nirma university institute of technology handout: … · 07.12.2013 · nirma university institute...

Nirma University Institute of Technology

Handout: 2CH002 -APCT July -2014 Lecture 1, 2:

Topics to be covered:

• Air Quality monitoring & its objectives • Classification of sampling methods • Difficulties encountered in sampling • Preliminary considerations and stages of sampling:

Air quality monitoring: Sampling and measurement of air pollutants generally known, as air quality monitoring. Monitoring is important: 1) Air quality can be evaluated 2)Information is helpful in implementing control measures for reducing pollutant concentration to acceptable levels 3) Assessing the effect of air pollution control strategies. Classification of sampling methods:

1. Sampling of impurities of every nature (Ranging from particulate matter to gases)

2. Sampling under various environmental conditions (ranging from samples taken from chimneys to samples taken in the open air)

3. Sampling methods varying according to the time factor (Ranging from intermittent to continuous sampling)

Air Quality measurement is undertaken in two situations:

1. Ambient air quality measurement 2. Stack monitoring

Ambient air quality measurement: Where the pollutant levels in the ambient atmosphere are measured. Stack sampling: It deals with the pollutants emitted from a source such as smoke stack and is known as stack sampling. Difficulties encountered in sampling: 1)Collecting samples of true representative character 2) Errors arising from methods used for the collection and separation of the various components of pollution.3) Difficulty in preventing any change in the concentration of particulate matter in suspension, as a result of sampling operation. Preliminary considerations and stages of sampling: Following principles should be followed to ensure correct sampling : 1) Statistical studies 2) Size of samples 3) Change in the sample during and after sampling 4) Continuous and intermittent sampling 5) Sampling of volatile constituents 6) Sampling of particulates 7) Sampling of waste gas 8) Sampling in the open air ------------------------------------------------------------------------------------------------------------


Handout: 2CH002 -APCT July -2014 Lecture 3, 4:


• Basic consideration of air sampling • Instruments for sampling waste gases and for atmospheric sampling

• Devices for general use : Meters, probes, suction devices • Devices for sampling gases and vapors: Absorbers , Adsorption

Basic consideration of air sampling 1. The sample collected must be representative in terms of time and location 2. The sample volume should be large enough to permit accurate analysis 3. The sampling rate must be such as to provide maximum efficiency of collection 4. The duration of sampling and frequency of sampling should reflect accurately the

occurrence of fluctuations in pollution level 5. The contaminants must not be modified or altered in the process of collection

Instruments for sampling waste gases and for atmospheric sampling 1. Devices for general use 2. Devices for sampling gases and vapors 1. Devices for general use

Meters: They are used to determine accurately the volume of the gas collected. Probes: They are tubes suitable for penetrating into the gas stream. Suction Devices: Any suction device that has the required volumetric capacity can be used.

2. Devices for sampling gases and vapors Absorption: The penetration of airborne chemicals into a collection medium, such as impinger fluid, where the chemicals will dissolve and chemically react.


Handout: 2CH002 -APCT July -2014 Adsorption: The collection of gases and vapors onto the surface of a collection medium such as the solid adsorbent material in adsorbent tubes.

(i) Absorbers:

Effluent gases are passed through absorber (scrubbers) which contain liquid absorbents that remove one or more of the pollutants in the gas stream. Absorbent are being used to remove sulphur dioxide, hydrogen sulphide, shulphur trioxide and fluorides and oxides of nitrogen Equipments using the principle of absorption for the removal of gaseous pollutants includes (1) Packed tower (2) Plate tower (3) bubble cap plate tower (4) Spray tower (5) Liquid jet scrubber absorber. A gas can be sampled by means of a suitable absorption reagent. For this purpose, U-shaped absorbers are used.

Sampling is carried out at an average rate of about 100 – 150 liters per hour of gas stream.

------------------------------------------------------------------------------------------------------------ Lecture 5:


• Instruments for sampling waste gases and for atmospheric sampling • Devices for sampling gases and vapors: Adsorption, Condensers,

Collector under reduced pressure, Plastics containers, Samples for Mass Spectrometric analysis

• Duration of Sampling Period: (1) Short period or Spot sampling and (2) Continuous sampling


Handout: 2CH002 -APCT July -2014 Devices for sampling gases and vapors (ii) Adsorption:

Adsorption is brought about by aspiring the air or gas to be sampled through adsorption column containing silica gel, activated charcoal or another suitable agents. Application: used for ozone and light H/C

(iii) Condensers:

The gas stream sampled is cooled in suitable containers, thus bringing about the condensation of the Volatile substances. Used for the sampling of odoriferous substances.

