COURTESY SIMPLOT FERTILIZER COMPANY
Superphosphate Plant, Pocatello, Idaho
FACTORS AFFECTING DEVELOPMENT WILLIAM H. WAGGAMANl AND ROSCOE E. BELL2 U. S. Department
S
UCCESSFUL develop-
ment of any large mineral resource depends on a wide market and a reasonable price for the h a 1 product. The ability to serve such a market a t a reasonable price, in turn, is contingent on the following three factors :
1. Low raw material costs -mining cost plus transportation cost to the factory 2. Low processing costs including labor, operation, maintenance, and energy 3. Low delivery coststransportation, sales, warehousing, and handling
of the Interior, Washington, D . C.
Although our greatest reserves of phosphate rock occur in the western part of the United States, certain factors have delayed the development of this valuable national asset. These adverse conditions are undergoing a profound change but in order to establish an extensive phosphate industry in this western area, it is essential that concentrated products be manufactured so that they can be shipped economically to established but distant markets. The various processes for producing these concentrates through the medium of thermal or chemical energy are described and the potential sources of electric power, fuel, and sulfuric acid required are reviewed and briefly discussed. The primary products that offer the greatest promise are elemental phosphorus and phosphoric acid from which nearly all commercial phosphorus compounds may be derived.
WE STERN PHOSPHATES
I n the case of phosphate rock, any one or all of these factors vary considerably from place to place depending on the character of the deposit, the availability and cost of power, fuel, or chemicals required for processing, and the distance that the raw materials and finished products must be transported. It is obvious that a phosphate deposit favorably situated with 1
respect to all these factors may delay the exploitation of one so located that the products cannot be sold a t competitive prices. Yet the history of our mineral industry has proved that such situations are often only temporary because depletion of developed deposits, increased d e m a n d s , improved mining practices, more efficient metallurgical and chemical processes, and better transportation facilities eventually bring these neglected resources into the economic picture.
The western phosphates are an outstanding example of a valuable national asset, the development of which has been greatly delayed. These phosphate deposits in the states of Utah, Idaho, Wyoming, and Montana are the most extensive known in the world (28, 37, 49). Not only do they contain vast tonnages of high grade rock suitable for treatment by any established process, but also almost unlimited quantities of what were formerly considered marginal and submarginal ores, which may be beneficiated
Present address, Bureau of Mines, Washington, D. C. address, Bureau of Land Management, Washington, D. C.
* Present
269
270
Vol. 42, No. 2
INDUSTRIAL AND ENGINEERING CHEMISTRY
Western D e p o t i t s 7,984,892QOOTons ( 6 0%)
Eastern Deposits 5,306651000 Tons
(4b-A')
Figure 1. Estimated Phosphate Reserves in the United States-U. S. Geological Survey
or treated by certain newly developed methods and manufactured into concentrated products. The estimated tonnage of the western phosphates compared with the more highly developed deposits of Florida and Tennessee are shown diagrammatically in Figure 1. The delayed large scale development of the western phosphates is attributed to five adverse conditions:
1. Inaccessibility of many deposits 2. Limited local demand for fertilizer 3. Inadequately developed local sources of electric energy and heavy chemicals 4. High cost of transportation to large established markets 5. Dilute nature of conventional phosphate fertilizers manufactured therefrom
stripping of the overburden is practicable, and under such conditions mining operations can be conducted very cheaply. The cost of mining, however, has not been a major factor in holding back the development of western phosphate deposits, although this factor may become increasingly important as the industry expands since the known deposits, susceptible of low cost mining located close to transportation, are limited. As a raw material for the manufacture of fertilizer or chemical products, phosphate rock moves under a relatively low freight rate, but even the highest grade rock contains only 32 to 35% of the marketable ingredient, phosphorus pentoxide, and hence the cost of transporting it per unit of plant food is rather high. Under normal conditions shipment of western phosphate rock was limited to fertilizer and chemical plants in California, Montana, Idaho, and British Columbia (1, 9). Manufactured phosphate products are employed for a wide variety of purposes and new uses are constantly being developed (16, .@,do, 34,36), but the vast bulk (probably more than 85%) of the rock mined is and always will be used in the manufacture of fertilizer materials. Therefore, in visualizing the future of any large deposit, the potential fertilizer market is of fundamental importance. Although the demand for fertilizer in the western states exceeds the present local production capacity, any great expansion of this industry depends on the practicability of reaching large fertilizer consuming centers located 800 to 1600 miles from these phosphate deposits. Seventeen western states are included because these are within the area which might be supplied from western production, assuming competitive production costs. Under such circumstances it is logical to look to more concentrated products manufactured near the source of the raw material as the most practical means of developing these phosphate reserves. Certain new and improved methods for producing such concentrates offer considerable promise, but so many interrelated factors must be considered in connection with a western phosphate industry that an economic appraisal can only be made after reviewing all established processes and products now employed in the eastern, southern, and midwestern states.
