Reaching another milestone for clean fuel technologies
Pre-combustion energy producing systems convert gaseous, solid or liquid fuel to create a mix of hydrogen (H2) and carbon dioxide (CO2). As well as being useful for electricity production, in the future the hydrogen generated could also heat homes and power vehicles. Crucially the process could be undertaken with almost zero emissions if the carbon dioxide is efficiently captured in the process and so it is often promoted as a useful technique in the fight against manmade climate change. However, one of the current stumbling blocks is that processes for separating the CO2, such as using the liquid ammine, occur at relatively low temperatures, which is costly, toxic to the environment and requires more energy. The EU-funded Advanced Solid Cycles with Efficient Novel Technologies (ASCENT) project, succeeded in providing a proof-of-concept for three innovative high temperature (more than 300 °C) processes that capture CO2 in cheaper and more environmentally friendly ways, while producing the hydrogen needed for highly efficient power production. Proof of concept for three processes Explaining the rationale for ASCENT, project coordinator Dr Stefano Stendardo says, “The main driving force for the research was to move the needle away from the current state of low carbon technologies, towards a step change which reduces the energy required.” Each of the three ASCENT high temperature processes were modelled to maximise power production, while minimising CO2 emissions. All processes under investigation combined a reaction which requires heat (endothermic) and a reaction which releases heat (exothermic), for a novel combination of the two heat generating approaches which made the whole process more efficient. The integration of these reactions within a single reactor permitted an increased fuel temperature for effective hydrogen production with the advantage of reduced equipment needs, alongside an increase in the volume of energy generated. Additionally, the waste heat generated during the separation of CO2 and the H2 production, can itself produce further power by means of a captive thermodynamic cycle. The three concepts under investigation for the production of hydrogen-rich fuel to be used in a power cycle or in industry, were designed to work complementarily. A Calcium-Copper looping cycle matching two endothermic-exothermic reaction pairs within the same fixed bed was tested. Secondly, the researchers looked at a concept dubbed CSHIFT, based on a highly innovative fluidized bed reactor system. Lastly, they trialled a sorption enhanced reforming (SER) process in a fluidized bed looping cycle. As Dr Stendardo recalls, “Our main challenge was testing each technology under industrially relevant pressure and temperature conditions, with materials manufactured at a scale needed for real implementation.” Once the ASCENT processes had achieved their proof of concept, they were subjected to modelling and simulation at the full scale necessary for industrial power production. Working to higher technology readiness levels The ASCENT project contributes to a number of environmentally focussed EU policies such as ambitions to improve energy efficiency and tackle climate change through the use of clean fossil fuel. It also helps address the pressing need to secure Europe’s energy supply long-term, alongside enhancing the competitiveness of European industry, including the involvement of small and medium enterprises Taking the work forward to build on the successful chemical and mechanical properties of the ASCENT materials, Dr Stendardo enthuses, “Our ambition is to continue further upscaling the development and manufacture of these materials. A potential evolution for the ASCENT technologies is their hybridisation with renewables, for energy storage and further reduction of CO2 emissions.”
Keywords
ASCENT, fossil fuel, clean energy, pre-combustion, climate change, CO2, hydrogen, power, electricity, heat, temperature, reactor