CONVERSION OF CO2 TO CHEMICAL ENERGY CARRIERS AND PRODUCTS

Abstract

The present invention relates to methods for the conversion of CO.sub.2 to chemical energy carriers and products, in particular via a methanation of the gas phase fraction from a Fischer-Tropsch synthesis.

Claims

1.-10. (canceled)

11. A method for converting CO.sub.2 into chemical energy carriers and products, wherein the method comprises or consists of: (a) provision of a synthesis gas comprising H.sub.2, CO and CO.sub.2, the synthesis gas having a CO.sub.2 content of at least 5 vol. %, (b) feeding the synthesis gas to a Fischer-Tropsch synthesis, and converting the synthesis gas to a Fischer-Tropsch synthesis product comprising at least the following fractions: (i) a fuel fraction, (ii) a wax fraction, (iii) a gaseous by-product phase, (iv) an aqueous phase, (c1) optionally, hydrogenation of the Fischer-Tropsch synthesis product obtained in (b) with addition of hydrogen, (c2) multi-stage separation of the Fischer-Tropsch synthesis product obtained in (b) or of the product obtained in (c1), and separation of fractions (i), (ii) and (iv), (d) methanation of the gaseous by-products in fraction (iii) with addition of H.sub.2, (e) optionally, further processing of fractions (i), (ii), (iv).

12. The method of claim 11, wherein (c1) is carried out.

13. The method of claim 11, wherein (e) is carried out.

14. The method of claim 11, wherein product obtained in (d) is fed directly into a natural gas network.

15. The method of claim 11, wherein the synthesis gas has been formed by a high-temperature co-electrolysis of H.sub.2O and CO.sub.2.

16. The method of claim 11, wherein the synthesis gas is processed by a CO.sub.2 activation by H.sub.2 from an H.sub.2O electrolysis via a reverse water gas shift (RWGS) reaction.

17. The method of claim 11, wherein water produced during the methanation in (d) is condensed out and separated.

18. An installation for the conversion of CO.sub.2, wherein the installation comprises or consists of the following components: (A) a device configured for providing synthesis gas containing CO.sub.2, (B) a Fischer-Tropsch synthesis device, (C1) optionally, a hydrogenation device, (C2) a multi-stage separation device, (D) a methanation device, (E) optionally, a device for introducing methanation product into a natural gas network, the components being in operative connection with one another.

19. The installation of claim 18, wherein (C1) is present.

20. The installation of claim 18, wherein (E) is present.

21. The installation of claim 18, wherein (C2) is present in the form of several individual separation devices arranged one after the other.

22. The installation of claim 18, wherein (C2) comprises a device configured for discharging and transferring a gaseous product fraction into device (D).

23. The installation of claim 18, wherein device (A) is a high temperature co-electrolysis device configured for high temperature co-electrolysis of H.sub.2O and CO.sub.2.

24. The installation of claim 18, wherein device (B) is a microstructure reactor for carrying out an exothermic reaction between two or more reactants, wherein reactants are passed in the form of fluids over one or more catalyst(s), comprising at least one stack sequence of (a) at least one layer comprising one or more catalyst(s) for carrying out at least one exothermic reaction, (b) at least one layer subdivided into two or more cooling fields, (c) at least one layer having distribution structures with lines for distributing coolant, with connections for supplying coolant to the lines of the distribution structure and for connection to the cooling fields, connections for discharging heated coolant from the cooling fields, and lines and connections for discharging heated coolant from the stack sequence.

25. The installation of claim 18, wherein devices (C1) and (C2) are separation devices.

26. The installation of claim 18, wherein devices (C1) and (C2) are distillation devices.

27. The installation of claim 18, wherein device (D) is (D1) a methanation reactor comprising a water separation device.

28. The installation of claim 27, wherein the water separation device is a device for condensation and phase separation or a distillation device.

29. The installation of claim 18, wherein device (D) is (D2) a methanation reactor and a downstream water separation device.

30. The installation of claim 29, wherein the water separation device is a device for condensation and phase separation or a distillation device.

