Special Issue "Feature Review Papers"

A special issue of Processes (ISSN 2227-9717).

Deadline for manuscript submissions: closed (30 September 2020).

Special Issue Editors

Prof. Dr. Juergen Hahn
E-Mail Website
Guest Editor
Department of Biomedical Engineering, Department of Chemical & Biological Engineering, Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Interests: systems biology; parameter estimation; experimental design; modeling
Special Issues and Collections in MDPI journals
Prof. Dr. Volker Hessel
E-Mail Website
Guest Editor
Faculty of Engineering, Computer and Mathematical Sciences, School of Chemical Engineering, University of Adelaide, Adelaide SA 5005, Australia
Interests: micro process technology; flow chemistry; process intensification; green processing; sustainability (life cycle assessment, cost analysis)
Special Issues and Collections in MDPI journals
Prof. Dr. Martha A Grover
E-Mail Website
Guest Editor
School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Dr. NW, Atlanta, GA 30332-0100, USA
Interests: self-assembly, dynamic programming, experimental design
Dr. John D. Hedengren
E-Mail Website
Guest Editor
Department of Chemical Engineering , 350 CB, Brigham Young University, Provo, UT, 84602, USA
Interests: advanced process control; APMonitor software; drilling automation; nonlinear optimization; state estimation; unmanned aerial vehicles
Special Issues and Collections in MDPI journals
Prof. Dr. Fausto Gallucci
E-Mail Website
Guest Editor
Inorganic Membranes and Membrane Reactors, Sustainable Process Engineering, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands
Interests: process design and intensification; membranes and membrane reactors; separation technologies
Special Issues and Collections in MDPI journals
Prof. Dr. Thomas A. Adams II
E-Mail Website
Guest Editor
Department of Chemical Engineering, McMaster University, 1280 Main Street West, 1280 Main St W, Hamilton, ON L8S4L7, Canada
Interests: sustainable energy conversion processes; modelling and simulation; new technologies for sustainable liquid fuel production; semi-continuous chemical separation processes
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue is designed to publish high-quality review papers in Processes. The issue will highlight a diverse set of topics related to process and systems technology for chemical, materials, biochemical, pharmaceutical, and biomedical applications. The scope of this Special Issue includes, but is not limited to: chemical and biochemical processes; cellular systems; material manufacturing; and systems modeling, simulation, optimization, and control. We are particularly interested in receiving manuscripts that review experimental and theoretical/computational studies as well as contributions from the industry.

Prof. Dr. Juergen Hahn
Prof. Dr. Volker Hessel
Prof. Dr. Martha A Grover
Prof. Dr. John D. Hedengren
Prof. Dr. Fausto Gallucci
Prof. Dr. Thomas A. Adams II
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Processes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Biomedical systems 
  • Chemical processes
  • Computational systems biology 
  • Dynamic modeling
  • Materials manufacturing 
  • Microbial systems 
  • Process control and optimization

Published Papers (23 papers)

Order results
Result details
Select all
Export citation of selected articles as:

Review

Review
Advances in Biomass Co-Combustion with Fossil Fuels in the European Context: A Review
Processes 2021, 9(1), 100; https://doi.org/10.3390/pr9010100 - 05 Jan 2021
Cited by 3 | Viewed by 644
Abstract
Co-combustion of biomass-based fuels and fossil fuels in power plant boilers, utility boilers, and process furnaces is a widely acknowledged means of efficient heat and power production, offering higher power production than comparable systems with sole biomass combustion. This, in combination with CO [...] Read more.
Co-combustion of biomass-based fuels and fossil fuels in power plant boilers, utility boilers, and process furnaces is a widely acknowledged means of efficient heat and power production, offering higher power production than comparable systems with sole biomass combustion. This, in combination with CO2 and other greenhouse gases abatement and low specific cost of system retrofit to co-combustion, counts among the tangible advantages of co-combustion application. Technical and operational issues regarding the accelerated fouling, slagging, and corrosion risk, as well as optimal combustion air distribution impact on produced greenhouse gases emissions and ash properties, belong to intensely researched topics nowadays in parallel with the combustion aggregates design optimization, the advanced feed pretreatment techniques, and the co-combustion life cycle assessment. This review addresses the said topics in a systematic manner, starting with feed availability, its pretreatment, fuel properties and combustor types, followed by operational issues, greenhouse gases, and other harmful emissions trends, as well as ash properties and utilization. The body of relevant literature sources is table-wise classified according to numerous criteria pertaining to individual paper sections, providing a concise and complex insight into the research methods, analyzed systems, and obtained results. Recent advances achieved in individual studies and the discovered synergies between co-combusted fuels types and their shares in blended fuel are summed up and discussed. Actual research challenges and prospects are briefly touched on as well. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
Gas Turbine Intercoolers: Introducing Nanofluids—A Mini-Review
Processes 2020, 8(12), 1572; https://doi.org/10.3390/pr8121572 - 28 Nov 2020
Cited by 1 | Viewed by 754
Abstract
Coolant is one of the main factors affecting the overall thermal performance of the intercooler for the gas turbine intercooled cycle. The thermal conductivity of conventional coolants, such as water, is relatively low when compared to solid conducting materials, and therefore can hinder [...] Read more.
