CFD技术在大型化裂解炉返炉膛配管研究中的应用.pdf

裂解炉乙烯工业2 0 2 4,3 6(1)3 3 3 6ETHYLENE INDUSTRYCFD技术在大型化裂解炉返炉膛配管研究中的应用林江峰，肖佳（中国石化工程建设有限公司，北京10 0 10 1）摘要：返炉膛烧焦是降低裂解炉污染物排放的有效措施之一，返炉膛配管布置对返炉膛烧焦效果有很大影响。文章应用CFD技术对返炉膛配管布置进行数值模拟。计算采用RNGk8 端流模型进行模拟，采用壁面函数StandardWall Fn对近壁面流动修正。计算结果表明：合理的返炉膛配管布置可使烧焦气均匀进入炉膛，不会对正常的操作产生影响。基于CFD技术的模拟计算能够较为准确的预测返炉膛烧焦气在管道内的流动情况，为裂解炉大型化下的返炉膛配管布置提供了技术参考。关键词：裂解炉CFD返炉膛配管烧焦气乙烯装置裂解炉根据裂解原料、工艺流程的不同，可分为气体炉、轻油炉、重油炉等。在裂解炉日常运行生产中，需要对其定期实施在线清焦操作，以除去辐射炉管、急冷换热器中生成的焦，以此提高裂解炉的热效率及超高压蒸汽产量。裂解炉通常采用空气与蒸汽混合的方式进行清焦，在清焦过程中不可避免会产生大量清焦副产物，如小粒径的焦粒。通常做法为设置清焦罐，使烧焦气经清焦罐后进一步分离，固体废渣留在罐底，烧焦气通过罐顶排放至大气为满足日益严格的环保要求,在GB31571一2015石油化学工业污染物排放标准中 2 1对工艺加热炉有机废气排放口的颗粒物指标进行了限制。为此，裂解炉烧焦气均由传统的经清焦罐顶直接向大气排放的方式改进为返炉膛进行烧焦后再排入大气。但根据已投产的裂解炉运行情况看，返炉膛操作对操作人员的要求较高，如操作不当，会造成操作波动，影响裂解炉的正常运行。且随着裂解炉单台规模从最初的2 0 kt/a,到现在的2 0 0 kt/a，甚至3 0 0 kt/a,返炉膛操作难度也进一步提高 3 。根据遇到的实际情况，要求在烧焦气返炉膛的设计中要充分考虑各种因素，以确保裂解炉返炉膛操作的平稳，最大程度降低操作人员的操作难度。李进锋等人借助CFX软件工具,应用CFD技术对某裂解炉返炉膛工况下辐射炉膛内的燃烧、传热、三维湍流等进行了分析 4。随着单台裂解炉规模增大，占地面积的增加，清焦管线的布置也愈发重要 5 。从工艺角度上，返炉膛蒸汽流速越大，对炉膛燃烧影响越大，返炉膛管径应尽可能的扩大，且清焦管线应最大程度的对称布置，以保证烧焦气均匀的分配到每个布置在炉底的烧焦气分布口中。但在实际配管中，除返炉膛管线，还需要在炉底配置燃烧器、空气预热器等多种设备的管线，使清焦管线管径与布置受到了限制。本文借助CFX软件,应用CFD技术，以某2 0 0 kt/a裂解炉为对象，对返炉膛清焦管线的不同配管方案进行研究。1几何模型与计算条件1.1几何模型按照某项目2 0 0 kt/a双辐射段裂解炉的实际尺寸，根据以往15 0 kt/a规模裂解炉返炉膛情况的研究，确定3 种工程可行的返炉膛管道配置方收稿日期：2 0 2 4-0 1-10；修改稿收到日期：2 0 2 4-0 2-19。作者简介：林江峰，男，2 0 17 年毕业于北京化工大学材料科学与工程专业，获工学硕士学位，现从事裂解炉工艺的设计工作，工程师，已发表论文2 篇。.34.案,如图1 所示。在保证计算精度的前提下，将裂解炉多组完乙烯工业全相同的单元模块进行切割，进一步简化了模型，简化后的CFD几何模型见图2。第3 6 卷方案1方案2图1返炉膛管道布置整体方案方案3方案11.2计算条件由流体力学的基本理论分析可知，管内的烧焦气流动的基本方程是一组由连续性方程、运动方程和能量方程构成的微分方程组，反应了流动过程遵循质量守恒、动量守恒与能量守恒的物理本质。计算选用RNGk-湍流模型进行模拟，采用壁面函数Standard Wall Fn对近壁面流动修正。模型人口边界条件采用速度入口，出口边界条件采用压力出口，采用Couple算法进行压力速度耦合计算，压力、动量采用二阶迎风离散格式,湍流动能采用一阶迎风离散格式。本计算人口边界为局部返炉膛管线模型中的烧焦气管线人口，烧焦气组成按蒸汽考虑，人口温度约为6 5 0 K。本文计算域出口为局部返炉膛管线模型中的各烧焦气管线出口，模型假设出口截面压力分布均匀，不同返炉膛口的压力均视为相同，即不考虑炉膛内部的压力分布差异，出口压力(表压)为0 MPa。1.3计算内容为得到本文研究的最佳返炉膛配管布置方案，计算3 种不同返炉膛配管布置下烧焦气的流方案2图2 返炉膛管道布置局部方案烧焦气流速分布见图3 图5。8.000e+017.200e+01(i-s.u)/率6.400e+015.600e+014.800e+014.000e+013.200e+012.400e+011.600e+018.000e+000.000e+008.000e+017.200e+016.400e+01(i-s:u)/率5.600e+014.800e+014.000e+013.200e+012.400e+011.600e+018.000e+000.000e+008.000e+017.200e+016.400e+01(r-5)/率5.600e+014.800e+014.000e+013.200e+012.400e+011.600e+018.000e+000.000e+00方案3门TTTTT234图3 方案一烧焦气流速分布23456789101112出口管口编号图4方案二烧焦气流速分布567891011 12出口管口编号速分布与基准流速情况并进行对比。2计算结果与分析2.1.速度场分布及分析根据模拟计算，3 种不同返炉膛配管布置方案234567891011.12出口管口编号图5 方案三烧焦气流速分布为对图3 图5 有更加清晰直观的了解,将各个方案烧焦气出口速度与基准速度比较做成点状第3 6 卷图，见图6,数据偏差对比见表1。