Ch 22 Pollution

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INDIABOILER DOT COMTUTORIAL FOR SECOND CLASS BOILER ENGINEERS PROFICIENCY EXAMINATION

DLP/BOE-II/ 1- 01092001

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CHAPTER - 22

Boiler Pollution Control

1. Introduction:Undesirable contamination of environment is termed Pollution. In all industrialprocesses, there are some byproducts that possess any commercial value and are armfulto humans and/or cattle beyond a certain concentration. When such byproducts aredisposed freely in the environment Pollution is caused. Uncontrolled disposal, intoenvironment, of these byproducts constitutes Pollution of Air and Water. In early timesadverse effects of such Pollution were not known. Hence it was taken for granted thatPollution is a necessary evil associated with industrialization. However, as more andmore knowledge is being gathered and Pollutants and their effects are being studied andrecorded, scientific norms for making disposal of polluting byproducts are evolving.Norms are being established about the degree of pollution that can be tolerated byeveryone harmlessly. Rules and Regulations have been made in almost all countries forthis purpose. In India too there are Acts of Law and Rules & Regulations for control of

Pollution. Certain standards have also been laid down for most potential forms ofPollution nuisance. Failure to comply constitutes a breach of the law with the possibilityof fines or even injunctions restricting production.

In the following have been discussed the sources of pollution associated with boilers andthe steps to abate them.

Persons engaged in the design operation and maintenance of industrial plant should aimat not only meeting the emission norms but also minimizing the nuisance.

Boilers can cause Pollution of Atmosphere through emissions, Water through effluentsand Noise. Sources of such pollution are shown in diagram below.


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2. Atmospheric Pollution

Atmospheric pollution can be caused by a) Dark smoke, b) Ash particles as Suspended

Matters or Particulate, c) Oxides of Sulphur, d) Acidic smut emission from oil firedboilers, e) Oxides of nitrogen and f) CO as described below.

2.1 Dark smoke:

Dark smoke causes blackening of buildings and by excluding sunlight it is detrimental tohealth and adversely affects the growing of crops.

It is due to the presence of particles of carbonaceous matter because of bad combustion,inefficient maintenance and cleaning of heating surfaces, faulty design and installation of

firing equipments, overloading of plants, insufficient air supply, improper draught, air

leakages from the brickwork and other openings and inadequate size of stack. Withmodern plant and skilled operators it can be avoided considerably.

The colour of smoke is measured by comparing it with a Ringlemann chart.

2.2 Ash particles or Particulates:

In pulverised coal firing 85% ash appear as fly ash and in others it is 25%. The term fly

ash is used when fine ash and slag particles are carried over to the exit end of the plant.Cleaning and washing coal is considered as one of the means to reduce pollution.

Flyash from the combustion process is collected using one of four major technologies:

a. electrostatic precipitator (ESP),

b. fabric filters (or baghouse),

c. mechanical collectors and

d.

wet scrubbers.

With todays removal requirements in excess of 99.9%, modern ESPs and fabric filters

dominate fly ash collection. Mechanical collectors are still used for specialty applications

as a preliminary collection device, especially where fly ash recycle is part of the

combustion process, but they are almost always followed by an ESP or fabric filter forfinal particulate control. Wet scrubbers are no longer used for primary particulate

collection because of their high energy requirements for the desired removal efficiencies.

In addition to efficient grit collection the use of high stacks distributes the residual ash

over a wide area. The dust can travel over a distance of 70 miles in a light wind from a

300 ft. stack.

2.3 Oxides of Sulphur:

Sulphur in the fuel burns off to liberate SO2which forms SO3in the final stage of flame

burning when there is an exigency of atomic oxygen. SO3is also produced from SO2onthe surface of the superheater deposits that act as a catalyst at elevated temperatures. SO3

reacts with the atmospheric moisture to form an aerosol of sulphuric acid which rains

down as acid rain.


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Historically, SOx pollution has been controlled by either dispersion or reduction.

