Patent ID: 12215072

DETAILED DESCRIPTION OF THE DRAWINGS

The plant shown inFIG.1in accordance with a first exemplary embodiment of the proposed plant is for the synthesis of methanol1and can be operated in accordance with the proposed method.

A synthesis gas stream2which substantially consists of hydrogen, carbon monoxide and carbon dioxide is obtained from an energy carrier stream11which is formed by natural gas and which is therefore carbon-containing, and which is fed to a synthesis gas reactor arrangement13. In the synthesis gas reactor arrangement13, autothermal reforming takes place in order to obtain the synthesis gas stream2. For autothermal reforming, an oxygen-containing stream22is supplied which in this case has been obtained from an air separation device23and which substantially consists of oxygen. The air separation device23in this case is configured to obtain a stream of oxygen—i.e. in this case the oxygen-containing stream22—from the ambient air. The synthesis gas stream2is obtained at a production pressure which is substantially 60 bar. The synthesis gas stream2is initially fed to a heat recovery arrangement10in which the synthesis gas stream2is cooled and in this manner, a portion of the heat produced during autothermal reforming is recovered. Next, the synthesis gas stream2is fed to a synthesis gas compressor3of the plant for further pressure-increased.

Next, the synthesis gas stream is fed to the first reactor stage21aof a methanol reactor arrangement4, in which reactor stage21a, synthesis of methanol takes place and at least a portion of the synthesis gas stream2is converted into methanol1. The methanol synthesis takes place at a synthesis pressure of more than 60 bar, and in particular at a synthesis pressure of substantially 80 bar.

The plant has a hydrogen recovery arrangement5configured as a pressure swing adsorption device24—which can also be termed a PSA—wherein a H recycle stream7is obtained from a recovery stream6, which H recycle stream7substantially consists of hydrogen. In addition, the remaining gas is discharged from the hydrogen recovery arrangement5as a purge8and is then burned in a fired heating device of the plant (not shown here). The H recycle stream7is fed to the synthesis gas stream2.

As can be seen inFIG.1, the plant of the first exemplary embodiment also has a recycle compressor14which compresses a residual gas stream15. The residual gas stream15has unreacted residual gas16bwhich in turn has substantially those components of the synthesis gas which have not been converted into methanol1in the methanol reactor arrangement4. Accordingly, the residual gas stream15contains unreacted oxides of carbon in particular. The residual gas stream15which has been pressure-increased in this manner is fed afresh to a first portion of the methanol reactor arrangement4.

The unreacted residual gas16a, bis obtained from a methanol separation device17of the methanol reactor arrangement4, which in this case comprises two condensation devices18a, b. By means of condensation, they respectively produce the unreacted residual gas16a, bon the one hand and a respective raw methanol stream19a, bon the other hand. The raw methanol streams19a, bare then fed into a distillation step20of the plant so that methanol1can be obtained from the raw methanol streams19a, b.

In the plant of the exemplary embodiment ofFIG.1, the methanol reactor arrangement4has two reactor stages21a, bfor methanol synthesis which are operationally connected in series. In this exemplary embodiment, the first reactor stage21ahas two isothermal reactors which are disposed in parallel and the second reactor stage21bhas a single isothermal reactor. In this regard, each of the two condensation devices18a, bis fed by the product stream from each of the reactor stages21a, b. In this regard, that reactor stage21ato which the synthesis gas stream2is fed directly is described as the first reactor stage21a. The reactor stage21bis then that which is operationally downstream such that it is fed by the unreacted residual gas16afrom the first reactor stage21afor conversion into methanol1.

In this exemplary embodiment ofFIG.1, the recovery stream6is diverted from the residual gas stream15which has been pressure-increased by means of the recycle compressor. This residual gas stream15which is fed to the recycle compressor14is not obtained from the unreacted residual gas16aof the first reactor stage21a, but from the unreacted residual gas16bof the reactor stage which is operationally downstream of the first reactor stage21aand is therefore termed the second reactor stage21b.

Similarly, this residual gas stream15also contains unreacted hydrogen from the first reactor stage21ain addition to the unreacted oxides of carbon which have already been mentioned. Any unreacted hydrogen from the residual gas16aof the first reactor stage21ais fed to the second reactor stage21b. Because a complete reaction of the hydrogen also does not take place in the second reactor stage21b, the unreacted residual gas16bof the second reactor stage21balso contains unreacted hydrogen from the first reactor stage21a.