(iv) Collector under reduced pressure:

The absorbent solution chosen is first introduced into the bottle and the pressure is thus reduced. Then the sample is admitted until the internal and external pressures are equal and the container is shaken continuously so as to ensure maximum absorption. Use for sampling the oxides on N2

(iv) Plastics containers:

Special polyethylene bags/plastics are used for collecting and transporting large volume of air. .Used for grab sampling and sample storage before analysis

(v) Samples for Mass Spectrometric analysis Duration of Sampling Period: Two types of sampling are used (1) Short period or Spot sampling and (2) Continuous sampling Spot sampling: Samples are collected over periods varying from less than 30 minutes to several hours for specific proposes. Continuous sampling: It can be carried out by the subsequent analysis of pollutant by appropriate analytical techniques. Gaseous pollutants: continuous monitoring Particulates: once every three days


Handout: 2CH002 -APCT July -2014 Lecture 6: Topics to be covered:

• Location of sampling sites: • Collection of Gaseous air Pollutants:

1. Grab sampling 2. Absorption in liquid 3. Adsorption on solids 4. Freeze-out Sampling

Location of sampling sites: Sampling sites must be carefully selected so as o be representatives of the area under study. Collection of Gaseous air Pollutants:

5. Grab sampling 6. Absorption in liquid 7. Adsorption on solids 8. Freeze-out Sampling

1. Grab sampling

Whole air can be inhaled up to the atmospheric pressure when a highly

evacuated cylinder is brought to the sampling place and its inlet valve is opened and closed. In case of the sampling on the ground or in an airplane, a mechanical pumping system is sometimes used to compress the sample air. These are called 'grab sampling' methods, which are applicable to the case that the atmospheric pressure is rather high, that is, on the ground or on a mobile station like an airplane, or up to the lower stratosphere.

Advantages: It is very simple. It is often used for an onboard sampler.


Handout: 2CH002 -APCT July -2014

Disadvantages: The volume of the sample cylinder must be larger as the sampling altitude becomes higher, because of rapid decrease in atmospheric pressure as altitude.

Surface to volume ratio (total area of the inner surface of the cylinder to its volume) becomes smaller, and therefore effect of adsorption or resolution of minor constituents on the inner surface may be appreciable.

Applications: This method is applicable to the case to sample the stable minor constituents of rather large mixing ratios, such as CH4, CO, CO2, H2, N2O, CF2Cl2, CFCl3.

2. Absorption in liquid Absorption separates the desire pollutant form air either through direct solubility in the absorbing medium or by chemical reaction.

1. Fitted glass absorber 2. Impingers 1. Fitted glass absorber

The gas stream is broken up into extremely small bubbles, thus promoting an intimate contact between the gas and the liquid. Frits designated coarse (50micron m pore size) are used for air sampling.

2. Impingers In the Impingers the gas stream is impinged at high velocity onto a flat surface thus providing good contact between the gas and liquid. The flat surface can be the bottom of the collector or a specially designed pate. Two types of Impingers: (1) Wet Impingers (2) Dry Impingers

Wet Impingers Collect a particle by causing them to impinge a surface submerged in a liquid. Dry Impingers: Referred to as impactors collect particles by impaction on a dry surface.

There are two types if Impingers (wet collector)

(i) Greenberg- Smith (ii) Midget type

Devices can handled sample flow rate of about 30 and 3 liter per minute respectively



Midget fitted impingers Standard midget impingers

Adsorption on solids: The sample air is passed through a packed column containing a finely divided solid adsorbent on whose surface the pollutants are retained and concentrated. Solid adsorbent: Granular porous solids: Activated Charcoal, Silica gel Disadvantages: Desorption of gases are complicated


Handout: 2CH002 -APCT July -2014 Freeze out Sampling: In freeze out sampling a series of cold traps, which are maintained at progressively lower temperature, are used to draw the air sample, whereby the pollutants are condensed. The traps are brought to the laboratory, the samples are removed and analyses by means of gas chromatographic, infrared or ultraviolet, spectrophotometer, and mass spectrometry or by wet chemical means. Disadvantages: Plugging of the system because of Ice formation ------------------------------------------------------------------------------------------------------------ Lecture 7: Topics to be covered:

