Fluidized Bed Technology Research Articles

Heat Treatment of AZ91 Magnesium Alloy Coated with an Al₂O₃ Thin Film with Fluidized Bed Technology.

Fluidized bed technology is a methodology widely known in the manufacturing environment for surface treatment of metals. Within the field of surface coating, it has already been exploited for the coating of a magnesium alloy creating a compact layer of Al2O3. The result was an improvement in mechanical and tribological properties, along with improved corrosion resistance. In this context, the work proposed is addressed towards the evaluation of the effects of thermal post-treatment on the alumina coating produced by means of the fluidized-bed technology. To analyse the effects of heat treatments the morphology, composition and hardness of the samples were investigated along with adhesion and wear resistance of the alumina film. The results obtained show how the temperature affects the surface morphology and promotes the diffusion of magnesium towards the alumina superficial layer. The mechanisms triggered by heat treatments increase the adhesion of the surface film obtained in the deposition process, improving its mechanical and tribological properties.

Influence of Dissolution Vessel Geometry and Dissolution Medium on In Vitro Dissolution Behaviour of Triamterene-Coated Model Stents in Different Test Setups.

The aim of this study was to investigate if the geometry of the dissolution vessel, the dissolution medium volume and composition might contribute to the variation in drug release from drug-eluting stents (DES) in different test setups, which has been observed in previous in vitro studies. Therefore, DES containing triamterene as model substance were produced via fluidised-bed technology. Dissolution testing was carried out using different incubation setups, the reciprocating holder (USP Apparatus 7) and two flow-through methods, a method similar to the USP Apparatus 4 (FTC) and the vessel-simulating flow-through cell (vFTC) equipped with a hydrogel as a second compartment simulating the blood vessel wall. The results indicate that dissolution vessel geometry and medium volume had no influence on the release behaviour and only the flow-through cell methods yielded a lower dissolution rate than the incubation setups (80.6 ± 2.0% released in the FTC after 14days compared to > 90% for all incubation setups). The composition of the hydrogel used in the vFTC also affected the dissolution rate (53.9 ± 4.5% within 14days with a hydrogel based on phosphate-buffered saline compared to 78.2 ± 1.2% obtained with a hydrogel based on water) possibly due to different solubility of triamterene in the release media as well as interactions between the coating polymer and the release medium. Hence, the introduction of a hydrogel as a second compartment might lead to a more biorelevant test setup.

A TECHNO-ECONOMIC FEASIBILITY ANALYSIS OF THE GASIFICATION OF USED TIRES FOR ENERGY GENERATION IN TURKEY

A techno-economic feasibility analysis for a 5 MWe scrap tire granules gasification facility is presented. Electricity generation is based on gas engines with the option of waste heat recovery. Based on our previous work, it is demonstrated that the best thermochemical option for waste tire disposal and energetic valorization is gasification using a mixture of preheated air and steam as the gasification agent. Also based on our previous work, the best gasification technology is shown to be the circulating fluidized bed technology. The study shows that under the regulatory and financial conditions prevalent in Turkey, the project is both technically and economically feasible.

Performance enhancement of all-solid CO2 absorbent based on Na2CO3-promoted MgO by using ZrO2 dispersant

MgO is a promising base material for CO2 absorbents to be used at elevated temperatures of 200–500 °C. To develop a CO2 capture process utilizing the fluidized bed technology, in which the absorbents are required to be mechanically robust, alkali carbonates are considered as the promoter for MgO. However, alkali carbonate-promoted MgO absorbents have the problems of low capacity and poor cycling characteristics. In the present study, we sought the solutions of these problems of alkali carbonate-promoted MgO absorbents by using a solid dispersing medium. We investigated the effect of using a large surface area tetragonal ZrO2 derived from ZrO(OH)2⋅xH2O as the dispersing medium of Na2CO3-promoted MgO absorbent on its CO2 absorption properties. The tetragonal phase of ZrO2 was formed through doping Mg and/or Na in the course of sample preparation. The presence of ZrO2 increases MgO conversion by 50%, conversion rates by 350%, and durability in repeated absorption and desorption cycles by 20%. The analysis data on the samples in various stages of CO2 absorption and desorption show that the ZrO2 dispersant induces a more homogeneous distribution of the active components and keep them from segregating from each other. The same principles work well with other promoters such as K2CO3.

