Page 187 - Advanced Mine Ventilation

Diesel Exhaust Control 167

Table 11.10 Comparison of Low- and High-Temperature Diesel Particulate Matter Filters

Low-Temperature High-Temperature
Characteristics Filters Filters
Heat exchanger Yes No
Cost $30e45,000 $3e5000
Size Very large Small and compact
Maintenance needed 8 h 2000 h
Collection efficiency (in conjunction 70%e95% 70%e90%
with a catalytic converter)

11.4 Diesel Exhaust Dilution

The ventilation air recommended by MSHA called the name plate ventilation (as
shown in Table 11.7) is adequate for dilution of gases in the exhaust. By judicious se-
lection of a catalytic converter and a filtration system, the DPM can also be diluted to
3
less than 0.12 mg/m with the name plate air. However, it is helpful to mathematically
analyze diesel applications in the coal mines to confirm that such assumptions are cor-
rect. Thakur [8] did extensive work in this area. Only a summary is presented here. For
details, the original work should be consulted.
There are four different applications of diesel equipment in coal mines as follows:

1. Single engine in a stationary mode.
2. Single engine moving in a straight airway.
3. Multiple engines (two to three) moving in a loop of straight airways.
4. Multiple engines (10e100 or so) working in a mine in different airways.
The last case was already analyzed in Chapter 5 of the book. The rest will be dis-
cussed here.

11.4.1 A Single Diesel Engine in a Single Roadway
Time-Independent Model:
The physical situation is represented by a stationary diesel engine (e.g., at loading
or unloading points and spot cleanup situations) and schematically illustrated in
Fig. 11.2.
The following assumptions are made for modeling:
1. Isotropic homogeneous turbulence, i.e., longitudinal coefficient of turbulent dispersions, (E x )
and transverse coefficient of turbulent dispersions (E r ) have same values.
2. Point source at the origin (0,0,0).
3. Concentration is being measured in the vicinity of the engine (i.e., no reflection from the
walls is likely), and hence, the free space solution is applicable.
4. Density of air and coefficient of dispersions is constant.