Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9495—Controlling the catalytic process

Definitions

• the invention is based on a method for introducing a reagent into an exhaust gas chamber of an internal combustion engine and a device for carrying out the method according to the type of the independent claims.
• DE 101 39 142 A1 describes an exhaust gas aftertreatment system of an internal combustion engine in which an SCR catalytic converter (selective catalytic reduction) is used to reduce the NOx emissions, which adds the nitrogen oxides NO and N02 contained in the exhaust gas with the reducing agent ammonia Nitrogen reduced.
• the ammonia is obtained from a urea-water solution in a hydrolysis catalytic converter arranged upstream of the SCR catalytic converter.
• the hydrolysis catalyst converts the urea contained in the urea-water solution with water to ammonia and carbon dioxide. To ensure an exact dosage, it is intended to determine the concentration of the urea-water solution.
• the urea-water solution is brought to a predetermined pressure with a pump.
• a dosing valve defines a given flow.
• Compressed air is added to the reagent in an isch chamber.
• the urea-water solution is mixed with the mixed air in the Exhaust gas sprayed in such a way that a largely uniform flow against the SCR catalytic converter is achieved.
• Flow elements such as baffles may have to be provided.
• An exhaust gas aftertreatment system of an internal combustion engine is known from EP 1 024254 A2, in which an SCR catalytic converter is used to reduce the NOx emissions.
• Ammonia is provided as the reducing agent, which is obtained in the exhaust duct from a urea-water solution.
• the amount of the measured urea-water solution is determined on the basis of an operating variable of the internal combustion engine, for example the fuel injection quantity and / or the speed and at least one parameter of the exhaust gas, for example the exhaust gas temperature.
• DE 100 65 105 A1 specifies a method which provides for modeling an exhaust gas temperature of an internal combustion engine.
• the exhaust gas temperature is calculated as a function of an air signal provided by an air sensor and as a function of the engine speed.
• the invention is based on the object of specifying a method for introducing a reagent into an exhaust gas duct of an internal combustion engine and a device for carrying out the method, which enable the most exact possible metering of a reagent and a high utilization of a catalyst.
• the pressure of a reagent is introduced upstream of at least one catalytic converter into the exhaust gas of an internal combustion engine, depending on a characteristic variable, to be set to a predetermined reagent pressure setpoint.
• the procedure according to the invention enables good atomization and a uniform distribution of the reagent in the exhaust gas stream upstream of the at least one catalyst.
• the reagent strikes the entire surface that the catalyst has in the flow direction of the exhaust gas.
• the reagent can therefore reach the entire available catalytic surface inside the catalyst.
• the procedure according to the invention therefore enables the best possible utilization of the catalytic surface made available by the catalyst. Through the efficient use of the catalyst, the desired purification of the exhaust gas is achieved with the smallest possible amount of reagent.
• At least one operating variable of the internal combustion engine is used as the parameter.
• An air signal for example, is suitable as the operating variable of the internal combustion engine.
• a torque and / or a fuel signal can be used in connection with the speed.
• the one or more operating variables are known to a controller. Additional sensors are not required.
• a parameter of the exhaust gas is used as the parameter.
• the exhaust gas volume flow or the exhaust gas velocity and / or the exhaust gas pressure and / or the exhaust gas temperature is suitable, for example, as a parameter of the exhaust gas.
• the one or more parameters of the exhaust gas can be determined from known operating parameters of the internal combustion engine. Additional sensors are not required in this case either. If necessary, an exhaust gas temperature sensor be provided for detecting the exhaust gas temperature. The measured exhaust gas temperature can also be used to check the plausibility of the calculated exhaust gas temperature.
• the reagent temperature is used as a parameter.
• the reagent temperature can be estimated, for example, on the basis of a temperature signal from an existing temperature sensor that detects the air temperature.
• a reagent temperature sensor is preferably used.
• the figure shows an internal combustion engine, in the environment of which a method according to the invention runs.
• the figure shows an internal combustion engine 10, in the intake area of which an air sensor 11 and in the exhaust duct 12, a spray device 13, an exhaust gas temperature sensor 14 and a catalytic converter 15 are arranged.
• the controller 20 receives an air signal mL provided by the air sensor 11, a speed N provided by the internal combustion engine 10, an exhaust gas temperature Tabglw measured by the exhaust gas temperature sensor 14, an actual reagent pressure value pRealw provided by a reagent pressure sensor 21, and one by a compressed air pressure sensor 22 provided compressed air pressure actual value pDLIw, a reagent temperature TRea provided by a reagent temperature sensor 23 and a torque setpoint mifa.
