PARK
`
`IP TRANSLATIONS
`
`November 13, 2012
`
`.Certification
`
`Park IP Translations
`
`This is to certify that the attached translation is, to the best
`of my knowledge and belief, a true and accurate translation from
`German into English of the article that is entitled "The SCRT®
`system
`a combination particle filter with SCR catalyst
`enables
`both particle
`and NOx
`emission
`to
`be
`reduced
`simultaneously
`in
`commercial vehicle diesel
`engines"
`and
`autho~ed by "Georg HUthwohl, Bernd Maurer and Gennadi Zikoridse".
`
`Abraham I. Holczer
`
`Project Manager
`
`Park Case # 34652
`
`134 W. 29th Street 5th Floor • New York, N.Y. 10001
`Phone: 212-581-8870 • Fax: 212-581-5577
`
`1
`
`JM 1005
`
`

`

`The SCRT® system - a combination particle filter with SCR catalyst- enables
`
`both particle and NOx emission to be reduced simultaneously in commercial
`vehicle diesel engines
`
`By Georg Hilthwohl, Bernd Maurer and Gennadi Zikoridse
`
`1.
`
`Introduction
`
`On 12/21/1998, the EU Environment Council agreed on new limits for heavy commercial
`vehicles. This proposal by the Commission corresponds in the essential points to the
`suggestions made by the Parliament. This will involve reducing the emission limits for
`nitrogen oxides (NOx) and particles in 2 stages. The test cycles applied will be the new
`European Steady Cycle (ESC) and in addition, for vehicles with exhaust gas after-treatment
`systems, the new European Transient Cycle (ETC).
`
`TABLE 1
`
`PROPOSED LIMIT BY THE EUROPEAN COMMISSION OF 12/21/1998
`
`Year I Standard
`2005
`EURO IV
`
`2008
`
`EUROV
`
`Cycle
`ESC
`ETC
`ESC
`ETC
`
`Particles [PM in g/kWh]
`0.02
`0.03
`0.02
`0.03
`
`Nitrogen oxides (NOx in g/kWh)
`3.5
`3.5
`2.0
`2.0
`
`In order to conform to the limits listed in TABLE 1, an improved fuel quality for the EU has
`been defined by the AUTO Oil Program. This sets the maximum level of sulphur at 50 ppm.
`Unfortunately, when the decision on fuel qualities was taken, the decision on emission limits
`for commercial vehicles was not yet known. The fuel quality defined clearly does not
`conform to the required emission values. So when highly active oxidation catalysts are
`used, such as those in the CRT® system, the sulphur contained in the fuel is oxidized
`completely into sulphates.
`In turn, the sulphates, together with the absorbed water, lead to
`an increase in particle mass. These components, which can only be influenced by fuel
`quality, necessarily result in emission values which lie above the required particle emission
`limit. In quantitative conversion of the sulphur, the limit of 0.02 g/kWh is reached at a sulphur
`. level of just 14 ppm in the fuel. One way out of this dilemma could lie in two steps to be
`passed by the legislation:
`
`• Certification will be permitted in the Ieng term with a fuel quality which is improved by
`comparison with that now on the market, i.e. the certification fuel has a sulphur level of
`10 ppm. The sulphates generated in actual use are thus not fully taken into account.
`The system must, however, work with functional safety even at higher sulphur levels.
`• The EU agrees on a limit of 10 ppm for sulphur levels which is stricter than the existing
`decision. Conversion in refineries appears to be possible, because this quality is already
`available in many countries. However, this results in a high investment volume for the oil
`industry.
`
`1
`
`2
`
`

