report ntpc good one

8/13/2019 Report Ntpc Good One

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INTRODUCTION

NTPC Ramagundam, a part of National Thermal Power

Corporation, is a 2600 MW Power station situate atRama!unam in the state of "nhra Praesh#Inia$%It is the

&urrent lar!est Power in 'outh Inia% It is the first I'O ()00(

&ertifie *'uper Thermal Power 'tation* in Inia%

+eneration of su&h humon!ous power inoles &om-ustion

of lar!e amount of &oal, whi&h results in prou&tion of hu!e

.uantities of /l "sh% Improper isposal of /l ash results inseere enironmental pro-lems an thus disposal of fly ash is


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of utmost importan&e% Disposal of /l ash is primaril one in

two methos1 Wet pro&ess an Dr Pro&ess% In NTPC

Rama!unam the wet pro&ess is aopte% The wet pro&ess

inoles isposal in an ash pond whi&h is -oune - an ash

3e%

This report is an attempt to es&ri-e the &onstru&tion an

maintenan&e of an "sh D3e%

D4'CRIPTION O/ 'IT41

The ash 3e is lo&ate near Rama!unam railwa station in

3arimna!ar istri&t of "nhra Praesh% The site is &ate!orise

into ) 5a!oons namel N(,'(,N2'2where N an ' ini&ates

that the 5a!oon is lo&ate in northern an southern parts of

the site respe&tiel an su-s&ript num-er ini&ates the orer

of &onstru&tion of 3es in the respe&tie re!ions %

This report es&ri-es the &onstru&tion of '23e% '23e is

sprea oer 700 a&res an -oune - D3e on 7 sies an

iier -un on the southern sie%


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/58 "'9 "ND IT' DI'PO'"51

/l "sh1

Fly ash is finel iie resultin! from the &om-ustion of

powere &oal% /l ash is !enerall &apture from the

&himnes of &oalfire power plants, an is one of two tpes

of ash that :ointl are 3nown as coal ash; the other, -ottom

ash, is remoe from the -ottom of &oal furna&es% Depenin!

upon the sour&e an ma3eup of the &oal -ein! -urne, the

&omponents of fl ash ar &onsiera-l, -ut all fl ash

in&lues su-stantial amounts of sili&on io


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Disposal of /l "sh1

The isposal of /l "sh is primaril one in two s&hemes1

(% Dr Disposal 2% Wet Disposal

Dr isposal1In r isposal, the fl ash is transporte -

tru&3, &hute or &oneor at the site an ispose off -

&onstru&tin! a r em-an3ment #3e$ or in a lanfill%

Wet isposal1In wet isposal, the fl ash is transporte as

slurr throu!h pipe an ispose off in impounment &alle*ash pon*%

Most of the power plants in Inia use wet isposal sstem,

an when the la!oons are full, four -asi& options are

aaila-le1

#a$ Constru&tin! new la!oons usin! &onentional

&onstru&tional material

#-$ 9aulin! of fl ash from the e


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ash pon whi&h are lo&ate within 6 3ilometres istan&e from

the power plant% Depenin! on the istan&e an eleation

ifferen&e, ener! re.uire for pumpin! is er hi!h

a&&orin!l the pumpin! sstem has -een esi!n aninstalle%

There is a -asi& ifferen&e -etween an ash pon an a water

reseroir% The ma:or ifferen&es are hi!hli!hte -elow%

?Onl the ash parti&les settle at the -ottom of the pon%

?The -un is not su-:e&te to hrostati& pressure oer the

full hei!ht of the -un Due to proision of 'an -lan3et ,'an &himne an Ro&3 Toe for !oo raina!e all alon! the

-un, the preti& line is maintaine at er low leel to ensure

that the -un safet%

The ash pon &an -e esi!ne e&onomi&all utili@in! the

aanta!e of low phreati& line as mentione a-oe% This paper

es&ri-es important issues relate to esi!n, operation an

maintenan&e of ash pon%

"'9 POND 5"8OUT1

/ollowin! points shall -e note while sele&tin! the lo&ation

an laout of the ash pon1

(% The area shall -e as &lose as possi-le to the power plant to

reu&e the pumpin! &ost%

2% Proisions shall -e mae for erti&al an hori@ontal

e


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)% In &oastal area were !roun water is alrea saline, area

with perious soil is prefera-le to effe&tiel rain the water

throu!h the -ottom of the ash pon %'u&h ash pon &an hae

!oo raina!e, !etsraine faster an hae -etter sta-ilit%A% In the interior areas, een if it is awa from water -oies, it

is prefera-le to hae a fairl imperious stratum to preent

mi!ration of ash water into the !roun water% "s per Pollution

Control Boar norms, an imperious mem-rane has to -e

proie to preent pollution of the !roun water%

6% If hill terrain is within reasona-le istan&e, a suita-le

alle &an -e ientifie for formin! the ash pon% In su&h&ase, the hill slopes will sere as ash 3e an the len!th of

the 3e to -e -uilt will !et &onsiera-l reu&e%

% In most of the ash pons, the total area aaila-le is iieinto two or more &ompartments so that anone of the

&ompartment &an -e in operation while other &ompartments

were ash has alrea -een eposite is allowe to r an

there after the hei!ht of the pon is further in&rease% If the

area &omprises of a sin!le pon, it is not possi-le to in&rease

the hei!ht while the pon is in operation% 4a&h &ompartment

is re.uire to hae &ertain minimum area to ensure that there

is ae.uate time aaila-le for settlement of ash parti&les while

this slurr traels from the is&har!e point to the outlet point%

This istan&e shoul -e minimum 200m to ensure that onl&lear water a&&umulates near the outlet%

It is an o-sere fa&t that the ash pons in N%T%P%CRama!unam are in a&&oran&e with the a-oe liste

&riterion%

D4'I+N O/ BUND1


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The &onstru&tional methos for an ash 3e &an -e !roupe

into three -roa &ate!ories1

#a$Upstream Constru&tion Metho

#-$Downstream Constru&tion Metho #&$Centreline Constru&tion Metho

#a$ Upstream Constru&tion Metho1 This is mostreferre esi!n as the earthwor3 .uantit re.uire isminimum%

Out of the a-oe 7 alternatie methos, the upstream methois mostl &hosen ue to its minimum &ost% The aspe&ts to -e

ta3en &are are ae.ua& of the eposite

parti&les to support the aitional wei!ht% "part from the

sta-ilit of the 3e, followin! features shall -e in&lue in

the esi!n1

(%The entire upstream fa&e of the 3e shall -e proie with

stone pit&hin! or -ri&3 linin! or pre&ast tile linin! to preent

erosion of the slope - wae a&tion urin! hea win%


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2% The entire ownstream slope shall -e proie with !rass

turfin! to preent erosion of the ownstream sie urin! rains%

7%" ro&3 toe an toe rain shall -e proie for safe e


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"fter e&antation, the &lear water shall -e raine off ensurin!

minimum hei!ht of water a-oe the ash eposition at the

outlet su&h that the suspene parti&les are within the

permissi-le limit of (00 ppm%

6%If natural alle is utili@e for ash pon, the surfa&e runoff

from natural hill slopes outsie the pon area shall not -e

allowe to enter the ash pon area% Instea it shoul -e

suita-l ierte to the surrounin! area - &onstru&tin! &at&hrains so that the loa on e&antin! sstem oes not in&rease

urin! monsoon% "lso a spillwa shall -e proie

for the unforeseen &ir&umstan&e of er hea rain an

-lo&3in! of the e&antin! sstem% If su&h spillwa is not

proie, slurr an rain water &an reu&e the minimum free

-oar re.uire an &an result in serious failure of the 3e%

Pre&autions for Upstream Constru&tion Metho1

(%The entire wei!ht of new &onstru&tion for raisin! the 3e is

supporte on &ompa&te founation up to AE of MDD%


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2%'in&e the entire se!ment of new &onstru&tion is supporte

