K. Balagurunathan, V. Arumugham and D. Ganesh
Thermal Science Division, Anna University, Chennai
Abstract
Now a days, Diesel Engines are gaining much importance due to its better thermal
efficiency and high fuel economy. Hence it is widely used in automobiles,
industrial units and power plants . In recent years concern over the
contribution of diesel engine particulate emissions - particulate matter (PM)
and oxides of Nitrogen (NOx) to environmental pollution has resulted in a
significant increase in research and regulatory activity in this area world
wide.
In this work, the experimental investigation on particulate emission control
using uncoated and bimetal catalyst coated ceramic filters for different brake
power output have been investigated. The bimetal catalyst used are
Chromium-Copper, Chromium-Barium,Chromium-Calcium and Chromium-Ferrous
combination. The smoke intensity was found to be reduced by more than 63% by the
use of ceramic filters. Chromium-copper bimetal combination have yielded a
maximum trapping efficiency of 84 % whereas Chromium-ferrous bimetal combination
have yielded only 50.9 % trapping efficiency.
Introduction
In recent years, The concern over our environment has led to substantial
action by the executive and legislative branches of government both the state
and Federal level(USA). The sources of air pollution are mainly automobiles,
industrial units and power plants. It is estimated that about 20 to 30% of air
pollution arises from automobile emissions. The major emission from diesel
engines are particulate matter (PM), smoke and NOx. The NOx exposure to sunlight
release ozone. This increases the lung ailment. Ozone also escapes to rural
areas where it reduces crop yields.
The present investigation aims at trapping the particulate by ceramic filters.
Particulate trap technology is the only acceptable choice among all available
measure. Trap system is extremely efficient method to curtain the finest
particles with higher filtration rate.
Particulate Trap system represent the Best Available Technology (BAT). There is
no chance for an abnormal influence of the exhaust gas emission through the trap
system. But on course time, the filter becomes loaded with particulate and
further trapping of particulate becomes difficult. These particulate oxides at
temperature above 500oC and this temperature is not easily attained during
normal engine operation. Therefore, a mechanism is necessary for removing these
particulate by oxidation so as to facilitate further trapping of particulate.
This process is referred to as regeneration. In the present investigation, this
regeneration is achieved by coating the ceramic filter with different catalyst
materials. When the ceramic filter is coated with a catalyst, the regeneration
temperature is significantly reduced and the particulate oxidize at much lesser
temperature which can be achieved during normal engine operation. The
particulate emission reduction is experimentally investigated by geometric
measurements by using filter papers. Parameter such as PM,Trapping Efficiency,
Pressure drop, Brake thermal efficiency, specific fuel consumption and smoke
intensity before and after coating of the filter have been Investigated.
Literary Work:
Horiuch et al[1] investigated the reduction behavior of diesel particulate
and soluble organic fractions by flow through type oxidation catalysts under
steady and dynamic energies conditions using a current fuel of Sulphur content
of 0.38% by weight.
WR Wade et al[2] have assessed thermal and catalytic techniques for regulating
particulate traps.
Toshihino Mihare et al[3] prepared honey comb mullite fibre filter for
collection of solid particulate.
N.A. Kyrikis et al[4] have developed a model for simulating the behavior of the
ceramic filter.
John H. Johnson et al[5] have developed the control catalysts in response to
more stringent EPA standards for diesel emissive.
Experimental Work:
The experimental procedure involves the investigation of the following
parameters namely Brake power, Specific fuel consumption, Particulate emission
measurement, Trapping efficiency, Pressure drop, Smoke intensity.
Particulate Emission Measurement:
Particulate emission is measured by weighing the filter paper on a electronic
micro balance before and after collection. The paper is exposed to the exhaust
for a period of five seconds and particulate emission is measured in g/h. Then
the specific particulate matter is calculated by using the formula
Specific PM = g / kWh
Trapping Efficiency:
Trapping efficiency is calculated by using the formula (Raw emission - Emission
with ceramic filter)
The figure shows that the particulate emission is less for Chromium - Copper
bimetal coated ceramic filter. This is due to good catalytic oxidation of
particulates.
Trapping Efficiency
The variation of trapping efficiency for different filters with brake power is
shown in Figure (3) It shows that the trapping efficiency decreases as brake
power increases. This is due to the following reasons.
(i) Increase in velocity of exhaust gas due to increased brake power
(ii) Formation of more diesel particulates with increased brake power.
Chromium - Copper bimetal coated ceramic filter offers the maximum trapping
efficiency of 84% at full load and this is due to very good catalytic activity
of Chromium - Copper combination when compared to other bimetal combination.
Chromium - Ferrous bimetal combination gives trapping efficiency of 50.9% at
full load and this is lowest trapping efficiency among all catalyst coated
ceramic filters. The least trapping efficiency is observed with uncoated filter
and it is 47.8% at full load.
Pressure Drop
The difference in pressure developed between upstream and downstream of the
ceramic filter is known as pressure drop. The trap inevitably increases the back
pressure. The negative consequences are increased pumping work and thus a
proportional deterioration of fuel consumption.
The variation of pressure drop with brake power is shown in Figure (4) It shows
that the pressure drop increases with brake power because of higher exhaust gas
velocity and also due to the collection of more particulates in the ceramic
filter. The pressure drop is minimum for Chromium - Copper bimetal coated
ceramic filter when compared to the other filters because the regeneration
temperature of the Chromium - Copper combination is low and it is 4.2 cm of
water column at 70% load and 3.15 cm of water column at full load. Chromium -
Ferrous and Chromium - Calcium combination have more pressure drop compare top
Chromium - Copper bimetal catalyst coated ceramic filter. Uncoated ceramic
filter have maximum pressure drop of 9.5 cm of water column at full load because
of more collection of particulate.
Brake Thermal Efficiency
The variation of brake thermal efficiency with brake power is shown in Figure(5)
It shows that the brake thermal efficiency is slightly reduced with ceramic
filters for increase of brake power due to the back pressure developed. Figure
reveals that uncoated ceramic filters has maximum reduction in brake thermal
efficiency of 10.8% at full load. Chromium - Copper bimetal coated ceramic
filter have lesser reduction in brake thermal efficiency because of effective
regeneration and the value is 3.6% at full load.
Brake Specific Fuel Consumption
The variation of brake specific fuel consumption (BSFC) with brakes power is
shown in Figure(6) with the use of various ceramic filters, the BSFC decreases
with increase of brake power. Chromium - Ferrous combination has much increase n
BSFC and this s due to higher regeneration temperature and hence more back
pressure. Chromium - Copper bimetal coated ceramic filter have lesser increase
in BSFC of 0.034 g/kWh from without filter at full load.
Smoke Intensity
The variation of smoke intensities for different filters with brake power is
shown in Figure(7) It shows that the smoke intensity increases with increase of
brake power. The maximum smoke intensity is observed at maximum brake power.
With the use of catalyst coated ceramic filters, the smoke intensities are
reduced Chromium - Copper bimetal coated ceramic filter gives the maximum smoke
reduction and it is 78.8% at full load. Smoke intensity is maximum for raw
emission and it is 7.2 BSU at full load. Chromium -Ferrous bimetal coated
ceramic filter have a relatively higher smoke intensity among other filters.
To sum up the results it is emphasized that the performance depends on the
following parameters.
Particulate deposits in the filter depends on
