Jean Pimentel

57201129887

Publications - 21

Exhaustive enumeration of heat exchanger networks with minimum utility consumption using graph-theoretic approach

Ákos Orosz Dhanaraj Turunawarasu Viknesh Andiappan Bing Shen How Jean Pimentel Sin Yong Teng Lip Siang Yeo Ferenc Friedler

Publication Name: Energy

Publication Date: 2025-10-30

Volume: 335

Issue: Unknown

Page Range: Unknown

Description:

Enhancement in energy recovery is always an essential element that requires academic spotlights to ensure its capability to contribute towards carbon neutrality. Recent works have extended to cover multi-solution heat exchanger networks (HEN) synthesis instead of generating a single best solution, which is not guaranteed to be practical. Nevertheless, owing to the technical challenges of synthesising all feasible networks, none of the existing works attempts to comprehensively elucidate how network topologies affect the network cost. To address this gap, P-HENS, a graph theoretic-based HEN synthesis tool, was utilised to generate the set of all heat exchanger networks with minimum utility consumption. Its effectiveness is demonstrated through an illustrative case study, which eventually generates more than 45,000 HENs. The impacts of structural variables on the cost, including the number of exchangers and the stream pairings, were analysed. The cost range of the networks was identified, revealing cost differences of 30 % despite minimum utility consumption or 15 % despite the minimum number of exchangers. Key stream pairs required to meet maximum energy recovery and influence cost were identified, leading to recommendations for improving solution searches. The solution set and the insight from this work are available to the research community for further analysis, offering valuable insights to enhance energy integration in the industry.

Open Access: Yes

DOI: 10.1016/j.energy.2025.137898

Towards the synthesis of reliable and resilient complex networks

Ákos Orosz Kirti M. Yenkie Jean Pimentel Andres Castellar-Freile

Publication Name: Current Opinion in Chemical Engineering

Publication Date: 2025-09-01

Volume: 49

Issue: Unknown

Page Range: Unknown

Description:

Process synthesis methodologies have traditionally focused on optimizing the economic criteria. However, owing to the complexity of real systems, external factors, such as expected or unexpected events or disturbances, negatively affect the performance of optimal networks. In this context, it becomes essential to consider the effect of such events on the performance of the network in the early design stages. This work presents a comprehensive review of the contributions related to this relevant topic, focusing on two widely utilized indicators: reliability and resilience. Reliability focuses on the probability of system failures due to disturbances, and resilience analyzes the behavior of the system after disturbances and its capacity to recover over time. Relevant contributions are reviewed, which present deterministic and stochastic methods to estimate these indicators, with a special focus on the design phase. Moreover, this work also presents a perspective on using machine learning methods on complex systems datasets as an emerging direction for enhancing the estimation of these properties. This contribution highlights recent advancements in this field and emphasizes the relevance of resilience and reliability as key metrics for developing safer processes with improved operability.

Open Access: Yes

DOI: 10.1016/j.coche.2025.101172

CO2 capture using blended amine − ionic liquid solvents: Thermodynamic modeling and process optimization

Teng Zhou Jean Pimentel Xuechong Ding Xingyang Li

Publication Name: Separation and Purification Technology

Publication Date: 2025-07-30

Volume: 362

Issue: Unknown

Page Range: Unknown

Description:

The hybrid ionic liquid (IL) − amine solvents have demonstrated high efficiency in CO2 capture. However, rigorous simulations of carbon capture processes employing IL-amine blended solvents have been scarce. This study presents detailed thermodynamic modeling and process simulations for carbon capture in the steel process and natural gas combined cycle (NGCC) power plant. We investigated two hybrid solvent systems, i.e., [BMIM][BF4]/PZ/MDEA and [BMIM][TF2N]/PZ/MDEA with the blended amine PZ/MDEA used as a benchmark. The phase equilibria of the CO2-PZ-MDEA-H2O-IL system was regressed with the NRTL model. The CO2 molar loading in the lean solvent (αlean) and mass fraction of ILs (xIL) in the mixture solvent were optimized to minimize the regeneration energy (Qreg) of the capture processes. The results indicate that the [BMIM][TF2N]/PZ/MDEA-based process is most energy-efficient (Qreg = 2.845 GJ/tCO2 at αlean = 0.14 and xIL = 1.0 wt%) for the steel plant and (Qreg = 2.749 GJ/tCO2 at αlean = 0.08 and xIL = 1.5 wt%) for the NGCC power plant. Compared to the PZ/MDEA-based benchmark process, IL's inclusion led to a 2.90 % and 0.11 % reduction in the regeneration energy for the steel process and NGCC power plant, respectively, demonstrating the benefit of introducing IL into the amine solvents for CO2 capture.

