[0001] The present invention relates to an apparatus for drying bulk particulate material
and a method of drying bulk particulate material, the bulk particulate material in
particular being sugar beet pulp.
Background of the invention
[0002] Drying of moist bulk particulate material by contacting the particulate material
with superheated steam under non-oxidizing conditions to evaporate liquid contained
in the material has been known since the early 1980s. Some documents showing related
art include:
AT 345769 B,
EP 0 268 819,
EP 0 955 511 A2,
EP 1 044 044 A1,
EP 1 070 223 A1,
EP 1 956 326 B1,
EP 2 457 649 A1,
US 4 602 438,
US 4 813 155,
US 5 357 686 A,
US 6 154 979 A,
US 6 266 895,
US 6 438 863 B1,
US 6 966 466 B2,
US 7 578 073 B2,
WO 2010/139331 A2.
[0003] An early disclosures of the above-mentioned steam drying technologies include
EP 0 058 651 A1 which relates to a method of preparing cattle feed from various agricultural products,
such as sugar beet pulp, molasses, citrus fruit pulp and peel and various fermentation
products.
[0004] Another disclosure is
EP 0 153 704 A2 which teaches a process of removing liquid from a particulate solid material in which
the material is passed through a row of interconnected cells and superheated steam
is introduced into said cells at their lower ends so as to impart a whirling movement
during which dried panicles are lifted out of the cells and into a common transfer
zone and into a discharge cell with no steam supply.
[0005] The prior art document
WO 92/01200 discloses an apparatus for drying a moist particulate material having a non-uniform
particle size with superheated steam. The apparatus comprises a cylindrical vessel
comprising a number of parallel, substantially vertical drying chambers located in
ring form. The preferred embodiment includes 15 drying chambers connected in series,
and a discharge chamber located between the first and the last drying chamber.
[0006] At the first drying chamber after the inlet, the particulate material will have a
high liquid content whereas the particulate material at the last drying chamber will
have a low liquid content. The drying chambers are adapted to induce a whirling movement
of the flow of superheated steam in order to improve the contact between the steam
and the particulate material and to cause the particulate material to remain a short
and uniform time period within each of the drying chambers. The drying chambers, however,
all have a substantially uniform size and shape and receive about the same amount
of superheated steam although it is evident that the particulate material will behave
differently when it is moist and when it is dry. In particular, the moist particles
tend to be heavier than the dry particles and thus cause a larger flow resistance.
[0007] It has been noted by the applicant that the moist particulate material, and in particular
the large and heavy particles, tend to accumulate in first drying chamber. Particulate
material remaining an extended time period in the first drying chamber may potentially
clog the first drying chamber and reduce the intensity of the whirling movement of
the flow of superheated steam. Previous technologies suggest the inclusion of means
for increasing the retention time of the particulate material in some of the drying
chambers and means for reducing the retention time of the particulate material in
some of the other drying chambers. However, such means may add to the flow resistance
and risk reducing the whirling movement of the flow of superheated steam which is
necessary for achieving an effective drying of the particulate material. The whirling
movement allows the particulate material to distribute more evenly within the chamber
which will result in a more effective drying than particulate material which clogs
up and forms large chunks of material.
[0008] It is thus an object of according to the present invention to provide technologies
for avoiding accumulation of material within the first drying chamber.
Summary of the invention
[0009] The above object and further objects which are evident from the below detailed description
are according to a first aspect of the present invention achieved by an apparatus
for drying bulk particulate materials, the apparatus comprising:
a vessel capable of maintaining superheated steam at a pressure equal to or larger
than the ambient pressure surrounding the vessel, the vessel defining a lower cylindrical
part defining a first cross-sectional area being perpendicular to the length of the
lower cylindrical part and an upper cylindrical part defining a second cross-sectional
area being perpendicular to the length of the upper cylindrical part,
an inner cylindrical part centrally located within the upper cylindrical part and
the lower cylindrical part of the vessel for establishing a first fluid path from
the upper cylindrical part to the lower cylindrical part within the inner cylindrical
part and a second fluid path from the lower cylindrical part to the upper cylindrical
part outside the inner cylindrical part,
a first number of partitioning walls extending radially within the lower cylindrical
part between the lower cylindrical part and the inner cylindrical part and defining
in the lower cylindrical part an inlet chamber, an outlet chamber and a second number
of intermediate chambers located between the inlet chamber and the outlet chamber
in a circumferential direction, the inlet chamber comprising a inlet for receiving
a moist bulk particulate material, the outlet chamber comprising an outlet for ejecting
a dry bulk particulate material, the inlet chamber and the intermediate chambers each
defining a steam permeable bottom, the outlet chamber defining a non-steam permeable
bottom,
a heat exchanger located within the inner cylindrical part for heating the superheated
steam,
an impeller for generating a flow of superheated steam along the first fluid path
from the upper cylindrical part through the heat exchanger within the inner cylindrical
part to the lower cylindrical part via the steam permeable bottom, and along the second
fluid path from the lower cylindrical part to the upper cylindrical part outside the
inner cylindrical part, and
the steam permeable bottom of the inlet chamber being adapted to receive between 20%
and 50% of the flow of superheated steam from the impeller, said inlet chamber being
larger than any of the intermediate chambers and hereby occupy a larger circular sector
of the ring-shaped space between the lower cylindrical part and the inner cylindrical
part.
[0010] The vessel is typically made of metal capable of withstanding temperatures of superheated
steam exceeding 100°C and pressures exceeding the ambient atmospheric pressure. Typical
pressures range from ambient atmospheric pressures to a pressure of up to 3 bar. The
vessel comprises a lower cylindrical part and an upper cylindrical part which form
part of the outer enclosure of the vessel. The vessel further comprises a top part
and a bottom part in order to form an essentially enclosed vessel.
