RU1819850C - Process for agglomeration of phosphate rock - Google Patents

Abstract

SUBSTANCE: phosphate raw material is mixed with coke before agglomeration. The mixture is moistened, pelletized and loaded onto the grate of the sintering machine. The mixture is heated by the flue gases until the coke is ignited, followed by the replacement of the flue gases with air sucked from top to bottom through a layer of pelletized mixture. At the end of the sintering process, a dust-air mixture containing 50 wt.% Boiler dust is passed over the surface of the furnace at a feed rate of 0.86-1.60 m3 / s for 1.20-1.50 minutes. The sinter is then crushed, cooled to obtain an agglomeration product. A fraction of minus 5 mm is returned to the mixing step. The strength of the agglomerate is 71.2% g / cm3. Yo

Description

The invention relates to a technology for the preparation of phosphate raw materials and the production of phosphorus from it by the electrothermal Method ..::; ; .; V-.; .

The purpose of the invention is to increase the yield of phosphorus by increasing the density of the agglomerate and improving the environment.

The goal is achieved by the fact that at the end of the sintering process a dusty mixture containing 50 wt.% Boiler dust is passed over the cake surface at a feed rate of 0.86-1.6 m / s for 1.20-1.50 minutes.

When blowing through the formed agglomerate dust, coming into contact with incandescent agglomerate particles through pores, cracks and cavities, fills them, the gas medium displaced from voids sinter. An iner, less porous, agglomerate texture is formed.

The agglomerate bushes increase the density from 1.58 to 1.75 g / cm3. The melting temperature of the boiler dust at which a strong contact is obtained is 760-1000 ° C. Due to the high content in boiler dust (up to 60%) of PsOio. the presence of Oa in the gas phase of the pore space, not only the complete oxidation of PbO-PbOi occurs and the sinter is enriched with this oxide by sublimation and adsorption in pieces (the degree of decarbonization of hot sinter is 90-95%). but the composition of the gas phase in closed pores and cavities also changes. The decrease in the amount of 02 occurs due to the oxidation of lower phosphorus oxides to PsOio and the red modification of phosphorus Pcr, amounting to 1-3 wt.%. Increasing the density of the agglomerate by reducing its porosity from 50 to 35% reduces the total

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the amount of gas phase in a piece of agglomerate, respectively, the average content of 02, N2, COa decreases. It is known that during the processing of agglomerate with porosity in an electrothermal furnace, 10.5 and 39.5% of 02 and Na additionally enter the furnace. If the porosity of the agglomerate is reduced by the proposed method, the amounts of 02 and N2 will decrease by 3.15 and 10.85%, respectively.

When calcium phosphate is reduced to P4 under the conditions of an electrothermal furnace, by reducing the sources of 02 with agglomerate, the possibility of the formation of unoxidized phosphorus and P2p5 compounds in the gas and dust stream decreases, which increases the phosphorus yield and also reduces the amount and toxicity of sludge.

With a decrease in the supply with agglomerate N2, the possibility of the formation of a highly toxic CN ion, which is formed at a high temperature (1500-1600 ° C) with an excess of carbon, under conditions corresponding to 111 temperature zones of the furnace, is excluded. A decrease in the CN content will not only reduce the toxicity of boiler milk, lower its pH to 8-8.5, but also reduce the release of cyanides into the atmosphere.

Example 1. An agglomeration mixture consisting of phosphorite ore, return and coke, after wetting and pelletizing, is loaded onto an agglomeration bowl, ignited with goreia products of natural gas, and sintered to replace flue gases with air that is sucked from top to bottom through a layer of pelletized mixture. At the end of baking to increase the temperature in the last vacuum chambers, a dust-air mixture containing 50 msec% boiler dust in the amount of 0.85 m / s is fed to the sinter surface for 1.2 minutes. The sinter is crushed, cooled, and a suitable product is isolated - an agglomerate strength of 70.5% is obtained. a density of 1.59 g / cm3, while returning a minus 5 mm fraction to the mixing step, the amount of phosphorus under-oxide in the sludge is 4.2% and cyanide is 6100 mg / l.

PRI me R 2, Everything as in example 1. with the exception of the flow of the mixture in an amount of 0.86 m / s An agglomerate is obtained with a strength of 70.6%, a density of 1.6 g / cm3, and a content of underoxides and cyanides in the sludge of 3.9% and 5500 g / l, respectively.

PRI me R 3. Everything is as in example 1, with the exception of the amount of supply of the mixture 1.2 m / s. An agglomerate is obtained with a strength of 71.2%, a density of 1.68 g / cm3 and

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the content of RhOy and cyanides in the sludge of 3.3% and 2100 mg / l,

PRI me R 4. Everything is as in example 1, except for the supply of the amount of dust-air mixture of 1.6 m3 / s. Agglomerate is obtained with a strength of 71.3%, a density of 1.71 g / cm3, and the amount of PxOy and cyanides, respectively, of 2.9% and 2000 mg / L.

PRI me R 5. Everything is as in example 1, except for the feed time of the mixture 1.8 min in the amount of 1.6 m3 / s. Moreover, the agglomerate has a strength of 71.4%, a density of 1.73 g / cm, the amount of PkhOu 2.8%. cyanide 1000 mg / l.

PRI me R 6. Everything is as in example 1, except for the feed time of the mixture of 1.5 min in an amount of 0.85 m / s, the agglomerate in this case has a strength of 70.3, a density of 1.58 g / cm3. The amount of PxOy is 4.5%, and the cyanide content in the sludge is 6100 mg / L.

Example. Everything is as in example 1, except for the feed time of the mixture of 1.5 minutes in an amount

1.6 m3 / s, while the agglomerate has a strength of 71.2, a density of 1.72 g / cm, the amount of PxOy is 3.7%, and the amount of cyanide is 1500 mg / l.

Example p8. Everything is as in example 1, except for the feed time of the mixture of 1.6 min in the amount

1.7 m / s. The sinter in this case has a strength of 70.8%, a density of 1.59 g / cm3. The amount of PxOy is 4.1% and the cyanide content in the sludge is 6100 mg / L.

The table shows that, subject to the limits specified in the formula, the goal is achieved in examples 2-5, 7 and not achieved in examples 1, 6 and 8.

SUMMARY OF THE INVENTION A method for agglomerating a phosphate feedstock, including mixing it with coke, moistening and pelletizing the mixture, loading the pelletized mixture onto the grate of the sintering machine, heating flue gases to ignite coke, sintering with replacing the flue gases with air, sucked from top to bottom through a layer of pelletized mixture crushing the cake, cooling it and isolating a suitable product, returning the fraction minus 5 mm to the mixing stage, characterized in that, in order to increase the yield of phosphorus by increasing the As a result of the agglomerate and environmental improvement, at the end of the sintering process, a dusty mixture containing 50 wt.% boiler dust is passed over the cake surface at a feed rate of 0.86-1.6 m3 / s for 1.20-1.50 minutes.