U.S. patent application number 11/540875 was filed with the patent office on 2007-04-19 for method and device for pelletizing unprocessed cellulosic fibrous material.
Invention is credited to Michael Curran, Pedro Ludovico Lana.
Application Number | 20070084385 11/540875 |
Document ID | / |
Family ID | 35478438 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070084385 |
Kind Code |
A1 |
Lana; Pedro Ludovico ; et
al. |
April 19, 2007 |
Method and device for pelletizing unprocessed cellulosic fibrous
material
Abstract
The present invention relates to a method and a device for
pelletizing unprocessed cellulosic fibrous material on an
industrial scale, and in particular to the use of said unprocessed
cellulosic fibrous material pellets as a combustible fuel
product.
Inventors: |
Lana; Pedro Ludovico; (Sao
Paulo, BR) ; Curran; Michael; (Yvoire, FR) |
Correspondence
Address: |
SALIWANCHIK LLOYD & SALIWANCHIK;A PROFESSIONAL ASSOCIATION
PO BOX 142950
GAINESVILLE
FL
32614-2950
US
|
Family ID: |
35478438 |
Appl. No.: |
11/540875 |
Filed: |
September 28, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60721358 |
Sep 28, 2005 |
|
|
|
Current U.S.
Class: |
110/219 ; 44/550;
44/629 |
Current CPC
Class: |
C10L 5/366 20130101;
Y02E 50/30 20130101; F23G 2201/101 20130101; F23G 2900/50206
20130101; F23G 5/04 20130101; C10L 5/363 20130101; F23G 5/02
20130101; F23G 7/02 20130101; Y02E 20/12 20130101; C10L 5/44
20130101; B30B 11/201 20130101; F23G 2201/602 20130101; C10L 5/48
20130101; B01J 2/12 20130101; Y02E 50/10 20130101 |
Class at
Publication: |
110/219 ;
044/550; 044/629 |
International
Class: |
F23G 5/02 20060101
F23G005/02; C10L 5/00 20060101 C10L005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 28, 2005 |
EP |
05021213.3 |
Claims
1. A method for drying a combustible cellulosic fibrous material,
wherein said method comprises the step of drying of said
combustible cellulosic fibrous material in a drying unit, wherein
said drying unit comprises a heat source that indirectly provides
heat to said combustible cellulosic fibrous material when drying
said combustible cellulosic fibrous material.
2. The method according to claim 1, wherein said drying unit is a
rotary dryer, in particular a spinning tube dryer (8).
3. The method according to claim 2, wherein said heat source
comprises a system of tubes, in particular bundled tubes, conveying
the heat source.
4. The method according to claim 3, wherein said heat source is
saturated steam.
5. The method according to claim 2, wherein the heat source is
applied at a temperature ranging from about 170 to about
185.degree. C. inside the tubes, resulting in temperatures ranging
from about 135 to about 140.degree. C. on the external surfaces of
the tubes in the drying unit.
6. The method according to any of claim 2, wherein the heat source
is applied at a pressure of about 8.34 bar to about 9.81 bar (8.5
to 10 kgf/cm2) inside the tubes.
7. A method for pelletizing combustible cellulosic fibrous
material, wherein said method comprises the following steps: (a)
providing and feeding of unprocessed combustible cellulosic fibrous
material into said method, (b) cleaning of said unprocessed
combustible cellulosic fibrous material, (c) drying of said cleaned
unprocessed combustible cellulosic fibrous material, (d)
pelletization of said dried combustible cellulosic fibrous
material, and (e) sorting and drying of said pelletized combustible
cellulosic fibrous material, wherein the drying in step (c)
comprises the step of drying of said combustible cellulosic fibrous
material in a drying unit, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material.
8. The method according to claim 7, wherein in step (a) unprocessed
combustible cellulosic fibrous material is continuously fed into
the method while said material is loosened and flattened.
9. The method according to claim 7, wherein in step (b) ferrous
material and impurities are removed from the unprocessed
combustible cellulosic fibrous material.
10. The method according to claim 7, wherein in step (c) said
drying step comprises applying a heat source that indirectly
provides heat to said combustible cellulosic fibrous material when
drying said combustible cellulosic fibrous material, wherein said
heat source optionally comprises a system of tubes, in particular
bundled tubes, conveying the heat source.
11. The method according to claim 10, wherein the heat source is
applied at a temperature ranging from about 170 to about
185.degree. C. inside the tubes, resulting in temperatures ranging
from about 135 to about 140.degree. C. on the external surfaces of
the tubes in the drying unit.
12. The method according to claim 10, wherein the heat source is
applied at a pressure of about 8.34 bar to about 9.81 bar (8.5 to
10 kgf/cm2) inside the tubes.
13. The method according to claim 10, wherein said combustible
cellulosic fibrous material remains inside the tube dryer for about
12 minutes, at about 4 rpm using about 2 to about 3 metric tons of
steam per hour.
14. The method according to claim 7, wherein in step (c) after the
combustible cellulosic fibrous material leaves the tubular bundles,
it is insufflated in counter flow with hot air by a duct coming
from a heat radiator fed by saturated steam (VS).
15. The method according to claim 14, wherein in step (c) the hot
and humid gases are removed on the opposite side of the entrance of
the dryer by a duct with forced exhaust, and sent to a cyclone, or
similar equipment, where the solid particles (powder) are separated
and sent to be burned by the boiler.
16. The method according to claim 7, wherein in step (d) the dried
combustible cellulosic fibrous material, with a humidity varying
between about 13 to about 20% is continuously fed to the
pelletizers, where the combustible cellulosic fibrous material
receives an injection of saturated steam, and then enters the
pelletizer's pressing system.
17. The method according to claim 7, wherein after step (d) the
combustible cellulosic fibrous material pellets are removed from
the pelletizers, in particular by a variable-speed cleated or
similar type conveyor belt.
18. The method according to claim 7, wherein in step (e) the
combustible cellulosic fibrous material pellets are sorted
according to their size, and/or in step (e) any rejected material
at the sifter, together with any excess with excess dried
combustible cellulosic fibrous material from the feeding conveyor
belt is returned to the feed box to be reused in said method.