60r50403020100-10-20-30-40方案一；方案二；方案三图6 不同方案烧焦气出口速度偏差对比表1不同方案烧焦气出口速度偏差对比项目方案一标准偏差(sd)2.35变异系数（cv）0.176本文研究引人了标准偏差与变异系数2 个评判指标来评价烧焦气流速分布性能。标准偏差用于反映数据分布的波动范围,其由总体样本的内聚程度决定。一般情况下,离散程度越大,则标准偏差越大,反之离散程度越小，则标准偏差越小，因此可以用标准偏差来表示一组数据分布的幅度大小。而变异系数则是概率分布离散程度中的一个归一化量度,其定义为标准差与平均值之比,它可消除测量尺度和量纲带来的影响，客观的对数据进行比较。变量值的平均水平高，其离散程度的测度值越大，反之越小。从表1可知：在平均线性速度基本相近的情况下，方案三的偏差程度最小，标准偏差为1.8 4，变异系数为0.13 6；而方案二的偏差程度最大，标准偏差为3.3 4,变异系数为0.2 49。因此方案三效果最好,其次是方案一，最后是方案二。从图1和图2 可看出：方案一与方案二总管均为一分三的形式,支管为一分四的形式;而方案三则为总管一分六的形式,支管为一分二的形式。3个方案中,尽管支管分配均为偶数形式，但方案一与方案二总管不能做到偶数分配,因此一分三的3 路不能够保证平均分配,最终导致12 个出口流速偏差变大。而其中方案二总管一分三的中间一路直接由总管直线抽出，该路与两边进人流量差异较大，导致方案二的12 个出口流速偏差最林江峰等.CFD技术在大型化裂解炉返炉膛配管研究中的应用23456789 1011 12出口管口编号方案二3.340.24935大。从3 种方案可得出，采用多级偶数平均分配的效果远好于多级奇数分配。因此，在新建项目中,如条件允许,尽可能的采用多级偶数平均布置返炉膛管线可达到最佳效果。而如遇到在现场空间有限且必须奇数分配的情况下，采用方案一这种一头进入的方式也要优于方案二这类出现总管中间抽出管道的分配方式。2.2方案优化及分析方案二总管为等径形式，3 个支路也为等径形式。如此导致进入中间一路的烧焦气流量远大于两端流量。而方案三总管为一分六型式，虽然做方案三到了平均分配，但两边的流量逐级减少。根据三1.840.136种方案的实际模拟情况，针对方案三进一步进行了优化：一分六总管2 个变径位置由出口6 总管与总管出口7 之间移动到出口4出口5 与出口8 出口9 之间,以确保该根管线各段流速基本一致。该方案CFD烧焦气流速分布速度云图结果见图7。8.000e+017.200e+016.400e+01(r-s.m)/率5.600e+014.800e+014.000e+013.200e+012.400e+011.600e+018.000e+000.000e+00123456789101112出口管口编号图7 方案三（优化）烧焦气流速分布同样，为对结果有一个更加清晰的认识，优化后的方案三与优化前的方案三烧焦气出口速度与基准速度比较见图8,数据偏差对比见表2。6050403020100-10-20-30-4013456789101112出口管口编号方案三（优化前）；方案三（优化后）图8 优化后的方案三烧焦气出口速度偏差对比36.表2 优化后的方案三烧焦气出口速度偏差对比项目方案三（优化前）标准偏差(sd)1.84变异系数(cv）0.136从表2 可看出：经过优化的方案三与优化前的方案三相比，烧焦气出口平均线性速度基本相近,但其标准偏差仅为1.16,变异系数为0.0 8 6,数据分布波动范围进一步缩小。因此，在确保多级偶数平均分配的布置情况下，将总管各段流速保持在同一水平可以使得进人各支管的流量更加均匀，可进一步提升烧焦气返炉膛效果。3结语1)借助CFX软件,应用CFD技术,结合RNGk-湍流模型与壁面函数Standard Wall Fn对近壁面流动修正，对2 0 0 kt/a双辐射段裂解炉3 种不同的返炉膛配管方案进行了数值模拟研究，得出了定性与定量的计算结果,并在此基础上进一步优化模型，为今后设计和优化大型化裂解炉返炉膛配管布置提供了参考，表明使用该种方法是可靠与可行的。2)计算结果表明,在工程可行的前提下,裂解炉返炉膛管线配置采用多级偶数平均分配的效果好于多级奇数分配。在这种情况下，配管可以最乙烯工业大程度上做到对称性布置，使得管道内的烧焦气方案三（优化后）流速分配较为平均，能够比较均匀的返回至裂解1.16炉膛。因此,在未来的新建项目中,应在满足工艺0.086要求下，及时做好配管设计整体的统筹规划工作，为清焦管线的布置提供可行性。3）此前的研究结果表明，返炉膛烧焦气流速对燃烧影响较大，需要降低烧焦气进炉膛时的流速以避免对燃烧的影响。但裂解气管线布置也应做到符合经济性原则，不能够无限制的扩大管径。因此，在满足工艺要求下，需要合理的设置管线变径位置，可有效提高返炉膛效果。参考文献：1吴家伟.裂解炉烧焦气排放系统改造效果分析 J.乙烯工业,2 0 18,3 0(1):43-46.2石油化学工业污染物排放标准：GB315712015S.北京：中国环境出版社,2 0 15.3何细藕.中国石化CBL裂解技术的大型化及其应用J.乙烯工业,2 0 15,2 7(1):49-5 2.4 李进锋，何细藕.CFX软件在裂解炉返炉膛烧焦研究中的应用 J.石油化工设备技术,2 0 15,3 6（3）：2 4-28.5 宋斌.浅谈裂解炉返炉膛清焦管线的配管设计 J.科学管理,2 0 17（8）：2 8 9-2 9 0.第3 6 卷乙烯在线兰州石化长庆乙烷制乙烯装置年产量突破8 0 0 kt2023年，兰州石化长庆乙烷制乙烯装置乙烯产量突破8 0 0 kt大关，标志着长庆乙烷制乙烯项目实现“开得起、稳得住、长周期”的生产目标。兰州石化长庆乙烷制乙烯装置采用中国石油自主研发技术建成的大型乙烷制乙烯生产装置，2 0 2 1年8 月3 日建成投产。两年多来，通过不断优化生产指标，装置生产潜能不断释放，提质增效成果显著。装置乙烯收率和能耗指标水平稳居集团公司同类装置前列，被中国石油和化工联合会评为“能效”“水效”领跑者标杆装置。