泥漿氣—液分離器設(shè)計(jì)【說明書+CAD】

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長江大學(xué)畢業(yè)設(shè)計(jì)(論文)任務(wù)書 學(xué)院（系） 機(jī)械工程學(xué)院 專業(yè) 過程裝備及其控制 班級 裝備10901 學(xué)生姓名 胡華山 指導(dǎo)教師/職稱 張慢來/講師 1.畢業(yè)設(shè)計(jì)(論文)題目： 泥漿氣—液分離器設(shè)計(jì) 2.畢業(yè)設(shè)計(jì)（論文）起止時(shí)間： 2013年3 月 日～2013年6 月 日 3.畢業(yè)設(shè)計(jì)(論文)所需資料及原始數(shù)據(jù)（指導(dǎo)教師選定部分） 原始數(shù)據(jù)： 液體處理量：270 m3/h 含氣量（體積百分比）：９％ 鉆井液比重：2.0-2.2g/cm3 鉆井液粘度：60-100s 可分離氣泡直徑 >0.8 mm。 資料： ⅰ 褚良銀，旋轉(zhuǎn)流分離理論，石油工業(yè)出版社，2002 ⅱ 徐繼潤，水力旋流器流場理論，科學(xué)出版社1998 ⅲ 孫啟才，分離機(jī)械，化學(xué)工業(yè)出版社，1993 4.畢業(yè)設(shè)計(jì)(論文)應(yīng)完成的主要內(nèi)容 (1) 氣-液分離技術(shù)及進(jìn)展 (2) 泥漿氣-液分離設(shè)計(jì)方案論證 (3) 設(shè)備定尺計(jì)算 (4) 結(jié)構(gòu)設(shè)計(jì)及強(qiáng)度計(jì)算 (5) 分離器分離性能預(yù)測 (6) 分離器殼體的有限元分析 5.畢業(yè)設(shè)計(jì)(論文)的目標(biāo)及具體要求 (1) 泥漿氣-液分離器裝配圖； (2) 進(jìn)口分離單元，殼體，封頭、支座等零件圖； (3) 進(jìn)口分離單元，殼體，封頭、支座等零件實(shí)體造型； (4) 英文翻譯； (5) 開題報(bào)告； (6) 設(shè)計(jì)說明書。 6.完成畢業(yè)設(shè)計(jì)(論文)所需的條件及上機(jī)時(shí)數(shù)要求 （1）熟悉Ansys或Comsol、Autocad、Aspen （2）上機(jī)200小時(shí) 任務(wù)書批準(zhǔn)日期 2013年 3 月 日 教研室(系)主任(簽字) 任務(wù)書下達(dá)日期 2013年 3 月 日 指導(dǎo)教師(簽字) 完成任務(wù)日期 年 月 日 學(xué)生（簽名） II 畢業(yè)論文(設(shè)計(jì)) 題目名稱： 泥漿氣-液分離器 題目類型： 畢業(yè)設(shè)計(jì) 學(xué)生姓名： 胡華山 院 (系)： 機(jī)械工程學(xué)院 專業(yè)班級： 裝備10901班 指導(dǎo)教師： 張慢來 輔導(dǎo)教師： 周志宏 時(shí) 間： 2013.3 至 2013.6 一．題目來源 生產(chǎn)實(shí)踐 二.研究目的和意義 由于井眼環(huán)空的循環(huán)液柱壓力低于所鉆地層的孔隙壓力，不可避免地使地層流體（主要是氣體）侵入井眼環(huán)空，并隨鉆井液一起上返，在地層氣體從井底向井口迀移過程中，由于液柱壓力的連續(xù)降低，溶解氣析出，因此氣侵后的鉆井液中的小氣泡特別多，對于切力和粘 度較高的鉆井液，在不采取除氣措施情況下，氣泡可能無 法浮到表面而破裂，或需要較長的駐留時(shí)間才能分離。鉆井液液氣分離器是氣侵鉆井液初級脫氣的專用設(shè)備，主要用于清除氣侵鉆井液中直徑大約在φ3～φ25mm的大氣泡。這些大氣泡是指大部分充滿井眼環(huán)空某段的鉆井液中的膨脹性氣體，若不除掉，容易引起井涌，甚至噴出鉆盤表面。因此對于這樣一種很有發(fā)展前景的泥漿氣液分離器的研究有非常重要的意義。 三.讀的主要參考文獻(xiàn)及資料名稱 [1]董大勤，袁鳳隱主編，壓力容器與化工設(shè)備實(shí)用手冊，第一版。 北京：化學(xué)工業(yè)出版社，2003.2 [2]賀匡國主編，化工容器及設(shè)備簡明設(shè)計(jì)手冊，北京：化學(xué)工業(yè)出版社，1989.12 [3]卓震主編，化工容器及設(shè)備，第一版，北京：中國石化出版社，2000.2 [4]鄒廣華，劉強(qiáng)主編，過程裝備制造及檢測，第一版，北京：化學(xué)工業(yè)出版社，2003.8 [5]張德姜，趙勇主編，石油化工管道設(shè)計(jì)與安裝，第一版， 北京：中國石化出版社，2002.2 [6]韓占中，王敬，蘭小平主編，F(xiàn)LUENT-流體工程仿真計(jì)算實(shí)例應(yīng)用，第一版， 北京：北京理工大學(xué)出版社，2004.6 [7]魏崇光，鄭曉梅主編，化工工程制圖，第一版， 北京：化學(xué)工業(yè)出版社，2000.8 [8]雷文平等主編，Solid Works 2001，第一版， 北京：清華大學(xué)出版社，2002.1 [9]劉朝儒，高政一等主編，機(jī)械制圖，第四版，北京：高等教育出版社 ，2000.12 [10]成大先主編，機(jī)械設(shè)計(jì)手冊，第四版，北京：機(jī)械工業(yè)出版社，2003.1 [11]曹學(xué)文， 黃慶宣 新型管柱式氣液旋流分離器 天然氣工業(yè) 2002 22(2) [12]學(xué)成， 山本恭二 開孔圓筒式液體旋流分離器的研究 通風(fēng)除塵 1998 17(1) [13]朱浩東， 楊敏 國內(nèi)外旋流分離器特點(diǎn)及發(fā)展方向 石油機(jī)械 1994 22(12) [14]陳麗萍. 立式重力氣液分離器工的工藝設(shè)計(jì) 天然氣化工:C1化學(xué)與化工 1999， 24(2) [15]K.E.Arnold， 王曉鳳. 李太平結(jié)構(gòu)緊湊的分離器系列 國外油田工程 2000，(8) [16]賈建貞， 張寶彥， 劉景云. 欠平衡鉆井液氣分離器的研制與應(yīng)用 石油機(jī)械 2001，(7) [17]M.F.Schubert， 李太平. 水力旋流分離系統(tǒng)的發(fā)展 國外油田工程 1999，(7) [18]袁惠新， 王躍進(jìn). 旋流分離技術(shù)在石油、石化工業(yè)中的應(yīng)用 化工設(shè)備與防腐蝕 2002，(3) [19]曹學(xué)文，黃慶宣. 新型管柱式氣液旋流分離器設(shè)計(jì)與應(yīng)用， 天然氣工業(yè) 2002， 22(2) [20]吳粵燊主編, 壓力容器安全技術(shù)手冊, 北京:機(jī)械工業(yè)出版社，1999.3. [21]張康達(dá)，洪起超主編. 壓力容器手冊(上/下), 北京:勞動人事出版社, 1988.2 [22]家禎主編, 壓力容器材料實(shí)用手冊（第一版）, 北京：化學(xué)工業(yè)出版社工業(yè)裝備和信息工程出版社 , 2000. 7 [23]吳粵榮主編 . 壓力容器安全技術(shù)（第二版）, 北京：化學(xué)工業(yè)出版社, 1993.11 [24]董振仁，魏新立主編. 過程裝備成套技術(shù),第一版。 北京： 化學(xué)工業(yè)出版社, 2001. 11 [25]郭年祥主編, 化工過程及設(shè)備, 北京：冶金工業(yè)出版社, 第一版,2003.3. [26]鄭津洋， 董其五， 桑芝富主編, 過程設(shè)備設(shè)計(jì),第一版, 北京：化學(xué)工業(yè)出版社, 2001.3 [27] (美)耶帝什.特.夏編, 氣液固反應(yīng)器設(shè)計(jì), 北京：烴加工出版社 , 1989. 