CS217690B1 - The method of producing magnesium sulfate - Google Patents

Abstract

Production of magnesium sulfate from magnesium raw materials containing carbonate or bicarbonate anion, or magnesium oxide or hydroxide in such a way that the aforementioned magnesium raw materials, preferably magnesium carbonate — magnesia, or calcined magnesium carbonate, or magnesium-calcium carbonate — dolomite, are subjected to a chemical reaction with calcium sulfate in an aqueous environment. The magnesium raw material used before its reaction with calcium sulfate and/or the reaction mixture of the magnesium raw material with calcium sulfate in the form of an aqueous suspension is subjected to a reaction with carbon dioxide and/or carbonic acid. Free carbon dioxide and possibly also the amount of carbon dioxide corresponding to the conversion of bicarbonates to normal carbonates are removed from the reaction mixture in a subsequent stage of the production process, preferably by heating and/or aerating the reaction mixture. The magnesium sulfate formed by the reaction is optionally further separated from the reaction mixture in the form of an aqueous solution, preferably by sedimentation, filtration or centrifugation, or the reaction mixture is processed into a magnesium-calcium suspension fertilizer.

Description

The invention relates to a process for the production of magnesium sulfate from magnesium raw materials containing a carbonate or bicarbonate anion.

Magnesium is an essential component of the plant green dye - chlorophyll. It affects the transfer of nutrients, especially phosphorus from old leaves and stems to growing organs of plants. It was also found to have a beneficial effect on the course of oxidation reduction processes in the plant. It is an activator of the biochemical reactions associated with carbohydrate formation and phosphorus conversion in plants. It has also been confirmed that in the absence of magnesium, monosaccharides accumulate in the leaves of plants.

The magnesium fertilizers we use to date include: Thomas meal (7% MgO); Kamex (3.5% MgO in the form of _MgSO4); Emgekali (5% MgO as a _MgSO4); Kieserite (technical MgSO ₄ ); dolomitic limestone containing approximately 20% MgO and magnesite drift containing 65% MgO.

In view of the ever-increasing consumption of concentrated phosphoric fertilizers produced mainly on the basis of phosphoric acid, the provision of assimilable sulfur in industrial fertilizers is becoming an increasingly urgent requirement of agricultural practice. This is particularly important, for example, in the cultivation of soy, legumes, peanuts, sunflowers and the like.

Magnesium sulphate - kieserite (MgSO ₄ ) is currently one of its most concentrated and most important fertilizers containing magnesium. This chemical compound is also an effective source of assimilable sulfur as another important biogenic element.

The importance of magnesium sulfate for the nutrition of agricultural crops is particularly highlighted by the fact that the magnesium contained in MgSO ₄ is one of the plant nutrients that the plants are able to absorb very well through the leaves. As reported by Jurgens G. (Der Erwerbs-Gártner No. 17 (26), April 1972); Wittwer SH ("Foliar Application of Fertilizer" - Department of Horticulture, Michigan State University, East Lansing, Michigan, USA), and Hudska G. (Agrochemistry 16 (5), 144 (1976)) the half-time of sorption of magnesium is 2 to 5 hours, for example, for calcium, zinc and manganese, a period of 1 to 2 days is reported, and 50% of the potassium uptake after foliar application is achieved after 10 to 24 days.

For these reasons, a number of special industrial fertilizers containing sulfur in addition to magnesium are produced, intended primarily for off-root plant nutrition. Magnesium sulphate, respectively, is the source of magnesium in virtually all the above-mentioned industrial fertilizers. magnesium-potassium sulfate. Also disclosed is the use of highly concentrated aqueous magnesium sulfate and urea solutions as liquid liquid N-Mg-S fertilizers suitable for the preventive and curative treatment of agricultural crops.

Technical magnesium sulphate - kieserite is currently produced mainly by fractional crystallization from drawn mixed water-soluble salts containing magnesium and sulphate anion, fractional crystallization of sea water and decomposition of so-called. poppy of burnt magnesite - magnesium oxide or crude magnesite with sulfuric acid (AO No. 200 677).

The above methods are relatively energy intensive and some require the use of often limited sulfuric acid.

Based on the results of the experimental work, we have now found that the deficiencies in the currently used magnesium sulfate production methods can be overcome by using a relatively simple and, in particular, economically and ecologically particularly advantageous production method of the invention.

