Terms Of Production Rate Research Articles

Digital Twin of a Water Supply System Using the Asset Administration Shell.

The concept of digital twins is one of the fundamental pillars of Industry 4.0. Digital twin allows the realization of a virtual model of a real system, enhancing the relevant performance (e.g., in terms of production rate, risk prevention, energy saving, and maintenance operation). Current literature presents many contributions pointing out the advantages that may be achieved by the definition of a digital twin of a water supply system. The Reference Architecture Model for Industry 4.0 introduces the concept of the Asset Administration Shell for the digital representation of components within the Industry 4.0 ecosystem. Several proposals are currently available in the literature considering the Asset Administration Shell for the realization of a digital twin of real systems. To the best of the authors' knowledge, at the moment, the adoption of Asset Administration Shell for the digital representation of a water supply system is not present in the current literature. For this reason, the aim of this paper is to present a methodological approach for developing a digital twin of a water supply system using the Asset Administration Shell metamodel. The paper will describe the approach proposed by the author and the relevant model based on Asset Administration Shell, pointing out that its implementation is freely available on the GitHub platform.

Modified mangrove pens for polyculture system in mud crab (Scylla serrata) and milkfish (Chanos chanos) production

The mangrove pens were modified to produce mud crab (Scylla serrata) and milkfish (Chanos chanos) in a polyculture system. The modification of mangrove pens was done by adding excavations inside the pen. The water quality parameters (dissolved oxygen (DO), pH, salinity, and temperature) were monitored, and the recovery and production rates in each pen were evaluated. The experiment was conducted for a rearing period of 143 days in nine mangrove pens, each having an area of 32 m2 and an average net enclosure height of 3 m from the soil surface. The three different pens constructed (existing design: canal only, 43% excavation by area, and 54% excavation by area) were designated as T1, T2, and T3, respectively. The water quality parameters recorded in the pens were favorable for the growth and recovery of the mud crab and milkfish, except for DO. For mud crab, the highest mean recovery was recorded in T2, followed by T3, and the lowest in T1. The production rate followed the same pattern as the recovery, with T2 having the highest, followed by T3, and T1 having the lowest. The statistical analysis revealed that the variations in mud crab recovery were not significant, while in terms of production rate, modified mangrove pens were found to be more effective than the existing design. Due to the total mortality of the cultured milkfish, the current set-up of modified mangrove pens was found to be unsuitable for the polyculture system of milkfish and mud crab production.

Model Development for Micellar/ Polymer Flooding Process

Flow of hydrocarbon from the reservoir is a function of pressure differential provided by natural reservoir energy at initial stage of production. The pressure declines over time with a corresponding reduction in production rate. To salvage for this, polymer/micellar flooding a chemical method deployed to enhance the recovery of oil from the reservoir. The key point here is to improve overall sweep efficiency. In this work, the reservoir was produced using a polymer injection well and analysis were made using a time step of 1 day over 100 days of production period. Simulation using Eclipse 100 result shows that similar cells in terms of relative permeability reduces with increasing polymer concentration and relative distance from the injector. The field performance in this work was analyzed in terms of production rate, field pressure, and saturation. Peak pressure value of 4470Psia was reached at the day 75 with peak oil production rate of 205STB/Day at day 68 with a continuous decline in oil saturation. Sensitivity study was performed in terms of polymer adsorption/injection rate in relation to time, polymer injection rate/oil production rate against time, fluid oil rate/field pressure against time. The overall result shows that the polymer adsorption weakens the interfacial tension of the in-situ of oil phase.

Bibliographical Mapping of Research into the Relationship between In Ovo Injection Practice and Hatchability in Poultry

Recent advances in poultry practice have produced new tools enabling the poultry industry to increase productivity. Aiming at increasing production quality, varying protocols of in ovo injection facilitate the introduction of exogenous substances into the egg to complement the nutrients that support embryonic development up to hatching, which are already available in the internal and external compartments. Due to embryonic sensitivity, adding any substance into the egg can be either advantageous or disadvantageous for embryonic survival and can influence hatch rates. Thus, understanding the relationship between poultry practices and production rates is the first step towards successful commercial application. This review aims to assess the influence on hatch rates of injecting different substances in ovo, including effects on embryo and chick health parameters where these are reported. Bibliographic mappings of co-authorship of citations, co-occurrence of keywords, and bibliographic coupling based on the in ovo injection technique and hatchability parameters were also performed. Using the Scopus database, 242 papers were retrieved, reviewed, and submitted for bibliographic mapping using the VOSviewer® software. This review provides a broad overview of just over 38 years' research on the subject, revealing that studies have significantly increased and peaked in 2020, being produced primarily by US researchers and published primarily in the journal Poultry Science. It also reveals that despite negative reports relating to some substances in the embryo, in ovo delivery of substances may possibly change the poultry industry for the better in terms of production rates (hatchability) and/or poultry health.

