DE4422034C1 - High grade sodium chloride purificn. by leaching and flotation - Google Patents

Abstract

Concn. of salt with a high percentage of NaCl, which also contains soluble and insol. impurities, comprises reducing the salt to a particle size less than 1 mm and contacting it with a soln. which is unsatd. w.r.t. the impurities, a flotation agent and finely-distributed air. In the process (a) a mashed slurry contg. flotation agent is mixed with an excess of several times of recycled soln.; (b) the slurry is passed rapidly into an annular chamber at the foot of a conical vessel, with a moving vertical central tube but no stirrer; (c) the coarsest fraction is dissolved and hydrolysed by a dwell in the bottom zone of the vessel; (d) the medium and fine particles rise into another turbulent zone in the middle of the vessel; (e) the slurry is clarified i.e. the solid is sepd. from the soln. in the top zone and the clarified soln. is discharged through an outlet pipe; (f) the pre-purified fraction sinks inside the central tube, from which fine air bubbles rise and particles of anhydrite and/or kieserite stick to these and are carried upwards, where they are removed with the froth; and (g) the purified grains are discharged at the bottom of the central tube, where a small amt. of circulating soln. enters and rises. Also claimed is the appts. used.

Description

The invention relates to a method and a Device for further concentration of an already hochprozen NaCl salt, which still impurities in soluble and contains insoluble form, wherein the salt is below a grain size crushed by 1 mm, with respect to the impurities subsaturated solution, a flotation agent and finely divided Air is brought into contact. The Cleaning process according to the invention and the Device according to the invention are alike suitable for cleaning natural products as well resulting from the processing of potash salts Residues.

From that obtained from potash deposits in Germany Raw salt is only about 25% for the production of Utilized potassium and magnesium products. The rest - in the main, sodium chloride - becomes elektrosta table, flotation or separated by hot dissolving and must be either as an offset in the deposit ver be deposited or deposited in surface piles.

The pending arrears consist of about 90% sodium chloride. The rest is composed of potassium chloride, calcium sulfate, magnesium sulfate, clay minerals and various double salts of the ions Na⁺, K⁺, Mg ²⁺ , Ca ²⁺ , Cl ^- and SO₄ ^2- . A treatment of these residues to industrial salt not only reduces the environmental pollution caused by bottlenecks, but also leads to a conservation of resources and, since this salt has already been brought to surface anyway, to energy savings.

According to the state of the art there is already a whole Series of proposals, mined stone salt or process-related rock salt residues to clean.  

The production of evaporated salt, being completely first dissolved and then crystallized by evaporation again is with a high energy consumption ver bound and expensive (see ULLMANN's Encyclopaedia of Technical Chemistry, 4th revised. and expand. pad, Verlag Chemie, Weinheim, New York 1979, Volume 17, p. 179 ff.). Furthermore, by direct or in direct flotation of sulphate and clay Minerals are separated, but this leads generally only a moderate success.

A partial solution offers z. For example, DE 40 25 371 A1, where after an electrostatic treatment by a Screening recovered mid-fraction in a NaCl solution slurried and the solid impurities under Addition of a flotation be floated.

Although simple washing processes suppress quality min enduring caustics, but lead only in limited Measures to increase quality. An improvement leaves By contrast, achieve by leaching.

According to DE 28 11 889 A1, the washing solution is a Mineral acid added and for several hours touched. But the effectiveness of this procedure limited and requires the neutralization of Residual solutions.

In the patent DD 2 90 405 A1 a leaching Ver recommended for the purification of sodium chloride conditions in which the salt in a pure, of hardness bildner free NaCl brine is leached. In one However, potash processing plant stands in the  Usually no pure NaCl brine available and she must be set accordingly fresh. this leads to to a significant additional burden of the Laugenhaushal tes in the relevant establishments, which in many Difficult to cope with. In addition, must for the production of pure brine - if no ent speaking, clean sodium chloride is available - Diverted a portion of the purified product become and thus lost as a yield.

The aim of the invention is, by a combination of Leaching and flotation in a simple apparatus Cleaning procedure and use of a wide Spectrum of treatment solutions a high quality NaCl product with a purity of <99% NaCl manufacture.

Suitable starting materials are rock salt lower quality residues of the potash industry, such as For example, in the electrostatic Tren tion, the flotation and the hot-dissolving of Kalirohsalzen accrue. In an application of the Procedure, it is advantageous if as a treatment solution a lye already in operation can be used. For example, arise at different decking solutions that Sodium chloride are saturated, but for potassium chloride chloride, magnesium chloride and sulfate and even for Calcium sulfate still have enough dissolving capacity.