Coolant is one of the main factors affecting the overall thermal performance of the intercooler for the gas turbine intercooled cycle. The thermal conductivity of conventional coolants, such as water, is relatively low when compared to solid conducting materials, and therefore can hinder the progress towards achieving a compact and highly effective intercooler. Nanofluids are advanced types of working fluids that contain dispersed nanoparticles in conventional basefluids, and as such possess superior thermal conductivity compared to their counterparts. In this paper, a short review on the effect of different nanofluids on the thermal performance of gas turbines intercoolers is presented for the first time. Firstly, this work reviews the different designs of intercoolers used in gas turbines intercooled cycles. Then, it explains the different types of nanofluids and their fabrication processes. The effective parameters, such as physical stability, thermal conductivity, and viscosity are also highlighted and discussed. Furthermore, the level of enhancement in the performance of intercoolers utilizing nanofluids is demonstrated and evaluated. Lastly, the current challenges and future research directions in this field are provided. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Challenges and Opportunities on Nonlinear State Estimation of Chemical and Biochemical Processes
Processes 2020, 8(11), 1462; https://doi.org/10.3390/pr8111462 - 15 Nov 2020
Cited by 2 | Viewed by 1293
Abstract
This paper provides an overview of nonlinear state estimation techniques along with a discussion on the challenges and opportunities for future work in the field. Emphasis is given on Bayesian methods such as moving horizon estimation (MHE) and extended Kalman filter (EKF). A [...] Read more.
This paper provides an overview of nonlinear state estimation techniques along with a discussion on the challenges and opportunities for future work in the field. Emphasis is given on Bayesian methods such as moving horizon estimation (MHE) and extended Kalman filter (EKF). A discussion on Bayesian, deterministic, and hybrid methods is provided and examples of each of these methods are listed. An approach for nonlinear state estimation design is included to guide the selection of the nonlinear estimator by the user/practitioner. Some of the current challenges in the field are discussed involving covariance estimation, uncertainty quantification, time-scale multiplicity, bioprocess monitoring, and online implementation. A case study in which MHE and EKF are applied to a batch reactor system is addressed to highlight the challenges of these technologies in terms of performance and computational time. This case study is followed by some possible opportunities for state estimation in the future including the incorporation of more efficient optimization techniques and development of heuristics to streamline the further adoption of MHE. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
A Review on the Modeling, Control and Diagnostics of Continuous Pulp Digesters
Processes 2020, 8(10), 1231; https://doi.org/10.3390/pr8101231 - 01 Oct 2020
Viewed by 854
Abstract
Being at the heart of modern pulp mills, continuous pulp digesters have attracted much attention from the research community. In this article, a comprehensive review in the area of modeling, control and diagnostics of continuous pulp digesters is conducted. The evolution of research [...] Read more.
Being at the heart of modern pulp mills, continuous pulp digesters have attracted much attention from the research community. In this article, a comprehensive review in the area of modeling, control and diagnostics of continuous pulp digesters is conducted. The evolution of research focus within these areas is followed and discussed. Particular effort has been devoted to identifying the state-of-the-art and the research gap in a summarized way. Finally, the current and future research directions in the areas have been analyzed and discussed. To date, digester modeling following the Purdue approach, Kappa number control using model predictive controllers and health index-based diagnostic approaches by utilizing different statistical methods have dominated the field. While the rising research interest within the field is evident, we anticipate further developments in advanced sensors and integration of these sensors for improving model prediction and controller performance; and the exploration of different AI-based approaches will be at the core of future research. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Freelancers in the Software Development Process: A Systematic Mapping Study
Processes 2020, 8(10), 1215; https://doi.org/10.3390/pr8101215 - 27 Sep 2020
Cited by 3 | Viewed by 1070
Abstract
[Context] Freelancers could catalyze the software development process by providing their niche skills to generate high quality outputs. They could help companies (including startups) to foster innovations by suggesting creative ideas and providing their expertise in implementing them (for instance, designing solutions, coding [...] Read more.
