Page 181 - Advanced Mine Ventilation

Diesel Exhaust Control 161

11.3 Diesel Exhaust Control Strategy

Thakur [5] and Schnackenberg [6] advocated separately a common strategy to mini-
mize diesel exhaust emissions. It consists of the following:

1. Reduce DPM generation.
a. Clean engines.
b. Clean fuel.
2. Collect/combust generated DPM.
a. A catalytic converter.
b. A soot filter on most engines.
3. Dilute DPM.
Adequate ventilation for all approved equipment to dilute DPM to safe levels.
4. Monitor DPM emissions.
Engine performance needs checked predeployment and postdeployment on a periodic
basis.
5. Maintenance.
Proper maintenance of diesel equipment is a must.
6. Training of mechanics and operators.
The operators and mechanics of diesel equipment must be properly trained, preferably by
the equipment manufacturers.

11.3.1 Clean Engines

The amount of DPM emitted in grams per brake horsepower (bhp) is known as “Spe-
cific DPM Emission” for the engine and it is a measure of clean engines. Only 20 years
back most permissible and nonpermissible diesel engines had very high DPM
emission.
Table 11.5 shows the specific emissions of some old and approved diesel engines.
The emissions are, obviously, very high. It required filters with 95% or better effi-
ciency to get an approval for mine use.
Fortunately, in the last 10 years, many diesel engine manufacturers have adopted
(1) turbocharging and (2) electronic ignitions that lowered the DPM emissions from
4 to 5 g/h for a typical 100 hp engine (a specific emission of less than 0.04e0.05 g/
bhp-h).
Each series of engines is tested by a certified laboratory in an 8-mode test according
to ISO 8178, protocol, C1 for off-road vehicles. These 8-modes are as shown in
Table 11.6 [7].
All gaseous and DPM emissions for a typical 8-mode test are reported as shown in
Table 11.7. All data are nonspecific to protect privacy of the manufacturer.

11.3.2 Clean Fuel
Traditionally all diesel fuels used in coal mines complied with ASTM D975 defined
standard for D 2 fuel. It had a sulfur content of 500 ppm (by weight), aromatic contents
less than 35%, and a cetane number of 40e48. Because sulfate typically constitutes