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This paper explores mass exchanging the outlet and inlet streams of a reactor, as a design heuristic within the hierarchical process design procedure by Douglas [AIChE J. 1985, 31 (3), 353–361 and Conceptual Design of Chemical Processes; McGraw–Hill, 1988], who worked on the HDA process to test the proposal. The heuristic is used at an early stage...
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... traditional process designed by Douglas 1,2 has an extent of reaction of 70%À75%. Figure 4 shows a flow sheet of this process before heat integration (heating and cooling are performed with external utilities, without exchanging heat among process streams), which is the last level of decisions in the hierarchy of Douglas. 1,2 The most relevant streams for a production of 125 kmol/h of benzene are presented in Table 1. ...
Citations
... MENS techniques have been widely applied in other applications such as hydrogen recovery networks (Fischer and Iribarren, 2011a), biodiesel production (Fischer and Iribarren, 2011b), water networks (Karthick et al., 2010), and process synthesis and integration (Dunn and Bush, 2001). However, these application areas are not reviewed in this paper. ...
This work provides the first systematic critical review of mass exchanger network synthesis literature. Mass exchanger networks play a central role in many pollution reduction and resource utilisation processes and contain many complex decisions to be made including exchanger types, sizing, and mass separating agent selection. We present a comprehensive review of the key milestones in the development of methods for mass exchanger network synthesis and focus on the key challenges that have hindered research in this area from flourishing in the manner of the conceptually similar heat exchanger network synthesis problem. We find that several important research questions remain for the methods to find wider use in industry. More efficient techniques for solving nonconvex mixed-integer nonlinear programs and better methods of including more accurate, higher-order unit models for industrial problems within network optimisation problems are particularly important, as current methods provide highly simplified unit representations that do not take into account many important practical design considerations that have significant cost implications. Furthermore, we identify significant potential for further research into increasing the scope of the problem to include issues such as flexibility and controllability, inter-plant mass exchanger networks, batch processes, retrofit and further integration of heat and mass exchanger networks, with research into these domains limited. Through further research of these under-developed applications of mass exchanger network synthesis, we envision that techniques for mass integration can become a powerful tool to enhance mass integration techniques for sustainable cleaner production technology.
... In this paper, we propose a novel hydrogen recovery structure in a cyclohexane production process, arrived at by following a mass exchange heuristic developed in previous works [1,2]. ...
... In previous works [1,2,8,9], we proposed and described in detail the use of the concept of Mass Exchange Network as a mass exchange heuristic at two levels of Douglas [3,4] hierarchical process design procedure. We considered applying the mass exchange heuristic to a process that involves a reaction between two or more gas-phase reactants, performed at medium or high pressure, which react to form a product and eventually byproducts. ...
... We successfully applied the mass exchange heuristics to a process for the synthesis of Biodiesel [8], the synthesis of Benzene from Toluene (HDA Process) [1,2], a Cyclohexane production process [15] (in this case at the higher hierarchy level), and an Ammonia synthesis loop [9], resorting to a novel counter-current mass exchanger equipment (a gas permeation membrane module) previously presented [1]. This paper focuses on analyzing the new recycle alternatives generated in a cyclohexane synthesis process, when applying the mass exchange heuristic at the end of the hierarchical design procedure, which leads to integrating streams entering and exiting the process [7]. ...
In this paper, we propose a novel hydrogen recovery structure in a cyclohexane production process, arrived at by following a mass exchange heuristic developed in previous works [1,2].In the cyclohexane production process considered, we explore the effect of process design variables and find the optimal design for a mass exchange between the purge stream and the feed of benzene to the process. We compare our results with a conventional process design lacking hydrogen recovery from the purge, and with a process design which implements a conventional membrane recovery system at the optimum setup of the decision variables. The process with recovery through mass exchange here proposed obtained a respectable 7.12% reduction of hydrogen consumption, resulting in an increase of the plant Net Annual Income of a 4.24% respect to the conventional process design without recovery. These figures are similar to the ones that result from implementing a process design with a conventional membrane recovery system. These results highlight the importance of considering a mass exchange between the process feed and purge stream as an alternative design of the recovery system.
