Công Nghệ Chế Biến Khí - Chương 7. Điều Khiển Công Nghệ Và Thiết Bị Điều...

8/11/2019 Cng Ngh Ch Bin Kh - Chng 7. iu Khin Cng Ngh V Thit B iu Khin

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CNG NGH

CH BIN KH

TrngihcCng nghip

TS. Nguyn Mnh Hun


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CHNG 7.IU KHIN CNGNGH V THIT B IU KHIN


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CC CH IU KHIN V LM TH NO IU KHIN N

NH

- Qu trnh lm vic trn gin nn kh trung tm c qu trnh lm vic

ca cc phn t v cc thit b iu khin khng cn s tham gia trc

tip ca con ngi l qu trnh iu khin t ng.

- Mi phn t iu khin nhn mt tn hiu vo t mt s b phn ca

h thng iu khin, v to nn mt tn hiu ra a vo phn t khc.

Cc tn hiu c th l: dng in, in p, p sut, nhit , lu lng,

vn tc, gia tc, v trqu o ca tn hiu c th l sng in, ng

dn, lin kt c.


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H thng h v h thng kn:

- H thng h l h thng khng so snh kt qu thc t vi tr s mong mun (setpoint)

sau tc ng iu khin.

- H thng kn l h thng to nn mt tc ng o lng gia tn hiu vo (gi tr cn

setpoint) v tn hiu ra (gi tr thc). Sai lch gia hai tn hiu ny c dng lm tn hiuvo ca c cu iu khin.

Hnh 1: h thng iu khin kn

PLC:

ProgrammableLogic Controller


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- Mch phn hi bt u t tn hiu ra Y c o (cm bin) bi thit b o lng (Pressure, level,

temperature, flow transmitter ,detector , qua c cu chuyn i (cng chnh l b phn ca thit b o

lng) bin thnh tn hiu c chuyn i Y t l vi Y. tn hiu Y c so snh vi tn hiu vo to

nn sai lch (error)

= X-Y = gi tr cn gi tr thc

c tnh ton qua c cu so snh (l c cu ca b iu khin).

- Thit b iu khin bin i thnh tn hiu tc ng u nh c cu iu khin. Tn hiu tc ng l tn hiu

vo ca h thng c iu khin. N s tc ng vo c cu tc ng, c cu tc ng thng c hai

phn l b chuyn i (converter) v phn t iu khin (van, qut, bm) lm thay i qu trnh l mt i

tng iu khin, nhm trit tiu sai lch hnh thnh.

- C cu iu khin thc hin cc ch iu khin nh sau: ch iu khin t l (P), ch tch phn

(I), ch o hm (D). Ch P c th s dng ring bit, hoc kt hp vi mt hoc hai ch khc.

Ch I c th dng ring r nhng thc t t dng. Ch D khng th dng ring r. Cc t hp hay

dng l PI, PD, PID.


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Tuyn tnh v phi tuyn- Khi phn tch v thit k hu ht cc h thng iu khin c coi l cc phn t tuyn tnh,tc l phn t iu khin cho tn hiu ra t l thun vi tn hiu vo.- Tuy nhin c nhiu dng phi tuyn khc nhau xut hin trong cc phn t iu khin nh : tr,khong cht, bo ho m c tnh ca n c th hin qua hnh:

Hnh 2: mi quan h gia tn hiu vo/ra(I/O) ca phn t iu khin

- a: tuyn tnh: l mi quan h gia tn hiu

vo/ra (I/O) ca phn t iu khin hon tonl mt ng thng- b: phi tuyn : c th thay th gn ng bngmt ng thng, ng ny t v tr sais b nht.- c: Di cht l mt dy cc gi tr m tnhiu vo X khng lm thay i tn hiu ra- d: Tr l tnh phi tuyn dn n gi tr tnhiu ra Y khng trng nhau khi tn hiu votng hay gim.- e: Tr v cht th hin sai lch ln nht catn hiu ra gii hn trn v di- f: Bo ho l gii hn ca mt dy cc gi trtn hiu ra Y. Mt phn t thc t n giihn bo ho khi tn hiu vo thay i tn hiu

ra khng thay i.


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Gim chn v n nh

- khuych i ca b phn iu khin xc nh mt c tnh quan trng ca h thng iu

khin l dng gim chn. c tnh ny c h thng th hin ra nh l mt p ng di tc

ng ca bn ngoi. p ng ca h thng iu khin th hin theo nm dng nh sau

Hnh 3: cc dng p ng

Khi khuych i tng png ca h thng thay i theocc dng nh sau:a: qu gim chn,

b: gim chn ti hn,c: gim chn tt dn,d: p ng bin khng i,e: p ng bin tng dn


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- Ba loi u c trng cho h thng n nh, hai loi sau c trng cho trng thi

khng n nh. K thut n nh c dng lm tng gim chn trong h

thng, v do cho php t c khuych i cao.

