Cht thi rn

Cht thi rn

1.Khi nim cht thi rn (CTR):Cht thi rn (CTR) c hiu l tt c cc cht thi pht sinh do cc hot ng ca con ngi v ng vt tn ti dng rn, c thi b khi khng cn hu dng hay khi khng mun dng na.

Thut ng cht thi rn c s dng trong ti liu ny l bao hm tt c cc cht rn hn hp thi ra t cng ng dn c th cng nh cc cht thi rn c th t cc ngnh sn xut nng nghip, cng nghip, khai khong ... Ti liu ny c bit quan tm n cht thi rn th, bi v s tch lu v lu ton cht thi rn c kh nng nh hng rt ln n mi trng sng ca con ngi.(TRNG I HC CNG NGHIP TP. H CH MINH VIN KHOA HC CNG NGH V QUN L MI TRNG ThS, NCS V NH LONG, ThS NGUYN VN SN)

2. Phn loi cht thi rn: (Theo ti ngh hen thy cng ok)* Phn loi theo ngun gc pht sinhC nhiu cch phn loi ngun gc pht sinh cht thi rn khc nhau nhng phn loi theo cch thng thng nht l:

1. Khu dn c

2. Khu thng mi

3. C quan, cng s

4. Khu xy dng v ph hy cc cng trnh xy dng

5. Khu cng cng

6. Nh my x l cht thi

7. Cng nghip

8. Nng nghip.

Cht thi th c th xem nh cht thi cng cng, ngoi tr cc cht thi t qu trnh ch bin ti cc khu cng nghip v cht thi nng nghip.

* Phn loi theo c im cht thi:

Cht thi rn pht sinh t nhiu ngun khc nhau, cn c vo c im cht thi c th phn chia thnh 3 nhm ln: 1. Cht thi th2. Cng nghip3. Cht thi nguy hi

3.X l CTR bng phng php nhit :

X l CTR v CTNH (cht thi y t, thuc bo v thc vt, cht thi nhim du) bng phng php t l mt phng php hiu qu v hin nay c s dng kh ph bin.

Phng php x l CTR bng nhit c nhng u im: Gim th tch CTR (gim 80-90% trng lng thnh phn hu c trong CTRtrong thi gian ngn, cht thi c x l khng trit ); Thu hi nng lng ; L thnh phn quan trng trong chng trnh qun l tng hp CTR; C th x l CTR ti ch m khng cn phi vn chuyn i xa, trnh c ccri ro v chi ph vn chuyn.

Song phng php t cng c nhng hn ch nh: i hi chi ph u t xy dng l t, chi ph vn hnh v x l kh thi ln. Vic thit k, vn hnh l t phc tp, ngi vn hnh l t i hi phi ctrnh chuyn mn cao. c bit qu trnh t cht thi c th gy nhim mi trng nu cc bin php kim sot qu trnh t, x l kh thi khng m bo.

3.1. H thng thiu t

Qu trnh t CTR l qu trnh oxy ha ha hc bin i cht thi rn bng oxy khng kh di tc dng ca nhit v qu trnh oxy ha ha hc. Vi phng php t, bng cch t cht thi, ta c th gim th tch ca CTR gim n 80 90%. Nhit bung t phi cao hn 800oC. Sn phm cui cng ca qu trnh t l

1) Cc bao gm kh c nhit cao bao gm kh nit, cacbonic, hi nc v tro

2) Nng lng c th c thu hi nh qu trnh trao i nhit t kh sinh ra c nhit cao. t thng quay, l t thng quay c s dng x l cc loi cht thi nguy hi dng rn, cn, bn v cng c th dng lng. Thng quay hot ng nhit khong1100oC, s dng cht thi nguy hi lm nguyn liu. y l phng php tiu hy cht thi bng cch t cng vi nhin liu thng thng khc tn dng nhit cho cc thit b tiu th nhit nh: ni hi, l nung, l luyn kim, l nu thy tinh. Lng cht thi b sung vo l t c th chim 12 25% tng lng nhin liu.

3.2 H thng nhit phn

Nhit phn l qu trnh phn hy hay bin i ha hc cht thi rn xy ra do nung nng trong iu kin khng c s tham gia ca oxy v to ra sn phm cui cng ca qu trnh bin i cht thi rn l cc cht di dng rn, lng v kh. Nguyn l ca vn hnh qu trnh nhit phn gm 2 giai on: Giai on 1 l qu trnh kh ha, cht thi c gia nhit tch cc thnh phn d bay hi nh kh chy, hi nc...ra khi thnh phn chy khng ha hi v tro. Giai on 2 l qu trnh t cc thnh phn bay hi iu kin ph hp tiu hy ht cc cu t nguy hi.

Nhit phn bng h quang plasma: thc hin qu trnh t nhit cao (c th n10.000oC) tiu hy cht thi c tnh c cc mnh. Sn phm l kh H2 v CO, kh acid v tro.

3.3 H thng ha hi thnh kh (bc hi)

Mt cch tng qut qu trnh ha hi thnh kh l qu trnh t cc loi vt liu trong iu kin thiu oxy. Mc d phng php ny c pht hin vo th k 19 nhng vic p dng x l cht thi rn ch c thc hin trong thi gian gn y i vi x l cht thi rn. K thut ha hi thnh kh l mt k thut c p dng vi mc ch l lm gim th tch cht thi v thu hi nng lng.

3.4 Cc h thng kim sot nhim mi trng khng kh cho cc qu trnh nhit

K thut x l cht thi rn p dng cc qu trnh nhit cng pht sinh mt s tc ng n mi trng xung quanh bao gm: kh, bi, cht thi rn, v cht thi lng. Do , khi p dng phng php nhit x l CTR, trong qu trnh x l bng nhit cc thit b phi c trang b h thng kim sot pht thi. i vi nhim khng kh cc cht nhim cn kim sot l: NOx, SO2, CO, v bi.

