US1162944A - Process of making phosphate fertilizers. - Google Patents

Description

S. B. NEWBERRY & H. N. BARRETT.

PROCESS OF MAKING PHOSPHATE FERTIL|ZERS..

APPLICATION FILED NOV. 4. 1912.

1,162,944. Patented Dec. 7, 19k").

invented a certain SPENCER B. 'NEWBERRY AND HARVEY N.

BARRETT, or BAYBRIDGE, oHIo.

PROCESS OF MAKING PHOSPHATE FERTILIZERS.

Appliciihn filed November 4, 1912. Serial N 6. 729,299.

To all whom it may concern:

Be it known that we, SPENCER B- NEW- BERRY and HARVEY N. BARRETT, citizens of the United States, residing at Baybridge, in the county of Erie new and useful Improvement in Processes of Making Phosphate Fertilizers, of which the following is a specification. s.

This invention relates to improvements in the process of rendering natural phosphates available for use as fertilizers.

The particular apparatus whereby the invention can be carried out is illustrated in the accompanying drawings, in which Figure 1 is a side elevation of the kiln and Fig. 2 is a section on line 2-2 of Fig. 1.

The kiln A rests upon rollers B B and is revolved by gearingnot shown in the drawing. It is heated internally by a flame or flames of coal-dust, oil or gas, blown in with air through G. The phosphate mixture is introduced into the space I, in which, if wet, it is rapidly dried by the hot gases and by contact with the hot lining. The dried mixture passes down the kiln, being lifted and turned over by the shelves F F, and is kept from reaching too' high temperature by radiation of heat through the lining E. Between the drying zone I and the middle point of the kiln the mixture is exposed to moderate temperature, and from the middle point to the lower end of the shelves it is subjected to the highest heat. The calcined product is discharged through the hood H into the cylinder C, in which it is (:(ioled by air drawn in by the draft of the st-ac In order that the process may be fully understood, we will describe it more or less in detail, and particularly set forth those details of operation which, when closely followed, are likely to give the best and most economical results, having reference to the process of calcination of I the addition of a small percentage of reagents, as for example, alkalis or alkalimetal salts. These details of operation are as follows:

1. The conversion to citrate-soluble con- Specification of Letters Patent.

and State of Ohio, have phosphates with Patented Dec. 7, 1915.

dition is brought about by exposure of the phosphate to sufficiently prolonged and intimate contact with a rapid current of highly heated gases. this intimate contact it is most important that the material treated shall be in a porous and cellular condition, in order that the gases may penetrate and envelop every particle or portion of the substance. This we accomplish by grinding the phosphate to a liquid slurry and introducing this slurry at the upper end of the revolving kiln in which the calcining is effected.

We wish it to be understood that wedo not limit ourselves to the above-described method of securing a porous cellular or laminated condition of the'phosphate mix-- ture, and that other devices or manipulations by which free circulation of the hot gases through all parts of the material treated may be secured do not constitute a departure from our forth.

2 If the phosphate in admixture with alkali-metal compounds is heated while at rest or out of intimate contact with the hot gases, it tends to fuse together into compact grains or lumps, which in the further process of calcination are scarcely at all converted into citrate-soluble form. To avoid this injurious effect it is necessarythat thematerial during the whole course of the heating shall be actively agitated and turned To produce and maintainprocess as herein set over, thus thoroughly promoting continued contact of the gases with every part of the charge and preventing the formation of lumps which would escape further action. This agitation is effected by the revolution of the kiln and increased by the lifting and rolling action of a number of shelves or ridges in the kiln lining, which extend from the end of the drying zone nearly to the point of discharge of the calcination product.

3. In the first stage of the heating the temperature of the charge increases rapidly, and under the combined action of heat, agitation and intimate contact with a rapid current of hot gases the alkali-metal comof its acid or'other' volatile constituents.