2023年，兰州石化持续推进管理提升，坚持目标导向、问题导向、结果导向，与上游乙烷保供单位建立协作机制，与业务承包单位建立联动管理机制，与检维修保运单位建立一体化生产运行机制，为装置高负荷长周期平稳运行奠定了坚实基础。通过积极开展难题攻关,进行技术改造，破解装置瓶颈，有效释放生产力；精细巡检、精心监盘、精准操作，避免生产波动，及时发现隐患并整改，确保装置平稳运行。摘自中国石油新闻中心2 0 2 4-0 1-0 2ABSTRACTSREVIEW OF SINOPECS ETHYLENE PRODUCTION IN20231Zeng Miaoyang,Zhang Xiaoming,Ma Guofeng,Zhang Wei.Chemical Department of SINOPEC,Beijing,P.C.100728Abstract:The achievement and performance of SINOPEC s ethyleneproduction in 2023 are introduced and analyzed briefly from theaspects of safety and environmental protection,feedstock andoperation optimization,energy saving and consumption reduction,technology research,long-term operation and maintenance,and theobjectives and focus of SINOPECs ethylene production in 2024 areput forward.Key words:SINOPEC;ethylene operation;reviewOVERVIEW OF PETROCHINAS ETHYLENE BUSINESS IN20237Shen Yang,Jiao Lifei,Liu Zhaohui,Liu Xiaozhou.PetroChinaRefining,Chemicals&New materials Company,Beijing,P.C.100007Abstract:This paper summarizes the development of PetroChinasethylene business in 2023,including the ethylene production,ethylene yield,yields of ethylene and propylene,processing lossratio and energy consumption _of its subordinate petrochemicalenterprises,as well as the feedstock optimization,long-termoperation,maintenance,technical modification and technicalmeasures.The_focus of work,concerning long-term optimumoperation of ethylene plants in 2024 is put forward.Key words:PetroChina;ethylene;overviewAPPLICATIONOFDEMULSIFIERAND SCALEINHIBITORINETHYLENEPLANT13Huang Zikun,Wang Zhicheng.SINOPEC-SK(Wuhan)Petrochemi-cal Company Limited,Wuhan,Hubei,P.C.430000Abstract:In recent years,affected by the diversification of rawmaterial to ethylene plant,the emulsification of quench wateroccurred.More and more benzene series remain in the system,leading to serious polymerization in process water system.Thepolymerization of process water not only leads to the blockage ofmultiple heat exchangers in the quench unit,but also may lead tothe shutdown of the quench unit in severe cases,which becomes one.of the main botlenecks for the long-term operation of ethylene plant.A new reagent is used in the quench water system to improve thewater quality and alleviate the emulsification and fouling problems ofthe water system,thus effectively prolonging the operation period ofthe ethylene plant.,Key words:quench water;emulsification;fouling;demulsifer andscale inhibitorCAUSE ANALYSIS AND OPTIMIZATION OF HIGH PRO-PYLENE CONTENTAT