`

`Today's particle measurement methods do not distinguish between the solid soot particles
`and the other components which contribute to the particle mass. The result of stating the
`undifferentiated particle mass is that, for example, the water absorbed by the sulphuric acid,
`which contributes over 50% of the sulphuric acid mass, is evaluated just as critically with
`respect to its potential risk as the soot, which is classified as carcinogenic. To counteract
`this incorrect evaluation, the measurement method should be reconsidered.
`
`According to the current state of the art, in order to conform to the new limits, the particle
`filter must be introduced in 2005, and in 2008 a further system for NOx reduction must be
`this means a
`For exhaust gas after-treatment in commercial vehicles,
`introduced.
`breakthrough similar to the introduction of the controlled three-way catalyst in cars. This
`development is clearly the political will [1]. This is a huge challenge for the vehicle and
`supplier industry.
`
`2.
`
`Drive systems in public transport
`
`The trailblazers for these technologies are the vehicles operated in city center areas, in
`·particular city buses. Attempts to lower particle emission substantially in this area have been
`going on for a long time. Since public transport is financed by the German Lander (states)
`and communities, this technology can be introduced here by the corresponding development
`guidelines. Following the large-scale soot filter trial of the Federal Environment Agency,
`which was largely a failure because the technology was not yet fully mature, the CRT®
`system - based on the technology of the catalyst manufacturer Johnson Matthey - was
`introduced in Germany in 1995 by HJS [2].
`
`The CRT® system consists of a special, highly active oxidation catalyst and a series(cid:173)
`connected particle filter. The NO emitted by the engine is partially oxidized into N02 in the
`oxidation catalyst. In turn, this N02 is the oxidant for the soot stored in the filter. The. CRT®
`system is thus a continuously working passive particle filter system which manages without
`any electronics whatsoever. The entire system is integrated into the housing of the standard
`silencer in the exhaust system. The exhaust gas back pressure, which is slightly increased
`compared with the standard silencer, is not measurably detrimental, at least in primarily low(cid:173)
`load city bus use, even in terms of fuel consumption. [2]
`
`A low-sulphur fuel quality has been developed as a special fuel for operating vehicles with
`the CRT® system. The sulphur level was initially 10 ppm. There is now almost 4 years of
`operational experience using the CRT® system with this fuel quality.
`In Germany alone,
`more than 1000 city buses have been equipped with it. The majority of the vehicles,
`however, are operated in Scandinavia, where the low-sulphur fuel required as boundary
`condition is available everywhere as City Diesel [Sweden Class 1].
`
`Using the CRT® system, it is already possible to conform to the particle emission limits as
`In engine test bench studies,
`required for EURO IV, when the corresponding fuel is used.
`correspondingly low emissions can be proven even at higher sulphur levels. This is,
`however, attributable to a storage effect in the system. The sulphates formed in the catalyst
`can be stored in the filter in a new system over a few hours. This means that even with
`
`2
`
`3
`
`

`

`higher sulphur-level fuel, there is compliance with the. particle emission limit. But meeting
`limits over just a few hours cannot be the political goal.
`
`Public transport, however, demanded at an early stage that the excellent emission values
`attained with. gas buses must also be maintained with diesel engines. In diesel engine
`operation, however, this can only achieved by combining a particle filter with an SCR
`catalyst. The combination of SCR catalyst and particle filter is known as the SCRT® system.
`This system - as will be necessary from 2008 for every new commercial vehicle in similar
`form according to the current status - has already been tested in a field trial a year ago by
`HJS.
`
`3.
`
`Description of the SCRT® system
`
`The SCRT® system, for use in city buses, in addition to its function as a soot filter, was also
`intended to include denitrification. Merely the use of SCR catalysts in vehicles represents a
`problem which has not yet been solved for mass production. Current SCR catalysts cannot
`be accommodated in the physical volume of today's city buses [4].
`It is disproportionately
`more difficult to integrate a further particle filter therein. This required new approaches to a
`solution with respect to the denitrification method.
`
`In the systems in most common use today, urea in aqueous solution is used as reducing
`agent. The reducing agent is usually blown into the exhaust gas system using air. Here the
`urea must decay, forming ammonia. An additional hydrolysis catalyst is often used to
`support this reaction. If the hydrolysis catalyst is not used, the urea decay takes place
`directly on the SCR catalyst surface.
`
`In order to reduce the required physical volume, ammonia is produced outside the exhaust
`gas system in the HJS SCRT® system, using an ammonia generator. The starting material
`for this is ammonium carbamate. The gaseous ammonia can be introduced via a ring nozzle
`directly in front of the filter. The soot filter of the CRT® system has been impregnated with
`SCR-active material. Through this, the volume of the soot filter will be already utilized for the
`SCR reaction. Consequently, only a proportionately smaller SCR catalyst has to be
`connected in series. A coated carrier catalyst from Johnson Matthey is used for this.
`In the
`current structure, a small oxidation catalyst is connected in series as a "police catalyst",
`which oxidizes any ammonia slip which may occur in the system if it is not yet optimally
`tuned, after the SCR system. The structure of the system is shown in diagram form in FIG. 1.
`
`The system layout is shown in TABLE 2. The volumes listed here allow the complete
`system to be installed in the standard silencer of the Citaro, the latest city bus generation
`from DaimlerChrysler.
`
`TABLE 2: LAYOUT OF THE SCRT® SYSTEM FOR ENGINE OM 447 HLA, 12 L, 184 kW
`
`Unit
`Oxidation catalyst 1
`~ ammonia injection
`filter
`SCR catalyst
`
`Dimensions
`10.5" x 4.5"
`
`11.25" x 12"
`10.5" x 6"
`
`Volume
`6.3751
`
`19.51
`8.51
`
`3
`
`4
`
`

