Dehumidification method and plant particularly for granular materials

• US 20070199203A1
• Filed: 02/09/2007
• Published: 08/30/2007
• Est. Priority Date: 02/10/2006
• Status: Active Grant

• Current Assignee: Moretto S.p.A. (Faita SA)
• Original Assignee: Moretto S.p.A. (Faita SA)
• Inventors: Federico, Critelli
• Granted Patent: US 7,662,211 B2
• Time in Patent Office: Days
• US Class Current: 34/416
• CPC Class Codes: B01D 2253/108 Zeolites
• CPC Class Codes: B01D 2259/402 using two beds
• CPC Class Codes: B01D 53/04 with stationary adsorbents B01D53/025 takes precedence
• CPC Class Codes: B01D 53/0407 Constructional details of adsorbing systems
• CPC Class Codes: B01D 53/261 by adsorption
• CPC Class Codes: B29B 13/065 of powder or pellets
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules
• CPC Class Codes: F26B 21/083 by using sorbent or hygroscopic materials, e.g. chemical substances, molecular sieves

Abstract

The present invention relates to a granular-material dehumidification plant including at least one silo or hopper (1) arranged to receive granular material (2) to be dehumidified at the top thereof and provided with a controlled lower delivering mouth (3), at least one feeding duct (8, 10) designed to be dipped in the granular material (2) contained in each hopper (1) to supply hot and dry processing air thereto, and at least one exhaust duct (5) for humid processing air; at least two molecular sieve towers (68, 69) arranged alternately to supply hot and dry processing air to the at least one hopper, each tower delimiting therein a space (67) for housing molecular sieves and a chamber (70) for housing heating means, the space and the chamber being in fluid communication with one another at one end thereof, while being in fluid communication, at the other end thereof, with a respective air inlet/outlet duct (65, 73; 66, 74); air pressurizing or pumping means (13) arranged to receive, at the suction (inlet) side thereof, humid processing air from a respective exhaust duct (5), and to feed pressured air, at the delivery side thereof, to each molecular sieve tower (68, 69); switching-shunting means (24) located between the delivery of the pressurizing means and the inlet/outlet ducts of the housing spaces (67) for molecular sieves thereby switching at least one of the molecular sieve towers between a processing step and a regeneration step; and a programmable electronic control unit (15). The granular-material dehumidification plant further comprises pressurizing valve means (77) located between the inlet/outlet ducts (73, 74) of the housing chamber (70) of the heating means for each molecular sieve tower (68, 69) and arranged to ensure a minimum pressure within a tower during a regeneration step, and temperature detecting means electrically connected to an input of the programmable electronic control unit.

Claims

1. A dehumidification plant for granular materials including at least one silo or hopper (1) for containing and dehumidifying granular material (2), which is provided with a controlled lower supplying mouth (3) arranged to receive at its top granular material (2) to be dehumidified, at least one feeding duct (8, 10) for hot and dry process air designed to draw within the granular material (2) contained in each hopper (1), and at least one exhaust duct (5) for humid process air;

at least two molecular sieve towers (68, 69) arranged to alternately supply hot and dry process air to each hopper, each delimiting a housing chamber for molecular sieves and a housing chamber for heating means, said housing chambers being in communication one with another at an end thereof, whereas they are in communication, at their other end, with a respective air inlet/outlet duct;

pressurizing or pumping means arranged to receive, at the suction (inlet) side, humid process air from said at least one exhaust duct, and to feed at the delivery side, pressured air to each molecular sieve tower;

switching-shunting means placed between the delivery side of said pressurizing means and said inlet/outlet ducts of said housing chambers for molecular sieves in order to switch at least one of said molecular sieve towers between a process step and a regeneration step; and

a programmable electronic control unit,

characterized in that it comprises pressurizing valve means placed between said inlet/outlet ducts of said housing chamber of said heating means for each molecular sieve tower and arranged to assure a minimum pressure within a tower during the regeneration step, and detecting means for temperature electrically connected to said programmable electronic control unit, at its input.

2. A plant as claimed in claim 1, characterized in that said valve means (77) comprises an inner chamber (78) in direct communication with said inlet/outlet ducts (73, 74), and in communication with an outlet (79) to at least one feeding duct (8) through an opening (80), which can be intercept by a shutter means (82) provided with a gauged opening/closing in function of the pressure within said inner chamber (78).

3. A plant as claimed in claim 2, characterized in that said shutter means (82) is supported by a rod or pin (83) slidingly mounted in a substantially vertical direction within the inner chamber (78), thereby opening and closing for gravity owing to the pressure variation of the air in said chamber (78).

4. A plant as claimed in claim 3, characterized in that said shutter means is elastically loaded in a gauged way, thereby opening and closing proportionally to the pressure within said inner chamber (78).

5. A plant as claimed in any previous claim, characterized in that it comprises intercepting means (39) in communication with at least one exhaust (38) from said switching-shunting means (24) and drivable by a means (27) designed to detect the pressure differential between the suction side (25) and the delivery side (29) of said pressurizing means (13).

