昆明電弧熔爐生產電熔氧化鎂(電熔鎂砂)的生產流程
發(fa)布日期:2022-08-21 瀏(liu)覽次數:26597電(dian)(dian)弧(hu)熔爐(lu)生產(chan)電(dian)(dian)熔氧化鎂的工(gong)藝(yi)流程主要(yao)包括:原料配料、電(dian)(dian)弧(hu)熔融、破(po)碎(sui)、選(xuan)別(bie)、粉碎(sui)、篩別(bie)、磁(ci)選(xuan)、分類包裝等。
(1)原料
我(wo)國有(you)豐富的(de)(de)優(you)質菱鎂(mei)礦石,氧(yang)化(hua)鎂(mei)含(han)量(liang)高(gao),又易(yi)于開采(cai),因(yin)此(ci),被廣泛用作電(dian)熔(rong)氧(yang)化(hua)鎂(mei)的(de)(de)原料(liao)。采(cai)用菱鎂(mei)石作原料(liao),碳酸鎂(mei)分(fen)解產生CO2氣體,由于有(you)大量(liang)氣體從爐內排出影(ying)響著電(dian)熔(rong)過程(cheng)的(de)(de)進行(xing):
MgCO3→MgO+CO2↑
對電熔氧化(hua)鎂(mei)的(de)結(jie)晶帶的(de)形(xing)成均有不利影(ying)響(xiang),由(you)于(yu)大量(liang)塵料飛損(sun),使物料損(sun)耗和能量(liang)消耗增高,也惡化(hua)了車間(jian)生產環境。但由(you)于(yu)優(you)質(zhi)菱(ling)鎂(mei)礦石容易獲得,價格很低廉,所以,仍是我(wo)國電熔氧化(hua)鎂(mei)用得最(zui)多最(zui)廣泛的(de)原料。
(2)配料
①菱鎂礦。菱鎂礦石中(zhong)氧(yang)化(hua)鎂的(de)含量(liang)高低和(he)化(hua)學成分直接(jie)影(ying)響到(dao)(dao)(dao)電(dian)熔(rong)(rong)凝氧(yang)化(hua)鎂的(de)質(zhi)量(liang),同時(shi)在電(dian)熔(rong)(rong)過(guo)程中(zhong)也直接(jie)影(ying)響到(dao)(dao)(dao)電(dian)熔(rong)(rong)凝氧(yang)化(hua)鎂得到(dao)(dao)(dao)的(de)品級(ji)比例,因此(ci),為了保(bao)證(zheng)電(dian)熔(rong)(rong)凝氧(yang)化(hua)鎂的(de)質(zhi)量(liang)和(he)品級(ji)比例,必須(xu)對各(ge)種礦石進行適當的(de)配(pei)比后進行熔(rong)(rong)煉(lian)。
②水鎂(mei)石(shi)(shi)。我國的(de)遼寧省(sheng)水鎂(mei)石(shi)(shi)的(de)礦源(yuan)非常豐富,水鎂(mei)石(shi)(shi)中(zhong)氧化(hua)(hua)鎂(mei)含量高于菱鎂(mei)礦石(shi)(shi)。它(ta)也是(shi)一種制造電熔凝氧化(hua)(hua)鎂(mei)的(de)原(yuan)料,部(bu)分地區水鎂(mei)石(shi)(shi)的(de)化(hua)(hua)學成分見表2。
表2水鎂石的化學成分(fen)/%
③輕(qing)燒氧化(hua)鎂(mei)。以(yi)輕(qing)燒氧化(hua)鎂(mei)作為電(dian)熔氧化(hua)鎂(mei)原料,可以(yi)使生產環境得到改善,可以(yi)降低運輸(shu)費用。由于電(dian)熔時排出氣(qi)體(ti)少,成分也(ye)較均(jun)勻(yun),對(dui)提高電(dian)熔氧化(hua)鎂(mei)質量有利。
