Chương 9: Trang bị phụ trong lò hơi

7/31/2019 Chng 9: Trang b ph trong l hi

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Chng 9. TRANG B PH9.1. Cc loi van

Van l mt thit b dng ng v ct mt thit b khi s lin thng vi thitb khc hoc vi h thng. Van phi m bo c tr lc nh khi m cho dng micht i qua v kn hon ton khi ng.

Phn loi: Theo nguyn tc lm vic, ngi ta phn thnh van kha, van iuchnh, van bo v. Cc loi van kha, van iu chnh c th thao tc bng tay hoctruyn ng bng kh nn, thy lc hoc bng in. Cc loi van bo v (van 1 chiu,van an ton) ng m hon ton t ng theo tc ng ca mi cht i qua n.

Trong thc t ch c van van kha v van bo v l yu cu c kn cao, cnvan iu chnh th khng cn thit phi kn tuyt i.

9.1.1. Van kha

Nhim v ca van kha l ng hoc ct dng mi cht khng cho dng chyqua. Cc loi van kha c biu din trn hnh 9.21, gm van a, van ca, van vinc.

Hnh 9.21. cc loi van kha

a-van a; b-van ca; c-van vi nc

9.1.2. Van iu chnh

Van iu chnhdng iu chnh lulng, p sut ca dongmi cht.

Nguyn tc lm vicca van iu chnh l thayi m ca van iuchnh lu lng mi chtqua nn iu chnhc p sut, lu lngca mi cht. Trn hnh9.22 biu din van iuchnh bng tay, hnh 9.23biu din van iu chnhbng ng c in.

9.1.3 Van bo v

Van bo v gm hailoi: van mt chiu v van


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Hnh 9.22. Van iu chnh bng tay

Van mt chiu: Van mt chiu l van ch cho mi cht chuyn ng theo mtchiu nht nh, van s t ng ng li khi dng mi cht chuyn ng ngc li.Van mt chiu gm van l xo; van t trng, c biu din trn hnh 9.29.

Van mt chiu thng c lp trn ng nc cp vo l, pha u y cabm, trc van chn nhm bo v bm khi b dng hi nng ph hoi khi ng, ctbm, hoc trn ng ni lin thng cc l tch bit cc l hi khi cn thit (hnh

9.25.Van an ton: Van an ton c tc dng khng ch p sut lm vic ca mi cht

khng vt qu tr s cho php, nhm bo v cho thit b lm vic an ton v lu di.

Tt c nhng thit b c p sut ln hn 0,7 kG/cm 2 u bt buc phi lp tvan an ton.

Van an ton c 3 loi, van an ton kiu l xo, kiu n by (qu t) v kiuxung lng. Cc loi van an ton c biu din trn hnh 9.26; 9.27 v 9.28.

loi van an ton kiu l xo v kiu n by, p sut tc ng ca van s ciu chnh cn bng vi lc nn ca l xo hoc sc ca h thng n by. Do psut gii hn cho php ca l khng ln hn p sut lm vic nh mc ca l nhiunn lc ca l xo ln a van tng i b, do van kh kn. Ngoi ra do tit din

l thot hi b nn kh nng thot mi cht chm, p sut ca l gim t

ng ichm. Chnh v vy chng ch c s dng cc l hi c p sut va v nh (di4Mpa).


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Hnh 9.23. Van iu chnh bng ng c in

Hnh 9.29. van mt chiu

a-van l xo; b-van t trng


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Van an ton kiu n by c u im l lm vic n nh, iu chnh van ngin, nhng cng knh, c dng ch yu cc l hi p sut trung bnh (di4Mpa).

Hinh 9.26. van an ton kiu l xo Hinh 9.27.van an ton kiu xung lng

Loi van l xo c cu to n gin, gn nh, nhng kh iu chnh, c dngch yu cc l hi p sut thp (di 2Mpa), sn lng nh.

