Climate change will have world-wide implications. Therefore it is very important to investigate every possible route to reduce emissions of greenhouse gases, the root cause of the problem. Various courses of actions could be taken to reduce greenhouse gas emissions, which vary in the scale of their effect, their cost and potential distribution. These options are: improvements in energy efficiency in power generation or end-use, switching to fuels containing less carbon, substitution of electricity from carbon-free sources and last but not least the capture, storage and utilisation of carbon dioxide. The advantage of using the latter option is that the society would continue to utilise the existing low-cost infrastructure of the fossil fuels while minimising the environmental impact. After the capture of carbon dioxide there are options of storing it (ocean, aquifers, oil and gas fields) or utilising it in order to produce other valuable products.
Carbon Dioxide Utilisation (CCU) technologies will help with public support of CCS and will also help support technology development of CO2, while simultaneously generating saleable products . However, to date there has been very little systematic research involving process engineering into the techno-economic analysis of the processes. In this paper we will present different options of CO2 utilisation routes as disposal of CO2 capture emissions. A techno-economic assessment of three CO2 utilisation (CCU) technologies for the production of methanol, urea and formic acid will be presented.
The three processes described were selected based on the estimated Technology Readiness Level (TRL) . Based on this analysis the current best-practice technologies as the most-likely-to be commercialised are the catalytic hydrogenation (with renewable H2) followed by distillation for the production of methanol, the CO2 stripping process (Stamicarbon) for the production of urea and the CO2 hydrogenation with renewable H2 for the production of formic acid. The three processes are evaluated in terms of key performance indicators (KPIs): process efficiency, energy requirements, avoided CO2 emissions, amount of CO2 utilised, capital and operating costs and average levelised production costs (LPC).
The methanol process was simulated at a scale of 400,000 t/yr and the NRTL model was used to calculate the thermodynamic properties of the stream, while the kinetics scheme for the reactor model and the amount of catalyst were calculated based on the work of Van-Dal and Bouallou . The urea process was simulated at a scale of 600,000 t/yr and the SR-POLAR model was used to describe the thermodynamic properties of the system. The formic acid process was simulated at a scale of 180,000 t/yr and the NRTL fluid package was used for the calculation of the thermodynamic properties. The three processes were modelled in the Aspen Plus and Hysys platform.
In addition to the results of the process modelling work we also present the results of an economic analysis related to the CCU product demand, market size and growth, production volume and pricing forecasts, and the sensitivities of the techno-economic process parameters to the price of CO2 will also be discussed.
The key conclusion of this study is that, in the absence of significantly negative price associated with CO2 utilisation, the three processes evaluated here do not as yet appear economically viable.
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