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 TissueControl10mg Photographs courtesy of Lung 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 DPFWith 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)‏

Soot Control Systems Compared

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 g/km

Progression of Euro Emission Limits For Trucks and Buses Over 85kW 0,36 8 0,15 7 PM [g/kWh] NO X [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, NO X [g/kWh] PM [g/kWh] EURO IV EURO V Current diesel engines EURO III EURO V (from 2008/2009)‏ EURO VI (from 2010)‏ proposals Cooled EGR + 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 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

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 : 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

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