Optimal Design of a Two-Stage Membrane System for Hydrogen Separation in Refining Processes

Abstract

This paper fits into the process system engineering field by addressing the optimization of a two-stage membrane system for H 2 separation in refinery processes. To this end, a nonlinear mathematical programming (NLP) model is developed to simultaneously optimize the size of each membrane stage (membrane area, heat transfer area, and installed power for compressors and vacuum pumps) and operating conditions (flow rates, pressures, temperatures, and compositions) to achieve desired target levels of H 2 product purity and H 2 recovery at a minimum total annual cost. Optimal configuration and process design are obtained from a model which embeds different operating modes and process configurations. For instance, the following candidate ways to create the driving force across the membrane are embedded: (a) compression of both feed and/or permeate streams, or (b) vacuum application in permeate streams, or (c) a combination of (a) and (b). In addition, the potential selection of an expansion turbine to recover energy from the retentate stream (energy recovery system) is also embedded. For a H 2 product purity of 0.90 and H 2 recovery of 90%, a minimum total annual cost of 1.764 M$·year −1 was obtained for treating 100 kmol·h −1 with 0.18, 0.16, 0.62, and 0.04 mole fraction of H 2 , CO, N 2 , CO 2 , respectively. The optimal solution selected a combination of compression and vacuum to create the driving force and removed the expansion turbine. Afterwards, this optimal solution was compared in terms of costs, process-unit sizes, and operating conditions to the following two sub-optimal solutions: (i) no vacuum in permeate stream is applied, and (ii) the expansion turbine is included into the process. The comparison showed that the latter (ii) has the highest total annual cost (TAC) value, which is around 7% higher than the former (i) and 24% higher than the found optimal solution. Finally, a sensitivity analysis to investigate the influence of the desired H 2 product purity and H 2 recovery is presented. Opposite cost-based trade-offs between total membrane area and total electric power were observed with the variations of these two model parameters. This paper contributes a valuable decision-support tool in the process system engineering field for designing, simulating, and optimizing membrane-based systems for H 2 separation in a particular industrial case; and the presented optimization results provide useful guidelines to assist in selecting the optimal configuration and operating mode.

Evaluation of Flowsheet Design Approaches to Improve Energy Efficiency in Multistage Membrane Processes to Recover Helium

“…12,13,28 Although previous works 13,14 suggested that the two-stage membrane system utilizing a mixed-mode driving force (CP + VP scheme) for CO 2 capture from flue gas (>13 mol % CO 2 in feed) or NG or biogas upgrading (40% CO 2 ) was the best, the feed concentration of the desired product and feed flow rate were much higher than that in this study. Another study by Arias et al 53 reported that the CP + VP scheme in the twostage process shows a cost-optimal process for H 2 separation from refinery processes, with 18 mol % H 2 in the feed. However, they did not include the CP + VP-1 scheme in their investigation, which is shown in our study as an optimal process configuration in a mixed-mode driving force using the two-stage cascade system.…”

A Novel Process of H2/CO2 Membrane Separation of Shifted Syngas Coupled with Gasoil Hydrogenation

“…Many researchers have thus turned their attention to the membrane separation process, due to its low investment cost and simple operation, to capture CO2 in the coal gasification hydrogen production process. Arias et al [10] proposed a two-stage membrane system for hydrogen separation in refining processes, a H2 product purity of 0.90 and H2 recovery of 90% are achieved. But these literatures have rarely been simultaneously coupled with hydrogen purification [10][11][12][13][14].…”

“…Arias et al [10] proposed a two-stage membrane system for hydrogen separation in refining processes, a H2 product purity of 0.90 and H2 recovery of 90% are achieved. But these literatures have rarely been simultaneously coupled with hydrogen purification [10][11][12][13][14]. Moreover, Chen et al [15] established a mathematical model for a dual membrane separator, which provided a new way to separate H2/CO2 of shifted syngas.…”

Modeling and Simulation of Reaction and Fractionation Systems for the Industrial Residue Hydrotreating Process

“…Since vacuum residue accounts for about half of the crude oil, more attention has been focused on vacuum residue hydroconversion processes, which are capable of converting heavy, inferior petroleum into light, valuable products such as gasoline, jet fuel, and diesel [3,4]. A good process model is important for monitoring the plant-level operation status, optimizing operating conditions, verifying the dynamic adjustment scheme, and maximizing the profit [5][6][7].…”