[Context] Freelancers could catalyze the software development process by providing their niche skills to generate high quality outputs. They could help companies (including startups) to foster innovations by suggesting creative ideas and providing their expertise in implementing them (for instance, designing solutions, coding solutions etc.). Freelancers could effectively and efficiently work as a virtual member of the software development team. The company must make informed decisions about which task to allot to the freelancer, which freelancer to select, pricing the task, and evaluating the submitted work. On the other hand, the freelancer should make an informed decision about evaluating the monetary value of the task to be charged, trusting the requester, analyzing the skills requirement of the task (finding matches between skill requirement and skills processed), selecting the best task, and maintaining the highest level of reputation. However, the literature does not provide freelancers and the companies the guidelines that support their decision making. However, if freelancers are selected carefully for the most suitable task, the companies will benefit a lot in terms of improved software development metrics. [Objectives] The objective of this paper is to provide the research community the research trends in freelancer-supported software development. This helps to understand that which software development areas have higher concentrations of research efforts, which area has the support of empirical evidence to support management decision makings, and which area requires the research attention. [Method] The systematic study is conducted by planning the mapping protocol, executing the protocol, and reporting the findings using various visualization tools like bar charts and pie charts. The search process was planned to be executed using set of inclusion and exclusion conditions on four bibliographic databases (IEEExplore, Springerlink, Sciencedirect, and ACM digital library). The relevant papers are selected by applying inclusion and exclusion conditions. The google citations of the relevant papers are subject to the inclusion and exclusion conditions again to include the more relevant papers. Finally, the systematic schema was created and populated after analyzing the studies abstracts. [Results] The results indicate the following (a) The research focus is on generic software development (78%) rather on individual life cycle activities. (b) The number of empirical studies is limited (25%). (c) A number of studies proposing solutions and evaluating on live cases in industrial settings are missing from the literature. This is in comparison to the validation approaches (72%) i.e., solutions tested in laboratory settings. (d) At present, the literature has limited ability to provide the software companies (including startups) with the guidelines (in the form of opinions and experience reports) for involving freelancers in the software development process. (e) The reported challenges include Collaboration and Coordination (33%), Developer Recommendation (or selection) (19%), Team Formulation (14%), Task Recommendation (allocation) (14%), Task Decomposition (11%), Privacy and Security (Confidentiality) (11%), Budget Estimation (8%), Recognition (8%), Trust Issues (8%), Market Dynamism (6%), Intellectual Property Issues (6%), Participation of Crowd Worker (6%), and Capacity Utilization (3%). These challenges are highly interactive, and each challenge impacts all other challenges. (e) Recent focus of the researchers (total 7 studies in 2019) is on generic software development handling the collaboration and coordination (3 studies out of 7), Developer recommendation (2 studies out of 7), and task recommendation (2 studies out of 7). [Conclusion] The freelancer-driven software engineering research area has got the attraction of the researchers, but it will take a long time to gain maturity. This puts an urgent call for more empirical studies and evaluation-based solution research that could help companies (including startups) to foster innovations. Further, the research focus should be well distributed among the various development phases to address the unique challenges associated with individual activities. The accurate management of the freelancer in the software development could help companies and startups to foster innovations and remain competitive in the marketplace. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Graphical abstract

Review
Model-Free Extremum Seeking Control of Bioprocesses: A Review with a Worked Example
Processes 2020, 8(10), 1209; https://doi.org/10.3390/pr8101209 - 25 Sep 2020
Cited by 1 | Viewed by 640
Abstract
Uncertainty is a common feature of biological systems, and model-free extremum-seeking control has proved a relevant approach to avoid the typical problems related to model-based optimization, e.g., time- and resource-consuming derivation and identification of dynamic models, and lack of robustness of optimal control. [...] Read more.
Uncertainty is a common feature of biological systems, and model-free extremum-seeking control has proved a relevant approach to avoid the typical problems related to model-based optimization, e.g., time- and resource-consuming derivation and identification of dynamic models, and lack of robustness of optimal control. In this article, a review of the past and current trends in model-free extremum seeking is proposed with an emphasis on finding optimal operating conditions of bioprocesses. This review is illustrated with a simple simulation case study which allows a comparative evaluation of a few selected methods. Finally, some experimental case studies are discussed. As usual, practice lags behind theory, but recent developments confirm the applicability of the approach at the laboratory scale and are encouraging a transfer to industrial scale. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Scope and Limitations of the Mathematical Models Developed for the Forward Feed Multi-Effect Distillation Process—A Review
Processes 2020, 8(9), 1174; https://doi.org/10.3390/pr8091174 - 17 Sep 2020
Viewed by 790
Abstract
Desalination has become one of the obvious solutions for the global water crisis due to affording high-quality water from seawater and brackish water resources. As a result, there are continuing efforts being made to improve desalination technologies, especially the one producing high-quantity freshwater, [...] Read more.
