have practically all of the alumina insoluble in water Iand practically all of the sulfate oi potasl cining, all the gases evolved throughout the potash present as rlhe gases ibom the second stage of the separately gases of the first stage of the calcining operation and are devoid of ad- -mirture with the tire gases or with the charge of The second stage of the calcining opera as above indicated, conducted in a Without, thatis to say,`by heat transinitt through the Walls .of the muilie from dre gases. ln. order to more etlectual'ly tribute the heat throughout the retor mutlle, lf admit a regulated quant-ity ot and, in order to saine time to partly cool the fully calcined portion of the charge prio-r to its exit from the retort, l first pass the air through that portion of the charge which has been `fully calcined and is about to be discharged from the Inutile. This not only preheats the air and partially cools the calcined ore, but

preheat tie air and at the it also eects an economy in fuel because it causes a more intimate distribution of the heat throughout the entire body otY the charge undergoing calcination. When it is desired to produce a weaker acid than fuming. sulfuric acid, a regulated aiount ot' steam, preferably' preheated, and in the same manner ,as the air, is introduced into the Inutile; or, by admittir,` regulated quantities of both air and steam, acid of intermediate strength can be obtained. llhen it is desired tou-make filming acid, steam is excluded. 'llhe sulfuric acid and SO., are recovered by condensation or'by condensation -and absorption, and the 80 free from the 'presence of moisture, is particularly' adapted for the making of sulfuric acid by the Contact process. In any case, the quantity of sulfurous anhydrid present in the gases drawn o from the second stage-of the caland sulfuric acid.

In the accompanying drawings, I have illustrated a furnace adapted for the practice of the invention upon al considerable commercial scale.

Figure 1 represents a longitudinal sectional view of such a furnace partly broken away midway of its length, so as to accommodate the view to the scale upon which the drawing is made; Fig. 2- represents a vertical transverse section thereof; Fig. 3 represents a horizontal transverse section and partial plan view; Figs, and 5 represent, respec tively, views takenrat right angles to each other and illustrating the discharge end of one of the upright muftles.

Similar letters of reference indicate similar parts throughout the several views.

Referring to the drawings A indicates a bench or fire chamber withinwhich are located a series of upright retorts or muliles a, whichmay, conveniently, be twelve in number, as indicated in Fig. 3. rlfhese retorts are similar to those used for the gasification of coal, and they may conveniently-be heated from three producers B, having flues b which discharge below the lowermost bench oor C. The bench is provided with a series of' such floors, one above the other, with an intervening space, and these floors are provided with appropriate openings so as to give the gases a'zig-zagcourse in rising through the tire chamber.- This is readily effected, for instance, by permitting the gases to rise through openings near the side walls ofthe fire chamber in alternate oors and through middle openings in the intermediate floors, as indicated by the arrows in Fig. 2. The floors, as shown, may be readily supported upon projections `on the outer sides of the retorts and like projections from the inner side walls of the fire chamber. At their upper ends, thc retorts a. open into perpendicular shafts Z of the same interior cross-sectional dimensions as the retort and of approximately the same length. It will be further noted that the re gases which have been used .for heating the retorts or muilies, likewise enter the perpendicular shafts (l referred to, and pass from their oints of entrance at the bottoml of the shafts d upward through the charge contained thef'ein finally making their exit through the exit. chimneys or flues e. These lues e are provided with regulatingdam# be automatically governed lgers f adapted to y any l.suitable intermediate mechanism, 1f

desired, from a pyrometer g. I have merely cining operation. tends to considerable diminution relatively to the sulfuric anhydridis inclined laterally,

Adrawn by, a Vpump F, or otherwise.A

.thus supplementin the-h at illustrated the intermediate mechanism diagranjlmatically, inasmuch as available constructions for this purpose are well known and 'do not require specific illustration and description.

The shafts d are adapted to be charged from suitable hoppers h having regulatlng gates Il. as shown, and the hoppers may be charged conveniently from suitable elevators or otherwise.

It is likewise convenient and desirable to have a single hopper feed a number of retorts, as indicated, for instance, in Fig. 1. To facilitate the draft, the exit flues e may be provided with an exhaust fan (not shown).

