DD280742A1 - METHOD FOR OBTAINING AND RECYCLING DOUBLE SULFATE SALT CRUSTS - Google Patents

Abstract

The invention relates to a process for the production and recovery of double sulfate-containing salt crusts from evaporation plants of the potash industry. The aim and object of the invention is to avoid loss of valuable material in the removal of double sulfate-containing salt crusts in evaporation plants and in the complete utilization of crust ingredients. According to the invention, the object is achieved by filling the incrusted parts of the apparatus with a portion of the process water at temperatures between 50 and 90 ° C. and adding the batch solution thus obtained in metered quantity to the process water of the potassium sulfate process.

Description

7iel the invention

The aim of the invention is the avoidance of material losses in the removal of double sulfate-containing salt crusts in evaporation plants and the complete utilization of crust ingredients.

Explanation of the essence of the invention

The technical Aufgabi the invention consists in the complete removal of salt crusts and the use of Krusteninhaltsstoffe for potassium sulfate production and thus their utilization while avoiding energy-consuming and costly evaporation steps.

This object of the invention is achieved

by periodically filling the encrusted parts of the apparatus with part of the process water of the potassium sulphate process,

the dissolution of the crusts into an unsaturated solution having a density of from 1060 to 1,12 g / cm ³ , their contents of potassium, magnesium, chloride and sulphate corresponding to the ratio of single and double solid salts in the crusts,

- the Zwichenstapelung the recovered, unsaturated rinse solution and their admixture with the process water for the potassium sulfate process in such a relation that the mixture has a density <1.050 g / cm ³ .

Surprisingly, it has been found that the rinsing solutions which form during the dissolution of the encrusted apparatus and whose relation K: Mg: SO ₄ : CI differs greatly from the ionic relation of the potassium sulfate, especially due to double sulfates, and furthermore also contains considerable amounts of Mg and chloride ions certain proportions can be added to the process water, wherein the content of recyclables can be recovered directly and almost completely as potassium sulfate. It has been found that the crusts which form within a cycle of several days during ongoing operation of the evaporation plant can be dissolved with a portion of the process water quantity required for potassium sulphate production, if after several days of operation the evaporation equipment is completely drained, filled with water from the process water tank, Subsequently, at temperatures of 50 to 9O ⁰ C in the course of several hours, depending on the nature and extent of encrustation, dissolved and in this way an unsaturated potassium and magnesium sulfate, partially chloride-containing solution is obtained. This solution has a density between 1.060 to 1.12 g / cm ³ and is discharged from the evaporation plant and during the following several days operating period of the potassium sulfate plant the process water in a certain proportion, which can be regulated according to the density mixed, and the mixture instead of pure Process water fed into the potassium sulfate conversion. Depending on the amount of seizure and the density of the rinsing solution, the rinsing water addition can take place over the course of a longer or shorter period in the following stage of the KjSO 2 production. Up to the density of 1.050 g / cm ³ in the mixture of rinsing solution and water surprisingly no negative effects of the potassium sulfate process occur. Above this limit, that is to say with forced feeding of the rinsing water in a shortened period of time, due to the high content of Mg and SO _4, chemical and salting-out of the finest germs can also cause physical quality effects, which can certainly be avoided if the relation Rinsing solution. Water is adjusted so that a density of 1.035 to a maximum of 1.050 g / cm ³ results. Down to the mixing density of 1.0 g / cm ³ (water), stepless mixing is possible. The invention will be explained in more detail in an embodiment.

embodiment

For this figure 1

An evaporation plant, consisting of radiator 1, Ausdampfkörper 2, circulation line 3 and circulating pump 4 is taken after a prolonged period of operation with formation of salt crusts of salts kainite, langbeinite and sylvin out of service and drained the suspension content by opening the valve 10. From the container 6, which is in communication with the reservoir 5 for hot process water and can be shut off by a valve 1, is pumped through the pump 8 warm, dissolvable water through the pipe 9 a in the Ausdampfkörper 2 until reaching the maximum level Internally, the pump 4 or additionally circulated externally via the pump 8 and the pipe 9 a and the container 6, for which purpose the valve 12 is to be opened. The entire salt crusts are dissolved and a solution with a density of 1.06 to 1.12 g / cm ³ obtained. After emptying all parts of the evaporation plant, this solution is in the container 6 and the evaporation plant is ready for use again. The pumped out of the container 5 and the pump 7 process water for the potassium sulfate process, the proportion of the potassium, magnesium and sulfate-containing rinsing solutions located in the container 6 is now mixed, the size of which is regulated by the self-adjusting density behind the pump 7. The setpoint for the process water density is 1.035 g / cm ³ . A density variation of up to 1,050ß / cm ³ is permitted. The density is regulated by adjusting the valves 3 and 4, valve 15 remains closed. Excess inflowing hot water flows from dom container 5 via the overflow 16.

