Evaluation of Diesel Particulate Filter Systems at Inco's Stobie Mine
| Principal investigator(s): | Jozef Stachulak
(Inco Limited) |
| Co-investigator(s): | Bruce Conard
(Inco Limited) |
| Sponsoring Institution: | Inco Limited |
Objective
The objective of this study was to test the long-term effectiveness of diesel particulate filter systems (PFSs) to reduce the concentration of diesel particulate matter (DPM) in underground environments. Of particular concern was the ability of PFSs to sustain long-term filtration efficiencies under the often harsh physical environment that exists for equipment operating in mining service. The primary reason for the past failures of PFSs in mining was recognized as being an improper matching of a PFS to the vehicle on which it was expected to perform.
Method
The study was conducted under the auspices of the Diesel Emissions Evaluation Program (DEEP) at Inco’s Stobie mine from April 2000 to December 2004. Five heavy duty Load/Haul/Dump (LHD) scooptrams were selected as representing the primary heavy duty workhorse in underground mining. One of these units had a dual exhaust Deutz engine and the other four had Detroit Diesel DDEC 60 engines. Four Kubota tractors were selected as being representative of light duty vehicles, which are increasingly being used in transporting underground personnel. The duty cycles of the candidate vehicles were monitored for six months prior to selecting the PFSs for testing.
A number of different PFSs were selected for testing.
For heavy-duty LHDs:
Completely passive systems: an Oberland-Mangold PFS with a knitted glass fiber filter and a fuel-borne catalyst. An Engelhard PFS with a cordierite honeycomb filter the internal surfaces of which had been coated with a catalyst.
Completely active systems: Two from ECS/Unikat with a SiC honeycomb filter and used on-board electrical heating for regeneration; one from Arvin Meritor, with a cordierite honeycomb filter with a built in burner for regeneration.
Mixed passive-active system: a Johnson Matthey PFS with SiC or cordierite honeycomb filters. The passive part of the system used a fuel-borne catalyst and the active part used on-board electrical heaters.
For light duty tractors:
Active systems: an ECS/3M with a ceramic fiber filter medium and an on-board electrical heater; an ECS/Unikat with a SiC honeycomb filter and an on-board electrical heater; a DCL with a SiC honeycomb filter and an off-board electrical heater.
Tests on the PFSs were conducted every 250 hours of vehicle operation for heavy duty machines and monthly for light duty machines. During these routine periodic tests an ECOM instrument was used to analyze for NO, NO2, CO, CO2, and O2 and measure Bacharach smoke numbers upstream and downstream of each filter. Three more extensive periods of testing all PFSs were conducted during the summers of 2001, 2002, and 2004. These tests used three reproducible steady state engine conditions and analyzed gases and smoke numbers upstream and downstream of the filters, measured particulate concentrations using a photoelectric aerosol analyzer, measured particle size distributions using a Scanning Mobility Particle Sizer, and measure exhaust opacity.
Conclusions
- Both heavy duty and light duty vehicles in underground mining operations can be retrofitted with high efficiency Particulate Filter Systems (PFSs) for DPM removal. However, all of the systems tested in the Stobie Project required more close attention than was desired, although there existed a wide variation in the amount of attention needed. Ideally, a PFS would be invisible to a vehicle’s operator and almost invisible to the maintenance department. That is, people would go about their jobs in a conventional manner and would not need to pay attention to the filter or its regeneration. This was clearly NOT the case for any of the filters being tested in the Stobie Project and this remains a critical issue in any successful program for retrofitting or for installing PFSs as OEMs.
- Taking time to correctly match the vehicle duty with an appropriate PFS is essential for a retrofitting program to be successful.
- This matching must be done to correctly size the filter medium so that an acceptable soot collection period is obtained. Too small a filter will result in loading the filter too quickly and will negatively impact on vehicle productivity. Too large a filter will result in cramped space for the unit on the vehicle and this could negatively impact safe use of the vehicle and ease of its maintenance.
- This matching must be done to obtain the optimum method of regeneration of the filter. The optimum method of regeneration must take into account issues such as the complexity of the regeneration system, the period of time needed for regeneration, maintenance of components of the regeneration system, ease of installation and use, and cost.
- Proper communication with vehicle operators is essential. The presence of a filter on the exhaust manifold of an engine means that the filter, when working, will cause an increase in the backpressure of the engine. Operators must be attentive to non-conventional alerts and alarms for high backpressure or else serious harm could be done to the engine.
- Simple, but effective, dashboard signals of the state of the filter are needed in order to give information to the vehicle operator about the filter’s effectiveness.
- The increased emission of noxious gases is often a consequence of the way in which some PFSs regenerate and these emissions, particularly NO2 must be watched carefully. While there may exist ways to control such emissions, system complexity by adding on components is undesirable.
- An emissions-based maintenance component of an overall vehicle/engine maintenance program is essential. Proper functioning of a PFS should be evaluated as part of routine maintenance. Training of maintenance personnel in the specifics of each PFS is essential.
For more information:
jstachulak@inco.com
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