Impact of turbulence model in coupled simulation of ethylene cracking furnace

doi:10.11949/j.issn.0438-1157.20181129

Abstract

Abstract:

The ethylene cracking furnace equipped with the bottom burner and the side wall burner is more and more widely used. Different combustion modes affect the turbulent flow state in the furnace. Considering the turbulent flow in the cracking furnace and the gas injection, the combustion and heat transfer are strong. The nonlinear coupling effect, for this purpose, explores the influence of different turbulence models in the cracking furnace/reactor coupling simulation is critical for the precise design and optimization of the cracking furnace. In this paper, a coupling simulation for a 100000 t industrial ethylene cracking furnace was carried out for different turbulence models. The turbulent flow model established by the standard k-ε model, RNG k-ε and Realizable k-ε model was evaluated by CFD numerical simulation. The simulation results of the three turbulence models are compared with the industrial data. The distribution of velocity, temperature and turbulence capacity in the cracking furnace is analyzed. The results show that the Realizable k-ε model is superior to the other two models in flame stability and reaction efficiency. And based on the Realizable k-ε turbulence equation, the calculation results of the heat flux and the outer wall temperature distribution of the furnace tube are closer to the actual working conditions.

Key words: turbulent flow, CFD, numerical simulation, cracking furnace, reactor coupling

摘要：

配备底部烧嘴和侧壁烧嘴的乙烯裂解炉应用越来越广泛，不同燃烧模式影响着炉膛内湍流流动状态，考虑到裂解炉中湍流流动与燃气喷料、燃烧和传热有较强的非线性耦合作用，为此探究不同湍流模型在裂解炉/反应器耦合模拟中的影响对于裂解炉的精确设计和优化至关重要。针对不同湍流模型对某十万吨工业乙烯裂解炉进行了耦合模拟，利用CFD数值模拟对采用标准k-ε模型、RNG k-ε和Realizable k-ε模型所建立的湍流流动模型进行评估。将三种湍流模型的模拟结果与工业数据进行比较，重点分析了裂解炉内的速度、温度、湍流能力等参数的分布情况，表明Realizable k-ε模型在火焰稳定性、反应效率等方面优于其他两种模型，且基于Realizable k-ε湍流方程的反应管模型在热通量、炉管外壁温度分布计算结果更接近实际工况。

关键词: 湍流, 计算流体力学, 数值模拟, 乙烯裂解炉, 反应器耦合

CLC Number:

Chengzhen NI, Wenli DU, Guihua HU. Impact of turbulence model in coupled simulation of ethylene cracking furnace[J]. CIESC Journal, 2019, 70(2): 450-459.

倪城振, 杜文莉, 胡贵华. 乙烯裂解炉耦合模拟中湍流模型的影响分析[J]. 化工学报, 2019, 70(2): 450-459.

Figures/Tables 14

Fig.1 SL-II cracking furnace structure

Table 1 Cracking furnace structure size and operating conditions

Item	Parameters
furnace segment
length (x-direction)/m	18.94
width (y-direction)/m	3.56
height (z-direction)/m	13.707
number of floor burners	36
number of wall burners	48
firing condition
fuel gas ?ow rate in bottom/(kg/s)	1.2439
fuel gas ?ow rate in side/(kg/s)	0.2025
oxygen excess/% (vol)	2
fuel composition/%(mass)
CH₄	97.686
H₂	0.516
CO	0.897
C₂H₄	0.899
reactor coils
number of reactor tubes	24
number of passes	2
inlet tube diameter×10³/m	64
outlet tube diameter×10³/m	121
thickness of tube×10³/m	6.5
feed rate/(kg/s)	11.11
steam dilution/(kg/kg)	0.6
coil inlet temperature/K	883
coil outlet pressure/kPa	206

Fig.2 Flue gas z-velocity component along width of furnace in plane 0.525 m at different heights

Fig.3 Temperature distribution of turbulence model in plane 0.225 m

Fig.4 Turbulence intensity distribution of turbulence model in plane 0.525 m

Fig.5 Turbulent flow energy of different turbulence models along height of furnace

Fig.6 Turbulent dissipation rate of different turbulence models along height of furnace

Fig.7 Turbulent viscosity of different turbulence models along height of furnace

Fig.8 NO concentration distribution of turbulence model in plane 0.225m

Fig.9 Distribution of NO mass fraction along height of furnace in different turbulence models

Fig.10 Heat flux of different turbulence models and temperature distribution curve of outer wall of furnace tube