on eposite ash, li.uefa&tion analsis of the eposite ash is

er important% If the eposit is not safe a!ainst li.uefa&tion,

suita-le remeial measures nees to -e aopte -efore raisin!3e%

#-$ Downstream Constru&tion Metho1 "fter the pon!ets fille upto the first sta!e of &onstru&tion, the pon hei!htis in&rease - epositin! the earth F fl ash on the

ownstream fa&e of the 3e ash shown in the fi!ure%

In this &ase it is possi-le to raise the hei!ht of the pon een

when the pon is in operation% 9oweer there is no reu&tion

in the .uantit of &onstru&tion whi&h is same as a sin!le sta!e

&onstru&tion%

#&$Centreline Constru&tion Metho1 In this metho, after thepon !ets fille up to the first sta!e, material is pla&e for

raisin! hei!ht of the 3e on either sie of &entre line of the

3e su&h that the &enter line of the 3e remains at the

same lo&ation% This re.uires part of the raw material to -e

pla&e on the eposite ash an part of the material on the

own stream fa&e of the e


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re.uire to -e eposite on the settle fl ash, it is not

possi-le to &arr out the &onstru&tion when the pon is in

operation% This metho &an -e aopte onl if the total area of

ash pon is iie into &ompartments%

In N%T%P%C Rama!unam the Upstream Constru&tion Metho

has -een aopte%

D3e Constru&tion an 5aout1

WORG' IN=O=54D IN CON'TRUCTION1

(%Preparation of wor3 areasF&learin! siteF:un!le &learan&e

2%'trippin!%

7%/ounation preparation an -en&hin! at :un&tions with

hi!her !roun or 3e%

)%/ormation of the 3e se&tion%

A%Constru&tion of san -lan3et, san &himne an san filter%

6%Constru&tion of ro&3 toe an filters%


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%RR Masonr wor3%

>% Insie slope prote&tion with -ri&3 linin! on flat A mm

thi&3 pain! an pointin! with (16 Cement mortar%% outsie slope prote&tion with !rass turfin!%

(0% Constru&tion of slope rains%

((% Constru&tion of roa%

(2% 4


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'an -lan3et1 The hori@ontal laer of san of spe&ifie

thi&3ness #A00 mm$ proie so as to ensure passa!e of water

from san &himne to rain%

'an &himne1 The erti&al laer of san of spe&ifie with

#A00 mm$%It has to ensure water passa!e from ash pon to

san -lan3et%


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A00mm Thi&34arth &oer on the upstream of

3e


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san &himne


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Bri&3 pit&hin! #Upstream sie$


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Constru&tion of rain


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Measurin! thi&3ness of san #shoul -e A00 mm when

measure perpeni&ular to the surfa&e$

M"N"+4M4NT O/ "'9 POND1

Proper operation an maintenan&e of "sh Pon is essential

-e&ause ash pon failure is isastrous% /or e atGin!ston /ossil Plant in Unite 'tates of "meri&a whi&h

resulte in massie eastation of life an propert% The

followin! !uielines are -ase on arious o-serations atarious sites an the &oer important points to -e followe

urin! operation of the 3e%

#a$Metho of 'lurr Dis&har!e1(% /or ash pons of this nature, it is most important that the

is&har!e of slurr is istri-ute uniforml oer the entire


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perimeter of the ash 3e, e


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#-$ De&antin! 'stem1The eleation of &as&ae wall or flash -ar or openin! in

e&antin! shaft is er important% This shall -e &hosen to

ensure the followin!1i% The .ualit of e&ante water shoul -e satisfa&tor with

total suspene solis less than (00ppm% If the eleation of

outlet is low, the suspene solis will in&rease%

"t an time urin! operation, if the out flowin! water oes

not meet the re.uirement, the eleation of the e


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shall -e raise% Water samples shall -e re!ularl &olle&te at