• Collection of particulate pollutants: Sedimentation, Filtration, Impingement, Electrostatic, Thermal Precipitation

• General considerations in site selections • Advantages & Disadvantage

Collection of particulate pollutants:

Particulate pollutants

Settle due to the force of gravity Those that remain suspended as aerosols (Particle size greater than 10µm) (Smaller size) Sedimentation Filtration Impingement

Electrostatic Thermal Precipitation

Sedimentation (Dust fall Jar): Suitable for larger particles having a size more than 10 µ. The jar method for dust fall is based on sedimentation.


Handout: 2CH002 -APCT July -2014 General considerations in site selections are:

1. The site should be free from overhead obstructions 2. The mouth of the dust fall collector should be no less than 2.5 m and no more

than 16 m above ground level, with a standard height of 6 m as recommended elevation

3. When sampling in urban areas, the dust fall collector should be set no less than 10 stack lengths from an operating smoke stack and no closer to vertical wall than the distance that provides a 300 angle from the sampler to the top of the wall or roof.

Advantages:

• Ease of procurement of 1-5 gram of weightable sample, on which a number of chemical and physical analyses can be performed.

• The method is simple and inexpensive and required no electrical power or moving parts.

Disadvantages:

• Lack of precision and inability to distinguish episode of peak dust fall due to integration of he total sample weight over the entire sampling period (up to 30 days)

• Particles collected are more less agglomerated and may not be representative of the original from and size of particulate matter suspended

------------------------------------------------------------------------------------------------------------ Lecture 8: Topics to be covered:

• Filtration - High Volume Filtration (The Hi-vol sampler) • Impaction on solid surface • Impingement in liquid • Electrostatic Precipitation • Thermal precipitation • Centrifugal method

Filtration: The particulate matter form air can be sampled by passing the air through a filter whose pore size is small enough to retain the particles. The selection of filter depends on (1) Objectives of sampling (2) size of the particles


Handout: 2CH002 -APCT July -2014 High Volume Filtration (The Hi-vol sampler): Errors in sampling by HVS

• Particulates may be lost in sampling manifold – so not too long or too twisted manifold must be used.

• If ‘isokinetic’ conditioned are not maintained, biased results may be obtained for particulate matters.

Advantages of HVS

• High flow rate at low pressure drop • High particulate storage capacity • No moisture regain • high collection efficiency • Low coast • Not appreciable increase in air flow resistance • Filter is 99% efficient and can collect the particles as fine as 0.3 µm • Absorption principle is 99% efficient in collecting the gases

Impaction on solid surface: When an air stream is deflected after sticking a surface, the particles are impacted due to inertial forces. Collection efficiency is high for particle size 1 µ. Sampler: Anderson impactor Impingement in liquid: The particles are separated form the air by the force of inertia as the air is deflected after sticking the liquid surface. The bubbler or impingers used for collection of particles are the same those used for collection of gaseous pollutants. Devices: (1) Green burg Smith standard (2) Midget Impingers Limitations: Not widely used for particulates because of low sampling rates Electrostatic Precipitation: During operation a negative charge is imparted to wire placed axially inside a cylinder that is positively charged.


Handout: 2CH002 -APCT July -2014 When the particle laden air stream passes through the cylinder, the particles acquire a negative charge from a corona discharge occurring on the central wire. The particles migrate towards the inner surface of the cylinder and are removed for subsequent chemical or microscopic analysis.

Thermal precipitation: Thermal precipitators operate on the principle that small particles, under the influence of a strong temperature gradient between two surfaces, have a tendency to move towards the lower temperature and get deposited on the colder of these two surfaces. Centrifugal Methods: Most centrifugal sampling devices are constructed on the principle of the cyclone. The dust-laden gas moving at high velocity is directed tangentially into a cylindrical chamber, in which it forms a confined vortex. The centrifugal force tends to drive the suspended particles to the wall of the cyclone body, from which they drop into a dust collection chamber. An axial outlet is provided for the clean gas.