Gender Marking and Clitic Pronoun Resolution in Simultaneous Bilingual Children

The acquisition of clitics still remains a highly controversial issue in Greek acquisition literature despite the bulk of studies performed. Object clitics have been shown to be early acquired by monolingual children in terms of production rates, whereas only highly proficient bilingual children achieve target-like performance. Crucially, errors in gender marking are persistent for monolingual and bilingual children even when adult-like production rates are achieved. This study aims to readdress the acquisition of clitics in an innovative way, by entering the variable of gender in an experimental design targeting to assess production and processing by bilingual and monolingual children. Moreover, we examined the role of language proficiency (in terms of general verbal intelligence and syntactic production abilities). The groups had comparable performance in both tasks (in terms of correct responses and error distribution in production and reaction times in comprehension). However, verbal intelligence had an effect on the performance of the monolingual but not of the bilingual group in the production task, and bilingual children were overall slower in the comprehension task. Syntactic production abilities did not have any effect. We argue that gender marking affects clitic processing, and we discuss the implications of our findings for bilingual acquisition.

Statistical and stochastic feasibility studies of potential liquid organic hydrogen carriers in a membrane reactor for simultaneous hydrogen storage and production: Technical, economic, and environmental aspects

With a global trend of transition to the hydrogen-based energy system, the importance of improved systems of hydrogen production and transportation is emphasized. Especially, liquid organic hydrogen carrier is introduced due to its significant advantages when it is employed as a hydrogen energy carrier. In this study, the comprehensive preliminary feasibility study in technical, economic, and environmental aspects for hydrogen production systems using several promising systems of dodecahydro-N-ethycarbazole, Perhydro-dibenzyltoluene, methylcyclohexane, and methanol in a membrane reactor is conducted to investigate its potential to be alternative hydrogen production and transportation. With process simulation using Aspen Plus® based on detailed reaction kinetics for dehydrogenation of each dehydrogenation system and steam reforming of methanol, technical performance in terms of production rate is revealed. In addition, unit hydrogen production costs and key economic parameters for each system at various scales are estimated and compared by itemized cost estimation. Furthermore, realistic uncertainty analysis reflecting detailed distributions of each economic parameter obtained by various regression types of triangular, Epsilon skew normal, Birnbaum-Saunders, and Rayleigh and environmental assessment using SimaPro® are conducted revealing possible ranges of unit hydrogen production cost and carbon dioxide emission rate.

A Case Study on Lead Time Improvement Using a Simulation Approach

During the shift from gasoline vehicles to electric ones, auto parts manufacturing companies have realized the importance of improvement in the manufacturing process that does not require any layout changes nor extra investments, while maintaining their current production rate. Due to these reasons, for the auto part manufacturing company, I-company, this study has developed the simulation model of the PUSH system to conduct a process analysis in terms of production rate, WIP level, and logistics work’s utilization rate. In addition, this study compares the PUSH system with other three manufacturing systems -KANBAN, DBR, and CONWIP- to compare the performance of these production systems, while satisfying the company’s target production rate. With respect to lead-time, the simulation results show that the improvement of 77.90% for the KANBAN system, 40.39% for the CONWIP system, and 69.81% for the DBR system compared to the PUSH system. In addition, with respect to WIP level, the experimental results demonstrate that the improvement of 77.91% for the KANBAN system, 40.41% for the CONWIP system, and 69.82% for the DBR system compared to the PUSH system. Since the KANBAN system has the largest impacts on the reduction of the lead-time and WIP level compared to other production systems, this study recommends the KANBAN system as the proper manufacturing system of the target company. This study also shows that the proper size of moving units is four and the priority allocation of bottleneck process methods improves the target company’s WIP and lead-time. Based on the results of this study, the adoption of the KANBAN system will significantly improve the production process of the target company in terms of lead-time and WIP level.

