一、真空凍干設備能耗高還是烘干能耗高

干燥物體主要有烘干和凍干兩種方式，凍干設備相(xiang)比烘干設(she)備具(ju)有保質期更長、可以有效保持物體的成分，不(bu)會(hui)改變物體形狀等優勢，不(bu)過它也有一個缺(que)點，那就是(shi)能耗要更高一些(xie)。

凍(dong)(dong)干(gan)產品加工(gong)工(gong)藝(yi)相比傳(chuan)統(tong)烘干(gan)，工(gong)藝(yi)更(geng)復(fu)雜，工(gong)藝(yi)流程(cheng)一般分為(wei)前處(chu)理、凍(dong)(dong)干(gan)和(he)后處(chu)理等流程(cheng)，本(ben)身(shen)的結構也更(geng)復(fu)雜，在凍(dong)(dong)干(gan)過程(cheng)中，制冷系統(tong)和(he)加熱系統(tong)需要(yao)消耗大量(liang)能量(liang)，因此能耗是(shi)比烘干(gan)設(she)備要(yao)更(geng)高(gao)的。

二、如何降低真空凍干機的能耗

真空凍干(gan)(gan)機的(de)能耗高低(di)(di)直(zhi)接影響到(dao)凍干(gan)(gan)成本，一般可以通過提高凍干(gan)(gan)速率的(de)方法來(lai)降低(di)(di)能耗，目前(qian)，通過工藝優化(hua)的(de)方法來(lai)提高食品(pin)干(gan)(gan)燥速率、降低(di)(di)能耗的(de)方法主要有(you)以下幾種：

1、控制適宜的預凍速度

對(dui)(dui)食品(pin)原料的(de)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)是(shi)冷凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)燥工藝的(de)前提步(bu)驟，研究表明，快速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)和慢(man)速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)對(dui)(dui)食品(pin)物料所需要(yao)的(de)凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)時(shi)間(jian)有(you)顯著影響，快速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)要(yao)比(bi)慢(man)速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)所需要(yao)的(de)凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)時(shi)間(jian)長，這是(shi)由(you)于食品(pin)進行(xing)快速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)時(shi)產(chan)生的(de)冰(bing)(bing)(bing)(bing)晶小，致密的(de)冰(bing)(bing)(bing)(bing)晶對(dui)(dui)于冰(bing)(bing)(bing)(bing)的(de)升(sheng)(sheng)華(hua)起阻礙作用，而在慢(man)速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)時(shi)，食品(pin)中形(xing)成的(de)冰(bing)(bing)(bing)(bing)晶大(da)，冰(bing)(bing)(bing)(bing)晶之間(jian)具有(you)較大(da)縫(feng)隙(xi)，能夠促(cu)進冰(bing)(bing)(bing)(bing)升(sheng)(sheng)華(hua)，但(dan)是(shi)冰(bing)(bing)(bing)(bing)晶越大(da)對(dui)(dui)凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)產(chan)品(pin)品(pin)質影響也越大(da)，特別是(shi)對(dui)(dui)一些生物制品(pin)進行(xing)凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)時(shi)，慢(man)速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)產(chan)生的(de)大(da)冰(bing)(bing)(bing)(bing)晶會破(po)環細胞結構，如果對(dui)(dui)終產(chan)品(pin)要(yao)求不高(gao)，可以考(kao)慮(lv)通(tong)過(guo)慢(man)速(su)(su)預(yu)(yu)(yu)(yu)凍(dong)(dong)(dong)(dong)(dong)(dong)來提高(gao)凍(dong)(dong)(dong)(dong)(dong)(dong)干(gan)速(su)(su)率。

