Thong tin khoa hpc cong ngh$ m o
NGHIEN curu QU^ TRJN^ PH^N HUY. PHONG HOfl CUfI THflN THEO BIEN DQNG Cdd NHIET DQ
In the coal mining and processing activities, for ensuring the safety purposes, it is essential to understand clearly the nature of the coal spontaneous combustion. The paper introduces some initial research results on the coal decomposition and weathering process depending on the temperature variation and In some cases they are considered as the major basis for the coal storage works.
KS. LA H6NG Dye
Vipn Khoa hgc Cdng nghp Md - Vinacomin
1. Qui trinh hda hgc phin huy than theo nhipt dp
Nhu- da bilt, khi phdn tich than, chit ble dLpge xdc djnh d nhidt dd 850°C, nhipt dp t h i p nhit khi than thodt chit b l e Id 550°C. Xem xet nhidt phdn huy cdc thdnh phin cua than theo chf s l jyJHsQ 6k h i l u can ke ban chit biln d i i hda hoc ede hdm iLpgng hCpu ca eua than dLPdi sy phdn huy theo nhidt dp, dde bidt Id c i u true phdn tCp vd tinh chit eua ehung tgi nhidt dp thip nhat ndo dd khi bat dau qud trinh thoat chit boc vd khi tang d i n nhipt dd trong mdi tru'dng y i m khi Id dieu c i n thilt.
Nhipt dp bat d i u qua trinh phdn huy ede logi than tgi thdi diem hinh thdnh chit b l e trong Id dLpgc xdc djnh nhLP trong bang 1.
Thanh phin vi iLpgng eua than da d i n 550°C phdn huy theo % thdnh phin chay cua than (thdnh phin tgo ndn chit ble) du'ge gidi thipu trong bang 2.
Nhipt dp phdn huy eua than, hay cdn gpi Id nhipt dp bat d i u tgo khi, lien quan d i n thdnh phan eacbon cua than dygc gidi thidu trong bang 3.
Tdm Igi, qua trinh phan huy cua than didn ra lien tuc. tang
d i n theo nhidt 66 dygc xdc djnh theo ode chf s l sau:
Nhidt dd b i t d i u qud trinh phdn huy than Id nhidt dd tgi thdi d i l m b i t d i u hinh thdnh pha khi (hinh thdnh chit bic) cua than.
- Nhipt dd phdn huy eua cdc Bdng 1
logi than tdng theo mu-c 66 biln tinh cua than, thip nhit Id than bun (~100°C) vd cao nhit la than antraxit (~380°C).
2. Qui trinh oxy hoa, ty chiy vi phong hoa cua than
2.1. Than tic dyng v&i oxy va cic chat oxy hoa khac.
Chiing lo^i than Than bun
Than ndu Than dd :
Than lu-a ddi Than khi Than md Than c i c Than giy Than antraxit
Nhipt dp bit diu phdn huy than (hinh thdnh chit boc), "C
<100 - 1 6 0
- 1 7 0 - 2 1 0 - 2 6 0 - 3 0 0 - 3 2 0 - 3 8 0 Bdng 2
Tdn cdc vl luxyng than
Vitren Fiuzen Bdo tu- 90% Ekzin
Nhya tesa
Phdn huy din nhipt dp 550°C ( % thdnh phan chdy cua than)
C 12,78
4,94 36,80 77,27
H' 3,19 1,60 5,80 10,85
C 7,64 3,44 4,29 2,91
Y^V=550 (C+H'+O')
23,64 9,98 46.89 91,03
KHCNM SO 12/2011* NGHIEN CtTU TRAO D O I
T h o n g tin k h o a hpc c o n g n g h e mo
Bdng 3
Thdnh phin cdcbon Nhipt dp phdn huy (bat dau t?o khi)
Than ndu C = 67%
C = 73%
tbd = 225 - 230°C tbd = 285 - 290°C Than dd
C = 77%
0 = 8 1 % 0 = 83%
C = 90%
tbd = 295 - 300°C tbd = 305-310°C tbd = 315-320°C tbd = - 365°C Dilm ddc bipt id e i u true
phdn tLP cdc hgp chit hCpu ea cua than rit nhgy cam khi tde dung vdi oxy vd cdc chit oxy hda khde trong nhu'ng dieu kipn khde nhau.
Qud trinh phan Cpng oxy hda than, cung nhLP mCpc do biln doi tinh chit eua than phy thude vdo c i u true ban dau cua than. Trong dieu kidn t y nhidn, d nhidt do khdng cao (20- 25°C), khdng phdt hipn thay hidn tLpgng oxy hod, do qud trinh oxy hda didn ra r i t chdm vd nhidt iLpgng tda ra bj tidu tan tCpc thdi, thyc t l hau nhLP than khdng biln doi.
