CS250380B1 - Process for treating ammonium sulphate waste solution - Google Patents

Abstract

The solution concerns a method of processing a waste ammonium sulfate solution into crystalline double magnesium ammonium sulfate, usable as a magnesium-nitrogen fertilizer and into a liquid nitrogen fertilizer of the DAM type (ammonium nitrate, urea, water). The proposed solution consists in mixing the ammonium sulfate solution with a magnesium nitrate solution, separating the sparingly soluble magnesium ammonium sulfate that has separated out, and dissolving ammonium nitrate and urea in the mother liquor in such an amount that the resulting solution has a concentration of 28 to 32% of total nitrogen. The significance of the aforementioned processing of the waste ammonium sulfate solution lies in the fact that ammonium sulfate or its solution, which is in little demand on the market, is processed into a desired magnesium nitrogen fertilizer and into a also desired liquid fertilizer of the DAM type.

Description

The invention relates to the treatment of an ammonium sulfate waste solution into a nitrogenous and nitrogen-magnesium fertilizer.

In many chemical productions, ammonium sulfate solution is formed as a by-product. These include the production of caprolactam, acrylic esters, ferric pigments by the Martin process and others. Ammonium sulfate solutions can be further processed by evaporation to a crystalline salt used as ¹ nitrogen fertilizer or converted to a liquid fertilizer by dissolving other salts to increase the nutrient content. This latter method is particularly important in order to save energy for the evaporation of solutions and also to accommodate the ever-increasing application of fertilizer in solution in agricultural production. These include the production of liquid fertilizers of the SADAM type, containing ammonium sulphate, ammonium nitrate, urea and water (F. Markalous et al .: Liquid nitrogen fertilizers DAM, SAM and SADAM, VÚAnCH study, 1978), or liquid fertilizers containing ammonium sulphate, ammonium phosphate and water (AO 235 883, 235 884 i.

In recent years, however, due to the expansion of chemical production associated with the production of ammonium sulphate, the market has become saturated and the lack of interest of agricultural holdings in further increasing the supply of this fertilizer, especially in crystalline form. Also, the presence of ammonium sulphate in liquid fertilizers at a higher concentration is not desirable. Due to ammonium sulphate, the solubility of other components, usually with a higher nutrient content than ammonium sulphate alone, is usually reduced, making it impossible to prepare a liquid fertilizer with a high nutrient content. For example, in the case of liquid fertilizers of the SADAM type, at a concentration of 30% by weight of ammonium sulphate. reaches a maximum total nitrogen concentration of only 20% by weight. (F. Markalous et al .: Liquid nitrogen fertilizers DAM, SAM and SADAM, Study VÚAniCH 1978], while the fertilizer type DAM (ammonium nitrate, urea, water) introduced in Czechoslovakia has a total nitrogen content in the range of 28 to 32 % wt.

In order to be able to carry out operations which do not involve the formation of ammonium sulphate as a by-product, a process for the treatment of these solutions has been developed which eliminates the disadvantages mentioned above.

According to the proposed procedure, a solution of magnesium nitrate is added to the ammonium sulfate solution, thereby precipitating the sparingly soluble double ammonium sulphate, separating it from the solution, and using the remaining sulphate-reduced ammonium nitrate solution to prepare some type of liquid fertilizer. A separate, double magnesium-ammonium sulphate is used as a new type of magnesium-nitrogen fertilizer. According to a preliminary farm survey, this fertilizer is of interest, thus ensuring its disposal.

Double magnesium-ammonium sulphate is a suitable nitrogen fertilizer on neutral and alkaline soils poor in magnesium, for hops, onions, garlic, horseradish, rape, mustard etc.

To achieve the maximum elimination of the sulphate component, a solution of magnesium nitrate is added to the ammonium sulphate solution in an amount such that 2 moles of ammonium sulphate would be 1 mol of magnesium nitrate according to the equation:

(NH4) 2SO4 + Mg (NO3) 2 + 6H2O = = MgSO4 (NH4) 2SO4.6H2O + 2NH4NO3

If the starting ammonium sulfate solution contains a soluble magnesium salt, the magnesium added in the form of magnesium nitrate is reduced by an equivalent amount.

If the magnesium nitrate solution used contains calcium nitrate (e.g., as an impurity), the 10 equivalent amount of magnesium nitrate addition is also reduced.

(NH 4) 2 SO 4 + Ca (NO 3) 2 + 2H 2 O = = CaSO 4. 2 H 2 O + 2 NH 4 NO 3

Since double magnesium-amino-sulphate is salinated with ammonium nitrate, it is advantageous to dissolve it in the reaction system before separating the double magnesium sulphate from the mother liquor after separating the double-magnesium ammonium sulphate from the mother liquor. or so on to further reduce its solubility. The solubility of double magnesium ammonium sulfate is in this case reduced by two factors. On the one hand, the salting out effect of ammonium nitrate and, on the other, the reduction in the temperature of the solution when dissolving ammonium nitrate.

Example 1

Exclusion of double ammonium sulfate from ammonium sulfate solution

To 24.04 g of 50% HNOs were gradually introduced with stirring 4.05 g of technical magnesium oxide with the following composition: MgO 78.87%, CaO 3.02% / o, R2O3 (mainly Fe2O3) 6.7%, CO2 7.55 %, H2O 0.68%. Upon dissolution of MgO, the temperature rose from 20 to 80 ° C. After the MgO was introduced, the reaction mixture was stirred at 70-80 ° C for 30 minutes. To this solution at 70-80 ° C was added 61.25 g of ammonium sulfate solution, 60-70 ° C warm with the following composition: (NH4) 2SO4 37.47%, MgSO4 2.55%, over 5 min with stirring. The reaction mixture was cooled to 28 ° C, 10.15 g of crystalline ammonium nitrate was added and stirred for 15 min while the temperature of the mixture after 250380 dropped to 20 ° C. The separated crystalline phase was separated by filtration (33.8 g). Filter cake composition: Total. N 8.02%, of which nitrate N 0.34%, MgO 10.1%, Fe ² O 3 0.61%, SO ^{4 2} '48.29%, 33.0% H ² O. Content tot. N in mother liquor 12.7%.

Preparation of liquid fertilizer of DAM type 38.5 g of ammonium nitrate and 47.3 g of urea were dissolved in 57.8 g of the filtrate from the previous preparation when heated to 20 ° C. The pH of the solution was adjusted to 7 by introducing 0.42 g of ammonia gas. Total nitrogen (by Jodlbauer) 29.23%, N (by Hanus) 7.64 why. (CSN 65 48 14), SO ₂ 1.53%, Fe ₂ O ₃ 0.20%, MgO 0.32%. (All concentration data are in% by weight). The solution at -10 ° C did not precipitate the crystalline phase.

Claims (2)

Process for treating an ammonium sulphate waste solution, characterized in that to an ammonium sulphate solution having a concentration of 5 to 50% by weight. a magnesium nitrate solution having a concentration of 40 to 70% by weight is added, the double magnesium ammonium sulphate is separated from the solution and the mother liquor is processed into a liquid fertilizer. 2. A process according to claim 1, characterized in that before separating the double magnesium ammonium sulfate from the solution, The present invention dissolves ammonium nitrate in an amount such that its total content in the solution is between 10 and 100 g ammonium nitrate per 100 g water, the double magnesium ammonium sulfate is separated and the mother liquor is processed by dissolving ammonium nitrate and urea into a liquid fertilizer of the type ammonium nitrate, urea,. water with a total nitrogen content of 28 to 32 why. wt.