Open Access: Yes

DOI: 10.1016/j.seppur.2025.131649

Designing cost-effective supply chains for plastics at the end-of-life

Gerardo Ruiz-Mercado Natalia A. Cano-Londoño Jean Pimentel Csaba T. Deak Baibhaw Kumar Heriberto Cabezas

Publication Name: Journal of Cleaner Production

Publication Date: 2025-04-10

Volume: 501

Issue: Unknown

Page Range: Unknown

Description:

Increased global plastic consumption and production boosted the amount of end-of-life (EoL) plastic. Also, 90 % of plastic EoL is either landfilled or incinerated. These unsustainable EoL pathways impact the environment and human health and waste valuable materials. Thus, improvements to the existing recycling infrastructure for sustainable plastic management are needed to enhance plastic circularity. Therefore, this contribution addresses optimizing cost-effective pathways for plastic recycling within the supply chain. The research uses mathematical optimization and the P-graph theoretical framework to calculate recycling costs, encompassing both capital expenditure and operational expenditure for various pathways of plastic recycling. The proposed methodology is applied through a detailed case study in Miskolc, Hungary, revealing estimated recycling costs ranging from 54.9 to 59.28 EUR/ton. This finding provides crucial insights into the economic implications of diverse recycling methods. Also, the study highlights the P-graph model's untapped potential as a resource for decision-makers in plastic recycling, particularly the enumeration of options for further consideration. The work's utility and novelty lie in the model's capability to design cost-effective pathways, offering a tangible contribution to the plastic recycling supply chain. Finally, this contribution offers economic solutions needed to ensure cost-effective sustainable plastic management solutions.

Open Access: Yes

DOI: 10.1016/j.jclepro.2025.145227

Systematic Method of Retrofitting Wastewater Transportation Systems for Enhanced Reliability

Ákos Orosz Kirti M. Yenkie Jean Pimentel Andres Castellar-Freile

Publication Name: Chemical Engineering Transactions

Publication Date: 2024-01-01

Volume: 114

Issue: Unknown

Page Range: 1075-1080

Description:

While the treatment of wastewater is an important issue that received significant attention in the past decades, improving the related technologies is only one part of a more complex task. Domestic wastewater is usually transported via the city's sewer system, and in many places, it is combined with rainwater. This means that disturbances, such as heavy rainfall or failures in the pipeline system, can lead to floods of polluted wastewater. Thus, it is important to design such transportation systems to be reliable. This work presents a methodology for generating several potential extensions to retrofit an existing water transportation network and increase its reliability. Reliability and feasibility evaluation is performed via the P-graph framework, after which the nondominated networks are collected. Results of the presented case study show that reliability can be increased 3 times by adding only some of the possible extensions to the network. The methodology proposed analysed 512 plausible retrofitting alternatives, from which 20 are non-dominated networks. This range of alternatives provides designers with insightful information to decrease water pollution and the vulnerability of wastewater systems.

Open Access: Yes

DOI: 10.3303/CET24114180

Optimization of vertical farms energy efficiency via multiperiodic graph-theoretical approach

Jean Pimentel Ferenc Friedler L. Balázs

Publication Name: Journal of Cleaner Production

Publication Date: 2023-09-01

Volume: 416

Issue: Unknown

Page Range: Unknown

Description:

A systematic method is proposed for enhancing the energy efficiency of vertical farms when integrated into urban infrastructure. The method relies on the optimization of a multiperiod model that determines the system's best operation plan considering variations in its parameters throughout the day. These parameters include factors such as resources availability from the urban infrastructure and fluctuations in electricity prices. The model is formulated and solved via the tools of the P-graph framework, which permits the automatic formulation of the rigorous superstructure and the efficient optimization of the integrated system's operation. The method is illustrated via a case study comprising three scenarios. The most efficient case demonstrates up to 40% electricity cost saving potential for a particular operation day, and up to 31% for the entire year. The method presented constitutes an optimization tool that can use real data on electricity prices and forecasts of weather conditions to reduce operating costs and enhance the energy efficiency and sustainability of vertical farming systems.

