返混对气-固反应特性测试和活化能表征的影响

doi:10.11949/0438-1157.20200413

化工学报 ›› 2021, Vol. 72 ›› Issue (3): 1354-1363.DOI: 10.11949/0438-1157.20200413

• 催化、动力学与反应器 • 上一篇下一篇

返混对气-固反应特性测试和活化能表征的影响

胡丹丹^1,^2,³(),耿素龙⁴,曾玺^3,⁵(),王芳^3,⁵,岳君容³,许光文^1,^2,³()

^1.沈阳化工大学资源化工与材料教育部重点实验室，辽宁沈阳 110142
^2.辽宁科技大学化学工程学院，辽宁鞍山 114051
^3.中国科学院过程工程研究所多相复杂系统国家重点实验室，北京 100190
^4.中国石化石油化工科学研究院，北京 100190
^5.北京工商大学生态环境学院，北京 100048

收稿日期:2020-04-20 修回日期:2020-11-08 出版日期:2021-03-05 发布日期:2021-03-05
通讯作者: 曾玺,许光文
作者简介:胡丹丹(1991—)，女，博士研究生，ddhu0826@163.com
基金资助:
国家重点研发计划项目(2018YFF01011401)

Gas back-mixing characteristics and the effects on gas-solid reaction behavior and activation energy characterization

HU Dandan^1,^2,³(),GENG Sulong⁴,ZENG Xi^3,⁵(),WANG Fang^3,⁵,YUE Junrong³,XU Guangwen^1,^2,³()

^1.Key Laboratory on Resources of Chemicals and Materials of Ministry of Education, Shenyang University of Chemical Technology, Shenyang 110142, Liaoning, China
^2.School of Chemical Engineering, University of Science and Technology Liaoning, Anshan 114051, Liaoning, China
^3.State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
^4.Sinpoec Research Institute of Petroleum Processing, Beijing 100190, China
^5.School of Ecology and Environment, Beijing Technology and Business University ; Beijing 100190, China

Received:2020-04-20 Revised:2020-11-08 Online:2021-03-05 Published:2021-03-05
Contact: ZENG Xi,XU Guangwen

摘要/Abstract

摘要：

采用冷态研究和高温反应相结合的方法，探究了气-固反应过程中返混对反应特性和动力学的影响。首先利用脉冲示踪法考察微型流化床内的气体停留时间分布规律和气体返混特性，揭示床内径D、表观气速U_g、介质颗粒粒径d_p对床内气体返混程度的影响，并分析气体流动偏离平推流的程度，得到其最大程度接近平推流的操作范围。进而，选取活性焦燃烧这一典型气-固反应，分析微型流化床反应分析仪中不同程度的返混状态下等温燃烧的反应行为和活化能演变，再现了D、U_g、d_p对反应测试结果的影响，即：随着床径减小及表观气速和介质颗粒粒径的增大，反应器内产物气体经历的返混程度减小，使得产物气体近平推流的输出并被即时检测，获得更好揭示反应本质特性的反应活化能。活化能数值随返混程度的减少而增大，且更易达到稳定反应状态。

关键词: 气体流动, 返混, 停留时间分布, 气固反应, 动力学, 微型流化床

Abstract:

Using the method of combining cold state research and high temperature reaction, the influence of backmixing on the reaction characteristics and kinetics in the gas-solid reaction process was explored. Firstly, the gas residence time distribution (RTD) was measured by the pulse tracer method to investigate the gas back-mixing characteristics in micro fluidized beds. Parametric influences on the gas back-mixing were analyzed with respect to bed diameter (D), superficial gas velocity (U_g) and medium particle size (d_p). The deviation degree of the gas flow in micro fluidized beds from the ideal plug flow of gas was quantitatively compared to obtain the appropriate operating parameters guaranteeing the minimal gas back-maxing or maximal approach to the ideal plug flow. On this basis, the combustion reaction of active coke was tested using the micro fluidized bed reaction analyzer to understand the variation of reaction kinetics with gas back-mixing at different operating conditions. Obvious effects of D, U_g and d_p were identified for the estimated activation energy of the combustion reaction. There was suppressed gas back-mixing by decreasing inner diameter of bed and increasing the particle size and superficial gas velocity. These make the gaseous reaction products reach the online detection instrument quickly via a nearly plug flow throughout the reactor so that the obtained activation energy is generally higher at lower gas-back mixing.

Key words: gas flow, gas back-mixing, residence time distribution, gas-solid reaction, kinetics, micro fluidized bed

中图分类号:

胡丹丹, 耿素龙, 曾玺, 王芳, 岳君容, 许光文. 返混对气-固反应特性测试和活化能表征的影响[J]. 化工学报, 2021, 72(3): 1354-1363.