`

`I Oxidation catalyst 2
`
`10.5" x 3"
`
`4.251
`
`CRT
`
`SCR
`
`O:itfgatiom;·
`kaiat a>aJvr
`
`FIGURE 1
`
`Schematic diagram of the SCRT® system
`(THE OXl-CAT CONNECTED IN SERIES TO THE SCR-CAT IS NOT SHOWN
`HERE)
`
`Key:
`Oxidationskatalysator = oxidation catalyst
`Partikelfilter = particle filter
`SCR-Katalysator = SCR catalyst
`Mischkammer = mixing chamber
`Luft= air
`Ventilblock = valve block
`SchnellverschluB = quick-release fastener
`Ammoniak = ammonia
`Wasserpumpe = water pump
`Wasser = water
`Ammoniumcarbamat = ammonium carbamate
`
`in which
`The ammonia generator is a reactor, heated by the engine cooling water,
`ammonium carbamate is decomposed. Ammonium carbamate decomposes completely and
`without any residue at temperatures above 60 °C into the gaseous components C02 and
`NH3. At a temperature of 85 °C, which usually arises in engine cooling water systems, a gas
`pressure of 3.5 bar arises in the generator. The reducing agent is now dosed into the
`exhaust gas system with the aid of a timing valve. The dosing unit is very compact in its
`
`4
`
`5
`
`

`

`latest variants. The dimensions are 50 x 50 x 150 mm. The dosing takes place as a
`function of a characteristics map, taking catalyst activity into account.
`
`Since the NH3 and C02 gases recombine into a solid at temperatures below the equilibrium
`temperature associated with the respective pressure, it is necessary to heat the entire
`dosing unit. This is done electrically. Once the required quantity has been dosed in each
`case, the C02/NH3 mixture is diluted with air in a mixing chamber. As a result, the back(cid:173)
`reaction into solid form is prevented, and the reducing agent can be passed through an
`unheated dosing line to the exhaust gas line. The air assistance also shortens the gas travel
`time in the system, so that the dosing unit need not be arranged in direct proximity to the
`SCR catalyst.
`
`If the two reducing agents, ammonium carbamate and urea, are compared, both substances
`can be classified as harmless in terms of environmental hazard. Solid ammonium
`carbamate, however, smells strongly of ammonia even at ambient temperatures.
`
`The following advantages also result for ammonium carbamate compared with the use of
`urea in aqueous solution:
`
`• ammonium carbamate has a higher ammonia content by a factor of 1.8 (volumetrically),
`so that the volume of the reducing agent tanks can be correspondingly smaller.
`• Urea in aqueous solution freezes at a temperature of -11 °C, which makes remedial
`measures necessary for winter use.
`
`4.
`
`Test bench studies
`
`In the run-up to the use of the SCRT® system; test bench studies were necessary. The
`SCRT® system was to be coordinated with a EURO II city bus engine. Firstly, the ammonia
`dosing was adapted to the NOx characteristics map of the engine. The co-ordination of the
`system took place under the boundary condition that no ammonia breakthrough takes place
`after the SCRT® system.
`
`Firstly, characteristics maps of the raw emissions were recorded on an engine test bench of
`the Forschungsinstitut Fahrzeugtechnik [Vehicle Research Institute].
`
`Following initiation of the SCRT® system, the reducing agent feed was adapted for the
`specified operating points. The optimal catalyst efficiency was determined by appropriate
`exhaust gas analysis, which involved ensuring that no ammonia breakthrough occurs.
`It is
`necessary for this property of the system to be maintained even in unsteady engine
`operation [abrupt changes in load and rpm]. This was to be proven on the basis of
`corresponding engine test bench trials and the subsequent vehicle testing of the SCRT®
`system. The results obtained from these studies were to be used for the base setting of the
`system controller.
`
`4.1
`
`Test set-up
`
`5
`
`6
`
`