19. The method according to claim 7, wherein in step (e) the
combustible cellulosic fibrous material pellets are cooled down to
room temperature of about 20 to about 40.degree. C.
20. The method according to claim 7, wherein in step (f) the final
combustible cellulosic fibrous material pellets, having a humidity
ranging from about 9 to about 13% and a density between about 0.55
to about 0.60 g/cm.sup.3 are advanced to a storage system.
21. The method according to claims 7, further comprising storing of
the dried combustible cellulosic fibrous material pellets in step
(f).
22. The method according to claim 7, wherein said method is a fully
automated and/or continuous method.
23. The method according to claim 7, wherein said combustible
cellulosic fibrous material is selected from at least one of paper
mill sludge, wood chips, paper fiber, cherry pits, olive pits,
sugar-cane bagasse, sweet sorghum bagasse, grass clippings, and fur
trees, and combinations thereof.
24. A device for converting unprocessed combustible cellulosic
fibrous material into combustible compressed cellulosic fibrous
material pellets by a method for pelletizing combustible cellulosic
fibrous material, wherein said method comprises the following
steps: (a) providing and feeding of unprocessed combustible
cellulosic fibrous material into said method, (b) cleaning of said
unprocessed combustible cellulosic fibrous material, (c) drying of
said cleaned unprocessed combustible cellulosic fibrous material,
(d) pelletization of said dried combustible cellulosic fibrous
material, and (e) sorting and drying of said pelletized combustible
cellulosic fibrous material, wherein the drying in step (c)
comprises the step of drying of said combustible cellulosic fibrous
material in a drying unit, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material, wherein said device comprises a drying unit for
drying of said combustible cellulosic fibrous material, wherein
said drying unit comprises a heat source that indirectly provides
heat to said combustible cellulosic fibrous material when drying
said combustible cellulosic fibrous material.
25. A device for converting unprocessed combustible cellulosic
fibrous material into combustible compressed cellulosic fibrous
material pellets by a method for pelletizing combustible cellulosic
fibrous material, wherein said method comprises the following
steps: (a) providing and feeding of unprocessed combustible
cellulosic fibrous material into said method, (b) cleaning of said
unprocessed combustible cellulosic fibrous material, (c) drying of
said cleaned unprocessed combustible cellulosic fibrous material,
(d) pelletization of said dried combustible cellulosic fibrous
material, and (e) sorting and drying of said pelletized combustible
cellulosic fibrous material, wherein the drying in step (c)
comprises the step of drying of said combustible cellulosic fibrous
material in a drying unit, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material, wherein said device comprises: (a) a continuous
feeding unit, (b) a cleaning unit, (c) a drying unit, (d) a
pelletization unit, and (e) a sorting and second drying unit, and,
optionally (f) a storing unit.
26. The device according to claim 25, wherein unit (a) comprises a
cleated or similar type conveyor belt, a feed box, and a
sprayer.
27. The device according to claim 25, wherein said feed box can
hold a 15-minute supply and has a rectangular flat-wall, a
flat-bottom, and a cleated or similar type conveyor belt.
28. The device according to any of claim 25, wherein unit (b)
comprises a cleated or similar type conveyor belt, an
electromagnet, and a di-stone.
29. The device according to claim 28, wherein said electromagnet
has a minimum magnetic capacity of about 1500 gauss, and said
di-stone is a rotating machine consisting of about 5 to 8
perpendicular axes with star-shaped knives that counter-rotate.
30. The device according to claim 25, wherein unit (c) comprises a
cleated or similar type conveyor belt, a spinning tube dryer, an
insufflating system, and an exhaust system featuring cyclones.
31. The device according to claim 30, wherein said spinning tube
dryer is fitted with deflectors positioned at about 45.degree.
attached to the tube bundles, and the minimum spacing between the
tubes is about 75 mm.
32. The device according to claim 25, wherein unit (d) comprises a
cleated or similar type conveyor belt, sloping spouts, conditioner
of the pelletizer, the pelletizers, and a variable-speed cleated or
similar type conveyor belt (13).
33. The device according to claim 32, wherein said sloping spouts
have adjustable gates and magnetic plates, said conditioner is a
spinning cylindrical metal box with a diameter of about 450 mm,
fitted with wings and driven by a motor of about 5 hp, and said
pelletizer comprises a pressing system, a cast-steel case, holding
the primary shafts, the hollow mold shafts, the compacting rollers
and the motor itself, whereas the main shaft fixes the two
compacting rollers and the scarpers.
34. The device according to claim 33, wherein said compacting
roller having a diameter ranging from about 140 mm to about 220 mm,
an eccentric shaft, a device with adjusting regulators and a metal
shield pressing, having a thickness ranging from about 15 mm to
about 40 mm and grooves about 2 to about 5 mm deep and about 2 to
about 5 mm wide, and spaced about 8 to about 12 mm apart.
35. The device according to claim 34, wherein said pelletizer's
pressing system has a mold rotating at about 360 rpm, two pressing
rollers, regulators and is driven by a motor of about 125 hp at
about 1750 rpm.
36. The device according to claim 35, wherein said mold is fixed at
the hollow rotating shaft, driven by gears and an electric motor
with power varying from about 100 hp to 400 hp, at about 220 rpm to
420 rpm, is a metal ring with a flange for fixing on the hollow
shaft and a surface with various holes, wheraes these holes can be
of various sizes, and comprises a mold diameter of about 520 to 820
mm, a diameter of the mold holes of about 4.76 mm to about 19.05 mm
( 3/16'' to 3/4''), a width of the track of the molds of about 100
to 220 mm, and a number of holes in the molds of about 860-4600
holes.
37. The device according to claim 25, wherein unit (e) comprises a
variable-speed cleated or similar type conveyor belt, a vibrating
sifter, a cooler with a cleated conveyor belt with a perforated
screen, and an exhaust system with a cyclone.
38. The device according to claim 25, further comprising a storing
unit (f)
39. The device according to claim 38, wherein unit (f) comprises a
cleated or similar type conveyor belt, big bags or silos.
40. The device according to claim 25, wherein unit (d) and unit (e)
are connected to unit (b) via a cleated or similar type conveyor
belt.