- tng chung l tm mt tn hiu chng li s thay i i lng c iukhin. Tn hiu l tc thay i i lng c iu khin. Nh ta bit o

hm ca mt bin l tc thay i ca bin v tn hiu lm n nh ny c

coi nh o hm ca i lng c iu khin.

- gim chn tng nu o hm ca i lng c iu khin c tr ra khitn hiu sai lch trc khi vo c cu iu khin. Mt tn hiu lm n nh khc l

o hm ca tn hiu sai lch, nu i lng iu chnh l mt hng, tn hiu ny

bng gi tr m ca o hm i lng c iu khin. Gim chn tng nu o

hm sai lch c cng vi tn hiu sai lch trc khi vo c cu iu khin.


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Mc tiu ca h thng iu khin:

Hnh 4: p ng ti bc thang

- Lm gim ti a gi tr ca tn hiu sai

lch, mt s h thng sai lch c th

gim n 0, trong khi cc h thng khc

i hi sai lch d b cho s thay

i ca ph ti.

- Trong c hai trng hp h thng iu

khin cn a tr s sai lch v gi tr

n nh, tr s khng thay i.

- Mc tiu th hai l gim n mc ti

thiu thi gian n nh t

- Mc tiu th ba l gim n mc ti

thiu sai lch d sau khi t c

trng thi n nh


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nh gi h thng iu khin :

Cho thay i ph ti theo hm bc thang sau quan st th nu bin ca

mt nh dng bng bin ca nh dng trc n khi dao ng l tt dn

hi t tt:

Hnh 5: Suy gim bin khi c ti bc thang


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SCADA v DCS

DCS (Distributed Control System - H thng iu khin phn tn)

- H thng iu khin phn tn da trn cc phn cng v phn mm iu khin v thu thp d liu trn c

s 1 ng truyn thng tin tc cao, cc module c phn tn v t chc theo 1 cu trc nht nh vi

mt chc nng v nhim v ring. Cc thit b giao tip trn ng truyn tc cao ny cho php ghp nid dng vi cc b PLC, Controller , cc my tnh iu khin gim st khc.

- Cc chc nng iu khin c phn b khp h thng thay v x l tp trung trn mt my tnh n l.

Mt h thng DCS tiu biu c cc trm iu khin hot ng c lp v iu khin tng b phn chuyn

dng ca nh my...

- Kh nng x l tn hiu tng t v chy cc trnh t phc tp l th mnh ca h thng DCSSCADA (Supervisory Control And Data Acquisition - H thng iu khin gim st v thu thp d liu)

- C th hiu SCADA l h thng dng trong cc ng dng iu khin qu trnh,cng nghip ha cht, truyn

ti in nng.. n da trn 1 my tnh x l trung tm (my ch) , d liu thu thp t cc cm bin t ti cc

phn xng, cc ta nh,.. hay cc trm t xa c gi v my tnh trung tm qun l v iu khin ( vi

1 s lng hn ch cc lnh iu khin c nh ngha trc, gi ti cc c cu chp hnh).


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SCADA (Superv isory Contro l And Data Acquis i t ion) hiu theo ngha truyn thng

l mt h thng iu khin gim st v thu thp d liu. Nhm h tr con ngi trong

qu trnh gim st v iu khin t xa.


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Programmable Automation Controllers (PACs)

Human Machine Interfaces (HMIs)

DCS(Distributed Control System - H thng iu khin phn tn)


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Cc v d iu khin trn gin nn kh trung tm:

- h thng iu khin mc bnh:

C h h bi kh


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- h thng iu khin p sut

C h h bi kh


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h thng iu khin lu lng:

C h h bi kh


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h thng iu khin nhit

C h h bi kh


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Ch iu khin t l P:

Ch iu khin t l to nn tn hiu ra b iu khin t l vi tn hiu sai lch . Chng c

mi quan h tuyn tnh c nh gia i lng c iu khin v v tr ca i tng iu

khin.

u = P+ uo

qua cng thc trn trong h thng iu khin mc cc bnh tch nu tng khuych i P

th ch cn mt sai lch b hn ca cng van m 100%, ni cch khc khuych i

ln i hi sai lch nh t c v tr ca van cn thit cho vic cn bng qu trnh tuy

nhin vic tng khuych i ny cng dn n xu hng tng dao ng ca i lngc iu khin cho nn cn chn phng n dung ho.

- Ch ny c dng cho nhng qu trnh c dung lng nh v thay i ph ti nhanh P

cn chn ln trnh dao ng.

C h h bi kh


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Ch iu khin tch phn I

ch iu khin tch phn lm thay i tn hiu ra u t l vi tch phn ca tn hiu sai lch.

