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1.
Viscosity data for honey, corn oil, mayonnaise, yogourt, blood and banana puree have been analyzed using two Theological models: the Herschel-Bulkley model and a proposed model. The proposed model contains three parameters: a yield stress, a parameter having the units of time and a parameter having the units of viscosity. The model parameters were obtained by non-linear regression and the proposed model was shown to compare favorably with the Herschel-Bulkley equation. An Arrhenius-type of correlation could be verified between the viscosity of banana puree and the inverse of the temperature. Also, the time parameter (t1) of the proposed model could be correlated with the temperature and the parameter η1. It is asserted that the proposed model should replace advantageously the commonly used Casson expression. 相似文献
2.
Stephen Whitaker 《Chemical Engineering Communications》1987,58(1):171-183
The analysis of nonisothermal transport phenomena in multiphase systems is almost always accompanied by the use of some type of volume-averaged or spatially-smoothed temperature. In such systems one always encounters parameters, such as a reaction rate coefficient or a viscosity, that are temperature dependent. Given the point relation for some generic parameter in the β-phase, i.e., ψβ = ψβ(Tβ), one can wonder how the volume-averaged form of this parameter depends on the volume-averaged temperature. In this paper we show that the local volume-averaged form of ψβ is given by
$
in which A represents a second order tensor that depends on the system parameters. A somewhat more complex form is encountered for area-averaged functions of the temperature. These functions are especially prevalent in reactor design calculations, which are considered both in terms of early intuitive developments and from the perspective of the method of volume averaging. 相似文献
$
in which A represents a second order tensor that depends on the system parameters. A somewhat more complex form is encountered for area-averaged functions of the temperature. These functions are especially prevalent in reactor design calculations, which are considered both in terms of early intuitive developments and from the perspective of the method of volume averaging. 相似文献
3.
Experimental investigations were carried out in model external-loop airlift reactors. Two reactors of laboratory scale (riser liquid height ranged between 1.16-1.56 m, riser diameter 0.03 m, AD/AR ratio between 0.111-1,000, total liquid volume VT = (1.189-2.446).10-3m3) and pilot-plant scale (riser liquid height of 4.4 and 4.7 m, respectively, riser diameter 0.200 m, AD/AR ratio of 0.1225 and 0.040 m, total liquid volume, VT = (0.144-0.170) m3) were used.
The influences of reactor geometry characterized by some parameter as: AD/AR ratio, liquid height in riser and downcomer and liquid height in gas separator, together with the amount of introduced air, on the basic hydrodynamic design parameters: gas holdup and liquid circulation velocity were analysed.
The influence of gas sparger design on gas holdup and liquid velocity was found to be negligible.
The experimental liquid circulation velocity was correlated using a simplified form of the energy balance in airlift reactors, valid for external-loop airlift reactors with almost complete phase separation at the top.
An original dimensionless correlation for gas holdup prediction involving superficial velocities of gas and liquid, cross sectional areas, dispersion height, riser diameter, as well as Froude number, was obtained. 相似文献
The influences of reactor geometry characterized by some parameter as: AD/AR ratio, liquid height in riser and downcomer and liquid height in gas separator, together with the amount of introduced air, on the basic hydrodynamic design parameters: gas holdup and liquid circulation velocity were analysed.
The influence of gas sparger design on gas holdup and liquid velocity was found to be negligible.
The experimental liquid circulation velocity was correlated using a simplified form of the energy balance in airlift reactors, valid for external-loop airlift reactors with almost complete phase separation at the top.
An original dimensionless correlation for gas holdup prediction involving superficial velocities of gas and liquid, cross sectional areas, dispersion height, riser diameter, as well as Froude number, was obtained. 相似文献
4.
The reference Henry's constant was determined from 110 solubility data found in the literature for the CO2/H2O system over a temperature range of 298 to 523 K and a pressure range of 3.40 to 72.41 MPa. Since the Krichevsfcy-llinskaya equation was used to model the system, a correlation for the A parameter was also developed.
