第30卷第2期針?biāo)銠C(jī)與應(yīng)用化學(xué)Vol 30, No. 22013年2月28日Computers and Applied ChemistryFebruary 28, 2013合成氣一步法制二甲醚分離工藝流程優(yōu)化模擬郭曉艷,孫蘭義(中國(guó)石油大學(xué)化學(xué)工程學(xué)院化學(xué)工程系,山東,青島,265摘要:為獲得合成氣經(jīng)漿態(tài)床一步合成二甲醚最優(yōu)的分離流程和工藝參數(shù),運(yùn)用化工流程模擬軟件 Aspen Plus對(duì)3種分離工藝過(guò)程進(jìn)行了模擬分析。提出用水吸收一步反應(yīng)氣相產(chǎn)物中的二甲醚,再用兩個(gè)精餾塔分離吸收液的工藝流程,模擬過(guò)程中汽液相平衡采用NRTL熱力學(xué)模型。對(duì)從吸收液中分離二甲醚的3種方法進(jìn)行了模擬計(jì)算值的比較,并與文獻(xiàn)中的實(shí)驗(yàn)值做了比較,最后采用了先通過(guò)第一精餾塔塔頂分離出CO2,塔底出甲醇和二甲醚,再通過(guò)第二精餾塔分離二甲醚和甲醇的方法。此種分離流程可使二甲醚的回收率達(dá)到911%,產(chǎn)品濃度達(dá)到9996%,高于文獻(xiàn)報(bào)道的結(jié)果。并對(duì)吸收塔的溫度、操作壓力、液氣比、塔板數(shù)等參數(shù)以及2個(gè)精餾塔的溫度、壓力、塔板數(shù)等參數(shù)進(jìn)行了優(yōu)化模擬,確定了優(yōu)化的工藝和設(shè)備參數(shù)。最優(yōu)的分離流程尚需經(jīng)過(guò)回收率和操作費(fèi)用綜合經(jīng)濟(jì)核算來(lái)確定關(guān)鍵詞:合成氣;二甲醚;一步法;優(yōu)化模擬中圖分類(lèi)號(hào):TQ0283文獻(xiàn)標(biāo)識(shí)碼:A文章編號(hào):100141602013)02-203-206DOI: 10. 11719/com. app. chem201302211前言2二甲醚分離流程二甲醚ODME)作為一種新興的基本化工原料,在燃料、農(nóng)藥、制藥等化學(xué)工業(yè)中有廣泛的用途。高純度的從漿態(tài)床反應(yīng)器出來(lái)的氣相產(chǎn)品中有二甲醚、甲醇二甲醚可代替氟里昂用作氣溶膠噴射劑和制冷劑,減少H2O和沒(méi)反應(yīng)的H2、CO、CO2N2組成的七元混合物,根據(jù)此復(fù)雜物系的特點(diǎn)以及二甲醚、甲醇、H2O、CO2汽對(duì)大氣環(huán)境的污染和臭氧層的破壞;二甲醚有含氧較短液相平衡物系的特點(diǎn)14,采用的分離方法是合成氣的分子式,沒(méi)有CC鍵,有高的十六烷值和低的自燃步反應(yīng)后氣體經(jīng)換熱冷凝進(jìn)入氣液分離器,冷凝后的氣點(diǎn),因而成為理想的替代燃料即,它還是未來(lái)制取低碳烯相產(chǎn)物進(jìn)入吸收塔,用水作吸收劑,其中的二甲醚、甲烴的主要原料之一近年來(lái),二甲醚在合成過(guò)程和應(yīng)用醇和部分CO2被水吸收后從塔底餾出與從氣液分離器的分的雙功能催化劑,因此,甲醇合成催化劑和甲醇脫水歐包/烈》畫(huà)領(lǐng)域的研究已成國(guó)內(nèi)外熱點(diǎn)之液相產(chǎn)物合并一起進(jìn)入精餾塔進(jìn)行下一步分離嗎16合成氣一步法制DME是在合成甲醇技術(shù)的基礎(chǔ)上分離流程如圖1所發(fā)展起來(lái)的③,它是由合成氣經(jīng)漿態(tài)床反應(yīng)器一步合成DME。目前,國(guó)內(nèi)外的研究重點(diǎn)是催化劑、催化反應(yīng)工二甲醚產(chǎn)品藝以及反應(yīng)器。催化劑采用具有甲醇合成和甲醇脫水組催化劑的比例對(duì)DME生成速度和選擇性有很大的影響。合成氣法現(xiàn)多采用漿態(tài)床反應(yīng)器4,其結(jié)構(gòu)簡(jiǎn)單,便于移出反應(yīng)熱,易實(shí)現(xiàn)恒溫操作。因此,漿態(tài)床合成氣法制DME具有誘人的前景,將是煤炭潔凈利用的途徑之Fig 1 Separation process of dimethyl ether圖1二甲醚分離流程目前,相比甲醇脫水制二甲醚而言,一步法合成二甲醚因?yàn)轶w系存在有未反應(yīng)完的合成氣以及二氧化碳,3模擬過(guò)程及分析要得到純度較高的二甲醚,分離過(guò)程比較復(fù)雜10,隨著流程模擬過(guò)程中涉及到的單元操作有吸收和精餾,漿態(tài)床合成方法研究的不斷成熟,研究二甲醚高效分離選擇合適的熱力學(xué)模型是準(zhǔn)確模擬計(jì)算分離過(guò)程的非常工藝的可行性有著重要的意義。