METHOD FOR THE PREPARATION OF SYNTHESIS GAS

Abstract

Method for the preparation of synthesis gas combining electrolysis of carbon dioxide, autothermal reforming and 5 optionally tubular steam reforming of a hydrocarbon feed stock.

Claims

1. Method for the preparation of synthesis gas comprising the steps of (a) providing a hydrocarbon feed stock; (b) preparing a separate carbon monoxide containing stream and a separate oxygen containing stream by electrolysis of carbon dioxide; (c) optionally tubular steam reforming at least a part of the hydrocarbon feed stock from step (a) to a tubular steam reformed gas upstream step (c); (d) autothermal reforming in an autothermal reformer the hydrocarbon feed stock or the optionally tubular steam reformed gas with at least a part of the oxygen containing stream obtained by the electrolysis of carbon dioxide in step (b) to an autothermal reformed gas stream comprising hydrogen, carbon monoxide and carbon dioxide; (e) introducing at least part of the separate oxygen containing stream from step (b) into the autothermal reformer (f) introducing at least part of the separate carbon monoxide containing stream from step (b) into the autothermal reformed gas stream from step (d); and (g) withdrawing the synthesis gas.

2. The method of claim 1, wherein the H2/CO ratio is less than 2.

3. The method of claim 1, comprising the further step of heat exchange reforming at least a part of the hydrocarbon feed stock from step (a) to a heat exchange reformed gas using at least part of the autothermal reformed gas stream from step (d) in combination with the heat exchange reformed gas as heating source for the heat exchange reformer to provide a reformed gas.

4. The method of claim 1, comprising the further step of separating air into a separate stream containing oxygen and into a separate stream containing nitrogen and introducing at least a part of the separate stream containing oxygen into the autothermal reformer in step (d).

5. The method of claim 1, wherein a part of the hydrocarbon feed stock from step (a) is bypassed the optional tubular steam reforming in step (c) and introduced to the autothermal reformer in step (d).

6. The method of claim 1, wherein the hydrocarbon feed stock comprises natural gas, methane, LNG, naphtha or mixtures thereof either as such or pre-reformed and/or steam reformed and/or desulfurized.

7. The method of claim 1, wherein the electrolysis of carbon dioxide in step (b) is powered at least in part by renewable energy.

8. The method of claim 1, wherein the separating of air is powered at least in part by renewable energy.

9. The method of claim 1, comprising the further step of introducing substantially pure carbon dioxide upstream step (c), and/or upstream of step (d), and/or downstream step (d).

10. The method of claim 1, wherein the electrolysis is operated such that all of the separate carbon monoxide containing stream from step (b) is added to the autothermal reformed gas stream downstream step (d) to provide a module M=(H.sub.2−CO.sub.2)/(CO+CO.sub.2) in the synthesis gas withdrawn from step (f) of between 1.9 and 2.2.

11. The method of claim 1, wherein the module M=(H.sub.2−CO.sub.2)/(CO+CO.sub.2) in the synthesis gas withdrawn in step (f) is in the range from 2 to 2.1.

12. The method of claim 1, wherein the synthesis gas withdrawn in step (g) is in a further step converted to a methanol product.

13. The method of claim 1, wherein the electrolysis is operated such that all of the separate carbon monoxide containing stream from step (b) is added to the autothermal reformed gas stream downstream step (d) to provide a module H2 to CO (H2/CO) in the synthesis gas withdrawn from step (g) of between 1.9 and 2.2, preferably of 2.0.

14. The method of claim 1, wherein the synthesis gas withdrawn in step (g) is in a further step converted to a Fischer-Tropsch product.

Description

EXAMPLE

[0035] The Table below shows an example of the process production of a synthesis gas of H.sub.2/CO=1.0. A first ATR produces a first synthesis gas. In parallel, the CO.sub.2 electrolysis produces a second synthesis gas stream of primarily CO.sub.2 mixed with CO. When combining the second synthesis gas stream with the first synthesis gas stream, the final synthesis gas is obtained with a lower H.sub.2/CO ratio than the first.

TABLE-US-00001 CO2 Combined synthesis ATR electrolysis gas product Inlet T [° C.] 625 850  Outlet T [° C.] 1050  850  Inlet P [barg]   34.5 5 Outlet P [barg]   33.5 5 Inlet: N.sub.2 [Nm.sup.3/h]  0 0 CO.sub.2 [Nm.sup.3/h] 682 1000   CH.sub.4 [Nm.sup.3/h] 916 0 H.sub.2 [Nm.sup.3/h]  0 0 CO [Nm.sup.3/h]  0 0 H.sub.2O [Nm.sup.3/h] 550 0 Oxygen feed: O.sub.2 T [° C.]: 240 O.sub.2 [Nm.sup.3/h]  571* N.sub.2 [Nm.sup.3/h]  10 H.sub.2O [Nm.sup.3/h]  5 Outlet: N.sub.2 [Nm.sup.3/h]  10 0 10 CO.sub.2 [Nm.sup.3/h] 453 800  1253 CH.sub.4 [Nm.sup.3/h]  9 0 9 H.sub.2 [Nm.sup.3/h] 1349  0 1349 CO [Nm.sup.3/h] 1135  200  1335 H.sub.2O [Nm.sup.3/h] 1018  0 1018 O.sub.2 [Nm.sup.3/h]  0 100** 0 Total outlet 3974  1100   4974 [Nm.sup.3/h] *100 Nm.sup.3/h supplied from CO2 electrolysis. **Separate outlet.

COMPARISON EXAMPLE

[0036] For comparison, the example below shows a single ATR for production of the same amount of synthesis gas (H2+CO) also at a H2/CO ratio of 1.0. Comparing the two tables, it can be seen that the combination of ATR and CO2 electrolysis gives a smaller ATR (exemplified by the lower total flow out of the ATR), but consequently also uses less oxygen and additionally supplies ca. 18% of the oxygen directly from the CO.sub.2 electrolysis unit. The required oxygen supply is consequently significantly decreased.

TABLE-US-00002 Stand-alone ATR Inlet T [° C.] 625 Outlet T [° C.] 1050 Inlet P [barg] 34.5 Outlet P [barg] 33.5 Inlet: N.sub.2 [Nm.sup.3/h] 0 CO.sub.2 [Nm.sup.3/h] 1000 CH.sub.4 [Nm.sup.3/h] 1000 H.sub.2 [Nm.sup.3/h] 0 CO [Nm.sup.3/h] 0 H.sub.2O [Nm.sup.3/h] 600 Oxygen feed: O.sub.2 T [° C.]: 240 O.sub.2 [Nm.sup.3/h] 645 N.sub.2 [Nm.sup.3/h] 13 H.sub.2O [Nm.sup.3/h] 6 Outlet: N.sub.2 [Nm.sup.3/h] 13 CO.sub.2 [Nm.sup.3/h] 655 CH.sub.4 [Nm.sup.3/h] 7 H.sub.2 [Nm.sup.3/h] 1346 CO [Nm.sup.3/h] 1338 H.sub.2O [Nm.sup.3/h] 1247 Total outlet [Nm.sup.3/h] 4606