These adverse conditions, however, are undergoing a profound change (1): improved highways and, in some instances, additional railroad facilities are rendering certain deposits more accessible; local fertilizer markets are expanding; additional sources of electric energy and heavy chemicals required for processing the rock are becoming available; and methods for manufacturing concentrated products which can be shipped economically over long distances are being well established. This trend toward expansion of the western phosphate industry is reflected in phosphate rock production figures (%), as shown diagrammatically in Figure 2. Although the sharp rise in the output in 1946 and 1947 wm due in part to the large tonnages of phosphate rock shipped to the Orient, definite plans of western interests point to accelerated development of these deposits. The location of the phosphate deposits, the railroads serving this area, and the existing and potential sources of raw materials and energy are shown in Figure 3. R A W V S . MANUFACTURED PHOSPHATE
Unlike many industrial minerals such as asbestos, barite, corundum, limestone, mica, potash, talc, and ordinary salt, which are marketed and used in their natural state, phosphate rock (with the exception of about 10% of that produced, which is applied directly to the land) is treated either by chemicals or thermal processes to obtain products suitable for commercial use. Therefore, in addition to low mining costs, the availability and price of other raw materials and reagents required for processing the phosphate rock are of prime importance. The average cost of mining western phosphate is somewhat higher than that of mining Florida pebble phosphate and more nearly approximates that of Tennessee rock. In certain places
100
837
I530
Figure 2.
1939
1940
1941
1942
1943
IM4
1945
1946
1947
Marketed Production of Western Phosphate Rock-1937-1947
INDUSTRIAL AND ENGINEERING ZHEMISTRY
February 1950
M LEGEND PRINCIPAL WESTERN RAILROADS PHOSPHATE ROCK DEPOSITES A CONCENTRATEDPHOSPHATE PRODUCTPLANTS 8 SUPERPHOSPHATE PLANTS 0 MISCELLANEOUS PHOSPHATE FERTILIZER P L A N T @ SULFURIC ACID PLANTS (HeSO4) @ SULFIDE ORE SMELTER (POTENTIAL SULFURIC ACID P L A N T S ) E3 COKE OVENS 0 COKING COAL GOVERNMENT TRANSMISSION S Y S T E M S (INSTALLED a AUTHORIZED) ---TRANSMISSION SYSTEMS (PROPOSED)
--+
b
P
9
4
M A P SOURCES
SCALE
0
IO
,a1
Figure 3.
100
200
+P 30OHl
s
THE NATIONAL FERTILIZER ASSOCIATION THE NATIONAL GEOGRAPHIC SOCIETY THE OFFICIAL GUIDE OF RAILWAYS OF T H E UNITE0 STATES DEPARTMENT OF COMMERCE U S DEPARTMENT OF T H E INTERIOR WESTERN PHOSPHATE FERTILIZER PROGRAM JULY 1948
Location of Western Phosphate Deposits and Fertilizer Plants; Present and Potential Sources of Sulfuric Acid, Coke and Electrical Energy, and Railroad Lines
271
INDUSTRIAL AND ENGINEERING CHEMISTRY
272
Vol. 42, No. 2
100
80
80 c
c
Q 0 L
Q
40
20
_.
Super p h e l Phate
Celclned Phosphate
Figure 4.
