DD244739A1 - METHOD FOR THE THERMAL ENTSULPATION OF CARNALITE SOLE - Google Patents

Abstract

The invention relates to the desulfurization of solutions which are obtained in the soltechnische extraction of carnallitite or in the processing of these sols. The goal and task are the processing of solutions with higher MgSO4 levels to high-quality Kaliduengemitteln, concentrated MgCl2 sols and other by-products and sulfated fertilizers with reasonable effort while avoiding sulfatic encrustations. According to the invention, the carnallis sols and / or the solutions obtained during the processing of the brine are desulphurized thermally with the excretion of langbeinite before and during the evaporation process which precedes the crystallization of the KCl-containing intermediate product. The technical solution can be used in brine processing after the soltechnische extraction of the crude salt carnallitite.

Description

Field of application of the invention

The process relates to the desulphation of solutions which are obtained in the soltechnische extraction of carnallitite and / or in the processing of the carnallitsolen obtained and from which in addition to high quality potash fertilizers and Magnesiumchloridsolen and other by-products are produced. In the processing of these solutions, sulphate supersaturations lead to encrustations of the heat transfer surfaces during preheating and evaporation processes as well as to sulphate precipitations in undesired modifications which can cause malfunctions. With the method according to the invention is a reduction of the sulfate content of the circulating solutions by the crystallization of the double salt Langbeinit, which can be separated by mechanical methods of the solutions separable and reprocessed to sulfatic fertilizers, with a reasonable additional energy and equipment expense possible. The application of the method is limited to the brine processing after soltechnische extraction of Kalirohsalzes carnallitite.

Characteristic of the known technical solutions

For the sol-extraction of carnallitite and for the production of potash fertilizers as the carnallitols various methods are known, according to which by the use of suitable solvents and solution conditions (temperature, residence time) a selective dissolution of carnallitite can be achieved. Secondary constituents such as sodium chloride and sulfatic salts remain largely in the sol chamber. While in DD WP33054 the highest possible sol temperatures are recommended (so-called hot solu- tion), which can only be reached to a limited extent due to the high heat losses, according to the DD WP 200020 dissolving temperatures of 50 to 60 ⁰ C should be used in the production caverns. The preparation of the intermediate product of artificial carnallite is carried out by evaporating and cooling the brine, wherein the solvent is prepared from part of the resulting mother liquor. To avoid adverse effects on the processing process by crystallization of sulphate salts and by In-crustations of heating surfaces, the magnesium sulfate content of the brine must be kept as low as possible, which limits the applicability of the method. According to the DD WP 202861 can be produced by the additional cost-effective withdrawal of water from the cycle of Carnallitsoleverarbeitung in addition to the potash fertilizer and a salable concentrated MgCl ₂ -SoIe. In this case, however, increasingly sulfatic supersaturations of the solution can occur with the mentioned negative effects on the processing process. This is particularly true for the method according to DD WP 220013, according to which the carnallisole to be processed is subjected to a so-called primary evaporation and cooling process, in which artificial carnallite (primary crystals) and mother liquor are obtained, which is further evaporated together with the solution of the processing of the artificial carnallite and then cooled.

Due to the high solution temperatures and MgCl ₂ concentrations in the secondary evaporation process, which should be carried out partly under pressure because of the desired full utilization of the vapor heat, it can lead to a sulfate failure in unwanted modifications and Heizflächenverkrustungen.

For the clearing of MgSCV-containing carnallitite deposits, a method was developed with which both carnallitite and kieserite (MgSO ₄ · H ₂ O) can be obtained from a sol chamber spatially and temporally separated from each other (DD WP 201173). The kieserite can be used to produce alkali or magnesium sulphates. When using the solvent, water traps two different quality, low and high MgSO ₄ sols. A disadvantage is the fact that no pure artificial carnallite can be produced from the accumulating Carnallitsole without significant expenditure, which is why these brine should be used mainly for the decomposition of the artificial carnallite from the process according to DD WP 200020. In addition to various precipitation methods and in addition to the freezing of the circulating solutions, methods of thermal desulfating are known for the reduction of sulphatic supersaturations, in which crystallization of MgSO ₄ can be achieved under high temperatures and turbulences and with a corresponding residence time of the solution. The required residence time of the solution can be reduced by the use of seed crystals (DD WP 129206, DD WP 142328, DD WP 200272). The seed crystals should consist as much as possible of the crust-forming constituents and be fine-grained (large specific surface area).

