Partition coefficients are measured for five amino acids (aspartic acid, asparagine, methionine, cysteine and histidine) and two peptides (glycyl-glycine and hexa-glycine) in dextran + poly(ethylene glycol) + water aqueous two-phase system. The partition coefficients of the amino acids and peptides are correlated using the osmotic virial equation. The interaction coefficients contained in the equation can be calculated by hydrophilic group parameters. The partition coefficients of α-amylase calculated by the osmotic virial equation with the hydrophilic group parameters are in fairly good agreement with the experimental data, though a relatively large discrepancy is shown for β-amylase.
The construction of heat exchangers using diverging-converging tubes is discussed in this paper. The enhanced performance efficiency exhibited by such a construction is highlighted by comparing its performance against that of a conventional shell and tube heat exchanger as well as a double pipe heat exchanger fitted with longitudinal fins, under the same operating conditions. It has been observed that such a construction, being called variable area exchanger, exhibits attractive performance features for successful industrial adaptation.
The kinetics of steady dynamic wetting of a liquid replacing a gas saturated with the liquid vapor on smooth solid surface in horizontal capillary tubes is investigated theoretically and experimentally. An approximate analytical method for advancing the dynamic meniscus of the liquids is proposed, and the effects of liquid flow, equilibrium contact angle, and adsorbed layer thickness at the gas-solid interface are studied. The analytical results show that dynamic wetting depends on liquid flow near the contact line, and the effect of the liquid flow far from there is insignificant. Furthermore, it is found that the dynamic contact angle is a function of not only capillary number, but also equilibrium contact angle, and adsorbed layer thickness. Experiments were carried out on dynamic wetting of hexane, octane and butanol in polytetrafluoroethylene tubes. The experimental data of dynamic contact angle in the present and previous studies are in fairly good agreement with the theoretical predictions over wide ranges of capillary numbers and equilibrium contact angles.
Axial mixing of liquid in bubble columns with a counter-current flow is investigated experimentally. Experiments were conducted in vertical columns 0.07 m in diameter and 4.25 m in height, and 0.15 m in diameter and 2.7 m in height. Air and tap water were used as the gas and liquid phases, respectively. The axial dispersion coefficient of liquid increases with increasing gas and liquid velocities, and is discussed by comparing with models based on the turbulent mixing-length theory, which was developed by Matsumoto et al., and on the internal recirculating flow model extended by Wachi et al. in a concurrent bubble column.
In order to effectively utilize the bagasse waste generated by sugar factories, an attempt is made to produce activated carbon from it by steam activation and chemical activation (with zinc chloride). Upon carbonization at temperatures from 1073 K to 1273 K, bagasse generates char having a specific surface area of 405–600 m2/g and a pore volume of 0.2–0.3 ml/g. A sample of activated carbon was prepared from mechanically-mixed and compressed bagasse by activation at 1073 K for 1 hour with steam added in an amount of 3.0 g-water/g-bagasse. The resulting activated carbon is found to have a specific surface area of 878 m2/g and a hardness of 2.5 × 10–3 kg/cm2. In addition, it has an adsorption equilibrium for aqueous phenol and acetic acid which can be expressed by either a Langmuir type or Freundlich type isotherm.
Nano-CdS-polythiourethane (PTU) composite particles (CdS-PTU) are prepared via making nano-CdS in a reverse micellar system, followed by surface-modification with thiol molecules, and polymerization (polyaddition) of hexamethylene diisocyanate (HDI) and dithiols (xylene-α, α′-dithiol: XDT) or 4-hydroxythiophenol (HTP) in the presence of the surface-modified nano-CdS. The effects of thiols used as the surface-modification agent and polymerizing monomer (XDT or HTP) on stability of CdS-PTU for photo-irradiation during photocatalytic H2 generation from aqueous solution of 2-propanol are investigated. The composite containing nano-CdS more dispersed exhibits improved photocatalytic properties, which are found to have been effected by employing benzyl mercaptan as the surface-modification agent for nano-CdS, and HTP as the monomer.