Open Access: Yes

DOI: 10.1016/j.jclepro.2023.137938

A comprehensive, semi-automated systematic literature review (SLR) design: Application to P-graph research with a focus on sustainability

Jean Pimentel Árpád Tóth Alex Suta Andres Argoti

Publication Name: Journal of Cleaner Production

Publication Date: 2023-08-20

Volume: 415

Issue: Unknown

Page Range: Unknown

Description:

Because of the vast number of academic products with focus on sustainability being currently generated, it is becoming exceedingly difficult and time-consuming to perform accurate literature reviews that have actual relationship with such a topic and correctly reflect its state of the art. Thus, this work proposes a comprehensive Systematic Literature Review (SLR) design as a novel approach for collecting the body of contributions for any given research field in general and sustainability in particular. This design is guided by a semi-automated procedure that aims at incorporating the best automation features of earlier SLRs and involves available scientific databases, e.g., Scopus and Web of Science. The results of the proposed SLR design include bibliometric analyses, a list of researcher and institution networks, and a qualitative assessment of practical applications of the field of interest. Moreover, the proposed semi-automated approach allows for the inclusion of subject categorization based on the generation of author-density maps and keyword co-occurrence networks. For illustration, the semi-automated SLR design is implemented by thoroughly reviewing the contributions pertaining to the P-graph (Process Graph) framework with a focus on sustainability. The P-graph framework has been applied to multiple areas, such as network design, optimization, and system integration; in particular, the framework has proven to be useful for the development of sustainable systems. Upon execution, the semi-automated SLR design collected 284 contributions related to P-graph, of which 139 were classified as sustainability-related, and further partitioned into specific categories. It is expected that the proposed semi-automated SLR design will help researchers in the sustainability community accelerate the generation of works in that area by rapidly generating accurate literature reviews.

Open Access: Yes

DOI: 10.1016/j.jclepro.2023.137741

Energy Management Systems in Smart Cities: A Review from the Perspective of Complex Networks Design

Lukács Balázs Jean Pimentel Istvan Drotar

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 107

Issue: Unknown

Page Range: 679-684

Description:

Smart cities are a very promising concept for achieving the sustainability of urban settlements. This is especially true for sustainability related to general aspects of energy management, e.g., generation, transformation, distribution, and storage. Despite their considerable potential, smart cities are complex systems in nature, as numerous individuals and subsystems participate in their performance. Because of this complexity, numerous challenges are presented for the conception of this type of system, i.e., during its design stage. The contribution provides a brief literature review that focuses on energy management in smart cities. Initially, an overview of the field is provided by analyzing the co-occurrence of keywords in the literature available in the SCOPUS database. Subsequently, strategies for energy management in smart cities, modeling approaches, and challenges and opportunities are discussed. For this, the work refers to earlier literature reviews that describe in detail relevant subjects from the perspective of networks design and optimization. The review aims at helping interested readers recognize the systematic tools available for the design of energy systems as well as the challenges offered in this rapidly evolving area, thereby contributing to the advancement of sustainable and efficient energy solutions within the context of urban environments.

