Effects of external DC/AC electric fields on particle motions and wall sticking in fluidized bed with electrostatics

doi:10.11949/0438-1157.20210414

Abstract

Abstract:

Regulating the particle motions in fluidized bed reactor can realize the enhancement of the reactor performance. Effects of external DC/AC (direct current/alter current) electric fields on particle motions in the fluidized bed with electrostatics were investigated by cold model experiments, and the method of regulating the wall sticking by the external electric field was established. The results showed that the Coulombic force dominated effects of external DC electric fields on particle motions at lower field strength. DC electric fields from the reactor wall to the center weakened the intensity of particle motions and the fraction of axial particle motions, while DC electric fields with opposite directions led to totally opposite results. At higher field strength, polarization forces dominated effects of external DC electric fields on particle motions and it always weakened the intensity of particle motions. Under external AC electric fields, polarization forces still led to the decrease of particle motions without the existing of Coulombic force. However, when the Coulombic force exists, the periodic change of the electric field strength and direction would make the particles oscillate periodically, which increased the intensity of particle motions. Besides, under the experimental operations in this work, external AC electric field can be used to reduce the wall sticking well. The sinusoidal AC electric field of 2.5 kV / cm and 50 Hz could reduce the adhesion of the bed by 76%. The research results can provide guidance for the safe operation and process enhancement of polyolefin fluidized bed reactors.

Key words: external electric fields, electrostatic, fluidized bed, particle motion, wall sticking, multiphase flow, reaction engineering

摘要：

对流化床反应器中的颗粒运动行为进行调控可达到强化反应器性能的目的。通过冷模实验研究了直流/交流电场对静电流化床中颗粒运动的影响规律与影响机制，建立了通过外加电场调控静电流化床中床层粘壁的方法。结果表明，在低场强条件下，库仑力主导外加直流电场对颗粒运动的影响，由床层壁面指向床层中心的外加直流电场使得颗粒运动强度和轴向颗粒运动分率降低，而由床层中心指向床层壁面的外加直流电场则作用相反；在高场强条件下，极化力主导外加直流电场对颗粒运动的影响，使得颗粒运动强度减弱。在外加交流电场中，无库仑力存在时，极化力仍在高电场强度下使得颗粒运动强度减弱，但当库仑力存在时，电场强度和方向的周期性改变使得颗粒发生周期性摆动，颗粒运动强度增强。在本文的实验条件下，外加交流电场是一种控制床层粘壁的良好方法。2.5 kV/cm、50 Hz的正弦交流电场使得床层粘壁下降76%。研究结果可为聚烯烃流化床反应器的安全运行和过程强化提供指导。

关键词: 外加电场, 静电, 流化床, 颗粒运动, 粘壁, 多相流, 反应工程

CLC Number:

TQ 051.13

Zhengliang HUANG, Peng ZHANG, Yao YANG, Congjing REN, Jingdai WANG, Yongrong YANG. Effects of external DC/AC electric fields on particle motions and wall sticking in fluidized bed with electrostatics[J]. CIESC Journal, 2021, 72(9): 4544-4552.

黄正梁, 张鹏, 杨遥, 任聪静, 王靖岱, 阳永荣. 外加电场对静电流化床中颗粒运动与床层粘壁的调控机制[J]. 化工学报, 2021, 72(9): 4544-4552.

Figures/Tables 11

Fig.1 Schematic diagram of the external electric field enhanced gas-solid fluidized bed

Fig.2 Particle size distribution of wall sheeting in the fluidized bed without electric fields

Fig.3 Variations of acoustic energies with the field strength under effects of DC electric field with different directions

Fig.4 Variations of the standard deviation of pressure fluctuations with the field strength under effects of DC electric field with different directions (H=200 mm)

Fig.5 Particles migration under the effects of Coulombic forces

Table 1 The frequency range of various levels after 5 scales wavelet decomposition

Scale	f/kHz
d₁	125—250
d₂	62.5—125
d₃	31.3—62.5
d₄	15.6—31.3
d₅	7.81—15.6
a₅	0—7.81

Fig.6 Variations of Dc/Df with the field strength of DC electric field at different axial positions

Fig.7 Variations of acoustic energy with the field strength of AC electric field at different axial positions

Fig.8 Variation of standard deviations of pressure fluctuations and the acoustic energy at different heights with the field strength when electrostatics were eliminated

Fig.9 Variations of Dc/Df with the field strength of AC electric field at different axial positions

Fig.10 Variations of Ws with the field strengths in the fluidized bed with different electric fields supplied