本文采用 ASPEN化工流關(guān)鍵的步驟。該物系中存在水,不含有電解質(zhì),因此選程模擬軟件,對(duì)一步法合成二甲醚的分離流程進(jìn)行了模用NTRL熱力學(xué)模型進(jìn)行模擬,該方法具有 Wilson方程擬計(jì)算與分析,確定了工藝優(yōu)化操作條件。的優(yōu)點(diǎn),適用于液液平衡計(jì)算,對(duì)含水系統(tǒng)具有較高的精確度,形式上收稿日期:2012-10-08;修回日期:2012-12-18YHt中國(guó)煤化工時(shí)強(qiáng)非理想混CNMHG聯(lián)系人:孫蘭義(1972),男,山東人,博+,教授, E-mail: sunlanvie@163cm作者簡(jiǎn)介:郭曉艷(1973),女,山東人,碩土研究生,Emat: gyan73@126co計(jì)算機(jī)與應(yīng)用化營(yíng)2013,30(2)合物和部分混溶系統(tǒng)的運(yùn)用能夠得到很好的結(jié)果在1.5Mpa,40℃的條件下對(duì)吸收塔理論塔板數(shù)對(duì)31吸收塔吸收效果的影響進(jìn)行了模擬,結(jié)果見(jiàn)圖4。當(dāng)理論塔板吸收塔的吸收劑采用水,其目的是將H2、CO、CO2、數(shù)為12時(shí),二甲醚的吸收率達(dá)到了1.0N2等氣體分離出去,二甲醚、甲醇被水吸收,其中H2(3)水用量對(duì)吸收效果的影響CO、N2在水中的溶解度很小,而CO2由于二甲醚和甲醇考察了15Mpa、2Mpa壓力,40℃下不同的液氣的存在增加了在水中的溶解度,導(dǎo)致二甲醚和CO2成為比對(duì)吸收效果的影響,模擬結(jié)果如圖5所示。分離系統(tǒng)的難分離物系。當(dāng)采用相同的液氣比操作時(shí),2Mpa壓力下的DME(1)吸收溫度與壓力的確定吸收率要優(yōu)于下的。但當(dāng)液氣比增加到1.2時(shí),般高壓低溫有利于氣體的吸收。從反應(yīng)器出來(lái)的兩個(gè)壓力下的吸收率趨于一致,且已接近于1。因此可氣體壓力為4Mpa,因此模擬了1.5Mpa~4Mpa壓力考慮采用的液氣比為13下從15℃~60℃之間吸收塔的吸收效果,結(jié)果見(jiàn)圖2綜上所述,吸收塔采用的工藝條件是1.5Mpa、溫從圖2中看出,當(dāng)壓力超過(guò)5Mpa的時(shí)候,二甲度是40℃,液氣比為13。醚的吸收率在15℃~60℃的范圍內(nèi)可達(dá)到1.0。ME吸收率但是隨著溫度降低、壓力升高,CO2在溶液中的溶解度也不斷增大,見(jiàn)圖3。溶液中過(guò)多的CO2會(huì)增加后續(xù)精餾塔的分離難度,因此適宜的壓力、溫度的選擇應(yīng)該在確保最高二甲醚吸收率的前提下,盡量降低CO2在溶液中的吸收率。因此選定吸收塔的操作壓力為15Mpa~2Mpa,溫度為40℃~60℃。塔板數(shù)Fig 4 Effects of number of stages on DME absorption圖4塔板數(shù)對(duì)DME吸收效果的影響Fig 2 Effects of pressure and temperature on DME absorption圖2壓力、溫度對(duì)二甲醚吸收率的影響000.20406081012141.61.8202.2液氣比Fig 5 Effects ofL/G on DME absorption rate圖5LG比對(duì)DME吸收率的影響3.2二氧化碳塔在精餾塔操作中,由于CO2的存在使得二甲醚和CO2分離困難,并最終影響二甲醚的回收率。從混合物中分離出二甲醚的方法有3種,方法一是通過(guò)第一精餾塔即二氧化碳塔將CO2從塔頂分出,DME溫度/℃甲醇與水從塔底分出,然后再通過(guò)第二精餾塔分離出Fig3 Effects of temperature and pressure on the mole fraction of CO2DME和甲醇得到方注二是C∩2和DME從圖3溫度、壓力對(duì)CO2在吸收液中的摩爾濃度影響塔頂分出,CO2中國(guó)煤化工產(chǎn)品,甲醇和水從塔底分出CNMHG、DME從側(cè)(2)塔板數(shù)的確定2013,30(2)郭曉艷,等:合成氣一步法制二甲醚分離工藝流程優(yōu)化模擬線分出、甲醇和水從塔底分出DME的產(chǎn)品純度為09996,DME經(jīng)過(guò)吸收塔和2精餾采用相同的理論板數(shù)、操作壓力和回流比對(duì)這3種塔回收率達(dá)到911%分離方法進(jìn)行了模擬計(jì)算,結(jié)果比較如表1各塔主要工藝參數(shù)和物流組成見(jiàn)表2。