Abstract: A process for producing an alkali metal hydrogencarbonate by reacting an aqueous solution containing alkali metal ions with carbon dioxide in a prescribed crystallizer to precipitate crystals of an alkali metal hydrogencarbonate, and in this process a part of a slurry containing the alkali metal hydrogencarbonate crystals in the aqueous solution is withdrawn from the crystallizer and, after dissolution of a part of the crystals, it is returned to the crystallizer.

Abstract: A method for producing a porous potassium carbonate, which comprises calcining potassium hydrogen carbonate crystals having a mean particle diameter of from 100 to 1,000 ?m at a temperature of the object to be calcined of from 100 to 500° C., while introducing a dry gas which has a dew point of not higher than 0° C. and a temperature of from 10 to 50° C.

Abstract: A method for producing sodium hydrogencarbonate crystal particles having a low caking property, which comprises lowering the potassium concentration in sodium hydrogencarbonate crystal particles having a mean particle diameter of from 50 to 500 ?m to a level of at most 50 mass ppm.

Abstract: A method for removing a halogen series gas, which comprises contacting a gas containing a halogen series gas forming at least one kind selected from the group consisting of HF, HCl, HBr and HI by water with a granule containing from 60 to 99.9 mass % of a solid base and from 0.1 to 40 mass % of a carbonaceous material to the total mass amount of the granule in the presence of water.

Abstract: To provide a process for easily obtaining an alkali metal hydrogencarbonate having a large crystal particle size in good yield by an industrially convenient installation by a crystallization method from an aqueous solution. A process for producing an alkali metal hydrogencarbonate, which comprises reacting an aqueous solution containing alkali metal ions with carbon dioxide in a prescribed crystallizer to precipitate crystals of an alkali metal hydrogencarbonate, characterized in that a part of a slurry containing the above crystals in the above aqueous solution, is withdrawn from the above crystallizer and, after a part of the above crystals is dissolved, returned to the above crystallizer.

Abstract: A sodium-based dechlorinating agent is added to a flue gas; hydrogen chloride contained in this flue gas is removed as residue of dechlorination; the thus removed residue of dechlorination is dissolved by adding water; water-insoluble constituents are separated from the resulting aqueous solution; and after adjusting pH of the aqueous solution remaining after separation of the water-insoluble constituents, mercury, dioxin, and the like are removed and discharged. The sodium-based dechlorinating agent is mixed with a hydrophilic anti-caking agent, with an angle of repose of 40° or more, a dispersibility of less than 50, and a floodability index value of less than 90. This permits inhibition of occurrence of a pressure drop and leakage in the filter cloth of the dust collector.

Abstract: A method for producing a porous potassium carbonate, which comprises calcining potassium hydrogen carbonate crystals having a mean particle diameter of from 100 to 1,000 &mgr;m at a temperature of the object to be calcined of from 100 to 500° C., while introducing a dry gas which has a dew point of not higher than 0° C. and a temperature of from 10 to 50° C.

Abstract: A method for removing a halogen series gas, which comprises contacting a gas containing a halogen series gas forming at least one kind selected from the group consisting of HF, HCl, HBr and HI by water with a granule containing from 60 to 99.9 mass % of a solid base and from 0.1 to 40 mass % of a carbonaceous material to the total mass amount of the granule in the presence of water.

Abstract: A method for treating a gas, which comprises contacting a gas containing a boric acid component in an amount of at least 15 mg/m3 as converted into B2O3 concentration in a standard state, with a solid alkali metal carbonate material comprising at least one member selected from the group consisting of alkali metal carbonates and alkali metal hydrogencarbonates, to remove the boric acid component from the gas.

Abstract: A method for treating a gas containing a SO3 component, which comprises adding a sodium carbonate powder having a mean particle diameter of at most 20 &mgr;m to the gas to remove the SO3 component from the gas.

Abstract: A method for treating a gas, which comprises contacting a gas containing a boric acid component in an amount of at least 15 mg/m3 as converted into B2O3 concentration in a standard state, with a solid alkali metal carbonate material comprising at least one member selected from the group consisting of alkali metal carbonates and alkali metal hydrogencarbonates, to remove the boric acid component from the gas.

