1. INTRODUCTION:

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm and discomfort to humans and also to other living organisms, or damages the natural environment, into the atmosphere. These substances, called pollutants, can occur naturally or they can be produced by human activities. Natural pollutants include dust, pollen, salt particles, smoke from forest fires, and gases from organic waste. Most pollution caused by human activities is directly or indirectly the result of burning of fuels in furnaces or engines.

The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems. Air pollution in the world has emerged as the focus of environmental remediation efforts because of their toxicity and threat to human beings. Due to the rapid growth of industrialization and urbanization with new technological advancements, the existing environments are contaminated by emission from automobile and industries containing organics, color, heavy metal etc.

Reduction of greenhouse effect gases (GHGs) has taken the attention of researchers and scientists around the globe. In recent years, these concerns have risen than ever before. The large amounts of carbon dioxide (CO₂) being emitted into the atmosphere could cause severe global climate changes [2].

Recent atmospheric observations confirm that the concentration of CO₂ in the atmosphere has increased by nearly 30% for the last 150 years, with an accelerating trend in last year’s. In 1997, world community including India accepted Kyoto Protocol. Its importance and possible implementation was emphasized in 2005. The objective was to address the problem of climate changes occurring due to human activities. Protocols were defined to follow the footwork of UN Framework Convention on Climate Change (UNFCCC) [1].

This is the largest increase observed for any decade in at least the last 200 years. From 1999 to 2005, global CO₂ emissions from fossil fuel increased at the rate of roughly 3% by year [5]. Through human activities, mainly due to burning of fossil fuels and by cutting down of forests adds to greenhouse effect and rise sea level. The CO₂ concentration level in the atmosphere should therefore be stabilized or reduced. Following are the advantages of aqueous ammonia process for CO₂ separation from flue gases:

§ The rate of corrosion due to ammonia is low, i.e. aqueous ammonia does not pose a corrosion problem.

§ Aqueous ammonia has high loading capacity. Approximately 1.2kg of CO₂ can be absorbed per kg of ammonia.

§ The energy requirement for ammonia regeneration is predicted to be much lower.

The major by-products from the Aqua Ammonia Process include ammonium sulphate, Ammonium nitrate and Ammonium bicarbonate. Ammonium sulphate and Ammonium nitrate are well known fertilizers for certain crops. Ammonium bicarbonate has been utilized by certain developing countries as a crop fertilizer for over 30 years with proven results in farmland practice which enhanced crop root development and leaf growth [3].

Ammonium bicarbonate was rated by Kirk-Othmer [4] as having definite fertilizing value. Considering all these advantages of ammonia, a concept is visualized to implement ammonia as a replacement for Platinum and Iridium catalysts in mufflers or silencers. Ammonia absorbs SO₂, NOx, and CO₂ so as to reduce the atmospheric pollution. The main advantage of this exhaust system is that the whole other systems are unaltered, so this concept can be implemented on existing automobiles too. It is currently envisioned that the aqua ammonia process can be used in automobile exhaust systems to capture all three major acid gases (SO₂, NO_X, and CO₂) and also HF, which may be present in the flue gases.

1.1. Scope of the project

There has been an increasing concern in recent years over the increasing transportation and discharge of industrial waste waters into the environment. The automobile emission contains air pollutants and other species. Almost all pollutants are toxic in nature. Some of the examples are CO, CO₂, NO_X, and Hydrocarbon. Among the air pollutants, all are most effective pollutants. Hence, the removal of pollutants was selected for the present study. Several expensive techniques are available in developed countries. But in developing countries like India is not applicable since adsorption technique is less expensive and economically feasible, it has been selected for the present study using some cheap cost chemicals as an effective adsorbent. Therefore the objective of the present work was to test the ability of some chemicals in removing air pollutants from automobile emission.

1.2. Engine emissions

Engine emissions can be classified into two categories:

a) Exhaust emissions

b) Non-exhaust emissions.

1.2.1 Exhaust emissions

As already mentioned major exhaust emissions are:

a) Unburnt hydrocarbons,(HC)

b) Oxides of carbon(CO and CO₂),

c) Oxides of nitrogen,(NO and NO₂),

d) Oxides of sulphur,(SO₂ and SO₃),

e) Particulates and smoke.