表1分離DME的3種方法比較表2各塔主要工藝參數(shù)和物流組成Table 1 Comparation of three method of separating DME.mposition of stream塔CO2塔DME塔分離方法方法1方法2方法方法2方法3工藝參數(shù)吸收塔吸收塔塔頂塔底實(shí)驗(yàn)值實(shí)驗(yàn)值料料塔頂溫度,℃溫度,℃177.845.8塔底溫度,℃18731793181.2壓力,MPa1950.8DME產(chǎn)品濃度099960.9900.9930.99270999DME回收率,%91.172386.5824流量, koth395376742214973760.2525525從表1看出,方法一DME的回收率達(dá)到了91.1%產(chǎn)品濃度為0996,與其他2種方法的模擬值和實(shí)驗(yàn)值Co0.152比較,明顯高于其他兩種方法。但是此時(shí)塔頂溫度為CO20.1850.00907553.946E063.62E05156℃,不能用水做冷劑,這無(wú)疑會(huì)增加塔的操作費(fèi)用。N20076420×1060.0421因此最終采用何種方法分離DME,應(yīng)結(jié)合產(chǎn)品的回收率CH40.031356×10°00379和操作費(fèi)用進(jìn)行綜合的經(jīng)濟(jì)核算來(lái)確定。在此,采用第CHO0.03100150.0163742E04種方法進(jìn)行模擬優(yōu)化計(jì)算,流程見(jiàn)圖1。H,O操作條件的優(yōu)選主要是綜合考察在滿足產(chǎn)品純度和DME0.1410.072592.0E040.07320.9996回收率的情況下,盡量使工藝的能耗最小。隨著二氧化塔壓力的升高,DME的回收率逐漸減小,但塔頂溫度是4結(jié)論逐漸升高的,二氧化碳精餾塔操作壓力對(duì)DME收率和塔(1)離開(kāi)漿態(tài)床反應(yīng)器的氣相混合物進(jìn)行了模擬分頂溫度的影響見(jiàn)圖6,DME的收率略微減少,而塔頂?shù)碾x:先用水做吸收劑吸收混合氣中的二甲醚、甲醇、CO2溫度呈明顯上升趨勢(shì),塔頂溫度越高,高品位冷能的使吸收液進(jìn)入第一精餾塔,塔頂分出二氧化碳,塔底的甲用越少,從而降低操作費(fèi)用。醇、DME和水溶液去第二精餾塔分離,塔頂出二甲醚產(chǎn)品(2)提出了從吸收液中分離出DME的3種方法,并進(jìn)行了比較,確定了在第一精餾塔塔頂分離二氧化碳,第二精餾塔分離DME的分離流程。二甲醚在第二精餾塔中的回收率達(dá)到了992%,二甲醚產(chǎn)品純度為9996%(3)模擬過(guò)程中,對(duì)各塔進(jìn)行了參數(shù)優(yōu)化,確定了塔的工藝參數(shù)。Referenc1 Li Hansheng, Renfei and Wang Jinfu, et al. 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ChemicalEngeering of Gas, 2007, 32(5): 1-4實(shí)驗(yàn)研究[門(mén)]天然氣化工,2007,32(5):1-4.Optimization simulation of separation process of dimethyl ether synthesized byone-step method from syngasGuo Xiaoyan and Sun Lanyi(College of Chemical Engineering, China University of Petroleum, Qingdao 266555, Shandong, China)Abstract: In order to obtain dimethyl ether synthesized by one-step method from syngas, a technological process was put forward thatdimethyl ether was