Gas-solid flow behaviors in a multi-stage circulating fluidized bed under elevated pressure

Pressurized circulating fluidized bed technology is promising in coal & biomass combustion and gasification. To get more detail information of pressure effects on gas-solids flow behaviors in a circulating fluidized bed reactor, we built a novel pressurized multi-stage circulating fluidized bed (MCFB) reactor a cold pilot setup with 14.5 m height. The experiment was carried out at the elevated pressure up to 0.9 MPa with the use of polystyrene particles (ρs = 1020 kg/m3, dp = 400 μm). We used differential pressure transducers to collect the pressure data and monitor the operating condition. Local solids holdup was measured by the optical fiber probes. Our results showed that the apparent solids holdup presented multi-flow regimes in the axial direction of MCFB. Under the same solids circulation rate and superficial gas velocity, the apparent solids holdup and local solids holdup decreased, and the axial flow structure and radial profiles of solids holdup became more uniform with increasing the pressure. When the fluidized gas mass flow rate and the solids circulation rate were kept the same, the solids holdup at axial and radial directions increased with the pressure. The speed of gas-solids flow development was different at various pressures with a slower speed at high pressure under the same solids circulation rate and superficial gas velocity. As a result, the elevated pressure significantly influences the gas-solids flow behaviors and provides better riser performance with good gas-solids contacting and mixing by the uniform radial and axial distributions than the atmospheric pressure at the same superficial gas velocity.

Numerical simulations on Oxy-MILD combustion of pulverized coal in an industrial boiler

The purpose of this study is to analyze the possibility of combining two innovative combustion technologies in large-scale pulverized coal fired plants: Moderate or Intense Low Oxygen Dilution (MILD) and oxy-combustion. The combination of both technologies, namely Oxy-MILD combustion, is expected to bring synergetic effects: NOx reduction, CO2 capture possibility, fuel flexibility and uniformity of heat fluxes and species concentrations. In this work, the predictable advantages of adopting this technology, with respect to conventional boilers, are evaluated by means of CFD modeling, in terms of pollutant emissions and uniformity of heat fluxes. In a previous work, the developed CFD model was validated against available experimental data of MILD combustion in a pilot-scale furnace and it was demonstrated that the proposed model captures the combustion features with good accuracy. In order to identify the effective potential of Oxy-MILD combustion and its possible uses on an industrial scale, an application in the boiler is analyzed in the current work. Results show that the temperature and species concentration distributions reach an acceptable level of uniformity in the boiler; similarly, the wall heat flux profile is uniform along the boiler height, as in the fluidized bed technology. The CO2 concentration at the boiler exit, for an excess oxygen ratio of 1.1, is about 95.8%; this value is slightly increased for lower excess oxygen ratio, even though in this case, incomplete combustion occurs. Finally, lower NOx (70 mg/MJ) than other technological solutions are obtained owing to the prevention of thermal and prompt NOx, owing to the absence of N2 in the oxidizer, and to the re-burning mechanism, which is predominant especially when recycled NOx is considered.

Oxinitrocarburizing in Fluidized Bed Technology Applied to Drawing Steels

Oxinitrocarburizing in Fluidized Bed Technology Applied to Drawing Steels

CHARACTERIZATION OF AN EXPERIMENTAL FACILITY FOR BUBBLING FLUIDIZED BED COMBUSTOR

Fluidized bed technology offers an attractive way for energy production with clean environment by the combustion of even low-grade waste derived fuels (WDF). This paper reports experimental results concerning the characterization of a small-scale bubbling atmospheric fluidized bed combustor with WDF batch feeding. The combustor having 0.215 m inner diameter and 1.88 m height is equipped with a packed-bed sandwich-type fluidizing air distributor. The experimental fluidized bed combustor (EFBC) is provided with facility items necessary for the operation, control, and measurements. Results of the measured fluidized bed pressure drop and temperature were investigated for cold flow, hot flow, and combustion tests during the characterization procedure. The results of these tests clearly indicated the good fluidization characteristics inherent to well-controlled operation of the EFBC facility. The characterization tests also indicated the reproducible and safe operation characteristics of the EFBC facility without appreciable leakage of fluidizing air and exhaust gases. Moreover, the obtained uniformity of the fluidized bed temperature together with the high estimated values of bed-to-immersed cooling coil heat transfer coefficient, added more evidence on the good combustion characteristics of the investigated EFBC facility.

