A conceptual design for the production of synthesis gas, suitable for methanol production, is presented. We propose the reforming of natural gas with high CO2 content by using H2O or H2O–O2 as coreactants. A thermodynamic analysis for two reforming processes is developed to get adequate operating conditions for the reformer. The flow scheme for the syngas-methanol plant, together with the corresponding mass balances, is presented. A H2 separation process is considered for syngas composition adjustment. The methanol-loop reactor was also included in the analysis to take into account its close relationship with the reformer’s energy balance. For a comparative study, the hypothetical expansion of an existing methanol plant based on steam reforming of natural gas was chosen. A fundamental economic study shows that combined reforming (CO2 + H2O) and tri-reforming (CO2 + H2O + O2) of CH4 are competitive processes, with lower operating and capital costs in comparison with steam reforming.

A process for methanol production from high CO 2 content natural gas (50−60%) is presented and analyzed in technical and economic terms. A conceptual design is proposed on the basis of partial hydrogenation of the feed by the reverse water gas shift (RWGS) reaction, prior to a combined reforming operation. Both the RWGS reactor and a Lurgi-type methanol reactor were rigorously simulated via gPROMS by taking into account kinetic expressions of commercial catalysts. The mentioned reactors, the reformer, and the flash separator were all simulated as separate modules and interconnected as a whole plant. The effect of CO 2 content, feed fraction to be hydrogenated, influence of the H 2 /CO ratio and the methanol recycle ratio on the total CO 2 conversion, H 2 consumption, methanol reactor size, and CO 2 emissions were investigated. It was found that the hydrogenation of 40% of a feed containing 60% CO 2 by using a H 2 /CO 2 ratio of 1.7 followed by a combined reforming furnace leads to a syngas that has an optimum composition for methanol production. An economic analysis demonstrated that the proposed process entails lower investment costs partially due to the smaller reformer size, as compared to a methanol plant of similar production based on CH 4 steam reforming. On the other hand, the operating costs are higher mainly because of the cost of H 2 . Consequently, a negative net present value is obtained under present market prices. However, for a feed containing 50% CO 2 , the proposed process would be economically viable for a H 2 price of 2.4 US$/kg or a methanol price of 500 US$/ton. Slightly higher price variations are necessary to obtain a financially feasible project for a feed containing 60% CO 2 . Nevertheless, the reduced H 2 demand has lower economic incidence, as compared to a methanol plant based on CO 2 and H 2 as raw materials.

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