• the controller 20 inputs a fuel signal mK to the internal combustion engine 10, a metering valve control signal qRea to a metering valve 30 Reagent pump control signal 31 to a reagent pump 32 and a compressed air control valve control signal 33 to a compressed air control valve 34.
• the controller 20 contains a first function block 41 for determining the exhaust gas velocity vabg, a second function block 42 for determining the exhaust gas pressure pabg, a third function block 43 for determining a calculated exhaust gas temperature TabgR and a fourth function block 44 for determining a torque Md.
• the controller 20 also contains a reagent pressure setpoint specification 50, which outputs a reagent pressure setpoint pReaSw to a reagent pump control 51, which provides the reagent pump control signal 31, and a compressed air pressure setpoint specification 52, which supplies a compressed air pressure setpoint pDLSw to a compressed air control valve.
• Control 53 outputs, which provides the compressed air control valve control signal 33.
• the reagent temperature sensor 23 detects the temperature of the reagent stored in a reagent container 60.
• the compressed air control valve 34 sets the compressed air pressure setpoint pDLSw of a compressed air which is available in a compressed air container 61.
• the compressed air flows through a supercritical throttle 62 and a check valve 63 and then reaches a mixer 64 which mixes the compressed air with the reagent introduced by the metering valve 30.
• the mixer 64 is connected to the spray device 13.
• the method according to the invention works as follows:
• the catalytic converter 15 arranged in the exhaust gas area of the internal combustion engine 10 is preferably an SCR catalytic converter which reduces the nitrogen oxides NO and NO 2 contained in the exhaust gas of the internal combustion engine 10 to nitrogen.
• the SCR catalytic converter 15 requires ammonia for the reduction reaction.
• the ammonia can be arranged in a hydrolysis catalyst (not shown in more detail) from a urea-water solution, which is arranged upstream of the SCR catalytic converter 15 can be obtained, which is introduced into the exhaust gas flow with the spray device 13.
• the urea-water solution is an example of a reagent.
• the reagent stored in the reagent tank 60 is brought by the reagent pump 32 to the reagent pressure setpoint pReaSw of, for example, 4 bar and then fed to the metering valve 30.
• the amount of reagent / unit of time is specified by the dosing valve control signal qRea.
• the control valve 20 can determine the metering valve control signal qRea from a predefined characteristic diagram which is spanned by the speed N and the fuel signal mK or which is spanned by the speed N and the torque Md.
• the metering valve control signal qRea causes the metering valve 30 to release a specific opening cross section for the reagent, for example.
• the reagent is mixed with the compressed air in the mixer 64.
• the compressed air is limited in the compressed air control valve 34 to a pressure of, for example, 8 bar.
• the pressure after the supercritical throttle 62 is to be set to a value which is sufficient for the check valve 63 in front of the mixer 64 to be opened and the compressed air to be able to penetrate into the mixer 64.
• a pressure of 4.6 bar occurs.
• the compressed air pressure in the mixer 64 is finally 4 bar.
• the torque Md is determined as a function of the torque setpoint mifa and as a function of other known variables of the internal combustion engine 10 in accordance with the prior art mentioned at the beginning.
• the specified reagent pressure setpoint pReaSw and the optionally specified compressed air pressure setpoint pDLSw should preferably be determined experimentally in such a way that good atomization after the spray device 13 and a uniform distribution of the reagent over the cross section of the exhaust duct 12 is achieved.
• the size of the reagent droplets obviously plays a role here.
• This measure means that the catalytic surface provided by the SCR catalytic converter 15 can be fully utilized. It should be taken into account here that after the reagent has entered the SCR catalytic converter 15 there is no longer any possibility for further mixing with the exhaust gas and for distribution on the catalytic surface.
• the procedure according to the invention further enables the required amount of reducing agent to be reduced by adapting to the actual demand in the SCR catalytic converter 15.
• the pressure of the reagent stored in the reagent container 60 can be brought to the specified reagent pressure setpoint pReaSw, which is, for example, 4 bar, by a corresponding determination of the reagent pump control signal 31 in the reagent pump control 51.
• the reagent mean pressure value pRealw can be detected with the reagent pressure sensor 21 and made available to the reagent pump control 51 for carrying out the regulation.
