SMS Technology is an Australian-based
application of safe, commercially available and industrially
proven technology that can be used to address the issue of
air quality in and around road tunnels.
It is an innovative approach to the treating of particulate
and gaseous emissions in tunnels. By adding to and harnessing
the inherent energy content of the pollutants in tunnels,
SMS Technology reduces the toxicity
of tunnel air pollutants and creates an energy surplus that
can be exported from the tunnel for commercial benefit.
SMS Technology reduces the harmful
effects of emissions both within and outside the tunnel, reduces
the overall greenhouse impacts of the tunnel system, reduces
the capital and operating cost of the tunnel complex, and
provides an embedded energy source beneath the ground that
can be utilised commercially.
The approach adopted by SMS is to maximise the use of existing
technology and innovatively apply that to the challenges of
fugitive emissions management. On this basis SMS is focused
on applications and process development rather than the development
of science or new technology.
Key elements to the application systems that SMS is developing
include technologies covering:
selective extraction of pollutants,
filtering particulates,
destroying combustible gases,
reducing oxides of nitrogen and
production of steam.
These elements can be integrated into a comprehensive system
package, or alternatively applied as sub-units for specific
applications that do not require a fully integrated system.
Being proven technology, SMS Technology
brings to owners and operators a low-risk option for introducing
this new methodology. It safely manages tunnel ventilation
and emission reduction and allows for electricity generation.
It can be retrofitted to existing road tunnels, where the
current air quality and emissions are a cause for concern.
It can be custom designed for integration into new road tunnels
to deliver optimum internal and external environmental conditions
from day one, and throughout the life of a tunnel as the traffic
demand increases over time.
Specifically, SMS Technology offers
the following improvements over current technologies used
around the world:
Operating improvements
particulate and gaseous contaminants in tunnel ventilation
air can both be reduced progressively along a tunnel, avoiding
gradual build-up in hazardous pollutant levels;
oxides of nitrogen can be reduced before exhaust air is
released to the receiving environment;
the amount of air required in a tunnel to maintain safe
operating conditions can be reduced, commensurately reducing
the amount of exhaust air that must be released to the receiving
atmosphere;
exhaust gases released from a tunnel with an elevated
temperature are likely to disperse more efficiently throughout
the receiving environment;
adverse toxicological and greenhouse gas impacts from
tunnel exhaust air can be reduced;
visibility and air quality can be improved within a tunnel,
leading to improved safety for users and operators;
flexibility with tunnel ventilation arrangements and
discharge systems to the atmosphere can be introduced to
accommodate the multiple surface, underground and socio-political
demands.
Commercial opportunities
energy can be generated by the system and can be beneficially
utilised in the buildings, residences and industry around
the tunnel route;
the demand for remotely generated coal-based electricity
can be reduced and a new embedded supply of gas-based electricity
can become available within the city precincts, reducing
demand on the electricity supply grid;
low impact
exhaust air discharges from vehicular tunnels can be distributed
along the route of a tunnel, minimizing the cost of exhaust
systems, minimizing the visual and physical impost of exhaust
structures, and minimizing the social and environmental
impact of exhaust air at any point along the route of the
tunnel;
capital and operating cost of tunnel ventilation systems
can be reduced, and the system is capable of paying for
itself;
risks associated with owning and operating road tunnels
can be reduced and better managed;
In short, the SMS Technology approach
to managing emissions in tunnels can deliver sustainable financial,
social and environmental benefits relative to current systems.
This paper further explores this premise.
...
SITUATION ANALYSIS
Gaseous and particulate emissions from vehicles in tunnels
are causing considerable concern for owner-operators of tunnels,
regulators, town planners and the community. These emissions
typically comprise a mix of particulates and waste gases,
which can have a detrimental affect on human health and the
receiving environment.
In addition, the level of pollutants in tunnel air can reach
dangerously high proportions within and outside vehicles,
especially when there are traffic jams or when there is an
accident in a tunnel. If untreated, the fouled tunnel air
can become a major cause for concern when vented to the outside
atmosphere.
The two current drivers for vehicular tunnel ventilation
design are:
management of air flows in the tunnel in the event of
fires to permit safe evacuation of the tunnel, and
maintenance of pollutant concentrations within the tunnel
below specified international standards – in particular
for carbon monoxide and nitrogen dioxide.
However, external air quality considerations are emerging
as an issue to be addressed in urban traffic tunnels, where
there are significant numbers of people living and working
in the vicinity of tunnel portals and exhaust stacks. Of particular
concern to these neighbours are the particulates from diesel
engines and the nitrogen dioxide – both of which have
been demonstrated to have adverse impacts on human health.