-
T r i p l e Super P h o r hbric Calcium Meto-Di-ammon. MonoPotassium Potassium Elementol P h o r p h a t e Acld?85%K) Phosphate Phosphate Phosphate Mota Phosphate Phorphorl
Percentage of Plant Food Ingredients in Varinus Phosphate Products
BASIC METHODS FOR TREATING PHOSPHATE ROCK
Four basic methods are used in decomposing phosphate rock to obtain products suitable for fertilizer purposes :
1. Sulfuric acid or wet process 2. Thermal reduction method 3. Calcium met,aphosphate method 4. Calcination or defluorination method All of these methods have been presented adequately in the technical literature. A bibliography of articles on these processes is given a t the end of this article. However, a brief description of the processes, raw materials, and reagents required and the nature, composition, and concentration of the final products makes for a clearer understanding of the relation bhey bear to the problem of developing the west.ern phosphates. Table I gives the established methods, their main products, and derivatives. The relative proportions of plant-food ingredients contained in the products are shown diagrammatically in Figure 4. SULFURIC ACID OR WE?' PROCESS
This general method is the oldest and still the most widely used in manufacturing phosphate fertilizer. It consists of decomposing finely ground phosphate rock by mixing it with sulfuric acid to produce either superphosphate or phosphoric acid. Large scale production of cheap sulfuric acid in this country has rendered the wet process highly successful, and the fertilizer value of the products derived thereby has been amply demonstrated. Normal Superphosphate. Where superphosphate is the desired product, the ratio of sulfuric acid (65y0H2S04)to high grade
rock used is approximately 0.83 to 1.00, or sufficient to couvert the phosphat,e into water-soluble or available form. The end product (superphosphate) is self-drying and is essentially a mixture of monocalcium phosphat,e and calcium sulfate ($4, 40). Although sulfuric acid acts on the other ingredients present in phosphate rock, the main reaction involved may be represented thus:
+
+
+
Ca3(P04)2 2Hk304 HzO = 2CaH4(P04)z.Hz0 Cas04 (1) Because no attempt is made to separate the phosphate salt from the calcium sulfate in the resultant mixture, superphosphate is a relatively dilute fertilizer, and even where the highest grade west,ern rock is used in its manufacture the product seldom contains over 20% available P 2 0 ~ Superphosphate is the simplest phosphate product to manufacture; it is the most widely used, and for local consumption is often the cheapest. Considerable advances have been made in methods of mising and handling superphosphate and stronger acid is being used, but factories and equipment are more or less standardized in design (@, &, 50, 63) and relatively small plants can be operated efficiently. The phosphate is largely water-soluble and readily available to crops when applied on a wide variety of soils, regardless of whether such soils are acid, alkaline, or neutral. On the other hand, superphosphate has a lower plant-food content than rock phosphate and, as a manufactured product, moves at a higher freight rate per ton; thus, the transportation cost per ton of phosphorus pentoxide is much greater. Superphosphate is usually manufactured at points close to the market and sometimes is hauled directly from factory to farm in bulk to reduce handling costs. Phosphoric Acid, Triple Superphosphate, and Other Phosphates. I n the manufacture of phosphoric acid by the wet process (13,24,
INDUSTRIAL A N D ENGINEERING CHEMISTRY
February 1950
273
TABLE I. PHOSPHATE ROCKPROCESSING AND POSSIBLE PRODUCTS AND BY-PRODUCTS Process Wet or sulfuric acid
Thermal reduction (electric or blast furnace)
Calcium metaphosphate CalcinationCor defluorination
Raw Materials and Reagents Phosphate rock, sulfuric acid
Phosphate rock siliceous flux b, coke (for reduction), electric energy or fuel coke, condensing water
Phqsphate rock, phosphorus, air or oxygen Phosphate rock, silica, water or steam, fuel
Main Products and Derivatives Superphosphate Phosphoric acid Triple superphosphate Monammonium phosphate Diammonium phosphate Monopotassium phosphate Phosphorus Phosphoric acid Triple superphosphate Monammonium phosphate Diammonium phosphate Monopotassium phosphate Potassium metaphosphate Calcium metaphosphate Defluorinated phosphate
Fertilizer Ingredient, % PZOS KzO NHa 18-20 .. .
.
40-65 45-48 61.5
,,
.. ..
50 52
34
229
..
40-65 40-48
..
.
.
14:7
34 40
.. ..
,
61.5 50
14: 7
25
.. ..
.. ,
..
52 60
,.
Possible By-Products Fluorine compounds; vanadiuma
25.7
Fluorine compounds. carbon monoxide: slag '(for RR ballast) : bferrophosphorub, vanadium
Fluorine compounds
60-65
..
20-32
.
.
Fluorine compounds
Vanadium is present in appreciable quantities only i n the western phosphates. Use of phosphate shale or siliceous phosphates may render the addition of silica unnecessary. Includes processes wherein phosphate rock is fused with alkali metal salts or magnesium silicate (olivine).