Van xung lng: i vi nhng l c p sut t 4Mpa tr ln thng s dngvan an ton kiu xung lng. Van an ton kiu xung lng c biu din trn hnh9.27. Van xung lng l mt t hp hai van, van chnh v van xung lng tn hiu.Nguyn l lm vic nh sau: Bnh thng a van c y bng p lc hi pha trcvan chnh ln hn lc nn ca l xo nhiu nn rt kn, khi p sut hi vt qu tr s

Hnh 9.25. Cchni van mt chiuvi van cp nc


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cho php th van xung lng tn hiu s m ra a mt phn hi ti pha sau vanchnh cn bng vi p lc y pha trc van chnh, do p lc trc v sau vanchnh cn bng nhau, khi a van chu tc dng ca lc y l xo nn s m ra chohi thot ra ngoi. V van c tit din l thot hi ln nn hi thot ra rt nhanh.

Hnh 9.28.Van an ton kiu n by

V tr t van an ton: Trong l hi, van an ton c t v tr cao nhtkhoang hi ca bao hi, cc ng gp ca b qu nhit, ca b hm nc, ng gphi chung.

Trong cc thit b khc, van an ton c t v tr cao nht ca thit b.Trong b hm nc bng gang, ngi ta t van an ton ng gp trc (pha voca nc).

S lng v kch thc van an ton: Mi l hi phi t t nht l hai van anton khoang hi, tr mt s l hi nh c th lp mt van.

nhng l hi t 2 van an ton th trong c mt van lm vic cn mt vankim tra, 2 van ny s c iu chnh t m cc p sut khc nhau.

p sut tc ng ca cc van an ton c iu chnh bng lc p ca l xohoc sc ca n by theo bng sau:Bng 9.1. Cc gi tr p sut ti cc van an ton bt u m.

p sut m van an tonp sut lm vic p, MN/m2Van kim tra Van lm vic

bao hi, khi p < 1,281,28 < p < 3,93

p > 1,93

b qu nhit, khi p < 1,28p > 1,28

ng gp vo ca b hm nc ng gp ra ca b hm nc

p + 0,02

1,03.p

1,05. p

p + 0,02

1,02. p

1,25. p1,10. p

p + 0,03

1,05. p

1,08. p

p + 0,02

1,02. p

1,25. p1,10. p

C th xc nh kch thc ca van an ton t cng thc sau y:


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n.d.h =p

D(4-1)

n: s lng van an ton.

d: ng knh trong ca l van (cm), ng knh ny khng c nh hn

25mm v khng ln hn 125mm.h: chiu cao nng ln ca van, c 2 loi: h =

20

dv h =

4

d

h =20

di vi loi van khng nng ln hon ton, h =

4

di vi loi van

nng ln hon ton.

A: h s ty thuc vo van nng ln hon ton hay khng hon ton. vi vannng ln khng hon ton: A=0,0075, vi van nng ln hon ton A=0,0150

D: Sn lng hi ca l (kg/h).

p: p sut tuyt i ca hi (N/m2).

ng knh d ca van c th l 25, 32, 40, 50, 60mm

9.2. p k

p k l thit b o p sut ca hi v nc trong l hi.

p k c t v tr cao nht ca thit b. Trn ng ni t bao hi ra p kphi t van 3 ng c ng xi phng. Trong ng xi phng c cha nc hoc khngkh bo v ng h khi b mi cht ph hng. ng th ba ca van s ni ngh mu kim tra chnh xc ca ng h ang dng, kim tra xem ng h clm vic khng.

Trn mt p k c thang chia , thang chia ca ng h c chn theo p

sut lm vic ca l. Thng thng chn gi tr ln nht ca thang chia bng 1,5ln p sut lm vic ca l.

Vi cc thit b p lc, ng knh mt ng h nh nht l 110mm.

Lp t ng h: Nu p k ngang tm mt th c t thng ng. Nu pk trn tm mt, xa khong 2m th phi t nghing khong 300.

9.3. ng thy

9.3.1. Nhim v ng thy

ng thy l mt thit b rt quan trng ca l hi, dng theo di mc nctrong l hi. ng thy c ni vi l hi theo nguyn tc bnh thng nhau, mt uca ng thy c ni vi khoang hi, mt u c ni vi khoang nc.

Vi l hi ng la ng, qui nh mc nc trong qu trnh l lm vic lunngp 2/3-3/4 ng la. Vi l hi ng la nm ngang, qui nh mc nc trong l caohn ng la trn cng l 10cm. ng thy lun c ni mc nc ca l nm giang thy.