Doi vdi than hogt tinh mgnh, thdi gian d i u bj oxy hda da d i y manh qud trinh oxy hda vd nhidt dp than bat dau tang cao.
Neu nhidt iLpgng cua than tda ra khdng thodt ra ngodi thi nhidt dp eua than edng tang cao vd thuc d i y qua trinh phan Cpng manh liet vdi oxy, nhipt lygng tda ra tang vpt vd bat dau thdi dilm than t y chdy (chu ky t y chdy). N l u trong qua trinh than t y chdy, nhiet iLPgng tda ra thodt ra ngodi manh thi than se dan giam nhidt dp (ngudi dan, trCp trydng hgp than vdn tilp tue qua trinh
oxy hda). Trong tru'dng hgp ndy, mCpc dp oxy hda than gidm dan, khdng xay ra hidn tLpgng t y chdy vd chuyin sang thdi dilm phong hda.
Chu ky chuyin tilp tdc dyng cua than vdi oxy phy thudc vdo dieu kidn ty nhidn, thdnh phin vd tinh chit eua than, dilu kidn xay ra qud trinh oxy hda than:
(nhidt dp eua than, mCpc dp thodt nhidt iLpgng tda ra trong qud trinh oxy hda, sy cd mat eua ede tdc nhdn xuc tde thuc day nhanh qua trinh oxy hda, lu'gng oxy) .v.v. Qud trinh oxy hda than phy thudc vdo tinh chit oxy hda. Cdc axit khodng t y nhidn (HNO3, H2SO4) Id chat oxy hda tdc dyng mgnh d i n
than, kit qua la qud trinh phan Cpng tgo ra san pham cdc goc tham ngu-ng tu phin hu-u ca cua than.
2.2. Qui trinh ty oxy hda cOa than vi sy thay doi tinh chat cua chung.
Qud trinh tilp xuc giu-a than vdi oxy trong khdng khi (hode oxy tinh khilt) d dp suit vd nhidt do binh thu-dng ed t h i khiln cho than ty oxy hda, ty chdy vd tiln tdi phong hda.
Trinh ty diln biln qua trinh tilp xuc giu-a than vdi oxy du-gc md phdng trdn hinh 1.
Giai doan dau tidn cua qua trinh tdc dung giu-a oxy vdi cac logi than du-gc goi Id giai doan hap thy oxy, tilp theo la phan Cpng oxy hda. Qua trinh hap thy oxy cua cdc loai than khac nhau vd dieu kipn de xdc dinh toe 60 qua trinh dd du-gc nhieu nhd khoa hpc trdn the gidi nghidn CCPU. Than hip thy chu y l u oxy tCp khdng khi. Than hip thy oxy nhanh han khi h i p thy nita. De dat trgng thdi cdn bang oxy trong than tgi pha khi chf mdt 2,5 gid, edn vdi nito phai m i t 20 gid (dieu kidn thi nghidm).
Kit qua thi nghidm cho
o
S
70
0 -Chuk^dminbidml (hSpphi/txcy)
lhdl^,ngdydSm
Hinh 1. Trinh tydiin biin qui trinh tiip xuc giira than v&i oxy
KHCNM S6 12/2011* NGHlfeN CtTU TRAO D 6 I
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Thong tin khoa hpc cong ngh^ m o
thiy: tgi nhidt dp 20°C, oxy hodn todn thodt ra khdi than.
Dilu dd eho thiy, oxy giu' trong than bing lye h i p thy vdt ly, n l u tang nhipt dd Idn 60°C vd Idn han thi iLPgng oxy thodt ra giam 3 lln. Trong dilu kidn dd, oxy hip thy tham gia vdo phdn Cpng hda hpc vdi than vi t h i ehung dLpgc giCp Igi trcng qud trinh thim thiu. Thyc nghipm cho thiy, phin oxy h i p thy vdo than chu y l u trdn b l mdt cdc hgt than. Khli lygng oxy h i p thy tdng ldn theo mCpc dd tdng cua cdc hgt than phdn tdn. Sy h i p thy oxy cua than xay ra lien tyc tu' khi than edn trong vfa, sau khi khai thdc vd trdn b l mgt cdc hgt than sau nghiln.
Thdi gian h i p thy phu thupc vdo kha ndng h i p thy cua than vdi oxy. xung quanh cdc hgt, eye than cd t i n g khi bao vd lam qud trinh hap thy oxy giam vd tdng phan u-ng oxy hda cua than. Tren b l mat cdc hgt than cd t h i hinh thanh mdng khodng oxy hda, gdy trd nggi hogc ngan chdn oxy t h i m sdu vdo cdc hgt than.
