Reflux condenser method

A method of operating a condenser, comprising:

• flowing a vapor stream including formaldehyde and water into a generally upright tube bundle in a vertical upflow reflux condenser, where a tube in the tube bundle has a length to outside diameter ratio of greater than about 170:1;
• flowing a cooling fluid on a shell-side of the vertical upflow reflux condenser to condense at least a portion of the vapor stream, where the condensed portion of the vapor stream and the vapor stream flow counter currently within the tube in the tube bundle and the condensed portion of the vapor stream forms a wetted tube internal surface area on each tube in the generally upright tube bundle;
• promoting methylene glycol formation by providing the wetted tube internal surface area for reacting formaldehyde and water to form methylene glycol;
• and
• maintaining the vapor stream velocity at a rate that provides a liquid residence time where formaldehyde condensed on the wetted internal surface area of each tube can react with water to form methylene glycol, removing at least sixty percent (60%) of formaldehyde from the vapor stream fed to the condenser.