BOTTOM OFPROPYLENE RECTI-FICATIONTOWER18Lai Xijiang,Wang Junbin,Zhang Lei,Huang Chaobo,ZhangYanglong.PetroChina Dushanzi Petrochemical Company,Dushanzi,Xinjiang,P.C.833699Abstract:With the increase in the load of propylene rectificationtower in a 220 kt/a ethylene plant,the propylene loss in thecirculating propane at the bottom of tower reached 10%.In order toreduce the propylene loss at the bottom of propylene rectificationtower,Aspen Plus was used to establish a propylene rectificationtower model with the operation data of propylene rectification tower,and the current operation of the propylene rectification tower wasanalyzed and studied.By identifying the deviation points betweenthe simulation data and the actual operating parameters,theoperation of propylene rectification tower was adjusted andoptimized,so as to reduce propylene loss at the bottom of tower,increase propylene production and achieve the purpose of improvingquality and efficiency.Key words:propylene rectification tower;simulation;optimizationCAUSE ANALYSIS OF VIBRATION OF SILENCER ANDPIPELINEAT OUTLET OF RECYCLEGAS COMPRESSORINBUTADIENEUNITAND THE MODIFICATION21Zhang Xiaowei,Feng Min,Sheng Nan,Ju Tao,Jiang Feng.PetroChina Dushanzi Petrochemical Company,Dushanzi,Xinjiang,P.C.833699Abstract:To solve the vibration problem of the silencer and pipelineat the outlet of screw compressor in a chemical company,the gasETHYLENEINDUSTRYStarted Publication in 1989,Quarterly.Mar:2024 Vol.36 No.1 Total 137thpulsation and pipeline vibration of the existing exhaust pipe wasanalyzed,the main causes of the pipeline vibration were identifiedcombined with the measured data of pipeline vibration on site,andsome corresponding modification measures were put forward.Somereasonable vibration elimination measures were taken such asreplacing the silencer with three-chamber impedance compoundsilencer,revamping the exhaust pipe,installing pipe supports andreinforcing the thermocouple branches.After modification,thepressure unevenness at each point inside the exhaust pipe can meetthe requirements of API 619,and the gas pulsation decreased by72%on average.The first-order natural frequency of the exhaustpipe system increased from 4.572 Hz to 8.862 Hz,and the high-order natural frequency was 10%away from the compressorexcitation frequency.The maximum vibration of the silencerdecreased by 64%to 32 mm/s and the maximum vibration of theoutlet pipe decreased by 87.5%to 10 mm/s compared with thosebefore the modification,proving the