10
(90). This would be the case, particularly for the operations
in the Canadian provinces that adopted the PEL for NO2
based on the current ACGIH ® TLV ® of 0.2 ppm (91), or
for the operations in the European Union member states
that have to comply with the 8-hour time-weighted aver-
age NO2 PEL of 0.5 ppm and short-term NO2 PEL of 1.0
ppm (36). Therefore, optimization of the catalyst formu-
lations (92,93) for underground mining applications and
incorporation of NO2 control technologies such as SCR
in the systems would be critical to protecting the health
of underground miners. The results of previous evaluations
of NO2-suppressing catalyst formulations washcoated to
the elements in DOC and DPF devices retrofitted to the
“traditional” engines demonstrate that CO emissions can
be adequately reduced without adversely affecting NO2
emissions (39,79). In the cases of the engines evaluated in
this study, the lowest NO2 emissions were found for the
DOC/SCR/ASC equipped Engine 3. The promulgation of
the particulate number and more stringent nitrogen oxide
(NOx) emission standard (48) should result in the devel-
opment of the diesel power packages with power outputs
between 19 kw (25 hp) and 560 kW (750 hp) that should
concurrently manage particulate number concentrations
for NO and NO2 emissions.
In addition to relatively low tailpipe emissions, “clean”
engines should have an advantage over “traditional” engines
in terms of the relatively low blow-by emissions. In the
case of “traditional” engine, blow-by emissions typically
vented through the unfiltered or filtered crankcase ventila-
tion system could contribute to the emissions of aerosols
and gases, particularly those originating from lubricating
oil (59,94,95). In the case of “clean” engines evaluated in
this study, the blow-by emissions were vented back to the
engine intake through the closed crankcase breather sys-
tems and technically integrated with tailpipe emissions. It
is important to note that the blow-emissions of Engine 4,
equipped with open crankcase ventilation system, were not
quantified and included in total emissions.
The wide implementation of “clean” diesel engine
technologies has the potential to substantially change the
physical and chemical properties of diesel aerosols and the
composition of criteria gases in the underground workings.
In order to better protect the health of underground min-
ers from the adverse effects of exposure to diesel aerosols,
the traditionally used mass-based diesel aerosols exposure
monitoring methodologies (32,34) might need to be com-
plemented with those using number- and/or surface area-
based methodologies (96,97,98,99,100). The additional
information on the aerosol chemistry might be needed to
properly assess the health risk associated with exposure to
those diesel aerosols (96,97,100). Since NO2 was identified
as one of the primary toxic components of the exhaust of
“clean” diesel engines (62), the monitoring of NO2 expo-
sures should be strengthened to protect the health of the
workers spending time downwind of those engines.
CONCLUSION
The results of this study confirmed that widespread imple-
mentation of “clean” diesel technologies, similar to those
evaluated in this study, could help the industry to substan-
tially reduce the contribution of diesel-powered mobile
equipment to mass concentrations of EC and OC in
underground mines. The results indicate that the highest
reductions in contributions to both mass and number con-
centrations of diesel aerosols could be achieved if selected
“clean” engines, preferably in all pertinent power classes,
are equipped with viable full-flow DPF systems. The sig-
nificant reductions in mass concentrations of EC and OC,
at somewhat lower levels from those achievable with the
“clean” engines fitted with the full-flow DPF systems, could
be expected if “traditional” engines are replaced with the
“clean” engines equipped with DOC and DOC/SCR/ASC
systems. However, in the case of “clean” engines that are not
fitted with DPF systems, the reductions in number con-
centrations could be substantially lower than those in mass
concentrations.
For the generated test conditions, the aerosols emit-
ted by “clean” engines were found to be bimodally distrib-
uted between nucleation and accumulation modes. The
size of accumulation mode aerosols emitted by the non-
DPF “clean” engines were noticeably smaller than the sizes
of aerosols emitted by the “traditional” engine indicating
more effective in-cylinder combustion controls. Outside of
the regeneration events, the concentrations of nucleation
mode aerosols were found to be relatively low, substantially
lower than those of accumulation mode aerosols.
The secondary NO2 emissions for the “clean” engines
fitted with the DOC and DOC/DPF systems proved to be
one of the major factors affecting the selection of “clean”
engines for underground mining applications. The catalyst
formulations in the similar systems used in underground
mining applications need to be formulated to efficiently
control CO and HC emissions and support DPF regen-
eration without substantially promoting secondary NO2
emissions. The integration of SCR/ASC into “clean” engine
systems destined for the underground mining applications
could potentially provide an alternative solution to NO2
emissions. The relatively low CO emissions observed for
the engines evaluated in this study indicate that controlling
those emissions does not present a major challenge.