Advantages: procurement of a dry chemically pure sample Disadvantages: particle size greater than 5 µ Solution Impingers: This consists of a drawn out tube through which air containing particles flows into a solution, where the particles are trapped. Disadvantages: unable to collect both particulate and vapor species. For this purpose oxidizing solution is used. Application is limited because the collection solution can be operated only at low flow rate (20 lit/min). Application: high atmospheric particulates loading exits, Simultaneous collection of particles and gases are required or alternative equipments are not available. ------------------------------------------------------------------------------------------------------------



• Stack sampling Techniques & its objectives • Planning the study • The important considerations for accurate representative sample collection • Particulate sampling train

Stack sampling Techniques: Stack sampling or source sampling may be defined as a method of collecting representative samples of pollutant laden air/gases at the place of origin of pollutants to determine the total amount of pollutants emitted into the atmosphere from a given source in a given time. Stack sampling is used for the assessment of the following:

1. To determine the quantity and quality of the pollutant emitted by the source. 2. To measure the efficiency of the control equipment by conducting a survey

before and after installation 3. To determine the effect on the emission due to changes in raw materials and

processes. 4. To compare the efficiency of different control equipments for a given condition. 5. To acquire data from an innocuous individual source so as to determine the

cumulative effect of many such sources. 6. To compare with the emission standards in order to assess the need for local

control Planning the study:

1. Familiarity of the process and operations to determine the time of cyclic operations, peak loading that might cause variations in the characteristics.

2. Method of sampling 3. Method of analysis of samples 4. Sampling time because certain industries undergo cyclic changes 5. Amount of sample required 6. Sampling frequency Representative sample: Sample collected must truly represent the conditions prevailing inside the stack. The important considerations for accurate representative sample collection include: 1. Accurate measurement of pressure, moisture, humidity and gas composition 2. The selection of suitable locations for sampling



3. Determination of the traverse point required for a velocity and temperature profile across the cross section of the stack and sampling for particulate matter

4. The measurement of the rate of flow of gas or air through the stack 5. Selection of suitable sampling train 6. Accurate isokinetic sampling rate essential for particulate sampling 7. Accurate measurement of weight and volume of samples collected

Particulate sampling train

------------------------------------------------------------------------------------------------------------ Lecture 10: Topics to be covered:

• Selection of Sampling Location • Size of sampling point • Traverse points • Determination of gas composition, moisture content, temperature, velocity

Selection of Sampling Location The sampling point should be as far as possible from any disturbing influence, such as elbows. Bends, transition pieces, baffles or other obstructions. The sampling point, wherever possible should be at a distance 5-10 diameter downstream from any obstructions and 3-5 diameters up-stream from similar disturbances.


Handout: 2CH002 -APCT July -2014 Size of sampling point: The size of sampling point may be made in the range of 7-10 cm, in diameter. Traverse points

• For the sample become representative, it should be collected at various points across the stack.

Cross section area of stack sq. m No. of traverse Points

0.2 4

0.2 to 2.5 12

2.5 and above 20

In circular stacks, traverse points are located at the center of equal annular areas across two perpendicular diameters as shown in Figure.



In case of rectangular stacks, the area may be divided in to 12 to 25 equal areas and the centers for each area are fixed.

Particulate sampling: The sample collected must be representative like a composite wastewater collection. This can be achieved by isokinetic sampling. Isokinetic conditions exits when the velocity in the stack Vs equals the velocity at the top of the probe nozzle Vn at the same point. Determination of gas composition: Gas composition can be determined by Orsat apparatus.

Determination of moisture Content: The moisture content in the stack may be determined by any one of the following methods:

1. Wet bulb and dry bulb temperature technique (Moisture content is less than 18 % and dew point is less than 51 0C and can not be used for acid stream)

2. Condenser technique 3. Silica gel tube

Determination of Temperature: The temperature probe is inserted into the stack and the readings are taken with the help of a pyrometer.

Types of probe Temperature range, 0C Chromel/Alumel 148.8 - 1260

Copper/Constantan 148.8 – 348.9 Iron/Constantan 115.5 - 1010

Platinum / Platinum 10 % & Rhodium 0 – 1537.7 Determination of velocity: The standard Pitot tube in combination with a differential manometer is widely used to measure velocity. ------------------------------------------------------------------------------------------------------------



• Chemical Methods • Instrumental Methods • Biological Methods

The methods used for analysis of atmospheric samples can be divided into three basic groups:

1. Chemical Methods 2. Instrumental Methods 3. Biological Methods

1. Chemical Methods

(a) Gravimetric Method (b) Volumetric Method (c) Colourimetric method (d) Turbidimetric and nephelometric method (e) Chromatographic method

(a) Gravimetric Method:

Weight of substance (Pollutant) is determined.

