METHOD AND APPARATUS FOR SEPARATION OF 13C16O FROM NATURAL CO

Abstract

Method and Apparatus for separating at least one CO isotope compound, especially isotope compound 13C16O, from natural CO, comprising: a rectification column system (110) comprising a plurality of rectification sections (112,114,116,118,120) arranged adjacent to one another in a chain-like manner, including an upper rectification section (112) and a plurality of lower rectification sections (114,116,118,120), each rectification section comprising a heating means (112a,114a,116a,118a,120a) to maintain evaporation of liquid present therein, provided that the heating means (112a) of the at least one of the plurality of rectification sections (112) is provided to comprise a heat pump cycle (112b).

Claims

1. Method for separating at least one CO isotope compound, especially isotope compound 13C16O, from natural CO, comprising: operating a rectification column system (110), comprising a plurality of rectification sections (112,114,116,118,120) arranged adjacent to one another in a chain-like manner, including an upper rectification section and a plurality of lower rectification sections, wherein maintaining evaporation of liquid present in the rectification column is achieved by heating the liquid by heating means provided in each rectification section, wherein the heating of at least one of the plurality of rectification sections is provided by heating means comprising a heat pump cycle (112b), wherein preferably the heating at the least one further one of the plurality of rectification sections is provided by means comprising an electrical heater.

2. Method according to claim 1, wherein the heating in the upper rectification section is provided to utilize a heat pump cycle connecting a reboiler (132) of the upper rectification section (112) and a condenser (122) associated with upper rectification section (112).

3. Method according to claim 1, wherein pressures within the rectification column system range from 0.5 bar abs in the upper rectification section to around 3 bar abs in a lowermost rectification section.

4. Method according to claim 1, wherein temperatures within the rectification column system range from 77K in the upper rectification section to around 95 K in a lowermost rectification section.

5. Method according to claim 1, wherein the liquefied working fluid of the heat pump cycle is supplied to the condenser (122) using at least one pump (210,220).

6. Method according to claim 1, wherein the working fluid of the heat pump cycle is nitrogen.

7. Method according to claim 1, wherein the working fluid of the heat pump cycle is the CO.

8. Apparatus for separating at least one CO isotope compound, especially isotope compound 13C16O, from natural CO, comprising: a rectification column system (110) comprising a plurality of rectification sections (112,114,116,118,120) arranged adjacent to one another in a chain-like manner, including an upper rectification section (112) and a plurality of lower rectification sections (114,116,118,120), each rectification section comprising a heating means (112a,114a,116a,118a,120a) to maintain evaporation of liquid present therein, wherein the heating means (112a) of at least one of the plurality of rectification sections (112) comprises an external heat pump cycle (112b).

9. Apparatus according to claim 8, wherein the heating means (112a) of the upper rectification section (112) comprises a heat pump cycle (112b) connecting a reboiler (132) of the upper rectification section (112) and a condenser (122) associated with upper rectification section (112).

10. Apparatus according to claim 8, wherein at least one of the plurality of lower rectification sections (114,116,118,120) comprises an electric heating means.

11. Apparatus according to claim 8, wherein rectification sections provided with heating means comprising a heat pump cycle (112b) are arranged overground, and rectification sections not provided with heating means comprising a heat pump cycle are arranged underground.

12. Apparatus according to claim 8, wherein the heat pump cycle (112b) comprises a compressor unit (130) adapted to compress gaseous nitrogen, an inlet pressure of the compressor unit (130) being around 0.5 to 1.5 bar abs, and an outlet pressure of the compressor unit being larger than 1.5 bar abs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention will now be further described with reference to the accompanying drawings. Herein,

[0041] FIG. 1 shows a first preferred embodiment of a process and apparatus according to the invention,

[0042] FIG. 2 shows a second preferred embodiment of a process and apparatus according to the invention and

[0043] FIG. 3 shows a third preferred embodiment of a process and apparatus according to the invention.

DETAILED DESCRIPTION

[0044] An apparatus according to a first preferred embodiment of the invention is generally designated 100. Apparatus 100 comprises a rectification column system 110 comprising an upper rectification section 112 and a plurality of lower rectification sections 114, 116, 118, 120. Rectification section 120 is referred to as the lowermost rectification section in the following. Each rectification section is provided with at least one packing, only one of which, designated 113, is provided with a reference numeral.

[0045] As indicated by line 102, rectification section 112 is arranged above-the-ground, while the further rectification sections 114 to 120 are arranged underground, i.e. below ground level. Such an arrangement provides stability for a rectification column system as a whole.

[0046] Each rectification section comprises a heating means, the upper section comprises a condenser for condensation purposes, as will be explained in the following.

[0047] Each of the lower rectification sections, in the embodiments as shown each of the underground rectification sections, is provided with electric heating means 114a, 116a, 118a, 120a. Electric heaters require little maintenance, so that an arrangement underground is feasible and reliable.

[0048] The heating means of upper rectification section 112 are generally designated 112a. They comprise a heat pump cycle, as will be explained in the following.

[0049] The heat pump cycle, which is referenced as 112b in the following, serves to provide a closed nitrogen cycle, and comprises a compression or compresser unit 130 comprising compressers and aftercoolers, a reboiler (also referred to as first heat exchanger) 132 arranged within the upper rectification section 112, and a main counter current heat exchanger (also referred to as second heat exchanger) 134. Heat pump cycle 112b connects reboiler 132, and a condenser 122 (also referred to as third heat exchanger) associated with the upper rectification section, and provided in the upper part or above the upper rectification section 112.

