Numerical simulation of coal pyrolysis with different moisture content in fixed-bed reactor

doi:10.16085/j.issn.1000-6613.2025-0153

Abstract

Abstract:

This study utilized numerical simulation techniques to investigate the pyrolysis characteristics of coal with varying moisture content in an externally-heated fixed-bed reactor. The two-fluid model was combined with Zehner-Bauer-Schlunder (ZBS) thermal conductivity model, Breitbach-Barthels (B-B) radiation model, phase transformation model, parallel reaction kinetics model of coal pyrolysis and secondary pyrolysis model of tar, to simulate the heat transfer, mass transfer and pyrolysis processes of coal in a fixed bed reactor. The effects of different moisture content on the generation of coal pyrolysis products were analyzed. The results showed that the temperature approached terminal pyrolysis temperature when the volatilization rate reached maximum at different radial position. The water content affected the temperature distribution, the rate of volatilization and the yield of pyrolysis products in the reactor. With the increase of moisture content, the heating rate of coal seam slowed down, the time for coal seam center to reach the pyrolysis temperature was significantly extended, the pyrolysis process was delayed, and the ^{pyrolysis efficiency was reduced. At the same time, the overall generation rate of pyrolysis products of high-moisture coal also decreased, especially the generation of volatiles was inhibited. In addition, the increase of moisture content affected the yield of each pyrolysis product. The yield of pyrolysis gas and pyrolysis water increased, while the yield of tar and semi-coke decreased. This study obtained the law of the influence of moisture content on coal pyrolysis behavior, which provided a theoretical basis for optimizing coal pyrolysis process for further improving coal conversion efficiency.}

Key words: coal pyrolysis, moisture content, reaction kinetics, numerical simulation

摘要：

利用数值模拟技术，深入探讨了固定床反应器中不同水分质量分数对煤热解特性的影响。采用双流体模型结合Zehner-Bauer-Schlunder（ZBS）气固相间导热模型、Breitbach-Barthels（B-B）辐射模型、相变模型、煤热解平行反应动力学模型和焦油二次裂解模型，模拟了煤在固定床反应器中的传热、传质及热解反应过程，分析了不同水分质量分数对煤热解产物生成的影响。模拟结果表明，不同径向位置挥发分生成速率最大时对应的温度都接近热解终温。水分质量分数影响了反应器内的温度分布、挥发分生成速率以及各热解产物的产率。随水分质量分数的增加，煤层升温速度减慢，煤层中心达到热解温度的时间显著延长，热解过程推迟，降低了热解效率。同时，高水分煤的热解产物总体生成速率也有所下降，尤其是挥发分的生成受到了抑制。此外，水分质量分数的增加影响了各热解产物的产率：热解气和热解水的产率上升，焦油和半焦的产率下降。该研究得到了含水率对煤热解行为的影响规律，为优化煤热解工艺、提高煤炭转化效率提供了理论依据。

关键词: 煤热解, 含水率, 反应动力学, 数值模拟

CLC Number:

TQ021.1

WANG Lanxin, LI Fei, QIAN Yanan, TIAN Yujie, SHEN Jun, WANG Wei. Numerical simulation of coal pyrolysis with different moisture content in fixed-bed reactor[J]. Chemical Industry and Engineering Progress, 2025, 44(8): 4513-4525.

王蓝欣, 李飞, 钱亚男, 田于杰, 申峻, 王维. 固定床反应器不同水分煤热解数值模拟[J]. 化工进展, 2025, 44(8): 4513-4525.

Figures/Tables 23

References 31

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反应器构体	尺寸/mm
反应器总高	250
反应器筒体直径	100
出口直径	32
出口高度	35
锥体高度	65

反应器构体	尺寸/mm
反应器总高	250
反应器筒体直径	100
出口直径	32
出口高度	35
锥体高度	65

参数	数值
颗粒粒径/mm	2
初始温度/K	300
初始空隙率	0.4
煤层高度/mm	150
加热壁面温度/K	1173
其他壁面温度	绝热
出口	压力出口
动量、能量及DO辐射方程离散	二阶迎风差分格式
质量守恒方程离散	QUICK
时间步长/s	0.1
最大迭代次数	20
收敛标准	10^-3

参数	数值
颗粒粒径/mm	2
初始温度/K	300
初始空隙率	0.4
煤层高度/mm	150
加热壁面温度/K	1173
其他壁面温度	绝热
出口	压力出口
动量、能量及DO辐射方程离散	二阶迎风差分格式
质量守恒方程离散	QUICK
时间步长/s	0.1
最大迭代次数	20
收敛标准	10^-3

含水率/%	产率/%
含水率/%	焦油	热解气	H₂O	半焦
0.41	6.08	13.08	8.82	72.02
3.51	5.98	13.81	8.86	71.36
7.98	5.92	14.55	9.04	70.49
11.68	5.90	14.78	9.38	69.93