DE1057072B - Process to reduce the hygroscopicity of inorganic salts - Google Patents

Description

Process for reducing the hygroscopicity of inorganic Salts The invention relates to a method for reducing hygroscopicity of inorganic salts.

It is known that a number of inorganic salts, in particular Potash salts, are hygroscopic to a considerable extent. Hygroscopicity is one of the causes that these salts by storage and during transport in humid Atmosphere are reduced in their pourability and that the become moist Salts firmly bake together during subsequent drying, thereby loading and unloading these products and their application, e.g. B. as fertilizer salt, is very difficult.

Attempts have already been made in various ways in processing Using crude potash salts to produce products that are as coarse-grained as possible and that stand out characterized by good flowability due to the absence of dust. So one has z. B. suggested the hot, saturated potassium chloride solutions produced from crude potassium salts Quantities (3 to 20 mg / l) of surface-active substances that delay crystallization to be added together with seed crystals of a certain type and quantity and the crystallization with constant, relatively rapid cooling while observing further procedural modalities perform. For this purpose, the surface-active substances used were pectin, Prestabit oil, alginates, also alkyl sulfates and alkyl sulfonates with a chain length of preferably 8 to 14 carbon atoms; an additive was recommended as particularly effective aliphatic primary amines or their salts with a chain length of 8 to 20 C atoms, e.g. B. an addition of oleylamine or oleylamine chlorohydrate.

The purpose of the process is to produce a free-flowing product by obtaining the most coarse-grained crystals possible from hot-saturated ones Crude salt solutions by way of cooling.

With a view to the fact that salts, such as. B. Sylvine (potassium chloride), often in the form of crystalline particles of relatively small size and because of the hygroscopic properties of the substance in moist air for caking tend has been recommended to wash the salt crystals with a saturated solution of the to treat the salt concerned, in which surface-active substances dissolved or dispersed as used as collectors in flotation can.

Primary aliphatic surfactants were named as such surfactants Amines of 10 to 20 carbon atoms or their water-soluble salts, e.g. B. the Chlorides or acetates of such amines, such as primary aliphatic amine acetate, the contains 16 to 18 carbon atoms in the chain, octadecylamine acetate (ClsH4oN02C2H3), Octadecenylamine acetate (C18H38N ° 2 C2 H3), hexadecylamine acetate (C16H36NO2C2H3). By however, this treatment will not sufficiently lower the moisture absorbency achieved because of this Additives not to the extent that they were used, soak on the salt crystals.

Furthermore, one has fertilizer salts to increase the flowability Prevention of caking and to improve shelf life little Quantities of water-insoluble salts of naphthenic acids or finely powdered polysaccharide glycolic acid ethers or dyes of sulfonated aromatic character in addition to surface-active substances Compounds mixed in. With a dry admixture of such small amounts of Additives will only be an insufficient distribution of these additives among the fertilizer salt crystals achieved.

Another known method aims at the caking of To prevent ammonium sulfate by giving this a very low, about 0.01 to 0, 05 ° / 0 amount of a polyethylene glycol with a molecular weight of over 150 is added.

A concentrated aqueous polyethylene glycol solution is added to the still ammonium sulfate crystals moist from the mother liquor are atomized in such a way that finally 100 g of polyethylene glycol are distributed to 1000 kg of ammonium sulfate, whereupon Drying takes place. In this process, too, there is a reduction in hygroscopicity inadequate.

After all, attempts have been made to determine the flowability of inorganic salts, z. B. ammonium salts, thereby improving and their tendency to caking to reduce by treating them with substances, such as glycerine or Glycol or its derivatives increase the tendency to absorb moisture and should thereby counteract caking.

In this hygroscopicity-increasing method, however, exists the risk of caking for in the event that the damp Ammonium salt is later exposed to heat in a dry atmosphere.

It has been found that to avoid these shortcomings the The hygroscopicity of inorganic salts, especially potash salts, is significant The amount can be reduced by treating the solid salts with their saturated, at the same time additives containing solutions and subsequent drying, if in the saturated treatment solutions as additives, water-insoluble partial esters polyvalent alcohols containing up to five hydroxyl groups with fatty acids of 10 to 22 carbon atoms emulsified using non-ionic emulsifiers will.

