# US 8,739,517 B2 · Vehicle-based strategy for removing urea deposits from an SCR catalyst > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,739,517 B2 - Document ID: US8739517B2 - Status: Granted - Kind: B2 - Application number: 13/465,879 - Filed: 2012-05-07 - Published: 2012-08-30 - Granted: 2014-06-03 - Earliest claimed: 2007-05-02 - Assignees: Ford Global Technologies, LLC - Applicants: Lifeng Xu; Williams Lewis Henderson Watkins; Shane Elwart; George Wade Graham - Inventors: Lifeng Xu; Williams Lewis Henderson Watkins; Shane Elwart; George Wade Graham - Web page: https://patentgrep.com/patent/US8739517B2 ## CPC - B01D 53/9431: {Processes characterised by a specific device} - B01D 53/9495: {Controlling the catalytic process} - B01D 53/96: Regeneration, reactivation or recycling of reactants - F01N 3/2026: {directly electrifying the catalyst substrate, i.e. heating the electrically conductive catalyst substrate by joule effect} - F01N 3/2066: {Selective catalytic reduction [SCR]} - F01N 3/208: {Control of selective catalytic reduction [SCR], e.g. by adjusting the dosing of reducing agent} - B01D 53/9477: {with catalysts positioned on separate bricks, e.g. exhaust systems} - B01D 2251/2067: Urea - B01D 2258/012: Diesel engines and lean burn gasoline engines - F01N 2560/026: for measuring or detecting NOx - F01N 2560/06: the means being a temperature sensor - F01N 2560/07: the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters - F01N 2560/08: the means being a pressure sensor - F01N 2560/14: having more than one sensor of one kind - F01N 2570/14: Nitrogen oxides - F01N 2610/02: the substance being ammonia or urea - F01N 2610/146: Control thereof, e.g. control of injectors or injection valves - F01N 2900/1402: Exhaust gas composition - F01N 2900/1622: Catalyst reducing agent absorption capacity or consumption amount - F01N 2900/1812: Flow rate - Y02A 50/20: Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters - Y02T 10/12: Improving ICE efficiencies - B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28) - F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16) - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A method is provided for controlling regeneration of an SCR catalyst. The method includes coordinating the regeneration duration and temperature (e.g., longer/shorter regenerations and/or lower/higher temperatures) to the urea deposit loading. In this way, improved regeneration may be achieved due to the particular nature of urea deposits on SCR catalysts. ## Claims ### Claim 1 A method, comprising: directing engine exhaust to a urea-based selective catalyst reduction (SCR) catalyst and then to a particulate filter; regenerating the particulate filter; and adjusting operating parameters to regenerate the SCR catalyst, including varying each of a SCR regeneration duration (longer/shorter) and a SCR regeneration temperature (lower/higher) based on an accumulated urea deposit amount on the SCR catalyst prior to its regeneration. ### Claim 2 (depends on 1) The method of claim 1 further comprising determining that a threshold for removal of urea deposit accumulation on the SCR catalyst has been met, and wherein upon making such determination, regenerating the SCR catalyst at a predetermined temperature for a predetermined time in response to the determination, and wherein the threshold is based on a pressure drop across the SCR catalyst. ### Claim 3 A method, comprising: directing engine exhaust to an oxidation catalyst, then a urea-based selective catalyst reduction (SCR) catalyst, and then to a particulate filter; regenerating the particulate filter; completing the particulate filter regeneration; and then regenerating the SCR catalyst, including varying each of a SCR regeneration duration (longer/shorter) and a SCR regeneration temperature (lower/higher) based on an accumulated urea deposit amount on the SCR catalyst prior to its regeneration. ### Claim 4 A method, comprising: directing engine exhaust to an aftertreatment device coupled downstream of the engine, the aftertreatment device including an oxidation catalyst, a urea-based selective catalyst reduction (SCR) catalyst, and a particulate filter; establishing a threshold urea deposit accumulation for regeneration of the SCR catalyst; determining that the threshold urea deposit accumulation in the SCR catalyst has been met; in response to the determination, regenerating the SCR catalyst by maintaining the SCR catalyst at a predetermined regeneration temperature for a predetermined interval, and after determining that the threshold urea deposit accumulation in the SCR catalyst has been met, delaying the SCR regeneration until a regeneration performed in the particulate filter is completed. ### Claim 5 (depends on 4) The method of claim 4, wherein determining that the threshold urea deposit accumulation in the SCR catalyst has been met includes measuring NOx emissions using a NOx sensor and one of an operating temperature, a urea flow rate, an exhaust flow rate, an exhaust pressure, and a pressure difference across the SCR catalyst. ### Claim 6 (depends on 4) The method of claim 4, wherein determining that the threshold urea deposit accumulation in the SCR catalyst has been met includes detecting that a pressure drop across the SCR catalyst meets or exceeds a predetermined pressure drop threshold corresponding to the threshold urea deposit accumulation. ### Claim 7 (depends on 4) The method of claim 4, wherein the predetermined regeneration temperature is 360-450° C. ### Claim 8 (depends on 4) The method of claim 4, wherein the predetermined interval is at least two minutes. ### Claim 9 (depends on 4) The method of claim 4, wherein a temperature of the SCR catalyst is raised to and maintained at the regeneration temperature by heating the SCR catalyst using a SCR catalyst heater. ### Claim 10 (depends on 4) The method of claim 4, wherein a temperature of the SCR catalyst is raised to and maintained at the regeneration temperature by injecting fuel to the oxidation catalyst to generate an exothermic reaction. ### Claim 11 (depends on 4) The method of claim 4, wherein determining that the threshold urea deposit accumulation in the SCR catalyst has been met includes: estimating urea deposit accumulation based on operation conditions of the SCR catalyst, and determining that the estimated urea deposit accumulation meets or exceeds the threshold urea deposit accumulation. ### Claim 12 (depends on 11) The method of claim 11, wherein the operating conditions include one of an operating temperature, a urea flow rate, an exhaust flow rate, an exhaust pressure, and a pressure difference across the SCR catalyst.