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Experimental and Numerical Study of Double-Pipe Evaporators Designed for CO2 Transcritical Systems
Junlan Yang, Shuying Ning
November 5, 2019 (v1)
Keywords: Carbon Dioxide, double-pipe evaporator, experimental study, heat transfer, Simulation
The performance of a CO2 double-pipe evaporator was studied through experiments and a simulation model that was established by the steady-state distribution parameter method and experimentally verified while using a CO2 transcritical water‒water heat pump system. The effects of different operating parameters on heat transfer performance were studied over a range of evaporation temperatures (−5 to 5 °C), mass velocity (100‒600 kg/m2s), and heat flux (5000‒15,000 W/m2). It was found that the dryout quality increased at a small evaporation temperature, a large mass velocity, and a small heat flux. The simulation yield means relative error (RE) of heat transfer for the evaporation temperature and that of the CO2 pressure drop for the chilled water inlet temperature were 5.21% and 3.78%, respectively. The effect of tube diameter on the performance of CO2 double-pipe evaporator is probed through simulations. At the same time, this paper defines a parameter α , which is the proportio... [more]
Multivariable System Identification Method Based on Continuous Action Reinforcement Learning Automata
Meiying Jiang, Qibing Jin
November 5, 2019 (v1)
Keywords: CARLA, closed-loop identification, MIMO, reinforcement learning
In this work, a closed-loop identification method based on a reinforcement learning algorithm is proposed for multiple-input multiple-output (MIMO) systems. This method could be an attractive alternative solution to the problem that the current frequency-domain identification algorithms are usually dependent on the attenuation factor. With this method, after continuously interacting with the environment, the optimal attenuation factor can be identified by the continuous action reinforcement learning automata (CARLA), and then the corresponding parameters could be estimated in the end. Moreover, the proposed method could be applied to time-varying systems online due to its online learning ability. The simulation results suggest that the presented approach can meet the requirement of identification accuracy in both square and non-square systems.
Investigation of Heat and Moisture Transport in Bananas during Microwave Heating Process
Wisara Thuto, Kittichai Banjong
November 5, 2019 (v1)
Keywords: banana, dehydration, microwave heating, multiphase porous media, ripening stages
The numerical method was used to investigate heat and moisture transport during dehydration of bananas from microwave heating. COMSOL multi-physics software was employed to perform the simulation task. A banana is defined as a porous medium. It has constituents of water, vapor, air as the liquid phase and a solid porous matrix. The numerical results of this study were validated with experimental data. The profiles of moisture, vapor and pressure are discussed in this study. Moreover, the effects of the ripening stages of the banana are examined. A higher heat flux was observed from the beginning period along with the increasing time steps until 50 s. Heat generation decreased during 50 s to 60 s, coinciding with a small rise in temperature, but the temperature gradient remained constant. The temperature distribution of both unripe and ripe banana samples was non-uniform. At the center of the banana, the temperature increased rapidly and reached its highest temperature with the negative... [more]
On the Selective Transport of Nutrients through Polymer Inclusion Membranes Based on Ionic Liquids
Z. Baicha, M.J. Salar-García, V.M. Ortiz-Martínez, F.J. Hernández-Fernández, A.P. de los Ríos, D.P. Maqueda Marín, J.A. Collado, F. Tomás-Alonso, M. El Mahi
November 5, 2019 (v1)
Subject: Materials
Keywords: ionic liquids, liquid membrane stability, nutrients, permeation, polymer inclusion membranes
In the last few years, the use of ionic liquid-based membranes has gained importance in a wide variety of separation processes due to the unique properties of ionic liquids. The aim of this work is to analyze the transport of nutrients through polymer inclusion membranes based on different concentrations of methyltrioctylammonium chloride, in order to broaden the application range of these kinds of membranes. Calcium chloride (CaCl2) and sodium hydrogen phosphate (Na2HPO4) nutrients were used at the concentration of 1 g·L−1 in the feeding phase. The evolution of the concentration in the receiving phase over time (168 h) was monitored and the experimental data fitted to a diffusion-solution transport model. The results show very low permeation values for CaCl2. By contrast, in the case of Na2HPO4 the permeation values were higher and increase as the amount of ionic liquid in the membrane also increases. The surface of the membranes was characterized before and after being used in the se... [more]