This' action' takes place actively at a-temperature'of 2000 degrees F. or over, provided the material is porous and-the current of hot gases 'siifliciently rapid. Under these conditions such alkali-metal compounds fro ' andc'arbon'dioxid, leaving a residue of al-- as hydrate, sulfate or carbonate, which are scarcelyaffected by heating to much highertemperatur'es when at "rest, are rapidly decomposed with evolution, respectively, of -water, sulfur dioxid and oxygen,

kal-i-Inetal-oxidwhich We term residual alfkali. The volatileconstituents may be said to be blown out of the salts by contact with the current of hot gases. It is probable that the residual alkali enters into com bination with the phosphate of lime,.forming an alkali-lime phosphate which is again in large measure decomposed atthe higher temperature ofthe later-stage of the process, and that this combination and subsequent decomposition plays an important part in the conversion of the phosphate into citrate-soluble condition.

'perature of about 2400 degrees to 2600 degrees is required, and in this stage, 'under the combined action'of heat, agitation and intimate contact with a rapid. current of highly heated gases, the residual alkali is in turn and in large measure volatilized, and

simultaneously with the expulsion of alkali the percentage of. citrate sol'uble phosphoricacid rapidly increases, until, with proper adjustment of temperature and duration of,

- heating, the conversion to citrate-soluble condition becomespractically complete, only traces of insolublephosp'horic' acid remaining. The product of the operation conducted as above described appears in the .form of brown or black masses or fragments,

. extremely porous and light, and so soft that it can be crushed to powder by pressure of the fingers. Dur1ng the entire courseof the calcination the exp ulsion' of the volatile constituents 'of the alkali metal compound and of the residual alkali tends to prevent ove r-heating and-fusion of the material. This expulsion takes place normally and rapidly if- .the'material is exposed to and I penetrated by a rapidly-moving current of -hot gases, for example sucha current as is produced by. introducing the fuel at the lower end of the kiln in admixture with a current of air under four or five ounces pressure andby maintaining a strong draft in the stack at the, upper end of the kiln. 1 Under these conditions the material remains 4. In the final stage of calcinat'iona te'min the finalstage of heating, and the phosphate is rendered practically completely citrate-soluble. On the other hand, if the current of hot gases is slow and sluggish or does not freely penetrate the charge, little or no decomposition and expulsion of the alkali-metal salt takes place, the material fuses 0r sinters together into impervious masses, and practically no conversion into citrate-soluble condition is effected.

I An additional safeguard against the fusion or agglomeration of the material, especially in the earlier stage of heating, consists in'carrying on the calcination in a kiln provided with a comparatively thin refractory lining, through which radiation of heat takes place to a considerable degree. The effect of this radiation is to keep the interior of the kiln walls at a somewhat lower temperature than that of the charge or the gases passing .through the apparatus, and thus to prevent the charge from becoming over-heated and fusedby contact with the hot lining. By alkali-metalcompound we mean any compound of the alkali-metals as potassium or sodium, with hydroxyl or the common acids, forexample the hydrate, carbonate,

chlorid, sulfate, bisulfate, nitrate, etc. We prefer to use sodium sulfate or bisulfate, on account of the cheapness of these reagents and the ease with which they undergo decomposition under the conditions of calci- -nation herein described. We find, however,

that any co'mpoundor' combination of the :alkali-metals substantially free from ingredients injurious to the process or product produces a result similar to that obtained -by the use of the alkali-metal salts above mentioned.

A The amount of alkali-metal compound required varies with the-nature of the phosphate; treated -and the temperature employed. Taking sodium sulfate as an example, the addition of 10 to'20 per cent. is sufiicient to accelerate and complete the transformation of the phosphate to citratesoluble condition By volatile constituents of alkali-metal compounds we mean such part thereof as may be driven off by the action of hot gases under the conditions herein described, leaving aresidue of alkali-metal oxid, as for example, water, sulfur dioxid and oxygen, carbon dioxid, oxids of nitrogen, etc. By residual alkali we mean the residue, consisting chiefly of alkali-metal oxid, remaining after the expulsion of the volatile constituents of alkali metal compounds.

7 By increasing temperature we mean a temperature, of the .material below that of fusion increasing from approximately 2000 degrees F. to 2500 degrees F. By high temperature we mean a temperature below the fusin vided the gether in phate mixtures as of a steel eter and short le n g point of the partially calcined material is not fused approximately 2500 degrees F. understood that higher temperathe above are not injurious proor balled tosuch manner as to interfere with the transformation desired.