• the compressed air pressure of the compressed air stored in the compressed air tank 61 can also be set to the specified compressed air pressure setpoint pDLSw before being introduced into the mixing chamber 64.
• a compressed air control valve 34 is provided, which is controlled by the compressed air control valve control signal 33 provided by the compressed air pressure control 53.
• the actual compressed air pressure value pDLIw can be detected with the compressed air pressure sensor 22 and fed to the compressed air pressure control 53 for carrying out the regulation.
• At least one operating variable of the internal combustion engine 10 is suitable as a parameter for determining the reagent pressure setpoint pReaSw and, if appropriate, for determining the compressed air pressure setpoint pDLSw.
• the air signal mL alone can be used.
• the torque Md and the fuel signal mK in each case in connection with the speed N are also suitable.
• the last-mentioned combinations of at least two operating variables mL, mK are particularly suitable.
• a one-dimensional or multi-dimensional relationship is established between the individual operating variables N, mL, Md, mK and the reagent pressure setpoint pReaSw to be specified and the compressed air pressure setpoint pDLSw, which may be specified.
• the named operating parameters N, mL, Md, mK have an influence on the parameters of the exhaust gas.
• Characteristics of the exhaust gas are the exhaust gas velocity vabg or the exhaust gas volume flow, the exhaust gas pressure pabg and, for example, the exhaust gas temperature TabgR, Tabglw.
• the characteristic variables vabg, pabg, TabgR of the exhaust gas can be determined from the known operating variables N, mL, Md, mK of the internal combustion engine 10 in the function blocks 41, 42, 43 entered within the controller 20.
• the exhaust gas velocity vabg can already be determined in the first function block 41 solely from the air signal mL. If necessary, the fuel signal mK can also be taken into account.
• the exhaust gas pressure pabg can be determined from the exhaust gas velocity vabg in the second function block 42.
• the exhaust gas velocity vabg and / or the exhaust gas back pressure pabg are preferably determined on the basis of a two-dimensional map which is spanned by the engine speed N and the fuel signal K or by the engine speed N and the air signal mL. If a turbocharger is provided, the boost pressure and / or the boost temperature can be taken into account as further operating variables of the internal combustion engine 10.
• the exhaust gas temperature TabgR which is determined in the third function block 43, also has an influence on the atomization of the reagent.
• the exhaust gas temperature TabgR is likely to have an influence in particular on the size of the reagent droplets.
• the determination can be carried out, for example, according to DE 10065 125 A1 mentioned at the outset, according to which the exhaust gas temperature TabgR is modeled from the speed N and from the air signal mL.
• the characteristics of the exhaust gas described so far are determined in the function blocks 41, 42, 43 from operating variables N, mL, Md, mK of the internal combustion engine 10.
• the characteristics of the exhaust gas can be measured with sensors.
• the exhaust gas temperature sensor 14 can be used, which forwards the actual exhaust gas temperature value Tabglw to the controller 20.
• the exhaust gas pressure could be measured with an exhaust gas pressure sensor, not shown in detail.
• the reagent temperature TRea which is detected by the reagent temperature sensor 23, which can be arranged on or in the reagent tank 60, for example, can be taken into account when determining the reagent pressure setpoint pReaSw and, if appropriate, the determination of the compressed air pressure setpoint pDLSw.
• the reagent temperature TRea generally corresponds to the ambient temperature, which can be measured with an existing temperature sensor, not shown. In this case, the additional reagent temperature sensor 23 can be omitted.
• the reagent with compressed air before it is introduced into the exhaust duct 12 Mixer 64 is mixed.
• the procedure according to the invention can of course also be used in systems without compressed air support.
• the metering valve 30 can be mounted directly on the exhaust duct 12, so that the metering valve 30 becomes identical to the spray device 13.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Combustion & Propulsion (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Exhaust Gas After Treatment (AREA)

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• 2004
  • 2004-04-15 DE DE102004018221A patent/DE102004018221A1/de not_active Withdrawn
• 2005
  • 2005-03-14 WO PCT/EP2005/051142 patent/WO2005099874A1/de active Application Filing
  • 2005-03-14 EP EP05717025A patent/EP1737559A1/de not_active Withdrawn
  • 2005-03-14 JP JP2007506754A patent/JP2007531843A/ja not_active Withdrawn
  • 2005-03-14 US US11/578,383 patent/US20070209349A1/en not_active Abandoned

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