METHOD AND DEVICE FOR PRODUCING AMMONIA OR HYDROGEN AND USE OF THE DEVICE

Abstract

An apparatus for producing ammonia or hydrogen may include a) a gas stream feed conduit having a connecting conduit to a steam reformer with a waste heat section; b) a heat exchanger downstream of the gas stream feed conduit; c) a gas stream preheater downstream of the heat exchanger; d) a recirculation conduit which is located downstream of the gas stream preheater and leads to the gas stream feed conduit or, upstream of the heat exchanger, to the connecting conduit; and e) the steam reformer with the waste heat section, where the waste heat section may be in thermal contact with the gas stream preheater and the flow of the gas stream which has been heated in the gas stream preheater through the recirculation conduit can be regulated. A process for producing ammonia or hydrogen may employ such an apparatus.

Claims

1.-11. (canceled)

12. An apparatus for producing ammonia or hydrogen, the apparatus comprising: a gas stream feed conduit that includes a downstream connecting conduit to a steam reformer having a waste heat section, wherein a heat exchanger and a gas stream preheater are disposed between the gas stream feed conduit and the downstream connecting conduit; the heat exchanger disposed downstream of the gas stream feed conduit and outside the waste heat section; the gas stream preheater located downstream of the heat exchanger; a recirculation conduit that is disposed downstream of the gas stream preheater and leads to the gas stream feed conduit and the downstream connecting conduit that is disposed downstream of the gas stream preheater and leads to the steam reformer; and the steam reformer with the waste heat section, where the waste heat section is in thermal contact with the gas stream preheater and a flow of a gas stream that has been heated in the gas stream preheater through the recirculation conduit is configured to be regulated.

13. The apparatus of claim 12 comprising a connecting conduit that connects the heat exchanger and a part of the apparatus that is configured for the formation or presence of process condensate, boiler feed water, or steam.

14. The apparatus of claim 12 comprising a gas blower for the gas stream feed conduit, which is located at least one of upstream of the heat exchanger or downstream of an entry of the recirculation conduit into the gas stream feed conduit.

15. The apparatus of claim 12 comprising a conduit from the gas stream preheater into the recirculation conduit and the connecting conduit.

16. A process for producing ammonia or hydrogen, the process comprising: providing an apparatus comprising: a gas stream feed conduit that includes a downstream connecting conduit to a steam reformer having a waste heat section, wherein a heat exchanger and a gas stream preheater are disposed between the gas stream feed conduit and the downstream connecting conduit, the heat exchanger disposed downstream of the gas stream feed conduit and outside the waste heat section, the gas stream preheater located downstream of the heat exchanger, a recirculation conduit that is disposed downstream of the gas stream preheater and leads to the gas stream feed conduit and the downstream connecting conduit that is disposed downstream of the gas stream preheater and leads to the steam reformer, and the steam reformer with the waste heat section, where the waste heat section is in thermal contact with the gas stream preheater and a flow of a gas stream that has been heated in the gas stream preheater through the recirculation conduit is configured to be regulated; operating the steam reformer and heating the gas stream preheater; introducing the gas stream into the gas stream preheater via the gas stream feed conduit to heat the gas stream; and introducing at least part of the gas stream that has been heated in the gas stream preheater via the recirculation conduit and the gas stream feed conduit into the heat exchanger to heat the heat exchanger.

17. The process of claim 16 comprising introducing the gas stream into the heat exchanger via a gas blower.

18. The process of claim 16 wherein the gas stream is a stream of combustion air.

19. The process of claim 16 comprising introducing process condensate, boiler feed water, or steam into the heat exchanger to operate the heat exchanger.

20. The process of claim 16 wherein the at least part of the gas stream that has been heated in the gas stream preheater is heated to a temperature of 5° C. or more.

21. The process of claim 16 wherein the at least part of the gas stream that is introduced via the recirculation conduit and the gas stream feed conduit into the heat exchanger is in a range from 0 to 30% by volume, based on a total gas stream leaving the gas stream preheater, wherein a second part of a remainder of the gas stream is fed to the steam reformer.