[0011] The first flow path inside the inner cylindrical part and the second flow path between
the outer enclosure of the vessel and the inner cylindrical part define the recirculation
of the superheated steam. The flow of superheated steam is established by the impeller
which is located in the lower cylindrical part below the steam permeable bottom and/or
between the inner cylindrical part and the steam permeable bottom of the lower cylindrical
part in order to establish a high pressure below the steam permeable bottom, which
in turn establishes a fluid bed and the re-circulating flow of superheated steam.
The inner cylindrical part includes the heat exchanger which maintains the re-circulating
steam in a superheated state for avoiding any condensation to occur within the vessel.
[0012] The drying is taking place by superheated steam contacting the moist particulate
material and transferring some of its heat to the moist particles. The liquid content
of the moist particulate material will vaporize and the vapor becomes part of the
superheated steam. The heat energy required for the vaporization and thereby removed
from the superheated steam is replenished at the heat exchanger in order to avoid
condensation of the superheated steam into liquid within the vessel. Any surplus steam
may be released via an overpressure valve at the top part of the vessel. The vessel
also includes means for inducing a circumferential flow component in order to cause
the particulate material to move slowly in a circumferential direction from the inlet
to the outlet.
[0013] The partitioning walls serve to delimit the lower cylindrical part into several chambers.
The first chamber is the inlet chamber which is connected to a closed off screw conveyor
or the like for injecting the moist particulate material into the inlet chamber. The
outlet chamber also comprises a closed off screw conveyor or the like for discharging
the dry particulate material. The intermediate chambers are located between inlet
chamber and the outlet chamber. The partitioning walls include openings for allowing
particulate material to be transported from the inlet chamber to the outlet chamber
via the intermediate chambers. The inlet chamber and the intermediate chambers receive
superheated steam from a steam permeable bottom and thus constitute drying chambers.
[0014] Within the drying chambers a whirling fluid bed and a whirling flow is established
which maintains most of the particulate material in the lower cylindrical part and
increases the contact between the superheated steam and the particulate material.
The outlet chamber does not have a steam permeable bottom to allow the particulate
material to settle before being discharged. The number of chambers determines the
retention time of the particulate material within the vessel and the mixing behaviour
of the particulate material within each of the chambers. A small number of chambers
reduces the retention time of the particulate material while allowing the particulate
material to distribute more uniformly within the chamber, and vice versa.
[0015] The particulate material arriving at the first drying chamber, i.e. the inlet chamber,
is moist and contains a large portion of liquid and thus tends to be heavy and clogging
up the chamber. These particles generate a large drag and the flow velocity of the
superheated steam is reduced due to the increased flow resistance. This leads to less
lift in the fluid bed, less whirling motion of the flow and less distribution of the
particulate material which results in the accumulation of moist particulate material
in some parts of the inlet chamber. The particulate material arriving at the last
drying chamber before the outlet chamber in which the now dried particulate material
is ejected, is substantially dry and light and well distributed within the chamber
since nothing is preventing the formation of an effective whirling flow of superheated
steam. This may lead to increased lift in the fluid bed and a large amount of particulate
material flowing into the upper cylindrical part of the vessel
[0016] Thus, in order to ensure the formation of a well established whirling flow of superheated
steam within the inlet chamber, the heavy and liquid particulate material contained
in the first chamber should receive a larger portion of the superheated steam received
from the inner cylindrical part via the impeller. By allowing the inlet chamber to
receive between 20% and 50% of the superheated steam, a sufficient flow of superheated
steam may form which will generate sufficient lift to be capable of overcoming the
drag of the moist particulate material. Thus, a uniform distribution of the particulate
material may be achieved in all of the drying chambers.
[0017] According to a first embodiment of the first aspect, the inlet chamber is adapted
to receive between 22% and 45% of the superheated steam received from the inner cylindrical
part, preferably between 25% and 40% of the superheated steam received from the inner
cylindrical part, more preferably between 30% and 35% of the superheated steam received
from the inner cylindrical part, such as 33% of the superheated steam received from
the inner cylindrical part, alternatively, the inlet chamber being adapted to receive
between 20% and 22% of the superheated steam received from the inner cylindrical part,
and/or between 22% and 25% of the superheated steam received from the inner cylindrical
part, and/or between 25% and 30% of the superheated steam received from the inner
cylindrical part, and/or between 30% and 35% of the superheated steam received from
the inner cylindrical part, and/or between 35% and 40% of the superheated steam received
from the inner cylindrical part, and/or between 40% and 45% of the superheated steam
received from the inner cylindrical part, and/or between 45% and 50% of the superheated
steam received from the inner cylindrical part.
[0018] Intense research performed by the applicant has indicated that for many drying applications
of moist particulate material, such as beet pulp drying, the optimal drying capability
is achieved by using the above percentages.
[0019] According to a further embodiment of the first aspect, the inlet chamber and the
intermediate chambers each define a flow area being parallel with the first cross-sectional
area, the flow area of the inlet chamber being greater than the flow area of any of
the intermediate chambers.
[0020] According to the invention, the inlet chamber is larger than any of the intermediate
chambers. In this way a larger portion of the superheated steam will enter the inlet
chamber. The cross-sectional area of the inlet chamber may thus constitute at least
20% of the cross-sectional area of all of the chambers, preferably any of the previously
mentioned percentages.
[0021] According to a further embodiment of the first aspect, the partitioning walls define
a first partitioning wall and a second partitioning wall both delimiting the inlet
chamber in the circumferential direction, the first partitioning wall and a second
partitioning wall defining an angle them between of between 50° and 180°, preferably
between 70° and 160, more preferably between 90° and 140°, such as 120°.
[0022] According to the invention, by allowing the inlet chamber to occupy a larger circular
sector of the ring-shaped space between the lower cylindrical part and the inner cylindrical
part, the inlet chamber will receive a larger portion of the superheated steam from
the impeller, provided the superheated steam is uniformly distributed over the ring-shaped
space.