2、調整液態食品的濃度或改變固態食品的形狀

液態(tai)食品(pin)的(de)凍(dong)干(gan)，需要充分(fen)考慮溶(rong)液的(de)濃度(du)，如果濃度(du)過高，則不利于水(shui)分(fen)的(de)升華，如果濃度(du)太低，雖然利于升華，但因含水(shui)多(duo)，則會(hui)耗(hao)時耗(hao)能(neng)造成浪費。應用凍(dong)干(gan)技術(shu)進行液態(tai)食品(pin)干(gan)燥時，要充分(fen)衡量(liang)能(neng)耗(hao)與產品(pin)質量(liang)的(de)關系，探索優化(hua)最(zui)佳凍(dong)干(gan)濃度(du)，進而提高凍(dong)干(gan)速(su)率。

固(gu)態食品進行(xing)凍(dong)干(gan)時(shi)，切片(pian)、粉碎是(shi)增大傳熱(re)面(mian)積、提高凍(dong)干(gan)速(su)率(lv)的(de)最佳方法。目前市售的(de)凍(dong)干(gan)產品如凍(dong)干(gan)蘋果(guo)片(pian)、凍(dong)干(gan)草莓(mei)片(pian)、凍(dong)干(gan)檸檬片(pian)等，都采取了切片(pian)的(de)方法。但是(shi)如果(guo)對固(gu)態食品形(xing)狀要求(qiu)嚴格，可以(yi)考慮對食品物(wu)料進行(xing)穿(chuan)刺(ci)處(chu)理，通(tong)過穿(chuan)刺(ci)孔通(tong)透性來增加傳質，提高凍(dong)干(gan)速(su)率(lv)。

3、控制食品原料裝盤量和厚度

不(bu)同型號凍干(gan)(gan)機冷阱均有最大(da)的捕水能(neng)力(li)，如(ru)(ru)果裝(zhuang)盤物料的水分超過了最大(da)捕水量(liang)，就會(hui)造成產(chan)品(pin)不(bu)能(neng)達(da)到一定(ding)的干(gan)(gan)燥(zao)程度，導致干(gan)(gan)燥(zao)失敗；如(ru)(ru)果裝(zhuang)盤物料過少(shao)，雖然會(hui)提高(gao)凍干(gan)(gan)速率，但會(hui)造成空間浪費，增加了產(chan)品(pin)成本。因此，在凍干(gan)(gan)前要根(gen)據冷阱的捕水能(neng)力(li)，確定(ding)放入合適量(liang)的食(shi)品(pin)原(yuan)料。

在冷(leng)凍(dong)(dong)干燥裝(zhuang)盤(pan)時，控(kong)制(zhi)適當的(de)(de)物料(liao)(liao)厚度(du)，可(ke)降(jiang)低傳熱、傳質阻力，提(ti)高干燥速(su)率(lv)；在實際生產過(guo)程(cheng)中(zhong)，如果物料(liao)(liao)厚度(du)太薄，裝(zhuang)盤(pan)量就會自然(ran)減(jian)小(xiao)，凍(dong)(dong)干速(su)率(lv)提(ti)高同時卻(que)增加了(le)單位(wei)凍(dong)(dong)干產品的(de)(de)成本，因此，并非物料(liao)(liao)的(de)(de)厚度(du)越小(xiao)越好(hao)，單位(wei)面積裝(zhuang)載(zai)的(de)(de)食品原料(liao)(liao)，需(xu)要綜合考慮原料(liao)(liao)裝(zhuang)盤(pan)量對干燥速(su)率(lv)和成本，根據冷(leng)阱捕水能(neng)力、物料(liao)(liao)性(xing)質、加熱方式以及干燥效率(lv)等(deng)而(er)定。

