9_Giáo Trình Hàn Khí

KHI NIM CHUNG

GII THIU V M UNHN KHI. V TR, NGHA, VAI TR CA M UN- L mn hc c b tr cho hc sinh sau khi hc xong cc mn hc chung.- L mn hc chuyn ngnh bt buc.II. MC TIU CA M UNSau khi hc xong m un ny ngi hc c kh nng sau:

- Lm vic trong cc c s sn xut c kh.

- Nhn bit ng cc loi vt liu dng trong hn kh nh kh xy, kh chy, que hn, thuc hn.

- Vn hnh, s dng thnh tho cc thit b, dng c hn kh.

- Tnh ch hn, chn phng php hn ph hp vi chiu dy vt liu v kiu lin kt hn.

- Hn cc mi hn c bn, hn p m bo yu cu k thut, mi hn khng r kh, t bin dng.

- Thc hin tt cng tc an ton phng chng chy n v v sinh phn xng.Bi 1: VN HNH V S DNG THIT B HN KH

I. Thc cht v c im

1/ Thc cht

Hn v ct bng kh l phng php hn hoc ct, s dng nhit ca ngn la sinh ra khi t chy cc cht kh chy (C2H2, CH4, C6H6 v.v...) hoc H2 vi xy nung chy kim loi.

Thng dng nht l hn v ct bng kh xy - Axtylen v nhit sinh ra do phn ng chy ca 2 kh ny ln v tp trung, to thnh ngn la c nhit cao (vng cao nht t ti 3200oC); cn ngn la gia O2 v cc 22000C. Tuy nhin khi hn(cht kh chy khc ch cho nhit t 2000 di nc thng dng ngn la gia O2 v H2 v C2H2 rt d n p sut cao v nhit ln.

2/ c im

C th hn c nhiu loi kim loi v hp kim (gang, ng, nhm, thp ... )

Hn c cc chi tit mng v cc loi vt liu c nhit nng chy thp.

Hn kh c s dng rng ri v thit b n gin v r tin.

Nng sut thp, vt hn b nung nng nhiu nn d cong vnh.

Hn kh dng nhiu khi hn cc vt hn c chiu dy b, ch to v sa cha cc chi tit mng, sa cha cc chi tit c bng gang, ng thanh, nhm, magi, hn ni cc ng c ng knh nh v trung bnh. Hn cc chi tit bng kim loi mu, hn vy kim loi, hn p hp kim cng v.v...

Ngn la kh hn cng c th dng ct cc loi thp mng, cc loi kim loi mu v nhiu vt liu khc.

3. Kh hn

Kh hn thng dng gm xy k thut v cc loi kh chy (C2H2, CH4, C3H8, C6H6v.v...) hoc H2.

Trong hn kh thng dng l C2H2 v nhit ngn la cao (3200oC) v c vng hon nguyn tt.

4 mm, hn gang, ng thau, hp kim nh,(Khi hn thp c chiu dy di 3 2200oC)(hn vy ta c th dng kh khc c nhit chy thp hn (2000 nh H2, kh than mtan, prpan, butan, xng, du ho....

a/ xy k thut

99,5% xy v khong(xy dng hn kh l xy k thut cha t 98,5 1,5%(0,5 tp cht (N2, Ar).

Trong cng nhip, sn xut xy dng phng php in phn nc hoc lm lnh v chng ct phn on khng kh. xy hn ch yu dng phng php lm lnh khng kh. Nh chng ta bit, trong thnh phn khng kh cha khong 78,03 % N2, 0,93 % Ar v 20,93 % O2, nhit ho lng ca chng tng ng l: (-195,80C), (-185,70C) v (-182,060C).

Bng phng php lm lnh khng kh xung nhit di -182,060C nhng trn nhit ha lng ca N2 v Ar, sau cho N2 v Ar bay hi ta thu c xy lng.

xy k thut c th bo qun th lng hoc kh. th lng, xy c cha bng cc bnh thp v gi nhit thp, khi hn cho xy lng bay hi, c 1 lt xy th lng bay hi cho 860 lt th kh iu kin tiu chun. Bo qun th lng, tuy i hi dung tch bnh cha b, nhng tn km trong khu bo qun lnh.