Each of the retorts discharges at its bottom into a water-jacketed casing 2', which may be made up of two sections as shown more fully in Figs. 4 and 5, having a water inlet at a" and a water exit at 2, the sections being connected by a communicating pipe 2. These water cooled casings serve to regulate the temperature of the calcined product on its way to the discharge chute C, which so as to sustain the main thereby appropriately that would otherwise discharge gate j. Be-

weight of the charge, relieving the weight be imposed upon the low the discharge gate j is located a swinging weighted valve la, Whose function 1s to prevent steam generated4 from the calcined product as it falls into the waterrecept-acle D- from entering the bottom of the retorts. The receptacle 4.D is provided with an inclined bottom and a water level is maintained, as indicated, with a suitable overflow pipe Z leadingy into a tank E from which the material collected can be with- An elevating screw conveyer Gr lifts the quenched calcined product and discharges'it intoV a suitable receptacle. Each of the waterjacketed casings isprovided with a tube p through which suitable test samples may be withdrawn from time to time, if desired.

At the bottom of each of the casings into which the retorts are dischargedl are located two pipes, one of which as m serves for the admission of air and the other, as n, serves 1for the admission of steam, both of these pipes being provided/with regulating valves so as to'permit the air .fand steam to be admitted in regulated amount. The air or A cined -alunite and become 'highly preheated before 'entering the reto t proper,`thereby iea-t `of the calcined ior of the retorts, imparted from without by the re gases. Furthermore, the upward passage of the air or steam, as the case may be, facilitates the removal of steam passes through` tleconipletely calmaking available the alunite foruse in the inte :the gases from the retorts and greatly decreases the fuel consumption.

Immediately above lthe tops of the repurpose of removing the and on opposite sides' of Losanna the retorts. inmediately the -retorts,giu: 1smuch `as the air orV other aeriform fluidthus admitted, acts as a bar- 'rier to the downliow into the retorts a of the tire gases, as is indicated by the arrows in F ig. 2, and this is edected Without in any Way interfering with the through the stacks d.

lt is important that thecombustion cham- Vbei' between the fire boxes or generators Bv and the retort-chamber should be sufficiently large to permitof practically complete combustion of the furnace gases before they enter the retort chamber Furthermore, the distribution of the gases on their circuitous course through the horizontal dues should be vcapable of regulation', as,for instance, by

Y fire-tile slides s whiclr-are capable of being gases Vin the bottoni of the shafts sampling tubes operated from the exterior of the furnace so as 'to regulate the ,edective size of the openings and to direct the gases in the desired direction, as isthe practice in the gasifyiugvof coal in vertical retorts heated by horizontal dues. The temperature of the the retort-heating chamber or bench should be approximately 1500o C., and the tire gases should leave the chamber and enter the bottom of the shafts dat about O C.

' `he alunite to be calcined is screened to a'convenient size, say one inch mesh. Any large amount of dust or fines should be re moved. and passes fl. ln starting the furnace, it is preferable to have each retort and shaft filled with ore that has previously been completely calcined.

rllhe products of combustion from the generators B should then be admitted into the retort-chamber and the temperature raised gradually until, as hereinbefore indicated, the temperature of the gases entering the shafts al is not less than 750o C. and those entering the retortchamber at the bottoln thereof not less than 1500D C. After these temperatureshave continued for about one hour,-and when the lower end of the vertical center of the charge of the retorts is not less than 900 (l, the au tomatic rotating gatesj are started. The ro tation' of the gates is continued until a sample of the alunite removed. through the 7) at the bottom of the yretorts liustshows a faint trace of soluble alumina.

The number of revolutions of the said automatic discharge gate should then be `very are used to admi't'air or other y proper updraft' .lhe ore is then fed into the hoppers therefrom into the upper end of restrict myself thereto, inasmuch as, in some instances, retorts or inutiles other than those of the upright or vertical type may be used to advantage."- It will also be iuiderstood that in using the expression retort or muftle, throughout it in the generic sense, that is to say, as including Aa calciningl chamber wherein `the alunite is undergoing calcinatiou and Whose walls are heated externally by the lire gases.