According to DD WP 212949, use of seed deposit or recirculation prevents heating surface incrustations in the evaporation of MgCl2 solutions, whereas DD WP 200 272 prevents seed crystals to lower the sulfate content of MgCl ₂ sols, ie from mother liquor solution (hard salt and carnallitite) by evaporation and cooling produced by crystallization of artificial camallite, should be used in the evaporation process. In both cases it is magnesium sulfate - ^5/4 hydrate, whose separation from the hot solution due to the small particle size of 10 to 50 / xm requires significant expenditure. Incomplete separation of the ^5/4 hydrate results in undesirable contamination of the artificial camallite intermediate and disturbances in the filtration of the carnallitite-containing solutions. Disadvantages are also the necessary high technical expenses for further processing of the ⁵ A hydrate, which is why the crystals are driven after separation in practice together with other products on waste heap.

According to DE AS 2513947, a reduction in the sulphate content by long-legite crystallization during the evaporation process is possible in the treatment of solutions containing potassium chloride and magnesium chloride and magnesium sulphate which are saturated with sodium chloride. Langbeinite seed recycling requires maintaining a high solids concentration in the evaporation plant. This process allows for partial desulfating of the solution, but has several disadvantages. So occurs at solids contents of about 200 g / l in the circulation of the evaporation plant, a high wear and the Entsulfatisierungsgrad the solution is relatively low. For processing KaIirohsalzen the so-called Hartsalztypes with multicomponent sulfate fractions is proposed in DD WP 222295 to lower the MgSO ₄ levels of the circulating operating solutions so far that no unwanted formation of processing double sulfates can be done. This should be done by thermal desulphation to crystallize Langbeinit. The process relates to the processing of salts with low levels of magnesium chloride, which present other problems compared to carnallitic crude salts.

Object of the invention

The invention has the object · to enable the processing of solutions with higher magnesium sulfate contents, which are obtained in the soltechnische extraction of camallite and / or in the processing of the obtained carnallitols to salable products and in which can occur with the known methods processing difficulties, so that with a justifiable additional economic effort in addition to high quality potash fertilizers, concentrated Magnesiumchloridsolenurtd other by-products and sulfatic fertilizers can be produced. With the invention, limitations in the applicability of known brine processing methods should be largely eliminated and their operational stability should be noticeably increased.

Explanation of the essence of the invention

The invention has for its object to achieve a Teilentsulfatisierung the solutions with a justifiable additional equipment and energy costs, so that during processing no stronger sulfate supersaturations may occur, leading to incrustations of the heat transfer surfaces and the sulfate excretion in undesirable modifications. It is a further object to carry out the crystallization in the form of langbeinite, which can be separated from the solution with relatively little effort by mechanical processes and can be further processed into sulphatic fertilizers by known processes. The object is achieved in that the Carnallitsole and / or in the processing of the brine to salable products resulting solutions before and during the evaporation process, which is upstream of the crystallization of the KCI-containing intermediate product is thermally desulfated with the elimination of langbeinite.

The required preheating of the solution to temperatures of 80 to 13O ⁰ C before the evaporation process technologically necessary anyway, while another requirement for the Langbeinitkristallisation, the KCI saturation of the solution must be created by dissolving KCI and / or camallite. By using Langbeinitimpfkristallen the effectiveness of the process can be increased, which ensures a homogenization of the composition of the solution (relatively constant and low MgSO ₄ content) at the entrance to the evaporation plant.

The processing of Carnallitsole carried out according to the known methods, which are extended by process stages for thermal desulphation and Langbeinitabtrennung and processing. The sulphate-containing solutions to be evaporated are preheated before the evaporation process by vapors of the expansion and circulation evaporation and, if necessary, by heating steam to temperatures above 8O ⁰ C and then the KCI saturation prepared by dissolving the said salts. During the Entsulfatisierungsprozesses an enrichment of Langbeinitkristallen carried out by recycling of suspended solids from the downstream separation apparatus or by using crystallizers with low-solids overflows. The achievable degree of desulfurization of the brine depends essentially on the residence time (size and number of crystallizers), on the temperature and on the solids content of the suspension. Another factor is the turbulence of the brine during desulphation.