Trong cc phn xng c kh, ch yu dng xy th kh, gim th tch bnh cha, thng thng xy c nn p sut cao v cha bng bnh thp c dung tch 40 lt, p sut 150 at.

b/ Kh Axtylen

Axtylen l hp cht ca ccbon v hyr c cng thc ha hc l C2H2, khi lng ring iu kin tiu chun 1,09 kg/m3, nhit tr 11.470 Cal/m3. Axtylen c sn xut t t n CaC2. Khi nu chy hn hp 2.3000C) ta(vi, than hoc than cc trong l in (nhit t 1.900 thu c t n k thut:

CaO + 3C ( (CaC2 + CO

25% CaO v khong 6 %(80% CaC2, khong 10(t n k thut cha khong 65 cc tp cht nh (CO2, SiO2). Khi cho t dn tc dng vi nc ta thu c Axtylen theo phn ng:

CaC2 + 2H2O = C2H2 + Ca(OH)2 + 30.400 Cal/mol

Tnh cht ca kh Axtylen

83,6oC) th lng, di(- C2H2 thuc nhm CnH2n-2. Nhit t (- 82,4 (- 85oC) th rn khi va chm d n.

- Nhit t bc chy khong 420oC ( p sut 1 at).

- D pht n khi p sut > 1,5 at v nhit trn 500oC hoc hn hp vi kh khc, v d: Hn hp vi khng kh (cha 82% C2H2), hn(t 2,2 hp vi xy (cha 93% C2H2) c kh nng pht n nhit (t 2,3 thng v p sut 1 at. Hn hp cha 45% C2H2 + 55% CH4 v hn hp cha 18% C2H2 + 82% H2 c kh nng pht n nhit thng v p sut trn 18 at.

- nhit v p sut thp d trng hp to thnh cc hp cht khc nh benzel (C6H6), stirn (C8H8) ...

S ha tan ca axtylen: c kh nng ho tan trong nhiu cht lng vi ho tan ln, c bit l trong axtn, v d:

- Ho tan trong nc : 1,15 lt C2H2/ lt.

- Ho tan trong Benzel : 4 lt C2H2/ lt.

- Ho tan trong du ho: 5,7 lt C2H2/ lt.

- Ho tan trong axtn (CH3COCH3): 23 lt C2H2/lt.

S ho tan trong axtn c s dng nhiu trong cng nghip: dng cc cht bt xp (than g, si aming, iatmit) thm t axtn vo bnh cha, sau nn axtylen vo bnh gim kh nng n ca axtylen p sut cao.

Cc tp cht trong axtylen

1,5%.(- Khng kh: lm tng kh nng gy n, nn ch cho php cha 0,5

- Hi nc: lm gim nhit ca ngn la hn.

- Hi axtn (CH3COCH3): nh hng xu n qu trnh hn, nn ch cho 50)g/m3 C2H2.(php cha (45

- PH3: l cht c hi v tng kh nng t n ca hn hp. cho php cha 0,09%.

- H2S: lm hi n cht lng mi hn, nn ch cho php cha 1,5)%.((0,08

II)Thit b hn kh

1. S chung ca mt trm hn kh

Cc thit b chnh ca mt trm hn hoc ct bng kh gm c cc b phn chnh sau: Bnh cha xy, bnh cha hoc thng iu ch axtylen, kha bo him, van gim p, dy dn kh, m hn.

2. Bnh cha kh

Bnh cha kh dng cha kh xy v kh axtylen, c ch to t thp 8 mm(tm dy 4 bng phng php dp hoc hn. Bnh c ng knh ngoi 219 mm, cao 1.390 mm, dung tch 40 lt, trng lng 67 kg. Bnh cha xy cha c mt lng kh c p sut khong 150 at tng ng vi 6 m3 kh ( 200C v 1 at) bn ngoi c sn mu xanh hoc xanh da tri.

Bnh cha axtylen cha c p sut kh np ti di 19 at, c sn mu vng. Trong bnh cha bt xp (thng l than hot tnh) v tm 230 gram axtn/ mt(320 gram than hot tnh tm 225(axtn (khong 290 lt th tch bnh cha).

3. Bnh iu ch axtylen

Bnh iu ch kh dng iu ch kh axtylen t t n. Trong thc t, ngi ta dng nhiu loi bnh iu ch kh khc nhau, c phn loi theo cc c trng c bn:

- Theo nng sut: c cc loi nh (di 3,2 m3/h) v loi ln (trn 5 m3/h).