Kh NOx: tn ti trong khng kh di 2 dng l: NO v NO2; NOx hnh thnh t 2 ngun l: Ngun th 1 hnh thnh do phn ng gia nit v oxy khng kh di tc dng ca nhit; ngun th 2 hnh thnh do phn ng oxy v nit hu c c trong thnh phn cc loi nhin liu s dng. NOx l tc nhn gip cho vic hnh thnh cht PAN (Peroxyl Acetal Nitrate) gy nn hin tng sng m ha cht.

Kh SO2: hnh thnh do qu trnh t nhin liu c cha lu hunh. SO2 kch thch h h hp, gy nn cc bnh nh vim mi, mt, vim hng. nng cao, SO2 c th l tc nhn gy nn bnh tt hoc gy t vong i vi nhng ngi mc cc chng bnh lin quan n phi nh l vim ph qun hay cung phi.

Kh CO: hnh thnh do qu trnh t CTR vt liu c cha carbon trong iu kin thiu oxy khi s cung cp oxy khng y . CO phn ng vi hemoglobin trong mu to thnh carboxylhemoglobyl (HbCO), gy c ch phn ng gia hemoglobin v oxy. C th con ngi ch thch ng vi oxyhemoglobin (HbO2), oxy s c chuyn n cc m trong c th. S thiu ht oxy s gy nn hin tng nhc u, chng mt.

Bi: hnh thnh do qu trnh t khng hon chnh nhin liu hoc l do c tnh vt l ca cc vt liu khng chy. Bi lm gim th gic v nh hng n sc khe. Bi c kchthc nh hn 10 m gi l bi h hp bi v n c th i su vo trong phi.Thit b kim sot nhim khng kh:

Kh v bi pht sinh trong qu trnh x l cht thi rn, c th c x l bng cc loi thit b kim sot v phn loi thnh 4 dng sau y:

- Lng tnh in, lc vi.- Tch ly ngun thi, kim sot qu trnh t, x l kh (kim sot NOx)- Tch ly ngun thi, thp ra kh hoc lc kh (kim tra SO2 v hi acid)- Kim sot qu trnh t (kim sot CO v HC).Mc ch ca qu trnh kim sot l la chn cng ngh v thit b t c hiu quloi tr cht thi, hiu qu loi tr c xc nh nh sau:

Trong :

E: hiu qu loi tr cht thi

E = Wvao WraWvao

100

(5-1)

Wvo: nng cht nhim u vo

Wra: nng cht nhim u ra

3.5.Cng ngh t

Hu ht cc phng php x l, lu tr v loi b iu lin quan n cng ngh t tc vic t chy cc cht mt cch c kim sot trong mt min kn nh mt phng tin x l v thi loi cht thi nguy hi. L mt phng thc qun l cht thi nguy hi, cng ngh t c mt s c th:

Th nht, nu c tin hnh ang theo qui cch, n c kh nng phn hy ton b cc c cht hu c trong cht thi nguy hi bng cch phn hy cc mi lin kt ha hc ca chng v a chng tr li dng cc nguyn t hp thnh ban u, qua lm gim thiu hoc loi b hon tan cc c tnh ca chng.

Th hai, n hn ch th tch ca cht thi nguy hi cn phi c thi loi b vo mi trng t bng cch bin i cc cht rn v lng thnh dng tro. So vi vic loi thi b cht thi nguy hi khng qua x l, vic thi b loi tro vo mi trng t an ton v hiu qu gp nhiu ln.

Cng ngh t l mt qu trnh x l kh phc tp. Trong qu trnh chy, cc cht hu c dng rn hoc lng s b chuyn i sang pha kh. Cc kh ny qua cc li t s tip tc b lm nng ln, n mt nhit no cc hp cht hu c ca chng s b phn hy thnh cc nguyn t thnh phn. Cc nguyn t ny kt hp vi oxy v to nn cc cht kh bn vng, cc kh ny sau khi qua cc thit b kim sot nhim s c thi vo bu kh quyn.

Thnh phn ca cc cht kh bn vng pht sinh t vic t cc hp cht hu c ch yu l CO2 v hi nc. Tuy nhin, ty thuc vo thnh phn ca cht thi rn, mt lng nh CO, NOx, HCl v cc kh khc c th s c hnh thnh. Cc cht kh ny l nguyn nhn tim n kh nng gy nguy hi cho sc khe con ngi v mi trng.

Vic qun l v thi loi b cc kim loi, tn tro v cc sn phm ph ca qu trnh t cng c th gy nhng tc hi nh cp. Tn tro l mt vt liu d lng, tro vi thnh phn ch yu l carbon, cc mui v cc kim loi. Trong qu trnh t, hu ht tn tro s tp trung y ca bung t (tro y). Khi lp tro ny c ly ra khi bung t n c th xem nh l cht thi nguy hi do bi cc qui tc chuyn ha hoc do n c 1 c tnh (nguy hi) no . Tuy nhin cc ht tro kch thc nh (vt cht dng ht m c th c cc kim loi km theo) cng s b cun theo cc cht kh ln cao (cn gi l tro bay). Cc ht tro ny cng cc kim loi c lin quan cng phi c xem xt bi cc qui nh p dng cho cng ngh t bi v chng c th mang cc hp phn nguy hi ra khi h thng thit b vo trong kh quyn. Do vic t khng phn hy c cc hp cht v trong cht thi nguy hi (cc kim loi chng hn), cc hp cht ny c th cng s tch t trong lp tro y v tro bay vi nng c hi. H thng l t cht thi nguy hi c trnh by nh sau

4.Tc hiNguyn Tn t g- 6 -