Filter system for a fluid bed granulator/dryer

A novel filter system for fluid bed granulator/dryer machines which utilizes pleated filter elements that can be stacked end to end so as to remove material from the exhaust air and wherein a number of filter elements can be mounted parallel to each other and end to end to obtain the desired filter capacity. In a first embodiment, the filters extend horizontally across the machine and in the second embodiment they extend it in a slanted plane across the machine. The filters can be cleaned by alternately providing reverse air flow through them.

BACKGROUND OF THE INVENTION 
Field of the Invention 
This invention relates in general to fluid bed granulators, coaters and 
dryers and in particular to a pleated filter cartridge system for such 
machines. The invention also provides a cleaning system in which 
alternately pressure is applied to the filters in the reverse direction so 
as to clean them automatically. 
Description of the Prior Art 
Prior art fluid bed granulator and dryer machines have used bag filters to 
remove material in the exhaust air and it has been a problem to maintain 
the filters free of material. 
SUMMARY OF THE INVENTION 
It is a feature of the present invention that it provides pleated 
cylindrical-shape filter elements which can be mounted in the exhaust 
system of a fluid granulator or dryer and wherein said filter elements can 
be mounted end to end to form a composite filter. One or more of the 
composite filter elements thus formed are mounted in communication with 
the exhaust outlet duct. The pleated filter cartridges contain a 
considerably larger filter fabric area than conventional filter socks. 
It is an object of the present invention to provide an improved filter 
system for a fluid bed granulator, coater or dryer. 
It is another object of the invention to provide a filter cleaning system 
which alternately cleans the filters by providing back flow through a 
filter element to remove particulate from its outside surface and where 
the back flow to particular elements is alternately applied. 
It is also an object of the invention to provide an automatic cleaning 
system for filter elements in a fluid bed granulator or dryer.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1-6 illustrate a fluid bed granulator/dryer machine 10 which has a 
lower portion 11 across which is mounted a screen 12 to support a product 
such as tablets or other material which is to be granulated or dried. 
Above the screen 12 is a tapered container portion 13 and above portion 13 
is a cylindrical portion 14. Explosion type vents 18 and 21 close the 
upper end of the cylindrical member 14 and a filter assembly 22 according 
to the invention is mounted in an upper portion 17 of the cylindrical 
portion 14. An inlet air duct 31 is connected to the lower portion 11 as 
shown in FIG. 1 and is connected to an input plenum 32 which has an input 
air duct 37 connected to its upper end as shown. A heat exchanger 33 is 
mounted in the plenum 32 and has an input steam pipe 34 and an output 
steam pipe 36 so that the heat exchanger 33 can heat air before passing 
through the granulator/dryer. A number of spray guns 16 are mounted in the 
spray/expansion chamber 14 about the periphery thereof and can be adjusted 
to vary the spray from outside of the vessel by controlling the solution 
spray rate, the atomization air volume, the spray pattern and the spray 
angle. 
The filter assembly 22 is mounted to the machine 10 by providing a pair of 
external transition members 28 and 29 which attach to the outer surface of 
the cylindrical portion 14 as shown in FIGS. 1, 2, 3 and 4. A pair of 
openings 101 and 102 are formed in the back plate 53 of the transition 
member 29. A first filter support 90 is connected as by welding to the 
back plate 53 about the opening 102 and comprises three longitudinal rods 
81, 82 and 83 which extend into the interior of the machine and which are 
provided with braces such as the braces 86 and 87 illustrated in FIG. 3. A 
second filter support 100 comprises longitudinally extending rods 210, 211 
and 213 which are welded to the end plate 53 about opening 101 and which 
have their opposite ends connected by rods 93 as shown in FIG. 3. The rods 
81, 82 and 83 are connected by end brace rods 92 as shown in FIGS. 3 and 
5. A rod 66 is welded to the end brace rods 92 and has a threaded portion 
98 upon which a threaded knob or handle 46 can be received. The end 52 of 
transition member 28 is formed with openings 160 and 170 and a cover plate 
43 which has an outer edge gasket 52 has an opening through which the 
threaded rod 66 extends and the cover plate 43 is held by the knob 46. A 
cover plate 42 fits over the opening 170 and has an outer gasket 51. A 
threaded knob 44 is threadedly received on a threaded shaft 94 which is 
connected to the end cross braces 93 of the filter support 100. The shaft 
94 passes through an opening formed in plate 42. 
