US2907637A

US2907637A - Process of winning elemental phosphorus

Info

Publication number: US2907637A
Application number: US538597A
Authority: US
Inventors: Tour Sam
Original assignee: EDDIE BURGESS BEITLER
Current assignee: EDDIE BURGESS BEITLER
Priority date: 1955-10-05
Filing date: 1955-10-05
Publication date: 1959-10-06
Anticipated expiration: 1976-10-06

Description

Oct. 6, 1959 s. TOUR 2,907,637

PROCESS OF WINNING ELEMENTAL PHOSPHORUS Filed 001;. 5, 1955 2 Sheets-Sheet 1 5AM TOUR.

ATTORNEY Oct. 6, 1959 s. TOUR 2,907,637

PROCESS OF WINNING ELEMENTAL PHOSPHORUS Filed Oct. 5, 1955 2 Sheets-Sheet 2 IN VENTOR 2- 5/1/14 TOUR ATTORNEY United States Patent irRocEs's 0F WINNING ELEMENTAL rnosrnorws Application October 5, 1955, Serial No. 538,597

12 Claims. (Cl. 23-423 This invention is a new and useful process of winning Telemental phosphorous from oxygenated ores containing the same, such as the so-called phosphate rock. The "invention is an improvement on the method described and claimed in application of Louis Burgess, Serial No. 530,507, filed August 25, 1955, the said application and the instant application being assigned to the identical assignee. This invention will be fully understood from following description read in conjunction with the drawings in which:

Fig. l is a diagrammatic vertical section thru apparatus in which the invention may be practiced;

Fig. 2 is a detailed vertical section through one elementbf the apparatus shown in Fig. 1;

Fig. 3 is a horizontal section through the plane indicated by 3-3 in Fig. 2; and

Fig. 4 is a horizontal section through the plane indicated by4-4 in Fig. 2.

i The elements of the process for the recovery of elemental phosphorus described in said application, Serial No. 530,507, are as follows:

(a) The formation of a coke throughout which the particles of the ore are disseminated in a supporting structure of carbon and in which the carbon is in excess of that consumable by reduction of the ore and other reducible substances present;

(b) Heating the coke so formed out of direct confact with combustion gases to a temperature at which the ore is reduced by carbon thereby producing elementa'l phosphorus and carbon monoxide in vapor phase, conducting away the vapor phase and condensing the phosphorus;

(c) Removing the residue of excess carbon and inorganic oxides froin the heating zone in solid form.

The substantially complete liberation of the elemental phosphorus in step (b) and the removal of the residuein solid form, step (c), are made possible by the preliminary step (a i.e., the formation of a coke in which the particles are disseminated and in which the carbon is in excess. The combined effect of the coke structure and the excess carbon in this coke structure is to hold the oxide particles apart up to the point of complete reduction and at this point, to provide sufficient residual carbon to hold the residual oxide particles apart and thereby prevent sintering. In the preferred embodiment, suflicient excess carbon is incorporated to maintain the physical form of the individual masses of which the charge is composed.

In one method of generating the desired coke structure, the oxide is mixed with sufiicient of a substance selected from the tars, pitches, and asphalts (including the oxidized asphalts), to occupy the spaces between the oxide particles. Sufficient coke breeze, anthracite 2,907,637 Patented Oct. 6, 1959 or bituminous coal of about the same particle size as the oxide particles, is also incorporated in amount sufficient to provide the requisite carbonzoxide ratio. In another method, the oxide and bituminous coal, are ground together in a state of extreme fineness for a period of several hours. The grinding is continued until the individual particles of oxide and coal are no longer separately distinguishable and the coal has acquired the property of flowing under extreme pressure. At this stage, the entire mix is briquetted by the application of pressures of the order of at least ten tons per square mc In either method, the coke-forming substance is converted into coke by raising the temperature progressively through the range of pyrolysis, i.e., about 350-1000 C., until pyrolysis is substantially complete. With cokeforming substances that become fluid below the temperature of pyrolysis, this heating is carried out in apparatus in which the mix is supported in a quiescent state, such as a coke oven or broad oven. With those coke-forming substances which become only plastic and not freely fluid up to the temperature of pyrolysis, the carbonization may becarried out in a vertical retort with top feed and bottom discharge.