[0023] According to a further embodiment of the first aspect, the steam permeable bottom
of the inlet chamber defines a steam permeability of between 20% and 45% of the steam
permeability of the total steam permeability of all of the steam permeable bottoms,
preferably between 25% and 40%, more preferably between 30% and 35%, such as 33% .
[0024] Alternatively, instead of making the inlet chamber larger, all chambers may have
the same size and the permeability of the steam permeable bottom may be higher for
the inlet chamber compared to the intermediate chambers. In this way, a larger portion
of the superheated steam will enter the inlet chamber.
[0025] According to a further embodiment of the first aspect, the steam permeable bottoms
of the inlet chamber and the intermediate chambers define perforations.
[0026] The perforations will be located between the impeller and the fluid bed. The size
of each individual perforation should be made such that no particulate material may
slip through into the impeller.
[0027] According to a further embodiment of the first aspect, the perforations of the steam
permeable bottoms of the inlet chamber define an area being 20% to 45% of the total
area of all of the perforations of all of the steam permeable bottoms, preferably
between 25% and 40%, more preferably between 30% and 35%, such as 33%.
[0028] Intense research performed by the applicant has indicated that for many drying applications
of moist particulate material, such as beet pulp drying, the optimal drying capability
is achieved by using the above percentages.
[0029] According to a further embodiment of the first aspect, the vessel comprises an intermediate
conical part interconnecting the lower cylindrical part and the upper cylindrical
part so that the second cross-sectional area is larger than the first cross-sectional
area.
[0030] In order to prevent the accumulation of particulate material in the upper cylindrical
part of the vessel, the lower cylindrical part and the upper cylindrical part may
be interconnected by the conical part in which the flow velocity will decrease due
to the increasing flow area, as described by the Bernoulli principle. In this way,
the lift will decrease in the upper cylindrical part and most of the particulate material
in the conical part will not reach the upper cylindrical part and any particulate
material appearing in the upper cylindrical part will fall back into the lower cylindrical
part.
[0031] According to a further embodiment of the first aspect, the second cross-sectional
is substantially equal to the first cross-sectional area.
[0032] Alternatively, there is no conical part and the first and second cylindrical parts
have the same diameter.
[0033] According to a further embodiment of the first aspect, all of the steam originates
from the moist bulk particulate material.
[0034] Preferably, no superheated steam must be separately added to the vessel as the superheated
steam may be generated from the liquid which is vaporized from the moist particulate
material. The surplus superheated steam may, as described above, be let out via an
overpressure valve or outlet, preferably into a heat exchanger in order to reuse some
of the heat energy of the steam.
[0035] According to a further embodiment of the first aspect, the second number of intermediate
chambers is between 6 and 40, preferably 10 to 25, more preferably 12 to 20, such
as 14.
[0036] The number of intermediate chambers may thus vary between any of the above numbers.
The total number of chambers adds the inlet chamber and the outlet chamber to the
above number. Some of the above prior art suggests a total of 16 chambers which may
be considered normal.
[0037] According to a further embodiment of the first aspect, the upper cylindrical part
comprises a cyclone for transporting particulate material from the upper cylindrical
part to the lower cylindrical part.
[0038] In this way the particulate material which may accumulate in the upper cylindrical
part may be returned to the lower cylindrical part.
[0039] The above object and further objects which are evident from the below detailed description
are according to a second aspect of the present invention achieved by a method of
drying bulk particulate material by providing an apparatus, the apparatus comprising:
a vessel defining a lower cylindrical part defining a first cross-sectional area being
perpendicular to the length of the lower cylindrical part and an upper cylindrical
part defining a second cross-sectional area being perpendicular to the length of the
upper cylindrical part,
an inner cylindrical part centrally located within the upper cylindrical part and
the lower cylindrical part of the vessel for establishing a first fluid path from
the upper cylindrical part to the lower cylindrical part within the inner cylindrical
part and a second fluid path from the lower cylindrical part to the upper cylindrical
part outside the inner cylindrical part,
a first number of partitioning walls extending radially within the lower cylindrical
part between the lower cylindrical part and the inner cylindrical part and defining
in the lower cylindrical part an inlet chamber, an outlet chamber and a second number
of intermediate chambers located between the inlet chamber and the outlet chamber
in a circumferential direction, the inlet chamber comprising a inlet, the outlet chamber
comprising an outlet, the inlet chamber and the intermediate chambers each defining
a steam permeable bottom, the outlet chamber defining a non-steam permeable bottom,
the steam permeable bottom of the inlet chamber being adapted to receive between 20%
and 50% of the flow of superheated steam from the impeller, said inlet chamber being
larger than any of the intermediate chambers and hereby occupy a larger circular sector
of the ring-shaped space between the lower cylindrical part and the inner cylindrical
part,
a heat exchanger located within the inner cylindrical part, and
an impeller,
the method comprising the steps of:
maintaining within the vessel a superheated steam at a pressure equal to or larger
than the ambient pressure surrounding the vessel,
receiving moist bulk particulate material at the inlet,
heating the superheated steam within the heat exchanger,
generating a flow of superheated steam along the first fluid path from the upper cylindrical
part through the heat exchanger within the inner cylindrical part to the lower cylindrical
part via the steam permeable bottom, and along the second fluid path from the lower
cylindrical part to the upper cylindrical part outside the inner cylindrical part,
by using the impeller, and
ejecting dry bulk particulate material at the outlet.
[0040] It is evident that the method according to the second aspect may be used together
with any of the apparatuses according to the first aspect.
Brief description of the drawings
[0041]
FIG. 1 illustrates a side sectional view of an apparatus for drying bulk particulate
material, in particular drying of beet pulp.
FIG. 2 illustrates a perspective view of the lower cylindrical part of the apparatus.
FIG. 3 shows a top sectional view of the lower cylindrical part of the apparatus.
FIG. 4 illustrates a perspective view of a lower cylindrical part of an alternative
embodiment of the apparatus.