According to the invention, the possibility of use of such cover solutions as a treatment solution the combination of a selective dissolving and created a pneumatic flotation.  

In addition, the selective dissolution is controlled by a controlled Loosening (digesting) the sodium chloride matrix accelerates. Therefore this sub-process should be referred to below as "active leaching" net. The two sub-processes active leaching and flotation are carried out simultaneously in the same apparatus.

The inventive method combines according to claim 1 in individual following features:

• - Mixing the mashed, flotation-containing Cloudy with a multiple excess of recycled solution.
• - Quick introduction of this pulp in the ring arm at the foot of a cone-shaped, stirrer-less container, which with a movable vertical central tube is provided.
• - Dissolving and digestion of the coarsest parts by staying in un lower parts of the cone-shaped container.
• - Rise of medium and fine particles in the also tur Bulente zone in the middle part of the container.
• - Clarify, d. H. Separate the solid from the solution in the top Part of the cone-shaped container and leaving the clarified Solution via a vent pipe.  
• - Lowering of the pre-cleaned parts in the vertical inner tube, from the finely divided air bubbles rising to anhydride or Kieseritkörner adhere and carry them up where they be removed with foam layer.
• - Peel off the cleaned grains at the bottom of the vertical Inner tube, at which point a small part of the circle running solution occurs and rises against the sinking parts.

Advantageously, the withdrawn through the (upper) exhaust pipe Circulation solution heated by a heat exchanger and up divides, with the vast majority at the foot of the cone-shaped Behäl ters enters the annulus and a small part in the inner tube entry.

The apparatus according to the invention is described in claim 7. It consists of a conical vessel 1 , in the top of a height adjustable product exhaust pipe 2 is incorporated. The mix-treated with the Be treatment solution 7 and 13 raw crystal is fed to coni rule end of the apparatus via a pump 14 coming from Anmaischgefäß 9 coming. An internal circulation flow 4 ensures that the raw material to be cleaned is held in suspension in a fluidized bed.

The crude crystals to be purified is usually one with respect to the Grain inhomogeneous mixture. It has been observed that Ver Impurities to a greater extent on the coarsest and the finest Grain fractions are distributed. In the cleaning process must therefore be be aware that the coarser  Grains require a longer residence time than the average Kornfraktio NEN. The ultrafine particles that have a higher specific surface should be resolved if possible.

According to the invention this is achieved by an internal classification. Coarser grains are retained in the apparatus due to the higher rate of descent. A diverted from the circulation flow 4 partial flow 17 is passed from below through the product exhaust pipe 2 , whereby the finest proportions are returned in the main amount back into the fluidized bed.

In addition, air 3 is introduced into the product discharge pipe 2 and thus simultaneously serves as a flotation region. The abge separated by the flotation difficult and insoluble impurities 19 are discharged at the upper end of the reaction vessel.

The device according to the invention is divided into three areas:

• a floating bed 1 a, in which the raw material is leached and the soluble impurities are separated,
• - A flotation and Classierstrecke 1 b, in which the alkaline earth sulfates and the insoluble constituents are removed and the ultrafine grain is transported back into the main reactor
• - And a calming zone 1 c in the upper part of the reactor, which allows a better separation of the flotation concentrate.

All sodium chloride solutions which still have a dissolving capacity for potassium chloride and magnesium sulfate are suitable as the treatment solution. It has been found that the implementation of the method according to the invention is better achieved if the treatment solution is slightly undersaturated with respect to sodium chloride. As a result, the digestion of impurities is promoted and accelerated leaching due to the partial dissolution of the coarser grains. For this purpose, water 11 may be added to the treatment solution.

For effective leaching and short residence times to achieve the cleaning of the invention at elevated temperature, preferably 30- 80 ° C performed.

In the examples, the invention is further erläu tert. The flotation agent HSO W 46453 from Stockhausen was used in each case as a 1% solution. The addition of the flotation agent was carried out continuously into the mash vessel 9 .

example 1

In Example 1, the device according to the invention with about 0.5 kg / h of crude NaCl of the composition:

NaCl | 94.1% KCl 1.9% MgSO₄ · H₂O 2.5% CaSO₄ 1.5%

and fed with about 0.5 l / h of pure NaCl brine. Both components were fed continuously. The cleaning process was carried out at about 60 ° C, the rate of dissolution was about 10%.
Flotation agent quantity: 100.