And a further issue yet to fully emerge will be the potential
severe health impacts from very fine particulates emitted
from most motor vehicles.
The flow of air in vehicular tunnels for both normal operation
and in emergency fire situations is facilitated by the installation
of fans along the tunnel route and/or at exit points from
the tunnel; while the concentration of hazardous gases is
managed by flooding the tunnel with large quantities of fresh
air to dilute the pollutants.
At present, emissions of fouled air are forced from tunnels
via a ventilation discharge system that may comprise a central
stack or series of stacks, the tunnel portals, or separate
ventilation exhaust tunnels. The motive force to drive the
emissions from the tunnels is provided by large fans variously
located along, and at exhaust points from, the tunnels. These
fans consume significant quantities of remotely sourced, coal-derived
electricity, which is difficult to supply via already overextended
city power grids, and contributes to the greenhouse impacts
of our community.
Current systems for disposing of fouled air from tunnels
rely significantly on dispersion of the exhaust gases within
the receiving atmosphere and dilution of the pollutants across
a wide-spread body of air. The dynamics of the dispersion
process are complex, but can be numerically modeled, and are
affected by, amongst other factors, the mixture of gases emitted
from the tunnel, the velocity and temperature of the gases,
the temperature of the receiving atmosphere, ambient wind
and pressure conditions and the presence of pollutants in
the receiving atmosphere from other sources unrelated to the
tunnel exhaust.
Examples of current technology that may
be used to reduce particulate and gaseous emissions are electrostatic
precipitators, wet chemical scrubbers and bio-absorbing beds.
These technologies not only add to the capital cost of the
ventilation system, but also increase the operating costs
of a tunnel system and contribute further negative greenhouse
gas impacts themselves. In addition, these individually do
not fully address the damaging affects of exhaust gases on
human health.
In the majority of instances, the capital and operating costs
of the current air cleaning systems are often assessed to
exceed the environmental and public health benefits that such
air cleaning systems can deliver. Accordingly, those systems
are often reported either not installed in the first place,
or, if installed, not run on a continuous basis (Road Tunnel
Ventilation in Norway, Report by RTA September 2001).
...
SMS TURBINE TECHNOLOGY
SMS Technology uses the polluted air in
a tunnel as combustion-air in a conventional gas turbine engine.
In the process, the gas turbine engine:
imparts significant motivating force to the tunnel ventilation
air, possibly sufficient to move air during normal operations
without support from existing fans;
captures large particulate contaminants and oxidizes many
of the noxious gases and fine particulates;
reduces the environmental and human health damaging potential
of the polluting gases and particulates within and outside
a tunnel; and
affords opportunity for energy production and export in
the form of electricity or heat.
SMS Technology draws polluted air
from a tunnel into the turbine through a particle filter.
This filter captures large particulate contaminants in the
air and minimises fouling of the blades in the engine compressor
section of the turbine. The polluted air is then compressed
and mixed with natural gas or LP gas. It is then combusted
and the hot gas used to drive the power turbine.
The large particulates are regularly removed from the filter
using an automated system and collected for later removal
from the tunnel. The volatile gaseous and small particulate
pollutants are consumed in the combustion process in the gas
engine, with the engine oxidizing these pollutants to inert
gases comprised principally of water and carbon dioxide. With
standard turbines, nitrogen oxides in the exhaust gas can
be further reduced using commercially available catalysts.
Exhaust gases from the turbines can then
be cooled and released to the receiving atmosphere without
the same degree of concerns for human and environmental health,
as is the case with current tunnel ventilation technologies.
While in operation, the gas turbines can be coupled to generating
devices to create electrical energy. They can also be coupled
to fans to provide additional ventilation pressure to move
air within a tunnel.
...
APPLYING SMS TECHNOLOGY
The gas turbine systems of the SMS Technology
can be arranged in a number of configurations within a tunnel
and ventilation system. Typically the options could include:
a) A single turbine system installed off the side of
a tunnel.
Polluted gas from the vehicle tunnel would be drawn to the
location of the turbine system by the pressure differential
created by running the turbine, the pollutants reduced and
the cleaned exhaust air discharged to the external atmosphere
or returned to the main tunnel.
b) A single turbine installed at or near a discharge
point from a tunnel system, drawing some of the polluted
air from the ventilation system, reducing the toxicity of
the tunnel air and discharging cleaned air to the atmosphere.