A pair of filter elements of general cylindrical-shape 61 and 62 are 
mounted on the filter support 100 as shown in FIGS. 3 and 5. The filter 62 
has an end gasket 68 which rests against the end 67 of the filter 61. The 
filter 61 has an end gasket 91 which engages the end plate 53 about the 
opening 101. A gasket 70 is mounted between the cover plate 42 and the end 
69 of the filter 62. 
A pair of filters 63 and 64 are mounted end to end on the filter support 
structure 90. The filter 64 has a gasket 71 which rests against the end 
plate 53 about the opening 102. The filter 63 has a gasket 73 on its end 
74 which rests against the end 72 of the filter 64. A gasket 77 is mounted 
between the cover plate 43 and the end 76 of the filter 63. As shown in 
FIGS. 1 and 3, an outlet duct 105 is connected to end wall 53 over the 
openings 101 and 102 and is connected by a flange 25 to an exhaust conduit 
24 to which is mounted an exhaust blower 26 which has an outlet duct 27. 
In operation, air is drawn into the inlet duct 37 through the plenum 32 
past the heat exchanger 33 and into the conduit 31 into the lower portion 
11 of the machine 10. The air passes up through the screen 12, through the 
product 13 being processed, past the sprayer 16 and through the chamber 
14. The air exhausts from the machine through the filters 61, 62, 63 and 
64 passing through the outer surface of the filters into the central 
openings formed therein as shown in FIG. 6 and through the opening 101 and 
102 into the member 23 and out the exhaust duct 24 to the exhaust blower 
26 and out the exhaust conduit 27. 
An automatic cleaning system is provided for the filters 61, 62, 63 and 64 
which is shown in FIG. 6. An air pressure tank 201 has outlet pipes 200 
and 202 and the pipe 200 is connected to a valve 204 which has an outlet 
pipe 206 which extends into the opening 101. The valve 203 is connected to 
pipe 202 and has an outlet pipe 205 which extends into the opening 102. A 
control 207 is connected by control wire 208 to valve 204 and to valve 203 
by a control wire 209. The valves 204 and 203 may be electrically or 
pneumatically actuated valves such as solenoid or pilot operated valves 
which can be energized by electrical or pneumatic signals supplied by the 
control 207 on the leads 208 and 209. The control 207 alternately opens 
and closes the valves 204 and 203. When valve 204 is opened and valve 203 
is closed, air enters from the air tank 201 into opening 101 and passes in 
the reverse direction through the filters 61 and 62 as shown in FIG. 6 and 
then from the inside of the machine into the filters 63 and 64 and out the 
opening 102 through the exhaust blower 26. When the air passes through the 
filters 61 and 62 in the reverse direction as shown in FIG. 6, the 
particulate material which is accumulated on the outer surface of the 
filters 61 and 62 is removed by the reverse air flow so as to clean the 
filters 61 and 62. After a predetermined time, the control 207 closes the 
valve 204 and opens the valve 203 such that air from the tank 201 passes 
through the pipe 205 into opening 102 to cause reverse flow through the 
filters 63 and 64 to clean them. Since the valve 204 is closed at this 
time, air can pass into the filters 61 and 62 and pass out through the 
exhaust blower 26. 
It is seen that this invention provides a novel filter and cleaning 
arrangement for filters of a fluid bed granulator or dryer. The explosion 
vents 18 and 21 may be mounted in the top or rear portion of the machine 
10 as illustrated in FIG. 1, for example. 
FIG. 7 illustrates a modification of the invention wherein the filters are 
mounted end to end on an axis which extends at a slant angle relative to 
the horizontal. A pair of transition members 310 and 311 are attached to 
the outer walls of the machine 10. The transition member 311 is formed 
with an opening 330 which communicates with the exhaust conduit 23 and has 
a shoulder 331 through which the opening 330 communicates and a filter 
support 332 is formed of rods 333, 334 and 336 which are connected as by 
welding to the shoulder 331. A threaded shaft 337 extends from the end 338 
of the filter support and passes through an opening in a cover member 339 
and a threaded knob 341 is received on the shaft 337. The cover 339 is 
formed with a gasket 412 which rests against the wall over opening 442 in 
the transition member 310 to provide a seal. It is to be realized that a 
second pair of filters may be mounted between the transition members 310 
and 311 parallel but offset from the filters 417 and 418. 
It is seen that the present invention provides a new and improved filter 
system for a fluid bed granulator/dryer and although it has been described 
with respect to preferred embodiments, it is not to be so limited as 
changes and modifications may be made therein which are within the full 
intended scope as defined by the appended claims.