Hydrate equilibrium model of hydrogen-containing gas considering hydrates structure transformation

doi:10.11949/0438-1157.20221326

Abstract

Abstract:

Hydrogen-containing gases commonly used in industry often contain many light hydrocarbons. The change of light hydrocarbons composition will cause the transformation of hydrate structure, which is one of the important reasons for reducing the calculation precision of hydrate thermodynamic model. Therefore, for the light hydrocarbon mixed system, a new hydrate structure parameter ( $n i I$ ) is introduced into the core equation of Chen-Guo hydrate model, and its coefficients are obtained by fitting experimental data, which can be used to judge and calculate the sⅠ/sⅡ hydrate transition. On this basis, hydrogen in hydrogen-containing gas is regarded as an inert gas adsorbed only by small cavities (link cavities) of hydrate, and an improved model considering hydrate structural transition is proposed to improve the prediction accuracy of hydrogen-containing gas. The calculated results show that the average relative deviation of the improved model for different light hydrocarbon gases is reduced from about 5.6% to 2.1%, and for different hydrogen-containing gases is reduced from about 8% to 2.3%. The prediction accuracy of the model has been significantly improved, which can meet the requirements of engineering applications.

Key words: model, light hydrocarbon, hydrogen, hydrate, phase equilibria, hydrate structure transformation, Chen-Guo model

摘要：

工业中常见的含氢气体往往含有较多的轻烃，而不同轻烃组成的变化能够引起水合物结构类型的转变，这也是影响水合物热力学模型预测精度的重要原因之一。因此，本文首先针对轻烃混合气体，在Chen-Guo水合物模型中引入新的水合物结构参数（ $n i I$ ）并通过实验数据拟合得到其参数值，以判断和计算因气体组成变化而引起的sⅠ/sⅡ型水合物转变的热力学相平衡。在此基础上，将含氢气体中的氢气视为只能被水合物小孔（联结孔）吸附的惰性气体，提出一种考虑水合物结构转变的相平衡模型，以提高含氢气体的水合物相平衡预测精度。结果表明，该模型对不同轻烃气体的水合物相平衡条件预测平均相对误差由约5.6%降至2.1%，对不同含氢气体的水合物相平衡条件预测平均相对误差由约8%降至2.3%，模型预测精度明显提高，能够满足工程应用要求。

关键词: 模型, 轻烃, 氢气, 水合物, 相平衡, 水合物结构转变, Chen-Guo模型

CLC Number:

TE 624

Jingbo GAO, Qiang SUN, Qing LI, Yiwei WANG, Xuqiang GUO. Hydrate equilibrium model of hydrogen-containing gas considering hydrates structure transformation[J]. CIESC Journal, 2023, 74(2): 666-673.

高靖博, 孙强, 李青, 王逸伟, 郭绪强. 考虑水合物结构转变的含氢气体水合物相平衡模型[J]. 化工学报, 2023, 74(2): 666-673.

Figures/Tables 12

Table 1 The prediction results of Chen-Guo model for hydrate equilibrium

组成	温度/K	组数	绝对平均相对误差/%	文献
甲烷（CH₄）	273~287	9	1.50	[10]
乙烷（C₂H₆）	274.8~283.1	15	0.78	[10]
丙烷（C₃H₈）	276~280.2	10	2.70	[15]
CH₄ + C₂H₆	273~287	32	4.81	[10]
CH₄ + C₃H₈	274.8~283.1	29	3.40	[11]
C₂H₆ + C₃H₈	276~280.2	36	6.38	[15]
H₂ + CH₄	274.3~278.3	10	4.57	[16]
H₂ + C₃H₈	274.2~278.3	14	7.78	[16]

Table 2 The prediction results of hydrate phase equilibrium （Lw + H +V） for （CH4 + C2H6 + H2O） system（Ⅰ）［10］

甲烷摩尔分数/%	温度/K	组数	平均相对误差/%	$n C 2 H 6 I$
1.6	283.9~286.6	3	1.13	1
4.7	279.4~287.6	4	1.26	1
17.7	281.6~287.0	5	0.14	1
56.4	274.8~283.2	4	1.20	0

Table 2 The prediction results of hydrate phase equilibrium （Lw + H +V） for （CH4 + C2H6 + H2O） system（Ⅰ）［10］

甲烷摩尔分数/%	温度/K	组数	平均相对误差/%	$n C 2 H 6 I$
1.6	283.9~286.6	3	1.13	1
4.7	279.4~287.6	4	1.26	1
17.7	281.6~287.0	5	0.14	1
56.4	274.8~283.2	4	1.20	0