Because the recovery stream6is diverted from the pressure-increased residual gas stream15, the H recycle stream7also contains unreacted hydrogen from the unreacted residual gas16aof the first reactor stage21a. In particular, a second portion of the pressure-increased residual gas stream15is diverted as the recovery stream6. Because the H recycle stream7is fed to the pressure-increased synthesis gas stream2, the unreacted hydrogen from the residual gas16aof the first reactor stage21ain the recovery stream6—and therefore also from the H recycle stream7—is fed to this first reactor stage21again for conversion into methanol. Between leaving the first reactor stage21aand being fed again to the first reactor stage21a, however, as a component of the residual gas stream15, the unreacted hydrogen of the H recycle stream7has undergone pressure-increase by means of the recycle compressor14, and in fact exactly once and together with the unreacted oxides of carbon in the residual gas stream15. Since the H recycle stream7is fed to the synthesis gas stream2operationally downstream of the synthesis gas compressor3, then pressure-increase of the hydrogen in the H recycle stream7does not take place. The residual gas stream15which is compressed by means of the recycle compressor14is then fed directly again to the aforementioned first portion of the first reactor stage21a.

The second exemplary embodiment of the proposed plant, shown inFIG.2, differs from the exemplary embodiment shown inFIG.1in that the recycle compressor14is operationally disposed between the first reactor stage21aand the reactor stage21bwhich is downstream of the former. As a consequence, the residual gas stream15which is fed to the recycle compressor14is obtained from the unreacted residual gas16aof the first reactor stage21a. The residual gas stream15which is compressed by means of the recycle compressor14along with the unreacted oxides of carbon is fed to the reactor stage21bwhich is downstream of the first reactor stage21a. The unreacted residual gas16bfrom this reactor stage21bis fed back to the first reactor stage21awithout further compression. In contrast to that shown in the first exemplary embodiment, the recovery stream6is obtained from the unreacted residual gas16aof the first reactor stage21a, wherein in addition, in agreement with the first exemplary embodiment, diversion of the recovery stream6is carried out operationally downstream of the recycle compressor14. As a consequence, in the second exemplary embodiment as well, pressure-increased of the unreacted hydrogen from the residual gas16aof the first reactor stage21ain the H recycle stream7takes place exactly once along with the unreacted oxides of carbon occurs by means of the recycle compressor14, before this unreacted hydrogen is fed to the first reactor stage21aagain.

In the third exemplary embodiment ofFIG.3, in similar manner to the second exemplary embodiment, the recovery stream6is obtained from the residual gas16aof the first reactor stage21a. In contrast to the second exemplary embodiment, however, there is no recycle compressor14between the first reactor stage21aand the second reactor stage21b. Moreover, the recycle compressor14is disposed operationally downstream of the second reactor stage21b, as was the case with the first exemplary embodiment.

In contrast to both the first exemplary embodiment and the second exemplary embodiment, in the third exemplary embodiment, the H recycle stream7is fed to the residual gas16bof the second reactor stage21bwhich is downstream of the first reactor stage21a. In particular, this feed takes place before the pressure-increase by means of the recycle compressor14. In this manner, the hydrogen in the H recycle stream7corresponding to the unreacted hydrogen from the residual gas16aof the first reactor stage21ais pressure-increased, by means of the recycle compressor14, in the recovery stream6along with the remaining unreacted residual gas16bof the second reactor stage21band in particular along with unreacted oxides of carbon. This pressure-increase is carried out before this unreacted hydrogen is fed to the first reactor stage21aagain, which compensates for the lack of pressure-increase due to the missing synthesis gas compressor.

In addition, in the third exemplary embodiment, a portion of the pressure-increased residual gas stream15is diverted and fed to the energy carrier stream11. This diverted portion of the pressure-increased residual gas stream15undergoes a further pressure-increase by means of the synthesis gas compressor2. For the non-diverted portion of the residual gas stream15, a pressure-increase by means of the recycle compressor14has been carried out exactly once. However, it is also possible to dispense with this diversion of a portion of the pressure-increased residual gas stream15.