For the implementation of the method of the invention, for example into consideration: partial esters of natural or synthetic fatty acids der named chain length, such as lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid, Eicosanic acid, Hendicosanic acid, behenic acid, and also partial esters of fatty acid mixtures of chain lengths C 10 to C 20, C 16 to C 20, C 18 to C 22 with polyvalent to to alcohols containing five hydroxyl groups, such as glycol, glycerine, hexanetriol, Pentaerythritol, diethylene glycol, triethylene glycol and other polyethylene glycols with up to six CH2 CH2 O groups, as well as amino alcohols such as diethanolamine and triethanolamine.

As nonionic emulsifiers, for. B. Fatty alcohol ethylene oxide adducts, Fatty acid ethylene oxide adducts or alkylarylethylene oxide adducts are used.

The process of the invention is expediently carried out as follows : The partial ester is mixed with water, in the amount of 5 to 10% des Ester weight of the nonionic emulsifier is added.

To a mixture of the solid inorganic salt and the corresponding Saturated mother liquor becomes aqueous in the cold or with slight warming Ester mixture added. It has proven to be advantageous to adjust the weight ratios to be chosen so that for about 70 parts by weight of solid salt about 30 parts by weight of mother liquor and 0.1 to 2 parts by weight of partial ester are omitted. With suitable agitators an even distribution of the treatment mixture is ensured. The deployed Fatty acid esters are practically completely deposited on the salt crystals. After removal of the liquid components by centrifugation, by suction The salt is placed in a rotary kiln using filter drums or in another technically common way dried.

In the dry product obtained by this treatment are the particles of which are provided with a water-repellent coating, which makes them hygroscopic of the product is significantly reduced.

The advantages of the method according to the invention are from the following Tables A to C can be seen.

Table A is based on the following experimental set-up: In wide crystallizing dishes (diameter 9 cm), 10 g of 60% dry potash salt were weighed out and distributed in such a way that the soil was evenly covered with a table A potash salt (60 o /. K2 O) Water absorption Amount used of the addition relative in 0 /, from the absolute in ° / 0 der Dry weight in ° / 0 from water absorption of the salt dry weight of the of the salt untreated Salt 1 2 3 4 I. Potash Salt 2 100 II. Potassium salt dried after treatment with aqueous Additions of 1. Acetate of aliphatic amines with a chain length of 12 to 14 carbon atoms .................... 1 22, 7 78 0, 1 18, 1 62 2. Aliphatic amines with a chain length of 12 to 14 carbon atoms ............................... 1 24, 0 82 0, 1 22, 8 78, 1 3. Acetate of aliphatic amines with a chain length of 16 to 18 carbon atoms .......................... 1 19, 4 66, 5 0, 1 22, 3 76, 3 4. Mixture of acetates 1 and 3 in a ratio of 1: 1 ... 1 19, 9 68 0, 1 20, 2 69, 2 5. Mixture of partial fatty acid esters from hexanetriol and synthetic chain length fatty acids from 16 to 20 carbon atoms (emulsifier: dodecyl poly- glycol ether, with nine CH2-CH2-O groups) ... 1 14, 1 48, 3 0, 1 14, 7 50, 3 6. Distearic acid triethanolamine ester (emulsifier: Do- decyl polyglycol ether, with twelve CH-CHg-0- 1 1 13, 5 46, 2 0, 1 14, 3 49 thin layer was covered. The samples consisted of either untreated salt or salt that had been treated with the various additives according to the prior art and method of the invention and dried.

The samples were placed in a climatic room with 100% relative humidity for 2 to 4 days Humidity set; the water absorption was then determined. The samples were then dried in a drying cabinet at 120 ° C. and weighed again. The difference between the two weighings gives the absolute water absorption under the given Conditions ; it is from column 3 in the form of percentages based on dry weight of the salt can be seen. The values of the rela- tive Water uptake are% / o rates that refer to the water uptake of the untreated salt are related.

Table B relates to influencing hygroscopicity of potash salt (60 ° lo K20) by adding polyethylene oxide in comparison with additives on partial fatty acid esters according to the process of the invention.

Table C contains information on the influence on the hygroscopicity of ammonium sulfate by treatment with polyethylene oxide versus treatment according to the method of the invention.

The experimental set-up for determining water absorption is for the tests of Tables B and C are the same as for those of Table A.