The first four are common to both SI and CI engines and last two are mainly from CI engines. The main non-exhaust emission is the unburnt hydrocarbons from fuel tank and crankcase blow by [6].

Figure 1.1 .Amount of emission in exhaust flow

The figure 1.1shows the variations of HC, CO and NOx emissions as a function of equivalence ratio for an SI engine. It is clearly seen that all the three emissions are a strong function of equivalence ratio. As can be noticed from the fig that a rich mixture does not have enough oxygen to react with all the carbon and hydrogen, and both HC and CO emissions increase. For Ǿ<0.8, HC emissions also increase due to poor combustion and misfire. The generation of nitrogen oxide emissions is a function of the combustion temperature, highest near stoichiometries condition when temperatures are at the peak value. Maximum NOx emissions occur at slightly lean conditions, where the combustion temperature is high and there is an excess of oxygen to react with the nitrogen.

Figure 1.2 NO, CO, HC Concentrations

The Figure 1.2 shows a qualitative picture of HC, CO and NOx emissions with respect to equivalence ratio, Ǿ for a four- stroke DI diesel engine. As can be seen HC will decrease slightly with increase in Ǿ due to higher cylinder temperatures, making it easier to burn up any over- mixed (very lean) or under-mixed (rich) fuel-air mixture. At high loads, however, HC may increase again if the amount of fuel in regions too rich to burn during the primary combustion process. CO emissions will be very low at all equivalence ratios since excess air is always available. NOx emission will steadily increase as Ǿ increase due to increasing fraction of cylinder contents being burnt gases close to stoichiometric during combustion, and also due to higher peak temperatures and pressure. In the following section the causes for these emissions and their controls will be dealt with in detail.

1.2.2. Non-Exhaust Emissions

Apart from exhaust emissions, there are three other sources in an automobile which emit emissions. They are,

a) Fuel tank: The fuel emits fuel vapours into the atmosphere.

b) Carburetor: The carburetor also gives out fuel vapours.

c) Crankcase: It emits blow-by gases and fuel vapours into the atmosphere.

The fourth source is the tail pipe exhaust emissions. The contribution of pollutants by sources like evaporative losses and blow-by and tail pipe.

Percentage emissions of various pollutants are as,

By exhaust,

HC 50 to 60%, CO 100%, NO_x 100%

By fuel tank and carburetor evaporation,

HC 15 to 25%

By crankcase blow-by,

HC 20 to 35%.

The evaporative losses are the direct losses of raw gasoline from the engine fuel system, the blow-by gases are the vapours and gases leaking into the crankcase from the combustion chamber and the pollutants from the exhaust pipe are due to the incomplete combustion.

1.2.3. Study of conventional silencer

Automobile Silencer is a device used in automobile vehicles to reduce the noise produced by the exhaust gases from the engine. Silencers are also used in many other engines and generators. The size, shape and construction of silencer differ according to the type and size of the engine.

A muffler is a device for reducing the amount of noise emitted by the exhaust of an engine. Mufflers are installed within the exhaust system of most internal combustion engines, although the muffler is not designed to serve any primary exhaust function. The muffler is engineered as an acoustic soundproofing device designed to reduce the loudness of the sound pressure created by the engine by way of Acoustic quieting. The majority of the sound pressure produced by the engine is emanated out of the vehicle using the same piping used by the silent exhaust gases absorbed by a series of passages and chambers lined with roving fiberglass insulation and/or resonating chambers harmonically tuned to cause destructive interference wherein opposite sound waves cancel each other out. An unavoidable side effect of muffler use is an increase of back pressure which decreases engine efficiency. This is because the engine exhaust must share the same complex exit pathway built inside the muffler as the sound pressure that the muffler is designed to mitigate.

When the flow of exhaust gases from the engine to the atmosphere is obstructed to any degree, back pressure rises and the engine's efficiency, and therefore power, is reduced. Performance-oriented mufflers and exhaust systems, thus strive to minimize back pressure by employing numerous technologies and methods to attenuate the sound. For the majority of such systems, however, the general rule of "more power, more noise applies. Several such exhaust systems that utilize various designs and construction methods. The figure 1.3 shows the silencer.

