優(yōu)化催化裂化裝置的烯烴和芳烴生產(chǎn)(共24頁)

1、優(yōu)化催化裂化裝置(zhungzh)的烯烴和芳烴生產(chǎn)摘要：由于越來越多的公司都在努力實現(xiàn)煉油(lin yu)和石化業(yè)務(wù)一體化，所以增加催化裂化裝置石化品產(chǎn)率則成為越來越多的公司關(guān)注焦點(jiodin)。關(guān)鍵詞：烯烴 乙烯 丙烯 催化劑 汽油 催化裂化流化催化裂化（FCC）裝置可以生產(chǎn)很多產(chǎn)品。自70多年前催化裂化技術(shù)誕生以來，其主要目的是生產(chǎn)高辛烷值燃料，并且目前很多催化裂化裝置仍在用于這一目的。然而，F(xiàn)CC裝置（FCCU）也可用于生產(chǎn)石化品。特別是隨著北美和中東乙烯原料輕質(zhì)化發(fā)展正給世界乙烯產(chǎn)業(yè)帶來深刻變化，但是乙烷裂解大量普及又造成了新的矛盾，即丙烯供應(yīng)不足，無法滿足世界丙烯需求的不斷增長，

2、所以增加催化裂化裝置石化品產(chǎn)率則成為越來越多的公司關(guān)注點。1 丙烯產(chǎn)率最大化在過去10年中，催化裂化裝置通常被設(shè)計為用于生產(chǎn)大量的丙烯。催化裂化裝置加工原料包括常規(guī)蠟油和加氫蠟油（GO），以及常壓渣油。推動催化裂化裝置多產(chǎn)丙烯發(fā)展主要包括以下幾方面因素，蒸汽裂解裝置越來越大，而且更多的是采用乙烷原料，而不是石腦油。使用乙烷進(jìn)行裂解時只會產(chǎn)生很少的丙烯，因而必須尋找其它來源來滿足不斷增長的丙烯需求。特別是世界范圍內(nèi)丙烯需求增速預(yù)計將超過乙烯需求增速。 現(xiàn)在催化裂化裝置也越來越大。普通催化裂化裝置處理量約200萬噸/年，現(xiàn)在新建裝置通常為250至600萬噸/年。這些催化裂化裝置產(chǎn)能足夠支持世界級規(guī)

3、模的聚丙烯（PP）生產(chǎn)設(shè)施。為了實現(xiàn)丙烯產(chǎn)率最大，通常要求更高的轉(zhuǎn)化率。提高丙烯產(chǎn)率主要是通過汽油沸程范圍的C6-C10烯烴的過度裂化來實現(xiàn)。為了實現(xiàn)較高轉(zhuǎn)換率，必須提高裂化操作條件，即較高的反應(yīng)器溫度，增加催化劑循環(huán)速率，較高的劑/油比（C/O），和/或較高的催化劑活性。所有最大化丙烯產(chǎn)率的催化裂化工藝都使用五元環(huán)中孔沸石(pentasil）來實現(xiàn)汽油裂化。無一例外，氫含量較高的原料可以產(chǎn)生更多的丙烯。2 催化裂化裝置的設(shè)計多產(chǎn)丙烯的催化裂化裝置通常都要求能夠增加反應(yīng)區(qū)的苛刻度。設(shè)計參數(shù)的變化包括：通過提升管的改進(jìn)或增加的床層裂化效果來增加催化裂化(cu hu li hu)過程的停留時間采用

4、下流式反應(yīng)(fnyng)流程在反應(yīng)系統(tǒng)中，采用先進(jìn)的進(jìn)料噴嘴，配以高水平的注入蒸汽(zhn q)噴射實現(xiàn)進(jìn)料霧化和最佳的烴分壓采用反應(yīng)器終止技術(shù)，以降低干氣和結(jié)焦由于裂化過程吸熱反應(yīng)，且反應(yīng)器溫度較高，使用較高的劑油比循環(huán)回收裂化后的石腦油改進(jìn)再生器設(shè)計，以允許添加多余的燃料以維持再生過程反應(yīng)使用改良和獨特的下游產(chǎn)品回收部分添加產(chǎn)品精制部分，用于生產(chǎn)化學(xué)級或聚合級丙烯產(chǎn)品，滿足石化品生產(chǎn)反應(yīng)器設(shè)計應(yīng)滿足最高丙烯產(chǎn)率所需要的溫度。2.1 雙提升管設(shè)計雙提升管的設(shè)計方案有很多種。一種配置方式是采用兩個平行的反應(yīng)提升管，反應(yīng)油氣終止于一個共同的反應(yīng)器-分離器，其中提升管流出物在此合并，然后在一個分餾

