NH3 exhaust gas fuel reforming tor diesel engine decarbonisation & lean NOx abatement over ...

211 Pages·2014·3.34 MB·English

by  Wang Wentao

NH Exhaust Gas Fuel Reforming for Diesel
3
Engine Decarbonisation & Lean NOx
Abatement over Silver/Alumina Catalyst

By

Wentao Wang

A thesis submitted to
The University of Birmingham for the degree of:
DOCTOR OF PHILOSOPHY

Department of Mechanical and
Manufacturing Engineering
School of Engineering
University of Birmingham
April 2014
University of Birmingham Research Archive

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ABSTRACT

The following thesis focuses on the potential roles and applications of ammonia in

transportation area, where ammonia is applied i) as a hydrogen carrier involved in a catalytic
reforming process for H production, ii) in its reformed form i.e. H – NH mixture for improved
2 2 3
NH combustion in CI engines (as a carbon – free energy carrier), and iii) as a reductant in engine
3
emission abatement under the incorporation of the NH3 reforming mechanism and catalytic
aftertreatment systems.
To implement the study, NH was firstly applied in a system of exhaust gas reforming under
3
diesel engine operation. The use of thermochemical recovery of the exhaust waste heat through
autothermal reforming mechanism with ammonia decomposition produced H – NH contented
2 3
reformate that is free of carbon.
Different amounts of NH reformate, either produced or simulated, were sent back to the
3
engine to replace part of the hydrocarbon fuel. The results showed that, under an intensive
combustion of the H content, the NH combustion could be thermally promoted and contribute to
2 3
significant reductions in CO , CO, THC and PM.
2
Following the above, the H – NH reformate‘s ignition, combustion and their effectiveness
2 3
in carbon removal were further strengthened by a liquid ignition improver i.e. diethyl glycol
diethyl ether (DGE), using the DGE‘s superior ignition properties and high oxygenation. While
the enhanced NH and H oxidations inevitably formed NOx, the use of DGE‘s was even shown to
3 2
suppress the engine NOx formation via its featured low temperature combustion.
i
Due to the fact that the reformate combustion could result in unburned NH and H , a
3 2
potential of associating these exhaust reformate with the engine emission such as NOx in a diesel
aftertreatment system was revealed. Therefore, both of the produced and simulated NH reformate
3
were applied with real diesel exhaust over an Ag/Al O – Selective Catalytic Reduction (SCR)
2 3
unit. This resulted in simultaneous NH – SCR and HC – SCR under H assistance. Over 90 % of
3 2
NOx reduction was obtained at low temperature and lean burn condition.
Finally, to prove the H assisted NH - SCR over Ag/Al O is associated with and improved
2 3 2 3
by a NO initiated intermediate mechanism i.e. NH /NO /NO – or ―Fast‖ – SCR, increased NO in
2 3 2 2
the SCR catalyst was achieved using the NH and H mixture (in the form of NH reformate)
3 2 3
and/or a use of Diesel Oxidation Catalyst (DOC) before the SCR catalyst. The results confirmed
the NO was essential over the Ag/Al O for low temperature NOx abatement, where part of the
2 2 3
―H effect‖ was to promote the silver catalyst‘s on – site NO formation, which in turn
2 2
strengthened the NH ‘s performance in the SCR process.
3

ii
Acknowledgement
I would like to express my deep sense of gratitude to my supervisors Dr. Athanasios Tsolakis
and Dr. Karl Dearn, for their guidance, experience and encouragement during my PhD study,
without them, a lot would be unachievable.
I‘m also grateful to Dr. Jose Martin Herreros for his advice, patience and technical assistance
to my research. The same is for all of the colleagues (friends) in the Future Power System Group.
The University of Birmingham and Department of Mechanical and Manufacturing
Engineering are acknowledged for the provision of a PhD scholarship for the duration of my study
A lot of thanks are given to Dr. Andrew York and our colleagues at Johnson Matthey
Technology Centre, Reading – UK, for the supply of the catalysts used in this research and for
their useful suggestions, advice and technical expertise throughout the experimental work. Shell
Global Solutions UK is acknowledged as well for the fuels used in this research.
At last but not least, I would like to give my sincere thanks to my wife Xiaoxi Zhang and my
parents Junmin Wang and Li Miao, for their yeas of invaluable support, care and love, without
these, this thesis would have been impossible.