Dispersion involves the utilization of a tall stack, which enables the release of pollutants

high above the ground and over any surrounding buildings, mountains, or hills, in orderto limit ground level SOx emissions. Today, dispersion alone is not enough to meet more

stringent SOx emission requirements; reduction methods must also be employed.Methods of SOx reduction include switching to low sulfur fuel, desulphurizing the fuel,

and utilizing a flue gas desulphurization (FGD) system. Fuel desulphurization, which

primarily applies to coal, involves removing sulfur from the fuel prior to burning. Fluegas desulphurization involves the utilization of scrubbers to remove SOx emissions from

the flue gases.

Flue gas desulphurization systems are classified as either non-regenerable or regenerable.

Non-regenerable FGD systems, the most common type, result in a waste product thatrequires proper disposal. Regenerable FGD converts the waste by-product into a

marketable product, such as sulfur or sulfuric acid. SOx emission reductions of 90-95%

can be achieved through FGD. Fuel desulphurization and FGD are primarily used forreducing SOx emissions for large utility boilers. Generally the technology cannot be cost

justified on industrial boilers.

For users of industrial boilers, utilizing low sulfur fuels is the most cost effective method

of SOx reduction. Because SOx emissions primarily depend on the sulfur content of the

fuel, burning fuels containing a minimal amount of sulfur (distillate oil) can achieve SOx

reductions, without the need to install and maintain expensive equipment.

2.4 Acidic smuts from oil fired boilers

The burning of high sulphur content fuel oil can give appreciable quantities of sulphuric

acid which together wilt particles of unburnt carbon can cause acidic soot to fall in anarea of about 1 mile radius. These smuts are very destructive to car finishes, clothing,

etc., although the total quantity is very low compared with coal burning.

Improved boiler operating technique and the use of chemical additives to limit sulphuric

acid formation has reduced the extent of the problem.

2.5 Oxides of nitrogen (NOX):

Oxides of nitrogen are produced by combustion of fuels. Nitrogen dioxide is a highly

dangerous air pollutant. NO + NO2 are produced in the high-temperature zones of the

flame. NOX may undergo a photochemical reaction with the hydrocarbons in theatmosphere in the presence of sunlight to release some toxic substances in the air.

The concentration of NOX in combustion gases largely depends on the combustion

technique in the furnace. Since the bulk of NOX produced in the combustion process

comes from chemical reaction between aerial nitrogen and oxygen in the hightemperature combustion zone (above 1600

oC), the chief means of limiting NOX

generation is to lower the temperature in the combustion zone.

2.5.1 NOx control technologies:

NOx controls can be classified into two types: post combustion methods and combustion

control techniques. Post combustion methods address NOx emissions after formation


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while combustion control techniques prevent the formation of NOx during the

combustion process. Post combustion methods tend to be more expensive than

combustion control techniques and generally are not used on boilers with inputs of lessthan 100 MMBtu/hr. Following is a list of different NOx control methods.

Post combustion control methods include:

Selective Non-Catalytic Reduction

Selective Catalytic Reduction

Combustion control techniques include:

Low Excess Air Firing

Low Nitrogen Fuel Oil

Burner Modifications

Water/Steam Injection

Flue Gas Recirculation

Each method results in a different degree of NOx control. For example, when firingnatural gas, low excess air firing typically reduces NOx by 10%, flue gas recirculation by

75%, and selective catalytic reduction by 90%

2.5.1.1 Post combustion control methods:

Selective Non-catalytic Reduction

Selective non-catalytic reduction involves the injection of a NOx reducing agent, such as

ammonia or urea, into the boiler exhaust gases at a temperature of approximately 1400-

1600 F. The ammonia or urea breaks down the NOx in the exhaust gases into water andatmospheric nitrogen. Selective non-catalytic reduction reduces NOx up to 70%.

However, the technology is extremely difficult to apply to industrial boilers that modulateor cycle frequently. This is because the ammonia (or urea) must be injected in the flue

gases at a specific flue gas temperature. And, in industrial boilers that modulate or cycle

frequently, the location of the exhaust gases at the specified temperature is constantlychanging. Thus, it is not feasible to apply selective non-catalytic reduction to industrial

boilers that have high turndown capabilities and modulate or cycle frequently.