63,66),50% more sulfuric acid is required, or an amount sufficient to convert the phosphate rock into phogphoric acid and calcium sulfate as shown in the following equation: Caz(P04)i
+ 3HzS04 + 2Hz0 = 2H&'04
-t3CaSO4.2H20 (2)
The insoluble calcium sulfate or gypsum is then separated from the dilute solution of phosphoric acid; the acid is concentrated by evaporation and used in treating a further quantity of phosphate rock for the manufacture of triple superphosphate (5, 4, 6, 11, 43), or i t may be combined with potash or ammonia to produce highly concentrated fertilizer salts such as diammonium phosphate (25, 27), potassium phosphate, and potassium metaphosphate (36). The equations showing the reactions involved in manufacturing typical concentrated products from phosphoric acid are as follows:
+ Caa(P04)%+ 3 H z 0 = 3CaH4(PO&.HzO Hap04 + 2"s = (NH4)zHPOd HaPo, + KCl = KHzPO4 + HCl 3- KCI + 1500" C. = KPOa + HCI + HzO
4H3P04
&!?Or
(3) (4 1 (5) (6)
Obviously the manufacture of triple superphosphate and other derivativea of phosphoric acid are more complex procedures than the normal superphosphate process; thus they require a larger investment and more labor, The products, however, carry a far greater proportion of plant food which may offset the higher production costs where long freight hauls are involved. THERMAL REDUCTION METHOD
Phosphorus Production. The thermal reduction method is based on the smelting of phosphate rock with carbon (coke) and a siliceous flux a t a temperature of approximately 1600 O C. Either fuel (15, 20,48,49,62) or electric power ( 5 , 8 ,11-13) is used as a source of heat energy. Under such conditions the calcium phosphate is decomposed, yielding elemental phosphorus, carbon monoxide, and calcium silicate. The phosphorus is volatilized, condensed in suitable equipment, and collected under water as a heavy liquid, whereas the impure calcium silicate is tapped from the furnace periodically as a molten slag. Small quantities of ferrophosphorus are also produced from the iron that is always present in phosphate rock; this is tapped from the furnace and marketed as a by-product. The main reactions involved in the thermal reduction method may be represented thus:
+ 3 s i o ~+ 5c = 3CaSi03 4-
Caa(PO4)z
5CO
+ Pp
(7)
Although large quantities of elemental phosphorus were employed for military purposes during World War 11, its peacetime uses are rather limited (26, 46). From a commercial standpoint,
therefore, phosphorus is chiefly an intermediate product and must be oxidized and converted into phosphoric acid and phosphate compounds before it has any wide industrial or agricultural application. As a product of shipment, however, elemental phosphorus has the advantage of being far more concentrated than any phosphate derivative (Table I and Figure 4). Phosphoric Acid from Elemental Phosphorus. Phosphoric acid is produced by burning elemental phosphorus with an excess of air or oxygen and hydrating the resultant oxide (P,Os). The reactions involved may be represented in their simplest forms as follows: 2Pz $. 502 = 2Pz06 2P206
+ 6Hz0 = 4HaPO4
(8)
(9)
The phosphoric acid in turn may be converted into the various phosphate fertilizers shown in Equations 3 to 6-for example, triple superphosphate, ammonium phosphate, and potassium phosphate. The thermal reduction method may be carried out either in an electric or blast furnace, the choice depending largely on the availability and relative costs of coke and electric energy a t or near the source of the phosphate rock. The thermal method requires a larger investment than the sulfuric acid or wet process but has the advantage of manufacturing pure highly concentrated products suitable for use in the food, chemical, and drug industries as well as for fertilizer purposes. CALCIUM METAPHOSPHATE METHOD
The manufacture of calcium metaphosphate, a relatively new fertilizer material, depends on a n available source of elemental phosphorus. Hence, this method of treating phosphate rock may be considered subsidiary to the thermal reduction process. The process and reactions have been adequately described by Copson ( 7 ) , Curtis (9, IO), and Frear (17, 18). Briefly, it involves the burning of elemental phosphorus in the lower part of a shaft furnace and forcing the resultant oxide up through a column of phosphate rock. At the high temperatures attained the phosphate rock and phosphorus pentoxide react t o yield a molten slag consisting largely of calcium metaphosphate, which is periodically tapped out and hardens into a glassy product: Caa(P04)t
+ 3P2 i502 = 3Ca(P03)2
(10)
Although calcium metaphosphate has concentration and physical properties in its favor, i t is not in water-soluble form and its suitability for many western soils, which are neutral or alkaline in nature, is questionable. The agricultural value of this product must be demonstrated by further experimentation before it is generally recommended as a fertilizer for use in the West.
INDUSTRIAL AND ENGINEERING CHEMISTRY
274
, 16.00
Assumin
pyrites were shipped t o phosphote deposits ond reCover*d in the form ot sulfuiic acid.