5、塔內(nèi)和下游氣體回收部分進(jìn)行回收。另一種方式也有兩個反應(yīng)器（提升管或向下流動），并設(shè)置有獨立的終止容器，反應(yīng)產(chǎn)物被分離后生產(chǎn)燃料，和聚合物級產(chǎn)品。這種設(shè)計方案可用于不同的操作模式和不同原料，一個提升管用于生產(chǎn)餾分油或汽油，另一個反應(yīng)器則用于丙烯生產(chǎn)。由于有兩個反應(yīng)區(qū)，這些設(shè)計的催化裂化裝置可以實現(xiàn)丙烯產(chǎn)率12（wt）。2.2 分餾部分主分餾和氣體回收部分也有不同考慮。由于多產(chǎn)丙烯的催化裂化工藝采用高轉(zhuǎn)化率和更高品質(zhì)的原料，塔底的產(chǎn)率為最小化。這就需要仔細(xì)研究主分餾塔的底循環(huán)和氣體回收部分的熱集成情況。另外，丙烷/丙烯分離塔也可以設(shè)置在氣體回收部分，以生產(chǎn)化學(xué)或聚合級丙烯。3 裂化裝置性能表1為傳

6、統(tǒng)汽油催化裂化裝置與高烯烴催化裂化裝置（HOFCCU）的汽油和輕質(zhì)烯烴產(chǎn)率對比。最大丙烯產(chǎn)率的缺點犧牲了汽油產(chǎn)率和汽油組成。另外，高苛刻度操作很容易地增加丙烯產(chǎn)率一倍或兩倍，但汽油產(chǎn)率將減少25-50。汽油組成中總芳烴含量也將增加一倍或兩倍。表2為目前催化裂化裝置的丙烯產(chǎn)率情況。表1催化裂化(cu hu li hu)裝置汽油和輕質(zhì)烯烴產(chǎn)率對比產(chǎn)品典型分布傳統(tǒng)FCC高烯烴FCC占新鮮原料%wt干氣1.5-33-12乙烯0.5-1.52-7總LPG16-2232-44丙烯4-712-22丁烯4-88-14汽油47-5330-40表2 催化裂化裝置(zhungzh)的丙烯產(chǎn)率傳統(tǒng)FCC傳統(tǒng)FCC高烯

7、烴FCC高烯烴FCCFCCFCC+ZSM-5HSFCCHSFCC+ZSM-5丙烯產(chǎn)率3%-5%wt6%-8%wt10%-13% wt15%-20% wt3.1汽油(qyu)產(chǎn)量傳統(tǒng)的催化裂化裝置以滿足汽油生產(chǎn)需求，以重質(zhì)蠟油（HGOs）或渣油為原料，一般丙烯產(chǎn)率為3（wt）-5（wt），實現(xiàn)最大量生產(chǎn)汽油。添加ZSM-5型添加劑后，丙烯產(chǎn)率平均增加了約3（wt）。高苛刻度操作催化裂化裝置（HSFCCU）模式則以加氫處理原料或高石蠟基原油的蠟油為原料，可以得到12的丙烯產(chǎn)率。催化劑和更苛刻的操作條件類似于傳統(tǒng)催化裂化裝置的操作。然而，這些高烯烴催化裂化裝置加工靈活性不夠，不能由丙烯生產(chǎn)方案向燃料

8、生產(chǎn)方案轉(zhuǎn)變。3.2高烯烴(xtng)操作開發(fā)(kif)高烯烴催化裂化裝置（HOFCCUs）的目的(md)是實現(xiàn)15（wt）至20（wt）的丙烯產(chǎn)率，并還可以生產(chǎn)高含量的其它輕質(zhì)烯烴。該HOFCC汽油芳烴含量也很高，而且是石油化工生產(chǎn)的優(yōu)選原料。例如，如果一個煉油廠有異丁烷原料可用，則HOFCCU裝置可為烷基化過程能提供充足的混合丁烯。在這種情況下，HOFCC汽油可與烷基化油調(diào)合，以滿足燃料規(guī)格。表3總結(jié)了一些操作調(diào)整方向，以提高丙烯產(chǎn)量。表3 提高丙烯產(chǎn)量的操作調(diào)整方案項目調(diào)整方案需考慮因素反應(yīng)器溫度增加材料等級劑油比增加催化劑循環(huán)，滑閥壓差停留時間，空速增加生焦量預(yù)熱增加爐負(fù)荷，再生器溫度