The dynamic simulation method proposed by Lu and Hwang (1993) has been extended to determine the relationships of cake porosity and specific filtration resistance versus solid compressive pressure from constant rate filtration data. The simulated results for different compactness materials agreed very well with the corrected compression-permeability cell (C-P cell) test data and dynamic analysis results of constant pressure filtration. Using the results obtained from these dynamic analyses to predict the performance of filtration of various slurries, the results agreed very well with an average deviation of around 4%, while the corrected C-P cell test data result in an average deviation of approximately 5%.
Synergistic extraction system of lactic acid is examined to develop on in situ extractive fermentation process. The addition of tri-n-butyl phosphate (TBP) to the extraction system of lactic acid (HA) with tri-n-octylamine (TOA) diluted by hexane causes a large synergism. Extraction reaction with the mixed extractant is interpreted quite well based on the formation of mixed complex, HA·TOA·2TBP. Though the addition of hexane solution containing TBP and TOA to the culture of Lactobacillus rhamnosus results in low lactate production, some lactate is produced.
The use of solid sorbents to capture trace metals (e.g., Pb, Zn and Cd) in sewage sludge, generated from the wastewater treatment process of a Picture-Tube factory, during fluidized bed incineration was investigated experimentally in this study. All experiments were carried out in a 90 mm I.D. laboratory scale fluidized bed using various sorbents including limestone, alumina, silica sand and bentonite. The variations in operating conditions included incineration temperature, sorbent species, air flow rate and incineration time. The amounts of metals captured in the sorbents were measured using Atomic Absorption Spectrometry after acid digestion. The results indicate that bentonite is best for zinc capturing and alumina for lead capturing. The volume of sewage sludge can be reduced to at most 40% using fluidized bed incineration.
This paper describes an experimental study on the drying of wet granules in an agitation fluidized bed. Wet granules composed of lactose and cornstarch were dried in an agitation fluidized bed under various air temperatures, air velocities and agitator rotational speeds. The effects of the conditions on the properties of granules such as mass median diameter, yield, shape and density of the granules are investigated. The relationships between the operating conditions and the drying rates were also examined. It is found that mass median diameter decreases with decreasing air temperature and velocity, and with an increase in agitator rotational speed, while the apparent density, shape factor and yield of fine granules increases. Granules are compressed by the tumbling and compaction effects due to the agitation rotation, which simultaneously diminishes the size of the granules by grinding them. It is also found that the drying rate over a constant drying period increases with air temperature and velocity, but decreases with agitator rotational speed. These results show that too much centrifugal force from agitator rotation forms condensed masses, leading to a decrease in the interfacial drying area. As a result, the mechanism of agitation fluidized bed drying is elucidated and optimal operating conditions are discussed from the view point of granule properties and drying rate.
Flow behavior of particles discharged from an orifice of a hopper is simulated three dimensionally by the Particle Element Method, PEM (Discrete Element Method, DEM), and the relation between the mass flow rate (W) and the orifice diameter (D) is discussed in conjunction with the cyclic formation-collapse phenomena of the arch formed over the orifice. The simulated relation is consistent with the empirical one, expressed as W ∝ Dn (n = 2.5–3.0). W is expressed as functions of three parameters, which are the cross sectional area of the orifice (A), the flow velocity (v), and the volume fraction of flowing particles at the orifice (γ). A is the parameter with most effection W, because it is proportional to D2. In addition, v influences W at one-quater of A’s contribution, while γ’s contribution is only one-quater of A’s one or less, depending on the frictional coefficient of particle. The frictional coefficient of the particle is an important factor for controlling the mass flow rate of particles.
