Patent ID: 7332070

Claim:
A method of preventing the fouling of a heat exchanger, which comprises adding 0.01 to 100 weight ppm of a nonionic surfactant to component (Z) comprising at least 70 wt % hydrocarbon at a temperature of 0 to 200° C. at a pressure of 0 to 10 MPa before cooling the component (Z) in the heat exchanger, wherein the nonionic surfactant is a polyoxyalkylene compound represented by the following general formula [II]: HO—(CH 2 CH 2 O) m —[CH 2 CH(CH 3 )O] n —(CH 2 CH 2 O) p H [II] wherein m, n and p each represent the average number of repeating units, and m is in the range of 1 to 20, n is 2 to 50 and p is 1 to 20.