化工学报 ›› 2021, Vol. 72 ›› Issue (11): 5675-5685.doi: 10.11949/0438-1157.20210650

• 分离工程 • 上一篇    下一篇

规整复合吸附剂真空变压吸附分离CH4/N2工艺模拟与分析

田军鹏(),沈圆辉,张东辉(),唐忠利   

  1. 天津大学化工学院,化学工程研究所,化学工程联合国家重点实验室,天津 300350
  • 收稿日期:2021-05-13 修回日期:2021-07-09 出版日期:2021-11-05 发布日期:2021-11-12
  • 通讯作者: 张东辉 E-mail:tianjunpeng@tju.edu.cn;donghuizhang@tju.edu.cn
  • 作者简介:田军鹏(1996—),男,硕士研究生,tianjunpeng@tju.edu.cn
  • 基金资助:
    国家重点研发计划项目(2019YFB1505000)

Simulation and analysis of CH4/N2 separation by vacuum pressure swing adsorption with structured composite adsorption media

Junpeng TIAN(),Yuanhui SHEN,Donghui ZHANG(),Zhongli TANG   

  1. State Key Laboratory of Chemical Engineering, Chemical Engineering Research Center, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China
  • Received:2021-05-13 Revised:2021-07-09 Published:2021-11-05 Online:2021-11-12
  • Contact: Donghui ZHANG E-mail:tianjunpeng@tju.edu.cn;donghuizhang@tju.edu.cn

摘要:

为减少甲烷排放,实现低浓度煤层气有效资源化利用,探究了使用规整复合吸附剂真空变压吸附富集低浓度煤层气的工艺。采用静态容积法测定了甲烷、氮气在规整复合吸附剂上的吸附等温线,同时建立了包括质量、热量和动量守恒在内的严格吸附床数学模型,设计了三塔连续进料的真空变压吸附工艺并进行模拟。分析了工艺达到循环稳态后吸附床层轴向温度分布和压力变化,并且探究了进料量、解吸压力、原料气中甲烷浓度和吸附压力对纯度、回收率、工艺能耗和吸附剂产率等工艺性能的影响。模拟结果表明,在进料量为100 L·min-1,解吸压力为0.1 bar(1 bar=0.1 MPa),原料气甲烷浓度为30%,吸附压力为3 bar时可以生产纯度为59.07%,回收率为93.64%的富CH4产品气,同时单位能耗为18.70 kJ·mol-1,吸附剂产率为4.56 mol·h-1·kg-1。表明规整吸附剂对CH4/N2具有良好的吸附分离效果,能够实现低浓度煤层气中甲烷高效富集。

关键词: 规整复合吸附剂, 真空变压吸附, 煤层气富集, 数值模拟, 甲烷

Abstract:

To reduce methane emissions and achieve effective resource utilization of low concentration coalbed methane, the process of using a structured composite adsorbent for vacuum pressure swing adsorption to enrich low-concentration coal-bed methane was explored. The equilibrium adsorption capacities of pure gases (CH4 and N2) on the structured composite adsorption medium were measured under different pressures at a series of fixed temperatures by using the static volumetric method. Thus, a rigorous and reasonable mathematical model, including a set of conservation equation of mass, energy and momentum balances, was developed to precisely describe the dynamic behavior of multiple components in adsorption bed. A typical three-bed VPSA process with continuous feeding was designed and simulated. A comprehensive analysis was presented, relating to the process characteristics and performance such as temperature and pressure distribution in axial adsorption bed at cycle steady state. Additionally, effects of feed flow rate, desorption pressure, feed concentration and adsorption pressure on purity, recovery, energy consumption and productivity were investigated. The results showed that an effective separation performance of 59.07% CH4 purity, 93.64% CH4 recovery and 4.56 mol·h-1·kg-1 productivity with an energy consumption of 18.70 kJ·mol-1, was finally got with the optimal parameters, while the feed flow rate, desorption pressure, feed concentration and adsorption pressure were 100 L·min-1, 0.1 bar, 30% and 3 bar, respectively. Overall, this study indicated there is an effective adsorption and separation performance on CH4/N2 of structured composite adsorption media, which can achieve high-efficiency enrichment of methane in low concentration coalbed methane.

