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Potassium sulfate (SOP)

  Time: 2022-04-06      Views:109

PROCESS DESCRIPTION

        The process implemented in this plant, the KCl (MOP, Potassium Chloride) reacts with Sulfuric Acid to yield K2SO4 (SOP) and HCl (Hydrochloric Acid) as a by-product.

2 KCl + H2SO4 → K2SO4 + 2 HCl

        The reaction of Sulfuric Acid with Potassium Chloride takes places in two stages:

KCl + H2SO4 → KHSO4 + HCl; KCl + KHSO4 → K2SO4 + HCl

The first reaction step is exothermic and proceeds at relatively low temperature. The second is endothermic and must be carried out at higher temperature. To minimize the Chloride content of the product, a small excess of Sulfuric Acid is used, which is later neutralized with Calcium Carbonate or Potassium Carbonate, depending on the purity requirements for the product.

The reaction is usually carried out in so-called Mannheim furnaces. The furnace has a closed dish-shaped chamber, with diameter up to 6 m, heated externally by an oil or gas burner. Potassium Chloride and Sulfuric Acid are fed into the chamber in the required ratio at an overhead central pointy. The mixture reacts with evolution of heat and its mixed by a slowly moving stirrer fitted with stirring arms with scrapers (rabbles), which propels the mixture from the center of the chamber to the periphery. Potassium Sulfate leaves the reaction chamber at this point and is neutralized and cooled.

2.1. Production of hydrogen chloride gas

Potassium sulfate and hydrogen chloride were produced by the reaction of potassium chloride and 98% sulfuric acid in Mannheim furnace at 530℃

2.2. Cooling of hydrogen chloride gas and washing of sulfate gas (mainly SO3):

(1) the outlet temperature of hydrogen chloride gas generated in the reaction chamber is as high as 450℃, and the heat exchange temperature should be lowered to ≤50℃ to facilitate the washing of sulfate gas and the preparation of hydrochloric acid, which is carried out in the graphite cooler. Because hydrogen chloride gas still contains trace amounts of dust and small particle, in order to prevent the blockage of the graphite cooler, it is accompanied by the mixed acid washing process. The washing liquid comes from the grade B acid washing pump and the flow of hydrogen chloride gas goes back to the sulfuric acid gas scrubber. The cooling water goes back and forth from the water distributor to the return water bucket, and multi-stage cooling is adopted from the bottom up.

(2) hydrogen chloride gas discharged from the reaction chamber is accompanied by a small amount of sulfate gas (mainly sulfur trioxide) and small particles. In order to produce high-quality hydrochloric acid, it is necessary to wash sulfur trioxide and particles clean. This process is carried out in the sulfate gas scrubber, and the mixed acid absorption liquid’s Baume is controlled to transfer continuously to the buffer tank of mixed sulfuric acid B. The replenishment of dilute hydrochloric acid is sent by the tail gas treatment system, and the hydrogen chloride gas after washing enters the acid production system. To prevent the outlet gas from carrying liquid, a demister is set to collect the acid mist back to the scrubber.

2.3. Preparation of hydrochloric acid

The washed hydrogen chloride gas and the dilute hydrochloric acid from the hydrochloric acid absorber flow downstream into the hydrochloric acid absorber A (series tube type) in parallel to complete the falling film absorbers, and the concentrated hydrochloric acid control Baume (Be0) in 18-19 is sent to the buffer tank of hydrochloric acid. Since the hydrogen chloride reaction in the absorption tower is an exothermic process, the reaction heat needs to be removed to facilitate the reaction, so the hydrochloric acid absorption tower is equipped with tube coolers. Water comes from the water distributor and returns from the bottom up to the return water bucket into the circulating tank, and the water temperature at the outlet is controlled to be less than 40℃.The unabsorbed hydrogen chloride gas enters the hydrochloric acid absorption tower (packed tower), and countercurrent contact with the pure water or dilute acid added to the tower completes the absorption process. The hydrogen chloride tail gas enters the first HCl gas scrubber, and the clean water and dilute acid are continuously input by the gravity dilute acid tank through the metering device and the appropriate amount is controlled (the gravity dilute acid tank maintains a stable liquid level, the dilute acid is recycled from the first HCl gas scrubber, and the water is provided by tap water and groundwater).

Hydrochloric acid in the buffer tank control a certain level of hydrochloric acid, when the predetermined level of the tank in time. Hydrochloric acid sample analysis qualified, with the acid pump into the hydrochloric acid storage tank sales filling.

2.4. hydrogen chloride tail gas recovery and tail gas emission:

The hydrogen chloride gas from the reaction furnace enters the sulfate scrubber tower, the packing tower, the multistage series falling film absorption tower, the hydrogen chloride fan, the multistage series chlorinated hydrogen scrubber tower, and the tail gas scrubber tower successively, and is discharged into the atmosphere from the tail gas chimney. Hydrogen chloride gas and dilute hydrochloric acid in the scrubber countercurrent contact reaction, in the multistage series scrubber hydrogen chloride tail gas concentration gradually decreased, dilute hydrochloric acid concentration gradually increased their concentration gradient. To add clean water in the final stage scrubber, and gradually move forward primary washing tower, absorbing liquid scrubber quantitative transfer to sulfate production concentration is 31% of the class B hydrochloride (high sulfate content), at the same time, the first level liquid at the same time, to the dilute acid washing tower high groove, groove by dilute acid high after the rotor flow metering and taken to A packed tower, and then enter the falling film absorber producing qualified get degrees for 31% of the grade A hydrochloride (low sulfate content).Because the contact reaction between dilute hydrochloric acid and hydrogen chloride gas is exothermic reaction, in order to reduce the temperature of dilute acid in the scrubber tower, a dilute acid cooler was added for cooling. In the hydrochloric acid production system, the operating pressure of the sulfate scrubber tower, the falling film absorber tower and the packed tower is slightly negative pressure, while the chlorinated hydrogen scrubber tower is positive pressure.

The Mannheim process is the most widely used method of producing Potassium Sulfate due to its simplicity, high yield, and the many ways in which the by-product can be utilized. Hydrogen Chloride is widely used to produce CaCl, Poly AlCl3, FeCl3 and Poly Vinyl Chloride. HCl is also widely utilized in the MSG making plant, as the resin regeneration.


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