Theo hLPdng khde, cdc nhd khoa hpc nghien CLPU kha ndng h i p thy oxy theo thanh phin thgch hpe than: d nhipt dd khdng cao (15-50°C). kha ndng h i p thy oxy Idn nhit Id Fiuzen cd b l mdt Idn. Kha ndng h i p thy oxy cua Vitren, Klaren. Diuzen d i u kdm han Fiuzen. Khi tdng nhidt dd ldn d i n 100°C. khd ndng h i p thy oxy cua Fiuzen Igi nhd nhit, cdn Vitren, Klaren cd kha ndng hap thy oxy cao nhit.
Qua trinh hap thy oxy cua than vd phan Cpng hda hpe giu-a ehung Idm cho nhipt dd trong than tang len. Khi nhipt dp
trong than tdng se xdy ra qud trinh tda nhidt cua than, d i n g thdi d i l n ra ngay cd khi than h i p thy hai nydc trong khdng khi. Cy t h i , nhidt lygng tda ra khi than bun khd t h i m nu-de Id 14,8cal/g, cua than dd Id 11,6 eal/g. Tru-dng hgp than ty chdy Id than k i t hgp vdi khdng khi khd (vdi oxy), phdn u-ng giO-a cdc hgp chit hO-u ca cua than vdi oxy tda nhidt nhu- sau:
C + O2 = CO2 .. + 4,199 cal/ml O2.
C + I/2O2 = CO2 ...+ 2,358 cal/ml O2
2H + I/2O2 = H2O2..+ 5,163 cal/ml O2.
Qud trinh thodt nhipt khi than t i l p xuc vdi oxy cd t h i xem nhy phan Cpng eua oxy vdi pirit cd trong than
2FeS2 + nH20 + 702 = 2FeS04.H20m + 2H2SO4.
H20(n-m) + 262,5 kcal/g moi FeS2
Thyc nghipm cho thiy. nhipt lu-gng tda ra khi oxy hda 1 % pirit lyu huynh eua than ed t h i lam tang nhidt dd eua 1 t i n than len 117°C. ddi khi Idn d i n 251 °C. Nhidt dd than tdng Idm tdng t i e dp qud trinh h i p thy oxy, t i c dd h i p thy oxy cua cdc logi than khde nhau se tdng Idn 2 l l n vd cao han khi mdi l l n tdng thdm nhidt dd ldn 30°C.
T i c 66 h i p thy oxy eua than phy thupc vdo sy thay d i i nhidt 66. Dk than h i p thy 1 % oxy d 100°C m i t 6 phut, n l u d 30°C thi phai m i t 6 ngdy dem.
Anh hifdng cua nydc trong than din tic dp hip thy oxy:
Cung mpt logi than, n l u d trgng thai can bang khd, se h i p thy 258 - 270 cm^oxy. n l u dgt dd I m 7%. than se h i p thy
du-gc 400 - 440 cms. Khi ed hai nu-de trong khdng khi, phan Cpng oxy hda vdi logi than biln tinh cao tdng nhanh, edn vdi logi than khi, than ICpa ddi phdn LPng xay ra chdm han.
Khd ndng h i p thy oxy cua than cdng eao thi than biln tinh cdng thip, lu-gng oxy h i p thy tdng Idn khi nhidt dd than tdng vd cdc chf s l tyang ty khde nhy kha ndng nghiln, dp I m ...cung tdng theo.
Tdm Igi, d nhidt dp thip tdc dyng giu-a than vdi oxy trong khdng khi bat d i u bing qua trinh h i p thy hda ly cua than.
Theo thdi gian, nhipt dp se tdng d i n vd t i c 66 phan ipng hda hpc tdng, qud trinh ndy gpi Id chu ky h i p thy. Sy tdc dung giO-a oxy vdi ede thdnh phan hu-u ea eua eae logi than du-gc gpi Id qud trinh oxy hda vd tiln d i n ehu ky t y chay hode du'ge gpi Id qud trinh didn biln ehgm cdc phan Cpng d i n phong hda cua than. Qua trinh ndy ed y nghTa r i t Idn trong thyc t l , ddc bidt Id trong d i l u kidn t y nhidn khi khai thdc. bao quan ede logi than khde nhau. Trong trydng hgp khdng bilt cdch bao quan than trong kho, cdch xap xlp khdng dung se gdy t i n thit than do bj oxy hda, thdm ehl cd t h i chdy, dde bidt r i t nguy hilm khi than chay trong ting, cdc vj tri Ip vfa... Qud trinh ty oxi hda Id qua trinh ty nhidn d i n d i n ty chay. thuc diy cac phan u-ng didn ra ngay trong qud trinh dang nhipt vd mgnh me han khi nhipt dp tang Idn.
D i l u dd dung theo ly thuylt phan u-ng chudi. xult hien cac phin tu- ed hogt tinh mgnh trong san phim du-gc tgo thanh.
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KHCNM S6 12/2011* NGHlfeN CtJtJ TRAO DOI