FIG. 5 shows a top sectional view of the lower cylindrical part of the alternative
embodiment of the apparatus.
Detailed description of the drawings
[0042] FIG. 1 shows a side sectional view of an apparatus 10 for drying bulk particulate
materials, in particular drying of beet pulp. The apparatus 10 comprises a vessel
12 comprising a lower cylindrical part 14, an intermediate conical part 16 and an
upper cylindrical part 18. The vessel 12 is closed off by a top 20 and a bottom 22.
The vessel 12 further comprises an inner cylindrical part 24 extending within the
vessel between the upper cylindrical part 18 and the lower cylindrical part 14. The
inner cylindrical part 24 includes a heat exchanger (not visible) and defines a first
fluid path from said upper cylindrical part 18 to said lower cylindrical part 14 within
said inner cylindrical part 24 and a second fluid path from said lower cylindrical
part 14 to said upper cylindrical part 18 outside said inner cylindrical part, as
shown by the arrows.
[0043] The vessel 12 further comprises an inlet 26 constituting a screw conveyor for introducing
moist particulate material into the lower cylindrical part 14 of the vessel 12 as
shown by the arrow, and an outlet 28 constituting a screw conveyor for ejecting dry
particulate material from the lower cylindrical part 14 of the vessel 12 as shown
by the arrow. The inlet 26 is located above and circumferentially shifted relative
to the outlet 28. A motor 30 is located below the vessel 12 for driving an impeller
32 located in the lower cylindrical part 14 below the inner cylindrical part 24. The
impeller 32 generates a flow of superheated steam along the above mentioned fluid
paths. A steam permeable bottom 34 is located above the impeller 32.
[0044] A number of partitioning walls 36 are radially extending between the lower cylindrical
part 14 and the inner cylindrical part 24 and dividing the space between the lower
cylindrical part 14 and the inner cylindrical part 24 into a number of chambers 38.
The chamber located at the inlet 26 is designated inlet chamber 38' and the chamber
located at the outlet 28 is designated outlet chamber 38". Typically, the inlet chamber
38' and the outlet chamber 38" are located adjacent each other, however, the particulate
material should not be able to move directly from the inlet chamber 38' to the outlet
chamber 38" without passing the intermediate chambers 38. The moist particulate material
is received in the inlet chamber 38' on a fluid bed established by the flow of superheated
steam above the steam permeable bottom 34. The partitioning walls 36 include whirling
blades 40 for inducing a circumferential whirl for transporting the particulate material
from the inlet chamber 38' to the outlet chamber 38" via the intermediate chambers
38 as shown by the arrows. The outlet chamber 38" has a non-permeable bottom which
allows the dried particulate material to be ejected via the outlet 28 as shown by
the arrow.
[0045] The upper cylindrical part 18 of the vessel 12 comprises guide blades 42 for generating
a cyclone field in upper cylindrical part 18. The guide blades 42 will establish a
whirling movement of the flow of superheated steam corresponding to the above mentioned
circumferential whirl and force any particles outwardly which have been lifted from
the lower cylindrical part 14 through the intermediate conical part 16 into the upper
cylindrical part 18. The outwardly forced particles will be collected in a cyclone
44 and returned to the lower cylindrical part 14 as shown by the arrows. The superheated
steam will be introduced into the inner cylindrical part 24 and be reheated by the
heat exchanger before returning to the impeller 32. A small portion of the superheated
steam will escape the vessel 12 via a centrally located steam exit 46. The superheated
steam exiting the vessel 12 is subsequently cooled off via a heat exchanger.
[0046] The drying of the moist particulate material is effected on the fluid bed above the
steam permeable bottom of the inlet chamber 38' and the intermediate chamber 38.
[0047] Each chamber 38 may include further blades or similar means for establishing a whirling
flow in the radial direction of the chamber 38. The whirling flow will increase the
distribution of the particulate material within the chambers 38 and thereby increase
the contact between the superheated steam and the particulate material, thereby increasing
the vaporization of fluid from the particulate material and improving the drying.
[0048] FIG. 2 shows a perspective view of the lower cylindrical part 14 of the apparatus
10. The inlet chamber 38' is larger than the intermediate chambers 38 for allowing
a larger portion of the superheated steam to enter the inlet chamber 38' compared
to the intermediate chambers 38. In this way the heavy liquid containing particulate
material entering the inlet chamber 38' may be distributed over a larger area, reducing
the flow resistance and thereby both preventing clogging and improving the drying.
[0049] FIG. 3 shows a top sectional view of the lower cylindrical part 14 of the apparatus
10. The radial partitioning walls 36 define the circular sector shape of the chambers
38. The particulate material may move in a clockwise direction from the inlet chamber
38' to the outlet chamber 38" via all of the chambers by flowing above the partition
wall 36 or through apertures 48 which may optionally exist in the partition wall 36.
The steam permeable bottom 34 is shown having perforations 50 for allowing superheated
steam to flow into the drying chambers.
[0050] FIG. 4 a perspective view of a lower cylindrical part 14 of an alternative embodiment
of the apparatus designated 10'. Instead of making the inlet chamber 38' larger, the
inlet chamber may be made as large as the intermediate chambers 38 and have a steam
permeable bottom 34' allowing a larger portion of the superheated steam from the impeller
(not shown) to pass compared to the intermediate chambers 38.
[0051] FIG. 5 shows a top sectional view of the lower cylindrical part 14 of the alternative
embodiment of the apparatus 10'. As an example, the perforations 50 may be larger
as shown in the present figure. Alternatively, there may be additional perforations.
The additional superheated steam allows the inlet chamber 38' to produce additional
lift overcoming the drag by the heavy liquid containing particulate material. The
intermediate chambers 38 have less or smaller perforations 50 since the particulate
material will be lighter and thereby less prone to clog.
[0052] As mentioned in the general part of the specification, ideally between 20% and 40%
of the steam from the impeller and heat exchanger will be directed to the inlet chamber
38' for achieving an optimal distribution of the particulate material.