9. [28]陳國理主編, 壓力容器及化工設(shè)備, 廣州：華南理工大學(xué)出版社, 1988.11 [29]余國宗主編, 化工機(jī)械工程手冊, 北京: 化學(xué)工業(yè)出版社, 2001. 7 [30]潭天恩等主編，化工原理，第二版. 北京：化學(xué)工業(yè)出版社, 2003. 1 [31]袁恩熙主編，工程流體力學(xué)，第一版. 北京：石油工業(yè)出版社，1986 .1 [32]同濟(jì)大學(xué)主編，高等數(shù)學(xué)，第四版。北京：高等教育出版社，2002. 2 [33]龔偉安， 鉆井液固相控制技術(shù)及設(shè)備，北京：石油大學(xué)出版社，1995 .4 [33] Wet Gas Separation in Gas-Liquid Cylindrical Cyclone Separator. Robiro MolinaShoubo WangLuis E. GomezRam S. MohanOvadia ShohamGene Kouba《Journal of Energy Resources Technology》, EI SCI 2008 4 [34]Gas-liquid reactor/separator:dynamics and operability characteristics. Ranade V.V.《Chemical Engineering Science》, EI SCI 1999 21 [35] NUMERICAL SIMULATION OF COMPRESSIBLE FLOW IN GAS LIQUID SEPARATOR. Sen LiZunce WangYan XuFengxia LvYuejuan YanYujie Song2010 [36]Gas/Liquid Separation Technology. Chemical Engineering Progress Group《Chemical Engineering Progress》, EISCI 2005 7 [37]Fluidic level control in gas-liquid separators. Priestman GH.Tippetts JR.《Transactions of the Institution of Chemical Engineers. Part A, Chemical Engineering Research & Design》, EI SCI 2000 A5 四．國內(nèi)外現(xiàn)狀和發(fā)展趨勢與研究的主攻方向 氣液分離技術(shù)是從氣流中分離出霧滴或液滴的技術(shù)，該技術(shù)廣泛的應(yīng)用于各個工程等工藝過程,用于分離清除有害物質(zhì) 或高效回收有用物質(zhì)。氣液分離技術(shù)的機(jī)理有重力沉降、慣性 碰撞、離心分離、靜電吸引、擴(kuò)散等,依據(jù)這些機(jī)理已經(jīng)研制出許多實(shí)用的氣液分離器。 1、 重力沉降分離 氣液重力沉降分離是利用氣液兩相的密度差實(shí)現(xiàn)兩相的重力分離,即液滴所受重力大于其氣體的浮力時(shí)，液滴將從氣相 中沉降出來,被分離。它結(jié)構(gòu)簡單、制造方便、操作彈性大，需要較長的停留時(shí)間,分離器體積大,笨重，投資高，分離效果差，只能分離較大液滴,其分離液滴的極限值通常為lOOum,主要用于地面天然氣開采集輸。經(jīng)過幾十年的發(fā)展，該項(xiàng)技術(shù)已基本成熟。當(dāng)前研究的重點(diǎn)是研制高效的內(nèi)部填料以提高其分離效率。此類分離器的設(shè)計(jì)關(guān)鍵在于確定液滴的沉降速度，然后確定分離器的直徑。 2、 過濾分離 通過過濾介質(zhì)將氣體中的液滴分離出來的分離方法即為過濾分離。其核心部件是濾芯,以金屬絲網(wǎng)和玻璃纖維較佳。氣體流過絲網(wǎng)結(jié)構(gòu)時(shí)，大于絲網(wǎng)孔徑的液滴將被攔截而分離出來。若液滴直接揸擊絲網(wǎng),它們也將被攔截。直接攔截可以收集 一定數(shù)置比其孔徑小的顆粒,除液滴直接撞擊絲網(wǎng)外。過濾型氣液分離器具有高效、可有效分離0.1?10um范圍小粒子等優(yōu)點(diǎn)，當(dāng)氣速增大時(shí),氣體中液滴夾帶量增加;甚至，使填料起 不到分離作用,無法進(jìn)行正常生產(chǎn);另外,金屬絲網(wǎng)存在清洗困 難的問題。故其運(yùn)行成本較高,現(xiàn)主要用于合成氨原料氣凈化 除油、天然氣凈化及回收凝析油以及柴油加氫尾處理等場合。 3. 慣性分離 氣液慣性分離是運(yùn)用氣流急速轉(zhuǎn)向或沖向檔板后再急速 轉(zhuǎn)向,使液滴運(yùn)動軌跡與氣流不同而達(dá)到分離。此類分離器主 要指波紋(折)板式除霧(沫)器，它結(jié)構(gòu)簡單、處理量大,氣速度 一般在15?25 m/s,但阻力偏大,且在氣體出口處有較大吸力 造成二次夾帶，對于粒徑小于25 i?ni的液滴分離效果較差，不適于一些要求較高的場合。其除液元件是一組金屬波紋板，其 性能指標(biāo)主要有:液滴去除率、壓降和最大允許氣流量(不發(fā)生再夾帶時(shí)),還要考慮是否易發(fā)生污垢堵塞。液滴去除的物理機(jī) 理是慣性碰撞,液滴去除率主要受液滴自身慣性的影響。通常用于：（1)濕法煙氣脫硫系統(tǒng)，設(shè)在煙氣出口處,保證脫硫塔出 口處的氣流不夾帶液滴；（2)塔設(shè)備中，去除離開精餾、吸收、解 吸等塔設(shè)備的氣相中的液滴，保證控制排放、溶劑回收、精制產(chǎn) 品和保護(hù)設(shè)備?，F(xiàn)在波紋板除霧器的分離理論和數(shù)學(xué)模型已經(jīng) 基本成熟,對其研究集中在結(jié)構(gòu)優(yōu)化及操作參數(shù)方面來提高脫液效率。國內(nèi)有學(xué)者對除霧器葉片形式作了比較,發(fā)現(xiàn)弧形葉片與折板形葉片的除霧效率相近,弧形除霧器的壓降明顯小于折板形，故弧形葉片除霧器的綜合性能比折板式除霧器要好。 4、 離心分離 氣液離心分離主要指是氣液旋流分離，是利用離心力來分 離氣流中的液滴,因離心力能達(dá)到重力數(shù)十倍甚至更多,故它比重力分離具有更高的效率。其主要結(jié)構(gòu)類型有： （1) 管柱式旋流氣液分離器 (GLCChGLCC在1995年首次用于多相流量計(jì)環(huán)， 經(jīng)過GLCC分離后的氣液兩相分別用單相流量計(jì)計(jì)量，然后再合并,避免了多相流測量中的問題;GLCC在地面和海上油氣分離、井下分離、便攜式試井設(shè)備、油氣泵、多相流量計(jì)、天然氣輸 送以及火炬氣洗滌等具有巨大的潛在應(yīng)用。 （2) 螺旋片導(dǎo)流式氣液分離器(CS)。 1996年國外專家成功研制了螺旋片導(dǎo)流式氣 液旋流分離器,直接在井口將氣液進(jìn)行分離,増加了采油回收率,分離后的氣體和液體用不同的管道輸送各相，降低了多相 流輸送時(shí)易出現(xiàn)的斷續(xù)流、堵塞和沉積等典型問題。 （3) 軸流式氣液旋流分離器。 軸流式氣液旋流分離器與切向入口式旋流器 的相比其離心力是靠導(dǎo)向葉片產(chǎn)生的，使旋轉(zhuǎn)流保持穩(wěn)定,并有助于維持層流特性,且阻力損失較小。此分離器結(jié)構(gòu)簡單、過流面積大,中間流道的連接和管柱整體結(jié)構(gòu)形式簡單,能夠與常規(guī)坐封工藝和起下作業(yè)工藝吻合,顯著降低了加工制造難度 和加工成本及現(xiàn)場操作技術(shù)難度,適宜于井下狹長空間環(huán)境的安裝操作，是用于井下氣液分離的理想分離設(shè)備。 