Abstract: A sodium carbonate supply device is provided that supplies sodium carbonate to flue gas at the outlet of a boiler 1, and an SO3 separation device 10 is provided that decreases the SO3 concentration in the flue gas while also separating and removing SO3 fraction from the flue gas at the inlet of a wet desulfurization device 7. The SO3 separation device is provided with a shell and tube type of heat exchanger that cools flue gas to below the dew point of H2SO4 gas by allowing flue gas to pass through the shell side and allowing boiler supply water to pass through the tube side. The SO3 component present in the flue gas is lowered in temperature and reacts with moisture in the flue gas to form H2SO4 gas, after which the H2SO4 gas condenses and adheres to the surface of the tubes. By then washing the liquid H2SO4 adhered to the tube surfaces with water, the SO3 component can be removed from the flue gas.

Abstract: A method is provided for removing a halogen series gas, by bringing a halogen series gas into contact with a granulated product, the granulated product being obtainable by granulating, employing various methods including compression molding, extrusion molding, rotating granulation and agitation granulation, a powder of hydrogencarbonate having a mean particle diameter of primary particles 10-500 &mgr;m, wherein the granulated product has a mean particle diameter of 0.5-20 mm and a minimum average hardness that is dependent on the mean particle diameter.

Abstract: A method for producing sodium hydrogencarbonate crystal particles having a low caking property, which comprises lowering the potassium concentration in sodium hydrogencarbonate crystal particles having a mean particle diameter of from 50 to 500 &mgr;m to a level of at most 50 mass ppm.

Abstract: It is an object of the present invention to obtain a composite sol capable of forming an ink-receiving layer having a high transparency and a high property for fixing dyes. The present invention provides a sol which is a colloidal solution having aggregate particles containing silica and alumina dispersed in an aqueous medium, wherein the silica is such that the primary particles are spherical and the average particle size of the primary particles is from 2 to 200 nm, the average particle size of the aggregate particles is at least twice the average particle size of the silica primary particles and at most 1,000 nm, the &zgr;-potential of the aggregate particles is at least +10 mV, and the pH of the solution is from 3 to 9.

Abstract: It is an object of the present invention to provide hollow glass microspheres having particle properties of a low particle density and grain size properties of a sharp grain size distribution, having a high homogeneity and having such strength that they are less likely to fracture during processing. In the present invention, a glass material containing a foaming agent and containing B2O3 in an amount of from 9 to 20%, is subjected to wet grinding to obtain a slurry having an average particle size of at most 3 &mgr;m, droplets thereof are heated, to obtain hollow glass microspheres having an average particle size of at most 15 &mgr;m, a maximum particle size of at most 45 &mgr;m, a particle density of at most 0.5 g/cm3 and a grain size gradient of at most 2.

Abstract: A method for removing an acidic deposit containing a sulfur compound, which comprises contacting the acidic deposit with an aqueous solution of an alkali metal carbonate and/or an alkali metal hydrogencarbonate to remove it.

Abstract: A sodium-based dechlorinating agent g is added to a flue gas G6; hydrogen chloride contained in this flue gas is removed as residue of dechlorination; the thus removed residue of dechlorination is dissolved by adding water i; water-insoluble constituents k are separated from the resulting aqueous solution j; and after adjusting pH of the aqueous solution 1 remaining after separation of the water-insoluble constituents k, mercury, dioxin and the like are removed and discharged. The sodium-based dechlorinating agent g is mixed with a hydrophilic anti-caking agent, with an angle of repose of 40° or more, a dispersibility of less than 50, and a floodability index value of less than 90. A mean particle diameter of sodium hydrogencarbonate is set within a range of from 2 &mgr;m to 30 &mgr;m. The hydrophilic anti-caking agent comprises silica, and is contained in an amount of 0.1 mass % or more in the sodium-based dechlorinating agent.

Abstract: A blasting medium which has an average grain size of at most 20 &mgr;m and contains at least 90 mass % of a water-soluble inorganic salt, wherein the content of grains having grain sizes of at least 50 &mgr;m is at most 5 mass %.

Abstract: A process for producing a spherical silica gel, which comprises supplying a liquid mixture of an alkali silicate solution and an acid solution to a spraying apparatus, spraying the liquid mixture to obtain droplets, bringing the droplets into contact with a liquid for recovering a silica gel, and recovering the formed spherical silica gel together with the liquid for recovering a silica gel, as a slurry.