Selective Catalytic Reduction

Selective catalytic reduction involves the injection of ammonia in the boiler exhaust

gases in the presence of a catalyst. The catalyst allows the ammonia to reduce NOx levels

at lower exhaust temperatures than selective non-catalytic reduction. Unlike selective

non-catalytic reduction, where the exhaust gases must be approximately 1400-1600 F,selective catalytic reduction can be utilized where exhaust gasses are between 500 F and

1200 F, depending on the catalyst used. Selective catalytic reduction can result in NOx

reductions up to 90%. However, it is costly to use and can rarely be cost justified on

boilers with inputs less than 100 MMBtu/hr.


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Efficiency:

Some low NOx controls reduce emissions by lowering flame temperature, particularly in

boilers with inputs less than 100 MMBtu/hr. Reducing the flame temperature decreasesthe radiant heat transfer from the flame and could lower boiler efficiency. The efficiency

loss due to the lower flame temperatures can be partially offset by utilizing externalcomponents, such as an economizer. Or, the offset technique can be inherent in the NOxdesign.

One technology that offsets the efficiency loss due to lower flame temperatures in afiretube boiler is flue gas recirculation. Although the loss of radiant heat transfer could

result in an efficiency loss, the recirculated flue gases increase the mass flow through the

boiler - thus the convective heat transfer in the tube passes increases. The increase inconvective heat transfer compensates for losses in radiant heat transfer, with no net

efficiency loss. When considering NOx control technology, remember, it is not necessary

to sacrifice efficiency for NOx reductions. Excess Air A boiler's excess air supply

provides for safe operation above stoichiometric conditions. A typical burner is usually

set up with 10-20% excess air (2-4% O2). NOx controls that require higher excess airlevels can result in fuel being used to heat the air rather than transferring it to usableenergy. Thus, increased stack losses and reduced boiler efficiency occur. NOx controls

that require reduced excess air levels can result in an oxygen deficient flame and

increased levels of carbon monoxide or unburned hydrocarbons. It is best to select a NOxcontrol technology that has little effect on excess air.

Carbon Monoxide (CO) Emissions:

High flame temperatures and intimate air/fuel mixing are essential for low CO emissions.

Some NOx control technologies used on industrial and commercial boilers reduce NOxlevels by lowering flame temperatures by modifying air/fuel mixing patterns. The lower

flame temperature and decreased mixing intensity can result in higher CO levels.An induced flue gas recirculation package can lower NOx levels by reducing flame

temperature without increasing CO levels. CO levels remain constant or are loweredbecause the flue gas is introduced into the flame in early stages of combustion and the air

fuel mixing is intensified. Intensified mixing offsets the decrease in flame temperature

and results in CO levels that are lower than achieved without FGR. But, the level of COdepends on the burner design. Not all flue gas recirculation applications result in lower

CO levels.

Total Performance:

Selecting the best low NOx control package should be made with total boiler

performance in mind. Consider the application. Investigate all of the characteristics of the

control technology and the effects of the technology on the boiler's performance. A NOxcontrol technology that results in the greatest NOx reduction is not necessarily the best

for the application or the best for high turndown, adequate capacity, high efficiency,

sufficient excess air, or lower CO. The newer low NOx technologies provide NOx

reductions without affecting total boiler performance.


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2.6 Carbon monoxide:

Carbon monoxide is a pollutant that is readily absorbed in the body and can impair the

oxygen-carrying capacity of the hemoglobin. Impairment of the body's hemoglobinresults in less oxygen to the brain, heart, and tissues. Even short-term over exposure to

carbon monoxide can be critical, or fatal, to people with heart and lung diseases. It mayalso cause headaches and dizziness in healthy people.

During combustion, carbon in the fuel oxidizes through a series of reactions to form

carbon dioxide (CO2). However, 100 percent conversion of carbon to CO2 is rarelyachieved in practice and some carbon only oxidizes to the intermediate step, carbon

monoxide.

Older boilers generally have higher levels of CO than new equipment because CO has

only recently become a concern and older burners were not designed to achieve low COlevels. In today's equipment, high levels of carbon monoxide emissions primarily result

from incomplete combustion due to poor burner design or firing conditions (for example,

an improper air-to-fuel ratio) or possibly a leaky furnace. Through proper burnermaintenance, inspections, operation, or by upgrading equipment or utilizing an oxygen

control package, the formation of carbon monoxide can be controlled at an acceptable

level.