`

`The SCRT® system was set up on the engine test bench. FIGURE 2 shows the SCRT®
`system installed in the exhaust gas line of the test engine. Both part.;systems, CRT and
`SCR, can be seen in the figure. The system was integrated into the exhaust gas line taking
`account of the installation conditions in the test vehicle.
`
`The tests were conducted on a diesel engine, type OM 447 hLA-EURO II. This is a basic
`engine for Mercedes-Benz city buses.
`
`ENGINE DATA:
`No. of cylinders:
`Bore size:
`Stroke:
`Capacity:
`Rated power:
`Rated torque:
`
`6
`128 mm
`155 mm
`11,967cc
`184 I 2200 kW/min-1
`1100 I 1100 Nm/min-1
`
`FIG. 2 THE SCRT® SYSTEM ON THE ENGINE TEST BENCH
`
`Diesel fuel with a sulphur content of less than 10 ppm was used for all the tests with the
`SCRT® system.
`
`In all measurements, the important engine data were recorded in general, such as rpm,
`torque, power, exhaust gas
`temperature,
`fuel consumption, boost pressure, boost
`temperature and exhaust gas back pressure, etc. The concentration of nitrogen oxides,
`hydrocarbons, carbon monoxide, carbon dioxide, oxygen and particles were measured in the
`exhaust gas. The ammonia slip was determined after the SCRT® system.
`
`6
`
`7
`
`

`

`4.2
`
`Determination of the raw emissions of the test engine
`
`On the engine test bench, characteristics maps of the raw emissions of the engine were
`firstly recorded. The characteristics maps were formed by 60 operating points (5 load points
`at 12 rpm figures in each case]. The NOx characteristics map was of primary interest for
`determining the characteristics maps of the ammonia dosing in the SCRT® system. Other
`pollutant components and engine parameters were likewise measured in this study, in order
`to gain initial information for system optimization.
`
`The raw emissions serve as the basis for comparison in determining the effectiveness of the
`SCRT® system. These were therefore determined according to the 13-stage test to ECE R49
`valid at that time.
`
`TABLE 3 shows the results of the 13-stage test of the test engine in comparison with EUR0-
`11 and EURO-Ill limits.
`
`TABLE 3: RAW EMISSIONS FROM THE TEST ENGINE IN THE 13-STAGE TEST TO ECE R49
`
`NOx
`co
`PM
`
`HC
`
`EURO-II limit
`
`EURO-Ill limit
`
`Raw emission
`
`[g/kWh]
`
`[g/kWh]
`
`7.0
`
`4.0
`
`0.15
`
`1.1
`
`5.0
`
`2.5
`
`0.1
`
`0.7
`
`[g/kWh]
`
`6.68
`
`0.59
`
`0.116
`
`0.47
`
`4.3
`
`Measurement of emissions from the test engine with SCRT® system
`
`The emissions from the OM 447 hLA test engine with SCRT® system were also determined
`according to ECE R49. At the same time, ammonia slip measurements were carried out. At
`each operating point tested, the emissions were measured with and without NH3 dosing.
`This made it possible to test both the reduction of exhaust gas components by each of the
`two part systems (CRT and SCR) and the effectiveness of the whole SCRT® system.
`
`The optimization of the reducing agent feed was conducted both in steady and in unsteady
`engine operation (abrupt changes in load and rpm). The aim of optimization was a
`maximum degree of system efficiency while reliably preventing any ammonia breakthrough.
`
`Various abrupt changes in load and rpm in the characteristics map of the engine were
`conducted on the engine test bench.
`In these studies, firstly the response time of the
`catalyst to the rapidly-changing exhaust gas parameters (exhaust gas volume, composition,
`temperature, etc.) and secondly the possibility of ammonia slip were studied.
`
`With the introduction of Euronorm Ill, a new test cycle is also to be introduced. It consists of
`13 stages with a stage time of 120 seconds each. In addition to no-load operation, this ESC
`
`7
`
`8
`
`

