SEPARATION OF MIXTURES By COMBINING RECTIFICATION AND FRACTIONAL CRySTALLIZATION PROCESSES

Various options of separation of binary mixtures by combining the processes of fractional crystallization and rectification are considered. The base mixture, depending on its composition, can be initially directed to the rectification stage or to one of the stages of separated components crystallization using the proposed variants. The flow diagrams of integrated heat exchanging systems and schemes involving open and closed type heat pumps under consideration for the determination of ways of reducing energy consumption of the coupled processes were suggested. These solutions enable improving the processes energy efficiency. In addition, the analysis of the effect of the composition and temperature of the initial mixture, the temperature of fractionation at the crystallization stage, the composition of distillates and bottom products on the separation parameters was carried out. It was found that when the initial mixture is fed to the stage of crystallization of one of the components, the energy costs for carrying out the process under consideration are usually lower than when the initial mixture is fed to the rectification stage. It is shown that using a combination of fractional crystallization and rectification processes can significantly expand the possible separation range and improve the technical and economic characteristics of the separation process.

crystallization, rectification, heat pumps, heat recovery, coupled processes, energy costs

1. Clasen H. Optimale Kombination von Kristallisation und Rektifikation zur Trennung nicht – isomerierbarer Isomerenqemischen // Chemie Ing. Techn. 1967. B. 39. Heft 22. S. 1279–1285.

2. Gelperin N.I., Nosov G.A. Separation of mixtures by combining some mass-exchange processes // Him. prom. (Chemical Industry). 1979. № 11. P. 677–681. (in Russ.).

3. Gelperin N.I., Nosov G.A. Fundamentals of fractional crystallization techniques. M.: Khimiya Publ., 1986. 304 p. (in Russ.).

4. Bessonov A.A. Separation of binary mixtures by a combination of fractional crystallization and fractional melting processes: diss. … Ph.D. Moscow, 2009. 143 p. (in Russ.).

5. Nosov G.A., Bel'skaya V.I., Zhil'tsov V.S. Separation of mixtures by a combination of crystallization and continuous distillation processes using heat pumps // Vestnik MITHT (Fine Chemical Technologies). 2014. V. 9. № 3. P. 31–35. (in Russ.).

6. Nosov G.A., Taran V.A., Zhil'tsov V.S. Separation of eutectic mixtures by a combination of fractional cryslallization and single distillation processes using open type heat pumps // Vestnik MITHT (Fine Chemical Technologies). 2014. V. 9. № 5. P. 11–15. (in Russ.).

7. Yantovsky E.I., Levin L.A. Industrial heat pumps. M.: Energoizdat Publ., 1989. 128 p. (in Russ.).

8. Uvarov M.E. Recrystallization of substances from solutions with the use of heat pumps: diss. … Ph.D. Moscow, 2013. 171 p. (in Russ.).

9. Khaybulina E.M. Separation of mixtures by fractional melting and countercurrent crystallization with the use of heat pumps: diss. …Ph.D. Moscow, 2013. 207 p. (in Russ).

10. Nosov G.A., Popov D.A., Belskaya V.I., Zhil'tsov V.S., Yakovlev D.S. The analysis of opportunities of use of heat pumps when carrying out vacuum-evaporating crystallization // Naukoemkie khimicheskie tekhnologii (High-Tech in Chemical Engineering). 2015. V. 10. № 6. P. 66–70. (in Russ.).

11. Sakashita S., Fujii M., Ohji K. Continuous crystallization system using a heat pump for the sugar refinery // Energy Saving System. Int. Sugar J. 1998. V. 100. № 1189. P. 35–42.

12. Supranto S., Chandra Ishwar, Unde M.B., Diggory P.J., Holland F.A. Heat pump assisted distillation. Alternative ways to minimize energy consumption in fractional distillation // Int. J. Energy Res. 1986. V.10. № 2. P. 45–161.

13. Fanyo Z., Benko N. Comparison of various heat pump assisted distillation configurations // Chem. Eng. Res. & Des. A. 1998. V. 76. № 3. P. 348–360.

14. Oliveira S.B.M., Parise I.A.R. Modelling of an ethanol – water distillation column assisted by an external heat pump // Int. J. Energy Res. 2002. V. 26. № 12. P. 1055–1072.

15. Nakaiwa M., Huang K., Endo A., Ohmori T. Internally heat integrated distillation columns. A review. // Chem. Eng. Res. & Des. 2003. V. 81. № 1. P. 162–177.