41. The device according to claim 25, wherein said units are
integrated into one system.
42. A pelletized combustible cellulosic fibrous material,
obtainable by a method for pelletizing combustible cellulosic
fibrous material, wherein said method comprises the following
steps: (a) providing and feeding of unprocessed combustible
cellulosic fibrous material into said method, (b) cleaning of said
unprocessed combustible cellulosic fibrous material, (c) drying of
said cleaned unprocessed combustible cellulosic fibrous material,
(d) pelletization of said dried combustible cellulosic fibrous
material, and (e) sorting and drying of said pelletized combustible
cellulosic fibrous material, wherein the drying in step (c)
comprises the step of drying of said combustible cellulosic fibrous
material in a drying unit, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material.
43. The pelletized combustible cellulosic fibrous material
according to claim 42, wherein said material has an upper calorific
content of about 4,500 to about 5,500 kcal/kg, a lower calorific
content of about 3,500 to about 4,500 kcal/kg, a density of about
500 to about 600 kg dry matter/m.sup.3, and a humidity of about 10%
to about 15%.
44. The pelletized combustible cellulosic fibrous material
according to claim 42, wherein said material is further blended
with coal.
45. The pelletized combustible cellulosic fibrous material
according to claim 42, wherein said pelletized combustible
cellulosic fibrous material is selected from pellets of at least
one of paper mill sludge, wood chips, paper fiber, cherry pits,
olive pits, sugar-cane bagasse, sweet sorghum bagasse, grass
clippings, and fur trees, and combinations thereof.
46. A method for generating energy and/or biofuel, comprising the
use of a pelletized combustible cellulosic fibrous material,
obtainable by a method for pelletizing combustible cellulosic
fibrous material, wherein said method comprises the following
steps: (a) providing and feeding of unprocessed combustible
cellulosic fibrous material into said method, (b) cleaning of said
unprocessed combustible cellulosic fibrous material, (c) drying of
said cleaned unprocessed combustible cellulosic fibrous material,
(d) pelletization of said dried combustible cellulosic fibrous
material, and (e) sorting and drying of said pelletized combustible
cellulosic fibrous material, wherein the drying in step (c)
comprises the step of drying of said combustible cellulosic fibrous
material in a drying unit, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material as a renewable biomass.
47. A method for producing a pelletized combustible cellulosic
fibrous material comprising the use of a device for converting
unprocessed combustible cellulosic fibrous material into
combustible compressed cellulosic fibrous material pellets by a
method for pelletizing combustible cellulosic fibrous material,
wherein said method comprises the following steps: (a) providing
and feeding of unprocessed combustible cellulosic fibrous material
into said method, (b) cleaning of said unprocessed combustible
cellulosic fibrous material, (c) drying of said cleaned unprocessed
combustible cellulosic fibrous material, (d) pelletization of said
dried combustible cellulosic fibrous material, and (e) sorting and
drying of said pelletized combustible cellulosic fibrous material,
wherein the drying in step (c) comprises the step of drying of said
combustible cellulosic fibrous material in a drying unit, wherein
said drying unit comprises a heat source that indirectly provides
heat to said combustible cellulosic fibrous material when drying
said combustible cellulosic fibrous material, wherein said device
comprises: (a) a continuous feeding unit, (b) a cleaning unit, (c)
a drying unit, (d) a pelletization unit, and (e) a sorting and
second drying unit, and, optionally (f) a storing unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 60/721,358, filed Sep. 28, 2005. The subject
application also claims priority to European Patent Application No.
05021213.3, filed Sep. 28, 2005.
FIELD OF THE INVENTION
[0002] The present invention relates to a method and a device for
pelletizing unprocessed cellulosic fibrous material, in particular
sugar-cane bagasse, on an industrial scale, and in particular to
the use of said unprocessed cellulosic fibrous material pellets as
a combustible fuel product.
BACKGROUND OF THE INVENTION
[0003] Since fossil fuel has become a finite energy source, in the
last decades many efforts have been put into the production of
alternative energy materials. These alternative materials should
not only be affordable and readily available, they also should be
preferably derived from renewable sources. Among the existing
renewable alternatives to fossil fuels, biomass has raised great
interest. Wood or wood by-products are prime examples of renewable
energy materials when used for the production of fuel briquettes or
pellets. The main source of firewood has been found in native
forests, mainly the Atlantic rain forests and the cerrados in
Brazil. It is simple to imagine that these sources are also finite
sources, and that an increase of wood fuel consumption would not
only lead to an increase in the price of these raw materials but
also to the loss of many forests since a tree needs a long growth
period, which decreases the desirability of wood as a renewable
energy source.
[0004] As an alternative to wood-based products, other agriculture
materials, such as sugar-cane, have been investigated. Sugar-cane
(Saccharum officinarum) belongs to the family of grasses (Poaceae).
It is a tall grass which is native in warm temperate to tropical
regions of the world. There are 13 million hectares of sugar-cane
plantations worldwide, and Brazil is one of the major growers of
sugar-cane. In Brazil, sugar-cane is currently used to produce
sugar as well as to provide the alcohol used in making gasohol
fuels.
[0005] Sugar from freshly harvested sugar-cane is extracted by
sugar-cane mills, mostly located in sugar-cane producing regions.
In a sugar mill, sugar-cane is washed, chopped and shredded, then
the shredded cane is repeatedly mixed with water and crushed
between rollers to collect juices containing 10-15% sucrose. The
remaining fibrous waste is commonly known as bagasse, and is
currently used on-site in sugar mills as a fuel, by feeding the
bagasse into the boilers to generate steam and power. In this way,
bagasse makes a sugar mill more than self-sufficient in energy. The
surplus bagasse can also be used for animal feed, in paper
manufacture, or burned to generate electricity for the local power
grid.
[0006] After extracting sugar from the fibrous residues, the
bagasse moisture content can vary considerably, containing up to
50% water. However in this state, the bagasse cannot be transported
elsewhere as a fuel due to the low calorific value (8-9 Giga Joules
per metric ton), and transporting issues.