Wentao Wang
April 2014
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CONTENTS
CHAPTER 1: INTRODUCTION ................................................................................................................... 1
1.1 Background ....................................................................................................................................... 1
1.2 Research objectives .......................................................................................................................... 5
1.3 Thesis outline .................................................................................................................................... 6
CHAPTER 2: LITERATURE REVIEW....................................................................................................... 10
2.1 Diesel engine operation .................................................................................................................. 10
2.2 Diesel emissions ............................................................................................................................. 13
2.2.1 NOx formation .................................................................................................................... 13
2.2.2 Particulate Matter (PM) ....................................................................................................... 15
2.2.3 Hydrocarbon emission......................................................................................................... 17
2.2.4 CO and CO emission ......................................................................................................... 18
2
2.3 Emission Control Technologies ...................................................................................................... 20
2.3.1 Exhaust Gas Recirculation .................................................................................................. 20
2.3.2 Aftertreatment ..................................................................................................................... 24
2.3.2.1 Diesel oxidation catalyst .............................................................................................. 24
2.3.2.2 Diesel Particulate Filter ................................................................................................ 26
2.3.2.3 Catalytic reduction of NOx .......................................................................................... 29
2.3.2.4 Ammonia and Urea SCR .............................................................................................. 30
2.3.2.5 Hydrocarbon SCR ........................................................................................................ 32
2.3.2.6 H assisted NH – SCR over Ag/Al O ........................................................................ 35
2 3 2 3
2.4 Alternative fuel/fuel substitution and dual fuel mode in diesel combustion ................................... 37
2.4.1 Biodiesel and oxygenated fuels ........................................................................................... 38
2.4.2 Hydrogen ............................................................................................................................. 41
2.4.2.1 Hydrogen combustion .................................................................................................. 41
2.4.2.2 Hydrogen storage ......................................................................................................... 43
2.4.2.3 Hydrogen on – board production .................................................................................. 44
2.4.3 NH and its potential vehicular applications ....................................................................... 47
3
2.4.4 Ammonia production and carbon/energy balance ............................................................... 53
2.4.4.1 NH production from biomass ...................................................................................... 54
3
2.4.4.2 Ammonium (NH + NH +) recovery from human and animal waste ........................... 56
3 4
2.5 Summary......................................................................................................................................... 60
CHAMPTER 3: EXPERIMENTAL SETUP ................................................................................................ 62
3.1 Test engine instrumentation ............................................................................................................ 62
3.2 Data Processing .............................................................................................................................. 63
3.3 Catalysts ......................................................................................................................................... 65
3.4 Mini Reactor Setup ......................................................................................................................... 66
3.5 Diesel Fuel ...................................................................................................................................... 69
3.6 Exhaust Gas Analysis and Measuring Equipment .......................................................................... 69
CHAPTER 4: AMMONIA AS A HYDROGEN CARRIER FOR TRANSPORTATION; INVESTIGATION
OF THE AMMONIA EXHUAST GAS FUEL REFORMING .................................................................... 73