References 28

1	郭慕孙, 李洪钟. 流态化手册[M]. 北京: 化学工业出版社, 2008.
	Kwauk M S, Li H Z. Handbook of Fluidization [M]. Beijing: Chemical Industry Press, 2008.
2	Abbasi M, Sotudeh-Gharebagh R, Mostoufi N, et al. Nonintrusive characterization of fluidized bed hydrodynamics using vibration signature analysis[J]. AIChE Journal, 2010, 56(3): 597-603.
3	Wittmann C V, Ademoyega B O. Hydrodynamic changes and chemical reaction in a transparent two-dimensional cross-flow electrofluidized bed(1): Experimental results[J]. Industrial & Engineering Chemistry Research, 1987, 26(8): 1586-1593.
4	Wittmann C V. Hydrodynamic changes and chemical reaction in a transparent two-dimensional cross-flow electrofluidized bed(2): Theoretical results[J]. Industrial & Engineering Chemistry Research, 1989, 28(4): 454-470.
5	van Willigen F K, van Ommen J R, van Turnhout J, et al. Bubble size reduction in a fluidized bed by electric fields[J]. International Journal of Chemical Reactor Engineering, 2003, 1(1): A21.
6	van Willigen F K, van Ommen J R, van Turnhout J, et al. Bubble size reduction in electric-field-enhanced fluidized beds[J]. Journal of Electrostatics, 2005, 63(6/7/8/9/10): 943-948.
7	van Willigen F K, Demirbas B, Deen N G, et al. Discrete particle simulations of an electric-field enhanced fluidized bed[J]. Powder Technology, 2008, 183(2): 196-206.
8	Yang Y, Ge S Y, Zhou Y F, et al. Effects of DC electric fields on meso-scale structures in electrostatic gas-solid fluidized beds[J]. Chemical Engineering Journal, 2018, 332: 293-302.
9	Hendrickson G. Electrostatics and gas phase fluidized bed polymerization reactor wall sheeting[J]. Chemical Engineering Science, 2006, 61(4): 1041-1064.
10	Yamaguchi Y, Suga S, Morikawa M, et al. Method for producing polyolefin:US5525687 [P]. 1995.
11	Park A H, Bi H, Grace J R. Reduction of electrostatic charges in gas-solid fluidized beds[J]. Chemical Engineering Science, 2002, 57(1): 153-162.
12	Goode M, Williams C, Hussein F, et al. Static control in olefin polymerization:US6111034 A [P]. 2000.
13	Wolny A, Opaliǹski I. Electric charge neutralization by addition of fines to a fluidized bed composed of coarse dielectric particles[J]. Journal of Electrostatics, 1983, 14(3): 279-289.
14	Dong K Z, Zhang Q, Huang Z L, et al. Experimental investigation of electrostatic reduction in a gas-solid fluidized bed by an in situ corona charge eliminator[J]. Industrial & Engineering Chemistry Research, 2014, 53(37): 14217-14224.
15	Taillet J. Elimination of static charges in the processing of bulk material[J]. Journal of Electrostatics, 1993, 30: 181-189.
16	Dong K Z, Zhang Q, Huang Z L, et al. Experimental investigation of electrostatic effect on bubble behaviors in gas-solid fluidized bed[J]. AIChE Journal, 2015, 61(4): 1160-1171.
17	Wang J D, Xu Y, Li W, et al. Electrostatic potentials in gas-solid fluidized beds influenced by the injection of charge inducing agents[J]. Journal of Electrostatics, 2009, 67(5): 815-826.
18	Revel J, Gatumel C, Dodds J A, et al. Generation of static electricity during fluidisation of polyethylene and its elimination by air ionisation[J]. Powder Technology, 2003, 135/136: 192-200.
19	Cody G D, Goldfarb D J, Storch G V, et al. Particle granular temperature in gas fluidized beds[J]. Powder Technology, 1996, 87(3): 211-232.
20	He L L, Zhou Y F, Huang Z L, et al. Acoustic analysis of particle-wall interaction and detection of particle mass flow rate in vertical pneumatic conveying[J]. Industrial & Engineering Chemistry Research, 2014, 53(23): 9938-9948.
21	Wang J D, Ren C J, Yang Y R. Characterization of flow regime transition and particle motion using acoustic emission measurement in a gas-solid fluidized bed[J]. AIChE Journal, 2010, 56(5): 1173-1183.
22	Dong K Z, Zhang Q, Huang Z L, et al. Experimental investigation of electrostatic effect on particle motions in gas-solid fluidized beds[J]. AIChE Journal, 2015, 61(11): 3628-3638.
23	Ren C J, Tang Y Q, Wang J D, et al. Online estimation of coke in a circulating fluidized bed based on acoustic emission sensors and multivariate calibration[J]. Industrial & Engineering Chemistry Research, 2011, 50(14): 8420-8429.
24	Zhou Y F, Ren C J, Wang J D, et al. Characterization on hydrodynamic behavior in liquid-containing gas-solid fluidized bed reactor[J]. AIChE Journal, 2013, 59(4): 1056-1065.
25	He Y J, Wang J D, Cao Y J, et al. Resolution of structure characteristics of AE signals in multiphase flow system—from data to information[J]. AIChE Journal, 2009, 55(10): 2563-2577.
26	Stein M, Ding Y L, Seville J P K, et al. Solids motion in bubbling gas fluidised beds[J]. Chemical Engineering Science, 2000, 55(22): 5291-5300.
27	Rokkam R G, Fox R O, Muhle M E. Computational fluid dynamics and electrostatic modeling of polymerization fluidized-bed reactors[J]. Powder Technology, 2010, 203(2): 109-124.
28	Parthasarathy M, Klingenberg D. Electrorheology: mechanisms and models[J]. Materials Science and Engineering: R: Reports, 1996, 17(2): 57-103.