9、控制烴分壓 裝置壓力降低更高的氣體生成，更多的壓縮機生產(chǎn)產(chǎn)品回收量 蒸汽速度增加增加酸性氣回收量循環(huán)循環(huán)裂化輕石腦油增加增加產(chǎn)品回收循環(huán)重質(zhì)油增加影響進(jìn)料，不足以滿足熱需求催化劑催化劑活性（計算）增加大劑量加入催化劑，金屬耐受性低，高氫轉(zhuǎn)移高Z/M比增加高氫轉(zhuǎn)移高催化劑ZSM-5添加量增加較低裂解催化劑活性晶胞尺寸大小降低低催化劑活性進(jìn)料較高品質(zhì)氫含量更高降低生焦量加氫苛刻度增加支出成本，更低焦炭前生物提高(t go)反應(yīng)器溫度(wnd)是從最大汽油操作(cozu)模式轉(zhuǎn)為更高丙烯和其他烯烴產(chǎn)率一個關(guān)鍵。汽油操作模式的反應(yīng)器溫度通常為493到538，而高苛刻度操作催化裂化裝置提升管溫度通常高于

10、550，采用冷壁提升管反應(yīng)器。從熱平衡角度考慮，也需要更高的劑/油比，并有助于實現(xiàn)所需要的高轉(zhuǎn)化率。較高的反應(yīng)溫度需要增加催化劑循環(huán)速率，同樣深度裂化也要求更高的吸熱。催化劑循環(huán)是一個因變量；然而，它是由熱負(fù)荷和生焦量確定。如果進(jìn)料的質(zhì)量非常高，火焰加熱器即可以合乎需要。生產(chǎn)丙烯的催化裂化工藝應(yīng)盡量降低烴分壓。這可以從降低反應(yīng)器壓力和/或通過提高蒸汽使用量來實現(xiàn)。提升管蒸汽用量為新鮮進(jìn)料的10（wt）的情況現(xiàn)實中并不少見，并且它可以更高達(dá)到30（wt）。主分餾塔需要被填充，以達(dá)到最低壓力。在反應(yīng)器中較長的停留時間是指蒸氣接觸時間。對于提升管配置的情形還需要額外的停留時間。有些時間控制是通過改變

11、提升管的長度和直徑來實現(xiàn)的。反應(yīng)物和產(chǎn)物仍然需要維持塞狀流，以防止所需烯烴發(fā)生不希望的反應(yīng)。額外的停留時間，也可以通過增加第二個提升管，循環(huán)烴進(jìn)反應(yīng)器，或把提升管催化劑床層下移來實現(xiàn)。油流經(jīng)過催化劑床層的速度通常為2英尺/秒至3英尺/秒，所以采用這樣的結(jié)構(gòu)可以獲得額外的5秒至15秒停留時間。由于輕烯烴通過pentasil（ZSM-5）沸石發(fā)生裂化，進(jìn)行裂化石腦油循環(huán)可增加丙烯產(chǎn)率。通常可增加丙烯2-3（wt）。由于原料中缺乏焦炭前體而生焦太低時，油漿循環(huán)可用于增加再生器的溫度。將渣油調(diào)入這些低康氏殘?zhí)吭现袑⒂兄诰S持裝置的熱平衡，因為反應(yīng)熱和操作苛刻度兩者均較常規(guī)FCC操作有所提高。進(jìn)料中的

12、雜質(zhì)應(yīng)該與排放，產(chǎn)品質(zhì)量，以及對催化劑的影響一同考慮。4 催化裂化原料催化裂化裝置進(jìn)料可以在丙烯產(chǎn)率方面起作顯著(xinzh)作用。丙烯含有約14.3的氫；因此，含氫更多的進(jìn)料也會產(chǎn)出更多的丙烯。通常使用進(jìn)料為經(jīng)過深度加氫處理的蠟油，當(dāng)然(dngrn)，具有高API比重(bzhng)的原油，如致密油/頁巖油，也是生產(chǎn)丙烯的理想原料。對于高烯烴催化裂化裝置（HOFCCUs），通常采用原料是深度加氫的減壓蠟油（VGO）。渣油單元主要在一個提升管內(nèi)進(jìn)行加氫處理的渣油，循環(huán)料和其它原料則進(jìn)入第二反應(yīng)區(qū)。原料深度加氫處理有利于產(chǎn)品的后處理，包括生產(chǎn)化學(xué)級和聚合物產(chǎn)品。4.1 焦化蠟油可以加工然而，焦化蠟

