Process and plant for producing methanol

Patent metadata

Field	Value
Publication number	US-11078141-B2
Application number	US-202016996280-A
Country	US
Kind code	B2
Filing date	Aug 18, 2020
Priority date	Aug 19, 2019
Publication date	Aug 3, 2021
Grant date	Aug 3, 2021

Abstract

The invention relates to a process for producing methanol and to a plant for producing methanol. A first fresh gas suitable for production of methanol is precompressed by a first compressor stage to obtain a second fresh gas. The second fresh gas is merged with a recycle gas stream and further compressed to synthesis pressure in a second compressor stage. Catalytic conversion of the thus obtained synthesis gas stream in a plurality of serially arranged reactor stages with intermediate condensation and separation of the crude methanol reduces the recycle gas amount in the synthesis circuit to such an extent that recycle gas may be directly recycled to the second fresh gas stream, thus ensuring that no recycle gas compressor stage is required and that the total compressor power may be reduced.

First claim

What is claimed is:

1. A process for producing methanol, comprising:
a) providing an input gas comprising carbon oxides and hydrogen;
b) introducing the input gas as a first fresh gas stream into a first compressor stage for precompression of the first fresh gas stream to obtain a second fresh gas stream;
c) introducing a recycle gas stream and the second fresh gas stream into a second compressor stage for compression of the recycle gas stream and the second fresh gas stream to synthesis pressure to obtain a synthesis gas stream;
d) catalytically converting the synthesis gas of the synthesis gas stream in a plurality of serially arranged reactor stages at synthesis pressure to obtain a product stream comprising methanol and unreacted synthesis gas per reactor stage;
e) cooling the product stream obtained per reactor stage for condensation and separation of methanol from unreacted synthesis gas and introducing unreacted synthesis gas into a respective subsequent stage of the serially arranged reactor stages;
f) withdrawing unreacted synthesis gas from at least one of the reactor stages as a recycle gas stream for introduction of the recycle gas stream into the second compressor stage according to step c).

2. The process according to claim 1 , wherein the proportion of carbon monoxide in the input gas, based on the total amount of the carbon oxides, is more than 20% by volume.

3. The process according to claim 1 , wherein after the withdrawing in step f) the recycle gas stream is introduced into the second compressor stage without preceding compression.

4. The process according to claim 1 , wherein according to step e) unreacted synthesis gas is completely introduced into the respective subsequent stage of the serially arranged reactor stages.

5. The process according to claim 1 , wherein according to step f) unreacted synthesis gas is withdrawn as a recycle gas stream from the last of the plurality of serially arranged reactor stages.

6. The process according to claim 1 , wherein the recycle gas stream and the second fresh gas stream are merged and introduced into the second compressor stage as a combined gas stream.

7. The process according to claim 1 , wherein the input gas has a stoichiometry number SN of 1.5 to 3.0, wherein

S
⁢

⁢
N

=

n
⁡

(

H
2

)

-

n
⁡

(

CO
2

)

n
⁡

(
CO
)

+

n
⁡

(

CO
2

)

,

with
⁢

⁢
n
⁢

⁢

in
⁢

[
mol
]

.

8. The process according to claim 1 , wherein for a recirculation rate R defined as

R
=

Volume
⁢

⁢
flow
⁢

⁢

(

recycle
⁢

⁢
gas
⁢

⁢
stream

)

Volume
⁢

⁢
flow
⁢

⁢

(

second
⁢

⁢
fresh
⁢

⁢
gas
⁢

⁢
stream

)

,

0.15
≤
R
≤

1.25
.

9. The process according to claim 8 , wherein the recirculation rate R: 0.1≤R≤0.5.

10. The process according to claim 1 , wherein based on the input gas a carbon oxides conversion of at least 80 mol % is achieved over the entirety of the plurality of serially arranged reactor stages.

11. The process according to claim 1 , wherein the plurality of serially arranged reactor stages comprises a number of 2 to 8 reactor stages.

Assignees

• Air Liquide
• Lair Liquide Socie Ete Anonyme Pour Letude Et Lexploitation Des Procedes Georges Claude

Inventors

• Schuhmann Timm

Classifications

• B01J2208/00017

  Controlling the temperature · CPC title

• B01J2219/00002

  Chemical plants · CPC title

• B01J8/04 Primary

  the fluid passing successively through two or more beds · CPC title

• C07C29/1516 Primary

  Multisteps · CPC title

• B01J2208/00628

  Controlling the composition of the reactive mixture · CPC title