A multi-objective optimization method of inflow control device configuration

Inflow control device (ICD) restricts flows of certain sections to achieve a uniform push of water oil contact along a horizontal well. The efficiency of ICD depends on its configuration (location, number of nozzles, and nozzle sizes). Traditionally, optimal ICD configurations have been selected using a trial and error approach simulating different configurations. This method is time-consuming and the outcome can be limited by pre-set candidates, thus may result in non-optimal configurations. In this paper, a method involving several optimization objectives is proposed to obtain the optimal ICD configuration, in order to reach an optimal total production before water breakthrough. A flow coupling model (permeation flow – nozzle flow – inner tubing flow) of horizontal wells completed by ICDs is established to calculate the inflow profile and the pressure distribution along the horizontal wellbore. The production rate and the water breakthrough time are the optimization objectives, and the sand control condition (production pressure drawdown < critical pressure drawdown of sanding onset) is taken as one of the constraints of optimization. Then the NSGA-II algorithm is employed to search for the Pareto frontier based on the model of coupled flow. Selected by the TOPSIS method from the Pareto frontier, the optimal ICD configuration ensuring optimal total production and no sanding is acquired. The original data of well A1 in SL oilfield are used for case study. The optimal configuration is compared with single-objective optimization results and open hole completion in terms of production rate and water breakthrough time. By predicting the total productions of different configurations before water breakthrough, we think the optimization method is capable of determining the optimal configuration. This research can provide some theoretical support for the determination of ICD configuration in horizontal wells.

Scalable production and application of Pichia pastoris whole cell catalysts expressing human cytochrome P450 2C9

BackgroundCurrently, the numerous and versatile applications in pharmaceutical and chemical industry make the recombinant production of cytochrome P450 enzymes (CYPs) of great biotechnological interest. Accelerating the drug development process by simple, quick and scalable access of human drug metabolites is key for efficient and targeted drug development in response to new and sometimes unexpected medical challenges and needs. However, due its biochemical complexity, scalable human CYP (hCYP) production and their application in preparative biotransformations was still in its infancy.ResultsA scalable bioprocess for fine-tuned co-expression of hCYP2C9 and its essential complementary human cytochrome P450 reductase (hCPR) in the yeast Pichia pastoris (Komagataella phaffii) is presented. High-throughput screening (HTS) of a transformant library employing a set of diverse bidirectional expression systems with different regulation patterns and a fluorimetric assay was used in order to fine-tune hCYP2C9 and hCPR co-expression, and to identify best expressing clonal variants. The bioprocess development for scalable and reliable whole cell biocatalyst production in bioreactors was carried out based on rational optimization criteria. Among the different alternatives studied, a glycerol carbon-limiting strategy at high µ showed highest production rates, while methanol co-addition together with a decrease of µ provided the best results in terms of product to biomass yield and whole cell activity. By implementing the mentioned strategies, up to threefold increases in terms of production rates and/or yield could be achieved in comparison with initial tests. Finally, the performance of the whole cell catalysts was demonstrated successfully in biotransformation using ibuprofen as substrate, demonstrating the expected high selectivity of the human enzyme catalyst for 3′hydroxyibuprofen.ConclusionsFor the first time a scalable bioprocess for the production of hCYP2C9 whole cell catalysts was successfully designed and implemented in bioreactor cultures, and as well, further tested in a preparative-scale biotransformation of interest. The catalyst engineering procedure demonstrated the efficiency of the employment of a set of differently regulated bidirectional promoters to identify transformants with most effective membrane-bound hCYP/hCPR co-expression ratios and implies to become a model case for the generation of other P. pastoris based catalysts relying on co-expressed enzymes such as other P450 catalysts or enzymes relying on co-expressed enzymes for co-factor regeneration.