13、油應(yīng)該經(jīng)過高壓加氫處理裝置進(jìn)行預(yù)處理，不僅降低其硫和氮含量，而且還可以對二烯烴和很多芳烴進(jìn)行飽和處理。這可以下游生產(chǎn)化學(xué)級或聚合物級丙烯所需的精制過程。4.2 天然氣凝析液最新的用于丙烯生產(chǎn)的原料為天然氣凝析液和致密油分離出來的石腦油。從致密油中制得的原油也被用于催化裂化的汽油/柴油操作生產(chǎn)。5 催化劑用于制備輕質(zhì)烯烴的裂化催化劑為固體酸性催化劑，包含一種或多種活性成分和基質(zhì)成分。USY型裂化催化劑具有低的晶胞尺寸，小于50的交換稀土（RE），適于最小的氫轉(zhuǎn)移。根據(jù)原料性質(zhì)，使用中等基質(zhì)活性。本應(yīng)用中催化劑體系使用的是高濃度的具有五元環(huán)晶體結(jié)構(gòu)的具有中等孔徑大小擇形沸石（ZSM-5），以及典型

14、的超穩(wěn)定Y型沸石。五元環(huán)沸石優(yōu)先對C6-C10直鏈/近直鏈汽油烯烴進(jìn)行裂化反應(yīng)，主要生成丙烯和丁烯，并產(chǎn)生很少量的汽油。圖1所示為基于中試數(shù)據(jù)的ZSM-5添加劑濃度對丙烯產(chǎn)率的影響，并已在商業(yè)應(yīng)用中得到驗證。如圖所示，丙烯產(chǎn)率隨著ZSM-5添加劑的濃度增加而增加，直到丙烯產(chǎn)率達(dá)到平臺值。 圖1 ZSM-5濃度(nngd)對丙烯(bn x)產(chǎn)率的影響(yngxing)。在汽油/柴油模式，為了產(chǎn)生更多的丙烯，在循環(huán)催化劑中ZSM-5的添加劑濃度為3（wt）-5（wt）。而在高苛刻度操作催化裂化裝置，ZSM-5的添加劑濃度可高達(dá)10。對于高烯烴催化裂化（HOFCC）過程常常采用專有的催化劑，沸石和沸

15、石添加劑來實現(xiàn)循環(huán)催化劑中的高五元環(huán)晶體濃度，進(jìn)而達(dá)到丙烯產(chǎn)率最大化目的。催化劑是高烯烴催化裂化工藝的關(guān)鍵。由于輕質(zhì)直餾石腦油、凝析液石腦油、致密油和來自其它煉油和石化工藝的含烯烴原料催化裂化過程不盡一致，也在不斷研究開發(fā)適用于這些組分加工的不同的沸石和裂化催化劑。所述ZSM-5添加劑可用于提高汽油選擇性和用于生產(chǎn)丙烯。本應(yīng)用也適合于柴油模式FCC操作中增加丙烯產(chǎn)率。另一個研究目的是使用更大分子-烯烴（C 12+）為原料進(jìn)行輕烯烴裂化反應(yīng)生產(chǎn)更多的丙烯和乙烯，還進(jìn)行了C10+裂化增加C3=/C4=烯烴的催化劑開發(fā)。6 催化烯烴FCC工藝可用于采用專門設(shè)計的催化裂解裝置使用各種原料來生產(chǎn)丙烯和乙

16、烯。這些新工藝技術(shù)正與蠟油和石腦油的蒸汽裂解工藝形成直接競爭。蒸汽裂解工藝是一個熱解過程，工作溫度高達(dá)1400+F（800），并且工作原理是基于自由基反應(yīng)機理生產(chǎn)主要產(chǎn)物為乙烯。這些FCC工藝工作原理則基于碳正離子催化裂化以及-斷裂機制，其熱裂化程度最小，可以獲得高的丙烯產(chǎn)率，并得到少量乙烯。表4列出了蒸汽裂解的輕烯烴產(chǎn)率。該表格同時列出了不同原料典型的乙烯和丙烯產(chǎn)率的重量。丙烯/乙烯（P/E）比率表示生產(chǎn)丙烯的裂化條件下的選擇性。表4 蒸汽裂解的典型輕烯烴產(chǎn)率進(jìn)料乙烯，wt%丙烯，wt%P/E比乙烷8030.04（0.0375）丙烷44150.34石腦油30160.53蠟油23150.65蠟