The process for producing magnesium sulfate from magnesium raw materials containing a carbonate or bicarbonate anion or magnesium oxide or hydroxide according to the invention is based on the conversion of the magnesium raw material by calcium sulfate. gypsum in an aqueous medium and in the presence of carbonic acid respectively. carbon dioxide. Magnesium feedstock containing a carbonate and / or bicarbonate anion and / or an oxide and / or magnesium hydroxide preferably magnesium carbonate (MgCO ₃ ) or calcined magnesium carbonate or magnesium calcium carbonate (CaMg (CO ₃ ) ₂ ) is subjected to a chemical treatment in an aqueous environment reaction with calcium sulphate (CaSO ₄ and CaSO _4. xH ₂ O, where x is usually 0.5 and 2.0). The magnesium feedstock before the reaction with calcium sulfate and / or the reaction mixture of the magnesium feedstock with calcium sulfate in the form of an aqueous suspension is reacted with carbon dioxide or carbonic acid. Free resp. physically bound carbon dioxide and optionally carbon dioxide corresponding to the conversion of the bicarbonates contained in the reaction system to normally carbonates are removed from the system in the next technological step, preferably by heating and / or aerating the reaction mixture. The magnesium sulfate formed by the reaction is separated from the reaction mixture in the next step in the form of an aqueous solution, preferably by sedimentation, filtration or centrifugation. If desired, the reaction mixture can also be directly processed into a suspension magnesium-calcium fertilizer without prior separation.

As can be seen from the foregoing, the process for producing the magnesium sulfate according to the invention can be illustrated by the following basic and considerably simplified chemical equations:

MgCO ₃ + CaSO ₄ - * MgSCT ₄ + CaCO ₃ (1) MgCO ₃ + CO ₂ + H ₂ O Mg (HCO ₃ ) ₂ (2) MgO + 2CO ₂ + H ₂ O - Mg (HCO ₃ ) ₂ (3) )

Mg (OH) ₂ + 2 CO ₂ Mg (HCO _{3) 2} (4)

Mg (HCO ₃ ) ₂ + CaSO ₄ - * MgSO ₄ + + Ca (HCO ₃ ) ₂ (5)

Ca (HCO ₃ ) ₂ - * CaCO ₃ + CO ₂ + H ₂ 0 (6)

It has been shown experimentally that the equilibrium in the system characterized by the first equation is only slightly shifted to the side of the desired products in the technologically interesting range.

However, a significant shift of the reaction from left to right has been observed in the presence of carbon dioxide, whose presence in the reaction system significantly increases the solubility of the magnesium reactant (the solubility of MgCO ₃ in water at room temperature is only 2.10 ^-3 to 2.10 -2 ^). however, the solubility of Mg (HCO 3) 2 at 18 ° C is about 13% by weight). Since the solubility of normal as well as calcium bicarbonate under these conditions is also very low (the solubility of CaCO3 in water at room temperature is 3.10 ³ % by weight and the solubility of Ca (HCO3) ₂ at 25 ° C is about 0.43%) carbon dioxide respectively. carbonic acid in accordance with the validity of the Guldberg-Waage law of the effect of masses (reaction 2-5) in favor of the formation of magnesium sulfate in an aqueous solution, with the simultaneous formation of Ca (HCO ₃ ) _2, respectively. CaCO ₃ . In accordance with the differences in the solubilities of the bicarbonate and calcium carbonate, further deepening of the reaction is achieved by converting the Ca (HCO ₃ ) ₂ contained in the reaction system to normal calcium carbonate (e.g. in the sense of reaction No. 6).

Compared to commonly used magnesium sulfate production technologies, the production method of the invention has a number of significant advantages. These include:

- The process enables unusually effective recovery of calcium sulphate - gypsum, which is produced as an unpleasant waste in several chemical technologies (production of phosphoric acid by so-called extraction - wet process, production of citric acid and the like).

- Compared to a number of methods used today for the recovery of waste gypsum by its chemical treatment (eg U.S. Pat. Nos. 3,582,276, 3,591,332 and others), the newly developed process is incomparably more advantageous, particularly from an energy point of view.

- The reactions leading to MgSO ₄ in the present system take place with high yields even without supplying energy in the form of heat from outside, favorably affecting in particular the fact that, over a range of temperatures of technological interest, the solubility of calcium sulfate increases with decreasing temperature. ₄ .

. 2H ₂ O in water at 100 ° C is 0.065 g / 100 g solution and at 20 ° C is 0.204 g / 100 g solution).

