Numerical simulation of 3D fluidized bed biomass gasification based on CPFD

doi:10.11949/0438-1157.20200613

Abstract

Abstract:

Based on computational particle fluid dynamics (CPFD), a three-dimensional bubbling fluidized bed steam-air mixed gasification numerical model was established, and it was verified with experiment trials. The results show that the simulation and experiment have good consistency. Based on the model, the gas distribution and temperature distribution in the gasifier were studied; meanwhile, the biomass properties (particle size, water content, types) and operating conditions (gasification temperature, bed height) were investigated. The results show that there is an optimal value for the impact of biomass particle size on gasification performance, with an average particle size of 0.6 mm being the best; a higher water content will reduce the output of combustible gas and is not conducive to the gasification reaction. Among the four types of biomass, sawdust gasification has the highest efficiency, the largest combustible gas production, and the highest gas calorific value. Rice husk is second only to sawdust but its carbon conversion rate is higher than that of sawdust; increasing the gasification temperature can increase the proportion of combustible gas and increase gasification efficiency; while the change of initial bed height can change the ratio of H₂/CO. This experiment provides a theoretical reference for biomass steam/air gasification, which is helpful for the selection and processing of biomass raw materials, and also facilitates the amplification and optimization of the gasifier.

Key words: biomass, gasification, numerical simulation, CPFD, fluidized bed

摘要：

基于计算颗粒流体动力学（CPFD）建立了三维鼓泡流化床水蒸气-空气混合气化的数值模型，并进行了模型验证，结果表明模拟和实验具有良好的一致性。在该模型的基础上，研究了气化炉内气体分布以及温度分布；同时探究了生物质属性（颗粒粒径、含水率、种类）以及操作条件（气化温度、床料高度）对气化特性的影响。结果表明，生物质颗粒粒径对气化性能的影响存在一个最优值，平均粒径为0.6 mm是最佳的；较高的含水率会降低可燃气体产量，不利于气化反应的进行；四种生物质中，锯末气化的效率最高、可燃气体产量最大、气体热值最高，稻壳仅次于锯末但其碳转化率高于锯末；提高气化温度可以增加可燃气体的比例、提高气化效率；而初始床层高度的变化可以改变H₂/CO的比例。本实验为生物质水蒸气/空气气化提供了理论参考，有助于生物质原料的选取和处理，也有助于气化炉的放大和优化。

关键词: 生物质, 气化, 数值模拟, CPFD, 流化床

CLC Number:

TK 6

REN Xixi,CHEN Qi,YANG Haiping,ZHANG Shihong,WANG Xianhua,CHEN Hanping. Numerical simulation of 3D fluidized bed biomass gasification based on CPFD[J]. CIESC Journal, 2020, 71(12): 5763-5773.

任喜熙,陈祁,杨海平,张世红,王贤华,陈汉平. 基于CPFD方法的流化床生物质气化数值模拟[J]. 化工学报, 2020, 71(12): 5763-5773.

Figures/Tables 22

Fig.1 Schematic diagram of bubbling fluidized bed gasification reactor

Table 1 Proximate analysis and ultimate analysis of rice husk

元素分析/%(mass, dry)					工业分析/%(mass, dry)				HHV/ (MJ/kg)
C	H	N	S	O	FC	V	M	Ash	HHV/ (MJ/kg)
38.43	2.97	0.49	0.07	36.36	14.99	55.54	9.95	19.52	15.68

Table 2 Governing equations[18-19,21]

名称	控制方程
连续性方程	$? ? t α g ρ g + ? · α g ρ g u g = δ m ˙ s, ????? δ m ˙ s = - ? f d m s d t d m s d u s d T s$
动量方程	$? ? t α g ρ g u g + ? ? α g ρ g u g u g = - α g ? p + α g ρ g g + ? ? τ g + F$
组分输运方程	$? ? t α g ρ g Y g, i + ? ? α g ρ g Y g, i u g = ? ? α g ρ g D g Y g, i + δ m ˙ g, i + δ m ˙ s, i$
能量守恒方程	$? ? t α g ρ g h g + ? ? α g ρ g h g u g = α g ? p ? t + u g ? ? p + φ - ? ? α g q + Q ˙ + S h + q ˙ D$
颗粒运动方程	$A = d u s d t = D s u g - u s + g - 1 α s ρ s ? τ s - ? p ρ s + F s$
颗粒碰撞模型	$τ s = 10 P s α s β m a x α c p - α s, δ 1 - α s$
颗粒能量传递模型	$m s C v d T s d t = ∑ j = 1 N p Q i j + Q s g + Q r a d i + Q r e a c$

