DD215300A1 - PROCESS FOR PRODUCING RARE CONCENTRATES - Google Patents

Abstract

The invention relates to the production of rare earth concentrates from nitric acid digestion solutions of rock phosphates in the production of NP and NPK fertilizers. The aim and object of the invention is to isolate rare earth compounds and optionally other constituents of the crude phosphate used without prior separation of calcium nitrate from the nitric acid Rohphosphataufschlussloesung is required. According to the invention, the crude phosphate digestion solution is gradually blunted to a defined residual acidity after separation of the digestion residue with gaseous ammonia.

Description

Process for the production of rare earth concentrates Field of application of the invention

The invention relates to the production of rare earth concentrates from nitric acid digestion solutions of rock phosphates in the production of NP and NPK fertilizers.

Characteristic of the known technical solutions

For the production of NP or NPK fertilizers, it is customary to digest crude phosphates with nitric acid. To obtain the rare earth compounds contained in the nitric acid raw phosphate solution, most of the calcium nitrate Ca (NOj) ₂ · 4H ₂ O present is crystallized out and separated, and then the mother liquor is partially ammoniated, whereby the rare earth rock phosphates are precipitated and separated (DE-OS 2,419,928, DD-PS 40,739, DD-PS 65 · 075, RO-PS 73,070). However, the processes mentioned have the disadvantage that besides the not "agile separation of the calcium nitrate as an additional process step, which further processing is required still, since Ca (N0 _{3) 2} .4H ₂ O due to its limited nitrogen content and its hygroscopicity only a relatively represents low-value fertilizer.

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Object of the invention

The aim of the present invention is to propose a process for the preparation of rare earth concentrates from nitric acid crude phosphate digestion solutions, which does not have the deficiencies and disadvantages of the prior art.

Explanation of the essence of the invention

The invention has for its object to isolate rare earth compounds and optionally other constituents of the crude phosphate used without a prior separation of calcium nitrate from the nitric acid Rohphosphataufschlußlösung is required. ''''"" ^:

It has been found that the co-precipitation of the calcium ions is decisively reduced if the blunting of the nitric acid crude phosphate digestion solution, from which the undissolved pulping residue was previously separated, proceeds stepwise to a defined residual acidity. In the digestion of the crude phosphate with nitric acid

" ³ J- - 2+ results in solutions which, in addition to PO ₄ , NO ₃ and Ca ions in the form of calcium nitrate and phosphoric acid, are mainly F ~, SiF ₆ ² ", Al ³⁺ , Fe ³⁺ , Mg ²⁺ , Sr ⁺ and SE ⁺ ions (SE a sum of the elements La ··· ··· Y). In the ammoniation of these solutions, the cations are converted depending on the Neutralisatipnsgrad in sparingly soluble phosphates, partially fluorides, "The implementation of calcium nitrate to dicalcium phosphate proceeds intermediately over monocalcium phosphate in weakly acidic range, where the hydrolysis of calcium silicofluoride begins to sparingly soluble calcium fluoride. Likewise in the weakly acidic medium, the precipitation of the rare earth phosphates takes place. Therefore, in the partial

Araraonization of solutions containing calcium levels corresponding to the total amount introduced with the crude phosphate compared to those from which the calcium ions were deposited largely by prior calcium nitrate crystallization, a substantial complication of the precipitation conditions of the rare earth phosphates to expect «

After erfindungsgeraaßen process raw phosphate, which has a content of rare earth compounds of at least 0.1 % SE ₃ O ₃ , digested with nitric acid, the digestion residue removed by known separation operations and the digestion solution with gaseous ammonia initially to a residual acidity of 1, 9 - η 2.2, and after reaching the constancy of precipitated rainfall per unit time to a residual acidity from 1.5 to 1.8 η · blunted the digestion of the phosphate rock with nitric acid is carried out (AE50% HNO ₃₎ at temperatures of 40-90 ⁰ The amount of acid used is at least 100 %, preferably 105-120%, of the stoichiometrically required amount, based on the sum of the cationic constituents of the crude phosphate. The ammonification of the digestion solution with gaseous ammonia is preferably carried out in a stirred tank into which the digestion solution and NH ₃ -GaS are introduced continuously * The ammoniation reaction takes place at a temperature of 60-140 ⁰ C, preferably 80-120 ⁰ C, instead of ammoniated suspension is continuously withdrawn from the reaction vessel and separated the separated concentrate of rare earth phosphates and then washed with water wa-rmfcm; The concentrates obtained at the different degrees of blunting at the beginning or in the further course of the precipitation have contents of> 15 % of SE ₂ O ₃ , preferably of 18-23 % of SO ₀ O ,, ". The process according to the invention makes it possible to recover