Reference numerals
[0053]
10. Apparatus for drying bulk particulate material
12. Vessel
14. Lower cylindrical part
16. Intermediate conical part
18. Upper cylindrical part
20. Top
22. Bottom
24. Inner cylindrical part
26. Inlet
28. Outlet
30. Motor
32. Impeller
34. Steam permeable bottom
36. Partitioning walls
38. Chambers
40. Whirling blades
42. Guide blades
44. Cyclone
46. Steam exit
48. Aperture
50. Perforations
1. An apparatus (10) for drying bulk particulate material, said apparatus comprising:
a vessel (12) capable of maintaining superheated steam at a pressure equal to or larger
than the ambient pressure surrounding said vessel (12), said vessel (12) defining
a lower cylindrical part (14) defining a first cross-sectional area being perpendicular
to the length of the lower cylindrical part (14) and an upper cylindrical part (18)
defining a second cross-sectional area being perpendicular to the length of the upper
cylindrical part (18),
an inner cylindrical part (24) centrally located within said upper cylindrical part
(18) and said lower cylindrical part (14) of said vessel (12) for establishing a first
fluid path from said upper cylindrical part (18) to said lower cylindrical part (14)
within said inner cylindrical part (24) and a second fluid path from said lower cylindrical
part (14) to said upper cylindrical part (18) outside said inner cylindrical part
(24),
a first number of partitioning walls (36) extending radially within said lower cylindrical
part (14) between said lower cylindrical part (14) and said inner cylindrical part
(24) and defining in said lower cylindrical part (14) an inlet chamber (38'), an outlet
chamber (38") and a second number of intermediate chambers (38) located between said
inlet chamber (38') and said outlet chamber (38") in a circumferential direction,
said inlet chamber comprising a inlet for receiving a moist bulk particulate materials,
said outlet chamber (38") comprising an outlet (28) for ejecting a dry bulk particulate
materials, said inlet chamber (38') and said intermediate chambers (38) each defining
a steam permeable bottom (34), said outlet chamber (38") defining a non-steam permeable
bottom,
a heat exchanger located within said inner cylindrical part (24) for heating said
superheated steam,
an impeller (32) for generating a flow of superheated steam along said first fluid
path from said upper cylindrical part (18) through said heat exchanger within said
inner cylindrical part (24) to said lower cylindrical part (14) via said steam permeable
bottom (34), and along said second fluid path from said lower cylindrical part (14)
to said upper cylindrical part (18) outside said inner cylindrical part (24),
characterised in that
said steam permeable bottom (34) of said inlet chamber (38') is adapted to receive
between 20% and 50% of said flow of superheated steam from said impeller (32),
and in that said inlet chamber (38') is larger than any of the intermediate chambers (38) and
hereby occupies a larger circular sector of the ring-shaped space between the lower
cylindrical part (14) and the inner cylindrical part (24).
2. The apparatus (10) according to claim 1, wherein said inlet chamber (38') being adapted
to receive between 22% and 45% of said superheated steam received from said inner
cylindrical part (24), preferably between 25% and 40% of said superheated steam received
from said inner cylindrical part (24), more preferably between 30% and 35% of said
superheated steam received from said inner cylindrical part (24), such as 33% of said
superheated steam received from said inner cylindrical part (24).
3. The apparatus (10) according to claim 1, wherein said inlet chamber (38') being adapted
to receive between 20% and 22% of said superheated steam received from said inner
cylindrical part (24), and/or between 22% and 25% of said superheated steam received
from said inner cylindrical part (24), and/or between 25% and 30% of said superheated
steam received from said inner cylindrical part (24), and/or between 30% and 35% of
said superheated steam received from said inner cylindrical part (24), and/or between
35% and 40% of said superheated steam received from said inner cylindrical part (24),
and/or between 40% and 45% of said superheated steam received from said inner cylindrical
part (24), and/or between 45% and 50% of said superheated steam received from said
inner cylindrical part (24).
4. The apparatus (10) according to any of the preceding claims, wherein said inlet chamber
(38') and said intermediate chambers (38) each define a flow area being parallel with
said first cross-sectional area, said flow area of said inlet chamber (38') being
greater than said flow area of any of said intermediate chambers.
5. The apparatus (10) according to any of the preceding claims, wherein said steam permeable
bottom (34) of said inlet chamber (38') defines a steam permeability of between 20%
and 45% of the steam permeability of the total steam permeability of all of said steam
permeable bottoms, preferably between 25% and 40%, more preferably between 30% and
35%, such as 33% .
6. The apparatus (10) according to any of the preceding claims, wherein said steam permeable
bottoms of said inlet chamber (38') and said intermediate chambers (38) define perforations
(50).
7. The apparatus (10) according to claim 6, wherein said perforations (50) of said steam
permeable bottoms of said inlet chamber (38') define an area being 20% to 45% of the
total area of all of said perforations of all of said steam permeable bottoms, preferably
between 25% and 40%, more preferably between 30% and 35%, such as 33%.
8. The apparatus (10) according to any of the preceding claims, wherein said vessel (12)
comprises an intermediate conical part (16) interconnecting said lower cylindrical
part (14) and said upper cylindrical part (18) so that said second cross-sectional
area is larger than said first cross-sectional area.
9. The apparatus (10) according to any of the claims 1-7, wherein said second cross-sectional
is substantially equal to said first cross-sectional area.
10. The apparatus (10) according to any of the preceding claims, wherein said second number
is between 6 and 40, preferably 10 to 25, more preferably 12 to 20, such as 14.
11. The apparatus (10) according to any of the preceding claims, wherein said upper cylindrical
part (18) comprises a cyclone (44) for transporting particulate material from said
upper cylindrical part (18) to said lower cylindrical part (14).
