Lignin is the main plant cell wall component responsible for recalcitrance in the process of lignocellulosic biomass conversion into biofuels. The recalcitrance and insolubility of lignin in ...different reaction media are due in part to the hydrogen bonds and π interactions that hold syringyl (S) and guaiacyl (G) units together and promote the formation of stable water-bridged dimeric complexes (WBDCs): S G and S S, in native lignin. The current understanding of how each type of interaction influences the stability of these complexes within lignin native cell walls is still limited. Here, we found by DFT calculations that hydrogen bonding is more dominant than π-stacking interaction between aromatic rings of WBDCs. Although there is a stronger interaction of hydrogen bonds between subunits and water and higher π-stacking interaction in the S S complex compared to the S G complex, the former complex is less thermodynamically stable than the latter due to the entropic contribution coming from the methoxy substituents in the S-unit. Our results demonstrate that the methoxylation degree of lignin units does not significantly influence the structural geometries of WBDCs; if anything, an enhanced dispersion interaction between ring aromatics results in quasi-sandwich geometries as found in "coiled" lignin structures in the xylem tissue of wood. In the same way as that with ionic liquids, polar solvents can dissolve S-lignin by favorable interactions with the aliphatic hydroxyl group in the α-position as the key site or the aromatic hydroxyl group as the secondary site.
The hydrogen bonds and π-stacking interactions cling together syringyl and guaiacyl subunits, promoting the formation of stable water-bridged dimeric complexes in S-G and S-lignins.
Due to stricter environmental regulations and lack of other alternatives, saline effluents reuse is becoming necessary in arid regions. Produced water generated in oil and gas exploration is a ...promising stream for this purpose, since remarkable quantities are available. In order to turn desalination routes into economically attractive options, it is mandatory to choose and to optimize technologies aiming to minimize capital and operational costs. Therefore, several combinations of technologies, involving forward osmosis (FO), reverse osmosis (RO), assisted reverse osmosis (ARO), microfiltration (MF), mechanical vapor compression (MVC), and membrane distillation (MD) were simulated and optimized for different reuse destinations. Results indicated MF-RO as the cheapest route for salinities lower than 90g/L, while FO-RO had the highest cost and could be unfeasible depending on salinity. For higher salt content, MF-ARO-RO was the cheapest alternative, followed by thermal processes (MF-MVC and FO-MVC, respectively). However, applicability of MVC depends on final water quality due to possible volatiles constraints. MF-ARO-RO process, which is a novel technology, was submitted to a retro-techno-economic analysis (RTEA) to investigate its potentialities. Although membrane parameters had minor influence, external parameters as ARO membrane cost, energy cost and interest rate play important roles on process cost.
•Electrical driven desalination technologies are modeled and optimized aiming to minimize treatment cost.•Reverse osmosis (RO) is the cheapest desalination route for produced water up to 90g/L salinity.•For higher salinities, assisted reverse osmosis (ARO) is the most economical choice.•Changes in ARO membrane properties can be damped by process variables without considerable changes in cost.
•State space that embraces deterministic limited by stochastic process behavior.•Use of discrete and continuous random variables at the state spaces connections.•Deepness concept to identify the set ...of process behavior in the events.•Absorbing event as the unique process feature that ends the simulated MC history.
Probabilistic Safety Assessment (PSA), characterized by process-behaviours modelling and event likelihood calculation, has great importance for quantitative risk evaluation. PSA presents some difficulties for implementation, mainly when the analysis of a dynamic process is required. In this work, a set of procedures to formulate and solve Probabilistic Dynamic System Problems (PDSPs) is presented. Such procedures explain how events should be modelled and connected with each other to build a process model that makes it possible to answer two main questions: (i) What is the discrete probability of occurrence of a specific process event? And, given its occurrence (ii) What is the distribution of event time to occurrence? After answering these questions, the event-occurrence probability in a specific length of time, which is the main goal of PSA, is easily calculated. To explain this proposal, two PDSPs are solved: the pressure change in a vessel caused by failure of two valves and the change in holdup tank level caused by failure of two pumps and one valve.
•Improvement of cause-consequence process interpretation of hazards analysis.•Use of the device change as a source of the process variables deviations.•Phenomenological model simulation applied for ...hazard process analysis.•Hazard analysis divided in Simulation Result Analysis and Hazard heuristic analysis.•Systematic procedure with high quality, less human error and quantitative deviation analysis.
To improve industrial safety, several hazard analyses of processes are available. The HAZOP is one of the most frequently employed and analyzes hazardous process deviations based on heuristic knowledge. Despite the wide application of the technique, new developments are especially important to enhance industrial safety. In this sense a systematic procedure is proposed for hazardous process deviation identification and analysis that employs process simulation and heuristic evaluation. Process simulation enables the analysis of process behaviors caused by device malfunctions and the performance of deviation analysis that considers the process non-linearities and dynamics. A comparison between the HAZOP and the proposed procedure is presented using a pump startup system case study, wherein the better system interpretation and results regarding abnormal process conditions are highlighted. A second case study applies the procedures to an offshore oil production process, showing the advantages of employing process simulation for studying deviation during a dynamic process’s abnormal behavior.
•An enhanced surrogate assisted framework for constrained global optimization is proposed.•Maximizing probability of improvement approach is used for selecting infill points.•Kriging meta-models of ...objective and constraints functions are updated in every iteration.•Meta-model of objective function is local optimized when it’s sufficient mature.•Numerical results indicate that the framework is suitable for use in solving computationally expensive and constrained black-box optimization.