In addition to the Krichevsky-Ilinskaya equation, another two-parameter correlation for the solubility of carbon dioxide in water was obtained by using the Krichevsky-Kasarnovsky equation. The reference Henry's constant and partial molar volume of carbon dioxide at infinite dilution were treated as adjustable parameters. The calculated values of the partial molar volume at infinite dilution did not correspond to experimentally determined values found in the literature. Therefore, a third correlation for the reference Henry's constant was obtained by using the Krichevsky-Kasarnovsky equation in conjunction with the correct values of the partial molar volume. This one parameter (Henry's constant) model did not fit the experimental data as well as the two-parameter models.
The decreased solubility of CO2 in brine was accounted for empirically by a single factor correlated to the weight percent of dissolved solids. A literature data set of 167 solubilities, with a temperature range of 298 to 523 K and a pressure range of 3.0 to 85.0 MPa, was used to develop this correlation. A wide scatter of data characterizes this correlation, which relates the CO2 solubility in brine to the CO2 solubility in water at the same temperature and pressure. The correlation is designed for applications in which the determination of concentrations of individual ions is impractical and the implementation of only one additional parameter is desirable, such as the use of compositional simulators to model miscible displacement in the petroleum industry.
These correlations can be easily implemented into reservoir simulation calculations to account for the effects of CO2 solubility in brine. These effects are often ignored even though they can have dramatic effects on the performance of the CO2 enhanced oil recovery process. The correlations presented in this paper for the Henry's constant and the effect of dissolved solids can adequately account for these CO2 solubility effects. 相似文献
In addition to the Krichevsky-Ilinskaya equation, another two-parameter correlation for the solubility of carbon dioxide in water was obtained by using the Krichevsky-Kasarnovsky equation. The reference Henry's constant and partial molar volume of carbon dioxide at infinite dilution were treated as adjustable parameters. The calculated values of the partial molar volume at infinite dilution did not correspond to experimentally determined values found in the literature. Therefore, a third correlation for the reference Henry's constant was obtained by using the Krichevsky-Kasarnovsky equation in conjunction with the correct values of the partial molar volume. This one parameter (Henry's constant) model did not fit the experimental data as well as the two-parameter models.
The decreased solubility of CO2 in brine was accounted for empirically by a single factor correlated to the weight percent of dissolved solids. A literature data set of 167 solubilities, with a temperature range of 298 to 523 K and a pressure range of 3.0 to 85.0 MPa, was used to develop this correlation. A wide scatter of data characterizes this correlation, which relates the CO2 solubility in brine to the CO2 solubility in water at the same temperature and pressure. The correlation is designed for applications in which the determination of concentrations of individual ions is impractical and the implementation of only one additional parameter is desirable, such as the use of compositional simulators to model miscible displacement in the petroleum industry.
These correlations can be easily implemented into reservoir simulation calculations to account for the effects of CO2 solubility in brine. These effects are often ignored even though they can have dramatic effects on the performance of the CO2 enhanced oil recovery process. The correlations presented in this paper for the Henry's constant and the effect of dissolved solids can adequately account for these CO2 solubility effects. 相似文献
5.
H. Masson 《Chemical Engineering Communications》1983,21(4):311-328
The interpretation of the signals generated by a double probe may be done by the three characteristic times method:
t1 the time duration of the pulses;
t2 the time shift between the signals of the two probes;
t3 the time interval between two pulses on one channel.
Each of these times is largely dispersed and the corresponding histograms may be constructed.
The present work is a trial to go over from the time histograms to physical properties of the bubbles combining a Monte-Carlo simulation and a flexible simplex optimisation procedure.
As a result, the percentage of oblique bubbles cutting just one level, the bubble size distribution, the average velocity-size relation, and the individual dispersion around it may be defined.
The procedure is finally applied to experimental results obtained with a light probe in a fluid bed of glass beads. 相似文献
t1 the time duration of the pulses;
t2 the time shift between the signals of the two probes;
t3 the time interval between two pulses on one channel.
Each of these times is largely dispersed and the corresponding histograms may be constructed.
The present work is a trial to go over from the time histograms to physical properties of the bubbles combining a Monte-Carlo simulation and a flexible simplex optimisation procedure.
As a result, the percentage of oblique bubbles cutting just one level, the bubble size distribution, the average velocity-size relation, and the individual dispersion around it may be defined.
