Antecedentes Institucionales

Research into new technology engines for the underground mining industry has not been as pronounced as the over-the-road diesel engine industry. This is due mainly to a small market and the lack of the same regulatory pressures as the over-the-road industry. In essence, whatever is developed for the large over-the-road industry will inevitably flow on to the underground mining industry. This process is well under way within the metalliferous industry with electronic controlled engines being in use for a number of years. The same cannot be said for the underground coal industry where newer generation engines are just starting to come on the horizon. This is especially the case within Australia where the Caterpillar 3126 engine is only now gaining acceptance.

Notwithstanding the above, considerable effort has been expended within the underground mining industry in recent years to demonstrate the benefits of newer design engines. Waytulonis (1992) reported on research at the US Bureau of Mines where the emissions from a normally aspirated diesel engine (Caterpillar 3304) of 1979 vintage were compared with a 1991 electronically controlled engine (DDC 8V-92 TA). Tests were conducted on a dynamometer at various peak torques (PT) and rated power (RP) settings (Table 6.1).

Table 6.1

Comparison of Exhaust Emissions From New & Older Design Engines

Engine Contaminant PT50 PT75 PT100 R50 R75 R100 Average

Detroit Diesel NOxg/kWhr 7.16 7.54 10.57 4.96 5.06 6.33 6.93

8V-92TA Particulates g/kWhr 0.07 0.075 0.084 0.07 0.055 0.055 0.070 Caterpillar NOx g/kWhr 12.60 8.28 4.05 12.48 9.30 5.19 8.66

3304 PCNA Particulates g/kWhr 0.23 0.12 0.70 0.84 0.31 0.21 0.40

What makes this comparison more impressive is the fact that the DDC 8V-92TA engine is 298.3 kW compared to 74.6 kW for the Caterpillar 3304 PCNA engine and that the results for the DDC engine were generated using a fuel with a sulphur content of 0.1% w/w versus 0.04% w/w for those results generated from the 3304 PCNA engine. It is clear from these results that the DDC 8V-92TA engine is much cleaner than the Caterpillar 3304 PCNA engine typically used in Australian underground coal mines. Grenier and Gangal (1993) evaluated the level of airborne emissions from an electronically controlled engine under mining conditions. In this project a Detroit Diesel 6V-92TA DDEC engine, installed in a Jarvis Clark haulage truck, was evaluated under haul and dump duty cycles under two different load requirements. Stationary sampling systems were established at the intake and exhaust points of the section of mine the vehicle was operating and measurements made for carbon monoxide, nitric oxide, nitrogen dioxide, sulphur dioxide and respirable combustible dust.

The conclusions from this study were that under the operating conditions of the test, concentrations of all measured contaminants remained well below the recommended worker exposure limits. No visible smoke was observed upon acceleration or on engine start-up.

In regard to engines used in the underground mining industry, an excellent comparison in regard to particulate generation is provided by the US Mine Safety and Health Administration (MSHA) via their “Particulate Index” for approved engines.

Under the MSHA index each engine undergoing the approval process is tested on a dynamometer and from the exhaust analysis MSHA determines the air quality necessary for dilution of the diesel particulate matter (measured gravimetricaly) to 1 mg/m3. Under these laboratory test conditions a lower particulate index is indicative of an engine with lower particulate matter emissions. These results are published on the MSHA website together with the particulate matter results in g/hr and g/bhp-hr.

Unfortunately this information has limited use within the Australian coal mining industry as none of the newer generation engines listed by MSHA are currently approved for use in NSW underground coal mines. Notwithstanding the above, it is interesting if a comparison is made between an engine commonly in use within Australian coal mines (Caterpillar 3306) and a new generation engine (Table 6.2).

Table 6.2

MSHA Particulate Index Data for Older & New Generation Engines

Engine Rated Power (kW) PI (m3_{/s) DP (g/kW-hr)}

Caterpillar 3306 PCNA 112 12.74 0.71 Detroit Diesel Series 50 DDEC 235 2.36 0.07

Given that the NSW Minerals Council (1999) recommends a best practice workplace exposure standard of 0.2 mg/m3 (measured as DP), the MSHA particulate index values would equate to 63.7 m3/s for the 3306 engine and 11.8 m3/s for the DDEC.

As the current minimum statutory ventilation rate for a Caterpillar 3306 PCNA engine is approximately 6.7 m3_{/s (based on}

the requirement of 0.06 m3_{/s/kW), it is doubtful that Australian}

operations could ever achieve the ventilation requirement prescribed by the MSHA process (especially when ventilation rates are additive for each individual engine). Newer generation engines would provide some opportunity to achieve MSHA ventilation requirements especially with lower power new generation engines instead of those indicated in Table 6.2.

From the above example it is clear that although newer generation engines bring significant benefit in reduced particulate generation, other control technologies may still be required if best practice workplace exposure standards are to be achieved.

6.5 METHODOLOGY AND TECHNIQUES 6.5.1 Introduction

The goal of the research detailed herein was to build on the initial work of Davies (2000) and attempt to make more precise emission comparisons, under mining conditions, between current transportation vehicles and a prototype transportation vehicle fitted with a newer design engine. As part of this exercise, techniques discussed in sections 2.4 and 3.2 of this thesis were utilised.