Process and plant for separatory processing of a starting mixture

Abstract

The present invention relates to a process (100) for separatory processing of a starting mixture containing predominantly hydrogen, methane and hydrocarbons having two or two or more carbon atoms, wherein at least a portion of the starting mixture is cooled to form one or more condensates using one or more heat exchangers (101, 103, 105, 107) and at least a portion of the condensate(s) is subjected to a rectification to form a gaseous methane-rich fraction. It is provided that the gaseous methane-rich fraction is used to form a first fluid stream which is at least partly compressed, in an unchanged composition with respect to the gaseous methane-rich fraction, to a liquefaction pressure level of 35 to 45 bar, and at least partly liquefied by cooling, and in that the first fluid stream, or a second fluid stream formed using the first fluid stream, is expanded to a delivery pressure and heated in the or at least one of the heat exchanger(s) (101, 103, 105, 107). A corresponding plant likewise forms part of the subject matter of the invention.

Claims

1. Process (100) for separatory processing of a starting mixture containing predominantly hydrogen, methane and hydrocarbons having two or two or more carbon atoms, wherein at least a portion of the starting mixture is cooled to form one or more condensates using one or more heat exchangers (101, 103, 105, 107) and at least a portion of the condensate(s) is subjected to a rectification to form a gaseous methane-rich fraction, characterized in that the methane-rich fraction is used to form a first fluid stream which is at least partly compressed, in an unchanged composition with respect to the gaseous methane-rich fraction, to a liquefaction pressure level of 35 to 45 bar, is at least partly liquefied by cooling, and is expanded to a delivery pressure level, and in that the first fluid stream, or a second fluid stream formed using the first fluid stream, is heated in the or at least one of the heat exchanger(s) (101, 103, 105, 107).

2. Process (100) according to claim 1, wherein the gaseous methane-rich fraction is formed at a temperature level of 95 C. to 100 C.

3. Process (100) according to claim 1, wherein the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) comprises the transferring of heat to the compressed and at least partially liquefied methane-rich fraction or the portion thereof.

4. Process (100) according to claim 1, wherein the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) is performed at a cooling pressure level below the liquefaction pressure level of the methane-rich fraction.

5. Process (100) according to claim 4, wherein the cooling is performed at a cooling pressure level of 25 to 40 bar and wherein the rectification is performed at a rectification pressure level 0.2 to 4 bar below the cooling pressure level.

6. Process (100) according to claim 5, wherein a hydrogen-rich fraction remaining in gaseous form in the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) is likewise heated in the or at least one of the heat exchanger(s).

7. Process (100) according to claim 6, wherein the hydrogen-rich fraction or the portion thereof is heated at the cooling pressure level.

8. Process according to claim 1, wherein the rectification affords a liquid, methane-rich fraction which is at least partly heated in the heat exchanger(s) (101, 103, 105, 107) together with the compressed and at least partly liquefied methane-rich fraction or the portion thereof.

9. Process according to claim 1, wherein the cooling is performed using a first heat exchanger (101), a second heat exchanger (103), a third heat exchanger (105) and a fourth heat exchanger (107).

10. Process according to claim 9, which comprises operating the first heat exchanger (101) using an ethylene-rich refrigerant at 50 C. to 60 C., the second heat exchanger (103) using an ethylene-rich refrigerant at 75 C. to 85 C. and the third heat exchanger (105) using an ethylene-rich refrigerant at 95 C. to 105 C.

11. Process according to claim 9, wherein the starting mixture or the portion thereof is passed consecutively through the first, the second, the third and the fourth heat exchanger (101, 103, 105, 107), a respective condensate being separated downstream of each heat exchanger.

12. Process according to claim 11, wherein fractions of a fraction that remains in gaseous form after cooling in the third heat exchanger (105) and has previously been cooled in the fourth heat exchanger (107) are heated using the fourth heat exchanger (107).

13. Process according to any of claims 9 to 12, wherein the methane-rich fraction or the portion thereof is consecutively heated in the third heat exchanger (105), passed through a further heat exchanger (115), compressed to the liquefaction pressure level, passed through the further heat exchanger (115) and cooled in the third and fourth heat exchanger (105, 107).

14. Plant for separatory processing of a starting mixture containing predominantly hydrogen, methane and hydrocarbons having two or two or more carbon atoms, comprising means for cooling at least a portion of the starting mixture to form one or more condensates using one or more heat exchangers (101, 103, 105, 107) and for subjecting at least a portion of the condensate(s) to a rectification to form a gaseous methane-rich fraction characterized by means which are adapted to use the gaseous methane-rich fraction to form a first fluid stream, by means by which are adapted to compress the first fluid stream at least partly to a liquefaction pressure level of 35 to 40 bar, to at least partly liquefy it by cooling, and to expand it to a delivery pressure level, and by means which are adapted to heat the first fluid stream, or a second fluid stream formed using the first fluid stream, in the or at least one of the heat exchanger(s) (101, 103, 105, 107).