The procedure is finally applied to experimental results obtained with a light probe in a fluid bed of glass beads. 相似文献
6.
The evaluation of the heat transfer coefficient hwp between a heat exchanging surface immersed in a gas fluidized bed and the adjacent layer of dense phase particles is analyzed in this contribution. Gas convective and radiant effects are not included in the present analysis.
The inclusion of hwp, or an equivalent formation, in mechanistic models describing heat transfer has been necessary because the sudden voidage variation close to the immersed wall restrains significantly the heat transfer rate. However, there is not at present a widely accepted expression to evaluate hwp.
A precise formulation for hwp accounting for transient conduction inside spherical particles, the Smoluchowski effect, the concentration of particles in the adjacent layer (Np) and an effective separation gap (l0) is developed here.
Although Np can be estimated, in principle, from experimental evidence in packed beds, and it is reasonably expected that l0 = 0, the analysis of experimental heat transfer rates in moving beds, packed beds, and bubbling fluidized beds indicate that values of hwp are, in general, smaller than expected from these assumptions. Appropriate values of l0 and Np are then stimated by fitting the experimental data.
The probable effect of surface asperities is also discussed by analyzing a simplified geometrical model. It is concluded that the parameter l0 can be also effective to account for particle roughness, independently of thermal properties. 相似文献
The inclusion of hwp, or an equivalent formation, in mechanistic models describing heat transfer has been necessary because the sudden voidage variation close to the immersed wall restrains significantly the heat transfer rate. However, there is not at present a widely accepted expression to evaluate hwp.
A precise formulation for hwp accounting for transient conduction inside spherical particles, the Smoluchowski effect, the concentration of particles in the adjacent layer (Np) and an effective separation gap (l0) is developed here.
Although Np can be estimated, in principle, from experimental evidence in packed beds, and it is reasonably expected that l0 = 0, the analysis of experimental heat transfer rates in moving beds, packed beds, and bubbling fluidized beds indicate that values of hwp are, in general, smaller than expected from these assumptions. Appropriate values of l0 and Np are then stimated by fitting the experimental data.
The probable effect of surface asperities is also discussed by analyzing a simplified geometrical model. It is concluded that the parameter l0 can be also effective to account for particle roughness, independently of thermal properties. 相似文献
7.
Basing on the capillary method for the determination of foam bubble size, a method was proposed for establishing values of permeability coefficients of several gases. The permeability coefficients of He, Ar, H2, N2, CH4 through the lamellae of static foam bubbles were preliminarily determined using this method.
A rough dependence of the N2 permeability coefficient through the lamellae of static foam bubbles on the foam wetness and surfactant concentration was also found.
The results obtained lead to the conclusion that the Princen-Mason diffusion model of gas permeation through an isolated soap film was inadequate in the case of permeation through lamellae of bubbles forming a static foam.
A hypothesis that the gas permeation through the lamellae of a static foam is primarily caused by liquid convection in the lamellae core was put forward. 相似文献
A rough dependence of the N2 permeability coefficient through the lamellae of static foam bubbles on the foam wetness and surfactant concentration was also found.
The results obtained lead to the conclusion that the Princen-Mason diffusion model of gas permeation through an isolated soap film was inadequate in the case of permeation through lamellae of bubbles forming a static foam.
A hypothesis that the gas permeation through the lamellae of a static foam is primarily caused by liquid convection in the lamellae core was put forward. 相似文献
8.
M.E. Abou-El-Hassan 《Chemical Engineering Communications》1983,22(3):243-250
A generalized bubble rise velocity correlation is developed to cover the range of conditions:
liquid-phase density = 45.1 to 74.7 lb/ft3,
liquid-phase viscosity = 0.233 to 59 cP., and
interfacial tension = 15 to 72 dynes/cm
The gas-phase is air and the bubble size ranged from 1.2 to 15 mm. The developed correlation is based upon new dimensionless groups which contain the parameters affecting bubble rise velocity as well as their interaction, The correlation is independent of flow regimes and applicable for Reynolds numbers from 0.1 to 104. It is in good agreement with work appearing in the literature. 相似文献
liquid-phase density = 45.1 to 74.7 lb/ft3,
liquid-phase viscosity = 0.233 to 59 cP., and
interfacial tension = 15 to 72 dynes/cm
The gas-phase is air and the bubble size ranged from 1.2 to 15 mm. The developed correlation is based upon new dimensionless groups which contain the parameters affecting bubble rise velocity as well as their interaction, The correlation is independent of flow regimes and applicable for Reynolds numbers from 0.1 to 104. It is in good agreement with work appearing in the literature. 相似文献
9.