我國各個行業(yè)需要進(jìn)行氣液分離的場合眾多，氣液分離的方法設(shè)備也相當(dāng)多,不的方法設(shè)備具有不同的優(yōu)缺點(diǎn),但各 種方法都具有相當(dāng)?shù)木窒扌?應(yīng)用范圍比較狹窄,具有通用性,并且大多數(shù)分離設(shè)備的分離機(jī)理并不十分清楚。在分離器方面目前在200年由中國石油大學(xué)多相流實(shí)驗(yàn)室研制了100mm 軸流式氣液旋流分離器較為先進(jìn),進(jìn)行了性能試驗(yàn)試驗(yàn)過程中發(fā)現(xiàn), 短路流和二次流夾帶對于分離器的分離效率影響較大,采用合理的溢流管結(jié)構(gòu)形式可以減少短路流和二次流夾帶, 提高分離效率。開發(fā)高效低阻具有普遍實(shí)用性的氣液分離技術(shù)，和多種分離技術(shù)的組合應(yīng)用,以及研究分離機(jī)理將是今后氣液分離技術(shù)的研究重點(diǎn)。 五.主要研究內(nèi)容、重點(diǎn)研究的關(guān)鍵問題及解決思路 主要研究內(nèi)容： 1． 氣液分離器原理； 2． 根據(jù)要處理的鉆井液類型及分離氣泡直徑確定分離器的類型； 3． 泥漿氣-液分離設(shè)計(jì)方案論證。 重點(diǎn)研究的關(guān)鍵問題： 4． 離心式氣液分離器的結(jié)構(gòu)設(shè)計(jì)及強(qiáng)度計(jì)算； 5． 離心式氣液分離器分離性能預(yù)測； 6． 分離器殼體的有限元分析。 解決思路： 1.查閱國內(nèi)外相關(guān)資料，了解基本的工作原理； 2.根據(jù)工作原理和工作方式確定結(jié)構(gòu)組成； 3.查閱國內(nèi)氣液分離器，進(jìn)行型號規(guī)格選擇； 4.依據(jù)給定參數(shù)選擇類型； 5.根據(jù)參數(shù)進(jìn)行計(jì)算分析確定結(jié)構(gòu)具體尺寸； 6.畫裝配圖； 7.畫出零件圖。 六.工作的主要階段、進(jìn)度與時(shí)間安排 畢業(yè)設(shè)計(jì)時(shí)間共計(jì)12周，具體安排如下： 第7周 查閱資料和翻譯外文資料 第8周 撰寫開題報(bào)告，準(zhǔn)備開題報(bào)告答辯 第9-10周 確定總體方案 第11周 液氣分離器設(shè)計(jì)方案論證 第12周 結(jié)構(gòu)設(shè)計(jì)及強(qiáng)度計(jì)算 第13-14周 分離器分離性能預(yù)測并使用Ansys等軟件模擬流場 第15周 設(shè)備參數(shù)計(jì)算 第16-17周 分離器各部分裝配圖的測繪 第18周 修改畢業(yè)設(shè)計(jì) 七.指導(dǎo)老師審查意見 VII SPE 50685 A NEW APPROACH TO GAS-LIQUID SEPARATION 5 SPE 50685 A New Approach to Gas-Liquid Separation A.C. Stewart, N.P. Chamberlain and M.丨rshad, Kvaerner Paladon Ltd. Copyright 1998, Society of Petroleum Engineers Inc. This paper was prepared for presentation at the 1998 SPE European Petroleum Conference held in The Hague, The Netherlands, 20-22 October 1998. This paper was selected for presentation by an SPE Program Committee following review of information contained in an abstract submitted by the author(s). Contents of the paper, as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are subject to publication review by Editorial Committees of the Society of Petroleum Engineers. Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A., fax 01-972-952-9435. Abstract Effective gas-liquid separation is important not only to ensure that the required export quality is achieved but also to prevent problems in downstream process equipment and compressors. Once the bulk liquid has been knocked out, which can be achieved in many ways, the remaining liquid droplets are separated from by a demisting device. Until recently the main technologies used for this application were reverse-flow cyclones, mesh pads and vane packs. More recently new devices with higher gas-handling have been developed which have enabled potential reduction in the scrubber vessel size. This paper will present some of the recent developments in scrubbing technology which have been aided by the use of computational fluid dynamics. In addition, this paper will review some of the latest compact separation systems which have also enabled a whole new approach to gas-liquid separation to be considered. There are several new concepts currently under development in which the fluids are degassed upstream of the primary separator. These systems are based on centrifugal and turbine technology and have additional advantages in that they are compact and motion insensitive, hence ideal for floating production facilities Introduction To avoid problems in compression or downstream processing, the normal criteria for the liquid content of processed gas is 0. 