`

`test [European Steady Cycle] will also be run at three different speeds with different load
`stages. Studies in accordance with ESC were also conducted for the assessment of the
`SCRT® system.
`
`4.4
`
`Interpretation of the measurement results
`
`The SCRT® system reduces the emission of carbon monoxide, particles, hydrocarbons and
`nitrogen oxides. The efficiency of the SCRT® system was evaluated on the basis of the
`results obtained. TABLE 4 shows the efficiencies in the individual stages of the 13-stage
`It can be seen that iii the case of the CO emissions, the
`test according to EGE R49.
`detection limit was sometimes reached. Hence the corresponding efficiencies are stated as
`100% [5].
`
`TABLE 4: EFFICIENCIES OF THE INDIVIDUAL STAGES OF THE 13-STAGE TEST TO ECE R49
`
`Stage No.
`
`Speed
`[rpml
`560
`1
`1320
`2
`1320
`3
`4
`1320
`1320
`5
`1320
`6
`7
`560
`2200
`8
`2200
`9
`10
`2200
`2200
`11
`2200
`12
`13
`560
`ECE R49 test- result
`
`Eff PM
`[o/o]
`72.12
`73.53
`94.96
`97.31
`99.31
`99.47
`99.29
`99.76
`99.68
`99.07
`99.74
`99.72
`95.89
`97.58
`
`Eff NOx
`Colo]
`0.00
`11.11
`58.48
`75.73
`60.75
`47.82
`78.63
`27.56
`46.41
`65.29
`61.43
`32.24
`77.10
`47.72
`
`Eff_THC
`[%]
`58.82
`64.58
`91.49
`95.24
`98.96
`98.89
`98.92
`98.17
`99.12
`97.67
`99.32
`99.40
`93.88
`94.52
`
`Eff_CO
`[%]
`43.14
`93.59
`98.70
`100.00
`100.00
`98.28
`98.04
`100.00
`100.00
`100.00
`100.00
`100.00
`98.04
`97.91
`
`TABLE 5 shows a comparison of the study results to EGE R49 and ESC with the current and
`future emission limits.
`·
`
`TABLE 5: COMPARISON OF STUDY RESULTS WITH LIMITS
`
`Emission
`[g/kWh]
`
`EUROll
`limit
`
`EURO
`Ill limit
`
`EURO
`IV limit
`
`ECE49
`
`. ESC
`
`ESC
`
`NOx
`co
`PM
`HC
`
`7.0
`4.0
`0.15
`1.1
`
`5.0
`2.1
`0.1
`0.66
`
`3.5
`1.6
`0.02
`0.46
`
`OM447
`hLA
`raw
`emission
`
`ECE R49
`6.68
`0.59
`0.116
`0.47
`
`SCRT"
`system
`
`Efficiency
`[%]
`
`ECE
`R49
`
`3.49
`0.0123
`0.0028
`0.0258
`
`ECE R49
`
`47.72
`97.91
`97.58
`94.52
`
`OM447
`hLA
`raw
`emission
`
`ESC
`7.85
`0.45
`0.103
`0.43
`
`SCRT"
`system
`
`Efficiency
`[%]
`
`ESC
`
`ESC
`
`3.47
`0.005
`0.006
`0.06
`
`55.79
`98.88
`94.17
`86.05
`
`The efficiencies of the SCRT® system according to EGE R49 and ESC are shown in
`FIGURE 3.
`
`The SCRT® system reduces particle emissions (PM) in the 13-stage test to EGE R49 by
`97.58% and according to ESC by 94.17%. CO emission is lowered by 97.91% (ECE R49)
`
`8
`
`9
`
`

`

`and 98.88% (ESC) respectively, hydrocarbon emission (THC) by 94.52% (ECE R49) and
`86.05% (ESC) respectively. The reduction in nitrogen oxide emission is 47.72% (ECE R49)
`and 55.79% (ESC). The studies have shown that by using the SCRT® system, not only the
`EURO-Ill norm, but also the EURO-IV norm can be met. The NOx emission using the
`SCRT® system .is very slightly below this limit. By optimizing the system further, a clear
`improvement in the NOx conversion is anticipated, so that the Euro-V norm would also be
`achievable.
`
`""""~..-----------
`
`i':-
`
`I
`i
`
`80
`...... 70
`...... ,,
`'<ft.
`60
`ta ...
`50
`C'I
`Ill
`O'I
`40
`c
`:I
`~ 30
`i
`20
`10
`
`0
`
`lllECE R49
`lll\'IESC
`
`NOx
`
`co
`PM
`Emlssion
`
`HC
`
`FIGURE 3 EFFICIENCIES OF THE SCRT® SYSTEM ACCORDING TO ECE R49 AND ESC
`
`Wirkungsgrad = efficiency
`
`The SCRT® system was optimized on the engine test bench with respect to the ammonia
`slip. The ammonia dosing was coordinated such that no ammonia breakthrough can occur.
`Comprehensive test bench studies with optimized NH3 dosing have confirmed this. The
`vehicle testing should confirm the optimization findings.
`
`5.
`
`System in service in city buses
`
`Following completion of the test bench studies, the SCRT® system will be tried in everyday
`service in a Mercedes-Benz city bus used by the transport operators in Leipzig. This vehicle
`is equipped with the same engine as was used for the test bench studies (OM 447 hLA).
`
`A measurement data recorder was installed to monitor the system, the measurement data
`being regularly read out and analyzed.
`
`9
`
`10
`
`