V. Rayatskas 《The Journal of Adhesion》1977,9(1):51-61
The characteristics of evaluation of heat resistance of adhesive joints, i.e. the stability loss temperature (TT8) is suggested. Theoretical base of this characteristic is that heat resistance should be regarded as durability, in dependence with loading and temperature change law.
Stability loss temperature is determined according to the principle of thermomechanical testing. The investigations showed that there is a relationship between stability loss temperature, loading and the thickness of the adhesive layer. This relationship for adhesive joints of soft materials has a hyperbolic form.
If for adhesive joints the principle of superposition of destructions (Bailey criterion) exists, then, having durability equations, the stability loss temperature may be determined by calculation. 相似文献
Stability loss temperature is determined according to the principle of thermomechanical testing. The investigations showed that there is a relationship between stability loss temperature, loading and the thickness of the adhesive layer. This relationship for adhesive joints of soft materials has a hyperbolic form.
If for adhesive joints the principle of superposition of destructions (Bailey criterion) exists, then, having durability equations, the stability loss temperature may be determined by calculation. 相似文献
10.
Sulfur dioxide is one of the major pollutants resulting from fuel combustion. Numerous dry, semi-dry and wet processes have been developed for pollution control of sulfur dioxide. Solid carbonates, natural and synthetic zeolites, ion exchange resins and carbon based sorbents are the most commonly used dry sorbents for sulfur dioxide removal
In this study, measurements of the adsorption properties of sulfur dioxide on zeolites were investigated. The adsorbents used in this work are 5A, 4A and AW300 type molecular sieve zeolites. Adsorption equilibrium parameters were determined from the pulse chromatographic response to injections of low concentrations of sulfur dioxide. The method of moments were used to evaluate the adsorption equilibrium parameters from pulse chromatographic experiments. Data, such as adsorption equilibrium constants or reaction rate parameters are essential in the design of adsorption systems or reactors in which sulfur dioxide is removed
The experiments were conducted in a temperature range of 523-718 K. The relatively strong adsorption properties of sulfur dioxide on zeolites necessitated the use of high carrier gas flow rates and subsequently non-isobaric operation. Non-isobaric pulse chromatography theory was found to describe accurately the adsorption trends." printpubdate="Adsorption equilibrium constants of S02 were found to decrease considerably with increasing temperature. It was also found out that adsorption of SO2 on the adsorbents investigated were found to decrease in the order of AW300 ≤ 4A ≤ 5A. The adsorption equilibrium parameter of S02 on 5A was found as 11.78 at 673 K, whereas it has a value of 157.11 at 523 K. The adsorption equilibrium parameter of S02 on 4A zeolite was determined to be 8.63 at 718 K and 213.78 at 523 K. 相似文献
In this study, measurements of the adsorption properties of sulfur dioxide on zeolites were investigated. The adsorbents used in this work are 5A, 4A and AW300 type molecular sieve zeolites. Adsorption equilibrium parameters were determined from the pulse chromatographic response to injections of low concentrations of sulfur dioxide. The method of moments were used to evaluate the adsorption equilibrium parameters from pulse chromatographic experiments. Data, such as adsorption equilibrium constants or reaction rate parameters are essential in the design of adsorption systems or reactors in which sulfur dioxide is removed
The experiments were conducted in a temperature range of 523-718 K. The relatively strong adsorption properties of sulfur dioxide on zeolites necessitated the use of high carrier gas flow rates and subsequently non-isobaric operation. Non-isobaric pulse chromatography theory was found to describe accurately the adsorption trends." printpubdate="Adsorption equilibrium constants of S02 were found to decrease considerably with increasing temperature. It was also found out that adsorption of SO2 on the adsorbents investigated were found to decrease in the order of AW300 ≤ 4A ≤ 5A. The adsorption equilibrium parameter of S02 on 5A was found as 11.78 at 673 K, whereas it has a value of 157.11 at 523 K. The adsorption equilibrium parameter of S02 on 4A zeolite was determined to be 8.63 at 718 K and 213.78 at 523 K. 相似文献
11.