1 U.S.gal/mmscf, thus the gas must be passed through a scrubber. In order to cope with slugging conditions, this is usually a two stage separator with an inlet device for free liquid knockout and a gas demisting device for removal of the entrained droplets. Inlet devices range from simple deflector plates to cyclonic separators. The more effective the inlet device the lower the liquid load to the demisting device which can result in more compact scrubbers, or in some cases reduce the number of separation stages required. The demisting devices most commonly used at present are vane packs, sometimes known as wave plates, wire mesh pads and reverse flow cyclones. More recently an alternative device, the axial flow cyclone, has also been re-introduced into the market. This device has the advantage of being able to handle a high gas throughput with a relatively small pressure drop and thus again offers the potential for smaller, lighter vessels. The drive to more compact technology has also had impact on the way in which gas-liquid separation is being addressed in three phase flows. Primary three phase separators are usually the largest process vessels on the facility and the restrictions on velocities in the gas phase play an important part in their sizing. The space reduction possible with the introduction of high technology demisting devices, are small compared to that which could be achieved if the gas flow through the vessel could be reduced or even eliminated. A number of initiatives are thus underway to develop efficient methods of preseparation of the gas, with the objective of substantially reducing the size of, or even eliminating the need for a three phase separator. Advantages of a Well Designed Inlet Device Most demisting devices are designed to handle liquid loadings of no more than 1% by volume. The fluid entering a scrubber may contain in the order of ten times this value, so it is imperative that the inlet device will knock out sufficient liquid to ensure the demister is not flooded. The exact nature of fluid entering the vessel is often unknown, although and indication of the flow structure in the inlet pipe can be estimated from a flow map of the type presented by Taitel el al (1). As the fluid enters the vessel it will be subjected to some degree of turbulent shear which will result in the formation of droplets, even if the flow is not fully dispersed upstream. The degree of shear will depend on inlet velocity, liquid characteristics and the type of inlet device used. An estimation of the maximum drop size entering the separator or scrubber can be made using the Hinze equation (Ref. 2): G .■⑴ 々0.6 ”0.4 P 8 ..(2) The biggest error in this calculation is in determining the value of 8, the energy dissipation. Computational fluid dynamics (CFD) can be used to estimated the turbulent dissipation in the inlet region but of course it is possible that there could be droplet break-up from shear imparted upstream. Despite this such correlation still provide a useful starting point for a comparative study of different technology. CFD can also be used to determine the percentage of particles in different size bands which will reach the demisting elements. For example figure 1 shows the comparison in performance between a simple deflector plate and a vane type inlet. This calculation has not assumed a maximum droplet size in either case. It shows that with the deflector plate the liquid knockout is very inefficient