纖維素燃料乙醇三塔精餾優(yōu)化

第24卷第2期纖維素科學(xué)與技術(shù)VoL 24 No. 22016年6月Journal of Cellulose Science and TechnologyJun.2016文章編號:1004-8405(2016)02-0060-06DOI:101656l/ cnki.xws201602.09纖維素燃料乙醇三塔精餾優(yōu)化楊靜1,杜江,趙錦2,張秋翔!,李雙喜1*(1.北京化工大學(xué)機電工程學(xué)院,北京10009:2.國網(wǎng)節能服務(wù)有限公司北京生物質(zhì)能源技術(shù)中心,北京10005)摘要:纖維素燃料乙醇生產(chǎn)過(guò)程中由于發(fā)酵醪液質(zhì)量分數較低(5%左右),精餾所需能耗較高,高能耗成為制約纖維素燃料乙醇工業(yè)化的重要原因?；?Aspen plus軟件建立纖維素乙醇三塔精餾工藝的計算模型,采用NRTL活度系數模型得到物料及能量衡算結果。分別優(yōu)化粗塔、常壓塔和加壓塔,得到各塔理論塔板數、進(jìn)料位置、回流比等參數對各塔再沸器負荷的影響規律,通過(guò)優(yōu)化各影響參數使綜合能耗最小,為纖維素燃料乙醇生產(chǎn)工業(yè)化提供理論支持。關(guān)鍵詞:纖維素:燃料乙醇;三塔精餾; Aspen plus中圖分類(lèi)號:TQ018;TS2622文獻標識碼:A燃料乙醇是指以薯類(lèi)、糖類(lèi)或纖維素等生物質(zhì)為原料,經(jīng)預處理、酶解、發(fā)酵、精餾、脫水得到995%(V)的燃料乙醇。生產(chǎn)過(guò)程不僅不會(huì )污染環(huán)境,而且可以實(shí)現二氧化碳的自然平衡。纖維素是地球上資源最為豐富的生物質(zhì)能源,以其作為原料生產(chǎn)燃料乙醇最具廣闊的發(fā)展前景習。傳統的纖維素燃料乙醇精餾工藝為雙塔精餾,生產(chǎn)1t燃料乙醇產(chǎn)品在精餾單元的新鮮蒸汽消耗為2.2~2.5t。由于其能耗較高逐漸被三塔精餾工藝取代15。但以纖維素為原料生產(chǎn)燃料乙醇的發(fā)酵醪液質(zhì)量分數低(5%左右),精餾單元能耗高,占整個(gè)生產(chǎn)總耗能的60%~70%。低能耗精餾成為一項重要研究?jì)热?對于降低生產(chǎn)成本具有重大意義。Aspen plus是大型化工流程模擬軟件,具有完備的物性數據庫。功能齊全,規模龐大,可應用于化工,煉油,石油化工,氣體加工,煤炭,醫藥,冶金,環(huán)境保護,動(dòng)力,節能,食品等許多工業(yè)領(lǐng)域。本文利用 Aspen plus軟件對纖維素燃料乙醇三塔精餾工藝進(jìn)行模擬并優(yōu)化各塔參數,為纖維素燃料乙醇工業(yè)化生產(chǎn)提供理論支持。1建立計算模型纖維素燃料乙醇三塔精餾工藝流程如圖1所示。發(fā)酵成熟醪液經(jīng)E-0504成熟醪1#預熱器、E0505成熟醪2#預熱器加熱到泡點(diǎn)進(jìn)入T0501粗塔上部。塔頂采出粗酒精,經(jīng)E0504成熟醪1#預熱器與原料換熱部分冷凝,未凝氣相在T0504洗滌塔中回收乙醇,冷凝液和T0501粗塔側線(xiàn)液相采出淡酒以及洗滌塔T0504塔底液匯合后經(jīng)E0506常壓塔進(jìn)料預熱器加熱到泡點(diǎn)進(jìn)入T0502常壓塔中下部。粗塔T0501塔底采出液經(jīng)E0505成熟醪2#預熱器回收熱量后去污水處理系統。T吣0502常壓塔塔頂氣相部分經(jīng)E-0501粗塔冷凝再沸器被粗塔塔釜液冷凝后回流,另一部分作為精餾產(chǎn)品去脫水單元。T0502常壓塔塔底液經(jīng)加壓塔進(jìn)料預熱器E0507預熱后進(jìn)入T0503加壓塔。T吣0503加壓塔塔頂氣相經(jīng)E-0502常壓塔冷凝再沸器被常壓塔釜液冷凝后分為兩股,一股作為加壓塔收稿日期:2015-1209中國煤化工作者簡(jiǎn)介:楊靜(1970~),女,講師;研究方向:纖維素乙醇技術(shù)。 dbutCNMHG*通訊作者:李雙喜(1977-),男,博士,副教授;研究方向:纖維素乙醇、技不.Isxbuct@l63.com第2期楊靜等:纖維素燃料乙醇三塔精餾優(yōu)化6T0503回流液,另一股回流至常壓塔T0502。塔底部分經(jīng)加壓塔進(jìn)料預熱器E0507回收熱量后去熱水罐區。成熟醪液產(chǎn)品去脫水單元二氧化碳放空飽和蒸汽洗滌水F0504T05014504T050廢液去三廢cE0505E0501T0502蒸汽凝液去鍋爐c→E0503E0506E0507E0502圖1纖維素燃料乙醇三塔精餾工藝流程圖按圖1工藝流程選用 Radfrac模塊并采用NRTL物性方法在 Aspen plus中建立計算模型如圖2所示H0510HT0504T0502T0500501圓0507osgB-0504E0505B8Toso]16T-0501 [os17]513051P0502P0503P0501圖2 Aspen plus建模計算流程圖通過(guò)計算得到物料平衡表,關(guān)鍵物流計算結果如表1所示。