Claims (2)

1. A process for the recovery and recovery of double sulfate-containing salt crusts by dissolving in water and obtaining a kaliun. , Magnesium and sulphate-containing rinsing solution, characterized in that the encrusted parts of the apparatus are filled with a part of the process water intended for the potassium sulfate process, the crusts are dissolved at temperatures between 50 and 90 ^G C, a K, Mg and SO ₄ - containing a rinse solution having a density between 1.060 and 1.12 g / cm ³ and in the subsequent period of operation in such a ratio is added to the process water of the potassium sulfate process that a mixture having a density of up to 1.050 g / cm ³ results, which instead of pure water is fed to the Kaliumulfatprcviß as a reaction medium. 2. The method according to claim 1, characterized in that the mixture density is preferably 1.035 g / cm ³ . For this 1 page drawing Field of application of the invention The invention relates to a Verfahi en for the recovery and recovery of double-sulfate salt crusts from evaporation plants, wherein under chaff sulfates potassium-containing compounds such as langbeinite (K ₂ SO ₄ 2 MgSO ₄ ), kainite (KCl MgSO ₄ - 2,75 H ₂ O), Leonite (K ₂ SO ₄ .MgSO ₄ .4H ₂ O) or its conversion product Schoenit (K ₂ SO ₄ .MgSO ₄ .6H ₂ O), which apart from potassium chloride or carnallite are deposited as crusts in evaporation plants and must be removed periodically , The method is preferably applicable to the potassium sulfide preparation of magnesium sulfate and potassium chloride followed by further processing of the MgCl ₂ -containing process solutions of the potassium sulfate process by evaporation. By the inventive method of recovery and recovery of double-sulfate salt crusts both the potassium component and the sulfate component of such salt crusts can be recovered and recycled in a cost-effective manner in the pre-treated potassium sulphate process. , Characteristic of the known state of the art Salt crusts settle in the course of the operating time in all apparatus of a potash factory and must be periodically removed at regular or irregular intervals. These are mostly sulphate-free crusts from KCI and NaCI, which must settle especially in the hot part of the potash processing process and especially in the cooling systems and must be removed after reaching certain incrustation levels. This occurs, for example, in the so-called rinsing pauses by dissolving with unsaturated hot dissolving solution and subsequent crystallization during cooling of the obtained partially saturated hot rinsing solutions. The dissolution of potassium salt-containing salt crusts with water is common practice. The kaliumhaltigon rinsing solutions obtained must either be used as a cover water in the covering process, or the water must be removed by evaporation. In the purification of Eindampfanlt conditions accumulating water are usually concentrated until reaching a minimum concentration of salts or by repeated use. Thereafter, by evaporation of the water, the dissolved recyclables are recovered, for example by admixing proportionate flushing water to the solution to be evaporated. The mechanical removal of salt crusts is also used in the potash industry. For example, crusts of Glat-Berz salt (Na ₂ SO ₄ - 10 H ₂ O) have long been removed from the cooling tubes by mechanical scraping devices. Evaporation systems sometimes precipitate considerable amounts of double salts both in the evaporation bodies, circulating lines and the heating tubes during the evaporation of sulphate-containing solutions from a potassium sulphate process. These may contain both the potassium and magnesium as cation in the sulfate (for example langbeinite) or only the magnesium (for example kainite). In addition, almost always more or less large proportions of chlorides (KCl, carnallite) are contained in the salt crusts. The mechanical removal of the crusts and the return of the recovered salts in the process of potassium sulfate production is eliminated because the salt crusts occur at various hard to reach places of the apparatus. Therefore, only the dissolution by water and the feeding of the rinsing water into the evaporation process remain as a recovery method. Because of the low solubility or dissolution rate of sulphate double salts in the water, large quantities of low-concentration rinsing waters are produced, but their feeds into the evaporation plant would be so expensive and energy-consuming. For this reason, it is not worth recovering a valuable substance from rinsing water by evaporation. Rinsing solutions from evaporation plants with alternating K-Mg-Cl-SO ₄ -relations are not used in the potassium sulfate production process. Although the prior art includes the use of potassium sulfate solution anrtelle of water for the implementation of Schönit to potassium sulfate (DD WP 212724). The ionic ratio K: SO ₄ in the addition medium corresponds to that of the potassium sulfate (2: 1 mol), which is not the case with rinsing solutions.