A method for denitrification of flue gases and a system, wherein flue gases generated in a rotary kiln are conveyed to a calcining zone for the deacidification of raw cement meal. Aqueous ammonia solution, ammonia, or ammonia-releasing substances for denitrifying the flue gases injected into the calcining zone according to the method of selective non-catalytic reduction (SNCR), and the flue gas stream, together with an ammonia slip generated during the denitrification, is passed through a heat exchanger and through at least one dedusting device. The flue gas is guided through a exhaust gas line via a catalyst for the decomposition of excess ammonia with residues of nitrogen oxide in accordance with a method of selective catalytic reduction (SCR), wherein the catalyst is arranged in a reactor provided in the exhaust line, and is no larger than is required for a sufficient decomposition of the ammonia.

There is provided a method for operating a cement plant capable of simultaneously optimizing both combustion in a calciner and a heat consumption rate. The method for operating a cement plant includes: feeding first fuel to a calciner; feeding second fuel for maintaining the inside at a burning temperature to a cement kiln along with combustion primary air, and introducing air for cooling cement clinker to a cooler; and feeding a part of the air as secondary air to the cement kiln, feeding as tertiary air to the calciner, and discharging the rest of the air from the cooler, wherein relation between a first oxygen concentration at an exhaust gas outlet of the calciner and a heat consumption rate determined by the first fuel and the second fuel, and relation between a second oxygen concentration at an exhaust gas outlet of the preheater and the heat consumption rate are beforehand obtained, and amounts of the secondary air and the tertiary air are adjusted such that both the first oxygen concentration and the second oxygen concentration fall within a range including values of the oxygen concentrations at which the heat consumption rate becomes at its minimum.

A method of preparing alkali-activated cement by stepwise calcination with sodium chloride includes the following steps. (1) Sodium chloride, a silicate and a carbonate are mixed and finely ground to obtain a raw material powder. (2) The raw material powder is calcined sequentially at 850-1050? C. and 1240? C. or more, and cooled to obtain a clinker. (3) The clinker is mixed with at least one of sodium hydroxide and potassium hydroxide, and ground finely to produce a cement powder.

A method and a sensor device for evaluating residual Sulphur in a cement preheater of a cement kiln, wherein the residual Sulphur is based on the values of the fuel Sulphur content, the fuel rate of consumption, the hotmeal quality and the clinker Sulphur content. A method for evaluating blockage in a cement preheater includes evaluating the residual Sulphur in the cement preheater, determining an agglomeration rate of Sulphur compounds agglomerating on an inner surface of the cement preheater based on the residual Sulphur, and evaluating a level of blockage in at least one predetermined pathway of the cement preheater using a blockage evaluation unit, wherein the level of blockage is based on the agglomeration rate.

The invention relates to a method of producing a binder comprising the steps of preparing (20) a residual material comprising amorphous alumina-rich and/or aluminium hydroxide-rich constituents, heating (30) the residual material to produce a fired material, the heating (30) of the residual material being at a temperature of >800 C.

The invention concerns: A) An assembly to reduce the emission of CO.sub.2 in a plant for the production of clinkers comprising two calciners and a carbonator arranged between the two calciners, wherein one of the calciners is an integral part of a conventional clinker production system. Thanks to this assembly, the plant can continue to operate in the clinker production process even if the CO.sub.2 capture system which uses the carbonator and the other calciner of the assembly is disconnected due to malfunctions or maintenance characterized in that said carbonator is free of recirculation to both said two calciners. B) The relative plants comprising both the assembly and the actual clinker production plant in which the clinker production plant is of the conventional type existed before and already operational, or said plant is installed simultaneously with the assembly units. C) The clinker production process with reduction of CO.sub.2 emission conducted in the plants B.

A method for preparing a general-purpose cement is provided. Raw materials containing all of SiO.sub.2, Al.sub.2O.sub.3, CaO, MgO and Na.sub.2O (or K.sub.2O) are mixed to obtain a raw meal, which is dried and ground into a raw meal powder. The raw meal powder is oxidatively calcined at no less than 1210 C. to reach a stable phase state, and rapidly cooled to obtain a clinker predominated by glass phase. The clinker is mixed with NaOH, KOH or a combination thereof and ground to obtain the general-purpose cement. Alternatively, the clinker is ground to obtain a clinker powder, which is mixed with an aqueous NaOH solution, an aqueous KOH solution or a combination thereof for use. The NaOH and/or KOH is/are added such that a weight ratio of NaOH+0.713KOH to the clinker powder is 0-0.03:1.

A plant for producing cement clinker, comprising as viewed in the direction of materials flow, a heat exchanger to preheat raw meal, a downstream calciner to calcine the raw meal, a rotary kiln to sinter the calcined raw meal, and a clinker cooler to cool the sintered cement clinker. A combustion device which carbonizes, pyrolysis or burns difficult fuels, is embodied as a pot reactor or gooseneck reactor in an inverted U-shape, and is positioned upstream of the calciner on the flow path of the exhaust gases from the rotary kiln to the calciner, and has a gas outlet that opens out above a tertiary-air line of the clinker cooler into the calciner. As a result, it becomes possible to burn fuel which is lumpy and/or has poor ignitability, and the gases from incomplete combustion in the reactor are available in the calciner in gaseous form for further combustion.

The invention relates to a clay calcination plant for activating clay as feed material, which has a proportion of at least 40% of thermally activatable layered silicates. The plant comprises a rotary kiln with a kiln inlet and a kiln outlet, wherein feed material is thermally treated while being conveyed through the rotary kiln. In addition, a gas infeed is provided at the kiln outlet and a gas outfeed at the kiln inlet. Furthermore, the clay calcination plant has a mixing chamber for generating a temperature-homogeneous flow of calcination gas, with a burner for generating flue gas and a process gas infeed for the infeed of warm process gas being provided.

A Portland cement production (PCP) process is conjoined with a waste-to-energy (WTE) process using refuse-derived fuels (RDFs). Both processes operate simultaneously to reduce harmful compounds being discharged into the environment. The PCP and WTE processes are conjoined by borrowing a minor portion of pre-heated comminuted limestone from a PCP process feedstream and diverting it to the WTE process. Some of the pre-heated comminuted limestone is converted to CaO. The calcium compounds from the pre-heated comminuted limestone act as a fluxing agents and sorbents to bind with and remove undesired impurities, such as elemental particulate matter, excess CO.sub.2 and acid gasses associated with sulfur and chlorine that are released during the pyrolization of RDFs. The ash, char waste and reacted calcium compounds from the pyrolization process can be comingled and returned to the PCP process as a secondary cement meal feedstock.