The separation of the resulting Langbeinits can be done in a downstream hot clarifier or in the crystallizers themselves (apparatuses with low-solids overflows), with a complete separation is not desirable, since the solid is used in the downstream evaporation of the prevention of Heizflächenverkrustungen. In addition to a abrasive effect in the heating tubes, the presence of the solid counteracts the formation of sulphate supersaturations during the evaporation process. Aufgrun'd the good Kläreigenschaften the langbeinithaltigen solution are the required clarification surfaces in comparison to other sulfate modifications, for example to MgSO ₄ · ⁵ U H ₂ O, low. Prior to the onset of camal crystallization in the flash vaporization unit, separation of residual langbeinite and possibly crystallized sodium chloride by hot clarification is required. Due to the different particle sizes, a separation of both solids by mechanical methods (clarification, cyclone) can be made. The Langbeinit to be carried out from the process can either be used as fertilizer after appropriate dewatering and drying or reacted by known methods to potassium sulfate. The resulting conversion solutions

MgCl ₂ KCI NaCl _MgSO4 H ₂ O 309 45 26 37 871

can be favorably incorporated into the process of processing the Camallitsole by the application of the method according to the invention of the thermal desulfating by being added to the solutions to be desulfated. A further explanation of the method is based on the following embodiments.

Embodiment 1

In a Carnallitsolverarbeitungsverfahren, which is characterized by a two-fold inclusion of evaporation and Abkühlanlagen and thus by a primary and a secondary crystallization of artificial carnallite (DD-WP 220013), is following the upstream primary flash evaporation system to heat a solution mixture from this Solution mixture is to withdraw water in a circulation evaporator and then withdraw in the secondary flash evaporation system further amounts of solvent and crystallize artificial carnallite (secondary crystals).

The solution mixture is from 350.4 m ³ / h (35 ⁰ C) mother liquor of the primary crystallization of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 391 17 10 28 866

and from 310.6 m ³ / h (2O ⁰ C) decomposition solution which is formed during the processing of the artificial camallite (primary and secondary crystals) and has the following composition:

g / i

The sulfate-containing solution to be evaporated mixture is heated by vapor of the secondary flash evaporation process at 100 ⁰ C and then by stirring with 188,4t / h wet, artificial carnallite following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

Percent 31.06 18.94 7.35 0.50 42.15

and with 10.7t / h of wet potassium chloride of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

Percent 0.70 79.00 9.30 - 11.00

produced the KCI saturation.

The KCI saturated solution is fed to a low solids crystallization crystallizer for the purpose of partial desulfation by Langbeinite crystallization. At the overflow, a suspension is taken from the crystallizer, which consists of 796.3 m ³ / h (85 ⁰ C) teilentsulfatisierter solution of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 367 77 23 21 819

and from 3.0t / h of langbeinite-NaCl solid mixture of the following composition

MgCl ₂ KCl NaCl MgSO ₄ K ₂ SO ₄ H ₂ O

Percent - - 53.33 27.07 19.60 -

The suspension is fed to the evaporation process, whereby Heizflächenvercrustungen and sulfatic supersaturations are largely reduced. After the fine separation of the present in small quantities NaCl Langbeinit solid mixture immediately after the evaporation process, the further processing of the solution by known methods (DD-WP 220013) take place.

Another result of the partial de-sulphating step is the 15.1 t / h of a wet salt mixture (langbeinite-NaCl mixture) having the following composition

percent

The main constituents NaCl and langbeinite are largely separated by known processes and the langbeinite is provided as fertilizer.

Embodiment 2

In addition to the components considered in Example 1 for the mixture of the sulphate-containing solution to be evaporated, even smaller amounts of excess solutions from the potassium magnesium transformation process and the potassium sulphate conversion process are to be co-processed

The mixed solution is prepared from 358.0 m ³ / h (35 ° C) mother liquor of the primary crystallization of the following composition

g / i

MgCl ₂ KCI NaCl _MgSO4 K ₂ SO ₄ H ₂ O 6.6 1.3 41.4 21.1 15.1 14.5

MgCl ₂ KCI NaCl _MgSO4 H ₂ O 391 17 10 28 866

from 351.4m ³ / h (2O ⁰ C) decomposition solution of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 309 45 26 37 871

from 7.3m ³ / h (5O ⁰ C) potassium sulphate solution of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 67 198 39 76 861

and from 10,1 m ³ / h (20 ⁰ C) of the following composition Kalimagnesiaumausetzungslösung

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 188 62 63 86 886

educated. The solution mixture is heated to 100 ° C by means of vapors of the secondary flash evaporation process, and then by stirring with 249.7t / h wet, artificial carnallite of the following composition

MgCl ₂ KCl NaCl MgSO ₄ .H ₂ O

Percent 31.06 18.94 7.35 0.50 42.15

and with 1.6t / h wet potassium chloride of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

