Study of reaction and flow characteristics in multi-nozzle pulverized coal gasifier with co-processing of wastewater

doi:10.11949/0438-1157.20230723

Abstract

Abstract:

Entrained-flow coal gasification technology is the key technology of cleaning coal utilization. During the industrial gasification process, it is difficult to treat the waste brought by production. In this paper, an industrial OMB pulverized coal gasifier is taken as the research object. The multiphase flow and reaction process in the gasifier are studied by numerical simulation. The effects of injection of low-temperature wastewater on reaction and heat transfer processes in gasifier are studied. The comparison between the simulation results and the industrial data shows that the simulation methods in this paper are reliable. The results show that the injection of wastewater can effectively reduce the temperature of the top and upper cone of gasifier, and can also reduce the temperature of the whole refractory materials. The wastewater flow blocks the impact of the rising refracted flow in the furnace on the top, reducing the temperature of the top space. The ash deposition rate on the top wall of the gasifier first increases and then decreases as the wastewater increases, while other wall surfaces are less affected. The carbon conversion rate slightly decreases, while the effective gas yield increases. The input of wastewater leads to a significant impact in particle deposition rate on the top wall, while other parts of the wall are less affected. Co-processing of wastewater can increase the effective gas output of the gasifier and extend the service life of the top burner, which makes it a good way to utilize waste resources. Research has found that the recommended mass flow rate of wastewater is 12—14 t·h^-1.

Key words: coal gasification, opposed multi-burner, refractory material, waste treatment, numerical simulation

摘要：

利用气化技术处理有机废液是废弃物资源化利用的新途径。以工业多喷嘴对置式粉煤气化炉为研究对象，采用数值模拟的方法研究了协同处理废液的气化炉内反应和流动过程。研究结果表明，废液的输入降低了出口合成气中CO的含量，增加了H₂、H₂O和CO₂的含量；废液输入使出口合成气温度降低，碳转化率降低，有效气收率增加。废液流阻挡了炉内上升折射流对顶部的冲击，降低了顶部空间的温度。气化炉顶部壁面的灰渣沉积速率随着废液增加呈现先增大后减小的趋势，其他部位壁面受影响较小。协同处理废液能够增加气化炉的有效气产量，延长顶部开工烧嘴的使用寿命，是良好的废弃物资源化利用途径。综合考虑，建议的废液输入量为12~14 t·h^-1。

关键词: 煤气化, 多喷嘴, 耐火材料, 废物处理, 数值模拟

CLC Number:

TQ 546

Chen HAN, Youmin SITU, Bin ZHU, Jianliang XU, Xiaolei GUO, Haifeng LIU. Study of reaction and flow characteristics in multi-nozzle pulverized coal gasifier with co-processing of wastewater[J]. CIESC Journal, 2023, 74(8): 3266-3278.

韩晨, 司徒友珉, 朱斌, 许建良, 郭晓镭, 刘海峰. 协同处理废液的多喷嘴粉煤气化炉内反应流动研究[J]. 化工学报, 2023, 74(8): 3266-3278.

Figures/Tables 22

Fig.1 Flowchat of the calculation process

Table 1 Reaction kinetics［14，29-30］

k	$A i$ /(kg·m^-2·s^-1·Pa^-ⁿ )	$E i$ /(J·kmol^-1)	n
$k 1$	6.8×10¹⁵	1.68×10⁸	—
$k 2$	2.2×10¹²	1.67×10⁸	—
$k 3$	3.0×10⁸	1.26×10⁸	—
$k 4$	4.1×10¹¹	1.68×10⁸	—
$k 5$	2.75×10¹⁰	8.38×10⁷	—
$k 6$	8710	17967	0.65
$k 7$	4.4	1.47×10⁸	0.6
$k 8$	1.33	1.62×10⁸	0.4

Table 1 Reaction kinetics［14，29-30］

k	$A i$ /(kg·m^-2·s^-1·Pa^-ⁿ )	$E i$ /(J·kmol^-1)	n
$k 1$	6.8×10¹⁵	1.68×10⁸	—
$k 2$	2.2×10¹²	1.67×10⁸	—
$k 3$	3.0×10⁸	1.26×10⁸	—
$k 4$	4.1×10¹¹	1.68×10⁸	—
$k 5$	2.75×10¹⁰	8.38×10⁷	—
$k 6$	8710	17967	0.65
$k 7$	4.4	1.47×10⁸	0.6
$k 8$	1.33	1.62×10⁸	0.4