17、油和石腦油原料進(jìn)行蒸汽裂解(li ji)對應(yīng)的P/E比率分別為0.65和0.53，表示進(jìn)料越重所得的丙烯/乙烯比值越大。從全球范圍(fnwi)來看，蠟油蒸汽裂解已越來越少，因為蠟油原料更多用來生產(chǎn)柴油和其他燃料，來滿足這些高需求產(chǎn)品的不斷增長的需求。另外，由于美國頁巖氣革命帶來天然氣產(chǎn)量激增，裂解工藝中更多使用乙烷原料，石腦油用作蒸汽裂解原料也逐漸減少。為了(wi le)得到更多的乙烯和丙烯產(chǎn)品，必須同時具備熱裂化和催化裂化工藝條件。這些裝置反應(yīng)器操作溫度將高達(dá)1150F（620）。不過反應(yīng)器溫度仍然低于低于蒸汽裂解爐的溫度1470F（800）。而再生溫度必須控制，以防止催化劑過度失活。這個工

18、藝過程的關(guān)鍵是催化劑，它可以同時提供兩種開裂機制（即自由基和碳正離子）。該催化劑具有的細(xì)孔徑分布，以確保汽油餾程內(nèi)的材料進(jìn)行二次C5C12烯烴開裂。第二個五元環(huán)沸石添加劑可能不需要，因為它通常用于最大丙烯產(chǎn)率工藝中。該催化劑具有強大的水熱性能和磨損性能，所以可在這些苛刻的操作條件下正常運行。原料方面，要求使用深度加氫處理/緩和加氫裂化處理的高含氫蠟油和渣油原料。表5列出了基于中試數(shù)據(jù)的催化烯烴FCC工藝、HOFCC和蒸汽裂解裝置的輕烯烴產(chǎn)率比較，所有原料為重油。表5 不同工藝輕烯烴產(chǎn)率比較工藝催化烯烴FCC高烯烴催化裂化（HOFCC）蒸汽裂解原料70%VGO+30%VTB85%VGO+15%

19、VTBAGO反應(yīng)溫度620545800 輕烯烴產(chǎn)率，wt%乙烯24.293.5931.30丙烯14.7022.9115.21丁烯6.7717.365.49丁二烯2.400.055.0注：VGO 減壓蠟油，VTB-減渣，AGO-常壓蠟油與高烯烴催化裂化工藝相比，催化烯烴工藝所產(chǎn)乙烯和丙烯收率更高。因為該工藝使用熱裂化和催化裂化兩種機理來產(chǎn)生所希望的烯烴。乙烯和丁二烯高產(chǎn)率的純熱蒸汽裂解的標(biāo)志。在高烯烴催化裂化工藝中，丙烯和丁烯均由于催化裂化過程的碳正離子機理所得。還一個發(fā)現(xiàn)是高烯烴催化裂化工藝中某些戊烯被轉(zhuǎn)化成了丙烯和乙烯。在現(xiàn)有(xin yu)的FCC裝置(zhungzh)或一個(y )專門設(shè)

20、計催化裂化裝置的一個獨立提升管中，碳數(shù)C4C8的低價值烯烴可以通過催化工藝顯著提高丙烯和乙烯的產(chǎn)率。潛在的烯烴原料還包括混合丁烷、FCC輕石腦油、焦化和減粘裂化石腦油、石腦油蒸汽裂解裝置的裂解汽油和其他選擇性加氫裝置殘液，都可以轉(zhuǎn)化成高價值的丙烯和乙烯。通過催化裂化工藝將鏈烷烴的石腦油生成輕烯烴，丙烯和乙烯，芳烴作為液體副產(chǎn)物，該項工藝技術(shù)正與石腦油蒸汽裂解制丙烯形成競爭。不過，使用+1100F（593）的較高反應(yīng)器溫度的嚴(yán)苛操作條件意味著將要求使用不同的催化劑。與石腦油蒸汽裂解的0.55 P/E比率相比，催化烯烴工藝的P/E比率可達(dá)0.7-2.4。7 芳烴高烯烴催化裂化（HOFCC）工藝獲得

21、輕烯烴高產(chǎn)率同時，但會降低汽油產(chǎn)率，而且汽油中芳烴含量也非常高。表6總結(jié)了蒸汽裂解和連續(xù)催化重整（CCR）等不同工藝的汽油芳烴含量特性。表6 不同工藝的汽油芳烴含量特性項目蒸汽裂解熱解汽油重整，低苛刻度重整，高苛刻度常規(guī)FCC汽油高烯烴催化裂化汽油Vol,%苯30-402-69-120.5-1.52-5甲苯15-2015-1922-285-1012-18二甲苯，乙苯5-1016-2222-282-1222-30C9+，芳烴5-1025-3516-3012-1832-40總計65-7060-7575-9020-4060-80HOFCC石腦油已被定性為高含硫重整油。如表6所示，HOFCC汽油中三苯

