Dosing Device for Introducing an Additive Into a Liquid Flow

Abstract

The invention relates to a dosing device for introducing an additive (A) in to a main liquid flow (L) in a conduit comprising a reciprocating differential piston pump ( 2 ) which is used for collecting and dosing the additive (A) from a container ( 1 ) and comprises a first inlet ( 7 ) for receiving the main liquid flow which ensures the pump actuation, a second inlet ( 8 ) for collecting the additive and an outlet ( 9 ) for mixing the additive and the main liquid. The inventive device comprises a Venturi ( 10 ) disposed in the conduit and the pump ( 2 ) connected in parallel position with respect thereto, wherein the first inlet ( 7 ) of the pump is connected to the Venturi input ( 11 ) and the outlet thereof is connected to the Venturi throat ( 12 ).

1 . A dosing device for introducing an additive (A) into a main liquid flow (L) circulating in a conduit, comprising a reciprocating differential piston pump for taking up the additive (A) into a container and dosing it, this pump including a first inlet for receiving a main liquid flow that drives the pump, a second inlet for taking up the additive, and an outlet for mixing the additive and the main liquid, characterized in that it comprises a venturi arranged in the conduit, and in that the pump is connected in parallel with the venturi, the first inlet of the pump being connected to the inlet of the venturi while the outlet of the pump is connected to the throat of the venturi.  
   
   
       2 . The device as claimed in  claim 1 , wherein the geometry of the venturi is adjusted to the pressure drop in the pump between the first inlet and the outlet.  
   
   
       3 . The device as claimed in  claim 1 , wherein the geometry of the venturi is adjusted to establish, in operation, a pressure difference of approximately 1.5 bar and less than 2 bar between the inlet pressure and the pressure at the throat.  
   
   
       4 . The device as claimed in  claim 1 , wherein the geometry of the venturi is adjusted such that the pressure drop created by the venturi is less than 0.5 bar.  
   
   
       5 . The device as claimed in  claim 1 , wherein an additional pressure drop is created in the secondary circuit of the pump.  
   
   
       6 . The device as claimed in  claim 5 , wherein the additional pressure drop is created by a jet.  
   
   
       7 . The device as claimed in  claim 6 , wherein the jet is placed at the outlet of the pump.  
   
   
       8 . The device as claimed in  claim 6 , wherein the jet is adjustable.  
   
   
       9 . The device as claimed in  claim 1 , wherein the venturi is regulated such that the ratio of the flow (Qe) passing through the venturi to the secondary flow (Qd) passing through the pump is equal to (R) so that with a pump enabling a flow (Qd) to be handled at a dosing rate x% the device makes it possible to handle a flow Qe=Qd.R, at a dosing rate close to x/R%.  
   
   
       10 . The device as claimed in  claim 9 , wherein the venturi is regulated such that the ratio (R) of the flow (Qe) passing through the venturi to the secondary flow (Qd) passing through the pump is equal to ten or is close to ten.  
   
   
       11 . The device as claimed in  claim 1 , wherein the pump is provided in order to allow a volume ratio between injected additive flow and drive liquid flow passing through the pump that is less than or equal to one one thousandth (  1/1000), while the volume dilution of the mixture exiting the pump in the main flow passing through the venturi is less than one percent ( 1%) such that the volume dosing in the main flow is less than or equal to 10 −5  or 10 ppm (10 parts per million).  
   
   
       12 . The device as claimed in  claim 1 , wherein the venturi and the pump form a single unit, and connecting means (Re, Rs) are provided at the inlet and at the outlet of the venturi for its insertion and connection to two portions (Te, Ts) of the conduit.