(724c) Application of a Systematic Methodology for Sustainable Carbon Dioxide Utilization Process Design

Application of a systematic methodology for
sustainable carbon dioxide utilization process design

Cristina Calvera, Rebecca Frauzem^*,
Rafiqul Gani

Department of
Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts
Plads Building 229, 2800 Kgs. Lyngby, Denmark

^* rebfra@kt.dtu.dk

As concerns about the environment
are growing, new efforts are needed to achieve more sustainable processes. One
such environmental concern is global warming, which is primarily caused by the greenhouse effect or the increase in
concentration of greenhouse gases [1]. The most significant greenhouse gases
are carbon dioxide, methane and nitrous oxide, of which carbon dioxide is the
highest constituent at 82%. Furthermore, the amount of carbon dioxide emissions
is growing with time. These trends make it evident that there is a need for
methods to reduce these greenhouse gases emissions. While there are two methods
of reducing carbon dioxide emissions, carbon capture and storage (CCS) and
carbon capture and utilization (CCU), CCU is considered promising as it makes
further use of the carbon dioxide as a solvent, raw material, and reagent to
produce valuable products [1]. Using such
utilization processes, the emissions can be reduced as they are being utilized
and profit can be obtained, or the cost of operation for the carbon dioxide
treatment can be returned, through this utilization process.

In order to systematically reduce
such emissions, carbon capture and utilization is considered rather than carbon
capture and storage. To achieve this a methodology is developed to design
sustainable carbon dioxide utilization processes. First, the information on the
possible utilization alternatives is collected, including the economic
potential of the process and the carbon dioxide emissions. The carbon dioxide
emissions can be classified as direct and indirect emissions in a chemical
process. The net carbon dioxide is determined for the utilization processes as
the indirect carbon dioxide emissions minus the carbon dioxide utilized.
Processes that presents zero or negative net carbon dioxide emission are
desired in order to reduce the carbon dioxide emissions. Using this estimated
preliminary evaluation, the top processes, with the most negative carbon
dioxide emission are investigated by rigorous detailed simulation to evaluate
the net carbon dioxide emissions. Once the base case design is established and evaluated,
targeted improvements are made by exploiting opportunities, for example,
optimization, heat integration and improved design decisions so that more
sustainable and lower net carbon dioxide emission alternatives are obtained. .

This method is applied to various
processes where carbon dioxide is used as raw material. First, the process data
are collected and compared. The economic feasibility is evaluated. From this, five
processes are selected and analyzed in detail: the production of dimethyl
carbonate, succinic acid, propylene carbonate, dimethyl ethylene and methanol. Not
all the studied processes could be designed for zero or negative net carbon
dioxide emission. Propylene carbonate production is found to have a negative
net carbon dioxide, where, implementing targeted process improvements minmized
the net carbon dioxide emission to -0.389 kg of carbon dioxide per kg of
propylene carbonate. On the other hand, for succinic acid production, even
after targeted improvements, the net carbon dioxide remained positive, even
though compared to the existing industrial processes there is a relative
reduction of upto 85%.

What this study shows is that for
meaningful net carbon dioxide reduction, the carbon dioxide utilization
processes need to be selected very carefully to obtain the best results.
However, the opportunity to potentially reduce the net carbon dioxide emissions
for the production of some bulk chemicals with carbon dioxide as feedstock
exists.

 [1] Yuan, Z., Eden, M.R.,
Gani, R., 2016. Toward the Development and Deployment of
Large-Scale Carbon Dioxide Capture and Conversion Processes. Ind. Eng. Chem. Res. 55, 3383–3419. doi:10.1021/acs.iecr.5b03277