Abstract: The present invention relates to the improvement of a replenishment method of a magnesium-based compound and to the improvement of a double decomposition method, which can be used in a magnesium hydroxide desulfurization method. In the improved replenishment method, the magnesium-based compound is supplemented with water and the ratio of Mg/H2O is adjusted to the total Mg/H2O in the desulfurization system. In the improved double decomposition method, a tank for use is provided with an inner cylinder which partitions the tank into an inner part and an outer part, but does not reach the bottom of the tank, and a part of the slurry drawn through the bottom of the tank is fed to the outer upper position in the tank.

Abstract: Formation of calcium sulfite in a desulfurization column for desulfurizing flue gas is prevented by maintaining the pH of the sorption liquid in the column in the range of 5.5-7.0 and the chemical oxygen demand of the sorption liquid below an upper value determined by the concentration of magnesium sulfate. The upper value of the chemical oxygen demand of the sorption liquid can be controlled by maintaining the quantity of magnesium sulfate in an oxidization vessel arranged downstream of the desulfurization column. The oxidized liquid discharged from the oxidization vessel is neutralized in a double composition vessel, and the thus-obtained slurry is returned directly to the desulfurization column. By preventing formation of calcium sulfite, high-quality gypsum is formed in the double composition vessel.

Abstract: A process for the preparation of pellets is disclosed which comprises mixing an iron ore raw material with a pitch material having a softening point of 30.degree. to 300.degree. C. in an amount in the range of 0.5 to 5% by weight of the iron ore raw material, molding the mixture, and heating the molded material under a reducing atmosphere to remove arsenic contained therein.

Abstract: A stirring method comprising placing particles of a magnetic material or particles of a magnetic material coated or covered with a non-magnetic material in an interface between two phases or in a specific layer, and subjecting said particles to influences of a rotating magnetic field to cause rotation and revolution in the particles. According to this method, transfer of substances and/or heat in the interface between the two phases or in the specific layer is promoted. Also disclosed is a stir method comprising placing particles of a magnetic material or particles of a magnetic material coated or covered with a non-magnetic material in a fluid under influences of a rotating magnetic field, to cause rotation and revolution in the particles in the fluid. According to this method, transfer of substances and/or heat in the interface between a phase of the particles and a phase of the fluid is promoted.