Desalination has become one of the obvious solutions for the global water crisis due to affording high-quality water from seawater and brackish water resources. As a result, there are continuing efforts being made to improve desalination technologies, especially the one producing high-quantity freshwater, i.e., thermal desalination. This improvement must be accomplished via enhancement of process design through optimization which is implicitly dependent on providing a generic process model. Due to the scarcity of a comprehensive review paper for modeling multi-effect distillation (MED) process, this topic is becoming more important. Therefore, this paper intends to capture the evolution of modeling the forward feed MED (most common type) and shed a light on its branches of steady-state and dynamic modeling. The maturity of the models developed for MED will be thoroughly reviewed to clarify the general efforts made highlighting the advantages and disadvantages. Depending on the outputs of this review, the requirements of process development and emerging challengeable matters of modeling will be specified. This, in turn, would afford a possible improvement strategy to gain a reliable and sustainable thermal desalination process. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Microfluidics for Two-Dimensional Nanosheets: A Mini Review
Processes 2020, 8(9), 1067; https://doi.org/10.3390/pr8091067 - 01 Sep 2020
Viewed by 823
Abstract
Since the discovery of graphene, there has been increasing interest in two-dimensional (2D) materials. To realize practical applications of 2D materials, it is essential to isolate mono- or few-layered 2D nanosheets from unexfoliated counterparts. Liquid phase exfoliation (LPE) is the most common technique [...] Read more.
Since the discovery of graphene, there has been increasing interest in two-dimensional (2D) materials. To realize practical applications of 2D materials, it is essential to isolate mono- or few-layered 2D nanosheets from unexfoliated counterparts. Liquid phase exfoliation (LPE) is the most common technique to produce atomically thin-layered 2D nanosheets. However, low production yield and prolonged process time remain key challenges. Recently, novel exfoliation processes based on microfluidics have been developed to achieve rapid and high yield production of few-layer 2D nanosheets. We review the primary types of microfluidic-based exfoliation techniques in terms of the underlying process mechanisms and the applications of the 2D nanosheets thus produced. The key challenges and future directions are discussed in the above context to delineate future research directions in this exciting area of materials processing. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Solid Particle Erosion Behaviour and Protective Coatings for Gas Turbine Compressor Blades—A Review
Processes 2020, 8(8), 984; https://doi.org/10.3390/pr8080984 - 13 Aug 2020
Cited by 4 | Viewed by 1752
Abstract
Gas turbines (GTEs) are often utilised in harsh environments where the GT components, including compressor vanes and rotor blades, are subject to erosion damage by sand and dust particles. For instance, in a desert environment, the rate of damage made by solid particles [...] Read more.
Gas turbines (GTEs) are often utilised in harsh environments where the GT components, including compressor vanes and rotor blades, are subject to erosion damage by sand and dust particles. For instance, in a desert environment, the rate of damage made by solid particles erosion (SPE) becomes severe, and therefore results in degradation to the GTE parts, lowering the cycle efficiency, reducing the device lifetime, and increasing the overall cost of the operation. As such, understanding the erosion mechanism caused by solid particles and the effects associated with it is crucial for selecting the appropriate countermeasures and maintaining the system performance. This review paper provides a survey of the available studies on SPE effects on GTEs and surface protective coatings. Firstly, the ductile and brittle SPE mechanism is presented, as well as the ductile-brittle transition region. Then, an in-depth focus on the parameters associated with the SPE, such as particles properties and impingement conditions, is introduced. Furthermore, the existing theoretical models are shown and discussed. Afterwards, erosion resistant coating materials for surface protection and their selection criteria are covered in the review. Finally, the gap in knowledge and future research direction in the field of SPE on GTEs are provided. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Recent Insights into Lignocellulosic Biomass Pyrolysis: A Critical Review on Pretreatment, Characterization, and Products Upgrading
Processes 2020, 8(7), 799; https://doi.org/10.3390/pr8070799 - 08 Jul 2020
Cited by 13 | Viewed by 1478
Abstract
Pyrolysis process has been considered to be an efficient approach for valorization of lignocellulosic biomass into bio-oil and value-added chemicals. Bio-oil refers to biomass pyrolysis liquid, which contains alkanes, aromatic compounds, phenol derivatives, and small amounts of ketone, ester, ether, amine, and alcohol. [...] Read more.