3. Water pollution:

Large boilers in thermal power station and of process industries contribute to water

pollution by way of discharging into the water basin the:

a.

boiler blowdown

b. SO2-scrubber waste

c. Cooling waters that mainly causes thermal pollution

d. Waste waters from waste treatment plants and demineralising units

e. Waste waters contaminated with petroleum products

f. Waste waters from hydraulic ash-disposal system.

These discharged waste waters carry a rich load of harmful impurities, viz heavier metal

cations, organic substances and coarse-dispersed solids besides dissolved salts. The toxic

substances added to the water basin from boiler plants may adversely affect thehydrobionts-all living organisms inhabiting the water basin. At higher concentrations

they will simply perish while at lower concentrations they may suffer from reducedmetabolism and growth rate, abnormal change in mutagenesis and reproductive capacity.

The load of impurities discharged into water basins can be decreased in two ways:1. by purifying the waste waters

2. by reducing the quantitative discharge of impurities from particular technological

process.

3.1 Boiler blowdown:This waste stream results from periodic purging of the impurities that

become concentrated in steam boiler systems. These pollutants include metals such as


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copper, iron and nickel, as well as chemicals added to prevent scaling and corrosion of

steam generator components.

3.2 Thermal pollution:The heat released by cooling water (open-circuit) from the turbine

condensers of super thermal power stations is enormous. This creates a high zone ofelevated temperature in the water basin, reduces its dissolved oxygen thereby impairs thegrowth and development of aquatic life. The zone of elevated temperature in a water

basin can be reduced by allowing the inflow of hot discharge water into the basin

through:

a. open type spillways with

i. transverse and side weir bulkheads

ii. distributing grill

b. submerged jet-type spillways

3.3 Waste waters from water treatment plants and DM units: Waste water of water

treatment plants (WTP) contains slime, coarse dispersed solid, organic substances,

magnesium hydroxide, calcium carbonate and salts of iron and aluminum. Thecomposition and concentration of various impurities in waste water depends on the

quality of raw water and the methods adopted for water treatment. In DM-unit,regeneration of H-cation exchanger and OH-anion exchanger is done by using H2SO4and

NAOH solutions and as a consequence, the disposed waste becomes respectively acidic

and alkaline in nature.

Purification: The waste water of WTP and discharge from DM-unit may be disposed as

follows:

a. transferring the waste water into the hydraulic ash handling system of coal

fired boiler unitsb. neutralizing the waste water (pH>9) of WTP with acid wastes of the DM-unit.

c. Subjecting the waste to slime separation, i.e. slime dewatering in drum type

vacuum filters and recycling the clarified water for washing of mechanical

filters.

Reducing waste water discharge of WTP and DM-units: The amount of impurities

discharged into the water basin by waste waters from the WTP and DM-unit can bediminished by adopting techniques that will minimise the use of reagents and water for

water treatment and regeneration purposes.

The quantity of water used for regeneration of mechanical filters can be drastically cut

down by increasing the filtering capacity of mechanical filters. By using expanded clayinstead of quartz sand in mechanical filters it is possible to use less water for regenerationby a factor 2.5-3.5.

The flowrate of wastes from the DM-unit can be effectively reduced by adopting the

process of:

a. continuous ion exchange


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b. stepwise counter-current ion-exchange

c. thermal regeneration (instead of chemical regeneration) of ion exchanges.

The colloidal impurities of waste water can be precipitated down by electrocoagulator

using either Fe or Al anodes.Stripping waste water of its dissolved salts can be effectively accomplished by a physical

process known as reverse osmosis.In this process, the waste water with dissolved salts isforced through a semi-permeable membrane at a pressure, exceeding the osmotic pressure

of the solution. The membrane allows only water and a small fraction of salts as ions to

pass with the effect that the filtrate contains an appreciably smaller quantum of dissolved

impurities. Reverse osmosis technique has drastically cut down the consumption ofreagents used for water treatment with the effect that the concentration of impurities in

discharged waste waters sharply declines.

The line up of reverse osmosis plant upstream of DM-units can slash down the dischargeof salt solution by 50% and the cost of desalted water by 25%.

Desalination of waste waters can be successfully carried out by another technique known

as electrodialysis. The apparatus consists of an assembly of parallel cation and anionexchange membranes flanked by a stainless steel cathode and platinum coated steel

anode. Electrodialysis substantially reduces the use of reagents for the waste water

treatment and consequently the amount of salt discharged to waste waters is also

diminished.

