Diesel Particulate Filters
Dec 28, 2015
Diesel Particulate Filters
Overview
• The case for air quality management• Explanation of diesel filtration technology• Benefits of diesel particulate filters• Implementation study : beneficiaries• Costs and financial issues• Practical considerations : system installation• Fuel requirements• Summary
The Case For Air Quality Management
Why Filter Diesel Exhaust? Health Risk Figures : Denmark
• Danish figures published 2005 : in a population of 5 million:
– 3,400 early deaths– 3,300 additional cases of chronic bronchitis– 11,600 new cases of acute bronchitis in children under 15– 160,000 additional asthma attacks
caused by particulate emissions
Swiss Health Risk Assessment
• Mortality from air pollution is 5 x number of traffic accident deaths
• Ultrafine particles cited in mortality from air pollution• Highest risk groups:
• Children• People in cities: bus passengers• Truck and bus drivers
• Diesel particulate filters (DPFs) are efficient : best available technology
• Cost effectiveness assessed:– Health costs are 3 x cost of fitting DPFs
Effect of Diesel Particulates on Rat Lung Tissue
ContrControlol
10m10mgg
Photographs courtesy ofLung and Particles Research Group, School of Biosciences, Cardiff University
DPF Technology
Exhaust gas filter
Solid particles (soot) trapped
Clean gas emitted from tailpipe
Filter can be made of ceramic
Sintered metal filters also widely used and very satisfactory
Diesel Particulate Filter (DPF)
Silicon Carbide DPF Element:Widely Used Filter Medium
“Jet” Sinter-Metal Filter Element
Sintered Metal Filter
Without DPF With DPF
DPF - Removal of Particulates
Effect of Using Particulate Filter
• All gas passes through filter : no bypass used• Clean exhaust gas emitted from tailpipe• Soot builds up inside the channels in the filter• Back pressure increases with soot accumulation• Essential to remove soot for normal operation• Soot removal is called “filter regeneration”• If soot is not removed, engine will stop : vehicle
cannot be used : filter must be removed
Soot Control Process
• There are three methods of soot control• Approximate balance between rate of soot
accumulation and burn-out• Continuously regenerating trap, catalytic soot filter
• Soot accumulation followed by periodic regeneration
• Fuel borne catalyst
• Accumulation only, with external action to regenerate
• Burners, electrical heating
Soot Build-up And Burn-Out (Filter Regeneration With FBC)
Gategourmet - Ford Cargo 1513
0
200
400
600
800
1000
7:20 7:25 7:30 7:35 7:40 7:45 7:50
Date 6-May-04
Tem
pera
ture
(°C
)
-300
-200
-100
0
100
200
Pre
ssur
e (m
bar)
Pre-DPF temperature Post-DPF temperature Pre-DPF pressure
Sudden drop in back pressure from soot burn out
Increase in outlet temperature (exotherm) from soot burn outCold start at 7.22 am :
rapid warm up leading to soot burn out at 7.30 am
Load increase : body lifting
Soot Control Systems Compared
System Fuel borne catalyst DPF Platinum catalysed DPF systems
Burner and electrical systems
Good Wide application (New, old, large small) Very active – rapid soot
burn out Low duty cycle possible Compact Sulphur tolerant NO2 reduction
Excellent for big trucks, many buses
OE use Simple and elegant Totally passive Low maintenance in
many cases
Active control system Any duty cycle Back pressure control Sulphur tolerant No NO2 increase Low ash accumulation
Not so good
Additive dependent Ash accumulation Needs robust filter
Fewer applications Sensitive PM : NOx Sulphur intolerant Duty cycle limits Exotherm damage NO2 emissions
More complex More expensive Reliability long term Fuel consumption Electrical demand Higher maintenance
Benefits of Diesel Particulate Filters
DPF Emissions Benefits I• DPFs cut diesel particulates (PM) very
significantly
• Very beneficial : elimination of black smoke, large particles
• Clear benefit – truck exhausts visibly cleaner
• Visible benefit easily checked by smoke test
• In-service monitoring is simple
DPF Cuts Particulates Over 90%
Fifty trucks fitted with a DPF emit less PM than one truck without
Independent Test Data: Taxi Particulates With and Without DPF