A systematic investigation of elutriation of particles is reported in the cold model of bubbling fluidized bed (BFB) and vortexing fluidized bed (VFB) of 0.19 m diameter and 4.0 m height. Glass beads were used as the fluidized material. The diameter of the coarse particles was 545 μm, the diameter of the fine particles used for the elutriation test ranged from 49 to 194 μm. The results indicate that the specific elutriation rate constant (K∞*) is a function of the initial concentration of elutriated fine particles. The minimum value of K∞* is obtained when the initial concentration of elutriated fine particles is reached 16 wt% in a BFB system. Based on the experimental data obtained from the BFB, a correlation is presented to estimate the K∞*. The K∞* is found to be a function of the particle terminal velocity, gas density, and modified Froude number (Fr*). For a wide particle size distribution (PSD) system, a new parameter, called particle size distribution factor, γ, is introduced to describe the specific elutriation rate constant of wide PSD elutriated fine particles. A method to estimate the specific elutriation rate constant of a multi-component system by using the specific elutriation rate constant of each component obtained from a binary particle mixture system is also presented in this study.
A systematic investigation on the transport disengaging height (TDH) in a vortexing fluidized bed (VFB) cold model was conducted in this study. The elutriated fine particles from a vortexing fluidized bed which has a diameter of 0.19 m was collected and measured by using a continuous receiving system. The experimental results indicate that the elutriation rate decreases significantly with the secondary air injection. The TDH increases with the primary air velocity and decreases with secondary air velocity and the static bed height. It is also found that the effect of the secondary air injection height on TDH can be neglected. Comparing experimental data in the vortexing fluidized bed (VFB) and the bubbling fluidized bed (BFB), the effect of the swirling flow on the transport disengaging height is not conspicuous. The freeboard of a vortexing fluidized bed can be divided into the free entrainment zone (FEZ) and the swirling effect zone (SEZ). The length of the swirling effect zone (SEZ) is the dominating factor for elutriation. A correlation is developed to estimate the TDH in the vortexing fluidized bed. The TDH is found to be a function of the primary air velocity, the ratio of the tangential air flow rate to the primary air flow rate, and the static bed height.
Based on the previous work on the yield of vanadium extracted in water leaching of EP dust followed by its dry mechanochemical treatment carried out using three different types of mills, the relation between the ball impact energy instead of the grinding time and the yield is investigated in this work. The impact energy of media balls in these mills during milling was simulated by the Particle Element Method under the condition of the powder presence. As a result, the relation was able to be expressed by a single curve, regardless of type of mill. This implies that the impact energy of balls in a mill is one of the most important factors controlling the dry mechanochemical reaction in EP dust.
The behaviors of particles in a gas-solid contactor with inclined baffle plates that form a zig-zag path are experimentally studied. To improve the gas-solid contact efficiency, a table discharger is installed at the bottom of the column. In this contactor solid particles slide down along the baffle plates and are fluidized at the openings between the wall and the edge of the baffle plates by the upflowing gas. This structure, called a “moving-fluidized bed”, has some of the advantages of both moving and fluidized beds. The feed rate of solid particles, the open spacing fraction and the inclination angle of the particle reflector were chosen as parameters for experimental conditions. The formation of bubbles was observed between the fluidized bed and moving bed regions and the bubble diameters were measured by using fiber optic probes. Particle velocities in the moving bed region along the baffle plate were measured as a measure of the circulating motion of the particles in the moving and fluidized bed region. It is concluded that the present apparatus performs at a high efficiency of gas-solid contact under dense flow conditions, as compared with a gas-solid contactor which was used in our earlier study.
A closed-loop identification procedure for multivariable systems utilizing set-point change in a rectangular pulse type, is proposed and applied to two example systems. The identified model composed of transfer functions of the first order plus dead time model is decoupled and separated into multiple single-input/single-output (SISO) loops. Then, the SISO PI/PID control loops are tuned using combined open-loop and closed-loop tuning guidelines. The performance of the control system is examined in the set-point tracking and regulatory performances and compared with the BLT tuning method. It is found that the performance of this study is better than that of the BLT tuning. Also, it is proved that the proposed identification method requires short identification time and leaves no disturbance in process output.
