(743a) Process Design and Intensification for Natural Gas Conversion to Methanol | AIChE

(743a) Process Design and Intensification for Natural Gas Conversion to Methanol


Monjur, M. S. - Presenter, Texas A&M University
Li, J., Artie McFerrin Department of Chemical Engineering, Texas A&M University
Demirel, S. E., The Dow Chemical Company
Hasan, F., Texas A&M University
Shale gas production in the U.S. has drastically increased in recent years due to the emergence of advanced drilling technologies, like hydraulic fracturing and horizontal drilling. The availability of cheap natural gas resources has presented opportunities for distributed manufacturing of both commodity chemicals and petrochemicals [1,2]. One such product is methanol, which has varied potential uses as a commodity chemical, clean-burning fuel, and an intermediate for several other important chemicals [3,4]. The currently used natural-gas-to-methanol process is one of the largest energy consumers in the chemical industry [5]. The large energy consumption also affects the profitability and sustainability. Novel design solutions are needed to alleviate the energy burden on the current methanol production technologies. Process integration strategies can be used towards increasing the energy efficiency, but they alone cannot suggest novel design solutions. Process intensification can be useful as a holistic approach as it seeks for novel designs with significant improvements in processing volume, energy efficiency, environmental impact, and economics, among others [6]. Hence, a simultaneous process integration and intensification methodology would be highly beneficial for methanol production. In this work, we use the building block representation [7-12] for the synthesis, integration, and intensification of the methanol process. This block based representation method is comprised of blocks positioned in a two-dimensional grid. Several chemical and physical phenomena e.g. vapor-liquid equilibrium, gas permeation, reaction, etc. can be represented by this method. We have considered partial oxidation reaction to produce the syngas and water gas shift reaction to further improve the syngas ratio. The syngas is then converted to methanol followed by product separation. To capture the details of reaction phenomena, reactors are modeled as plug flow reactors with LHHW type reaction kinetics. When the superstructure is solved with the objectives of profit and sustainability, several intensified flowsheets are obtained. For example, an optimized membrane reactor replaces the conventional methanol reactor and significantly increases the single-pass conversion which in turn reduces the cost of down-stream methanol separation. Furthermore, the intensified membrane reactor reduces the energy consumption and operates at milder conditions. Overall, the new design can achieve significant improvement in total annual profit compared to the base case flowsheet reported in the literature [13].


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