摘要:

AbstractA statistical procedure for determining whether process variables have undergone a change of steady states is developed by using a composite statistical test. Factors influencing the power of the test and the probability of Type I errors were studied through theoretical analysis, computer simulation, and application to plant data. They include the number of variables to be tested together, the number of measurements used in time averaging, the levels of significance of the tests, and the appropriate formulation of the hypotheses. The procedure developed here is useful in process data reconciliation and in applications that require an analysis of process trends.

ISSN:0001-1541    

DOI:10.1002/aic.690320902

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe overall nonideality of an aqueous mixed electrolyte solution is characterized in terms of a newly defined parameter Γ*, called the overall reduced ionic activity coefficient. It is shown that Γ* for the mixed solution is simply related to the properties of single‐electrolyte solutions. Γ* is related to the vapor pressure of a mixed‐electrolyte solution through well‐known thermodynamic equations. This leads to a predictive equation for the vapor pressure of a mixed‐electrolyte solution in terms of the vapor pressures of single‐electrolyte solutions of the components. This equation is valid over the entire concentration range encountered in practice, without any empirical constants, and has a predictive accuracy of 2%. A predictive equation for the latent heat of vaporization is also developed and tested against exper

ISSN:0001-1541    

DOI:10.1002/aic.690320903

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe overall reduced ionic activity coefficient Γ* is useful in characterizing the overall nonideality of an aqueous mixed‐electrolyte solution. It has been shown in Part I that Γ* can be simply related to Γ of single‐electrolyte solutions containing the component electrolytes without using empirical constants. This basic relationship is used in this paper for deriving predictive equations for several properties in terms of corresponding properties of single‐electrolyte solutions containing the component electrolytes. The predictive equations need no empirical constants. The properties covered include volume properties such as density and adiabatic compressibility, thermal properties such as enthalpy and specific heats, and others such as free energy, expansibility, and depression in freezing point. Comparison with experimental data shows that the predictive equations have an accuracy varying from 0.03% for density to 2% for freezing point depression, and are valid for the entire range of concentrations encountered in

ISSN:0001-1541    

DOI:10.1002/aic.690320904

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA criterion is developed for the selection of the best pairing of the control and manipulated variables of a multiloop control system. This criterion is based on the difficulty caused by the interaction terms (the off‐diagonal elements) in finding the inverse of the steady state gain matrix. From an analysis based on the proposition that the most desired or best pairing is that one for which the system most closely resembles a set of independent single‐loop systems, a quantitative measure of the best pairing is obtained. Although the development of the pairing criterion is based on purely algebraic principles, the validity of the pairing criterion is evident from analogous developments obtained within the control framework. Furthermore, it is shown that the pairing criterion may be used to determine the stability of a multiloop control system, thus enhancing the value of the criterion presen

ISSN:0001-1541    

DOI:10.1002/aic.690320905

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractUrea adsorbs on the ruthenium titanium oxide electrode, depressing the observed current. For artificial kidney dialysate concentrations of urea and NaCl (0.50 kg/m3and 100 mol/m3, respectively), the major electrolysis products are N2, CO2, O2, and H2, and the reaction mechanism is solution oxidation of urea by anodically generated active chlorine. A nitrogen‐yielding direct electrode reaction is observed at high urea concentration (30 kg/m3) and low NaCl concentration (10–100 mol/

ISSN:0001-1541    

DOI:10.1002/aic.690320906

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper focuses on two aspects of smelting operation that are highly dependent on the rate of heat transfer in the molten bath. As a consequence of the elevated temperature and the corrosive nature of the fluoride mixture, the cell sidewalls are designed so that some electrolyte will freeze onto them, protecting the carbon from erosion and at the same time insulating the cell against excessive heat loss. The thickness and dynamic variation of this frozen ledge are determined by the convective heat transfer from the bath to the freeze surface.Another situation where the rate of convective heat flow exerts a subtle influence is the dissolution of aluminium oxide powder in the bath. The localized feeding of large quantities of the powder causes transient electrolyte freezing on some of the added material, hindering its dissolution and causing the formation of an alumina sludge below the molten aluminium pad.

ISSN:0001-1541    

DOI:10.1002/aic.690320907

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA rule of hydrodynamic similarity for a scale change of fluidized beds has been developed based on the governing equations of bubble and interstitial gas dynamics. When geometrically similar scale‐up is to be carried out maintaining hydrodynamic similarity, the proposed similarity rule requires that two conditions be satisfied. The first condition assures a similarity in bubble coalescence. The second assures the similarities in bubble splitting and in the interstitial flow pattern. The present work proves theoretically that these two conditions are the necessary, and almost sufficient, conditions for hydrodynamic similarity. They consider not only bubble coalescence but also bubble splitting. The theory proposed was first tested by previous correlations for bubble diameter and grid zone structure, and second by experiment. It has been proved that as long as the present rule is satisfied, the longitudinal distribution of the average bubble diameter, stochastic variation around it, and the radial distribution of superficial bubble velocity can be maintained similar for a scale change.Application of the present rule to predict the bubbling and solid circulation characteristics in a large‐scale unit by a small‐scale experiment has thus proved promising, at least for Geldart group B particles. In order to further study the possibility of a similarity in mass transfer and chemical reactions, computation was carried out using the three‐phase bubble assemblage model. If the effect of molecular diffusion is negligible, as in the case of fluidized bed combustion, even a chemical similarity is found to be p

ISSN:0001-1541    

DOI:10.1002/aic.690320908

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA thermal gravimetric method was used to measure rates of decomposition of NAHCO3particles. Such decomposition produces a highly porous Na2Co3that reacts with SO2rapidly and completely at moderate temperatures. Hence, NaHCO3decomposition provides a reactant with attractive features for SO2removal. The rapid rate of decomposition combined with the high heat effect prevented determining intrinsic rates by constant temperature runs when the temperature level was above 400 K. However, rising‐temperature runs, which allowed time for heat transfer to equilibrate temperatures of the thermocouple and particles, gave reliable results at high temperatures. The activation energy was 102 kJ/mol. Porosimeter data verified the large increase in pore volume (from 0.03 to 0.39 × 10−3m3/kg) on converting the NaHCO3particles to Na2CO3. First‐order kinetics were observed up to high conversions, after which the apparent order decreased. However, the sodium bicarbonate could be completely converted to

ISSN:0001-1541    

DOI:10.1002/aic.690320909

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe sulfation model of Simons and Rawlins (1980) is extended to include the effect of product deposits. The model includes: 1. the plugging of the smallest pores and the subsequent loss in the internal surface area, 2. the diffusion of the SO2through the product deposits, and 3. the loss of intraparticle diffusion due to the complete plugging of the largest pores. It is shown that the plugging of the smallest pores is generally rate‐controllin

ISSN:0001-1541    

DOI:10.1002/aic.690320910

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractSimultaneous measurements were made of the size and the axial and radial velocity of drops entrained by the gas in annular flow. A model is developed to use these data to compute the rate of deposition or entrainment and the pressure gradient, ▽ρE, due to drop interchange. ▽ρEis a significant fraction of the measured total gradien

ISSN:0001-1541    

DOI:10.1002/aic.690320911

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY