Prediction of point efficiencies on sieve trays. 1. Binary systems

Chan, Hong Hao; Fair, James R.

doi:10.1021/i200027a032

Cited by 94 publications

(64 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…At lower weir heights on the larger tray the point efficiencies are likely to approach each other. This agrees with the results of Chan and Fair (1982) and Fair et al (1983), who emphasized that better agreement between the point efficiencies deduced from the FRI (Fractionation Research Incorporated) data of Sakata and Yanagi (1979) and Yanagi and Sakata (1982) and an Oldershaw column with internal downcomers could be obtained at lower weir heights on the commercial scale tray.…”

Section: Discussionsupporting

confidence: 90%

“…11 (Kreis and Raab, 1979;Biddulph and Dribika, 1986). Chan and Fair (1982), improving on the AIChE method, developed a correlation for the volumetric vapor-phase mass transfer coefficient in terms of vapor diffusivity, liquid holdup, and fractional approach to flooding. However the correlation was estimated to have an accuracy of ~2 0 % in efficiency prediction.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Scaling‐up distillation efficiencies

Dribika

Biddulph

1986

AIChE Journal

View full text Add to dashboard Cite

This paper describes a study of the possibility of using point efficiencies, measured in a small laboratory column, in the scale-up of distillation efficiencies. The conditions on a large rectangular tray were closely duplicated in a small glass Oldershaw column with one sieve tray having similar hole size and percent free area. Point efficiencies on the large rectangular sieve tray were deduced from the composition profiles and compared with the point efficiencies measured in the small column. A simple relationship between the two columns was found in terms of the froth heights and liquid holdups. The results demonstrate that the slightly lower point efficiencies measured in the Oldershaw column could be used in conjunction with a mathematical mass transfer model based on the eddy diffusion concept, to relate the point efficiencies to the tray efficiences, resulting in a conservative design provided either that allowance is made for other factors, such as nonuniform flow patterns and stagnant zones, or that these are eliminated. A wide range of composition was covered using the two systems MeOH-nPrOH and EtOH-nPrOH operating in the froth region. M. M. Dribika, M. W. BiddulphUniversity of Nottingham Department of Chemical Engineering University Park, Nottingham, England SCOPEThe prediction of the performance of a large-scale distillation tray column is difficult, particularly if a new system is being processed. It is a problem that has attracted a considerable amount of attention over many years. However, the prediction of tray efficiency is still a very uncertain part of the design unless operating data from a similar size column distilling a similar system are available. The problem is that both mass transfer characteristics and tray hydraulic considerations are involved, and so the tray efficiency is a function of system and tray size. This paper is concerned with the mass transfer part of the problem. It describes a study of the relationship betwen point efficiencies, measured in a small glass Oldershaw Column, and the efficiencies inferred at points along a rectangular tray with a liquid flow path length of about 1 m. The tray used is a sieve type with small hole sizes typical of those used in the cryogenic distillation of air. The hole sizes and percent free area in the two trays being compared are similar. CONCLUSIONS AND SIGNIFICANCEThe relationship between point efficiencies measured in a small laboratory column and the point efficiencies that actually exist on a large rectangular tray were studied using two systems, MeOH-nPrOH and EtOH-nPrOH, and covering a wide range of composition. The composition profiles across the tray were measured and used to infer the values of point efficiencies using a mathematical mass transfer model based on the eddy diffusion concept.Similar conditions to those on the large rectangular 1864November 1986 sieve tray were used in a small Oldershaw column with one sieve tray and external downcomers. The results indicate that the point efficiencies obtained on the large rectangu...

show abstract

Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Scaling‐up distillation efficiencies

Dribika

Biddulph

1986

AIChE Journal

View full text Add to dashboard Cite

show abstract

“…Seven NTU prediction correlations were used to calculate point efficiencies for the different outlet weir heights. These correlations were: AIChE [3, 41, Chen and Chuang [5], Chan and Fair [6], Hughmark [7], Zuiderweg [8], Stichlmair [9] and the correlations (27) and (28) presented in this study, The outlet weir heights studied were 0, 0.05,. . .…”

Section: Two-pass Trays Vs One-pass Traysmentioning

confidence: 68%

“…The liquid flowpath length for the one-pass trays was 1.350 m and for the two-pass trays 0.567 m. The simulations were carried out for real trays using a simulator which can update efficiencies while solving the column model [16]. Point efficiencies were calculated using the NTU correlations of Chan and Fair [6] and the point efficiencies were related to the Murphree tray efficiencies using Figure 1. Murphree tray efficiencies of one-pass and two-pass trays calculated using the NTU correlations presented in this study.…”

Section: Two-pass Trays Vs One-pass Traysmentioning

confidence: 99%

Effect of two‐pass trays on distillation efficiencies

Klemola¹,

Ilme

1997

Chem Eng & Technol

View full text Add to dashboard Cite

Two important structural factors that affect distillation efficiencies, the outlet weir heigh and the liquid flowpath length, are investigated. Performance and efficiency data of an industrial scale i‐butane/n‐butane distillation column equipped with two‐pass trays are used as a basis for the calculations. A mathematical development for a new method for predicting the numbers of vapor and liquid phase transfer units is given. This method together with some other NTU calculation methods is used to assess the effect of the outlet weir height on efficiencies. The effect of outlet weir height on the Murphree tray efficiencies is investigated using the observed point efficiencies and different point efficiency to the Murphree tray efficiency relation methods. The effect of varying liquid flowpath lengths on efficiencies is studied by calculating the Murphree tray efficiencies for one‐pass and two‐pass trays. The results obtained using the NTU calculation method presented in this study show that a certain outlet weir height point efficiency reaches its maximum. Most of the other methods give opposite results giving a minimum for point efficiency at a certain outlet weir length. The results also show that the Murphree tray efficiencies for one‐pass trays are higher than for two‐pass trays. Obviously, this is caused by the longer liquid flowpath length of one‐pass trays. The Murphree tray efficiencies are also calculated for an industrial‐scale MTBE purification column. The column is equipped with two‐pass trays in the stripping section and with one‐pass trays in the rectifying section. The Murphree tray efficiencies of one‐pass trays are considerably higher than the two‐pass tray Murphree tray efficiencies.

show abstract

“…One of them comes from the AIChE Bubble Tray Design Manual [55], which represented the first comprehensive estimation procedure for numbers of transfer units. The method of Chan and Fair [56] was devised for sieve trays, but is widely used for valve trays as well. Vapor phase Original:…”

Section: Numbers Of Transfer Units From Empirical Correlationsmentioning

confidence: 99%