Process for ammonia and methanol co-production

Details Process for ammonia and methanol co-production Process for ammonia and methanol co-production

1998-02-24

2001-12-25

Langel, Wayne (Department: 1754)

Chemistry of inorganic compounds

Nitrogen or compound thereof

Ammonia or ammonium hydroxide

C422S170000, C422S171000, C518S704000

Reexamination Certificate

active

06333014

ABSTRACT:

FIELD OF APPLICATION
The present invention relates to a process for the ammonia and methanol co-production in a plant comprising a secondary reformer section, a high-temperature CO conversion section and a low-temperature CO conversion section, arranged in series, and an ammonia synthesis section, the process comprising the steps of:
taking a gaseous flow comprising CO, CO
2
, H
2
and H
2
O coming from said secondary reformer section;
feeding the gaseous flow to a cooling and H
2
O separation section;
cooling said gaseous flow and separating the H
2
O contained therein in said cooling and H
2
O separation section;
feeding a substantially H
2
O-free gaseous flow coming from said cooling and H
2
O separation section to a methanol synthesis section;
reacting said substantially H
2
O-free gaseous flow in said synthesis section for methanol production;
feeding a gaseous flow comprising CO, CO
2
, H
2
and CH
3
OH coming from said methanol synthesis section to a methanol separation section;
separating a fluid flow comprising methanol from a substantially methanol-free gaseous flow and comprising CO, CO
2
, and H
2
in said methanol separation section, and
feeding said substantially methanol-free gaseous flow coming from said methanol separation section to said low-temperature CO conversion section.
The present invention also relates to a plant for ammonia and methanol co-production for carrying out the above mentioned process, and to a modernization method for an ammonia synthesis plant.
As known, there is an ever growing requirement in the field of ammonia and methanol co-production to provide easily implemented synthesis processes, which allow achievement of the desired production capacity at low operating and investment costs and with low energy consumption.
PRIOR ART
For the purpose of meeting the above mentioned requirement, there have recently been proposed in the field synthesis processes for ammonia and methanol co-production, wherein a flow of gas rich in CO, CO
2
and H
2
coming from the secondary reformer section of an ammonia synthesis plant, is diverted to a section for condensation and separation of the water contained therein and then conveyed into a synthesis section for methanol production. The unreacted gas is subsequently reintroduced downstream of the high-temperature CO conversion section of the ammonia plant.
Although advantageous in some ways, the above described process exhibits a series of drawbacks, the first of which is the fact that the unreacted gaseous flow coming from the methanol synthesis section before being returned into the ammonia synthesis process is mixed with a steam flow at high or medium pressure to bring the temperature and the H
2
O concentration to values such as to aid the subsequent CO conversion.
It follows that, due to high steam consumption, operating costs and energy consumption resulting from the ammonia and methanol co-production process according to the prior art are such as to considerably frustrate the advantages deriving from utilization of the gas present in the ammonia plant for methanol production.
In addition, in the process just described, the methanol is produced in a reaction section comprising a synthesis loop, at a pressure generally comprised between 50 bar and 100 bar, which is substantially higher than the pressure present in the secondary reformer section of the ammonia plant.
For this reason the plant for carrying out the process according to the prior art requires special equipment for recycling of the unreacted gas to the synthesis reactor and for compression of the gas flow coming from the secondary reformer section, thus involving high structural complexity as well as high investment costs.
SUMMARY OF THE INVENTION
The problem underlying the present invention is to provide a process for ammonia and methanol co-production which would be simple to apply and permit achieving the desired production capacity at low operating and investment costs in addition to low energy consumption.
The above mentioned problem is solved according to the present invention by a process for ammonia and methanol co-production of the above mentioned type, which is characterized in that it comprises the step of feeding to the substantially methanol-free gaseous flow coming from the methanol separation section a liquid flow comprising H
2
O appropriately heated by indirect heat exchange with the gaseous flow coming from the secondary reformer section.
Advantageously, it is possible to achieve effective saturation with H
2
O and temperature regulation of the substantially methanol-free gaseous flow to be conveyed to the low-temperature CO conversion section, by utilizing indirectly the heat of the gaseous flow coming from the secondary reformer.
There is thus avoided utilization of energy sources external to the ammonia and methanol co-production process as for example, with reference to the prior art, introduction of water in steam form, and therefore energy consumption is considerably reduced.
Preferably, the temperature of the liquid flow comprising H
2
O fed to the substantially methanol-free gaseous flow is between 100° C. and 300° C., so that the temperature of the gaseous flow returned to the ammonia synthesis process is such as to aid the conversion reaction in the low-temperature CO conversion section.
In addition, in accordance with a particularly advantageous embodiment of the process according to the present invention the liquid flow containing H
2
O comes at least partly from the cooling and H
2
O separation section.
In this manner, the process according to the present invention allows recovery and utilization of the water obtained by condensation in the cooling and H
2
O separation section upstream of the methanol synthesis section, by recirculating it to the unreacted gaseous flow before it is returned to the ammonia synthesis process.
Consequently, the concentration of H
2
O in the gaseous flow conveyed to the low-temperature CO conversion section can be advantageously controlled by limiting or even eliminating the necessity of adding outside water to the ammonia and methanol co-production process, while achieving a simplification of the plant and reducing operating and investment costs and energy consumption.
Advantageously, the substantially H
2
O-free gaseous flow is reacted in a synthesis section for methanol production of the ‘once-through’ type. This allows simplification of the synthesis section equipment, and hence considerable reduction of investment costs as compared with a plant provided with a methanol reaction section including a synthesis loop of the type described with reference to the prior art.
In the following description and the annexed claims, the term: synthesis section of the ‘once-through’ type, is understood to mean a reaction section in which the unreacted effluents are not recycled to the synthesis reactor.
For carrying out the above mentioned process, the present invention advantageously makes available a plant for ammonia and methanol co-production comprising:
a secondary reformer section, a high-pressure CO conversion section and a low-temperature CO conversion section, arranged in series;
an ammonia synthesis section in fluid communication with the low-temperature CO conversion section;
a cooling and separation section for the H
2
O contained in a gaseous flow coming from said secondary reformer section and also comprising CO, CO
2
and H
2
;
a synthesis section for methanol production fed by a substantially H
2
O-free gaseous flow coming from said cooling and H
2
O separation section;
a methanol separation section fed by a gaseous flow coming from said methanol synthesis section for separation of a fluid flow comprising methanol from a substantially methanol-free gaseous flow and comprising CO, CO
2
and H
2
;
an H
2
O saturation section for said substantially methanol-free gaseous flow in fluid communication with the low-temperature CO conversion section;
which is characterized in that it comprises a heating section for a liquid flow comprising H
2
O for indirect heat exchange with said

Affiliated with

Also associated with

Rating

Process for ammonia and methanol co-production does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for ammonia and methanol co-production, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for ammonia and methanol co-production will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2562493