90% oPsuciur
#15.00
Ea8ed on f r d
$12.50
8 12.07 $10.00
87.85
$7.50
!II
# 5.00 $2.50
jte ) !o
0.00 c
P( 4 y r5i tYe S s)
Sulfuric Acid Process
Pha Thermal R e d u c t i o n Process
Figure 5. Relative C o s t s of Shipping Raw Materials and Transmitting Energy Required to Produce 1 Ton of Phosphorus Pentoxide as Phosphoric Acid Shipping distance, 300 miles
DEFLUORINATION OR CALCINATION METHOD
The defluorination method, as its name implies, is based on the removal of the fluorine combined in the lime-phosphate molecule of the natural phosphate minerals. Nost phosphate rock, except that of very recent oxigin, has a definite fluorine-phosphoric acid ( P 1 0 6 )ratio, corresponding fairly closely to that in fluorapatite CajF(P04)3. Since the fluorine fises or ties up the phosphate of lime in a highly insoluble form, there is little doubt that the presence of this element is largely responsible for the preservation of vast beds of phosphate rock (38). When fluorine is removed, therefore, the solubility of the phosphate of lime in certain media is greatly enhanced and under some soil conditions is readily available to the growing plant (31). To separate the fluorine, the rock is either sintered or fused with silica while it is exposed to water vapor at a temperature of 1400" C. or higher. Under these conditions gaseous compounds of fluorine are driven off, and the resultant residue consists largely of tricaicium phosphate and calcium silicate. The fundamental experiments establishing this important fact were conducted by Jacob and eo-workers at a sintering temperature (39, 46, 47), but investigations were later carried out on a large scale by TVA a t temperatures sufficiently high to fuse the rock (21,57). The main reactions of the defluorination process are: 2CarF(PO&
+ Si02 + H20 = 3Ca3(P0& + CaSi03 + 2HF
feed supplement (66),but the Tennessee Valley Authority is producing substantial quantities of the fused phosphate with a view to establishing its fertilizer value. Somewhat analogous to defluorinated phosphate are products obtained by calcining phosphate rock with alkali compounds (19) and magnesium silicates (25, 41, 54). A phosphate glass is being produced on a commercial scale a t Permanente, Calif., by fusing a mixture of phosphate rock and serpentine a t a temperature of 1500" C. The solubility of this product also is probably due to the physical or chemical change in the original apatite molecule, although considerable fluorine is still present in the glasslike product. A similar product is now being manufactured in the electric furnace from phosphate rock and olivine at Seattle, Wash. ( 4 2 ) . AVAILABILITY O F REAGENTS AND SUPPLEMENTARY RAW MATERIALS
,J[2.12Tond
I:
Vol. 42, No. 2
(11)
Because calcium silicate is not separated from the fertilizer, defluorinated phosphate may contain approximately the same percentage of phosphorus pentoxide (20 to 32%) as the rock from which it is produced. This phosphorus pentoxide, however, is largely soluble in a neutral solution of ammonium citrate, the conventional solvent for reporting the availability of manufactured phosphates. Greenhouse and field experiments have shown that this product is quite effective on acid soils but not entirely satisfactory when applied to many soils that are neutral or alkaline in nature. Further experimental and demonstration work will be required before this product is generally used as a phosphate fertilizer. At present, the one company manufacturing the sintered product disposes of it chicfly as an animal-
If the number, nature, concentration, and demand for the products obtained by each of the processes are considered, the socalled wet method and the thermal process are best suited to the development of a large western phosphate industry. No economic analysis of these processes can be made, however, without a careful review of the availability and cost of the other raw materials and facilities required in manufacturing these products. Currently, certain raw materials and the electric energy required by these two processes must be shipped and transmitted over considerable distances. This assembling expense necessitates the selection of plant sites that not only will render it practicable to obtain the necessary materials at the lowest possible cost, but permit the ready distribution of the manufactured products (1, 2 ) . Figure 5 shows the relative costs of hauling and transmitting (over a specified distance) the raw materials and electric power required to produce 1 ton of phosphorus pentoxide in the form of phosphoric acid by these two methods. These distances are approximately representative of transmission or transportation requirements for the development of southeastern Idaho phosphate deposits. Wet Process. The only primary reagent necessary for treating phosphate rock by the wet method is sulfuric acid, of which the western states have adequate potential resources. I n roasting and smelting western metalliferous ores, enormoue quantities of sulfur dioxide are produced, but only a small proportion is actually utilized. In the concentration of many ores prior to smelting, large quantities of pyrites are also discarded; these could be concentrated a t low cost. Roasting of pyrites is a standard method for obtaining sulfur dioxide for conversion into sulfuric acid, and by increasing the facilities for handling this gas or for roasting pyrites, the output of sulfuric acid could be greatly increased. Much of this acid is largely by-product, and its cost is appreciably lower than that of acid produced in many eastern and midwestern plants, using elemental sulfur shipped from Louisiana and Texas. Several of these smelters are relatively close to the western phosphate area, and sulfuric acid is being produced at three of them for use in the phosphate industry. Figure 3 shows the location of western sulfuric acid plants as well as the smelters handling sulfide ores. At two factories where triple superphosphate is being manufactured, phosphate rock is shipped 200 to 350 miles to the acid; a t another plant the sulfuric acid is being shipped 150 to several hundred miles to the rock. Even for relatively short shipping distances the transportation of sulfuric acid is a large item of cost, and it is cheaper to ship phosphate rock to the acid than acid to the rock (Figure 5). On the other hand, if pyrite containing 45% or more sulfur were recovered from the tailings a t the smelters, it probably could be moved at the same cost per ton as phosphate rock. Under such conditions, it n-ould be more economical to ship pyrite from
February 1950
INDUSTRIAL AND ENGINEERING CHEMISTRY
#m $ so. $ 40.
FrelqM rate effective Aprll I , 1948
$30. x
# eo. b IO.
t
0..
Figure 6 . Transportation Costs per Ton of Plant Food in Various Phosphate Products Shipping distanoe, 1000 miles
the smelters to the phosphate deposits, for conversion into sulfuric acid, than t o transport phosphate rock to the smelters. Of the products derived from phosphate rock by the wet procem,only triple superphosphate and the relatively pure salts can be considered for shipment to existing large fertilizer markets in the Midwest and on the Pacific Coast. Although liquid phosphoric acid may be highly concentrated, the high freight rate on this product makes it considerably more costly to ship than triple superphosphate (Figure 6). There are no large nearby sources of synthetic ammonia in the phosphate area. Ammonia is being manufactured a t Trail, B. C., chiefly t o produce ammonium salts a t that place. A substantial part of the far western market need is supplied by shipment of anhydrous ammonia from Kansas, Texas, and Arkansas. Thus the western manufacture of ammonium phosphate will probably be limited t o that required in the far west until ammonia plants are established closer to the phosphate deposits. The nearest source of potash salts is in northwestern Utah, about 200 miles west of the phosphate deposits. Therefore the manufacture of potassium phosphates for shipment to California would mean an additional haul of 400 miles for the potash contained therein. The disposal of the by-product hydrochloric acid might also constitute a serious problem in this area. On the other hand, potassium metaphosphate contains practically 100% plant food against 48% in triple superphosphate; hence the potash in the former product may be said to have a free ride from the phosphate fields to points of fertilizer consumption. The manufacture of both potassium and ammonium phosphates at or near the western phosphate deposits offers attractive possibilities fof future developments. Thermal Process. The outstanding advantages that the thermal or volatilization method has over any other process are that lower grade siliceous phosphates, not susceptible to economical treatment by standard methods of beneficiation can be utilized and elemental phosphorus, from which nearly all phosphate compounds can be produced, is obtained. Phosphorus is the most concentrated product derived from phosphate rock, and though it carries a higher freight rate per ton than either phosphoric acid or triple superphosphate, the cost of shipping the unit of plant food eventually derived therefrom is appreciably lower than that of any other phosphate product except potassium metaphosphate (Figure 6).
27s
The successful exploitation of the western phosphates by the thermal or volatilization method also depends on adequate quantities of either electrical energy or fuel coke; the western states have large potential sources of both. The larger power developments of the federal government lie a t some distance (300 t o 600 miles) from phosphate deposits. However, projected developments of the federal government a t Hungry Horse Dam in Montana (less than 100 miles), Hells Canyon, Idaho (300 miles), Echo Park, Utah (less than 100 miles), and others, when and if completed, should provide government power in quantities and a t rates feasible for phosphate development. Power plants under construction by private power companies also will be able to furnish some power for phosphate furnace operations. Both the electric furnace and the blast furnace modifications of the thermal method require coke for reduction and the latter must have large additional quantities for fuel purposes. The nearest source of such coke a t present is a t Provo, Utah, a distance of about 150 miles, and much of this production is now being used in the steel industry. It is unlikely that the capacity of these coke ovens is sufficient to take care of any large outside demands, and there is no doubt that coking facilities would have to be expanded to provide enough fuel for a large phosphorus blast furnace. Deposits of a fair grade of coking coal occur near Kemmerer, Wyo., about 50 miles from some of the phosphate mines, but no coke is being produced from this coal a t the present time. I n Utah coking coal lies relatively close t o some phosphate deposits. The installation of by-product ovens a t this place could not only provide the necessary fuel for a blast furnace but yield an appreciable quantity of