Abstract: A process for producing ammonium nitrate is disclosed, which process comprises exposing a gaseous oxidizer feed composed at least substantially of ammonia, steam and an oxidizing gas to conditions whereby the ammonia is oxidized to produce a reaction mixture including nitrogen monoxide and water vapor. The reaction mixture is cooled in a heat exchanger whereby the nitrogen monoxide is oxidized, the water vapor is condensed and the products of the nitrogen monoxide oxidation react with and are absorbed by the condensed water to form a nitric acid stream, with substantially all of the nitrogen monoxide in the reaction mixture being converted to nitric acid. The nitric acid stream is reacted with a stream of ammonia to form the ammonium nitrate.

Abstract: A process for producing ammonium nitrate is disclosed, which process comprises exposing a gaseous oxidiser feed composed at least substantially of ammonia, steam and an oxidising gas to conditions whereby the ammonia is oxidised to produce a reaction mixture including nitrogen monoxide and water vapour. The reaction mixture is cooled in a heat exchanger whereby the nitrogen monoxide is oxidised, the water vapour is condensed and the products of the nitrogen monoxide oxidation react with and are absorbed by the condensed water to form a nitric acid stream, with substantially all of the nitrogen monoxide in the reaction mixture being converted to nitric acid. The nitric acid stream is reacted with a stream of ammonia to form the ammonium nitrate.

Abstract: An embodiment of a method for recovering nitric acid from acid pickling solution includes introducing a treating material comprising at least one chemical into a pickling solution comprising free nitric acid. The treating material reacts with at least a portion of the free nitric acid in the pickling solution and produces NOx. A gas stream comprising at least a portion of the NOx is contacted with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is contacted with water, thereby forming nitric acid, and at least a portion of the nitric acid is collected.

Abstract: Methods and systems for treating a gas stream comprising NOx are disclosed. In one embodiment of the method, the gas stream comprising NOx is reacted with ozone to form oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is reacted with water to form nitric acid, and a solubilized form of the nitric acid is collected and may be reused or otherwise utilized. Systems for conducting the method also are disclosed.

Abstract: A process for producing ammonium nitrate is disclosed and in which: a) a gaseous oxidizer feed composed at least substantially of ammonia, steam and an oxidizing gas is exposed to conditions whereby the ammonia is oxidized to produce a reaction mixture including nitrogen monoxide and water vapor, b) the reaction mixture is cooled in a heat exchanger whereby the nitrogen monoxide is oxidized, the water vapor is condensed and the products of the nitrogen monoxide oxidation react with and are absorbed by the condensed water to form a nitric acid stream, with substantially all of the nitrogen monoxide in the reaction mixture being converted to nitric acid, and c) the nitric acid stream is reacted with a stream of ammonia in an ammonium nitrate producing stage to form the ammonium nitrate.

Abstract: The present invention relates to the use of a zeolite catalyst comprising at least one transition metal and in addition sulfur and/or phosphorus atoms for reducing the content of nitrogen oxides in a gas, and also to a process for reducing the content of nitrogen oxides in a gas by bringing this gas into contact with such a zeolite catalyst.

Abstract: A method for decomposing N2O is described. The method uses, as a catalyst, an oxide based on cerium and lanthanum, which further includes at least one oxide of an element chosen from zirconium and rare earths other than cerium and lanthanum. This catalyst is stable, enabling it to be used at high temperatures.

Abstract: Sulfur dioxide (SO2) may be removed from carbon dioxide feed gas by contacting the carbon dioxide at an elevated temperature and an elevated pressure with a catalyst for oxidizing SO2, in the presence of oxygen (O2) to convert SO2 to sulfur trioxide (SO3); contacting SO3 in the resultant SO3-enriched carbon dioxide gas with water to produce sulfuric acid and SO2-depleted carbon dioxide gas; and separating the sulfuric acid from the SO2-depleted carbon dioxide gas. If present, NOx is also removed from the carbon dioxide feed gas as nitric acid to produce SO2-depleted, NOx-lean carbon dioxide gas. The method has particular application in the removal of SO2 and NOx from flue gas produced by oxyfuel combustion of a hydrocarbon fuel or carbonaceous fuel, within or downstream of the CO2 compression train of a CO2 recovery and purification system.