我(wo)國(guo)有(you)一(yi)些電熔(rong)(rong)凝氧(yang)化(hua)鎂(mei)以(yi)輕(qing)(qing)燒(shao)氧(yang)化(hua)鎂(mei)制(zhi)成(cheng)球料(liao)入爐電熔(rong)(rong)。輕(qing)(qing)燒(shao)氧(yang)化(hua)鎂(mei)的(de)(de)氧(yang)化(hua)鎂(mei)含量(liang)達到(dao)98%,以(yi)此料(liao)能生產出白色大結晶電熔(rong)(rong)氧(yang)化(hua)鎂(mei)。但由于成(cheng)球費用(yong)高,影(ying)響(xiang)生產成(cheng)本。目(mu)前(qian),有(you)的(de)(de)廠(chang)家采用(yong)反射爐輕(qing)(qing)燒(shao)氧(yang)化(hua)鎂(mei),以(yi)一(yi)定的(de)(de)粒度加入熔(rong)(rong)爐電熔(rong)(rong),電熔(rong)(rong)氧(yang)化(hua)鎂(mei)的(de)(de)質量(liang)比用(yong)菱鎂(mei)礦石好,成(cheng)本又比用(yong)球料(liao)作(zuo)原料(liao)時便宜,因而得到(dao)了一(yi)定的(de)(de)推(tui)廣。
④燒(shao)結鎂(mei)(mei)砂(sha)(sha)。為(wei)(wei)了某些電(dian)(dian)(dian)熔凝氧(yang)化(hua)(hua)鎂(mei)(mei)的(de)(de)(de)(de)特(te)殊要求(qiu),有時(shi)必須在電(dian)(dian)(dian)熔過程(cheng)中采用(yong)(yong)(yong)燒(shao)結鎂(mei)(mei)砂(sha)(sha)作為(wei)(wei)電(dian)(dian)(dian)熔原料,如采用(yong)(yong)(yong)海(hai)水(shui)鎂(mei)(mei)砂(sha)(sha)作為(wei)(wei)電(dian)(dian)(dian)熔原料,一般首先利(li)用(yong)(yong)(yong)處(chu)理海(hai)水(shui)和石(shi)灰乳作用(yong)(yong)(yong)生(sheng)產氫氧(yang)化(hua)(hua)鎂(mei)(mei),將氫氧(yang)化(hua)(hua)鎂(mei)(mei)煅燒(shao)成輕(qing)燒(shao)氧(yang)化(hua)(hua)鎂(mei)(mei)。用(yong)(yong)(yong)其他方(fang)法也可以(yi)制得輕(qing)燒(shao)氧(yang)化(hua)(hua)鎂(mei)(mei)(詳見工業氧(yang)化(hua)(hua)鎂(mei)(mei)的(de)(de)(de)(de)制取方(fang)法),采用(yong)(yong)(yong)輕(qing)燒(shao)氧(yang)化(hua)(hua)鎂(mei)(mei)作為(wei)(wei)原料生(sheng)產電(dian)(dian)(dian)熔凝氧(yang)化(hua)(hua)鎂(mei)(mei)。奧絲脫(AusT)和拉特(te)爾(Ruttere)等研究認為(wei)(wei),極(ji)少(shao)量(liang)的(de)(de)(de)(de)雜質(zhi)氣體(ti)(ti)(相(xiang)(xiang)(xiang))也屬于晶(jing)(jing)(jing)體(ti)(ti)的(de)(de)(de)(de)雜質(zhi),可明顯影響(xiang)晶(jing)(jing)(jing)粒(li)的(de)(de)(de)(de)長大。因為(wei)(wei)雜質(zhi)相(xiang)(xiang)(xiang)的(de)(de)(de)(de)作用(yong)(yong)(yong)在于增(zeng)加晶(jing)(jing)(jing)界運動所需的(de)(de)(de)(de)能(neng)量(liang)。當(dang)晶(jing)(jing)(jing)界與第二(er)相(xiang)(xiang)(xiang)相(xiang)(xiang)(xiang)遇(yu)時(shi),晶(jing)(jing)(jing)體(ti)(ti)能(neng)量(liang)降低,其降低量(liang)與第二(er)相(xiang)(xiang)(xiang)橫(heng)截面(mian)積(ji)成正比,所以(yi)必須提高晶(jing)(jing)(jing)界能(neng),晶(jing)(jing)(jing)界才能(neng)離開第二(er)相(xiang)(xiang)(xiang)繼續運動。