Application of the Technology of Combustion of Solid Fuels in a Circulating Fluidized Bed

It is shown that the basic variations in the energy market are related to increasing requirements designed to assure ecological cleanliness as well as increase efficiency, reliability, and maneuverability. The ability of the technology underlying the combustion of solid fuels in a circulating fluidized bed to respond to these variations is demonstrated using concrete examples. It is noted that the efficiency of the circulating fluidized bed technology is determined basically by the quality of the fuel and the capacity of the power station with specified constraints imposed on discharges of harmful substances. Attainment not only of the norms on harmful substances existing in the Russian Federation, but also of prospective norms without the use of desulfurization and denitrogenization devices, is an important condition for optimal use of the technology. Another major advantage is the diversification of fuel deliveries. The first boiler in Russia employing a circulating fluidized bed was built at Unit No. 9 of a condenser type electricity-only thermal power station (GRES) at Novocherkassk, Rostov oblast’. Delivery of the boiler was performed by the firm of JSC EMAl’yans Inzhiniring while delivery of certain critical parts and auxiliary equipment, by the firm of Amec Foster Wheeler (now Sumitomo Foster Wheeler, or SFW). The first results of the operation of a circulating fluidized bed boiler are presented and an analysis of trial data on the thermal balance of the heating surfaces is presented. In the case of similar values of the trial and design heat absorption of the boiler guard screens, the temperature of the gases in the boiler is substantially higher than the design temperatures. Certain difficulties associated with the technology of combustion are identified in the process of adjustment and early use of the circulating fluidized bed boiler in Unit No. 9 of the Novocherkassk GRES. The need for a more detailed study of the processes involved in production of additional measurements and of studies on operational development of the equipment and thermal circuit, and optimization of the operating conditions is demonstrated.

Two-phase heat transfer model of a beam-down gas-solid fluidized bed solar particle receiver

Beam-down concentrating solar power for thermochemical and energy absorption applications stands as an attractive approach that can enhance the renewable energies deployment. This work explores the integration of beam-down optics with fluidized bed technology proposing a model to calculate both gas and bed temperatures. The beam-down system concentrates the energy from the solar field into a fluidized bed receiver. A novel phenomenological model is proposed to adapt the well-known two-phase theory to the heat transfer process of a bed operating in the bubbling regime while it is directly irradiated from the top. In this way, this simple model can be used as a design tool for beam-down fluidized bed receivers. The top bed surface is considered as an opaque diffuse layer formed by gray particles. A single layer model is applied to estimate the effective emissivity between the heterogeneous bed surface and the ambient conditions in the freeboard. The vertical temperature profile is obtained considering particle phase heat conduction, particle to gas heat convection, solid convection, bubble convection and radiation heat transfer mechanisms. The model is validated using silicon carbide and zirconia fluidized bed experiments reported in the literature. The model shows that the solid convection is the dominant heat transfer mechanism for a beam-down fluidized bed receiver. Further results explore the influence of the operating conditions on the fluidized bed receiver for a bed of silicon carbide particles, showing that energy concentration fluxes of 35 · 104 W/m2 can reach bed temperatures of 1000 °C when operating at a gas velocities of 3·Umf.