... Applying the concept of MEN at an early stage strongly modifies the separations and recycling structure of the process. Fischer and Iribarren [8] explored this approach on the HDA Process for producing benzene from toluene, using a proposed counter current gas permeation equipment to exchange hydrogen from the reactor outlet stream (the reaction requires an excess of hydrogen that must be removed afterward) and the toluene inlet stream. This new Mass Exchanger did not completely removed the original separation and recycle structure of Douglas [1,2] process, but strongly reduced its size and cost, and rendered an interesting reduction of the overall hydrogen consumption of the process. ...
... In this paper we use the concept of MEN as a last refinement step of the traditional HDA Process, designing the hydrogen recovery from the purge stream by implementing the counter current gas permeation equipment recently proposed by Fischer and Iribarren [8] to exchange hydrogen between the purge and the toluene feed to the process. The goal of this design is recovering part of the hydrogen available in the purge stream, and results in a process alternative different from other recently proposed by Bouton and Luyben [4] also resorting to gas permeation membrane units, but to a different type of membranes and in a traditional arrangement. ...
... Simulation of the counter current gas permeation mass exchanger required building an ad hoc module, because it has an extra inlet stream and depending on the concentrations on both sides of the membrane, the flux of some components may be toward the opposite side of the membrane. The module to perform this exchange is described in detail in Fischer and Iribarren [8] and was developed in Aspen Custom Modeler V7.2 to be used in Aspen Plus V7.2 to simulate the mass exchange of hydrogen in the recycle and separation system of the HDA Process. ...
In this paper we use the concept of Mass Exchange Networks to design the hydrogen recovery from the purge stream of an HDA Process by implementing a recently proposed counter current gas permeation equipment to exchange hydrogen between the purge and the toluene feed to the process. This design would correspond to the final design refinement step in the Douglas 1 and 2 hierarchical process design procedure, proposed by Fischer and Iribarren [3]. The goal of this design is recovering part of the hydrogen available in the purge stream, and results in a process alternative different from other flow sheet recently proposed by Bouton and Luyben [4], also resorting to gas permeation membrane units, but in a traditional arrangement. Two different types of available zeolite ceramic membranes were studied, of different permeability and selectivity. The here proposed mass exchange design recovers a similar amount of hydrogen as the process alternative proposed by Bouton and Luyben [4] who use a less expensive type of polymeric membrane, but need a compressor to recycle the permeate stream because they use transmembrane pressure as the driving force. The here proposed design at actual cost of zeolite membranes allows an 153.9% increase of the Net Annual Savings with respect to the pressure driven membrane system when using the less selective ceramic membrane, while this figure descents to a 32.61% when using the most selective (which is also the most expensive alternative).
... It resorts to novel counter-current mass exchanger equipment (a gas permeation membrane module) previously presented. 7 This exchanger takes advantage of the concentration gradients between the process gaseous streams to perform hydrogen exchange, significantly reducing the cost of both the separation and the recycle loop, as well as the amount of hydrogen feed, thus improving the overall performance of the process. ...
... This is the key feature that gives the mass exchange heuristic a good chance to be successfully applied. 7 Out of all these existing processes, we are more interested in those whose reactants and products are in the gaseous state, because then we can resort to a previously proposed 7 novel mass exchanger that uses the concentration difference as the driving force. To illustrate the application of the mass exchange heuristic we will use the Hydrar process, because it is the one that uses the greater hydrogen excess, that is, a large driving force to perform the mass exchange. ...
... Therefore, the mass exchanger (MASSHX) is placed in the gas stream (GAS) leaving the flash separator, where the hydrogen molar fraction is 0.78 as shown in Figure 2. Table A2 (in Supporting Information) presents the properties of the main streams of this configuration for a membrane area of 50 m 2 . The module with the model of the mass exchanger equipment is described in a previous paper, 7 and it is provided for this paper as Supporting Information for use only in Aspen Plus V7.2. ...
In this paper, we propose changes in the design of a cyclohexane production process, following a mass exchange design heuristic developed in a previous work (Ind. Eng. Chem. Res. 2011, 50 (11), 6849-6859). In the study case considered, an optimal design was obtained which exhibits a significant 40.08% reduction in the power of the compressor that recycles unreacted reagents, and a respectable 3.59% reduction of the hydrogen consumption, resulting in an increase of the plant Net Annual Income of a 1.3196. These results highlight the importance of considering a mass exchange between the input and output streams from the reactor, at the time of synthesizing a new process.
