One of the main barriers to producing methanol using DAC and CO₂ electrolysis is that for a power-to-methanol pathway to be a viable green process, electricity needs to be provided by a low carbon source. These electricity sources often have variable capacities and cannot be relied on to deliver continuous power.  GSS considered various locations and energy sources across Canada and determined that hydroelectric power in Quebec was the best choice.  Hydropower has very low emissions (1.2gCO₂/kWh) and is not weather-dependent like solar or wind power.  In addition, HydroQuebec offers low-cost power ($0.0346/kWh) and has a high capacity (40 000 MW) to deliver continuous power. 

Traditional methanol production relies on the production of syngas from methane or coal. GSS’s design uses the power-to-methanol pathway to generate syngas using electrolysis powered by renewable energy to advance the ambitious goal of reducing the impact on the climate.

The proposed design sequesters CO₂ from air using the chemical binding adsorption method with potassium hydroxide (KOH) as the sorbent. The concentrated CO₂ stream is converted to CO in a solid oxide electrolysis cell (SOEC). The hydrogen required is provided by the electrolysis of water in a proton exchange membrane (PEM) electrolysis cell.  These gases are fed into a reactor to produce methanol using a copper/zinc oxide/alumina catalyst. This methanol can then be used in a variety of industrial processes.

One way of presenting how effective our design solution is to see how successful DAC is with removing non-point, historical emissions from the atmosphere despite the extremely low concentrations of CO₂. Using the KOH sorbent, the DAC unit can successfully capture 75% of the CO₂ from air stream entering system.

The combined technology in the proposed GSS designed facility provides a green alternative to conventional methanol production making the overall process an effective solution to removing CO₂ from air while producing a viable revenue stream.

Detail design was conducted only for the reactor and separation unit.

Our proposed design solution was validated using hand calculations, process simulation, and additional programs such as KG Towers and MATLAB for Distillation Column and Methanol Reactor respectively.

Methanol Reactor

A plug flow reactor was modeled for methanol synthesis. The kinetics used were from papers by Graaf et al. 1986-1988 and were programmed into VMG Symmetry using the Advanced Peng Robinson property package. Using literature and plant data from Samimi et al. 2017 and Muflih et al. 2020 a comparison to output flows was done, shown in the tables below.

The fugacity coefficients used in the advanced kinetics of VMG Symmetry were programmed and calculated in MATLAB to confirm the kinetic model comparing to Chang et al. (1986) as shown in the figures below.

Distillation Column

A partial condenser distillation column for separating and purifying methanol was initially simulated in VMG Symmetry using the Advanced Peng Robinson property package. After the detailed design of the column, the ideal number of stages was found to be 32 with a reflux ratio of 0.98. This distillation column produces a methanol purity of 99.8wt%. VMG Symmetry Tower Sizing option and KG-Towers Software were used as independent methods to validate the column design.

Methods	Diameter (ft)
VMG Symmetry	11.5
KG-Tower	11.2

Results calculated from the VMG Symmetry are very close to the results from KG-Tower. The diameter of the distillation column is essentially chosen to be 12ft. The distillation column is chosen to be tray type due to the easy control and the tray type was selected to be sieve as it is suitable for low to moderate pressure drop.

Advanced Peng Robinson property package was validated comparing isobaric vapor-liquid equilibrium (VLE) data of methanol and water from VMG Symmetry and 1993 experimental binary data.

The cradle-to-gate life cycle analysis for GSS’s process, when powered by hydroelectricity, concluded that for every ton of methanol produced –0.81 tons of CO₂ will be removed from the atmosphere. The amount of CO₂ emitted when methanol is produced by coal is 3 tCO₂/tMeOH and 0.67 tCO₂/tMeOH for methanol from steam methane reforming.

The technologies for SOEC and PEM are rapidly improving and in the next 20 years it is expected that the cost for PEM and SOEC will decrease by 50% and 80%, respectively. This will improve the Net Present Value (NPV) by 27%.  

From an economics perspective, our NPV is -$10.1B which suggests the process isn’t profitable. This is mainly due to the high initial investment of the DAC unit, PEM, and SOEC equipment and the high costs associated with operating the process. However, with further improvement of these technologies decreasing these costs and government and other industry support such as grants, tax credits, and public procurement due to the process being net-negative, the process can be more economically feasible.