CS259784B1 - A method for obtaining rare earth phosphate concentrate - Google Patents

Abstract

The separation of rare earths in the production of phosphates from extraction phosphoric acid is achieved by pre-neutralizing the extraction phosphoric acid from 5 to 80% in the first stage, the resulting sludge is separated and processed further as a rare earth phosphate concentrate. Before pre-neutralization, 0.05 to 3 tons of sludge from the previous neutralization can be dissolved in the extraction phosphoric acid. The amount of lime phosphate is based on 10 tons of phosphoric acid.

Description

The present invention relates to a process for obtaining a rare earth phosphate concentrate in the production of phosphates.

Apatites and phosphites processed into phosphoric acid extract or NPK fertilizer contain a number of other compounds besides phosphorus, among them rare earth compounds Apatites of different localities contain in the converted state 0.5 to 1% by mass · rare earth oxides, phosphorus mostly mostly by less · In the production of NPK fertilizers by nitrosulphate and nitrophosphoric freezing, apatite is always decomposed first with nitric acid · From the pure slurries formed as an intermediate in the production of NPK fertilizers, rare earth phosphate concentrate can be isolated · The procedure is based on the fact that neutral! zaoi clear slurries first fall out of rare earth phosphates · These are separated separately and further processed as needed into individual scarce soils, while the slurry after separation of rare earths is further processed by conventional technologies to NPK fertilizer ·

The decomposition of phosphoric raw material with sulfuric acid produces phosphoric acid and calcium sulphate, so-called · phosphorous gypsum · 20 to 40% of the original content of rare earths in the phosphorous raw material is transferred to the extraction phosphoric acid ·

Depending on the rare earth content of the phosphorous raw material and the degree of transition of the rare earths to the acid, the extracting acid is 0.1 to 25% of the rare earth oxides.

Further processing of the phosphoric acid extract into phosphoric salts results in a neutralizing sludge, called lime-phos, into which all the rare earth content of phosphoric acid is concentrated. Its content in limestone depends on the rare earth content of the starting phosphoric acid and the degree of neutralization. When neutralized to the second stage, the content of rare earth oxides in lime-phosphos is from 1 to 3.7% by weight.

While in the separation of rare earths from apatite in the production of NPK fertilizers, rare earths pass into a frozen slurry almost quantitatively, in the production of phosphoric acid, a considerable part of the rare earths are lost in the phosphogypsum. The separation of the rare earths that remain in the phosphoric acid extraction would be inefficient using the above-mentioned procedures due to its low concentration. Existing procedures do not allow the isolation of rare earths from limephos deposited in landfills.

The object of the invention is to provide a rare earth phosphate concentrate for the production of phosphates according to the invention, wherein the phosphoric acid extract is pre-neutralized from 5 to 80% to the first stage formed the sludge is separated from the pre-neutralized phosphoric acid solution and further processed as a rare earth phosphate concentrate. Prior to pre-neutralization, 0.05 to 3 tonnes of sludge (lime-phosphate) from the previously carried out neutralization of phosphoric acid, for example from the heaps, based on 10 tonnes of phosphoric acid, can be dissolved in the phosphoric acid extraction.

The inventive method allows to obtain a concentrate containing 4-10% rare earth oxide, and in the case of addition to the VAP ¹ nofosu 9-16% rare earth oxides without disrupting its own technology for producing phosphates EI modifications. In other words, the present process solves the recovery of those rare earths which are not used in the current phosphoric acid or salt process and are weighed with lime-phosphate as landfill. raw materials and is not bound to the production of only one phosphorus salt ·

The invention is based on the preliminary formation of only a portion of lime-phosphos by performing pre-neutralization to the first stage of only 5 to 80%, as rare earth phosphates are preferentially eliminated * Rare earth concentrations in lime phosphate in normal phosphate production are relatively low and pre-neutralized to 4 to 10% rare earth oxides. The only modification of the phosphate production technology is that after pre-neutralization the precipitated sludge is separated and pre-neutralized phosphoric acid is stored instead of the phosphoric acid stored today. In the next stage of processing into phosphoric salts, only the amount of caustic to be neutralized is reduced by the amount used in the pre-neutralization.

The procedure for isolating the rare earth phosphate concentrate consists of the following sub-operations: continuous production of phosphoric acid, continuous pre-neutralization, continuous concentration of the rare earth phosphate suspension and discontinuous filtration of the concentrated suspension on a pressure filter. A discontinuous solution of pre-neutralization and suspension thickening on any suitable type of filter is also possible.

In the plants producing phosphoric acid »phosphoric acid and phosphate salts, alluvial heaps of neutralizing sludge of vepnofos are available. Due to its rare earth content, it is also appropriate to obtain these. To this end, limephos is dissolved in phosphoric acid extraction in the first stirred neutralizer of the pre-neutralization line. Upon dissolution, the rare earth enriched phosphoric acid is pre-neutralized, precipitating the rare earth phosphates which are separated. % of the phosphoric acid used and the rare earth content is increased to 9 to 16 wt. expressed as oxides. The choice of the neutralizing agent (cation) is determined by the requirement for the composition of the phosphorus salt.

Example 1

For the continuous production of phosphoric acid from the Apatite Wheel, a continuous pre-neutralization of this acid of 20% of the total amount of sodium hydroxide required to neutralize the phosphoric acid to the first stage is followed. The precipitated sludge is continuously concentrated and filtered on a pressure filter. In this way, a rare earth phosphate concentrate containing 8% rare earth oxides is obtained.

Example 2

Extractive phosphoric acid is produced in a continuous manner by decomposing the Apatite Wheel with sulfuric acid. In the phosphoric acid prepared this way, the neutralizing sludge from lime-phosphorus deponia from previous years is continuously dissolved.

After dissolution of lime phosphate, phosphoric acid is continuously pre-neutralized with the 20% sodium hydroxide needed to neutralize phosphoric acid to the first stage. slightly, the rare earth oxide content of this sludge (concentrate) increased to 13% by weight; expressed in oxides ·

Claims (2)

OF THE INVENTION Process for obtaining a rare earth phosphate concentrate in the production of phosphates, characterized in that the phosphoric acid extract is pre-neutralized from 5 to 80% to the first stage, the resulting sludge is separated from the pre-neutralized phosphoric acid solution and further processed as a rare earth phosphate concentrate 2 · Method. according to claim 1, characterized in that 0.05 to 3 tonnes of sludge from a previously carried out neutralization of phosphoric acid, for example, waste, based on 10 tonnes of phosphoric acid, are dissolved in the phosphoric acid before the pretreatment.