外浮頂油罐邊緣密封型式的選用與油氣損耗

1、外浮頂油罐邊緣密封型式的選用與油氣損耗何麗娟(中國(guó)石油股份有限公司哈爾濱分公司, 黑龍江哈爾濱150056摘要:分析了外浮頂油罐的油氣損耗機(jī)理和估算方法, 列舉了國(guó)內(nèi)外常用的浮頂邊緣密封結(jié)構(gòu)型式, 并對(duì)其優(yōu)缺點(diǎn)進(jìn)行了分析對(duì)比, 同時(shí)對(duì)密封型式的選擇及一次密封與二次密封的搭配提出了建議。關(guān)鍵詞:外浮頂油罐; 邊緣密封型式; 選用中圖分類號(hào):TE97文獻(xiàn)標(biāo)識(shí)碼:B文章編號(hào):100628805(2002 03200392031前言外浮頂油罐是目前地上儲(chǔ)存原油的主要設(shè)施之一。外浮頂油罐從原理上講很簡(jiǎn)單, 就是在敞口圓筒形容器內(nèi)有一個(gè)能在油面上浮動(dòng)的罐頂來控制揮發(fā)性液體蒸發(fā)損耗。由于浮頂?shù)拇嬖? 大大減

2、少了石油損耗以及對(duì)環(huán)境的影響。但是, 經(jīng)過對(duì)現(xiàn)役外浮頂油罐的調(diào)查分析, 發(fā)現(xiàn)有時(shí)會(huì)因選用邊緣密封形式和結(jié)構(gòu)不合理而造成揮發(fā)性液體損耗, 因此會(huì)給用戶造成經(jīng)濟(jì)損失。本文根據(jù)作者多年來的設(shè)計(jì)經(jīng)驗(yàn), 并參考國(guó)內(nèi)外有關(guān)資料, 重點(diǎn)介紹了外浮頂油罐的各種密封形式與損耗, 并進(jìn)行了綜合比較分析, 同時(shí)提出了優(yōu)先選用的幾種形式, 供有關(guān)讀者參考。2邊緣密封損耗機(jī)理分析以及邊緣密封與儲(chǔ)液之間氣相空間的大小。另外, 在邊緣密封上方流動(dòng)的風(fēng), 使在邊緣密封和罐壁之間的任何縫隙中的空氣產(chǎn)生渦流, 渦流可使新鮮的空氣與縫隙中的油氣相混合, 結(jié)果降低了縫隙中的油氣濃度, 使更多的液體蒸發(fā), 以再建立相近的平衡狀態(tài)。在這

3、種情況下, 液體蒸發(fā)的程度取決于邊緣密封與罐壁之間的縫隙面積以及邊緣密封與罐壁垂直接觸面的高度。通過上述分析可以看出, 邊緣密封損耗與密封本身的密封性、密封與罐壁之間縫隙、密封與儲(chǔ)液之間氣相空間大小及密封與罐壁垂直接觸面高度等因素有關(guān)。3邊緣密封損耗估算(注:以下算式為原文書中的算式, 本文未改動(dòng), 故各量的單位仍用英制由于邊緣密封引起的損耗主要由二部分組成, 即邊緣密封靜止蒸發(fā)損耗和抽出損耗。靜止蒸發(fā)損耗主要指發(fā)生在邊緣密封處油氣的蒸發(fā)損耗; 抽出損耗主要指儲(chǔ)液被抽出時(shí)粘附在罐壁上的儲(chǔ)液蒸發(fā)所造成的損耗。邊緣密封引起的靜止蒸發(fā)損耗可按式(1 估算:(1 L S =F r D PM v K c

