Thong tin khoa hoc cong nghe mo
7 THUNGHIEM XAC DINH NHIET DO BAT LUA CUA BUI THAN
Coal dust generated from the coal production links has played an important role, impacting on the safety assurance of mine fire and explosion at underground coal mines. In this paper, the au- thors refer to the role of coal dust in forming potential hazards at underground coal mines such as mine fire, coal dust and firedamp explosions underthe combination with the heat source.
Moreover, the authors introduce the experimental results from the determination the ignition temperature of coal dust for review- ing the hazards caused by coal dust at underground coal mines nowadays
ThS. Le TRUNG T U Y £ N ThS. N G U Y E N T U A N A N H
TS. TAKEHIRO ISEI Chuyen gia tinh nguydn cao cip JICA Vien Khoa hoc Cdng ngh$ Md - Vinacomin Bidn tip: ThS Pham Chin Chinh
Nhu da d l cgp trong nhirng bdi bdo lien quan [1], byi than phat sinh trong cdc khdu san xudt ed vai trd quan trpng, anh hudng d i n viec dam bdo an todn v l chdy n l trong ede md h i m Id.
Trong bdi bdo ndy, tdc gia de egp d i n vai trd eua bgi than d l i vdi sy hinh thdnh cdc nguy co tiem I n trong md h i m Id nhu chdy md, n l khi vd bgi than khi cd sy kit hgp cua bgi than vd ede nguon nhlgt. bdn cgnh dd, tdc gia gidi thigu phuong phdp cung nhu eae k i t qua cua viec thii' nghlgm xdc djnh nhlgt dp bat chdy cua byi than d l tif dd ed cdi nhin chung v l hiem hog eua byi than trong edc md him Id hign nay
1. Phugng phdp xac djnh nhiet do b i t lua ciia bi^i than
Trdn thyc t l , khi quan sdt trong md ham Id, ddc bi§t Id tren vd cdc thilt bj, vi chong, bang tai diu cd hi^n tugng byi than tich tg lai thdnh ldp byi cd dp day hay mdng phg thudc vao dilm phat sinh byi cung nhu cdng tdc vg sinh trong cdc md him Id. Cdc ldp bgi than tich tg tren cdc b l mat dpng eo, cdc eo d u chuyen ddng sinh nhiet cd t h i bit lu-a khi nhlgt dp cua be mat tilp xiic tich tg dii d l Idm chdy ede Idp bgi than. D l phdng ngira vigc bit lira edc ldp bgi than cd t h i gay ra chdy n l , d n phai xdc djnh nhiet dp bit lifa nhd nhit cua cde Idp bgi than cung nhu khing c h i edc ylu t l lidn quan den sy bit lira cua bgi than.
Phuong phdp d l xdc dinh nhlgt bat lira tdi thilu cua bgi than thudng dugc ap dgng hien nay la vi$c md phdng cdng gan cdng tot edc dilu kign thyc t l tgi hign tnpong Theo dd, bgi than dugc rdi ra trdn b l m$t kim logi phdng hinh trdn Mat trdn cua Idp bgi than dugc tiep xiic vdi khdng khi, mdt dudi tilp xuc tryc tilp vdi t i m kim logi
dugc gia nhiet Thdng thudng, thi nghiem se dugc lap dl lap lgi vdi sy thay doi v l nhlgt dp cua tam kim loai d mdi lln thif nghiem eho d i n khi nhiet dp bat lira cua byi than dugc xdc djnh Diu hieu d l xac dinh nhiet dp bat lira eua bui than ed t h i can cip theo ede hien tuong xay ra nhu sau [2]:
- Cd d i u higu xdc djnh rd rang nhu vigc xuit hien d i m lira dd hoac ngon lira,
- Gdc doc cua d l thi bilu thj nhlgt dp tai tam Idp bui than lien tyc tang - toe dp gia nhiet Idn.
- Nhiet dp cua Idp bui than Idn hon khoang 50°C so vdi nhiet dp tam kim loai.
- B I mat Idp bui bj "mIm hoac ran nift".