Abstract: Methods and systems for treating a gas stream comprising NOx are disclosed. In one embodiment of the method, the gas stream comprising NOx is reacted with ozone to form oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is reacted with water to form nitric acid, and a solubilized form of the nitric acid is collected and may be reused or otherwise utilized. Systems for conducting the method also are disclosed.

Abstract: An embodiment of a method for recovering nitric acid from acid pickling solution includes introducing a treating material comprising at least one chemical into a pickling solution comprising free nitric acid. The treating material reacts with at least a portion of the free nitric acid in the pickling solution and produces NOx. A gas stream comprising at least a portion of the NOx is contacted with ozone, thereby forming oxidation products including nitrogen sesquioxide and nitrogen pentoxide. At least a portion of the nitrogen sesquioxide and nitrogen pentoxide is contacted with water, thereby forming nitric acid, and at least a portion of the nitric acid is collected.

Abstract: By a method and a device for preventing corrosion on and in the region of a gas inlet nozzle during nitric acid condensation, contact of the condensing gas with the nozzle and with the surroundings of the nozzle are supposed to be minimized. This is achieved in that the gas inlet nozzle has a sleeve on the inside in the transition region to the interior of the condenser, by which sleeve a gas inlet orifice in the form of an annular gap is formed, whereby the annular space is provided with at least one feed opening for secondary air, so that an enveloping flow of secondary air is produced around the entering NO gas.

Abstract: Sulfur dioxide (SO2) is removed from carbon dioxide feed gas comprising SO2 as a contaminant by maintaining the carbon dioxide feed gas at an elevated pressure in contact with an alkaline sorbent for a period of time sufficient to react said alkaline sorbent with SO2. Where NOx, oxygen (O2) and water are also present, not only is the rate of reaction with the sorbent increased, but also additional SO2 is removed by conversion to sulfuric acid, and NOx is removed as nitric acid. The method has particular application in the removal of SO2 and NOx from flue gas produced by oxyfuel combustion of a hydrocarbon or carbonaceous fuel.

Abstract: Carbon dioxide is purified by processes employing NOx-rich sulfuric acid that can be formed by removal of SO2 from the carbon dioxide.

Abstract: Carbon dioxide is purified by processes employing NOx-rich sulfuric acid that can be formed by removal of SO2 from the carbon dioxide.

Abstract: Carbon dioxide is purified by processes employing NOx-rich sulfuric acid that can be formed by removal of SO2 from the carbon dioxide.

Abstract: Compounds are provided comprising at least one neutral, positive, or negative hydrogen species having a binding energy greater than its corresponding ordinary hydrogen species, or greater than any hydrogen species for which the corresponding ordinary hydrogen species is unstable or is not observed. Compounds comprise at least one increased binding energy hydrogen species and at least one other atom, molecule, or ion other than an increased binding energy hydrogen species. One group of such compounds contains one or more increased binding energy hydrogen species selected from the group consisting of Hn, Hn?, and Hn+ where n is an integer from one to three.

Abstract: It is an high efficiency and low cost apparatus for simultaneous dry desulfurization and denitration (10), capable of simultaneous oxidation of nitrogen monoxide and sulfur dioxide by chain reaction with OH radical, provided with an OH radical supplying unit (12), a reactor (14), a sulfuric acid recovering unit (16), and a nitric acid recovering unit (18). Exhaust gas at 600-800° C. containing sulfur compounds from a boiler (2) is introduced into the reactor (14), nitric acid is spray-supplied from an OH radical supplying unit (12) into the reactor (14), sulfur dioxide and nitrogen monoxide are simultaneously oxidized with OH radicals generated from pyrolysis of nitric acid as an initiator to form sulfur trioxide and nitrogen dioxide, thereby exhaust gas is treated.

Abstract: Process for removing sulfur oxides, mercury vapor, and fine particulate matters from industrial flue gases that contain such pollutants. Pollutants are removed by modules, which contain microporous adsorbent (i.e., sorbent) material held within a polymer matrix. The composite material that contains the microporous absorbent material held within a polymer matrix removes sulfur oxides by converting them into high concentration sulfuric acids. SULFURIC acid produced inside the composite material is automatically expelled onto the external surfaces of the composite material and is drained into an acid reservoir together with the fine particulate mailers which are washed from the external surfaces of the composite material by the constant dripping of the sulfuric acid along the external surfaces of the composite material.