Ultrafiltration of black liquor was carried out using an asymmetric membrane and the results were compared with that of polyethylene glycol, a standard macromolecule, in a stirred batch cell. The effects of system parameters, e.g., pressure, concentration and stirrer speed on permeate flux and solute rejection were studied extensively for both the solutes.
An osmotic pressure model was used to analyze experimental results. To take into account the phenomena of concentration polarization, an extra resistance term, called the polarization layer resistance (Rp), was incorporated into the model. The polarization layer resistance was found to be a function of flow regime and concentration at the membrane. To correlate these, the following two types of relationship were examined and tested with the experimental results,
and
where a, b, c, a1, b1, are constants. 相似文献
An osmotic pressure model was used to analyze experimental results. To take into account the phenomena of concentration polarization, an extra resistance term, called the polarization layer resistance (Rp), was incorporated into the model. The polarization layer resistance was found to be a function of flow regime and concentration at the membrane. To correlate these, the following two types of relationship were examined and tested with the experimental results,
and
where a, b, c, a1, b1, are constants. 相似文献
12.
M. F. Tse 《The Journal of Adhesion》1998,66(1):61-88
This work continues our study of the hot melt adhesive (HMA) model published earlier [1]. This HMA model was developed based on the pressure sensitive adhesive (PSA) tack model established previously [2]:
P = P0BD (1)
where P is the adhesive bond strength, P0 is the interfacial (intrinsic) adhesion term, B is the bonding term and D is the debonding term. The previous paper [1] describes the B and D terms in detail. However, only a brief discussion of the P0 term was given. The present paper will provide a more in-depth but still rather qualitative study of the P0 term within the framework of the adhesion model described in Eq. (1). HMAs studied are ethylene/vinyl acetate copolymer (EVA)/tackifier/wax blends. Substrates studied are untreated and corona-discharge-treated polyolefins such as polypropylene (PP) and polyethylene (PE). First, it has been found that the tackifier surface tension could be roughly correlated with one of its thermodynamic parameters: the solubility parameter dispersion component. Secondly, except for EVA/tackifier binary blends, the compatibility of any two of these three components, the EVA polymer, the tackifier and the wax, in a HMA can be estimated from surface tension and X-ray photoelectron spectroscopy (XPS) measurements. Thirdly, based on the study of the EVA/mixed aliphatic-aromatic tackifier/wax model HMA system, it has been observed that the HMA/polyolefin substrate interfacial composition depends on the wax/substrate compatibility. The cause of an inferior peel strength of a HMA containing a high wax content to a polyolefin substrate is possibly due to the formation of a weak boundary layer (WBL) of wax at the interface and/or low dissipative properties of the HMA.
Also, the relationship between EVA/tackifier/wax interactions and HMA peel strength will be discussed. A correlation between the EVA/tackifier compatibility measured by cloud point and viscoelastic experiments to the debonding term, D, in Eq. (1) has been found. 相似文献
P = P0BD (1)
where P is the adhesive bond strength, P0 is the interfacial (intrinsic) adhesion term, B is the bonding term and D is the debonding term. The previous paper [1] describes the B and D terms in detail. However, only a brief discussion of the P0 term was given. The present paper will provide a more in-depth but still rather qualitative study of the P0 term within the framework of the adhesion model described in Eq. (1). HMAs studied are ethylene/vinyl acetate copolymer (EVA)/tackifier/wax blends. Substrates studied are untreated and corona-discharge-treated polyolefins such as polypropylene (PP) and polyethylene (PE). First, it has been found that the tackifier surface tension could be roughly correlated with one of its thermodynamic parameters: the solubility parameter dispersion component. Secondly, except for EVA/tackifier binary blends, the compatibility of any two of these three components, the EVA polymer, the tackifier and the wax, in a HMA can be estimated from surface tension and X-ray photoelectron spectroscopy (XPS) measurements. Thirdly, based on the study of the EVA/mixed aliphatic-aromatic tackifier/wax model HMA system, it has been observed that the HMA/polyolefin substrate interfacial composition depends on the wax/substrate compatibility. The cause of an inferior peel strength of a HMA containing a high wax content to a polyolefin substrate is possibly due to the formation of a weak boundary layer (WBL) of wax at the interface and/or low dissipative properties of the HMA.
