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CO2 methanation is a promising technology to store renewable energy by converting carbon dioxide with green hydrogen into methane, which is known as power to gas (PtG). In this study, CO2 methanation performance of a Ni/Al2O3 catalyst was investigated in a bubbling fluidized bed (BFB) and the axial gas concentration, temperature, and CO2 conversion were densely analyzed. Moreover, a modified reaction kinetic model was proposed, and the results were compared with experimental data. The bed temperature increased by 11 °C from 340 °C to 351 °C within the first 30 mm of the fluidized bed. The CO2 conversion was approximately 90% within 50 mm from the bottom of the reactor and was maintained above this height. The Ni/Al2O3 catalyst exhibited the highest CO2 conversion (95%) at 320 °C. Using a simple plug-flow reactor model, three optimized kinetic modification factors (1.5094, 0.0238, and 0.2466) were used to fit the experimental data. The hydrodynamic effects significantly influenced the chemical reaction kinetics of the BFB.

A multiphase computational fluid dynamics (CFD) model coupled with the population balance equation (PBE) was developed in a homogeneous air–kerosene bubble column under elevated pressure (P). The specific pressure drop (ΔP/L), gas holdup (αG), and Sauter mean diameter (d32) were experimentally measured in the bubble column with 1.8 m height and 0.1 m inner diameter, which was operated at a superficial gas velocity of 12.3 mm·s−1, and P = 1–35 bar (1 bar = 105 Pa). A modified drag coefficient model was proposed to consider the effect of bubble swarm and pressure on hydrodynamics of the bubble column. The Luo breakage model was modified to account for liquid density, viscosity, surface tension and gas density. The ΔP/L, αG, and d32 obtained from the CFD model were compared with experimental data, and the gas density-dependent parameters of the CFD model were identified. With increasing P from 1 to 35 bar, the αG varied from 5.4% to 7.2% and the d32 decreased from 2.3 to 1.5 mm. The CFD-PBE model is applicable to predict hydrodynamics of pressurized bubble columns for gas–organic liquid in the homogeneous regime.

This study aims to investigate hydrodynamic and heat transfer characteristics of a BFB reactor with immersed heat exchange tubes for CO2 methanation using a two-dimensional (2D) gas-solid Eulerian computational fluid dynamics (CFD) model. A reaction kinetics model for Ni-based catalyst was coupled with the CFD model. The 2D-CFD model with the Huilin and Gidaspow drag was validated with experimental data for the bed expansion of Geldart B particles according to gas velocity. It was demonstrated that the heat of reaction was effectively removed in the BFB reactor with a 25% heat exchange area and that the reactor maintained isotherm conditions. The CO2 conversion was 92% in the BFB reactor at 400 °C and 5 bar. The overall heat transfer coefficient from the bed to the heat exchange tubes was estimated at 114 W/m2/K for an inlet gas velocity of 0.13 m/s.

The bubble breakage rate in gas-liquid bubble columns increases for organic liquid and at high pressure. This study developed a breakage model that accounts for different liquid properties in gas-liquid pressurized bubble columns in the homogeneous regime. The Luo (1996), Lehr (2002), and Wang (2003) breakage models, which are widely used for the population balance equation (PBE) of bubble columns, were compared in terms of the total breakage rate, daughter size distribution, and computational time. The model with two empirical equations, modified from Luo’s breakage kernel, was proposed. One represented bubble deformation behavior in different liquid properties in terms of buoyancy, surface tension, and viscosity. The other considered the effect of operating pressure (or gas density) on the breakage rate. The modified model was compared with experimental data and a rigorous breakage model from the literature. The proposed breakage model shows good agreement with experimental data and computational efficiency. This breakage model is applicable for computational fluid dynamics with PBE in pressurized bubble columns with organic liquids.