[0007] Therefore, it would be useful to convert the bagasse into a
compact transportable fuel, which can be achieved by drying and
pelletizing. In addition, the resulting pellets can be blended with
coal in an effort to reduce emissions in coal-fired power
stations.
[0008] U.S. Pat. No. 4,363,636 (WO 83/01457 A1) (BR 8207930)
describes bagasse as a source of energy that is increased by a
flexible operation adapted to the power requirements, fuel storage
requirements and other variables of a sugar mill operation. Part or
all of a primary stream of bagasse from the sugar mill is dried
from its initial moisture content, e.g. in the order of 50%, to a
lower moisture content of about 25-40% using a portion of the hot
flue gases from the boilers which are used to supply power for the
sugar mill operation. The resulting drier material is separated to
provide an oversize particle stream which may be sent directly to
the boiler for burning, to storage in the bagasse house, or to a
secondary drying operation, and a secondary stream of fine particle
size bagasse components which are most suitable for further
processing and densification. This secondary stream, with optional
addition of oversize particles from the primary drying operation,
is then dried in contact with another portion of hot flue gases to
a moisture content suitable for densification, about 6-12% where a
pellet mill is employed, and is further subjected to particle size
selection, if necessary, and then subjected to densification in a
pellet mill or other suitable equipment. The densified material is
then sent to storage, returned to the boilers for part or all of
the fuel requirement or transported to other potential users.
[0009] MU 6801860 U describes a sugar cane bagasse dryer intended
to eliminate the low effectiveness of burning the wet bagasse, as
it comes from compression. This arrangement basically comprises a
diffuser that holds a carrier mat with the crushed sugar cane
bagasse. Such carrier mat is provided with a flow channel to drain
the liquid from the bagasse. Such bagasse is inserted in the upper
portion of a drying column and leaves dry in the lower portion due
to heated air provided by the furnace.
[0010] BR 8801542 also describes a dryer for solid bagasse, i.e.
sugar cane bagasse, without jeopardizing the necessary thermal
power used as direct heat source, cut cane straw and/or foliage in
general.
[0011] BR 8100104 describes a cyclone, a dryer operative under the
simultaneous principle of pneumatic heat and mass, a separator
cyclone and pelletizer, and using the fluid from solid fuel burn
called "BIOCOM" as drying agent, generating vapour to cook the
product, which is rich in nutritive substances. Similarly, BR
8100102 describes a process for obtaining a dry and solid fuel with
high heat power from sugar cane bagasse and its plant which
includes a bagasse dryer operating under the heat transference
principle and pneumatic mass, followed by a separator cyclone and a
agglomerated and continuous presser, working as dryer agent, the
fluid being originated from the burning of fuel obtained in a
furnace, the final product being dry and compact, such product
being able to be economically stored and carried, without the
difficulties of the original product.
[0012] BR 8102291 describes a process to increase the apparent
specific heat power of sugar cane bagasse and its available energy,
inside or outside the sugar factory. This process makes use of the
wasted heat or the heat wrongly used in sugar cane and alcohol
factories by drying or dehydrating the bagasse, increasing its
lower heat power (Kcal/Kg). This causes a great excess of bagasse,
which will be packaged in the adequate grain measure and compacted
to obtain a greater heat concentration, in order to facilitate its
transport or storage to be used as alternative energy and/or animal
food and similar.
[0013] U.S. Pat. No. 4,326,470 describes an individual bagasse
drier that realizes a system of utilization of the chimney gases to
decrease the moisture of the bagasse left from the mill in 10 or 15
points, increasing the steam production between 13.5% to 15.45%
respectively. It consists of a drier for each furnace, and consumes
54% of the power installed per ton of dry bagasse, in relation to
the existing systems in the market.
[0014] U.S. Pat. No. 4,613,339 describes a method for preparing and
using a combustible fuel product using sweet sorghum. A sorghum
variety high in sugar, high in biomass, and low in nitrogen is
first processed to remove a majority of sugars therefrom. The
remaining ligno-cellulosic residue, commonly known as bagasse, is
converted into combustible pellets or alternatively stored for
future pelletization. Storage is accomplished by first piling the
bagasse on a hard surface. The bagasse is then compressed to form a
compacted mass. Compression frees trapped air in the pile,
hindering oxidative degradation by bacteria and other
microorganisms. U.S. Pat. No. 4,613,339 further discloses that
sugarcane is not preferred for the method, since it requires
temperate, humid growing conditions that are not found in the US.
U.S. Pat. No. 4,613,339 discusses about spontaneous combustion, a
feature that appears to be inherent to pelletization. U.S. Pat. No.
4,613,339 proposes to use low-nitrogen sorghum in order to address
this problem. Thus, this method can only be used for the
pelletization of some materials.
[0015] U.S. Pat. No. 4,015,951 discloses pellets adapted to be
burned in industrial applications that are prepared by adjusting
the particle size of organic fibrous material to not more than
about 85% of the minimum dimension of the pellets to be produced,
adjusting the moisture content of the fibrous particles to about
16% to about 28% by weight, pelletizing the particles into
substantially symmetrical pellets having a maximum dimension of
about one-half inch at a pressure whereby constituents of the
particles exude and form a coating of wax-like material on the
surface of the pellets, and adjusting the moisture of the pellets
to a content which is in equilibrium with the atmosphere. U.S. Pat.
No. 4,015,951 further discloses a method of making fuel pellets of
organic fibrous material. The method includes providing and feeding
a raw material of random particle size, conveying the material to a
hammer mill, while foreign particles are removed, adjusting the
particle size to a maximum dimension of 85% of the pellet (or
less), transporting the particles to a rotary drum type dryer,
adjusting the moisture content to about 16-28 wt % "free moisture"
(regarded as important step), conveying the material to a
pelletizer, compression of the material at about 325 to 350.degree.
F., and adjusting the temperature and moisture content by a fan to
about 7 to 8% equilibrium moisture. The size of the pellets shall
be one-eighth to one-half inch, the density is about 65 pounds per
cubic foot. The organic fibres are described as agricultural or
wood waste materials. U.S. Pat. No. 4,015,951 requires to adjust
the moisture in equilibrium with the atmosphere, and that the
moisture content should be uniform before storing, since the
pellets in the pile will have a different moisture, compared to the
surface pellets (apparently in order to reach uniform burning).
