Showing papers on "Selective catalytic reduction published in 1988"

Method for removal of nitrogen oxides from exhaust gas of diesel engine

Abstract: A method for the removal of nitrogen oxides from the exhaust gas of a diesel engine through catalytic reduction by the use of honeycomb catalyst in the presence of ammonia, which method comprises feeding ammonia into said exhaust gas proportionately to the product of the revolution number of said diesel engine multiplied by the torque of said diesel engine.

Process for removal of nox from fluid streams

Abstract: There is provided a process and apparatus for carrying out the process, to remove nitrogen oxides from a gas stream. The process is characterized by passing the gas stream through a first catalytic zone in the absence of added ammonia and in the presence of an oxidation catalyst to convert the NO content thereof to NO 2 , thereafter introducing ammonia into the gas stream, and catalytically reducing the NO 2 to nitrogen and water in the presence of a catalyst. Higher conversion to innocuous materials is obtained.

High Temperature Solid Lubrication by Catalytically Generated Carbon

Abstract: The wear process in bearings generates a clean active surface. Carbon is known to form readily on catalytic surfaces through the reduction of carbon oxides or hydrocarbon. Carbon, through the adsorption of hydrocarbons, water vapor, or oxygen, becomes an effective lubricant. If these three phenomena can be made to work together, a new concept of high temperature lubrication would be available. This paper presents laboratory investigations towards the development of this concept. Carbon has been successfully produced through catalytic reduction of ethylene on a variety of metallic and ceramic surfaces containing nickel. This carbon has been shown to reduce friction at a sliding interface at elevated temperatures.

UNSTEADY-STATE PERFORMANCE OF NO x CATALYTIC REDUCTION BY NH 3

Abstract: Experimental results of studying NOx catalytic reduction by NH3 under periodic reversals in the direction of filtration of the mixture purified in a catalyst bed are discussed.

Process for eliminating nitrogen oxide from exhaust gases

Abstract: Nitrogen oxides are eliminated from exhaust gases by selective catalytic reduction by means of reaction with ammonia. The catalysts used are iron silicate zeolites. Iron silicate zeolites of the pentasil type are particularly active catalysts.

Method for the removal of nitrogen oxides from the exhaust gas of a diesel engine

Abstract: A method for the removal of nitrogen oxides from the exhaust gas of a diesel engine (1) through catalytic reduction by the use of honeycomb catalyst (10) in the presence of ammonia (11), which method comprises feeding ammonia into the exhaust gas in amount which is proportional to the product of the engine revolution level multiplied by the torque of the diesel engine. Sensors (3,4) detect the engine revolutions and the torque and feed signals to an arithmetic unit (5) which in turn controls an ammonia flow control valve (6).

Catalyst for removing nitrogen oxides

Abstract: A catalyst for removing nitrogen oxides contained in exhaust gases, particularly those containing vapor-form catalyst poisons, by catalytic reduction with ammonia, while retaining a high denitration performance for a long time, which catalyst comprises titanium oxide as a first component, molybdenum oxide and/or tungsten oxide as a second component and vanadium oxide and/or sulfate as a third component, the atomic ratio of the respective elements being Ti:Mo and/or W:V=80-96.6:3-15:0.5-5, and the size of the crystallite of the titanium oxide according to Sherrer's equation being in the range of 185 Å to 300 Å in the direction of a plane (101) (interplanar spacing: d=3.52 Å).

Method of removing nitrogen oxides from a flue gas stream

Abstract: In the selective reduction of nitrogen oxides of flue gases with ammonia, the ammonia is added as ammonia water upstream of the reduction zone. Residual gas phase ammonia and ammonia compounds collected with the flyash serve as recycled ammonia sources and ammonia is formed from them and, in an ammoniacal solution, is added to the ammonia water supply vessel.

Process for separating off nitrogen oxides from exhaust gases by selective catalytic reduction

Abstract: For demand-dependent NH3 metering for the selective catalytic reduction, a precisely preset exhaust gas sample volume is taken off from the exhaust gas leaving the reactor (3) and completely condensed in a condenser (9). The pH of the condensate is measured and the volumetric flow rate of the NH3 fed to the reactor is controlled in dependence on the pH measured in such a way that the NH3 slip is below the odour threshold.