The product was at the bottom of the product hood collected, filtered and dried. there the following final quality was achieved:

NaCl | 99.5% KCl 0.2% MgSO₄ · H₂O 0.2% CaSO₄ 0.06%

Example 2

In example 2, a larger apparatus was used at about 5 kg / h Crude NaCl of the composition:

NaCl | 92.3% KCl 2.8% MgSO₄ · H₂O 3.0% CaSO₄ 1.9%

and about 15 l / h of a treatment solution together translation:

NaCl | 313 g / l KCl 11 g / l MgSO₄ · H₂O 5 g / l CaSO₄ 2 g / l

continuously applied.
Flotation agent quantity: 200

The cleaning was at 50-60 ° C with a trigger rate of about 10%. The filtered and dried product had the following quality:

NaCl | 99.6% KCl 0.1% MgSO₄ · H₂O 0.03% CaSO₄ 0.3%

Example 3

In this example again about 5 kg / h Rohma material of composition:

NaCl | 92.4% KCl 2.6% MgSO₄ · H₂O 3.1% CaSO₄ 1.9%

and about 15 l / h of the following treatment solution:

NaCl | 294 g / l KCl 23 g / l MgSO₄ · H₂O 42 g / l CaSO₄ 2 g / l

fed.
Flotation agent quantity: 200

The cleaning was again carried out at 50-60 ° C, but at a dissolution rate of about 20%. It was received the following product:

NaCl | 99.2% KCl 0.1% MgSO₄ · H₂O 0.05% CaSO ₄ 0.6%

Claims (7)

1. A method for further concentration of an already hochprozen term NaCl salt, which still contains impurities in soluble and insoluble form, wherein the salt comminuted to a particle size of 1 mm, undersaturated with respect to the impurities, a flotation agent and finely divided air in contact brought by the combination of the following characteristics:

• Mixing the mashed flotation-containing pulp with a multiple excess of recirculated solution.
• - Rapid introduction of this slurry in the annulus at the foot of a cone-shaped, stirrerless container, which is provided with a movable vertical central tube.
• - Dissolving and digesting the coarsest parts by staying in the lower part of the cone-shaped container.
• - Upgrading of the medium and finer particles in the likewise turbulent zone in the middle part of the container.
• Clarifying, ie separating the solid from the solution in the upper part of the cone-shaped container and leaving the clarified solution via a flue.
• - Lowering of the pre-cleaned parts in the ver tical inner tube from which rise the finely divided air bubbles, which adhere to anhydrite or Kieseritkörner and carry them upwards, where they are removed with a foam layer.
• - Remove the cleaned grains at the bottom of the vertical inner tube, at which point a small part of the circulation solution occurs and rises against the sinking parts.

2. The method according to claim 1, characterized in that by the trigger tube withdrawn circulatory solution using a Heat exchanger is heated and split, wherein the vast majority at the foot of the cone-shaped Container enters the annulus and a clot ger part enters the inner tube. 3. The method according to claim 1 and 2, characterized in that the for treatment in Reaction space, used circulatory solution KCl content <30 g / l, a MgSO₄ content <50 g / l and a CaSO₄ content <2 g / l. 4. The method according to claim 1 to 3, characterized in that the for treatment in Reaction space used circulatory solution Saturation with respect to NaCl, which is a triggering agent allow the treated grains up to 40% can, has.   5. The method according to claim 1 to 4, characterized in that the temperature in Reaction vessel, between 30 ° and 80 ° C. 6. The method according to claim 1 to 5, characterized in that as a flotation agent Fatty acids and sulfated or sulfonated fat acids - supplemented as required by adhesion promoters - be used. 7. Apparatus for carrying out the method according to claims 1 to 6, characterized in that a conical stirrerless reaction vessel ( 1 ) with a verti len product exhaust pipe ( 2 ), which has variable height by essays and in which the flotation air flow ( 3 ) is entered , Is provided, and that the reaction vessel ( 1 ) via a zugeord Neten circuit ( 4 ) for supporting the solid bed and the withdrawal of the solution from the reac tion vessel ( 1 ) and with an associated heat exchanger ( 5 ) and with the Anmaischgefäß ( 9 ) through the lines ( 7 ) and ( 15 ) for the import of the clean, the batch and with the exhaust pipe ( 2 ) through a conduit ( 17 ) for the screening of the grains in the product exhaust pipe in connection.