with droplets of up to 3500 ^m reaching the demister. By replacing this with the vaned inlet diffuser the liquid knock is dramatically increased and with a maximum drop size reaching the demister reduced to 650 |im and a significant percentage of smaller droplets being separated. This is partly due to increased coalescense and gravity knockout by the inlet device and partly due to a better flow distribution downstream. Figure 2 shows the flow distribution in the vessel in each of these cases as predicted by CFD. It can be seen with the vane-type inlet the velocity profile across the vessel is much flatter, with none of high velocity gas streams present in the previous case. The maximum drop size determined from equation 1 can be then be inputted into a probability function (3) to predict the size distribution at the vessel inlet. If information of type presented in figure 1 is then used to determine the percentage knockout by the inlet device, the liquid loading to the demister can be estimated. Even more effective liquid knockout can be achieved through the use of a cyclonic inlet device. These devices which were initially developed to reduce foaming in three phase separators (4,5) have now been adapted to treat the high GORs typical of scrubber applications, and have been successfully installed and operated North Sea gas platforms. A typical scrubber layout with a cyclone inlet is shown in figure 3. Laboratory studies have shown that the liquid removal from these device is typically around 98%, compared to around 60% from a vane type device and 30% from a deflector plate. Thus the liquid loading on the demisting device is significantly decreased and in some cases there may no longer be the need for a secondary device. In addition to the improved liquid knockout these devices can handle much higher inlet momentums than other inlet devices and hence are ideal for debottlenecking. Advances in Demisting Technology The devices used for the removal of liquid mist from gas can be divided into two main categories. The first of these are the direct interception devices which includes filters and mesh pads. While these devices maintain high efficiencies down to small droplet sizes, they are prone to fouling problems, giving high maintenance costs, and hence are generally restricted to clean, solid free applications. The second category of gas- liquid separator is the inertial devices which cyclones and vane packs. Conventional reverse flow cyclones have been used for over 40 years and clean both solids and liquids from gas streams. They also have high efficiencies for small droplet sizes but at high liquid loadings a two stage design with secondary drainage is required requiring additional control expenditure. The high pressure drop characteristics also makes them unfavourable in some cases. Vane packs by comparison have a relatively low pressure drop. The efficiency of these devices is dependant on the geometry of the device and some of the more sophisticated designs compete favourably with mesh pads. The performance of vane packs is dependant on two independent factors. The first of these is its drop removal efficiency. The second is liquid strip-off characteristics. Prediction of drop removal efficiency has been given a lot of attention over the last decade. Assuming a uniform flow field Burkholz (6) derived the following expression for separation