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Emissions Control Technologies
→Ecoflex
→Catalytic
Converters - Gasoline
→Catalytic
Converters - Diesel
→Diesel
Particle Filters
→Thin
& Ultra Thin Wall Substrates
New emission
regulations being put in place throughout the world are aimed at
reducing the gaseous and particulate emissions into the atmosphere.
These regulatory drives demand the need to improve technology.
The market is moving to meet
these demands by:
- The introduction of more
efficient thinner walled catalytic converters. This is driving
force for Ecoflex® non-intumescent mat systems to enable thin
wall substrates to be supported and canned without risk of damaging
the monolith.
- Moving the catalytic converter
closed to the engine (close-coupled or pre-converter). This is
the driving force for higher performance materials to withstand
high operating temperatures (up to 1050°C) and high vibration
forces when the converter is connected directly to the manifold.
Ecoflex® mats deliver high temperature performance giving
outstanding durability in CCC applications.
- Introduction of Diesel Emission
Control Systems to remove both the particulate (DPF) and NOx (SCR)
from diesel engines.
Design Challenges
When designing a catalytic converter
the aim is to meet the emissions regulations set by the various
governing bodies whilst retaining engine performance.
Key considerations include:
- Engine type (i.e. Gasoline
or Diesel)
- Converter location (i.e.
close coupled, toe board, under body)
- Converter Size and Cell/Wall
Configuration
- Available space
- Hot face / shell requirements
- Acceptable pressure
drop (power loss) across the system
Catalytic Converters & Diesel
Particulate Filters
A catalytic converter helps control harmful emissions
from engine sources by converting the hydrocarbons (HC), nitrogen
oxides and carbon monoxide (CO) in the engine’s exhaust into
carbon dioxide (CO2), nitrogen (N2) and water (H2O) vapour.
The essential components of a catalytic converter
are as follows:
Substrate
A ceramic honeycomb structure (typically cordierite) made up of
mostly square channels, to which the exhaust gas can flow through
and over the precious metal catalyst. The channels provide a large
surface area for the application of wash-coat and precious-metal
catalyst to convert the engine exhaust to less harmful components.
The application trend in ceramic substrates is increase
the efficiency of the converter by manufacturing the internal walls
thinner and increasing the number of channels / cells (cell density).
The advantage of thin / ultra thin wall substrates
are a greater geometric surface area (active surface area) for catalytic
conversion so less catalyst can be used (base metal prices for catalyst
are US $ 300 – 700 / oz) or you can have a more efficient converter
to meet future regulations. However, thinner wall substrates are
also much more fragile so there is in increased risk of damage during
manufacture and operation with expanding support mats.
Washcoat
The washcoat is applied on to the ceramic substrate and contains
the active catalyst (precious metals such as Platinum, Palladium,
Rhodium) and converts the exhaust gases into less harmful gases
and water vapour.
Unique types of wash-coats and processes have been
developed by catalysing specialists to help auto manufacturers reach
specific goals, including: reducing the amount of precious metals
loading required to meet emissions regulations, accommodating a
variety of ceramic substrate material compositions and mitigating
the effects of engine fluctuations.
Active Substrates
This type of honeycomb combines an extruded ceramic with a catalyst
in one material. The current types have been developed preferred
for heavy-duty applications. Due to their low isostatic strength
the same design criteria can be applied as for ultra thin wall substrates.
Support Mat
The mat supports the ceramic catalysed substrate within the exhaust,
and provides a holding force on the system to prevent substrate
slippage at operating temperatures and vibration conditions. The
mat also insulates the system to ensure the shell temperature meet
the desired values. Mats are available typically in fibre only or
intumescent format.
Click
here for details of Ecoflex® Substrate Support Systems
Shell / Can
The shell is the outer metal component that houses the catalytic
converter and support mat and is integrated as part of the exhaust
system.
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