Method of removing scale

摘要

A method of removing scale in a cooling water system in which scale is formed comprises adding 0.01 weight % or more based on the total amount of water contained in the cooling water system of a copolymer containing vinyl monomer units having a carboxyl group or salt thereof and vinyl monomer units having a sulfo group or salt thereof in amounts to make the mol ratio of the carboxyl group to the sulfo group in the range of 30:70 to 95:5 and having weight average molecular weight calibrated with polystyrene in the range of 1,000 to 100,000 to the cooling water system while operating the cooling water system and the cleaved or dissolved scale is discharged out of the cooling water system by blowing. The scale removing agent for a cooling water system has excellent ability to remove scale, does not require much man power nor causes loss of productivity because the scale can be cleaned and removed without stopping the circulation of the cooling water while the ordinary operation of the system is maintained and has no possibility of such danger to operator as found in conventional acid cleaning processes because the agent is used in less acidic condition. Furthermore, the polymer itself has the characteristic that is not easily formed. The finishing point of the scale removal can be found easily by measuring the pH value on the spot of the operation without stopping the operation of the cooling water system.