Table 3 The prediction results of hydrate phase equilibrium （Lw + H +V） for （CH4 + C2H6 + H2O） system（Ⅱ）［10］

甲烷摩尔分数/%	温度/K	压力/MPa	预测值/kPa	相对误差/%	$n C 2 H 6 I$
90.4	274.8	1.52	1.52	0.39	0.85
	277.6	2.10	2.09	0.48	0.95
	280.4	2.89	2.81	2.87	1
	283.2	3.97	3.70	6.66	1
95.0	274.8	1.84	1.85	0.22	0.80
	277.6	2.53	2.51	0.95	0.85
	280.4	3.45	3.46	0.32	0.95
	283.2	4.77	4.69	1.76	1
97.1	274.8	2.16	2.16	0.23	0.85
	277.6	2.96	2.94	0.71	0.90
	280.4	4.03	4.07	0.97	1
平均相对误差				1.20

Table 3 The prediction results of hydrate phase equilibrium （Lw + H +V） for （CH4 + C2H6 + H2O） system（Ⅱ）［10］

甲烷摩尔分数/%	温度/K	压力/MPa	预测值/kPa	相对误差/%	$n C 2 H 6 I$
90.4	274.8	1.52	1.52	0.39	0.85
	277.6	2.10	2.09	0.48	0.95
	280.4	2.89	2.81	2.87	1
	283.2	3.97	3.70	6.66	1
95.0	274.8	1.84	1.85	0.22	0.80
	277.6	2.53	2.51	0.95	0.85
	280.4	3.45	3.46	0.32	0.95
	283.2	4.77	4.69	1.76	1
97.1	274.8	2.16	2.16	0.23	0.85
	277.6	2.96	2.94	0.71	0.90
	280.4	4.03	4.07	0.97	1
平均相对误差				1.20

Table 4 The prediction results of hydrate phase equilibrium （Lw + H +V） for （C2H6 + C3H8 + H2O） system（Ⅰ）［15］

乙烷摩尔分数/%	温度/K	组数	平均相对误差/%
28.0	276~278	3	2.24
44.3	275.9~277.4	5	2.06
45.9	275.8~278	5	1.96
65.8	273.9~277.6	5	0.76
74.0	274.5~277.1	5	3.03

Table 4 The prediction results of hydrate phase equilibrium （Lw + H +V） for （C2H6 + C3H8 + H2O） system（Ⅰ）［15］

乙烷摩尔分数/%	温度/K	组数	平均相对误差/%
28.0	276~278	3	2.24
44.3	275.9~277.4	5	2.06
45.9	275.8~278	5	1.96
65.8	273.9~277.6	5	0.76
74.0	274.5~277.1	5	3.03

Table 5 The prediction results of hydrate phase equilibrium （Lw + H +V） for （C2H6 + C3H8 + H2O） system（Ⅱ）［15］

乙烷摩尔分数/%	温度/K	压力/MPa	预测值/kPa	相对误差/%	$n C 2 H 6 I$
81.4	273.1	0.54	0.53	1.54	0
	273.8	0.64	0.62	2.78	0
	274.3	0.66	0.65	1.36	0.09
	274.7	0.71	0.71	0	0.09
	276.8	0.94	0.93	1.49	0.28
	278.9	1.21	1.20	0.77	0.43
	279.6	1.30	1.29	0.62	0.48
85.0	275.7	0.74	0.77	3.69	0.4
	277.2	0.90	0.93	3.00	0.49
	280.6	1.37	1.39	1.33	0.62
85.7	279.7	1.19	1.19	0.08	0.63
85.7	280.2	1.30	1.29	0.35	0.63
平均相对误差				1.82

Table 5 The prediction results of hydrate phase equilibrium （Lw + H +V） for （C2H6 + C3H8 + H2O） system（Ⅱ）［15］

乙烷摩尔分数/%	温度/K	压力/MPa	预测值/kPa	相对误差/%	$n C 2 H 6 I$
81.4	273.1	0.54	0.53	1.54	0
	273.8	0.64	0.62	2.78	0
	274.3	0.66	0.65	1.36	0.09
	274.7	0.71	0.71	0	0.09
	276.8	0.94	0.93	1.49	0.28
	278.9	1.21	1.20	0.77	0.43
	279.6	1.30	1.29	0.62	0.48
85.0	275.7	0.74	0.77	3.69	0.4
	277.2	0.90	0.93	3.00	0.49
	280.6	1.37	1.39	1.33	0.62
85.7	279.7	1.19	1.19	0.08	0.63
85.7	280.2	1.30	1.29	0.35	0.63
平均相对误差				1.82