[0016] U.S. Pat. No. 5,643,342 discloses a fuel pellet and a method
of manufacturing a fuel pellet capable of burning in either a
stoker or pulver furnace. The pellet is formed by an extrusion
process and method for drying a combustible cellulosic fibrous
material, wherein said method comprises the step of drying of said
combustible cellulosic fibrous material in a drying unit, wherein
said drying unit comprises a heat source that indirectly provides
heat to said combustible cellulosic fibrous material when drying
said combustible cellulosic fibrous material contains particles.
The pellet is about 3/4 to about 3 inches in length (i.e. larger
than the pellets as claimed herein). The pellet is always composed
of several components to be extruded. The screening as described by
U.S. Pat. No. 5,643,342 appears to be suitable only to exclude
material that is present as excess particles (i.e. smaller than 80
mesh).
[0017] So far, the operation technology of pelletization machinery
and similar equipment, such as briquetters, are generally known to
the person of skill in the art. However, their use with unprocessed
sugar-cane bagasse had never been performed on an industrial scale
without the use of the hot flue gases from the boilers. While the
literature mentions the production of pellets from unprocessed
sugar-cane bagasse, the manner in which this method is described is
not feasible to solve the particular problems and needs that derive
from the secure industrial production perspective.
[0018] Some basic studies involving pelletization in a lab
environment have been carried out in Australia, showing that
long-lasting pellets can be produced with 10% humidity,
60-100.degree. C., and eight-second compression time in the
pelletization equipment at pressures of 80 to 320 kgf/cm.sup.2, all
of which led to a final product density between 450 kg to 600 kg of
dry material per cubic meter. However, in all these tests
production was way below the pelletizers' nominal capacity.
[0019] In regard to the phase involving the unprocessed sugar-cane
bagasse, which is a key step to ensure sound method performance, it
is essential to mention some experiments, wherein the unprocessed
sugar-cane bagasse using the boiler exhaust gases in a counter-flow
with the bagasse in suspension.
[0020] The pellet-production facilities Centro de Tecnologia
Canavieira developed had a first model applied on an industrial
scale next to a sugar mill. This model operated on-and-off during
the 1982 crop and it basically produced hydrolyzed sugar-cane
bagasse pellets for animal-feed applications. Another aspect
analyzed was the high bagasse drying temperature, which rendered
operations unsafe because of the fire risk. This technology also
faced operational difficulties in relation to the air-bagasse
counter-flow, mainly frequent clogging of the system.
[0021] It should be noted, that the pelletization method is
basically the compressing of unprocessed sugar-cane bagasse, which
has variable density and humidity. The raw material used in
producing the pellets is unprocessed sugar-cane bagasse with
following characteristics: TABLE-US-00001 Upper calorific content
in damp state: 2,150 kcal/kg Lower calorific content: 1,750
kcal/kg. Density: 0.13 kg/m.sup.3 Humidity: 50%
[0022] For comparison the average calorific content of some types
of firewood are shown: TABLE-US-00002 Acacia mangium: 4,619
kacl/kg. Eucalyptus grandis: 4,641 kcal/kg. Alnus subcordata: 4,700
kcal/kg. Eucalyptus dunnii: 4,732 kcal/kg.
[0023] As already mentioned, bagasse has been used as a fiel and
pelletized. However, for its use as nationally registered biofuel
and to freight the pellets overseas the final pellets should have
similar calorific content as the above mentioned firewood and a
certain moisture.
[0024] Thus, among the existing renewable alternatives to fossil
fuels, the biomass has raised the greatest interest. Since firewood
found in native forests is a finite energy source, it is essential
to replace the firewood biomass for unprocessed bagasse pellets.
This invention refers to a secure continuous pelletization method
on an industrial scale compressing unprocessed sugar-cane bagasse,
using steam to dry during the spinning dryer. In addition, this
method is environmentally clean and reuses all industrial
rejects.
[0025] Moreover, this product will have the following additional
advantages: [0026] The product is from 100% recycled origin and is
environmentally friendly because it reduces deforestation. [0027]
The product has a calorific charge similar to firewood. [0028] The
product requires reduced storage capacity, thus enabling emergency
and buffer stocks. [0029] It is a clean product without the
drawbacks of firewood. [0030] The product's low humidity raises
temperature quickly and the product releases less smoke, ashes and
soot when compared to firewood. [0031] It has a more homogeneous
calorific charge than firewood. [0032] It has a higher flame
temperature. [0033] It causes less pollution because it is a
renewable fuel. [0034] The present invention addresses the issue of
problems arising with combustion and fire in an industrial
environment during the drying step(s). The state of the art is
silent about the use of special security measures when processing
sugar cane bagasse. [0035] The state of the art furthermore does
not discuss the energy consumption required when producing the
sugar cane bagasse.
SUMMARY OF THE INVENTION
[0036] It is an object of the present invention to provide a method
and a device on an industrial scale for pelletizing unprocessed
sugar-cane bagasse in order to obtain pellets having the following
preferable characteristics: Upper calorific content: about 4,500 to
about 5,500 kcal/kg; lower calorific content: about 3,500 to about
4,500 kcal/kg; density: about 500 to about 600 kg dry
matter/m.sup.3; and humidity: about 10% to about 15%.
[0037] Another object of this invention is to provide a method and
a device for the production of unprocessed sugar-cane pellets,
correcting the operational difficulties faced by the previous
mentioned attempts on an industrial scale, e.g. the high bagasse
drying temperature and therefore the high fire risk. One further
object of this invention is to provide unprocessed sugar-cane
bagasse pellets to be used in place of fossil fuels for
steam-generation processes, hot-gas generators, and equipment that
generates thermal energy. In line with this it is another object of
this invention to provide unprocessed sugar-cane bagasse pellets
transportable to regions, such as Europe or Japan with shortages of
biomass of high calorific value, as a cleaner fuel with all the
necessary specification, consistency and price requirements.