Table 2 Criterion of particles adhesion［22］

项目	$T p$ ≥ $T c v$				$T p$ < $T c v$
	碳转化率≥ $C c r$		碳转化率< $C c r$		碳转化率≥ $C c r$		碳转化率< $C c r$
	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$
$T w$ ≥ $T c v$	黏附	黏附	反弹	黏附	反弹	黏附	反弹	黏附
$T w$ < $T c v$	反弹	黏附	反弹	黏附	反弹	反弹	反弹	反弹

Table 2 Criterion of particles adhesion［22］

项目	$T p$ ≥ $T c v$				$T p$ < $T c v$
	碳转化率≥ $C c r$		碳转化率< $C c r$		碳转化率≥ $C c r$		碳转化率< $C c r$
	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$	$W e$ ≥ $W e c r$	$W e$ < $W e c r$
$T w$ ≥ $T c v$	黏附	黏附	反弹	黏附	反弹	黏附	反弹	黏附
$T w$ < $T c v$	反弹	黏附	反弹	黏附	反弹	反弹	反弹	反弹

Table 3 Boundary conditions

参数	数值
氧气流量/(k·h^-1)	104956.48
粉煤流量/(kg·h^-1)	139868.00
CO₂流量/(kg·h^-1)	29145.15
粉煤密度/(kg·m^-3)	1400
废液密度/(kg·m^-3)	848
废液温度/K	320
渣厚度/mm	10
渣热导率/(W·m^-1·K^-1)	1.42
锅炉水压力/MPa(G)	5.0
操作压力/MPa(G)	4.0

Table 4 Coal analysis data

工业分析/%（质量）				元素分析/%（质量）
挥发分	固定碳	灰分	水分	C	H	O	N	S
19.76	56.15	21.89	2.20	62.18	4.16	9.36	1.18	0.74

Table 5 Wastewater composition

成分	占比/%（质量）
环己酮	1.99
环己醇	0.46
苯	1.34
己内酰胺	25.57
水	52.74
盐类及杂质	17.89

Fig.2 Schematic diagram and grid of a gasifier

Fig.3 CO volume fractions under different grid numbers

Table 6 Comparison of simulation data with industrial data of gasifier outlet syngas

数据	CO/%	CO₂/%	H₂/%	N₂/%	碳转化率/%	出口温度/K
工业数据Ⅰ	71.99	1.01	25.5	0.8	99.5	1608
模拟数据Ⅰ	71.42	1.11	25.15	0.62	99.9	1589
工业数据Ⅱ	70.94	1.29	21.65	5.78	99.0	1852
模拟数据Ⅱ	69.65	1.23	22.86	6.04	99.3	1877
工业数据Ⅲ	47.84	15.54	36.16	0.44	98.9	1562
模拟数据Ⅲ	48.76	14.23	36.08	0.34	98.82	1602

Fig.4 Velocity comparison of simulation and industry measurement

Fig.5 Gas velocity distribution in gasifier

Fig.6 Gas temperature distribution in gasifier

Fig.7 Distribution of gas components in gasifier

Table 7 Gasification performance under different wastewater mass flow rates

废液流量/(t·h^-1)	CO/%（体积）	H₂/%（体积）	H₂O/%（体积）	CO₂/%（体积）	出口温度/K	碳转化率/%
0	64.15	22.53	7.20	5.31	1780	99.48
2	63.33	23.10	7.25	5.40	1763	99.37
4	62.53	23.62	7.33	5.55	1746	99.28
6	61.98	24.09	7.44	5.62	1731	99.18
8	61.34	24.46	7.61	5.76	1719	99.09
10	60.65	24.80	7.68	5.97	1705	99.00
12	59.98	25.05	7.89	6.18	1691	98.94
14	59.21	25.18	8.15	6.33	1677	98.82
16	58.63	25.30	8.48	6.63	1667	98.68

Fig.8 Effect of wastewater mass flow rate on carbon conversion and effective gas yield

Fig.9 Gas velocity distribution at the top of gasifier under different mass flow rates of wastewater

Fig.10 The relationship between the position of the stagnation point and wastewater mass flow rate

Fig.11 Distribution of CO and H2 components under different mass flow rate of wastewater

Fig.12 Gas temperature contours of the gasifier at different mass flow rates of wastewater

Fig.13 Temperature decay on the axis

Fig.14 Average gas temperature near the top wall of gasifier

Fig.15 Particle accretion rate of gasifier wall

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