并且當(dang)晶(jing)(jing)(jing)界與第二(er)相(xiang)(xiang)(xiang)相(xiang)(xiang)(xiang)遇(yu)時(shi),與第二(er)相(xiang)(xiang)(xiang)橫(heng)截面(mian)積(ji)相(xiang)(xiang)(xiang)等的(de)(de)(de)(de)晶(jing)(jing)(jing)界必須變(bian)形,第二(er)相(xiang)(xiang)(xiang)數量(liang)愈(yu)多,晶(jing)(jing)(jing)粒(li)長大的(de)(de)(de)(de)極(ji)限尺(chi)寸愈(yu)小。
另一方面為了降低電熔凝氧化(hua)(hua)鎂的(de)顯(xian)氣孔率,也應盡量減(jian)少原料(liao)氧化(hua)(hua)鎂的(de)氣體排出,因此,采用(yong)燒(shao)結(jie)鎂砂電熔有其顯(xian)著優點。
⑤電(dian)熔氧化鎂(mei)單晶的化學(xue)原料質量要(yao)求:
(3)電弧熔融
這些特性(xing)是(shi)同原(yuan)子(zi)(zi)和(he)(he)分子(zi)(zi)的量(liang)子(zi)(zi)力(li)學本(ben)性(xing)如離(li)子(zi)(zi)半徑的尺寸,離(li)子(zi)(zi)的電(dian)位(wei)數值,離(li)子(zi)(zi)的電(dian)子(zi)(zi)外層結構等相關聯(lian)。而氧(yang)化(hua)(hua)鎂的離(li)子(zi)(zi)尺寸、質量(liang)和(he)(he)電(dian)荷、陽離(li)子(zi)(zi)和(he)(he)陰(yin)離(li)子(zi)(zi)之間(jian)的結合特性(xing)和(he)(he)強度(du)、離(li)子(zi)(zi)的極化(hua)(hua)作用(yong)、結晶構造等決定它是(shi)一高熔點化(hua)(hua)合物(wu)。
氧化(hua)鎂的熔點(dian)(dian)和結構(gou)參數:陽離子半徑(jing)0.074mm;陰離子半徑(jing)0.53mm;結構(gou)類型(xing)NaCl;配(pei)位數6;有效配(pei)位數8.5;密度3.65g/cm3;熔點(dian)(dian)2800℃。
電熔(rong)(rong)凝氧(yang)(yang)化(hua)(hua)(hua)(hua)鎂制造的(de)(de)最重要(yao)過(guo)(guo)程(cheng)是由(you)各種(zhong)鎂質原(yuan)料,通過(guo)(guo)各種(zhong)形式的(de)(de)加熱方(fang)(fang)法產(chan)生(sheng)高(gao)溫(wen)使鎂質材料(MgO)熔(rong)(rong)化(hua)(hua)(hua)(hua),變(bian)成氧(yang)(yang)化(hua)(hua)(hua)(hua)鎂熔(rong)(rong)體。要(yao)使氧(yang)(yang)化(hua)(hua)(hua)(hua)鎂熔(rong)(rong)融,必須消耗大量的(de)(de)熱能(neng),以克服離子間的(de)(de)引(yin)力(li)。通過(guo)(guo)強大電弧(hu)產(chan)生(sheng)高(gao)溫(wen)而熔(rong)(rong)化(hua)(hua)(hua)(hua)氧(yang)(yang)化(hua)(hua)(hua)(hua)鎂的(de)(de)方(fang)(fang)法叫做(zuo)電弧(hu)熔(rong)(rong)融法。這個融化(hua)(hua)(hua)(hua)過(guo)(guo)程(cheng)一(yi)般包括(kuo)熱的(de)(de)傳(chuan)導、脫水、脫碳、熔(rong)(rong)化(hua)(hua)(hua)(hua)、析晶(jing)、晶(jing)體長(chang)大等一(yi)系(xi)列物理化(hua)(hua)(hua)(hua)學(xue)變(bian)化(hua)(hua)(hua)(hua)的(de)(de)過(guo)(guo)程(cheng)。