An 8.5-Gb/s/pin (Gb/s) 12-Gb LPDDR5 SDRAM is implemented in a second-generation 10-nm DRAM process with a hybrid-bank architecture that provides a power-optimized bank solution depending on the bank modes (4B/4BG, 16B-merged bank, 8B-split bank). Based on the specified bank modes, vertical and horizontal skew-cancel schemes for high density and an RBUS-based DBI ac to minimize data transition are newly proposed. Thus, the switching power of RBUS DBI ac is saved by 8.9% compared to that of DBI ac “OFF.” To improve the rank interleaving efficiency with a current increase, partially enabled WCK (PE-WCK) mode is proposed, which minimizes the number of enabled circuits for maintaining the WCK2CK synchronization. Therefore, the current can be saved by 62% without a timing constraint compared to the WCK always-ON mode. To achieve high-speed operation beyond 6.4 Gb/s, speed-boosting techniques, namely, the two-step duty corrector, active resonant load (ARL), and one-tap decision feedback equalizer (DFE) with offset calibration, are newly adopted. In the coarse step in the two-step duty corrector, the value of the duty error decreases to below 5% by suppressing the dc signal. In the fine step, the remaining duty error is further reduced within 2.5 ps by the duty cycle monitor (DCM) and duty cycle adjustor (DCA). Moreover, the skew increase beyond 6.4 Gb/s due to the bandwidth limit by the heavy loading of four-phase WCK signals is alleviated by the ARL, where the four-phase skew is within 5 ps irrespective of process, voltage, and temperature (PVT) variations. The direct feedback DFE enables fast feedback (< 118 ps) for tap coefficient control, and offset calibration reduces the three-sigma offset of the four dynamic latches in DQ within 5 mV.

The economic feasibility of a bio heavy-oil (BHO) production process from 100 t/d sewage sludge (SS) using super- and sub-critical water was evaluated. The process included a super- or sub-critical reaction, BHO recovery via a condenser and centrifuge, BHO purification via extraction, phase separation and filtration, hydrotreating desulfurization, and wastewater treatment. For techno-economic analysis (TEA), two cases were considered: BHO production with supercritical (Case 1) and subcritical (Case 2) water. The four-level economic potential approach was used for the TEA. The minimum fuel selling price (MFSP) of the BHO plants was approximately 0.91 $/L, which was higher than the actual selling price of 0.55 $/L. Case 2 showed higher economic values than Case 1 owing to the lower capital and production costs. When the SS treatment credit is > 120 $/t or the BHO price is higher than the MFSP, the BHO plant with subcritical water (Case 2) is profitable. This study shows economic potentials for the SS hydrothermal liquefaction process with an upgrading unit.

The solvothermal liquefaction of sewage sludge (SS) has received much attention as an ecofriendly method of liquid fuel production. In this study, we evaluated the economic feasibility of bio-heavy-oil (BHO) production from 100 t/d SS using supercritical ethanol (scEtOH) and methanol (scMeOH). The process included a dryer, supercritical reactor, BHO separator, steam boiler, wastewater treatment unit and storages. Two cases for the techno-economic analysis (TEA) were considered: BHO production with scEtOH (Case 1) and with scMeOH (Case 2). The four-level economic potential approach (4-level EP) was used for the TEA. The total capital investments of Cases 1 and 2 were 19.6 and 19.5 million dollars, respectively. Case 2 showed higher economic potential than Case 1 because of the low price of methanol. The BHO plant using scMeOH was economically feasible with a return on investment of 21%/a.

A three-dimensional computational fluid dynamics (CFD) model with new permeability and off-gas emission equations was developed in a four-zone low-temperature furnace (LTF) for carbon fiber carbonization. Four performance criteria (residence time, dead-volume ratio, tow temperature standard deviation, and tar formation area) were proposed to identify the optimal ratio between the two N2 flow rates introduced into the front and rear of LTF. A higher N2 flow rate at the front rather than at the rear was preferred to reduce tar formation. The tar formation area calculated from carbon activity provides useful guideline for determining optimal LTF design and operating conditions.