Energy consumption and process characteristics of picosecond laser de-coating of cutting tools

Abstract Laser de-coating is a promising technology for selective coating removal to facilitate reuse of coated tools in a circular economy. It is timely to understand and optimise the quality, energy requirements and environmental footprint of the laser de-coating process. This paper reports on an investigation into process characteristics, energy demands and carbon footprints in coating removal from tungsten carbide tool inserts using high power picosecond laser sources with different pulse widths and wavelengths. The results demonstrate that although the 355 nm wavelength, 10 ps pulse width laser, has higher processing efficiency in terms of production rates, and lower specific energy for laser beam and material interaction, and results in better surface quality, the overall laser system energy consumption is much higher than that of using the 1064 nm wavelength, 150 ps pulse width laser for the removal of coatings on tungsten carbide cutting tools. This is largely due to the high energy demand of the water cooling system needed for the 355 nm wavelength picosecond laser whilst the 1064 nm ps is air cooled. There is therefore a need to optimise the total system energy consumption in the 355 nm ps laser, to support its superior laser de-coating performance. The paper shows the importance and challenges of optimising the energy consumption at different system boundaries.

EVALUATING THE SAWABILITY OF ROCKS BY CHAIN-SAW MACHINES USING THE PROMETHEE TECHNIQUE

One of the most significant factors in the estimation of dimension stone quarry cost is the production rate of rock cutting machines. Evaluating the production rate of chain-saw machines is a very significant and practical issue. In this research, it has been attempted to evaluate and select the suitable working-face for a quarry by examining the maximum production rate in the Dehbid and Shayan marble quarries. For this purpose, fi eld studies were carried out which included measuring operational characteristics of the chain-saw cutting machine, the production rate and sampling for laboratory tests from seven active case studies. Subsequently, the physical and mechanical properties of rocks including: Uniaxial Compressive Strength (UCS), Brazilian Tensile Strength (BTS), Los Angeles abrasion, quartz content, water absorption percentage, porosity, Schmidt hardness and grain size for all sample measurements were studied after transferring the samples to a rock-mechanics laboratory. Finally, the sawability of the quarried working-faces was evaluated using the PROMETHEE multi-criteria decision-making (MCDM) model according to the physical and mechanical properties. The results of the study indicated that the number 1 and 5 working-faces from the Dehbid and Shayan quarries are the most suitable working-faces in terms of production rate with the maximum recorded production values (4.95 and 3.1 m2 /h), and with net fl ow rates (2.67 and -0.36) respectively.

Effect of different low salinity flooding schemes and the addition of alkali on the performance of low-salinity waterflooding during the recovery of heavy oil from unconsolidated sandstone

Low salinity waterflooding (LSW) is a promising enhanced oil recovery process. The LSW advantage has been associated to changes in rock wettability toward a more water wet state. This study evaluated the effect of different flooding schemes on the performance of LSW in terms of production rate and incremental oil recovery from sand-pack systems. This work also investigated the main mechanism prompting sand wettability changes during LSW.Flooding Scheme-1 consisted of high salinity waterflooding, low salinity waterflooding, alkali aided low salinity waterflooding, and low salinity waterflooding. Flooding Scheme-2 consisted of low salinity waterflooding, alkali aided low salinity waterflooding, and low salinity waterflooding. Flooding Scheme-3 consisted of alkali aided low salinity flooding and low salinity waterflooding. The main mechanism causing wettability reversal was verified employing contact angle analysis, inductively coupled plasma spectrometry, and scanning electron microscopy.This new study reveals in a straightforward manner the effect of low salinity waterflooding schemes on both production rate and incremental oil recovery. LSW in secondary mode, as conducted in FS-2, expedited the oil production rate by 15% and increased the overall oil recovery by 20% relative to flooding schemes FS-1 and FS-3. Furthermore, this study determined that multi-component ionic exchange was the dominant mechanism for the reversal of sand wettability to a more water wet state.This paper provides new insights for heavy oil producers on the relevance of the flooding schemes during LSW and on the dominant mechanism for wettability alteration during the recovery of heavy oil from unconsolidated sands.

(Invited) Advanced Alkaline Electrolysis Cells for the Production of Sustainable Fuels and Chemicals

Amongst the different electrolysis technologies, alkaline electrolysis (AE) stands out as the most well established for large-scale electrolytic hydrogen production, with commercially available multi-MW units combined in plants of 100s of MW and operated for decades. Besides proven reliability and availability, a key advantage of AE over alternative technologies when it comes to large-scale deployment is the relatively abundant and inexpensive materials it relies on. Nevertheless, AE suffers from relatively poor performance in terms of production rate and efficiency when compared to proton exchange membrane electrolysis (PEME) and solid oxide electrolysis (SOE).One of the main reasons is associated with the sluggish hydrogen evolution reaction (HER) kinetics in alkaline environment [1]. Recent improvements in HER catalysts, have reduced the HER kinetics difference between alkaline and acidic environment. Furthermore, the far lower price of these catalysts (e.g. Ni, Ni1-xMox) compared to Pt, allow for much higher catalyst loadings, which can circumvent this challenge in conjunction with the much higher ionic conductivity of concentrated aqueous KOH as compared to PEME and SOE electrolytes. Taking full advantage of this opportunity requires a careful optimization of the AE electrode microstructure to achieve both a high electrochemically active surface area in close proximity to the separator as well as macro-porosity to enable gas evolution with minimal blocking of the active area. This was attempted here by applying high surface area catalytic coatings of Ni and Ni1-xMox on porous conducting supports with varying macro-pore structure. Furthermore, a finite element multi-physics simulation model was employed to provide further insight and guidance to the microstructural optimization effort.Raising the operating temperature offers an additional means to drastically improve performance, as both ionic transport and reaction kinetics are strongly activated with temperature [2]. The development of a corrosion resistant ceramic separator [3] has enabled a novel concept of alkaline electrolysis cells operating at 200-250 °C and 20-50 bar [4,5], showing pronounced thermal activation, and achieving a current density of up to 3.75 A cm-2 at a cell voltage of 1.75 V at 200 °C and 20 bar [6]. The feasibility and promise of this concept, as well as the challenges that lie ahead are also discussed.[1] V. R. Stamenkovic, D. Strmcnik, P. P. Lopes and N. M. Markovic, Nature Materials, 2017, 16, 57–69.[2] M. H. Miles, G. Kissel, P. W. T. Lu and S. J. Srinivasan, J. Electrochem. Soc., 1976, 123, 332-336.[3] F. Allebrod, C. Chatzichristodoulou, P. L. Mollerup and M. B. Mogensen, Int. J. Hydrogen Energy, 2012, 37, 16505-16514.[4] F. Allebrod, C. Chatzichristodoulou and M. B. Mogensen, J. Power Sources, 2013, 229, 22–31.[5] F. Allebrod, C. Chatzichristodoulou and M. B. Mogensen, J. Power Sources, 2014, 255, 394-403.[6] C. Chatzichristodoulou, F. Allebrod and M. B. Mogensen, J. Electrochem. Soc., 2016, 163, F3036-F3040.

Comparative study of well soaking timing (pre vs. post flowback) for water blockage removal from matrix-fracture interface

Abstract Water blockage after hydraulic fracturing is one of the major challenges in shale oil recovery which affects the optimal production from the reservoir. The water blockage represents a higher water saturation near the matrix-fracture interface, which decreases the hydrocarbon relative permeability. The removal of water blockage in the field is typically carried out by soaking the well (i.e., shut-in) after hydraulic fracturing operation is finished. This soaking period allows water redistribution, which decreases the water saturation near the matrix-fracture interface. However, previous field reports show that there is not a strong consensus on whether shut-in is beneficial in terms of production rate or ultimate oil recovery. Due to the large number of parameters involved in hydraulic fracturing and tight formations, it is challenging to select which parameter plays the dominant role in determining the shut-in performance. Furthermore, literature on field case studies does not frequently report the parameters which are of researchers’ interest. In other words, the challenge of evaluating shut-in performance not only lies on the complexity of parameters and effects involved within the reservoir, but also the limited number of field case studies which report a comprehensive list of fracturing and reservoir parameters. This paper aims to investigate the effect of well soaking timing on shut-in performance. This idea to investigate the shut-in timing effect is motivated by the fact that in the field, shut-in can take place either immediately after hydraulic fracturing but before the first flowback (i.e., pre-flowback) or sometime after the first flowback (i.e., post-flowback). The timing of shut-in is believed to influence the production performance, because it dictates how much water is allowed to imbibe from the fractures to the matrix before the extended production. A numerical model is built and validated by a successful history match with numerous data from core-flood experiments. Our previous study shows that shut-in performance depends heavily on the desiccation state of the formation: in non-desiccated formations, longer shut-in (pre-flowback) results in a lower regained hydrocarbon relative permeability, but in desiccated formations, longer shut-in (pre-flowback) does not affect the regained hydrocarbon relative permeability. In this study, our model further demonstrates that shut-in performed after the first flowback (i.e., post-flowback) can help ensure a higher regained oil relative permeability than shut-in performed before the first flowback (i.e., pre-flowback) in such non-desiccated formations. A mechanistic analysis on the water blockage mitigation from these two shut-in timings is also presented. As a result, this study proposes that flowback should be carried out immediately following hydraulic fracturing, even if an extended shut-in is to be performed later.

