微波加热干燥煤泥热质传递及其能耗特性分析

doi:10.11949/0438-1157.20230122

化工学报 ›› 2023, Vol. 74 ›› Issue (6): 2382-2390.DOI: 10.11949/0438-1157.20230122

微波加热干燥煤泥热质传递及其能耗特性分析

王光宇¹^,²(), 张锴¹^,²(), 张凯华¹^,², 张东柯³

^1.华北电力大学热电生产过程污染物监测与控制北京市重点实验室，北京 102206
^2.华北电力大学电站能量传递转化与系统教育部重点实验室，北京 102206
^3.西澳大学能源中心（M473），西澳大利亚 6009，澳大利亚

收稿日期:2023-02-17 修回日期:2023-05-11 出版日期:2023-06-05 发布日期:2023-07-27
通讯作者: 张锴
作者简介:王光宇（1991—），男，博士研究生，guangyu15@163.com
基金资助:
国家自然科学基金联合基金重点项目(U1910215)

Heat and mass transfer and energy consumption for microwave drying of coal slime

Guangyu WANG¹^,²(), Kai ZHANG¹^,²(), Kaihua ZHANG¹^,², Dongke ZHANG³

^1.Beijing Key Laboratory of Emission Surveillance and Control for Thermal Power Generation, North China Electric Power University, Beijing 102206, China
^2.Key Laboratory of Power Station Energy Transfer Conversion and System (North China Electric Power University), Ministry of Education, Beijing 102206, China
^3.Centre for Energy (M473), The University of Western Australia, Western Australia 6009, Australia

Received:2023-02-17 Revised:2023-05-11 Online:2023-06-05 Published:2023-07-27
Contact: Kai ZHANG

摘要/Abstract

摘要：

采用微波加热方法考察了煤泥干燥过程基本特征及其热量和质量传递特性，阐述了不同阶段动力学和能耗变化基本规律。结果表明煤泥微波干燥可以分为预热升温、恒速干燥和降速干燥三个阶段，其中自由水主要在预热升温和恒速阶段去除，而结合水则在降速阶段去除。恒速和降速干燥阶段的动力学特征可以采用线性模型和修正的Page模型(Ⅰ)分别描述，进而获得所选样品在降速阶段的表观活化能为3.23 W/g。样品在恒速干燥阶段脱水能耗(2.94~5.90 kJ/g)明显低于预热升温和降速干燥阶段，且脱水能耗随着微波功率(500~800 W)增大或初始质量(150~300 g)增加而逐渐降低。

关键词: 煤泥, 微波, 干燥, 传递过程, 动力学, 能耗

Abstract:

The basic characteristics of the coal slime drying process and its heat and mass transfer characteristics were investigated by microwave heating method, and the basic laws of dynamics and energy consumption changes in different stages were expounded. The results show that the process of microwave drying of coal slime may be divided into three stages, i.e., preheating stage, constant-rate drying stage and decreasing-rate drying stage. The free water within coal slim is removed mainly in the both preheating stage and constant-rate drying stage, whilst the bound water is removed in the decreasing-rate drying stage. The linear model and modified Page Ⅰ model can be used to describe the corresponding kinetic processes in the constant-rate and decreasing-rate stage, respectively. Furthermore, the apparent activation energy of the selected sample in the decreasing-rate stage is obtained as 3.23 W/g. The energy consumption in the constant-rate drying stage ranges from 2.94 kJ/g to 5.90 kJ/g, which is significantly lower than that in the preheating or decreasing-rate drying stage. The energy consumption is decreased gradually with the increase of microwave power ranging from 500 W to 800 W or initial mass from 150 g to 300 g.

Key words: coal slime, microwave, drying, transport processes, kinetics, energy consumption

中图分类号:

TQ 536

王光宇, 张锴, 张凯华, 张东柯. 微波加热干燥煤泥热质传递及其能耗特性分析[J]. 化工学报, 2023, 74(6): 2382-2390.

Guangyu WANG, Kai ZHANG, Kaihua ZHANG, Dongke ZHANG. Heat and mass transfer and energy consumption for microwave drying of coal slime[J]. CIESC Journal, 2023, 74(6): 2382-2390.

