Factors to consider when selecting a CO2 capture technology for post-combustion

There are a number of critical factors to consider when selecting a capture process from an end-user's perspective. Here are a few key items:

  • To what extent does the flue gas stream from the process need to be compressed?
    The scale and flow rate of flue gas emissions from power plants is much larger than many industrial processes. Any unit operations that involve compression of the flue gas stream are highly capital and energy intensive. Highly energy intensive processes create large "parasitic" loads on the plant, i.e. can de-rate the plant.

  • Is the capture process batch or continuous in nature?
    Flue gas emissions are produced in large volumes and are typical at atmospheric pressure. Continuous operation is critical when the scale of operation is huge. Any batch type of operation will require an extraordinary material inventory. For example, if the cycle time of a batch process is half an hour, then the CO2 holding within the system will be about 250 tonnes for a 500 MWe power plant.

  • Does the capture process produce secondary waste products? If so, at what volume and regularity?
    The management of secondary waste streams can create major challenges for plant operations as well as create large cost outlays and regulatory concerns.

  • Can the process be readily incorporated into existing plants?
    The ability to retrofit existing plants with the capture process provides flexibility for end users.

  • Does the process use existing process equipment or can existing equipment be modified readily to incorporate the process?
    This is important factor when considering technical risk mitigation as well as the likelihood that OEMs will provide sufficient warranties to enable the process to viable from a financial risk perspective.

  • What type of energy is required to perform the separation of CO2 from the flue gas stream?
    A separation process requires energy. For examples, distillation, absorption/stripping, extraction and crystallization use heat as their separating energy, whereas, a membrane process, an electrochemical process and a pH based separation processes use other sources as their separation energy. The theoretical minimum work requirement of CO2 capture from post-combustion flue gases is approximately 0.118 kWh/kgCO2, which is the same for any separation processes. However, a power plant uses heat to generate electricity (work). A separation process that uses heat will be more desirable since steam can be used directly. Other methods not based on heat could incur large inefficiencies.

Here are some attractive characteristics of a CO2 capture technology for post -combustion applications
  • Good economy of scale
  • Uses heat as separation energy
  • Operates in a continuous fashion
  • Separation agent can be regenerated(cyclical processes)
Carbon Capture Scientific is specifically designing capture process that exhibit these characteristics. Processes that are designed FROM THE END-USER'S PERSPECTIVE.