US1695558A - Process for the production of phosphoric acid - Google Patents

Description

Dec. 18, 1928.-

A. NOBLE PROCESS FOR THE PRODUCTION OF PHOSPHORIC ACID Filed Feb. 29, 1924 Patented Dec. 18, 1928.-

UNITED siufres` 1,695,558 PATENT oFFicE.

ALBERT NOBLE, OF ANNISTON, ALABAMA, ASSIGNOR TO FEDERAL PHOSPHORUS COMPANY, OF BIRMINGHAM, ALABAMA, A CORPORATION OF ALABAMA.

PROCESS FOR THE PRODUCTION OF PI-IOSPHORIC ACID.

Application filed February 29, 1924. `Serial N'o. 695,945.

This invention relates to the smelting of phosphatic material and more particularly, but not exclusively, t0 the manufacture of phosphoric acid; and comprises a method wherein a cliaige composed, for example, of phosphaterock, carbon, and silica or a silicate, is heated by the combustion of powdered coal, fuel oil, natural or producer gas, at sufficient temperature to cause the phosphorus to beI eliminated from the molten slag and subsequently oxidized and collecti ed, the heat from the oxidation of the gases being utilized tov preheat the air for conibustion and oxidation.

The object of this invention is to provide for the treatment in fuel heated furnaces of. phosphatic material and especially low grade phosphate rock whereby phosphoric acid may be economically produced, in a manner not heretofore possible;

In Order'that my invention may be fully understood, and clearly differentiated from the prior art, the following' description is given, whereby those skilledin the art'may practice my invention.

I proposeto combine With a hearth upon Which the charge is smelted an overhead stack of substantially less width than the hearth, through which the charge descends to the hearth and is there subjected on one sideto the action of an impinging flame or flames which smelt it, causing .its evolved gases to pass from the other side of the charge to a combustion chamber to which air is admitted by which they are completely oxidized, the air being preferably caused to flow down the stack through the charge. It is an important step in my invention that the intense heat of oxidation of the evolved gases is largely saved and economically utilized by its transfer to the air supplied to the furnace for the purposes of combustion or oxidation orboth, but yespecially for oxidation as this air can he caused to flow slowly down through the dc'- sceiiding charge in the stack in such manner as to transfer its heat to the charge in the most efficient manner and to prelieat the L latter and thus proportionately reduce the fuel required to smelt it. Obviously, the preheating of the air of combustion Will also conserve fuel and increase the temperature of the impinging flames."

My invention lcontemplates the employ- .deep penetration'of the flames. lsinelting, therefore, results from the imping- 'ing and enveloping flame principally on one nient of a flame or flames in the heating chamber at one side of the hearth which play over the stock pile resting on the hearth, impinging` against it and flowing freely over its spreading base towards the combustion or oxidizing chamber at the other Side of the hearth, causing the principal fusion zone to extend about the side of the stock pile adjacent to the flame. This results in sealing with the fusing stock the pile against the A surface side and the smelting stock seals that side so that air of oxidation flowing down through the stack will pass out therefrom through the stock only on the sidetowards` the combustion chamber. In this Way I maintain the reducing atmosphere desirable Iin the heating chamber and supply the necessary air in the most effective Way-to the oxidizing chamber, This gives a free flow of air through the charge in the'feedin stack and permits its uniform escape into t e oxidizing compartment. Moreover the down. flow of air through the stock causes the dust to be filtered out of it, as the smaller particles melt quicker than the larger pieces of stock and will adhere to the latter and thus will not tend to become entrained with the air.

I have found that it is an advantage to have the preheated air enter the furnace' along` with and in the saine direction as the 'descending stock, as I thereby -avoid the tendency of the charge to scaffold or adhere to the side walls of the feed stack. If the evolved gases pass up through the feed stack, these highly heated gases, given sufficient. airv for combustion, will sinter the charge and cause it to stick to the side Walls of the stack. I have also found that by burning the evolved gases near the surface ofthe charge on the hearth, there is an improvement in the smelting efficiency in that the heat is reflected to the surface of the melting charge.

Ifit is desirable to do so, feldspar, shale, or other potash bearing silicates may be used as a substitute for sand. In such cases,'the potash is driven off and ma be collected along with the phosphoricacid fume. The silica of combustion in the silicate reacts with the lime in the phosphate rockand isremoved from the furnace in a. manner simiy of the component materials.

CaaPZOsJfBsiO2e+=5C=eCasio3+2P+5Go. The mixture is based on chemical analysis Additional coke is added to the mixture, equivalent tol i approximately in excess of that necesinto tlle Vfeed stack 1.

sary for the above equation, because it has been found that a certain portion is always burned away bythe air and some is carried olf entrained in the gases; hence the necessity for additional coke.

