塑(su)料(liao)的(de)幹(gan)燥(zao)對(dui)於(yu)每(mei)一(yi)個(ge)塑(su)料(liao)加(jia)工(gong)商(shang)來(lai)說(shuo)都(dou)是(shi)不(bu)可(ke)避(bi)免(mian)的(de)。同(tong)時(shi),為(wei)了(le)生(sheng)產(chan)出(chu)高(gao)質(zhi)量(liang)的(de)產(chan)品(pin),這(zhe)一(yi)過(guo)程(cheng)也(ye)是(shi)非(fei)常(chang)重(zhong)要(yao)的(de)。選(xuan)擇(ze)合(he)理(li)的(de)幹(gan)燥(zao)技(ji)術(shu)有(you)助(zhu)於(yu)節(jie)約(yue)成(cheng)本(ben)、降低能耗,而對幹燥技術和成本的正確評估對於選擇合適的幹燥技術具有重要的意義。
水(shui)含(han)量(liang)的(de)增(zeng)加(jia)會(hui)逐(zhu)漸(jian)降(jiang)低(di)物(wu)料(liao)的(de)剪(jian)切(qie)黏(nian)度(du)。在(zai)加(jia)工(gong)過(guo)程(cheng)中(zhong),由(you)於(yu)熔(rong)體(ti)流(liu)動(dong)性(xing)能(neng)的(de)變(bian)化(hua),產(chan)品(pin)的(de)質(zhi)量(liang)以(yi)及(ji)一(yi)係(xi)列(lie)的(de)加(jia)工(gong)工(gong)藝(yi)參(can)數(shu)也(ye)會(hui)隨(sui)之(zhi)發(fa)生(sheng)相(xiang)應(ying)的(de)變(bian)化(hua)。例(li)如(ru),停(ting)滯(zhi)時(shi)間(jian)過(guo)長(chang)會(hui)使(shi)殘(can)餘(yu)水(shui)分(fen)含(han)量(liang)太(tai)低(di)從(cong)而(er)造(zao)成(cheng)黏(nian)度(du)的(de)增(zeng)加(jia),這(zhe)將(jiang)導(dao)致(zhi)填(tian)模(mo)不(bu)充(chong)分(fen),同(tong)時(shi)也(ye)會(hui)造(zao)成(cheng)物(wu)料(liao)發(fa)黃(huang)。另(ling)外(wai),某(mou)些(xie)性(xing)能(neng)的(de)變(bian)化(hua)並(bing)不(bu)能(neng)直(zhi)接(jie)用(yong)肉(rou)眼(yan)觀(guan)察(cha)到(dao),而(er)隻(zhi)有(you)通(tong)過(guo)對(dui)材(cai)料(liao)進(jin)行(xing)相(xiang)關(guan)的(de)測(ce)試(shi)才(cai)能(neng)發(fa)現(xian),如(ru)機(ji)械(xie)性(xing)能(neng)和(he)介(jie)電(dian)強(qiang)度(du)的(de)改(gai)變(bian)。
在zai選xuan擇ze幹gan燥zao過guo程cheng時shi,鑒jian別bie材cai料liao的de幹gan燥zao性xing能neng具ju有you至zhi關guan重zhong要yao的de意yi義yi。物wu料liao可ke以yi分fen成cheng吸xi濕shi性xing和he非fei吸xi濕shi性xing兩liang種zhong。吸xi濕shi性xing物wu料liao能neng夠gou從cong周zhou圍wei環huan境jing吸xi收shou水shui分fen,非fei吸xi濕shi性xing材cai料liao不bu能neng從cong環huan境jing中zhong吸xi收shou水shui分fen。對dui於yu非fei吸xi濕shi性xing物wu料liao,任ren何he環huan境jing中zhong存cun在zai的de水shui分fen都dou保bao留liu在zai表biao麵mian,成cheng為wei“表麵水分”而易於被清除。不過由非吸濕性 物wu料liao製zhi成cheng的de膠jiao粒li也ye可ke能neng因yin為wei添tian加jia劑ji或huo填tian料liao的de作zuo用yong而er變bian得de具ju有you吸xi濕shi性xing。另ling外wai,對dui一yi個ge幹gan燥zao工gong藝yi過guo程cheng的de能neng耗hao的de計ji算suan,可ke能neng會hui與yu加jia工gong作zuo業ye的de複fu雜za程cheng度du以yi及ji其qi他ta因yin素su有you關guan,所suo以yi這zhe裏li所suo介jie紹shao的de數shu值zhi僅jin供gong參can考kao。
對流式幹燥
對(dui)於(yu)非(fei)吸(xi)濕(shi)性(xing)物(wu)料(liao),可(ke)以(yi)使(shi)用(yong)熱(re)風(feng)幹(gan)燥(zao)機(ji)進(jin)行(xing)幹(gan)燥(zao)。因(yin)為(wei)水(shui)分(fen)隻(zhi)是(shi)被(bei)物(wu)料(liao)與(yu)水(shui)的(de)界(jie)麵(mian)張(zhang)力(li)鬆(song)散(san)地(di)約(yue)束(shu),易(yi)於(yu)去(qu)除(chu)。此(ci)類(lei)機(ji)器(qi)的(de)原(yuan)理(li)是(shi),利(li)用(yong)風(feng)扇(shan)來(lai)吸(xi)收(shou)環(huan)境(jing)中(zhong)的(de)空(kong)氣(qi)並(bing)將(jiang)其(qi)加(jia)熱(re)到(dao)幹(gan)燥(zao)特(te)定(ding)物(wu)料(liao)所(suo)要(yao)求(qiu)的(de)溫(wen)度(du),被(bei)加(jia)熱(re)後(hou)的(de)空(kong)氣(qi)經(jing)過(guo)幹(gan)燥(zao)料(liao)鬥(dou),並(bing)通(tong)過(guo)對(dui)流(liu)的(de)方(fang)式(shi)加(jia)熱(re)物(wu)料(liao)以(yi)除(chu)去(qu)水(shui)分(fen)。