3.4 Waste waters contaminated with petroleum products: The petroleum products likelube oils, fuel oils, kerosene. etc. find their way to the water basin in an emulsified,

colloidal or dissolved state. They are particularly dangerous for water basins. The

maximum allowable concentration of petroleum products in the water basin is 0.5 mg/kg

of water. They form films on the water surface, inhibit the natural aeration of water andthereby inflict serious harm to aquatic life.

Purification: The oil contaminated waste water is charged to oil traps that separate outefficiently the course oil particles of size 80-100 m or more. The clarified water is then

fed into the flotator where finer oil particles are separated from water at a high rate under

pressure flotation. The purified water is then filtered through a mechanical filter. Theformer consists of double layer packing of quartz sand and anthracite. The carbon filter

consists of bed of activated carbon to adsorb oily suspensions. The final effluent water of

this plant is 95% free from oil.

3.5 Waste water of hydraulic ash disposal system: In a hydraulic ash disposal system

water is allowed to act upon the ash, a part of which dissolves and the rest forms a pulp(suspension) which is pumped to ash settling ponds where the course impurities settledown and the clarified water can either be discharged directly into a water basin or

recycled for reuse.

The composition and concentration of impurities transferred from ash to water depends

largely upon the chemical composition of ash which may vary appreciably.


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SiO3: 10-70%; Al2O3: 10-40%; Fe2O3: 2-30%; CaO: 2-70%; MgO: 0-10%;

K2O + Na2O: 0-10%.

It may also contain traces amount of compounds of vanadium, germanium, arsenic,

mercury, beryllium and fluorine.

Decontamination of ash disposal water: The high flowrate and high concentration ofimpurities in the waste water of a hydraulic ash disposal system prevent purification of

the entire bulk of the ash disposal system. What can be achieved is decontamination of

toxic impurities to a safe level and the principal processes involved are as follows:

1. Precipitation as well as co-precipitation of impurities

2. Sorption of impurities

3. Oxidation reduction followed by precipitation.

Removal of impurities by forming sparingly soluble precipitates or by adsorption on the

surface of the solid phase separated in the water mass during the course of the chemical

treatment of ash disposal water is the most popular one

3.6 Zero liquid discharge:

Utilities are looking for waste water treatment techniques to retrieve almost entire gamutof their effluents as a high quality distillate for reuse and to convert the contaminants of

waste steam into manageable solid wastes for disposal. The most popular among these

techniques is the ZERO LIQUID DISCHARGE (ZLD) system that can recover 90-99%of the waste water as a high quality distillate suitable for reuse in the boiler makeup or

the cooling tower while simultaneously producing a clean salt for byproduct sale with

only a minor volume of contaminants.

4.0 Pollution Control Acts In India

Environmental Laws

1. The water (Prevention and Control of Pollution) Act, 1974;

2. The water (Prevention and Control of Pollution) Cess Act, 1977;

3. The Air (Prevention and Control of Pollution) Act, 1981;

4. The Environment (Protection) Act, 1986;

I. Water (Prevention and Control of Pollution) Act, 1974:

The water (Prevention and Control of Pollution) Act, 1974 provides for the preventionand control of water pollution and the maintaining or re-storing of wholesomeness of

water. Under the scheme of the Act, the relevant provisions, casting obligations onpersons may be referred under sections - 24, 25/26 and 31 of the Act.Section - 24,prohibits on the use of stream or well for the disposal of polluting matters,

which is in excess of the standards laid down by the Board. In other words, people areunder obligation to observe the standards laid down by the Board, in the matter of use of


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stream or well by way of disposal of the polluting matters, determined in accordance with

the Board's Standard.

Section - 25/26, restricts establishment or use of new or existing outlets or dischargewithout prior consent from the Board. In other words, person are under obligation to

apply for consent, before they are taking steps to establish any industry or are bringinginto use any new outlet or are continuing with the existing Outlet for the discharge ofsewage or trade effluent.

Section - 31, cast obligation on any industry, operation or process to furnish information

to the Sate Board, including other agencies, about accidental discharge of any poisonousmatter into a stream or well or sewer on land. Failure to carry out the aforesaid

obligations attracts penal provisions under sections 43, 44 and 42 respectively.