Percent 0.70 79.00 9.30 - 11.00

produced the KCI saturation. The KCI saturated solution is fed to a low solids crystallization crystallizer for the purpose of partial desulfation by Langbeinite crystallization. At the overflow, a suspension is taken from the crystallizer, which consists of 896m ³ / h (85 ⁰ C) teilentsulfatisierter solution of the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 367 77 23 21 819

and from 4.1 t / h of langbeinite-NaCl solids mixture of the following composition

MgCl ₂ KCl NaCl MgSO ₄ K ₂ SO ₄ H ₂ O

Percent - - 58.54 24.05. 17,41 -

This suspension is fed to the evaporation process, whereby Heizflächenvercrustungen and sulfatic supersaturations are largely reduced. After fine separation of the present in small quantities Langbeinit-NaCl solid mixture immediately after the evaporation process in the circulation evaporation plant, the further processing of the solution can be carried out by known methods (DD-WP 220013). Another result of the Teilentsulfatisierungsstufe are 20.7t / h of a wet salt mixture (Langbeinit-NaCl) having the following composition

percent

The NaCl is separated by mechanical process (serious differences in grain size) as far as possible from the langbeinite and the remaining 9.0t / h moist Langbeinit with the following composition

percent

are used as starting material for the production of potassium sulfate. The wet long legite is stirred with 14.7m ³ / h of Kaiiumsulfatesetzungslösung incurred in the further processing of said composition and the forming Schönitkristallisat separated from the KalimagnesiaumsetzungsEs resulting 10.1 m ³ / h Kalimagnesiaumsetzungslösung said composition, which is used as a component for the mixture the sulfate-containing, to be evaporated solution in the manner described in the processing process are recycled, and 14,1 t / h of wet crystals of the following composition

percent

The moist Kalimagnesia is then stirred at 60 ⁰ C with 18.1 m ³ / h KCl solution prepared by dissolving wet potassium chloride in water and having the following composition

MgCl ₂ KCl NaCl MgSO ₄ H ₂ O

g / l 3 293 34-850

MgCl ₂ KCI NaCl _MgSO4 K ₂ SO ₄ H ₂ O 6.38 1.35 45.31 19.13 13.57 14.25

MgCl ₂ KCI NaCl _MgSO4 K ₂ SO ₄ H ₂ O 6.22 1.33 3.78 -43.56 31.22 13.89

MgCl ₂ KCI NaCl _MgSO4 K ₂ SO ₄ H ₂ O 3.19 7.80 1.84 22.40 30.33 34.44

The potassium sulfate crystals which form is separated from the potassium sulfate reaction solution. There are 22m ³ / h Kaiiumsuifumsatzsetzungslösung the composition

g / i

wherein 14.7m ³ / h for Kalimagnesiaherstellung and 7.3m ³ / h are used as a component for the mixture of the sulfate-containing, evaporating solution in the manner described. Furthermore arise 8.2 t / h of moist potassium sulfate of the following composition

MgCl ₂ . KCI NaCl _MgSO4 H ₂ 67 198 39 76 861

MgCl ₂ KCI NaCl _MgSO4 K ₂ SO ₄ H ₂ 1.22 3.66 0.73 1.46 76.83 16.10

Percent The moist potassium sulfate is dried and provided as fertilizer.

Claims (2)

Invention claim: 1. A process for the thermal desulphation of camallitose and / or the solutions resulting from the processing of carnallitsole by Langbeinitkristallisation by heating the solutions to be desulfated, saturated KCI, provided with Langbeinitimpfkristallen and turbulence, characterized in that the desulfurization before and during the evaporation process and thus before the crystallization of the total amount or a subset of the KCI-containing intermediate product is carried out, wherein the solution preheated by vapors of the evaporation process and, if necessary by heating steam to temperatures between 80 and 130 ⁰ C, the KCI saturation by reading , made by KCI and / or carnallite, an enrichment of Langbeinitkristallen by solids recycling or made by use of crystallizers with low-solids overflow and the resulting langbeinite is partially separated and partially with the solution in the evaporation process is performed to Heizflächencrust and sulfatic supersaturations to reduce, and from the hot evaporated solution, a mechanical separation of Langbeinits together with optionally accumulating sodium chloride before the crystallization of KCI-containing intermediate product is carried out. 2. The method according to item !, characterized in that the resulting Kristallisatzu sulfatischen fertilizers is processed by the Langbeinit mechanically separated from the solid NaCl and used after dehydration and drying itself as fertilizer and / or reacted by known methods to potassium sulfate, the reaction solutions in involved in the process of Carnallitsoleverarbeitung by mixing with the solutions to be desulfated.