Dynamic real‐time optimization with closed‐loop prediction

Process plants are operating in an increasingly global and dynamic environment, motivating the development of dynamic real‐time optimization (DRTO) systems to account for transient behavior in the determination of economically optimal operating policies. This article considers optimization of closed‐loop response dynamics at the DRTO level in a two‐layer architecture, with constrained model predictive control (MPC) applied at the regulatory control level. A simultaneous solution approach is applied to the multilevel DRTO optimization problem, in which the convex MPC optimization subproblems are replaced by their necessary and sufficient Karush–Kuhn–Tucker optimality conditions, resulting in a single‐level mathematical program with complementarity constraints. The performance of the closed‐loop DRTO strategy is compared to that of the open‐loop prediction counterpart through a multi‐part case study that considers linear dynamic systems with different characteristics. The performance of the proposed strategy is further demonstrated through application to a nonlinear polymerization reactor grade transition problem. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3896–3911, 2017     

Flow chemistry—Microreaction technology comes of age

Over the past two decades, microreaction technology has matured from early devices and concepts to encompass a wide range of commercial equipment and applications. This evolution has been aided by the confluence of microreactor development and adoption of continuous flow technology in organic chemistry. This Perspective summarizes the current state‐of‐the art with focus on enabling technologies for reaction and separation equipment. Automation and optimization are highlighted as promising applications of microreactor technology. The move towards continuous processing in pharmaceutical manufacturing underscores increasing industrial interest in the technology. As an example, end‐to‐end fabrication of pharmaceuticals in a compact reconfigurable system illustrates the development of on‐demand manufacturing units based on microreactors. The final section provides an outlook for the technology, including implementation challenges and integration with computational tools. AIChE J, 2017 © 2016 American Institute of Chemical Engineers AIChE J, 63: 858–869, 2017     

Porosity reduction of polyethylene glycol phase change materials by using nanoscale thermal‐energy‐conducting medium during crystallization process

Poly(ethylene glycols) (PEGs) are phase change materials (PCMs) that exhibit undesirable heat transfer properties, which restrict their industrial utility. Apart from the intrinsic material properties, a large quantity of micropores in the crystalline PEG polymers cause poor heat transfer performance. In this work, the formation and growth of micropores are reported through in situ characterization. The addition of a nanoscale thermal‐energy‐conducting medium into PCMs has been proposed for reducing their porosity. The mechanism for reducing porosity is reported for prepared composite PCMs. The intrinsic causes are thought to be the following. Metal oxide nanoparticles can migrate with the liquid PEG flow, which can reduce the thermal stresses in the crystal growth process. In addition, the nanoscale medium promotes heterogeneous nucleation. The results of this study show that reducing the porosity of the polymer crystals is an important approach for improving the heat transfer properties of the PEG PCMs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45446.     

Kinetic modeling and process analysis for Desmodesmus sp. lutein photo‐production

Lutein is a high‐value bioproduct synthesized by microalga Desmodesmus sp. In the current study two aspects of this process are thoroughly investigated: identifying the complex effects of light intensity and nitrate concentration on biomass growth and lutein synthesis, and constructing an accurate kinetic model capable of simulating the entire bioprocess dynamic performance, neither of which has been previously addressed. Three original contributions are presented here. First, it is found that completely opposite to a nitrogen‐limiting culture, under nitrogen‐sufficient conditions a higher lutein content is caused by a higher light intensity and lower nitrate concentration. Second, contrary to lutein content, total lutein production always increases with the increasing nitrate concentration. Third, through experimental verification, the proposed kinetic model is characterized by high accuracy and predictability, indicating its competence for future process design, control, and optimization. Based on the model, optimal light intensities for lutein production and microalgae growth are identified. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2546–2554, 2017     

An economic model predictive control approach to integrated production management and process operation

Managing production schedules and tracking time‐varying demand of certain products while optimizing process economics are subjects of central importance in industrial applications. We investigate the use of economic model predictive control (EMPC) in tracking a production schedule. Specifically, given that only a small subset of the total process state vector is typically required to track certain scheduled values, we design a novel EMPC scheme, through proper construction of the objective function and constraints, that forces specific process states to meet the production schedule and varies the rest of the process states in a way that optimizes process economic performance. Conditions under which feasibility and closed‐loop stability of a nonlinear process under such an EMPC for schedule management can be guaranteed are developed. The proposed EMPC scheme is demonstrated through a chemical process example in which the product concentration is requested to follow a certain production schedule. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1892–1906, 2017     

Experimental research of drop‐on‐demand droplet jetting 3D printing with molten polymer