①脫(tuo)水(shui)(shui)過(guo)程。用水(shui)(shui)鎂石(shi)作原(yuan)料有一脫(tuo)水(shui)(shui)過(guo)程。水(shui)(shui)鎂石(shi)的主要成分是氫氧化鎂Mg(OH)2。其(qi)脫(tuo)水(shui)(shui)過(guo)程是:
Mg(OH)2→MgO+H2O
②脫(tuo)碳(tan)過(guo)程。用菱(ling)鎂(mei)(mei)礦作為原料時有一個脫(tuo)碳(tan)過(guo)程,脫(tuo)碳(tan)過(guo)程包括兩(liang)個方面。一方面是菱(ling)鎂(mei)(mei)礦石的(de)熱分(fen)解,菱(ling)鎂(mei)(mei)礦石的(de)主要成分(fen)是碳(tan)酸(suan)鎂(mei)(mei)(MgCO3):
MgCO3→MgO+CO2
另(ling)一方面,由(you)于(yu)在(zai)電(dian)熔過程中(zhong)往(wang)往(wang)在(zai)原料(liao)氧化鎂中(zhong)加入石墨粉末添(tian)加物(助(zhu)劑),在(zai)電(dian)熔爐起動(dong)過程中(zhong)需在(zai)三電(dian)極(石墨電(dian)極)的(de)下(xia)端用石墨粉末鋪成三角形或(huo)(huo)星形導線路,在(zai)通電(dian)過程中(zhong)受(shou)熱(re)燒損或(huo)(huo)完全燃燒除去(qu)石墨。
C+O2→CO2↑
③熔(rong)(rong)化過(guo)程。熔(rong)(rong)化過(guo)程即氧(yang)(yang)化鎂(mei)(mei)中鎂(mei)(mei)離子和(he)氧(yang)(yang)離子在強電(dian)(dian)弧產生(sheng)的熱(re)(re)能(neng)(neng)作用下,克服(fu)單晶體(ti)中的晶格(ge)能(neng)(neng)的束(shu)縛,變(bian)成(cheng)能(neng)(neng)自(zi)由運(yun)動的過(guo)程。也就是說(shuo),氧(yang)(yang)化鎂(mei)(mei)加熱(re)(re)到一定溫度(熔(rong)(rong)點)就會由固體(ti)變(bian)成(cheng)液體(ti),叫熔(rong)(rong)化。在這(zhe)(zhe)一過(guo)程中需(xu)消耗(hao)大量(liang)的電(dian)(dian)能(neng)(neng)。據電(dian)(dian)熔(rong)(rong)凝氧(yang)(yang)化鎂(mei)(mei)生(sheng)產者對用水鎂(mei)(mei)石作原料生(sheng)產電(dian)(dian)熔(rong)(rong)凝氧(yang)(yang)化鎂(mei)(mei)的熱(re)(re)平衡(heng)的衡(heng)算,熱(re)(re)消耗(hao)的比例如下:氧(yang)(yang)化鎂(mei)(mei)晶體(ti)生(sheng)成(cheng)熱(re)(re)消耗(hao)值(zhi)(zhi)34.9%,渣皮消耗(hao)熱(re)(re)值(zhi)(zhi)15.3%,散砂(sha)生(sheng)成(cheng)熱(re)(re)耗(hao)值(zhi)(zhi)3.0%,冷卻(que)水耗(hao)熱(re)(re)值(zhi)(zhi)8.4%,冷卻(que)爐(lu)殼(ke)的水耗(hao)熱(re)(re)值(zhi)(zhi)7.9%,爐(lu)子表(biao)面散熱(re)(re)值(zhi)(zhi)6.4%,煙氣帶(dai)走熱(re)(re)值(zhi)(zhi)28.8%。電(dian)(dian)能(neng)(neng)損(sun)失值(zhi)(zhi)3.2%,從這(zhe)(zhe)些統計(ji)數據可以看出,在電(dian)(dian)熔(rong)(rong)