ABSTRACT
Air pollution is most important from the public health point of view, because everyindividual person breathes approximately 22000 times a day, inhaling about 15 to 22 Kg of airdaily. Polluted air causes physical ill effect decides undesirable aesthetic andphysiologicaleffects.Airpollutioncanbedefinedasadditiontoouratmosphereofanymaterial, which will have a deterious effect on life upon our planet. The main pollutantscontribute by automobiles are carbon monoxide (CO), unburned hydrocarbon (UBHC), oxidesof nitrogen (Nox) and Lead. Automobiles are not the only source of air pollution, other sourcessuch as electric power generating stations, industrial and domestic fuel consumption, refuseburning, industrial processing etc. also contribute heavily to contamination of our environmentso it is imperative that serious attempts should be made to conserve earth’s environment fromdegradation.Anaquasilencerisanattempt inthisdirection, it ismainlydealingwithcontrolof emission and noise. An aqua silencer is fitted to the exhaust pipe of engine. Sound producedunder water is less hearable than it produced in atmosphere. This mainly because of smallsprockets in water molecules, which lowers its amplitude thus, lowers the sound level. Becauseof this property water is used in this silencer and hence its name AQUA SILENCER. The noiseand smoke level isconsiderable less thenthe conventionalsilencer, itischeaper, no need ofcatalytic converter andeasy to install
CONSTRUCTION
Basically an aqua silencer (fig. 1) consists of a perforated tube which is installed at theend of the exhaust pipe. The perforated tube may have holes of different diameters. The verypurpose of providing different diameter hole is to break up gas mass to form smaller gasbubbles The perforated tube of different diameter is shown in fig. 2. Generally 4 sets of holesare drilled on the perforated tube. The other end of the perforated tubeis closed by plug.Around the circumference of the perforated tube a layer of activated charcoal isprovided and further a metallic mesh covers it. The whole unit is then placed in a watercontainer. A small opening is provided at the lop of the container to remove the exhaust gasesandadrainplugisprovidedatthebottomofthecontainerforperiodicallyCleaningofthecontainer. Also a filler plug is mounted at the top of the container. At the inlet of the exhaustpipe a non-return valveis provided which prevents the back flow of gases and wateras well.
WORKING PRINCIPLE
As the exhaust gases enters in to the aqua silencer, the perforated tube converts highmass bubbles in lo low mass bubbles after that they passes through charcoal layer which againpurifythe gases.Itishighly porous andpossesextrafreevalencessoithashigh absorptioncapacity.After passing over the charcoal layer some of the gases may dissolved in to the waterand finally the. exhaust gases escape through the opening in to the atmosphere. Hence aquasilencer reduces noise and pollution.
1.Mountings2.FillerPlug3.CharcoalLayer4.PerforatedTube5.WireMesh6.DrainPlug
EFFECTS OF DISSOLVED GASES ON WATER
The water is a good absorbing medium. In aqua silencer the gases are made to bedissolved in water. When these gases dissolved in water they form acids, carbonates,bicarbonates etc,
Action of dissolved SO2:-
When Sox is mixed in water, itform SO2, SO3, SO4, H2SO4, H2SO, i.e. sulfur Acid (H2SO3,), it forms Hydrogen Sulphide which causes fol rotten egg smell, acidify and corrosionof metals.
Action of dissolved CO2:-
The dissolved carbon dioxide forms bicarbonate at lower PH and Carbonates at higherPH. This levels 40-400 mg/liter. The form a scale in pipes and boilers. The carbon dioxidemixes with water to form Carbonic acid. Itis corrosive to metals and causes green house effect.
Effect ofdissolved NOx:-
TheNitrogeninwaterundergoesOxidationtoform ammonia,Nitrate,Nitrite,Nitricacid. This synthesis of protein and amino acids is effected by Nitrogen. Nitrate usually occursin trace quantities in surface water. A limit of 10 mg per liters Nitrate is affordable in drinkingwater.
METHODS TO CONTROL THE WATER POLLUTION
In aqua silencer the water gets polluted by the dissolved gases As in above topics saidthese gases are mixed with water to form carbonate, acids like carbonic acid, sulfuric acid, andNitrous acid etc. the petroleum products contains phenols which gives suffocating smell. Thesulfur gas mixes with water to form hydrogen sulfide, which give rotten egg smell. Theseshould be controlled to minimum the waterpollution.There are two methods:1)Limewaterwashmethod2)Absorptionprocess
LIME WATER WASH METHOD
The water is treated with the calculated quantities of slaked lime. One should have thequantitative analysis of water to go for this process. After mixing the heavy precipitates settledown assludge atthe bottom ofthe tankareremoved from time totime.Lime canneutralizeany acid present in the water. SO2, gases are removed from the flue gases forming calciumsulphate. The precipitates dissolved carbon dioxide as calcium carbonate and convertsbicarbonate ions into carbonates. Theequations are given below.The SO2gas is removed from the flue gases forming calcium sulphateCa(OH)2+ SO2...... CaSO3+H2oNeutralizes any acid present in water2HCL + Ca(OH)2...... Cacl2+ 2H2H2SO4+ Ca (OH)2...... CaSo4+2H20Precipitates bicarbonate as calcium carbonateCO2+ Ca(OH)2...... CaCO3+2H2OPrecipitates bicarbonate as calcium carbonateCa(HCO3)2+ 2Ca (OH)2...... 2CaCO3+ 2H20Converts bicarbonate ions (Like NaHCO3, KHCO3etc.) into carbonates.NaHCO3+ Ca(OH)2...... CaCO3+ H20 + Na2CO3
LIMITATIONS OF LIME WATER WASH METHOD
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Amount of neutralization capacity is limited
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It is very difficult tohandle
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Bridging and form areformed
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It is expansive
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Regeneration is possible
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Lime in any form it is difficult to handle
ABSORPTION PROCESS
Activated charcoal is available in granular or powdered form. As it is highly porous andpossess free valencies. So it posses high absorption capacity.Activated carbonis morewidely usedfor theremoval of tasteandodorousfrom thepublic water supplies because it has excellent properties of attracting gases, finely divided solidparticles and phenol type impurities, The activated carbon, usually in the powdered form isadded to the water either before or after the coagulation with sedimentation. But it is alwaysadded before filtration. Feeding devices are similar to those used in feeding the coagulants.
ADVANTAGES OF ABSORPTION PROCESS.
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It increases the coagulation power of the process.
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Its use reduces the chlorine demand.
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The excessive dose of activated carbon is not harmful.
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The treatment process is very simple and it requires nearly no skill.
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The efficiency of removing color, odour and taste is quite high.
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It can be easily regenerated
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It has excellent properties of attracting gases
CONCLUSION
The aqua silencer is more effective in the reduction ofemission gases from the engineexhaust using perforated tube and charcoal,
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By using perforated tube the backpressure will remain constant and the soundlevel is reduced.
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By using perforated tube the fuel consumption remains same as conventionalsystem.
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Byusingwaterasamediumthesoundcanbeloweredandalsobyusingactivated charcoal in water we can control the exhaust emission to a greaterlevel.
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The water contamination is found tobe negligible in aqua silencer.
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It is smokeless and pollution free emission and also it is very cheap. This aquasilencer’s performance is almost equivalent to the conventional silencer. It canbealsousedboth for twowheelers andfourwheelers and alsocan beusedinindustries.