Description

DESCRIPTION OF THE FIGURES

[0085] The present invention is explained in more detail below with reference to the drawings. The drawings are not to be construed as limiting and are not to scale.

[0086] Furthermore, the drawings do not contain all the features that are present in conventional plants, but are reduced to the features that are essential for the present invention and its understanding.

[0087] FIG. 1 shows an example of a method as it corresponds to a variant of the present invention. Synthesis gas 1 comprising H.sub.2, CO and CO.sub.2 is introduced into a Fischer-Tropsch reactor D. Pressurised water 5 is also introduced into this Fischer-Tropsch reactor D and pressurised steam 6 is led off by indirect heat exchange from the reactor. This steam 6 can be used for energy recovery, in particular via heat exchangers or turbines, or also to supply heat for reactions (neither of which is shown in the figure). The resulting FT product (comprising four fractions) is then led via a first heat exchanger WT to a first separation device A, where the wax fraction ii) is separated as bottoms. The remaining fractions leave the unit A overhead and are led via a second heat exchanger WT to a second separation device B, where the fuel fraction (oil phase) i) and the aqueous phase iv) are separated as bottoms. The gaseous by-products iii) are discharged overhead. Hydrogen 2 is then optionally added to this phase iii) and the mixture is fed into a methanation reactor E via a third heat exchanger WT. Pressurized water 5 is also introduced into this methanation reactor E and by pressurized steam 6 is led off indirect heat exchange from the methanation reactor E. The product is discharged from the methanation reactor E and passed via a fourth heat exchanger WT to a third separation device C, where the water 3 produced during methanation is condensed out and discharged and the remaining product gas 4 is discharged as synthetic gas capable of being fed into a natural gas network. The latter can then be fed-in into a natural gas network (not shown in the figure).

[0088] FIG. 2 shows in principle the same structure and procedure as FIG. 1. The only difference being that the FT product coming from the FT reactor D is fed with addition of hydrogen 2 via a heat exchanger WT into a hydrocracking reactor F, where the FT product is subjected to hydrogenation cracking so that, compared to FIG. 1, a lower content of wax fraction ii) and a higher content of fuel fraction i) are obtained before the first separation takes place. Subsequently, the transfer to a first separation device A and the same procedure as in FIG. 1 take place. The gas fractions are similar in both cases.

LIST OF REFERENCE SIGNS

[0089] 1 synthesis gas [0090] 2 hydrogen [0091] 3 condensed water [0092] 4 product gas (as synthetic gas that can be fed into a natural gas network) [0093] 5 pressurised water [0094] 6 pressurised water vapour [0095] i) fuel fraction [0096] ii) wax fraction [0097] iii) gaseous by-product phase [0098] iv) aqueous phase [0099] A first separation device [0100] B second separation device [0101] C third separation device [0102] D FT reactor [0103] E methanation reactor [0104] F hydrocracking reactor [0105] WT heat exchanger

EXAMPLES

[0106] The invention will now be further explained with reference to the following non-limiting examples.

Example 1

[0107] A gas stream of 100 kg/h originating from a high temperature co-electrolysis with a composition of about 30 vol. % carbon monoxide, 64 vol. % H.sub.2 (H.sub.2/CO=2.2) and 6 vol. % CO.sub.2 was converted with a CO conversion of 70% in a microstructured FT synthesis reactor at 20 barO. As a value product, only 19.9 kg/h FT product (sum of oil and wax) were obtained and 30.5 kg/h water (by-product of the synthesis). This meant that about 50% of the entering mass flow was not usable and would have had to be recycled at great expense in terms of energy. The composition of the gas was as follows in vol. %:

TABLE-US-00001 16.57 CO.sub.2 25.33 CO 0.07 H.sub.2O 50.10 H.sub.2 6.26 CH.sub.4 0.33 C2 0.59 C3 0.42 C4 0.21 C5 0.08 C6 0.02 C7 0.01 C8

[0108] By downstream addition of a single methanation reactor, the outlet temperature of which was set to 350° C., an almost complete conversion of the off-gas from the hydrocracking stage could be achieved by additional addition of further merely about 5.3 kg/h hydrogen. The composition of the product gas after methanation in vol. % was:

TABLE-US-00002 CO 0.01 CO.sub.2 2.64 H.sub.2 6.35 H.sub.2O 0.06 CH.sub.4 85.84 C2 0.79 C3 1.83 C4 1.32 C5 0.78 C6 0.35 C7 0.08 C8 0.02

[0109] (C2 to C8 represent the sum of the hydrocarbons with the corresponding carbon number).