22、（BTX）含量較高，如果BTX要回收用作石油化工原料，還需另外精制提取和處理。對71以上的加石腦油進(jìn)行加氫處理將脫除大部分的硫，抽余油可以再循環(huán)到催化裂化裝置或送到重整裝置。業(yè)界還有很多關(guān)于(guny)討論(toln)以進(jìn)一步增加HOFCC汽油(qyu)中二甲苯產(chǎn)量的討論。在目前這個階段，增加HOFCC二甲苯產(chǎn)量會影響到裝置靈活性問題。增加催化劑稀土含量僅能通過氫轉(zhuǎn)移反應(yīng)小幅增加芳烴產(chǎn)量，但這將不利于ZSM-5添加劑中的輕烯烴生產(chǎn)。生產(chǎn)二甲苯的關(guān)鍵是最大限度提高丙烯的轉(zhuǎn)化率，這將集中在石腦油餾分中的芳烴，如表6所示。HOFCC工藝汽油的苯含量為2vol5vol,常規(guī)FCC汽油中苯含量為0.5v

23、ol1.5vol，由此會造成許多國家對汽油池滿足目前1vol規(guī)范的擔(dān)心。 在美國，汽油含苯規(guī)范是0.62vol,因而必須采用降苯工藝技術(shù)。使用乙烯進(jìn)行烷基化處理應(yīng)該是該問題的最有成本效益的方法。如果將苯回收用于三苯（BTX）的生產(chǎn)，那將需要增加設(shè)備投資。苯的產(chǎn)量主要與原料相關(guān)。高芳烴含量的原料就會生產(chǎn)出更多的苯和總芳烴產(chǎn)品。更高的轉(zhuǎn)化率也將產(chǎn)生更多的苯和總芳烴。環(huán)己烷脫氫或烷基苯脫烷基化反應(yīng)都將增加苯的產(chǎn)量。更高的稀土交換的沸石會提供更多的氫轉(zhuǎn)移反應(yīng)，中等沸石/基質(zhì)比率也有利于苯生產(chǎn)。甲苯生產(chǎn)不受反應(yīng)器溫度影響，以及增加苯/甲苯比例而促進(jìn)苯生產(chǎn)的影響。此外，高的沸石/基質(zhì)沸石催化劑傾向于抑制額

24、外甲苯的形成。 表7為不同工藝的BTX組成對比。表7中數(shù)據(jù)源自中試裝置。蒸汽裂解原料較輕，從而獲得更多的苯，較高的乙烯和丁二烯產(chǎn)率是由于熱裂化反應(yīng)。然而，催化烯烴工藝過程也顯示出三苯產(chǎn)率較高，尤其是二甲苯可用于生產(chǎn)石化產(chǎn)品。表7 不同工藝的BTX組成對比工藝催化烯烴FCC高烯烴FCC蒸汽裂解原料70%VGO+30%VTB85%VGO+15% VTBAGO反應(yīng)溫度620545800 石腦油中C6-C8，wt%苯4.61.5737.75甲苯16.565.6914.85二甲苯23.739.962.92苯乙烯1.09-3.55結(jié)束語如果(rgu)一個煉油廠配置有一套連續(xù)(linx)催化重整和一套高烯烴

25、(xtng)催化裂化裝置，可以生產(chǎn)大量的C2C4烯烴和BTX。中間餾分油則作為高價值柴油出售，塔底渣油可以進(jìn)焦化或加氫處理，并根據(jù)市場情況進(jìn)行裂化工藝過程處理。如果還配置有生產(chǎn)乙烯的蒸汽裂解裝置，則通過C2+和C3+精煉產(chǎn)品回收可以大幅提高煉油生產(chǎn)靈活性和煉油盈利平臺。由于FCC工藝具有很寬范圍的原料加工能力，未來FCC工藝將繼續(xù)發(fā)揮著煉油廠中心作用，可以大大降低重質(zhì)燃料的生產(chǎn)，并生產(chǎn)包括運輸燃料和石化產(chǎn)品的范圍廣泛產(chǎn)品。摘譯自hp20141101Optimize olefins and aromatics production HYPERLINK /ArticleByDate.aspx?Pu

26、bDate=11-01-2014 o Click here to search for other stories from 11-01-2014 11.01.2014| HYPERLINK /SubjectAuthorIndex.html?Key=D l Dean, C. Dean, C., High Olefins FCC Technology Services, LLC,Houston, Texas; HYPERLINK /SubjectAuthorIndex.html?Key=L l Letzsch, W. S. Letzsch, W. S., Technip Stone & Webs

