Viscosity and separation performance of a gas-solid separation fluidized beds

A theoretical model of viscosity in gas-solid separation fluidized beds is established according to the two-phase flow theory of fluidized beds. After comparing theoretical and measured values, the correlation coefficient between the two is as high as 0.99, showing that the model has good predictability for the viscosity of fluidized beds. Meanwhile, the viscosity and its influencing factors were studied using a Brookfield viscometer. The study shows that smaller medium particles (0.074–0.15?mm) can reduce the viscosity of fluidized beds, but they will aggravate the viscosity fluctuation at more than 5?wt% addition, which is unfavorable to the stability of fluidized beds. In addition, in the actual separation process, the external factors (such as moisture and coal powder content) also affect the viscosity of the fluidized beds. Increasing the moisture increases the viscosity of the fluidized bed, whereas coal dust has the opposite effect. In order to ensure the stability of the fluidized bed, the bed moisture content should be controlled below 1?wt%, while the content of coal powder should be limited below 5?wt%. Based on separation tests, reducing the viscosity will improve the separation performance of a fluidized bed at the proper fluidized gas velocity, with the lowest possible error E_p of 0.085.     

Important Parameters for the Manufacture of Slow-Release Matrix Pellets With an Aqueous Dispersion of Quaternary Poly(meth)acrylates in the Rotary Fluidized Bed

ABSTRACT

The manufacture of slow-release matrix pellets with an aqueous dispersion of quaternary poly(meth)acrylates was investigated in the rotary fluidized bed. By considering the moisture content of the fluidized bed to be the key process parameter, it was measured on-line throughout the whole manufacturing process. A specially designed sampling device opened new ways to apply NIR spectrometry in laboratory scale processes. It was shown that reproducibly improved pellet properties can be achieved by reproducing the moisture content of the (rotary) fluidized bed. Moisture plateaus proved to be a suitable way to optimize the sphericity of the pellets. Premoisturizing was found to be a very effective tool to achieve slow-release dissolution of the model drug theophylline.     

Important parameters for the manufacture of slow-release matrix pellets with an aqueous dispersion of quaternary poly(meth)acrylates in the rotary fluidized bed

The manufacture of slow-release matrix pellets with an aqueous dispersion of quaternary poly(meth)acrylates was investigated in the rotary fluidized bed. By considering the moisture content of the fluidized bed to be the key process parameter, it was measured on-line throughout the whole manufacturing process. A specially designed sampling device opened new ways to apply NIR spectrometry in laboratory scale processes. It was shown that reproducibly improved pellet properties can be achieved by reproducing the moisture content of the (rotary) fluidized bed. Moisture plateaus proved to be a suitable way to optimize the sphericity of the pellets. Premoisturizing was found to be a very effective tool to achieve slow-release dissolution of the model drug theophylline.     

Moisture distribution in granular material during drying in a fluidized bed

This paper gives the results of a determination of the moisture content gradient and an investigation of the moisture distribution in a granular material during drying in a fluidized bed.     

Studies on the effects of physical properties of feed samples on the performance of fluidized bed dryer

The physical properties of grains are analysed at different levels of moisture contents using a fluidized bed dryer. The performance of fluidized bed dryer measured in terms of its efficiency is determined by using different grains as feed samples in the present work. The effects of various system parameters on the moisture content of the samples in turn on the dryer performance are studied. Again, effects of moisture content on different properties of sample, namely, grain volume, surface area, sphericity, bulk density, true density and porosity are studied. These properties of feed sample which determine the flow characteristics of the sample in a fluidized bed dryer are found to affect the dryer efficiency, in turn, the drying quality. An attempt is made to correlate the performance of the dryer against these physical properties of the materials. Thus, the efficiencies of the dryer calculated through the developed correlation and as per the literature are compared with each other. The comparison results show good agreement, thereby implying that the proposed correlation can be used for estimating the dryer performance over a wide range of parameters. With this study, the dryer can be designed properly in a cost-efficient manner.     

Numerical analysis of the process of combustion and gasification of the polydisperse coke residue of high-ash coal under pressure in a fluidized bed

A numerical analysis of the process of “wet” gasification of high-ash coal under pressure in a low-temperature fluidized bed has been performed. The applicability of the previously developed computational model, algorithm, and program for the case under consideration has been noted. The presence of “hot spots” (short-time local heatings) at different points of the bed has been confirmed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 5, pp. 160–171, September–October, 2007.     

