摘要:

AbstractThe objective of this investigation was to study the separation of krypton and xenon from nuclear reactor atmospheres by selective permeation through silicone rubber capillaries. Effective permeability coefficients for pure krypton xenon, nitrogen, and oxygen were determined between 0 and 40°C and at pressure differences across the capillary walls (Δp) of up to 3.45 × 105N/m2(50 psi). The silicone rubber capillaries had an O.D. of 635 μm (0.025 in.) and an I.D. of 305 μm (0.012 in.), and were pressurized externally. The effective permeability coefficients decreased with increasing Δp, due to the elastic deformation of the capillaries, in general agreement with a deformation analysis of thick‐walled elastic tubes.Gas separation studies were made with a Kr‐Xe‐N2‐O2mixture in a permeator containing a bundle of silicone rubber capillaries. The permeator had an effective permeation area of 0.480 m2(5.165 ft2) at a packing density of 4132 m2m3permeator volume (1260 ft2/ft3), and was operated in a countercurrent mode. The separation studies were conducted at −10 and 20°C and at three Δpvalues. The separation achieved in the permeator at Δp's of 1.38 × 105N/m2(20 Ib/in.2) and 2.07 × 105N/m2(30 Ib/in.2) was in good agreement with that predicted from a theoretical model of a permeation stage with countercurrent flow. At 3.45 × 105N/m2(50 Ib/in.2), the separation approached that predicted from a “perfect mixing” model. This behavior probably was due to local collapses of the capillaries at weak spots in their walls, as was evidenced also by a sharp increase in the axial pressure dr

ISSN:0001-1541    

DOI:10.1002/aic.690260602

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractMultistage permeation cascades have been designed for the removal of radioactive krypton and xenon from nuclear reactor atmospheres. These cascades could serve for the decontamination of the atmosphere within a reactor containment dome following a nuclear accident and for other applications of interest to the nuclear industry. The stages of the cascades are assumed to consist of permeator modules using silicone rubber capillaries as separation membranes. All stages are to be operated in a countercurrent mode with shell‐side feed.It is shown that it is possible to design an ideal cascade for the separation of multicomponent mixtures by matching the concentrations of a suitable key component in interstage streams that are mixed. This procedure minimizes the cascade volume and power requirement. It is also possible to design a cascade with constantstage cutsin its enriching and stripping sections that approximates the performance of an ideal cascade. The krypton and xenon content of a feed mixture containing about 1 × 10−3mol% Kr and 1 × 10−2mol% Xe in air can be lowered by factors of 103and 108respectively in a 27‐stage permeation cascade. Methods of reducing the number of stages and the effects of irradiation on the membrane performance are also

ISSN:0001-1541    

DOI:10.1002/aic.690260603

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractThe requirements of thermodynamic data predictors in process simulation applications are especially rigorous. The calculation of vapor and liquid density by the Benedict, Webb, Rubin, Starling equation of state has been reformulated to better satisfy these requirements; the necessary mathematical and programming techniques have been developed and are presented here. The resulting algorithm is believed superior for process simulation purposes.

ISSN:0001-1541    

DOI:10.1002/aic.690260604

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractA number of approaches to the optimal selection of sensor locations are presented, and some of these are applied to determine optimal thermocouple positions in a packed bed tubular reactor. As expected, the optimal locations were found to be those surrounding the hot spot location. The theory also revealed that for good state estimation and for goodlinear quadratic control of the reactor, only one or two well located temperature measurements are necessary rather than the entire temperature profile.

ISSN:0001-1541    

DOI:10.1002/aic.690260605

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractDue to rising energy costs, there is an increasing need to include the goal of energy conservation as an integral part of process synthesis. This paper discusses the problem of finding the optimum sequence of distillation columns for separating a multicomponent mixture, when heat exchange is permitted between the columns. The major difficulties are associated with the nonserial nature of the problem, the large combinatorial variety and the size of the optimization task. The synthesis strategy presented here overcomes these problems by the use of a bounding technique together with the Lagrangian theory from nonlinear programming. Accurate lower bounds on the optimal costs permit the elimination of nonoptimal sequences with minimal computational effort.

ISSN:0001-1541    

DOI:10.1002/aic.690260606

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractA model is derived for solids mixing and material transport in a continucus flow rotary dryer or reactor. Detailed analysis of the particle motions in the turnover process provides an opportunity to apply well‐known reactor models to several subregions and to relate the overall results to different design geometries and operating conditions. The essential parameters of the model are the number of stages, the volume fractions of mixed flow and plug flow in each stage, the recycle ratio and the bypass rati

ISSN:0001-1541    

DOI:10.1002/aic.690260607

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractA detailed mathematical model of a single catalyst pellet has been developed to describe its behavior under transient conditions encountered during the warmup period of automobile exhaust catalytic converters. In contrast to the converter models previously reported in the literature, this model is capable of describing the time‐dependent behavior of a composite catalyst pellet, and thus provides a convenient means of examining the effects of poison penetration and various noble metal impregnation strategies in the activity‐time (rather than activity‐temperature) domain.Extensive calculations were carried out to investigate the effects of various catalyst design parameters and converter operating conditions on the lightoff behavior of a spherical, platinum‐alumina catalyst pellet. Due to the complex kinetics of the CO and hydrocarbon oxidation reactions, catalyst lightoff was found to exhibit interesting behavior with respect to variations of the system's design parameters and operating conditions. Graphs are presented to illustrate the parameteric sensitivity of these

ISSN:0001-1541    

DOI:10.1002/aic.690260608

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractAdsorption equilibrium constants and intraparticle diffusivities were determined for the adsorption of carbon dioxide on an activated carbon derived from bituminous coal particles. The moment method was used to extract these results from pulse‐response measurements for beds of carbon particles. The activated carbon had a very broad pore‐size distribution: average radius of micropores was 11Å and macropores 3750Å. Bulk molecular and Knudsen diffusion could not explain mass transfer in the micropores. An activated surface migration concept (Chihara et al., 1978) did give reasonable results. The adsorption rate was also significantly retarded by intraparticle diffusion in the macro

ISSN:0001-1541    

DOI:10.1002/aic.690260609

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractAnalytical expressions are developed for the time‐dependent reactant concentration and catalyst activity in an isothermal CSTR with Langmuir‐Hinshelwood kinetics of deactivation and reaction. Several parallel and series posioning mechanisms are considered for a reactor which, without poisoning, would operate at a unique steady state. The use of matched asymptotic expansions and abandonment of the usual initial‐steady‐state assumption give results, valid from startup to final loss of activity, whose accuracy can be improved systema

ISSN:0001-1541    

DOI:10.1002/aic.690260610

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY

摘要:

AbstractWe have obtained values for interaction second viral coefficients of the helium‐carbon dioxide system in the range 230 ⩽T/K ⩽ 300. Our experimental technique is essentially the Burnett mixing method described by Hall and Eubank (1973, 1974). We have modified the analysis to account for higher‐order effects and to detect significant systematic errors. We also report virial coefficients for the pure components: helium in the range 100 ⩽T/K ⩽ 300 and carbon dioxi

ISSN:0001-1541    

DOI:10.1002/aic.690260611

出版商:American Institute of Chemical Engineers    

年代:1980

数据来源: WILEY