Pyrolysis process has been considered to be an efficient approach for valorization of lignocellulosic biomass into bio-oil and value-added chemicals. Bio-oil refers to biomass pyrolysis liquid, which contains alkanes, aromatic compounds, phenol derivatives, and small amounts of ketone, ester, ether, amine, and alcohol. Lignocellulosic biomass is a renewable and sustainable energy resource for carbon that is readily available in the environment. This review article provides an outline of the pyrolysis process including pretreatment of biomass, pyrolysis mechanism, and process products upgrading. The pretreatment processes for biomass are reviewed including physical and chemical processes. In addition, the gaps in research and recommendations for improving the pretreatment processes are highlighted. Furthermore, the effect of feedstock characterization, operating parameters, and types of biomass on the performance of the pyrolysis process are explained. Recent progress in the identification of the mechanism of the pyrolysis process is addressed with some recommendations for future work. In addition, the article critically provides insight into process upgrading via several approaches specifically using catalytic upgrading. In spite of the current catalytic achievements of catalytic pyrolysis for providing high-quality bio-oil, the production yield has simultaneously dropped. This article explains the current drawbacks of catalytic approaches while suggesting alternative methodologies that could possibly improve the deoxygenation of bio-oil while maintaining high production yield. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
The Evolution of Cell Free Biomanufacturing
Processes 2020, 8(6), 675; https://doi.org/10.3390/pr8060675 - 08 Jun 2020
Cited by 3 | Viewed by 1390
Abstract
Cell-free systems are a widely used research tool in systems and synthetic biology and a promising platform for manufacturing of proteins and chemicals. In the past, cell-free biology was primarily used to better understand fundamental biochemical processes. Notably, E. coli cell-free extracts were [...] Read more.
Cell-free systems are a widely used research tool in systems and synthetic biology and a promising platform for manufacturing of proteins and chemicals. In the past, cell-free biology was primarily used to better understand fundamental biochemical processes. Notably, E. coli cell-free extracts were used in the 1960s to decipher the sequencing of the genetic code. Since then, the transcription and translation capabilities of cell-free systems have been repeatedly optimized to improve energy efficiency and product yield. Today, cell-free systems, in combination with the rise of synthetic biology, have taken on a new role as a promising technology for just-in-time manufacturing of therapeutically important biologics and high-value small molecules. They have also been implemented at an industrial scale for the production of antibodies and cytokines. In this review, we discuss the evolution of cell-free technologies, in particular advancements in extract preparation, cell-free protein synthesis, and cell-free metabolic engineering applications. We then conclude with a discussion of the mathematical modeling of cell-free systems. Mathematical modeling of cell-free processes could be critical to addressing performance bottlenecks and estimating the costs of cell-free manufactured products. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
A Critical Review of the Modeling and Optimization of Combined Heat and Power Dispatch
Processes 2020, 8(4), 441; https://doi.org/10.3390/pr8040441 - 08 Apr 2020
Cited by 4 | Viewed by 917
Abstract
Combined heat and power (CHP) systems are attracting increasing attention for their ability to improve the economics and sustainability of the electricity system. Determining how to best operate these systems is difficult because they can consist of many generating units whose operation is [...] Read more.
Combined heat and power (CHP) systems are attracting increasing attention for their ability to improve the economics and sustainability of the electricity system. Determining how to best operate these systems is difficult because they can consist of many generating units whose operation is governed by complex nonlinear physics. Mathematical programming is a useful tool to support the operation of CHP systems, and has been the subject of substantial research attention since the early 1990s. This paper critically reviews the modeling and optimization work that has been done on the CHP economic dispatch problem, and the CHP economic and emission dispatch problem. A summary of the common models used for these problems is provided, along with comments on future modeling work that would beneficial to the field. The majority of optimization approaches studied for CHP system operation are metaheuristic algorithms. A discussion of the limitations and benefits of metaheuristic algorithms is given. Finally, a case study optimizing five classic CHP system test instances demonstrates the advantages of the using deterministic global search algorithms over metaheuristic search algorithms. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Approximate Moment Methods for Population Balance Equations in Particulate and Bioengineering Processes
Processes 2020, 8(4), 414; https://doi.org/10.3390/pr8040414 - 01 Apr 2020
Cited by 2 | Viewed by 909
Abstract
Population balance modeling is an established framework to describe the dynamics of particle populations in disperse phase systems found in a broad field of industrial, civil, and medical applications. The resulting population balance equations account for the dynamics of the number density distribution [...] Read more.
Population balance modeling is an established framework to describe the dynamics of particle populations in disperse phase systems found in a broad field of industrial, civil, and medical applications. The resulting population balance equations account for the dynamics of the number density distribution functions and represent (systems of) partial differential equations which require sophisticated numerical solution techniques due to the general lack of analytical solutions. A specific class of solution algorithms, so-called moment methods, is based on the reduction of complex models to a set of ordinary differential equations characterizing dynamics of integral quantities of the number density distribution function. However, in general, a closed set of moment equations is not found and one has to rely on approximate closure methods. In this contribution, a concise overview of the most prominent approximate moment methods is given. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
Forward Osmosis: A Critical Review
Processes 2020, 8(4), 404; https://doi.org/10.3390/pr8040404 - 30 Mar 2020
Cited by 15 | Viewed by 2222
Abstract
The use of forward osmosis (FO) for water purification purposes has gained extensive attention in recent years. In this review, we first discuss the advantages, challenges and various applications of FO, as well as the challenges in selecting the proper draw solution for [...] Read more.