(b) Volumetric Method In this components are not weighted but determine by means of reagents of known concentrations 1. Acidimetric or Alkalimetric Method 2. Oxidation and reduction method 3. Precipitation method

(c) Colourimetric method

A very large number of elements, radicals and organic compounds form colored complexes with special reagents and such colourimetric reactions are sensitive to detect even the minutest amount of the compound. Apparatus used: Filter Photometer Use for analysis of gas and particulate matter

(d) Turbidimetric and nephelometric method

Precipitate obtained by means of specific reaction are analyzed by optical measurement of light passing through the corresponding suspension



(e) Chromatographic method The separation and identification of many substances by means of adsorption on adsorption columns or on specially sensitized paper, followed by elution of the various compounds adsorbed with selective solvents.

2. Instrumental Methods

1. Emission Spectrometric method 2. Absorption spectrometric method (Spectrophotometry) 3. X ray diffraction method 4. Mass spectrometric method 5. Polarogaphic method 6. Method using microscopy 7. Refractometric method 8. Thermal conductivity method 9. Radioactivity method 10. Sound absorption method 11. Atomic absorption spectroscopy

3. Biological Methods By studying effects on plant and animals

Sulphur Dioxide Ambient Air Measurement The most common methods are Colourimetry, iodimery or turbidimetry. (1) Method for determination of Sulphur Dioxide in Air: Modified West and Gaeke Method Principle: Sulphur dioxide from air is absorbed in a solution of potassium tetrachloromercurate (TCM) to form a stable and nonvolatile dichlorosulphitomercurate complex. Once formed, this complex is stable to strong oxidants such as ozone and oxides of nitrogen and therefore, the absorber solution may be stored for some time prior to analysis. The complex is made to react with pararosaniline and formaldehyde to form the intensely colored pararosaniline methylsulphonic acid. The absorbance of the solution is measured by means of a suitable spectrophotometer. Interferences: Interferences by oxides of nitrogen are eliminated by sulphamic acids which destroy the nitrate ion prior to color formation. Ozone is made to decompose by allowing the solution to stand for some time prior to analysis. The interference of trace metals (lowering the


Handout: 2CH002 -APCT July -2014 apparent SO2 conc.) may be eliminated by the addition of ethylenediamine tetra acetic acid (EDTA) to the absorbing solution prior to sampling. Several automatic instruments for monitoring sulphur dioxide:

1. Conductometric 2. Colourimetric 3. Flame photometric

------------------------------------------------------------------------------------------------------------ Lecture 12: Sulphur Dioxide from Stack Measurement (1) Bromocoulometric analyzer: (2) Electrochemical method:

SO2 gas diffuses through a semi permeable membrane and a thin electrolyte layer to get absorbed at the sensing electrode where it undergoes an electrochemical reaction. The resulting current is proportional to SO2 Concentration. Advantages: Simple, lower cost and immediate result

(3) Infrared and ultraviolet spectrophotometry: Analysis of Nitrogen Oxides: 1) Griess – Saltzman 2) Chemiluminescent analyzer

Analysis of carbon monoxide:

1) Non dispersive infrared analyzer 2) Chromatographic analysis 3) Electrochemical analysis

------------------------------------------------------------------------------------------------------------


Handout: 2CH002 -APCT July -2014 Lecture 13:


• Air quality standards:

1. Ambient air quality standards 2. Other air quality standards

i. Quasi emission standards ii. Soiling index iii. Odour standards iv. Visibility standards v. Standards for particulate matter deposited

• Emission standards

Air quality standards

Air quality standards are legal limits placed of air pollutants in the ambient air during a given period of time.

Single or multiple standards:

There should be one standard for an entire area or different standard for different area.

Kinds of air quality standards:

3. Ambient air quality standards 4. Other air quality standards

i. Quasi emission standards ii. Soiling index iii. Odour standards iv. Visibility standards v. Standards for particulate matter deposited

1. Ambient air quality standards

These are the legal limits placed on the conc. of air pollutants in a community where people and things are exposed.