A three-dimensional (3D) computational fluid dynamics (CFD) model of an annulus steam methane reforming (SMR) reactor was developed for producing 2.5 Nm3/h of H2 from natural gas. The feed and combustion gases played a role in a counter-current heat exchange owing to a narrow sleeve equipped between the combustor and catalytic reactor. The momentum, energy, and mass conservation equations were integrated with a realizable k–e turbulence model, discrete ordinates radiation model, and reversible SMR reaction kinetics. The CFD results such as axial temperature profiles and producer gas compositions were validated against the experimental data measured in this study. The thermal efficiency of the compact SMR reactor was 60%, and the heat flux through the reactor wall was 39 kW/m2. The overall heat transfer coefficient from the sleeve to the catalytic reactor was 158 W/m2/K. The sleeve-type SMR reactor flattened the temperature profile along the reactor length.

A three-dimensional (3D) multiphase Eulerian computational fluid dynamics (CFD) model was developed to investigate the effect of a simultaneous three-angular motion (roll, yaw and pitch) on the performance of an air-water-oil separator. The dynamic mesh method with a 3D rotational matrix was used to simulate the three-phase separator under simultaneous three-angular motion. The pressures at water and oil outlets were adjusted by a user-defined function based on a proportional control algorithm. The CFD model was validated against experimental free oscillations of an immiscible two-fluid system under a pitching motion. The simultaneous three-angular motion with an amplitude 2° and a period of 8 s showed an oil purity of 98% and an oil recovery of 99%, which were comparable to those of the onshore separator. However, the 4° simultaneous three-angular motion deteriorated the oil recovery to 92% and the water purity to 75%. As the separation performance of the pitching motion was similar to that of the simultaneous three-angular motion, the performance of the three-phase separator can be tested simply by the pitching motion.

This review covers the scope of multiscale computational fluid dynamics (CFD), laying the framework for studying hydrodynamics with and without chemical reactions in single and multiple phases regarded as continuum fluids. The molecular, coarse-grained particle, and meso-scale dynamics at the individual scale are excluded in this review. Scoping single-scale Eulerian CFD approaches, the necessity of multiscale CFD is highlighted. First, the Eulerian CFD theory, including the governing and turbulence equations, is described for single and multiple phases. The Reynolds-averaged Navier–Stokes (RANS)-based turbulence model such as the standard k-ε equation is briefly presented, which is commonly used for industrial flow conditions. Following the general CFD theories based on the first-principle laws, a multiscale CFD strategy interacting between micro- and macroscale domains is introduced. Next, the applications of single-scale CFD are presented for chemical and biological processes such as gas distributors, combustors, gas storage tanks, bioreactors, fuel cells, random- and structured-packing columns, gas-liquid bubble columns, and gas-solid and gas-liquid-solid fluidized beds. Several multiscale simulations coupled with Eulerian CFD are reported, focusing on the coupling strategy between two scales. Finally, challenges to multiscale CFD simulations are discussed. The need for experimental validation of CFD results is also presented to lay the groundwork for digital twins supported by CFD. This review culminates in conclusions and perspectives of multiscale CFD.

A three-phase transient Eulerian computational fluid dynamics (CFD) model was developed to investigate the effect of three angular motions (rolling, yawing, and pitching) on the separation efficiency of an air–water–oil separator. The horizontal cylindrical separator included a feed inlet, a gravity separation zone with a coalescer for water and oil separation, and a mist elimination zone. The CFD model consisted of the continuity, momentum, and standard k-e turbulence equations. The CFD equations were solved in a moving reference frame to take into account the angular motions. The exit pressures at the water and oil outlets were controlled using a user-defined function since the CFD model without pressure control resulted in backflow from the water outlet, which was not realistic. CFD cases, such as no motion, rolling, yawing, 2° pitching, and 4° pitching with a period of 8 s were simulated with exit pressure control. The angular motions with pressure control showed a stable cyclic behavior with a high oil separation efficiency. However, the 4° pitching motion decreased the oil recovery to 93% with 77% water purity at the water outlet.