Any of the coke-forming substances mentioned may, with sufliciently rigorous preliminary treatment, be converted into forms that become only plastic and not free ly fluid up to the temperature of pyrolysis. Those preeminently suited for this purpose are, however, the coal tar pitches of about C. or higher melting point, as determined by the cube in air method and the bituminous coals processed in the manner hereinabove described. It is to this embodiment of the invention described in said application, Serial No. 530,507, that my improvement is directed.

Referring to the drawings, 1 designates a retort of the vertical type, with provision for top feed and bottom discharge. By reference to Fig. 2 which shows details of construction, heating zone 2 is bounded by transverse walls 3 and 4 and end walls 5 and 6 (Figs. 3 and 4). These are of refractory heat-conducting material, such as fused alumina or bonded silicon carbide.

Wall 4 is heated by the application of combustion gases to surface 7 thereof. For this purpose, burner 8 is provided which may be supplied with air and gas through the valved pipes 9 and 10 respectively. Burner 8 discharges into combustion space 11 defined by the refractory panels 12, 13 and 14. From the combustion space, the products of combustion move upwardly through duct 15 defined by the

refractory Walls

4, 5, 6 and 16. They follow a sinuous path over the staggered horizontal bafiles 17 as indicated by arrows 18, eventually passing out through the stack 19, by which they are discharged.

Transverse wall 3 is heated by the application of combustion gases to surface 20 thereof. For this purpose, burner 21 is provided which may be supplied with air and gas through valved pipes 22 and 23. The burner discharges into combustion space 24 defined by the refractory panels 25, 26 and 27. From the combustion space 24, the products of combustion move upwardly through duct 28 defined by the

refractory walls

3, 5, 6 and 29. They follow a sinuous path over staggered baffles 30 as indicated by arrows 31 passing off through the stack 32 by which they are discharged.

Material to be supplied to heating zone 2 is dumped end 38 of heating zone 2 by means of turnable grate bars 39. The grate bars are rotated preferably continuously, by any suitable means, not shown. Material discharged by grate bars 39 drops into space 41 from which it may be continuously or intermittently removed .by the operation of worm conveyor 42. A carrier gas may be introduced into space 41 through valved pipe 43. ,n Provision is made for the take-01f of gases from adjacent the upper part of heating zone 2 through the horizontal ducts 44 and 45 (Figs. 2 and 3) discharging intothe main 46 controlled by valve 47. Provision is also made for the take-offof gases from a mid-point of heating zone 2 through the horizontal ducts 48 and 49 (Figs. 2 and 4) discharging into the main 50 controlled by valve 51. Main 46 is provided with pressure gauge 52 by means of which the pressure obtaining at this point is indicated. Gases passing otf through the main 46 are discharged into the quench tank 53. A liquid such as tar, may be supplied to the upper end of tank 53 through valved pipe 54. This liquid is restrained by transverse perforated plate 55 from which it is discharged downwardly in a large number of small streams. This liquid, together with any material condensed out of the gases entering through main 46, accumulates in base 56 of tank 53 up to the level indicated by line 57. Any excess over this may be continuously withdrawn through valved overflow pipe 58 passing through the cooler 59 in which it passes downwardly through pipes 60 carried in

headers

61 and 62. A liquid may be passed into the space between

headers

61 and 62 through pipe 63 passing .off through pipe 64. From cooler 59, the liquid introduced through valved pipe 58 is diverted to storage through valved pipe 651. From tank 53, the gases supplied through'main 46, less any constituents which'may have been condensed in the tank 53, pass off through valved pipe 71 to pump 72 by which they are supplied to the mid-section of rectifying column 73. This column is spanned by a number of horizontal trays 74 equipped with bell caps and overflow pipes, not shown, for the purpose of dispersing any ascending vapor into the layer of liquid carried by each such tray. It is also equipped with a reboiler coil 75 in the base 76 and with a valved overflow pipe 77 by which liquid accumulating in'the base over that necessary to maintain the level indicated by line 78, may be Withdrawm From the upper end 81 of the rectifying column 73 gases are conducted away through pipe 82 communieating with condenser 83. In condenser 83, the gases move downwardly through tubes 34 carried in