The Clean Air Act established two types of national air quality standards.

i. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly.



ii. Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

2. Other air quality standards a. Quasi emission standards (point of impingement standards)

Quasi emission standards which are the limits on specific pollutants of the ambient air at ground level required by national, state, or local regulations to be used in diffusion computations to determine limits of emission from specific sources.

b. Soiling index

Soiling index which is the measurement of transmitted or reflected light through or from a spot of particulate matter collected on a filter for a prescribed period of time. (The darkness of strains produced by drawing polluted air through filter paper has between used to estimate suspended particulate matter concentration.



National Ambient Air Quality Standards

Pollutants Time-weighted average

Concentration in ambient air Method of measurement Industrial Areas

Residential, Rural & other Areas

Sensitive Areas

Sulphur Dioxide (SO2) Annual Average*

80 µg/m3 60 µg/m3 15 µg/m3 - Improved West and Geake Method - Ultraviolet Fluorescence

24 hours**

120 µg/m3 80 µg/m3 30 µg/m3

Oxides of Nitrogen as (NO2)

Annual Average*

80 µg/m3 60 µg/m3 15 µg/m3 - Jacob & Hochheiser Modified (Na-Arsenite) Method

24 hours**

120 µg/m3 80 µg/m3 30 µg/m3 - Gas Phase Chemiluminescence’s

Suspended Particulate Matter (SPM)

Annual Average*

360 µg/m3 140 µg/m3 70 µg/m3 - High Volume Sampling, (Average flow rate not less than 1.1 m3/minute).

24 hours**

500 µg/m3 200 µg/m3 100 µg/m3

Respirable Particulate Matter (RPM) (size less than 10 microns)

Annual Average*

120 µg/m3 60 µg/m3 50 µg/m3 - Respirable particulate matter sampler

24 hours**

150 µg/m3 100 µg/m3 75 µg/m3

CarbonMonoxide (CO) 8 hours**

5.0 mg/m3 2.0 mg/m3 1.0 mg/ m3

- Non Dispersive Infra Red (NDIR)

1 hour 10.0 mg/m3

4.0 mg/m3 2.0 mg/m3

Spectroscopy

*

Annual Arithmetic mean of minimum 104 measurements in a year taken twice a week 24 hourly at uniform interval.

**

24 hourly/8 hourly values should be met 98% of the time in a year. However, 2% of the time, it may exceed but not on two consecutive days.



Emission Standards:

Emission standards established permitted emission level for specific groups of emitters and require that all members of these groups emit no more than these permitted emission levels.

1. Emission standard for mobile sources 2. Emission standards for stationary sources

1. Emission standard for mobile sources

Mobile sources include aircraft, ships, motor vehicles and rail-road locomotives. Motor vehicles are subdivided into automobiles, trucks, buses and motorcycles. Emission standards prescribe limits of contaminants discharged into the atmosphere, so that when the standards are met, adverse effects from air pollution will be minimized or eliminated.

Emission Standards for Gasoline vehicles (GVW< 3500 kg), g/km

Year Reference CO HC HC+NOx 1991 - 14.3- 27.1 2.0 – 2.9 - 1996 - 8.68 – 12.4 - 3.00 – 4.36 1998* - 4.34 – 6.20 - 1.50 – 2.18 2000 Euro 1 2.72 – 6.90 - 0.97 – 1.70 2005! Euro 2 2.2 – 5.0 - 0.5 – 0.7

*For catalytic converter fitted veghicle

! Mumbai, Kolkata, Chennai, Banglore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and agra

Emission Standards for Diesel Truck and Bus engines, g/KWh

Year Reference CO HC NOx PM 1992 - 17.3 – 32.6 2.7 – 3.7 - - 1996 - 11.20 2.40 14.4 - 2000 Euro I 4.5 1.1 8.0 0.36*

2005 ! Euro II 4.0 1.1 7.0 0.15 2010 ! Euro III 2.1 0.66 5.0 0.10

* 0.612 for engine below 85 KW

! Mumbai, Kolkata, Chennai, Banglore, Hyderabad, Ahmedabad, Pune, Surat, Kanpur and agra

2. Emission standards for stationary sources



Stationary source emission standards are standards relating to a stationary site, process, stack, chimney or vent intended to help achieve the desired air quality. They include standards for buffer zones, stack height, equipment design and fuel composition and those that directly limit the amount or conc. of a pollutant emitted from a source.

