Tank system having melting devices
Publication Date: 2011-Apr-11
The IP.com Prior Art Database
The inventions relates to a tank primarily containing a solution of water and urea for a use in a SCR system for reducing nitrogen oxides in the exhaust gases from an internal combustion engine. During cold weather conditions the solution will freeze. This invention will speed up the heating of frozen urea solution. This is done by use of a small tank 3 containing a heat exchanger 11 in which cooling fluid from the engine is used to heat the urea solution. After the fluid has passed though the heat exchanger 11 it is lead to a second heat exchanger 12 in a main tank 2 to speed up the heating of the urea solution contained therein. Immediately after start of the engine the urea solution in the small tank 3 is heated and frozen urea solution will quickly be in liquid form. This enables full functionality of the SCR system quickly after start. After a while also the urea solution in the larger main tank 2 is in liquid form and can supply the urea solution to the exhaust gases.
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Tank system having melting devices
SCR (Selective Catalytic Reduction) is one method of reducing nitrogen oxides in the exhaust gases from an internal combustion engine. A catalyst is arranged in the exhaust system in which the nitrogen oxides are converted to nitrogen and water. An injection system comprises an injector for injection a solution of urea (Adblue) into the exhaust gases before they are lead to the catalyst. The solution of urea comprises an amount of water, usually only 32 % is urea and most of the rest is water. This water makes the urea solution susceptible to freeze at lower temperatures. To enable full functionality of the SCR system after a cold start of an engine it is known to heat the tank containing the urea solution. This can be done with electric heaters or with the use of cooling liquid for the engine.
However the tank may sometimes be quite large and a large volume has to be heated before the urea solution is in a liquid mode. Therefore it has been suggested to use two separate tanks for the urea solution, one smaller tank which can be heated quickly and a larger tank containing the main part of the urea solution. Immediately after start of the engine the urea solution in the small tank is heated and frozen urea solution will quickly be in liquid form. This enables full functionality of the SCR system quickly after start. After a while also the urea solution in the larger main tank is in liquid form and can supply the urea solution to the exhaust gases.
One known system of such a tank system is described in patent US 7912360, which describes a how a small tank is heated. Although the urea solution is heated it can take some time before the urea solution in the main tank has melted. This can lead to a situation that the urea in the small tank is empty before urea can be supplied to SCR system due to the fact that the urea solution is still frozen in the main tank.
This invention will solve this problem. This invention comprise a small tank that in the same way as described above is heated and will enable full functionality of SCR system immediately after start of the engine. It also comprises main tank that also is heated which will speed up the melting of the urea solution in the main tank. Thereby the supply of urea solution to the SCR system is ensured under all conditions. The heating of the small tank and the main tank is accomplished by cooling fluid from the engine. The cooling fluid from the engine is first lead to a first heat exchanger in the small tank and thereafter is lead to second heat exchanger in the main tank. This means that hot cooling fluid is lead to the small tank which enabled quick heating of the urea solution in the small tank. Thereafter the cooling fluid is not as hot as when entered the first heat exchanger but it still contains a lot of heat that can be used to speed up the heating of the urea solution in the main tank.
Enclosed drawing shows an example of the invention. A...