Esp Principle and Design

7/31/2019 Esp Principle and Design

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Welcome to

Electrostatic Precipitator


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Air Pollution


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Air Pollution


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CONTRIBUTION FROM POWER STATION


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Pollution Distribution Pattern

Man Made


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POWER POSITION IN INDIA


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EFFECTS OF AIR POLLUTION

LUNG CANCER.

SKIN, EYE

ASTHMA.

CENTRAL NERVES SYSTEM.

SUFFOCATIONAL DEATH.

ACID RAIN.

DEPLETION OF OZONE LAYER. GREEN HOUSE EFFECT AND

GLOBAL WORMING.


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Effect of Air Pollution on Humen


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GENERAL

VISIBILITY REDUCTION DUE TO SCATTERING OF LIGHT

FROM SURFACES OF AIR BORNE PARTICLES

MATERIAL DAMAGE

AGRICULTURAL DAMAGE DUE TO ASH DEPOSITION

LOSS AND REDUCTION OF GREEN PLANT PIGMENT

CALLED CHLOROPHYLL RESULTING IN YELLOWING AND

EVEN DROPPING OF LEAVES.

DAMAGE TO BUILDINGS, MONUMENTS OF MARBLE

ETC.


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HUMAN HEALTH

OCCUPATIONAL SKIN DECEASE

AFFECTS LUNGS - SILICOSIS FOR FOUNDRY WORKMEN

RESPIRATORY CONDITION DUE TO TOXIC AGENTS

ACUTE CONJUNCTIONS DUE TO CHEMICAL DUSTS, FUMES

AND GASES

DISORDER DUE TO PHYSICAL AGENTS - ENVIRONMENTAL

HEAT OR LOW TEMPERATURE EYE IRRITATION, COUGH AND BREATHLESSNESS

FORMATION OF CARBOXYL HEMOGLOBIN WHICH

PREVENTS O2 CARRIAGE BY BLOOD


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Rapid economic growth

Rapid industrialization and urbanization

Increased industrial production

Population explosion

Growth in demand for power

Increase in requirement for thermal power plants

More number of old coal based power plantsdesigned for high emission & low ash content coal

High ash content or deterioration in quality of coal

reserve


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National Ambient Air Quality Standards


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TYPES OF DUST COLLECTING EQUIPMENTS

Sl.NO.

Type of Dustcollectors

Pressuredrop

mmWc

Collectioneffieicny,

%Remarks

1. Gravity Settlingchamber

25-30 30 to 40 Less efficiency, morespace required andnot suitable for powerplant

2. Inertial Collectors Impact Centrifugal

(cyclones)

30 40

60-80

30 40

75 to 80

Not for power plant Were widely used in

power plants butcan not satisfy thepresent daypollution controlrequirement


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Sl.NO.

Type of Dustcollectors

Pressuredrop

mmWc

Collectioneffieicny,

%Remarks

3. Scrubbers(wet) 50 to 60 80 to 90 Used mainly in processindustries and can notsatisfy the pollutioncontrol requirement

4. Electrostaticprecipitators

15-25 99.99 Can meet any efficiencand mostly used in all

power plants.5 Fabric Filter 125 to

15099.99 Can meet any efficienc

and used many poweplants abroad. Gainingmomentum in Indian

Power plants also.

TYPES OF DUST COLLECTING EQUIPMENTS


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PURPOSE OF POLLUTION CONTROL EQUIPMENT

Recovery of material for economic reasons

Pulp and Paper Industries (Sodium Sulphate)

Removal of abrasive material in the dust toreduce wear and tear of the Fan components

Removal of objectionable matter in the dust

NO2 and SO2


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ADVANTAGES OF ELECTROSTATIC PRECIPITATORS

Very high collection efficiency

Low pressure drop

capacity to collect sub-micron particles

Robust construction - Longer life

Less maintenance

Adaptability


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ELECTROSTATIC PRECIPITATOR PRINCIPLE


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ESP - CORONA GENERATION

Due to the ionisation of gas molecules, + ve ions, -ve ions and freeelectrons are generated.


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CORONA DISCHARGE IN SPIRAL ELECTRODE


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ESP - PARTICLE CHARGING

The -ve charges of ions and free electrons travel towards +ve electrodeand the +ve charges of ions travel towards -ve electrodes.

When -ve ions travel towards +ve electrodes, the -ve charges getattached to the dust particles and thus the dust particles are

electrically charged,


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ESP - PARTICLE COLLECTION


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ESP - REMOVAL OF PARTICLE


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PRINCIPLE


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ESP SIZING THEORY

DEUTSCH - ANDERSON EQUATION

Collection Efficiency = 1 - e - w. SCA

where,

w = Migration velocity

SCA = Specific Collecting Area

Migration Velocity

The velocity which the dust particle travel towards the collecting electrodeunder the influence of electric field.