Application of Bioaugmentation Technology in Cold-Rolling Emulsion Wastewater Treatment and Analysis of Microbial Community

Cold-rolling emulsion wastewater (CREW) is characterized by high oil content, complex organic components and certain toxicity. By traditional physical and chemical methods, it could not be completely degraded at low cost. In order to optimize treatment process of CREW, a highly effective strain (Pseudomonas fluorescens) was isolated and combined with bioaugmentation technology, biofilm and fluidized bed technology to treat CREW. After 78 days of the system operation, the removal rate of COD and oil reached 94% and 97%. COD and oil content of the effluent were stably below 70mg/L and 4.7mg/L, which met the first order of the national discharge standard (GB8978-1996). The result of high throughput 16SrRNA sequencing showed there were 23 genera of bacteria in the biofilm community of the reactor. This microbial community structure could effectively degrade COD and oil in CREW. At phylum level, γ-proteobacteria, Firmicutes and β-proteobacteria widely existed in carrier and were the main members of pollutant degradation.

ON THE MONITORING OF THE GAS-SOLID FLOWS IN INDUSTRIAL FLUIDIZED BEDS BY USING ELECTRICAL CHARGE SENSORS

The fluidized bed technology has been used in many industrial processes. It promotes good rates of heat, mass transfer and chemical reaction by generating high level of gas-solid mixture. However, the assurance of quality and efficiency of these processes requires the monitoring of the gas-solid flow. For this propose, there are some sensing techniques that allows generating dynamic signals from cold or hot fluidized beds. They are based on pressure fluctuations, acoustic and mechanical vibrations, electrical capacitance and on electrical charges. Electrical charge sensors were proposed originally for measuring the flow velocity in pneumatic conveying. They are composed of one or more metallic electrodes that detect electrical charges in the gas-solid flow, which are generated by particle-particle and particle-wall interaction due to triboelectric effect. In this work, such sensors are explored as a robust and inexpensive solution for the monitoring of industrial fluidized beds. However, since research investments are requested specially on the design of the sensor, concerning the flow quantity of interest and the electrification processes acting on the sensor, in this work different configurations were classified from information in literature, and other were proposed in this work concerning their use with industrial fluidized beds. Although the relation between magnitude of the detected charges and some physical quantities of the flow, such as concentration, is still not clear, other important information can be obtained by analyzing dynamic signals, as velocity or bubbles frequency, or even for identifying of the fluidization regime. It was stated that each configuration, with its own shape and arrangement, can promote or not one or other electrification process by contact, friction or induction and, therefore, each one has a different perception of the flow.

Exploring novel hydrogen production processes by integration of steam methane reforming with chemical-looping combustion (CLC-SMR) and oxygen carrier aided combustion (OCAC-SMR)

This article discusses the concept of combining steam methane reforming (SMR) with fluidized beds of oxygen carrier particles and presents results from process simulations in Aspen Plus of new process outlines with and without carbon capture. Conventionally, heat to steam reforming tubes is provided by gas-fired burners, which transfer heat to the tube’s surface mainly by radiation. An alternative approach to provide heat to the endothermic SMR reaction is to use fluidized bed technology, utilizing oxygen carrier particles as bed material. Two novel configurations of the steam reforming process are proposed. The first concept incorporates SMR with a single bubbling fluidized bed reactor of oxygen carrier particles, or Oxygen Carrier Aided Combustion (OCAC). The second combines Chemical Looping Combustion (CLC) with an external fluidized bed heat exchanger (FBHE) used for SMR. Here, biomass is used as supplementary fuel in the furnace. The results for the OCAC-based system show that the cold gas efficiency can be increased compared to a reference case describing a conventional process, and at the same time decrease CO2 emissions by 4%. The biomass-fuelled CLC configuration displays surprisingly large negative CO2 emissions, corresponding to a CO2 emission reduction by 151% compared to the reference case.

High-grade activated carbon from pyrolytic biochar of Jatropha and Karanja oil seed cakes—Indian biodiesel industry wastes

Most of the commercially available pyrolysis plants use fluidized bed technologies where bio-oil is the major product and the biochar produced is combusted for process heat. However, auger-based technologies are now gaining importance because of their small to medium scale of operation and decentralized nature where biochar is obtained as a by-product. One of the factors which may greatly influence the techno-economic viability of such decentralized plants is making high-grade carbon from pyrolytic biochar. In the present study, Jatropha and Karanja oil seed cake-based biochar is obtained as a by-product in a pilot-scale (20 kg/h) direct gas-fired auger pyrolysis process at 500 °C under fast pyrolysis conditions that is originally aimed at maximizing the bio-oil yield. The biochar has low surface area and porosity. To value add to this carbon, downstream physical and chemical activation are carried out in an externally heated laboratory-scale reactor. CO2 activation resulted in the formation of activated carbon with BET surface area up to ~ 200 m2/g with marginal improvement in porosity, while K2CO3 activation enhanced the surface area to as high as 2400 m2/g along with substantial enhancement of porosity.