進(jìn)料物流(代號0501)中乙醇質(zhì)量分數為59%,不凝氣通過(guò)洗滌塔T0504塔頂放空(代號051),主要成分為CoO°常壓塔T0502塔頂產(chǎn)出乙醇去脫水單元,從表1可知產(chǎn)品物流(代號0520)質(zhì)量分數為925%中國煤化工度。粗塔塔底廢水(代號0514)以及高壓塔塔底水(代號0525)中乙醇質(zhì)量分數CNMHG纖維素科學(xué)與技術(shù)第24卷表1關(guān)鍵物流計算結果溫度壓力總質(zhì)量流總體積流量質(zhì)量流量/(kgh)質(zhì)量分數/%/C /kPa /(kg h)/(m-b /(109C2H60H,OCHO H0 CO20501323002435995014371.2311446157218708542959939050477.560402734.714-3.742171.376187.8914282742646.710.7051437457087697998932-1386350.87787689220100ppm10510255010662381073-1691101066238051125.150428850.213-0.3891.16241.718frace27973051774.5501661346380.166-245.7051445.28151671.18287091371pm052096420011364124226626.371051181840481.182925740.102515896015021764729351505150480100gm102優(yōu)化工藝參數以玉米秸稈為原料生產(chǎn)燃料乙醇,發(fā)酵醪液乙醇質(zhì)量分數在6%左右,含有水、二氧化碳、醇、醛、酸、脂、硫酸鹽以及固形物等雜質(zhì)。本次模擬忽略固形物和微量組分對精餾工藝的影響。利用 Aspen plus中的靈敏度分析分別研究理論板數、進(jìn)料位置、回流比等參數對綜合能耗的影響。21粗塔T0501參數優(yōu)化粗塔T0501為負壓操作,主要排出不凝氣及大量水,塔頂酒氣經(jīng)冷凝器冷凝,不凝氣通過(guò)洗滌塔回收乙醇后排放。冷凝液和洗滌塔塔底液匯總后進(jìn)入常壓塔。粗塔模擬基礎數據如表2所示。表2粗塔T0501模擬計算基礎數據名稱(chēng)數據進(jìn)料組分及質(zhì)量分數/%乙醇(594)、水(93.89)、二氧化碳(017243599塔頂壓力/kPa(A)理論板數25(可調)冷凝器溫度/℃67(可調)側線(xiàn)采出量/(moh)800(可調塔底出料質(zhì)量分數/%乙醇≤001由于粗塔塔頂進(jìn)料,塔頂采出氣相冷凝后不回流,故回流比恒定不變。塔頂氣相冷凝溫度會(huì )影響洗滌塔進(jìn)料中乙醇質(zhì)量分數,從而影響洗滌塔用水量。因此,粗塔冷凝器的冷凝溫度為主要優(yōu)化參數,除此之外,理論塔板數和側線(xiàn)釆出量是影響塔底再沸器能耗的主要因素。利用 Aspen plus軟件的靈敏度分析得到冷凝溫度與洗滌水用量的關(guān)系如圖3所示,理論板數對塔底再沸器負荷的影響如圖4所示。由圖3可以看出,隨冷凝溫度的降低洗滌水用量減少,冷凝溫度在67℃以下時(shí)洗滌水用量變化較小因此優(yōu)化冷凝溫度為67℃,此時(shí),洗滌水用量742kmoh。由圖4可知,隨著(zhù)理論板數的增加塔釜再沸器能耗減小,塔釜乙醇質(zhì)量分數降低,當理論板數為21塊時(shí)達到分烹要成·日理診板數珥繼續增加對塔底乙醇質(zhì)量分數影響較小,因此優(yōu)化理論板數為21,此時(shí)塔底再沸中國煤化工CNMHG第2期楊靜等:纖維素燃料乙醇三塔精餾優(yōu)化633.429再沸器能耗/(×10°Jh塔底乙醇質(zhì)量分數0.04勺N3.4210.00粗塔冷凝溫度/℃C理論板數圖3冷凝溫度與洗滌水用量的關(guān)系圖4理論板數與再沸器能耗和塔底乙醇質(zhì)量分數的關(guān)系三塔精餾工藝增加側線(xiàn)采岀量,可減輕粗塔塔釜能耗,通過(guò)模擬計算得到側線(xiàn)采出量越大塔底負荷越小,最大采出量為800kmoh,采出位置為第2塊塔板。22常壓T0502塔參數優(yōu)化粗塔冷凝液和洗滌塔塔底產(chǎn)出液匯總作為常壓塔的進(jìn)料,塔頂產(chǎn)出體積分數95%、質(zhì)量分數92.5%的乙醇,塔底采出液進(jìn)入加壓塔,常壓塔模擬基礎數據如表3所示。表3常壓塔T0502模擬基礎數據名稱(chēng)數據進(jìn)料組分及質(zhì)量分數/%乙醇(87)、水(913)進(jìn)料量/(kgh)16613.5塔頂壓力/kP理論板數30(可調)回流比4(可調)進(jìn)料位置14(可調)塔頂出料質(zhì)量分數/%乙醇≥93常壓塔主要優(yōu)化參數有回流比、理論板數、進(jìn)料位置。通過(guò)計算得到不同回流比下塔頂乙醇質(zhì)量分數及再沸器負荷關(guān)系如圖5所示,理論塔板數與塔頂乙醇質(zhì)量分數和再沸器負荷的關(guān)系如圖6所示,進(jìn)料位置與塔釜再沸器負荷和冷凝器負荷關(guān)系如圖7所示。