efficiency for one bend: apd ud2 18^s This can be extended by assuming partial remixing of the droplet laden gas, to give the following expression for total efficiency: nt = 1 - (1 -nP)n where n is the number of bends. Figure 4 shows a comparison between experimental data (7) and that predicted by the Burkholz formula. It shows the theory gives a good indication of the performance however it does slightly over predict the measured efficiency. More recently computational fluid dynamics, CFD, has been used to gain a better understanding of the flow field with the wave plates and to give an alternative method of predicting efficiency. Drop removal efficiency data obtained using CFD code CFX is also shown in figure 4. In this case the model under predicts the efficiency, particularly for the small drop sizes, but gives a very accurate prediction of the cut-off size. The advantage of this technique is that it gives also gives a good indication of the flow distribution of the channel. Typical gas flow distribution patterns for two simple vane channels are shown in figure 5. In the channel without the hook, it can be seen that large recirculation zones exist at each bend, this is potentially dangerous as liquid collected in these zones would be re-entrained into the gas. The presence of such a hook, as shown in the lower pictiure, improves performance by providing a drainage channel for the separated ..(3) liquid but it also reduces the size of these recirculation zones. K When the velocity exceeds a certain critical value it strips liquid off the separated film on the vane wall and re- entrains it into the gas phase. In terms of bulk liquid, the carry-over from this source is often more than that from the presence of small droplets which have not been removed. This critical velocity can be determined from the following expression (Ref. 1): .(4) 2 pg Where the K is the Kutateladze number, which depends on the characteristics of the vane. For a simple vane geometry, K has been reported to have a value of 2.46 (8). New vane types have been developed however, with a construction designed to lower the exit velocity and hence minimise strip-off, in these devices higher values of K can be obtained. These new vanes also incorporate a coalescing section which increases their drop removal efficiency. Over the last few year another type of demisting device has also introduced successfully into the oil and gas market, the axial flow cyclone. The axial flow concept, shown in figure 6, as been around for many years, however, it has only been through recent development work that the concept has been developed into a viable separator for demisting applications. In contrast to a conventional reverse flow cyclone, the gas stream in an axial flow cyclone does not change direction but takes a path straight through the device. The tangential velocity in this case is developed by passing the gas over a vaned section which forces the droplets to the cyclone wall. The film is then drained either through a series of slots and/or an annular gap, assisted by a small gas flow which is recycled through the central body. The processed gas then exits via the vortex finder. In work carried out at Delft University (8,9), a number of different geometries were tested at atmospheric conditions in the vertical orientation. Further development work has recently been carried out (10) in which