Apparatus for Maintaining a Urea Solution in a Liquid State for Treatment of Diesel Exhaust

Abstract

A system for keeping a reservoir solution of urea in a liquid state at normally sub-freezing temperatures comprising a reservoir tank module disposed in a solution storage tank. Solution in the storage tank is heated partially by passage of heat through the walls of the reservoir tank module. Additional heat is derived from waste heat in engine exhaust gas and is added to the system by passing a portion of the exhaust gas stream through a gas/liquid heat exchanger disposed within the solution in the storage tank. The cooled gas is returned to the exhaust system or is sent to the engine intake manifold for EGR.

1 . A system for keeping a solution of urea in a liquid state at normally sub-freezing temperatures or liquefying such solution if frozen, for delivery to an emissions abatement system of an internal combustion engine, comprising:
 a) a storage tank for said urea solution;   b) first apparatus for deriving an exhaust gas portion from an exhaust system of said engine; and   c) second apparatus for exchanging heat from said exhaust gas portion with said solution of urea in said storage tank.   
     
     
         2 . A system in accordance with  claim 1  wherein said second apparatus includes said storage tank and a gas/liquid heat exchanger disposed within said storage tank. 
     
     
         3 . A system in accordance with  claim 1  wherein said second apparatus includes at least one of a temperature sensor and a pressure sensor. 
     
     
         4 . A system in accordance with  claim 1  wherein said first apparatus includes a diverter valve mounted on said exhaust system for diverting said exhaust gas portion from an exhaust gas stream flowing therewithin. 
     
     
         5 . An internal combustion engine comprising a system for keeping a reservoir solution of urea in a liquid state at normally sub-freezing temperatures, or liquefying such solution if frozen, for delivery to an emissions abatement system of an internal combustion engine, wherein said system includes,
 a storage tank for said urea solution,   first apparatus for deriving an exhaust gas portion from an exhaust system of said engine, and   second apparatus for exchanging heat from said exhaust gas portion with said solution of urea in said storage tank.   
     
     
         6 . A method for keeping a reservoir solution of urea in a liquid state at normally sub-freezing temperatures, or liquefying such solution if frozen, for delivery to an emissions abatement system of an internal combustion engine, comprising the steps of:
 a) providing a storage tank for said urea solution;   b) providing a gas/liquid heat exchanger within said urea solution in said storage tank;   c) deriving an exhaust gas portion from an exhaust system of said engine; and   c) passing said exhaust gas portion through said gas/liquid heat exchanger to heat said solution of urea.   
     
     
         7 . A method in accordance with  claim 6  further comprising the step of returning said exhaust gas portion from said gas/liquid heat exchanger to said exhaust system. 
     
     
         8 . A method in accordance with  claim 6  further comprising the step of directing said exhaust gas portion from said gas/liquid heat exchanger to an intake manifold of said engine.