1,5 at) cao(0,1 at), trung bnh (0,1(- Theo p lc kh: thp (0,01 1,75 at).((1,5

- Theo nguyn tc tc dng gia t t n v nc: ri vo nc, nc ri vo v tip xc vi nc Hnh (H.4.2) gii thiu s nguyn l ca mt s bnh iu ch kh in hnh.

Bnh iu ch kiu ri vo nc (H.4.2a) c hiu sut sinh kh cao (trn 95%), kh C2H2 c lm ngui v lm sch tt, nhng i hi t n c ht u, tn nhiu nc, kch thc ln v iu chnh phc tp.

Kiu bnh iu ch nc ri vo (H.4.2b) c kch thc b, tn t 90 %), kh C2H2(nc, khng cn c ht u nhng hiu sut thp (85 khng c lm sch v b nung nng mnh. Hai loi bnh trn thuc loi iu chnh lng kh bng cch iu chnh lng cht tham gia phn ng. Kiu bnh iu ch tip xc vi nc (H.4.2c) c kt cu n gin, thun tin trong s dng nhng kh C2H2 cng khng c lm sch v lm ngui.

4. Kho bo him

trnh hin tng ngn la chy ngc theo ng dn kh tr v bnh iu ch kh gy n bnh ngi ta dng kha bo him. Trong qu trnh hn, do mt nguyn nhn no , lu lng kh phun ra m hn hoc m ct gim mnh hoc tc chy ca hn hp tng, dn n tc chy ca hn hp lan truyn nhanh hn tc i ra ca kh s gy ra hin tng ngn la qut.

S gim lu lng kh xy ra khi tit din l dn kh m hn hoc m ct gim, ng dn b tc ... S tng tc chy xy ra khi nhit kh v nhit mi trng tng, lng xy tng...

Kho bo him c phn loi theo cc c trng sau:

Theo kt cu: loi h, loi kn.

Theo lng tiu th kh: loi nh, loi ln.

Kha bo him kiu h (H.4.3a) dng cho bnh c p lc thp. Kh C2H2 c dn vo qua ng (1), i qua nc vo ngn cha kh ti ng (2) i ra m hn hoc m ct. Khi c ngn la qut, p sut trn mt nc ca ca kha bo him tng ln, y nc dng ln trong ng (1) chn khng cho kh i vo, ng thi mc nc h xung, ming ng thot (4) h, kh qua ng thot i ra ngoi.

Kho bo him kiu kn (H.4.3b), dng cho bnh c p lc trung bnh. Khi C2H2 dn vo qua ng (1), y vin bi ca van (5) ni ln v i qua van, tp trung ngn cha kh, sau qua ng (2) i ti m hn hoc m ct.

Khi c ngn la qut, p sut trn mt nc tng, vin bi b y xung ng kn ng dn kh, nu p sut kh trong van vt qu gi tr cho php, mng chn ca van an ton (6) b ph v kh thot ra ngoi.5. Van gim p

Van gim p l dng c dng gim p sut kh trong bnh cha xung p sut lm vic cn thit v t ng duy tr p sut mc n nh. i vi kh xy p sut kh trong bnh t ti 150 at, p sut kh lm 16(4 at, cn kh axtylen p sut trong bnh ti 15(vic vo khong 3 1,5 at.(at, p sut lm vic 0,1

Trn hnh sau trnh by s nguyn l ca mt s van gim p:

i ti m hn hoc m ct. p lc kh trong bung h p (6) ph thuc vo m ca van (3). Khi l xo chnh (7) cha b nn, van (3) chu tc dng ca l xo ph (2) v p lc ca kh, ng kn ca van khng cho kh vo bung h p (6). Khi vn vt iu chnh (8), lm cho l xo chnh (7) b nn, van (3) c nng ln, ca van m v kh i sang bung h p.

Tu thuc vo nn ca l xo chnh (7), nn ca l xo ph (2), chnh p trc v sau van, ca van (3) c m nhiu hay t, ta nhn c p sut cn thit trong bung h p. Nh c mng n hi (9), van c th t ng iu chnh p sut ra ca kh.