Also, the relationship between EVA/tackifier/wax interactions and HMA peel strength will be discussed. A correlation between the EVA/tackifier compatibility measured by cloud point and viscoelastic experiments to the debonding term, D, in Eq. (1) has been found. 相似文献
13.
A flow model is proposed to investigate the transition of flow regime from bubbling to turbulent fluidization postulating that the flow in the emulsion phase follows the Richardson-Zaki equation.
Void fraction of the whole bed εf and the mean velocity of bubbles Ub were measured in fluidized beds of 0.3 and 0.5 m ID, in which slanting blade baffles were positioned. Mo-catalyst, silica gel, sand and glass beads with size between 135-443 μm were fluidized by air.
Void fraction of the emulsion phase ε e was calculated on the basis of the above model. Correlating ε e with superficial gas velocity Uƒ, we found that ε e was very close to ε mƒ in the bubbling regime and that e, increased with increasing Uƒ in the turbulent regime.
Calculated values of the volume fraction of bubble phase δ were correlated with Uƒ, from which apparent transition point from bubbling to turbulent regime was estimated. Combining information obtained, transition of flow regime in the above type of fluidized beds is discussed 相似文献
Void fraction of the whole bed εf and the mean velocity of bubbles Ub were measured in fluidized beds of 0.3 and 0.5 m ID, in which slanting blade baffles were positioned. Mo-catalyst, silica gel, sand and glass beads with size between 135-443 μm were fluidized by air.
Void fraction of the emulsion phase ε e was calculated on the basis of the above model. Correlating ε e with superficial gas velocity Uƒ, we found that ε e was very close to ε mƒ in the bubbling regime and that e, increased with increasing Uƒ in the turbulent regime.
Calculated values of the volume fraction of bubble phase δ were correlated with Uƒ, from which apparent transition point from bubbling to turbulent regime was estimated. Combining information obtained, transition of flow regime in the above type of fluidized beds is discussed 相似文献
14.
ABSORPTION OF NO BY NaClO2 SOLUTION: PERFORMANCE CHARACTERISTICS 总被引:4,自引:0,他引:4
The absorption of lean NO (200 ∼ 1000 ppm) gases in aqueous NaClO2 solution was investigated in both a mechanically stirred vessel and a packed tower. The chemical reaction rate between NO and NaClO2 in alkaline solution was shown to be second-order with respect to NO concentration and first-order to NaClO2 concentration. After including mass transfer considerations, the absorption rate equation established in this work (under the condition of NaClO2 concentration less than 1.0 M and temperature at 30°C) is given as:
$
In addition, a robust design method was also used to study the performance of this de NOx process by NaClO2 solution in a packed tower. S/N analysis of the results indicated that the pH of liquor, NaClO2 concentration and NaOH concentration were the major factors in affecting both NO oxidation and absorption efficiencies. 相似文献
$
In addition, a robust design method was also used to study the performance of this de NOx process by NaClO2 solution in a packed tower. S/N analysis of the results indicated that the pH of liquor, NaClO2 concentration and NaOH concentration were the major factors in affecting both NO oxidation and absorption efficiencies. 相似文献
15.
R. Aravamuthan W.Y. Chen K. Zargarian Gary C. April 《Chemical Engineering Communications》1988,69(1):115-127
A two-stage acid hydrolysis process is currently used in the production of ethanol from hardwoods. In this process, dilute sulfuric acid in water at high pressure and short residence times hydrolyzes the wood and first stage substrate. The chemical action is particularly impeded in the second stage by the presence of acid condensed lignin.
Presulfonation followed by delignification is proposed using a sulfur dioxide/water sulfuric acid/ethanol treatment step in place of the first stage acid hydrolysis step to alleviate this problem.