Three‐dimensional (3D) printing technology has become an effective method for parts manufacturing and got a certain application in many fields. Now, drop‐on‐demand droplet jetting 3D printing appears as a new method of manufacturing technology which has a proven research progress for metal, colloid, and liquid resin materials. However, there are hardly any researches of droplet jetting 3D printing with molten polymer. So, considering molten polymer as the jetting material with droplet jetting method is an explorative direction. In order to attain the molten polymer droplets and achieve droplet jetting 3D printing with molten polymer, the 3D printing technology of differential melt (3DPDM) is developed independently. According to 3DPDM, a complete set of drop‐on‐demand droplet jetting 3D printer have been developed. In this work, PP (6820) was chosen as the experimental material. Under the different print parameters such as the rotation speed of screw, nozzle diameter, mechanical impact frequency, heating temperature, the space between nozzle and platform, the form, and deposition of droplets were studied. Furthermore, the optimal print parameters were summarized. By printing models with the optimal print parameters, it turned out that the 3DPDM is able to achieve drop‐on‐demand droplet jetting 3D printing with molten polymer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45933.     

Dielectric cure determination of a thermosetting epoxy composite prepreg

Evaluation of degree of cure (DoC) of a glass reinforced epoxy composite prepreg used for manufacturing of printed circuit board (PCB) is an intensive issue because of its practical importance and cost reduction in industry. Typical techniques such as differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR) are destructive and require curing a material during a chosen time, quenching the sample to stop cure before performing analysis. Thus, it is necessary to remove the temperature influence on the determination of DoC. In this study, the feasibility of nondestructive dielectric sensing method as an in situ DoC measuring technique through cure monitoring of prepreg is presented, where a vacuum packing configuration has been established so as for the prepreg to evaluate accurately the DoC in a quenched state at an ambient temperature. The optimal curing condition to get the fully cured state of a prepreg material is determined by the dielectric cure monitoring based on the behavior of ion viscosity. The temperature effect compensated DoC of prepreg is correlated and compared with that evaluated by DSC and FTIR. The correlated DoC with ion viscosity has identified the curing behavior of prepreg by determining cure kinetic parameters. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44707.     

Preparation and property of starch nanoparticles reinforced aldehyde–hydrazide covalently crosslinked PNIPAM hydrogels

Injectable, de‐crosslinkable, and thermosensitive hydrogels are obtained by hydrazide‐functionalized poly(N‐isopropylacrylamide) and aldehyde‐functionalized dextrin through in situ crosslinked method. Natural based and degradable starch nanoparticles (SNPs) are used as fillers in order to improve mechanical property of hydrogels. Internal morphology, dynamic modulus, thermosensitivity property, de‐crosslinking performance, drug release, and in vitro cytotoxicity of hydrogels are investigated. Results show that SNPs disperse well throughout hydrogel and have no significant influence on gelation time and de‐crosslinking performance. Elasticity property of composite hydrogel prepared from 9.0 wt % precursors with 1.5 wt % fillers is improved significantly by SNPs and maximum storage modulus reaches 399.2 kPa, but 89.6 kPa of unreinforced hydrogels. Hydrogels exhibit good thermosensitive performance at alternating cyclic temperature of 25 and 37 °C. Doxorubicin hydrochloride‐loaded hydrogels can release more than 25 days. No significant cytotoxicity to L929 fibroblast cells is observed through a CCK‐8 assay for hydrogels, precursors, and SNPs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45761.     

Tough thiourethane thermoplastics for fused filament fabrication

Fused filament fabrication (FFF) is the most common form of additive manufacturing. Most FFF materials are variants of commercially available engineering plastics. Their performance when printed can widely vary, thus there is an increasing volume of research on alternative materials with thermal and mechanical performance optimized for FFF. In this work, thiol–isocyanate polymerization is used for the development of a one‐pot synthesis for polythiourethane thermoplastics for tough three‐dimensional (3D) printing applications. The thiol–isocyanate reaction mechanism allows for rapid polymer synthesis with minimal byproduct formation and few limitations on reaction conditions. The resulting elastomer has high toughness and a low melting point, making it favorable for use as a 3D printing filament. The elastomer outperforms commercial filaments in tension when printed. Considering the rapid advancement of additive manufacturing and the limitations of many engineering polymers with the 3D printing process, these results are encouraging for the development of bespoke 3D printing thermoplastics. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45574.     

Carbon nanotubes from renewable feedstocks: A move toward sustainable nanofabrication

A recent development in the manufacturing of carbon nanotubes is the usage of renewable feedstocks as a carbon source. This new development is receiving much support and is a source of excitement among the global research communities due to the positive environmental impacts, reduced carbon footprints, and economic benefits. Various types of renewable feedstocks such as vegetable oils, plant derivatives, and other types of biomasses have been used for the green synthesis of carbon nanotubes by employing conventional fabrication techniques. As the global demand increases for green manufacturing, efforts to synthesize carbon nanotubes from renewable resources are receiving immense attention while also strengthening the concept of biorefinery. This also enables the efficient use of resources as well as improved waste management. The present review summarizes the recent developments and current status of the synthesis of carbon nanotubes using renewable feedstocks along with technical discussions, opportunities for novel precursors, and future directions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44255.     

