The story of the phosphorus in the Tennessee area began some six hundred million years ago when an inland sea left the skeletons of millions of microscopic animals which were later leached by ground waters into a surprisingly pure matrix of phosphate and lime. But the earth did not yield up Its tightly-held secret easily, and it was not until modern man with his inquisitive mind and the advent of commercial electricity that the phosphate matrix was forced to release its pure element.

Monsanto, Oxidental, and Stuffar Chemical Companies pioneered in the development of the electric furnace method of extraction. Other necessary raw materials used to large quantities are coke, used as a reduction agent in the furnace, silica rock, used as a flux to remove impurities, and carbon electrodes. By-products of the electric furnace process are CO gas, ferro-phosphorus (iron), and slag.

The pure element is converted into phosphatic compounds for use in products in Industry and everyday service of mankind. Its end products can be found in the food we eat, the detergents with which we wash our clothes, and in the medicines prescribed by our physicians and dentists, and in many other items which we encounter daily.

The basic chemical reaction underlying production of high quality elemental phosphorus is the intra-reaction of phosphate rock, coke, and silica sand. The reaction equation reduced to its simplest form is:

Ca2P2O3 + 5C + 3SiO2 = 3CaSiO3 + 2P + 5CO

Phosphate Matrix + Coke + Silca Sand = Elemental Phosphorus

The reaction requires a temperature of 1300-1500^o C, to start. When this heat is obtained, the coke reduces free phosphorus pentoxide to elemental phosphorus vapor; the silica sand combines with the resulting lime to form calcium silicate slag.

Yellow phosphorus is condensed from the top of the reaction chamber and a molten slag is tapped off the furnace bottom. As the slag spills out down directed run-out troughs, a compound of phosphorus, ferrophosphorus, separates out. This iron-phosphorus compound is the steel industry's principal source of phosphorus for special steels.

ELEMENTAL PHOSPHORUS PRODUCTION PROCESS SUMMARY

MINING:

Phosphate ore Is removed from the ground using a strip mining method and most of the plant's ore is mined locally -- from Maury County and surrounding counties. The ore is transported to the plant by trucks and railroad cars.

WASHER:

The Washer Department receives the ore from the mines. The ore is "washed" to remove impurities (clay) in order to upgrade the phosphatic content of the ore. At this point, the ore Is called concentrates.

BLENDING:

The concentrates are pumped or conveyed to the craneway from the Washer. The material is dried and then it is conveyed to the blending area. The blending process provides a constant feed material to the kilns.

NODULZING:

The material Is fed to three rotary kilns where it is upgraded by removing the moisture, organic compounds and gaseous products of calcination. The nodulizing process also fuses the material into nodules for furnace use.

SCREENING AND SCALES:

The nodules are sized and stored in bins for furnace use. Coke and silica gravel are also stored in bins for furnace use. These raw materials (nodules, coke, and silica) are weighed in stoichiometric proportions and charged to the furnaces.

FURNACE:

The electric furnaces supply the heat necessary to cause the reaction of the raw materials. This reaction produces gaseous elemental phosphorus, ferrophosphorus metal, slag and CO gas. The CO gas is recycled to nodulizing where It Is used as fuel to fire the kilns.

PHOSPHORUS:

The gaseous elemental phosphorus is condensed and collected in tanks prior to shipping to other Monsanto plants via railroad tank cars.

BY-PRODUCTS:

Calcium silicate and ferrophosphorus metal are solidified and then processed for shipment to our customers.