4、 抽出損耗可按式(2 估算:L W =01943Q CD邊緣密封油氣損耗的機(jī)理比較復(fù)雜, 通過試驗(yàn)研究發(fā)現(xiàn)風(fēng)是導(dǎo)致邊緣密封損耗的主要因素。國(guó)外進(jìn)行的風(fēng)洞試驗(yàn)表明, 向上流過浮頂油罐頂部的空氣在儲(chǔ)罐的上風(fēng)側(cè)浮頂上方產(chǎn)生一個(gè)低壓區(qū), 導(dǎo)致空氣從浮頂?shù)南聜?cè)沿著浮頂周邊向上邊緣密封方向移動(dòng)。穩(wěn)定的風(fēng)可在浮頂上下風(fēng)側(cè)建立壓差, 高壓在下風(fēng)側(cè), 低壓在上風(fēng)側(cè)。浮頂上下風(fēng)側(cè)形成的壓差和空氣流動(dòng)的模式是兩種基本風(fēng)致?lián)p耗產(chǎn)生的原因。一種是壓差引起空氣進(jìn)入浮頂下風(fēng)側(cè)邊緣密封正下面的連續(xù)邊緣氣相空間, 然后空氣沿周邊流過邊緣氣相空間, 在浮頂?shù)纳巷L(fēng)側(cè)使空氣與油氣混合物通過邊緣密封吹出, 因此降低了氣相空間油氣濃度,

5、 使更多的液體蒸發(fā)出來, 以重新建立起相近的平衡狀態(tài)。在這種情況下, 液體蒸發(fā)的程度取決于邊緣密封系統(tǒng)的密封性、邊緣密封與罐壁之間縫隙的大小(2收稿日期:2002201221, 女, 黑龍江人,1984年畢業(yè)于大作者簡(jiǎn)介:何麗娟(1963慶石油學(xué)院化工機(jī)械專業(yè), 獲學(xué)士學(xué)位, 畢業(yè)后一直從事石油化工設(shè)備與機(jī)械設(shè)計(jì)工作, 工程師, 已發(fā)表論文2篇。式中:L S 邊緣密封靜止損耗,lb/a ;F r 邊緣密封損耗系數(shù), 與邊緣密封結(jié)構(gòu)和嚴(yán)密程度有關(guān),lb mol/ft a ;D 儲(chǔ)罐直徑,ft ; P 蒸氣壓函數(shù), 無因次;M v 儲(chǔ)料蒸氣的平均分子量,lb/lb mol ; K c 產(chǎn)品系數(shù);

6、L W 抽出損耗,lb/a ; Q 每年凈流出量,bbl/a ; C 罐壁粘附系數(shù),bbl/1000ft 2; W 1在平均儲(chǔ)存溫度下的儲(chǔ)液平均密連接起來形成一個(gè)環(huán)。鋼滑板一般高為900mm1500mm , 與罐壁形成了較大接觸面積, 鋼滑板的下端延伸到液面以下, 以封閉鋼滑板和浮頂之間的環(huán)形氣相空間。鋼滑板、浮頂邊緣和液面所包圍的環(huán)形空間與大氣的密封, 是通過螺栓和夾子在鋼滑板到浮頂邊緣之間固定一條有涂層的編織物來完成的, 實(shí)現(xiàn)了一次密封。為了減少氣相空間, 一般要求固定在鋼滑板和邊緣板上的密封纖維盡量接近液面, 并在浮頂上提供呼吸閥來消除邊緣氣相空間中的超壓和真空。對(duì)于約200mm 寬的環(huán)

7、形空間, 機(jī)械滑板式密封通常設(shè)計(jì)成能適應(yīng)±130mm 的局部變化, 以滿足密封環(huán)形空間間距的變化。機(jī)械滑板式一次密封具有如下特點(diǎn):1 鋼滑板與罐壁有很長(zhǎng)的接觸長(zhǎng)度, 其密封效果好;2 鋼滑板浸入液體內(nèi), 與邊緣環(huán)形氣相空間實(shí)現(xiàn)了隔離, 更好地控制了液體蒸發(fā)損耗。3 密封壓緊力在使用期間變化很小, 能夠保證長(zhǎng)期的密封效果;4 整體結(jié)構(gòu)有較長(zhǎng)的使用壽命, 一次密封纖維可隨時(shí)更換;5 金屬結(jié)構(gòu)可采用不銹鋼材料以適應(yīng)較嚴(yán)重的腐蝕場(chǎng)合;6 使用很少的非金屬材料, 并且不接觸儲(chǔ)液, 幾乎沒有由于產(chǎn)品破損造成的二次污染, 更換、廢棄處理方便, 并可回收, 處理費(fèi)用低;7 制造、安裝精度要求較高。b