A suitable kiln for the treatment of cylinder of relatively large phosherein described consists diamgth as compared with the kilns used in cement burning. For example,

a length eter of 8 dimensions.

is revolved b at, a speed per minu relatively con of from 30 to 50 feet and a to 10 feet diamare appropriate relative The kiln rests upon rollers and y power in the usual manner, of approximately 1 revolution The. inclination of the kiln is siderable, preferably f} inch to 1 inch per foot-of length. It will be understood, however, and increased in effect on above figures that since increased the movement of the charg may be varied conside The interior of the kiln is lined with a of refractory material, of fire-brick in'the u ment clinker or magne part. This lining is her of 1 preferably cons provided with a ow shelves lengthwise of the kiln, preferably begi at about upper end and extend one-fourth charge end of the kiln; the purpose of ridges is and thus terial to nally by to turn the the inner su speed clination produce a similar e, the rably.

layer isting pper portion and cesite brick in the lower,

or ridges, extending nning the length from the ing nearly to the disthese charge over and prevent it from sliding on rface,

to promote exposure of the ma intimate contact with the rapidly The kiln is heated a ame or flames or gas, and the heat so regulated that a erately high length of the interior. gases discharged from the lized in well-known methods.

cooling the discharged of air and utilizing the port. combustion of the f with adv We cla 1. The

pulverizing natural phosphate of ing the with a ra temperature extends the interof coal-dust, oil

modentire The heat of the kiln may be utiboilers or for other purposes, by

antage. We

e process herein set Suitable devices for product by a current air so heated to supuel may be employed wish it to be undere do not limit our ina revolving kiln as forth y earried 'on in any type e in whlch the required of hot gases process of making fertilizer by pid current of hot gases whil lime, phosphate with alkali-metal pound, an

mix-

com-

d calcining the mixture in contact e agi- .ing the phosphate With at increasing temperature until the alkalimetal compound is substantially decomposed withevolution of volatile constituents, and finally at high temperature until the phosphate becomes substantially citrate-soluble.

2. The process of making fertilizer by pulverizing natural phosphate of lime, mixing the phosphate with alkali-metal compound and calcining themixture in contact with a rapid current, of hot gases while agitating to present renewed surfaces to heat at increasing temperature until the alkali-metal compound is substantially decomposed with evolution of volatile constituents, and finally at high temperature until the residual alkali is partly expelled and the phosphate becomes substantially citrate-soluble.

3. The process of making fertilizer by pulverizing natural phosphate of lime, mixing the phosphate with alkali-metal compound and calcining the mixture in contact with a current of hot gases of such velocity and temperature that volatile constituents of the alkali-metal salt and part of the residual alkali shall be expelled and the material prevented from fusing and kept in a porous condition, at increasing temperature and finally at high temperature until the plhosphate becomes substantially citratesolu- :4.- The process of making fertilizer by pulverizing natural phosphate of lime, mixalkali-metal compound and water, drying the mixture rapidly in such manner that it shall take a porous cellular form, and calcining the dried porous mixture in contact with a rapid current of hot gases while agitating to present renewed surfaces to heat, at increasing temperatureland finally at high temperature until the phosphate becomes substantially citrate-soluble.

, 5. The process of making fertilizer pulverizing natural phosphate of lime, mixing the phosphate with alkali-metal compound and water, drying the mixture rapidly in such manner that it shall take a porous cellular form, porous mixture in contact with a rapid current of hot gases whil'c agitating to present renewed surfaces to heat, at increasing temperature until the alkali-metal compound is substantially decomposed with evolution ofv volatile constituents and finally at high temperature until the residual alkali is partly expelled and the phosphate becomes sub stantially citrate-soluble.

6.' The process of making fertilizers by pulverizing natural phosphate of lime, mixing the phosphate with alkali-metal compound, preparing the mixture in such'inanneras to give it a porous and open structure, freely permeable by gases, and calcining the and calcining the dried prepa 'ed Inixture in eentact with a rapid Signedat SandhskjOhio, this thirty-first current of hot gases, at increasing temperaday of October, 1912.

ture until the alkalimetal compound is sub- A stantially decomposed with evolution of volv 3f atile constituents and finally at high tem-' perature until the residual alkali is partly Witnesses:

expelled and the phosphate becomes substan .HATTIE M. MEGGITT,

tially citrate -s0luble. I k ALLEN KUBACH.

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