Improving the Performance of Entities in the Mining Industry by Optimizing Green Business Processes and Emission Inventories
Ionica Oncioiu, Sorinel Căpuşneanu, Dana-Maria Oprea Constantin, Mirela Cătălina Türkeș, Dan Ioan Topor, Florentina Raluca Bîlcan, Anca Gabriela Petrescu
November 5, 2019 (v1)
Subject: Energy Policy
Keywords: business process optimization, economic sustainability, green activities, mining industry, performance, suspended and sedimental powders
Due to environmental considerations, environmental sustainability has become the main target of contemporary organizations, which has a direct influence on increasing their performance. The purpose of this study was to present the efficiency of green business process optimization for the performances of mining entities. Quantitative research was carried out on a sample of 209 people in an economic entity in the mining industry. The results of the study indicated real possibilities to achieve the objectives set in the research undertaken. Using business process management, the authors examined how green business processes can be optimized in a Romanian mining entity. The main results determined the degree of pollution from suspended and sedimentary dust particles due to coal production from the mining entity that was studied. Moreover, the present research proved that certain key environmental indicators underlie the performance and optimization of green business processes. The practica... [more]
Comparison of Surface Tension Models for the Volume of Fluid Method
Kurian J. Vachaparambil, Kristian Etienne Einarsrud
November 5, 2019 (v1)
Keywords: capillary rise, rising bubbles, surface tension modelling, VOF
With the increasing use of Computational Fluid Dynamics to investigate multiphase flow scenarios, modelling surface tension effects has been a topic of active research. A well known associated problem is the generation of spurious velocities (or currents), arising due to inaccuracies in calculations of the surface tension force. These spurious currents cause nonphysical flows which can adversely affect the predictive capability of these simulations. In this paper, we implement the Continuum Surface Force (CSF), Smoothed CSF and Sharp Surface Force (SSF) models in OpenFOAM. The models were validated for various multiphase flow scenarios for Capillary numbers of 10 − 3 −10. All the surface tension models provide reasonable agreement with benchmarking data for rising bubble simulations. Both CSF and SSF models successfully predicted the capillary rise between two parallel plates, but Smoothed CSF could not provide reliable results. The evolution of spurious current were studied f... [more]
Numerical Investigation of a High-Pressure Submerged Jet Using a Cavitation Model Considering Effects of Shear Stress
Yongfei Yang, Wei Li, Weidong Shi, Wenquan Zhang, Mahmoud A. El-Emam
November 5, 2019 (v1)
Keywords: cavitation model, Computational Fluid Dynamics, nozzle, Optimization, shear stress, submerged jet
In the current research, a high-pressure submerged cavitation jet is investigated numerically. A cavitation model is created considering the effect of shear stress on cavitation formation. As such, this model is developed to predict the cavitation jet, and then the numerical results are validated by high-speed photography experiment. The turbulence viscosity of the renormalization group (RNG) k-ε turbulence model is used to provide a flow field for the cavitation model. Furthermore, this model is modified using a filter-based density correction model (FBDCM). The characteristics of the convergent-divergent cavitation nozzle are investigated in detail using the current CFD simulation method. It is found that shear stress plays an important role in the cavitation formation in the high-pressure submerged jet. In the result predicted by the Zwart-Gerber-Belamri (ZGB) cavitation model, where critical static pressure is used for the threshold of cavitation inception, the cavitation bubble on... [more]
Fault Ride-Through Capability Enhancement of Type-4 WECS in Offshore Wind Farm via Nonlinear Adaptive Control of VSC-HVDC
Yiyan Sang, Bo Yang, Hongchun Shu, Na An, Fang Zeng, Tao Yu
November 5, 2019 (v1)
Keywords: fault ride-through, nonlinear adaptive control, VSC-HVDC system, wind energy conversion system