12. An method of drying bulk particulate materials by providing an apparatus (10), according
to claim 1,
said method comprising the steps of:
maintaining within said vessel (12) a superheated steam at a pressure equal to or
larger than the ambient pressure surrounding the vessel (12),
receiving moist bulk particulate material at said inlet (26),
heating said steam within said heat exchanger,
generating a flow of superheated steam along said first fluid path from said upper
cylindrical part (18) through said heat exchanger within said inner cylindrical part
(24) to said lower cylindrical part (14) via said steam permeable bottom (34), and
along said second fluid path from said lower cylindrical part (14) to said upper cylindrical
part (18) outside said inner cylindrical part, by using said impeller (32), and ejecting
dry bulk particulate material at said outlet (28).
1. Vorrichtung (10) zum Trocknen von partikelförmigem Schüttmaterial, wobei die Vorrichtung
Folgendes umfasst:
einen Behälter (12), der in der Lage ist, überhitzten Dampf auf einem Druck zu halten,
der gleich oder größer als der Umgebungsdruck ist, der den Behälter (12) umgibt, wobei
der Behälter (12) einen unteren zylindrischen Teil (14), der eine erste Querschnittsfläche
definiert, die senkrecht zu der Länge des unteren zylindrischen Teils (14) verläuft,
und einen oberen zylindrischen Teil (18), der eine zweite Querschnittsfläche definiert,
die senkrecht zu der Länge des oberen zylindrischen Teils (18) verläuft, definiert,
einen inneren zylindrischen Teil (24), der sich zentral innerhalb des oberen zylindrischen
Teils (18) und des unteren zylindrischen Teils (14) des Behälters (12) befindet, um
einen ersten Fluidweg von dem oberen zylindrischen Teil (18) zu dem unteren zylindrischen
Teil (14) innerhalb des inneren zylindrischen Teils (24) und einen zweiten Fluidweg
von dem unteren zylindrischen Teil (14) zu dem oberen zylindrischen Teil (18) außerhalb
des inneren zylindrischen Teils (24) einzurichten,
eine erste Anzahl von Trennwänden (36), die sich radial innerhalb des unteren zylindrischen
Teils (14) zwischen dem unteren zylindrischen Teil (14) und dem inneren zylindrischen
Teil (24) erstreckt und in dem unteren zylindrischen Teil (14) eine Einlasskammer
(38'), eine Auslasskammer (38") und eine zweite Anzahl von Zwischenkammern (38), die
sich zwischen der Einlasskammer (38') und der Auslasskammer (38") in einer Umfangsrichtung
befindet, definiert, wobei die Einlasskammer einen Einlass zum Aufnehmen eines feuchten,
partikelförmigem Schüttmaterials aufweist, wobei die Auslasskammer (38") einen Auslass
(28) zum Ausstoßen eines trockenen partikelförmigem Schüttmaterials aufweist, wobei
die Einlasskammer (38') und die Zwischenkammern (38) jeweils einen dampfdurchlässigen
Boden (34) definieren, wobei die Auslasskammer (38") einen nicht dampfdurchlässigen
Boden definiert,
einen Wärmetauscher, der sich innerhalb des inneren zylindrischen Teils (24) befindet,
um den überhitzten Dampf zu erhitzen,
ein Laufrad (32) zum Erzeugen einer Strömung von überhitztem Dampf entlang des ersten
Fluidwegs von dem oberen zylindrischen Teil (18) durch den Wärmetauscher innerhalb
des inneren zylindrischen Teils (24) zu dem unteren zylindrischen Teil (14) über den
dampfdurchlässigen Boden (34) und entlang des zweiten Fluidwegs von dem unteren zylindrischen
Teil (14) zu dem oberen zylindrischen Teil (18) außerhalb des inneren zylindrischen
Teils (24), dadurch gekennzeichnet, dass
der dampfdurchlässige Boden (34) der Einlasskammer (38') dazu geeignet ist, zwischen
20 % und 50 % der Strömung von überhitztem Dampf von dem Laufrad (32) aufzunehmen,
und dadurch, dass die Einlasskammer (38') größer als jede der Zwischenkammern (38)
ist und dadurch einen größeren kreisförmigen Sektor des ringförmigen Raums zwischen
dem unteren zylindrischen Teil (14) und dem inneren zylindrischen Teil (24) einnimmt.
2. Vorrichtung (10) nach Anspruch 1, wobei die Einlasskammer (38') dazu geeignet ist,
zwischen 22 % und 45 % des überhitzten Dampfs, der von dem inneren zylindrischen Teil
(24) empfangen wird, bevorzugt zwischen 25 % und 40 % des überhitzten Dampfs, der
von dem inneren zylindrischen Teil (24) empfangen wird, mehr bevorzugt zwischen 30
% und 35 % des überhitzten Dampfs, der von dem inneren zylindrischen Teil (24) empfangen
wird, wie etwa 33 % des überhitzten Dampfs, der von dem inneren zylindrischen Teil
(24) empfangen wird, aufzunehmen.
3. Vorrichtung (10) nach Anspruch 1, wobei die Einlasskammer (38') dazu geeignet ist,
zwischen 20 % und 22 % des überhitzten Dampfs, der von dem inneren zylindrischen Teil
(24) empfangen wird, und/oder zwischen 22 % und 25 % des überhitzten Dampfs, der von
dem inneren zylindrischen Teil (24) empfangen wird, und/oder zwischen 25 % und 30
% des überhitzten Dampfs, der von dem inneren zylindrischen Teil (24) empfangen wird,
und/oder zwischen 30 % und 35 % des überhitzten Dampfs, der von dem inneren zylindrischen
Teil (24) empfangen wird und/oder zwischen 35 % und 40 % des überhitzten Dampfs, der
von dem inneren zylindrischen Teil (24) empfangen wird und/oder zwischen 40 % und
45 % des überhitzten Dampfs, der von dem inneren zylindrischen Teil (24) empfangen
wird, und/oder zwischen 45 % und 50 % des überhitzten Dampfes, der von dem inneren
zylindrischen Teil (24) empfangen wird, aufzunehmen.
4. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei die Einlasskammer
(38') und die Zwischenkammern (38) jeweils eine Strömungsfläche definieren, die parallel
zu der ersten Querschnittsfläche verläuft, wobei die Strömungsfläche der Einlasskammer
(38') größer als die Strömungsfläche einer beliebigen der Zwischenkammern ist.
5. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei der dampfdurchlässige
Boden (34) der Einlasskammer (38') eine Dampfdurchlässigkeit zwischen 20 % und 45
% der Dampfdurchlässigkeit des Gesamtdampfdurchlässigkeit aller dampfdurchlässigen
Böden, bevorzugt zwischen 25 % und 40 %, mehr bevorzugt zwischen 30 % und 35 %, wie
etwa 33 %, definiert.
6. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei die dampfdurchlässigen
Böden der Einlasskammer (38') und der Zwischenkammern (38) Perforationen (50) definieren.
7. Vorrichtung (10) nach Anspruch 6, wobei die Perforationen (50) der dampfdurchlässigen
Böden der Einlasskammer (38') eine Fläche definieren, die 20 % bis 45 % der Gesamtfläche
aller Perforationen von allen der dampfdurchlässigen Böden, vorzugsweise zwischen
25 % und 40 %, besonders bevorzugt zwischen 30 % und 35 %, wie etwa 33 %, ausmacht.
8. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei der Behälter (12)
einen konischen Zwischenteil (16) aufweist, der den unteren zylindrischen Teil (14)
und den oberen zylindrischen Teil (18) so miteinander verbindet, dass die zweite Querschnittsfläche
größer als die erste Querschnittsfläche ist.
9. Vorrichtung (10) nach einem der Ansprüche 1-7, wobei die zweite Querschnittsfläche
im Wesentlichen gleich der ersten Querschnittsfläche ist.
10. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei die zweite Anzahl
zwischen 6 und 40, bevorzugt 10 bis 25, mehr bevorzugt 12 bis 20, wie etwa bei 14,
liegt.
11. Vorrichtung (10) nach einem der vorhergehenden Ansprüche, wobei der obere zylindrische
Teil (18) einen Zyklon (44) zum Transportieren von partikelförmigem Material von dem
oberen zylindrischen Teil (18) zu dem unteren zylindrischen Teil (14) umfasst.
12. Verfahren zum Trocknen von partikelförmigem Schüttmaterial durch Bereitstellen einer
Vorrichtung (10) nach Anspruch 1, wobei das Verfahren die folgenden Schritte umfasst:
Halten eines überhitzten Dampfes in dem Behälter (12) auf einem Druck, der gleich
oder größer als der Umgebungsdruck ist, der den Behälter (12) umgibt,
Empfangen von feuchtem partikelförmigem Schüttmaterial an dem Einlass (26),
Erhitzen des Dampfes innerhalb des Wärmetauschers,
Erzeugen einer Strömung von überhitztem Dampf entlang des ersten Fluidwegs von dem
oberen zylindrischen Teil (18) durch den Wärmetauscher innerhalb des inneren zylindrischen
Teils (24) zu dem unteren zylindrischen Teil (14) über den dampfdurchlässigen Boden
(34) und entlang des zweiten Fluidwegs von dem unteren zylindrischen Teil (14) zu
dem oberen zylindrischen Teil (18) außerhalb des inneren zylindrischen Teils durch
Verwenden des Laufrads (32) und Ausstoßen von trockenem, partikelförmigem Schüttmaterial
an dem Auslass (28).
1. Appareil (10) de séchage de matière particulaire en vrac, ledit appareil comprenant
:
une cuve (12) capable de maintenir de la vapeur surchauffée à une pression égale ou
supérieure à la pression ambiante entourant ladite cuve (12), ladite cuve (12) définissant
une partie cylindrique inférieure (14) définissant une première aire de section transversale
perpendiculaire à la longueur de la partie cylindrique inférieure (14) et une partie
cylindrique supérieure (18) définissant une seconde aire de section transversale perpendiculaire
à la longueur de la partie cylindrique supérieure (18),
une partie cylindrique intérieure (24) située au centre de ladite partie cylindrique
supérieure (18) et de ladite partie cylindrique inférieure (14) de ladite cuve (12)
permettant d'établir un premier trajet de fluide de ladite partie cylindrique supérieure
(18) jusqu'à ladite partie cylindrique inférieure (14) à l'intérieur de ladite partie
cylindrique intérieure (24) et un second trajet de fluide de ladite partie cylindrique
inférieure (14) jusqu'à ladite partie cylindrique supérieure (18) à l'extérieur de
ladite partie cylindrique intérieure (24),
un premier nombre de parois de séparation (36) s'étendant radialement à l'intérieur
de ladite partie cylindrique inférieure (14) entre ladite partie cylindrique inférieure
(14) et ladite partie cylindrique intérieure (24) et définissant dans ladite partie
cylindrique inférieure (14) une chambre d'entrée (38'), une chambre de sortie (38")
et un second nombre de chambres intermédiaires (38) situées entre ladite chambre d'entrée
(38') et ladite chambre de sortie (38") dans une direction circonférentielle, ladite
chambre d'entrée comprenant une entrée destinée à recevoir une matière particulaire
en vrac humide, ladite chambre de sortie (38") comprenant une sortie (28) permettant
d'éjecter une matière particulaire en vrac sec, ladite chambre d'entrée (38') et lesdites
chambres intermédiaires (38) définissant chacune un fond perméable à la vapeur (34),
ladite chambre de sortie (38") définissant un fond imperméable à la vapeur,
un échangeur de chaleur situé à l'intérieur de ladite partie cylindrique intérieure
(24) permettant de chauffer ladite vapeur surchauffée,
une roue (32) permettant de générer un écoulement de vapeur surchauffée le long dudit
premier trajet de fluide depuis ladite partie cylindrique supérieure (18) à travers
ledit échangeur de chaleur à l'intérieur de ladite partie cylindrique intérieure (24)
jusqu'à ladite partie cylindrique inférieure (14) par le biais dudit fond perméable
à la vapeur (34), et le long dudit second trajet de fluide de ladite partie cylindrique
inférieure (14) à ladite partie cylindrique supérieure (18) à l'extérieur de ladite
partie cylindrique intérieure (24), caractérisé en ce que
ledit fond perméable à la vapeur (34) de ladite chambre d'entrée (38') est adapté
pour recevoir entre 20% et 50% dudit flux de vapeur surchauffée provenant de ladite
roue (32),
et en ce que ladite chambre d'entrée (38') est plus grande que l'une quelconque des chambres intermédiaires
(38) et occupe ainsi un secteur circulaire plus grand de l'espace en forme d'anneau
entre la partie cylindrique inférieure (14) et la partie cylindrique intérieure (24).