The plant in accordance with the fourth exemplary embodiment ofFIG.4corresponds to the third exemplary embodiment ofFIG.3. However, it includes a water gas shift reaction device9to which a portion of the pressure-increased synthesis gas stream2is fed. The water gas shift reaction which occurs in the water gas shift reaction device9results in raising the proportion of hydrogen in the diverted portion of the pressure-increased synthesis gas stream2. In this case, the portion of the synthesis gas stream2from the water gas shift reaction device9which has been diverted in this manner and which has undergone the water gas shift reaction forms a further recovery stream which is fed to the hydrogen recovery arrangement5together with the recovery stream6. In the same manner as in the exemplary embodiment ofFIG.3, the H recycle stream7is fed to the residual gas16bof the second reactor stage21bwhich is downstream of the first reactor stage21a, so that therefore, even with this exemplary embodiment, pressure-increase is carried out by means of the recycle compressor14along with the unreacted oxides of carbon.

The fifth exemplary embodiment ofFIG.5disposes the recycle compressor14between the reactor stages21a, bof the methanol reactor arrangement4, in similar manner to that of the second exemplary embodiment on which the fifth exemplary embodiment is also based. In contrast to the second exemplary embodiment, the recovery stream6is obtained from the residual gas16bfrom the second reactor stage21b. In this manner, the pressure of the hydrogen in this recovery stream6and therefore also in the H recycle stream7is increased by means of the recycle compressor14, and in fact in particular before being fed to the second reactor stage21b.

The sixth exemplary embodiment ofFIG.6is in principle based on the first exemplary embodiment ofFIG.1. In contrast to the latter, and in fact in similar manner to the fifth exemplary embodiment ofFIG.5, the recovery stream6is obtained from the unreacted residual gas16bof the second reactor stage21b. Another distinction from the first exemplary embodiment ofFIG.1and in similar manner to the third and fourth exemplary embodiments ofFIGS.3and4, the H recycle stream7is recycled to the residual gas16bof the second reactor stage21bwhich is downstream of the first reactor stage21a. This infeed is operationally downstream of the diversion for the recovery stream6.

The seventh exemplary embodiment ofFIG.7is based initially on the third exemplary embodiment ofFIG.3, but without the diversion of a portion of the pressure-increased residual gas stream15to the energy carrier stream11. The seventh exemplary embodiment shows three respectively alternative ways of connecting compared with the third exemplary embodiment. In this context, the seventh exemplary embodiment includes three subsidiary exemplary embodiments.

The first variation proposes a first bypass stream25awhich branches from the pressure-increased synthesis gas stream2and is fed to the unreacted residual gas16aof the first reactor stage21a. The feed to the unreacted residual gas16aof the first reactor stage21ais carried out operationally downstream of the diversion of the recovery stream6. Thus, in this manner, a portion of the synthesis gas stream2is diverted in order to form a further synthesis gas stream26which corresponds to the first bypass stream25aand which bypasses the first reactor stage21a. In accordance with the layout ofFIG.7, this diversion is operationally upstream of the feed of the pressure-increased residual gas stream15. However, it would also be possible to envisage this diversion being made operationally downstream of the feed for the pressure-increased residual gas stream15.

The second variation, which is an alternative to the first variation, proposes a second bypass stream25bwhich branches off from the pressure-increased residual gas stream15and which is fed to the unreacted residual gas16aof the first reactor stage21a, and in fact is again downstream of the diversion for the recovery stream6. In this manner, then, partial by-passing of the first reactor stage21aoccurs by means of the pressure-increased residual gas stream15.

The third variation, which is an alternative to the first two variations, proposes a third bypass stream25cwhich is operationally downstream of the diversion for the recovery stream6from the unreacted residual gas16aof the first reactor stage21aand which is fed to the residual gas stream15prior to pressure-increase. In this manner, therefore, a portion of the unreacted residual gas16aof the first reactor stage21ainitially by-passes the second reactor stage21b.

The eighth exemplary embodiment ofFIG.8is based on the fifth exemplary embodiment ofFIG.5and also respectively shows three alternative connection variations, in this case with respect to the fifth exemplary embodiment. These three connection variations correspond to connection variations of the seventh exemplary embodiment ofFIG.7with the bypass streams25a,25b,25c.