Ch ny to nn mt tc ng iu khin lm tng lin tc tc ng iu chnh theo thi

gian. Nu sai lch nh ch tng I c tc dng hiu chnh chm, nu sai lch lnch I tng tc dng hiu chnh nhanh hn. I l tc tch phn (1/s) c tnh I/O nh sau:

Hnh 6: c tnh I/O

ca ch Ich I hu nhlun dng vi P

Cng ngh ch bin kh


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Ch iu khin o hm Du = D(d/dt)

D l hng s thi gian o hm

Hnh 7: p ng bc v dc ca ch D l tng

- Ch iu khin o hm cho tn hiu ra

u t l vi vn tc thay i ca chnh l

d/dt. Ch D ngn chn mt sai lch ln

bng cch to nn mt tc ng hiu chnh

chn li s pht trin ca n.

- Ch D ch tc ng vo tn hiu ra ca

b iu khin khi tn hiu sai lch thay i

(tn hiu ra khng ph thuc vo gi tr ca

sai lch). V th ch D khng s dng

ring bit m kt hp vi ch khc.

-p ng bc v dc ca ch o

hm l tng c minh ho hnh bt

c thi im no, tn hiu ra ca b iu

khin D lun t l vi dc, hoc tc

thay i ca sai lch .

-p ng bc ch ra nguyn nhn lm cho

ch D khng dng ring trong thc t v

mi v tr thay i bc tn hiu ra u c dc v cc

Cng ngh ch bin kh


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Ch iu khin PI

Hnh 8: c tnh I/O ca ch PI

Cng ngh ch bin kh


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- Ch PI l t hp ca ch P v I. y khi thay i tn hiu vo th ban u b PI

lm vic nh khu t l tc l tn hiu ra u t l vi sai lch , sau ch I to ra s thay

i b xung tn hiu ra tc l lm cho n t l vi tch phn ca tn hiu sai lch.

Tc tch phn I l s o ca thi gian cn thit ch I thch ng li s thay i

ca tn hiu ra do ch P a n.

- Ch I c xu hng lm tng dao ng ca i lng c iu khin. khuych i

P cn phi gim khi kt hp ch I. iu ny lm gim kh nng ca b iu khin

p ng s thay i nhanh ca ph ti. Nu qu trnh c thi gian tr ln tn hiu sai lch

khng p ng kp thi sai lch hin c trong qu trnh, s tr ny s dn n qu hiuchnh, ch I tip tc lm thay i tn hiu ra ca b iu khin sau khi sai lch

gim n 0.

- Ch PI thng dng qu trnh c thay i ph ti ln khi mt mnh ch P khng

c kh nng gim dao ng v ch I to nn tc ng hiu chnh trit tiu dao ng.

Cng ngh ch bin kh


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Ch iu khin PDu = P+ PD(d/dt) - (du/dt) + uo

: h s gii hn ca o hm. Ch kt hp ny cho php gim xu hng dao ng v

cho php tng khuych i t l. ch PD, khu P to nn s thay i ca tn hiu ra

t l vi tn hiu sai lch, khu D to nn s thay i b sung ca tn hiu ra t l vi vn tc

thay i ca tn hiu sai lch ngn chn trc gi tr mi ca tn hiu sai lch v thay i tn

hiu ra mt cch tng ng. Tc ng ngn nga trc lm cho khu D rt hu dng

trong iu khin qu trnh c ph ti thay i t ngt

Ch iu khin PID

Khu I dng trit tiu sai lch t l khi thay i ph ti. Khu D gim dao ng v tc ng

ngn chn s thay i tn hiu sai lch. V th PID c dng qu trnh c ti trng thay

i t ngt, mc thay i ln .

Cc b PID thc t c chen h s gii hn o hm vo khu PD nn u s l

Cng ngh ch bin kh


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VAN

Hai loi van thng dng l van trt v van

xoay

- Van trt tiu biu l van cu (globe valve)- Van xoay tiu biu l van bm, van bi

Hnh 9. Van iu khin

Cng ngh ch bin kh


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Tu thuc yu cu cng

ngh m ngi ta dng van

c u x (plug) khc nhau,

cho bit mi loi u x c

kh nng cho mi cht i

qua tu hnh trnh tng i

ca van hnh 10

Hnh 10: Cc loi u x ca van

Cng ngh ch bin kh


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Hnh 11 : m v lu lng ca van-ng c tnh van

Cng ngh ch bin kh


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Kch c van :

- Chn van c kch c ng l rt quan trng, nu van qu nh n c th khng p

ng c yu cu cho dng lu cht i qua, nu qu ln s lng ph v lm vic

khng n nh.

- Mi van iu khin u c mt h s Cv khc nhau ph thuc vo kch c v loi

van iu khin.