8、 彈性填充式一次密封彈性填充式一次密封是用有涂層的彈性纖維密封袋與罐壁滑動(dòng)接觸。密封袋內(nèi)可填充液體(管式密封 、彈性泡沫(彈性泡沫密封 等材料, 與罐壁實(shí)現(xiàn)接觸密封。密封袋安裝在浮頂?shù)倪吘? 它既可與液體接觸, 也可在密封件與液面之間保留一定的邊緣氣相空間。彈性填充式密封的儲(chǔ)罐經(jīng)常裝有擋雨板或二次密封。彈性填充式密封比較柔軟, 對(duì)于約200mm 寬的環(huán)形空間, 彈性填充式一次密封通常設(shè)計(jì)成能適應(yīng)±100mm 的正常變化, 以滿足密封環(huán)形空間間距的變化。彈性填充式密封具有如下特點(diǎn):1 彈性填充式密封比較柔軟, 能夠適應(yīng)罐壁局部的形狀突變;度,lb/gal 。由上述公式可以看出, 在特定

9、地區(qū)儲(chǔ)存特定產(chǎn)品的外浮頂油罐, 其邊緣密封靜止損耗主要影響因素是邊緣密封損耗系數(shù)F r , 此系數(shù)與邊緣密封結(jié)構(gòu)和嚴(yán)密程度有關(guān); 抽出損耗主要影響因素是每年凈流出量Q 和罐壁粘附系數(shù)C , 罐壁粘附系數(shù)C 取決于罐壁內(nèi)表面粗糙程度及邊緣密封的嚴(yán)密程度。通常抽出損耗比邊緣密封靜止損耗小的多, 因此決定邊緣密封損耗的主要因素為邊緣密封損耗系數(shù)F r 。邊緣密封損耗系數(shù)F r 按式(3 計(jì)算:F r =K r V n(3式中:K r 邊緣密封損耗系數(shù),lb mol/(mile/h n ft a ;4邊緣密封系統(tǒng)結(jié)構(gòu)型式與損耗分析邊緣密封系統(tǒng)主要有三種型式:a 只有一次密封:常用的一次密封有兩種基本形

10、式:1 機(jī)械滑板式密封;2 彈性填充式密封; b 一次密封+擋雨板; c 一次密封+二次密封。411一次密封結(jié)構(gòu)型式與損耗分析a 機(jī)械滑板式一次密封機(jī)械滑板式一次密封是比較常用的密封形式, 目前機(jī)械密封主要有兩種常用結(jié)構(gòu):重錘式和彈簧板結(jié)構(gòu)。機(jī)械密封主要用輕型金屬帶與罐壁作滑動(dòng)接觸, 金屬帶由機(jī)械裝置支撐并頂向罐壁。金屬帶用薄鋼板制成(稱之為滑板 , 鋼滑板互相第23卷第3期何麗娟. 外浮頂油罐邊緣密封型式的選用與油氣損耗412 制造、安裝的精度要求比較低;3 耐磨性較差, 罐壁內(nèi)凹凸不平可能磨損或降低其使用壽命, 因此該種密封主要應(yīng)用在罐內(nèi)壁有涂層的場(chǎng)合;4 密封接觸面積較小, 容易造成蒸發(fā)