Abstract: SO2 and/or NOx are removed from gaseous CO2 at elevated pressure(s) in the presence of molecular oxygen and water and, when SO2 is to be removed, NOx, to convert SO2 to sulfuric acid and/or NOx to nitric acid. The sulfuric acid and/or nitric acid is/are then removed from the gaseous carbon dioxide to produce SO2-free, NOx-lean carbon dioxide gas. The invention has particular application in the removal of SO2 and/or NOx from carbon dioxide flue gas produced in an oxyfuel combustion process, for example, in a pulverized coal fired power station.

Abstract: Methods and apparatus utilizing hydrogen peroxide are useful to reduce NOx, SOx and mercury (or other heavy metal) emissions from combustion flue gas streams. Continuous concentration of hydrogen peroxide to levels approaching or exceeding propellant-grade hydrogen peroxide facilitates increased system efficiency. In this manner, combustion flue gas streams can be treated for the removal of NOx, SOx and heavy metals, while isolating useful by-products streams of sulfuric acid and nitric acid as well as solids for the recovery of the heavy metals.

Abstract: N2O is removed in nitric acid manufacture by using catalysts comprising three-dimensional structures coated with catalytically active materials.

Abstract: Stirred acid resistant shallow cylindrical reactors are used to produce both nitric and sulfuric acid from a feed gas stream arranged to contain both sulfur dioxide and nitrogen oxides passed over or through the mixed acids. The homogeneous catalytic mixture of sulfuric and nitric acids uses the highly oxidizing nitrosyl ion to further oxidize the gaseous oxide stream to sulfuric and nitric acids. Oxygen or air then oxidizes the nitrosyl ion reduction products back to nitrosyl ion for further reaction. The acids are separated by distillation, and concentrated using heat from the burner and the reaction heat. The modified sulfur burner used operates at temperatures to oxidize some of the nitrogen in the air. The temperature required may be obtained by increasing the oxygen of the air by pure oxygen. More nitrogen oxides may be produced by a glow discharge into the burner air or burning of ammonia. Any heavy metals such as mercury will be first oxidized then precipitated as sulfates.

Abstract: A process for producing nitric acid of a concentration in the range of 68 to 76% by weight, using the mono-pressure or the dual-pressure process in which the ammonia feedstock is combusted with the aid of compressed process air. The water vapour content of the process air used for combustion and/or stripping and imported from outside the system, is reduced in this process.

Abstract: A method process to convert inhibited red fuming nitric acid (IRFNA) and/or nitrogen tetraoxide to either dilute or concentrated (98%+) nitric acid. The method describes a process to remove all of the normal inhibitors (if required), that have been reported to been used in IRFNA. The process described will provide nitric acid free of contaminates which are undesirable when using the nitric acid in reactions to produce other products.

Abstract: A method for removing NOX from gas streams emanating from stationary combustion sources and manufacturing plants utilizes the injection of hydrogen peroxide into the gas stream for rapid gas-phase oxidation of NO to NO2 and water-soluble nitrogen acids HNO2 and HNO3. The nitrogen acids may be removed from the oxidized gas stream by wet scrubbing or by contact with a particulate alkaline material to form a nitrite/nitrate salt.

Abstract: The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of: a) directing a vapor stream containing at least one nitrogen-containing oxidizing agent to a first contact zone, b) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen-containing oxidizing agent, c) directing said acid(s) as a second stream to a second contact zone, d) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.

Abstract: System for removal of targeted pollutants, such as oxides of sulfur, oxides of nitrogen, mercury compounds and ash, from combustion and other industrial process gases and processes utilizing the system. Oxides of manganese are utilized as the primary sorbent in the system for removal or capture of pollutants. The oxides of manganese are introduced from feeders into reaction zones of the system where they are contacted with a gas from which pollutants are to be removed. With respect to pollutant removal, the sorbent may interact with a pollutant as a catalyst, reactant, adsorbent or absorbent. Removal may occur in single-stage, dual-stage, or multi-stage systems with a variety of different configurations and reaction zones, e.g., bag house, cyclones, fluidized beds, and the like. Process parameters, particularly system differential pressure, are controlled by electronic controls to maintain minimal system differential pressure, and to monitor and adjust pollutant removal efficiencies.

Abstract: A method process to convert inhibited red fuming nitric acid (IRFNA) and/or nitrogen tetraoxide to either dilute or concentrated (98%+) nitric acid. The method describes a process to remove all of the normal inhibitors (if required), that have been reported to been used in IRFNA. The process described will provide nitric acid free of contaminates which are undesirable when using the nitric acid in reactions to produce other products.