22. A method for controlling temperature of a gas stream to be introduced into a heat exchanger where an ambient temperature is in a range of −50° C. to +5° C., the method comprising utilizing an apparatus that includes a gas stream feed conduit that includes a downstream connecting conduit to a steam reformer having a waste heat section, wherein the heat exchanger and a gas stream preheater are disposed between the gas stream feed conduit and the downstream connecting conduit; the heat exchanger disposed downstream of the gas stream feed conduit and outside the waste heat section; the gas stream preheater located downstream of the heat exchanger; a recirculation conduit that is disposed downstream of the gas stream preheater and leads to the gas stream feed conduit and the downstream connecting conduit that is disposed downstream of the gas stream preheater and leads to the steam reformer; and the steam reformer with the waste heat section, where the waste heat section is in thermal contact with the gas stream preheater and a flow of the gas stream that has been heated in the gas stream preheater through the recirculation conduit is configured to be regulated.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0026] FIG. 1 shows a schematic depiction of a working example of the apparatus of the invention for producing ammonia or hydrogen; and

[0027] FIG. 2 shows a schematic depiction of a further working example of the apparatus of the invention for producing ammonia or hydrogen.

EMBODIMENTS OF THE INVENTION

[0028] FIG. 1 schematically shows an apparatus 1 for producing ammonia according to the present invention. The apparatus 1 comprises a heat exchanger 2, a steam reformer 3 with a waste heat section 4 and an air preheater 5.

[0029] The waste heat section 4 serves to transport away heat which arises in the steam reformer 3 in order to prevent overheating of the steam reformer 3. As a result, the temperature within the waste heat section 4 is higher than ambient temperature.

[0030] The air preheater 5 is arranged so as to be in thermal contact with the waste heat section 4. In this way, it is normally ensured that the temperature in the air preheater 5 corresponds substantially to the temperature of that part of the waste heat section 4 with which thermal contact occurs (or is only slightly below this temperature), but in any case is likewise greater than the ambient temperature.

[0031] A gas stream (for example combustion air) introduced through the gas stream feed conduit 9 into the apparatus 1 is heated in the air preheater 5. This is made possible, as indicated above, by the thermal contact of the air preheater 5 with the waste heat section 4 which has been heated by operation of the steam reformer 3. The gas stream 11 which has been preheated in this way in the air preheater 5 can then be fed via a recirculation conduit 8 back to the gas stream feed conduit 9 and, in an advantageous embodiment, mix there with the combustion air introduced from outside. As a result, preheated combustion air or a preheated combustion air mixture goes into the heat exchanger 2. Low temperatures in the heat exchanger 2 have been prevented by the introduction of the heated combustion air into the heat exchanger 2. For instance, freezing of a process condensate used for operating the heat exchanger 2 can be avoided in this way. As a result, the combustion or ambient air 9 can be heated by means of the flue gas waste heat from the steam reformer 4 with the apparatus of the invention. This partially preheated air can then be introduced via a conduit 11 coming from the gas stream preheater firstly partly via the conduit 8 into the cold combustion or ambient air and the remaining part can secondly be introduced via the connecting conduit 10 into the reformer 3.

[0032] The apparatus shown in FIG. 2 comprises all constituents of the apparatus of FIG. 1. There is also a connection 6 which connects the heat exchanger 2 to another part of the apparatus 7, with a process condensate being produced in the other part of the apparatus. The connection 6 between the heat exchanger 2 and the other part of the apparatus 7 is such that the process condensate can be transported from the other part 7 to the heat exchanger 2 in order to be able to take the latter into operation by introduction of the process condensate.

WORKING EXAMPLES

[0033] Further features and advantages of the process of the invention may be derived from the following detailed description of working examples.

[0034] In a conventional ammonia plant which comprises, in this order in respect of a combustion air stream fed in, a combustion air blower, a heat exchanger, an air preheater and a steam reformer having a waste heat section, with the air preheater being arranged in the waste heat section of the steam reformer, the start-up of the plant was simulated with the objective of keeping the temperature of a combustion air stream which was fed into the heat exchanger by means of the combustion air blower above .sub.5° C. The dependence of the measures necessary for this purpose on the ambient temperature was examined.

[0035] Suitable conditions can be obtained when the load on the steam reformer was at least 80%. At an ambient temperature of −37° C., a gas temperature of 5° C. within the heat exchanger could thus be obtained when 20% by volume of the combustion air passing through the air preheater was fed by means of the combustion air blower to the heat exchanger. At an ambient temperature of −10° C., a recirculation of 7% by volume of the combustion air proved to be sufficient. The temperature in the waste heat section was about 300° C. here.

[0036] The features of the invention as disclosed in the above description and in the claims can be of significance both individually and in any combination for realization of the invention in its various embodiments.