As illustrative of a typical ap aratus elnbodying the essential elements or carrying out in the preferred manner the operation of my process, reference is made to the fol-" "lovgng drawing, in which ed stack 1, superimposed on a heating chamber 2, is shown, having burners 3 and a tap hole 4. The mixture of phosphatic material, `coke and silica is introduced through a charging door4 5iills the feed st'ack 1 and rests on a hearth 6, Where theilame from burners 3 plays on it. Pren heated air is introduced through an inlet 7, and Aafter passing downward with the stock, combines with the evolved phosphorus and carbon monoxide at the surface of the stock 8. The 'products of combustionV from the fuel burners and evolved gases commingle in the chamber 9 and ass out into a heat interchange 10 whic is conventionally illustrated. Air is drawn through ports 11, and after passing through the heat interchange, is forced by a fan 12 After the heat has been -absorbed from the phosphoric acid bearing gases, they are drawn away by a fan 13 and forced into the header of an electrical precipitator 14 which comprises pipes 15, in-

sulated wires 16, a source of current 17, a

round connection 18, and an acid receiving asin 19.`

. I prefer conducting my process in this apparatus in the following manner A normal charging mixture may consist of 1500 lbs. phosphatefrock, analyzing 15% 1 phosporus, 350 lbs. sand and 357 lbs. coke,

includingthe excess required to make up losses. There will be variations from these I proportions, depending on the analysis of the component materials. This mixture is introduced through the charging door 5 until the` charge il s up that portion of the 'feed' stack connecting with the heating.

have been in operation a short time, the heat begins to decompose the pliosphatic material, principally on the burner side of the stock pile 8 when phosphorus fume and carbon monoxide will be evolved. These ga'ses are burned principally at the surface of.the other side of the stock pile 8 and supply heat through the interchanger to raise the temperature of the combustion of the evolved gases. When the gases are being evolved at a uniform rate the feed stack is filled to air inlet 7. As the slag collects on the hearth it is kept iri a molten condition by the flame iml'iinging on and cnveloping or encircling the stock on the hearth 6, so that periodically this slag may be tapped as is practiced in an slagging furnace operation. The phosphoric acid produced may be collected in the electrical precipitator as shown, or in any `satisfactory collecting equipment as an absorption tower or condenser.

Though I have described with great particularity the details of the embodiment of the invention herein shown, it is not to be construed that I am limited thereto, as

changes in arrangement and substitution of equivalents may be made by those skilled inthe art Without departing from the invention as defined in the appended claims.

I do not claim herein the apparatus, as this application, because of divisionalrequirements, is limited to the process hereinbefore described.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is

1. A process for the manufacture of phosphoric acid, which consists in charging a mixture of phos hate rock, silica and carbon into a fee stack disposed over the hearth of a heating chamber, impinging a flame on the charge in the heating chamber, passing air downwardly through the feed stack, oxidizing the evolved gases during their sojourn in the heating chamber, transferring heat from the gases to for combustion of the fuel, an collecting the oxidized phos horus compounds.

2. A process or the manufacture of phosphoric acid, which consists in charging a mixture of hosphate rock, silica and carbon into a. eed stack disposed over the hearth of a heating chamber, impingingea flame on the charge inthe heatin cham passing air downwardly throng the feed stack, oxidizing the evolved gases during their sojourn in the heating chamber, transferring heat from the gases to reheat air for combutsion of the fuel and or the oxidization of the gases, and collecting the oxidized phosphorus compounds.

3. A process forA the'manufacture of phosphoric acid, whichA consists in charging a mixture of phosphate rock, silica and carreheat air memes hon into a feed stach dispesed over the hearth of a heating chamber, impinging a lame on one side only of the charge in the heating chamber, passing air downwardly through the feed stack, oxidizing the evolved gases ,during their sojourn in'the heating chamber, transferring heat from the gases to preheat air for combustion of the fuel, and collecting the oxidized phosphorus compounds.

4. A process for the manufacture of phosphoric acid, whicl1 consists in charging a mixture of phosphate'rock, silica and carbon through a feed stack onto a hearth, irnpinging a flame on the surface of thecharge on thehearth, passing preheated air down- 5. A process for the manufacture of phos-` phoric acid, which consists in charging a mixture of phosphate rock, silica and carhonthrough a feed stack onto a hearth, impingingv a flame on one side of the surface of the charge resting on the hearth, admitting air to the gases on the other side of the charge for oxidation, and collectingthe oxidized phosphorus compounds.

In tcstimf'my Whereof alhx my signature.

' ALBERT NBLE.

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