I'm not an expert in the field, but Elsevier's Dictionary of the Gas Industry gives borrelen = gas scrubbing. Hence borrelpot = scrubber.

-> "Gas scrubbing, involves the removal of hazardous or toxic gases from a gas stream. The pollutant is removed from the gas phase and usually absorbed in a liquid, often water based. The types of compound treated would include Oxides of Nitrogen (NOx), Sulphur dioxide (SOx), Mercaptans, Formaldehyde and Sulphides and reduced sulphur species. Gas absorbed can be reacted in the liquid phase directly or be collected and subsequently reacted or disposed of. A method of absorbing the gas is in a scrubber, where the gas is contacted intimately with a large surface area of the liquid, this can be achieved in a number of ways."
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