Process for reducing the content of NOx and N2O from an input tail gas (10) of a nitric acid process, said input tail gas having a temperature lower than 400 C., the process comprising an abatement stage at least including a deN2O stage and deNOx stage and providing a conditioned tail gas (12) having a temperature greater than the input tail gas (10), wherein, prior to submission to said abatement stage, said input tail gas (10) is pre-heated to a temperature of at least 400 C. by indirect heat exchange with at least a portion of said conditioned gas (12).

Oxygen is removed from a gas feed such as a landfill gas, a digester gas or an industrial CO.sub.2 off-gas by heating the feed gas, optionally removing siloxanes and silanols from the heated feed gas, optionally removing part of the sulfur-containing compounds in the heated feed gas, injecting one or more reactants for oxygen conversion into the heated feed gas, carrying out a selective catalytic conversion of any or all of the volatile organic compounds (VOCs) present in the gas, including sulfur-containing compounds, chlorine-containing compounds and any of the reactants injected, in at least one suitable reactor, and cleaning the resulting oxygen-depleted gas. The reactants to be injected comprise one or more of H.sub.2, CO, ammonia, urea, methanol, ethanol and dimethyl ether (DME).

A NO.sub.x and SO.sub.x oxidation with atmospheric oxygen to remove NO.sub.x and SO.sub.x from flue gases. The combined system for catalytic oxidation and wet-scrubbing of NO.sub.x and SO.sub.x from a flue gas and manufacturing fertilizers includes: an air separation unit for separating atmospheric oxygen from air and producing an air stream enriched with atmospheric oxygen, an adsorption and oxidation reactor containing an oxidation catalyst and carrying out the catalytic oxidation of NO.sub.x and SO.sub.x by said oxygen to yield nitric and sulphuric acids, a separator and reactor control unit for separation of products and liquids and controlling the reaction; and a vessel containing ammonia streaming said ammonia into the reactor or into the control unit to react with the nitric and sulphuric acids and to yield the fertilizers.

A built-in apparatus and method for treating air including a housing with an air inlet and an air outlet. An air mover positioned near the air outlet is configured to draw the air through the air inlet. The housing encloses an air treatment zone, such as including an oxidizing zone, and an ozone removal zone positioned downstream of the air treatment zone and oxidizing zone. The air treatment zone includes UV light and/or ozone that partially oxidizes the chemical contaminants in the air treatment zone. A catalyst in the oxidizing zone oxidizes elements within the air treatment zone. The ozone removal zone includes a second, different catalyst material. A UV bulb that may or may not generate ozone is positioned within or downstream of the first and/or second catalyst materials to assist catalyst oxidation and/or self-clean the apparatus.

A built-in apparatus and method for treating air including a housing with an air inlet and an air outlet. An air mover positioned near the air outlet is configured to draw the air through the air inlet. The housing encloses an air treatment zone, such as including an oxidizing zone, and an ozone removal zone positioned downstream of the air treatment zone and oxidizing zone. The air treatment zone includes UV light and/or ozone that partially oxidizes the chemical contaminants in the air treatment zone. A catalyst in the oxidizing zone oxidizes elements within the air treatment zone. The ozone removal zone includes a second, different catalyst material. A UV bulb that may or may not generate ozone is positioned within or downstream of the first and/or second catalyst materials to assist catalyst oxidation and/or self-clean the apparatus.

A system and method of pre-purification of a feed gas stream is provided that is particularly suitable for pre-purification of a feed air stream in cryogenic air separation unit. The disclosed pre-purification systems and methods are configured to remove substantially all of the hydrogen, carbon monoxide, water, and carbon dioxide impurities from a feed air stream and is particularly suitable for use in a high purity or ultra-high purity nitrogen plant. The pre-purification systems and methods preferably employ two or more separate layers of hopcalite catalyst with the successive layers of the hopcalite separated by a zeolite adsorbent layer that removes water and carbon dioxide produced in the hopcalite layers. Alternatively, the pre-purification systems and methods employ a hopcalite catalyst layer and a noble metal catalyst layer separated by a zeolite adsorbent layer that removes water and carbon dioxide produced in the hopcalite layer.

Method and system for the removal of nitrogen oxides, from flue gas at low temperatures.

An apparatus is provided for treatment of process gas formed during nitric acid production by catalytic oxidation of NH.sub.3. The apparatus includes a reactor, a first catalyst bed for N.sub.2O decomposition, an absorption tower to react the NO.sub.x formed with an absorption medium downstream of the first catalyst bed, a device for adding NH.sub.3 added to tailgas entering the second catalyst bed, and a second catalyst bed for NO.sub.x reduction and further decrease in N.sub.2O in the tailgas exiting the absorption tower. The second catalyst bed contains at least one iron-loaded zeolite catalyst. N.sub.2O removal in the first catalyst bed is limited such that the process gas exiting the first catalyst bed exhibits a N.sub.2O content of >100 ppmv and a molar N.sub.2O/NO.sub.x ratio of >0.25. Treated gas exiting the second catalyst bed has a NO.sub.x concentration of <40 ppmv and a N.sub.2O concentration of <200 ppmv.

A process for treating an H.sub.2S- and CO.sub.2-comprising fluid stream, in which a) the fluid stream is treated in a first absorber at a pressure of 10 to 150 bar with a first substream of a regenerated H.sub.2S-selective absorbent to obtain a treated fluid stream and an H.sub.2S-laden absorbent; b) the H.sub.2S-laden absorbent is heated by indirect heat exchange with regenerated H.sub.2S-selective absorbent; c) the heated H.sub.2S-laden absorbent is decompressed to a pressure of 1.2 to 10 bar in a low-pressure decompression vessel to obtain a first CO.sub.2-rich offgas and a partly regenerated absorbent; d) the partly regenerated absorbent is regenerated in a desorption column to obtain an H.sub.2S-rich offgas and regenerated absorbent; e) the H.sub.2S-rich offgas is fed to a Claus unit and the offgas from the Claus unit is fed to a hydrogenation unit to obtain hydrogenated Claus tail gas; f) the hydrogenated Claus tail gas and the first CO.sub.2-rich offgas are treated in a second absorber at a pressure of 1 to 4 bar with a second substream of the regenerated H.sub.2S-selective absorbent to obtain a second CO.sub.2-rich offgas and a second H.sub.2S-laden absorbent; and g) the second H.sub.2S-laden absorbent is guided into the first absorber. Also described is a plant suitable for performance of the process. The process is notable for a low energy requirement.

Disclosed herein are systems and methods for reducing the particulate matter content of an exhaust gas from a carbon black process.