effectiveness of the modificationmeasures.Key words:screw compressor;silencer;pipeline vibration;mea-sureCAUSE ANALYSIS AND PREVENTIVE MEASURES FORLEAKAGE OF TUBE BUNDLESOF STEAM-WATER HEATEXCHANGERS24Zhang Changsong,Huang Chaobo,Li Wenting,Du Zhiqi,LeiQian.PetroChina Dushanzi Petrochemical Company,Dushanzi,Xin-jiang,P.C.833699Abstract:To solve the leakage of steam-water corrugated-tube heatexchanger in hydrogen plant,the causes of the leakage of heatexchanger tube bundle were analyzed combined with the specificoperating conditions,the analysis results were obtained combinedwith the actual inspection report based on the corrosion mechanismof corrugated tubes in the environment of chlorine-containingmedium,and some specific preventive measures were developedcorrespondingly based on the cause analysis.The corrosion hazardswerecompletely eliminated throughheat exchange tubemodification,the operating cycle of the heat exchanger wasextended,and the long-term operation of the heat exchanger wasensured.Key words:steam-water heat exchanger;corrosion;leakage;improvementCAPACITY EXPANSION SCHEMES OF QUENCH SYSTEMINETHYLENEPLANT28Song Zhiqi,Ma Guomin,Ding Shaohui,Wu Liaosha,Xu Wenming.PetroChina Dushanzi Petrochemical Company,Dushanzi,Xinjiang,P.C.833699Abstract:In 2019,the capacity of a megaton ethylene plant wasexpanded in the overhaul window period,including the installationof an ethane cracking furnace,a viscosity reducing tower system anda toluene extraction system as well as the transformation of relatedsupporting equipment and facilities,so that the capacity reached1.15 million tons per year.This paper analyzes and summarizes theoperation of the ethylene plant after two overhauls in 2015 and 2019respectively,in order to find out the operation bottleneck of quenchsystem and formulate targeted optimization plans.Key words:ethylene plant;quench system;capacity expansion;long period operationAPPLICATION OF CFD TECHNOLOGY IN THE RE-SEARCH ON PIPING LAYOUT FOR RECYCLING DECOK-ING EFFLUENT TO FIREBOX OF LARGE-SCALE CRACK-INGFURNACE33Lin Jiangfeng,Xiao Jia.SINOPEC Engineering Incorporation,Bei-jing,P.C.100101Abstract:Recycling decoking effluent to firebox of cracking furnaceis one of the effective measures to reduce pollutant emissions fromthe cracking furnace,and the piping layout for recycling decokingeffluent to firebox has a significant impact on the decoking effect.This article uses CFD technology to numerically simulate the pipinglayout for recycling decoking effluent