Urea depollution circuit compromising a double-seat valve selectively ensuring the degrassing or the recirculation of the aqueous urea solution

A circuit intended to transfer, by means of a pump, a first fluid from a reservoir to a destination point, said circuit being likely to contain, in addition to the first fluid, a second fluid, whose density and dynamic viscosity are lower than those of the first fluid, said circuit comprising, downstream of the pump and of the reservoir, a downstream circuit portion which includes, on the one hand, a first branch, called main branch, which leads to the destination point and, on the other hand, a second branch, called bypass branch, which bifurcates from the first branch, at a bifurcation located upstream of the destination point, in order to return to the reservoir, said circuit wherein the bypass branch is provided with a double-seat valve which comprises a shutter which is movably mounted between a first seat connected to the main branch and a second seat connected to the reservoir, said double-seat valve being arranged to adjust the position of the shutter depending on the drag exerted by the fluid which penetrates into said valve, so as to be able to selectively and automatically adopt:

• a first configuration, called purge configuration, in which the shutter adopts, under the action of the second fluid, an intermediate position between the first seat and the second seat, thus placing the valve in an open configuration, so as to allow a purge of said second fluid out of the main branch and a return of said second fluid to the reservoir by the bypass branch,
• a second configuration, called pressurized supply configuration, in which the shutter is positioned into sealing contact with the second seat, under the action of the first fluid, when said first fluid is driven by the pump according to an operating regime called pressurized supply regime, so as to direct the first fluid towards the destination point, through the main branch, under a pressure equal to or higher than a predetermined pressure threshold called working pressure threshold (P_thresh),
• and a third configuration, called recirculation configuration, in which the shutter adopts, under the action of the first fluid, an intermediate position between the first seat and the second seat, thus placing the valve in an open configuration, when said first fluid is driven by the pump according to an operating regime called recirculation regime, that is distinct from the pressurized supply regime and that imparts to said first fluid a head lower than said pressurized supply regime, so as to allow an at least partial recirculation through the bypass branch, and to the reservoir, of said first fluid coming from said reservoir.