89248新?tīng)枤wN將4.0°氟爾N塔頂乙醇質(zhì)量分數/%再沸器能耗(x0)3891.8塔頂乙醇質(zhì)量分數%3491.6再沸器能耗(×10Jh)323.04.0精塔1回流比中國煤化工圖5回流比和塔頂乙醇質(zhì)量分數圖CNMHG分數及再沸器負荷的關(guān)系纖維素科學(xué)與技術(shù)第24卷由圖5可知,回流比增加塔頂乙醇質(zhì)量分數和再沸2.0器負荷都增加,回流比為4時(shí)塔頂乙醇質(zhì)量分數達標,此時(shí)塔釜再沸器負荷為4265×10°h,因此優(yōu)化常壓塔60回流比為4。5.5再沸器能耗由圖6可知,理論塔板數達到35塊時(shí),塔頂乙醇質(zhì)50冷凝器能耗量分數達到要求,此時(shí)再沸器負荷3403×10Jh。由圖455.07可知隨進(jìn)料位置的下移再沸器和冷凝器的負荷均降低,但為了實(shí)現常壓塔的冷凝器與粗塔再沸器能量平衡,1416需選擇合適的進(jìn)料位置,從圖中可得到冷凝器的負荷為精塔1進(jìn)料位置3424×109Jh時(shí)進(jìn)料板為第14塊,此時(shí)再沸器的負圖7進(jìn)料位置與塔釜再沸器負荷荷為3.516×109Jh,故優(yōu)化進(jìn)料位置為第14塊塔板和冷凝器負荷關(guān)系23加壓塔T0503參數優(yōu)化常壓塔塔底液經(jīng)預熱器預熱后進(jìn)入加壓塔。加壓塔主要作用為減小常壓塔塔底再沸器負荷,加壓塔塔頂冷凝器和常壓塔塔底再沸器共用。同理,與常壓塔優(yōu)化方案相同,經(jīng)優(yōu)化后的回流比為8.74,塔板數為進(jìn)料位置為253優(yōu)化結果及結論綜上所述,利用 Aspen plus軟件優(yōu)化了粗塔、常壓塔和加壓塔的操作參數,在保證精餾純度的前提下,實(shí)現了三塔的物料及熱量平衡。三塔精餾工藝的各塔參數及能耗如表4所示。表4優(yōu)化后各塔參數及能耗塔頂溫度塔底溫度塔頂壓力能耗塔板數回流比進(jìn)料位置/ KPa (A)/(×10Jh2)粗塔T0501常壓塔T05021199加壓塔T050315895808.743.868本文利用 Aspen plus軟件完成纖維素燃料乙醇三塔精餾工藝模擬及優(yōu)化,得到如下結論:1)通過(guò)對粗塔操作參數的優(yōu)化,得到粗塔塔頂最佳冷凝溫度、理論塔板數及進(jìn)料位置,以及優(yōu)化洗滌水用量。2)通過(guò)對常壓塔回流比、理論塔板數和進(jìn)料位置優(yōu)化,在保證精餾乙醇純度的同時(shí)降低了常壓塔能耗,實(shí)現了常壓塔冷凝器與粗塔再沸器能量平衡。3)通過(guò)對加壓塔參數優(yōu)化,實(shí)現加壓塔冷凝器與常壓塔再沸器能量平衡,優(yōu)化精餾綜合能耗。參考文獻:[]閆莉,呂惠生,張敏華,等纖維素乙醇生產(chǎn)技術(shù)及產(chǎn)業(yè)化進(jìn)展門(mén)釀酒科技,2013(10:808489[2]胡徐騰.纖維素乙醇研究開(kāi)發(fā)進(jìn)展門(mén)化工進(jìn)展,201130(1):137-1433]岳國君,武國慶,林鑫,等纖維素乙醇工程化探討生物工程學(xué)報2014,3060:816827[4]張敏華呂惠生,董秀琴,等燃料乙醇生產(chǎn)裝備及方法:中國,101157890[200649[5]Huanga H J, Ramaswamya S, Tschimer U w, et al. A review of separation中國煤化工 ure biorefineries[Separation and Purification Technology, 2008, 62(1): 1-2CNMHG(下轉第76頁(yè))76纖維素科學(xué)與技術(shù)第24卷Experimental Research on Effectof Lignocellulosic Steam-Exploded FiltrationLIU Yan, JIN Zhao-xu, LI Shuang-xi, CAI Ji-ning, ZHANG Qiu-xiang(1. Beijing Aerospace Test Technology Research Institute, Beijing 1000742. College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029)Abstract: In order to ferment the sugar mixture in the hydrolysate of lignocellulose efficiently, the test device ofteam-exploded filtration was designed, machined and installed. The moisture content and monose yield of thecake and filtrate was measured and compared. The feasibility of steam-exploded filtration technology and theimpact of some parameters on the steam-exploded filtration effect was analyzed. Results of the research showedthat the moisture content of the cake was 70. 