Experimental study on influence of multiple factors on liquid CO2 freeze-thaw cracking coal

doi:10.16265/j.cnki.issn1003-3033.2023.07.0116

Abstract

Abstract:

In order to study the coupling influence of multi-factor on liquid CO₂ freeze-thaw cracking coal, a liquid CO₂ freeze-thaw cracking test device was designed. The nuclear magnetic resonance testing technology was used to measure the porosity of coal after liquid CO₂ freeze-thaw cracking under different influencing factors. The effects of liquid CO₂ freezing time (t), number of freeze-thaw cycles (n) and water saturation (W) on coal porosity (φ) were studied. The quadratic regression response surface model of φ with t, n and W was constructed by response surface method. The sensitivity of t, n and W to φ single and coupled was analyzed, and the influence characteristics were predicted, optimized and verified under different influencing factors. The results show that the φ changes exponentially with the increase of t and n, and linearly with the increase of W. The influencing factors t, n and W are all extremely significant terms of φ (significant discriminant value P<0.01), and the influence relationship of to φ is as follows: n>W>t. The interaction between nt and Wt is very significant, followed by nW and Wt. The primary and secondary effects on φ are nt>nW>Wt. When t, n and W are 57 min, 19 times and 96%, respectively, the maximum value of φ is 9.47%. The average error between the four test values and the predicted value of the model is 2.98%, and the measured average value of φ is 9.58%, which is 7.16% higher than that before optimization (8.94%).

Key words: freeze-thaw cracking, liquid CO₂, porosity, freeze time, number of freeze-thaw cycles, water saturation

ZHOU Xihua, ZHOU Luhan, JIANG Yanhang, BAI Gang, LIU Tianxiang, WANG Xuepeng. Experimental study on influence of multiple factors on liquid CO₂ freeze-thaw cracking coal[J]. China Safety Science Journal, 2023, 33(7): 58-67.

Figures/Tables 15

Tab.1

Fig.1

Tab.2

Fig.2

Fig.3

Fig.4

Fig.5

Fig.6

Fig.7

Fig.8

Tab.3

Tab.4

Tab.5

Analysis of variance of regression equation

来源	平方和	自由度	均方	F值		P值
模型	56.14	9	6.19	30.25		< 0.000 1
X_t	2.17	1	2.17	13.62		0.008 2
X_n	26.79	1	26.79	130.88		< 0.000 1
X_w	3.69	1	3.69	18.00		0.003 8
X_tn	18.45	1	18.45	90.11		< 0.000 1
X_tw	0.66	1	0.66	3.21		0.116 5
X_nw	1.99	1	1.99	9.71		0.016 9
$X t t$	0.90	1	0.90	4.41		0.073 8
$X n n$	1.13	1	1.13	5.52		0.051 1
$X w w$	1.70	1	1.70	8.31		0.023 5
残差	1.43	7	0.20	—		—
失拟项	0.43	3	0.12	0.98		0.474 2
纯误差	0.084	4	0.021	—		—
总和	58.42	16	R²=0.975		$R A d j 2$ =0.942 8

Tab.5

Fig.9

Tab.6

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试验号	X_t /min	X_n /次	X_w /%	φ/%
1	100.00	15.00	70.00	6.7
2	50.00	20.00	70.00	8.87
3	100.00	20.00	40.00	3.89
4	100.00	10.00	100.00	5.94
5	100.00	15.00	70.00	6.85
6	100.00	15.00	70.00	6.59
7	50.00	15.00	40.00	3.82
8	50.00	10.00	70.00	3.45
9	150.00	15.00	40.00	3.85
10	150.00	10.00	70.00	7.01
11	100.00	15.00	70.00	6.76
12	50.00	15.00	100.00	6.69
13	150.00	15.00	100.00	8.34
14	150.00	20.00	70.00	3.84
15	100.00	20.00	100.00	8.94
16	100.00	10.00	40.00	3.71
17	100.00	15.00	70.00	6.97

序号	φ/%		误差/%
序号	预测值	试验值	误差/%
1	9.47	9.78	3.27
2	9.47	9.73	2.75
3	9.47	9.13	3.59
4	9.47	9.69	2.32

Experimental study on influence of multiple factors on liquid CO₂ freeze-thaw cracking coal

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试验序号	t /min	n /次	W/%	备注
1	10	0	100	冻结时间影响
2	25	0	100
3	50	0	100
4	100	0	100
5	150	0	100
6	10	5	100	循环次数影响
7	10	10	100
8	10	15	100
9	10	20	100
10	10	0	0	含水饱和度影响
11	10	0	20
12	10	0	40
13	10	0	60
14	10	0	80

影响因素	代号	编码及水平			间隔
影响因素	代号	-1	0	+1	间隔
t/min	X_t	50	100	150	50
n/次	X_n	10	15	20	5
W/%	X_w	40	70	100	30

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