Abstract: Oxygen is removed from natural gas by contacting oxygen-containing natural gas with nitric oxide under conditions sufficient to produce nitrogen dioxide.

Abstract: A method is provided for performing catalytic or non-catalytic processes which uses oxygen supplied from the permeate side of a mixed oxygen ion and electron conducting membrane by means of a sweep gas at an elevated temperature. The sweep gas is formed by burning fuel in a sweep gas preheater. The sweep gas containing oxygen picked up from the membrane is reacted with a hydrocarbon fuel in a catalytic reactor to form a syngas containing nitrogen and hydrogen. The nitrogen and hydrogen containing syngas is worked up into ammonia; the ammonia is burned in an ammonia burner to produce a nitrogen oxides containing gas, and the nitrogen oxides containing gas is used in the production of nitric acid. The process is able to directly transfer the oxygen containing sweep gas to the catalytic reactor, without any intermediate cooling; recompression and reheating.

Abstract: Methods for concentrating nitric acid in aqueous solution are known wherein reduction of some nitric acid initially present in the solution oxidizes nitric oxide obtained for example from exhaust vapors of heterogneously catalytically combusted ammonia, but gas effluence and solution dilution associated with such methods have necessitated recirculation piping to convey fluids of varying content to and fro between separated reactor units adapted to conduct different sub-reactions subsumed under an overall process which is inherently unworkable in batch mode operations. Herein the invention features joint execution of all necessary reactions in a single reactive solution body, and resorts to a liquid phase homogeneous catalysis involving nitrate and/or nitrosyl ions, in a process which is effective whether in continuous or batch processing.

Abstract: An improved process for either the manufacturing of nitric acid, recycling of nitric acid, or recovering of nitric acid, comprising the steps of: providing a source of NOx; reacting NO from the source of NOx with HNO3 in the presence of NO2− to produce a resulting product; and reacting the resulting product with O2 and H2O to produce nitric acid.

Abstract: A process for the production of nitric acid using the dual-pressure process in which the ammonia is burnt at an initial low pressure with the aid of compressed process air and the nitrous gases formed during combustion are at least partly absorbed by water at a second pressure which is higher than the first. This causes nitric acid to be produced and the pressure of the residual gas, which is not absorbed, is reduced to atmospheric pressure in a residual gas expander for the purpose of winning compression potential. Said process provides a solution aimed at optimising the production of nitric acid whilst improving the production parameters and the materials and energy balances. This is achieved by supplying a multishaft geared centrifugal compressor separately with process air and nitrous gas, the process air being compressed to the initial pressure and the nitrous gas being compressed to a second pressure.

Abstract: A method for recovering nitrate ions as nitric acid from nuclear industry effluents by thermally decomposing the nitrate ions in solution, and recovering the NOx vapors generated by the heat treatment in an aqueous medium. The resulting nitric acid may be recycled in the nuclear industry.

Abstract: Nitric oxide is removed from a gas stream by contacting the gas stream with oxygen in the presence of a metal-cation exchanged zeolite, thereby oxidizing the nitric oxide to nitrogen dioxide, then contacting the resulting nitrogen dioxide-containing gas stream with ozone, thereby converting the nitrogen dioxide to nitric acid, nitric acid precursors or mixtures thereof, then contacting the gas stream with an aqueous liquid, thereby scrubbing the nitric acid, nitric acid precursors or mixtures thereof from the gas stream. Contact of the gas stream with oxygen in the presence of a zeolite is carried out at a temperature above the temperature at which significant adsorption of nitrogen dioxide occurs, and the aqueous liquid used as scrubbing agent preferably has a pH greater than 7.

Abstract: Nitrogen oxides are removed from a waste gas stream by contacting the waste gas stream with ammonia, thereby reducing the nitrogen oxides to nitrogen. Residual nitrogen oxides and unreacted ammonia in the waste gas stream leaving the nitrogen oxides reducing step are oxidized to nitrogen pentoxide or nitric acid by contacting this gas stream with ozone. Contact of the ozone and waste gas is preferably carried out in the presence of an aqueous solution at a pH above about 9 and at a temperature above about 75° C., and this step is preferably carried out in the presence of an ammonia-oxidizing catalyst.