Table 2 Governing equations[18-19,21]

名称	控制方程
连续性方程	$? ? t α g ρ g + ? · α g ρ g u g = δ m ˙ s, ????? δ m ˙ s = - ? f d m s d t d m s d u s d T s$
动量方程	$? ? t α g ρ g u g + ? ? α g ρ g u g u g = - α g ? p + α g ρ g g + ? ? τ g + F$
组分输运方程	$? ? t α g ρ g Y g, i + ? ? α g ρ g Y g, i u g = ? ? α g ρ g D g Y g, i + δ m ˙ g, i + δ m ˙ s, i$
能量守恒方程	$? ? t α g ρ g h g + ? ? α g ρ g h g u g = α g ? p ? t + u g ? ? p + φ - ? ? α g q + Q ˙ + S h + q ˙ D$
颗粒运动方程	$A = d u s d t = D s u g - u s + g - 1 α s ρ s ? τ s - ? p ρ s + F s$
颗粒碰撞模型	$τ s = 10 P s α s β m a x α c p - α s, δ 1 - α s$
颗粒能量传递模型	$m s C v d T s d t = ∑ j = 1 N p Q i j + Q s g + Q r a d i + Q r e a c$

Table 3 Heterogeneous kinetic parameters and expressions[18-19]

反应名称	化学方程式	化学反应速率表达式
焦炭燃烧R₁	$C + O 2 → C O 2$	$R 1 = 5.957 × 102 T e x p - 17975 T 6 d p O 2$
二氧化碳气化R₂	$C + C O 2 → 2 C O$	$R 2 = 1.272 m s T e x p - 1.88 × 108 R T C O 2 - ??????? 1.0436 × 10 - 4 m s T 2 e x p - 1.97 × 107 R T - 20.92 C O 2$
水蒸气气化R₃	$C + β H 2 O → 1 - β C O + β - 1 C O 2 + β H 2$	$R 3 = 1.272 m s T e x p - 1.88 × 108 R T H 2 O - ??????? 1.0436 × 10 - 4 m s T 2 e x p - 5.25 × 107 R T - 17.29 C O$
甲烷化反应R₄	$C + 2 H 2 → C H 4$	$R 4 = 1.368 × 10 - 3 m s T e x p - 8087 T - 7.087 H 2 - ??????? 0.151 m s T 0.5 e x p - 13578 T - 0.372 C H 4 0.5$

Table 3 Heterogeneous kinetic parameters and expressions[18-19]

反应名称	化学方程式	化学反应速率表达式
焦炭燃烧R₁	$C + O 2 → C O 2$	$R 1 = 5.957 × 102 T e x p - 17975 T 6 d p O 2$
二氧化碳气化R₂	$C + C O 2 → 2 C O$	$R 2 = 1.272 m s T e x p - 1.88 × 108 R T C O 2 - ??????? 1.0436 × 10 - 4 m s T 2 e x p - 1.97 × 107 R T - 20.92 C O 2$
水蒸气气化R₃	$C + β H 2 O → 1 - β C O + β - 1 C O 2 + β H 2$	$R 3 = 1.272 m s T e x p - 1.88 × 108 R T H 2 O - ??????? 1.0436 × 10 - 4 m s T 2 e x p - 5.25 × 107 R T - 17.29 C O$
甲烷化反应R₄	$C + 2 H 2 → C H 4$	$R 4 = 1.368 × 10 - 3 m s T e x p - 8087 T - 7.087 H 2 - ??????? 0.151 m s T 0.5 e x p - 13578 T - 0.372 C H 4 0.5$

Table 4 Homogeneous kinetic parameters and their expressions[6,18-19,25]

