Drying and gas or vapor contact with solids – Process – With fluid current conveying or suspension of treated material
Reexamination Certificate
1999-10-04
2001-05-22
Wilson, Pamela (Department: 3749)
Drying and gas or vapor contact with solids
Process
With fluid current conveying or suspension of treated material
C034S370000, C034S483000, C034S484000, C034S485000, C034S491000
Reexamination Certificate
active
06233842
ABSTRACT:
The invention relates to a method for operating a drying device comprising at least two chambers provided with bottoms for bulk material to be dried, and means for supplying to each chamber and discharging from each chamber a gaseous medium, wherein the bulk material, after being partially dried by means of said gaseous medium, is transported from a first chamber to a second chamber.
The invention also relates to a device which is suitable for carrying out such a method.
With a similar method, which is known from German patent No. 379,730, air is passed through a number of chambers lying one above the other, whereby bulk material present on the bottom of said chambers is dried. The bulk material is introduced into the device via an uppermost chamber, and it is successively passed through the bottom of a chamber and deposited on the bottom of the chamber present thereunder. With the known method, the temperature of the inflowing air is controlled. In order to achieve a desired drying effect with regard to the bulk material that has been introduced into the drying device, the moisture content of the bulk material must be determined after drying, after which the temperature of the gaseous medium being supplied must be changed, if necessary. This procedure must be repeated until the bulk material has the desired moisture content.
During the period of time that the moisture content of the dried bulk material is being determined, there is a risk that the bulk material emanating from the device will be relatively too dry or too moist. The latter is undesirable, of course, because this means that the bulk material is delivered which does not have the desired moisture content.
When bulk material, such as cattle feed, pet food, etc., is being dried, the percentage of moisture which eventually remains behind in the bulk material must stay within predetermined limits. If too much moisture remains behind, this may lead to decay of the bulk material. If the bulk material is too dry, more energy has been used for drying than is necessary, which is energetically and thus economically inefficient. In the case of fish feed the moisture content also determines the floating or sinking capacity of the fish feed.
In addition to the above drawbacks of the method known from said German patent, such a method is furthermore unsuitable when the bulk material to be dried is changed regularly, because the period of time that is required for determining the desired air temperature, is often longer than the period of time during which a predetermined amount of bulk material is dried.
The object of the invention is to provide a method wherein bulk material is dried to a desired moisture content in a relatively simple manner.
This objective is accomplished with the method according to the invention in that the energy increase brought about by the energy supplied to the chamber by means of the gaseous medium and the energy given out by the bulk material, is determined for each chamber, after which the amount of moisture that has evaporated from the bulk material is determined on the basis of said energy increase, after which the amount of moisture expected to be present in the bulk material discharged from the device is determined on the basis of the difference between the amount of moisture present in the bulk material introduced into the device and the amount of moisture that has evaporated.
With such a method, the amount of moisture contained in the bulk material present in each chamber is known. If the amount of moisture that is calculated to have evaporated from the bulk material present in a chamber deviates from the desired amount of moisture that has evaporated, the degree to which drying takes place can be directly adapted. Such a method may be used with a number of chambers disposed one above the other, whereby the bottom of one chamber forms the ceiling of a chamber present thereunder. It is also possible, however, to use the method with bulk material that is transported by means of an elongated conveyor belt, whereby the conveyor belt extends through a number of chambers lying side by side and whereby the conveyor belt is passed through said chambers in steps.
It is noted that a continuously moving conveyor belt, which transports bulk material, is known per se, whereby air is passed through the conveyor belt.
One drawback of such a conveyor belt is the fact that the moisture content of the bulk material can only be determined afterwards.
The invention will be explained in more detail hereafter with reference to the drawing, in which:
FIG. 1
is a diagrammatic cross-section of a device according to the invention;
FIGS. 2A-5B
show graphs of the method for drying bulk material, wherein
FIGS. 2A
,
2
B,
4
A,
4
B relate to a continuous conveyor belt which is known per se, whilst
FIGS. 3A
,
3
B and
5
A,
5
B relate to the method according to the invention.
Corresponding parts are indicated by the same numerals in the figures.
The device which is shown in
FIG. 1
comprises a housing
1
, in which a number of chambers
7
-
10
, which are separated from each other by bottoms
2
-
5
, are disposed one above the other. Said bottoms are provided with a large number of openings, in a similar manner as for example described and illustrated in the aforesaid patent, which openings can be closed by means of adjustable valves, all this in such a manner that when the valves are adjusted from a position in which the openings are closed to a position in which the openings are released, bulk material present on a bottom, for example cereals, cattle feed or similar granular material, can fall through the openings in the respective bottom onto a bottom present thereunder.
Connected to the upper side of the housing is a supply pipe
12
bounding an inlet passage, in which a lock means, for example a cell wheel lock
13
, is accommodated.
In a similar manner, a discharge pipe
14
bounding an outlet passage, which accommodates a lock means, for example a cell wheel lock
11
, is on the underside of housing
1
connected to a conically extending space
6
present under bottom
5
.
By using the lock means, the bulk material can be supplied to housing
1
or be discharged therefrom without this causing an undesirable inflow of ambient air into the housing or an outflow of air from the housing when bulk material is respectively supplied to the housing and discharged therefrom.
A discharge branch
15
is provided at the upper end of housing
1
for discharging a gaseous medium, for example air, from housing
1
, which air is supplied to a dust extraction cyclone
17
via a pipe
16
. A fan
19
is connected to cyclone
17
, via a pipe
18
, for drawing in air from housing
1
, via which fan the air drawn in from housing
1
is exhausted into the atmosphere in a direction indicated by arrow P
1
.
Chamber
10
is connected to a fan
22
via a pipe
21
and a pipe
20
present between bottoms
4
and
5
, which fan draws in air from chamber
10
. An adjustable valve
23
is mounted in pipe
21
, by means of which the amount of air drawn in by fan
22
per unit tine can be controlled.
The discharge side of fan
22
is connected to chamber
9
via a pipe
24
and a pipe
25
present between bottoms
3
and
4
. A heating element
26
is disposed in pipe
24
for heating the air transported by pipe
24
.
A pipe
27
is connected to housing
1
of the drying device, at a point located under bottom
5
. Air is drawn into chamber
11
, via pipe
27
, by means of fan
22
. Pipe
27
is fitted with a heating element
28
for heating the air that is introduced into housing
1
, and also with an adjustable control valve
29
, by means of which the amount of air that is supplied via pipe
27
per unit time can be controlled.
An air temperature sensor
30
is provided near discharge branch
15
, bulk material temperature sensors
31
,
32
,
33
,
34
,
35
are disposed at a small distance from bottoms
2
,
3
,
4
,
5
and lock means
11
respectively, an air temperature sensor
36
is disposed between bottoms
2
and
3
, an air te
Geelen Techniek B.V.
MacPherson Alan H.
Skjerven Morrill & MacPherson LLP
Wilson Pamela
LandOfFree
Method for operating a drying device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for operating a drying device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for operating a drying device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2443503