Process and apparatus for the separation of light-boiling components from hydrocarbon mixtures

Abstract

A process and apparatus for the separation of a feed mixture into higher-boiling and lower boiling fractions in a continuously operated distillation apparatus uses at least one inlet pipe for feeding feed mixtures, an outlet for the lower-boiling fraction, an outlet for the higher-boiling fraction and a heating device. The distillation apparatus includes at least two condensation stages, each of a different temperature level, the condensation stages upstream in direction of the vapour flow having a higher temperature level than the downstream stages. Separation-effective internals are installed between the condensation stages, partial condensation taking place in the condensation stages, partial amounts that have not condensed in these stages being fed to downstream separation-effective internals or condensation stages of lower temperature level and partial amounts that have condensed are passed via separation-effective internals in direction of the outlet means for the higher-boiling fraction. A basically vaporous fluid is obtained at the condensation stage of the lowest temperature level, where it partially condenses, the uncondensed part of the fluid being fed to the outlet for the lower-boiling fraction and the condensed part being passed to a section of the distillation apparatus which is upstream of the condensation stage having the lowest temperature level. The condensation stage of the lowest temperature level having a temperature of below −40 ° C.

1 - 19 . (canceled) 
     
     
         20 . A process for the separation of a feed mixture obtained from the catalytic dehydrogenation of hydrocarbons, which contains less than 2 mol-% each of carbon dioxide and water or water vapour, into a higher-boiling and a lower-boiling fraction in a continuously operated distillation apparatus comprising at least one inlet pipe for feeding one or more feed mixtures, an outlet means for the lower boiling fraction, an outlet means for the higher boiling fraction and a heating device, comprising:
 providing a distillation apparatus including at least two condensation stages, each of a different temperature level;   setting a higher temperature level in the condensation stages provided upstream in direction of the vapour flow than the downstream condensation stages;   providing separation-effective internals between the condensation stages; wherein   partial condensation takes place in the condensation stages;   partial amounts that have not condensed in these stages are fed to downstream separation-effective internals or condensation stages of lower temperature level and. partial amounts that have condensed are passed via separation-effective internals in direction of the outlet means for the higher-boiling fraction;   a substantially vaporous fluid is obtained at the condensation stage of the lowest temperature level, where it partially condenses;   the uncondensed part of the fluid is fed to the outlet means for the lower-boiling fraction and the condensed part is passed to a section of the distillation apparatus which is upstream of the condensation stage having the lowest temperature level; and   the condensation stage of the lowest temperature level has a temperature of below −40° C.   
     
     
         21 . The process according to  claim 20 , wherein the distillation apparatus comprises three to five successive condensation stages, each having a different temperature level. 
     
     
         22 . The process according to  claim 20 , wherein the condensation stage of the lowest temperature level is operated at a temperature between −120° C. and −70° C. and a pressure of at least 2 MPa absolute. 
     
     
         23 . The process according to  claim 22 , wherein the condensation stage of the lowest temperature level is operated at a temperature between −120° C. and −70° C. and a pressure of at least 3 MPa absolute. 
     
     
         24 . The process according to  claim 20 , wherein the mixture which leaves the distillation system as lower boiling fraction is depressurised, the mixture thereby cooling down by exploitation of the Joule-Thompson effect and thus being used to cool the condensation stage of the lowest temperature level. 
     
     
         25 . The process according to  claim 24 , wherein the depressurisation is performed by an expansion turbine. 
     
     
         26 . The process according to  claim 20 , wherein:
 the feed mixture substantially comprises hydrogen, hydrocarbons of up to two carbon atoms and hydrocarbons of at least three carbon atoms;   at the outlet means for the lower-boiling fraction a mixture is obtained which contains hydrogen and hydrocarbons of up to two carbon atoms and basically no hydrocarbons of at least three carbon atoms; and   at the outlet means for the higher-boiling fraction a mixture is obtained which contains hydrocarbons of at least three carbon atoms and basically neither hydrogen nor hydrocarbons of up to two carbon atoms.   
     
     
         27 . The process according to  claim 20 , wherein the segment of the distillation apparatus, via which that part of the feed mixture condensed in the condensation stage of the highest temperature level is passed to the outlet means for the higher-boiling fraction, is provided as a stripping section of the distillation apparatus. 
     
     
         28 . The process according to  claim 20 , wherein feed mixtures of a small content of components of low boiling point are preferably fed at a point below the condensation stage of the highest temperature level. 
     
     
         29 . The process according to  claim 20 , wherein feed mixtures of a high content of components of low boiling point are preferably fed at a point above the condensation stage of the highest temperature level. 
     
     
         30 . The process according to  claim 20 , wherein the condensation stages are provided in the form of condensers. 
     
     
         31 . The process according to  claim 20 , wherein the condensation stages are cooled by cooling water, ammonia, propane, propene and/or by exploitation of the Joule-Thompson effect when depressurizing the mixture leaving the distillation system as a lower-boiling fraction. 
     
     
         32 . The process according to  claim 20 , wherein one or more heating devices are operated by external waste heat. 
     
     
         33 . Distillation apparatus to operate a process according to  claim 20 , comprising:
 a) one or more inlet pipes for feeding one or more feed mixtures;   b) an outlet means for the lower-boiling fraction;   c) an outlet means for the higher-boiling fraction;   d) at least one heating device;   e) at least two successive condensers; and   f) separation-effective internals installed between the condensers; wherein the distillation apparatus comprises a cascade of several distillation columns, in   which condensers are provided between the distillation columns.