An adaptive predictive control for steam-reforming plant which consist of a steam-gas reformer and a waste heat steam-boiler was studied by using MIMO bilinear model. ARMA model was used in the process identification and the adaptive predictive control. The simulation experiments of the process identification were performed by using linear and bilinear models. From the simulation results it was found that the bilinear model represented the dynamic behavior of a steam-reforming plant very well. To verify the performance and effectiveness of the adaptive predictive control method proposed in this study the simulation results of the adaptive predictive control based on bilinear model for steam-reforming plant were compared to those of linear model. The simulation results showed that the adaptive predictive control method based on bilinear model provides better performance than those of linear model.
TiO2 particles were immobilized on activated charcoal granules by means of a sol-gel method to use as a photosterilization catalyst capable of adsorbing microbial cells. The amounts of Escherichia coli cells adsorbed to the TiO2-immobilized activated charcoal (T/AC) granules were determined at temperatures of 288 to 303 K, and the maximum and minimum amounts of adsorbed cells were obtained at 288 and 293 K, respectively. At a temperature of 298 K, the relation between the amounts of adsorbed and suspended cells can be expressed by the Freundlich adsorption isotherm in the range of T/AC concentrations of 0.1 to 1.0 kg/m3. Under light irradiation with a black light fluorescent lamp, sterilization of E. coli cells was carried out in the slurry of T/AC granules at temperatures of 288 to 303 K and T/AC concentrations of 0 to 0.4 kg/m3. The sterilization rates changes depending on the temperatures, and the highest and lowest rates are obtained at 288 and 293 K, respectively. The apparent sterilization rate constants are determined on the basis of a series-event model under various sterilization conditions. The rate constants can be correlated with the concentration of T/AC granules by taking into account the adsorption of cells to the T/AC granules.
A commercially available pectinase which shows chitosanolytic activity was covalently modified with polyalkyleneoxide(PAO)-maleic anhydride(MA) copolymers, and the effects of modification of enzyme on chitosanolytic characteristics, such as initial hydrolysis rate, Michaelis-Menten kinetic parameters, and thermostability, are investigated. Moreover, the time-course of chitosan hydrolysis with modified enzymes was obtained experimentally. Enzymatic characteristics change significantly, depending on the hydrophilicity of the modifier and degree of modification. Even though modification of the enzyme causes a reduction of initial activity in any case, it shows favorable characteristics: an increase in the affinity of enzyme to chitosan, an enhancement of thermostability, and an improvement of reducing sugar production with long-term hydrolysis. Especially when the enzyme is highly modified with a relatively hydrophilic copolymer, AKM-1510, these effect increased significantly.
An earlier investigation has presented a novel procedure in the chromatographic reactor, capable of efficiently determining the enantioselectivity of the enzyme for a biocatalyzed process. In this work, a mathematical model including the effect of axial dispersion is formulated to describe the transient behavior of the fixed-bed used to evaluate the enantiomeric ratio. A valuable relationship among the enantioselectivity, Pèclet number, and transient responses at the exit of reactor is also established through the theoretical analysis. In addition, a relation is proposed to evaluate the significance of axial dispersion in the fixed-bed, allowing us to apply this criterion to assess the necessity of further studying the Pèclet number.
Radical polymerization methods are prone to runaway under extreme process conditions. A review of case histories of polymerization incidents indicate that human error coupled with equipment failures, loss of cooling, temperature control and mischarging of reactants are the primary cause for triggering runaway accidents. Many of these accidents can be reduced or eliminated by changing the materials, alternative synthetic chemistry routes and process variables. Runaway hazard evaluation is the principle approach to assess and eliminate the inherent hazards. In this paper, hazard characterization of bulk and suspension methods of styrene polymerization, by microcalorimetric techniques is studied. The investigation indicates that suspension polymerization of styrene is less hazardous than the bulk polymerization method. The kinetics autocatalytic nature of suspension polymerization is presented. The coolant requirements for safe operation, as well as the temperature shoot up profiles for its failure for a typical 4000-kg batch commercial styrene polymerization reactor is simulated by employing reaction calorimetric data. ARC study indicates that a large excess of water present in the reaction mixture acts as a thermal sink and rules out the possibility of severe thermal hazards.