图/表 12

表1 煤泥样品工业分析和元素分析

Table 1 Proximate and ultimate analysis of coal slime

样品	工业分析/%(质量)					元素分析/%(质量)					热值Q_b.ad/(MJ/kg)
样品	M_ar	M_ad	A_ad	V_ad	FC_ad	C_ad	H_ad	N_ad	S_ad	O^*_ad	热值Q_b.ad/(MJ/kg)
煤泥	27.82	1.35	26.46	12.31	59.88	61.76	2.86	1.28	0.40	5.89	24.94

图1 煤泥粒径分布

Fig.1 Particle size distribution of coal slime

图2 微波干燥系统示意图1—微波源；2—微波腔；3—干燥器；4—电子天平；5—光纤温度计；6—功率计；7—排风扇；8—计算机

Fig.2 Schematic diagram of microwave drying system

图3 不同功率下煤泥水分随温度变化过程

Fig.3 Variation of moisture of coal slime with temperature under different power levels

图4 不同功率下煤泥的干燥速率特征

Fig.4 Characteristics of coal slime drying rate at various microwave power levels

表2 恒速干燥阶段不同模型的统计分析结果

Table 2 Statistical fitting results of the mathematical models in the constant-rate stage

模型	功率/W	R²	χ²	RSS
Lewis模型 MR=exp(-kt)	500	0.670	0.014	0.154
	600	0.711	0.013	0.130
	700	0.638	0.016	0.115
	800	0.621	0.018	0.110
Page模型 MR=exp(-ktⁿ )	500	0.997	1.091×10^-4	0.001
	600	0.996	1.500×10^-4	0.001
	700	0.999	5.567×10^-5	3.340×10^-4
	800	0.999	2.423×10^-5	1.211×10^-4
修正Page模型(Ⅰ) MR=exp[-(kt) ⁿ ]	500	0.997	1.091×10^-4	0.001
	600	0.996	1.500×10^-4	0.001
	700	0.999	5.567×10^-5	3.340×10^-4
	800	0.999	2.423×10^-5	1.211×10^-4
修正Page模型(Ⅱ) MR=aexp(-ktⁿ )	500	0.997	1.046×10^-4	9.419×10^-4
	600	0.996	1.467×10^-4	0.001
	700	0.999	2.476×10^-5	1.236×10^-4
	800	0.999	1.375×10^-5	5.502×10^-5
线性模型 MR=at+b	500	0.999	4.985×10^-5	4.985×10^-4
	600	0.999	5.872×10^-5	5.285×10^-4
	700	0.999	6.192×10^-5	3.715×10^-4
	800	0.998	1.022×10^-4	5.108×10^-4

图5 恒速干燥阶段含水率MR实验值与线性模型预测值对比

Fig.5 Comparison of experimental and predicted moisture ratios by the linear model in the constant-rate stage

表3 降速干燥阶段不同模型的统计分析结果

Table 3 Statistical fitting results of the mathematical models in the decreasing-rate stage

模型	功率/W	R²	χ²	RSS
Lewis模型 MR=exp(-kt)	500	0.643	0.002	0.024
	600	0.495	0.004	0.020
	700	0.557	0.004	0.022
	800	0.586	0.004	0.021
Page模型 MR=exp(-ktⁿ )	500	0.995	2.887×10^-5	2.887×10^-4
	600	0.990	7.870×10^-5	3.148×10^-4
	700	0.990	8.146×10^-5	4.073×10^-4
	800	0.998	1.192×10^-5	4.768×10^-5
修正Page模型(Ⅰ) MR=exp[-(kt) ⁿ ]	500	0.995	2.883×10^-5	2.883×10^-4
	600	0.990	7.574×10^-5	3.029×10^-4
	700	0.990	8.029×10^-5	4.014×10^-4
	800	0.998	1.189×10^-5	4.756×10^-5
修正Page模型(Ⅱ) MR=aexp(-ktⁿ )	500	0.995	3.566×10^-5	3.209×10^-4
	600	0.978	1.639×10^-4	4.918×10^-4
	700	0.988	9.559×10^-5	3.824×10^-4
	800	0.998	1.456×10^-5	4.369×10^-5
线性模型 MR=at+b	500	0.909	5.728×10^-4	0.006
	600	0.978	1.679×10^-4	6.717×10^-4
	700	0.964	3.613×10^-4	0.002
	800	0.953	5.970×10^-4	0.002

图6 降速干燥阶段含水率MR实验值与修正Page模型(Ⅰ)预测值对比

Fig.6 Comparison of experimental and predicted moisture ratios by the modified Page (Ⅰ) model in the decreasing-rate stage

图7 降速干燥阶段不同微波功率下lnk和W0/P拟合曲线

Fig.7 Fitting curve of lnkvsW0/P with different microwave power levels in the decreasing-rate stage

图8 不同初始质量下煤泥微波干燥特征曲线

Fig.8 Drying curves of coal slime at various initial masses

图9 煤泥微波干燥过程中脱水能耗特征

Fig.9 Characteristics of energy consumption in microwave drying of coal slime

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微波加热干燥煤泥热质传递及其能耗特性分析

Heat and mass transfer and energy consumption for microwave drying of coal slime

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