CO2 capture from natural gas (NG) can be done by several technologies, e.g. solvent scrubbing, membranes, adsorption or cryogenic processes. The future demand in NG might trigger development of NG fields with high CO2 partial pressure, for which pressure swing adsorption (PSA) processes could be more suitable than the other options. Besides, PSA processes have the potential to reduce energy consumption and costs. Hence, there is a requirement to evaluate the feasibility of PSA processes for CO2capture from NG at high pressures.
The aim of this work was to evaluate PSA processes for removal of CO2 from NG at high pressure. For this, the study performed a techno-economic comparison of PSA with an amine based solvent process and identified candidate materials for the PSA process. Researchers from SINTEF Chemistry & Materials and SINTEF Energy Research have carried out this study for IEAGHG.
The key messages from the report are:
- An iterative pathway was applied to find a PSA cycle design with maximum CO2 purity. The final design consists of a 12-column multi-feed cycle with around 85% CO2 purity and is the first reported design for the separation of CO2 and CH4 at a pressure of 70 bar and flowrates of 500 000 Sm³/h.
- The final PSA design has about 50% higher costs of CO2 removal (including CO2 conditioning, transport and storage) and NG sweetening than the reference amine process. However, the process is not yet optimised, so there is ample room for improvement.
- Data availability for suitable adsorbent materials is severely limited. This study used a carbon molecular sieve (CMS) and identified other materials worthwhile of further investigation, such as certain zeolites, titanosilicates, metal organic frameworks (MOFs), zeolitic imidazolate frameworks (ZIFs) and honeycomb monoliths.
- A combined approach of material and process optimisation could significantly reduce the cost of the proposed PSA design, potentially even below the cost for the reference case of amine scrubbing.
- Improving the feasibility of the PSA process for CO2 capture from NG requires more work in several areas. This includes optimisation of the PSA cycle to minimise NG losses, investigation of novel cycle concepts (e.g. hybrid of single and dual PSA), evaluation of advanced adsorption materials and data for suitable adsorbents at high pressure. This is basic research and modelling work that should be taken up by related research groups from academia and industry.