A multi-scale simulation approach was proposed to predict the degree of impregnation (DoI) in thermoplastic unidirectional carbon fiber prepreg (UD-CFP). The multi-scale approach included a two-dimensional (2D) micro-scale computational fluid dynamics (CFD) in a representative elementary volume (REV) of carbon fiber (CF) tow, a 3D macro-scale CFD of an entire impregnation die with 15 sliding CF tows, and a process-scale simulation assembling data from the micro- and macro-scale CFDs. In the macro-scale steady-state CFD, thermoplastic resin injection and CF tow insertion were considered for an impregnation die 10 cm in width. In the micro-scale transient CFD, impregnation mechanisms of resin into CF filaments 7 μm in diameter were identified in terms of surface coverage, capillary permeation, and penetration through CF filaments. The DoI as a function of pressure and time was obtained from the micro-scale CFD within a range of pressures found in the macro-scale CFD. In the process-scale simulation, the cumulative DoI of the 15 tows was predicted along the impregnation die length with the aid of the micro- and macro-scale CFD results. Combining the multi-scale models gives a potential to predict the uniformity of the transverse resin amount in the final UD-CFP product.

A total of 10 t/d of bio-solid (BS) fuel was produced from 45 t/d of organic solid waste (OSW) containing 80 wt% water using a fry-drying and torrefaction (FDT) plant. This study aimed at evaluating economic feasibility of the FDT plant in terms of the total capital investment (TCI), total production cost (TPC), return on investment (ROI) and payback period (PBP). Two different heating sources for steam generation were used: Case 1 using BS produced in this plant, and Case 2 using LNG provided externally. A four-level economic potential approach was applied to evaluate economic feasibility. A sensitivity analysis was conducted to determine the major factors influencing ROI. Case 1 using BS showed a higher ROI than Case 2 using LNG because the LNG cost overwhelmed the TCI increment of Case 1. For Case 1 with 45 t/d of OSW, the TCI, TPC, ROI and PBP were $3.6 million, $1.3 million/yr, 6.0%/yr and 9.8 yr, respectively. To achieve a desired ROI of 10%/yr, the plant sizes of Cases 1 and 2 were 60 and 90 t/d, respectively. When the OSW treatment credit increased from 100 $/t to 120 $/t, ROI exceeded 10% in Case 1 with 45 t/d.

A modeling and simulation were conducted to study the slurry phase hydrocracking of vacuum residue in a bench-scale slurry bubble column reactor (SBCR). The reactor model was based on axial dispersion, and the intrinsic kinetic information was reported in continuous stir tank reactor (CSTR) using the same feedstock in our previous study. The model was validated over a wide range of operating conditions using experimental data from the bench scale unit. The reactor model predicted product yields, sulfur and asphaltenes content with an average error of less than 10%. The bench-scale SBCR demonstrated better hydrocracking (HCK) and hydrotreating (HDT) performance compared to CSTR, mainly due to the mixing behavior in the SBCR. A stability index of asphaltene was proposed from the data reported in our previous study to evaluate the operating conditions. Based on the simulation results, the optimal operating conditions for recycle operating mode were suggested using the simultaneous optimization variables technique.

In this study, we develop physics-informed neural networks (PINNs) to solve an isothermal fixed-bed (IFB) model for catalytic CO2 methanation. The PINN includes a feed-forward artificial neural network (FF-ANN) and physics-informed constraints, such as governing equations, boundary conditions, and reaction kinetics. The most effective PINN structure consists of 5–7 hidden layers, 256 neurons per layer, and a hyperbolic tangent (tanh) activation function. The forward PINN model solves the plug-flow reactor model of the IFB, whereas the inverse PINN model reveals an unknown effectiveness factor involved in the reaction kinetics. The forward PINN shows excellent extrapolation performance with an accuracy of 88.1% when concentrations outside the training domain are predicted using only one-sixth of the entire domain. The inverse PINN model identifies an unknown effectiveness factor with an error of 0.3%, even for a small number of observation datasets (e.g., 20 sets). These results suggest that forward and inverse PINNs can be used in the solution and system identification of fixed-bed models with chemical reaction kinetics.

