Diesel Particulate Filters. Overview The case for air quality management Explanation of diesel...

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