Open Access: Yes

DOI: 10.3303/CET23107114

Technoeconomic Assessment of Recycling Routes for Chemicals: A Case Study of n-Hexane

Gerardo Ruiz-Mercado Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2023-01-01

Volume: 103

Issue: Unknown

Page Range: 349-354

Description:

The circular economy has become one of the most popular topics in worldwide sustainability research. The imperious necessity of reducing resource consumption and decreasing waste generation has led to reincorporating materials at the end-of-life (EoL) stage into the productive chain. Nonetheless, the presence of hazardous substances in the EoL stage materials poses a significant challenge for the transition toward the production model. The adequate transformation of these materials into feedstocks requires their correct allocation into recovery plants and final destinations. Such an allocation can be decided by resorting to optimisation by generating the best alternative networks, from where the stakeholders may decide the most suitable recycling scheme. In this work, a graph-theoretic approach is introduced to identify the best alternatives to reincorporate industrial EoL chemicals into the productive chain. This contribution presents the initial approach to this problem, demonstrated through a case study considering the data reported on the publicaccess release inventory data for n-hexane. Different recycling routes are proposed for the case study by optimising the total treatment cost, and their advantages and disadvantages are discussed; moreover, their efficiency concerning the circular economy is measured by comparing the amount of recovered chemicals. By generating plausible recycling alternatives, this work contributes positively to analysing potential alternatives for circular economy and resource conservation in industry.

Open Access: Yes

DOI: 10.3303/CET23103059

Framework to embed machine learning algorithms in P-graph: Communication from the chemical process perspectives

Ákos Orosz Bing Shen How Jean Pimentel Sin Yong Teng Ferenc Friedler Jeroen J. Jansen

Publication Name: Chemical Engineering Research and Design

Publication Date: 2022-12-01

Volume: 188

Issue: Unknown

Page Range: 265-270

Description:

P-graph is a popularly used framework for process network synthesis (PNS) and network topological optimization. This short communication introduces a Python interface for P-graph to serve as a linkage to modern programming ecosystems. This allows for a wider application of the fast and efficient P-graph solver, to provide structural and topological enumeration in numerous fields. The proposed framework allows for more integrative usage in Artificial Intelligence (AI), machine learning, process system engineering, chemical engineering and chemometrics. Large and repetitive topologies can also be automated using the new programming interface, saving time and effort in modelling. This short communication serves as a demonstration of the newly developed open-sourced P-graph interface.

Open Access: Yes

DOI: 10.1016/j.cherd.2022.09.043

Enabling technology models with nonlinearities in the synthesis of wastewater treatment networks based on the P-graph framework

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Mihály Csaba Markót Heriberto Cabezas Ferenc Friedler

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-11-01

Volume: 167

Issue: Unknown

Page Range: Unknown

Description:

Designing effective wastewater treatment networks is challenging because of the large number of treatment options available for performing similar tasks. Each treatment option has variability in cost and contaminant removal efficiency. Moreover, their mathematical models are highly nonlinear, thus rendering them computationally intensive. Such systems yield mixed-integer nonlinear programming models which cannot be solved properly with contemporary optimization tools that may result in local optima or may fail to converge. Herein, the P-graph framework is employed, thus generating all potentially feasible process structures, which results in simpler, smaller mathematical models. All potentially feasible process networks are evaluated by nonlinear programming resulting in guaranteed global optimum; furthermore, the ranked list of the n-best networks is also available. With the proposed tool, better facilities can be designed handling complex waste streams with minimal cost and reasonable environmental impact. The novel method is illustrated with two case studies showing its computational effectiveness.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.108034

General formulation of resilience for designing process networks

Ákos Orosz Jean Pimentel Ferenc Friedler Andres Argoti

Publication Name: Computers and Chemical Engineering

Publication Date: 2022-09-01

Volume: 165

Issue: Unknown

Page Range: Unknown

Description:

Herein, the formula proposed for quantifying the resilience of engineering systems, including processing systems, is general in several aspects. The structure of a system can be highly complex where the numbers of loops, raw materials, and products are not limited. The mathematical models of the operating units can be either linear or nonlinear for simulating the effect of the failures. The damage caused by an unexpected event can result in various levels of operation for the operating units. The proposed formula is also general in the sense that all possible combinations of failures are considered. The problem formulation, the related structure representation, the enumeration and evaluation of possible failures are based on the P-graph framework and its algorithms. The proposed formula for resilience is applicable to any complex engineering system whose behavior is primarily determined by its structure, including supply chains, information systems, municipal infrastructures, and electrical transmission networks.