HU Dandan, GENG Sulong, ZENG Xi, WANG Fang, YUE Junrong, XU Guangwen. Gas back-mixing characteristics and the effects on gas-solid reaction behavior and activation energy characterization[J]. CIESC Journal, 2021, 72(3): 1354-1363.

图/表 9

图1 返混测试用冷态实验装置(a)及微型流化床反应分析仪(b)

Fig.1 Equipment for gas back-mixing measurement (a) and micro fluidized bed reaction analyzer (b)

图2 卷积计算实例(D = 15 mm, Hs = 20 mm, Ug = 5 Umf)

Fig.2 Example of Eout calculation for a typical RTD test in a bed of D = 15 mm, Hs = 20 mm and Ug = 5 Umf of quartz sand

图3 微型流化床测试的气体产物曲线及数据处理

Fig.3 Generation curve of gaseous product by MFBRA and data treatment approach

图4 不同条件微型流化床系统的气体停留时间分布函数E(t)曲线

Fig.4 Gas residence time distribution curves E(t) for different conditions in the fluidized bed reactors

表2 不同条件下微型流化床内气体RTD特征参数

Table 2 Characteristic parameters of RTDs in micro fluidized bed under different conditions

d_p/μm	D/mm	H_s/mm	U_g/U_mf	$t ˉ$ /s	E(t)_h/s^-1	σ_t²/s²	D_a,g/(m²·s^-1)	Pe_a,g	Δt_a/s	Δt_r/%
90	15	20	5	2.08	0.65	0.470	0.00019	18	0.210	11.1
155	10	20	5	0.64	2.44	0.030	0.00040	27	0.044	7.5
	15	20	3	1.38	1.37	0.098	0.00020	27	0.080	7.6
			4	0.85	1.84	0.054	0.00030	26	0.059	7.4
			5	0.68	2.31	0.035	0.00040	25	0.048	7.5
			6	0.58	2.53	0.030	0.00055	22	0.048	9.1
			7	0.50	2.81	0.024	0.00068	21	0.045	9.9
	20	20	5	0.70	1.79	0.063	0.00070	15	0.081	13.2
185	15	20	5	0.47	4.04	0.010	0.00035	41	0.022	4.9

表2 不同条件下微型流化床内气体RTD特征参数

Table 2 Characteristic parameters of RTDs in micro fluidized bed under different conditions

d_p/μm	D/mm	H_s/mm	U_g/U_mf	$t ˉ$ /s	E(t)_h/s^-1	σ_t²/s²	D_a,g/(m²·s^-1)	Pe_a,g	Δt_a/s	Δt_r/%
90	15	20	5	2.08	0.65	0.470	0.00019	18	0.210	11.1
155	10	20	5	0.64	2.44	0.030	0.00040	27	0.044	7.5
	15	20	3	1.38	1.37	0.098	0.00020	27	0.080	7.6
			4	0.85	1.84	0.054	0.00030	26	0.059	7.4
			5	0.68	2.31	0.035	0.00040	25	0.048	7.5
			6	0.58	2.53	0.030	0.00055	22	0.048	9.1
			7	0.50	2.81	0.024	0.00068	21	0.045	9.9
	20	20	5	0.70	1.79	0.063	0.00070	15	0.081	13.2
185	15	20	5	0.47	4.04	0.010	0.00035	41	0.022	4.9

图5 MFBRA中温度对活性焦燃烧转化率(a) 与反应速率 (b) 的影响

Fig.5 Effect of temperature on conversion (a) and reaction rate (b) during active char combustion in MFBRA

图6 不同转化率下ln(dx/dt)与1/T的拟合关系

Fig.6 Correlation between ln(dx/dt) and 1/T at different conversions

表3 不同温度和转化率条件下的活化能E

Table 3 Reaction activation energy at different temperatures and conversions

Conversion x	E^*/(kJ·mol^-1)
Conversion x	600—750℃	750—900℃
0.1	168.4	30.7
0.2	176.1	27.8
0.3	201.1	26.9
0.4	231.4	28.8
0.5	239.3	36.1
0.6	241.9	41.1
0.7	203.8	52.8
0.8	157.3	71.1
0.9	108.8	87.5
average	237.5	44.8

图7 不同气体返混条件下活性焦燃烧反应活化能变化趋势

Fig.7 Variation of activation energy in active char combustion under different gas back-mixing conditions

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返混对气-固反应特性测试和活化能表征的影响

Gas back-mixing characteristics and the effects on gas-solid reaction behavior and activation energy characterization

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