20%so the solid-liquid separation was obvious. The steam-explodedfiltration effect was better with blowout pressure 1.0 MPa and throat diameter 25 mm. The faster the filter velocitywas, the better the steam-exploded filtration effect under experiment conditions was. This method can make fulluse of the kinetic energy of steam-explosion, overcome the limitation of pressure filter for non-flowing aqueousmaterial, separate the solid and liquid phase of the steam-explosion product, finally achieve the separatedenzymolysis of cellulose and hemicellulose, and increase the yield of enzymolysis and economic value ofKey words: lignocellulose; steam-exploded filtration; experiment; moisture content; monose yield(上接第64頁(yè))[6]陳俊英,馬曉建,楚德強,等.降低酒精生產(chǎn)能耗的關(guān)鍵技術(shù).釀酒科技,2006(8):24-26.[7 Aspen Technology Inc. Aspen Plusll 1Unit Operation Models. US: Aspen Technology Inc, 2002[8]張敏華,董秀芹,呂惠生,等.生物乙醇節能生產(chǎn)方法:中國,CN10177802A[P]2010-6-2[9] Aspen Plus Reference Manual-Volume 2. Physical Property Methods and Models, 1996: 2-54, 3-77[10]岳國君.纖維素乙醇工程概論M北京:化學(xué)工業(yè)出版社,2014:291-292Optimization of Cellulosic Fuekethanol Distillation with Three TowersYANG Jing, DU Jiang, ZHAO Jin, ZHANG Qiu-xiang, LI Shuang-xi*(1. College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing 100029, China;2. State Grid Energy Conservation Bio-Energy Technology Center, Beijing 100052, China)Abstract: The low concentration of fermenting slurry in the process of the cellulose fuel-ethanol production ledhigh energy consumption in distillation. The high energy consumption had became the most important reason thatrestrict the industrialization of cellulosic fuel-ethanol. The calculative model of cellulosic fuel-ethanol distillationwith three towers was built based on NRTL activity coefficient model in Aspen plus. The mass balance and energybalance of this process was calculated. The relation between the duty of reboiler and plate number, feedinglocation and the reflux ratio of each towers was established by optimizing crude tower, normal pressure tower andpressurized tower. The minimum comprehensive energy consumptionresults provided theoretical support for the industrialization of cellulosic中國煤化 Tparameter.TheKey words: cellulose; fuel-ethanol; distillation with three towers; Asper.CNMHG