Apparatus and method for screening powders

An assembly for screening powder, wherein said assembly comprising a first screening device and a second screening device, wherein each of the first screening device and the second screening device comprises:

• a screening space comprising a first chamber and a second chamber, wherein the first chamber and the second chambers are adjacent and have a common partition wall, and
• a screen, wherein the screen forms at least a part of the partition wall,
• wherein the first chamber comprises a raw material inlet and a residual particle outlet,
• wherein the second chamber comprises a product material outlet and a rotatable blade, wherein the rotatable blade comprises one or more nozzles which are configured for blowing gas against the screen,
• wherein the screen is placed obliquely or vertically, and in that the first chamber further comprises a float gas unit, wherein the float gas unit is configured for, in use, providing an upwards directed flow of float gas directly into a part of the first chamber, and wherein the screening device is configured for, in use, providing a pressure difference between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber,
• wherein the raw material inlet is arranged at a top side of the first chamber, and wherein the float gas unit is arranged at a bottom side of the first chamber and is configured to direct the float gas in the upwards direction such that the float gas provides a counter flow directly against a flow of raw material from the raw material inlet,
• wherein the assembly further comprises a connection between the raw material inlet of the second screening device and the product material outlet of the first screening device.

A method for screening powder using a screening device comprising:

• a screening space comprising a first chamber and a second chamber, wherein the first chamber and the second chambers are adjacent and have a common partition wall, and
• a screen, wherein the screen forms at least a part of the partition wall,
• wherein the first chamber comprises a raw material inlet and a residual particle outlet,
• wherein the second chamber comprises a product material outlet and a rotatable blade, wherein the rotatable blade comprises one or more nozzles which are configured for blowing gas against the screen,
• wherein the screen is placed obliquely or vertically, and in that the first chamber further comprises a float gas unit, wherein the float gas unit is configured for, in use, providing an upwards directed flow of float gas directly into a part of the first chamber, and wherein the screening device is configured for, in use, providing a pressure difference between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber,
• wherein the raw material inlet is arranged at a top side of the first chamber, and wherein the float gas unit is arranged at a bottom side of the first chamber and is configured to direct the float gas in the upwards direction such that the float gas provides a counter flow directly against a flow of raw material from the raw material inlet,
• wherein the method comprising the steps of:
• providing powder in the first chamber via the raw material inlet, wherein the powder comprises an assembly of particles having a variety of dimensions;
• activating the float gas unit in the first chamber to provide the counter flow configured for at least partially suspending or floating at least part of the particles of the powder in the first chamber;
• blowing gas against the screen by means of one or more nozzles of the rotating blade;
• providing the pressure difference between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber;
• and
• allowing the particle of said powder with dimensions smaller than openings in the screen to pass through the screen into the second chamber, wherein the particles arriving in the second chamber are part of a product material which exits the second chamber via the product material outlet.

A method for screening powder using an assembly comprising a first screening device and a second screening device, wherein each of the first screening device and the second screening device comprises:

• a screening space comprising a first chamber and a second chamber, wherein the first chamber and the second chambers are adjacent and have a common partition wall, and
• a screen, wherein the screen forms at least a part of the partition wall,
• wherein the first chamber comprises a raw material inlet and a residual particle outlet,
• wherein the second chamber comprises a product material outlet and a rotatable blade, wherein the rotatable blade comprises one or more nozzles which are configured for blowing gas against the screen,
• wherein the screen is placed obliquely or vertically, and the first chamber further comprises a float gas unit, wherein the float gas unit is configured for, in use, providing an upwards directed flow of float gas directly into a part of the first chamber, and wherein the screening device is configured for, in use, providing a pressure difference between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber,
• wherein the raw material inlet is arranged at a top side of the first chamber, and wherein the float gas unit is arranged at a bottom side of the first chamber and is configured to direct the float gas in the upwards direction such that the float gas provides a counter flow directly against a flow of raw material from the raw material inlet,
• wherein the assembly further comprises a connection between the raw material inlet of the second screening device and the product material outlet of the first screening device
• wherein the method comprising the steps of:
• providing powder in the first chamber via the raw material inlet, wherein the powder comprises an assembly of particles having a variety of dimensions;
• activating the float gas unit in the first chamber to provide the counter flow configured for at least partially suspending or floating at least part of the particles of the powder in the first chamber;
• blowing gas against the screen by means of one or more nozzles of the rotating blade;
• providing the pressure difference between the first chamber and the second chamber such that the pressure in the second chamber is lower than the pressure in the first chamber;
• and
• allowing the particle of said powder with dimensions smaller than openings in the screen to pass through the screen into the second chamber, wherein the particles arriving in the second chamber are part of a product material which exits the second chamber via the product material outlet, wherein the product material of the first screening device of the assembly is at least partially lead into the raw material inlet of the second screening device of the assembly.