CS259685B1 - Process for the preparation of calcium magnesium fertilizer - Google Patents

Abstract

The purpose of the solution was to find a suitable method of processing flue gas desulfurization products using wet magnesium technology into a usable product. This oil is achieved by allowing the thickened calcium soda sludge to react with a solid magnesium desulfurization product while kneading, in a ratio of 10 to 100 parts by weight of these desulfurization products per 100 parts by weight of the thickened and washed calcium soda sludge. The resulting reaction mixture is allowed to mature and adjusted to a form suitable for application, as needed.

Description

The invention relates to a method for preparing a lime-based fertilizer.

When soda is produced using the Solvay process, 1 ton of

About 10 to 12 m of soda ash produced, which at a density of 1100 to 1113 kg/m ³ contains

95 kg/ra ³ CaCl ₂ 45 *( 50 kg/m ³ NaCl kg/m ³ OaCO^ 3^5 kg/m ³ CaS0 ₄ 3 4 kg/m ³ CaO

In addition, there is tailings from lime slaking and slag from steam boiler furnaces, or possibly from technological furnaces.

These wastes are disposed of either together or separately by being floated into tanks where the solid phase is captured. When thickening our own soda sludge, the clarified chloride solution is drained for further processing, or the excess is discharged into the watercourse, and the thickened solid phase is dumped, even at the cost of an adverse impact on the environment.

All attempts to use these thickened sludges in construction or agriculture have so far been unsuccessful. In addition to the residual chloride content, the high moisture content also prevents direct use, so the physical properties of these sludges are unfavorable for any manipulation with them. The eco-nomic results of the individual proposed processes are more or less unfavorable precisely for the cost-intensive operations necessary to reduce the content of both chlorides and moisture, and in addition, the costs of the sludge treatment itself are also increasing. For the same reasons, the method according to AO 193 921, which consists in the reaction of soda ash sludge with calcium oxide to form powdered calcium fertilizer, was not implemented.

The method of processing calcium soda sludge into fertilizer according to AO No. 242 284 appears to be more advantageous, the essence of which is that the thickened sludge, stripped of part of the original chloride content, is subjected to a reaction with kieserite, or possibly with anhydrous alkali metal sulfate until the reaction mixture is compacted. The solidified mixture is ground to the required fineness and the resulting calcium-magnesium fertilizer is applied with conventional agricultural spreaders. In addition to calcium, magnesium is also supplied to the soil in an easily accessible hydroxide or oxide form. The implementation of this invention is demanding in terms of transport, since kieserite is imported to the Czechoslovak Socialist Republic. In addition, kieserite can be used separately without the rennet that occurs in the implementation of AO No. 242 284.

Therefore, a method of preparing a calcium-magnesium fertilizer based on the processing of thickened calcium soda sludge, freed from at least 50% by weight of the original chloride content according to the present invention, the essence of which lies in the fact that the thus treated calcium soda sludge is allowed to react for at least 5 minutes with a solid mixture of, in particular, magnesium compounds, which is formed during flue gas desulfurization using wet magnesium technology, in a ratio of 10 to 100 parts by weight of solid, in particular, magnesium compounds per 100 parts by weight of thickened and washed calcium soda sludge, after which the resulting reaction mixture is allowed to mature and adjusted to a shape suitable for application, as needed.

The invention is based on the finding that a fertilizer with practically the same effect as a fertilizer prepared by the method according to AO No. 242 284 can be prepared by reacting soda lime sludge with a mixture of, in particular, magnesium compounds that are formed during flue gas desulfurization using wet magnesium technology. This mixture is hereinafter referred to as technical magnesium sulfite. Compared to kieserite, the use of technical magnesium sulfite is more advantageous in that it does not introduce additional chlorides into the final calcium-magnesium fertilizer (kieserite contains 1.5 to 4% chlorides), which extend the ripening time of the fertilizer, i.e. the transition of the prepared reaction mixture from a plastic to a solid state.

The advantage of the presented solution is indisputable, because according to the invention, an effective calcium-phosphorus fertilizer is obtained by the reaction of two completely undesirable and unnecessary wastes. Another advantage is that the place of consumption of the fertilizer prepared in this way is, due to the negative effect of flue gases on the soil, the area where at least one of the two components is available, which means minimizing the transport requirements. The method according to the invention produces a fertilizer that can be freely stored without the risk of whipping. The calcium sulfite contained in the fertilizer contributes, under appropriate agrochemical conditions, such as soil reaction and others, to the mobilization and accessibility of soil phosphorus reserves.