27、ter Process Technologies,Houston, TexasPetrochemical yields from the FCCU is an area of increasing interest as more companies try to integrate refining and petrochemical operations.Keywords: HYPERLINK /SearchResults.aspx?Keywords=olefins olefins HYPERLINK /SearchResults.aspx?Keywords=ethylene ethyle

28、ne HYPERLINK /SearchResults.aspx?Keywords=propylene propylene HYPERLINK /SearchResults.aspx?Keywords=catalysts catalysts HYPERLINK /SearchResults.aspx?Keywords=gasoline gasoline HYPERLINK /SearchResults.aspx?Keywords=catlytic+cracking catlytic crackingThe fluid catalytic cracking (FCC) process can p

29、roduce a wide range of products. FCCtechnologywas introduced almost 72 years ago to facilitate the production of high-octane fuels, and many units are still operated for that purpose. However, the FCC unit (FCCU) can also be used to producepetrochemicals. Ongoing changes in ethane cracking operation

30、s do not produce sufficient propylene to meet growing demand. Petrochemical yields from the FCCU is an area of increasing interest as more companies try to integraterefiningandpetrochemicaloperations.1PROPYLENE MAXIMIZATIONIn the last 10 years, the FCCU has typically been designed to produce large a

31、mounts of propylene. This has been true for catalytic crackers running both conventional and hydrotreated gasoils (GOs) and atmospheric resids. Several factors are contributing to this trend. Steam crackers are getting larger, and more are operating on ethane rather than naphtha. Ethane produces ver

32、y little propylene, and other sources must be found to meet the required propylene demand. To make the situation even more acute is that propylene demands are once again expected to outpace ethylene demand. FCCUs are also getting larger. While the average FCCU processes about 40 Mbpd, new units typi

33、cally range from 50 Mbpd120 Mbpd. These units are large enough to support world-scale polypropylene (PP)facilities.To produce maximum levels of propylene, higher unit conversions are required. The increase in propylene yield comes primarily at the expense of overcracking the C6C10olefins in the gaso

34、line boiling range. These higher conversions are obtained by operating in more severe cracking conditions, i.e., higher reactor temperatures, increased catalyst circulation rates for higher catalyst/oil (c/o) ratios, and/or higher catalyst activity. All of the commercial processes that maximize prop

35、ylene use a pentasil (medium-sized pore) zeolite to overcrack the gasoline. Without exception, feeds that are higher in hydrogen content produce more propylene.FCCU designsUnit designs for producing propylene enable increased severity in the reaction zone. Variations in the design parameters include

36、:Increasing cracking residence times by riser modifications or the addition of bed crackingUsing a downflow reaction schemeUsing advanced feed injectors with high levels of steam injection for feed atomization and optimal hydrocarbonpartial pressure in the reaction systemApplying reactor-termination

37、 technology that reduces excessive dry gas and cokeUsing higher c/o ratios due to the endothermic heat of cracking and operating at elevated reactor temperaturesRecycling cracked naphthaModifying the regenerator design to allow for the addition of extraneous fuel to maintain regeneration kineticsUsi

38、ng modified and unique downstream product recovery sectionsAdding product treating sections for producing a chemical- or polymer-grade product for petrochemical purposesUsing reactor designs that are compatible with the required temperatures for maximum propylene.Dual risersThere are options with du

39、al riser designs. One configuration has two parallel reactor risers terminating into a common reactor-disengaging vessel, where the riser product effluents are combined and are recovered in a single fractionation and gas-plant recovery section. A second option is to have two reactors (riser or down

40、flow) with separate termination vessels. The reaction products are segregated to produce fuel- and polymer-grade products. This design option allows for different operating modes andfeedstocks to produce distillates or gasoline in one riser along with propylene in the second reactor. With the two re

41、action zones, these units can achieve propylene yields at the 12 wt% level.2, 3Fractionator concernsThe main fractionator and gas concentration plants have different concerns. Due to the high conversions and better quality feedstock, the bottoms yields are minimized. This requires a careful review o

42、f the main column bottoms circuit and heatintegrationin the gas concentration unit.4Additionally, a propane/propylene splitter may be included in the gas concentration to produce chemical- or polymer-grade propylene. If this is the case, additional processing units are included for treating propylen

43、e for contaminant removal.PerformanceTable 1shows the gasoline and light-olefin yields for a conventional gasoline FCCU vs. a high-olefin FCCU (HOFCCU) for propylene.5One drawback to producing maximum propylene is that it comes at the expense of gasoline yields and gasoline composition. While higher