Apparatus for catalytically reducing noxious substances in flue gas

Abstract: Apparatus for catalytically reducing noxious substances in flue gas employes, in a first embodiment wherein combustion air is also pre-heated, a two-part heat-exchanger which is traversed from top to bottom by a plurality of catalytically active, separately movable heat-storage elements. Combustion gas is heated in a first portion of the heat-exchanger by heat transferred from the heat-storage elements and the noxious gases are catalytically reduced in a second portion of the heat-exchanger downstream from the first portion in the presence of ammonia and the heat-storage elements. The heat-storage elements can be removed from circulation and replaced by unspent or regenerated elements when the residual content of noxious substances in the flue gas remains elevated. In a second embodiment, flue gas cooled downstream of a desulfurization system is conducted through the bottom section of the heat exchanger where it is preheated by the heat storage elements and is then heated to a predetermined reaction temperature by an external heating means. Ammonia is added and the flue gas is conducted at least once through at least one middle section for the catalytic reduction. Then, the flue gas is conducted through the top section so as to cool it to a predetermined chimney entrance temperature. The apparatus prevents decreases in catalytic activity and prevents adverse affects on catalyst efficiency due to leakages from a gas preheater for the flue gas. The heat exchanger can be used advantageously downstream of a desulfurization system.

Catalyst for denitration by catalytic reduction using ammonia and a process for producing the same

Abstract: A catalyst for denitration by catalytic reduction using ammonia capable of preventing catalyst deterioation due to vapors of heavy metal compounds contained in exhaust gases and having a high strength and a superior resistance to poisons and a process for producing the catalyst are provided, which catalyst comprises TiO2, oxide(s) of at least one of V, Cu, Fe and Mn and oxide(s) of at least one of Mo, W and Sn, the total of the mol number(s) of the oxide(s) of at least one of Mo, W and Sn falling within a range of 2×10-6 to 20×10-6 mol/m2 per the unit specific surface of the catalyst, and which process comprises having oxide(s) of at least one of Mo, W and Sn absorbed and supported onto a composition comprising TiO2 prepared in advance and oxide(s) of at least one of V, Fe, Cu and Mn so as to give the above-specified total of the mol number(s) of oxide(s) of at least one of Mo, W and Sn.

The Hammett Relationship in the Reduction of Aldehydes with 2-Propanol by Catalysis with Hydrous Zirconium Oxide

Abstract: A linear correlation of the Hammett relationship was obtained for a catalytic reduction of substituted benzaldehydes with 2-propanol with hydrous zirconium oxide. The reaction constant ρ was 1.35, indicating that the electronic effect on the reaction is larger than that on the standard one.

Process for removal of nitrogen oxides from a flue gas stream

Abstract: In most of the flue gas denitrification processes actually used in practice, ammonia is mixed into the flue gas stream. If excess ammonia is fed in to obtain a high degree of denitrification, the denitrified flue gas stream still contains residual gaseous ammonia. In addition, the entrained fly dust in most cases contains solid ammonium compounds which have been formed by reaction of the ammonia with acidic flue gas constituents. … As is known per se, the gaseous ammonia is scrubbed out of the flue gas and recovered. Ammonia is likewise recovered from the fly ash by thermal treatment or extraction. The recovered ammonia is fed in aqueous solution into a stock of aqueous ammonia. The ammonia used for denitrification is taken from this device and mixed as an aqueous solution into the flue gas stream.

Process for the catalytic reduction of nitrogen oxide

Abstract: not available for EP0325811Abstract of corresponding document: US4950139A process is disclosed wherein NO contained in a gas is reduced by means of NH3 as a reducing agent. A mixture of the NO-containing gas and NH3 is reacted at 290 DEG to 450 DEG C. in the presence of a catalyst, which comprises a support of SiO2 and contains 5 to 15% by weight manganese sulfate and iron sulfate. The mole ratio of manganese sulfate and iron sulfate, which is calculated as FeSO4, is between 1:10 and 10:1. The support has a pore volume of 0.6 to 1.6 ml/g and an average pore diameter of 10 to 100 nm.