Key words: structured composite adsorption media, vacuum pressure swing adsorption, coalbed methane enrichment, numerical simulation, methane

中图分类号: 

  • TQ 028.1

图1

三塔VPSA工艺整体流程图"

图2

循环工艺流程及甲烷吸附前沿示意图"

表1

三塔VPSA循环时序"

步骤塔1塔2塔3时间/s
1ADERED10
2ADPRVU120
3EDADER10
4VUADPR120
5EREDAD10
6PRVUAD120

表2

吸附床模型方程"

项目数学模型
质量平衡-εbDax,i?2ci?z2+?vgci?z+[εb+1-εbεp]?ci?t+ρp(1-εb)?qi?t=0(1)
Dax,i=0.73Dm,i+vgrpεb1+9.49εbDm,i2vgrp(2)
热量平衡

气相

-kgεb?2Tg?z2+Cvgvgρg?Tg?z+εpCvgρg?Tg?t+P?vg?z+hf(Tg-Ts)+4hwDb(Tg-Tw)=0

(3)

固相

-ks?2Ts?z2+Cpsρb?Ts?z+ρbi=1n(Cpa,iqi)?Ts?t+ρbi=1n(ΔHi?qi?t)-hfap(Tg-Ts)=0

(4)

塔壁

-kw?2Tw?z2+Cpwρw?Tw?z-hw4Db(Db+Wt)2-Db(Tg-Tw)+hamb4(Db+Wt)2(Db+Wt)2-Db2(Tw-Tamb)=0

(5)
动量平衡?P?z=±150×10-5μvg(1-εb)2εb3(2rpψ)2+1.75×10-5M(1-εb)ρg2rpψεb3vg2(6)
传质速率?qi?t=kLDF,i(qi*-qi)=15De,irp2(qi*-qi)(7)
De,i=εpτ×Dk,iDm,iDk,i+Dm,i?,???Dk,i=97.0rpTMi(8)

表3

工艺性能评价指标"

指标方程
纯度0tcycleFoutyout,targetdt0tcycleFoutdt
回收率0tcycleFoutyout,targetdt0tcycleFinyin,targetdt
能耗dW=0tcycleVinPoutγη(γ+1)Pout/Pin1-(1/γ)-1dt0tcycleVproductyproductdt
产率36000tcycleFoutyout,productdttcyclemadsorbents

表4

吸附床参数"

参数数值
Hb /m1.00
Db /m0.20
Wb /m0.005
Cpw/ (kJ·kg-1·K-1)0.502
hw/ (W·m-2·K-1)60
ρw/ (kg·m-3)7800
hamb/ (W·m-2·K-1)60
hf/(W·m-2·K-1)217
kg/(W·m-1·K-1)0.342
ks /(W·m-1·K-1)0.3
Tf /K298.15
Pf /bar3.0

表5

规整复合吸附剂参数"

参数数值
εb0.75
εp0.64
SBET/ (m2·g-1)880.06
Vt /(cm3·g-1)0.509
ρs/ (kg·m-3)175
Wa /m3.5×10-4
Cps /(kJ·kg-1·K-1)0.857

图3

CH4和N2在规整复合吸附剂上的吸附等温线"

表6

Extended Langmuir 2吸附等温线方程参数"

参数CH4N2
IP1/(mol·kg-1·kPa-1)1.32×10-89.75×10-7
IP2/K24762186
IP3/kPa-12.84×10-72.59×10-6
IP4 /K27261740
ΔH/(kJ·mol-1)-19.05-15.93

表7

三塔VPSA模拟结果"

工况进料量/ (L·min-1)