Figure 1.3.Silencer

2. COMPONENTS AND DESCRIPTION:

2.1. Components

a) Perforated Tube.

b) Charcoal Layer.

c) Outer Shell.

d) Non Return Valve.

e) Flange.

f) H-Nipple.

2.2. Description

2.2.1. Perforated tube

The perforated tube consists of number of holes of different diameters. It is used to convert high mass bubbles to low mass bubbles. The charcoal layer is pasted over the perforated tube as shown in figure 2.1.

Figure 2.1. Perforated tube

2.2.2. Charcoal layer

The charcoal layer has more absorbing capacities because it has more surface area. This charcoal is called as Activated Charcoal as shown in figure 2.2. It is produced by heating the charcoal above 1500 ‘c for several hours in a burner. Its surface area gets increased.

Figure 2.2. Charcoal layer

2.2.3. Outer shell

The whole setup was kept inside the outer shell as shown in figure 2.3. It is made up of steel. The water inlet and outlet exhaust tube was provided in the shell itself.

Figure 2.3 outer shell

2.2.4 Non return valve

The non-return valve is a mechanical device, which normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. An important concept in check valves is the cracking pressure which is the minimum upstream pressure at which the valve will operate. Typically the check valve is designed for a specific cracking pressure. The Aqua silencer was filled with water and it is directly connected to the exhaust pipe of the engine. There is a chance for the water to get enter into the engine cylinder. To avoid this, Non return valve is used. It allows the flow of fluid in one direction only. The schematic diagram of non-return valve is shown in figure 2.4.

Figure 2.4 non-return valve

2.2.5 Flange

A flange joint is a connection of pipes, where the connecting pieces have flanges by which the parts are bolted together. Here flange is used to connect the silencer with the engine as shown in figure 2.5.

Figure 2.5 flange joint

2.2.6 H- NIPPLE

It is a device which is used to connect two pipes together. It consists of two threaded sides as shown in figure 2.6.

Figure 2.6.H Nipple

3. MATERIAL AND METHODS:

3.1. Construction

Basically an aqua silencer consists of a perforated tube which is installed at the end of the exhaust pipe. The perforated tube may have holes of different diameters. The very purpose of providing different diameter hole is to break up gas mass to form smaller gas bubbles the perforated tube of different diameter.Generally 4 sets of holes are drilled in the perforated tube. The other end of the perforated tube is closed by a plug. Around the circumference of the perforated tube a layer of activated charcoal is provided and further a metallic mesh covers it. The whole unit is then placed in a water container. A small opening is provided at the Top of the container to remove the exhaust gases and a drain plug is provided at the bottom of the container for periodical cleaning of the container. Also a filler plug is mounted at the top of the container. At the inlet of the exhaust pipe a non-return valve is provided which prevents the backflow of gases and water as well. The aqua silencer is shown in figure 3.1.

3.2. Working principle

As the exhaust gases enter into the aqua silencer, the perforated holes convert high mass bubbles into low mass bubbles after that they pass through the charcoal layer which again purify the gases. It is highly porous and possess extra free valences so it has a high absorption capacity. After passing over the charcoal layer some of the gases may dissolve into the water and finally the. Exhaust gases escape through the opening into the atmosphere.

Hence aqua silencer reduces noise and pollution.Exhaust gases are analyzed. Then 5 g of adsorbent is taken by weighing accurately. The filter was fixed exhaust hollow pipe as shown in figure 3.2. Then the filter fitted with the IC engine. Now engine was started and outgoing gases are analyzed at sequence time interval i.e. 60 min to 360 min. Then weight of adsorbent and flow rates are changed and analyzed.

Figure 3.2 Working principle

3.3. Effects of dissolved gases on water

The water is a good absorbing medium. In aqua silencer the gases are made to be dissolved in water. When these gases dissolved in water they form acids, carbonates, bicarbonates etc.