headers

85 and 86. Provision is made for cooling the gases in their passage through tubes 84 by the introduction of a coolant, such as water, through valved pipe 87 to the space between

headers

85 and 86, passing off through valved pipe 88. Condensate together with uncondensed gas passing oil from condenser 83 moves downwardly through pipe 89 into the receiving tank 90. Any excess of condensate over that necessary to maintain the liquid level indicated by line 91 is continuously withdrawn through pipe 92. A part of this is recycled through valved pipe 93 by means of pump 94 discharging through pipe 95 into the upper end 81 of column 73, to serve as reflux in column 73. The balance is continuously withdrawn to storage through valved pipe 96. Bottoms accumulating in the lower end 76 of rectifying column 73 may be continuously withdrawn to storage through valved pipe 77. Uncon 4 densed gas is withdrawn from tank 90 through valved pipe 97. Provision is made for the ascertainment of pressures obtaining in the heating zone by means of a number of pressure gauges, such as 101-106, spaced vertically along, and communicating with, the interior of heating zone 2.

Provision is also made for the ascertainment of temperatures obtaining in the heating zone by means of a number of temperature responsive devices such as shielded thermocouples 107-112 spaced vertically along transverse wall 35'.

In the operation of the apparatus described, I first compound a suitable charge. One charge which I may use is compounded of the following materials: phosphate rock analyzing about 70% tricalcium phosphate or its equivalent in P 0 content, roughly two-thirds through 100rnesh and roughly 50% through 200 mesh; silica and coke breeze of roughly the same particle size as the phosphaterock; coal tar pitch M.P. 100 C. or higher, as determined bythe cube in air method, coking value at least 40%.

These materials should be mixed in the following proportions:

Parts Phosphate ro 360 Silica 120 Coke breeze Coal tar pitch Parts Phosphate ro 360 Silica Bituminous coal The'mix is ball-milled together for a period of at least 12 hours and until the coal has developed the property of flowing under relatively higher pressures. At this point the entire charge is briquetted under a pressure of. about 15 tons per square inch. The briquettes so formed are strong and dense and may therefore be charged into the heating zone up to the level indicated by line 37, through the hoppers 33 and 35, by operation of hell valves 34 and 36. When this has been done, a carrier gas, such as carbon monoxide, is introduced through valved pipe 43 into base 41 of retort 1, at such a rate as to maintain positive pressure in the base, and the burners 8 and 21 are started in operation. During this stage valve 51 in main 50 is closed, and as soon as the temperature of pyrolysis is reached and thereafter the vapors produced are taken ofl through main 46 into quench tank 53, in

which the heavier hydrocarbons are condensed by contact with incoming coal tar from 54, and the residual hydrocarbons, principally aromatics, are taken over into rectifying column 73. In column 73, by adjustment of the amount of reflux returned through line 95 and the amount of heat supplied through reboiler coil 75, these residual hydrocarbons are split into two cuts, i.e., heavier aromatics taken oif from the base of the column through the valved pipe 77 and a lighter overhead consisting principally of benzol and toluol, which is taken oil? through valved pipe 82. Uncondensed gas is taken off through valved pipe 97.

Whenever a temperature of about 1000 C. is reached in the base 38 of the heating zone, the valve 51 in main 50 is partly opened and the phosphorous vapor, together with the carbon monoxide simultaneously produced by reduction, are: conducted away through main 50 to suitable condensers (not shown) At the same time, flow through main 46 is controlled by means of valve 71 and/or 11am ratewhich will carry the heavier products oflpyrolysis overhead through main 46 and therebyprevent them from co-mingling with and contaminating the phosphorus simultaneously produced. One way of establishing this adjustment is to make provision for a continuous sampling of the phosphorus coming off through main 50 and to maintain such a flow through main 46, by means of pump 72, as is necessary to insure that this phosphorus will not show tar contamination.

Another way is to maintain such a rate of fiow by means of the valve in pipe 71 and/ or by means of pump 72 that the maximum pressure in that part of the heating zone above outlets 48 and 49 occurs at the 700-800 C. (preferably about 750 C.) temperature level. This will insure that products of pyrolysis generated above this level move upwardly, whereas those generated below this level move downwardly. Below this level, i.e., above this temperature, the products of pyrolysis are principally of lower molecular weight and in such limited amounts as not to seriously contaminate the phosphorus produced.