反应名称	化学方程式	化学反应速率表达式
一氧化碳燃烧R₅	$C O + 0.5 O 2 → C O 2$	$R 5 = 5.62 × 1012 e x p - 133031 R T C O O 2 0.5$
氢气燃烧R₆	$H 2 + 0.5 O 2 → H 2 O$	$R 6 = 5.159 × 1015 T - 1.5 e x p - 28517 R T O 2 H 2 1.5$
甲烷燃烧R₇	$C H 4 + 2 O 2 → C O 2 + 2 H 2 O$	$R 7 = 3.552 × 1011 T - 1 e x p - 130530 R T O 2 C H 4$
甲烷与蒸汽反应R₈	$C H 4 + H 2 O → 3 H 2 + C O$	$R 8 = 3.0 × 108 e x p - 125000 R T H 2 O C H 4$
水煤气转化反应R₉	$C O + H 2 O ? C O 2 + H 2$	$R 9 = 7.68 × 1010 T e x p - 304641 R T C O 0.5 H 2 O - ???????? 6.4 × 109 T e x p - 326425.7 R T H 2 0.5 C O 2$

Table 4 Homogeneous kinetic parameters and their expressions[6,18-19,25]

反应名称	化学方程式	化学反应速率表达式
一氧化碳燃烧R₅	$C O + 0.5 O 2 → C O 2$	$R 5 = 5.62 × 1012 e x p - 133031 R T C O O 2 0.5$
氢气燃烧R₆	$H 2 + 0.5 O 2 → H 2 O$	$R 6 = 5.159 × 1015 T - 1.5 e x p - 28517 R T O 2 H 2 1.5$
甲烷燃烧R₇	$C H 4 + 2 O 2 → C O 2 + 2 H 2 O$	$R 7 = 3.552 × 1011 T - 1 e x p - 130530 R T O 2 C H 4$
甲烷与蒸汽反应R₈	$C H 4 + H 2 O → 3 H 2 + C O$	$R 8 = 3.0 × 108 e x p - 125000 R T H 2 O C H 4$
水煤气转化反应R₉	$C O + H 2 O ? C O 2 + H 2$	$R 9 = 7.68 × 1010 T e x p - 304641 R T C O 0.5 H 2 O - ???????? 6.4 × 109 T e x p - 326425.7 R T H 2 0.5 C O 2$

Table 5 Simulated boundary conditions and parameters[7,15,18,27-29]

参数	数值	参数	数值
生物质入口质量流率/(kg/h)	0.3	时间步长（Δt）/s^-1	0.0001
生物质颗粒直径/mm	0.25~0.35	粒子与壁面的法线动量保留系数，e_n	0.3
生物质颗粒密度/(kg/m³)	750	粒子与壁面的切线动量保留系数，e_t	0.99
焦炭密度/(kg/m³)	1300	固相应力模型的无量纲常数，β	3
沙粒密度/(kg/m³)	2300	固相应力模型的无量纲常数，σ	10^-8
气化温度/℃	800	固相最大堆积密度下的体积分数，α_cp	0.6
压力/Pa	101325	碰撞最大动量重定向，ξ	40%

Fig.2 Change of outlet gas mass flow rate with time

Table 6 Sand particle size distribution

Size/μm	Mass fraction/%
<250	2.5
250—400	8.3
400—500	18.7
500—600	56.5
600—700	9.4
>700	4.6

Fig.3 Variation of outlet gas mole fraction with the number of grids

Fig.4 Comparison of experimental data and simulated data

Fig.5 The average distribution of gas changes along the axis of the gasifier (ER=0.3, S/B=0.5)

Fig.6 Fluid temperature changes along the axis

Fig.7 Contour of fluid temperature changing along the axis

Fig.8 Effect of particle size on the mole fraction of syngas （800℃，ER=0.35，S/B=0.5）

Fig.9 Effect of particle size on CGE, LHV and carbon conversion rate（800℃，ER=0.35，S/B=0.5）

Fig.10 Effect of biomass moisture content on the mole fraction of syngas (800℃, ER=0.35, S/B=0.5)

Table 7 Gas composition of pyrolysis experiment

原料	气体成分/%（体积）
原料	H₂	CO₂	H₂O	CH₄	CO
稻壳	1.72	23.27	8.04	13.58	53.39
锯末	1.71	25.86	11.60	12.24	48.59
树皮	1.80	30.80	9.31	11.48	46.61
玉米秸秆	1.86	28.27	11.29	12.58	45.99