The use of forward osmosis (FO) for water purification purposes has gained extensive attention in recent years. In this review, we first discuss the advantages, challenges and various applications of FO, as well as the challenges in selecting the proper draw solution for FO, after which we focus on transport limitations in FO processes. Despite recent advances in membrane development for FO, there is still room for improvement of its selective layer and support. For many applications spiral wound membrane will not suffice. Furthermore, a defect-free selective layer is a prerequisite for FO membranes to ensure low solute passage, while a support with low internal concentration polarization is necessary for a high water flux. Due to challenges affiliated to interfacial polymerization (IP) on non-planar geometries, we discuss alternative approaches to IP to form the selective layer. We also explain that, when provided with a defect-free selective layer with good rejection, the membrane support has a dominant influence on the performance of an FO membrane, which can be estimated by the structural parameter (S). We emphasize the necessity of finding a new method to determine S, but also that predominantly the thickness of the support is the major parameter that needs to be optimized. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
A Review of Landfill Leachate Treatment by Microalgae: Current Status and Future Directions
Processes 2020, 8(4), 384; https://doi.org/10.3390/pr8040384 - 26 Mar 2020
Cited by 7 | Viewed by 1623
Abstract
Solid waste generation has been projected to increase worldwide. Presently, the most applied methodology to dispose of solid waste is landfilling. However, these landfill sites, over time release a significant quantity of leachate, which can pose serious environmental issues, including contamination of water [...] Read more.
Solid waste generation has been projected to increase worldwide. Presently, the most applied methodology to dispose of solid waste is landfilling. However, these landfill sites, over time release a significant quantity of leachate, which can pose serious environmental issues, including contamination of water resources. There exist many physicochemical and biological landfill leachate treatment schemes with varying degrees of success. With an increasing focus on sustainability, there has been a demand for developing eco-friendly, green treatment schemes for landfill leachates with viable resource recovery and minimum environmental footprints. Microalgae-based techniques can be a potential candidate for such a treatment scenario. In this article, research on microalgae-based landfill leachate treatments reported in the last 15 years have been summarized and critically reviewed. The scale-up aspect of microalgae technology has been discussed, and the related critical factors have been elucidated. The article also analyzes the resource recovery potential for microalgal techniques with respect to leachate treatment and explores possible methodologies to minimize the environmental footprints of the microalgae-based treatment process. The future research potential in the area has been identified and discussed. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
A Review of Exergy Based Optimization and Control
Processes 2020, 8(3), 364; https://doi.org/10.3390/pr8030364 - 21 Mar 2020
Cited by 3 | Viewed by 1562
Abstract
This work presents a critical review of the use of exergy based control and optimization for efficiency improvements in energy networks, with a background of exergy based analysis given for context. Over the past three decades, a number of studies using exergy were [...] Read more.
This work presents a critical review of the use of exergy based control and optimization for efficiency improvements in energy networks, with a background of exergy based analysis given for context. Over the past three decades, a number of studies using exergy were conducted to gain a performance advantage for high energy consumption systems and networks. Due to their complexity and the increased scale of the systems, the opportunity to misuse energy inevitability leads to inefficient operations. The studies accomplished in this area are grouped into either control or optimization to highlight each method’s ability to minimize system irreversibilities that lead to exergy destruction. The exergy based optimization and control studies featured demonstrate substantial improvements (as high as 40%) over traditional methods based on the first law of thermodynamics. This paper reviews the work completed in the area of exergy based optimization and control as of the end of September 2019, outlines the progress made, and identifies specific areas where future work can advance this area of study. A relatively small amount of publications are available compared to other fields, with most work occurring in the area of exergy based multi-objective optimization. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
Evaluation of Polymeric Materials for Chemical Enhanced Oil Recovery
Processes 2020, 8(3), 361; https://doi.org/10.3390/pr8030361 - 21 Mar 2020
Cited by 10 | Viewed by 1359
Abstract
Polymer flooding is a promising enhanced oil recovery (EOR) technique; sweeping a reservoir with a dilute polymer solution can significantly improve the overall oil recovery. In this overview, polymeric materials for enhanced oil recovery are described in general terms, with specific emphasis on [...] Read more.