Theo cdc thif nghiem ve nhiet dp bit ICpa toi thilu cua bui than, ed 3 y l u t l anh hudng ehinh d i n nhiet dp bat lira t i i thieu bao gIm: tinh chit than, cd hgt va chilu ddy Idp bgi than. Tuy thupc vdo cac yeu t l anh hudng md nhiet dp bat chdy edu bgi than Id khac nhau Tuy nhien, trudc khi xem xet d i n yeu to cd anh hudng Idn nhit, ehung ta ciing xem xet cdc thi nghiem da duge tlln hanh d l xac djnh sy anh hudng ciia mdi ylu t l d i n nhiet dp bat lua ciia bgi than.
Thi nghiem cua Yael Miron vd Charles P Laz- zara (1988) - Cgc md Hoa Ky, chi ra sy lien he giifa tinh chit bgi than vd nhiet dp bat lifa cua byi than Theo dd, n l u chdt boc ciia bui than Idn thi nhiet dp bat chay cua bui than nhd va ngugc Igi. Theo thi nghiem eua Bowes vd Townshend [3], anh hudng Idn nhat d i n nhiet dp bat lifa cua bui than la chilu ddy Idp bgi than Cd hgt bgi khdng anh hudng nhilu den nhiet dp bat lira nlu xet trong pham vi rdng. Mat dp hgt chi anh
KHCNM s d 9/2014- \N TOVN MO
Thong tin khoa hoc cong nghe m o
d... J [i}-^
Bfeu khien nhlgt dp i Sensor nhiet
h=S / ^
A: Bd didu khidn nhidt; B: Cdng tic; C: Tim kim loai D: Sensor; E. Miy tinh
a: Tim kim loai; b: Vong kim loai; c: Ld di bd tri sensor, d: Sensor do nhi$t do byi; e: Sensor do nhi0t 60 tim kim loai; f: Tim cich nhiet; g, h: Ngudn dien cho tim kim loai vi diiu khidn nhidt
Hinh 1. Nguyen ly va he thing thidt bi thd nghiem hudng d i n Idp bgi cd chilu day mdng.
Hien nay, cdc tieu chudn lien quan d i n thif nghiem nhiet dp bat lu-a cua bgi than dugc quy djnh theo Tieu chudn ASTM E 2021 (My) hode Tieu chudn ciia Uy ban Ky thudt dien quIe t l lEC 62141-10 [4]. Theo dd, ASTM E 2021 quy dinh chilu ddy Idp bgi than thu nghiem la 12,7mm, sai so la 5mm. lEC 62141-10 quy dinh chilu day ldp bgi than thif nghiem Id 12,5 hoac 15mm
Theo quy djnh cua lEC 61241- 2004 (phin 0 vd phan 10 - Phg igc B), tif kit qua xdc djnh nhiet dp bdt ICpa toi thilu cua bgi than va chilu ddy ldp bgi than se quy djnh nhiet dp tdi da ciia be mat ddng CO theo nhu quy djnh tai dilu lEC 62141- 10. Theo quy djnh, neu chilu day Idp bgi day d i n 5 mm thi ap dgng theo quy luat 1. Theo dd, nhiet dd cho phep ciia b l mat ndng phai bang hoac nhd hon nhlgt dp bat lira nhd nhit ciia Idp bgi than ddy d i n 5mm d gid trj 75°C.
Tmax = T 5 m m - 7 5 ° C Trong dd:
- T5 mm Id nhiet dp bat lifa nhd nhat cua Idp bgi than day 5mm.
Nlu chieu day ldp bgi nam d khoang 5 d i n 50 mm thi se dp dyng nhiet dp toi da theo quy lugt 2 Theo quy luat 2, tren dd thj hinh 1 dua ra quy dinh ve nhiet dp t i i da ciia b l mat khi chilu ddy Idp byi ndm d trong khoang 5-50,mm. Vi dy, n l u Idp bgi day 5 mm bat lira d mire 305°C (trong khoang 250°C-320°C) nhiet dp t i i da cho phep eiia b l mat ndng cd ldp bgi than tich tg 10mm se chi Id 150°C. Cung theo gia thilt neu tren, nhiet dp cho phep toi da tren be mat ndng
cd Idp bgi than tich tg ddy 30 mm se phai nhd hon 100°C (khoang 90°C)
2. Thi nghiem xac djnh nhiet do bdt 10*3 ciia bui than Viet Nam
Tuy hien nay ehua cd nhilu nghien cifu v l nhiet dp bat lira cua bui than tai Vigt Nam nhung sy t i n tai lugng bgi than trong cdc md him Id Viet Nam la thyc t l dd dugc ghi nhgn. Xem xet d i n v i n d l bgi than theo khia cgnh an todn chdy nd, thi nghiem xdc dinh nhigt dp bat lu'a eua bui than la viec cdn phai thyc hien.