Fig.1 Gas fugacity curves of C2H6 in gas mixture system and equilibrium fugacity curves of pure C2H6

Table 6 Diameter ratio of hydrogen to sⅠ and sⅡ hydrates

项目	直径/0.1 nm	直径比
氢气	2.3
sⅠ水合物小孔	3.95	0.58
sⅡ水合物小孔	3.91	0.59

Table 7 Antonie expression parameter of H2［25］

	X/Pa	Y/K	Z/K
H₂	5.64×10^-11	120.78	253.10

Table 8 Antoine constants of f0（T）［27-28］

分子种类	I型水合物			Ⅱ型水合物
分子种类	A×10^-9/MPa	B/K	C/K	A×10^-22/MPa	B/K	C/K
H₂	0.1	0	0	1	0	0
CH₄	1584.4	-6591.43	27.04	5.2602	-13088	4.08
C₂H₆	47.500	-5465.60	57.93	0.0399	-11491	30.4
C₃H₈	—	—	—	4.1023	-13106	30.2

Table 9 The prediction results of hydrate phase equilibrium （Lw + H +V） for （H2 + CH4 + H2O） system［16］

氢气摩尔分数/%	温度/ K	相平衡压力/ MPa	Chen-Guo模型预测压力/MPa	相对误差/ %	改进方法预测压力/MPa	相对误差/ %
平均相对误差/%			4.57		2.57
36.18	274.3	4.46	4.57	2.38	4.45	0.12
	275.3	4.85	5.09	4.87	4.95	1.96
	276.3	5.32	5.67	6.48	5.49	3.17
	277.3	5.88	6.31	7.36	6.10	3.66
	278.3	6.63	7.02	5.82	6.77	2.12
22.13	274.3	3.72	3.70	0.59	3.65	1.86
	275.4	4.03	4.16	3.15	4.05	0.57
	276.2	4.36	4.53	3.83	4.50	3.18
	277.2	4.75	5.04	6.08	5.00	5.17
	278.2	5.34	5.61	5.09	5.55	3.91

Table 10 The prediction results of hydrate phase equilibrium （Lw + H +V） for （H2 + C3H8 + H2O） system［16］

氢气摩尔分数/%	温度/ K	相平衡压力/ MPa	Chen-Guo模型预测压力/MPa	相对误差/ %	改进方法预测压力/MPa	相对误差/ %
平均相对误差/%			11.45		2.22
87.22	276.2	2.58	2.74	6.09	2.50	3.25
	277.3	3.20	3.66	14.22	3.23	0.99
	278.3	4	4.83	20.70	4.12	2.90
81.64	275.2	1.44	1.46	1.67	1.37	4.68
	276.3	1.74	1.93	10.80	1.78	2.05
	277.3	2.22	2.50	12.57	2.25	1.33
	278.1	2.72	3.10	14.08	2.73	0.32

Table 11 The prediction results of hydrate phase equilibrium （Lw + H +V） for （H2 + CH4 + C2H6 + C3H8 + H2O） system

甲烷摩尔分数/%	乙烷摩尔分数/%	丙烷摩尔分数/%	温度/ K	相平衡压力/ MPa	Chen-Guo模型预测压力/MPa	相对误差/ %	改进方法预测压力/MPa	相对误差/ %
平均相对误差/%					7.92		2.25
6.25	3.55	6.00	279.55	4.73	5.05	6.77	4.80	1.56
			280.25	5.32	5.65	6.20	5.35	0.65
			281.35	6.33	6.72	6.14	6.33	0.01
			281.95	7.11	7.37	3.66	6.92	2.62
			282.75	8.05	8.34	3.60	7.78	3.29
			283.35	8.54	9.134	6.96	8.53	0.17
			283.95	9.72	10.01	2.98	9.31	4.22
6.18	3.35	8.00	279.05	3.56	3.98	11.71	3.78	6.08
			279.75	4.13	4.48	8.36	4.23	2.49
			280.35	4.45	4.95	11.24	4.65	4.60
			281.35	5.32	5.83	9.68	5.45	2.51
			281.95	5.82	6.44	10.65	5.99	2.92
			282.35	6.23	6.87	10.24	6.37	2.28
			282.95	6.95	7.56	8.78	6.99	0.55
			283.35	7.35	8.06	9.66	7.43	1.05
			283.75	7.82	8.60	9.97	7.90	0.96

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