Nu do mt nguyn nhn no , p sut kh ra (p2) tng, p lc tc dng ln mt trn ca mng n hi (9) tng, y mng n hi dch xung v thng qua con i van (3) b ko xung, lm ca van ng bt li, lng kh i vo bung h p gim, lm p sut kh ra gim. Ngc li, nu p2 gim, ca van (3) m ln hn, lng kh vo bung h p tng, lm p2 tng tr li.

6. Dy dn kh

Dy dn kh dng dn kh t bnh cha kh, bnh ch kh n m hn hoc m ct. Yu cu chung i vi ng dn kh: chu c p sut ti 10 at i vi dy dn xy, 3 at vi dy dn axtylen, mm cn thit nhng khng b gp khc. Dy dn c ch to bng vi lt cao su, c ba loi kch thc sau:

- ng knh trong 5,5 mm, ng knh ngoi khng quy nh.

- ng knh trong 9,5 mm, ng knh ngoi 17,5 mm.

- ng knh trong 13 mm, ng knh ngoi 22 mm.

7. M hn

y l dng c dng pha trn kh chy v xy, to thnh hn hp chy c t l thnh phn thch hp nhn c ngn la hn hoc ct theo yu cu. M hn c 2 loi l m hn kiu ht v m hn ng p.

M hn kiu t ht (H.4.5a) s dng khi hn vi p sut kh C2H2 thp v trung bnh. 1,2 at) c dn vo qua ng (1),(Kh C2H2 (p sut 0,01 4 at) c dn vo qua ng (2). Khi dng xy phun(cn kh xy (p sut 1 ra u ming phun (5) vi tc ln to nn mt vng chn khng ht kh C2H2 theo ra m hn. Hn hp tip tc c ho trn trong bung (6), sau theo ng dn (7) ra ming m hn v c t chy to thnh ngn la hn. iu chnh lng kh xy v C2H2 nh cc van (3) v (4). Nhc im ca m hn t ht l thnh phn hn hp chy khng n nh.

M hn ng p dng khi hn vi p lc kh C2H2 trung bnh. Kh xy v 1 at) v tip(C2H2 c phun vo bung trn vi p sut bng nhau (0,5 tc c ha trn trong ng dn ca m hn, i ra ming m hn t chy to thnh ngn la.

3. Thuc hn

Thuc hn l nhng cht dng kh xy cho kim loi, to ra cc hp cht d chy, d tch khi vng hn v to mng x che ph mi hn. Thuc hn ch yu dng khi hn mt s thp hp kim, gang v kim loi mu.

Yu cu i vi thuc hn:

- Nhit chy phi thp hn nhit chy ca kim loi vt hn.

- Thuc hn phi nh v c tnh chy long tt, khng gy n mn kim loi.

- Khng sinh kh c, d lm sch mi hn

Khi hn gang thng dng hn hp K2O v Na2O; Khi hn ng , ng thau thng dng borc (Na2B4O7), axit boric (H3BO3); Khi hn nhm thng dng mui florua. III)Cc loi ngn la hnKhi hn kh, tu thuc vo t l thnh phn ca hn hp chy c th nhn c ba loi ngn la hn khc nhau: Ngn la bnh thng, ngn la xy ha, ngn la ccbon ha. Ngn la hn c th chia lm 3 vng: nhn ngn la c mu sng trng, vng trung tm c mu sng vng, vng ui (xy ho) mu vng sm c khi.

4.1. Ngn la bnh thng

Ngn la bnh thng nhn c khi t l .

a/ Vng nhn ngn la

Trong vng ny xy ra phn ng phn hy C2H2: 2C + H2. Ngn la(C2H2 c mu sng trng, nhit thp v thnh phn kh giu ccbon.

b/ Vng chy khng hon ton

Trong vng ny xy ra phn ng chy khng hon ton ca ccbon:

(C2H2 + O2 = 2CO + H2 + Q

Ngn la vng ny c mu sng xanh, nhit cao nht (3.2000C), kh cha nhiu CO v H2 l nhng cht hon nguyn.

Nhng cht ny khng tham gia vo cc phn ng cacbon ho v xy ho nn gi l vng hon nguyn.

c/ Vng chy hon ton

Trong vng ny xy ra phn ng chy hon ton: sn phm ca vng trn chy vi xy ca khng kh: 2CO + H2 + 1,5O2kk (= 2CO2 + H2O + Q

Ngn la vng ny c mu vng sm, cha nhiu CO2 v H2O l nhng cht xy ho v nhit thp hn vng gia.