The recovery ofthe sulfuric acid from the retorts or muliies is effected, as hereinbefore indicated, by 'withdrawing the gases through the exit pipes H, or the like, provided for the purpose, this Withdrawal be ing effected by any suitable exhaust (not shown), familiar to the art. They are first, preferably, received in a suitable condenser or condenser-s wherein the sulfuric acid and SU, are recovered by condensation, or by condensation assisted by absorption, andthe "SO2 is converted into sulfuric acid either by the lead chamber process or by the contact process, as the case may be. ln fact, the particular manner of recovering the gases available as sulfuric acid may be appropriately varied to accommodate itself to the particular choice of the operator, the local market conditions, freight facilities, and the like, the process being sufficiently licxible to fpermitthe necessary selection in this regard.

Having thus described my invention what l claim is:

l. The method of calcining alunite, which comprises dividing the calcining operation into two stages, in the first of which the alunite is traversed by furnace gases, and in the-second of which the partly calcined alunite is heated frdm without, carrying olf separately the gases evolved from the second stage of the `calciiiing operation and recovering sulfuric acid therefrom; substantially yas described.

2. The method of calciniug alunite, which comprises dividing the calciniug operation into two stages, in the first of whichl the op eration is conducted at a tinal temperature of about G00O C., and in the second of which the calcining operation is completed at a final temperature ranging from 900o C. t0 1000o C., and carrying off separately the gases evolved in the second stage of the calcining operation and recovering sulfuric acid therefrom; substantially as described.

3. The method of calcining alunite, which comprises dividing the calcining operation the specification, l use L' lli into two stages, the partly calcined product from the first stage being progressively supplied to take the place of the f-ully calcined product withdrawn from the second stage, and the gases evolved from the second stage of the operation being carried off separately from those evolved in the first stage thereof; substantially as described.

4. The method of calcining alunite, which comprises dividing the calclning operation into two stages, in the first stage of which the alunite is traversed by furnace gases and in the second of which the partly calcined product from the first stage 1s heated from without, the gases evolved from the second stage being carried off separately from those evolved in the first stage; substantially as described.

5. The method of calcining alunite, which comprises subjecting an u rlght column of alunite to calcination, by fire gases applied externally to the lower portion of the column and admitted internally into the upper part of the column, thereby dividing the calcining operation into two stages, and carrying off separately gases evolved from the lower portion of the column; substantially as described.

6. The method of calcining alunite, which comprises subjecting an upright column of alunite to calcinaton, by fire gases applied externally tothe lower portion of the column and' admitted internally into the upper part of the column, thereby dividing the calcining operation into two stages, maintaining a dra-ft for the fire gases through the upper part of the column, drawing off separately gases from the lower part of the column, and substantially neutralizing any tendency for the fire gases to enter the lower part of the column by introducing belowthe point of entrance of the fire gases into the upper portion of the column an aeriform fluid under pressure; substantially as described.

7. The method of calcining alunite with the recovery of the sulfuric acid therefrom, which comprises dividing the calcining operation into two stages, in the first of which the moisture and the writer of composition are substantially ex lled from the alunite, and in the second 0 which the sulfuric anhydrid and the sulfuric acid evolved is recovered b condensation and absorption; substantia ly as described.

8. Thel method of calcining alunite with the recovery of sulfuric acld therefrom, which comprises dividing the calcining operation into two stages, in the first of which the moisture and the water of composition are substantially expelled from the alunite,

and in the second stage of which steam is admitted in such proportion as to convert a large part of the sulfurous anhydrid and sulfuric anhydrid into sulfuric acid and recoverin the remainder of sulfuric anhydrid by con ensation and absorption; substantially as described. l

9. The method of calcining alunite with the recovery of-sulfuric anhydrid and sulfuric acid, which comprises dividing the calcining operation into two stages, in the first of which the moisture and the water of composition rare substantially expelled from the alunite, and in the second of which air is admitted in regulated quantity, and recovering the sulfuric anhydrid and acid by condensation and absorption; substantially as described.

10. The method of calcining alunite with the recovery of sulfuric anhydrid and sulfurie acid, which consists in dividing the calcining operation into two stages, in the first of which the.moisture and water of composition are substantially expelled from the alunite, and in the second of which steam and air are admitted in regulated quantity, and recovering the resulting sulfuric acid and the remnant sulfuric anhydrid by condensation and absorption; substantially as described.

In testimony whereof I aix my signature, in presence of two witnesses.

HOWARD F. CHAPPELL.. Witnesses z l MARTIN M. BRASSEE, WALTER MANAssE.

Copies of this patent may be obtained for ve cents each, by addressing the Commissioner o! Patents, Washington, D. C.

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