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9.3.2. Cc loi ng thy

Thng c hai loi ng thy: ng thy sng v ng thy ti.

ng thy sng cho php nhn thy mc nc qua ng thy tinh nu l ng thytrn, hoc qua tm thy tinh nu l ng thy dt. y ng hoc tm thy tinh u lthy tinh chu nhit.

ng thy tinh ca ng thy trn chu lc km d b v, do thng cdng cho cc l hi c p sut thp, nhit nc nh hn 2500C. cc l p sutcao, ngi ta thng dng ng thy dt. Cu to cc loi ng thy c biu din trnhnh 9.29 v 9.30.

Theo qui phm an ton l hi th mi l hi phi c t nht l 2 ng thy tc lp vi nhau.

i vi nhng l hi nh, din tch b mt t nh hn 100m2, c th cho phpthay th mt ng thy sng bng mt ng thy ti. ng thy ti thng gm 3 vanc ni mc nc cao nht, trung bnh v thp nht ca l.

c th t phng iu khin trung tm theo di c mc nc bao hi trncao, ngi ta dng ng thy di (ng thy ko di). Hnh 9.30 v ng thy ko dica l hi

Hnh 9.29. ng thy dt.1-tm thy tinh; 2-hp kim loi;

Hnh 9.30. ng thy trn.1. ng thy tinh; 5-hp kim loi;2, 3, 4 van ni ng thy vi l;


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9.4. Bm nc cp- qut gi- qut khi

9.4.1. Bm nc cp

* Nhim v ca bm nc cp: bm n

c cp c nhim v cp n

c cho ltrong qu trnh l lm vic. Mi l hi thng yu cu phi c 2 bm nc cp.Ring i vi nhng l cng sut nh hn 500kg/h c th cho php dng 1 bm.

* Cu to bm cp: c 2 loi bm cp, bm piston v bm ly tm .

+ Bm pit tng: Bm piston thng c p sut cao nhng sn lng khng lnnn thng dng cho cc l hi nh. Trong cc x nghip cng nghip, cc l hinh thng dng bm pit tng chy bng hi lm bm gi tr phng khi mt in.

+ Bm ly tm: Cc l hi ca nh my in thng lm vic p sut cao nnphi dng bm ly tm nhiu cp (nhiu lt), mi mt cp gm mt dy cnh ng vmt dy cnh tnh, s lng cp ty thuc vo p sut ca l. Khi chn bm phi lu, p sut bm phi ln hn p sut mi cht trong bao hi mc c th khc phcc tr lc ng ng dn t bm n bao hi. Cu to ca bm ly tm c biu

din trn hnh 9.31.

Hnh 9.31. Bmly tm.

a) bm mt cp;

1-c vo,

2-Cnh ng,

3-v,

4-ming ra,

b) bm nhiucp

1, 2, 3, 9. cc

tng cnh

ng


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Cc cnh ng c c gn trn rotor ca bm, cn tt c cc cnh tnh gntrn thn bm gi l stato. Khi lm vic, trc ca bm quay tc l cc cnh ngquay, nn nc trong bm lm cho p sut tng dn t u vo ti u ra.

Bm c c th c dn ng bng ng c in hoc hi. i vi cc bmc cng sut ln thng c dn ng bng tuabin hi.

Thng s ca bm l: p sut v lu lng

9.4.2. Qut gi- qut khi

Vi cc l hi ln c b mt t phn ui, qut gi c nhim v cung cpkhng kh cho qu trnh chy, cn qut khi c nhim v ht khi ra khi l. Qutgi v qut khi to nn h thng thng gi cho l hi, h thng gi l h thngthng bng, lun to cho p sut ca khi t bung la n khi ra khi l nh hn psut kh quyn. to p lc tng i ln th qut gi v qut khi thng dngqut ly tm c dn ng bng ng c in. Nguyn l cu to qut ly tm cch ra trn hnh 9.32.

i vi cc l hi nh, qut gi c nhim v cung cp khng kh cho qu trnhchy nhin liu, cn chiu cao ca ng khi c nhim v ht khi ra khi l.

Cc c tnh k thut ca qut: c tnh k thut ca qut l lu lng qut, ctp u ht v u y.

* Lu lng qut gi:

Khi khng c ti tun hon khng kh nng.