4.2. Ngn la xy ha

Ngn la xy ho nhn c khi t l .

Qu trnh chy cng chia ra thnh 3 vng v vng chy khng hon ton xy ra theo phn ng sau: C2H2 + 1,5O2 = 2CO + H2 + (0,5O2 + Q

Sau chng li chy tip vi xy ca khng kh:

2CO + H2 + 0,5O2 + O2kk (= 2CO2 + H2O + Q

Chng ta nhn thy nhn ca ngn la ngn li, vng gia d O2 v cha c CO2 nn c tnh xy ha mnh v gia 2 vng khng phn bit r ranh gii, ngn la c mu t vng nht n vng sm.

Ngn la xy ha ch dng khi hn ng thau, ct v t sch b mt cc chi tit my hoc kt cu my.

4.3. Ngn la cc bon ha

Ngn la ny nhn c khi t l .

(Qu trnh chy nh sau: C2H2 + 0,5O2 = CO + H2 + C + Q

Sau chy tip vi xy ca khng kh: CO + H2 + C + 2O2kk = 2CO2 + (H2O +Q

Nhn ca ngn la ko di, vng gia c mt nguyn t cacbon t do nn ngn la mang tnh ccbon ho v c nu sm.

Ngn la ccbon ha c dng khi hn gang, thp gi v thp hp kim, hoc ti b mt cc chi tit my.

Bi 2: MI HN GIP MII) Cc loi mi hn:

Cn c vo hnh dng chi tit, v tr mi hn trong khng gian trong hn kh thng dng nht l mi hn gip mi. Khi hn vt mng dng mi hn kiu cun mp v khng cn dng que hn ph khi hn. Khi hn vt dy hn 5 mm cn vt mp ch V hoc X.II) K thut hn gip mi bng phng php hn kh:1- Phng php: 1.1- Hn phi

- M hn dch t tri sang phi,

- M hn i trc que hn, dng vt liu hn dy t 3mm tr ln

1.2- Hn tri:

- M hn dch t phi qua tri, que hn i trc m hn, dng hn vt liu t 3mm tr xung

S cc phng php hn kha) Hn phi b) Hn tri

1) M hn 2) Que hn ph 3) Mi hn 4) Vt hn

2- Ch hn kh: 2.1- Gc nghing m hnGc nghing m hn () so vi mt phng hn c chn theo nguyn tc sau: Chiu dy cng ln, gc nghing m hn cng ln; Nhit chy v dn nhit ca vt liu hn cng cao, gc nghing cng ln.2.2 Cng sut ngn la:

Cng sut ngn la tnh bng lng kh tiu hao trong mt gi, chn theo nguyn tc: vt hn cng dy, cng sut ngn la cng ln; vt liu c nhit chy v dn nhit cng cao, cng sut ngn la cng ln.

- Khi hn thp ccbon thp, ng thau, ng thanh thng chn lng tiu hao C2H2 trong mt gi theo cng thc sau:

VC2H2 = (100 - 120).S [lt/h] - i vi hn tri

VC2H2 = (120 -150).S [lt/h] - i vi hn phi

Trong S l chiu dy vt hn [mm].

- Khi hn ng do tnh dn nhit ln nn tnh theo cng thc sau: VC2H2 = (150 - 200).S [lt/h].

- T l Oxy/ Axetylen trung bnh = 1,2.III) Trnh t hn gip mi bng phng php hn khSTTCC BC THC HINYU CU K THUT

B1- c bn v- Nm c cc kch thc c bn trn bn v nh kch thc phi, kch thc mi hn

B2- Chn ch hn- ng theo vt liu hn v chiu dy vt liu hn

B3- Kim tra phi, thc hin g nh phi - Phi phi m bo sch, g nh phi m bo chc chn

B4- Tin hnh hn Hn ng gc , ng t th

Mi hn khng c khuyt tt

B5- Kim tra- Pht hin c cc khuyt tt ca mi hn

IV) H hng thng gp nguyn nhn v bin php khc phcSTTTn sai hng, khuyt ttNguyn nhnCch khc phc

1- B mt mi hn b chy en.- Do chn ngn la hn khng ng- Chn li ch hn ph hp vi vt liu v chiu dy vt hn

2- Mi hn khng ngu. Do hn sai gc , t th.