Whenever a temperature of 1260 C. is obtained in the base 38 of heating zone 2, the grate bars 39 are started in rotation for the continuous removal of exhausted charge. Simultaneously fresh charge is supplied intermittently by operation of bell valves 34 and 36 to maintain an upper level substantially at the line 37. In continuous operation the temperature at the level of outlets 48 and 49 should be held between about 950 C. and 1050 C. (preferably about 1000 C.) and the rate of rotation of the grate bars set to provide a residence time of at least 3 hours from the 1100 C. level down to the final level of about 1260 C. This will liberate about 95% of the phosphorus content of the ore. As heretofore explained, the rate of operation of the valve 71 and/or pump 72 is set to carry the heavier products of pyrolysis overhead through outlets 44 and 45.

In continuous operation the temperature adjacent the outlets 44 and 45 should be maintained between about 300-400 C., preferably about 350 C.

Of the products of pyrolysis passing off through main 46, as heretofore described, the tars are knocked down in quench tank 53 by contact with fresh tar introduced through valved pipe 54, and after passing through cooler 59 are carried 01f to storage through valved pipe 65. The remaining hydrocarbons passing oif through valved pipe 71 and pump 72 into rectifying column 73 are split roughly into two fractions, i.e., an overhead fraction con sisting principally of benzol and toluol, the excess of which over that recycled as reflux through line 95 is carried off through valved pipe 96, and a bottoms of heavier aromatics carried off through valve pipe 77.

I claim:

1. The continuous process of winning phosphorus from oxygenated ores containing the same which comprises mixing such an ore in particulate form with a carbonizing agent which becomes only plastic and not freely fluid up to the temperature of pyrolysis, thereby forming a mixture, said mixture containing sufficient carbon-yielding substance to form a coke in which the carbon is in excess over that consumable in the reduction of the P and other reducible oxides present, thereafter briquetting said mixture, maintaining, a charge of such briquettes in a vertically oriented heating zone with provision for top feed and bottom discharge, heating said charge in the upper portion of said heating zone out of direct contact with combustion gases to a temperature between about 350-1000 C. for a period of time sufiicient to substantially complete pyrolysis, thereafter further heating said charge in the lower portion of said heating zone to a temperature of between 950 and 1050 C. at which reduction proceeds with the formation of carbon monoxide and pho'sphorus in gas' phase and until at" least a n'iajtii part of the phosphorus content of said ore has been liberated, adding fresh briquettes to said charge at the upper end thereof and removing residual carbonand residual ore particles from said heating zone at the lower end thereon-conducting away said carbon monoxide and phosphorus in gas phase fromsaid charge at an intermediate point and separately conducting away the heavier products of pyrolysis from said charge at a higher point.

2. Process according to claim 1 in which said carbon monoxide and phosphorus in gas phase are taken off from said charge between about a temperature level of 950- 1050" C.

3. Process according to claim '1 in which said carbon monoxide and phosphorus are taken on from said charge at a temperature level of about the 1000 C.

4. Process according to claim 1 in which said heavier products of pyrolysis are taken 01f from said charge at a temperature level of between about the BOO-400 C.

5. Process according to claim 1 in which said products of pyrolysis are principally taken off from said charge at a temperature level of about the 350 C.

6. Process according to claim 1 in which said carbon monoxide and phosphorus in gas phase are taken off from said charge at a temperature level of between about 9501050 C., and said heavier products of pyrolysis are taken 01f from said charge at a temperature level of about between 300400 C.

