Review of Cryogenic Carbon Capture Innovations and Their Potential Applications

Our ever-increasing interest in economic growth is leading the way to the decline of natural resources, the detriment of air quality, and is fostering climate change. One potential solution to reduce carbon dioxide emissions from industrial emitters is the exploitation of carbon capture and storage (CCS). Among the various CO2 separation technologies, cryogenic carbon capture (CCC) could emerge by offering high CO2 recovery rates and purity levels. This review covers the different CCC methods that are being developed, their benefits, and the current challenges deterring their commercialisation. It also offers an appraisal for selected feasible small- and large-scale CCC applications, including blue hydrogen production and direct air capture. This work considers their technological readiness for CCC deployment and acknowledges competing technologies and ends by providing some insights into future directions related to the R&D for CCC systems.

Evaluation of Thermoacoustic Applications Using Waste Heat to Reduce Carbon Footprint

Thermoacoustics (TA) engines and refrigerators typically run on the Stirling cycle with acoustic networks and resonators replacing the physical pistons. Without moving parts, these TA machines achieve a reasonable fraction of Carnot’s efficiency. They are also scalable, from fractions of a Watt up to kW of cooling. Despite their apparent promise, TA devices are not in widespread use, because outside of a few niche applications, their advantages are not quite compelling enough to dislodge established technology. In the present study, the authors have evaluated a selected group of applications that appear suitable for utilization of industrial waste heat using TA devices and have arrived at a ranked order. The principal thought is to appraise whether thermoacoustics can be a viable path, from both an economic and energy standpoint, for carbon mitigation in those applications. The applications considered include cryogenic carbon capture for power plant exhaust gases, waste-heat powered air conditioning/water chilling for factories and office buildings, hydrogen liquefaction, and zero-boiloff liquid hydrogen (LH2) storage. Although the criteria used for evaluating the applications are somewhat subjective, the overall approach has been consistent, with the same set of criteria applied to each of them. Thermoeconomic analysis is performed to evaluate the system viability, together with overall consideration of a thermoacoustic device’s general nature, advantages, and limitations. Our study convincingly demonstrates that the most promising application is zero-boiloff liquid hydrogen storage, which is physically well-suited to thermoacoustic refrigeration and requires cooling at a temperature and magnitude not ideal for standard refrigeration methods. Waste-heat powered air conditioning ranks next in its potential to be a viable commercial application. The rest of the applications have been found to have relatively lower potentials to enter the existing commercial space.

Comparison of Performance of Alternative Post Combustion Carbon Capture Processes for a Biogas Fueled Micro Gas Turbine

The urgent need to decrease greenhouse gases (GHG) has prompted countries such as the UK and Norway to commit to net zero emissions by 2050 and 2030, respectively. One of the sectors contributing to GHG emissions is agriculture, by approximately 10% in the EU in 2017. GHG reductions in the production side should involve avoidance at source, reduction of emissions and/or removal of those emissions, with the potential for negative emissions by carbon capture. This paper focuses on the utilisation of agricultural waste that can be converted into biogas, such as livestock and crops residues which represent around 37% of GHG emissions by agriculture in the EU. The biogas can be used to produce electricity and heat in a micro gas turbine (MGT). Then, the exhaust gases can be sent to a carbon capture plant. This offers the potential for integration of waste into energy for in-house use in farms and fosters a circular-bioeconomy, where the captured CO2 could be used in greenhouses to grow vegetables. This could even allow the integration of other renewable technologies, since the MGT offers flexible operation for rapid start-up and shut down or intermittency of other technologies such as solar or wind. Current carbon capture processes are very costly at the smaller scales typical of remote communities. The alternative A3C (advanced cryogenic carbon capture) process is much more economical at smaller scales. The A3C separates CO2 from process gas that flows counter-currently with a cold moving bed, where the CO2 desublimes on the surface of bed material as a thin layer of frost. This allows enhanced heat transfer and avoids heavy build-up of frost that reduces severely the heat transfer. The phase change separation process employed by A3C and the large thermal inertia of the separation medium gives good flexibility of capture for load changes and on-off despatch. This study integrates a combined heat and power MGT, Turbec T100, of 100 kWe output. This include developed models for the MGT using characteristics maps for the compressor and turbine and for the cryogenic carbon capture plant, using two software tools, IPSEpro and Aspen Plus, respectively.