煤气化细渣陶瓷膜真空脱水试验与数值模拟

doi:10.16085/j.issn.1000-6613.2021-2152

摘要/Abstract

摘要：

气化细渣是煤炭气化过程的废弃物，高效脱水是其资源化利用、减量化处置的必要前提。本文采用陶瓷膜真空过滤系统开展了脱水实验并对脱水过程进行了数值模拟。气化细渣料浆浓度和液下吸附时间影响滤饼厚度且滤饼厚度增加导致水分运移路径增长，使得有效脱水时间增加；滤饼脱水过程的脱水速率值呈现非线性降低趋势且滤饼水分极限值为40%，这与气化细渣物化性质有关；真空度>0.08MPa时气化细渣滤饼中“通道水”能够在约24s有效脱除。Fluent数值模拟过程选用了欧拉模型并确定了陶瓷膜滤板和气化细渣滤饼的阻力系数，脱水过程的实验值与模拟结果误差小于5%，证实了模型可靠性。模拟过程分析了气化细渣脱水过程中压力场和水分含量分布云图的演变规律，结果表明，增加脱水系统真空度、降低滤饼厚度、提高“通道水”比例以及增大气化细渣颗粒等效当量直径能够提高气化细渣脱水效率。此外，陶瓷膜真空脱水过程所得滤液洁净度高且部分指标达到了工业用水的标准。

关键词: 煤气化细渣, 陶瓷膜, 过滤, 脱水特性, 数值模拟

Abstract:

Gasification fine slag (GFS) is the waste of coal gasification process and its efficient dewatering is a prerequisite for its resource utilization and reduction disposal. In this paper, the dewatering experiment and numerical simulation were carried out by using ceramic membrane vacuum filtration system. The gasification fine slag slurry concentration and subaqueous adsorption time affected the filter cake forming thickness, and the increase of filter cake thickness caused increasing water transport path, which extended the effective dewatering time. The dewatering rate value of filter cake dewatering process showed a non-linear decrease trend and there was a limit value of 40% for dewatering process, which was related to the physicochemical properties. When the vacuum degree was less than 0.08MPa, the “channel water” of GFS filter cake can be effectively removed at about 24s. In the Fluent numerical simulation, Euler model was selected to determine the resistance coefficient of ceramic membrane filter plate and GFS filter cake. The error between experimental value and simulation result of dewatering process was less than 5%, which confirmed the reliability of the model. The evolution laws of vacuum pressure field and water content distribution cloud diagram were analyzed during the GFS dewatering process. The results indicated that dewatering efficiency of fine gasification slag can be improved by increasing dewatering vacuum degree, decreasing filter cake thickness and increasing “channel water” ratio and GFS particles equivalent diameter. Moreover, the filtrate obtained from ceramic membrane vacuum dewatering system had high cleanliness and some indexes met the standard of industrial water. The results had guiding significance for improving the dewatering efficiency and reducing energy consumption of GFS dewatering process, which was in line with the policy goal of “Carbon peak and Carbon neutral” in China.

Key words: coal gasification fine slag, ceramic membrane, filtration, dewatering characteristics, numerical simulation

中图分类号:

TD94

郭凡辉, 武建军, 张海军, 郭旸, 刘虎, 张一昕. 煤气化细渣陶瓷膜真空脱水试验与数值模拟[J]. 化工进展, 2022, 41(8): 4047-4056.

GUO Fanhui, WU Jianjun, ZHANG Haijun, GUO Yang, LIU Hu, ZHANG Yixin. Coal gasification fine slag vacuum dewatering by ceramic membrane and numerical simulation[J]. Chemical Industry and Engineering Progress, 2022, 41(8): 4047-4056.

图/表 21

图1 神宁炉气化细渣黑水真空脱水装置图

表1 气化细渣黑水经陶瓷膜真空过滤所得滤液的指标

名称	悬浮物含量/mg·L^-1	浊度/NTU	pH
工业用水标准指标	≤30	≤ 5	6.5～9
滤液指标	6～16	2.95	8.3～8.96

图2 气化细渣黑水真空脱水滤膜及模型构建

表2 滤膜基本物性参数

名称	孔隙率/%	厚度/mm	凹槽平均占比/%	总体积/mm³	总孔隙率/%
涂层	41.46	0.06	—	600	34.71
基材	34.65	6.5	41	73200	—

图3 模拟真空脱水过程的物理模型和网格划分模型

表3 滤膜的多孔介质模型选择

名称	过滤板吸水过程	气化细渣滤饼吸水过程	真空脱水过程
过滤板	多孔介质模型	多孔介质模型	多孔介质模型
滤饼	无	多孔介质模型	多孔介质模型

表4 滤膜阻力系数及出口水流量对比

孔隙率/%

黏性阻力

系数/m^-2

惯性阻力

系数/m^-1

图4 不同厚度气化细渣滤饼条件下滤膜出口水流量对比

图5 厚度6.25mm气化细渣滤饼吸水过程的压力场分布

表5 不同厚度气化细渣滤饼含水量随时间变化

气化细渣滤饼厚度 /mm	真空力场作用时间 /s	气化细渣滤饼含水量 /%	真空度 /MPa
3.0	5	42.28	0.084
	10	42.93	0.087
	15	41.74	0.090
	20	42.68	0.091
	24	41.84	0.095
4.5	5	46.85	0.087
	5	46.85	0.087
	10	45.52	0.090
	10	45.52	0.090
	15	44.61	0.092
	15	44.61	0.092
	24	43.58	0.095
	24	43.58	0.095
5.5	5	49.44	0.090
	10	47.25	0.092
	15	45.03	0.094
	20	44.13	0.095
	24	44.12	0.095
6.25	5	51.26	0.091
	10	49.36	0.093
	15	47.61	0.095
	20	47.35	0.096
	24	46.08	0.096

图6 脱水过程“仓室水”含量变化数值模拟

图7 脱水过程滤饼中“通道水”含量变化的数值模拟

图8 细渣滤饼含水量随时间变化的数值模拟与实验值对比

图9 气化细渣滤饼中“通道水”含量在真空力场作用下随时间的变化

图10 脱水真空度对气化细渣滤饼中“通道水”脱除速率的影响规律

图11 脱水真空度对气化细渣滤饼水分含量的影响规律

图12 气化细渣滤饼厚度对滤饼中“通道水”脱除速率的影响

图13 气化细渣滤饼厚度对滤饼中水含量脱除速率的影响

图14 “仓室水”含量对气化细渣滤饼脱水的影响

图15 颗粒等效当量直径对脱水的影响

图16 颗粒等效当量直径对25s时“通道水”含量的影响

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