摘要:

AbstractThis paper reviews the literature about fluidized combustion of char and volatiles from coal. While the rate of combustion of particles bigger than about 2 mm is mainly limited by the rate of diffusion of oxygen, there is usually an effect of chemical rate. As particle diameter decreases, the influence of chemical rate increases. Char particles are porous and combustion occurs in pores near their exterior. Char reactivity can be modelled by an effective pore area for combustion.At high bed temperatures (>1,150 K), the rate of combustion of volatiles is limited by the rate of mixing of fuel and oxygen. At low bed temperatures (<1,000 K), combustion reactions are inhibited by the inert particles in the bed.

ISSN:0001-1541    

DOI:10.1002/aic.690300602

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractExperimental results from an X‐ray study of gas bubbles entering a fluidized bed of two differently sized powders are presented and their significance for chemical reactions taking place in the distributor region of a fluidized bed reactor are examined using a simple two‐phase mo

ISSN:0001-1541    

DOI:10.1002/aic.690300603

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe behavior of bubbles in a cocurrent gas‐liquid‐solid fluidized bed was investigated in a column of 76.2 mm ID in this study. The particles used were glass beads of 3 and 6 mm and a binary mixture of these particles. A novel dual electrical resistivity probe system was developed and utilized to obtain bubble properties including bubble size and rise velocity. The distributions of the bubble properties in the gas‐liquid‐solid fluidized bed were evaluated for three flow regimes: the dispersed bubble flow regime; the coalesced bubble flow regime; and the slug flow

ISSN:0001-1541    

DOI:10.1002/aic.690300604

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractAramco vacuum gas oil was catalytically hydrotreated to conversions of 20, 40 and 60%, and subsequently fractionated into naphtha, kerosene, gas oil, and hydrotreated vacuum gas oil. These fractions were thermally cracked to test their potential as feedstock for olefins and BTX production. The olefin yields from the hydrotreated vacuum gas oil obtained from hydrotreating with 40 and 60% conversion favorably compare with those of straight‐run naphthas. Cracking in conventional naphtha/atmospheric gas oil units becomes possible. The naphtha, kerosene and gas oil fractions are preferably added to standard refinery stream

ISSN:0001-1541    

DOI:10.1002/aic.690300605

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractNew sets of transformations that convert an original two‐point boundary value problem into an equivalent initial value problem have been proposed and illustrated in the solution of the diffusion‐reaction problem for a monodispersed catalyst pellet. The use of the transformations reduces the computational effort considerably. The method is especially useful in the analysis of more complex cases, such as bidispersed catalyst pellets, catalysts undergoing decay, and gas‐solid noncatalytic reactions where the use of the conventional numerical techniques is quite involved and cumbersome. The method is applied to some known and to some yet‐unresolved cases and the new results obtained are di

ISSN:0001-1541    

DOI:10.1002/aic.690300606

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractMass transfer studies were conducted in a stable liquid foam reactor under various operating conditions to evaluate gas holdup, effective interfacial area, liquid‐phase mass transfer coefficient and a modified interfacial mass transfer coefficient to include the surface‐active agents employed. Gas holdup and effective interfacial area were evaluated experimentally. The interfacial mass transfer coefficient was evaluated semitheoretically, by considering the interfacial region as a separate phase and using the experimental data developed for mass transfer accompanied by a fast first‐order chemical reaction. The liquid‐phase mass transfer coefficient was also evaluated semitheoretically, using Danckwert's theory for the liquid phase and the experimental data on mass transfer accompanied by a slow pseudofirst‐order chemical reaction.An experimental unit was set up to provide a stable flowing foam column, simulating the foam reactor. Mass transfer rates were studied for superfacial gas velocities in the range from 1.5 × 10−2m/s to 5 × 10−2m/s, giving gas residence times in the range from 20 to 55 seconds. A cationic and nonionic surface‐active agent and three different wire mesh sizes, giving bubble size distributions in the range from 2.2 to 5.4 mm Sauter mean diameters, were employed.It is observed that gas holdup is insensitive to the type of surface‐active agent; it is however, dependent on wire mesh size and gas velocity. The bubble diameter and, hence, the interfacial area are found to be insensitive to gas velocity in the range studied; they are, however, strong functions of wire mesh size. The liquid‐phase mass transfer coefficient increases with increase in gas velocity. The surface‐active agent introduces additional resistance to mass transfer in both reaction cases, this being the controlling one in the case of the fast reaction. A comparison with conventional packed bed contactors indicates the mass transfer rates to be about 8 times lower for the foam reactor, for the fast reaction case; for slow reactions, the foam reactor has mass transfer rates approximately 2‐4 times higher than those for conventio

ISSN:0001-1541    

DOI:10.1002/aic.690300607

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractGraphical and numerical procedures are presented for the design and analysis of cocurrent and countercurrent multistaged mixer‐settler units for liquid membrane extraction operations—these are based on the recently developed Advancing Front Model of Ho et al. (1982) and Hatton et al. (1983). The numerical results indicate that the extraction efficiency in a countercurrent cascade is only slightly improved over that for cocurrent operation. However, for any given stage, marked improvements in extraction efficiency are indicated if an external emulsion recycle over the mixer settler unit is used to ensure adequate holdup ratios in the mixer. Premixing of the emulsion feed and recycle streams will impair the extraction performance, howe

ISSN:0001-1541    

DOI:10.1002/aic.690300608

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe rates of desorption of carbon dioxide from supersaturated water solutions into pure carbon dioxide or nitrogen gas stream were measured at 15,25, and 35°C in a baffled agitated vessel with a flat gas‐liquid interface operated in a continuous manner. The volumetric liquid‐phase mass transfer coefficients for the bubbles generated in the agitated liquid and the enhancement factors of the volumetric liquid‐phase mass transfer coefficient for the free liquid surface due to the bubbling were calculated from the measured desorption rates and correlated as functions of the relative supersaturation of the solution and the liquid‐phase Reynold

ISSN:0001-1541    

DOI:10.1002/aic.690300609

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe operational characteristics of the grate‐type MVS with screen were studied in detail. First, theory was developed to predict how the current needed to operate the valve was related to the valve geometry. Then experiments were made to see how bed height, screen aperture, grate spacing, the presence of nonmagnetic solids in the mixture all affected the current needed to operate the valve and on the mass flux of solids. The response time of the valve was also determined.The experiments were compared with the predictions of the theor

ISSN:0001-1541    

DOI:10.1002/aic.690300610

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThis paper reports on the operating characteristics of the collar type MVS which uses either orifice plates or screens as supports for the solids.The optimum placement for the support (screens or orifice plates), the current needed to operate the valve as a function of vessel size (up to 0.55 m) and screen or orifice opening, and the response characteristics of the valve were all determined. These findings were then compared with theory.Finally, the operational characteristics of the MVS (magnetic valve for solids) when handling a mixture of magnetic and nonmagnetic solids were briefly examined.

ISSN:0001-1541    

DOI:10.1002/aic.690300611

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY