Column structure for an absorption column

A method of assembly of a column structure for containment of packing material and absorbent liquid reagent for removal of a target gas from a gas stream comprising:

• providing at least one vessel module each comprising a plurality of sub-modules configured to be assembled together and having an elongate upright structure, and providing a column top support structure;
• assembling multiple such pluralities of sub-modules together in elongate array to form multiple elongated vessel modules;
• arranging the vessel modules together alongside one another to constitute collectively said column structure such that the vessel modules collectively comprise a columnar vessel assembly;
• supporting each vessel module mechanically in a vicinity of an upper part of the column structure so assembled via the top support structure,
• wherein each vessel module is assembled by assembly of each of its plurality of constituent sub-modules successively from a top downwards.