7. The continuous process of winning phosphorus from oxygenated ores containing the same, which comprises mixing such an ore in particulate form with a carbonizing agent which becomes only plastic and not freely fluid up to the temperature of pyrolysis, thereby forming a mixture, said mixture containing sufficient carbonyielding substance to form a coke in which the carbon is in excess over that consumable in the reduction of the P 0 and other reducible oxides present, thereafter briquetting said mixture, maintaining a charge of such briquettes in a vertically oriented heating zone with provision for top feed and bottom discharge, heating said charge in the upper portion of said heating zone out of direct contcat with combusion gases, to a temperature between about 350-1000" C. for a period of time sufficient to substantially complete pyrolysis, thereafter further heating said charge in the lower portion of said heating zone to a temperature of between about 950 and 1050 C. at which reduction proceeds with the formation of carbon monoxide and phosphorus in gas phase and until at least a major part of the phosphorus content of said ore has been liberated, adding fresh briquettes to said charge at the upper end thereof and removing residual carbon and residual ore particles from said heating zone at the lower end thereof, conducting away said carbon monoxide and phosphorus in gas phase from said charge at an intermediate point and separately conducting away the heavier products of pyrolysis from said charge at a higher point, the rate of flow of said heavier products of pyrolysis being established at a rate that produces a maximum pressure in the upper part of said heating zone above the point at which said carbon monoxide and phosphorus in gas phase are conducted away between the 700800 C. temperature levels.

'8. Process according to claim 7 in which said carbon monoxide and phosphorus in gas phase are taken off from iaidlcharge between about the 9501050 C. temperature eve s.

9. Process according to claim 7 in which said carbon monoxide and phosphorus are taken oif from said charge at about the 1000 C. temperature level.

10. Process according to claim 7 in which the said heavier products of pyrolysis are taken off from said charge between about the 300-400 C. temperature levels.

11. Process according to claim 7 in which said products of pyrolysis are principally taken off from said charge at about the 350 C. temperature level.

112. Process according to claim 7 in which said carbon monoxide and phosphorus in gas phase are taken off from said charge between about/she 95 0-1050 C. temperature 5 levels and said heavier products of pyrolysis are taken ofi from said charge between the 300 400 C. temperature levels,

References Cited in the file of 'this patent UNITED STATES PATENTS Curtis Feb. 4, '1936 France June 16, 1930

Claims

1. THE CONTINUOUS PROCESS OF WINNING PHOSPHORUS FROM OXYGENATED ORES CONTAINING THE SAME WHICH COMPRISES MIXING SUCH AN ORE IN PARTICLE FORM WITH A CARBONIZING AGENT WHICH BECOMES ONLY PLASTIC AND NOT FREELY FLUID UP TO THE TEMPERATURE OF PYROLYSIS, THEREBY FORMING A MIXTURE, SAID MIXTURE CONTAIING SUFFICIENT CARBON-YIELDING SUBSTANCE TO FORM A COKE IN WHICH THE CARBON IS IN EXCESS OVER THAT CONSUMABLE IN THE REDUCTION OF THE P2O5 AND OTHER REDCUCIBLE OXIDES PRESENT, THEREAFTER BRIQUETTING SAID MIXTURE, MAINTAINING A CHARGE OF SUC BRIQUETTES IN A VERTICALLY ORIENTED HEATING ZONE WITH PROVISION FOR TOP FEED AND BOTTOM DISCHARGE, HEATING SAID CHARGE IN THE UPPER PORTION OF SAID HEATING ZONE OUT OF DIRECT CONTACT WITH COMBUSTION GASES TO A TEMPERATUE BETWEEN ABOUT 350-1000*C. FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY COMPLETE PYROLYSIS, THEREAFTER FURTHER HEATING SAID CHARGE IN THE LOWER PORTION OF SAID HEATING ZONE TO A TEMPERATURE OF BETWEEN 950 AND 1050*C. AT WHICH REDUCTION PROCEEDS WITH THE FORMATION OF CARBON MONOXIDE AND PHOSPHORUS IN GAS PHASE AND UNTIL AT LEAST A MAJOR PART OF THE PHOSPHORUS CONTENT OF SAID ORE HAS BEEN LIBERATED, ADDING FRESH BRIQUETTES TO SAID CHARGE AT THE UPPER END THEREOF AND REMOVING RESIDUAL CARBON AND RESIDUAL ORE PARTICLES FROM SAID HEATING ZONE AT THE LOWER END THEREOF, CONDUCTING AWAY SAID CHARGE AT AN AND PHOSPHORUS IN GAS PHASE FROM SAID CHARGE AT AN INTERMEDIATE POINT AND SEPARATELY CONDUCING AWAY THE HEAVIER PRODUCTS OF PYROLYSIS FROM SAID CHARGE AT A HIGHER POINT.