For our works, Mass Exchangers (MEs) are membrane equipment that exchange some component between two streams in a countercurrent arrangement. In previous works these were proposed to use them (with the goal of hydrogen recovery, energy saving and waste minimization) at different stages of the hierarchical decision procedure for process synthesis by Douglas: at an early design stage, when deciding the recycle structure of the process (resulting in considerable changes in the process structure); or at a final design stage, before deciding the mass and energy integrations of process streams (resulting in minor changes in the process structure).
The heuristic allocation of MEs was used independently at both design stages in previous works, with the goal of comparing with other design alternatives reported in the literature that use membranes in the conventional configuration (one feed stream and two exit streams; retentate and permeate). In contrast, the present work compares the results of using MEs, when they are used individually at both design stages, and when they are used jointly at both design stages, in different configurations. For the case study example (the HDA Process), the use of a ME at an early design stage reduces the fresh hydrogen consumed by 3.37%, and the recycle compressor power by 4.09%. The use of a ME at a final design stage reduces the fresh hydrogen consumed by 31.64%, but it does not reduce the recycle compressor power. The joint use of the MEs at both design stages reduces the fresh hydrogen consumed by 14.54%, and the recycle compressor power by 2.91%.
The joint use of MEs at both design stages retains the principal benefits of its use at early and final design stages (energy saving and hydrogen recovery, principally), so when both a reduction in the fresh hydrogen consumed and in the recycle compressor power is desired, it is the most appropriate option.
Hydrometallurgy is a widely studied recovery process to recover NiMH battery, but the large chemical consumption restricted its application in industry. To achieve a low chemical consumption recovery process of NiMH battery anode alloy, an integrated process with selective leaching and multi-stage extraction was designed. In selective leaching, the leaching procedure was divided into four stages. The acid used could be reacted with the battery anode alloy totally except in the last stage. The metal components of the alloy have different reaction activities with acid, they were leached into liquor by the sequence: La>Pr>Nd>Ce>Al>Mn>Co>Ni. Hence, the selectivity of metals was achieved to make the following extraction much easier. The total chemical consumption was calculated by the ratio of UMAC/UMACmin and S, which in this integrated process was 60% less than in traditional recovery process. Through this recovery process, the recovery rate of rare earth elements (REEs) reached 90.5%, and the purity of REO product exceeded 99%. This integrated process was considered as a practical approach to recover the waste alloy.
In this work, we propose a new arrangement for integrating an Autothermal Reforming of Ethanol process with oxygen production with the technology of ITM membranes. In the conventional configuration O2 is first separated from the air and then injected in the reforming process, while in the new configuration O2 is depleted from the air in a counter-current arrangement with a reforming process stream, used as sweep gas. We took from the literature a process for Autothermal Reforming of Ethanol in its optimal operating condition, and scaled it up to pilot size. We assessed the performance of both configurations with Aspen Plus V8.7 and found that the configuration in counter-current arrangement with a process sweep stream has a reduction of the total annualized cost of 27.3% with respect to the conventional separation configuration. Furthermore, we optimize the operating conditions and ancillary structure of the counter-current integrated process, achieving a total annualized cost reduction of 72.2% with respect to the conventional design.
In this work we analyze different design alternatives for the integration of a gasification process with the oxygen production process, through ITM membranes. We analyze the conventional separation design compared with a novel configuration in a countercurrent arrangement with sweep gas (using the gas permeation module as a mass exchanger). To assess the oxygen transfer in the permeation modules, they are modeled with Aspen Custom Modeler V8.4 and the different design alternatives are simulated in Aspen Plus V8.6. The economic analysis carried out shows that the counter-current arrangement with a sweep stream has a Total Annualized Cost 13.5% lower than the conventional separation design.
A mathematical model for the design of membrane distillation (MD) processes applied to the water recovery from brines is developed in this study. The highly saline concentration inherent to this kind of system requires a robust thermodynamic method for water activity prediction and the consideration of temperature and concentration polarization effects for model accuracy. The MD model fitted reasonably well to experimental data and was further extended to incorporate balance and energy equations for a membrane distillation crystallization (MDC) process. A hierarchical design approach to be used alongside the model is suggested for MDC processes.