3.3.1Action of dissolved SO₂:-

When Sox is mixed in water, it form SO₂, SO₃, SO₄, H₂SO₄, i.e. sulfur Acid (H₂SO₃,), it forms Hydrogen Sulphide which causes rotten egg smell, acidify and corrosion of metals.

3.3.2Action of dissolved CO₂:-

The dissolved carbon dioxide forms bicarbonate at lower PH and Carbonates at higher PH. This levels 40-400 mg/liter. The form a scale in pipes and boilers. The carbon dioxide mixes with water to form Carbonic acid. It is corrosive to metals and causes greenhouse effect.

3.3.3Effect of dissolved NOx :-

The Nitrogen in water under goes Oxidation to form ammonia, Nitrate, Nitrite, Nitric acid. This synthesis of protein and amino acids is affected by Nitrogen. Nitrate usually occurs in trace quantities in surface water. A limit of 10 mg per liters Nitrate is affordable in drinking water.

3.4. 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, and Nitrous acid etc. the petroleum products contains phenols which gives suffocating smell. The sulfur gas mixes with water to form hydrogen sulfide, which give rotten egg smell. These should be controlled to minimum the water pollution. There are two methods:

a) Lime water wash method

b) Adsorption process

3.4.1 Lime water wash method

The water is treated with the calculated quantities of slaked lime. One should have the quantitative analysis of water to go for this process. After mixing the heavy precipitates settle down as sludge at the bottom of the tank are removed from time to time. Lime can neutralize any acid present in the water. SO₂, gases are removed from the flue gases forming calciumsulphate. The precipitates dissolved carbon dioxide as calcium carbonate and converts bicarbonate ions into carbonates. The equations are given below.

The SO₂gas is removed from the flue gases forming calciumsulphate.

Ca(OH)₂+ SO₂ CaSO₃+ H₂O

Neutralizes any acid present in water

2HCl+Ca(OH)₂ CaCl₂+ 2H₂H₂SO₄+ Ca (OH)₂ CaSo₄+ 2H₂O

Precipitates bicarbonate as calcium carbonate

CO₂+ Ca(OH)₂ CaCO₃+2H₂O

Precipitates bicarbonate as calcium carbonate

Ca(HCO₃)₂+ 2Ca (OH)₂ 2CaCO₃+ 2H₂O

Converts bicarbonate ions (Like NaHCO₃, KHCO₃etc.) into carbonates.

NaHCO₃+ Ca(OH)₂ CaCO₃+ H₂O+ Na₂CO₃

3.4.2 Limitations of lime water wash method

Ø Amount of neutralization capacity is limited

Ø It is very difficult to handle.

Ø Bridging and form are formed.

Ø It is expansive.

Ø Regeneration is possible.

Ø Lime in any form it is difficult to handle.

3.4.3 Adsorption process

Activated charcoal is available in granular or powdered form. As it is highly porous and possess free valences. So it possesses high absorption capacity. Activated carbon is more widely used for the removal of taste and odorous from the public water supplies because it has excellent properties of attracting gases, finely divided solid particles and phenol type impurities, The activated carbon, usually in the powdered form is added to the water either before or after the coagulation with sedimentation. But it is always added before filtration. Feeding devices are similar to those used in feeding the coagulants.

3.4.4 Advantages of adsorption process

Ø It increases the coagulation power of the process.

Ø Its use reduces the chlorine demand.

Ø The excessive dose of activated carbon is not harmful.

Ø The treatment process is very simple and it requires nearly no skill.

Ø The efficiency of removing color, odour and taste is quite high.

Ø It can be easily regenerated

Ø It has excellent properties of attracting gases.

3.5. Two stroke engine

Figure 3.3 Two stroke engine

A two-stroke, two-cycle, or two-cycle engine is a type of internal combustion engine which completes a power cycle in only one crankshaft revolution and with two strokes, or up and down movements, of the piston in comparison to a "four-stroke engine", which uses four strokes to do so(shown in figure 3.3). This is accomplished by the end of the combustion stroke and the beginning of the compression stroke happening simultaneously and performing the intake and exhaust or (scavenging) functions at the same time. Two-stroke engines often provide high power-to-weight ratio, usually in a narrow range of rotational speeds called the "power band", and, compared to 4-stroke engines, have a greatly reduced number of moving parts, are more compact and significantly lighter. The first commercial two-stroke engine involving in-cylinder compression is attributed to Scottish engineer Dugald Clerk

, who in 1881 patented his design, his engine having a separate charging cylinder. The crankcase-scavenged engine, employing the area below the piston as a charging pump, is generally credited to Englishman Joseph Day.