Open Access: Yes

DOI: 10.1016/j.compchemeng.2022.107932

Synthesis of Integrated Vertical Farming Systems with Multiperiodic Resource Availability

Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2022-01-01

Volume: 94

Issue: Unknown

Page Range: 1039-1044

Description:

Vertical farming (VF) has been proposed as an approach to decrease the land required for growing agricultural products. This technique consists of growing produce in vertical orientation within a controlled environment. However, one of the most significant barriers for its implementation is the uncertain economic feasibility, derived from the elevated consumption of energy and the high investment costs. A strategy to enhance VF efficiency proposes its integration with municipal infrastructure, thus establishing closed-loop systems where VF seizes organic waste, manure, CO2, and excess energy from productive plants and local power stations. Because of the economic uncertainty of its development, the optimal synthesis of such a closed-loop system (i.e., the selection and specification of its components, and their connections) is of utmost importance for the implementation of this strategy. The difficulty of the synthesis task arises from the combinatorial nature of the problem and the variability of the resources and market conditions in time. This work employs a graph-theoretic approach for the synthesis of a closed-loop system of VF considering the variability of the resources during multiple periods of operation. The proposed method relies on the P-graph framework which permits the identification of the n-best alternatives for the system’s design, employing the properties of the problem’s structure to enhance the effectiveness of the solution procedure. Consequently, the most cost-effective systems are identified together with their policy of operation for the different periods. This method constitutes a powerful tool for the assessment of systems for VF integration that enhance the sustainability of agricultural activity.

Open Access: Yes

DOI: 10.3303/CET2294173

The P-graph approach for systematic synthesis of wastewater treatment networks

Ákos Orosz Kirti M. Yenkie Jean Pimentel Heriberto Cabezas Ferenc Friedler

Publication Name: Aiche Journal

Publication Date: 2021-07-01

Volume: 67

Issue: 7

Page Range: Unknown

Description:

Wastewater treatment consists of three or four sequential stages: preliminary, primary, secondary, and tertiary. Each stage can comprise multiple alternative technologies that can perform the same tasks with different efficiencies, operating times, and costs. Thus, we propose a systematic approach for designing wastewater treatment networks by utilizing principles of mathematical modeling and generating an exhaustive enumeration of all the possible technologies and their connections during the early stages of designing a treatment facility. Some of these structures are nonintuitive and include recycling, reprocessing, bypasses, and multiple technologies in parallel or series to remove the same contaminant. The nonintuitive structures with multiple technologies may provide a measure of resilience compared to typical heuristic designs. Thus, the combination of P-graph methodology and the sequence of treatment technologies predicted via the optimization algorithm from the maximal structure is based on holistic considerations and does not lead to suboptimal solutions.

Open Access: Yes

DOI: 10.1002/aic.17253

Conceptual design of a negative emissions polygeneration plant for multiperiod operations using P-graph

Kathleen B. Aviso Ákos Orosz Raymond R. Tan Jean Pimentel Ferenc Friedler

Publication Name: Processes

Publication Date: 2021-02-01

Volume: 9

Issue: 2

Page Range: 1-19

Description:

Reduction of CO2 emissions from industrial facilities is of utmost importance for sustainable development. Novel process systems with the capability to remove CO2 will be useful for carbon management in the future. It is well-known that major determinants of performance in process systems are established during the design stage. Thus, it is important to employ a systematic tool for process synthesis. This work approaches the design of polygeneration plants with negative emission technologies (NETs) by means of the graph-theoretic approach known as the P-graph framework. As a case study, a polygeneration plant is synthesized for multiperiod operations. Optimal and alternative near-optimal designs in terms of profit are identified, and the influence of network structure on CO2 emissions is assessed for five scenarios. The integration of NETs is considered during synthesis to further reduce carbon footprint. For the scenario without constraint on CO2 emissions, 200 structures with profit differences up to 1.5% compared to the optimal design were generated. The best structures and some alternative designs are evaluated and compared for each case. Alternative solutions prove to have additional practical features that can make them more desirable than the nominal optimum, thus demonstrating the benefits of the analysis of near-optimal solutions in process design.