II. The water (Prevention and Control of Pollution) Cess Act, 1977:

The water (Prevention and Control of Pollution) Cess Act, 1977 provides for the levy and

collection of Cess on water consumed by persons carrying on specified industry and bylocal authorities, with a view to augmenting the resource of Central and State Board's for

the prevention and Control of water pollution, constituted under the Water (Preventionand Control of Pollution) Act, 1974. The relevant provisions casting obligation under this

Act may be referred under sections 3,4 and 5.

Section - 3 casts liability on every person carrying on any specified industry underSchedule I of the Act, and also on every authority to pay a Cess for the purpose of the

Water (Prevention and Control of Pollution) Act, 1974 and utilization of water there

under.

Section - 4, requires every person carrying on any specified industry and every localauthority to affix meters of prescribed standard, so as to measure the quantity of water

consumed by them.Section - 5, requires the said persons to furnish returns in the prescribed format, showingthe quantity of water consumed in the previous month.

Failure to carry out the obligations and liability, as aforesaid, attracts the penal provisionunder section 14 of the Act.

III. Air (Prevention and Control of Pollution) Act,1981:

The Air (Prevention and Control of Pollution) Act, 1981provides for the prevention,

control and abatement of air pollution.

The liability/obligations imposed on the concerned persons under the scheme of this Actmay be referred under the provisions of sections 21,22 and 23.

Section - 21, similar to the provision under section 25/26 of the Water Act, 1974, puts

obligation by way of restriction on any person on the establishment or operation of anyindustrial plant in an air pollution control area, without obtaining prior consent from the

concerned Board.


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Section - 22 is also comparable to section 24 of the Water Act, 1974. It requires any

person carrying on any industrial plant to allow discharge or emission only within the

prescribed standard.

Section - 23is also comparable to section 31 of the Water Act, 1974, where under any

person, carrying on an industrial plant, shall furnish information to the State Board orother agencies, in case due to any accident or other unforeseen act or event emission hasoccurred in excess of the standards laid down by the Board.

In the event of failure to carry out ones obligations or liabilities, as aforesaid, penal

provision under Section - 37 of the Act is attracted.IV. Environment (Protection) Act, 1986;

It provides for the protection and improvement of environment and the matters connected

therewith. This legislative piece was brought into existence by the Parliament, as

Umbrella Act, which intended to cover all the specific and general provisions left by theearlier enactments.

The instant Act, being broader in approach, has broader catch also in creating liabilities

and obligations on the Nation. The obligations created under this Act may be broadlyreferred under sections 7,8,and 9.

Section - 7puts obligation on every person carrying on any industry or operation to allow

emission or discharge only within the standards prescribed by the Central Government.

Section - 8 requires any person handling hazardous substance to handle them in

accordance with such procedure and safe - guards as has been prescribed by the Central

Government by the following Rules . These Rules, further break obligations and

liabilities on certain persons to carry out, as discussed below separately :-

(A.) The Hazardous Wastes (Management and Handling) Rules, 1989:

These rules apply to hazardous wastes, as specified in its Schedule but shall not apply todischarge or emissions covered under the the Water Act, 1974 and the Air Act, 1981;

shall not apply to wastes arising out of the operation from ships, beyond 5 Kilometers inthe sea; and shall also not apply to Radio-Active Wastes covered under the Atomic

Energy Act, 1962.

These rule create liability on all such persons, who are handling or causing to be handledhazardous wastes specified in its schedule.

Rule - 4creates responsibilities on the occupiers, who generate hazardous waste listed in

column - II of the schedule in quantities equal to or exceeding the limit given in column -III of the said Schedule, to take all proper steps during handling and disposal of such

waste without creating any adverse effect.

He is also required to give specified information by the State Board to the operator of afacility intending to get his hazardous Waste treated.

Under Rule 5, every occupier generating hazardous wastes and having facility for

collection, treatment, storage and disposal of such wastes, is required to obtain

authorization for handling such hazardous wastes from State Pollution Control Board.


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Similarly, any person, who intends to or is operating a facility for the collection,

reception, treatment, transport, storage and disposal of hazardous wastes, shall have to

obtain authorization from the State Board.