interal of ( wee3 an &he&3 for total suspene solis% "re!ister shall -e maintaine with re&ors of su&h

measurements% 9i!her &on&entration of parti&les is li3el to&reate more eposition in the re&ir&ulation sump raisin! the

outlet eleation an it ma re.uire ea&uation% " ela in

raisin! the outlet eleation will result in hi!h &on&entration of

ash% On the other han, too earl raisin! will result in

in&rease area of e&ante water pon an reu&e the -ea&hlen!th%

#&$Raisin! of "sh D3e1The pon whi&h has alrea -een filleup shall -e allowe tor without an further is&har!e of slurr for a minimum

perio of ( month -efore the &onstru&tion for raisin! the

hei!ht is ta3en up% The pon whi&h is not -ein! use shall -eproie with water sprinklers at re!ular interals to ensure


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that the surfa&e of the pon is maintaine moist to preent

ust pollution%

Too mu&h of water sprain! shall -e aoie as this is li3elto ma3e the surfa&e slush an moement of the ehi&les for

&onstru&tion purpose will -e iffi&ult%

#$ Maintenan&e of "sh D3e1It is er important to &onstantl superise the ash 3e an

&arrout ne&essar remeial measures% /ollowin! aspe&ts

hae to -e &onsiere urin! inspe&tion of the 3e1(% Wet patches on downstream slope1 If the wet pat&hes&ontinue to appear, the area shall -e prote&te - pla&in! a

san filter laer followe - a laer of stones to preent

pipin! failure% Whereer relief wells are proie, the outflow

from the relief wells shall -e monitore% " re!ister shall -e

maintaine re&orin! rate of flow from ea&h relief well% 'u&h

measurements shall -e ta3ena fre.uen& of (A as% If an of the is&har!e pipe from the

relief well is foun to hae -een -lo&3e, the same shall -e

&leare for effe&tie relief of the seepa!e water%

2. Gulley formation1The ownstream fa&e &an hae !ulle

formation ue to surfa&e water flow urin! rain% This &an-epreente - maintainin! !rass turfin! an - sele&tin! non

eroi-le earth &oer urin! the 3e &onstru&tion% If an

!ulle formation is noti&e, the same shall -e -a&3fille with

&ohesie soil #not fl ash$ an &oere with !rass turfin!%

7% Rat holes / animal burrows1Durin! inspe&tion if an rat

holes or animal -urrows are noti&e, the same shall -e

plu!!e usin! &ohesie soil an &oere with !rass turfin!%

). Softening of downstream area1"part from the 3e slope,

the are a:a&ent to ownstream of the ro&3 toe shall also -e

inspe&te% If an softenin! of the !roun is noti&e ue to


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'ewa!e of water, the area shall -e proie with an inerte

filter -lan3et% "t su&h lo&ations, relief well shall -e installe

for safe e% The 3e shall -e isite parti&ularl after eents li3e

earth.ua3e, &&lone, hea rains, hi!h floo in the rier, et&%

an a report prepare -ase on the o-seration% If an ama!e

is noti&e, the same shall -e re&tifie as per the !uielines

!ien in this note% If no suita-le !uielines are foun for the

nature of the ama!e, the esi!ner of the 3e shall -e

&onsulte immeiatel%


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4N=IRONM4NT"5 I''U4'1

Thou!h fl ash is 3nown to -e an inert material, there isan apprehension a-out &ertain solu-le &hemi&als in the

e&ante water whi&h &an hae aerse effe&t if su&h e&ante

water is let into a rier -o or !roun water% /or thispurpose, the norms of Pollution Control Boar insist on

proiin! a plasti& liner oer the entire -ottom of the pon

an upstream fa&e of the ash 3e% New ash pons -ein!

&onstru&te hae to proie the plasti& liner to preentpollution of !roun water% Due to the presen&e of plasti& liner,

proision of the raina!e -e&omes iffi&ult an as result the

eposite seiments &oul not !et &onsoliate to the same

e

report ntpc good one

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