This paper proposes a perturbation estimation-based nonlinear adaptive control (NAC) for a voltage-source converter-based high voltage direct current (VSC-HVDC) system which is applied to interconnect offshore large-scale wind farms to the onshore main grid in order to enhance the fault ride-through (FRT) capability of Type-4 wind energy conversion systems (WECS). The VSC-HVDC power transmission system is regraded as a favourable solution for interconnecting offshore wind farms. To improve the FRT capability of offshore power plants, a de-loading strategy is investigated with novel advanced control of the VSC-HVDC systems. The proposed NAC does not require an accurate and precise model and full state measurements since the combinatorial effects of nonlinearities, system parameter uncertainties, and external disturbances are aggregated into a perturbation term, which are estimated by a high-gain perturbation observer (HGPO) and fully compensated for. As the proposed NAC is adaptive to s... [more]
Digitalizing the Paints and Coatings Development Process
Tomaž Kern, Eva Krhač, Marjan Senegačnik, Benjamin Urh
November 5, 2019 (v1)
Keywords: coatings industry, development process, digitalization, process analysis, process simulation, technical enabler
Numerous laboratory tests are used to determine the appropriateness of new formulations in the development process in the paint and coatings industry. New formulations are most often functionally inadequate, unacceptable for environmental or health reasons, or too expensive. Formulators are obliged to repeat laboratory tests until one of the formulations fulfills the minimum requirements. This is cumbersome, slow, and expensive, and can cause ecological problems, wasting materials on tests that do not produce the desired results. The purpose of this research was to find out if there might be a better way forward to increase efficiency and free up formulators to focus on new products. In this experiment, a new paints and coatings development process was redesigned based on the potential benefits of formulation digitalization. Instead of laboratory testing, a digital platform was used that has been developed and stocked with relevant, up-to-date, and complete, usable data. This study fou... [more]
Adsorption of NO Gas Molecules on Monolayer Arsenene Doped with Al, B, S and Si: A First-Principles Study
Keliang Wang, Jing Li, Yu Huang, Minglei Lian, Dingmei Chen
November 5, 2019 (v1)
Subject: Materials
Keywords: arsenene, doping, first principles study, gas adsorption, two-dimensional
The structures and electronic properties of monolayer arsenene doped with Al, B, S and Si have been investigated based on first-principles calculation. The dopants have great influences on the properties of the monolayer arsenene. The electronic properties of the substrate are effectively tuned by substitutional doping. After doping, NO adsorbed on four kinds of substrates were investigated. The results demonstrate that NO exhibits a chemisorption character on Al-, B- and Si-doped arsenene while a physisorption character on S-doped arsenene with moderate adsorption energy. Due to the adsorption of NO, the band structures of the four systems have great changes. It reduces the energy gap of Al- and B-doped arsenene and opens the energy gap of S- and Si-doped arsenene. The large charge depletion between the NO molecule and the dopant demonstrates that there is a strong hybridization of orbitals at the surface of the doped substrate because of the formation of a covalent bond, except for S... [more]
Digital Twin for Monitoring of Industrial Multi-Effect Evaporation
Rafael M. Soares, Maurício M. Câmara, Thiago Feital, José Carlos Pinto
November 5, 2019 (v1)
Keywords: digital twin, dynamic model, evaporation modeling, monitoring, multi-effect evaporation, softsensor, sugar industry
Digital twins are rigorous mathematical models that can be used to represent the operation of real systems. This connection allows for deeper understanding of the actual states of the analyzed system through estimation of variables that are difficult to measure otherwise. In this context, the present manuscript describes the successful implementation of a digital twin to represent a four-stage multi-effect evaporation train from an industrial sugar-cane processing unit. Particularly, the complex phenomenological effects, including the coupling between thermodynamic and fluid dynamic effects, and the low level of instrumentation in the plant constitute major challenges for adequate process operation. For this reason, dynamic mass and energy balances were developed, implemented and validated with actual industrial data, in order to provide process information for decision-making in real time. For example, the digital twin was able to indicate failure of process sensors and to provide est... [more]
Recovering Cobalt and Sulfur in Low Grade Cobalt-Bearing V−Ti Magnetite Tailings Using Flotation Process
Junhui Xiao, Yushu Zhang
November 5, 2019 (v1)
Subject: Materials