Development of cryptotanshinone-loaded pellets for angina chronotherapy: In vitro/in vivo prediction and evaluation

The clinical manifestations of variant angina is unevenly distributed during the 24 h, thus the in vivo performance of drugs should be tailored according to the angina circadian rhythm. Cryptotanshinone (CTN) is one of the representative bioactive lipid-soluble components of Danshen which has been commonly used for cardiovascular diseases such as angina pectoris. The aim of this study was to develop a novel CTN sustained-released pellets (CTN-SRPs) to precisely synchronize the CTN plasma concentrations with predicted occurrence of angina pectoris for angina chronotherapy. A deconvolution-based method was applied to develop and optimize the CTN-SRPs. The plasma concentration-time curve of CTN immediate-released formulation after oral administration in rats was used as the weight function. The predicted plasma concentration-time curve of CTN-SRPs simulated according to the incidence of variant angina during 24 h was used as the response function. Then the desired drug release profile of CTN-SRPs was calculated based on deconvolution using weight function and response function, and subsequently used for guiding the formulation optimization. CTN-SRPs were prepared with the combinations of PVP, poloxamer 127 and EC as matrix using fluidized bed technology. An orthogonal design was employed to obtain the optimal formulation with its release profile similar with the desired one. Pharmacokinetic studies validated that the actual plasma concentration-time curve of these optimized CTN-SRPs was similar with the predicted one. In addition, the percent errors (%PE) of CTN plasma concentrations in 8–12 h were less than 10%. In conclusion, this deconvolution-based method could be applied to adjust the in vivo performance of drugs for angina chronotherapy.

Evaluation of Shake-and-Catch Mechanism in Mechanical Harvesting of Apples

Abstract. Damaged fruit is the most important barrier to success in the mechanical harvesting of fresh market apples using mass harvesting methods. To address fruit quality issues and expedite the commercialization of mechanical harvesting of fresh market apples, an innovative air suspension-based catching (ASC) mechanism was designed and fabricated to collect fruit detached with a mechanical shaking device (tree limb shaker). The objective of this study was to evaluate the shake-and-catch mechanism in mechanical harvesting of apples. Three apple varieties with different physical characteristics (‘Honeycrisp’, ‘Pacific Rose’, and ‘Pink Lady’) were used in the field trials. The air pressure settings for the ASC mechanism played an important role in reducing the risk of apple damage and improving fruit quality. The effect of the shaking frequency of the tree limb shaker on fruit quality was not significant. When the air pressure increased from 0 to 1030 kPa, the fruit quality greatly improved. Keywords: Air pressure, Air suspension-based catching mechanism, Fluidized bed technology, Fresh market apples, Fruit quality, Mass harvesting, Shaking efficiency.

Developments in Fluidized Bed Technology

Fluidization of granular material is the process of converting static solid like state to dynamic fluid like state. A fluidized bed technology generally uses nanoparticles for better heat transfer rate. Fluidized beds have variety of applications in manufacturing and process industries. Because of effectiveness of fluidized bed, their applications are increases day by day. In recent years, researchers suggested many techniques to improve the fluidization of the variety of nanoparticles. This article review developments and advancements done in fluidized bed technology. Extensive review is done on the basis of performance characteristics of fluidized bed, nanoparticle properties for fluidization, agglomerates issue, heat transfer characteristics and external assisted mediums to enhance output from fluidized bed.