An incompressible gas phase three dimensional (3D) computational fluid dynamics (CFD) model with turbulence and radiation was developed to investigate hydrodynamics of a low temperature furnace (LTF) for polyacrylonitrile (PAN)-based fiber carbonization. Thirty PAN-fiber tows moving at a constant linear speed emitted off-gas and their porosity increased during carbonization. The CFD model included off-gas mass flow rates of eight species with respect to temperature, which were treated as a source term from the tows. Velocity, temperature, and concentration profiles along the furnace length were examined according to three duct positions (e.g., front, middle and rear sides of LTF). The off-gas residence time, dead-zone (or stagnant gas region) ratio, and temperature uniformity were used as performance criteria of LTF. An optimal duct position was determined on the front side of LTF considering the three performance criteria.

The effect of the center of gravity (CoG) position on the CO 2 removal efficiency was investigated for a pilot-scale amine absorber with Mellapak 250.X (M250X) structured packing subject to the pitching motion (i.e., 12 s period and 1.57° amplitude). A porous medium Eulerian computational fluid dynamics (CFD) model with porous resistance, drag force between gas and liquid, and dispersion force was used to represent the hydrodynamic properties of M250X. Three CoG positions, namely, bottom of the column (Case 1), vertically under the column (Case 2), and diagonally under the column (Case 3), were considered for two different diameters of the absorber. Case 3 showed the biggest liquid maldistribution because of a long distance between the amine absorber and CoG position. The CO 2 removal efficiency was lowest in Case 3 for the absorber having the larger column diameter. However, the difference between the CO 2 removal efficiencies of Cases 2 and 3 was not substantial.

A commercial fry-drying and torrefaction (FDT) plant for producing bio-solid fuel from 45 ton/d organic sludge with 80% water was proposed. The FDT plant was modeled by a process simulator with the aid of plant data. Two double-effect evaporators were used in series to vaporize water, using heat-carrying oil. Torrefied and pelletized bio-solid was produced at 413 kg/h, comprising 4.4 and 4.8% of water and oil, respectively, and 67% of its mass was used as heat source. The total energy consumption was 1,369 kW, including 93 kW electrical and 1,276 kW thermal energies. The total heat duty was 788 kcal/kg-water.

Energy efficiency in mobile devices is a pivotal criteria from the overall system point of view, Although the 7,5Gb/s 8Gb LPDDR5 [1], with low-power schemes (internal data copy, dynamic-voltage-frequency scaling (DVFS), and a deep-sleep mode (DSM)), achieves improved energy efficiency compared to the previous LPDDR4X [2], the market demands for higher density and speed gradually increase for high-end applications including hand-held artificial intelligence (AI) and advanced driver assistance system (ADAS), To achieve higher density and speed in a power-efficient manner, this paper proposes a 8,5Gb/s 12Gb LPDDR5 with a hybrid bank architecture (split/merged bank), a skew-tolerant scheme, bus-based ROBI AC, and speed-boosting techniques based on 2nd generation 10nm DRAM process, Adopting a hybrid bank architecture and skew-tolerant scheme enables high speed and power-optimization for each bank-mode in high density memories, Moreover, bus-based RDBI AC achieves 2,1 % current gain and command-based WCK control scheme achieves 36mA saving at WCK-always-on mode, The speed-boosting techniques (duty-cycle correction (DCC), an active-resonant load, and at-tap DFE receiver) provide improved operating speeds from 7,5Gb/s to 8,5Gb/s@VDD2H = 1, 05V, where the read/write DQ valid windows are 0,60UI and 0.64UI (1UI = 118ps).

In this work, a three-dimensional volume-of-fluid computational fluid dynamics (VOF-CFD) model was developed for a coagulation bath of the dry-jet wet spinning (DJWS) process for the production of polyacrylonitrile (PAN)-based carbon fiber under long-term operating conditions. The PAN-fiber was assumed to be a deformable porous zone with variations in moving speed, porosity, and permeability. The Froude number, interpreted as the wave-making resistance on the liquid surface, was analyzed according to the PAN-fiber wind-up speed ( v P A N ). The effect of the PAN speed on the reflection and wake flow formed by drag between a moving object and fluid is presented. A method for tracking the wave amplitude with time is proposed based on the iso-surface of the liquid volume fraction of 0.95. The wave signal for 30 min was divided into the initial and resonance states that were distinguished at 8 min. The maximum wave amplitude was less than 0.5 mm around the PAN-fiber inlet nozzle for v P A N = 0.1&ndash, 0.5 m/s in the resonance state. The VOF-CFD model is useful in determining the maximum v P A N under an allowable air gap of the DJWS process.

