Analysis of key parameters affecting product purity of natural gas ethane recovery process via ZIF-8 nanofluid

doi:10.11949/0438-1157.20230562

Abstract

Abstract:

Porous nanofluid absorption-adsorption coupling separation is an emerging gas separation technology based on ZIF-8/water-glycol nanofluid, which can recover ethane in natural gas with high efficiency and low consumption by using the traditional absorption-desorption process. The equilibrium stage method is used to model the new process, and improving the ethane product purity is an important goal of process simulation. The simulation results indicate that the theoretical stage number of the absorption-adsorption column and the flash pressure are key parameters affecting the product purity. As the theoretical stage number of the absorption-adsorption column increases, the product purity first rises and then tends to remain constant. It can be seen from the y-x diagram that the reason why the product purity is difficult to increase continuouslyis that the operating line approaches the phase equilibrium line, which reduces the efficiency of each theoretical stage. The flash pressure affects the product purity by the flash boilup ratio. When the flash pressure decreases, the flash boilup ratio of the absorption-adsorption column increases, and the ethane content of the slurry phase from the reboiler (flash tank) increases, resulting in an increase in the ethane product purity.

Key words: natural gas, light hydrocarbon recovery, absorption, adsorption, gas separation, process simulation

摘要：

天然气乙烷回收可为乙烷裂解制乙烯提供优质的原料。多孔纳米流体吸收-吸附耦合分离是一种新兴的气体分离技术，基于ZIF-8/水-乙二醇纳米流体，利用传统的吸收-解吸流程，可高效低耗地回收天然气中的乙烷。利用平衡级法对多孔纳米流体天然气乙烷回收工艺建模，提高乙烷产品纯度是流程模拟的一个重要目标，而模拟结果表明吸收-吸附塔理论板数和闪蒸压力是影响乙烷产品纯度的关键因素。随着吸收-吸附塔理论板数增加，乙烷产品纯度先明显升高，后趋于稳定。通过绘制y-x图可知，乙烷产品纯度难以持续升高的原因是操作线趋近了相平衡线。随着闪蒸压力降低，乙烷产品纯度升高，其原理为闪蒸压力影响了吸收-吸附塔的闪蒸再沸比，而闪蒸再沸比与乙烷产品纯度呈正相关。

关键词: 天然气, 轻烃回收, 吸收, 吸附, 气体分离, 流程模拟

CLC Number:

TQ 028.8

Ruihang ZHANG, Pan CAO, Feng YANG, Kun LI, Peng XIAO, Chun DENG, Bei LIU, Changyu SUN, Guangjin CHEN. Analysis of key parameters affecting product purity of natural gas ethane recovery process via ZIF-8 nanofluid[J]. CIESC Journal, 2023, 74(8): 3386-3393.

张瑞航, 曹潘, 杨锋, 李昆, 肖朋, 邓春, 刘蓓, 孙长宇, 陈光进. ZIF-8纳米流体天然气乙烷回收工艺的产品纯度关键影响因素分析[J]. 化工学报, 2023, 74(8): 3386-3393.

Figures/Tables 7

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组分	含量/%(mol)
C₁	82.700
C₂	9.730
C₃	5.740
iC₄	0.770
nC₄	0.770
iC₅	0.050
nC₅	0.050
C₆	0.010
N₂	0.180

组分	含量/%(mol)
C₁	82.700
C₂	9.730
C₃	5.740
iC₄	0.770
nC₄	0.770
iC₅	0.050
nC₅	0.050
C₆	0.010
N₂	0.180

吸收-吸附塔理论板数	闪蒸压力/MPa	解吸压力/MPa	气液比	乙烷产品纯度/%
3	0.1	0.01	60	91.0
4	0.1	0.01	60	93.0
5	0.1	0.01	60	94.0
6	0.1	0.01	60	94.4
7	0.1	0.01	60	94.6
6	0.05	0.01	60	99.2
6	0.3	0.01	60	74.2
6	0.5	0.01	60	67.7
6	0.1	0.005	60	93.4
6	0.1	0.03	60	96.0
6	0.1	0.05	60	94.8
6	0.1	0.01	40	85.6
6	0.1	0.01	50	90.7
6	0.1	0.01	70	96.5

吸收-吸附塔理论板数	闪蒸压力/MPa	解吸压力/MPa	气液比	乙烷产品纯度/%
3	0.1	0.01	60	91.0
4	0.1	0.01	60	93.0
5	0.1	0.01	60	94.0
6	0.1	0.01	60	94.4
7	0.1	0.01	60	94.6
6	0.05	0.01	60	99.2
6	0.3	0.01	60	74.2
6	0.5	0.01	60	67.7
6	0.1	0.005	60	93.4
6	0.1	0.03	60	96.0
6	0.1	0.05	60	94.8
6	0.1	0.01	40	85.6
6	0.1	0.01	50	90.7
6	0.1	0.01	70	96.5

P/MPa	V_tk/ (mol/h)	L_tk/ (mol/h)	LV_tk/ (mol/h)	FR	DR	x_tk,2/ %(mol)	y_de,2/ %(mol)
0.03	349	10694	108	0.0326	3.23	99.9	99.9
0.05	298	10743	156	0.0278	1.91	99.8	99.7
0.07	257	10775	188	0.0239	1.37	99.1	98.9
0.09	224	10783	196	0.0208	1.14	96.7	95.9
0.1	212	10786	199	0.0197	1.07	95.4	94.4
0.2	151	10809	223	0.0140	0.678	84.9	82.4
0.3	119	10830	243	0.0110	0.489	77.3	74.4