The Techno-Economic Benefit of Sorption Enhancement: Evaluation of Sorption-Enhanced Dimethyl Ether Synthesis for CO2 Utilization

Abstract

Dimethyl ether (DME) is an important platform chemical and fuel that can be synthesized from CO2 and H2 directly. In particular, sorption-enhanced DME synthesis (SEDMES) is a novel process that uses the in situ removal of H2O with an adsorbent to ensure high conversion efficiency in a single unit operation. The in situ removal of steam has been shown to enhance catalyst lifetime and boost process efficiency. In addition, the hydrogen may be supplied through water electrolysis using renewable energy, making it a promising example of the (indirect) power-to-X technology. Recently, major advances have been made in SEDMES, both experimentally and in terms of modeling and cycle design. The current work presents a techno-economic evaluation of SEDMES using H2 produced by a PEM electrolyzer. A conceptual process design has been made for the conversion of CO2 and green H2 to DME, including the purification section to meet ISO fuel standards. By means of a previously developed dynamic cycle model for the SEDMES reactors, a DME yield per pass of 72.4 % and a carbon selectivity of 84.7% were achieved for the studied process design after optimization of the recycle streams. The production costs for DME by the power-to-X technology SEDMES process at 23 kt/year scale are determined at ∼€1.3 per kg. These costs are higher than the current market price but lower than the cost of conventional DME synthesis from CO2. Factors with the highest impact on the business cases are the electricity and CO2 cost price as well as the CAPEX of the electrolyzer, which is considered an important component for technology development. Furthermore, as the H2 cost constitutes the largest part of the DME production cost, SEDMES is demonstrated to be a powerful technology for efficient conversion of green H2 into DME.

Model Analysis of the Role of Kinetics, Adsorption Capacity, and Heat and Mass Transfer Effects in Sorption Enhanced Dimethyl Ether Synthesis

“…Simulations are first performed by doubling the GHSV cat from 805 to 1610 h –1 considering the mechanical mixture configuration with a 4/1 w/w adsorbent/catalyst ratio and the standard 1/1 w/w MeOH/DME catalyst weight ratio. Referring to the whole bed volume, these GHSVs correspond to 140 and 280 h –1 , which are values within the range reported in the literature SEDMES techno-economic analysis . Results reported in Tables and show that by doubling the GHSV, the productivity grows from 25.6 to 32.5 kg DME /(h m 3 ).…”

“…Referring to the whole bed volume, these GHSVs correspond to 140 and 280 h −1 , which are values within the range reported in the literature SEDMES techno-economic analysis. 41 Results reported in Tables 8 and 9 show that by doubling the GHSV, the productivity grows from 25.6 to 32.5 kg DME /(h m 3 ). However, the DME yield, as well as CO 2 and CO x conversions, drops by more than 20%.…”

“…Effect of Operating Variables. A techno-economic analysis recently reported in the literature 41 shows that installation costs of the SEDMES unit play a significant role in DME production costs. Results in the previous section point out that catalyst distribution at the pellet scale may significantly improve the DME yield/productivity performances of the reactor.…”

“…The results reported above on the effect of both the pellet configuration and the operating window of a SEDMES reactor, could provide a basis for the refinement of the technoeconomic analysis of the DME production process, 41 which is needed to fully assess the potential of the process intensification options herein investigated.…”

“…De Falco et al reported that a DME yield of 75% can be obtained with a membrane reactor configuration for an optimized case with an operating pressure of 70 bar. Comparable performances are obtained at 30 bar using the reactive steam adsorption. − In this process configuration, also known as sorption enhanced DME synthesis (SEDMES), the two catalysts (methanol synthesis and dehydration) used for the direct DME synthesis are mixed with a selective water adsorbent such as LTA zeolite 3A or 4A. − The resulting lumped stoichiometries, considering CO and CO 2 as carbon sources, and the corresponding reaction enthalpies evaluated assuming a water adsorption enthalpy of Δ H ads = −46.0 kJ/mol, are reported in eq and , respectively. SEDMES is an intrinsically cyclic process in which the adsorption/reaction step is followed by a regeneration phase, required to remove the water stored in the adsorbent material. , …”