Open Access: Yes

DOI: 10.3390/pr9020233

Processing systems design considering resilience

Ákos Orosz Jean Pimentel Ferenc Friedler

Publication Name: Computer Aided Chemical Engineering

Publication Date: 2021-01-01

Volume: 50

Issue: Unknown

Page Range: 807-812

Description:

The resilience of a system is defined as the system's capability of recovering from failures. Traditionally, only predictable aspects are considered when designing processing systems. Evaluation of these aspects is performed via assessment of exact indicators and enumeration of all cause-effect options. However, such evaluation is not appropriate for determining the resilience of processing systems, since resilience is based on unexpected events in addition to the expected ones. Consequently, the cause part of the cause-effect relation is not known or not effective. In the current work, the general formula for determining resilience of a system is embedded into a P-graph based process synthesis algorithm. Thus, the resilience can be considered when selecting the most preferred process during its synthesis. The result is illustrated by synthesizing a process of adipic acid production by nitric acid oxidation of KA oil.

Open Access: Yes

DOI: 10.1016/B978-0-323-88506-5.50126-1

Systematic Design and Evaluation of Energy-Efficient Alternatives of Heterogeneous Azeotropic Distillation: Furfural Case Study

Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 619-624

Description:

Separation of azeotropic mixtures receives special attention for their impact on various significant industrial processes. Because of the non-ideal behaviour of these mixtures, it is impossible to separate them by conventional distillation. Instead of a single distillation unit, a system of multiple operations is to be employed. Heterogeneous azeotropic distillation (HAD) is an example of this kind of systems, where entrainers are applied to modify the behaviour of the mixture. The selection of the best separation system is a key objective during the synthesis of the process network. However, synthesis of HAD is especially difficult because of the complex interaction between its continuous and discrete features. Therefore, traditional separation network synthesis tools are incapable of solving this problem. In this work, the properties of the ternary vapor-liquid-liquid equilibrium diagram are exploited for systematically identifying plausible operating units that perform the separation of the azeotrope. Subsequently, energy consumption of the entire network is estimated through rigorous simulation. The P-graph framework is employed to represent the system’s structure. Additionally, its combinatorial algorithms generate a rigorous superstructure for the synthesis problem, and the set of n-best designs that minimize energy consumption. The method is illustrated by synthesizing the dehydration of furfural through HAD. The results demonstrate that it constitutes a valuable tool for the designer by being effective in the systematic identification and assessment of HAD alternatives.

Open Access: Yes

DOI: 10.3303/CET2188103

Energy Integration of Vertical Farms for Higher Efficiency and Sustainability

Jean Pimentel Ferenc Pongrácz György Ágoston Zoltán Sejpes Zsolt Bukodi István Kenyeres Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 727-732

Description:

As a result of the increasing human population, the availability of resources per capita has been vastly diminished in the last decades. Naturally, the depletion of valuable environmental assets such as water and arable land, poses a threat to mankind’s sustainable development. In this regard, various novel ideas have been proposed for processing agricultural products ecologically and sustainably; one of such ideas is vertical farming (VF). VF is a novel production technology that aims at enhancing both the yield and the product quality, by growing them in highly packed, high energy-density systems with high mass-flow rates and in a controlled environment. The technologies required for VF have been developed and successfully tested, thereby producing crops that meet the requirements of food safety, adequate nutrient content, and maximum yield. However, the extremely high biomass densities and high turnover rates employed to give rise to challenges regarding to energy efficiency and homogeneity patterns. In this work, a P-graph model is presented for the integration of VF systems. The algorithmic approach is employed to evaluate options for process integration and intensification of VF with plausible synergetic production processes into a dense urban environment. As a result, 115 integrated process alternatives are identified for the base case, with the best structure exhibiting a total cost of 41,920 EUR/y, thereby yielding reductions up to 11% for the total cost of the integrated network. The pareto front of economic performance and CO2 emission is presented to illustrate the potential benefits of integration, and the capability of the methodology to evaluate alternative designs.

