DE602378C - Process for the processing of low-phosphorus ferrophosphorus - Google Patents

Description

Process for the processing of low-phosphorus ferrophosphorus The at the production of phosphorus from rock phosphates by the thermal process as By-product resulting from the use of ferrous starting materials or additives Phosphorus iron has different chemical compositions depending on the mode of operation; in particular, the reduction in the presence of silica usually results in alloys, at the same time larger amounts of silicon. contain and correspondingly less phosphorus. Since the commercial value of ferrophosphorus is based solely on the phosphorus content is assessed and in many cases a maximum silicon content is also prescribed is, the phosphorus iron obtained in this way was often not or only with difficulty salable.

It has already been suggested to use inferior phosphorus iron, that of iron ore, tricalcium phosphate and coal as the main product according to one was obtained based on the pig iron production and therefore only one has a very low content of free silicon, with substances containing phosphorus, in particular citrate-soluble phosphate, to be remelted, with a high percentage Phosphorus iron is to be obtained.

The present invention relates to a method which allows the volatilization of phosphorus when using iron-containing raw materials or surcharges incurred, more or less silicon-rich and low-phosphorus Ferrophosphorus in a practically silicon-free, high-phosphorus product convict. According to the invention, that is obtained from the volatilization of the phosphorus silicon-containing ferrophosphorus, possibly still in a liquid state, with new ones Pho, sphatme, ngen, preferably tricalcium phosphate, mixed and m a non-oxidizing The atmosphere is melted, with the phosphate being replaced by that contained in the errophosphorus Silicon is reduced. The resulting silica combines with the from the phosphate released lime to a silicate slag, while through the Reduction of liberated phosphorus from then partially desilicated ferrophosphorus is absorbed with the formation of an alloy with a higher phosphorus content; partially but also escapes in elemental form and in a known manner outside the furnace condensed or burned to phosphoric acid.

It was surprising that even with relatively low silicon contents in the ferrophosphorus serving as the starting material, the reaction with then. added phosphate proceeds smoothly and almost quantitatively, since it had to be assumed that the phosphorus iron, which is already fused in the presence of phosphates and is used here as the starting material, is in an equilibrium with regard to its silicon and phosphorus content, which has a reducing effect of the silicon on others Excludes amounts of phosphate. Nevertheless, the reaction, which begins at around 1450 ° C, takes place quickly and completely between 1500 and 160 ° C.

Since no gases that dilute the phosphorus vapor are produced during the conversion, there is a very high partial pressure of phosphorus in the furnace, which achieves that the desilicated phosphorus iron is partly. phosphorus levels not yet reached at all which can be up to 30%. By mixing ferrophosphorus and Phosphate in suitable proportions is easily possible, even when used of phosphorus iron of various compositions and of any origin with high phosphorus content, to produce low-silicon alloys with a uniform consistency. As functional Calcium phosphate has been found to ensure the smooth and rapid course of the reaction in an excess (for example about 50%) over that for the oxidation of silicon theoretically required amount to be used.

The separation of the high-phosphorus ferrophosphorus from the silicate slag produced at the same time takes place smoothly thanks to the considerable difference in the specific weights of the two phases, so that ferropliosphorus and slag can be tapped separately from the furnace. Example ii Part by weight of ferrophosphorus with the composition 42.8% silicon, 10% phosphorus, the remainder iron and impurities. was mixed with 3.6 parts by weight Pehblephosphat with phosphorus 14.04 010 m a. non-oxidizing atmosphere in; melted through an electric furnace. During tapping, the following were obtained: o.64 parts of ferrophosphorus with the composition o, 4% Si, 28.6% P, the remainder iron and impurities and 3; i parts by weight of a thin slag with the composition 3o, 61 /, Si02, 54.4 / o Ca0.9.2 0t0 P205, while 0.29 parts by weight of phosphorus were volatilized.

Example 2 In a further example, continuous operation Used in the electric furnace: 22501 g of ferrophosphorus with a composition of 18.8 % Si, 16.6% P, remainder iron and impurities and 4c! 5okg pebble phosphate with 14, o4 % @ Phosphorus. 1925 kg of ferrophosphorus with a composition of 0.9% Si, 29, o ° / o P, remainder iron and impurities and 406kg slag of the composition 35.4% S1.02, 49.5% Ca0, 6.5 0'o P205 and 2831g elemental phosphorus through condensation.

The yield of elemental phosphorus is slightly higher than the theory since the carbon of the electrode participates in the phosphorus reduction.

Claims (2)

PATENT CLAIMS: i. Process for the processing of low-phosphorus ferrophosphorus to ferrophosphorus with a high phosphorus content by fusing with phosphorus-containing substances, characterized in that silicon-rich phosphorus iron is remelted finite tricalcium phosphate for the purpose of simultaneous removal of the silicon without the special addition of carbon as a reducing agent to the mixture to be remelted and in a non-oxidizing atmosphere. 2. The method according to claim i, characterized in that the phosphorus iron to be desiliconized in: the required thosphate-containing remelting furnace iti introduced in liquid form will.