Results presented include the effects caused by varying treatment time, sulfur dioxide concentration, temperature and ethanol concentration on the degree of delignification, and, on the recovery of C5 and C6 sugars in the hydrolysates. A preliminary economic feasibility analysis is made to determine the impact of improved ethanol yields and lignin by-product values in the production of ethanol from hardwoods. 相似文献
Presulfonation followed by delignification is proposed using a sulfur dioxide/water sulfuric acid/ethanol treatment step in place of the first stage acid hydrolysis step to alleviate this problem.
Results presented include the effects caused by varying treatment time, sulfur dioxide concentration, temperature and ethanol concentration on the degree of delignification, and, on the recovery of C5 and C6 sugars in the hydrolysates. A preliminary economic feasibility analysis is made to determine the impact of improved ethanol yields and lignin by-product values in the production of ethanol from hardwoods. 相似文献
16.
Oxidation of nitric oxide is an important step in NOx absorption. Recent advances namely catalytic oxidation and the use of slrong oxidizing agents have been reviewed. The refinements which have been made in the kinetics of NO oxidation have been discussed. Several liquid phase absorbents have been suggested for the NO removal, particularly for the purpose of pollution abatement. Different models for NO oxidation using nitric acid have been analysed and the limitations of published information have been brought out.
Absorption of tetravalent nitrogen oxide (NO2 and N2O4) has received considerable attention. The absorbents include water, nitric and sulfuric acids, sodium hydroxide, sodium sulfite and sodium chlorite. Absorption in water and nitric acid is important in the manufacture of nitric acid. The published information on the mechanism of NO2 and N2O4 absorption in water has been critically analysed. The problem of nitrous acid decomposition has been analysed on the basis of film theory. The predictions agree favourably with the available experimental data.
A new mathematical model has been developed for a packed column. Performance charts have been prepared which take into account the effects of concentration of nitric acid, superficial liquid velocity, temperature and the partial pressures of various components. A simplified model on the basis of NO oxidation has also been presented.
Various process design aspects have been discussed in detail. Optimum values for various operating parameters exist and basis for their selection has been explained. Some engineering aspects such as the selection of equipment and material of construction have also been discussed. A comparison between semi-batch and continuous modes of operation has been presented. The problem of the manufacture of pure nitrites has been analysed
Specific recommendations have been made regarding the use of equations and procedures in design. The knowledge gaps have been clearly brought out and suggestions have been made for future work 相似文献
Absorption of tetravalent nitrogen oxide (NO2 and N2O4) has received considerable attention. The absorbents include water, nitric and sulfuric acids, sodium hydroxide, sodium sulfite and sodium chlorite. Absorption in water and nitric acid is important in the manufacture of nitric acid. The published information on the mechanism of NO2 and N2O4 absorption in water has been critically analysed. The problem of nitrous acid decomposition has been analysed on the basis of film theory. The predictions agree favourably with the available experimental data.
A new mathematical model has been developed for a packed column. Performance charts have been prepared which take into account the effects of concentration of nitric acid, superficial liquid velocity, temperature and the partial pressures of various components. A simplified model on the basis of NO oxidation has also been presented.
Various process design aspects have been discussed in detail. Optimum values for various operating parameters exist and basis for their selection has been explained. Some engineering aspects such as the selection of equipment and material of construction have also been discussed. A comparison between semi-batch and continuous modes of operation has been presented. The problem of the manufacture of pure nitrites has been analysed
Specific recommendations have been made regarding the use of equations and procedures in design. The knowledge gaps have been clearly brought out and suggestions have been made for future work 相似文献
17.
The effect of a liquid in the failure of an assembly depends strongly on the ability of the liquid to follow the fracture front. Thus, the existence of a critical rate of separation above which the liquid has no effect on the strength of the assembly, has been clearly demonstrated.
From a crack model, parameters determining the penetration rate of the liquid in the growing fracture have been established and are:
—the viscosity of the liquid
—its surface energy
—and the solid/liquid interactions.
This analysis also shows that the dimension of the crack opening is of the order of a micron. 相似文献
From a crack model, parameters determining the penetration rate of the liquid in the growing fracture have been established and are:
—the viscosity of the liquid
—its surface energy
—and the solid/liquid interactions.