Open Access: Yes

DOI: 10.3303/CET2188121

Efficient Design and Sustainability Assessment of Wastewater Treatment Networks using the P-graph Approach: A Tannery Waste Case Study

Ákos Orosz Kirti M. Yenkie Jean Pimentel Emmanuel A. Aboagye Heriberto Cabezas Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2021-01-01

Volume: 88

Issue: Unknown

Page Range: 493-498

Description:

In the tannery industry approximately, 30 - 35 m3 of wastewater (WW) is generated per ton of rawhide processed. The WW comprises high concentrations of salts, ammonia, dye, solvents, and chromium. Of particular interest is chromium, which has been proven to cause dermatological, developmental, and reproductive issues on exposure. Thus, there is a need for appropriate treatment of the tannery WW before it is discharged for natural remediation. However, designing a treatment process is multifaceted due to the availability of multiple technologies that can perform similar tasks and the complex composition of waste streams. This necessitates the treatment to be performed in stages namely, primary, secondary, and tertiary. In some cases, pretreatment is required to enhance the recovery in the following stages. Due to the combinatorial nature of this problem, the P-graph approach, which uses principles from graph theory, can be used to synthesize a treatment pathway by selecting appropriate technologies at each stage, while meeting required purity specifications. Furthermore, the P-graph approach can provide alternate feasible treatment structures ranked based on Economics as well as Sustainability indicators, such as the Sustainable Process Index (SPI). In this work, a tannery WW case study is investigated with multiple stages and treatment technologies. A complex maximal structure is generated comprising all possible technologies, flows, connections, bypasses, mixers, and splitters. The models for each technology involve capital and operating costs, efficiency, and SPI at each stage of the treatment process. This problem is formulated in P-graph and solved using the Accelerated Branch-and-Bound algorithm.

Open Access: Yes

DOI: 10.3303/CET2188082

General formulation for the resilience of processing systems

Ákos Orosz Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2020-01-01

Volume: 81

Issue: Unknown

Page Range: 859-864

Description:

Resilience is one of the key indicators of processing systems, it expresses the behaviour of the system as a result of expected or unexpected failures. This indicator can be essential during systems design and operation, especially, when the system is part of or related to a critical infrastructure. The numerous contributions on systems resilience are related to a wide range of applications, however, there is no general uniform framework for resilience evaluation. For instance, most studies examine resilience as a function of the continuous parameters of the system, usually avoiding the influence of its structure. In the current work, a general framework for determining the structural resilience of processing systems is presented. This framework derives on formulas that satisfy the requirements of the original definition of resilience. The formerly developed P-graph framework is the mathematical basis of the procedure for determining the indicator. The resilience of the system is calculated as a function of the operative subprocesses for all possible failures and is a normalized indicator on [0, 1]. The examination of two industrial case studies shows that the proposed resilience can be an appropriate indicator to be considered in process design.

Open Access: Yes

DOI: 10.3303/CET2081144

Automated synthesis of process-networks by the integration of P-graph with process simulation

Ákos Orosz Raymond R. Tan Jean Pimentel Ferenc Friedler

Publication Name: Chemical Engineering Transactions

Publication Date: 2020-01-01

Volume: 81

Issue: Unknown

Page Range: 1171-1176

Description:

Chemical process simulation has become one of the most important tools for the analysis of process networks. The simulation software currently available are not capable of automatically generating the process structure, the designer must provide it as an input for the simulation. This limits the contribution of simulation to the latter stages of design after the structure has been clearly defined. Since the P-graph methodology was originally conceived to generate process structures systematically, it can be used to produce the topology of the problem automatically based on rigorous combinatorial axioms and algorithms. In this work, the properties of two P-graph algorithms are exploited to automatically generate alternative structures in a commercial simulator, conferring the latter an improved capacity to assist during the early stage of design. Initially, the maximal structure generation (MSG) algorithm is employed to identify a rigorous superstructure from the initial set of plausible operating units. The solution structure generation (SSG) algorithm is then used to enumerate all combinatorially feasible processes included in the superstructure. Each process structure is individually exported to Aspen Plus®, where rigorous models are used to simulate its performance. A set of alternative processes ranked by their economic performance can be generated. This integrated methodology is employed in a case study for producing methyl lactate from methanol and lactic acid. This work demonstrates that integration of P-graph with rigorous simulation constitutes an enhanced tool for process synthesis that automates the generation of process alternatives, providing useful information and additional insight of the synthesis problem.

Open Access: Yes

DOI: 10.3303/CET2081196