11、損耗; 5 在某些情況下有涂層的纖維密封袋與同類烴類產(chǎn)品接觸, 會(huì)降低壽命, 增加維護(hù)成本;6 雖然設(shè)計(jì)成浸液式結(jié)構(gòu), 但在操作過程中很難做到全程浸液, 容易造成更大的蒸發(fā)損耗;7 彈性泡沫密封短期效果非常好, 隨著彈性元件老化及過分變形, 彈性下降, 密封效果降低;8 彈性泡沫密封破損容易造成二次污染, 被油品污染的泡沫很難處理, 無法回收, 環(huán)保性較差, 處理費(fèi)用高;9 密封袋一旦破損即全部失效, 因此對(duì)密封袋性能要求很高。管式密封破損會(huì)造成儲(chǔ)罐內(nèi)儲(chǔ)液污染。412二次密封與擋雨板二次密封可分為兩類:滑板安裝式和邊緣安裝式?；灏惭b式二次密封只與機(jī)械滑板式一次密封一起使用, 它對(duì)于降低因滑板

12、和罐壁之間的縫隙造成的損耗是有效的, 但是不能降低由于一次密封缺陷產(chǎn)生的損耗。邊緣安裝式二次密封蓋住了整個(gè)邊緣氣相空間故更能有效地減少損耗。二次密封除了可以保護(hù)一次密封免遭風(fēng)雨等的破壞, 延長(zhǎng)一次密封的壽命外, 還可以減少揮發(fā)性液體的二次蒸發(fā)。擋雨板為葉片型結(jié)構(gòu), 可用機(jī)械或鉸鏈把擋雨板連接到浮頂上。擋雨板可以保護(hù)一次密封免遭風(fēng)雨等的破壞, 延長(zhǎng)一次密封的壽命。413邊緣密封系統(tǒng)的使用情況液相安裝(或氣相安裝 的彈性填充式一次密封與二次密封一起使用在我國(guó)也比較常見, 此種型式可以把蒸發(fā)損耗減小到比較低的程度, 但由于不可避免地有一定的氣相空間存在, 液體蒸發(fā)損耗稍大。5各種邊緣密封型式綜合分析

13、通過以上介紹, 并根據(jù)使用經(jīng)驗(yàn), 對(duì)各種邊緣密封型式進(jìn)行綜合比較分析, 如表2所示。表2邊緣密封型式綜合比較一次密封壽命使用、維修機(jī)平衡結(jié)械重錘較長(zhǎng)構(gòu), 需清密動(dòng)臂式罐維護(hù)封安裝簡(jiǎn)彈簧較長(zhǎng)單, 可修板式復(fù)彈泡沫式適中可修復(fù)性填充式安裝較密充液式適中難, 維護(hù)封較復(fù)雜性能業(yè)績(jī)?cè)靸r(jià)推薦產(chǎn)品較好多國(guó)外較高國(guó)外較好初期較好, 易失彈性多國(guó)外較高國(guó)外國(guó)外較高, 國(guó)內(nèi)國(guó)內(nèi)低多較好少國(guó)外較高國(guó)外二次密封結(jié)構(gòu)形式橡膠刮板型舌型壽命使用、維修性能業(yè)績(jī)?cè)靸r(jià)推薦產(chǎn)品適中操作簡(jiǎn)單好多適中國(guó)內(nèi)適中操作簡(jiǎn)單好少適中國(guó)內(nèi)6選用建議目前廣泛使用的邊緣密封系統(tǒng)是一次密封加二次密封型式, 一次密封單獨(dú)使用在國(guó)內(nèi)外已經(jīng)非常少見,