- chn c ng van phi bit iu kin dng chy thc t v phng php

tnh ton Cv yu cu.

- Cc cng thc tnh kch thc van c chun ho bi ISA c s dng kh

rng ri i vi cht lng dng bn ti hn ( khi P < Ps *FL2)

Cng ngh ch bin kh


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Cng ngh ch bin kh


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Cng nghchbinkh


Cng ngh ch bin kh


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Cng ngh ch bin kh


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Cng ngh ch bin kh


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Cng nghchbinkh


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g g


Cng nghchbinkh


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g g


Cng nghchbinkh


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g g


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g g


Cng nghchbinkh


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g g


VAN AN TONC ba dng ph bin sau:

1. Van an ton dng khng cn bng

-y l dng van an ton c cu to n gin

nht, thng c s dng khi x kh v h

thng khng c p sut hoc ra mi trng.

- V khng c c cu cn bng nn s hot

ng ca van b nh hng rt ln ca p sut

h thng x (p sut ngc).

- Khi p sut h thng x (p sut ngc) ln

hn 10% p sut t van an ton, van dng

khng cn bng khng c s dng.

Hnh 12. Van an ton dng khng cn bng

Cng nghchbinkh


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g g


Hnh 13. Van an ton dng cn bng

2. Van an ton dng cn bng

S khc bit gia van cn bng v

khng cn bng l ch van dng

cn bng c thit k thm mtpitong hoc mt ng sinphng t

pha trn a lm kn nhm loi tr s

tc ng ca p sut ngc ln a

lm kn.

Cng nghchbinkh


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g g


3. Van an ton dng iu khin pilot

- Hai dng van cn bng v khng cn bng trnh by trn u dng lc l xo tc ng

trc tip ln a lm kn, khi p lc t di thng c lc l xo th van s m. i vi van

c p sut ln v lu lng ln i hi l xo phi c kch c ln tng ng, do s tng

ng k kch c ca van an ton.-im u vit ca van an ton dng iu khin pilot l dng mt van an ton nh-pilot

iu khin van chnh, do khng cn dng l xo tc ng trc tip ln a lm kn. p

sut ngun s tc ng ng thi ln b mt trn v b mt di ca a lm kn (pitong),

do tit din tip xc ca mt trn ln hn mt di nn khi lm vic bnh thng a lm

kn s b tc ng ng cht. Khi p sut tng vt qu p sut t ca van an ton nh

iu khin (dng l xo), phn p sut pha trn a lm kn s b x i, p sut pha di s

y a m.

- Van an ton dng iu khin pilot b hn ch s dng trong cc trng hp khi mi

cht c nhiu tp cht bn c th gy tc cc ng dn iu khin.

Cng nghchbinkh


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Hnh 14. Van an ton dng iu khin pilot

Cng nghchbinkh


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2. o lu lng kiu turbine

-o lu lng kiu turbine c

ng dng rng ri, ngoi tr cho

cht lng c nht cao, khi lm

vic turbine s quay m tc

quay ph thuc vo lu lng v

tnh cht ca mi cht qua n Xc

nh c tc ca turbine l s

xc nh c lu lng. Do

thit b o lu lng bng turbine

l thit b o tc quay ca

turbine.

- Mi vng quay s tng ng vi

mt lu lng th tch, c xc

nh bng h s turbine .

Hnh 15. B o lu lng kiu turbine

Cng nghchbinkh


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Cng nghchbinkh


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Cng nghchbinkh


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Cng nghchbinkh


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V d: ng ng kh v b t gin nn kh trung tm c cc thng s nh sau, hy

tnh kh nng vn chuyn ca ng ng.

cng thc Panhandle B

Lu : trn ng ng c cc thit b nh valve , co, ct, u ni ti y tn

hao p lc do ma st s ln hn do thay i hng dng chy v thit din thu

nh, thng c gi l tn hao cc b. Thng thng ngi ta s qui i cc

thit b trn thnh cc on ng tng ng sau cng vo di thc

t thnh di tng ng tnh ton.

Cng nghchbinkh


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Bng sau hng

dn qui i cc

thit b ng ng

thnh cc on ng

c tn hao tng

ng.

Hnh 16.Tn haop lc quii cavan, uni.

Cng nghchbinkh


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Cng nghchbinkh


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NPS:Nominal Pipe Size (inches),

Cng nghchbinkh


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Hnh 16.

ng v cc

thng s ghi

trn thn


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Cng nghchbinkh

CHNG 7 IU KHIN CNG


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Cng nghchbinkh

CHNG 7 IU KHIN CNG


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Công Nghệ Chế Biến Khí - Chương 7. Điều Khiển Công Nghệ Và Thiết Bị Điều...

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Transcript of Công Nghệ Chế Biến Khí - Chương 7. Điều Khiển Công Nghệ Và Thiết Bị Điều...