ammonia for production of ammonium phosphate. Under present conditions the logical products of the thermal reduction process, for shipment to distant markets, appear t o be elemental phosphorus, pure phosphoric acid, and triple superphosphate. An electric furnace for the manufacture of phosphorus has been erected a t Pocatello, Idaho, and another is in the course of construction. Although this indicates the physical suitability of locating phosphate installations in western areas, it should be pointed out that the output of this plant is destined for relatively high cost products in the chemical field, with phosphorus cost a much smaller fraction of total cost than is true for fertilizer phosphates. Economic feasibility of a fertilizer phosphate installation is not automatically indicated by the existence of this private plant. CONCLUSION
This general review of the raw materials available and the methods for converting phosphate rock into products suitable for fertilizer use is intended merely t o give the reader an over-all picture of the problems involved in the development of a western phosphate industry. Articles on pages 276 and 286 discuss in detail probable mining and manufacturing costs, the possibilities of beneficiating and utilising marginal deposits, the relative economics of shipping various types of phosphate products (based on the established freight rates structure), and show the areas in which such products can be expected to compete with those derived from the highly developed phosphate deposita of Florida and Tennessee. This paper has brought out the following points:
1. Phosphate deposits sufficient to support a substantial western phosphate industry are now accessible by rail and other feasible transportation. 2. Local demand for fertilizer is increasing but is still inadequate to warrant a large fertilizer production. A greatly expanded western phosphate industry must depend on the shipment of manufactured products to consuming areas 800 to 1600 miles away. 3. Developed local sources of electrical energy and heavy chemicals are still inadequate. However, potential hydroelectric power resources are less than a hundred miles away, and erection of generating facilities and transmission lines from those areas
276
INDUSTRIAL AND ENGINEERING CHEMISTRY
has been proposed ab part of future federal power development in the West. Sources of coking coal and sulfuric acid exist, but additional manufacturing facilities will have to be installed if the western phosphate industry is t o be greatly expanded. 4. Certain highly concentrated fertilizers, that would improve the transportation economics of the finished product, have been produced on a demonstration scale. However, those products which appear to be of more immediate interest in establishing a large western phosphate industry are eleniental phosphorus, phosphoric acid, and triple superphosphate. BIBLIOGRAPHY
Bell, 1%.E., U. S. Dept. Interior, Borineviile Power Adm. (December 1946). Bell, R. E., and Griffith, D. T., Ibid. (June 1947). Bridger, G . L., Burt, R. B., and Cerf, 777. w., IND.ENG.CHEhi., 37, 829 (1945). Bridger, G. L., Wilson, R. b.,and Burt, R.. B., Zbid., 39, 1265, (1947). Carothers, J. N., T r a m . Electrochem. Soc., 73, 42 (1938) Copson, R. L.,et al., IND. ENG.CHEM.,29, 175 (1937). Ibid., 34, 26 (1942). Curtis, H. A., Chem. & >Wet.Eng., 42, 320-4 (1933). Curtis, H. A., Copson, R. L., and Abrams, A. J., Ibid., 44, 140 (1937). Curtis, H. A., Copson, It. L., Abrams, A . J., and Junkins. J. N., Trans. Am. Inst. Chem. Engrs., 34, No. 3, 287 (1938). Curtis, H. A,, Miller, A. SI.,and Junkins, J. &I., Chern. & Met. E ~ Q 43, . , 583-7, 647-50 (1936). Curtis, H. A , . Miller, 4.M., Newton, R. H.. Ibid., 45, 116-20 (1938). Zbid., pp. 193-7. Diamond, R. W., T’mns. Can. Inst. X i r r i n g .Met., 37, 442-60 (1934). Easterwood, H. W., Chem. & N e t . Eng., 40, 283--7 (1933). Fordyce, E. G., Ibid., 53, 276 (1946). Frear, G. L., Deese, E. F., and Lefforge, J. W., IND. ENG.CHEW., 36,835 (1944). Frear, G. L., and Hull, L. H., Ibid., 33, 1560 (1941). Hawes, J. R., and Lea, F. M., E. S. Dept. Commerce, Washington, D. C . , BIOS Final Rept., No. 107, PB 18915, August 1945. Hignett, T. P., Chem. Eng. Progress, 44, Nos. 10, 11, 12 (1948). Hignett, T. P . , and Hubbuch, T. N., IND. Exa. CHEM.. 38, 1208 (1946). Hill, W.L., et al., Ibid., 24, 1064 (1932). Hill, W.L., et a!., , J . Assoc. Ofic. A g r . Chemials. 31, No. 2. 381 (1948).