[0038] These and other objects and advantages of the present
invention will become more readily apparent from the following
detailed description.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0039] The present invention involves a method and a device on an
industrial scale for pelletizing unprocessed sugar-cane bagasse in
order to obtain pellets.
[0040] In a first aspect of the present invention, the object
thereof is solved by providing a method for drying a combustible
cellulosic fibrous material, wherein said method comprises the step
of drying of said combustible cellulosic fibrous material in a
drying unit, wherein said drying unit comprises a heat source that
indirectly provides heat to said combustible cellulosic fibrous
material when drying said combustible cellulosic fibrous
material.
[0041] Preferred is a method according to the invention, wherein
said drying unit is a rotary dryer, in particular a spinning tube
dryer (8). Such dryers are known to the person of skill and are
commercially available (for example as manufactured by the Masiero
Industrial S/A, Brazil), and can be readily adjusted by the person
of skill for performing the inventive method in an industrial
scale. One preferred example of a rotary dryer, in form of a
spinning tube dryer with a bundled tube arrangement, is shown in
FIGS. 4A and 4B.
[0042] Preferred is a method according to the invention, wherein
said heat source comprises a system of tubes, in particular bundled
tubes, conveying the heat source. More preferably, said heat source
is saturated steam.
[0043] Further preferred is a method according to the invention,
wherein the heat source is applied at a temperature ranging from
about 170 to about 185.degree. C. inside the tubes, resulting in
temperatures ranging from about 135 to about 140.degree. C. on the
external surfaces of the tubes in the drying unit (i.e. the steam
inside the pipes dry without contact with the bagasse, whilst the
steam flow heating the internal surface of the pipes and bagasse
has contact with the external surface of the pipes). This results
in the temperatures ranging from about 135 to about 140.degree. C.
Preferably, said sugar-cane bagasse starts to dry as soon as it
gets in contact with the bundle of tubes.
[0044] Preferred is a method according to the invention, wherein
the heat source is applied at a pressure of about 8.34 bar to about
9.81 bar (8.5 to 10 kgf/cm2) inside the tubes.
[0045] In another preferred embodiment of the method of the present
invention, said spinning tube dryer is fitted with deflectors
positioned at an angle of about 45.degree. attached to the tube
bundles, in order to increase efficiency in the transportation and
drying of bagasse inside the dryer.
[0046] In a second aspect of the present invention, the object
thereof is solved by providing a method for pelletizing combustible
cellulosic fibrous material, comprising: [0047] (a) providing and
feeding of unprocessed combustible cellulosic fibrous material into
said method, [0048] (b) cleaning of said unprocessed combustible
cellulosic fibrous material, [0049] (c) drying of said cleaned
unprocessed combustible cellulosic fibrous material, [0050] (d)
pelletization of said dried combustible cellulosic fibrous
material, and [0051] (e) sorting and drying of said pelletized
combustible cellulosic fibrous material, wherein the drying in step
(c) comprises a method according to the invention as described
above.
[0052] Preferably, the dried combustible cellulosic fibrous
material pellets are suitably stored in an additional step (f).
[0053] Preferably, in step (a) of the method of the present
invention, unprocessed combustible cellulosic fibrous material is
continuously fed into the method while the bagasse is loosened and
flattened.
[0054] In one embodiment of the method according to the present
invention, unprocessed combustible cellulosic fibrous material is
fed in step (a) through a feed box (2) and loosened and flattened
by a sprayer (3).
[0055] In a preferred embodiment of the method of the present
invention said feed box can hold a 15-minute supply in relation to
the plant output capacity.
[0056] In another preferred embodiment of the method of the present
invention, said feed box has a cleated or similar type conveyor
belt to transport the unprocessed combustible cellulosic fibrous
material.
[0057] In a particular preferred embodiment of the method of the
present invention, said feed box comprises a rectangular flat-wall
and a flat-bottom.
[0058] In one embodiment of the method of the present invention, in
step (b) ferrous material and impurities of the unprocessed
combustible cellulosic fibrous material are removed. More
preferably, said ferrous material is removed by an electromagnet
(5), and any other impurities are removed by a di-stone (6).
[0059] In another preferred embodiment of the method according to
the present invention, subsequently a fiber remover and a separator
of coarse impurities are used.
[0060] In another preferred embodiment of the method of the present
invention, said feeding conveyor belt is fitted with the said
electromagnet (5) having a minimum magnetic capacity of about 1,500
gauss. This electromagnet is placed far enough above the conveyor
belt so that it can remove ferrous material and does not halt the
method and the pelletizer. This electromagnet is cleaned frequently
to have removed any ferrous material attracted thereto.
[0061] In another particular preferred embodiment, said
electromagnet is installed in the passage between conveyor belts,
an area where the combustible cellulosic fibrous material is moved
considerably.
[0062] In a further particular preferred embodiment said di-stone
(6) is a rotating machine consisting of 5 to 8 perpendicular axes
with star-shaped knives that counter rotate.
[0063] In one embodiment of the method of the present invention,
said unprocessed combustible cellulosic fibrous material is dried
using saturated steam in step (c).
[0064] In a preferred embodiment of the method according to the
present invention, the cleaned unprocessed combustible cellulosic
fibrous material is transported by a cleated or similar type
conveyor belt (7) to the spinning tube dryer (8) using a system of
bundled tubes conveying saturated steam at about 8.34 bar to about
9.81 bar (8.5 to 10 kgf/cm.sup.2), at a temperature ranging from
about 170 to about 185.degree. C. inside the tube, providing
indirect contact with the product in the tube's external wall (i.e.
the steam inside the pipes dry without contact with the combustible
cellulosic fibrous material, whilst the steam flow heating the
internal surface of the pipes and combustible cellulosic fibrous
material has contact with the external surface of the pipes). This
results in temperatures ranging from about 135 to about 140.degree.
C. Preferably, said combustible cellulosic fibrous material starts
to dry as soon as it gets in contact with the bundle of tubes.
[0065] In another preferred embodiment of the method of the present
invention, said combustible cellulosic fibrous material is dried
from a moisture in the range of about 44 to about 55% to about 13
to about 20% in a drying step. Then, in one embodiment of the
method according to the present invention, the dried combustible
cellulosic fibrous material having a humidity varying between about
13 to about 20% is taken to the pelletizers by a cleated or similar
type conveyor belt.