`

`Deductions can also be derived from the data on the operating characteristics of the bus
`Uourney times, average speed, etc.), from which connections between the use of the vehicle
`and the ammonia consumption become clear.
`
`TABLE 6 shows the current configuration of the measuring channels.
`
`The measurement parameters are scanned at 10 ms and stored once a second.
`
`FIGURE 4 shows the basic configuration of the measurement arrangement. The unit for
`measurement data capture receives its information from the engine control unit (EDC) via
`the diagnostic interface (K-Line) and also directly as analogue or digital value from the
`SCRT® control device and/or the corresponding sensors.
`
`TABLE 6: MEASUREMENT CHANNELS IN THE TEST VEHICLE
`
`Measurement channel marking
`Volume is
`rpm
`speed
`cooling water
`boost air temperature
`boost pressure
`PWM
`NH3-pressure
`NHs-DRM-pressure
`
`H20 in
`H20 out
`CAT temperature
`Exhaust gas pressure
`
`Meaning
`fuel quantity measurement
`engine rpm
`speed
`temperature of cooling water
`boost air temperature
`boost pressure
`NH3 dosing
`internal pressure of the ammonia generator
`pressure after the pressure-reducer on the ammonia
`generator
`water temperature at SCRT input
`water temperature at SCRT output
`exhaust gas temperature before SCR catalyst
`exhaust gas back pressure before entire SCRT®
`system
`
`10
`
`11
`
`

`

`Motor OM 447 hLA
`
`···r
`
`j···--1···· :l
`
`.• !
`I
`I
`
`a:
`U
`(/)
`.-J,
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`
`.
`l
`l
`
`'·N:
`·....
`Tl
`',I
`.,...
`\,
`.·•
`i--·-··--···--·--····•'
`' d .. · · .. ·.
`: : _
`
`SCRT·
`Steuerung
`
`. I
`
`.....
`
`E::---l,,::~'.'.~-.· -J·· ·"''l~I
`.------'
`~__._ __ ..___ --~r=== ___ .__ __ ~ _ _._ __ __.~~:-
`
`~'1::::mot'G¢ Abnasoeuendtur,:;ir.
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`Ltt00<.111¥.!t
`
`J::~·-~ .. ~
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`
`N-t1.oo.-.~1•.itlJ c~::'~ ~;:r.t· r>1~1
`
`MeBdatenerfassung
`
`FIGURE 4 SCHEMATIC DIAGRAM OF THE MEASUREMENT ARRANGEMENT IN THE TEST
`VEHICLE IN LEIPZIG
`
`Ammoniakgenerator = ammonia generator
`Vorratsbehalter = reservoir
`Druckminderer =pressure reducer
`Taktventil =time valve
`Oxikat = oxidation catalyst
`Partikelfilter = particle filter
`SCRT Steuerung = SCRT control
`Wasser_aus =water out
`Wasser_ein =water in
`NH3 dosierung =ammonia dosing
`Carbamat-Druck = carbamate pressure
`NH3 ORM Druck = pressure after the pressure-reducer on the ammonia generator
`Mel1datenerfassung = measurement data capture
`Kraftstoffmenge = fuel quantity
`Drehzahl = speed
`Abgasgegendruck = exhaust gas back pressure
`Geschwindigkeit = sped
`Ladedruck = boost pressure
`T wasser-motor = T water-engine
`T ladeluft = T boost pressure
`
`The vehicle testing and system optimization will be completed by the end of '99. After that,
`statistically-supported information about the ammonia consumption per unit travelled, the
`
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`