Table B Potash Salt (60% K2O) Water absorption Amount used of the addition absolutely relative @@@@@@@ in the in% of in% of water absorption ° dry weight of of the salt of the salt untreated Salt 1 2 3 4 I. Potash Salt 5 100 II. Potassium salt dried after treating the dry Salt with saturated potassium salt solution with the addition of 1. Polyethylene oxide (molecular weight 560) ....... 1 22, 3 75, 6 0, 1 19, 4 65, 8 2. Mixture of partial fatty acid esters from hexanetriol and synthetic chain length fatty acids from 16 to 20 carbon atoms (emulsifier: dodecyl polyglycol ether, with nine CH2-CH2-O groups) 1 13, 8 46, 8 0, 1 14, 2 48, 1 Table C ammonium sulfate Water absorption Amount used of the addition relative in% of absolute in% of Dry weight in% of water absorption of the salt dry weight of the of the salt untreated Salt 2 3 4 I. Ammonium sulfate 68 100 II. Ammonium sulfate dried after treatment 1. by atomizing concentrated aqueous Polyethylene oxide solution (molecular weight 560) the crystals moist from mother liquor ...... 0, 05 2, 47 92, 1 0, 01 2, 32 86, 6 2. of dry salt with saturated ammonium sulfate solution with the addition of a) Polyethylene oxide (molecular weight 560) ..... 1 2, 23 83, 2 0, 1 1, 89 70, 5 b) Mixture of partial fatty acid esters from hexane triol and synthetic fatty acids of a chain length of 16 to 20 carbon atoms (emulsifier: Do- decyl polyglycol ether with nine CH2-CH2-O- C H2 O- Groups) ...... .. 1 1, 22 45, 5 0, 1 1, 38 51, 5 Example 1 1 ton of potassium salt with 60% K2 0 is slurried with 300 kg of the saturated cover liquor in a mixing vessel and kept moving. 2.5 kg of an esterification mixture, mainly containing diesters, of hexanetriol and synthetically produced fatty acids with a chain length of 16 to 20 carbon atoms and 0.25 kg of dodecyl polyglycol ether with nine CH2 CH2-O groups, dissolved in 50 kg of water, are added. After a treatment time of 5 minutes, the solid components are separated off by means of a filter drum and dried in a rotary kiln.

Example 2 10 t of potash salt with 50 ° / 0 K2O are placed in a mixing tank with 4 t of saturated brine of the same type of potassium salt and with 100 kg of an aqueous one Stirred emulsion containing 10 kg of a mixture of monoesters of glycol with synthetic Fatty acids with a chain length of 18 to 22 carbon atoms and 0.5 kg of oleic acid ethylene oxide adduct with twenty CH-CH-0 groups. The mixture is stirred well after a few Minutes, the solid components are separated from the liquid by means of a filter drum Components separated and dried in a rotary kiln.

Example 3 A slurry of 1 t of potash salt with 60% K2O in 400 kg of the corresponding cover liquor is mixed with 50 l of an aqueous emulsion which 10 kg diester from hydrogenated sperm oil fatty acid (essentially from stearic acid consisting) with hexanetriol and 1 kg of dodecyl polyglycol ether with nine CB'CHg-0 groups contains.

During the addition of the aqueous emulsion, the mixture is agitated held and fed to the filter drum after a few minutes. The departed solid components are dried in the rotary kiln.

Example 4 1 ton of Glauber's salt is dissolved in 300 kg of a saturated Glauber's salt solution slurried and mixed with 50 kg of an aqueous emulsion, the 5 kg of a distearic acid triethanolamine ester and 0.2 kg of dodecyl polyglycol ether with twelve CH2-CH2-O groups. After good Stirring is filtered. The solids are dried in the usual way.

Example 5 1000 kg of ammonium sulfate are in 300 kg of a saturated Ammonium sulfate solution and suspended with 50 kg of an aqueous emulsion, the 10 kg Monopalmitic acid triethylene glycol ester and 0.2 kg of oleyl polyglycol ether with twelve Contains CH2 # CH2 # groups, stirred. The crystal slurry is spun off in a centrifuge and dried in a rotary kiln.

Claims (1)

PATENT CLAIM: Process for reducing the hygroscopicity of inorganic salts, in particular of potash salts, by treating the solid salts with their saturated, at the same time additives containing solutions and subsequent Drying, characterized in that in the saturated solutions as additives water-insoluble partial esters of polyvalent ones containing up to five hydroxyl groups Alcohols with fatty acids of 10 to 22 carbon atoms using nonionic ones Emulsifiers are emulsified. Considered publications: German Patent Specifications No. 687 751, 950 559, 911 729.