SU61922A1 - The method of cleaning flue gases from sulfur dioxide - Google Patents

Description

A known method for extracting sulfur dioxide from flue gases is by treating gases with a suspension of magnesium oxide to produce solid sulfite and magnesium sulfate.

According to the proposed method, the cleaning of flue gases from sulfuric anhydride is carried out by the introduction of magnesite milk into the spent absorption liquid. In this case, magnesium bisulfite is neutralized and better magnesium sulfite is obtained in the classifier.

The drawing shows the process.

The gas entering the SO2 purification is preliminarily purified from mechanical impurities (ash, underburning, etc.), then the gas is sent to a scrubber, where, under the action of a suspension of magnesium sulfite bisulfite with pH 5.8-6.3, SO2 is absorbed according to the equation; MgSOs + SOs + N.O- Mg (H503) 2.

Gases purified in a scrubber at 98-99% of SO2 are emitted into the atmosphere.

The absorption solution from the scrubber is sent to the crystallizer, where magnesite milk is introduced. Under the action of magnesite milk, magnesium bisulfite is neutralized and precipitated after forming crystalline sulfite precipitates according to the equation: Mg (HS03) 2 + Mg (OH) 2-2MgS63 + 2H20

From the crystallizer, the main part of the solution is sent back to the scrubber irrigation, and the remainder goes to the classification, the purpose of which is to separate magnesium sulphite crystals from the solution with minimal ash content. This operation is extremely necessary, since the scrubber removes the ash that is not caught in the ash collector and therefore in the solution, except for magnesium sulfite crystals; ash is also contained.

The magnesium sulphite crystals are separated from the solution by filtration, then dried by drying, are dehydrated from crystallization moisture, and calcined with reference No. 61922-2 are heated in an oven at a temperature of 900-1100 °. In the furnace, magnesium sulfite decomposes into magnesium oxide and SO2: MgSOs - MgO + SOz.

Calcination can be carried out: in rotary tube furnaces with internal heating — to obtain 7–87 o S02 or in a muffle — to obtain highly concentrated SOg. Furnace gases containing SO2 can be converted to sulfuric acid, elemental sulfur, etc.

Magnesium oxide, together with additives that compensate for its loss, is sent from the furnace to the preparation of magnesite milk, which is introduced into the cycle of the absorption solution (into the crystallizer).

The ash enriched solution, after classification, is sent to the sludge. The sludge from the sump is filtered, then it goes to the dump.

The clarified solutions resulting from the filtration of sulphite and ash crystals, as well as from the settling tank, are returned to the cycle of the absorption solution. Magnesium sulphite is partially oxidized to magnesium sulphate, whose concentration is therefore increased. To limit the concentration of magnesium sulfate, a portion of the clarified solution is taken from the system, evaporated to crystalline magnesium sulfate, which is discharged as a marketable product.

Thus, both products can be obtained quantitatively in any ratios, depending on the requirements.

Subject invention

The method of purifying flue gases from sulfur dioxide by treating them with an aqueous suspension of magnesium oxide hydrate to produce solid sulfite and magnesium sulfate, characterized in that in order to release magnesium sulfite magnesite milk is introduced into the waste absorption liquid to neutralize magnesium bisulfite and sulfite is released. isolated from the classifier.