Fig.11 Comparison of Prandtl numbers for different turbulence models

Table 2 Comparison of simulated and industrial values between different turbulences

项目	工业值	标准 k-ε模型	Realizable k-ε模型	RNG k-ε模型
出口油气温度/K	1108	1102.8	1104.6	1099.6
最大管壁温度/K	1247.6	1251.9	1253.5	1260.4
过剩氧含量/%(vol)	2	1.81	1.90	1.90
炉管油气压降/MPa	0.0433	0.0350	0.0366	0.0355
P/E	0.68	0.72	0.68	0.0.74
乙烯收率/%(mass)	30.143	29.86	29.74.	29.46

G_k	——由平均速度梯度引起的湍流动能
U_i	——速度矢量
Y $_{i}^{*}$	——时间τ^*后细微尺度内组分i的质量分数
μ_t	——湍流黏性系数
ξ^*	——细微尺度长度分数
ρ	——流体密度
σ_ε	——湍流Prandtl数
τ^*	——反应时间尺度

G_k	——由平均速度梯度引起的湍流动能
U_i	——速度矢量
Y $_{i}^{*}$	——时间τ^*后细微尺度内组分i的质量分数
μ_t	——湍流黏性系数
ξ^*	——细微尺度长度分数
ρ	——流体密度
σ_ε	——湍流Prandtl数
τ^*	——反应时间尺度