Process for cleaning the off-gas from incineration plants, and device for carrying out the process

Abstract: To deNOx the off-gases from thermal power plants, the process of selective catalytic reduction of the nitrogen oxides using ammonia (NH3) is used. This needs a process temperature of 320 to 400 degree C. The off-gases from the incineration plant FA are fed via an economizer ECO for feed water preheating to the heat-dissipating part of a heat exchanger WT. This is followed by the dedusting and desulphurization of the off-gases using a dedusting filter EF and a desulphurization installation REA. Then, the off-gases, which have been cooled to below 100 degree C, are heated in the heat-adsorbing part of the heat exchanger WT to the temperature which is required for the selective catalytic reduction of the nitrogen oxides and are fed to a deNOxing installation SCR. The use of the heat exchanger WT avoids the use of an additional gas burner for reheating the off-gases. The heat of the off- gas downstream of the incineration plant FA is utilized indirectly, since deNOxing of the off-gas before the desulphurization leads to the formation of ammonium hydrogen sulphate, which greatly contaminates the subsequent parts of the off-gas cleaning installation.

Temperature control method in catalytic reduction

Abstract: PURPOSE:To promote the simplification of an equipment, by providing a reaction heat exchanger tube, which contains a heat absorbing reaction catalyst to be built, in the downstream of a gas turbine and heating the catalyst by exhaust of the gas turbine CONSTITUTION:A fuel processing system, comprising a combustor 12, reactor 11 with a built-in catalyst, air heater 10 and an evaporator 9, is provided in the downstream of a gas turbine 2 A waste heat boiler system 3 is provided branching from the fuel processing system The fuel processing system provides in its inlet part and outlet part respectively dampers 8b, 8c, and their opening is determined so that circulating gas obtains a temperature of catalytic reduction In this way, since exhaust of the gas turbine serves for a heating source of the reactor, an equipment can be simplified with no necessity for separately providing a heating equipment

A catalyst for removing nitrogen oxides.

Abstract: A catalyst for removing nitrogen oxides contained in exhaust gases, particularly those containing vapor-form catalyst poisons, by catalytic reduction with ammonia, while retaining a high denitration performance for a long time, which catalyst comprises titanium oxide as a first component, molybdenum oxide and/or tungsten oxide as a second component and vanadium oxide and/or sulfate as a third component, the atomic ratio of the respective elements being Ti:Mo and/or W:V = 80-96.5:3-15:0.5-5, and the size of the crystallite of the titanium oxide according to Sherrer's equation being in the range of 185 ANGSTROM to 300 ANGSTROM in the direction of a plane (101) (interplanar spacing: d = 3.52 ANGSTROM ).

Catalytic reduction of nitric oxide by carbon monoxide in the presence of platinum(II), copper(I), and copper(II)

Abstract: Rapid reductions of NO to N2O by CO can be achieved at ambient temperature in aqueous solution containing K2PtCl4, CuCl, CuCl2, HCl, and LiCl: the average rates for the N2O and CO2 evolution are 30.5 and 38.1 turnovers per hour over the first 10 hours.

Design of monolith catalysts for power plant NO/sub chi/ emission control

Abstract: A mathematical model is developed to describe the performance of a monolith-type catalyst employed in the selective catalytic reduction of nitrogen oxide emissions from fossil-fueled power plants. The model is then employed for the design of a new catalyst by optimizing its pore structure. The predicted 50% improvement in point activity is verified in experiments.

Process for eliminating nitrogen oxides from exhaust gases emanating from coal combustion.

Abstract: of EP0272620For the removal of nitrogen oxides by selective catalytic reduction with ammonia, catalysts are used which essentially contain titanium oxide and catalytically active quantities of oxides of vanadium, tungsten and/or molybdenum. The catalysts have a BET surface area from 5 to 60 m /g and a pore volume of 0.15 - 0.40 ml/g and contain at most 35 % of pores of diameters < 200 A.

Preparation and Performance of a Silica-Supported V205 on Ti02 Catalyst for the Selective Reduction of NO with NH3

Abstract: Received April 22, 1987; revised July 20, 1988 A preparation technique is described in which a layer of TiOz completely covering the support can be deposited onto silica. Onto the support thus modified, V,05 can be applied to result in a catalyst suitable for the selective catalytic reduction (SCR) of NO, with NH3. To ohtain the required selectivity in the reduction of NO, the silica surface must be completely covered with TiOz. Catalysts prepared according to the above procedure exhibit good activity and a completely selective reduction of NO to Nz at temperatures to 350°C. At higher temperatures selective oxida- tion of the NH3 to Nz is observed. 0