Manufacture of Slow-Release Matrix Granules by Wet Granulation with an Aqueous Dispersion of Quaternary Poly(meth)acrylates in the Fluidized Bed

ABSTRACT

Slow-release matrix granules were manufactured in the fluidized bed using an aqueous dispersion of quaternary poly(meth)acrylates (Eudragit® RS 30 D) as binder for granulation. A factorial design was carried out to investigate the influence of the following parameters, spraying rate, applied polymer amount, and inlet air temperature, on various granule properties. Prerequisites for a slow release of the model drug theophylline are high spraying rate, high amount of polymer, and low inlet air temperature. No considerable decrease of the drug release rate can be achieved without a subsequent curing of the dry granules. A clear correlation exists between the moisture content of the fluidized bed, indicated by the terminal moisture content (TMC), and the mean dissolution time for 80% of the drug (MDT₈₀).     

Numerical analysis of probability characteristics for temperature processes of fluidized-bed treatment of material

Probability characteristics of the duration of stay, temperature, and degree of burning for particles in a fluidized bed are investigated. An unknown-boundary problem is used as a model to calculate the process of limestone particle dissociation. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 6, pp. 924–929, November–December, 1997.     

Manufacture of slow-release matrix granules by wet granulation with an aqueous dispersion of quaternary poly(meth)acrylates in the fluidized bed

Slow-release matrix granules were manufactured in the fluidized bed using an aqueous dispersion of quaternary poly(meth)acrylates (Eudragit® RS 30 D) as binder for granulation. A factorial design was carried out to investigate the influence of the following parameters, spraying rate, applied polymer amount, and inlet air temperature, on various granule properties. Prerequisites for a slow release of the model drug theophylline are high spraying rate, high amount of polymer, and low inlet air temperature. No considerable decrease of the drug release rate can be achieved without a subsequent curing of the dry granules. A clear correlation exists between the moisture content of the fluidized bed, indicated by the terminal moisture content (TMC), and the mean dissolution time for 80% of the drug (MDT₈₀).     

Effects of rapid heating on aging characteristics of T6 tempered Al–Si–Mg alloys using a fluidized bed

Effects of rapid heat transfer using a fluidized bed on the heat-treating response of Al–Si–Mg alloys (both unmodified and Sr modified) were investigated. Heating rate in fluidized bed (FB) is an order of magnitude greater than in conventional air convective furnaces (CF). On aging using FB, it was observed that the nucleation rate of Mg₂Si particles was greater than in CF. Thermal analyses show an endothermic reaction during aging in CF. No such transformation was observed during aging in FB. The endothermic transformation could be due to the dissolution of GP zones or metastable phase(s). The total heat treatment time for T6 temper was reduced to less than 2 h using FB.     

Monitoring and control of coating and granulation processes in fluidized beds – A review

This review presents a compilation of works of the main techniques for monitoring and control fluidization regimes, particle size and moisture content during coating and granulation processes in the fluidized bed. The development of monitoring and control systems for coating and granulation of particles is highly desirable, not only to allow the operation in a stable bubbling fluidization regime, which intensifies heat and mass transfer, but also to ensure strict quality specifications for products, such as, uniform particle size distribution, low moisture content and good flowability. This paper focuses on the discussion of methods used and results obtained in studies on monitoring and control of granulation and coating process in the fluidized bed reported in the literature in the last decades. Pressure fluctuation signal analysis is widely discussed as a tool of regime monitoring. To monitor particle size, techniques such as, Near Infrared spectroscopy (NIR), Focused Beam Reflectance Measurements (FBRMs), among others are presented in detail. As for moisture content tracking, the methods are reviewed like acoustic signals, capacitance, microwave resonance and spectroscopy. It is evident that although these processes are highly complex, the techniques presented here have evolved mainly due to the efforts of several research groups, showing great potential for applications in industry, emphasizing the importance of this research field.     

Model of coal combustion in a fluidized bed and its experimental identification

The author has formulated a system of one-dimensional steady-state differential equations for the balance of oxidizer, fuel and energy in the diffusion approximation. The model of coal combustion in a fluidized bed is identified from the experimental data, and the unknown parameters of the model describing the rate of oxidation of fuel and the intensity of gas and fuel transfer in the bed are determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 6, pp. 913–918, June, 1991.     

Fast pyrolysis of an ensemble of biomass particles in a fluidized bed

A combined approach to the modeling of fast pyrolysis of biomass particles in a fluidized bed has been used. We used models of different levels: two models of pyrolysis of a single particle — with lumped and distributed parameters — and a model of pyrolysis of an ensemble of biomass particles based on the continuum equations for the gas blown through the bed and the equations of motion for individual particles. We have determined optimal (in terms of the biofuel yield) temperatures of the process for various particle sizes of wood biomass and various values of its moisture.     