Chn ch hn khng ng Thc hin hn ng gc

Chn ch hn ph hp

3 - Mi hn b ng cc - Di chuyn que hn ph v ngon la hn qu nhanh hoc qu chm- Di chuyn que hn v ngon la u v ph hp

V) AN TON LAO NG V V SINH CNG NGHIP1. T chc ni lm vic :

- Khu vc lm vic hn ct kim loi phi c din tch t nht l 4 m2 v c thng gi tt.

- Ni hn ct phi c che chn phng s bt la gy chy hoc chy lan.

- Chai OXY, chai Axtylen phi c t ng, bt cht vo cc gi v cch xa ngun nhit t nht 5 mt, bnh sinh kh Axtylen phi cch xa ngn la t nht 10 mt. Khng d tr qu 1 chai xy, Axtylen ti khu vc hn.

- Khi phi lm vic di ng, cc chai Oxy, Axtylen phi t chc chn trn gi hoc xe y chuyn dng. Xe phi c mi che v khng dnh du m.

Yu cu v thng gi t nhin khu vc lm vic c Axtylen.

2. Vn hnh thit b:

- Ch s dng bnh sinh kh Axtylen, chai Oxy, chai Axtylen c kim nh v ng k ng qui nh. Khng dng bnh sinh kh Axtylen t ch, chai xy, chai Axtylen qu hn kim nh.

- S dng t n ng c ht theo thit k ca bnh sinh kh Axtylen. Khng cho php dng c ht t n nh hn qui nh

Bi 3: HN GP MP TM MNG

I) K thut hn gp mp bng phng php hn kh:

Dung hn gip mi hai tm thp mng c chiu dy di 3mm. Trc khi hn phi hn phi c gp mp ng theo bn v hn v phi m bo yu cu k thut.

Dng phng php hn phi hn mi hn gp mp.

II) Trnh t hn gp mp tm mng bng phng php hn khSTTCC BC THC HINYU CU K THUT







III) H hng thng gp nguyn nhn v bin php khc phcSTTTn sai hng, khuyt ttNguyn nhnCch khc phc




Chn ch hn ph hp


IV) AN TON LAO NG V V SINH CNG NGHIP1. T chc ni lm vic :






2. Vn hnh thit b:



Bi 4: HN GCI)K thut hn gc bng phng php hn kh:

Thng s dng phuong php hn gc hn ni hai tm thp v gc to thnh gia hai tm thp l 90 . S dng phng php hn gc v tr ngang thc hin hn

Gc que hn khi hn i vi hn gc ging nh gc que hn khi hn bng phng php hn h quang.

II) Trnh t hn gc bng phng php hn khSTTCC BC THC HINYU CU K THUT











Chn ch hn ph hp








2. Vn hnh thit b:



Bi 5: HN P MT TR TRNI) K thut hn p: Hn p ch yu s cha cc chi tit, thit b, v dng c hng do hao mn, n c ngha v kinh t v k thut rt ln. V bn cht ni chung, hn p tng t nh cc phng php hn khc. Trong k thut hn p ng dng cc phng php hn bng kh, h quang. Chn thnh phn kim loi p ph thuc vo iu kin cng tc ca chi tit. S hao mn c th gy ra do ma st, do va p, nhit bnh thng, nhit cao trong mi trng n mn.

Trc khi hn p, ch hn p phi c lm sch cc tp cht v cht bn. Lm cho kim loi c nh kim nh ban u ri mi c th hn p ng th nht, khi hn p ng th 2 cn phi lm chauy 1/3 chiu rng ca ng th nht

Khi hn cn ch trnh ch kt thc ca mi hn sinh ra nhng rnh h quang qu su lm nh hng n s hnh thnh lp sau

Khi p mt tr trn c th p theo ng sinh hoc chu vi.

II) Trnh t hn p bng phng php hn khSTTCC BC THC HINYU CU K THUT











Chn ch hn ph hp








2. Vn hnh thit b:


- S dng t n ng c ht theo thit k ca bnh sinh kh Axtylen. Khng cho php dng c ht t n nh hn qui nh1

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9_Giáo Trình Hàn Khí