A non-dominated sorting Differential Search Algorithm Flux Balance Analysis (ndsDSAFBA) for in silico multiobjective optimization in identifying reactions knockout

Metabolic engineering is defined as improving the cellular activities of an organism by manipulating the metabolic, signal or regulatory network. In silico reaction knockout simulation is one of the techniques applied to analyse the effects of genetic perturbations on metabolite production. Many methods consider growth coupling as the objective function, whereby it searches for mutants that maximise the growth and production rate. However, the final goal is to increase the production rate. Furthermore, they produce one single solution, though in reality, cells do not focus on one objective and they need to consider various different competing objectives. In this work, a method, termed ndsDSAFBA (non-dominated sorting Differential Search Algorithm and Flux Balance Analysis), has been developed to find the reaction knockouts involved in maximising the production rate and growth rate of the mutant, by incorporating Pareto dominance concepts. The proposed ndsDSAFBA method was validated using three genome-scale metabolic models. We obtained a set of non-dominated solutions, with each solution representing a different mutant strain. The results obtained were compared with the single objective optimisation (SOO) and multi-objective optimisation (MOO) methods. The results demonstrate that ndsDSAFBA is better than the other methods in terms of production rate and growth rate.

Sonofluidic fabrication of microbubbles for imaging and therapy

Gas-filled microbubbles are routinely used in diagnostic ultrasound imaging as contrast agents, and are under investigation for therapeutic application including drug delivery and ablation enhancement. They typically consist of a high molecular weight gas surrounded by a coating of surfactant, denatured albumin and/or a polymer. The acoustic response of microbubbles is profoundly influenced by their physical characteristics, in particular their size, size distribution, and the rheological properties of the coating. These in turn depend on the chemical formulation of the microbubble shell and the production technique. Sonication is the most commonly employed method and can generate high concentrations of microbubbles rapidly but with a broad size distribution and wide variability in acoustic response. Microfluidic devices provide excellent control over size, but the small-scale architectures required are often challenging to manufacture, offer low production rates, and are prone to clogging. Microfluidic generated microbubbles may also have inferior surface characteristics and stability compared to those produced by sonication. In order to address the limitations of the existing methods, we have developed a hybrid “sonofluidic” device. Monodisperse bubbles of a few 100 µm in diameter are first produced using a simple T-junction with relatively large channel dimensions (254µm x 50µm). Consequently high flow rates can be used with minimal risk of clogging or leakage. After formation, the large bubbles are exposed to ultrasound from a transducer embedded within the device for 1s over a frequency range of 71-73kHz. This promotes controlled fragmentation of the large bubbles to generate bubbles of the size required for clinical applications. Microbubbles were prepared using the sonofluidic device, a conventional microfluidic system or a standard sonication protocol. They were compared in terms of their size, size distribution, concentration, stability, acoustic response, and surface molecular concentration using quantitative fluorescence microscopy. The characteristics of the microbubbles produced by the sonofluidic device were found to be equivalent in terms of production rate and stability to those formed by sonication; but to have a narrower size distribution, closer to that obtained with microfluidics. These differences were reflected in the measured acoustic response and surface properties.