2. Appareil (10) selon la revendication 1, dans lequel ladite chambre d'entrée (38')
est adaptée pour recevoir entre 22% et 45% de ladite vapeur surchauffée reçue de ladite
partie cylindrique intérieure (24), de préférence entre 25% et 40% de ladite vapeur
surchauffée reçue de ladite partie cylindrique intérieure (24), de manière davantage
préférée entre 30% et 35% de ladite vapeur surchauffée reçue de ladite partie cylindrique
intérieure (24), tel que 33% de ladite vapeur surchauffée reçue de ladite partie cylindrique
intérieure (24).
3. Appareil (10) selon la revendication 1, dans lequel ladite chambre d'entrée (38')
est adaptée pour recevoir entre 20% et 22% de ladite vapeur surchauffée reçue de ladite
partie cylindrique intérieure (24), et/ou entre 22% et 25% de ladite vapeur surchauffée
reçue de ladite partie cylindrique intérieure (24), et/ou entre 25% et 30% de ladite
vapeur surchauffée reçue de ladite partie cylindrique intérieure (24), et/ou entre
30% et 35% de ladite vapeur surchauffée reçue de ladite partie cylindrique intérieure
(24), et/ou entre 35% et 40% de ladite vapeur surchauffée reçue de ladite partie cylindrique
intérieure (24), et/ou entre 40% et 45% de ladite vapeur surchauffée reçue de ladite
partie cylindrique intérieure (24), et/ou entre 45% et 50% de ladite vapeur surchauffée
reçue de ladite partie cylindrique intérieure (24).
4. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel ladite
chambre d'entrée (38') et lesdites chambres intermédiaires (38) définissent chacune
une zone d'écoulement parallèle à ladite première aire de section transversale, ladite
zone d'écoulement de ladite chambre d'entrée (38') étant plus grande que ladite surface
d'écoulement de l'une quelconque desdites chambres intermédiaires.
5. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel ledit
fond perméable à la vapeur (34) de ladite chambre d'entrée (38') définit une perméabilité
à la vapeur comprise entre 20% et 45% de la perméabilité à la vapeur de la perméabilité
à la vapeur totale de l'ensemble desdits fonds perméables à la vapeur, de préférence
entre 25% et 40%, de manière davantage préférée entre 30% et 35%, tel que 33%.
6. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel lesdits
fonds perméables à la vapeur de ladite chambre d'entrée (38') et desdites chambres
intermédiaires (38) définissent des perforations (50).
7. Appareil (10) selon la revendication 6, dans lequel lesdites perforations (50) desdits
fonds perméables à la vapeur de ladite chambre d'entrée (38') définissent une surface
représentant 20% à 45% de la surface totale de toutes lesdites perforations de l'ensemble
desdits fonds perméables à la vapeur, de préférence entre 25% et 40%, de manière davantage
préférée entre 30% et 35%, tel que 33%.
8. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel ladite
cuve (12) comprend une partie conique intermédiaire (16) reliant ladite partie cylindrique
inférieure (14) et ladite partie cylindrique supérieure (18) de sorte que ladite seconde
aire de section transversale est plus grande que ladite première aire de section transversale.
9. Appareil (10) selon l'une quelconque des revendications 1 à 7, dans lequel ladite
seconde aire de section transversale est sensiblement égale à ladite première aire
de section transversale.
10. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel ledit
second nombre est compris entre 6 et 40, de préférence 10 à 25, de manière davantage
préférée 12 à 20, tel que 14.
11. Appareil (10) selon l'une quelconque des revendications précédentes, dans lequel ladite
partie cylindrique supérieure (18) comprend un cyclone (44) destiné à transporter
la matière particulaire de ladite partie cylindrique supérieure (18) vers ladite partie
cylindrique inférieure (14).
12. Procédé de séchage de matières particulaires en vrac en fournissant un appareil (10),
selon la revendication 1,
ledit procédé comprenant les étapes de :
maintien à l'intérieur de ladite cuve (12) d'une vapeur surchauffée à une pression
égale ou supérieure à la pression ambiante entourant la cuve (12),
réception d'une matière particulaire en vrac humide au niveau de ladite entrée (26),
chauffage de ladite vapeur à l'intérieur dudit échangeur de chaleur,
génération d'un écoulement de vapeur surchauffée le long dudit premier trajet de fluide
depuis ladite partie cylindrique supérieure (18) à travers ledit échangeur de chaleur
à l'intérieur de ladite partie cylindrique intérieure (24) jusqu'à ladite partie cylindrique
inférieure (14) par le biais dudit fond perméable à la vapeur (34), et le long dudit
second trajet de fluide de ladite partie cylindrique inférieure (14) à ladite partie
cylindrique supérieure (18) à l'extérieur de ladite partie cylindrique intérieure,
à l'aide de ladite roue (32), et en éjectant la matière sèche particulaire à travers
ladite sortie (28).