(90). This would be the case, particularly for the operations
in the Canadian provinces that adopted the PEL for NO2
based on the current ACGIH ® TLV ® of 0.2 ppm (91), or
for the operations in the European Union member states
that have to comply with the 8-hour time-weighted aver-
age NO2 PEL of 0.5 ppm and short-term NO2 PEL of 1.0
ppm (36). Therefore, optimization of the catalyst formu-
lations (92,93) for underground mining applications and
incorporation of NO2 control technologies such as SCR
in the systems would be critical to protecting the health
of underground miners. The results of previous evaluations
of NO2-suppressing catalyst formulations washcoated to
the elements in DOC and DPF devices retrofitted to the
“traditional” engines demonstrate that CO emissions can
be adequately reduced without adversely affecting NO2
emissions (39,79). In the cases of the engines evaluated in
this study, the lowest NO2 emissions were found for the
DOC/SCR/ASC equipped Engine 3. The promulgation of
the particulate number and more stringent nitrogen oxide
(NOx) emission standard (48) should result in the devel-
opment of the diesel power packages with power outputs
between 19 kw (25 hp) and 560 kW (750 hp) that should
concurrently manage particulate number concentrations
for NO and NO2 emissions.
In addition to relatively low tailpipe emissions, “clean”
engines should have an advantage over “traditional” engines
in terms of the relatively low blow-by emissions. In the
case of “traditional” engine, blow-by emissions typically
vented through the unfiltered or filtered crankcase ventila-
tion system could contribute to the emissions of aerosols
and gases, particularly those originating from lubricating
oil (59,94,95). In the case of “clean” engines evaluated in
this study, the blow-by emissions were vented back to the
engine intake through the closed crankcase breather sys-
tems and technically integrated with tailpipe emissions. It
is important to note that the blow-emissions of Engine 4,
equipped with open crankcase ventilation system, were not
quantified and included in total emissions.
The wide implementation of “clean” diesel engine
technologies has the potential to substantially change the
physical and chemical properties of diesel aerosols and the
composition of criteria gases in the underground workings.
In order to better protect the health of underground min-
ers from the adverse effects of exposure to diesel aerosols,
the traditionally used mass-based diesel aerosols exposure
monitoring methodologies (32,34) might need to be com-
plemented with those using number- and/or surface area-
based methodologies (96,97,98,99,100). The additional
information on the aerosol chemistry might be needed to
properly assess the health risk associated with exposure to
those diesel aerosols (96,97,100). Since NO2 was identified
as one of the primary toxic components of the exhaust of
“clean” diesel engines (62), the monitoring of NO2 expo-
sures should be strengthened to protect the health of the
workers spending time downwind of those engines.
CONCLUSION
The results of this study confirmed that widespread imple-
mentation of “clean” diesel technologies, similar to those
evaluated in this study, could help the industry to substan-
tially reduce the contribution of diesel-powered mobile
equipment to mass concentrations of EC and OC in
underground mines. The results indicate that the highest
reductions in contributions to both mass and number con-
centrations of diesel aerosols could be achieved if selected
“clean” engines, preferably in all pertinent power classes,
are equipped with viable full-flow DPF systems. The sig-
nificant reductions in mass concentrations of EC and OC,
at somewhat lower levels from those achievable with the
“clean” engines fitted with the full-flow DPF systems, could
be expected if “traditional” engines are replaced with the
“clean” engines equipped with DOC and DOC/SCR/ASC
systems. However, in the case of “clean” engines that are not
fitted with DPF systems, the reductions in number con-
centrations could be substantially lower than those in mass
concentrations.
For the generated test conditions, the aerosols emit-
ted by “clean” engines were found to be bimodally distrib-
uted between nucleation and accumulation modes. The
size of accumulation mode aerosols emitted by the non-
DPF “clean” engines were noticeably smaller than the sizes
of aerosols emitted by the “traditional” engine indicating
more effective in-cylinder combustion controls. Outside of
the regeneration events, the concentrations of nucleation
mode aerosols were found to be relatively low, substantially
lower than those of accumulation mode aerosols.
The secondary NO2 emissions for the “clean” engines
fitted with the DOC and DOC/DPF systems proved to be
one of the major factors affecting the selection of “clean”
engines for underground mining applications. The catalyst
formulations in the similar systems used in underground
mining applications need to be formulated to efficiently
control CO and HC emissions and support DPF regen-
eration without substantially promoting secondary NO2
emissions. The integration of SCR/ASC into “clean” engine
systems destined for the underground mining applications
could potentially provide an alternative solution to NO2
emissions. The relatively low CO emissions observed for
the engines evaluated in this study indicate that controlling
those emissions does not present a major challenge.