[0066] In another preferred embodiment of the method of the present
invention, said spinning tube dryer is fitted with deflectors
positioned at an angle of about 45.degree. attached to the tube
bundles, in order to increase efficiency in the transportation and
drying of combustible cellulosic fibrous material inside the
dryer.
[0067] In a further embodiment of the method of the present
invention, the minimum spacing between the tubes is about 75 mm,
helping to prevent any combustible cellulosic fibrous material
accumulation inside the dryer, which eventually might lead to
combustion.
[0068] In another preferred embodiment of the method of the present
invention, in step (c) said unprocessed combustible cellulosic
fibrous material remains inside the spinning tube dryer for about
12 minutes, at about 4 rpm using about 2 to about 3 metric tons of
steam per hour.
[0069] In a particular preferred embodiment of the method according
to the present invention, after the combustible cellulosic fibrous
material leaves the tubular bundles, it is insufflated with hot air
by a duct coming from a heat radiator (9) fed by saturated steam
(VS). This operation heats the gases in counter flow with the
combustible cellulosic fibrous material, thus helping the drying
method and preventing any accumulation of solid residues (powder)
inside the dryer.
[0070] In another preferred embodiment of the method of the present
invention, the hot and humid gases in step (c) are removed on the
opposite side of the entrance of the dryer by a duct with forced
exhaust (10), and sent to a cyclone, or similar equipment, where
the solid particles (powder) are separated and sent to be burned by
the boiler.
[0071] In one embodiment of the method according to the present
invention, the dried combustible cellulosic fibrous material having
a humidity varying between about 13 to about 20% is taken to the
pelletizers by a cleated or similar type conveyor belt.
[0072] In one embodiment of the method according to the present
invention, in step (d) the said dried combustible cellulosic
fibrous material is fed continuously to the pelletizer by spouts to
the conditioner of the pelletizer (12).
[0073] In a preferred embodiment of the method of the present
invention, said spouts in step (d) are sloping spouts with
adjustable gates and magnetic plates that withhold any ferrous
impurities that have not been collected before in order to prevent
any damage to the pelletizers.
[0074] In a more preferred embodiment of the method of the present
invention, the combustible cellulosic fibrous material is fed by
the spout to the conditioner of the pelletizer (12), which is a
spinning cylindral metal box with about 450 mm diameter, fitted
with wings and which loosens the combustible cellulosic fibrous
material and feeds the pelletizer. This machine is driven by a 5 hp
motor. In said conditioner, the combustible cellulosic fibrous
material receives an injection of saturated steam (VS) which helps
pelletization and adjusts humidity to levels as above.
[0075] In one embodiment of the method according to the present
invention, the combustible cellulosic fibrous material enters the
pelletizer's pressing system in step (d).
[0076] In a preferred embodiment of the method of the present
invention, said pelletizer's pressing system is driven by a motor
of about 125 hp at about 1750 rpm.
[0077] In another preferred embodiment of the method of the present
invention, said pelletizer's pressing system has a mold rotating at
about 360 rpm, and two pressing rollers and regulators.
[0078] In a more preferred embodiment of the method of the present
invention, said pelletizer comprises a cast-steel case, holding the
primary shafts, the hollow mold shafts, the compacting rollers and
the motor itself, whereas the main shaft fixes the two compacting
rollers and the scrapers.
[0079] In a particular preferred embodiment of the method of the
present invention said mold is affixed to the hollow rotating
shaft, driven by gears and an electric motor with power varying
from about 100 hp to about 400 hp, at about 220 rpm to about 420
rpm, depending on the type of raw material the pelletizer is
processing.
[0080] In another preferred embodiment of the method of the present
invention said mold comprises a mold diameter of about 520 to about
820 mm, a diameter of the mold holes of about 4.76 mm to about
19.05 mm ( 3/16'' to 3/4''), a width of the track of the molds used
of about 100 to about 220 mm, and a number of holes in the molds
used of about 860 to about 4600 holes.
[0081] In a further preferred embodiment of the method of the
present invention said compacting rollers having a diameter ranging
from about 140 mm to about 220 mm, an eccentric shaft, and a metal
shield pressing. They also feature a device with adjusting
regulators that enable greater roller pressure on the mold and thus
increase the pressure on the unprocessed combustible cellulosic
fibrous material, which ensures more consisting compacting of the
pellets and consequently greater density.
[0082] In a particular preferred embodiment of the method of the
present invention said metal pressing shield of the compacting
roller has thickness ranging from about 15 mm to about 40 mm and
grooves about 2 to about 5 mm deep and about 2 to about 5 mm wide,
spaced apart about 8 to about 12 mm. In contact with the
unprocessed combustible cellulosic fibrous material, these grooves
ensure better traction and improve pressing against the mold.
[0083] In another particular preferred embodiment of the method of
the present invention, said mold is a metal ring with a flange for
fixing on the hollow shaft and a surface with various holes,
whereas these holes can be of various sizes, as demanded by the
method.
[0084] In a further preferred embodiment of the method of the
present invention, the unprocessed combustible cellulosic fibrous
material is pelletized, by using a 650 mm diameter mold with 890
9.525 mm (3/8'') holes. Said mold is 125 mm wide and has an actual
thickness of 30 mm and an additional thickness of 30 mm for relief.
In the relief thickness, the diameter is 1-2 mm larger than the
hole in the actual thickness. This mold system is called a relief
mold, because it has a compacting chamber in the diameter desirable
and the remaining thickness of the mold has a larger diameter, in
which the compacted pellets are released from the actual pressing
chamber, without the pressure of the hole walls, thus ensuring
greater flow in the mold.
[0085] In one embodiment of the method according to the present
invention, following step (d) the combustible cellulosic fibrous
material pellets are removed from the pelletizers.
[0086] In a preferred embodiment of the method of the present
invention the combustible cellulosic fibrous material pellets are
removed by a variable-speed cleated or similar type conveyor belt
after step (d).
