In my article, Emissions we have studied about emissions, types, contents of emission gases and their major sources viz. C.I. Engines and S.I. Engines.
We have also discussed about emission control in Petrol Engines and Diesel Engines particularly. The reason behind discussing these both sources is that, they are the sources which contribute highest in total Worlds’ Emissions. Here We will see some more kind of Emission Control Devices.
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Emission Control Devices:
1. Catalytic Converter:
Catalytic converter is the device which is fitted on the way of outgoing gases from the engine to atmosphere. Catalytic converter compromises of some chemicals or active chemicals which reacts with content of outgoing gases like CO and NOX. Moreover, they take part in reaction as catalyst which causes their presence unchanged at the end of reaction. After reaction reactants like CO are converted into acceptable emissions like Carbon Di Oxide. Depending upon fuel quality, catalyst material, working temperature etc. life of catalytic converter varies. But generally they have good life and produce effective results.
Some of Major Kinds of Catalytic Converters are As Below:
a. Fast Light off Catalyst:
Allows the catalytic converter to work sooner by decreasing the exhaust temperature required for operation. Untreated exhaust emitted at the start of the legislated emissions test and on short journeys in the real world is curtailed. Changes to the thermal capacity of substrates and type and composition of the active precious metal catalyst have together affected big improvements.
b. Hydrocarbon Adsorber System:
They incorporate special materials, such as zeolites, into or ahead of the catalyst. Hydrocarbon emissions are collected when exhaust temperatures are too low for effective catalyst operation. The hydrocarbons are then desorbed at higher temperatures when the catalyst has reached its operating temperature and is ready to receive and destroy the hydrocarbons.
c. Electrically Heated Catalyst System:
As name suggest, it is provided with electrical heater for heating the catalyst material. At higher temperature, rate of reaction grows and hence electrical heating encourages the catalyst work better.
d. Lean Combustion:
Lean combustion is essential to limit carbon dioxide emissions and to reduce fuel consumption. New diesel technologies with greater use of electronic management and direct injection with unit injectors or common rail injection, can achieve further fuel consumption improvements. The conventional three-way catalyst technology used on petrol engines needs a richer environment with lower air:fuel ratios to reduce NOx, so a radical new approach is required.
e. DeNOx (or Lean NOx) Catalysts:
f. NOx adsorbers (NOx traps):
g. Thermally Durable Catalyst:
So, these are various methods of emission control by using Catalytic Converter. There is one more method for Controlling of NOX from engine.
Exhaust Gas Recirculation:
Exhaust gas recirculation is one of the popular methods now a days. This method mainly controls the NOX emissions. NOX is generated due to very high engine temperature which ranges from 1000 to 1100 degree Celsius. Engine runs at such high temperature due to rich mixtures provided for combustion. In EGR method on the part of outgoing (exhaust) gases is redirected to the input of engine. This suppresses the richness of mixtures. This causes to lower down the temperature of engine which in turn lowers the NOX percentage in exhaust.
More Emission Control Measures are provided in next article.