`reliability of the dosing system and the range of an ammonium carbamate load will be in
`hand.
`
`6.
`
`Refinement of the system
`
`As development stands at present, the SCRT® system exhibits two essential weaknesses,
`which should be eradicated by corresponding improvements:
`
`a) Reloading the ammonium carbamate is comparatively expensive.
`b) Thermal transfer from the cooling water through the container wall to the solid
`deteriorates with increased volume of ammonium carbamate in the container,
`because a gas space forms between container wall and solid, which acts as an
`additional resistance for the thermal transfer.
`
`When reloading the solid, there is also the fact that the reservoir installed on board the
`vehicle is under pressure, but leakage of NH3 during the tank reloading procedure absolutely
`must be prevented. Since ammonium carbamate exhibits a certain tendency to release NH3
`even at ambient temperature, the reducing agent would also have to be handled in closed
`circuits.
`
`The obvious solution to this problem is to use replaceable cartridges. This is a feasible
`option for city buses, since logistics and servicing costs must be guaranteed in the depots.
`
`However, it would be better if the reservoir, which is at the same time also the reaction
`vessel, could remain on board the vehicle and only the reducing agent itself would be
`reloaded. Therefore alternative approaches to a solution are being sought. The currently
`favored solution is to fill the container with the aid of a carrier medium. Ammonium
`carbamate is a substance which e.g. does not dissolve in oil. The ammonium carbamate
`forms a suspension with the oil, which can then be pumped into the reactor. Oil and
`ammonium carbamate are separated in the reactor by a filter. The oil is carried back to the
`filling station through a return line. The oil is not used up. So even a pressurized generator
`could be filled without any problem.
`
`The use of a fluid carrier medium simultaneously offers the advantage that the remaining
`part of the oil in the generator itself acts to transfer heat between the container wall and the
`ammonium carbamate.
`
`By using this concept, both the system weaknesses described above can be cancelled out
`simultaneously.
`
`7.
`
`Summary
`
`The SCRT® system has been tested on the engine test bench on a typical city bus engine.
`The currently valid 13-stage test to ECE R49 for the certification of commercial vehicles was
`used as the test procedure.
`
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`
`

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`The components contained in the raw exhaust gas: nitrogen oxides (NO and N02),
`hydrocarbons, carbon monoxide and particles, were measured. These were also intended
`to be recorded for comparison after initiation of the SCRT® system, with the ammonia
`concentrations also being recorded. With respect to the gaseous pollutants, the main focus
`was on the emission of nitrogen oxides, hydrocarbons and carbon monoxide, since these
`exhaust gas components are limited by the EURO limits and these will be further tightened
`in future.
`
`Without NH3 dosing, only the pollutants carbon monoxide (CO), with a total efficiency of
`97.91 % (to ECE R49) and 98.88% (to ESC) respectively, particles (PM) with an efficiency of
`97.58% (ECE R49) and 94.17% (ESC) and hydrocarbons (THC) with an efficiency of
`94.52% (ECE R49) and 86.05% (ESC) respectively were reduced by the components of the
`SCRT® system. The values are in each case the efficiency over the entire 13-stage test.
`
`The reduction of nitrogen oxides starts with the NH3 dosing. As a result of this, the exhaust
`is able to reduce all
`the currently limited exhaust gas
`gas after-treatment system
`components. The catalyst efficiency for nitrogen oxides is 48% (to ECE R49) and 56% (to
`ESC) for the entire 13 stage test. There can, however, at the same time be considerable
`differences between the individual stages. From 0%, due to insufficient catalyst temperature
`(no NH3 dosing) in no-load operation (stage 1) up to 79%, the efficiencies are wide-ranging.
`The lowest efficiency with NH3 dosing was 28% at nominal speed and full load, thus at the
`highest space velocity in the SCRT® system.
`
`By further optimization of the system, a significant improvement of the NOx conversion can
`be expected, so that in future it will be possible to comply with the EURO-V norm with EURO
`II engine tuning. The current practical testing will deliver further optimization approaches.
`
`8.
`
`[1]
`
`[2]
`
`[3]
`
`[4]
`
`Literature
`
`EU-Umweltrat beschlier..t Katalysator und Rul1filter tor schwere Nutzfahrzeuge. [EU
`Environment Council decides on catalyst and soot filter for heavy commercial
`vehicles] BMU Press release, 12/21/1998
`im
`G. HOthwohl, R. Christ: Das CRT-System - Beitrag zur Luftreinhaltung
`innerstadtischen Verkehr. [Contribution to air pollution abatement in city center traffic]
`In: Tagungsband [conference report] 1, Nahverkehrsforum [local traffic forum]
`Paderborn, 1997
`Ein gleichzeitig wirtschaftliches und
`-
`G. HOthwohl: Der Dieselmotor
`umweltfreundliches Antriebsaggregat durch Abgasreinigung. [The diesel engine - A
`drive unit which is both economical and environmentally friendly due to exhaust gas
`purification] In: Umweltgerecht und Bezahlbar - Antriebskonzepte des Nahverkehrs
`mit Zukunft, [Environmentally compatible and affordable: drive concepts for local
`traffic with a future] Tagungsband 2, Nahverkehrsforum Paderborn, March 11-, 1998
`tor
`K.J. Marquardt, T. Braun, K. Binder: Ein Abgasnachbehandlungssystem
`Dieselmotoren auf Basis der SCR-Technologie. [An exhaust gas after-treatment
`system for diesel engines based on SCR technology] In: Kraftfahrwesen und
`Verbrennungsmotoren [Automotive engineering and internal combustion engines],
`Tagungsband 3. Stuttgarter Symposium February 23-25, 1999
`
`13
`
`14
`
`

