Simulations and Optimization of a Reduced CO₂ Emission Process for Methanol Production Using Syngas from Bi-reforming

Abstract

A low CO2 emission process for methanol production using syngas generated by combined H2O and CO2 reforming with CH4 (bi-reforming) is proposed in this work. A detailed process model was developed using Aspen Plus. The operating conditions of the bi-reforming and methanol synthesis were derived from a detailed sensitivity analysis using plug flow reactor models with Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetics. A molar feed ratio of CH4:CO2:H2O of 1:1:2, instead of conventional 3:1:2 in the bi-reforming was found to be optimum and resulted in ∼99% conversion of CH4, 44% conversion of CO2, and a H2/CO ratio of 1.78 at 910 °C and 7 bar. A higher methane conversion eliminated the need for cryogenic separation of CH4. The optimum feed ratio of 1:1:2 resulted in an ∼33% higher consumption of CO2 per mole of CH4 required than the conventional process. An acid gas removal process using MDEA was used for CO2 separation, and a network of heat exchangers was configured for heat recovery. The proposed process resulted in ∼0.37 tonne of CO2 per tonne of methanol, which is ∼2–4 times lower than several published data and commercial methanol processes.

Design Strategy, Synthesis, and Mechanism of Ni Catalysts for Methane Dry Reforming Reaction: Recent Advances and Future Perspectives

“…have successfully converted carbon dioxide to valuable hydrocarbons. − However, the conversion efficiency in electrocatalysis and photocatalysis is relatively low. In comparison, thermocatalysis has been maturely developed for decades and has been considered the most applicable technique because of the high conversion efficiency. , Methane, another main contributor to the greenhouse effect, is abundant in natural gas and shale gas. It is also a carbon resource that can be used for value-added energy fuel production. − Because of the difficult C–H activation by photocatalysis and electrocatalysis under mild conditions, the methane conversion rate is rather slow.…”

“…In comparison, thermocatalysis has been maturely developed for decades and has been considered the most applicable technique because of the high conversion efficiency. 6,7 Methane, another main contributor to the greenhouse effect, is abundant in natural gas and shale gas. It is also a carbon resource that can be used for value-added energy fuel production.…”

Optimized Process for Methanol Production via Bi-reforming Syngas

“…They found that higher CO 2 in the feed did not impact the conversion of CH 4 , increased the CO 2 conversion, and decreased the H 2 /CO ratio in the product stream. Recently, Acquarola et al 19 used a feed ratio of 1:1:2 in the bi-reforming step and reported significantly lower CO 2 emission in their process. Heat integration or heat recovery in such a two-step process is extremely critical to the reduction of CO 2 emission in the process.…”

“…For example, a few studies 5,15,20,21 considered the conditions of feed components (CO 2 , H 2 O, and CH 4 ) to be at the reactor inlet temperature or pressure or both. In reality, CH 4 is typically available at high pressure and H 2 O is available at ambient conditions as considered by Acquarola et al 19 and Nguyen and Zondervan. 13 In this two-step process, it is also critical to adjust the CO 2 concertation in the gas stream coming out of the bi-reforming step.…”

“…Both reactors (R-1 and R-2 in Figure 2) were modeled as PFRs using detailed reaction kinetics. The reaction kinetic models of bi-reforming and methanol synthesis discussed in Acquarola et al 19 were used in the current study. Both PFRs were modeled as multitubular catalytic reactors with a bed voidage of 0.4 and constant operating conditions without a pressure drop.…”