Under Rule 10, the occupier or the operator of a facility shall be under obligation to

report immediately to the state Board about any accident occurring at the facility or on ahazardous wastes site.

Water Pollution:

THERMAL POWER PLANTS

ParametersMaximum limiting concentration milligram per

liter

(Except for pH and temperature)

1. CONDENSER COOLING WATERS ( ONCE THROUGH COOLING

SYSTEM )

pH 6.5 to 8.5

TemperatureNot more than 5

0C higher than the intake water

temperature.

Free available chlorine 0.5

II.

BOILERBLOWDOWNS

Suspended Solids 100

Oil & Grease 10

Copper ( total ) 1.0

Iron ( total ) 1.0

III. COOLING TOWER

BLOW DOWN

Free available chlorine 0.5

Zinc 1.0

Chromium ( Total ) 0.2

Phosphate 5.0


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IV. ASH POND

EFFLUENT

P

H

6.5 - 8.5Suspended Solids 100

Oil and grease 20

Standards prescribed for emissions of Air Pollutants under Air

(Prevention & Control of Pollution) Act, 1981

1. (a) STACK EMISSION STANDARDS FOR BOILER PLANTS

SteamGenerating

Required particular matter

Capacity A B

Area upto 5 Km from the periphery of

class I and class II Townother than "A"

less than 2

ton/ht800 mg/NM

3 1200 mg/NM

3

2 ton to 10

ton/hr500 mg/NM

3 1000 mg/NM

3

above 15ton/hr

150 mg/NM3

150 mg/NM3

All emissions normalized to 12% carbon dioxide

(1)) STANDARDS FOR STACK HEIGHT FOR BOILER PLANTS

Steam Generating Capacity Stack Heights

1 More than 2 ton/hr. 9 meters or 2.5 times the height of

neighboring building whichever is more

2.more than 2 ton/hr to5 ton/hr. 12 meters



5.more than 15 ton/hr to 20 ton/hr. 21meters

6.more than 20 ton/hr to 25 ton/hr. 24 meters


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7.more than 25 ton/hr to 30 ton/hr. 27 meters

8.more than 30 ton/hr 30 meters or using the formula H = 14

(Q)0.3

where Q So2 emission in kg/hr.For higher KVA rating, stack height H (in meter ) shall be worked out

according to the formula H=h+0.2 Where h=height of the building in meters

where the generator set is installed. For the industries which install the facilities

for removal of particulate or gaseous emissions to adhere to the limits pre-

scribed, the stack height can be relaxed as under: b) H= 14 (Q)0.3 where Qg is

the gaseous emissions in kg/hr. c) H=74 (Qp is the quantity of particular matter

in tonnes /hr minimum stack height in all cases shall be 9 meters or as calculated

from relevant formula whichever is more.

2. STACK EMISSION STANDARD FOR FURNACES

1) cupola Furnace Capacity of the furnace

Particular matter i) Less than 3 tonnes /hr=450 mg/NM3

ii) 3 tons /hr and above = 150 mg/NM3

2) Are Furnace

Particular matter All sizes = 150 mg/NM3

3) Induction Furnace


4) Reheating (Reverberatory

Furnace


3. EMISSION STANDARDS FOR THERMAL POWER PLANT

A) STANDARDS FOR PARTICULAR MATTER EMISSIONS

i) Less than 210

MW

150 mg/NM3 350mg/NM

3

ii)210 MW &

above

150 mg/NM3 350mg/NM

3

B) STANDARDS FOR SULPHUR DIOXIDE EMISSIONS

i) So2 when emitted shall not

exceed 600 ng/i

of energy produced


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ii) Control through stack Height

Boiler size Stack Height

Less than 210 MW H=14 (Q)0.3

210 MW to less than 500 MW 220 meters

500 MW and more 275 meters

Where Q = SO2 , emission in kg/hr.

H = Stack height in meters.

Examples from Examination

Q.1 What are the elements in flue gases which pollute the atmosphere? How they can be

controlled?

Q.2 What are the measures for controlling the air pollution? (8.8.1989)

Q.3 Enumerate objectionable ingredients in flue gases with respect to air pollution control.

(11.10.95)

Q.4 What causes heavy black smoke when fuel oil is burnt? (9.2.1988)

Ch 22 Pollution

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Transcript of Ch 22 Pollution