Western Phosphates
Vol. 42, No. 2
Hill, W. L., and Hendricks, S. B., IND.ENG.CHEM.,28, 440 (1936). Hofman, I. L., Trans. Sei. Inst. Fertilizers Insectofungicidea (U.S.S.R.), NO. 153, 202-14 (1940). Hufferd, R. W., Chem. Eng., 53, No. 10, 110 (1946). Ionass, A. A., and Kobrin, M. M., Trans. Sei. Inst. Fertilizers Insectofungicides (U.S.S.R.), No. 153, 193-201 (1940), Jacob, K. D., Com. Fertilizer Yearbook, 1938, p. 28. Jacob, K. D., IND.ENG.CHEM.,23, 14 (1931). Jacob, K. D., iMi.rzing and Met., 25, No. 454, 488 (1944). Jacob, K. D., et al., J. Agr. Research, 50, No. 10, 837 (1935). Johnson, B. L., and Tucker, E. M., “Minerals Yearbook, 1946,” pp. 988-1005, Washingt,on,D. C., U. S. Bureau of Mines, 194s. Larison, E. L. Am. Inst. Mining Met. Engrs., Contrib. 70 (March 1934). Loque, Paul, Chem. Inds., 49, No, 3, 302 (1941). Maas, A. R., Chem. & Met. Eng., 52, No. 12, 112 (1945). Madorsky, S. L., and Clark, K. G., IND. ENG.CHEM.,32, 244 (1940). Mansfield, G. 13.. Am. Insl. Mining Met. Engrs., Tech, Pub. 1208 (1940). Mansfield, G. R., Am. J. Sci., 238, 863-79 (1940). Marshall, H. L., et al., IND.ENG.CHEM.,29, 1295 (193’73. Ibid.,32, 1631 (1940). Moulton, R. W., Chem. Eng. Progress, 43, KO.4, 163 (1947). Moulton, R. W., Chem. Eng., 102 (July 1949). Newton, R. H., and Copson, R. L., IND. EXG.CHEM.,28, 1182 (1936). Parrish, P., Fertilizers, Feeding Stu$s Farm Supplies J . , 21, KO. 14, 384; No. 15, 411 (1936). Prentiss, A. M., and Waggaman, W.H., Chemistru, 19, No. 11, 1-10 (1946). Reynolds, D. S.,et al., IND.ENG.CHEM.,26, 406 (1934). Ibid., 27, 87 (1935). Royster, P. H., et at., U. S.Dept. Agr., Tech. Bull. 543 (1937). Royster, P. H., and Turrentine, J. W., IND.ENG.CHEM.,24, 223 (1932). Stevenius-Nielsen, H., Die Chemie, 56, 175-8 (June 26, 1943). Waggaman, W. H., Chem. & Met. Eng., 46, No. 2, 66 (1939). Waggaman, W. H . , IND. ENG.CHEM.,24, 983 (1932). Waggaman, W. H., and Easterwood, H . W., A.C.S. Monograph Series, No. 34, Chap. 6. pp. 192-204, New York, Chemical Catalog Co., 1937. Walthall, J. H., and Bridger, G. L., Ibid.,35, 774 (1943). Weber, W.C., Chem. & Met. Eng., 39, No. 12, 659 (1932). Whitney, W.T., and Hollingsworth, C. A., IND.EKG.CHEM.. 41, 1236 (1949). Williams, D. E., et al.. Ibid.. 38, 651 (1946). RECEIT E D October 1.5, 1948
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COMPARISON OF SULFURIC ACID AND THERMAL REDUCTION PROCESSING WILLIA,M H. W_4CGAMAN1AND ROSCOE E. BELL’ U . S . Deportment of t h e Interior, Washington, D. C. Under western conditions the thermal reduction method and the sulfiiric acid process seem best adapted for treating phosphate rock to produce concentrated products for fertilizer and other purposes. A n economic comparison of these two general methods is made from a long range I iewpoint, taking into consideration the mining and preparation of the raw materials, the capital investments required, and the availability and costs of sulfuric acid, electric energy, and coke fuel. Crude phosphoric acid and triple superphosphate for fertilizer can be produced more economically by the sulfuric acid process than through the medium of either the electric or hlast 1 2
Present address, Bureau of Mines, Washington, D C . Present addrew, Bureau of Land Management Waqhirigton I). C
furnace even where electric power and coke are available at relatively low cost. However, in manufacturing pure phosphoric acid and chemical grade phosphate salts, the thermal reduction method has certain distinct advantages over the sulfuric acid process. Of the two modifications of the thermal reduction method-namely, the electric furnace process and blast furnace process, the former seems to offer some economic advantage where electric energy is available at low cost.
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previous article (36) it was shown that the extensive development of the phosphate deposits in the western states, where the present demand for fertilizer is limited, depends on the economic production of highly concentrated phosphate produck