0
0.05
0.1
0.15
0.2
0.25
Taxi # 1 Taxi # 2 Taxi # 3 Taxi # 4 Euro 3
No DPFWith DPF
g/km
Progression of Euro Emission LimitsFor Trucks and Buses Over 85kW
0,36
8
0,15
7
PM [g/kWh]
NOX [g/kWh]
5
0,10
3,52
0,02
0
EURO I (1992)EURO II (1996)EURO III (2000)EURO IV (2005)EURO V (2008)
Possible Strategies for EURO IV and EURO V for Heavy Commercial Vehicles
0
0,02
0,04
0,06
0,08
0,1
0 1 2 3 4 5 6 7 8 9 10 11 12
NOX [g/kWh]
PM
[g
/kW
h]
EURO IVEURO V
Current diesel engines
EURO III
EURO V (from 2008/2009)
EURO VI (from 2010)
proposals
Cooled EGR + DPF
DPF
DeNOx
Cooled EGR + modification of the injection system
DPF+DeNOx
Cooled EGR + Alternative combustion
process
Effect of Diesel Particulate Filter
• Typical particulates reduction: step of 2 Euro emissions limits
• If widely applied gives significant air quality benefits
• Euro II truck with DPF can meet Euro IV
• Euro II limit effective from 1996
• Euro IV effective from 2005
• Instantaneous effect : worth almost 10 years progress
Euro II Truck Particulate Emissions: Independent Data
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
DAF 45 DAF 85
Original equipmentEuro IV limitWith DPF
g/kWh
DPF Emissions Benefits II
• DPFs also cuts 99% invisible ultrafine particles
• Ultrafine particles : main health hazard associated with diesel particulates
• Ultrafines are ingested deep into the lung : can cause chronic lung disease
• With DPFs, exhaust gas close to ambient air particulate levels : major benefit to air quality
ELPI Particle Number Data From Euro III Truck
1 .E + 0 5
1 .E + 0 7
1 .E + 0 9
1 .E + 1 1
1 .E + 1 3
0 .0 1 0 .1 0 1 .0 0 1 0 .0 0
S iz e µ m (D 5 0 % )
Par
ticl
e em
issi
on r
ate
(num
ber/
s)
S ta n d a rd e x h a u s t
W ith D P F /F B C
Who Benefits From DPFs?
• Government : air quality is an emotive subject• Environmental bodies : DPFs are an effective tool • General population : pollution affects everyone• Medical profession : reduced respiratory disease• Drivers : pollution affects air inside cars• Vehicle manufacturers : cost effective PM
reduction increasingly being adopted by OEMs
Case Study
European Emission Controls
Particulate Regulations
• For vehicles and machines in enclosed spaces• Emissions control in place for some years
• Switzerland• Austria• Germany• Netherlands• Belgium
• Some countries control off road and on road emissions:
• Switzerland• Netherlands• Germany
Low Emission Zones
• Sweden - four in operation• Denmark - Copenhagen• Italy - Milan• Netherlands - Utrecht July 2007• Britain - London : starts Feb 2008• Germany : planned for 20 cities• Greece - expected for Athens• Spain - expected Madrid in 2008
London Low Emission Zone
• Will be implemented from February 2008• Affects big trucks initially• Will progessively affect smaller vehicles• Initially demands Euro III PM limit• In 2012 will demand Euro IV PM limit• DPFs expected to play major role• Follows earlier control of buses and taxis
Costs and Financial Issues
Cost of After Treatment Systems
• Diesel particulate filters specially designed
• Fabrication and installation mainly by hand
• Typical costs range from:• $3000 US for light duty installation : 3.5 tonne van
• $5000-$7500 US for mid range heavy duty truck : 10-20 tonnes
• Up to $10,000 US for 44 tonne truck
Funding and Implementation
• After-treatment can be mandated : most effective approach : can be combined with incentives
• Cost can be severe for some operators• Incentives in many countries:
• 30%-50% capital grant to operators can be provided• Rebate on vehicle licence each year (UK)• Annual inspection and function check : rebate if satisfactory
• Capital grant and licence rebate may be combined : needs control and inspection
• Payback time of perhaps 5 years is acceptable
System Design And Installation
System Design And Installation
• Requires the following facilities• Workshop• Stores• Fabrication capability• Installation control• In-service support• After sales, complaints handling, rectification
• Systems must be robust and well designed
• Installation by competent trained staff
Workshop Facilities : System Installation
Specialist Design Capability