[0050] The rectification column system 110 serves to separate the fraction containing the lighter isotope C12O16 from the fraction containing heavier isotope C13O16 from a feed of natural CO. To achieve this, a natural, gaseous CO-feed which contains roughly 1% of 13C16O, is introduced into the upper rectification section 112 via feed line 111. Be it noted that in this description, arrows indicated with contours only or as white triangles, such as in feed line 111, designate gaseous flows, while arrows indicated as filled out or black triangles, such as for example line 132a as mentioned below, designate liquid flow through respective flow lines or channels.

[0051] The rectification column system as shown serves to separate this CO feed into one distillate fraction, i.e. C12O16-reach fraction, exiting the rectification column system 110 in the head portion of upper rectification column 112 via line 112c, and one bottoms fraction, i.e. C13O16-reach fraction, exiting the rectification column system through lines 123a (in vapour form) and 123b (in liquid form), these lines being provided in the lowermost rectification section 120.

[0052] The rectification column system requires a reflux for operation. Such reflux is achieved by means of condenser 122 provided above the upper rectification section 112, by means of which at least a portion of the condensed overhead liquid product is returned to the upper part of the rectification column system.

[0053] Inside the rectification column system, the down-flowing reflux liquid provides cooling and condensation of up-flowing vapours, thereby increasing the efficiency of the system, as is well known in the art.

[0054] Typically, structured packing is provided in each of the rectification sections 112,114,116,118,120, one of which is designated with reference numeral 117. This packing provides good physical contact between the up-flowing vapour and the down-flowing liquid.

[0055] Liquid nitrogen LIN from a liquid nitrogen source 124 is introduced into the condenser 122 via line 124a, where it interacts in a heat exchanging manner with C12O16-enriched vapor entering the condenser 122 via line 122a, i.e. the distillation fraction which is to be isolated and extracted in the upper rectification section 112. After this interaction, condensed, i.e. liquid C12O16-reach re-enters condenser 122 via line 122b.

[0056] As already mentioned, a part of the C12O16-reach fraction exits the upper rectification section 112 in vaporous form via line 112c. A further part of vaporous C12O16-reach, as also outlined above, enters condenser 122, where it condenses due to heat exchanging interaction with liquid nitrogen. Hereby, liquid nitrogen is heated and, as gaseous nitrogen GAN, fed to the main counter current heat exchanger 134, where, flowing through line 122b, it is heated against itself. Be it noted that part of the gaseous nitrogen can also released from the system to the surroundings of the system via line 155.

[0057] After exiting main counter current heat exchanger 134, the gaseous nitrogen passes through compressor unit 130 and returns through main counter current heat exchanger 134, from where it is fed into reboiler 132, still as gaseous nitrogen. Expediently, for redundancy purposes, compresser unit is provided with two separate and independently operable compressers, each provided with an aftercooler, as shown in FIG. 1.

[0058] Reboiler 132 serves as an evaporator within the first or upper rectification section 112. The nitrogen passed into reboiler 132 as gaseous nitrogen exits the reboiler as liquid nitrogen and, via a line 132a, is throttled through a throttle or expansion valve 132b, and re enters condenser 122 in liquefied form.

[0059] For typical processes, a heating system comprising reboiler 132 as evaporator for the upper rectification section 112 can provide at least 50% of the total evaporation power required in the rectification column system as a whole.

[0060] For the compressor unit 130, inlet pressures typically range from 0.5 to 1.5 bar abs, while outlet pressures are typically above 1.5 bar abs.

[0061] FIG. 2 shows a second preferred embodiment of a rectification column system according to the invention. Herein, components corresponding to those used in the first embodiment shown in FIG. 1 are provided with the same reference numerals.

[0062] In this embodiment, two redundant pumps 210, 220 are provided for pumping liquefied nitrogen LIN from a liquid nitrogen source 224 and liquid nitrogen exiting reboiler 132 to condenser 122 via line 132a. Advantageously, a phase separator 240 is provided downstream of the pumps 210,220 to prevent any gaseous nitrogen from entering line 132a. Again, by means of throttle 122b, this liquefied nitrogen pumped by pumps 210,220 is further cooled by means of throttling (expansion or throttle valve 122b) before entering condenser 122. As opposed to the first embodiment shown in FIG. 1, in which liquid nitrogen can be introduced directly into condenser 122, in the embodiment according to FIG. 2 it is introduced downstream of pumps 210, 220, as mentioned from source 224.

[0063] Any remaining evaporated gaseous nitrogen can be removed by phase separator 240 after passing through the reboiler 132, as shown. Such a phase separator could also be arranged upstream of the reboiler 132.

[0064] In a further embodiment of the rectification column system according to the invention, shown in FIG. 3, like components are again shown with the same reference numerals.

[0065] In this embodiment, the upper rectification section 112 and an adjacent lower rectification section 114 are heated by means of heating means 112a comprising a heat pump cycle 112b. Herein, gaseous nitrogen exiting main counter current heat exchanger 134 is introduced into reboiler 132 provided in upper rectification section 112, and a further heat exchanger or reboiler 136 provided in the lower rectification section 114 arranged below the first or upper rectification section 112.

[0066] By thus heating two reboilers 132, 136, by means of this heat pump cycle, typically at least two-thirds of the heat demand of the rectification column system can be provided.

[0067] The rectification column system shown in FIG. 3 can be provided with pumps 210, 220 for pumping liquid nitrogen into condenser 122, as shown, in a corresponding manner to the embodiment of FIG. 2, or without such pumps, corresponding to the embodiment of FIG. 1. Again, a phase separator 240 is advantageously provided upstream of pumps 210,220, in order to effectively capture any gaseous nitrogen exiting reboiler 132 or reboiler 136 via lines 132b and 136b respectively.