15. Process (100) according to claim 2, wherein the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) comprises the transferring of heat to the compressed and at least partially liquefied methane-rich fraction or the portion thereof.

16. Process (100) according to claim 2, wherein the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) is performed at a cooling pressure level below the liquefaction pressure level of the methane-rich fraction.

17. Process (100) according to claim 3, wherein the cooling of the starting mixture or of the portion thereof in the heat exchanger(s) (101, 103, 105, 107) is performed at a cooling pressure level below the liquefaction pressure level of the methane-rich fraction.

18. Process according to claim 2, wherein the rectification affords a liquid, methane-rich fraction which is at least partly heated in the heat exchanger(s) (101, 103, 105, 107) together with the compressed and at least partly liquefied methane-rich fraction or the portion thereof.

19. Process according to claim 3, wherein the rectification affords a liquid, methane-rich fraction which is at least partly heated in the heat exchanger(s) (101, 103, 105, 107) together with the compressed and at least partly liquefied methane-rich fraction or the portion thereof.

20. Process according to claim 4, wherein the rectification affords a liquid, methane-rich fraction which is at least partly heated in the heat exchanger(s) (101, 103, 105, 107) together with the compressed and at least partly liquefied methane-rich fraction or the portion thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] FIG. 1 shows a non-inventive process in the form of a schematic process flow diagram.

[0044] FIG. 2 shows a process according to one embodiment of the invention in the form of a schematic process flow diagram.

DETAILED DESCRIPTION OF THE DRAWINGS

[0045] In the figures that follow, mutually corresponding elements bear corresponding reference numerals and for the sake of simplicity are not repeatedly elucidated.

[0046] FIG. 1 illustrates a non-inventive process for separatory processing of a starting mixture containing predominantly hydrogen, methane and hydrocarbons having two carbon atoms in the form of a schematic process flow diagram to illustrate the background to the present invention. The process is employed in particular for separatory processing of a starting mixture formed from a crude gas from a steam cracking process where predominantly or exclusively liquid inputs, for example naphtha, are processed.

[0047] It is expressly emphasized that FIG. 1 serves merely to illustrate the principles of the present invention and it is quite possible to deviate from the specific configuration of the depicted apparatuses shown here without providing a fundamentally different separation process.

[0048] The starting mixture or a portion thereof in the form of the material stream A is initially passed through a first heat exchanger 101 and cooled inter alia using a material stream B which may be for example ethylene at a temperature level of about 57 C.

[0049] The material stream A is transferred into a first separation vessel 102 from which a liquid material stream C and a gaseous material stream D are withdrawn. The gaseous material stream D is passed through a second heat exchanger 103 and here cooled further inter alia with a material stream E which may be ethylene at a temperature level of about 80 C.

[0050] The material stream D is transferred into a further separation vessel 104 from which a liquid material stream F and a gaseous material stream G are withdrawn. The material stream G is passed through a third heat exchanger 105 and there cooled inter alia with a material stream H which may be ethylene at a temperature level of about 100 C.

[0051] The material stream G is subsequently transferred into an absorption column 106 which is operated with a methane-rich liquid material stream I as reflux. A liquid material stream K is withdrawn from the bottom of the absorption column 106 and, in the example shown, heated in the heat exchanger 105.

[0052] A gaseous material stream L from the top of the absorption column 106 is cooled further in a heat exchanger 107 and subsequently transferred into a further separation vessel 108, the so-called hydrogen separator. A liquid methane-rich material stream M and a gaseous hydrogen-rich material stream N are withdrawn from the separation vessel 108. The material stream M is expanded to a lower pressure level; the material stream N remains at the higher pressure level at which it is withdrawn from the separation vessel 108. Both material streams are heated in the heat exchangers 107, 105, 103 and 101 and provided as the methane-rich product fraction and the hydrogen-rich product fraction respectively.

[0053] The abovementioned liquid material streams C, F and K are transferred into a rectification column 109, the introduction thereof being effected at different heights depending on composition and temperature. The rectification column 109 is operated with a bottoms evaporator 110 using a typical C3 refrigerant. A gaseous material stream O is withdrawn from the top of the rectification column 109 and supplied to a tops condenser having the overall designation 111. The tops condenser 111 comprises a heat exchanger 112 which may be operated with ethylene at a temperature level of about 100 C. as the refrigerant. Obtained in a separation vessel 113 arranged downstream of the heat exchanger 112 a liquid material stream P, one portion of which is applied as reflux to the rectification column 109 and one portion of which is applied as reflux to the absorption column 106 in the form of material stream I. A non-liquefied proportion of the material stream O is withdrawn from the separation vessel 113 in the form of the material stream Q and as a methane-rich material stream combined with the material stream M.