44、-severity operations can easily double or triple propylene yields, gasoline make will be reduced by 25%50%. The gasoline composition is 2 to 3 times higher in total aromatics.6Further breakouts of propylene for the current operating modes are shown inTable 3.Gasoline production.Conventional FCCU uni

45、ts were designed to meet gasoline demand by cracking heavy GOs (HGOs) or resids that generally produce propylene yields from 3 wt%5 wt% in a maximum gasoline mode. With the addition of a ZSM-5 additive, the propylene is increased about 3 wt% on average.The high-severity FCCU (HSFCCU) mode utilizes m

46、ore severely hydrotreatedfeedstocksor GOs from highly paraffinic crude oils to produce 12 wt% propylene yield. The catalysts and more severe operating conditions are similar to those in the traditional operation. However, these HSFCCUs are limited in processing flexibility to shift from propylene to

47、 fuels. Due to the recovery sections, these units are also limited in feedstock flexibility.High-olefin operation.The HOFCCUs were developed to produce propylene yields from 15 wt% to 20+ wt% and will yield high levels of other light olefins. The HOFCC gasoline is highly aromatic, and it is preferen

48、tially a petrochemical feedstock. However, it can be used in unique gasoline-blending pools. For example, if arefineryhas isobutane available, then the HOFCCU can produce enough mixed butylenes for an alkylation process. In this case, the HOFCC gasoline may be blended with alkylate to meet fuel spec

49、ifications.Table 2summarizes the directional changes in the operating variables to raise propylene production, and the concerns regarding unit operation.Operating at elevated reactor temperatures is a key to producing higher propylene and other olefin yields from maximum gasoline operations. Gasolin

50、e modes have reactor temperatures ranging from 920F to 1,000F, while HSFCCUs require riser temperatures above 1,020F and a cold-wall riser reactor design.7Higher cat/oil ratios are needed from heat balance considerations and to help achieve the required high conversions. Higher reactor temperatures

51、require increased catalyst circulation rates, as does the higher endothermic heat of cracking common to propylene processes.7Catalyst circulation is a dependent variable; however, it is set by the heat load and coke. This can limit the quality of the feed for units designed for c/o ratios above 12.

52、If the feed quality is very high, a fired heater may be desirable.Hydrocarbon partial pressure should be minimized for producing propylene. This is achieved from lowering reactor pressure and/or by increasing steam usage. A riser steam usage of 10 wt% on fresh feed is not uncommon, and it can be as

53、high as 30 wt%. Main fractionators need to be packed to achieve the lowest pressures. The vessels will be larger, but less feed will need to be processed to produce an equivalent amount of propylene.Higher residence time in the reactor refers to the vapor contact time. Extra residence time is needed

54、 for riser configurations. Some control of the time is achieved by varying the riser length and diameter. Plug flow of the reactants and products is still desired to prevent unwanted reactions of the desired olefins.Additional residence time can also be facilitated by adding a second riser, recyclin

55、g hydrocarbons to the reactor, or putting a catalyst bed downstream of the riser. The velocity of the oil going through the catalyst bed is normally 2 ft/sec to 3 ft/sec, so an extra 5 sec to 15 sec can be obtained with this configuration.Recycling of the cracked naphtha will produce additional prop

56、ylene due to light-olefin cracking over pentasil (ZSM-5) zeolites. Additional 2 wt%3 wt% propylene can potentially be obtained.8Recycling of slurry may be practiced to increase the regenerator temperature when the coke is too low due to the lack of coke precursors in the feed. Other techniques for i

57、ncreasing coke have been discussed in papers and presentations covering the FCCU heat balance.Blending resid into these low-concarbon feeds can help with the unit heat balance, as both the heat of reaction and operation severity are elevated over conventional FCC operation. The feed contaminants sho

58、uld be considered with regard toemissions, product qualities, and impact on the catalyst.9FeedstocksFCCU feeds can play a significant role in determining the propylene yields. Propylene contains about 14.3% hydrogen; therefore, feedstocks that contain more hydrogen can, and will, make more propylene

59、. Severely hydrotreated GO feeds are typically used, and crudes with high API gravity, such as tight/shale oils, are ideal as propylene feedstocks.For HOFCCUs, the typical feedstocks are extremely hydrotreated VGOs. Resid units primarily crack hydrotreated residue in one riser and add recycle and ot

60、her feedstocks to a second reaction zone. This high degree of hydrotreating has additional advantages with regard to product post-treating for producing chemical- and polymer-quality products.Coker GOs can be processedHowever, these feeds should be pretreated by a high-pressure hydrotreater that not