EVALUATION OF THE NUMBER OF TRANSFER UNITS(NTU) AND THE COLUMN HEIGHT BY USING ON-LINE TEMPERATURE MEASUREMENTS FOR A PILOT SCALE PACKED BATCH DISTILLATION COLUMN

Abstract

There have been relatively few experimental attempts at evaluating the column height and comparing experimental results obtained from a pilot scale packed batch distillation column with theoretical ones. In the present study, the pilot plant packed batch distillation column was used to distillate the binary methanol-water mixture, and to obtain on-line temperature values. The top temperature changes with time were observed at steady-state and dynamic conditions. The column was operated initially for approximately one hour at the total reflux. In this case, There were no feed and product flows. Temperature samples were taken on-line from the top and bottom of the column. Temperature profiles observed on the computer were recorded. Refractive index of the samples were determined. When the temperatures were constant, the system was at a steady-state condition for total reflux. After the system reached the steady-state condition the reflux ratio was adjusted to a certain level. From experimental top and bottom temperature values, two models were obtained between mol fraction and temperature. The mass transfer coefficient was calculated, and the final mol fraction of reboiler was determined. The column height was calculated and compared with the real packed height. It is noted that the equation used for mass transfer coefficient is considerable well

Keywords

• Batch distillation, packed column, packed height, mass transfer coefficient

References

1. Betlem B.H.L., Krijnsen H.C. and Huijnen H. (1998). Optimal batch distillation control based on spesific measures. Chemical engineering journal 71 111-126.
2. Elgue S., Prat L., Cabassud M., Lann J.M.Le., Cezerac J. (2004). Dynamic models for start-up operations of batch distillation columns with experimental validation. Computers and chemical engineering 28 2735-2747.
3. Karacan S., Hapoğlu H., Cabbar Y., Alpbaz M. (1997). Pole placement self tuning control for packed distillation column Chemical engineering and processing 36 309-315.
4. Kim Y. Han (1999). Optimal design and operation of a multi-product batch distillation column using dynamic model. Chemical engineering and processing 38 61-72.
5. Liu G.B., Yu K.T., Yuan X. G. and Liu C.J. (2009). A numerical method for predicting the performance of a randomly packed distillation column. International journal of heat and mass transfer 52 5330-5338.
6. Muddu M., Narang A., Patwardhan S.C. (2010). Reparametrized ARX models for predictive control of staged and packed bed distillation columns. Control engineering practice. 18 114-130.
7. Noda M., Kato A., Chida T., Hasebe S., Hashimoto I. (2001). Optimal structure and on-line optimal operation of batch distillation column. Computers and chemical engineering. 25 109-117.
8. Rejl J.F., Linek V., MouchaT., Prokopova E., Valenz L. and Hovarka F. (2006). Vapour and Liquid side volumetric mass transfer coefficients measured in distillation column.Comparison with data calculated from absorption correlations. Chemical engineering science. 61 6096-6108.

9. Sadeghifar H., Kordi A.A.S. (2011). A new and applicable method to calculate mass and heat transfer coefficients and efficiency of industrial distillation columns containing structured packings. Energy. 36 1415-1423.
10. Sahay B.N. and Sharma M.M. (1973). Effective interfacial area and liquid and gas side mass transfer coefficients in a packed column. Chemical engineering science 28, 41-47.
11. Senol A. (2001). Mass transfer efficiency of randomly-packed column: modeling considerations. Chemical engineering and processing. 40 41-48.
12. Zuiderweg F.J. (1999). Distillation composition profiles –What do they tell us? Institution of chemical engineers, Trans IChemE. 77 (A) 475-481. TO