吸附压力/

bar

解吸压力/ bar原料气甲烷 浓度/%CH4纯度/%CH4回收率/%能耗/(kJ·mol-1)产率/ (mol·h-1·kg-1)
18030.13052.2898.9518.463.86
29030.13056.0496.8118.544.25
310030.13059.0793.6418.704.56
411030.13061.4890.4518.954.85
512030.13063.1685.8919.575.02
613030.13064.7182.3720.055.22
714030.13066.0879.0220.595.39
810030.053059.5496.3619.324.70
910030.0753059.2394.5618.924.61
1010030.1253058.7290.7318.344.42
1110030.153058.2888.0718.324.29
1210030.1753057.9185.9418.304.19
1310030.203057.5684.6918.254.13
1410030.11026.1695.2852.781.55
1510030.11537.1194.3235.752.30
1610030.12045.3293.9227.023.05
1710030.12552.8193.7521.693.81
1810030.13565.0593.5516.335.32
1910030.14070.4193.4814.656.08
2010010.13040.2390.349.664.40
2110050.13068.7692.8138.374.52

图4

VPSA工艺吸附塔内气相温度轴向分布和压力分布"

图5

进料量对VPSA工艺性能的影响"

图6

解吸压力对VPSA工艺性能的影响"

图7

原料气甲烷浓度对VPSA工艺性能的影响"

图8

吸附压力对VPSA工艺性能的影响"