Lecture 14, 15:

Human Activities generate three broad sources of air pollution: stationary or point, mobile (outdoor) and indoor. Air pollution generated from mobile sources such as automobiles contributes major air quality problems in urban and industrialized. The use of automobiles increases exponentially day to day. About 50 million cars are produced every year, and over 700 million cars are used worldwide. The number of vehicles in India has increased from 1.86 million in 1971 to 32 million in 1996 and about 53 million in 2000. Most vehicular transportation relies on combustion of gasoline, diesel and jet fuels with attendant emission of carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxides (NOx), and particulates matter (PM)-fine particulates in the respirable range having diameters less than 2.5 µ m (PM2.5) are especially a concern. Motor vehicles account for more than 50 % of the man made emissions of CO, HC and NOx. In the United States, transportation is responsible for 77 % of CO, 47 % of hydrocarbon emissions, 60 % of NOx and 27 % of PM2.5 emissions in urban areas. Carbon monoxide is a noted poison which has an affinity for hemoglobin in the blood 210 times greater than the oxygen affinity prolonged exposure to levels above 9 ppm can lead to reduce mental acuity for some individuals. HC and NOx lead to photochemical smog in sunlight, giving rise to the photochemical oxidant, ozone, nitrogen dioxide & peroxyacyl nitrate. Exposure to these oxidants above 0.08 ppm can cause eye irritation & impairment of lung function in person with chronic pulmonary disease. The oxidants also cause damage to vegetation and rubber tires. In addition to photochemical smog, global environmental problems such as acid rain, the green house gas effect and depletion of the ozone layer are also attributable in part to emissions from motor vehicle. The auto exhaust also affects our valuable cultural heritage, historical places/ monuments/ architecture and the environment.


Handout: 2CH002 -APCT July -2014 Classification of Automotive Engine

Types of fuels Pollutant emissions from motor vehicles are determined by the vehicle’s engine type and the fuel it uses. Ideal fuel must have certain physical, chemical and combustion properties, such as high energy density, good combustion qualities, high thermal stability, low deposit forming tendencies, compatibility with engine hardware, good fire safety, low toxicity, low pollution, easy transferability and on-board vehicle storage. Commonly use fuels are gasoline and diesel. Main sources of emission from automobiles are: The amount of pollutants that an automobile emits depends upon number of factors, including the design and operation (ideal, acceleration etc.) Of the hydrocarbons emitted by a car with no controls, the exhaust gases accounts for roughly 65 %, evaporation from the fuel tank and carburetor for roughly 15% and blow by or crank case emission (gases that escape around the piston rings) for about 20 %. Carbon monoxide, nitrogen oxides and lead compounds are emitted almost exclusively in the exhaust gases.

The emission produced by a vehicle fall into three basic categories:


Handout: 2CH002 -APCT July -2014 1. Evaporative Emissions

2. Crankcase Emission (also called running loss emissions)

3. Exhaust Emission

(i) Evaporative Emissions

Evaporative emissions are HC vapors lost constantly and directly to the atmosphere due to volatile nature of petrol, mainly from the fuel line’s, fuel tank and carburetor depending upon fuel composition, engine operating temperature and ambient temperature. Volatile organic compounds (VOC) also escape into the air through fuel evaporation. Evaporative losses can account, on hot days, for a majority of the total VOC pollution. ii) Crankcase Emission (also called running loss emissions)

"Crankcase emissions" means substances emitted directly to the atmosphere from any opening leading to the crankcase of a motor vehicle engine.

Crankcase emissions are unburnt or partially burned fuel components that, under pressure, escape from the combustion chamber, pass the pistons and enter the crankcase. This mixture is called blow-by. The main constituent of blow-by emission is HCs. If uncontrolled, it may constitute 13–25% of total emissions. Since, diesel engines compress only air, blow-by contain very low levels of pollutants.

(iii) Exhaust Emission The products of burning fuel in the vehicle's engine, emitted from the vehicle's exhaust system. It is tailpipe emission. Emission Control Technology

1. Air-Fuel Ratio 2. Evaporative Emissions Control System

2.1 Carbon Canister 2.2 Positive Crankcase Ventilation 2.3 On-Board Refueling Vapor Recovery (ORVR)

2 Crankcase Emissions and Control

3 Catalytic Converter

http://wikicars.org/en/Internal_combustion_engine

nirma university institute of technology handout: … · 07.12.2013 · nirma university institute...

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