Micro-continuum Framework for Pore-Scale Multiphase Fluid Transport in Shale Formations

A micro-continuum simulation framework is proposed to study the complex pore-scale dynamics associated with hydrocarbon recovery from shale gas. The model accounts for the presence of immiscible fluid phases and for transport mechanisms in the nanoporous structures including slip flow, adsorption, surface and Knudsen diffusion. We employ the concept of sub-grid models to simulate the transport phenomena in shale gas. Specifically, we use high-resolution FIB–SEM images that provide information on the spatial distribution of the minerals, resolved pore space, and sub-resolution porous regions. The model is used to investigate several production scenarios at the pore-scale. In one setting, the organic matter is in direct contact with a micro-crack; in the other setting, clay regions are sandwiched between the organic matter and the “open” crack. The simulations show that it is important to account for the presence of multiple immiscible fluid phases because they can play a critical role in hydrocarbon production from shale-gas formations both in terms of production rate and in terms of residual mass of hydrocarbon. Moreover, we show that, because of wettability conditions, the rate of hydrocarbon recovery, as well as the ultimate recovery, depends strongly on the spatial distribution of the kerogen and clay in the vicinity of the micro-cracks.

CO2 to succinic acid – Estimating the potential of biocatalytic routes

Microbial carbon dioxide assimilation and conversion to chemical platform molecules has the potential to be developed as economic, sustainable processes. The carbon dioxide assimilation can proceed by a variety of natural pathways and recently even synthetic CO2 fixation routes have been designed. Early assessment of the performance of the different carbon fixation alternatives within biotechnological processes is desirable to evaluate their potential. Here we applied stoichiometric metabolic modeling based on physiological and process data to evaluate different process variants for the conversion of C1 carbon compounds to the industrial relevant platform chemical succinic acid. We computationally analyzed the performance of cyanobacteria, acetogens, methylotrophs, and synthetic CO2 fixation pathways in Saccharomyces cerevisiae in terms of production rates, product yields, and the optimization potential. This analysis provided insight into the economic feasibility and allowed to estimate the future industrial applicability by estimating overall production costs. With reported, or estimated data of engineered or wild type strains, none of the simulated microbial succinate production processes showed a performance allowing competitive production. The main limiting factors were identified as gas and photon transfer and metabolic activities whereas metabolic network structure was not restricting. In simulations with optimized parameters most process alternatives reached economically interesting values, hence, represent promising alternatives to sugar-based fermentations.

Integrated control policy of production and preventive maintenance for a deteriorating manufacturing system

Abstract This paper addresses the integrated control of production and preventive maintenance for a deteriorating single-machine manufacturing system. The machine is subjected to deterioration and random failures. Both corrective maintenance and preventive maintenance are performed to maintain the machine’s reliability. The previous literature in this field normally assumes the periodicity of preventive maintenance and obtains only its fixed time interval for execution. Maintenance level, which represents the time and cost invested in the maintenance activity, is usually ignored in the literature. Therefore, we propose an integrated control model that considers not only the flexible time interval of preventive maintenance but also its level. The problem is then formulated as an infinite time horizon dynamic programming problem of a semi-Markov decision process. The objective is to develop the optimal control policy in terms of production rate, hedging level, maintenance rate and maintenance level such that the total production cost is minimized. The successive value iteration algorithm is applied to obtain the near optimal control policy. We compared the obtained policy with previous control policies reported in the literature through several numerical examples. Additionally, sensitivity analysis is performed to illustrate the impact of several cost parameters on the control policy and to validate the structure of this policy. This paper contributes to fill the research gaps mentioned above and provides a more practical production and preventive maintenance control model for industrial practitioners.

Assessment of Flexible Operation in an LNG Plant

Process industries are becoming increasingly reliant on electrical power for reasons of efficiency and sustainability. A large industrial site typically has its own power management system to distribute electricity to the process and to manage electrical contingencies such as partial loss of supply. Recent work has illustrated more flexible alternatives to load shedding whereby an industrial process plant can continue to operate at a lower level making use of available electrical power. This paper presents a way for achieving such flexibility in a Liquefied Natural Gas (LNG) plant. It analyzes the consequences for production of varying the consumed power, and assesses the maximum flexibility within the feasible operating envelope of the process. The study has been conducted by modeling and simulation of an LNG plant using the Linde process with three refrigeration cycles. The results also show the relationships between electrical power consumption and production in terms of production rate and product characteristics. They also show that the vapour-liquid equilibrium plays a crucial role in establishing the operating points and setting the boundaries in which the process has to work. Thus, through the assessment and simulation of an LNG plant, this work demonstrates that flexible operation has benefits over alternatives. It achieves more operating points and therefore adds more flexibility.