Specific collecting area

Amount of collecting area required to be provided to collect dust in gasflow rate of 1 m3/s.


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DEFINITIONS


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EFFECT OF VARIOUS PARAMETERS

Gas velocity

velocity is decided by the gas flow and collection efficiency

required Higher the gas velocity, higher the carryover of dust

particles without collection - Re-entertainment

Very poor velocity alters the flow distribution and effectssettling of dust particles

optimum velocity depends upon the application willimprove the performance.


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Aspect ratio

During the rapping, the falling of dust particle take a trajectory

form Lower the aspect ratio, the trajectory dust travel along with gas

flow without falling in to hoppers - Leads to re-entrainmentloss.

Higher the ratio, performance will be good

optimum aspect ratio depends on allowable velocity, requiredcollection efficiency and available space.


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Treatment time

Time available for capturing the dust particle

more treatment time at reasonable velocity improves thecollection efficiency

Probability of capturing the re-entrained partilces improveswith time.


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ENVIRONMENTAL REGULATIONS IN INDIA

Prior to 1984

1974 water act

1977 water cess act

1981 air actThe cost of compliance was more than that ofnon-compliance:

1986 Environmental Protection Act

comprehensive act with command & control

Future trend is to internalize the environmentalimprovement cost


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REVISED EMISSION STANDARD(GAZETTE NOTIFICATION BY MINISTRY OF E&F DATED 19 05 93)

SUSPENDED PARTICULATE MATTER (SPM) : < 150 mg/Nm3

STANDARD ALSO STATES THAT

FOR POWER PLANTS

CAPACITY LESS THAN 62.5 MW AND

COMMISSIONED BEFORE 01 01 1982 : 350 mg/Nm3

FOR CEMENT PLANTS (TOTAL EMISSIONS)

CAPACITY LESS THAN 200 TPD : 400 mg/Nm3

CAPACITY MORE THAN 200 TPD : 250 mg/Nm3


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ENVIRONMENTAL REGULATIONSTODAYS WORLD

World Banks proposed guide lines

For new thermal power plants (TPP) for

capacities 50 MW

Pollution control at project formulation levelitself

Site specific emission guide line

Propose standard of 50 mg/Nm3

Aided projects are to abide by this

Further implication on technical, economic &institutional


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National Ambient Air Quality Standards


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Emission of various pollutants under thebusiness-as-usual scenario

Projection

0.1582.82434.022.0736.22011

0.1252.19338.019.6605.52006

0.0891.75259.117.9511.02001

0.0491.340.3016.162428.01996

SOX

NOX

SPMCOCO2

POLLUTANTS (MT)YEAR


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WORLD BANK NORMS


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COMPARISON OF PARTICULATE EMISSIONNORMS IN OTHER COUNTRIES

150India

4356Sweden194250Australia

3950Europian community

3950Germany

2836USA

ppmMg/Nm3Country


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COAL REQUIREMENT FOR BOILERS TYPICAL

151.266.634.2Ash entering ESP tph

18983.2542.75Ash generated tph

42018595Coal required in tph

500 MW210 MW110 MW

Coal with ash content 45 % and HHV 3000 Kcal / Kg


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Boiler circuit with Precipitator


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BHEL ESP for different application

Boiler PF / CFBC / AFBC / stoker

Recovery Boiler for paper plant

Lime Kiln for paper plant

Biomass Bagasse / Ricehusk / wood chips

Cement plant - cooler / kiln / coal mill / cement mill

Steel plant Sponge Iron / Sinter plant

Glass plant


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ESP REFERENCEAPPLICATION NO. OF PROJECTS NO. OF ESPs

UTILITY BOILERS - PF Fired - 15 to 660 MW437 1074

INDUSTRIAL BOILERSCPP, VU40, Stoker, etc 104 134

AFBC BOILERS25 to 165 TPH 57 57

CFBC BOILERS30 to 250 MW 18 33

CHEMICAL RECOVERY BOILERS75 to 900 TPD 46 70

OIL FIRED BOILERS -125 MW 3 3

BIOMASSUpto 20 MW 50 50

CEMENT 16 16

STEEL 11 13

GLASS FURNACE 2 2

LIME KILN170 TPD - Paper plant 1 1

REFRACTORY - Magnesite 1 1

TOTAL 746 1454

NOTE: The above list is applicable for the contracts with zero date up to 14.08.2007


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BHEL ESP NOMENCLATURE

4 X F A A 8 X 45 M 2 X 96 150 - 2

Type of Hopper:

1 Trough; 2 Pyramidal3 No hopper Flat bottom

Nominal Height of CE, In deci metre

Nominal width of ESP, in deci metre

Number of Bus sections per field

Electrode spacing in mm,F - 250; H - 300; M - 400

Nominal length of field, in deci metre

Number of fields per ESP

Material of casing, A Steel;

C - Concrete

Direction of gas flow, A Horizontal; T- Vertical

F Electrical filter

Number of ESP per Unit

ESP DESIGN CONSIDERATIONS


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EMISSION VS ESP EFFICIENCY FOR

DIFFERENT DUST BURDEN

99.25

99.5

99.75

100

25 50 75 100 125 150

EMISSION REQUIREMENT-

mg/Nm3

EF

FICIENCYREQUIREMENT-%

20g/Nm3

40 g/Nm3

60 g/Nm3

80 g/Nm3

100 g/Nm3

HIGH INLET DUST REQUIRES LARGER ESP


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DESIGN DATA REQUIRED FOR ESP

Application Process data

Gas composition

Gas pressure

Gas moisture

Dust composition

Particle size distribution

Basic design data

Gas flow rate

Gas temperature Inlet dust concentration

Environmental data

Outlet emission


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FACTORSW CONSIDERED FOR ESP SELECTION

Gas flow

Gas temperature Inlet dust concentration

Required outlet emission

Required collection efficiency

Moisture in gas

Sulphur content in coal Ash resisitivity

Particle size distribution

No. of ESPs per boiler

Minimum number of fields required

Minimum Specific collecting area

Maximum gas velocity

Minimum aspect ratio

Maximum area connected to one TR set

Collecting electrode spacing


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Effect of emission over increase of gas flow

150 165172.5 180 187.5

100

190

260

360

490

0

100

200

300

400

500

600

100% 110% 115% 120% 125%Gas flow

Emission

Flow

Emission

Graph shows the effect on ESP emission, due to increase of gas flow only,

without considering variation in gas temp. & dust load.

Variation of ESP emission w.r.t. gas flow is not linear.

For 25 % increase of gas flow, emission shoots up by about 5 times.

Effect on emission due to increase of gas


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Effect on emission due to increase of gas

temperature

135 140145 150

155

100 107

130

152

202

0

50

100

150

200

250

Base 5 10 15 20

Gas temperature

Gas Temp.

EmissionEmission

Graph shows the effect on ESP emission, due to increase of gas temperature only, without

considering variation in gas flow & dust load.

Variation of ESP emission w.r.t. gas temperature is not linear.

For 20 deg. C (15 %) increase of gas temperature, emission shoots up by

about2 times.

ESP DESIGN PARAMETERS FOR UNITS NTPC VINDHYACHAL


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ESP DESIGN PARAMETERS FOR UNITS 7 & 8, 9&10 NTPC VINDHYACHAL

PARAMETERS UNITS 7&8 UNITS 9&10

ESP TYPE FAA 7X45H 2X96130 FAA 8X45H 2x90135

GAS FLOW RATE 872.74 m3/sec 851.00 m3/sec

Flue gas temerature 130 deg C 130 deg C

INLET DUST

CONCENTRATION

40.47 gms / Nm3 38.90 gms / Nm3

OUTLET DUSTCONCENTRATION

50 mg / Nm3 27 mg / Nm3

Specific collecting

area

240.23 m2 / m3 / sec 274.12 m2 / m3 / sec


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BOILER OPERATING PARAMETERS FOR UNITS 7 & 8, 9&10

PARAMETERS UNIT 8 UNIT 9

LOAD 508 MW 507 MW

STEAM FLOW 1571 T/ Hr 15 92 T/HR

STEAM PRESSURE 172 KG/CM2 170 KG/CM2

FURNACE PRESSURE -3 MM WC -8 MM WC

STEAM TEMPERATURE 540 DEG C 540 DEG C

COAL FLOW 315 T/Hr 310 T/Hr

TOTAL AIR FLOW 1560 T / Hr 1815 T/Hr

O2 PERCENTAGE 4.5 % 3.0% 3.6 %

FLUE GAS TEMPERATURE AT

APH OUTLET

A B

140 / 170 150/ 175

A B

133 /137 140/130

FLUE GAS TEMPERATURE AT ID

INLET

A B

152 164

A B

127 122

FD FAN CURRENT 45 43 130 124

ID FAN CURRENT 360 / 370 340 / 328 252/270 294/295


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FLY ASH RESISTIVITY

Resistivity is an important factor, affecting ESP performance.

Ash with low resistivity is prone to re-entrain when the collecting

plates are rapped.

Ash with high resistivity can cause back corona and reduce ESP

performance.