References 31

1	陈滨. 乙烯工学[M]. 北京: 化学工业出版社, 1997: 63-67.
	ChenB. Ethylene Engineering[M]. Beijing: Chemical Industry Press, 1997: 63-67.
2	韩云龙, 章名耀, 程相杰. 乙烯裂解炉内燃烧、传热与裂解反应的模拟计算[J]. 石油学报（石油加工）, 2006, 22(6): 63-68.
	HanY L, ZhangM Y, ChengX J. Numerical simulation on combustion, heat transfer and naphtha pyrolysis reactions in ethylene cracking furnace[J]. Acta Petrolei Sinica (Petroleum Processing Section), 2006, 22(6): 63-68.
3	蔡树棠, 刘宇陆. 湍流理论[M]. 上海: 上海交通大学出版社, 1993.
	CaiS T, LiuY L. Turbulence Theory[M]. Shanghai: Shanghai Jiao Tong University Press, 1993.
4	王烨. 封闭腔内湍流自然对流换热及工程应用[M]. 北京: 科学出版社, 2015.
	WangY. Turbulent Natural Convection Heat Transfer in Enclosed Cavity and Its Engineering Application [M]. Beijing: Science Press, 2015.
5	李鹏飞, 徐敏义. 精通CFD仿真与案例实战[M]. 北京: 人民邮电出版社, 2017.
	LiP F, XuM Y. Proficient in CFD Simulation and Case Combat [M]. Beijing: Posts and Telecom Press, 2017.
6	GasserH, MohamedP. Predictions of CO and NO_x emissions from steam cracking furnaces using GRI 2.11 detailed reaction mechanism — a CFD investigation[J]. Computers and Chemical Engineering, 2013, 58(45): 68-83.
7	王国清. 裂解炉数值模拟技术进展[J]. 石油化工, 2010, 39(5): 476-481.
	WangG Q. Progress in numerical simulation technology of cracking furnace[J]. Petrochemical Technology, 2010, 39(5): 476-481.
8	HabibiA, MerciB, HeynderickxG J. Multiscale modeling of turbulent combustion and NO_x emission in steam crackers[J]. AIChE Journal, 2007, 53(9): 2384-2398.
9	ShihT H, LiouW W. A new k-ε eddy viscosity model for high Reynolds number turbulent flows: model development and validation[J]. Comput Fluids, 1995, 24 (3) : 227-238.
10	ArmanB, RabasT J. Two-layer-model predictions of heat transfer inside enhanced tubes[J]. Number Heat Transfer, Part A, 1994, 25: 727-741.
11	肖志祥, 李凤蔚, 鄂琴. 三种湍流模型模拟能力的对比 [J]. 西北工业大学学报, 2002, 20(3) : 351-355.
	XiaoZ X, LiF W, E Q. Comparison of three turbulence model simulation capabilities[J]. Journal of Northwestern Polytechnical University, 2002, 20(3): 351-355.
12	陈银. 涡耗散概念燃烧模型耦合简化机理的多维数值模拟[D]. 合肥: 中国科学技术大学, 2015.
	ChenY. Multi-dimensional numerical simulation based on eddy dissipation concept combustion model coupling reduced chemical reaction[D]. Hefei: University of Science and Technology of China, 2015.
13	刘时涛. SL-Ⅱ型工业乙烯裂解炉内燃烧传热与裂解反应的耦合模拟[J]. 化工学报, 2011, 62(5): 1308-1318.
	LiuS T. Coupled simulation of combustion with heat transfer and cracking reaction in SL-Ⅱ industrial ethylene [J]. CIESC Journal, 2011, 62(5): 1308-1318.
14	王菁. 大型燃气乙烯裂解炉燃烧过程的模拟研究 [D]．天津: 天津大学, 2016.
	WangJ. The simulation of the combustion process for the large-scale ethylene cracking furnace [D]. Tianjin: Tianjin University, 2016.
15	毕文涛, 郭英锋. 乙烯裂解炉管内裂解反应的CFD模拟[J]. 天津科技大学学报, 2008, 23(1): 49-52.
	BiW T, GuoY F. CFD simulation of cracking reaction in ethylene cracking furnace[J]. Journal of Tianjin University of Science and Technology, 2008, 23(1): 49-52.
16	DenisonM K, WebbB W. A spectral line-based weighted-sum-of-gray-gases model for arbitrary RTE solvers[J]. Journal of Heat Transfer, 1993, 115(4), 1002–1013.
17	蓝兴英, 高金森, 徐春明. 乙烯裂解炉内传递和反应过程综合数值模拟研究（Ⅲ）: 炉膛内燃烧和传热过程的数值模拟[J]. 石油学报(石油加工), 2004, 20(1): 46-48.
	LanX Y, GaoJ S, XuC M. Numerical simulation study on the transfer and reaction process in ethylene pyrolyzer（Ⅲ）: Numerical simulation of combustion and heat transfer process in furnace[J]. Acta Petrolei Sinica (Petroleum Processing Section), 2004, 20(1): 46-48.
18	孙明波, 白雪松. 湍流燃烧火焰面模式理论及应用 [M]. 北京: 科学出版社, 2014.
	SunM B, BaiX S. Theory and Application of Turbulent Combustion Flame Surface Mode [M]. Beijing: Science Press, 2014.
19	ChenQ. Comparison of different k-ε models for indoor air flow computations[J]. Numerical Heat Transfer, Part B, 1995, 28: 353-369.
20	蒲宁. 航空发动机燃烧室数值仿真中湍流模型的比较研究 [D]. 沈阳: 沈阳航空工业学院, 2009.
	PuN. Comparison of turbulence models for aero-engine combustor numerical simulation[D]. Shenyang: Shenyang Aerospace University, 2009.
21	StefanidisG D, MerciB. CFD simulations of steam cracking furnaces using detailed combustion mechanisms[J]. Computers and Chemical Engineering, 2006, 30: 635-649.
22	HuG H, CarlM S. Impact of radiation models in coupled simulations of steam cracking furnaces and reactors[J]. Industrial & Engineering Chemistry Research, 2015, 54(9): 2453-2465.
23	申海女, 何细藕. 计算流体力学在裂解炉设计上的应用[J]. 乙烯工业, 2004, 16(4): 34-37.
	ShenH N, HeX O. Application of computational fluid dynamics in design of cracking furnace[J]. Journal of Ethylene Industry, 2004, 16(4): 34-37.
24	ZhangY, QianF. Impact of flue gas radiative properties and burner geometry in furnace simulations[J]. AIChE Journal , 2015, 61(3): 936-954.
25	WuH L, PengX F, YeP, et al. Simulation of refrigerant flow boiling in serpentine tubes[J]. International Journal of Heat and Mass Transfer, 2007, 50(6): 1186-1195.
26	TakamasaT, HazukuT, HibikiT. Experimental study of gas-liquid two-phase flow affected by wall surface wettability[J]. International Journal of Heat and Fluid Flow, 2008, 29(6): 1593-1602.
27	YangZ, PengX F, YeP. Numerical and experimental investigation of two phase flow during boiling in a coiled tube [J]. International Journal of Heat and Mass Transfer, 2008, 51(5): 1003-1016.
28	DziakJ, KubalaM. Heat and mass transfer during thin-film evaporation of two-component liquid solutions [C]//20th European Symposium on Computer Aided Process Engineering. 2010: 613-626.
29	王力军, 蔡久菊. 湍流燃烧混合对NO_x生成的影响[J]. 冶金能源, 2003, 22(4): 22-24.
	WangL J, CaiJ J. Effect of mixture in turbulent combustion on NO_x formation[J]. Energy for Metallurgical Industry, 2003, 22(4): 22-24.
30	LiuZ, BiQ, GuoY, et al. Heat transfer characteristics during subcooled flow boiling of a kerosene kind hydrocarbon fuel in a 1mm diameter channel[J]. International Journal of Heat and Mass Transfer, 2012, 55(20): 4987-4995.
31	HuG H, WangH G. Coupled simulation of an industrial naphtha cracking furnace equipped with long-flame and radiation burners[J]. Computers and Chemical Engineering, 2012, 38(38): 24-34.

