[ e-methanol ] multi-component catalytic systems based on a copper-zinc-aluminium catalyst ( Cu / ZnO / Al 2
O 3
).
In terms of temperature , the optimal range in the reactor is between 200 ° C and 300 ° C , while operating pressures must be between 40 and 100 bar .
In the e-methanol production process , previously compressed H 2 and CO 2 are fed into the methanol synthesis reactor . In this reactor , the hydrogenation of CO 2 takes place , producing a stream of methanol diluted in water ( crude methanol ).
Since CO 2 hydrogenation is an exothermic reaction ( releasing energy , approximately 49.8 kJ per mol of methanol produced ), the system requires efficient heat removal . For this purpose , a water-cooling system can be employed , which takes advantage of the latent heat of vaporization of water to remove the waste heat of the reaction , generating steam ( a concept known as Boiling Water Reactor , BWR ). Alternatively , the inlet gas ( the mixture of H 2 and CO 2
) can also be used to cool down the system , allowing the reactor outlet stream to preheat the mixture fed to the synthesis loop .
Given that the reaction does not achieve 100 % conversion , the reactor effluent is separated in a high-pressure separator to recycle unreacted gases and send the crude methanol to the distillation system . In this stage of the process , components are separated based on their boiling points , obtaining practically pure streams of methanol ( CH 3
OH ) and water ( H 2
O )
( Figure 2 ). To achieve this separation , it is necessary to apply heat . Therefore , the waste heat generated in the reactor can be used in this stage , reducing the need for external energy . The heat dissipated can be used to produce between 0.6 and 0.7 tons of steam per ton of methanol .
Even with the implementation of heat integration , the distillation process generally requires the import of heat , for example , in the form of low-pressure steam . The specific requirements vary between 0.4 and 2 tons of steam per ton of methanol . Hence , we can see that methanol production requires additional heating sources , unlike ammonia synthesis , which does not .
To purify crude methanol via distillation , there are various strategies depending on the specific objectives : from maximizing purity ( such as AA grade ) to balancing operating costs ( OPEX ) and investment ( CAPEX ). To obtain high-quality methanol , more than one distillation column may be required , depending on factors such as the by-products generated and the end use of the methanol ( chemical industry or fuel ).
The first option consists in the use of two distillation columns , where the first separation unit is used to eliminate possible light byproducts and the second one for methanol
Table 1 . Estimated consumption figures for a typical 80-KTA e-methanol plant |
Parameter |
H 2 consumption ( t ) |
16,000 |
CO 2 consumption ( t ) |
112,000 |
Electricity consumption ( MW ) |
8 |
Thermal demand ( MWt ) |
3 |
Cooling demand ( MWt ) |
20 |
Investment ( M €) |
70 – 100 |
Footprint ( m ², excluding offsites and utilities ) |
7,000 – 8,000 |
Value
Hydrogen Tech World | Issue 20 | February 2025 33