SELECTING THE OPTIMUM SCHEME OF THE SEPARATION OF HYDROCARBON GASES BY DISTILLATION

The heat costs in distillation columns were determined for the purpose of separating a four-component gas mixture in gas fractionators with various component selection sequences. A method for selecting the optimal scheme was developed. It is based on the concept of “internal energy saving” upon rectification. Internal energy saving means multiple steam operation on the plates of a distillation column, namely, its condensation on each plate with the release of the heat of condensation, which is used for the evaporation of the liquid entering the plate to obtain a new steam composition. It was shown that when binary and three-component mixtures are separated and products of equal purity are obtained, the heat costs are related to the internal energy saving. The calculation of the internal energy saving in a three-column system for the separation of a four-component mixture was carried out. The calculation confirms that, as the internal energy saving increases and, accordingly, the average internal energy saving in the system of columns increases, the total heat consumption is reduced. The results of calculating three separation schemes of the four-component mixture were compared using the program Aspen Plus with different methods for describing the phase equilibrium (NRTL, Peng-Robinson, Chao-Seader) was carried out. It was shown that the calculations with the use of Peng-Robinson and Chao-Seader methods match.

rectification, gas fraction plant, four-component mixture, reflux ratio, internal energy saving

1. Mullakhmetova L.I., Cherkasova E.I. Associated petroleum gas: Preparation, transportation and processing. Vestnik Kazanskogo tekhnologicheskogo universiteta = Bulletin of the Kazan’ Technological University. 2015; 18(19): 83-90. (in Russ.)

2. Mullakhmetova L.I., Cherkasova E.I., Sibgatullina R.I., Bikmukhametova G.K., Mustafina A.M., Salakhov I.I. Gas fractionation. Vestnik Kazanskogo tekhnologicheskogo universiteta = Bulletin of the Kazan’ Technological University. 2016; 19(24): 49-55. (in Russ.)

3. Leffler U.L. Petroleum refining. 2nd Edition, revised. Transl. from Engl. Moscow: Olimp-Biznes Publ., 2004. 224 p. (in Russ.)

4. Timoshenko A.V., Anokhina E.A. Energy saving methods for the distillation of organic mixtures. Polzunovskiy vestnik (Polzunov Bulletine). 2010; (3): 134-136. (in Russ.)

5. Kim Y.H. Design and control of energy-efficient distillation columns. Korea J. Chem. Eng. 2016; 33: 2513-2521.

6. Soave G., Feliuv J.A. Saving energy in distillation towers by feed splitting. Appl. Therm. Eng. 2002; 22: 889-896.

7. Anokhina E.A., Timoshenko A.V., Rudakov D.G., Timofeeev V.S., Tatsiyevskaya G.I., Matyushenkova Yu.V. Energy saving in distillation using complexes with associated flows. Vestnik MITHT (Fine Chem.Tech.). 2011; 6(4): 28-39. (in Russ.)

8. Nakaiwa M., Huang K., Endo A., Ohmori T., Akiya T., Takamatsu T. Internally heat-integrated distillation columns: A review. Chem. Eng. Res. Design. 2003; 81(1): 162-177.

9. Halvorsen I.J., Skogestad S. Energy efficient distillation. Journal of Natural Gas Science and Engineering. 2011; 3: 571-580. doi:10.1016/j.jngse.2011.06.002.

10. Koeijer G., Rosjorde A., Kjelstrup S. Distribution oh heat exchange in optimum diabatic distillation columns. Energy. 2004; (29): 2425-2440.

11. Petlyuk F.B. Distillation Theory and its Application to Optimal Design of Separation Units. New York: CUP, 2004. 360 р.

12. Saxena N., Mali N., Satpute S. Study of thermally coupled distillation systems for energyefficient distillation. Sadhana. Academy Proceed. in Engineering Sciences. 2017; 42: P. 119-128.

13. Zakharov M.K. Ways of energy saving during energy intensive technological processes. Tekhnologii nefti i gaza (Gas and Oil Technology). 2006; (1): 63-72. (in Russ.)

14. Ainshteyn V.G., Zakharov M.K., Nosov G.A. Optimization of the heat pump in the processes of chemical technology. Khimicheskaya promyshlennost’ (Chemical Industry). 2001; (1): 18-27. (in Russ.)

15. Zakharov M.K. Energy efficiency of distillation process. Tonkiye khimicheskiye tekhnologii / Fine Chemical Technologies. 2015; 10(1): 29-33. (in Russ.)

16. Zakharov M.K., Shvets A.A. Interrelation of external and internal energy saving during distillation of binary mixtures. Tonkiye khimicheskiye tekhnologii / Fine Chemical Technologies. 2016; 11(1): 40-44. (in Russ.)

17. Zakharov M., Nosov G., Pisarenko Yu., Gil`tsova L., Shvets A. Comparison of distributed heat supplies along the height of fractionating columns with conventional fractionation. Theoretical Foundations of Chemical Engineering. 2017; (51)5: 708-715.

18. Zakharov M.K. Analysis of energy saving in distillation processes. Khimicheskaya tekhnologiya (Chemical Technology). 2008; 9(4): 177-182. (in Russ.)

19. Abbasi M. Energy saving in the processes of distillation of binary and multicomponent mixtures: Ph.D. (Eng.) Thesis. Moscow, 2014. 122 p. (in Russ.)