Keywords: cobalt, cobalt pyrite, flotation, linneite, pyrite, V–Ti magnetite tailings
There is 0.032% cobalt and 0.56% sulfur in the cobalt-bearing V−Ti tailings in the Panxi Region, with the metal sulfide minerals mainly including FeS2, Fe1−xS, Co3S4, and (Fe,Co)S2, and the gangue minerals mainly including aluminosilicate minerals. The flotation process was used to recover cobalt and sulfur in the cobalt-bearing V−Ti tailings. The results showed that an optimized cobalt−sulfur concentrate with a cobalt grade of 2.08%, sulfur content of 36.12%, sulfur recovery of 85.79%, and cobalt recovery and 84.77% were obtained by flotation process of one roughing, three sweeping, and three cleaning under roughing conditions, which employed pulp pH of 8, grinding fineness of <0.074 mm occupying 80%, flotation concentration of 30%, and dosages of butyl xanthate, copper sulfate, and pine oil of 100 g/t, 30 g/t, and 20 g/t, respectively. Optimized one sweeping, two sweeping, and three sweeping conditions used a pulp pH of 9, and dosages of butyl xanthate, copper sulfate, and pine oi... [more]
Application of Transformation Matrices to the Solution of Population Balance Equations
Vasyl Skorych, Nilima Das, Maksym Dosta, Jitendra Kumar, Stefan Heinrich
November 5, 2019 (v1)
Keywords: agglomeration, dynamic flowsheet simulation, milling, multidimensional distributed parameters, population balance equation, process modelling, solids, transformation matrix
The development of algorithms and methods for modelling flowsheets in the field of granular materials has a number of challenges. The difficulties are mainly related to the inhomogeneity of solid materials, requiring a description of granular materials using distributed parameters. To overcome some of these problems, an approach with transformation matrices can be used. This allows one to quantitatively describe the material transitions between different classes in a multidimensional distributed set of parameters, making it possible to properly handle dependent distributions. This contribution proposes a new method for formulating transformation matrices using population balance equations (PBE) for agglomeration and milling processes. The finite volume method for spatial discretization and the second-order Runge−Kutta method were used to obtain the complete discretized form of the PBE and to calculate the transformation matrices. The proposed method was implemented in the flowsheet mod... [more]
Effects of Bromelain and Trypsin Hydrolysis on the Phytochemical Content, Antioxidant Activity, and Antibacterial Activity of Roasted Butterfly Pea Seeds
Kah-Yaw Ee, Li-Ying Khoo, Wen-Jie Ng, Fai-Chu Wong, Tsun-Thai Chai
November 5, 2019 (v1)
Subject: Biosystems
Keywords: antibacterial activity, antioxidant activity, enzymatic hydrolysis, phenolic compounds, roasted butterfly pea
Butterfly pea (Clitoria ternatea L.) is a traditional medicinal and edible herb, whose health-promoting benefits have been attributed to its phenolic constituents. In this study, the effects of enzymatic hydrolysis on total phenolic content (TPC) and total flavonoid content (TFC), antioxidant (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)) and antibacterial activities of raw and roasted (200 °C, 10−20 min) butterfly pea seeds were investigated. Roasting reduced the yield of seed aqueous extracts, but it increased the TPC and FRAP values, hence the reducing ability, of the extracts. Bromelain hydrolysis enhanced the TPC and TFC of the roasted seeds up to 2- and 18-fold higher, respectively. Trypsin hydrolysis drastically increased the TPC, but not TFC, of roasted seeds; trypsin-hydrolyzed, 20 min roasted sample had the highest TPC (54.07 μg gallic acid equivalent (GAE)/mg... [more]
Slow Mode-Based Control Method for Multi-Point Temperature Control System
Song Xu, Seiji Hashimoto, Wei Jiang, Yuqi Jiang, Katsutoshi Izaki, Takeshi Kihara, Ryota Ikeda
November 5, 2019 (v1)
Keywords: multi-input multi-output (MIMO) temperature system, slow-mode-based control, temperature differences, transient response
In recent years, thermal processing systems with integrated temperature control have been increasingly needed to achieve high quality and high performance. In this paper, responding to the growing demands for proper transient response and to provide more accurate temperature controls, a novel slow-mode-based control (SMBC) method is proposed for multi-point temperature control systems. In the proposed method, the temperature differences and the transient response of all points can be controlled and improved by making the output of the fast modes follow that of the slow mode. Both simulations and experiments were carried out, and the results were compared to conventional control methods in order to verify the effectiveness of the proposed method.