Such an arrangement could be used to “bleed-off”
some of the total load from the ventilation system, reducing
the demand on the ventilation system and reducing the total
amount of pollutants discharged to the atmosphere. This
approach is very suitable for retrofit in existing tunnels
where current ventilation systems are struggling to maintain
health and environmental conditions at acceptable levels.
c) Turbines in a by-pass, cut-through or linking tunnel.
Polluted gas from the vehicle tunnel would be drawn to the
location of the turbine system in the bypass tunnel by the
pressure differential created by running the turbine, the
pollutants reduced and the cleaned exhaust air discharged
either back into the traffic tunnel to further dilute pollutants
or to the external atmosphere via a dedicated cleaned air
stack.
d) Multiple turbine systems installed along a tunnel.
Typically these could be micro turbines that might occupy
much the same space as the existing jet fans.
In this type of installation, each turbine system would
process part of the polluted air stream as it is drawn along
the length of the tunnel and through each turbine. In this
configuration, each turbine engine would impart motivating
force to the air stream as the turbines draw tunnel air
into the units and provide general thrust for the overall
tunnel ventilation system. Thus the turbines would maintain
ventilation pressure in the system, in a similar manner
to the existing jet fans, at the same time, reduce the pollutants
in the air that passes through each turbine. Exhaust from
these in-line turbines could be directed out of the tunnel
through small diameter bored vents that permit distributed
dispersion of cleaned air to the atmosphere along the length
of the tunnel route, or it could be discharged back into
the tunnel after cooling.
In most instances, the SMS
Technology would be installed to process and
clean-up only part of the tunnel air at any point, eliminating
the progressive build-up in pollutants that currently occurs,
and distributing along the length of the tunnel route relatively
small discharges of cleaned exhaust air that can be directed
to the surface for dispersion.
This approach also distributes the motivating force of the
turbines on the tunnel ventilation air stream along the tunnel,
keeping velocities managed to acceptable levels. It also distributes
both the energy demand and energy supply along the tunnel
route.
...
MANAGING POLLUTANTS
SMS Technology addresses both gaseous
and particulate pollutants. Self-cleaning filters at the inlet
to the gas turbines automatically capture and discard particulates
that exceed a pre-determined size. This clears the polluted
air of solid materials that could adversely affect the operation
of the turbine compressor system, and discharges those particulates
into receptacles for later removal from the tunnel.
Very small particles that pass through
the filter with the fouled air are burnt along with combustible
pollutant gases in the combustion zone of the gas turbine
engine. Collectively, they are converted into inert exhaust
gases comprised mainly of water and carbon dioxide. In the
process, the energy embodied in those pollutants is captured
by the turbine and converted into electricity.
The pollutants can be eliminated progressively along a tunnel,
maintaining the quality of tunnel air at safe levels at all
time and all locations. Alternatively, the pollutants can
be eliminated near exit points from a tunnel.
...
MANAGING TUNNEL AIR QUALITY
It is essential to maintain the quality of air in road tunnels
in a condition such that workers and users of tunnels are
not exposed to poor visibility and health-threatening conditions.
SMS Technology has the capability
to progressively reduce the particulate and gaseous pollutants
as they arise and thus maintain high levels of air quality
throughout the length of a tunnel.
The exhaust gases from current generation
turbines, coupled with suitable catalysts or reburner technology,
are the cleanest of all combustion-based engine systems, sufficiently
clean to permit re-introduction of exhaust gases from the
turbines back into the tunnel air stream, once the gas has
been sufficiently cooled.
Significantly, the application of SMS Technology
with progressive capture and reduction of in-tunnel pollutants,
reduces the demand in the tunnel for “diluting air”.
This leads to less air introduced into the tunnel, less fouled
air to be managed in the tunnel and less cost to operate the
tunnel ventilation system, without compromising in-tunnel
air quality.
...
MANAGING DISCHARGES TO ATMOSPHERE
SMS Technology cleans fouled tunnel
air of both particulate and gaseous pollutants before it is
discharged to the receiving atmosphere. The system also raises
the temperature of the air as it passes through the turbines.
This “waste” heat may be recovered for additional
energy purposes. Notwithstanding recovery of the waste heat,
residual heat can be left in the exhaust gases, generally
elevating the temperature of the air mass to be removed from
a tunnel.
