Liquid dispensing system with internal recirculation

An electrostatic spray nozzle assembly (16) comprising:

• a nozzle body (30) having a fluid delivery line (20) coupled to a fluid supply (21) and a fluid return line (66) coupled to said fluid supply (21);
• a fluid delivery tube (36) supported by said nozzle body (30);
• a fluid spray tip (38) having a fluid discharge orifice (38c) supported at a downstream end of said fluid delivery tube (36);
• a fluid return tube (60) supported within said fluid delivery tube (36);
• said fluid delivery tube (36) and fluid return tube (60) defining a fluid delivery passage

An electrostatic spray drying system (10) comprising a processing tower (11) in the form of an upstanding cylindrical structure that defines a drying chamber (12);

• a top closure arrangement (14) at an upper end of said drying chamber (12) having a heating air inlet (15) and an electrostatic spray nozzle mounted therein, a bottom closure arrangement (18) into which dried powder is directed, and said heating air inlet (15) being coupled to a heating air supply (19) for directing heated drying air into said drying chamber (12);
• said electrostatic spray nozzle assembly (16) includes a nozzle body (30) having a fluid delivery line (20) coupled to a fluid supply (21) and a fluid return line (66) coupled to said fluid supply (20);
• a fluid delivery tube (36) supported by said nozzle body (30);
• a fluid spray tip (38) having a fluid discharge orifice (38c) supported at a downstream end of said fluid delivery tube (36);
• a fluid return tube (60) supported within said fluid delivery tube (36);
• said fluid delivery tube (36) and fluid return tube (60) defining a fluid delivery passage

(64) therebetween communicating between said fluid delivery line (20) and said spray tip (38);

• said fluid return tube (60) defining a fluid return passage (65) communicating between said spray tip (38) and said fluid return line (66);
• a piston assembly (50) having a shut off head (50b) supported within said fluid return tube (60) for movement between a first retracted position that permits direction of fluid from said fluid delivery line (20) through said fluid delivery passage (64) for discharge from said spray tip fluid discharge orifice (38c) and a second extended position that blocks the fluid from said fluid delivery passage (64) to said spray tip fluid discharge orifice (38c) and enables the direction of fluid from said fluid delivery passage (64) to said fluid return passage (65) and fluid return line (66) for recirculation in said fluid supply (21);
• said nozzle body (30) having a forwardly extending atomizing gas directing tube (31) in surrounding relation to said fluid delivery tube (36) for defining an atomizing gas passage (45) therebetween communicating between an atomizing gas supply (24), and said gas directing tube having an annular atomizing gas discharge orifice (40) in surrounding relation to said spray tip discharge orifice (38c) for directing atomizing gas to atomize fluid discharging form said spray tip discharge orifice (38c);
• and
• said piston connecting rod (50a), piston shut off head (50b), fluid spray tip (38), and fluid delivery and return tubes (36, 60) being in electrically conductive relation to each other, and a high voltage connector (73) for electrically charging said connecting rod (50a), shut off piston head (50b), fluid spray tip (38) and fluid and delivery tubes (36, 60) such that fluid directed through said spray nozzle assembly, both during spraying with said shut off head (50b) in said retracted open position and during fluid recirculation when said shut off head (50b) is in said spray tip discharge orifice closing position the fluid is subject to electrostatic charging.

(64) therebetween communicating between said fluid delivery line (20) and said spray tip (38);

• said fluid return tube (60) defining a fluid return passage (65) communicating between said spray tip (38) and said fluid return line (66);
• a piston assembly (50) having a shut off head (50b) supported within said fluid return tube (60) for movement between a first retracted position that permits direction of fluid from said fluid delivery line (20) through said fluid delivery passage (64) for discharge from said spray tip fluid discharge orifice (38c) and a second extended position that blocks the fluid from said fluid delivery passage (64) to said spray tip fluid discharge orifice (38c) and enables the direction of fluid from said fluid delivery passage (64) to said fluid return passage (65) and fluid return line (66) for recirculation in said fluid supply (21);
• said piston connecting rod (50a), piston shut off head (50b), fluid spray tip (38), and fluid delivery and return tubes (36, 60) being in electrically conductive relation to each other, and a high voltage connector (73) for electrically charging said connecting rod (50a), shut off piston head (50b), fluid spray tip (38), and fluid and delivery tubes (36, 60) such that fluid directed through said spray nozzle assembly, both during spraying with said shut off head (50b) in said retracted open position and during fluid recirculation when said shut off head (50b) is in said spray tip discharge orifice closing position the fluid is subject to electrostatic charging, and
• during operation of said electrostatic spray drying system with said piston shut off head (50b) in said retracted open position solids in said solid containing fluid dried in said drying chamber are directed to the bottom closure arrangement (18).