METHOD FOR THE PREPARATION OF SYNTHESIS GAS

Abstract

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

2. 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.

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

4. 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 desulfurized.

5. The method of claim 1, wherein the electrolysis of water and/or steam in step (b) is powered at least in part by renewable energy.

6. The method of claim 2, wherein the separating of air is powered at least in part by renewable energy.

7. 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).

8. The method of claim 1, wherein the electrolysis is operated such that all the hydrogen produced by the electrolysis is added to the reformed gas downstream step (d) to provide a module M=(H.sub.2CO.sub.2)/(CO+CO.sub.2) in the synthesis gas withdrawn from step (f) of between 1.9 and 2.2.

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 The method of claim 1, wherein the module M=(H.sub.2CO.sub.2)/(CO+CO.sub.2) in the synthesis gas withdrawn in step (f) is in the range from 2 to 2.1.

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 The method of claim 1, wherein the synthesis gas withdrawn in step (f) is in a further step converted to a methanol product.

Description

EXAMPLE

[0033] In the below table a comparison between conventional 2-step reforming and 2-step reforming+electrolysis according to the invention is provided.

TABLE-US-00001 COMPARISON TABLE 2-step 2-step reforming + reforming electrolysis Tubular reformer inlet T 625 625 [ C.] Tubular reformer outlet T 706 669 [ C.] Tubular reformer inlet P 31 31 [kg/cm.sup.2 g] Tubular reformer min. 13,38 9,48 Required fired duty [Gcal/h] Tubular reformer outlet 67180 64770 flow [Nm.sup.3/h] Feed to SMR H2 [Nm.sup.3/h] 4099 4091 CO2 [Nm.sup.3/h] 897 895 CH4 [Nm.sup.3/h] 22032 21993 CO [Nm.sup.3/h] 14 14 H2O [Nm.sup.3/h] 30313 30259 N2 [Nm.sup.3/h] 0 0 ATR feed inlet T [ C.] 708 669 ATR oxidant inlet T [ C.] 240 240 ATR outlet T [ C.] 1050 1050 ATR inlet P [kg/cm2 g] 29 29 ATR outlet flow [Nm.sup.3/h] 101004 100937 Feed to ATR H2 [Nm.sup.3/h] 21538 17792 CO2 [Nm.sup.3/h] 3598 3320 CH4 [Nm.sup.3/h] 17119 18235 CO [Nm.sup.3/h] 2226 1348 H2O [Nm.sup.3/h] 22698 24075 Oxidant to ATR H2O [Nm.sup.3/h] 100 108 N2 [Nm.sup.3/h] 212 228 O2 [Nm.sup.3/h] 10393 11148 Electrolysis product H2 [Nm.sup.3/h] * 0 1493 O2 [Nm.sup.3/h] ** 0 747 Oxygen from ASU O2 [Nm.sup.3/h] 10393 10401 Product gas H2 [Nm.sup.3/h] 52099 52358 CO2 [Nm.sup.3/h] 4679 4942 CH4 [Nm.sup.3/h] 364 319 CO [Nm.sup.3/h] 17901 17642 H2O [Nm.sup.3/h]* 25750 26941 N2 [Nm.sup.3/h]* 212 2289 Module 2.10 2.10 * Included in product gas ** Included in oxidant to ATR

[0034] As apparent from the Comparison Table above, the required duty for the tubular reformer can be significantly reduced by the current invention. This duty will in practice translate in to less use of natural gas for heating the SMR. Besides the lower consumption figures of natural gas, this results with an added benefit of less CO.sub.2 emissions in the flue gas stack. Furthermore, the investment of the tubular reformer is substantially reduced.