This study experimentally and numerically investigated the hydrodynamics, reaction kinetics, and heat transfer of a bench-scale bubbling fluidized bed (BFB) reactor for CO2 methanation. A three-dimensional gas–solid Eulerian computational fluid dynamics (CFD) model coupled with a modified Syamlal–O’Brien drag model and reaction kinetics for Ni-based catalysts was developed. The CFD model was validated against experimental data for pressure, temperature, and gas composition at 1 bar and an inlet flow rate of 2 L/min with an inlet N2 content of 77.5%. The axial pressure drop, solid volume fraction, temperature, gas composition, and bed-to-wall heat transfer coefficient (HTC) were compared for four inlet N2 contents: 77.5%, 50%, 25%, and 0%. As the inlet N2 content decreased, the mean bed temperature increased from 340 to 456 °C, the gas volume decreased owing to the reaction, the fluidizing number (ug/umf) decreased from 4.1 to 3.5, and the solid holdup increased. Consequently, the HTC increased from 327 to 386 W/m2/K. This study identified successfully the effects of hydrodynamics and reaction kinetics on HTC in the BFB for CO2 methanation.

Empty fruit bunches (EFB) of oil-palm are one of the most recent renewable energy resources. The objective of this study is to find the most economically-feasible pathway among three energy conversions from 400 t/d wet EFB, which are bioethanol and jet fuel by bioconversion, combined heat and power via gasification, and hydrocarbons through fast pyrolysis and biooil upgrading. A hierarchical four-level economic potential approach (4-level EP) was employed to perform the preliminary techno-economic analysis (TEA) for the three pathways. The 4-level EP includes the input/output structure, the flowsheet structure, the heat integration (HI), and the economic feasibility. The economic potential of the three plants was compared at each level, and the most promising process among them was identified at Level 4, where economic criteria including return on investment (ROI), payback period (PBP), and internal rate of return (IRR) were evaluated. It was found that the biooil hydrocarbon plant is most economical due to the highest economic potential, ROI, and IRR. The heat consumption was reduced considerably by HI in the bioethanol and jet fuel plant. The sensitivity analysis informed that the plant size, the product yield, and the total capital investment highly influenced ROI and PBP in all three processes.

A kinetic model for the slurry-phase hydrocracking of vacuum residue was proposed under conditions of: 410–450 °C, 0.25–1 hr−1, 160 bar, 1500 Nm3/m3 of H2 to oil ratio, and 500 ppm catalyst (Mo-octoate). A five-lump model with ten reaction pathways was adopted to describe the hydrocracking kinetics, while the hydrotreating reactions were modeled by the power-law approach. The kinetic parameters were estimated considering the change in liquid density with reaction time. The kinetic model predicted product yields and concentrations with an average error of less than 10%. As for the hydrocracking reaction, it was demonstrated that the secondary cracking of VGO mainly produced MD at high temperature and the high conversion of RES. As for hydrotreating, it was confirmed that asphaltene conversion proceeded to increase the removal level of other impurities. Finally, a hydrogen consumption rate model was proposed based on HCK and HDT, which provides consistent information for further uses in reactor modeling and process modeling.

The performances of three catalytic reactors for CO2 methanation, i.e., single fixed-bed (1FxB), two-stage fixed-bed (2FxB), and bubbling fluidized-bed (BFB), were evaluated at a feed flow rate of 166.5 Nm3/h. A heterogeneous catalytic reaction model (HCRM) combining the one-dimensional plug-flow model on the reactor scale and the reaction–diffusion model on the particle scale was used for 1FxB and 2FxB. A two-phase reaction model (TPRM), including the mass transfer between the bubble and emulsion phases and axial dispersion, was proposed for the BFB. The results from HCRM and TPRM were in good agreement with experimental and modeling data. The 1FxB, 2FxB, and BFB were optimized via the parametric study considering the hot spot temperature, operating temperature and pressure, space velocity, flue gas recirculation ratio, and operational stability. The catalyst weights of 1FxB, 2FxB, and BFB required for a 90% CO2 conversion were 191, 40, and 34 kg, respectively. The proposed models were able to identify the flow behaviors, mass transfer, and reaction kinetics of the fixed- and fluidized-beds, which are useful for the optimal design of CO2 methanation reactors.