Polymer flooding is a promising enhanced oil recovery (EOR) technique; sweeping a reservoir with a dilute polymer solution can significantly improve the overall oil recovery. In this overview, polymeric materials for enhanced oil recovery are described in general terms, with specific emphasis on desirable characteristics for the application. Application-specific properties should be considered when selecting or developing polymers for enhanced oil recovery and should be carefully evaluated. Characterization techniques should be informed by current best practices; several are described herein. Evaluation of fundamental polymer properties (including polymer composition, microstructure, and molecular weight averages); resistance to shear/thermal/chemical degradation; and salinity/hardness compatibility are discussed. Finally, evaluation techniques to establish the polymer flooding performance of candidate EOR materials are described. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Optimization Methods for the Extraction of Vegetable Oils: A Review
Processes 2020, 8(2), 209; https://doi.org/10.3390/pr8020209 - 08 Feb 2020
Cited by 9 | Viewed by 1839
Abstract
Most seed oils are edible while some are used generally as raw material for soap production, chocolate, margarine, and recently in biodiesel formulations as potential candidates capable of replacing fossil fuels which are costly and destructive to the environment. Oilseeds are a green [...] Read more.
Most seed oils are edible while some are used generally as raw material for soap production, chocolate, margarine, and recently in biodiesel formulations as potential candidates capable of replacing fossil fuels which are costly and destructive to the environment. Oilseeds are a green and major reservoir which when properly exploited can be used sustainably for the production of chemicals at both the laboratory and industrial scales. Oil extraction is one of the most critical steps in seed oil processing because it determines the quality and quantity of oil extracted. Optimization of the extraction conditions for each extraction method enhances yield and quality meanwhile a carefully chosen optimization process equally has the potential of saving time and heat requirements with an associated consequence on cost reduction of the entire process. In this review, the techniques used to optimize oil extraction from plant materials which can be consulted by stakeholders in the field are brought to focus and the merits and demerits of these methods highlighted. Additionally, different types of optimization techniques used for various processes including modeling and the software employed in the optimization processes are discussed. Finally, the quality of the oil as affected by the methods of extraction and the optimization process used are also presented. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
Interfacial Thermal Conductivity and Its Anisotropy
Processes 2020, 8(1), 27; https://doi.org/10.3390/pr8010027 - 24 Dec 2019
Viewed by 934
Abstract
There is a significant effort in miniaturizing nanodevices, such as semi-conductors, currently underway. However, a major challenge that is a significant bottleneck is dissipating heat generated in these energy-intensive nanodevices. In addition to being a serious operational concern (high temperatures can interfere with [...] Read more.
There is a significant effort in miniaturizing nanodevices, such as semi-conductors, currently underway. However, a major challenge that is a significant bottleneck is dissipating heat generated in these energy-intensive nanodevices. In addition to being a serious operational concern (high temperatures can interfere with their efficient operation), it is a serious safety concern, as has been documented in recent reports of explosions resulting from many such overheated devices. A significant barrier to heat dissipation is the interfacial films present in these nanodevices. These interfacial films generally are not an issue in macro-devices. The research presented in this paper was an attempt to understand these interfacial resistances at the molecular level, and present possibilities for enhancing the heat dissipation rates in interfaces. We demonstrated that the thermal resistances of these interfaces were strongly anisotropic; i.e., the resistance parallel to the interface was significantly smaller than the resistance perpendicular to the interface. While the latter is well-known—usually referred to as Kapitza resistance—the anisotropy and the parallel component have previously been investigated only for solid-solid interfaces. We used molecular dynamics simulations to investigate the density profiles at the interface as a function of temperature and temperature gradient, to reveal the underlying physics of the anisotropy of thermal conductivity at solid-liquid, liquid-liquid, and solid-solid interfaces. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
The State of Art in Particle Swarm Optimization Based Unit Commitment: A Review
Processes 2019, 7(10), 733; https://doi.org/10.3390/pr7100733 - 14 Oct 2019
Cited by 2 | Viewed by 806
Abstract
Unit Commitment (UC) requires the optimization of the operation of generation units with varying loads, at every hour, under different technical and environmental constraints. Many solution techniques were developed for the UC problem, and the researchers are still working on improving the efficiency [...] Read more.
