Method for the purification of exhaust gas from the production of cement clinker in a rotary kiln, in which raw materials are ground in a mill to form raw meal, raw meal is preheated in countercurrent in a preheater with exhaust gas from the rotary kiln and optionally precalcined, preheated and optionally precalcined raw meal is supplied to the rotary kiln and burned in the rotary kiln to form cement, the exhaust gas from the rotary kiln is denitrified before entering the preheater of a selective non-catalytic nitrogen oxide reduction with a reagent which provides ammonia, and wherein, according to the invention, the exhaust gas from the preheater is subjected to gas conditioning and catalytic oxidation of ammonia. The object is further solved by means of a device for gas conditioning and catalytic oxidation which is arranged between the preheater and the mill.

Process for producing sodium carbonate with ammonia and/or for producing refined sodium bicarbonate, wherein: a low CO.sub.2 content gas generated by a unit for producing sodium carbonate with ammonia and/or generated by a unit for producing refined sodium bicarbonate is enriched into a CO.sub.2-enriched gas by using a CO.sub.2 concentration module, such as an amine-type or ammonia or PSA or TSA or cryogenic distillation or membrane-type CO.sub.2 concentration module, and said CO.sub.2-enriched gas has an increased CO.sub.2 content of: +10% (at least) to +90% (at most), by volume on a dry gas basis relative to the CO.sub.2 concentration of the low content gas, and the CO.sub.2-enriched gas is subsequently recycled to the unit for producing sodium carbonate with ammonia and/or to the unit for producing refined sodium bicarbonate, to produce sodium carbonate, or sodium bicarbonate, or to carbonate at least one part of effluent from the unit for producing sodium carbonate and/or from the unit for producing sodium bicarbonate.

Industrial gas streams such as flue gas streams are treated for nitrogen oxides and other contaminants in dry or semi-dry scrubbers. After the flue gas stream has been contacted with a sorbent, ozone is mixed downstream into the flue gas stream thereby oxidizing the nitrogen oxides and other contaminants. The oxidized contaminants is contacted with sorbent present in the gas stream in the remaining height or volume of the scrubber downstream of ozone injection; and The sorbent is then separated from the flue gas stream leaving the dry or semi-dry scrubber.

The absorption of CO.sub.2 from a gas mixture by contacting the gas mixture with an absorption medium that comprises water and 5 to 50 wt % of amino acid salts of formula R.sup.1R.sup.2CHNHCH.sub.2COOK, in which R.sup.1 and R.sup.2 are n-alkyl radicals and the radicals R.sup.1 and R.sup.2 together have 2 to 4 carbon atoms, affords a high CO.sub.2 absorption capacity per unit weight in the cyclical operation of absorption and desorption.

In a device for baking of clinker, heat generated in a furnace can be used in a particularly efficient and versatile manner if the heat generated in the furnace is transferred, by means of at least one first heat exchanger, to a heat carrier fluid, the heated heat carrier fluid is transported to at least one second heat exchanger, and the heat is then discharged to a heat sink, for example, in order to heat a flow of flue gas to a temperature required for denitrification thereof.

An absorbent solution is provided for removing acid compounds contained in a gaseous effluent and a method of removing acid compounds contained in a gaseous effluent contacts the gaseous effluent with the absorbent solution. The absorbent solution includes at least one of the following two nitrogen compounds belonging to the family of tertiary diamines: 1-dimethylamino-3-(2-dimethylaminoethoxy)-2-propanol ##STR00001## 1,1-oxybis[3-(dimethylamino)-2-propanol] ##STR00002##
and water.

A system and method for treating cement kiln dust is provided. The method includes the steps of receiving cement kiln dust (CKD) from a kiln; heating the collected CKD; forming a gas stream of vaporized metal and CKD by sufficient heating to separate at least one heavy metal from the collected CKD stream to create a cleaned CKD stream and a metal stream; providing a water soluble alkaline-earth metal polysulfide; combining the heavy metal stream with the water soluble alkaline-earth metal sulfide to create a combined stream; and removing at least a portion of one heavy metal from the combined stream.

Methods and apparatus for reducing the content of controlled acidic pollutants in clinker kiln emissions are disclosed. The methods and apparatus include introducing bypass dust produced during production of clinker into one or more locations between the preheater exhaust and the inlet to a dust filter including into a gas conditioning tower. Total bypass dust separated from the kiln exhaust gas may be used. The bypass dust can be separated into a fine and coarse portions. Fine or total bypass dust can be mixed with water to form a bypass dust slurry that can be introduced into the gas conditioning tower. Bypass dust can be used to reduce the content of acidic pollutants such as hydrogen chloride HCl and sulfur oxides SO.sub.x from clinker kiln emissions.

Provided is a simple and low-cost method for efficiently fixing a sufficient amount of carbon dioxide contained in a carbon dioxide-containing gas (e.g. a plant exhaust gas). The method of fixing carbon dioxide comprises a contact step of bringing a carbon dioxide-containing gas having a temperature of 350 C. or more into contact with a cementitious hardened body to fix carbon dioxide in the carbon dioxide-containing gas to the cementitious hardened body. The carbon dioxide-containing gas may be a gas that is free from being supplied with moisture before the contact step and during the contact step. One of examples of the carbon dioxide-containing gas is a plant exhaust gas.

Provided herein are methods of removing carbon dioxide from an aqueous stream or gaseous stream by: contacting the gaseous stream comprising carbon dioxide, when present, with an aqueous solution comprising ions capable of forming an insoluble carbonate salt; contacting the aqueous solution comprising carbon dioxide with an electroactive mesh that induces its alkalinization thereby forcing the precipitation of a carbonate solid from the solution and thereby the removal of dissolved inorganic carbon by electrolysis; and removing the precipitated carbonate solids from the solution, or the surface of the mesh where they may deposit. Also provided herein are flow-through electrolytic reactors comprising an intake device in fluid connection with a rotating cylinder comprising an electroactive mesh, and a scraping device and/or liquid-spray based device for separating a solid from the mesh surface.