Proportional control of moisture content of granules by adjusting inlet air temperature in fluidized bed granulation using near-infrared spectroscopy

For process control of fluidized bed granulation process, we investigated proportional (P) moisture content control via adjustment of inlet air temperature in proportion to the difference between measured and target moisture content of granules. Here, we first validated P moisture content control by comparison with bed temperature control. We then confirmed that P moisture content control is effective in maintaining the moisture content, and in minimizing the variance of the particle size of granules following granulation. Furthermore, we observed that when the target temperature was higher than the measured value of inlet air temperature the P moisture content control response was accelerated. In contrast, when the target temperature was less than the measured value of inlet air temperature (<50 °C) the response was delayed. In summary, P moisture content control has good scalability and can be introduced without changing granulation conditions in the development of orally administered pharmaceutical products.     

Relationship between moisture content and temperature of dispersed material in drying in a fluidized bed

Solution of the differential calorimetric equation of the heat balance of a fluidized bed leads to a relationship between the moisture content and the temperature of the dispersed material during the constant and falling drying rate periods.     

Drying of thermally-weak organic powder in a centrifugal fluidized bed

The drying characteristics of thermally-weak organic powders of [2,2-Azobisisobutyrinitrile(AIBN) and HN] were studied in a centrifugal fluidized bed, since any kind of heating and hot gas cannot be employed for the drying of thermally-weak organic powders to prevent from sensitive reaction or decomposition during being dried. It could be a solution to use highly amount of gas in the centrifugal field for the drying of thermally-weak organic powders, which could overcome the limitation of gas velocity for the more efficient drying. The effects of gas velocity, rotational speed of the bed, initial moisture content of the powder, and amount of powder loading on the drying characteristics were determined. The pressure drop in the bed displayed an almost constant value that had a plateau, with increasing gas velocity. The moisture content of the organic powder decreased with an increase in the gas velocity or rotational speed of the bed, however, its variation trend did not change considerably with a variation of feed loading or an initial moisture content within this experimental conditions. The variation of the drying rates with respect to the moisture content was almost linear in the falling rate period.     

Control of moisture content in capillary-porous materials by microwave methods

Based on a linear model of a moist capillary-porous material that is located in an electromagnetic microwave field, basic relations between the measured parameters and moisture content been obtained for amplitude and resonator methods. Calculated and experimental dependences of the attenuation of the microwave energy on moisture content and variants of application of moisture meters of the Microradar series are presented. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 1, pp. 22–26, January–February, 2007.     

Drying of granular materials in circulating fluidized beds

It is attempted in the present investigation to dry solid materials in the riser of circulating fluidized bed covering a wide range of operating parameters. The effects of initial moisture content, temperature and flow rate of the heating medium, and solid circulation rate on rate of drying, have been critically examined. It has been observed that the solids material used in the present investigation exhibits a falling rate period, and the rate of drying is influenced by the temperature and flow rate of the heating medium, solids circulation rate and solid initial moisture content.     

Simulation of co-gasification of coal and wood in a dual fluidized bed system

A comprehensive three-dimensional (3D) model based on multiphase particle-in-cell (MP-PIC) approach is developed to simulate the co-gasification process of coal and wood in a dual fluidized bed (DFB) system. The pyrolysis of coal and wood, formation and conversion of tar and gaseous pollutants, as well as gasification and combustion reactions are integrated with dense gas-solid flow and heat transfer. The pilot DFB system comprises a bubbling bed gasifier and a fast fluidized bed combustor connected by loop seals. The model correctly predicts profiles of pressure and temperature, the yield and components of the product gas. The gas composition distributions, allocations of particle mass, and solid residence time inside the reactors are explored. The effects of various fuel blend ratios and particle sizes on gasification performances are also investigated. The results show that increasing coal ratio accelerates the steam gasification due to higher char content, which results in the increment of H₂ and CO concentrations. The tar content in the product gas continues to decline, while the emissions of NH₃ and H₂S increase. The size variation of feedstock is not enough to dramatically affect product gas components. The tar content and product gas yield appear a slight upward trend with the smaller size. The variations of NH₃ and H₂S concentrations are consistent with those of bed temperature.     

Numerical simulation of processes of thermochemical transformation of single coal particles at elevated pressures

Mathematical models, algorithms, programs, and results of calculations of processes of thermochemical processing of single high-ash coal particles at elevated pressures corresponding to functioning conditions of installations with a circulating fluidized bed are considered. Scientific and Technical Center for Coal-Processing Electrical Technologies of the National Academy of Sciences and the Energy and Electrification Ministry of Ukraine, Kiev, Ukraine. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 6, pp. 1000–1005, November–December, 1996.