The gases that are released to the atmosphere are primarily
inert and present little or no hazard to human health or the
receiving environment. Thus, the exhaust gases do not require
large elevated discharge stacks, which are needed with the
current foul-air discharge systems to disperse and dilute
the hazardous pollutants. In addition, the possibly elevated
temperature of the exhaust gases, over that of the receiving
atmosphere, will almost certainly improve the efficiency of
dispersion in terms of both the height of dispersion and improved
mixing dynamics.
In applications where SMS
Technology systems are located along the tunnel,
the discharges to atmosphere are relatively small in quantity,
requiring only small, distributed discharge points at intervals
along the route of the tunnel. These small volume discharge
points can be situated at surface locations either directly
above or slightly distant from the tunnel route, such as to
cause minimum intrusion and impact on the neighbouring community.
In particular, the structures used for the discharge at the
surface will be visually and physically unobtrusive.
...
MANAGING ENERGY
The gas turbine engines used in SMS Technology
can be direct coupled to generators to create electrical energy.
In addition, the waste heat from the turbines could be used
to generate hot water, steam or hot oil, with the hot fluid
used for process heat for industry, or for heating and cooling
industrial, commercial or domestic buildings. Alternatively
the hot fluid could be used to generate additional electricity
in a combined cycle application such as steam turbines or
Organic Rankine Cycle engines.
A tunnel with ventilation and pollution managed using SMS
Technology will be a net generator of energy
– satisfying the internal demands of the whole tunnel
complex and supplying surplus power into the local grid in
the vicinity of the tunnel route.
With SMS Technology
a city tunnel becomes a dual utility for the city, providing
clear and rapid thoroughfare for vehicles away from congested
city surface roads, as well as being an embedded power source
for the city, supplying power at peak demand times into city
buildings without placing additional demand on the existing
overloaded grid. It is possible that, a tunnel complex traversing
the CBD of one of Australia’s major cities might be
capable of supplying something in excess of 20 MW of power
into the city precinct power network.
The coincidence of peak ventilation and pollution control
demand within city traffic tunnels, with peak electricity
demand in the buildings and houses in the city, affords operators
of the SMS Technology power generating
plants a significant opportunity to export power to consumers
at those times when high demand prices are paid for electricity
from the grid. This can provide a significant independent
revenue stream to further reduce the total operating cost
of a city tunnel ventilation and pollution control system
and more rapidly repay the investment made in the technology.
...
MANAGING NITROGEN OXIDES
The gas turbine engine form of combustion used in SMS
Technology will reduce the amount of carbon
monoxide, small particulate matter, volatile organic compounds
and other unburnt hydrocarbon content of the polluted air
in a tunnel. This is achieved via oxidation – combustion
– of those pollutants in the gas engines and converting
them to inert exhaust gases comprised primarily of water and
carbon dioxide. However:
conventional gas turbine engines will not reduce the NOx
content of the tunnel pollution that is produced by the
motor vehicles in a tunnel; and
the combustion process within the gas turbine engines
will of itself, create oxides of nitrogen.
To overcome this issue of managing NOx emissions from road
tunnels, the following approaches can be applied with SMS
Technology.
a) Micro turbines are recognised to be the cleanest burning
of all combustion-based engines currently in use. Data from
installations in the USA demonstrate that per unit of power
output, the NOx emissions from micro turbines can be up
to –
- 60 times less than an internal combustion engine, and
- 25 times less than that from coal-fired power stations.
On this basis, the additional NOx added to the exhaust air
in a tunnel supported by micro turbine based SMS
Technology will be small relative to the NOx
already within the tunnel, and unlikely to contribute significantly
to the overall NOx emissions from the tunnel.
b) Using micro turbines along a tunnel, and targeting zones
of high pollutant concentrations within the tunnel cross
section, it is possible that a significant proportion of
pollutants in tunnel air can be extracted and treated, without
the need to process all of the air passing through a tunnel.
On this basis, and given the already low NOx emissions from
micro turbines, the increase in total NOx emissions from
the tunnel will be very small from a SMS Technology
supported tunnel.
c) An enhancement of the standard SMS Technology
could be the use of reburner technology, which has been
demonstrated to reduce NOx content of polluted air streams
that is drawn into the gas turbines.
The heat exchangers and extended surface reburner for this
particular application have been developed but have not
been configured for use with a standard turbine. The chemical
and physical restraints of such a system have been modeled
and tested but have not been used in this specific application.
The technology for this approach is the intellectual property
of one of the partners of Stack Management Systems Pty Ltd.