)h

m(,

273

t273V)(BQ

3

kkl

0skkngblbltt1g

++= (4-2)

1: h s an ton, 1 = 1,1;Btt : lng nhin liu tiu hao tnh ton, (kg/h),

bl: h s khng kh tha trong bung la;

bl: h s khng kh lt vo bung la;

ng: h s khng kh lnh lt vo h thng nghin than;

s: h s khng kh lnh lt vo b sy khng kh;V0

: lng khng kh l thuyt, (m3 tc/kg),tkkl: nhit khng kh lnh, (

0C),

* Lu lng qut khi

)h

m(;

273

t273)VV(BQ

3kkl

0dthtt1g

++= (4-3)

Vth: L

ng khi thi ra khi l, (m

3

tc/kg),tth: nhit khi thi ra khi l, (0C),

od: h s khng kh lnh lt trong ng ng dn khng kh;

* Cng sut ca qut gi:

Ng = 1,1.g

gg HQ

3600, Kw;


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* Cng sut ca qut khi:

Nk = 1,1.k

kk HQ

3600, Kw;

Qg, Qk: lu lng khng kh v khi ca l,Hg, Hk: p sut ca u y ca qut gi, qut khi,g, k: hiu sut ca qut gi v qut khi,

9.5. H thng cung cp nhin liu

9.5.1. H thng du t:

Du c th dng lm nhin liu chnh trong cc l hi t nhin liu lng,hoc dng lm nhin liu t ph tr khi cng sut thp hoc khi cng sut cc ihoc khi khi ng l trong cc l hi t nhin liu rn (than, b ma hoc ci).Thng thng du t trong cc l l du FO (du en). H thng du ca nh my

c th hin trn hnh 9.33. nhit mi trng, du c nht ln, do cn phi c thit b sy du

gim nht nhm vn chuyn d dng hn, ng thi du c th bc chy.Thng thng c th sy du n nhit khong 900C-1000C. Bn cnh b sy cnc thm b lc loi nhng cn bn trnh hin tng tc vi phun du.

Hnh 9.33. s nguyn l h thng du.


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* Cc loi vi phun du: c 2 loi vi phun du, vi phun thi v vi phun ckh. Yu cu vi phun phi phun du thnh cc ht bi nh, cc ht cng nh cng dbc chy.

- Vi phun c kh: du c phun thnh bi nh bm cao p nn ln n psut t 10 n 30 at v khi i qua cc l nh ca vi phun s phun thnh bi.

- Vi phun thi: dng du c phun thnh bi qua vi phun nh ng nngca dng hi hoc kh nn c p sut t 3-5 at.

9.5.2. H thng chun b bt than

Hnh 9.39. H thngchun b bt than.

a) H thng vi mynghin bi v phu than

trung gian;b) H thng vi gingnghin thi thng;c) H thng c qutnghin.1-Phn li mn;

2, 11 v 21-ng dnkhng kh;

3-Vt ti rut g;4-Phu bt than;5-Qut gi;6-Bung la;

7-B sy khng kh;8-Vi phun;9-Hp khng kh;10-Bung hn hp;12-Hp phn phi;13-Qut nghin;14-Phn li bt than;15-My nghin;16-Hp u vo;17-My cp than;18-Phu than nguyn;19-Cn;

20-Khothan nguyn;22-Ca l khi nn .


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H thng chun b bt than c nhim v nghin mn than thnh bt v vnchuyn bt than n cung cp cho l hi. Than c nghin mn nh cc my pba v cc my nghin. Sau c vn chuyn i trong ng nh khng kh nng.Khng kh nng va c nhim v vn chuyn bt than, va sy nng bt than. Sau bt than c phn li (tch ra khi khng kh) nh cc my phn ly tinh (hay phn lykiu xiclon). Bt than c cp n cc vi phun ca l nh my cp than bt. Hthng cung cp bt than c biu din trn hnh 9.39.

9.6. H thng thi tro x

H thng thi tro x c th dng vt ti rut g; ging thi x hoc thuyn x.

- H thng vt ti rut g: gm 1 vt xon rut g t trong 1 ng.

- Ging thi x.- Thuyn x.

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Chương 9: Trang bị phụ trong lò hơi