A process for synthesis of a waste-derived CO.sub.2-activated clinker, which comprises firing nodules at temperatures between 1000-1100 C. for a time sufficient to obtain CO.sub.2-reactive clinker phases within the nodules, cooling the clinker nodules, and reducing to powder to obtain a clinker powder; wherein the nodules are agglomerates of a stoichiometric mix of uniformly-sized powders of municipal solid waste (MSW) incineration residues; wherein the stoichiometric mix respects the primary compositional requisite of containing Ca, Al, and Si in their oxide forms within the ranges of 35-45 wt. % CaO, 2-8 wt. % AI.sub.2O.sub.3, and 12-20 wt. % SiO.sub.2; wherein the fmal stoichiometric mix has a total-sulfur content of 1 to 10 wt. %, total-carbon content of 2 to 20 wt. %, and a total-chlorine content of 2 to 15 wt. %.

A process for synthesis of a waste-derived CO.sub.2-activated clinker, which comprises firing nodules at temperatures between 1000-1100 C. for a time sufficient to obtain CO.sub.2-reactive clinker phases within the nodules, cooling the clinker nodules, and reducing to powder to obtain a clinker powder; wherein the nodules are agglomerates of a stoichiometric mix of uniformly-sized powders of municipal solid waste (MSW) incineration residues; wherein the stoichiometric mix respects the primary compositional requisite of containing Ca, Al, and Si in their oxide forms within the ranges of 35-45 wt. % CaO, 2-8 wt. % AI.sub.2O.sub.3, and 12-20 wt. % SiO.sub.2; wherein the fmal stoichiometric mix has a total-sulfur content of 1 to 10 wt. %, total-carbon content of 2 to 20 wt. %, and a total-chlorine content of 2 to 15 wt. %.

There is provided a method for reforming unburned carbon-containing coal ash of the present invention, including: a receiving process of measuring L value and b value of unburned carbon-containing coal ash in a Lab color order system and sorting unburned carbon-containing coal ash of which the L value is 54 or more and the b value is 2 or more and 10 or less; and a classifying process of classifying the unburned carbon-containing coal ash sorted in the receiving process under a condition that a residue on a 45 m sieve of reformed coal ash which has been reformed by classification is 8% by mass or less.

A system for the calcination of powder materials comprising a plurality of vertical reactor tubes in which a falling powder is heated about a heating zone by radiation from the externally heated walls of the reactor tubes, in which the calcination process of the powder may be a reaction which liberates a gas, or induces a phase change; wherein the average velocity of the particles of falling powder during its transit through the reactor tubes is 1.0 m/s or less; the powder material flux for each tube is preferably in the range of 0.5-1 kg m-2 s-1, and wherein the length of the heating zone is in the range of 10 to 35 m.

A process for synthesis of a waste-derived CO.sub.2-activated clinker, which comprises firing nodules at temperatures between 1000-1100? C. for a time sufficient to obtain CO.sub.2-reactive clinker phases within the nodules, cooling the clinker nodules, and reducing to powder to obtain a clinker powder; wherein the nodules are agglomerates of a stoichiometric mix of uniformly-sized powders of municipal solid waste (MSW) incineration residues; wherein the stoichiometric mix respects the primary compositional requisite of containing Ca, Al, and Si in their oxide forms within the ranges of 35-45 wt. % CaO, 2-8 wt. % AI.sub.2O.sub.3, and 12-20 wt. % SiO.sub.2; wherein the final stoichiometric mix has a total-sulfur content of 1 to 10 wt. %, total-carbon content of 2 to 20 wt. %, and a total-chlorine content of 2 to 15 wt. %.

A process for synthesis of a waste-derived CO.sub.2-activated clinker, which comprises firing nodules at temperatures between 1000-1100? C. for a time sufficient to obtain CO.sub.2-reactive clinker phases within the nodules, cooling the clinker nodules, and reducing to powder to obtain a clinker powder; wherein the nodules are agglomerates of a stoichiometric mix of uniformly-sized powders of municipal solid waste (MSW) incineration residues; wherein the stoichiometric mix respects the primary compositional requisite of containing Ca, Al, and Si in their oxide forms within the ranges of 35-45 wt. % CaO, 2-8 wt. % AI.sub.2O.sub.3, and 12-20 wt. % SiO.sub.2; wherein the final stoichiometric mix has a total-sulfur content of 1 to 10 wt. %, total-carbon content of 2 to 20 wt. %, and a total-chlorine content of 2 to 15 wt. %.

The present application pertains to methods for making metal oxides and/or citric acid. In one embodiment, the application pertains to a process for producing calcium oxide, magnesium oxide, or both from a material comprising calcium and magnesium. The process may include reacting a material comprising calcium carbonate and magnesium carbonate. Separating, concentrating, and calcining may lead to the production of oxides such as calcium oxide or magnesium oxide. In other embodiments the application pertains to methods for producing an alkaline-earth oxide and a carboxylic acid from an alkaline earth cation-carboxylic acid anion salt. Such processes may include, for example, reacting an alkaline-earth cation-carboxylic acid anion salt with aqueous sulfur dioxide to produce aqueous alkaline-earth-bisulfite and aqueous carboxylic acid solution. Other useful steps may include desorbing, separating, and/or calcining.

Embodiments herein provide a system for electrically heated gas mixture mediated industrial plant processes providing a fossil fuel free approach. The system utilizes a gas mixture as heating medium that directly transfers heat to a raw material required for processing the raw material into an end product. The gas mixture used as a heating medium can be a byproduct generated during processing or a combination of stable gases that are reutilized and recirculated to carry heat and dissipate the heat at various stages of processing in accordance with a heating medium design loop. The heating medium design loop disclosed is designed such that it eliminates the need of heat management equipment like a Thermal Energy Storage (TES) system used by existing approaches. Entire heating of the plant is carried out using electric gas heaters heated using renewable electric sources to provide the fossil fuel free design.

Some embodiments are directed to a method to avoid the negative effect of both sulphur and vanadium presence contained in solid fuel used in cement clinker manufacturing line (build-up, kiln rings, etc.). Some embodiments are methods to prepare, dose and use a fuel additive based on an alkaline earth metal to allow the combination of vanadium and sulphur with said added alkaline earth metal, so that corrosion, build-up, crusts and ring formation in cement pre-heaters and kilns due to the presence of those components are avoided.

Methods for producing pozzolanic or latent hydraulic cement clinker substitutes may involve calcining clay with a fuel comprising a mineral substance at temperatures in the range from 500 to 1250 C., preferably from 550 to 1150 C., most preferably from 700 to 900 C. A resulting mixture of mineral substance from the fuel and the calcined clay forms a pozzolanic or latent hydraulic cement clinker substitute, in which a fraction of the mineral substance incorporated into the pozzolanic or latent hydraulic cement clinker substitute by the fuel is 1-60% by weight.