Ngudn nhiet chCi y l u lien quan d i n viee bat lu'a bgi than bao gom nguon lira hd va cdc b l mat sinh nhiet. Nguon lipa hd cd t h i xuat phdt tif vy chdy no khi, than t u chdy, chay vat ligu va Idm chay bgi than, Cde be mat sinh nhiet chii y l u tdp trung vdo cde vd ddng co hogt dpng, cdc bO phdn ehuyin ddng tao ma sat sinh nhlgt.
Xet d i n ede y l u to anh hudng d i n nhiet dp b i t lua ciia bui than, mdt so yeu t l dugc logi tap dya tren tinh chat than, dieu kien thyete tai hign trudng md. Nhu da neu trong ede bai bdo lien quan [1], bgi than vd than antraxit ndi ehung cd he s i ty le VRM t h I p nen y l u to no ti? bgi than antraxit cd t h i dieoc log! trip. Theo edc k i t qga rut ra tif cde thi nghiem, thu" nghlgm thyc hign tai Trung tam An todn Md dugc t i i n hanh ed tham khao den cac tieu chuan ASTM va lEC, thilt bj va cdc budc thir nghiem dugc md ta nhu tren hinh 1 nhu sau.
Theo dd, thip nghlgm duge t l l n hanh theo cdc budc:
+ Dgt tam kim logi cd kha ndng ddn nhigt tit len phia tren Id gia nhigt (nhigt dp d i n 1000°C).
KHCNM S 6 9/2014 • AN TOAN MO
Thong tin khoa hoc cong nghe m o
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Hinh 4. Bim liia vi khdi xuit hiin l<hi Idp bui than bit lira (Miu than cua md Kushiro - Nhit Bin)
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Hinh 6. Nhi^t dd gia nhidt cOa miu than sd 5 + Trdn t i m kim loai dgt 02 sensor nhiet dp d l do nhi§t dd m l u than vd nhigt dp tam kim logi.
+ Dua lugng byi than ed cd hgt dudi 250gm Idn trdn t i m kim logi cd kha nang ddn nhigt, chilu ddy Idp bgi than Id 1,5em.
+ Kit n l i cdc sensor nhi$t vdi thilt bi t y dpng ghi dO* li$u.
+ Gia nhi0t cho t i m kim logi chira m l u than
Thdi gian, phOt
Hinh 3. Dudng nhi$t dd cOa miu than nim dudi dt dudng nhidt 66 cua tim kim loai vi cit nhau tai
didm duoc goi li diim bit Ida.
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Hinh 5. Nhi$t 60 gia nhi$t cua miu than sd4S
Thoi giaa.pbat
Hinh 7 Nhietai bitlua cua mot si mlu than thCrnghiim 3C theo too dp 10 d i n 15°C/phut.
+ Nhiet dp bat li>a cua bui than la diem nhiet dp t?i do ghi nhan nhiet dp cua mau than Ion hon nhiet dp cua tam kim ioai.
Theo each thu'c hien neu tren, mpt s6 kit qua thu" nghiem du-pc tien hanh cho cac mlu than tgi mpt mo ham 16 Vipt Nam
Qua thu nghiem cho ket qua theo bang nhu sau.
KHCNM S 6 9/2014 • AN TOAN MO
Thong tin khoa hoc cong nghe m o
Hinh 8, Nhiet dg gia nhidt cOa mau than sd4 C Luu y: Ten cic miu than sd dung theo mi miu Bang 1.