6. A plant as claimed in claim 5, characterized in that said intercepting means comprises a diaphragm valve (39), whose diaphragm (42) delimits two inner compartments (40, 41), a compartment (40) communicating with at least one exhaust opening (43), whereas the other (41) is in fluid communication with said pressure differential detecting means (27).

7. A plant as claimed in claim 5 or 6, characterized in that said pressure differential detecting means comprises a solenoid valve (27) having two inlets (26, 28) in fluid communication with, respectively, the suction side and the delivery side of said air pressurizing means (13), and its outlet (44) in fluid communication with said compartment (41).

8. A plant as claimed in any previous claim 5 to 7, characterized in that said switching-shunting means comprises a slide valve means (24), and driving means (52-55) of said slide valve assembly designed to drive it both in a continuous and pulsating way.

9. A plant as claimed in claim 6, characterized in that said slide valve assembly (24) presents

a valve body internally delimiting two side chambers (45, 46), and a intermediate chamber (47), which communicate each other through openings (50, 51), said intermediate chamber communicating with the delivery side of said air pressurizing or pumping means (13), whereas said side chambers (45, 46) communicate with both a respective air inlet/outlet duct (65, 66) and a respective exhaust opening (50a, 51a) to said intercepting means (39), and

comprises a rigid rod (52), which extends through said side chambers (45, 46) and intermediate (47), supports a pair of shutter means (56, 57) fixed thereto and designed to open-close said openings (50, 51;

50a, 51a), and exits from the valve body thereby cinematically connecting to said driving means.

10. A plant as claimed in claim 9, characterized in that said driving means comprises a reversible linear operating means including a reversible electric motor (53) drivable by a programmable electronic control unit (15) and a reducer (54), and a rack (55) cinematically connected to said reducer and moving integral with said rigid rod (52).

11. A plant as claimed in claim 9, characterized in that said linear operating means comprises two spaced stops (58, 59) fixed on said rigid rod (52), an elastic loading means (60, 61) for each stop designed to abut against a member fixed with respect to said rigid rod (52), a pair of micro-switches (62, 63) carried by the rod (52) and arranged to abut against a intermediate contact (64) fixed with respect to the rod (52) and arranged to permit said reversible motor (53) to stop at two working positions of said shutters (56, 57).

12. A plant as claimed in any previous claim, characterized in that it comprises cooling means designed to cool the air flowing in said at least one exhaust duct (5) for humid process air directed to said air pressurizing means (13).

13. A plant as claimed in claim 12, characterized in that said cooling means comprises an assembly of parallel pipes (18) subjected to the action of at least one fan (19) operable by a respective electric motor (20).

14. A plant as claimed in any previous claim, characterized in that it comprises a heat probe (86) arranged to detect the temperature of the air coming out the regeneration tower (65), and electrically connected to said programmable electronic control unit (15).

15. A plant as claimed in any previous claim, characterized in that said programmable electronic control unit (15) includes a first memory portion designed to store treating parameters concerning a first multiplicity of granular materials, and a second memory portion designed to store treating parameters of experimental materials.

16. A plant as claimed in any previous claim, characterized in that it comprises a user interface (91) with said programmable electronic control unit (15).

17. A plant as claimed in claim 16, characterized in that said user interface (91) comprises a display unit, and data inputting means in said programmable electronic control unit (15).

18. A plant as claimed in claim 17, characterized in that said display unit is of touch-screen type.

19. A plant as claimed in any previous claim, characterized in that it comprises adjusting means (87) controlled by said programmable electronic control unit (15) and designed to adjust the air flow-rate coming out from said pressurizing and pumping means (13).

20. A plant as claimed in claim 19, characterized in that said adjusting means (87) of the air flow-rate coming out from said pressurizing and pumping means (13) comprises an inverter (87).

21. A plant as claimed in any previous claim, characterized in that it comprises means (92) form measuring the air flow-rate entering into the hopper 1 electrically connected with said programmable electronic control unit (15).

22. A plant as claimed in claim 21, characterized in that said flow-rate measuring means comprises a Venturi tube (92).

23. A method for regenerating a molecular sieve tower (68) in a dehumidifying plant for granular material as claimed in any claim 1 to 22, comprising, in sequence, heating of the molecular sieved (67) to a temperature of about 300°

C., and cooling the molecular sieves, characterized in that said cooling comprises the controlled mixing of the air within the tower to be cooled (68) by means of process air coming from another molecular sieve tower (69), said mixing being controlled through said switching-shunting means (24) in response to the temperature detected by said temperature detecting means (9).

24. A method as claimed in claim 23, characterized in that said mixing through said switching-shunting means (24) is carried out in a gradual or pulsating way.

25. A method as claimed in claim 24, characterized in that said tower (68) to be cooling during the mixing step is isolated from the outer by intercepting means (39).

26. A method as claimed in any claim 23 to 25, characterized in that it comprises a waiting step for said tower to be cooled when its cooling is ended.

27. A method as claimed in any claim 23 to 26, characterized in that it comprises a hot and dry air flow-rate modulating step within said air pressurizing or pumping means (13), which is controlled by said programmable electronic control unit (15).