An enhanced surrogate assisted framework, based on Probability of Improvement (PI) method, is proposed in this paper. We made some modifications to the original PI approach to enhance the performance of the modeling and optimization framework, leading to fewer rigorous simulations to find the optimal solution without loss of accuracy. We also extended the algorithm for handling general constraints using a fully probabilistic approach. The behavior of the proposed framework was investigated through a set of 9 Unconstrained Test Functions (UTF), 7 Constrained Optimization Problems (COP) and 3 Chemical Engineering Problems (CEP). The numerical results indicate that a lower number of rigorous model simulations were needed for optimizing UTF compared to the classic PI method and that the proposed framework was capable of achieving sustained near optimal solutions for COP and CEP. These results indicate that the proposed framework is suitable for solving computationally expensive constrained black-box optimization problems.
Gas lift technology is one of the most common methods used for wells with insufficient reservoir pressure. It makes use of gas reinjection to enhance individual well production. When several wells ...are used to produce a reservoir, a problem arises regarding the selection about how to produce each well so that overall production can be maximized. To accomplish it, one needs to determine the optimal production of each well and how much gas ought to be injected. In this article, we revise previous efforts and present a new MINLP model, which we solve globally using RYSIA, a recently developed global optimization algorithm (Faria and Bagajewicz, AICHE J. 58 (8) 2320–2335).
As an incipient but preeminent technology for multiphase nanomaterials/fluids, exact compatibilizing mechanisms of Janus particles in polymer blends and the consequent morphology remain unknown. The ...contributions of Janus nanorods to slip suppression and momentum transfer across the interface have been explored through dissipative particle dynamics simulations under shear flow at unentangled polymer-polymer interfaces. Rods have been then grafted with flexible polymer chains to unveil interfacial structure-property relationships at a molecular level when compared with flexible diblock copolymer surfactants. When Janus rods are sparsely grafted with necessarily longer grafts, they favor a greater degree of graft interpenetration with polymer phases. This yields less effective momentum transfer that impacts droplet coalescence processes; dynamic heterogeneities at complex interfaces; and helps map their efficiency as compatibilizers.
Janus rods interfacially grafted with longer polymers penetrate homopolymer phases and yield less effective momentum transfer across the interface.
•Formulation of looped pipeline network problem without independent loops selection.•Resolution of pipeline network problems by reduced system of equations.•Simultaneous-modular procedure employed on ...looped pipeline network problems.•Looped pipeline as part of process simulation problem for industrial design.
It is proposed a novel method to solve looped pipeline network problems that seeks to deal with limitations of the available methods The problem is modeled as a nonlinear system of equations formed by equations that cannot be solved sequentially, characterizing the resolution as a simultaneous-modular procedure. The equations of the system are the differences between the final pressure of the pipes that end at the same network nodes and the difference between the specified and calculated design variables. At the solution both Kirchhoff’s laws are met, being the method main advantages the no need of independent loops selection and the formulation of a reduced system of equation. Case studs with a small and a big looped water pipeline network, and an industrial installation with looped pipeline configuration, are solved. The latter shows the method applicability for design process, highlighting its advantages in comparison with the traditional simulation procedures.
While there are software tools available for helping to conduct life cycle assessment (LCA), such as OpenLCA, these tools lack integration with process design, simulation, and optimization software. ...As LCA has a critical role in sustainable product design, this paper presents a platform called EMSO_OLCA, which integrates the LCA provided by OpenLCA into the Environment for Modeling, Simulation, and Optimization (EMSO). EMSO_OLCA incorporates a database of environmental impact assessment methodologies from OpenLCA and aligns with the principles of LCA outlined in ISO 14040 and ISO 14044. Validation tests were conducted to compare the results obtained by the LCA of sugarcane ethanol using OpenLCA and EMSO_OLCA, revealing a high level of agreement. The average relative error was 0.045%, indicating a negligible discrepancy between the tools. Moreover, it took only 0.3 s for the calculation, which is desirable for use with process system engineering tools. A second case study was applied to combined steam and electricity production from the combustion of sugarcane bagasse and straw in a combined heat and power system. The results show the integration of LCA with simulation and sensitivity analysis tools, thus supporting sustainable decision-making processes. EMSO_OLCA bridges the gap between LCA and process engineering, enabling a holistic approach to the sustainability, design, and implementation of environmentally friendly solutions.
In moving bed biofilm reactors (MBBR), the removal of pollutants from wastewater is due to the substrate consumption by bacteria attached on suspended carriers. As a biofilm process, the substrates ...are transported from the bulk phase to the biofilm passing through a mass transfer resistance layer. This study proposes a methodology to determine the external mass transfer coefficient and identify the influence of the mixing intensity on the conversion process in-situ in MBBR systems. The method allows the determination of the external mass transfer coefficient in the reactor, which is a major advantage when compared to the previous methods that require mimicking hydrodynamics of the reactor in a flow chamber or in a separate vessel. The proposed methodology was evaluated in an aerobic lab-scale system operating with COD removal and nitrification. The impact of the mixing intensity on the conversion rates for ammonium and COD was tested individually. When comparing the effect of mixing intensity on the removal rates of COD and ammonium, a higher apparent external mass transfer resistance was found for ammonium. For the used aeration intensities, the external mass transfer coefficient for ammonium oxidation was ranging from 0.68 to 13.50 m d−1 and for COD removal 2.9 to 22.4 m d−1. The lower coefficient range for ammonium oxidation is likely related to the location of nitrifiers deeper in the biofilm. The measurement of external mass transfer rates in MBBR will help in better design and evaluation of MBBR system-based technologies.
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•A MBBR reactor operating for ammonium oxidation and COD removal is studied.•A methodology to determine in-situ external mass transfer coefficients is proposed.•Higher external mass transfer resistance is found for NH4 oxidation.•Mixing intensity has a strong influence on external mass transfer and conversions.