[1]	Zhanyu YE, He SHAN, Zhenyuan XU. Performance simulation of paper folding-like evaporator for solar evaporation systems [J]. CIESC Journal, 2023, 74(S1): 132-140.
[2]	Yifei ZHANG, Fangchen LIU, Shuangxing ZHANG, Wenjing DU. Performance analysis of printed circuit heat exchanger for supercritical carbon dioxide [J]. CIESC Journal, 2023, 74(S1): 183-190.
[3]	Zhiguo WANG, Meng XUE, Yushuang DONG, Tianzhen ZHANG, Xiaokai QIN, Qiang HAN. Numerical simulation and analysis of geothermal rock mass heat flow coupling based on fracture roughness characterization method [J]. CIESC Journal, 2023, 74(S1): 223-234.
[4]	Jiahao SONG, Wen WANG. Study on coupling operation characteristics of Stirling engine and high temperature heat pipe [J]. CIESC Journal, 2023, 74(S1): 287-294.
[5]	Siyu ZHANG, Yonggao YIN, Pengqi JIA, Wei YE. Study on seasonal thermal energy storage characteristics of double U-shaped buried pipe group [J]. CIESC Journal, 2023, 74(S1): 295-301.
[6]	Kaijie WEN, Li GUO, Zhaojie XIA, Jianhua CHEN. A rapid simulation method of gas-solid flow by coupling CFD and deep learning [J]. CIESC Journal, 2023, 74(9): 3775-3785.
[7]	Song HE, Qiaomai LIU, Guangshuo XIE, Simin WANG, Juan XIAO. Two-phase flow simulation and surrogate-assisted optimization of gas film drag reduction in high-concentration coal-water slurry pipeline [J]. CIESC Journal, 2023, 74(9): 3766-3774.
[8]	Hao WANG, Zhenlei WANG. Model simplification strategy of cracking furnace coking based on adaptive spectroscopy method [J]. CIESC Journal, 2023, 74(9): 3855-3864.
[9]	Chen HAN, Youmin SITU, Bin ZHU, Jianliang XU, Xiaolei GUO, Haifeng LIU. Study of reaction and flow characteristics in multi-nozzle pulverized coal gasifier with co-processing of wastewater [J]. CIESC Journal, 2023, 74(8): 3266-3278.
[10]	Xiaosong CHENG, Yonggao YIN, Chunwen CHE. Performance comparison of different working pairs on a liquid desiccant dehumidification system with vacuum regeneration [J]. CIESC Journal, 2023, 74(8): 3494-3501.
[11]	Wenzhu LIU, Heming YUN, Baoxue WANG, Mingzhe HU, Chonglong ZHONG. Research on topology optimization of microchannel based on field synergy and entransy dissipation [J]. CIESC Journal, 2023, 74(8): 3329-3341.
[12]	Rui HONG, Baoqiang YUAN, Wenjing DU. Analysis on mechanism of heat transfer deterioration of supercritical carbon dioxide in vertical upward tube [J]. CIESC Journal, 2023, 74(8): 3309-3319.
[13]	Lei XING, Chunyu MIAO, Minghu JIANG, Lixin ZHAO, Xinya LI. Optimal design and performance analysis of downhole micro gas-liquid hydrocyclone [J]. CIESC Journal, 2023, 74(8): 3394-3406.
[14]	Chengying ZHU, Zhenlei WANG. Operation optimization of ethylene cracking furnace based on improved deep reinforcement learning algorithm [J]. CIESC Journal, 2023, 74(8): 3429-3437.
[15]	Kexin HUANG, Tong LI, Anqi LI, Mei LIN. Mode decomposition of flow field in T-junction with rotating impeller [J]. CIESC Journal, 2023, 74(7): 2848-2857.