Bubble characteristics of air-kerosene system and air-water system in a pressurized bubble column were analyzed. Experiments were carried out at system pressure up to 3.5 MPa on a cylindrical stainless column with an inner diameter of 0.097 m and a height of 1.8 m. Kerosene and tap water were used as liquids while air was used as gas. Bubble characteristics were observed by varying gas velocity up to 98 × 10−3 m/s at 0.1 MPa and up to 31.1 × 10−3 m/s at 3.5 MPa. Bubble chord length and bubble rising velocity were measured with a single tip probe installed at the top of the distributor at 0.5 m. In addition, pressure difference between the top and bottom of the column was measured with a differential pressure transducer to confirm gas holdup. In the air-kerosene system, gas holdup tended to increase with increasing system pressure. From the analysis of drift flux, transition from homogeneous to heterogeneous flow regime was observed only under atmospheric pressure. In the air-kerosene system, drift flux tended to be kept constant as gas holdup increased under pressurized conditions. The system pressure was varied from 0.1 MPa to 3.5 MPa to confirm micro-bubble generation under pressurized conditions. Dynamic gas disengagement (DGD) analysis and image analysis at the same time showed that gas holdup fraction of micro-bubbles was almost constant (em/eg = 0.4) at atmospheric pressure. However, it was increased from 0.48 at gas velocity of 12.3 × 10−3 m/s to 0.57 with gas velocity of 32.1 × 10−3 m/s at 3.5 MPa.

The adoption of oxy-combustion in a circulating fluidized bed (CFB) producing ultra-supercritical (USC) steam has been investigated to increase energy efficiency and reduce CO2 emissions of coal-fired power plants. This paper presents a techno-economic analysis for 500 MWe USC-CFB power plants with air- and oxy-combustion in the presence of CO2 capture. An amine absorber unit (AAU) and a CO2 processing unit (CPU) were used to capture CO2 in the air- and oxy-combustion power plants, respectively. The air-combustion power plant without CO2 capture (Case 1) showed the highest net electricity efficiency (46%), whereas the introduction of an AAU in the air-combustion power plant (Case 2) reduced the net efficiency to 36%. The net efficiency (39%) of the oxy-combustion power plant with CPU (Case 3) was higher than that of Case 2 owing to the recycling of hot flue gas. The levelized cost of electricity (LCOE) of Case 3 (59 $/MWh) was lower than that of Case 2 (64 $/MWh), which demonstrated that oxy-combustion was advantageous compared to air-combustion in a scenario with CO2 capture. The sensitivity analyses of the electricity price and CO2 credit showed economic situations where Cases 2 and 3 would be profitable.

This article presents a preliminary result on deciding whether to use simulated moving-bed (SMB) technology in a conventional petrochemical complex (cPCC) to increase olefins and aromatics production. A process model including an SMB unit, naphtha hydro-treating (NHT), naphtha thermal cracking (NTC), and naphtha catalytic reforming (NCR) was constructed to evaluate the economic feasibility of the retrofit petrochemical complex (rPCC) with the SMB unit for 2500 kt/yr naphtha treatment. The chemical reaction kinetics of NTC and NCR were used to estimate the increase of olefins and aromatics production. The incremental total capital investment for the SMB and additional NHT areas, estimated by the factorial method, was 97.5 $M. The incremental total production cost concerning utility and fixed costs was 25 $M/yr. It was found that the rPCC has economic benefits, because the return on investment (ROI) after tax, payback period (PBP), and internal rate of return (IRR) are 18%, 3.7 yr, and 20%, respectively. The SMB recovery of n-paraffins was most influenced on ROI and IRR in sensitivity analysis.