Unit Commitment (UC) requires the optimization of the operation of generation units with varying loads, at every hour, under different technical and environmental constraints. Many solution techniques were developed for the UC problem, and the researchers are still working on improving the efficiency of these techniques. Particle swarm optimization (PSO) is an effective and efficient technique used for solving the UC problems, and it has gotten a considerable amount of attention in recent years. This study provides a state-of-the-art literature review on UC studies utilizing PSO or PSO-variant algorithms, by focusing on research articles published in the last decade. In this study, these algorithms/methods, objectives, constraints are reviewed, with focus on the UC problems that include at least one of the wind and solar technologies, along with thermal unit(s). Although, conventional PSO is one of the most effective techniques used in solving UC problem, other methods were also developed in literature to improve the convergence. In this study, these methods are grouped as extended PSO, modified PSO, and PSO with other techniques. This study shows that PSO with other techniques are utilized more than any other methods. In terms of constraints, it was observed that there are only few studies that considered Transmission Line (TL), Fuel (F), Emission (E), Storage (St) and Crew (Cr) constraints, while Power Balance (PB), Generation limit (GL), Unit minimum Up or Down Time (U/DT), Ramp Up or Ramp Down Time (R-U/DT) and system Spinning Reserve (SR) were the most utilized constraints in UC problems considering wind/solar as a renewable source. In addition, most of the studies are based on a single objective function (cost minimization) and, few of them are multi-objective (cost and emission minimization) based studies. Full article
(This article belongs to the Special Issue Feature Review Papers)
Review
Recombinant Proteins for Industrial versus Pharmaceutical Purposes: A Review of Process and Pricing
Processes 2019, 7(8), 476; https://doi.org/10.3390/pr7080476 - 24 Jul 2019
Cited by 16 | Viewed by 3380
Abstract
Recombinant proteins have been produced for over 30 years. Applications range from enzymes used in laundry detergents to antigen-detecting antibodies in cancer therapy. Despite similarities in manufacturing, drastic differences in retail pricing between recombinant proteins used for industrial (non-medical) versus pharmaceutical purposes exist. [...] Read more.
Recombinant proteins have been produced for over 30 years. Applications range from enzymes used in laundry detergents to antigen-detecting antibodies in cancer therapy. Despite similarities in manufacturing, drastic differences in retail pricing between recombinant proteins used for industrial (non-medical) versus pharmaceutical purposes exist. Industrial proteins often have a retail price in the tens of dollars per kilogram while recombinant proteins for medical use may cost billions of dollars per kilogram. This manuscript will briefly review manufacturing techniques and contrast the differences between industrial versus pharmaceutical production. Maximizing manufacturing technologies to reduce cost-of-goods (CoG) is desirable. However, the major reason for the very high pricing of pharma protein products does not reflect CoG, but the financial obligations of clinical trials, research and development, patent constraints, marketing, and return on investment. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
Do Bioreactor Designs with More Efficient Oxygen Supply to Ovarian Cortical Tissue Fragments Enhance Follicle Viability and Growth In Vitro?
Processes 2019, 7(7), 450; https://doi.org/10.3390/pr7070450 - 15 Jul 2019
Cited by 2 | Viewed by 1257
Abstract
Background: Autotransplantation of cryopreserved ovarian tissue is currently the main option to preserve fertility for cancer patients. To avoid cancer cell reintroduction at transplantation, a multi-step culture system has been proposed to obtain fully competent oocytes for in vitro fertilization. Current in vitro [...] Read more.
Background: Autotransplantation of cryopreserved ovarian tissue is currently the main option to preserve fertility for cancer patients. To avoid cancer cell reintroduction at transplantation, a multi-step culture system has been proposed to obtain fully competent oocytes for in vitro fertilization. Current in vitro systems are limited by the low number and health of secondary follicles produced during the first step culture of ovarian tissue fragments. To overcome such limitations, bioreactor designs have been proposed to enhance oxygen supply to the tissue, with inconsistent results. This retrospective study investigates, on theoretical grounds, whether the lack of a rational design of the proposed bioreactors prevented the full exploitation of follicle growth potential. Methods: Models describing oxygen transport in bioreactors and tissue were developed and used to predict oxygen availability inside ovarian tissue in the pertinent literature. Results: The proposed theoretical analysis suggests that a successful outcome is associated with enhanced oxygen availability in the cultured tissue in the considered bioreactor designs. This suggests that a rational approach to bioreactor design for ovarian tissue culture in vitro may help exploit tissue potential to support follicle growth. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Review
The Use of Polymers in the Flotation Treatment of Wastewater
Processes 2019, 7(6), 374; https://doi.org/10.3390/pr7060374 - 17 Jun 2019
Cited by 10 | Viewed by 1642
Abstract
The use of flotation for the treatment of wastewaters in general, but especially for the removal of oil, grease, general organic matter, and suspended solids, is well established as a low energy process. Polyelectrolytes (PEs) can enhance performance without adding to the solids [...] Read more.
The use of flotation for the treatment of wastewaters in general, but especially for the removal of oil, grease, general organic matter, and suspended solids, is well established as a low energy process. Polyelectrolytes (PEs) can enhance performance without adding to the solids load that occurs with inorganic additives such as alum. The bridging of pollutants and the attachment of the resulting aggregates to the air-water interface can be effectively carried out with most wastewaters. Hydrophobic modification of the PEs can be useful for difficult species. It should be applied to the flotation of polyfluoroalkyl substances, for example, as they are not amenable to economical conventional treatment. Similarly, the removal of microplastic particles from sewage effluents by flotation could be enhanced. Full article
(This article belongs to the Special Issue Feature Review Papers)
Show Figures

Figure 1

Back to TopTop