CS221359B1 - Method of treating the magnesium sulphate - Google Patents

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for the treatment of magnesium sulphate produced by the capture of sulfur dioxide.

One of the known methods for capturing sulfur dioxide from flue gases is the so-called magnesite process. It consists of scrubbing the flue gases with an aqueous suspension of magnesium oxide to form magnesium sulfite. It is poorly soluble and, depending on the temperature conditions, crystals of trihydrate or hexahydrate are formed. The solid magnesium sulfite is separated from the liquid phase and thermally cleaved to form magnesium oxide and sulfur dioxide. Sulfur dioxide is used in the production of sulfuric acid and magnesium oxide is returned to the flue gas scrubber. Burnt magnesium is used to replenish losses of magnesium oxide that are not small.

This desulphurisation process is difficult to implement, in particular the cleavage of magnesium sulfite is technically and energy intensive. In addition, the purity and reactivity of recycled magnesium oxide gradually decreases by accumulating impurities and due to the high temperature of the decomposition itself. The only preferred product of this desulfurization technology is sulfur dioxide.

The process of treating magnesium sulphite produced by the capture of sulfur dioxide with the magnesium compounds of the present invention appears to be substantially more advantageous in that magnesium sulphite is decomposed with nitric acid to form sulfur dioxide and magnesium nitrate solution.

The method according to the invention can be roughly described by the equation:

MgS03. x H ₂ 0 + 2 HNO 3 = Mg (NO 3) 2 + + SO ₂ + (x + 1) H ₂ O

Magnesium sulphite is easy to handle and can be transported from the site of collection to the distant sulfuric acid plants, even in bulk.

An advantage of the process according to the invention is that most sulfuric acid plants are part of fertilizer complexes, so that the nitric acid required for decomposition is also produced in the plant. The second decomposition product is a concentrated magnesium nitrate solution, which has recently gained importance as N - Mg liquid fertilizer. In order to satisfy the agricultural needs in the field of fertilizers, it is sufficient to predispose a portion of the nitric acid hitherto used for the production of the ammonium nitrate to produce the magnesium nitrate according to the invention, not only producing the desired fertilizer,

The magnesium nitrate solution can be used as a raw material to produce high-quality magnesium hydroxide or oxide, roughly according to the equations:

Mg (NO3) 2 + 2 NH 3 + 2 H 2 O = Mg (0H) 2 + 2 NH 4 NO 3 heat

Mg (OH) ₂ - MgO + H2O, while ammonium nitrate can be used as fertilizer. Thus, in this variant, the process according to the invention makes it possible, in addition to fertilizer production, to produce high-quality magnesium oxide.

The invention is particularly applicable in the capture of sulfur dioxide from the flue gases by the magnesite method and in the treatment of the magnesium sulphite thus obtained.

Example

3500 kilograms of a 40% Mg (NO 3) 2 solution was charged to a stirred, stirred off-line reactor, heated to 90 ° C, 215 kg of MgSCb 6 H 2 O crystals were added, and then introduced over 5 minutes with stirring 130 kg 50% HNO3. The exhaust was discharged with steam containing 50% by weight. H2O, 49 wt. SO2 and 1 wt. NO _X. 3800 kg of a 40% Mg (NO 3) 2 solution remained in the reactor.

Claims (1)

Subject A process for the treatment of magnesium sulfite formed by the capture of sulfur dioxide with magnesium compounds, characterized in that the magnesium sulfite is decomposed with nitric acid to form sulfur dioxide and a magnesium nitrate solution.