Device and method for suppressing formation of high-melting-point pipe-clogging substance

A method for preventing pipe clogging due to a high-melting-point substance, comprising:

• disposing a urea-solution supply pipe configured to supply pressurized air and a urea solution into a pipe through which exhaust gas flows,
• connecting a urea-solution spray nozzle near a tip of the urea-solution supply pipe,
• providing a mixing section configured to mix the exhaust gas flowing through the pipe and a sprayed urea solution sprayed from the urea-solution spray nozzle, and
• forming a hydrolysis catalyst layer on an inner surface of a metal sheet circumferentially provided on all or part of an inner wall surface of the pipe in a belt-like manner around the mixing section, wherein the hydrolysis catalyst layer is configured to promote hydrolysis of urea,
• wherein the urea solution sprayed from the urea-solution spray nozzle is brought into contact with the hydrolysis catalyst layer to promote hydrolysis of isocyanic acid (HN═C═O) and cyanic acid (HOCN), thereby producing ammonia and also decreasing an amount of cyanuric acid formed.