`

`[5)
`
`G. Zikoridse, U. Hofmann: Abstimmung eines SCRT-Systems an einem EURO II
`Stadtbusmotor auf dem MotorenprOfstand. [Coordinating an SCRT® system to a
`EURO II city bus engine on the engine test bench] Untersuchungsbericht [Study
`report], HTW Dresden, April 1999.
`
`Authors
`
`Dr.-lng. Georg HOthwohl and Dr. rer. nat. Bernd Maurer,
`HJS Fahrzeugtechnik
`
`Dr.-lng. Gennadi Zikoridse,
`HTW Dresden, Forschunginstitut Fahrzeugtechnik
`
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`
`15
`
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`16
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`Das SCRT® System - Die Kombination Partikelfilter mit
`SCR-Katalysator - ermoglicht die gleichzeitige Verminderung der
`Partikel- und NOx-Emission bei Nutzfahrzeugdieselmotoren
`
`von Georg Huthwohl, Bernd Maurer und Gennadi Zikoridse
`
`1 Einleitung
`
`fOr schwere
`Der EU-Umweltrat hat sich am 21. 1 2.1998 auf neue Grenzwerte
`Nutzf ahrzeuge geeinigt. Dieser Vorschlag der Kommission stimmt in wesentlichen
`Punkten mit den Vorstellungen des Parlamentes uberein. Hierbei werden die
`Emissionsgrenzwerte fOr Stickoxide (NOx) und Partikel in 2 Stufen abgesenkt. Als
`Testzyklen werden der neue Europa Stationarzyklus (ESC = European Steady Cycle)
`und tur Fahrzeuge mit Abgasnachbehandlungssystemen zusatzlich der neue Europa
`Transient Test (ETC = European Transient Cycle) herangezogen.
`
`TABELLE 1 GRENZWERTVORSCHLAG DER EUROPAISCHEN KOMMISSION VOM 21. 12. 1998
`
`I Standard
`Jahr
`2005 EURO IV
`
`2008 EURO V
`
`i
`
`Zyklus
`
`ESC
`
`ETC
`
`ESC
`
`ETC
`
`Partikel (PM in g/kWh)
`0,02
`0,03
`0,02
`0,03
`
`Stickoxide (NOx in g/kWh))
`3,5
`3,5
`2,0
`
`2,0
`
`Zur Einhaltung der in T ABELLE 1 aufgefOhrten Grenzwerte wurde aus dem AUTO Oil
`Programm eine verbesserte Kraftstoffqualitat fOr die EU definiert. Hierbei liegt der
`maximale Schwefelanteil bei 50 ppm. Leider war bei der Entscheidung zu den
`fOr
`Kraftstoffqualitaten noch nicht die Entscheidung der Emissionsgrenzwerte
`Nutzfahrzeuge bekannt. Die definierte Kraftstoffqualitat paP-.t eindeutig nicht zu den
`geforderten Emissionswerten. So wird der im Kraftstoff enthaltene Schwefel beim
`Einsatz hochaktiver Oxidationskatalysatoren, wie sie beispielsweise im CRT®-System
`Verwendung finden, vollstandig zu Sulfaten oxidiert. Die Sulfate wiederum fOhren
`zusammen mit dem angelagerten Wasser zur Erhohung der Partikelmasse. Diese nur
`durch die Kraftstoffqualitat zu beeinflussenden Komponenten fOhren zwangslaufig zu
`Emissionswerten, die oberhalb des geforderten Partikelemissionsgrenzwertes liegen. Bei
`der quantitativen Umsetzung des Schwefels wird bereits bei einem Schwefelgehalt von
`14 ppm im Kraftstoff wird der Grenzwert van 0,02 g/kWh erreicht. Ein Ausweg aus
`dem Dilemma konnte in zwei van der Gesetzgebung zu verabschiedenden Schritten
`liegen:
`
`• Die Zertifizierung wird langfristig zugelassen mit einer gegenuber der auf dem Markt
`befindlichen verbesserten Kraftstoffqualitat, d. h. der Zertifizierungskraftstoff hat
`einen Schwefelgehalt von