Disclosed are thermal energy storage systems and methods that utilize metal carbonate eutectics that can undergo high temperature reversible reactions to form mixtures of metal oxides. The metal oxides undergo an exothermic reaction with carbon dioxide to form the molten metal carbonate eutectics, and the molten metal carbonate eutectics undergo an endothermic decarbonization reaction to form the metal oxides and carbon dioxide. By carrying out the reversible reactions at a temperature above the melting point of the carbonate eutectic, the systems provide high thermal conductivity and reversible stability for thermal energy storage.

Disclosed are thermal energy storage systems and methods that utilize metal carbonate eutectics that can undergo high temperature reversible reactions to form mixtures of metal oxides. The metal oxides undergo an exothermic reaction with carbon dioxide to form the molten metal carbonate eutectics, and the molten metal carbonate eutectics undergo an endothermic decarbonization reaction to form the metal oxides and carbon dioxide. By carrying out the reversible reactions at a temperature above the melting point of the carbonate eutectic, the systems provide high thermal conductivity and reversible stability for thermal energy storage.

Methods for reducing moisture content of alkaline earth metal carbonate may include introducing alkaline earth metal carbonate having a moisture content ranging from about 0.1% by mass to about 10% by mass into a primary crusher and operating the primary crusher to obtain alkaline earth metal carbonate particles having a top cut particle size d.sub.90 of 90 microns or less. The method may also include introducing the particles into a primary grinder and operating the primary grinder to obtain reduced-size alkaline earth metal carbonate particles having a median particle size d.sub.50 of about 60 microns or less. The method may further include introducing the reduced-size particles into a classifier mill and operating the classifier mill to obtain further-reduced-size alkaline earth metal carbonate particles having a median particle size d.sub.50 of about 12 microns or less, and a moisture content of about 0.15% by mass or less.

Effluent water is combined with carbon dioxide sourced from a carbon dioxide-containing emission stream to produce a reaction solution. The pH of the reaction solution is controlled to induce precipitation of a carbonate salt from the reaction solution.

To provide a sodium transition metal polyanion suitable as a cathode active material of a sodium secondary battery, and a simple method for producing it.

A sodium transition metal polyanion, which has a purity of 90 mass % or higher, has a crystallite size of 90 Å or longer and 400 Å or shorter, and is represented by the formula Na.sub.3-xMPO.sub.4CO.sub.3 (M is at least one member selected from the group consisting of Fe, Mn, Ni and Co, and 0≤x≤2).

To provide a sodium transition metal polyanion suitable as a cathode active material of a sodium secondary battery, and a simple method for producing it.

A sodium transition metal polyanion, which has a purity of 90 mass % or higher, has a crystallite size of 90 Å or longer and 400 Å or shorter, and is represented by the formula Na.sub.3-xMPO.sub.4CO.sub.3 (M is at least one member selected from the group consisting of Fe, Mn, Ni and Co, and 0≤x≤2).

The present invention provides a method for treating a gas, comprising: step (A): collecting a gas comprising carbon dioxide and fine particulate matter; step (B): rinsing the gas with water to obtain a rinsed gas; and step (C): contacting the rinsed gas with a basic solution in a way of co-current flow to absorb the carbon dioxide in the rinsed gas by the basic solution to obtain a treated gas and a weak basic solution; wherein the pH value of the basic solution is between 9 and 14, and the pH value of the weak basic solution is between 8 and 8.5. The method can reduce the content of both fine particulate matter and carbon dioxide.

The present invention provides a method for treating a gas, comprising: step (A): collecting a gas comprising carbon dioxide and fine particulate matter; step (B): rinsing the gas with water to obtain a rinsed gas; and step (C): contacting the rinsed gas with a basic solution in a way of co-current flow to absorb the carbon dioxide in the rinsed gas by the basic solution to obtain a treated gas and a weak basic solution; wherein the pH value of the basic solution is between 9 and 14, and the pH value of the weak basic solution is between 8 and 8.5. The method can reduce the content of both fine particulate matter and carbon dioxide.

Powder compositions comprising alkali metal bicarbonate particles and an additive. A process for preparing alkali metal bicarbonate particles by spray-drying of an aqueous solution or suspension comprising 1-10% by weight of alkali metal bicarbonate and a resin acid or a fatty acid as additive. A process for preparing alkali metal bicarbonate particles by co-grinding the alkali metal bicarbonate in the presence of a resin acid as additive. A process for preparing alkali metal bicarbonate particles by fluidized bed coating of the alkali metal bicarbonate in the presence of a resin acid, fatty acid or a wax as additive.

Powder compositions comprising alkali metal bicarbonate particles and an additive. A process for preparing alkali metal bicarbonate particles by spray-drying of an aqueous solution or suspension comprising 1-10% by weight of alkali metal bicarbonate and a resin acid or a fatty acid as additive. A process for preparing alkali metal bicarbonate particles by co-grinding the alkali metal bicarbonate in the presence of a resin acid as additive. A process for preparing alkali metal bicarbonate particles by fluidized bed coating of the alkali metal bicarbonate in the presence of a resin acid, fatty acid or a wax as additive.