468882 Conceptual Analysis of Process Alternatives for Solar Thermochemical Methanol Production: The Role of Chemical Storage

Thursday, November 17, 2016: 10:10 AM
Powell (Hilton San Francisco Union Square)
Bruno A. Calfa, Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI and Christos T. Maravelias, Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI

Conceptual Analysis of Process Alternatives for Solar Thermochemical Methanol Production:

The Role of Chemical Storage

Bruno A. Calfa[1] and Christos T. Maravelias NOTEREF OLE_LINK1 \h  \* MERGEFORMAT 1 08D0C9EA79F9BACE118C8200AA004BA90B02000000080000000A0000004F004C0045005F004C0049004E004B0031000000

In this talk, we study the production of fuels and chemicals from a renewable source, namely solar energy. In a solar refinery, solar energy is utilized to convert raw materials, such as CO2 emitted from fossil fuel power plants (and sometimes with H2O), into value-added products; e.g., methanol and Fischer-Tropsch (F-T) fuels (Herron et al., 2015). While different solar-based technologies have been investigated to carry out the conversion, in this paper, we consider the solar thermochemical splitting of CO2 and H2O (see Meier and Steinfeld (2013) and references therein), which has some similarities with Concentrated Solar Power (CSP) technology in the electric power industry.

The viability, based on systems-level analyses, of a solar-driven (thermochemical cycle technology) process to produce methanol and/or F-T fuels from syngas produced from CO2 and H2O splitting has recently been evaluated in the literature (Kim et al., 2011; Kim et al., 2012; Kim et al., 2013; Rytter et al., 2016; Falter, Batteiger, and Sizmann, 2016). However, all aforementioned works considered a continuously operated process. However, one fundamental aspect of the production of solar fuels is the inherent intermittency of solar energy. Therefore, since the splitting reactions cannot take place when there is not sufficient solar irradiance (i.e., cloudy days or at night), there is a need to consider chemical storage.

In this work, we provide a systems-level analysis of three process configurations, a base case and two alternatives, which employ solar-thermal technology for the conversion of CO2 and H2O to syngas, which is further upgraded to methanol. We propose and assess the use of chemical storage to cope with the intermittency of solar-based chemical technologies. The base case requires intermediate gas storage, since all streams are treated as continuous from a high-level perspective (typically assumed in the literature).

First we determine the number of compression stages that minimizes the total annualized cost of compression and storage of CO2/CO and H2 streams. Material and energy balances followed by an economic analysis indicate that gas compression and storage significantly contribute to the production cost in the base case, which makes it less economically favorable than its alternatives. We perform sensitivity analysis for key process parameters (e.g., chemical conversion of the solar reactors, cost of the solar field and solar reactors, and solar refinery capacity) to investigate their effect on the production cost of methanol.

The two alternative process configurations do not require gas storage, since the syngas production step is operated entirely intermittently. One process alternative uses a reverse water-gas-shift reactor to further convert CO2 to CO and correct the stoichiometric number (H2:CO ratio) required for the methanol synthesis step, whereas the other process alternative has a membrane-based CO2/CO separation that is operated intermittently. Our analyses show that the process alternatives have overall lower total capital investment and operating costs than the base case, whose compression, storage, and amine-based CO2/CO separation costs represent major components of the production cost.

References

Falter, C.; Batteiger, V.; and Sizmann, A. 2016. Climate Impact and Economic Feasibility of Solar Thermochemical Jet Fuel Production. Environmental Science & Technology. 50(1):470-477.

Herron, J. A.; Kim, J.; Upadhye, A. A.; Huber, G. W.; and Maravelias, C. T. 2015. A General Framework for the Assessment of Solar Fuel Technologies. Energy & Environmental Science. 8(1):126-157.

Kim, J.; Henao, C. A.; Johnson, T. A.; Dedrick, D. E.; Miller, J. E.; Stechel, E. B.; and Maravelias, C. T. 2011. Methanol Production from CO2 Using Solar-Thermal Energy: Process Development and Techno-Economic Analysis. Energy & Environmental Science. 4(9):3122-3132.

Kim, J.; Johnson, T. A.; Miller, J. E.; Stechel, E. B.; and Maravelias, C. T. 2012. Fuel Production from CO2 Using Solar-Thermal Energy: System Level Analysis. Energy & Environmental Science. 5(9):8417-8429.

Kim, J.; Miller, J. E.; Maravelias, C. T.; and Stechel, E. B. 2013. Comparative Analysis of Environmental Impact of S2P (Sunshine to Petrol) System for Transportation Fuel Production. Applied Energy. 111:1089-1098.

Meier, A., and Steinfeld, A. 2013. Solar Energy. New York, NY: Springer New York. chapter Solar Energy in Thermochemical Processing, 521-552.

Rytter, E.; Sou__kov‡. F; Lundgren, M. K.; Ge, W.; Nannestad, . D.; Venvik, H. J.; and Hillestad, M. 2016. Process Concepts to Produce Syngas for Fischer-Tropsch Fuels by Solar Thermochemical Splitting of Water And/Or CO2. Fuel Processing Technology. 145:1-8.



[1] Department of Chemical and Biological Engineering. University of Wisconsin-Madison. Madison, WI 53706. USA.


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