[1]	Ruitao SONG, Pai WANG, Yunpeng WANG, Minxia LI, Chaobin DANG, Zhenguo CHEN, Huan TONG, Jiaqi ZHOU. Numerical simulation of flow boiling heat transfer in pipe arrays of carbon dioxide direct evaporation ice field [J]. CIESC Journal, 2023, 74(S1): 96-103.
[2]	Yue YANG, Dan ZHANG, Jugan ZHENG, Maoping TU, Qingzhong YANG. Experimental study on flash and mixing evaporation of aqueous NaCl solution [J]. CIESC Journal, 2023, 74(8): 3279-3291.
[3]	Ming DONG, Jinliang XU, Guanglin LIU. Molecular dynamics study on heterogeneous characteristics of supercritical water [J]. CIESC Journal, 2023, 74(7): 2836-2847.
[4]	Zhenghao YANG, Zhen HE, Yulong CHANG, Ziheng JIN, Xia JIANG. Research progress in downer fluidized bed reactor for biomass fast pyrolysis [J]. CIESC Journal, 2023, 74(6): 2249-2263.
[5]	Zhihang ZHENG, Junnan MA, Zihan YAN, Chunxi LU. Study on the pressure pulsation characteristics in jet influence zone of riser [J]. CIESC Journal, 2023, 74(6): 2335-2350.
[6]	Juhui CHEN, Qian ZHANG, Lingfeng SHU, Dan LI, Xin XU, Xiaogang LIU, Chenxi ZHAO, Xifeng CAO. Study on flow characteristics of nanoparticles in a rotating fluidized bed based on DEM method [J]. CIESC Journal, 2023, 74(6): 2374-2381.
[7]	Yuanyuan ZHANG, Jiangyuan QU, Xinxin SU, Jing YANG, Kai ZHANG. Gas-liquid mass transfer and reaction characteristics of SNCR denitration in CFB coal-fired unit [J]. CIESC Journal, 2023, 74(6): 2404-2415.
[8]	Zihan YUAN, Shuyan WANG, Baoli SHAO, Lei XIE, Xi CHEN, Yimei MA. Investigation on flow characteristics of wet particles with power-law liquid-solid drag models in fluidized bed [J]. CIESC Journal, 2023, 74(5): 2000-2012.
[9]	Xinya LI, Lei XING, Minghu JIANG, Lixin ZHAO. Research on performance of downhole oil-water separation hydrocyclone enhanced by inverted cone gas injection [J]. CIESC Journal, 2023, 74(3): 1134-1144.
[10]	Shaohang YAN, Tianwei LAI, Yanwu WANG, Yu HOU, Shuangtao CHEN. Visual experimental study on cavitation of R134a in micro clearance [J]. CIESC Journal, 2023, 74(3): 1054-1061.
[11]	Chenghao ZHANG, Jing LUO, Jisong ZHANG. Advances in continuous aerobic oxidation based on nitroxyl radical catalyst in microreactors [J]. CIESC Journal, 2023, 74(2): 511-524.
[12]	Hao XIONG, Xiaoyu LIANG, Chenxi ZHANG, Haolong BAI, Xiaoyu FAN, Fei WEI. Heavy oil to chemicals: multi-stage downer catalytic pyrolysis [J]. CIESC Journal, 2023, 74(1): 86-104.
[13]	Dongwang ZHANG, Hairui YANG, Tuo ZHOU, Zhong HUANG, Shiyuan LI, Man ZHANG. Cold-state experimental study on ash deposition of convection heating surface of biomass boiler [J]. CIESC Journal, 2022, 73(8): 3731-3738.
[14]	Xinhua LIU, Zhennan HAN, Jian HAN, Bin LIANG, Nan ZHANG, Shanwei HU, Dingrong BAI, Guangwen XU. Principle and technology of low-NO _x decoupling combustion based on restructuring reactions [J]. CIESC Journal, 2022, 73(8): 3355-3368.
[15]	Gang WANG, Zhihao XIA, Xiyan LI, Hong ZHANG, Zhennan HAN, Xingfei SONG, Guangwen XU. Effect of atmosphere on active performance of light-burned magnesium oxides from calcined magnesite in fluidized bed [J]. CIESC Journal, 2022, 73(8): 3699-3707.