A method is presented for estimating an amount of ammonia stored in a urea-based SCR catalyst based on a dynamic model of the catalyst. The model takes into account chemical and physical properties of the catalyst, such as catalyst volume, the number of available ammonia storage cites, adsorption and desorption dynamics, as well as poisoning, thermal aging, and different catalyst operating temperatures, and generates the estimate based on a measured or estimated amount of NOx in an exhaust gas mixture upstream of the catalyst, an amount of reductant injected into the catalyst to facilitate NOx reduction, and on a measured value of NOx in an exhaust gas mixture downstream of the catalyst. The estimated ammonia storage amount is then used to control the amount of reductant injected into the catalyst to maintain desired ammonia storage amount such that maximum NOx conversion efficiency coupled with minimum ammonia slip are achieved.

Exhaust gas aftertreatment systems

A safe, reliable SCR system for reducing NOx emissions from a lean-burn internal combustion engine utilizes urea in aqueous solution. A modular assembly is provided for mounting inside an urea reagent tank (30) which enables controlled feeding of an aqueous urea solution to an injector. The assembly includes a reagent quality sensor (152), a reagent temperature sensor (143), a reagent level sensor (154) and a pump (137).

Reducing NOx emissions from an engine by temperature-controlled urea injection for selective catalytic reduction

A method and system may be provided to perform a process for controlling NO x emissions of an target engine. In one embodiment of the invention, the process may include determining predicted NO x values based on a model reflecting a predetermined relationship between control parameters and NO x emissions, wherein the control parameters include ambient humidity, manifold pressure, manifold temperature, fuel rate, and engine speed associated with the engine. Further, the process may include adjusting the model based on a determination of whether the predicted NO x values meet a predetermined criteria associated with actual NO x values. The adjusted model may be stored in a memory associated with the engine whereby NO x emissions exhausted from the engine may be reduced based on virtual NO x emission values determined from the adjusted model.

NOx emission-control system using a virtual sensor

A method of selectively catalysing the reduction of NO x in an exhaust gas flowing in an exhaust system of an internal combustion engine comprising a filter ( 40 ) for particulate matter comprising a catalyst capable of selectively catalysing the reduction of NO x with a reducing agent, which method comprising introducing a reducing agent, or a precursor thereof, into the exhaust gas and contacting the resulting gas with the filter ( 40 ).

Selective catalytic reduction

An accurate thermodynamic model of an Active Lean NOx (ALNC) Catalyst is presented. The model takes into account hydrocarbon storage and release mechanisms of the ALNC, as well as the degradation in the ALNC hydrocarbon conversion efficiency due to ageing, and thus provides a more accurate estimate of an exotherm generated by hydrocarbon combustion in the ALNC. The estimated exotherm can them be used to detect system degradation and identify components responsible for the degradation.

Diesel aftertreatment systems

Urea is pyrolyzed in a chamber designed to facilitate gasification of the urea by pyrolysis with conversion of urea to ammonia and isocyanic acid (HNCO) with water vapor and carbon dioxide The product gases are introduced into exhaust gases from a lean-burn engine, preferably upstream of a turbocharger The exhaust gases are then contacted with an SCR catalyst

Urea pyrolysis chamber and process for reducing lean-burn engine NOx emissions by selective catalytic reduction

Urea or other solid NO x -reducing reagent is employed in a selective catalytic reduction process on emissions from diesel and lean-burn gasoline engines. The solid reagent is fed to a gas generator that produces a reactant gas by heating. In one embodiment the reactant gas is maintained at elevated temperatures to prevent condensation products from forming. The reactant gas contains ammonia and is fed to the exhaust on an as-needed basis.

Reducing NOx emissions from an engine by selective catalytic reduction utilizing solid reagents

Diesel and other lean-burn engines emit less NOx, when the of fuel comprises an emulsion of hydrocarbon fuel and an aqueous solution of a nitrogenous NOx -reducing reagent which is separated into its two principal portions prior to combustion. The hot exhaust gases produced by burning the fuel contain NOx, but the NOx is reduced by introducing the separated aqueous solution of nitrogenous NOx -reducing reagent into at least a portion of the exhaust gases and directing them to a catalyst for selective catalytic reduction of NOx. The fuel emulsion preferably comprises a continuous phase comprising diesel fuel and from about 1 to about 20% (most preferably, from about 2 to about 10%) of a discontinuous phase comprising an aqueous solution of nitrogenous NOx -reducing reagent. It is also preferred to include in the fuel a corrosion inhibitor and biocide, and optionally a lubricity additive and emulsifier.

System for fueling and feeding chemicals to internal combustion engines for NOx reduction

An injector for delivery of a fluid into a stream of hot gas is disclosed. The injector has a valve body with an elongated chamber in fluid communication with an orifice. A valve seat surrounds the orifice. A valve plunger is disposed within the chamber, an end of the plunger being adapted to sealingly interengage the seat. The plunger is slidably movable between an open and a closed position to open and close the orifice. A fluid inlet and outlet cool the valve by circulating fluid in an annular fluid passageway in the chamber adjacent to the valve seat. A portion of the fluid is expelled through the orifice when the valve is opened. The plunger is biased closed, being movable into the open position by an actuator. The injector is mounted on an exhaust conduit in fluid communication with the exhaust gases. A heat shield surrounding the orifice is interposed between the exhaust gases and the valve body. A radiant heat reflector is positioned between exposed parts of the injector and the exhaust conduit. An atomizing hook faces the orifice to control the dispersion characteristics of the expelled fluid.

Theodore J. Tarabulski

Papers

Reducing NOx emissions from an engine by temperature-controlled urea injection for selective catalytic reduction

Urea pyrolysis chamber and process for reducing lean-burn engine NOx emissions by selective catalytic reduction

Reducing NOx emissions from an engine by selective catalytic reduction utilizing solid reagents

System for fueling and feeding chemicals to internal combustion engines for NOx reduction

Fluid-cooled injector