Gasoline (spark ignition) versions are particularly useful in lightweight (portable) applications such as chainsaws and small, lightweight and racing motorcycles, and the concept is also used in diesel compression ignition engines in large and weight insensitive applications, such as ships, locomotives and electricity generation. The heat transfer from the engine to the cooling system is less in a two-stroke engine than in a traditional four-stroke, a fact that adds to the overall engine efficiency; however, traditional 2-strokes have a poor exhaust emissions.

The two-stroke petrol engine was very popular throughout the 19th-20th century in motorcycles and small-engine devices, such as chainsaws and outboard motors, and was also used in some cars, a few tractors and many ships. Part of their appeal was their simple design (and resulting low cost) and often high power-to-weight ratio. The lower cost to rebuild and maintain made the two stroke engine incredibly popular, until for the USA their EPA mandated more stringent emission controls in 1978 (taking effect in 1980) and in 2004 (taking effect in 2005 and 2010). The industry largely responded by switching to four-stroke petrol engines, which emit less pollution. Most small designs use petrol lubrication, with the oil being burned in the combustion chamber, causing "blue smoke" and other types of exhaust pollution. This is a major reason why two-stroke engines were replaced by four-stroke engines in many applications.

Simple two-stroke petrol (gas) engines continue to be commonly used in high-power, handheld applications such as string trimmers and chainsaws. The light overall weight, and light-weight spinning parts give important operational and even safety advantages. For example, a four-stroke engine to power a chainsaw operating in any position would be much more expensive and complex than a two-stroke engine that uses a gasoline-oil mixture. These engines are still preferred for small, portable, or specialized machine applications such as outboard motors, high-performance, small-capacity motorcycles, mopeds, underbones, scooters, tuktuks, snowmobiles, kats, ultralights, model airplanes (and other model vehicles) and lawnmowers and dirt bikes. The two-stroke cycle is also used in many diesel engines, most notably large industrial and marine engines, as well as some trucks and heavy machinery. A number of mainstream automobile manufacturers have used two-stroke engines in the past, including the Swedish Saab and German manufacturers DKW and Auto. The Japanese manufacturer Suzuki did the same in the 1970s. Production of two-stroke cars ended in the 1980s in the West, but Block countries continued until around 1991, with the Trabant and Wartburg in East Germany. Lotus of Norfolk, UK, has a prototype direct-injection two-stroke engine intended for alcohol fuels called the Omnivorewhich it is demonstrating in a version of the Exige. As this uses direct fuel injection, there are dramatic decreases in emission levels and increases in fuel efficiency. The Construction connecting Engine and Aqua silencer is shown in figure 3.4.

Figure 3.4 Construction connecting Engine and Aqua silencer

3.5.1. Merits of aqua silencer

Ø No vibration when the engine is running.

Ø Starting the engine is easy.

Ø Control emission and noise in greater level.

Ø Carbon is precipitated.

Ø Easy to understand the working.

3.5.2. Limitations

Ø Frequent water filling is required.

Ø Silencer weight is more comparing to conventional silencer.

Ø Cost of activated charcoal is more.

4. RESULTS AND DISCUSSIONS:

4.1. Results analysis on emission

The Results analysis on emission without aqua silencer is shown in figure 3.5.The experimental set up is shown in figure 3.7.

Figure 3.5 without aqua silencer

The Results analysis on emission without aqua silencer is shown in figure 3.5

Figure 3.6 with aqua silencer

4.2. Results analysis on noise

Ø First the noise of the engine with 4-stroke single cylinder diesel engine in our laboratory was up to 105db.

Ø Then the noise produced after the aqua silencer was fitted up to 75db.

Ø Thus the noise reduction was achieved and the noise was measured by a using decibel meter.