1 Lavoie T N, Shepson P B, Gore C A, et al. Assessing the methane emissions from natural gas-fired power plants and oil refineries[J]. Environmental Science & Technology, 2017, 51(6): 3373-3381.
2 Gu M, Zhang B, Qi Z D, et al. Effects of pore structure of granular activated carbons on CH4 enrichment from CH4/N2 by vacuum pressure swing adsorption[J]. Separation and Purification Technology, 2015, 146: 213-218.
3 Bello G, Garcı́a R, Arriagada R, et al. Carbon molecular sieves from Eucalyptus globulus charcoal[J]. Microporous and Mesoporous Materials, 2002, 56(2): 139-145.
4 Kim J, Maiti A, Lin L C, et al. New materials for methane capture from dilute and medium-concentration sources[J]. Nature Communications, 2013, 4: 1694.
5 Howarth R W. A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas[J]. Energy Science & Engineering, 2014, 2(2): 47-60.
6 Saleman T L, Li G, Rufford T E, et al. Capture of low grade methane from nitrogen gas using dual-reflux pressure swing adsorption[J]. Chemical Engineering Journal, 2015, 281: 739-748.
7 Effendy S, Xu C, Farooq S. Optimization of a pressure swing adsorption process for nitrogen rejection from natural gas[J]. Industrial & Engineering Chemistry Research, 2017, 56(18): 5417-5431.
8 Gao T, Lin W S, Gu A Z, et al. Coalbed methane liquefaction adopting a nitrogen expansion process with propane pre-cooling[J]. Applied Energy, 2010, 87(7): 2142-2147.
9 Baker R W, Lokhandwala K. Natural gas processing with membranes: an overview[J]. Industrial & Engineering Chemistry Research, 2008, 47(7): 2109-2121.
10 Lokhandwala K A, Pinnau I, He Z J, et al. Membrane separation of nitrogen from natural gas: a case study from membrane synthesis to commercial deployment[J]. Journal of Membrane Science, 2010, 346(2): 270-279.
11 Carreon M A. Molecular sieve membranes for N2/CH4 separation[J]. Journal of Materials Research, 2018, 33(1): 32-43.
12 Bhadra S J, Farooq S. Separation of methane-nitrogen mixture by pressure swing adsorption for natural gas upgrading[J]. Industrial & Engineering Chemistry Research, 2011, 50(24): 14030-14045.
13 Rufford T E, Smart S, Watson G C Y, et al. The removal of CO2 and N2 from natural gas: a review of conventional and emerging process technologies[J]. Journal of Petroleum Science and Engineering, 2012, 94/95: 123-154.
14 Zhong D L, Daraboina N, Englezos P. Recovery of CH4 from coal mine model gas mixture (CH4/N2) by hydrate crystallization in the presence of cyclopentane[J]. Fuel, 2013, 106: 425-430.
15 Ning X, Koros W J. Carbon molecular sieve membranes derived from Matrimid® polyimide for nitrogen/methane separation[J]. Carbon, 2014, 66: 511-522.
16 Yang J F, Tang X, Liu J Q, et al. Down-sizing the crystal size of ZK-5 zeolite for its enhanced CH4 adsorption and CH4/N2 separation performances[J]. Chemical Engineering Journal, 2021, 406: 126599.
17 Jiang N, Shen Y H, Liu B, et al. CO2 capture from dry flue gas by means of VPSA, TSA and TVSA[J]. Journal of CO2 Utilization, 2020, 35: 153-168.
18 Wu T B, Niu Z Y, Feng L, et al. Performance analysis of VPSA process for separating N2O from adipic acid tail gas[J]. Separation and Purification Technology, 2021, 256: 117750.
19 Canevesi R L S, Andreassen K A, da Silva E A, et al. Pressure swing adsorption for biogas upgrading with carbon molecular sieve[J]. Industrial & Engineering Chemistry Research, 2018, 57(23): 8057-8067.
20 Durán I, Álvarez-Gutiérrez N, Rubiera F, et al. Biogas purification by means of adsorption on pine sawdust-based activated carbon: impact of water vapor[J]. Chemical Engineering Journal, 2018, 353: 197-207.
21 Regufe M J, Ferreira A F P, Loureiro J M, et al. New hybrid composite honeycomb monolith with 13X zeolite and activated carbon for CO2 capture[J]. Adsorption, 2018, 24(3): 249-265.
22 Olajossy A, Gawdzik A, Budner Z, et al. Methane separation from coal mine methane gas by vacuum pressure swing adsorption[J]. Chemical Engineering Research and Design, 2003, 81(4): 474-482.
23 Lu B, Shen Y H, Tang Z L, et al. Vacuum pressure swing adsorption process for coalbed methane enrichment[J]. Chinese Journal of Chemical Engineering, 2021, 32: 264-280.
24 Yang J F, Bai H H, Shang H, et al. Experimental and simulation study on efficient CH4/N2 separation by pressure swing adsorption on silicalite-1 pellets[J]. Chemical Engineering Journal, 2020, 388: 124222.
25 Bao Z B, Yu L, Dou T, et al. Adsorption equilibria of CO2, CH4, N2, O2, and Ar on high silica zeolites[J]. Journal of Chemical & Engineering Data, 2011, 56(11): 4017-4023.
26 Yang B, Xu E L, Li M. Purification of coal mine methane on carbon molecular sieve by vacuum pressure swing adsorption[J]. Separation Science and Technology, 2016, 51(6): 909-916.
27 Zhang J H, Qu S J, Li L T, et al. Preparation of carbon molecular sieves used for CH4/N2 separation[J]. Journal of Chemical & Engineering Data, 2018, 63(5): 1737-1744.
28 Shi W R, Yang H W, Shen Y H, et al. Two-stage PSA/VSA to produce H2 with CO2 capture via steam methane reforming (SMR)[J]. International Journal of Hydrogen Energy, 2018, 43(41): 19057-19074.
29 Oreggioni G D, Brandani S, Luberti M, et al. CO2 capture from syngas by an adsorption process at a biomass gasification CHP plant: its comparison with amine-based CO2 capture[J]. International Journal of Greenhouse Gas Control, 2015, 35: 71-81.
30 Liu Z, Grande C A, Li P, et al. Multi-bed vacuum pressure swing adsorption for carbon dioxide capture from flue gas[J]. Separation and Purification Technology, 2011, 81(3): 307-317.
31 Tang X, Wang Z F, Ripepi N, et al. Adsorption affinity of different types of coal: mean isosteric heat of adsorption[J]. Energy & Fuels, 2015, 29(6): 3609-3615.
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