Such a reburner configuration could be co-located with a
standard gas turbine engine system at or near the main discharge
points for ventilation air from a tunnel. The combined system
could provide final clean-up of residual tunnel air pollutants
and virtually eliminate the emission of oxides of nitrogen
from the main tunnel ventilation system.
d) SMS has established a collaborative
agreement with the manufacturer and exporter of a new photocatalytic
paint that absorbs oxides of nitrogen. Designs have been
developed to apply this product onto existing air quality
management systems and remove significant amounts of pollutant
NOx and NO2.
e) Using SMS Technology does not
preclude the use of any of the existing NOx treatment systems.
If an existing technology is preferred for NOx then such
systems can be installed in the conventional manner in combination
with SMS Technology. Equally, with only a small increase
in NOx from the turbines, existing stack discharge practices
would most likely be permitted to continue.
...
MANAGING GREENHOUSE IMPACTS
Vehicular tunnel systems are known to have significant negative
greenhouse impacts. By contrast, a road tunnel supported by
SMS Technology can deliver major improvements over current
systems. Typically these improvements can be demonstrated
in:
reduced demand for coal-based electricity for the tunnel;
the lower greenhouse gas intensity of electricity generated
from gas relative to electricity generated from coal;
supply of gas-based electricity from the tunnel to nearby
industry and residences, to replace coal-based energy consumption
at those sites;
potential to reduce NOx emissions from a tunnel system;
and
reduction in the amounts of carbon monoxide, volatile
organic compounds and unburnt hydrocarbons from vehicle
emissions that are exhausted from a tunnel.
...
MANAGING RISKS
Implementing SMS Technology to
support operations of a road tunnel system provides owners
and operators a major platform for managing risks and demonstrating
genuine initiative to improving the management of pollution
associated with road tunnels.
For the “early-mover” tunnel owner/operator considering
the introduction of SMS Technology
it is essential to develop an implementation plan that minimises
risk and maximizes opportunity, at the same time demonstrating
a serious interest in improving in-tunnel and outside tunnel
air quality. SMS Technology offers
significant flexibility in this respect, and is very suitable
for a staged approach to introduction.
Given that the core components of SMS Technology
are commercially available and can be observed in operation
in many places around the world, there is very little risk
associated with the core equipment.
The key areas for effort, attention and management of risk
when introducing SMS Technology
for the first time will be in the associated engineering to
integrate the system into existing tunnels. Here again, the
staged approach that is possible with SMS Technology
will facilitate such introduction, allowing rapid progression
from proof of concept to fully functioning systems.
Beyond the first-starter risks inherent in adopting an alternative
approach, three other areas are emerging as key risk management
issues for owners and operators of road tunnels. These are:
increased regulation in the management of air quality
within and outside a tunnel;
increased awareness of communities to the potential health
threat from tunnel emissions; and
increased private sector ownership and operation of road
tunnels.
There is a growing expectation from both the community and
the regulators, that the current level of emissions and pollution
management strategies will not be tolerated into the future,
especially when alternative approaches are known to be cost
effective and available to manage pollutants and emissions.
With the introduction of new regulations and monitoring by
regulators and the community, it is reasonable to expect that
breaches of operating licences could lead to financial penalties
and possibly closure of a tunnel.
The community is becoming increasingly
educated about the issues and un-accepting of status quo approaches
that do not adequately address their concerns and questions.
The perceived grievances of the community rapidly become political
realities and often become the basis by which future operations
are permitted to proceed.
The transfer of ownership and operation of traffic tunnels
from the public sector to the private sector, of itself, does
not change the risk elements for owners and operators of a
road tunnel. However, it does significantly alter the risk
profile that the private sector owner and operator must assume.
...
MANAGING COSTS
A traffic tunnel complex that incorporates SMS Technology
from the outset stands to gain significant cost advantage
over tunnels that adopt current or conventional approaches
to ventilation and pollution control. While the initial capital
cost of gat turbine technology might be relatively high, the
following aspects contribute to a net positive financial picture
for a tunnel with micro turbines distributed along the tunnel
length:
fire suppression systems may be changed significantly,
the total amount of air required for tunnel ventilation
may be significantly reduced,
exhaust air discharge structures may become significantly
smaller and less costly,
power generated from the system supplies all of the needs
of the tunnel complex,
power can be exported from the tunnel complex at times
in the day when peak demand prices are maximized,
the ventilation and pollution control system becomes a
net revenue earning aspect of the tunnel complex,
the system may be fully amortised within a relatively
short period of the tunnel life.
CONTACT SMS
Postal Address: PO Box 877
Newport Beach, NSW, Australia, 2106