Abstract: A process is described for producing nitric acid involving oxidizing ammonia gas to form dinitrogen tetroxide gas, reacting the dinitrogen tetroxide with water in an absorption zone to form aqueous nitric acid and nitric oxide gas, removing a nitric acid/nitric oxide stream from the absorption zone and feeding the stream into a nitric acid bleaching zone, removing impurities from the nitric acid in the bleaching zone to form nitric acid product and adding supplemental oxygen gas to one or more of the reaction streams to increase nitric acid production and or strength. The improvement involves injecting the supplemental oxygen into a nitric acid-containing process stream to form a gas bubble/liquid mixture in the stream, the mixture forming a fine dispersion of gas bubbles having diameters of less than about 0.1 mm.

Abstract: An exhaust gas stream containing oxides of nitrogen and sulfur from a fossil fuel fired boiler, a fired process heater, or a chemical process are diverted from a stack prior to emission to the atmosphere through a duct system to a mixer where an oxidant, such as ozone, is added to the exhaust gas at a preselected molar ratio for a preselected residence time to transform the oxides to higher order nitrogen oxides. The oxidized contaminants are treated with a reagent solution. The reagent solution absorbs the oxidized contaminants and unreacted oxidant in the exhaust gas stream. Nitrogen and sulfur oxides in the gas steam are transformed to dilute acids which are neutralized to form salts suitable for discharge to a municipal waste water treatment plant or landfill disposal. The salt solution is also useful as a fertilizer or in the manufacture of fertilizers. The treated exhaust gas is then emitted from an exhaust stack containing NO.sub.x and SO.sub.

Abstract: A process for reducing particulate, Hg, NOx, and SO.sub.2 emissions from the combustion of fossil fuel while providing the capability of producing an end product that is commercially useful comprising the steps of oxidizing Hg, NOx and SO.sub.2 using a barrier discharge reactor to produce the HgO and acids HNO.sub.3 and H.sub.2 SO.sub.4, collecting the HgO, acids and particulates in a wet ESP, and then draining them from the wet ESP to remove them from the flue gas stream.

Abstract: The invention relates to a process for removing nitrogen oxides from a gas stream containing same, which comprises passing the gas stream(A) through a stage for absorbing the nitrogen oxides other than N.sub.2 O in an absorbent or reacting the nitrogen oxides other than N.sub.2 O with an absorbent at a pressure of from 1,5 to 20 bar, and(B) through a stage for reducing the amount of N.sub.2 O, preferably employing the pressure level of step A, and to apparatus therefor and the use thereof.

Abstract: The present invention describes a process for converting vapor streams from sources containing at least one nitrogen-containing oxidizing agent therein to a liquid fertilizer composition comprising the steps of:a) directing a vapor stream containing at least one nitrogen-containing oxidizing agent to a first contact zone,b) contacting said vapor stream with water to form nitrogen oxide(s) from said at least one nitrogen-containing oxidizing agent,c) directing said acid(s) as a second stream to a second contact zone,d) exposing said second stream to hydrogen peroxide which is present within said second contact zone in a relative amount of at least 0.

Abstract: Provided is a process having an increased production capacity for nitric acid, which moves can be operated safely and efficiently. The process comprises forming a reaction mixtures by mixing air, ammonia, oxygen and an inert cooling fluid, preferably water, and then reacting the ammonia with oxygen in a reaction zone to form nitric oxide. The amount of inert cooling fluid in the reaction mixture is sufficient to control the temperature of the mixture and maintain the ammonia percentage below the lower explosion limit for the mixture. The nitric oxide produced in the reaction zone is then oxidized to nitrogen dioxide and its dimer, with additional oxygen being introduced into the process for oxidizing the nitric oxide. The nitrogen dioxide and its dimer is then reacted with water to form the nitric acid.

Abstract: A catalyzer is provided for promoting chemical reactions, such as the reaction between ammonia and air to produce nitrogen monoxide which, in turn, can be used to manufacture nitric acid or the purification of flue gas from incineration plants. The catalyzer is made by forming a mixture of a combustible pore forming substance, such as a polymer, vegetable material or graphite, and a ceramic material, such as alumina, zirconia, titanium dioxide, silica, tungsten carbides, silicon nitrides and mixtures thereof, and thermally spraying this mixture onto a support net to result in a net having porous ceramic deposited thereon.