to firebox.RNG k-8turbulence model is used for the simulation,and the wall functionStandard Wall Fn is used to correct the near wall flow.Thecalculation results indicate that a reasonable piping layout canensure the even entry of decoking effluent into the firebox withoutABSTRACTSaffecting the normal operation.The simulation calculation based onCFD technology can accurately predict the flow of decoking effluentin pipelines,providing technical reference for the piping layout forrecycling decoking effluent to firebox of large-scale cracking fur-nace.Key words:cracking furnace;CFD;recycling to firebox;piping;decoking effluentINFLUENCE OF OPERATING MODE OF FIVE OPERA-TING CRACKING FURNACES ON QUENCH SYSTEM ANDTHEOPTIMIZATIONMEASURES37Zhang Lei,Luo Lingli,Li Zhonghua,Ren Chongxin,LyuXiaogang.PetroChina Dushanzi Petrochemical Company,Dushanzi,Xinjiang,P.C.833699Abstract:In order to reduce the energy consumption of the 220 kt/aethylene plant in Dushanzi,it was proposed to change the operatingmode of cracking furnace from 6 for operation and 1 standby to 5 foroperation,1 stopped and 1 standby based on the energy consumptionanalysis of the ethylene plant and the current working conditions ofcracking furnace and cracking gas compressor.In order to select theoptimal operating mode of 5 for operation,1 stopped and 1 standby,the working conditions were tested in 5 stages.By comparing thedesign parameters of the No.2 gasoline fractionator(C-103),therelationship between the cracking gas load of the tower and themiddle pumparound and gasoline reflux was optimized and adjusted,ensuring the stable and controlled quench oil viscosity and quenchwater quality.Through optimizing the operating mode of crackingfurnace,the goal of energy saving and consumption reduction of theethylene plant was quickly achieved.Key words:cracking furnace;operating mode;quench system;optimizationCAUSE ANALYSIS AND PREVENTIVE MEASURES FORTUBEBUNDLELEAKAGEINCONDENSER OF CRACKINGGASCOMPRESSOR42Shang Yongfu,Wang Chenyu,Li Wenting,Dai Chuan,GaoWanfeng,PetroChina Dushanzi Petrochemical Company,Dushanzi,Xinjiang,P.C.833699Abstract:The condenser of cracking gas compressor in ethyleneplant is the accessory equipment of cracking gas compressor,and itsleakage will affect the long-term operation of the ethylene plant.Thecauses of tube bundle leakage in the heat exchanger are analyzed,and some corresponding preventive measures are developed to extendthe operation cycle of heat exchanger and reduce the probabilit