A process for producing caustic calcined magnesia (CCM) includes calcining a magnesium containing material, such as magnesite, in a primary calciner to produce a primary calcined material and a primary exhaust comprising dust; subjecting the primary exhaust to separation to recover a dust material includes incompletely calcined dust particles; calcining the dust material in the secondary calciner to produce calcined dust, wherein the dust material is not co-calcined with the magnesium containing material or the primary calcined material. The primary calcined material and the calcined dues thus form two CCM products, which can be kept separate or combined. The primary calciner can be a multiple hearth furnace (MHF) while the secondary calciner can be a gas suspension calciner (GSC). Using a secondary calciner in such a manner can increase throughput of the primary calciner and provide other advantages for the calcination process.

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.

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.

A method for reducing pollution in a cement kiln environment and a system for treating cement kiln exhaust gas are provided. The method includes the steps of: treating a cement kiln exhaust gas stream with a treating fluid, such as a water soluble alkaline-earth metal sulfide. In one application, the treating fluid is injected by spraying droplets into the cement kiln exhaust gas stream. A system for treating cement kiln exhaust gas includes a reagent containing a water soluble alkaline-earth metal sulfide in water, and a nozzle to spray the reagent into the cement kiln exhaust gas stream.

A method for decreasing an amount of a harmful substance of a chlorine-containing off-gas stream formed or used in a thermal treatment of a material may comprise dividing the chlorine-containing off-gas stream into a main stream and a substream, separating at least some chlorine from the main stream, lowering an amount of the harmful substance in the main stream by introducing a chlorine-containing additive into the main stream to enhance separation of the harmful substance, and filtering the substream such that a filter cake separated from the substream comprises at least part of the chlorine-containing additive.

Disclosed is a bypass system for use with off gases that have exited a cement kiln utilized in a cement making process. The bypass system is adapted to remove both NOx and volatile components that are present in the off gases while the off gases are in the bypass duct.

In a method for reducing the NOx emissions of a rotary kiln of a clinker production plant, fuel supplied through a burner of the rotary kiln is burned along with primary air fed through the burner, wherein the primary air has a lower oxygen content and the primary air has an oxygen content reduced relative to that of the ambient air and a temperature increased relative to that of the ambient air, and the primary air is obtained by mixing ambient air with exhaust gas from the rotary kiln or from a heat exchanger connected to the rotary kiln and used for preheating raw meal. The primary air is further obtained by mixing with hot air, in particular waste air from a clinker cooler.

In a method for reducing the NOx emissions of a rotary kiln of a clinker production plant, fuel supplied through a burner of the rotary kiln is burned along with primary air fed through the burner, wherein the primary air has a lower oxygen content and the primary air has an oxygen content reduced relative to that of the ambient air and a temperature increased relative to that of the ambient air, and the primary air is obtained by mixing ambient air with exhaust gas from the rotary kiln or from a heat exchanger connected to the rotary kiln and used for preheating raw meal. The primary air is further obtained by mixing with hot air, in particular waste air from a clinker cooler.

For the purification of waste gas containing carbon compounds and nitrogen oxides by means of a regenerative post-combustion system, at least two regenerators (A, B, C) filled with heat accumulator bodies (7a, 7b, 7c) and connected by a combustion chamber (10) are provided, wherein the waste gas is alternately heated in a regenerator (A, B, C), the carbon compounds are oxidised in the combustion chamber (10), and, with the addition of a nitrogen-hydrogen compound, the nitrogen oxides are reduced in the combustion chamber (10) thermally and thus not catalytically. Remaining nitrogen oxides are removed by means of a catalytically active heat accumulator layer (6a, 6b, 6c) and the addition of a further nitrogen-hydrogen compound in the regenerator (A, B, C) from which the clean gas exits.

A process and device separate off a volatile component from the off-gases in cement clinker production. Raw materials for cement clinker production are passed through a preheater with heat exchange with the off-gases and are then burnt in a rotary kiln. Owing to the heating in the preheater, the volatile component bound in the raw materials is vaporized and separated off. A first raw material stream having a relatively high concentration of the volatile component is applied to a first line of the preheater and a second raw material stream having a lower concentration of the volatile component is applied to a second line. The volatile component is separated off from the first substream of the off-gases. The first raw material stream heated to a temperature of at least 250 C. with the first substream of the off gases in the first line is combined with the second raw material stream.