Investigation of a novel & integrated simulation model for hydrogen production from lignocellulosic biomass

Process simulation and modeling works are very important to determine novel design and operation conditions. In this study; hydrogen production from synthesis gas obtained by gasification of lignocellulosic biomass is investigated. The main motivation of this work is to understand how biomass is converted to hydrogen rich synthesis gas and its environmentally friendly impact. Hydrogen market development in several energy production units such as fuel cells is another motivation to realize these kinds of activities. The initial results can help to contribute to the literature and widen our experience on utilization of the CO2 neutral biomass sources and gasification technology which can develop the design of hydrogen production processes. The raw syngas is obtained via staged gasification of biomass, using bubbling fluidized bed technology with secondary agents; then it is cleaned, its hydrocarbon content is reformed, CO content is shifted (WGS) and finally H2 content is separated by the PSA (Pressure Swing Adsorption) unit. According to the preliminary results of the ASPEN HYSYS conceptual process simulation model; the composition of hydrogen rich gas (0.62% H2O, 38.83% H2, 1.65% CO, 26.13% CO2, 0.08% CH4, and 32.69% N2) has been determined. The first simulation results show that the hydrogen purity of the product gas after PSA unit is 99.999% approximately. The mass lower heating value (LHVmass) of the product gas before PSA unit is expected to be about 4500 kJ/kg and the overall fuel processor efficiency has been calculated as ∼93%.

Importance of spinel reaction kinetics in packed-bed chemical looping combustion using a CuO/Al2O3 oxygen carrier

Chemical looping combustion is especially competitive for electrical power generation with integrated CO2 capture when it is operated at high temperatures (1000–1200 °C) and high pressures (15 bar or higher). For these demanding conditions, dynamically operated packed bed reactors have been proposed, providing a good alternative to fluidized bed technology. This work addresses the importance of including the formation and reduction kinetics of spinel compounds to proper predict the packed bed reactor performance by validating a pseudo-homogeneous packed-bed reactor model to describe the redox kinetics of a CuO/Al2O3 oxygen carrier with experiments in a lab-scale packed bed reactor setup. A grain model describing the reaction kinetics of all solid species, including both spinel compounds (CuAl2O4 and CuAlO2), was included in a particle model and used to develop correlations for the effectiveness factor as a function of the particle conversion in order to account for internal solids concentration profiles and mass transfer limitations. The particle effectiveness factors were subsequently included in the source terms of the component mass balances of the reactor model accounting for all the reactions of the spinel compounds. Cyclic experiments (oxidation with air and reduction with a H2-N2 mixture) have been carried out in a lab-scale packed bed reactor with a 12.5 wt% CuO/Al2O3 oxygen carrier at different temperatures ranging from 600 to 1000 °C. The experimental results are well described by the packed bed reactor model, only when including the developed particle effectiveness factors to fully account for the kinetics of the formation and reduction of the spinel compounds. The results confirm that it is neccesary to include a detailed description of the redox kinetics at the particle level to be able to accurately estimate the breakthrough time, cycle time, final amount of Cu present in the bed and the temperature rise in the reactor after reduction/oxidation reactions for packed-bed chemical looping combustion with a CuO/Al2O3 oxygen carrier.

Potential of Electricity Generation from Rice Husk-A Case Study of Rice Mill

Energy crisis is a major problem in Pakistan now a days, in order to overcome this energy crisis an alternate renewable source must be exploited. Biomass has become an alternate source of energy for developing countries, where the economy is dependent on agriculture and forestry. Rice husk (RH) that is being generated in the mill can be utilized efficiently through fluidized bed (FB) technology to meet the energy demand and increase the production capacity of the mill, this will results in cost savings, greenhouse gases reduction and environmentally sustainable supply of electricity. The purpose of this study is to access resource potential of RH generated in the rice mill and to carryout technical and economic evaluation of RH based 1 MW fluidized bed combustion (FBC) power plant. In order to quantify the RH generated in the mill data regarding the potential of RH was collected from mill personnel and from the literature. It is estimated that through the FBC power plant, annual electricity of 5360 MWh can be generated with RH fuel consumption of 6968 tons; cost of generating electricity through FBC is approximately Rs. 4/kWh. Hence it can be concluded that FBC technology is more economically feasible than conventional systems for the power generation