14、一次密封加擋雨板的組合使用在國(guó)內(nèi)外也比較少見。目前國(guó)內(nèi)正在將原先的擋雨板改為二次密封。機(jī)械滑板式一次密封與邊緣安裝式二次密封一起使用, 能夠非常有效地減少損耗, 因?yàn)檫吘壈惭b式二次密封又一次蓋住了整個(gè)邊緣氣相空間, 故能非常有效地減少液體蒸發(fā)損耗。目前這種型式的密封在國(guó)內(nèi)外使用經(jīng)驗(yàn)較多, 尤其在國(guó)外外浮頂油罐大部分都使用機(jī)械密封。密封效果好、經(jīng)濟(jì)耐用是選用密封型式的前提。為了降低油氣蒸發(fā)損耗、減少污染物的排放、保護(hù)環(huán)境、節(jié)約能源, 設(shè)計(jì)者在設(shè)計(jì)外浮頂儲(chǔ)罐時(shí)對(duì)邊緣密封結(jié)構(gòu)型式的選用應(yīng)慎重, 盡量選用國(guó)內(nèi)外使用經(jīng)驗(yàn)多, 技術(shù)成熟可靠的產(chǎn)品。通過以上分析, 建議參照以下順序進(jìn)行選用:a 機(jī)械滑板式一

15、次密封加邊緣安裝式二次密封;b 液相安裝的彈性填充式一次密封加邊緣安裝式二次密封;c 氣相安裝的彈性填充式一次密封加邊緣安裝式二次密封。EXPAN DER UN DER SPECIAL CON DITIONJi Jiang , et al. S IN O PEC Beiji ng design i nsti 2t ute , P. C Beiji ng , 100011Song Q uanxi. L uoyang branch com pany , ref i n 2ery , P. C L uoyang , 471012Abstract In accordance with the high

16、 failure rate of ammonia gas compressor of finishing system in sewage stripping unit , and affecting seriously the long period operation of system ,the reason was analized. The corre 2sponding countermeasures were proposed.K eyw ords Sewage stripping ,Ammonia gas compres 2sor ,Failure analysis ,Coun

17、termeasureAbstract In accordance with two typic conditions of the valve closing time being respective 115s and 6s ,be 2ginning at the overspeed limit of flue gas turbine 2ex 2pander , the overspeed situation under special working condition of coupling rupture for flue gas turbine 2ex 2pander is anal

18、ized. Finally , the protection of flue gas turbine 2expander under special condition is proposed. K eyw ords Flue gas turbine 2exspander ,Special work 2ing condition , Protection , Closing time , Constant pow 2er ,Variable powerAPPL ICATION OF VARIAB L E FREQUENCY SPEE DREGU LATIONTECHN OLOG YONFEE

19、DING PUMP OF STEAM POWER PLANTY ang Guang. Daqi ng pet rochem ical com pany , steam power plant , P. C Daqi ng , 163714THE APPL ICATION OF E 2138FL UE G AS TUR 2BINE 2EXPAN DER ON FCCUW ang Xi nw u , et al. S IN O PEC L uoyang branch com pany , P. C L uoyang , 471012K eyw ords Variable frequency spe

20、ed regulation , Mo 2tor ,Frequency converterAbstract The feature , type selection and actual ap 2plied effect of E 2138flue gas turbine 2expander are men 2tioned emphatically. In combination with the problems existed in energy recovery of flue gas turbine 2expander , the corresponding solutions are

21、made. Same measures and proposal to secure the long period operation of ma 2chine set are given.K eyw ords Main air compressor ,Flue gas turbine 2ex 2pander ,Catalytic cracking ,Energy recoveryTHE INSPECTING EVAL UATION AN D APPL I 2CATIONOFH YD R OGENATE DREACT ORWITH OVERPR OOFE D FERRITE CONTENTM

22、eng Qi ngji u. S IN O PEC i nternational af f ai rs com pany , P. C Beiji ng , 100101Abstract The E3472l overlay welding layer of inside wall for hydrogenated reactor is diphase structure of austenite and ferrite ,according to standard , the ferrite content should be 3%10%,but the ferrite content of

23、 overlay welding layer for hydrogenated reactor imported from French Famatong company is overproofed seri 2ouoly ,several points reached unexpectedly to 30%.By means of repair , nondestructive examination , metallo 2graphic analysis ,hardness testing and strength calcula 2tion ,the reactor can be us

