Apparatus for maintaining a urea solution in a liquid state for treatment of diesel exhaust

摘要

A system (110) for keeping a reservoir solution of urea in a liquid state at normally sub-freezing temperatures comprising a reservoir tank module (116) having a heater (26) and disposed in a solution storage tank. Solution in the storage tank is heated by passage of heat through the walls of the reservoir tank module (116) which are formed of a hybrid of plastic polymer (142) and metal (140), preferably a urea-resistant stainless steel, such that the thermal conductivity of the walls is sufficient to liquefy frozen solution in the storage tank in a practical time frame at an acceptable net manufacturing cost for the tank module (116).
The hybrid combination may be formed in any of various arrangements such as, but not limited to, a lower portion formed of metal (140) and an upper portion formed of plastic (142), or alternating bands and/or strips of metal and plastic. The optimum thicknesses of metal and plastic may be determined conventionally.