DE1492916C3 - Process for eliminating potassium from industrial by-products - Google Patents

Description

The present invention relates to a method for reducing the potassium content of industrial by-products, such as yeast or distillation liquor, for the production of animal feed, a sulphate or sulfuric acid being added to the vinasse and the potassium sulphate formed by filtration or centrifugation.

A method is already known from US Pat. No. 1,886,045, with which a mixture of Potassium and organics that are a by-product in fermentation processes or in the sugar industry accrues, can be separated. In this known method, an aqueous solution of this mixture Ammonium sulfate was added, the solution was concentrated, potassium sulfate and ammonium chloride were precipitated and separated from the solution by means of ethyl alcohol. The potassium sulfate precipitate formed during separation consists of very small crystals that are very difficult to filter out or centrifuge out. The separation the potassium salts can only be done with an additional expenditure of energy, which in none Ratio to profit, d. H. to increase the market value of the product.

For the above reason are therefore generally the yeast or distillation vinasse that are highly enriched in nitrogenous organic matter and have large amounts of sodium and Contains potassium salts, used only for fertilization purposes.

Also known from the German patent specification 860 737 for the treatment of molasses liquor with hydrochloric acid and then with ammonia to excrete the potassium only leads to excretion of potassium in fine crystalline form. So here, too, is an expensive filtration process Separation necessary. The price to be paid for this is also out of proportion to that for the feed obtained in this way achievable market price.

ίο In this known method there is also no Separation of the thickened amount of stillage mixed with sulfuric acid or sulphate into two parts, which can be further processed in different ways and then brought together again.

Sulfuric acid or sulfates are added in such a way that the crystals precipitate immediately, and in fine crystalline form.

The German patent specification 873 491 also already discloses a method for removing the potassium content known from industrial waste products. Here is the potassium of the molasses by a suitable one Ion exchanger removed. To do this, the molasses must first be diluted with 25 to 30% water and then brought into contact with a cation exchanger. The amount of water used must can be removed later. After the ion exchange has taken place, the potassium salts of the molasses in organic Acids are converted, the absorbed by the ion exchanger must be replaced by an acid Potassium is replaced by hydrogen ions and so the ion exchanger for a new potassium removal can be made useful. In this process, the ion exchange column is saturated very quickly, see above that a very high expenditure on equipment is necessary. This also makes this process uneconomical.

The object of the present invention is to provide a with simple economic means Excretion of potassium salts, which are present in a dissolved state in liquid industrial by-products are to enable.

This is achieved in the method of the type mentioned at the beginning by the following procedural steps:

a) The stillage is concentrated to a content of approximately 45 g of K ₂ O per liter;

b) a sulphate or sulfuric acid is added to the concentrated stillage up to a ratio, in which no precipitate of potassium sulfate occurs;

. c) a small amount of this solution is concentrated in a crystallizer to a content of 75 to 80 g K ₂ O per liter;

d) with continuation of the vacuum evaporation process, the other part of the Solution supplied;

e) the solution with the potassium sulfate crystals contained therein is cooled to approximately 35 ° C;

f) the potassium sulfate crystals are known in Way separated from the solution by centrifugation.

In this process, a small part of the concentrated stillage is first added Sulfuric acid or sulfate are added and further thickened in a further vacuum evaporation process becomes, with then continually the other part

is added to the solution, achieved with a corresponding cooling that the crystals become larger, so that the coarsely crystalline potassium sulfate crystals obtained in this way can be easily filtered or centrifugation. The separation process is thus simplified and cheaper.

In the case of yeast pulp, we recommend sulphation by adding ammonium sulphate to be carried out, since the addition of sulfuric acid alone produces an end product that is too acidic. the The addition of baking soda increases the sodium content of the stillage freed from potassium, which is often the case is not desirable in view of the use of these by-products.

Crystallization is used to produce large crystals that can be easily separated from the solution carried out in a non-continuously working crystallizer, its construction allows the mass to stir well during crystallization.

Example
Removing potassium from a yeast liquor

The stillage is first thickened so that its dry matter content is 260 g per liter; the dry matter had the following composition:

Potassium (in K ₂ O) 15.8%

Sulphates (in SO ₂ ) 5.8%

Nitrogen, total 5.5%

Ammonia nitrogen 0.5%

The pH is 6.9.

For 5401 stillage, 201 ammonia (density 0.92), followed by 81 sulfuric acid (density 1.84) added.

200 1 of this treated stillage are evaporated in vacuo until the dry matter content 500 g per liter, with potassium sulfate crystals forming.

The rest of the stillage (340 l) is added in such a way that the concentration increases progressively. At the end of the thickening process, the density of the mother liquor is about 1.4, which is a proportion of Dry matter of about 1075 g per liter.

ίο The thus obtained residue amount of 145 1 is cooled for 12 hours at about 35 ⁰ C. Separation of the residue by centrifugation (without washing) yields 125 liters of stillage, which is greatly reduced in its potassium content, and 40 kg of crystalline mass.

The stillage obtained in this way has a pH value of 5.9 and has the following composition:

Dry matter 74.5%

Weight

_ao potassium (in K ₂ O) 5.0%

of the dry material

Nitrogen, total 7.3%

of the dry material

Ammonia nitrogen 2.5%

of the dry material

The crystalline mass shows the following composition:

Dry matter 88.0%

Potassium (K ₂ O) 39.5%

Sulphates (SO ₁ ) 41.5%

Chloride (Cl) 0.5%

Sodium and Calcium (in Na ₂ O and

CaO) 6.5%

Total nitrogen 3.0%

Ammonia nitrogen l> 0%

Claims (2)

Patent claims: 1. Process for reducing the potassium content of industrial by-products, such as Yeast or distillation vinasse, for the production of animal feed, whereby vinasse is a Sulphate or sulfuric acid added and the potassium sulphate formed by filtration or centrifugation disconnected, characterized by the following steps: a) The stillage is concentrated to a content of approximately 45 g of K ₂ O per liter; b) the concentrated stillage becomes a sulphate or sulfuric acid up to a ratio added at which no precipitate of potassium sulfate occurs; c) a small amount of this solution is concentrated in a crystallizer to a content of 75 to 80 g K ₂ O per liter; d) with continuation of the vacuum evaporation process, the other part is continuously added to the solution; e) the solution with the potassium sulfate crystals contained therein is cooled to approximately 35 ° C; f) the potassium sulfate crystals are removed in a known manner from the solution by centrifugation severed. 2. The method according to claim 1, characterized in that for the separation of the potassium Ammonium sulfate is used.