tests were carried out in both the horizontal and vertical orientation. It was found that the axial flow cyclone was efficient over a wide flow range and that the droplet cut-off sizes, were lower than those obtained for a vane pack. Typical performance curves at different air flow rates are given in figure 7. It was also found that at high liquid loadings, the design of the drainage system is crucial to the cyclone’s performance and the optimum design has been shown to depend on the orientation of the device. A slot system has been found to be more effective for vertical operation and an annular system for horizontal installations. Axial flow cyclones have now been installed in a number of separators and scrubbers in North Sea fields. Their high gas handling capacity means that they can be retrofitted to help debottlenecking in fields with increasing gas flows and in new fields they offer the potential of smaller vessel sizes. Particularly if used in conjunction with an effective inlet device which produces a good flow distribution at the inlet to the demister. CFD can be a useful tool to help optimise the design of internals for specific systems and to show if a good flow distribution will be obtained (see figure 2). Comparison of the Performance of Demisting Devices Despite the advantages of axial flow cyclone, it does not offer the best solution for all applications. In order to chose the best demisting device for a particular service a number of factors have to be taken into account,. these are summarised in Table 1. The four devices are rated from best (1) to worst (4) in the first five categories. and the in the last case the approximate cut-off size is given. The turndown of the cyclonic devices tends to be better that other demisters. In independent tests (11) multicyclones were found to have a turndown of around 1:6 and still maintain particle removal efficiency. This is much higher than could be achieved for any of the other demisters. In terms of gas handling capacity vane packs still come out top at low pressures but at higher operating pressures axial flow cyclones are better as the velocity through the device does not have to be significantly reduced to prevent strip-off. While mesh pad have a limited turndown and gas handling capacity their relatively low costs means they are often used as a coalescer upstream of other demisters in cases where there is a concern over carryover of small drops. In this situation they operate under flooded conditions but the liquid re-entrained into the outlet gas has a larger drop size distribution than that at the inlet. The values given for drop removal are for a generic device of each type but it should be remembered that in each case there are a wide range of products of each type on the market and the performance of individual devices may vary. These figures also depend very much on the process conditions. It has been shown that efficiency in terms of particle/droplet removal is directly proportional to pressure drop. Figure 8 shows how the cut-off size varies with pressure drop for a range of devices. Thus if a high performance is required it is necessary to accept a pressure drop penalty. Preseparation of Gas The size vessel reduction which can be achieved by the introduction of high performance demisting devices is relatively small compared to the saving that could be made if the gas was taken out