Introduction

Natural gas (NG) is projected to play a vital role in the energy mix of the 21st century. Its demand is forecasted to grow 2.5% a year for the next 10 years, ranking it second in the global energy mix in 2030.  This study was commission to provide a technical evaluation and cost assessment of capturing CO2 contained in produced natural gas and also CO2 emitted by fuel combustions for power generation for LNG trains and refrigerant cycle compressors in liquefied natural gas (LNG) plants, including small scale (SSLNG) and floating (FLNG) plants.  Prior to this study there was a lack of information on CO2 capture in LNG plants.

Consequently, the results of this study will be of direct interest to developers of LNG projects, the related capture technology, as well as vendors and policy makers

Key Messages

• Although pre-combustion and oxyfuel options are available for capturing fuel related CO₂ emissions, post-combustion CO₂ capture, using well proven chemical absorption technology, will be the preferred route for baseload LNG (with a liquefaction capacity of 4.6 mtpa, 2mol% feed gas, state-of-the-art C3MR refrigeration process, proprietary amine CO₂ capture and located on the US Gulf Coast), as it can be installed without affecting the performance of the core process.  This option reduces technical risks and process complexity.

• The cost of CO₂ captured for a baseload LNG plant (as described above) was estimated at €47.3/tCO₂ with the cost of CO₂ avoided at €55.2/tCO₂.  The levelised cost of LNG for the baseload LNG plant without CCS is €1.18/MMBtu (or €54.5/tLNG), with CO₂ capture this cost increases by ~20% to €1.41/MMBtu (or €65.4/tLNG). 

• The total range of cost encountered during the sensitivity analysis was €13 - €57/tCO₂ for the capture cost and €14 - €78/tCO₂ for the avoidance cost.  A CO₂ emissions price of at least €129/tCO₂ would be required to make the base case LNG plant with CCS economically feasible.

• A CO₂ capture design that is incorporated into an exclusive acid gas removal unit (AGRU), instead of capturing the fuel related emissions as well, could bring down costs significantly to about €30/tCO₂.  This figure is more in line with current CO₂ prices in certain countries, for example Norway and Finland, which indicates the potential for the implementation of CCS.

• Both SSLNG and FLNG plants have comparatively limited global capacity and therefore limited global CO₂ emissions.  Global CO₂ emissions from SSLNG are an order of magnitude smaller in comparison with emissions from baseload LNG plants and three orders of magnitude smaller than global CO₂ emissions from power plants (8 - 10 mtpa vs 75 - 100 mtpa vs 10,000 mtpa).  In addition, application of currently available CO₂ capture technologies face severe technical as well as economic challenges in these plants.  Thus, efforts should focus on CCS in baseload LNG plants with capture capacity plants of around 3,000 t/CO₂ day equivalent to 1 mtpa.
• Large scale LNG trains (such as those found in Qatar with a capacity of 7.8 mtpa LNG) may provide greater benefits for CO₂ capture as a result of economies of scale.  The total capture cost for plants this size is reduced by 12% with respect to the base case to about €41.6/tCO₂ and avoidance cost reduced to about €48.4/tCO₂.

• Recommendations for further work include:
  • Pursuing general efforts to make CO₂ capture systems more efficient
  • Assessment/development of other capture technologies as suitable for LNG
  • Developing strategies to reduce compression power requirement
  • Improving thermal efficiency of liquefaction process, e.g. through use of electric motor drives
  • Developing exhaust gas recycle (EGR) technology with particular focus on gas turbines in LNG
• Demonstrating CCS in LNG on the fuel gas combustion processes