As a magnesium raw material, abundant amounts of naturally occurring minerals, preferably magnesia, can be used. MgCO ₃ (a calcite mineral of the calcite group, hardness 4–4.5; occurring in very high purity and, in large quantities, especially in Austria, USA and Brazil; in Czechoslovakia, especially in the locations Hnúšťa - Rimavská Sobota, Jelšava - Rožňava, Sedlice - Benesov, Oslansko - Brno-countryside, Sobotin - Sumperk) or dolomite - CaMg (CO ₃ ) ₂ (gem mineral; hardness 3.5-4; abundant especially in Austria, Switzerland, the GDR and the USA; in the locations Pribram, Banska Stiavnica - Ziar nad Hronom, Ruzomberok - Liptovsky Mikulas). It is also possible to use for the production of technical magnesium oxide, the source of which can be, for example, products of thermal treatment of magnesite, so-called magnesite. "Poppy" calcined with magnesia (in Czechoslovakia is supplied under the commercial designation of brick or steel flour).

- The source of carbon dioxide may be degasses from several processes of inorganic or organic chemical technology of CO ₂ scrubbing in connection with the synthesis of the NH ₃ synthesis mixture, decarbonisation processes, some silicate chemistry technologies, fermentation chemistry and the like). In connection with the process of production of magnesium sulphate resp. The gaseous products of the various combustion processes as well as the air can also be used as a source of carbon dioxide in accordance with the process according to the invention.

- Both basic reactants are fully recovered by the process, since in addition to MgSO ₄ , which constitutes the main reaction product, the second component - CaCO ₃ resp. Ca (HCO ₃ ) ₂ also in agriculture. Due to the colloidal nature in the reaction system of the resulting calcium carbonates, they are characterized by a high neutralization efficiency, which can be advantageously used in the stock amelioration fertilization of the soil by the calcium component. Starting from the colloidal nature of the solid particles contained in the equilibrium system, calcium carbonate may be used, which in essence is preferably used for the preparation of highly stable calcium suspension fertilizers.

- In certain circumstances, in particular for fertilizing the soil with magnesium while liming is needed, the reaction mixture can be used after adjusting its physico-mechanical properties (stabilization of dispersed solid particles) directly as an effective magnesium-calcium fertilizer containing assimilable sulfur containing the major part of magnesium in good plant accessible form.

- The process of producing magnesium sulphate with the simultaneous recovery of calcium sulphate is extremely simple, does not impose high demands on the machine no-technological equipment neither in terms of its atypical solution of individual apparatuses nor in terms of corrosion aggressiveness of individual components occurring in the process.

The technology does not envisage the use of any flammable, corrosive or toxic substances, does not impose any special requirements on operation and can be continualised.

Example 1-8

6.44 g MgCO 3 (powdered pure), 13.20 g CaSO ₄ .2H ₂ O (pure) were weighed into six 500 cm ³ stohman flasks and 80.34 ml ( (g) boiled distilled water at a temperature of about. Deň: 22 ° C.

Weighed 9.70 g and 10.7 g, respectively, into the seventh and eighth flasks. 3.85 g MgCO ₃ and 9.9 g resp. 15,79 g CaSO ₄ .2H ₂ O of the same quality. The quantity and quality of the water added was the same as for the samples no. 1-6.

The flasks were sealed and placed in a Wagner rotary shaker. After vigorously stirring the contents of the flasks by shaking for the prescribed time (0.5; 1; 2; 4; 6 and 8 hours), the reaction mixture was separated by vacuum filtration through a pre-weighed funnel equipped with a S-4 filter glass frit. Magnesium and calcium were determined by complexometric titration in the filtrate prepared as described above. Examples 9 and 10

104.7 g of distilled water were weighed into two 250 cm ³ glass flasks,

8.4 g of magnesium carbonate (1'ahký, powder, pure) and 17.2 g CaSO ₄ .2H ₂ O (neat).

A suspension of this composition was saturated at room temperature with carbon dioxide gas, obtained by evaporating the crushed solid CO ₂ for 8 hours.

Then, one of the slurry flasks was heated for about 2 hours in a water bath (95-100 ° C) to expel the free and carbonate-bound carbon dioxide.

The solid phase was separated from the liquid by filtration through a S-4 glass frit.

The filtrate thus obtained was subjected to chemical analysis for magnesium, calcium and sulphate content.

The sample filtered without previous 'boiling out' of carbon dioxide contained:

1.165% magnesium (as Mg)

0.092% calcium (as Ca)

4.01% sulphates (as SO ₄ ^2- )

It follows that the Mg / SO ₄ ² - weight ratio = 0.2905 (the Mg / SO ₄ ² ratio in magnesium sulphate is 0.2531.)

The sample of the suspension filtered after CO ₂ displacement by heating was determined to:

2.278% magnesium (as Mg)

0.062% calcium (as Ca)

8.78% of sulfates (as SO ₄ ² ').

