METHOD AND SYSTEM COMBINATION FOR THE PREPARATION OF UREA

Abstract

The invention relates to a process (100), in which, with the inclusion of an air-separation method (10), an oxygen-rich substance flow (b) is formed, which is subjected with a methane-rich substance flow (e) to a method for oxidative coupling of methane (20). From a product flow (e) of the method for oxidative coupling of methane (20), a carbon-dioxide-rich substance flow (i) is formed and subjected to a urea-synthesis method (50). A corresponding combined plant also forms the subject matter of the invention.

Claims

1. A process, in which, with the inclusion of an air-separation method, an oxygen-rich substance flow is formed, which is subjected, with a methane-rich substance flow, to a method for oxidative coupling of methane, characterised in that a carbon-dioxide-rich substance flow is formed from a product flow of the method for oxidative coupling of methane and subjected to a urea-synthesis method.

2. The process according to claim 1, in which, with the inclusion of an air-separation method, a nitrogen-rich substance flow is further formed and subjected to an ammonia-synthesis method.

3. The process according to claim 2, in which, from the product flow, a hydrogen-rich substance flow is further formed and subjected to the ammonia-synthesis method.

4. The process according to claim 3, in which the methane-rich substance flow contains nitrogen, wherein the nitrogen contained in the methane-rich substance flow is partially or completely transferred into the hydrogen-rich substance flow and subjected to the ammonia-synthesis method within the latter.

5. The process according to claim 4, in which the methane-rich substance flow contains up to 20 mole percent nitrogen.

6. The process according to claim 3, in which the oxygen-rich substance flow contains nitrogen, wherein the nitrogen contained in the oxygen-rich substance flow is partially or completely transferred into the hydrogen-rich substance flow and subjected to the ammonia-synthesis method within the latter.

7. The process according to claim 6, in which the oxygen-rich substance flow contains up to 20 mole percent nitrogen.

8. The process according to claim 1, in which, from the product flow, one or more olefin-rich substance flows are further formed, and, with the inclusion of an air-separation method, one or more further oxygen-rich substance flows are formed, wherein the olefin-rich substance flow or flows and the further oxygen-rich substance flow or flows are subjected to an epoxidation method.

9. The process according to claim 1, in which, from the product flow, at least one further substance flow is formed, which is again subjected to the method for oxidative coupling of methane.

10. The process according to claim 1, in which the waste heat of the method for oxidative coupling of methane is used for the pre-heating or heating of one or more substance flows and/or of one or more reactors, which are used in the synthesis method for the production of the nitrogen-containing synthesis product or products.

11. A combined plant which comprises an air-separation plant and at least one reactor equipped for the implementation of a method for oxidative coupling of methane, wherein the combined plant comprises means, which are equipped, with the inclusion of an air-separation method implemented in the air-separation plant, to form an oxygen-rich substance flow and to subject the latter, with a methane-rich substance flow, to a method for oxidative coupling of methane in the at least one reactor, characterised in that means are provided which are equipped to form a carbon-dioxide-rich substance flow from a product flow of the method for oxidative coupling of methane and to subject it to a urea-synthesis method.

12. The combined plant according to claim 11, which is equipped to implement a method comprising a process in which, with the inclusion of an air-separation method, an oxygen-rich substance flow is formed, which is subjected, with a methane-rich substance flow, to a method for oxidative coupling of methane, characterised in that a carbon-dioxide-rich substance flow is formed from a product flow of the method for oxidative coupling of methane and subjected to a urea-synthesis method.

13. The process according to claim 5, in which the methane-rich substance flow contains from 5 to 10 mole percent nitrogen.

14. The process according to claim 7, in which the oxygen-rich substance flow contains from 5 to 10 mole percent nitrogen.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0032] FIG. 1 shows a process for manufacturing reaction products according to a particularly preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWING

[0033] In FIG. 1, a process according to a particularly preferred embodiment of the invention is shown in the form of a schematic process-flow diagram and marked as a whole with 100.

[0034] The process 100 comprises an air-separation method 10 and a method for oxidative coupling of methane 20. Input air in the form of a substance flow a is supplied to the air-separation method 10. Air-separation methods 10 suitable for use within the scope of the process 100 have been described extensively elsewhere.

[0035] With the use of a corresponding air-separation method 10 in the illustrated example, an oxygen-rich substance flow b and a nitrogen-rich substance flow c are prepared. However, arbitrary further substance flows, which can comprise air-separation products, can also be provided with the use of the air-separation method 10, for example, further oxygen-rich and/or nitrogen-rich substance flows and/or substance flows which are rich in one or more noble gases, as is known in principle.

