Method for composition for cleaning tubular systems employing moving three-phase lines

A method for cleaning an internal surface of a narrow diameter channel, the method

• comprising the steps of:
• i) flowing a liquid cleaning medium and a gas through the channel under a flow regime that provides surface flow entities in contact with and sliding along the internal surface of the channel, said surface flow entities having three-phase contact lines and associated menisci, said surface flow entities detaching contaminants with which they come in contact from the internal surface of the channel, wherein the flow regime is Discontinuous Plug Flow, Discontinuous Plug Droplet Flow, or a combination of Discontinuous Plug Flow and Discontinuous Plug Droplet Flow, by pulsing aliquots of the liquid cleaning medium into the channel with a pulse time Pt and having the liquid flow at a rate sufficient to form a flowing plug of cleaning medium pushed through the channel by a flowing gas, said flowing plug either remaining intact throughout the channel length or forming fragments, said fragments remaining attached to and slide along the surface, said liquid plug and fragments detaching contaminants from the internal surface of the channel by the sweeping of the surface of the channel with the three-phase contact lines of the liquid plug or the fragments formed there from;
• ii) rinsing the internal surface of the channel to remove residual liquid cleaning medium and detached contaminants from the channel;
• wherein during step i):
• the detachment of contaminants from the internal surface of the channel is produced by a sweeping of the internal surface of the channel with the three-phase contact lines of the surface flow entities,
• the cleaning medium is not predispersed in the gas as droplets before entering the channel, and
• less than 10% of the surface of the channel is covered by a contiguous annular film.