4、設定適當的真空度

維持冷(leng)(leng)凍(dong)(dong)干燥(zao)(zao)時真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)的(de)耗(hao)能(neng)(neng)(neng)(neng)(neng)約(yue)占凍(dong)(dong)干總(zong)耗(hao)能(neng)(neng)(neng)(neng)(neng)的(de)26%，真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)越低，有利于(yu)能(neng)(neng)(neng)(neng)(neng)量(liang)傳(chuan)遞，但卻(que)增(zeng)加(jia)了水汽擴散(san)阻力從而耗(hao)能(neng)(neng)(neng)(neng)(neng)。實際凍(dong)(dong)干過(guo)程(cheng)中，每種食品原料都存在(zai)一個最佳的(de)真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)，因此(ci)可以(yi)使能(neng)(neng)(neng)(neng)(neng)耗(hao)降(jiang)(jiang)到最低。凍(dong)(dong)干機的(de)真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)受阱(jing)溫(wen)度(du)(du)和真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)泵(beng)性能(neng)(neng)(neng)(neng)(neng)決定(ding)，在(zai)升華干燥(zao)(zao)階段，一般冷(leng)(leng)阱(jing)溫(wen)度(du)(du)越低、真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)越高可促(cu)進(jin)水汽凝結，提高凍(dong)(dong)干速率，但高真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)對真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)泵(beng)有特殊的(de)要求，真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)過(guo)高，會增(zeng)加(jia)維持真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)能(neng)(neng)(neng)(neng)(neng)耗(hao)；當凍(dong)(dong)干工(gong)藝處于(yu)在(zai)解析(xi)干燥(zao)(zao)階段則應逐漸(jian)降(jiang)(jiang)低干燥(zao)(zao)室的(de)真(zhen)(zhen)(zhen)空(kong)(kong)(kong)(kong)(kong)度(du)(du)，來促(cu)進(jin)傳(chuan)熱和傳(chuan)質，達到降(jiang)(jiang)低凍(dong)(dong)干能(neng)(neng)(neng)(neng)(neng)耗(hao)的(de)目的(de)。

5、控制隔板加熱溫度

目前，大部分的真空凍干設備都安裝了隔(ge)板(ban)(ban)加熱(re)裝置(zhi)，以提高(gao)物(wu)料(liao)升(sheng)華所需要能量(liang)，提高(gao)擱板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)可提高(gao)干(gan)燥速率。對(dui)擱板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)的(de)(de)(de)控(kong)制包括控(kong)制凍(dong)(dong)結層和已(yi)干(gan)層的(de)(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)，對(dui)于(yu)凍(dong)(dong)結層的(de)(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)應(ying)首先保證低(di)于(yu)共(gong)融(rong)點前提下越高(gao)越好；對(dui)于(yu)已(yi)干(gan)層的(de)(de)(de)溫(wen)(wen)(wen)(wen)度(du)(du)(du)，在不出(chu)現因溫(wen)(wen)(wen)(wen)度(du)(du)(du)升(sheng)高(gao)造成產品(pin)(pin)塌陷或變性(xing)現象的(de)(de)(de)前提下，盡量(liang)采用(yong)較高(gao)的(de)(de)(de)隔(ge)板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)，在解析干(gan)燥階段(duan)，應(ying)密(mi)切注意產品(pin)(pin)溫(wen)(wen)(wen)(wen)度(du)(du)(du)和隔(ge)板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)差別，保持隔(ge)板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)高(gao)于(yu)樣(yang)品(pin)(pin)溫(wen)(wen)(wen)(wen)度(du)(du)(du)5 ℃左右，同時(shi)對(dui)于(yu)小型(xing)凍(dong)(dong)干(gan)機要設法降低(di)控(kong)制熱(re)量(liang)輻(fu)射的(de)(de)(de)影響，擱板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)要緩慢升(sheng)高(gao)，但一(yi)(yi)般(ban)不高(gao)于(yu)70℃，對(dui)于(yu)一(yi)(yi)些活性(xing)生物(wu)制品(pin)(pin)則(ze)應(ying)當一(yi)(yi)直維持更(geng)低(di)的(de)(de)(de)隔(ge)板(ban)(ban)溫(wen)(wen)(wen)(wen)度(du)(du)(du)。