Table 8 Industrial analysis and elemental analysis of the four biomass

原料	元素分析/%(mass)						工业分析/%(mass)				LHV/ (MJ/kg)
原料	C_ad	H_ad	O_ad	N_ad	S_ad	M_ad	FC_ad	V_ad	A_ad	M_ad	LHV/ (MJ/kg)
稻壳	40.11	5.28	35.59	0.32	0.07	6.2	15.65	65.7	12.45	6.2	15.55
锯末	45.82	5.63	38.69	0.32	0.12	8.91	16	74.59	0.5	8.91	16.91
树皮	38.39	5.03	31.41	0.53	0.11	11.6	14.64	60.83	12.93	11.6	14.5
玉米秸秆	30.64	4.07	29.9	0.87	0.1	8.6	16.71	48.87	25.82	8.6	11.12

Fig.11 Combustible gas production from different biomass gasification（800℃,ER=0.35,S/B=0.5）

Fig.12 CGE, LHV and carbon conversion rate of different biomass gasification（800℃,ER=0.35,S/B=0.5）

Fig.13 Effect of gasification temperature on gas production (ER=0.35, S/B=0.5)

Fig.14 Effect of initial bed height on outlet gas mole fraction (ER=0.35, S/B=0.5)

References 29

1	Cheng Y, Thow Z, Wang C H. Biomass gasification with CO2 in a fluidized bed[J]. Powder Technology, 2016, 296: 87-101.
2	虞君武, 何榕, 张衍国. 鼓泡流化床中生物质气化的数值模拟[J]. 燃烧科学与技术, 2014, (6): 471-477.
	Yu J W, He R, Zhang Y G. Numerical simulation of biomass gasification in bubbling fluidized bed[J]. Journal of Combustion Science and Technology, 2014, (6): 471-477.
3	苏德仁, 刘华财, 周肇秋, 等. 生物质流化床氧气-水蒸气气化实验研究[J]. 燃料化学学报, 2012, 40(3): 309-314.
	Su D R, Liu H C, Zhou Z Q, et al. Experimental study on oxygen-water vaporization of biomass fluidized bed[J]. Journal of Fuel Chemistry, 2012, 40(3): 309-314.
4	Gerber S, Behrendt F, Oevermann M. An Eulerian modeling approach of wood gasification in a bubbling fluidized bed reactor using char as bed material[J]. Fuel, 2010, 89(10): 2903-2917.
5	Yu X, Blanco P H, Makkawi Y, et al. CFD and experimental studies on a circulating fluidised bed reactor for biomass gasification[J]. Chemical Engineering and Processing-Process Intensification, 2018(130): 284-295.
6	Eri Q, Peng J, Zhao X. CFD simulation of biomass steam gasification in a fluidized bed based on a multi-composition multi-step kinetic model[J]. Applied Thermal Engineering, 2018, 129: 1358-1368.
7	Kraft S, Kirnbauer F, Hofbauer H. CPFD simulations of an industrial-sized dual fluidized bed steam gasification system of biomass with 8 MW fuel input[J]. Applied Energy, 2017, 190: 408-420.
8	Radmanesh R, Chaouki J, Guy C. Biomass gasification in a bubbling fluidized bed reactor: experiments and modeling[J]. AIChE Journal, 2006, 52(12): 4258-4272.
9	Shayan E, Zare V, Mirzaee I. Hydrogen production from biomass gasification; a theoretical comparison of using different gasification agents[J]. Energy Conversion and Management, 2018, 159: 30-41.
10	Fremaux S, Beheshti S M, Ghassemi H, et al. An experimental study on hydrogen-rich gas production via steam gasification of biomass in a research-scale fluidized bed[J]. Energy Conversion and Management, 2015, 91: 427-432.
11	Pauls J H, Mahinpey N, Mostafavi E. Simulation of air-steam gasification of woody biomass in a bubbling fluidized bed using Aspen Plus: a comprehensive model including pyrolysis, hydrodynamics and tar production[J]. Biomass and Bioenergy, 2016, 95: 157-166.
12	车德勇, 李少华, 韩宁宁, 等. 生物质流化床空气-水蒸气气化模拟[J]. 中国电机工程学报, 2012, 32(35): 101-106.
	Che D Y, Li S H, Han N N, et al. Simulation of air-water vaporization of biomass fluidized bed[J]. Proceedings of the CSEE, 2012, 32(35): 101-106.
13	Zhao L, Lu Y. Hydrogen production by biomass gasification in a supercritical water fluidized bed reactor: a CFD-DEM study[J]. The Journal of Supercritical Fluids, 2018, 131: 26-36.
14	Cardoso J, Silva V, Eusébio D, et al. Comparative 2D and 3D analysis on the hydrodynamics behaviour during biomass gasification in a pilot-scale fluidized bed reactor[J]. Renewable Energy, 2019, 131: 713-729.