Study on Interfacial Surface in Modified Spray Tower
Marek Ochowiak, Sylwia Włodarczak, Ivan Pavlenko, Daniel Janecki, Andżelika Krupińska, Małgorzata Markowska
November 5, 2019 (v1)
Keywords: confusor, interfacial surface, modified spray tower, Sauter mean diameter
This paper presents an analysis of the changes in interfacial surface and the size of droplets formed in a spray tower. The interfacial surface and the size of droplets formed are of fundamental importance to the performance of the equipment, both in terms of pressure drop and process efficiency. Liquid film and droplet sizes were measured using a microphotography technique. The confusors studied were classical, with profiled inside surface, and with double profiled inside surface. The liquids studied were water and aqueous solutions of high-molecular polyacrylamide (PAA) of power-law characteristics. The ranges of process Reynolds number studied were as follows: ReG ∈ (42,700; 113,000), ReL ∈ (170; 15,200). A dimensionless correlation for reduced Sauter mean diameter is proposed.
Impact of Ornamental Vegetation Type and Different Substrate Layers on Pollutant Removal in Constructed Wetland Mesocosms Treating Rural Community Wastewater
Sergio Zamora, Luis Sandoval, J. Luis Marín-Muñíz, Gregorio Fernández-Lambert, M. Graciela Hernández-Orduña
November 5, 2019 (v1)
Subject: Biosystems
Keywords: constructed wetlands, ornamental vegetation, phytoremediation, water cleaning
Improving water quality is a relevant environmental aspect, and using constructed wetlands (CWs) is a sustainable option for this; both porous material filled cells and plants that collectively remove contaminants must be readily available and inexpensive. This study evaluated CWs and their functionality by comparing two ornamental plants (Spathiphyllum wallisii and Hedychium coronarium) planted in experimental mesocosm units filled with layers of porous river rock, tepezil, and soil, or in mesocosms with layers of porous river rock, and tepezil, without the presence of soil. The findings during the experiments (180 days), showed that the removal of pollutants (chemical oxygen demand (COD), total solids suspended (TSS), nitrogen as ammonium (N-NH4), as nitrate (N-NO3), and phosphate (P-PO4) was 20−50% higher in mesocosms with vegetation that in the absence of this, and those mesocosms with the soil layer between 33−45% favored removal of P-PO4. Differences regarding of vegetation remov... [more]
A Wind Farm Active Power Dispatch Strategy Considering the Wind Turbine Power-Tracking Characteristic via Model Predictive Control
Wei Li, Dean Kong, Qiang Xu, Xiaoyu Wang, Xiang Zhao, Yongji Li, Hongzhi Han, Wei Wang, Zhenyu Chen
November 5, 2019 (v1)
Keywords: automatic generation control, frequency-domain analysis, Model Predictive Control, power-tracking characteristic, wind farm
In this paper, an industrial application-oriented wind farm automatic generation control strategy is proposed to stabilize the wind farm power output under power limitation conditions. A wind farm with 20 units that are connected beneath four transmission lines is the selected control object. First, the power-tracking dynamic characteristic of wind turbines is modeled as a first-order inertial model. Based on the wind farm topology, the wind turbines are grouped into four clusters to fully use the clusters’ smoothing effect. A method for frequency-domain aggregation and approximation is used to obtain the clusters’ power-tracking equivalent model. From the reported analysis, a model predictive control strategy is proposed in this paper to optimize the rapidity and stability of the power-tracking performance. In this method, the power set-point for the wind farm is dispatched to the clusters. Then, the active power control is distributed from the cluster to the wind turbines using the c... [more]
Production Planning to Reduce Production Cost and Formaldehyde Emission in Furniture Production Process Using Medium-Density Fiberboard
Taeho Kim
November 5, 2019 (v1)
Keywords: formaldehyde emission, furniture production process, medium density fiberboard, production cost, two-dimensional bin packing/cutting stock problem
This research seeks to improve the production process in the Korean furniture industry by reducing the amount of medium-density fibreboard, that is commonly used to produce furniture, in order to reduce production costs and formaldehyde emissions. This research selects a representative company from the Korean furniture industry to examine its optimal amount of medium-density fibreboard used, using the variables of a previous company; the sale levels, the Korea National Productivity Award Index, and technical efficiencies obtained from a previous study. By using its 2016 production level, we compare it with the amount of medium-density fibreboards actually used in 2016, and apply the results to the entire Korean furniture industry. In conclusion, the Korean furniture industry can minimize the amount of medium-density fibreboards used without reducing current production levels, and thereby save production costs, and contribute to substantially reducing formaldehyde emissions.