對吸濕性物料的幹燥一般分為三個幹燥段:第一個幹燥段是將物料表麵的水分蒸發掉;第二個幹燥段則將蒸發的重點放在材料內部,此時幹燥速度緩慢降低,而被幹燥物料的溫度開始上升;zaizuihouyigejieduan,wuliaodadaoyuganzaoqitidexishipingheng。zaizhegejieduan,neibuhewaibujiandewenducha別jiangbeixiaochu。zaidisanduanmoduan,ruguobeiganzaowuliaobuzaishifangchushuifen,zhebingbuyiweizhetabuhanshuifen,erzhishibiaomingjiaolihezhouweihuanjingzhijianyijingjianliqilepingheng。
zaiganzaojishuzhong,kongqideludianwendushiyigefeichangzhongyaodecanshu。suoweideludianwendujiushizaibaochishikongqidehanshiliangbubiandeqingkuangxia,shiqiwenduxiajiang,dangxiangduishidudadao100%時(shi)所(suo)對(dui)應(ying)的(de)溫(wen)度(du)。它(ta)表(biao)示(shi)空(kong)氣(qi)達(da)到(dao)水(shui)分(fen)凝(ning)結(jie)時(shi)所(suo)對(dui)應(ying)的(de)溫(wen)度(du)。通(tong)常(chang),用(yong)於(yu)幹(gan)燥(zao)的(de)空(kong)氣(qi)的(de)露(lu)點(dian)愈(yu)低(di),所(suo)獲(huo)得(de)殘(can)餘(yu)水(shui)量(liang)就(jiu)愈(yu)低(di),幹(gan)燥(zao)速(su)度(du)也(ye)愈(yu)低(di)。
muqian,shengchanganzaokongqizuiweipubiandefangfashiliyongganzaoqitifashengqi。gaishebeiyiyoulianggefenzishaizuchengdexifuxingganzaoqiweihexin,kongqizhongdeshuifenzaizhelibeixishou。zaiganzaozhuangtaixia,kongqiliujingfenzishai,fenzishaixishouqitizhongdeshuifen,weiganzaotigongchushiqiti。zaizaishengzhuangtaixia,fenzishaibeirekongqijiarezhizaishengwendu。liujingfenzishaideqitishoujibeichuqudeshuifen,bingjiangqidaizhizhouweihuanjingzhong。lingyizhongshengchengganzaoqitidefangfashijiangdiyasuoqitideyali。zhezhongfangfadehaochushigongyingwangluozhongdeyasuoqitiyouzhejiaodideyaliludian。zaiyalijiangdiyihou,qiludiandadao0℃左右。如果需要更低的露點,可以利用膜式或吸附式幹燥器在壓縮空氣壓力降低之前進一步降低空氣的露點。
在除濕空氣幹燥中,生產幹燥氣體所需的能量必須進行額外計算。在吸附式幹燥中,再生狀態的分子篩必須從幹燥態的溫度(約60℃)被加熱至再生溫度(約200℃)。為wei此ci,通tong常chang的de做zuo法fa是shi通tong過guo分fen子zi篩shai將jiang被bei加jia熱re氣qi體ti連lian續xu加jia熱re至zhi再zai生sheng溫wen度du,直zhi至zhi它ta在zai離li開kai分fen子zi篩shai時shi達da到dao特te定ding溫wen度du。理li論lun上shang再zai生sheng所suo必bi要yao的de能neng量liang由you加jia熱re分fen子zi篩shai及ji其qi內nei部bu吸xi附fu的de水shui所suo需xu要yao的de能neng量liang、克服分子篩對水的附著力所需要的能量、蒸發水分和水蒸汽升溫所必需的能量幾個部分組成。
一般,吸附所得露點與分子篩的溫度與水分攜帶量有關。通常,小於或等於30℃的露點可以使分子篩達到10%的水分攜帶量。為了製備幹燥氣體,由能量計算所得的理論能量需求值是0.004kWh/m3。danshi,shijizhongzhegeshuzhibixushaogao,yinweijisuanmeiyoubafengshanhuoreliangsunshikaolvzainei。tongguoduibi,butongleixingdeganzaoqitifashengqidetedingnenghaojiukeyibeiqueding。yibanlaishuo,chushiqitiganzaodenenghaozai0.04kWh/kg~0.12kWh/kg之間,這要根據物料和初始水分含量而變化。在實際操作中,也可能達到0.25kWh/kg或更高。
幹gan燥zao膠jiao粒li所suo需xu的de能neng量liang由you兩liang部bu分fen組zu成cheng,一yi部bu分fen是shi將jiang物wu料liao由you室shi溫wen加jia熱re至zhi幹gan燥zao溫wen度du所suo需xu要yao的de能neng量liang,另ling一yi部bu分fen是shi蒸zheng發fa水shui分fen所suo需xu要yao的de能neng量liang。在zai確que定ding物wu料liao所suo需xu的de氣qi體ti量liang時shi,通tong常chang是shi以yi幹gan燥zao氣qi體ti進jin入ru或huo離li開kai幹gan燥zao料liao鬥dou時shi的de溫wen度du為wei基ji礎chu。一yi定ding溫wen度du的de幹gan燥zao空kong氣qi通tong過guo對dui流liu的de方fang式shi將jiang熱re量liang輸shu送song至zhi膠jiao粒li中zhong也ye是shi一yi種zhong對dui流liu幹gan燥zao過guo程cheng。
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