Uncertainty‐conscious methodology for process performance assessment in biopharmaceutical drug product manufacturing

This work presents an uncertainty‐conscious methodology for the assessment of process performance—for example, run time—in the manufacturing of biopharmaceutical drug products. The methodology is presented as an activity model using the type 0 integrated definition (IDEF0) functional modeling method, which systematically interconnects information, tools, and activities. In executing the methodology, a hybrid stochastic–deterministic model that can reflect operational uncertainty in the assessment result is developed using Monte Carlo simulation. This model is used in a stochastic global sensitivity analysis to identify tasks that had large impacts on process performance under the existing operational uncertainty. Other factors are considered, such as the feasibility of process modification based on Good Manufacturing Practice, and tasks to be improved is identified as the overall output. In a case study on cleaning and sterilization processes, suggestions were produced that could reduce the mean total run time of the processes by up to 40%. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1272–1284, 2018     

Pinch‐based shortcut method for the conceptual design of adiabatic absorption columns

Shortcut methods are valuable tools for the fast evaluation of key performance indicators in the early phase of conceptual process design. For the design of absorption columns, operation at minimum solvent demand represents a thermodynamically sound indicator, which is, however, difficult to determine because an infinite number of separation stages need to be considered. Instead, the suggested shortcut model exploits the existence of the pinch point to identify operation at minimum solvent demand. Existing shortcut concepts, such as the well‐known equation of Kremser (Natl Pet News, 22, 43–49, 1930), are significantly outperformed by the novel shortcut model, which can be gradually refined to any desired accuracy. Integration into a stepwise procedure results in reliable solutions. The model covers rigorous thermodynamics; no simplifications regarding phase equilibrium, heat effects, or number of components are required. The performance of the method is illustrated by several case studies with up to seven components. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1213–1225, 2017     

Integrated B2B‐NMPC control strategy for batch/semibatch crystallization processes

The uncertainty in crystallization kinetics is of major concern in manufacturing processes, which can result in deterioration of most model‐based control strategies. In this study, uncertainties in crystallization kinetic parameters were characterized by Bayesian probability distributions. An integrated B2B‐NMPC control strategy was proposed to first update the kinetic parameters from batch to batch using a multiway partial least‐squares (MPLS) model, which described the variances of kinetic parameters from that of process variables and batch‐end product qualities. The process model with updated kinetic parameters was then incorporated into an NMPC design, the extended prediction self‐adaptive control (EPSAC), for online control of the final product qualities. Promising performance of the proposed integrated strategy was demonstrated in a simulated semibatch pH‐shift reactive crystallization process to handle major crystallization kinetic uncertainties of L‐glutamic acid, wherein smoother and faster convergences than the conventional B2B control were observed when process dynamics were shifted among three scenarios of kinetic uncertainties. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Thermo‐hydraulic analysis of refinery heat exchangers undergoing fouling

A complete, systematic approach is presented for the analysis and characterization of fouling and cleaning in refinery heat exchangers. Bringing together advanced thermo‐hydraulic dynamic models, some new formulations, and a method for dynamic analysis of plant data, it allows: extracting significant information from the data; evaluating the fouling state of the units based on thermal measurements and pressure drops, if available; identifying the range of deposit conductivity leading to realistic pressure drops, if pressure measurements are unavailable; estimating key fouling and ageing parameters; estimating the effectiveness of cleaning and surface conditions after a clean; and predicting thermal and hydraulic performance with good accuracy for other periods/exchangers operating in similar conditions. An industrial case study demonstrates the performance prediction in seamless simulations that include partial and total cleanings for over 1000 days operation. The risks of using thermal effects alone and the significant advantages of including pressure drop measurements are highlighted. © 2016 American Institute of Chemical Engineers AIChE J, 63: 984–1001, 2017     

Pinch‐based shortcut method for the conceptual design of isothermal extraction columns

Shortcut methods are valuable tools for a comprehensive evaluation of key performance indicators in the early phase of conceptual process design. For the design of extraction columns, operation at minimum solvent demand represents a thermodynamically sound indicator, which is, however, difficult to determine. The suggested shortcut model therefore exploits the existence of the pinch point to directly identify operation at minimum solvent demand. It is solved quickly and reliably by a step‐by‐step procedure. The final step allows a reduction of the approximation error to any desired degree of accuracy. No simplifications regarding the number of components in the mixture or its thermodynamic behavior are introduced. Hence, arbitrary mixtures can be tackled. The performance of the method is highlighted by a fully automated screening of thousands of solvents for the recovery of fermentation products acetone, 1‐butanol, and ethanol from aqueous solution. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1236–1245, 2017     