Towards Quality by Design to recover high-quality products from waste and wastewater streams
Céline Vaneeckhaute
November 2, 2019 (v1)
Subject: Optimization
Keywords: Mathematical modelling, Optimization, Process control, Product quality, Quality by Design, Resource Recovery
Recovering nutrients from wastewaters and wastes, such as sewage sludge and food waste, as sustainable bio-based products provides a key solution to major environmental problems. Classical technology development approaches for resource recovery largely ignore the real-world variability in raw waste materials, which currently hinders the successful implementation of recovery strategies. A major challenge is to create a consistent, sustainable and environmentally friendly supply of high-quality end-products that can compete with fossil-derived products currently on the market. There is urgent need for a paradigm shift from classical technology development approaches to sustainable integrated end-user focused strategies, supported by a reliable, competitive and repeatable quality assurance framework. An improved balance between efficiency and cost in bio-based production chains is needed, while continuously assuring product quality and safety. This
presentation suggests the use of a qual... [more]
Numerical Simulation of Effects of Different Operational Parameters on the Carbon Solution Loss Ratio of Coke inside Blast Furnace
Mingyin Kou, Heng Zhou, Li Pang Wang, Zhibin Hong, Shun Yao, Haifa Xu, Shengli Wu
October 26, 2019 (v1)
Keywords: blast furnace, carbon solution loss, coke, numerical simulation
Carbon solution loss reaction of coke gasification is one of the most important reasons for coke deterioration and degradation in a blast furnace. It also affects the permeability of gas and fluids, as well as stable working conditions. In this paper, a three dimensional model is established based on the operational parameters of blast furnace B in Bayi Steel. The model is then used to calculate the effects of oxygen enrichment, coke oven gas injection, and steel scrap charging on the carbon solution loss ratio of coke in the blast furnace. Results show that the carbon solution loss ratio of coke gasification for blast furnace B is almost 20% since the results of a model are probably only indicative. The oxygen enrichment and the addition of steel scrap can reduce the carbon solution loss ratio with little effect on the working condition. However, coke oven gas injection increases the carbon solution loss ratio. Therefore, coke oven gas should not be injected into the blast furnace unl... [more]
Modeling and Simulation of Crystallization of Metal−Organic Frameworks
Anish V. Dighe, Roshan Y. Nemade, Meenesh R. Singh
October 26, 2019 (v1)
Keywords: mechanism of MOF synthesis, modeling and simulation of MOF synthesis, population balance modeling
Metal−organic frameworks (MOFs) are the porous, crystalline structures made of metal−ligands and organic linkers that have applications in gas storage, gas separation, and catalysis. Several experimental and computational tools have been developed over the past decade to investigate the performance of MOFs for such applications. However, the experimental synthesis of MOFs is still empirical and requires trial and error to produce desired structures, which is due to a limited understanding of the mechanism and factors affecting the crystallization of MOFs. Here, we show for the first time a comprehensive kinetic model coupled with population balance model to elucidate the mechanism of MOF synthesis and to estimate size distribution of MOFs growing in a solution of metal−ligand and organic linker. The oligomerization reactions involving metal−ligand and organic linker produce secondary building units (SBUs), which then aggregate slowly to yield MOFs. The formation of secondary building u... [more]
Mathematical Modeling and Simulation on the Stimulation Interactions in Coalbed Methane Thermal Recovery
