化工学报 ›› 2020, Vol. 71 ›› Issue (2): 669-679.doi: 10.11949/0438-1157.20190857

• 分离工程 • 上一篇    下一篇

基于MPC控制技术优化VPSA制氧工艺的模拟

邢瑞(),江南,刘冰,安亚雄,汪亚燕,张东辉()   

  1. 化学工程联合国家重点实验室,天津大学化工学院化学工程研究所,天津 300072
  • 收稿日期:2019-07-25 修回日期:2019-12-24 出版日期:2020-02-05 发布日期:2020-01-04
  • 通讯作者: 张东辉 E-mail:347929872@qq.com;donghuizhang@tju.edu.cn
  • 作者简介:邢瑞(1995—),男,硕士研究生, 347929872@qq.com
  • 基金资助:
    化学工程联合国家重点实验室开放课题(SKL-ChE-16B05)

Simulation of oxygen production via VPSA optimized based on MPC control strategy

Rui XING(),Nan JIANG,Bing LIU,Yaxiong AN,Yayan WANG,Donghui ZHANG()   

  1. State Key Laboratory of Chemical Engineering, Research Center of Chemical Engineering, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
  • Received:2019-07-25 Revised:2019-12-24 Online:2020-02-05 Published:2020-01-04
  • Contact: Donghui ZHANG E-mail:347929872@qq.com;donghuizhang@tju.edu.cn

摘要:

针对真空变压吸附制氧在gPROMS软件中建立了严格的数学模型,基于LiLSX吸附剂设计了两塔八步的真空变压吸附流程生产纯度为92%的O 2。对此流程进行优化,其纯度和回收率有了明显的改进。在此基础上,引入实际生产中经常存在的如进料流量的变化以及吸附性能降低等扰动因素,使模拟工作更接近实际。根据产品气中O 2纯度的反馈,采用模型辨识技术设计了MPC控制器,用于预测控制VPSA过程的动态行为。开环和闭环控制结果的对比显示,流程在设计的MPC控制下展现出更好的结果,这表明MPC控制策略可以明显改善空气分离制氧的生产过程。

关键词: 吸附, 制氧, VPSA模拟, 优化, 模型预测控制

Abstract:

A rigorous mathematical model was established in the gPROMS software for vacuum PSA oxygen production. Based on the LiLSX adsorbent, a two-stage, eight-step vacuum PSA process was designed to produce O 2 with a purity of 92%. Changes in feed flow rate as well as the decrease of the adsorption property were set as disturbances to make the simulation work more close to reality. Meanwhile, time duration was set to change consistently according to the feedback of O 2 purity in product. The system identification model was then adopted and was used to predict the dynamic behavior of the VPSA process and to develop an MPC controller. Detailed performance under open-loop and closed-loop was listed and compared. The results demonstrated that the model shows an enhanced performance with the presence of random disturbances under closed-loop control. This suggested that the MPC control strategy can be implied to improve the oxygen-production process.

Key words: adsorption, oxygen production, VPSA simulation, optimization, model-predictive control

中图分类号: 

  • TQ 028.1

表1

扩展Langmuir模型的拟合参数"

ParameterN 2O 2Ar
IP 1/(kmol·kg -1·Pa -1) 7.107×10 -106.861×10 -96.254×10 -9
IP 2/K 291015671334
IP 3/Pa -12.563×10 -84.625×10 -84.374×10 -8
IP 4/K 1612441.3450.6
Δ H/(kJ·mol -1) -23.43-13.22-12.65

表2

传质传热模型参数"

ParameterValue
Tfeed/K 298
c pg/(kJ·kg -1·K -1) 1.03
c ps/(kJ·kg -1·K -1) 1.21
Rp/m 8.5×10 -4
Dv,N2/(m 2·s -1) 1.30×10 -4
Dv,O2/(m 2·s -1) 1.29×10 -4
D, v, Ar/(m 2·s -1) 1.24×10 -4
h/(W·m -2·K -1) 0.3
kg/(W·m -1·K -1) 0.02452
ks/(W·m -1·K -1) 0.48

图1

两塔-八步VPSA模拟过程"

表3

VPSA流程的时序"

时间 /sBED1BED2
6AD 1VU 2
3AD 2PUR
3EDER
10VU 1FR
6VU 2AD 1
3PURAD 2
3ERED
10FRVU 1

图2

各循环步骤操作示意图"

表4

VPSA过程模型方程"

方程方程表达式
组分质量方程-εbDax?2yi?z2+?(vgci)?z+εb+1-εbεp?ci?t+ρp1-εb?qi?t=0 (1)
总质量方程?(vgc)?z+εb+1-εbεp?c?t+ρp1-εb?q?t=0 (2)
能量衡算方程

εb+1-εbεpi=1Ncicpg,i-R+1-εbρpcps+1-εbρpi=1Nqicpg,i-R?T?t+vgρg

i=1Ncpg,i?T?z+1-εbρpi=1N?qi?tHi+2hT-TwRb-εb+1-εbεp?P?t-kg?2T?z2=0 (3)

动量方程?p?z=-150μ1-εb2εb3(2Rp)2vg+1.751-εbρg2Rpεb3vgvg (4)
Langmuir 吸附等温方程qi*=IP1eIP2TPi1+iIP3,ieIP4,iTPi (5)
线性推动力方程?qi?t=15Dc,iRp2qi*-qi (6)
扩散系数Dax=0.73Dm+vgRPεb1+9.49εbDm2vgRP;Dc,i=εpτDk,iDmDk,i+DmDk,i=48.5DpTMi;Dm=0.1013T1.751MA+1MBP(Dv,A1/3+Dv,B1/3)2 (7)
边界条件z=0vg,z0,?Tz=Tin,?yi,z=yin,i;?else,??Tz?z=0,??yi,z?z=0z=Hbvg,z<0,?Tz=Tout,?yi,z=yin,i;else,??Tz?z=0,??yi,z?z=0 (8)
阀门方程unidirection:?if?Pin>Pout,?then?F=cv(Pin-Pout)106;else,?then?F=0bidirection:?F=cv(Pin-Pout)106 (9)

表5

决策变量与优化目标的上限值、下限值、初始值以及最佳值"

变量初始值下限值上限值优化值
决策变量
进料流量/(m 3·h -1) 3.01.015.04.2
终升压流量/(m 3·h -1) 4.81.015.06.0
抽真空流量/(m 3·h -1) 7.21.030.018.6
吸附出口阀门开度/(mol·(bar·s) -1) 0.20.01100.00.97
均压步骤阀门开度/(mol·(bar·s) -1) 0.20.0110.00.86
冲洗步骤阀门开度/(mol·(bar·s) -1) 0.20.0130.02.6
优化目标
纯度/%90.29210092.03
回收率/%58.76010060.5
能耗/(kW·h·m -3) 0.420.31

图3

N 2轴向气相分布优化前后对比 "

图4

吸附时间(a)和终升压时间(b)的改变对纯度的影响"

图5

吸附步骤和终升压步骤结束时塔内N 2气固相分布 "

图6

状态空间模型与原始数据的比较"

图7

扰动前后塔内压力变化"

图8

情况1条件下O 2纯度的变化比较 "

图9

N 2和O 2在LiLSX上的吸附等温线 "

图10

不同吸附性能条件下O 2纯度的变化 "

图11

无控制和MPC控制两种情况下O 2纯度的变化 "

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