70-80% of the introduced with the raw phosphate "rare earth and ensures a practically constant composition of the Seltenerdkonzentrats obtained during the total duration of the precipitation process If the dulling of the digestion solution, in contrast to the invention process already precipitation beginning to Restaciditäten from - =:. l _f 9 »So the obtained concentrates contents of only - = 10 % SE ₂ O ₃ on.

The resulting after removal of the rare earth concentrate solution is treated to precipitate calcium sulfate with ammonium sulfate or sulfuric acid and then processed by known methods to NP or NPK complex fertilizer · The inventive method has the advantage that it ^ the separation of concentrates of rare earth directly from the nitric acid crude phosphate digestion solution, ie without prior reduction of the calcium content of the digestion solution, allows ¹ · The precipitation of the concentrates is designed «so that their uniform composition is given * The effects of fluctuations or stoppages in the production process are thus eliminated · Under the conditions of the inventive method consistently good filtration and washable rare earth concentrates are obtained.

A further advantage consists in that the residue of the nitric acid rock phosphate digestion to be separated off by the process according to the invention can be used for the recovery of further constituents of the crude phosphate.

The invention will be explained in more detail with reference to an embodiment.

embodiment

In a Ruhrwerksbehälter per hour 1000 parts by weight Kolaapatit concentrate are digested continuously with 2460 parts by weight of 53% nitric acid at 60 ⁰ G * After separation of the digestion residue (66 parts by weight / h), the resulting digestion solution, which Contains 8 parts by weight SEgOj, continuously in

a further stirred tank at 90 ⁰ C treated with 58 parts by weight / h of gaseous ammonia, which sets in the agitator a Restacidität of 1.8 η. From the resulting suspension, the solid is separated by filtration.

In the course of continuous precipitation, the following solids contents of the suspension result:

precipitation time Solids content (Min) (G / i) '60 86 120 67 180 41 240 29 300 28

After a precipitation time of 300 minutes, 62 parts by weight / h are obtained. After washing this amount with 180 parts by weight / h of water and drying remain 28 parts by weight / b rare earth con zeh occurred with a content of 18.9% SE ₀ O, in the course of the precipitation, the NH ₃ supply on 78 parts by weight / h * increased, the Restacidität the > suspension is lowered to 1.5 η. Depending on the precipitation time, the following solids contents of the suspension result:

precipitation time Solids content (Min) (G / i) 360 34 420 38 480 41 560 42 620 42

88 parts by weight of solid are obtained per hour, from which, after washing with 180 parts by weight / h of water and subsequent drying, 39 parts by weight / h of rare earth concentrate with a content of 16.6 % SEpO ₃ result. The filtrate becomes NPK fertilizer further processed · For this purpose, it is first treated with 45 parts by weight / h of magnesium sulfate and 565 parts by weight / h ammonium sulfate, then with 160 parts by weight / h of gaseous ammonia in further stirred agitation tanks. After addition of 1005 parts by weight / h potassium chloride (60 % K ₂ O) and 1500 parts by weight / h Rücklaufgut the mixture is granulated and dried. The resulting NPK fertilizer has levels of 14 % nitrogen, 8 % phosphate (P ₂ ⁰ S), ^{and 14} % potash (K ₂ O).

Claims (3)

ferfindungsanspruch 1. A process for the preparation of rare earth concentrates from nitric acid digestion solutions of rock phosphates in the production of NP or NPK fertilizers, characterized marked «that the crude phosphate digestion solutions after separation of the digestion residue with gaseous ammonia initially to a residual acidity of 1.9 -2.2 η and, after achieving the constant precipitation amount precipitated per unit of time, be blunted to a residual acidity of 1.5-1.8 η. 2. The method according to item 1, characterized in that the blunting of the crude phosphate digestion solutions at temperatures of 60 - 140 ⁰ C takes place. 3 «method according to item 1, characterized in that the digestion residue is worked up to obtain further ingredients of the crude phosphate.