Abstract: A process and apparatus for reducing particulate, nitrogen oxides ("NOx"), sulfur dioxide ("SO.sub.2 "), and mercury ("Hg") emissions from the combustion exhaust of fossil fuel fired plants while producing an end product that is commercially useful, comprising the steps of oxidizing Hg, NOx and SO.sub.2 using a barrier, pulse, corona, or electron beam electrical discharge apparatus to produce HgO and the acids HNO.sub.3 and H.sub.2 SO.sub.4, collecting the HgO, acids and particulates in a wet ESP, and separating the particulates from the collected acid mixture, then separating and concentrated the acids for industrial use.

Abstract: A process is described for the removal of nitrogen oxides from waste gases with the recovery of nitric acid or a nitrate solution. The waste gas is reacted with hydrogen peroxide in an amount appropriate to the desired degree of removal of nitrogen oxides, on a catalyst, at a temperature of less than 800.degree. C., preferably in the range of 20.degree. to 100.degree. C., to give the valuable product, nitric acid or a nitrate solution. This may be done in accordance with the invention by bringing the hydrogen peroxide as a solution, i.e., in the liquid phase, into contact with the catalyst through which the waste gas is flowing. The reaction product is either utilized in a gaseous form or processed to nitric acid or a nitrate solution. Alternatively, the hydrogen peroxide may be introduced in a gaseous form, using a honeycombed catalyst, and wherein the hydrogen peroxide is present in at least one half of the stoichiometrically determined amount.

Abstract: The present invention relates to processes and apparatus for mixing oxidizable reactants with oxidant and/or oxidizing oxidizable reactants. Through using particular mixing and/or oxidizing arrangements, the risk of flammable or explosive reactions can be significantly reduced or prevented. When ammonia is used as the reactant, nitric acid can be obtained.

Abstract: Exhaust gases containing oxides of nitrogen and sulfur from a fired process heater, a fossil fuel fired boiler, or a chemical process are diverted from a stack prior to admission to the atmosphere through a duct system containing heat exchangers that reduce the exhaust gas from an elevated temperature, if any, to about ambient temperature. Any heat extracted from the exhaust gas may be transferred to the boiler feed water which would serve to reduce the energy cost of operating a boiler. Once the exhaust gas is cooled to about ambient temperature, the gas is then mixed with an oxidant, such as ozone, at a preselected molar ratio to transform the oxides to higher orders of nitrogen and sulfur oxides to increase the absorbability of the nitrogen and sulfur oxides in a reagent solution. The reagent absorbs the oxidized contaminants from the exhaust gas. The oxides are transformed to dilute acids which are then neutralized to form salts that are acceptable for discharge to a municipal waste water treatment plant.

Abstract: A method of maintaining a given content of a substance A in an aqueous solution where it is continuously consumed and where the redox potential E, at least within the range of concentration used, approximately satisfies the equation:E=G+F(x)wherein x is the content of A, F is a function of x whose derivative dF/dx approaches zero when x assumes a high value, and G on the whole is independent of x but is influenced by other parameters, such as pH, temperature or the like. The addition of A is controlled in such manner that a set value of the redox potential is maintained. The set value is determined by increasing or decreasing the addition of A in a predetermined manner, whereupon the redox potential is measured, and the measured value is used for determining the set value.

Abstract: During the pickling, etching, chemical shaping etc. of steels, stainless steels, special alloys and special metals and the dissolution of those metals, metalliferous solutions of the acids employed arise in the course of such processes which must either be disposed of by neutralization or be used for the recovery of the acids and metals by expensive processes. According to the invention the production or recovery of nitric acid or a mixture of nitric acid and hydrofluoric acid takes place by spray-roasting the solutions at temperatures of 200.degree. to 500.degree. in a reactor (1) and subsequent absorptions or condensation of the gases generated in column means (7, 8) at temperatures of 0.degree. to 70.degree. C.

Abstract: A method for the removal of nitrogen oxides from waste gases and for obtaining nitric acid is described. The waste gas is charged with the required amount of hydrogen peroxide, converted into the gas phase, and the gas mixture is reacted on a solid catalyst to hydrogen nitrate, which is either withdrawn for further use or is converted into nitric acid either by condensation or by scrubbing with water. The method permits the removal of NO.sub.x at low concentrations below 2000 ppm with efficiencies above 90%.