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4.1 Introduction .................................................................................................................................... 73
4.2 NH decomposition over Ru – Al O catalyst ........................................................................ 76
3 2 3
4.3 Combined NH oxidation and decomposition: NH – ATR and NH exhaust gas reforming 79
3 3 3
4.3.1 Temperature profiles ........................................................................................................ 79
4.3.2 NH conversion and H production. ................................................................................ 81
3 2
4.4 Reforming efficiencies.................................................................................................................... 83
4.5 Summary......................................................................................................................................... 85
CHAPTER 5: COMBUSION OF NH REFORMATE ON DIESEL OPERATION; THE IMPACTS IN
3
ENGINE PERFORMANCE AND EMISSIONS .......................................................................................... 87
5.1 Introduction .................................................................................................................................... 87
5.2 The impact of small amount of reformate on engine combustion and emission ............................ 89
5.3 Effects on engine combustion and emission using reformate simulated at larger amounts ............ 95
5.3.1 Engine combustions under large amount of reformate additions ........................................ 95
5.3.2 Engine emissions under high amount of reformate addition ............................................. 102
5.4 Summaries: ................................................................................................................................... 108
CHAPTER 6: IMPROVED H – NH REFORMATE COMBUSTION FOR EFFECTIVE DIESEL
2 3
ENGINE DECARBONISATION THROUGH USE OF DGE AS AN IGNITION ENHANCER ............. 110
6.1 Introduction .................................................................................................................................. 110
6.2 Liquid fuel replacement ....................................................................................................... 113
6.3 Combustion characteristics ........................................................................................................... 114
6.4 Unburned gaseous additions and brake thermal efficiency .......................................................... 118
6.5 Gaseous emissions ........................................................................................................................ 120
6.6 Particulate matter emissions ......................................................................................................... 123
6.7 Summaries .................................................................................................................................... 126
CHAPTER 7: H – NH REFORMATE ASSISTED LEAN NOx ABATEMENT OVER
2 3
SILVER/ALUMINA CATALYST .............................................................................................................. 127
7.1 Introduction .................................................................................................................................. 127
7.2 H assisted NH – HC – SCR ....................................................................................................... 130
2 3
7.3 Influence of NH :NOx ratio on the SCR reactions ....................................................................... 133
3
7.4 Influence of the C :NOx ratio on the SCR reactions .................................................................... 137
1
7.5 Influence of NOx concentration in the SCR reactions.................................................................. 141
7.6 Summaries .................................................................................................................................... 144
CHAPTER 8: INCREASED NO CONCENTRATION IN THE DIESEL ENGINE EXHAUST FOR
2
IMPROVED H – NH – SCR ACTIVITY OVER Ag/Al O CATALYST ................................................ 147
2 3 2 3
8.1 Introduction .................................................................................................................................. 147
8.2 NO to NO conversion through H addition over DOC (Pt/Al O ) .............................................. 151
2 2 2 3
8.3 NO to NO conversion through H addition over Ag/Al O for NH – SCR reaction .................. 153
2 2 2 3 3
8.4 SCR activity at low reaction temperature (< 200 °C) with increased NO concentration ............ 155
2
8.5 SCR activity at high reaction temperature with increased NO concentration ............................. 159
2
8.6 Summaries .................................................................................................................................... 162
8.7 Appendix....................................................................................................................................... 164
CHAPTER 9: CONCLUSIONS ................................................................................................................. 166
v
LIST OF AUTHOR'S PUBLICATIONS AND AWARDS………………………………………….173
REFERENCE……………………………………………………………………………………………...174