It follows that the Mg / SO ₄ ² 'weight ratio in the sample was 0.2594. Given the magnesium content of the filtrate and its truly isolated amount (53.9 g), neglecting the magnesium contained in the solid phase bound to the solid phase (filter cake), it can be concluded that under these conditions the process yield on magnesium represented 66.1% .

attempt no. Návažky zákl. reaction. Ingredients (g) Reaction time - sample shaking time (min) Quantity (g) Weight content Výťaž- Nost * magnesium (%) MgCOg powder, clean CaSO ₄ . . 2H ₂ O pure boiled distilled water (25 ° C) wet a filtration Joint pie clear filtrate magnesium in the filtrate (% Mg) calcium in the filtrate (% Ca) 1 6.44 13.20 80.36 30 59,13 36,63 0,045 0,052 0.89 2 6.44 13.20 80.36 60 60.41 34.89 0,057 0,052 1.07 3 6.44! 13.20 80.36 120 53,19 42,93 0,087 0,049 2.01 4 6.44 13.20 80.36 240 58,01 38.59 0.13 0,049 2.70 5 6.44 13.20 80.36 360 57.31 38.80 0,152 0,046 3.18 6 6.44 13.20 80.36 480 56.34 - 0,182 0,044 - 7 9.70 9.90 80,40 480 67.11 27.69 0,204 0,044 2.02 8 3.85 15.79 80,40 480 47.59 49.10 0,197 0,046 8.71

Note: * The stoichiometric magnesium content of the pure raw material - MgCO ₃ used was taken into account in the Mg recovery calculation and the presence of the filtrate in the filter cake was not considered.

Example 9-13

Into a tall beaker volume of 400 cm ³ we gradually weighed 6.16 g of so-called. light magnesium oxide, pa, 26.30 g of calcium sulphate - CaSO ₄ .2H ₂ O, and a mixture of powdery substances were poured into 154.72 g of cold] boiled distilled water. The suspension in the beaker was stirred at room temperature using an electric stirrer while saturating with gaseous carbon dioxide - bubbling through. The CO ₂ (g) used for this purpose was obtained by evaporating solid carbon dioxide in a boiling flask adapted as a gas generator. In each of the experiments of this series, 13.44 g CO ₂ (g) was suspended into the beaker by capillary. After the prescribed amount of carbon dioxide was added and the reaction mixture stirred for the prescribed time, the beaker suspension was separated by vacuum filtration through a S-4 filter glass frit, with or without previous boiling on a water bath (depending on whether the boiling effect of the oxide was observed). carbon dioxide - see data in the table). We determined the weight of the obtained filtrate and the wet filter cake and we determined the content of magnesium and calcium in the filtrate and the content of sulphates (by conductometric titration with standard solution of BaCl ₂ ).

The table of endpoints for the experiments in this series is shown in Table 2.

Table 2

Experiment - example number time mieša- nia susp. (Min) Mass amount obtained by separation of the reaction mixture Content of analytically determined components in · filtrate (% by weight) remark filtrate (G) wet filter. pie (G) ca mg SO ₄ 9 30 141.0 40.85 0,065 0,617 1,360 without CO ₂ production 10 60 143.92 40,35 0,092 0,785 1,794 without CO ₂ production 11 60 - 45.53 0,058 - 3,040 sample was 60 min. boiled to water. bath 12 120 135.15 46.36 0,081 0,720 2,047 without CO ₂ production 13 120 94,51 34.87 0,049 0,924 3,518 sample was 60 min. boiled to water. bath

OBJECT OF THE INVENTION

Claims (1)

Process for producing magnesium sulfate from magnesium raw materials containing a carbonate or bicarbonate anion or an oxide or magnesium hydroxide characterized in that the magnesium raw material comprises a carbonate and / or bicarbonate anion and / or an oxide and / or magnesium hydroxide, preferably magnesium carbonate or calcined the magnesium carbonate or magnesium-calcium carbonate in the aqueous medium is chemically reacted with calcium sulfate, the magnesium material used prior to its reaction with calcium sulfate and / or the reaction mixture of the magnesium raw material with calcium sulfate in the form of an aqueous suspension is reacted with carbon dioxide and / or with carbonic acid, wherein the free carbon dioxide and optionally the amount of carbon dioxide corresponding to the conversion of the bicarbonate to the normal carbonate is from the reaction mixture to the next stage of the production process. The magnesium sulfate is removed further from the reaction mixture in the form of an aqueous solution, preferably by sedimentation, filtration or centrifugation, or the reaction mixture is worked up into a magnesium-calcium suspension fertilizer.