of the vessel completely. This has prompted a whole new approach to the problem of gas liquid separation. There are a number of different concepts beingdeveloped to remove the gas from the process fluid upstream of the primary gravity two or three phase separator or electrostatic coalescers. Most of these make us a centrifugal separators which in addition to being compact have the added advantage of being insensitive to motion and hence could be of particular value on FPSO installations. Figure 9 shows how a cyclonic pre-degasser which could be used in conjunction with a two phase separator to replace a three phase separator, with substantial space and weight reduction. The main component of the device is a bulk gas liquid cyclone similar to that used as an inlet device for two and three phase separators. The cyclonic inlet, which has been developed over the last five years, has been installed successfully in a number of three phase separators in the field. From field an laboratory tests it has been shown that this device reduces gas carry-under into the vessel to less than 1% and hence eliminates foaming and in addition, the outlet gas contains less than 2% volume liquid. In the well-head degasser, the outlet gas then passes into a primary scrubber stage in which a vaned swirl element imparts further spin on the gas throwing most of the entrained liquid to the vessel walls where it drain down to the liquid drainage section at the bottom of the vessel. In order to ensure the required gas quality of 0.1 USgal/mmscf the gas is then passed through a second scrubber stage in a second chamber which contains axial flow cyclones of the type described above. Another new separator concept currently under development is separators illustrated in figure 10. It is a compact centrifugal separator based on a turbine concept with the added advantage of power recovery. The technology, which has already been used successfully in geothermal and refrigeration applications (12), is currently being developed for two and three phase separation and well-head energy recovery. A field test of the prototype two phase separator is currently underway at Texaco’s Humble test facility. The fluid is introduced at high velocity through a contoured two phase nozzle and impinged tangentially onto the inner surface of the rotating cylindrical rotor. The high centrifugal force produces an immediate separation of the gas and the liquid. The separated liquid forms a layer on the cylindrical surface where most of its kinetic energy is transferred to the rotor by shear forces, before it is removed through a specially designed scoop or internally cast reject channels. The separated gas flows through the vanes attached to the turbine supplying further kinetic energy. The main limitations with these new compact technologies is that by their very nature there is only limited fluid volume available in the system. This has obvious implications for control particularly under slugging conditions. These problems are being addressed and it seems certain that novel compact technologies will play a large role in offshore separation in the future, with the centrifugal devices described above, being of particular value in the development of separation trains for floaters. Conclusions Recent developments in technology have made it possible to reduce the size of gas-liquid separation vessels or to increa