PROCESS AND APPARATUS FOR PRODUCING LOW-NITROGEN SYNTHESIS GAS FROM NITROGEN-CONTAINING NATURAL GAS

Abstract

Process and apparatus for producing a low-nitrogen synthesis gas from a natural gas containing nitrogen and carbon dioxide, from which water and carbon dioxide are removed in a first temperature swing adsorption plant and subsequently nitrogen is removed in a cryogenic gas fractionator, to give a low-nitrogen, water-free and carbon dioxide-free natural gas, which is next supplied to a thermochemical conversion, so as to recover a crude syngas comprising hydrogen, carbon monoxide, water and carbon dioxide, from which the low-nitrogen synthesis gas is obtained at least by the removal of water and carbon dioxide in a second temperature swing adsorption plant. The characteristic feature here is that at least a part of the low-nitrogen, water-free and carbon dioxide-free natural gas prior to its thermochemical conversion is used as regenerating gas in the regeneration of the first and/or second temperature swing adsorption plant.

Claims

1. A process for producing a low-nitrogen synthesis gas from a natural gas containing nitrogen and carbon dioxide, from which water and carbon dioxide are removed in a first temperature swing adsorption plant and subsequently nitrogen is removed in a cryogenic gas fractionator, to give a low-nitrogen, water-free and carbon dioxide-free natural gas, which is next supplied to a thermochemical conversion, so as to recover a crude syngas comprising hydrogen, carbon monoxide, water and carbon dioxide, from which the low-nitrogen synthesis gas is obtained at least by the removal of water and carbon dioxide in a second temperature swing adsorption plant, wherein at least a part of the low-nitrogen, water-free and carbon dioxide-free natural gas prior to its thermochemical conversion (K) is used as regenerating gas in the regeneration of the first and/or second temperature swing adsorption plant.

2. The process according to claim 1, wherein the part of the low-nitrogen, water-free and carbon dioxide-free natural gas used as regenerating gas is fed to the thermochemical conversion together with the substances desorbed during adsorber regeneration.

3. The process according to claim 1, wherein the part of the low-nitrogen, water-free and carbon dioxide-free natural gas, which is intended as regenerating gas, is separated into a first and a second part, the first part being used as regenerating gas exclusively in the first and the second part being used as regenerating gas exclusively in the second temperature swing adsorption plant .

4. The process according to claim 1, wherein carbon dioxide present in the natural gas containing nitrogen and carbon dioxide is removed upstream of the first temperature swing adsorption plant.

5. The process according to claim 1, wherein the thermochemical conversion is carried out as autothermal reforming or partial oxidation or steam reforming or as a combination of at least two of these processes.

6. An apparatus for producing a low-nitrogen synthesis gas from a natural gas containing nitrogen and carbon dioxide, having a first temperature swing adsorption plant for removing water and carbon dioxide from the natural gas containing nitrogen and carbon dioxide and for recovering a nitrogen-containing, water-free and carbon dioxide-free natural gas, a cryogenic gas fractionator with which a low-nitrogen, water-free and carbon dioxide-free natural gas can be obtained from the nitrogen-containing, water-free and carbon dioxide-free natural gas by the removal of nitrogen, a thermochemical converter for converting the low-nitrogen, water-free and carbon dioxide-free natural gas to crude syngas comprising hydrogen, carbon monoxide, water and carbon dioxide, and a second temperature swing adsorption plant with which water and carbon dioxide can be removed from the crude syngas to obtain the low-nitrogen synthesis gas, wherein the cryogenic gas fractionator is connected to the thermochemical converter via the first and the second temperature swing adsorption plant in such a way that at least a part of the low-nitrogen, water-free and carbon dioxide-free natural gas prior to its reaction in the thermochemical converter can be used as regenerating gas in the regeneration of the first and/or second temperature swing adsorption plant.

7. The apparatus according to claim 6, wherein both the first and the second temperature swing adsorption plants are connected to the thermochemical converter in such a way that the part of the low-nitrogen, water-free and carbon dioxide-free natural gas used as regenerating gas can be fed to the thermochemical converter together with the substances desorbed during adsorber regeneration.

8. The apparatus according to claim 6, wherein the cryogenic gas fractionator is connected to the first and the second temperature swing adsorption plants in such a way that a first part of the low-nitrogen, water-free and carbon dioxide-free natural gas intended as regenerating gas can be used as regenerating gas exclusively in the first temperature swing adsorption plant and a second part can be used as regenerating gas exclusively in the second temperature swing adsorption plant .

9. The apparatus according to claim 6, wherein it comprises a device arranged upstream of the first temperature swing adsorption plant for removing carbon dioxide, with which carbon dioxide contained in the containing nitrogen and carbon dioxide can be removed.

10. The apparatus according to claim 6, wherein the thermochemical converter is configured as an autothermal reformer or partial oxidation reactor or steam reformer or as a combination of at least two of these apparatuses.

Description

[0030] FIG. 1 shows a variant of the invention in which a low-nitrogen oxide gas is produced from natural gas containing nitrogen and carbon dioxide.

[0031] Via line 1, natural gas containing nitrogen and carbon dioxide is fed to the purification device R, where substances such as mercury are removed in a first purification step. The natural gas 2 treated in this way is subsequently fed to an acid gas scrubber W1 for removal of the main part of the carbon dioxide 3 present, which acid gas scrubber is, for example, an amine scrubber. With a reduced carbon dioxide content, the natural gas flows via line 4 to the first TSAP T1, where water and any remaining carbon dioxide are removed and a nitrogen-containing, water-free and carbon dioxide-free natural gas 5 is produced, which is decomposed in the cryogenic gas fractionator N into a low-nitrogen, water-free and carbon dioxide-free natural gas 6 and a fuel gas fraction 7 that is rich in nitrogen. After a pressure increase in the compressor P1, the low-nitrogen, water-free and carbon dioxide-free natural gas 8 is split into a first 9 and a second partial flow 10, of which the first 9 is used as regenerating gas in the adsorber regeneration in the first TSAP T1, while the second part 10 is fed, for the same purpose, to a second TSAP T2 arranged further downstream for gas drying. The two regenerating gas streams 11 and 12 loaded with desorbed water and carbon dioxide are recycled and applied to the thermochemical converter K as a natural gas feedstock via line 13. In the thermochemical converter K, the natural gas feedstock 13 is converted, together with steam 14 as well as carbon dioxide 15 and optionally oxygen 22, to a crude syngas 16 comprising hydrogen, carbon monoxide, water and carbon dioxide, which crude syngas, after cooling in the cooling device G, is conducted via line 17 into a further acid gas scrubber W2, which can likewise be designed as an amine scrubber, for the removal of carbon dioxide 18. In the second TSAP T2, the crude syngas 19 with a reduced carbon dioxide content is purified from water and carbon dioxide residues, wherein a nitrogen-free synthesis gas 20 consisting largely of hydrogen and carbon monoxide is obtained as product. The carbon dioxide 18 separated from the cooled crude syngas 17 is recycled as feedstock into the thermochemical converter K by means of the second compressor P2 and the line 15 after adding carbon dioxide 3 separated from the natural gas 2 and imported carbon dioxide 21 to increase the carbon monoxide production.