Slot coating flows of non‐colloidal particle suspensions

Slot coating is used in the manufacturing of functional films, which rely on specific particle microstructure to achieve the desired performance. Final structure on the coated film is strongly dependent on the suspension flow during the deposition of the coating liquid and on the subsequent drying process. Fundamental understanding on how particles are distributed in the coated layer enables optimization of the process and quality of the produced films. The complex coating flow leads to shear‐induced particle migration and non‐uniform particle distribution. We study slot coating flow of non‐colloidal suspensions by solving the mass and momentum conservation equations coupled with a particle transport equation using the Galerkin/Finite element method. The results show that particle distribution in the coating bead and in the coated layer is non‐uniform and is strongly dependent on the imposed flow rate (wet thickness). © 2016 American Institute of Chemical Engineers AIChE J, 63: 1122–1131, 2017     

Processing and mechanical properties of bio‐derived vinyl ester resin‐based composites

A “green” vinyl ester resin (GVER) is investigated for use in structural applications. The GVER was formulated using a monodisperse vinyl ester created via a novel synthetic route capable of using bio‐waste material from paper and biodiesel industries. The GVER was used either as a neat resin or as blended with a commercial vinyl ester resin. The processing viscosity and gel times are investigated. The GVER reaches a similar viscosity as the commercial resin with only half the styrene monomer content, thereby reducing the volatile organic compounds associated with manufacturing. Composites of the GVER matrix reinforced by carbon fabric were tested for their tensile and flexural properties. The mechanical performance of the GVER compares favorably with commercial resin and provide a route for composites manufacturing from sustainably sourced vinyl ester matrix. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44642.     

Quasi‐isothermal DSC testing of epoxy adhesives using initial fast heating rates

Three major factors decrease the accuracy of the cure measurement in standard‐isothermal testing using differential scanning calorimetry (DSC). First, cure occurs during the heating step. Second, data are lost during the stabilization period between the dynamic and isothermal step. Third, the baseline selection requires a modification to the protocol. An alternative, which is explored in this study, is the use of fast ramps, which decrease the heating time, but this has been avoided due to overshoot that occurs between the dynamic and isothermal step, which is troublesome for systems with autocatalytic kinetics. By mitigating these factors, a quasi‐isothermal protocol was developed. Therefore, more complete cure kinetics were captured with the implementation of fast DSC to decrease the ramp time and through the optimization of furnace parameters to decrease stabilization time and temperature overshoot. The data suggested this quasi‐isothermal analysis more accurately measured the isothermal curing kinetics of a commercial epoxy adhesive at 110, 115, and 120 °C for fast ramps of 175, 350, and 500 K/min compared to the traditional ramp of 5 K/min. The enthalpy spike at the dynamic to isothermal transition remains an issue; however, an empirical shift can be used to compensate for the enthalpy signal lag. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45425.     

A new manufacturable filter design approach for spectral reflectance estimation

Selection of the best possible filter set among a set of available filters is the obvious method of increasing dimension of camera signals for spectral reflectance reconstruction. There are also methods that are focusing on the filter design regardless of noticing to the constructability of the designed filters. This study shows that direct optimization of physical variables of filter manufacturing technique is more reliable than indirect approach of designing and then physical manufacturing of the designed filters. Direct optimization of the transmission‐controlling primaries in filter manufacturing process would guarantee having the designed filters in reality. Combination of some solvent dyes was used as the spectral transmission matching system for filter manufacturing. As a conventional technique, filters were designed and best possible dye concentrations that match the desired filters were calculated. As an alternative approach, filters were also designed using direct optimization of dyes concentrations. The results showed that direct optimization of dye concentrations exhibits better performance in comparison with the conventional technique. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 316–326, 2017     

Effect of ingredient ratios of rigid polyurethane foam on foam core panels properties

One‐step manufacturing process (in‐situ foaming) provide great potential for the production of foam core panels. Polyurethane (PU) foam showed good applicability for use for in‐situ foaming. Here, the effect of ingredient ratios of rigid PU foam on foam performance and panel properties is investigated. It was observed that the isocyanate (ISO) content and polyols (PO) type and content significantly change the foam and panel properties. Foam cell density, as the most important factor influencing the foam characteristics, was higher in foams with higher ISO and polyether content. Bending strength, internal bond and screw withdrawal resistance of the foam core panels were significantly enhanced when the ISO and polyether content was increased in the foam formulation. Varying the ISO content had no influence on panel properties with higher content of polyester (60%) in the PO blend. Varying the foam ingredient ratios did not change the thickness swelling, while the water absorption was dependent on the foam components ratios. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44722.