absorbed with water firstly, then absorption liquid was separated by means of two distillation columns. Optimizationsimulation of three separation process flows has been made with chemical process simulation software-Aspen plus, and NRTL thermodynamicmodel was adopted. The influence of temperature, operating pressure, liquid-gas ratio and number of stages on the absorption rate of dimethylether were discussed. Finally 40 C, 1.5 Mpa, liquid-gas ratio of 1.5 and the number of theoretical plate of 10 were adopted in the absorptiontower. There were three methods of separating dimethyl ether from absorption liquid. The first method was that COz was separated from the topof one distillation tower, and dimethyl ether, methanol and water separated from the bottom firstly, then through another column dimethyl etherand methanol were separated. The second method was that Co2 and dimethyl ether were separated from the top of the column, and cOzcolumn, dimethyl ether separated by means of lateral extractions, and methanol and water separated from the bottom. Simulation of these threeflows has been made on the same number of stages, operating pressure and reflux ratio. and the results showed that recovery rate for dimethylether of the first method reached 91.1% and concentration of product reached 0.9996, higher than the values of two other methods and literature.But the temperature at the top of this column was -15. 1 C, and water cannot be used as a cooling medium, which can increase the operationcost of the tower. So the appropriate separation process of dimethyl ether should be determined through comprehensive economic calculationthat combined with the recovery rate and operation cost of the product. In this paper, the first separation flow was adopted. The influence oftemperature, operating pressure and number of stages on the recovery rate of dimethyl ether were discussedKeywords: syngas, dimethyl ether, one-step method, optiReceived:2012-1008; Revised:2012-12-18)中國(guó)煤化工CNMHG