Lesson 11 - Carbon Dioxide Recovery Technology SAQ

*/**Describe the operation of the following two sub-processes of a recovery plant: a washer (scrubber); and a deodoriser.

Response:

In comparing and contrasting the two sub-processes, it is worthwhile having a template in mind as it gives some focus to the discussion.

So, let us consider the following aspects: key function; principle of operation; technology involved, and operational philosophy. You may have considered more but below are some brief comments using this template against the two sub-processes:

• Washer (scrubber)

  • Key function: to remove water-soluble components from the CO₂ gas.

  • Principle of operation: absorption of the water-soluble components in water.

  • Technology: increase of surface area to increase the rate of absorption by use of packing material held within a column.

  • Operating philosophy: contact the gas and water over the packing material to remove sufficient quantities of contaminant from the gas as a counter-current absorption column. This can be tracked by assessing the scrubbing efficiency based on the percentage of ethanol removal.

• Deodoriser:

  • Key function: to remove aroma components from the CO₂ gas.

  • Principle of operation: adsorption of the aroma compounds using an adsorbent, most typically activated charcoal.

  • Technology: the adsorbent is held in two columns operated in a duty-standby configuration, and the gas flows over the adsorbent.

  • Operating philosophy: the duty column is fed with gas and is deodorised until the adsorbent becomes saturated at which point the gas feed is switched to the standby column. The saturated column is regenerated using steam, and following regeneration, the column is available as a standby column. After repeated regeneration cycles, the effectiveness of the adsorbent is too low, and the adsorbent is reactivated, typically off-site.