[0036] In the illustrated example, the oxygen-rich substance flow b and a methane-rich substance flow d, which can be, for example, conditioned or non-conditioned natural gas, are supplied to the method for oxidative coupling of methane 20. In the method for oxidative coupling of methane 20, a product flow e is generated, which can contain, inter alia, unconverted methane of the substance flow d, unconverted oxygen of the substance flow b, inert gases such as nitrogen optionally contained in the substance flow d, and reaction products of the oxidative coupling of methane, such as hydrogen, carbon dioxide, ethylene or propylene.

[0037] The product flow e is subjected to a separation method 30, which can comprise non-cryogenic and cryogenic separation steps. In particular, the separation method 30 can also comprise a gas scrubbing. Especially a hydrogen-rich substance flow f, an ethylene-rich substance flow g, a propylene-rich substance flow h and a carbon-dioxide rich substance flow i can be provided with the use of the separation method 30. The hydrogen-rich substance flow f, the propylene-rich substance flow g and the ethylene-rich substance flow h are typically produced in one or more cryogenic separation steps of the separation method 30. The carbon-dioxide-rich substance flow i is typically separated in advance. In the separation method 30 or respectively in corresponding separation steps, further substance flows can also be provided, which have, however, not been shown in FIG. 1 for the sake of visual clarity.

[0038] In the embodiment shown in FIG. 1, the implementation of an ammonia-synthesis method 40 takes place, to which, the nitrogen-rich substance flow c, which is prepared with the use of the air-separation method 10, and the hydrogen-rich substance flow f, which is prepared with the use of the method for oxidative coupling of methane and the downstream separation method 30, are supplied in the illustrated example within the framework of the process 100. However, as mentioned several times, a corresponding hydrogen-rich substance flow f can also originate from other sources, for example, from a steam reforming method. In principle, ammonia can also originate from different sources.

[0039] It should be emphasised that, with the use of the method for oxidative coupling of methane 20 or respectively of the downstream separation method 30, further hydrogen-rich flows can also be provided, which need not necessarily be supplied in their entirety to the ammonia-synthesis method 40. Similarly, the nitrogen supplied to the ammonia-synthesis method 40 need not originate or need not originate exclusively from the nitrogen-rich substance flow c from the air-separation method 10. At least a part of the nitrogen can also be contained in the hydrogen-rich substance flow f, as explained above, especially if the latter originates from a method for oxidative coupling of methane.

[0040] With the use of the ammonia-synthesis method 40, two ammonia-rich flows k and l are provided in the illustrated example. The particularly preferred embodiment of the process 10 illustrated in FIG. 1 comprises a urea-synthesis method 50. In this context, the ammonia-rich flow l, which is prepared with the use of the ammonia-synthesis method 40, and the carbon-dioxide-rich flow i, which is prepared with the use of the method for oxidative coupling of methane 20 and the downstream separation method 30, are supplied to the urea-synthesis method 50. It goes without saying that the entire ammonia formed in the ammonia-synthesis step 40 and/or the entire carbon dioxide provided in the method for oxidative coupling of methane 20 and the downstream separation method 30 need not be supplied to the urea-synthesis method 50. In each case, only partial quantities of the named compounds can also be used; the remainder can be output from a corresponding process 100, for example, as a product or respectively by-product. A corresponding case is shown in FIG. 1 with the ammonia-rich substance flows k and l.

[0041] In the illustrated example, the ammonia-rich substance flow k is output from the process. With the use of the urea-synthesis method 50 in the particularly preferred embodiment of the invention illustrated in FIG. 1, a urea-rich substance flow m is provided and supplied as required to appropriate conditioning steps.

[0042] The methods explained in the following are also not necessarily a component of a corresponding process 100. This means that the propylene-rich substance flow g and/or the ethylene-rich substance flow h can also, in each case, be output as products from a corresponding process 100.

[0043] The illustrated example shows an epoxidation method 60 which can also be provided separately for the propylene-rich substance flow g and the ethylene-rich substance flow h or only for one of these substance flows. Furthermore, an oxygen-rich substance flow n, which can, in particular, be provided with the use of the air-separation method 10, is supplied to the epoxidation method 60. With the use of the epoxidation method 60, a propylene-oxide-rich substance flow o and/or an ethylene-oxide-rich substance flow p can be provided. Here also, the entire propylene and/or ethylene provided in the method for oxidative coupling of methane 20 or respectively the downstream separation method need not be subjected to the epoxidation method 60. In particular, partial flows of corresponding propylene or respectively ethylene can be output as products from the process 100.