Teng Teng, Yingheng Wang, Xiang He, Pengfei Chen
October 26, 2019 (v1)
Keywords: coalbed methane thermal recovery, heat-gas-coal model, modeling and simulation, thermal stimulation interaction
Heat stimulation of coalbed methane (CBM) reservoirs has remarkable promotion to gas desorption that enhances gas recovery. However, coalbed deformation, methane delivery and heat transport interplay each other during the stimulation process. This paper experimentally validated the evolutions of gas sorption and coal permeability under variable temperature. Then, a completely coupled heat-gas-coal model was theoretically developed and applied to a computational simulation of CBM thermal recovery based on a finite element approach of COMSOL with MATLAB. Modeling and simulation results show that: Although different heat-gas-coal interactions have different effects on CBM recovery, thermal stimulation of coalbed can promote methane production effectively. However, CBM thermal recovery needs a forerunner heating time before the apparent enhancement of production. The modeling and simulation results may improve the current cognitions of CBM thermal recovery.
High Pressure Injection of Chemicals in a Gravel Beach
Xiaolong Geng, Ali Abdollahi-Nasab, Chunjiang An, Zhi Chen, Kenneth Lee, Michel C. Boufadel
October 26, 2019 (v1)
Subject: Other
Keywords: bioremediation, Exxon Valdez oil spill, high pressure injection, tidal beach, tracer study
The remediation of beaches contaminated with oil includes the application of surfactants and/or the application of amendments to enhance oil biodegradation (i.e., bioremediation). This study focused on evaluating the practicability of the high pressure injection (HPI) of dissolved chemicals into the subsurface of a lentic Alaskan beach subjected to a 5 m tidal range. A conservative tracer, lithium, in a lithium bromide (LiBr) solution, was injected into the beach at 1.0 m depth near the mid-tide line. The flow rate was varied between 1.0 and 1.5 L/min, and the resulting injection pressure varied between 3 m and 6 m of water. The concentration of the injected tracer was measured from four surrounding monitoring wells at multiple depths. The HPI associated with a flow rate of 1.5 L/min resulted in a Darcy flux in the cross-shore direction at 1.15 × 10−5 m/s compared to that of 7.5 × 10−6 m/s under normal conditions. The HPI, thus, enhanced the hydraulic conveyance of the beach. The resul... [more]
Computational Fluid Dynamics Simulation of Gas−Solid Hydrodynamics in a Bubbling Fluidized-Bed Reactor: Effects of Air Distributor, Viscous and Drag Models
Ramin Khezri, Wan Azlina Wan Ab Karim Ghani, Salman Masoudi Soltani, Dayang Radiah Awang Biak, Robiah Yunus, Kiman Silas, Muhammad Shahbaz, Shiva Rezaei Motlagh
October 26, 2019 (v1)
Keywords: Computational Fluid Dynamics, fluidized bed, gasification, hydrodynamics, multiphase flow
In this work, we employed a computational fluid dynamics (CFD)-based model with a Eulerian multiphase approach to simulate the fluidization hydrodynamics in biomass gasification processes. Air was used as the gasifying/fluidizing agent and entered the gasifier at the bottom which subsequently fluidized the solid particles inside the reactor column. The momentum exchange related to the gas-phase was simulated by considering various viscous models (i.e., laminar and turbulence models of the re-normalisation group (RNG), k-ε and k-ω). The pressure drop gradient obtained by employing each viscous model was plotted for different superficial velocities and compared with the experimental data for validation. The turbulent model of RNG k-Ɛ was found to best represent the actual process. We also studied the effect of air distributor plates with different pore diameters (2, 3 and 5 mm) on the momentum of the fluidizing fluid. The plate with 3-mm pores showed larger turbulent viscosities above th... [more]
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