TT
1 2 3 5
Am lam viec (%) 7.21 6.44 10 24
5 63
Am phan tich (%)
3 99 3 79 7.06 3 90
Tro (%) TB 41.25 37.66 38.85 37.35
Quy l<hd 42.96 39.14 41.80 38.86
Nhiet dg bat Ilea
CC) 504.80 420.00 490.00 520.00 Qua kit qua thi nghiem cho thiy, nhiet dp bat lua nho nhat cua m l u than dCing che thtr nghiem c6 nhiet dp bat lua thIp nhit la 420oC. Gia tri ve nhiet dp b i t lira neu tren chi la gia trj xac djnh tren m l u bgi than thi> nghiem chu chua mang tinh tdng t h i cho m l u than an tra xit tai cac mo ham 16 Viet Nam.
Day chi la cac k i t qua ap dung d l giai thieu ve thi> nghiem xac dinh nhiet dp bat li>a cua m l u bui than. D l xay dung dupc co so* du lieu ve gia tn bit lua cua bui than, can phai thue hien thu nghiem tren vo'i cac m l u bui than cua cac mp than khac nhau cung nhu phai phan tich cac tinh chit cua bui than va cac y l u t6 co the anh huo-ng den viec bit lua cua bui than.
3. K i t luan
Trong thue te khai thae tai cae mo than h i m lc Vipt Nam chua c6 nhilu nghien cuu v l mirc dp va anh huong cua bui than d i n cac van d l hen quan d i n an toan ve chay n l bui than. Bui than trong cae mp ham 16 hien nay dupc coi la CO nguy co nghiem trpng lien quan d i n v i n d l ho h i p hpn la v i n de v l chay n l bui than. Trong cac mo ham io hipn nay, phan Ion d i u dung eac vol phun nuoc dang suong d l dap bui tai cae
diem rot tai hole phun nudc l i m I m via truoc khi no min nham tranh bui (via 9T muc -25/+30 mo Khe).
Tuy nhien, qua cac vu tai ngn xay ra trong mo ham 16 thoi gian qua, d i e biet la nhung yu lien quan den nguyen nhan chay, y l u to ve dilm bat ngu6n chay du'p'c gia dinh trong do co nguyen nhan tCr chay bui than do io-p than tich tu tren cSc be mat nong gay ra chay. Xem xet d i n v i n de neu tren, mpt s6 thi nghiem o quy mo nho v l so lupng m i u - da dupe tien hinh tai Trung tam An tpan M P - Vien Khoa hpc Cong nghe Mo de xac djnh nhiet do b i t lua t i i thieu cCia bui than.
Tuy nhien, quy mo cua cac thi nghiem neu tren so voi cac yeu c i u nghien ci>u v l hilm hoa cua bui than xet ve khia canh nhipt dp bat lua t i i thieu c6n phai thyc hien nhieu nghien cuu. Xem xet den cac quy dinh cua lEC ve thilt bi dien dung trong moi tnro'ng bui no cho thay con nhilu thong so ve bui than, moi quan hp giua b l day 16'P bui va vi tri cua lop bui hole ban than chieu day ldp bui vol nhiet dp bat lua c i n phai thue hien nhilu thue nghiem. Ngoai ra, la c i c bl$n phap dam bao an toan khi thiet bi hole dpng cc lam viec trong moi truo'ng bui than can phai dupe de xuat.
Thong qua cac k i t qua thi nghiem, t i e gia mu6n gio'i thieu v l gpi md mpt s6 van d l can dupc t i p trung nghien cuu, danh g i i trong thoi gian tdi, d l tir dc, co c i c bien phap ph6ng ngira tich cue, dam bap an tPln trpng san xuit than h i m 16./.
Tai lieu tham khao
1. Le Trung TuyIn v l nnk: "Hiem hqa ve bui than trong mo ham 16", Hpi nghj Khpa hpc Ky thuat Mo Viet Nam 2014.
2. National Academy of Sciences, 1982, Com- mittee on Evaluation of Industrial Hazards, Clas- sification pf Cpmbustible Dusts Relative to Electrical Equipment in Glass II Hazardcus Lo- cations, NMAB 3 5 3 ^ , National Academy Press, Washington, DC.
3. Bovi/es, P.C. and Townshend, S.E 1962,
"Ignition of Combustible Dusts on Hot Surfaces,"
Btlt. J.AppL Phys., 13, 105-114.
4. Tieu chuin ASTM E2021 (My); Tieu chuin cua Uy ban Ky thult dipn quoc t l lEC 62141-10.
KHCNM S 6 9/2014 • AN TOAN MO