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LIST OF FIGURES

Figure 1.1: European emission standards for passenger cars (EEC, 1993; EC, 1994; EC, 1996; EC,
1998a; EC, 1998b; EC, 2002; EC, 2007)…………………………………………………………..2
Figure 2.1: The phases of combustion of direct injection compression ignition engine……..…..11
Figure 2.2: EU CO emissions: (a) EU overall GHG emissions against the transport emissions, (b)
2
CO emissions in various sectors and (c) sources of CO in transportation sectors……………...19
2 2
Figure 2.3: Equivalence ratio – temperature region of diesel soot precursor formation…………23
Figure 2.4: Diesel particulate filter…………………………………………………………….....26
Figure 2.5: Reaction mechanisms for H assisted HC – SCR and NH – SCR over
2 3
Ag/Al O …………………………………………………………………………………………..37
2 3
Figure 2.6: Exchanging the glycerol compounds of the triglycerides molecules for lighter
compounds from the lighter alcohols……………………………………………………………..38
Figure 2.7: Combined urea storage and NH – H generator/separator
3 2
system……………………………………………………………………………………………..51
Figure 2.8: CO emission life cycle assessment of ammonia and petroleum being used in
2
vehicular application. Adapted from: S. Ishimatsu, T. Saika and T. Nohara; Ammonia Fueled Fuel
Cell Vehicle: The New Concept of a Hydrogen Supply System; SAE International, 2004 – 01 –
1925…………………………………………………………………………………………….…53
Figure 2.9: The flat membrane system adopted in poultry house for ammonium recovery; adapted
from M. J. Rothrock Jr., A. A. Szogi and M. B. Vanotti; Recovery of ammonia from poultry litter
using flat gas permeable membranes; Waste Management, 2013. 33(6): p. 1531 – 1538………58
Figure 2.10: Microbial fuel cell (MFC) system for ammonium recovery and energy production
from urine; adapted form P. Kuntke et al, Ammonium recovery and energy production from urine
by a microbial fuel cell; Water Research, 2012. 46: p. 2627 – 2636………………………….….59
Figure 3.1: Engine instrumentation……………………………………………...………….…....62
Figure 3.2: Detailed reactor/reformer setup and its schematic diagram…………………..…......67
Figure 4.1: Experimental setup for NH exhaust gas reforming………………..…...…………....75
3
Figure 4.2: NH decomposition over Ru – Al O catalyst: (a) 2 l/min (GHSV = 18000 h-1) of
3 2 3
pure ammonia decomposed at different temperatures, (b) 2 – 4 l/min of pure ammonia
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decomposition at different GHSV, and (c) ammonia conversion at different NH concentrations in
3
the NH – N mixtures and temperatures………………………………………………………….76
3 2
Figure 4.3: Temperature profiles: (a) and (b) temperature profiles of NH - ATR over 8g and 16g
3
catalyst beds (c) temperature profiles of NH exhaust gas reforming over 16g catalyst bed…....79
3
Figure 4.4: (a) NH conversion in NH – ATR at different O /NH ratios over 8g and 16g
3 3 2 3
catalysts; dotted line: 16g catalyst, solid line: 8g catalyst. (b) – (d): H production as a function of
2
NH concentration and O /NH ratio; (b) NH – ATR over 8g catalyst, (c) NH –ATR over 16g
3 2 3 3 3
catalyst and (d) NH exhaust gas reforming over 16g
3
catalyst………………………………………………………………………………………….…81
Figure 4.5: NH exhaust gas reforming Process efficiencies……………….........................……84
3
Figure 5.1: Experimental setup for large amount of simulated NH reformate applied in diesel
3
combustion……………………………………………………………………………………...…89
Figure 5.2: Engine in-cylinder pressure and rate of heat release at different reformate (produced)
additions………………………………………………………………………………………..….90
Figure.5.3: Engine performance and emissions under different NH reformate (produced)
3
additions: (a) engine brake thermal efficiency, (b) diesel fuel replacement, (c) CO emissions, (d)
2
total hydrocarbon emission, (e) CO emissions………………………………………….….……..91
Figure 5.4: Engine NOx emissions under produced reformate additions: (a) NO and NO
2
emissions, (b) N O emission…………………………………………………………….…….…..92
2
Figure 5.5: Diesel fuel replacement by different H and NH
2 3
additions…………………………………………………………………………………....…..….95
Figure 5.6: Coefficient of variation of IMEP under the H and NH additions at engine load
2 3
condition of (a) 5 bar IMEP and (b) 3 bar IMEP………………………………………………….96
Figure 5.7: In – cylinder pressure and ROHR of the combustions with different additions of H
2
and NH : (a) at 5 Bar IMEP and (b) at 3 Bar IMEP………………………………………………98
3
Figure 5.8: Engine brake thermal efficiencies and different combined additions of H and
2
NH ………………………………………………………………………………………………100
3
Figure 5.9: Unburned H and NH with different combined additions of H and NH : (a) H and
2 3 2 3 2
(b)
NH ………………………………………………………………………………………............101
3
Figure 5.10: NOx emissions obtained at different combined H and NH additions: (a) NO, (b)
2 3
NO and (c) N O…………………………………………………………………………………102
2 2
Figure 5.11: Carbonaceous emissions with different combined H and NH additions: (a) CO , (b)
2 3 2
CO and (c) THC…………………………………………………………………………………104
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