[0054] The process illustrated in FIG. 1 thus initially forms a liquid, methane-rich fraction in the form of the bottoms liquid from the separation vessel 108, which is subsequently provided in the form of the material stream M, and a gaseous methane-rich fraction in the form of the tops gas from the separation vessel 113, which is subsequently provided in the form of the material stream Q.

[0055] The elucidated operation of the rectification column 109 makes it possible to withdraw from the bottom thereof a liquid material stream R which is rich in hydrocarbons having two carbon atoms. In the example shown said stream is heated in the heat exchanger 101 and subsequently for example subjected to a separation to obtain ethane and ethylene in a so-called C2 splitter.

[0056] As previously elucidated, separately obtaining a hydrogen-rich fraction at a high pressure level becomes increasingly difficult the higher the hydrogen proportion relative to the methane proportion in a corresponding starting mixture, since the heat exchanger 107 is cooled exclusively with product streams and the heat balance around the heat exchanger 107 becomes increasingly unfavourable the higher the hydrogen proportion relative to the methane proportion in a corresponding input mixture.

[0057] Illustrated in FIG. 2 in the form of a schematic process flow diagram and designated 100 is a process for separatory processing of such a starting mixture according to one embodiment of the invention. The process 100 is employed in particular for separatory processing of a starting mixture formed from a crude gas from a steam cracking process where a mixed input, as elucidated hereinabove, is processed.

[0058] Here too, the starting mixture or a portion thereof in the form of a material stream A is initially passed through a first heat exchanger 101 and cooled inter alia using a material stream B which may be for example ethylene at a temperature level of about 57 C.

[0059] Here too, the material stream A is transferred into a first separation vessel 102 from which a liquid material stream C and a gaseous material stream D are withdrawn. Here too, the gaseous material stream is passed through a second heat exchanger 103 and here cooled further inter alia with a material stream E which may be ethylene at a temperature level of about 80 C.

[0060] Here too, the material stream D is transferred into a further separation vessel 104 from which a liquid material stream F and a gaseous material stream G are withdrawn. Here too, the material stream G is passed through a third heat exchanger 105 and there cooled inter alia with a material stream H which may be ethylene at a temperature level of about 100 C.

[0061] However, in contrast to the process illustrated in FIG. 1, the material stream G is now transferred not into an absorption column 106 but rather into a further separation vessel 116, from which a liquid material stream K and a gaseous material stream L are withdrawn. The material stream L is cooled further in a heat exchanger 107 and subsequently transferred into a further separation vessel 108 which here too constitutes a hydrogen separator.

[0062] Here too, a liquid methane-rich material stream M and a gaseous hydrogen-rich material stream N are withdrawn from the separation vessel 108. The material stream M, the amount of which is limited by a valve not separately designated here, is heated in the heat exchanger 107. In the example shown only the material stream N is consecutively heated in the heat exchangers 107, 105, 103 and 101 at the cooling pressure level and provided as a hydrogen-rich product fraction.

[0063] The abovementioned liquid material streams C, F and K and also the material stream M are transferred into a rectification column 109 under limitation of valves not separately designated here, the introduction of said streams being effected at different heights depending on composition and temperature. Here too, the rectification column 109 is operated with a bottoms evaporator 110 using a typical C3 refrigerant. As before, a gaseous material stream O is withdrawn from the top of the rectification column 109 and supplied to a tops condenser having the overall designation 111. However, the tops condenser 111 is here integrated into the rectification column 109. Said tops condenser comprises a heat exchanger 112 which may be operated with ethylene at a temperature level of about 100 C. as the refrigerant. Accumulating in a separation vessel 113 connected downstream of the heat exchanger 112 but here likewise integrated into the rectification column 109 is a liquid fraction which is here applied to the rectification column 109 without a pump but rather via an overflow. Since there is no absorption column present, no reflux is required therefor. Thus after expansion a liquid material stream I is supplied to a heating in the heat exchangers 107, 105, 103 and 101 and discharged from the process 100.

[0064] Here too, a non-liquefied proportion of the material stream O is withdrawn from the separation vessel 113 in the form of the material stream Q but now is initially heated into the heat exchanger 105, subsequently passed through a further heat exchanger 115 and compressed in a booster 117. Subsequently, the material stream Q is again passed through the heat exchangers 117, 105 and 107, expanded, combined with the material stream I and finally heated in the heat exchangers 107, 105, 103 and 101 and discharged from the process 100.

[0065] Here too, the elucidated operation of the rectification column 109 makes it possible to withdraw from the bottom thereof a liquid material stream R which is rich in hydrocarbons having two carbon atoms. In the process 100 too, said stream is for example subjected to a separation to obtain ethane and ethylene in a so-called C2 splitter.