Technical magnesium sulfite - a mixture of magnesium salts produced during flue gas desulfurization contains on average:

76.4

9.0

1.3

5.3

6.3 1.8

mass· MgSO^ mass· MgSO ₄ mass· MgO mass· CaSO ₄ · 0.5 HgO mass· impurities from the default magnessite mass· ash

The reaction of calcium hydroxide with magnesium sulfite is as follows:

and both main components of the technique proceed roughly according to the following Ca(OHg) + MgS0 ₃ + 2 H ₂ 0 » Ca(0H) ₂ + MgSO ₄ + 2 HgO CaS0 ₃ · 2 1^0·+ Mg(0H) ₂ CaS0 ₄ . 2 HgO + Mg(0H) ₂ /1/ /2/

Calcium-magnesium fertilizer is prepared by thoroughly kneading both components. The mass ratio of both components dosed into the mixer or kneader is governed by the calcium hydroxide content and residual moisture in the calcium soda sludge. The most advantageous ratio appears to be 22 to 27 parts by mass of technical magnesium sulfide per 100 parts by mass of calcium soda sludge. The resulting reaction mixture, after appropriate kneading, usually needs to be allowed to mature and crushed to the required size.

Design examples

Example 1 kg of washed lime soda ash containing 28.9 wt% total CaO, 28.4 wt% CaO utilized, 0.84 wt%

MgO, 0.95 wt% Cl", 0.02 wt% SO^", 23.6 wt% CO^*,

4.5 wt. % of admixtures and 45.0 wt. % of H^O were mixed and kneaded for 5 minutes with 13.3 kg of technical magnesium sulfite obtained during flue gas desulfurization, the composition of which was given above. The resulting plastic mixture was left to mature in a pile for 60 hours. During the maturation, the fertilizer solidified. The matured fertilizer was then ground into a spreadable form. The fertilizer prepared in this way had the following composition: 25.1 wt. % CaO total, 5.6 wt. % MgO, 0.8 wt. % Cl", 1.5 wt. % SO*", 8.4 wt. % 30*", 20.2 wt. % CO*,

5.0% by weight of impurities and 34% by weight of moisture.

Example 2 kg of soda ash sludge with the composition given in Example 1 was mixed and kneaded for 5 minutes with 30 kg of technical magnesium sulfite with the composition given in the text. In order to senile the resulting reaction mixture and prepare it for spreading, it was necessary to leave it undisturbed for 24 hours. The resulting fertilizer had the following composition: 21.6 wt. % CaO total·, 9.7 wt. % MgO, 0.7 wt. % Cl", 2.9 wt. % SO*, 16.0 wt. % SO^", 17.2 wt. % C0*~, 29 wt. % moisture.

Example 3 kg of calcium soda sludge with a composition of 34.3 wt. % CaO total, 33.9 wt. % CaO utilized, 1 wt. % MgO, 0.7 wt. % Cl“, 28.2 wt. % 5.4 wt. % admixtures and 35 wt. % H^O was mixed and kneaded for 5 minutes with 20 kg of technical magnesium sulfite with the composition given in the text. A moist, crumbly mass fell out of the kneader immediately ready for dispatch and spreading. The fertilizer had the composition: 27.8 wt. % CaO total, 7.6 wt. % MgO, 0.6 wt. % Cl“, 11.7 wt. % SO*“, 2.1 wt. % SO^“,

22.5% wt. CO*" and 23.0% wt. moisture.

Claims (1)

Process for preparing calcareous fertilizer based on the treatment of concentrated calcium sodium sludge, free of at least 50% by weight of its original chloride content, characterized in that the treated calcium sludge is reacted for at least 5 minutes with kneading with a solid mixture of particularly flammable compounds flue gas by wet combustible technology in the ratio of 10 to 100 parts by weight of solid, especially 100 parts by weight · parts of concentrated and washed calcium sodium sludge, whereupon the resulting reaction mixture is aged as necessary and made into a shape suitable for application ·