[0110] Despite the content of residual CO.sub.2 and residual H.sub.2, this composition could be fed directly as synthetic natural gas with 0.282 kg/h, since the Wobbe index in this composition was about 53 MJ/m.sup.3 or 15.3 kWh/m.sup.3. During methane formation, another 0.289 kg/h of water was formed, which was condensed out. The gas quality was very good.

[0111] In an arrangement according to FIG. 1, method data were determined as follows:

TABLE-US-00003 Stream Type Flow Rate [kg/h] synthesis gas 1 feed 100 hydrogen 2 feed 5.4 fuel fraction ii) product 13.1 product gas 4 product 25.8 wax fraction ii) product 6.6 aqueous phase iv) by-product 30.5 water 3 by-product 29.4

[0112] The operating parameters were as follows:

TABLE-US-00004 Inlet Inlet Outlet Pressure Temperature Temperature Installation Part [bar.sub.a] [° C.] [° C.] FT reactor D 21 220 235 methanation reactor E 20 275 350 separation device A 20 200 200 separation device B 20 10 10 separation device C 19 10 10

[0113] In this example, no treatment of the FT product was carried out (no hydrogenating cracking), but the FT product went directly into a multi-stage separation from which the four fractions were obtained. The product gas had a Wobbe index of 53 MJ/m.sup.3, as already mentioned.

Example 2

[0114] This example is largely identical to example 1, only slightly different compositions of the feed into the methanation result from the hydrocracking (that is reactor F in FIG. 2).

[0115] With identical educt gas composition, the FT product was post-treated by direct subsequent hydrocracking so that the wax fraction was finally less than 5 wt. % of the product yield (17.6 kg/h oil, 1.5 kg/h wax). An off-gas composition from the FT synthesis in vol. % was obtained as follows:

TABLE-US-00005 13.77 CO.sub.2 21.15 CO 0.07 H.sub.2O 58.36 H.sub.2 5.23 CH.sub.4 0.27 C2 0.56 C3 0.34 C4 0.17 C5 0.06 C6 0.02 C7 0.00 C8

[0116] In an arrangement according to FIG. 2, a conversion was carried out with the following characteristics:

TABLE-US-00006 Stream Type Flow Rate [kg/h] synthesis gas 1 feed 100 hydrogen 2 feed 5.4 fuel fraction ii) product 17.6 product gas 4 product 26.3 wax fraction ii) product 1.5 aqueous phase iv) by-product 30.5 water 3 by-product 29.4

[0117] The operating parameters were as follows:

TABLE-US-00007 Inlet Inlet Outlet Pressure Temperature Temperature Installation Part [bar.sub.a] [° C.] [° C.] FT reactor D 21 220 235 hydrocracking reactor F 20 255 255 methanation reactor E 19 275 350 separation device A 20 200 200 separation device B 20 10 10 separation device C 19 10 10

[0118] In this example, the FT product first went into hydrogenating cracking and only then into a multi-stage separation, from which again the four fractions were obtained. The product gas also had a Wobbe index of 53 MJ/m.sup.3.

[0119] The product gas of the methanation had the following composition in vol. %:

TABLE-US-00008 CO.sub.2 1.80 CO 0.01 H.sub.2O 0.06 H.sub.2 7.22 CH.sub.4 87.79 C2 0.61 C3 1.25 C4 0.77 C5 0.37 C6 0.13

[0120] In Example 1, more waxes were obtained compared to Example 2.

[0121] In Example 2, on the other hand, the yield of fuels was maximized and only little wax was obtained compared to Example 1.

[0122] In both Examples 1 and 2, a product gas suitable for feed-in was obtained.

[0123] Thus, in both Examples a high carbon yield is obtained without recirculation.