This analysis also shows that the dimension of the crack opening is of the order of a micron. 相似文献
18.
Effective shear rate is one of the indispensable parameters for the design of aerobic fermentors using a viscous non-Newtonian system. The estimation of effective shear rate in airlift loop bioreactors has been investigated with liquid circulation velocity. An empirical correlation of effective shear rate in airlift loop reactors is proposed.
γeπ= 3.26-3.51 ; 102UG + 1.48 104U2G
It is found that the effective shear rate is lower in airlift reactors than in bubble columns. This equation can be used for the cultivation of cells sensitive to shear stress. 相似文献
γeπ= 3.26-3.51 ; 102UG + 1.48 104U2G
It is found that the effective shear rate is lower in airlift reactors than in bubble columns. This equation can be used for the cultivation of cells sensitive to shear stress. 相似文献
19.
The adhesion phenomena of monodispersed barium sulfate (BaSO4) particles on gelatin-coated glass beads were evaluated using the packed column technique and compared with the same system in the absence of the protein.
Multilayer deposition was observed with the uncoated glass beads at pH 4, 5 and 6, while at pH 9, which is above the isoelectric point (pH ∼ 6) of BaSO4 particles, monolayer deposition took place, even though the BaSO4 particles and glass beads bore the same sign of charge. At pH = 10, no uptake was observed on the glass beads, but the addition of 10-4 mol dm-3 BaCl2 induced multilayer deposition due to the adsorption of the Ba2+ cation on BaSO4 particles, which causes a reversal of their charge to positive.
The formation of multilayers was found to occur over a much wider pH range on the gelatin coated glass beads.
BaSO4 particles deposited in multilayers could not be removed from either glass beads or gelatin-coated glass beads by rinsing the loaded column with solutions of pH 11.5, but could be detached from monolayers on glass beads only. 相似文献
Multilayer deposition was observed with the uncoated glass beads at pH 4, 5 and 6, while at pH 9, which is above the isoelectric point (pH ∼ 6) of BaSO4 particles, monolayer deposition took place, even though the BaSO4 particles and glass beads bore the same sign of charge. At pH = 10, no uptake was observed on the glass beads, but the addition of 10-4 mol dm-3 BaCl2 induced multilayer deposition due to the adsorption of the Ba2+ cation on BaSO4 particles, which causes a reversal of their charge to positive.
The formation of multilayers was found to occur over a much wider pH range on the gelatin coated glass beads.
BaSO4 particles deposited in multilayers could not be removed from either glass beads or gelatin-coated glass beads by rinsing the loaded column with solutions of pH 11.5, but could be detached from monolayers on glass beads only. 相似文献
20.
—It has been shown that quenched Pb(Sc1/2Ta1/2)O3 (PST) disordered ceramics and crystals show diffuse dispersive dielectric properties, while well annealed ordered materials exhibit normal sharp first order transition. The pyroelectric depolarization measurements taken using a Hewlett Packard Model 4140B picoammeter/DC Source under computer controlled heating cycle also have shown different behaviors between disordered and ordered materials.
In this work pyroelectric measurements by Chynoweth method under DC bias up to 1.8 KV/mm within a temperature range of 70°C around the temperature of maximum dielectric constant have been studied. A very significant enhancement of the pyroelectric signal under DC bias is observed in thermally quenched disordered samples. The largest enhancement of the signal appears at temperatures some degrees below the temperature of maximum dielectric constant.
The existence of microdomains in disordered materials is believed to be responsible for this new extrinsic component of reversible pyroelectricity.
The large reversible pyroelectric effect is a promising phenomenon for developing new pyroelectric devices. 相似文献
In this work pyroelectric measurements by Chynoweth method under DC bias up to 1.8 KV/mm within a temperature range of 70°C around the temperature of maximum dielectric constant have been studied. A very significant enhancement of the pyroelectric signal under DC bias is observed in thermally quenched disordered samples. The largest enhancement of the signal appears at temperatures some degrees below the temperature of maximum dielectric constant.
The existence of microdomains in disordered materials is believed to be responsible for this new extrinsic component of reversible pyroelectricity.
The large reversible pyroelectric effect is a promising phenomenon for developing new pyroelectric devices. 相似文献