15	Di Nardo A, Calchetti G, Stendardo S. Modeling and simulation of an oxygen-blown bubbling fluidized bed gasifier using the computational particle-fluid dynamics (CPFD) approach[J]. Journal of Applied Fluid Mechanics, 2018, 11(4): 825-834.
16	Xie J, Zhong W, Jin B, et al. Eulerian–Lagrangian method for three-dimensional simulation of fluidized bed coal gasification[J]. Advanced Powder Technology, 2013, 24(1): 382-392.
17	Loha C, Chattopadhyay H, Chatterjee P K. Energy generation from fluidized bed gasification of rice husk[J]. Journal of Renewable & Sustainable Energy, 2013, 5(4): 1367-1377.
18	Loha C, Chattopadhyay H, Chatterjee P K. Three dimensional kinetic modeling of fluidized bed biomass gasification[J]. Chemical Engineering Science, 2014, 109(16): 53-64.
19	Snider D M, Clark S M, Rourke P J. Eulerian–Lagrangian method for three-dimensional thermal reacting flow with application to coal gasifiers[J]. Chemical Engineering Science, 2011, 66(6): 1285-1295.
20	Smagorinsky J S. General circulation experiments with the primitive equations (I): The basic experiment[J]. Monthly Weather Review, 1963, ( 91): 99-164.
21	Wang S, Luo K, Hu C, et al. Impact of operating parameters on biomass gasification in a fluidized bed reactor: an Eulerian-Lagrangian approach[J]. Powder Technology, 2018, 333: 304-316.
22	Gungor A. Two-dimensional biomass combustion modeling of CFB[J]. Fuel, 2008, 87(8): 1453-1468.
23	Thapa R K, Pfeifer C, Halvorsen B M. Modeling of reaction kinetics in bubbling fluidized bed biomass gasification reactor[J]. Energy and Environment, 2014, 5(1): 35-44.
24	de Souza-Santos M L. Comprehensive modelling and simulation of fluidized bed boilers and gasifiers[J]. Fuel, 1989, 68(12): 1507-1521.
25	Gómez-barea A, Leckner B. Modeling of biomass gasification in fluidized bed[J]. Progress in Energy & Combustion Science, 2010, 36(4): 444-509.
26	Gonzalo C. Kinetics of CO2 gasification for coals of different ranks under oxy-combustion conditions[J]. Combustion & Flame, 2013, 160(2): 411-416.
27	Chen C, Werther J, Heinrich S, et al. CPFD simulation of circulating fluidized bed risers[J]. Powder Technology, 2013, 235: 238-247.
28	Abbasi A, Ege P E, de Lasa H I. CPFD simulation of a fast fluidized bed steam coal gasifier feeding section[J]. Chemical Engineering Journal, 2011, 174(1): 341-350.
29	Ku X, Li T, Løvås T. Influence of drag force correlations on periodic fluidization behavior in Eulerian-Lagrangian simulation of a bubbling fluidized bed[J]. Chemical Engineering Science, 2013, 95: 94-106.

[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]	Zhewen CHEN, Junjie WEI, Yuming ZHANG. System integration and energy conversion mechanism of the power technology with integrated supercritical water gasification of coal and SOFC [J]. CIESC Journal, 2023, 74(9): 3888-3902.
[7]	Jiali ZHENG, Zhihui LI, Xinqiang ZHAO, Yanji WANG. Kinetics of ionic liquid catalyzed synthesis of 2-cyanofuran [J]. CIESC Journal, 2023, 74(9): 3708-3715.
[8]	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.
[9]	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.
[10]	Jiaqi CHEN, Wanyu ZHAO, Ruichong YAO, Daolin HOU, Sheying DONG. Synthesis of pistachio shell-based carbon dots and their corrosion inhibition behavior on Q235 carbon steel [J]. CIESC Journal, 2023, 74(8): 3446-3456.
[11]	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.
[12]	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.
[13]	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.
[14]	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.
[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.