Figure 3.7.Experimental set up

Table 4.1 Comparisons of emission pollutants

Petrol

Aqua silencer

Pollutants

%(or) ppm

Pollutants

%(or) ppm

LOAD 1

O₂

XAIR

NO₂

NO_X

SO₂

C_XH_Y

10.9

5.546

110

0.00

O₂

XAIR

P_I

NO₂

NO_X

SO₂

C_XH_Y

15.4

0.807

285

5817

LOAD 2

O₂

XAIR

NO₂

NO_X

SO₂

C_XH_Y

6.7

8.649

153

O₂

XAIR

P_I

NO₂

NO_X

SO₂

C_XH_Y

17.2

1.047

472

4946

LOAD 3

O₂

XAIR

NO₂

NO_X

SO₂

C_XH_Y

5.8

14.26

168

O₂

XAIR

P_I

NO₂

NO_X

SO₂

C_XH_Y

20.4

0.273

1391

32760

LOAD 4

O₂

XAIR

NO₂

NO_X

SO₂

C_XH_Y

9.3

9.144

2537

145

O₂

XAIR

P_I

NO₂

NO_X

SO₂

C_XH_Y

14.9

1.632

253

9617

Table 4.2 Comparison between aqua silencer and normal silencer

S.no	Aqua silencer	Normal silencer
1	Control emission and noise in greater level	Control noise in high level but doesn’t control emission
2	Carbon is precipitated	Carbon is not precipitated
3	It is very easy and cheap to construct	It is not very economical.
4	Perforated tube and charcoal is used to reduce noise and emission.	Muffler is used to reduce noise.
5	Weight is more slightly more than the conventional silencer.	Lesser weight.
6	Lesser smoke is produced	Smoke is produced.

5. CONCLUSION:

The aqua silencer is more effective in the reduction of emission gases from the engine exhaust using perforated tube and charcoal,

§ By using perforated tube the backpressure will remain constant and the sound level is reduced.

§ By using perforated tube the fuel consumption remains same as conventional system.

§ By using water as a medium the sound can be lowered and also by usingLimestone in water we can control the exhaust emission to a greater level.

§ The water contamination is found to be negligible in aqua silencer.

§ It is smokeless and pollution free emission and also it is very cheap. This aqua silencer’s performance is almost equivalent to the conventional silencer. It can be also used both for two wheelers and four wheelers and also can be used in industries.

6. REFERENCES:

[1]. UNFCCC, “The mechanisms under the Kyoto Protocol: joint implementation, the clean development mechanism and emissions trading” (2005).

[2]. Resnik, K.P., Yeh, J.T. and Pennline, H.W., “Aqua ammonia process for simultaneous removal of CO2, SO2 and NOx”, Int. J. Environmental Technology and Management, Vol. 4, Nos. 1/2, pp.89–104 (2004).

[3]. NPCC, “Study on CO2 sequestration by spray concentrated aqueous NH3 and production of modified NH4HCO3 fertilizer – a proposal for US – China joint research”, State Engineering Technology Research Center of Combustion of Power Plants (NPCC), China. (2000).

[4]. Kirk-Othmer, “Encyclopedia of Chemical Technology”, 2nd edition, Vol. 2.” (Ed.) (1963).

[5]. K. Thomsen and P. Rasmussen, “Modeling of Vapor-liquid-solid equilibrium in gas-aqueous electrolyte system”, Department of Chemical Engineering, Chemical Engineering Science 54 (1999).Singaram P . Removal of Chromium from tannery effluent by using water weeds. Indian J. Environ. Health Vol. 36(3); 1994:197-199.

[6]. P. Balashanmugam, G. Balasubramanian. Developments of Emission and Noise Control Device (Aqua Silencer). International Journal of Modern Trends in Engineering and Research.2 (1); 2015:209-222

[7]. http://www.epa.gov/nonroad/proposal/r01049.pdf

[8]. www.wikipedia.com

Received on 20.07.2015 Accepted on 26.09.2015

Research J. Engineering and Tech. 6(4): Oct. - Dec., 2015 page 418-426

DOI: 10.5958/2321-581X.2015.00065.3