Fly ash resistivity dependent on:

- Gas temperature

- Gas moisture

- Sulphur content in coal

- Ash composition (SiO2, Na2O3, CaO etc)

- Carbon content in ash

- Particle size of dust


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ESP DESIGN CONSIDERATIONSHIGH INLET DUST REQUIRES LARGER ESP

EMISSION VS ESP EFFICIENCY FOR

DIFFERENT DUST BURDEN

99.25

99.5

99.75

100

25 50 75 100 125 150

EMISSION REQUIREMENT-

mg/Nm3

EFFIC

IENCYREQUIREMENT-%

20g/Nm3

40 g/Nm3

60 g/Nm3

80 g/Nm3

100 g/Nm3


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Variation of Coal ash content

1.54

7.710.76

12.98

16

45

0

5

10

15

20

25

30

35

40

45

50

INDONESIA CHINA AUST RALIA SOUT H

AFRICA

US (OHIO) INDIA

ASH,%



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ESP COLLECTION EFFICIENCY VS SIZE

0

1

2

3

4

5

67

8

9

90 91 92 93 94 95 96 97 98 99 100

COLLECTION EFFICIENCY - %

CO

MPARATIVEESPS

IZE

BASE : ESP SIZE FOR 90% = 1


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ELECTROSTATIC PRECIPITATOR


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ELECTROSTATIC PRECIPITATOR


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FIELD 1 FIELD 2 FIELD 3 FIELD 4 FIELD 5

Collectionefficiency,%

81.4 13,8 3.5 0.91 0.272

Ashcollection,kg / Hr

26142 4432 1124 292 87

Emissionwith allfields,mg / NM3

100

Emissionwith 1 fieldoff,mg / NM3

265


765


2440


9550

Collection efficiency with 5 fields = 99.882 %

ASH COLLECTION & EMISSION PATTERN


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Different ESP size for same boiler capacity

Different fuel

Different coal quality (CV / ash)

Different emission value (150/100/75/50 mg/Nm3)

Emission with all fields or with one field off or both

ESP with one dummy field

ESP with one dummy filed & one field off

ESP selection for worst coal & guarantee for normal operation with

Design coal

ESP selection based on minimum SCA


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EMITTING ELECTRODE


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UPGRADING ESP - COMPONENTS FOR REPLACEMENT

RAPPING MECHANISM AND TUMBLING HAMMERS


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SUSPENSION ARRANGEMENT OF HIGH VOLTAGE SYSTEM


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DISCHARGE ELECTRODE RAPPING MECHANISM


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COLLECTING SYSTEM


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SUSPENSION ARRANGEMENT OF

HIGH VOLTAGE SYSTEM


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ESP CASING


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ESP HOPPERS


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METHODS OF IMPROVING

ESP

PERFORMANCE


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FLUE GAS CONDITIONING

FGC HAS BEEN INSTALLED AT BHATINDA,UKAI, KOLAGHAT & HWB MANUGURU

M/S CHEMITHON CLAIMS EXCELLENT

PERFORMANCE

THE SPM FIGURES GIVEN BY UTILITYDOES NOT CONFIRM

PERFORMANCE IMPROVEMENT IS NOTPROVEN.

THERE IS A HIGH COST OF INSTALLATIONAND RECURRING RUNNING COST


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USE OF BAG FILTERS

BAG FILTERS ARE EXTENSIVELY USED IN

CEMENT INDUSTRY

IT HAS 100% EFFICIENCY PERFORMANCE INDEPENDENT OF LOAD

DUE TO HIGH AMBIENT TEMPERATURE

NYLON BAGS HAVE TO BE USED WHICH

ARE EXPENSIVE

BAGS REPLACEMENT COST IS HIGH


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BAG FILTERS IN SERIES

THIS HAS BEEN TRIED AT KORADIMAHARASHTRA

PERFORMANCE IMPROVEMENT ISTHERE BY ABOUT 15%

REPLACEMENT COST OF NYLONBAGS IS VERY HIGH

THIS HAS ALSO NECESSIATED THEREPLACEMENT OF ID FANS


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NEED FOR UP-GRADATION

TO MEET REVISED EMISSION REQUIREMENT TO AVOID UNFORESEEN OUTAGES

TO OPTIMIZE INSPECTION AND MAINTENANCE

SCHEDULE

UP-RATING / CHANGE IN PLANT CAPACITY CHANGE IN FUEL OR RAW MATERIAL

CHARACTERISTICS

CHANGE IN OPERATING CONDITION OF BOILER

CORROSION OR EROSION OF MECHANICAL

COMPONENTS

DETERIORATION IN PERFORMANCE DUE TO AGING


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UPGRADING ESPEXTENDING CASING HEIGHT

OPTION 1 OPTION 2


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Thank you

By,

G.R.SHARIEF,

MANAGER/FES,

BHEL,RANIPET.

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Esp Principle and Design