24、ed contineously under design condition , but should enhance the monitor during ser 2vice.K eyw ords Hydrogenated reactor , E347L overlay welding layer ,overproofed ferrite content ,InspectionDOMESTICATION OF PV 525VAL VE FOR PTA UNITREGU LATINGHan Zhengmi n , et al. Jiangsu Yiz heng chemical f iber

25、Co. L et , P. C Yiz heng , 211900Abstract The serious wear corrosion of present PV525regulating valve of PTA unit imported from I 2taly for Y izheng chemical fiber works was occured after only three monthes operation. After the domestication regulating valve core was tried out ,the service life was

26、prolonged about one times ,the expense was cut down one half. This have considerable prospect for applica 2tion.K eyw ords PTA unit ,Valve core ,Regulating velveRIM SEAL T YPE SE L ECTION OF FLOATING R OOF TANK AN D ITS H YD R OCARB ON LOSSHe L ij uan. CN PC Haerbi n branch com pany , P. C Haerbi n

27、, 150056FAI L URE ANALYSIS AN D COUNTERMEA 2Abstract The hydrocarbon loss mechanism and its es 2timated method of floating roof tank are analized. TheSURE ON AMMONIA G AS COMPRESSORcommon structure types of floating roof rim seal at home and abroad are listed. Its strong and weak points are compared

28、 and analized. The seal type selection and the collocation of the first seal with secondary seal are proposed simultaneously.K eyw ords Floating roof tank , Rim seal type , Selec 2tionthe hydrogen sulfide content in storage medium being overproof , it is easy to make the storage vessel shell (inchud

29、ing weld seam and base metal occure hydrogen sulfide stress corrosion or hydrogen blister. The reasons of hydrogen sulfide stress corrosion crack on 1000m 3propylene spherical tank and hydrogen blister on 400m 3L PG spherical tank are analized in detail. The matters needing attention of design mater

30、ial selection , tankRECONSTRUCTION OF CO WASTE B OI L ERFORHEAV YOI LCRACKING UNITHEAT manufacture , construction , installation and maintenace etc. are proposed.serviceCATALYTICK eyw ords Hydrogen sulfide stress corrosion , Hydro 2gen blister , Spherical tank , Design material selection , Construct

31、ion and instalation ,Service maintenaceW ang B aogong , et al. S hengli oil f iel d pet ro 2chemical com plex , P. C Dongyi ng , 257000Abstract In accordance with the low steam produc 2tion and low superheat steam temperature ,a group of low temperature superheaters were provided at the e 2conomizer

32、 top fire box to heat the additional saturated steam; and the ash blow method of waste heat boiler was improved. So the steam production and produced steam temperature was raised effectively.K eyw ords Heavy oil catalytic cracking , CO waste heat boiler ,Low temperature superheaterTHE CORR OSION AN

33、D PR OTECTION OF PR O 2CESS EQUIPMENTS REFINE D SOUR CRU DE OI LZuom i n. Zhenhai ref i ned chemcial Co L t d , P. C N i ngbo , 315207Abstract In refining (or mixed refinign import sul 2fur 2bearing high acid value crude oil ,the process equip 2ments and pipeline are caused serious corrosion. The co

34、rrosion situation of equipments and pipeline of atomo 2spheric vacuum and gas desulfurization unit for Zhenhai refined chemical company in refining import crude oil are mentioned emphatically. The corrosion reason and corrosion mechanism are analized. Some corrosion pro 2tections are presented by th

35、e author combined with ac 2tual work.K eyw ords Sulfur 2bearing high acid value crude oil , Refinement ,Corrosion ,ProtectionDAMAGE REASON AN D STRUCTURE IM 2PR OVEMENT ON R OOF L INING OF ETH Y 2L ENE CRACKING FURNACEMeng Zhaoyue. Daqi ng pet rochemical com pany , the f i rst chem ical plant , P. C Daqi ng , 163714Abstract The reason of roof lining o