[0087] In another embodiment of the method according to the present
invention, in step (e) the combustible cellulosic fibrous material
pellets are sorted according to their size.
[0088] In a preferred embodiment of the method of the present
invention the combustible cellulosic fibrous material pellets are
sorted by a vibrating sifter (14) in step (e).
[0089] In a more preferred embodiment of the method of the present
invention any material that is rejected in the sifter in step (e),
together with any excess dried combustible cellulosic fibrous
material from the feeding conveyor belt (11) is returned to the
feed box to be reused in the method.
[0090] In a particular preferred embodiment of the method of the
present invention, in step (e) the combustible cellulosic fibrous
material pellets are cooled down to room temperature of about 20 to
about 40.degree. C., preferably 30 to about 40.degree. C.
[0091] In a more particular preferred embodiment of the method of
the present invention said the combustible cellulosic fibrous
material pellets after the pellets are sorted, go to the cleated
conveyor belt cooler (16) with a perforated screen and an exhaust
system featuring a powder retention cyclone or similar device (17).
This removes any solid material, which goes back to the
pelletization method.
[0092] In another preferred embodiment of the method of the present
invention said cooler consists of two cleated conveyor belts with a
perforated screen. Above it there is an exhaust system that aspires
all solid particles (dust) from the air and cools the pellets to
room temperature of between 20 to 40.degree. C.
[0093] In one embodiment of the method according to the present
invention the final combustible cellulosic fibrous material, with a
humidity ranging from about 9 to about 13% and a density between
about 0.55 to about 0.60 g/cm.sup.3 are taken to a storage system
in step (f) by a conveyor belt (18).
[0094] In a preferred embodiment of the method of the present
invention, in step (f) said final combustible cellulosic fibrous
material pellets are stored in big bags or silos (19 and 20).
[0095] In another preferred embodiment of the method of the present
invention said storage system requires airtight facilities to
prevent environmental damage from the dust formed during handling
and storage.
[0096] In a preferred embodiment of the method of the present
invention, said combustible cellulosic fibrous material is selected
from at least one of paper mill sludge, wood chips, paper fiber,
cherry pits, olive pits, sugar-cane bagasse, sweet sorghum bagasse,
grass clippings, and fur trees, and combinations thereof. Most
preferred is unprocessed sugar-cane bagasse.
[0097] In one additional preferred embodiment, the method according
to the present invention is selected from fully automated and/or
contiguous processes.
[0098] The other object of the invention is solved by providing a
device for converting unprocessed combustible cellulosic fibrous
material into combustible compressed cellulosic fibrous material
pellets by a method according to the invention as above, wherein
said device comprises a drying unit for drying of said combustible
cellulosic fibrous material, wherein said drying unit comprises a
heat source that indirectly provides heat to said combustible
cellulosic fibrous material when drying said combustible cellulosic
fibrous material.
[0099] Yet another object of the invention is solved by providing a
device for converting unprocessed combustible cellulosic fibrous
material into combustible compressed cellulosic fibrous material
pellets by a method according to the invention as above, wherein
said device comprises: [0100] (a) a continuous feeding unit, [0101]
(b) a cleaning unit, [0102] (c) a drying unit, [0103] (d) a
pelletization unit, and [0104] (e) a sorting and second drying
unit, and, optionally [0105] (f) a storing unit
[0106] In preferred embodiments of the devices according to the
present invention, said unit (a) comprises a cleated or similar
type conveyor belt (1), a feedbox (2), and a sprayer (3).
[0107] In preferred embodiments of the devices according to the
present invention, said feed box can hold a 15-minute supply and
has a cleated or similar type conveyor belt.
[0108] In particular preferred embodiments of the devices of the
present invention, said feed box is a rectangular flat-wall and
flat bottom feedbox.
[0109] In embodiments of the devices according to the present
invention said unit (b) comprises a cleated or similar type
conveyor belt (4), an electromagnet (5), and a di-stone (6).
[0110] In preferred embodiments of the devices of the present
invention, said electromagnet has a minimum magnetic capacity of
about 1500 gauss.
[0111] In particular preferred embodiments of the devices of the
present invention, said di-stone is a rotating machine consisting
of about 5 to 8 perpendicular axes with star-shaped knives that
counter rotate.
[0112] In embodiments of the devices according to the present
invention, said unit (c) comprises a cleated or similar type
conveyor belt (7), a spinning tube dryer (8), an insufflating
system (9), and an exhaust system featuring cyclones (10).
[0113] In a preferred embodiments of the devices of the present
invention, said spinning tube dryer is fitted with deflectors
positioned at an angle of about 45.degree. attached to the tube
bundles, whereas the minimum spacing between the tubes is about 75
mm.
[0114] In embodiments of the devices according to the present
invention, said unit (d) comprises a cleated or similar type
conveyor belt (11), sloping spouts, conditioner of the pelletizer,
the pelletizers (12), and a variable-speed cleated or similar type
conveyor belt (13).
[0115] In preferred embodiments of the devices of the present
invention, said sloping spouts have adjustable gates and magnetic
plates.
[0116] In other preferred embodiments of the devices of the present
invention, said conditioner is a spinning cylindrical metal box
with a diameter of about 450 mm, fitted with wings and driven by a
motor of about 5 hp.
[0117] In yet other preferred embodiments of the devices of the
present invention, said pelletizer comprises a pressing system, a
cast-steel case, holding the primary shafts, the hollow mold
shafts, the compacting rollers and the motor itself, whereas the
main shaft fixes the two compacting rollers and the scrapers.
[0118] In particularly preferred embodiments of the devices of the
present invention, said pelletizer's pressing system has a mold
rotating at about 360 rpm and two pressing rollers and regulators
and is driven by a motor of about 125 hp at about 1750 rpm.
[0119] In other particularly preferred embodiments of the devices
of the present invention, said mold is fixed at the hollow rotating
shaft, driven by gears and an electric motor with power varying
from about 100 hp to 400 hp, at about 220 rpm to 420 rpm depending
on the type of raw material the pelletizer is processing.
[0120] In further particularly preferred embodiments of the devices
of the present invention, said mold is a metal ring with a flange
for fixing on the hollow shaft and a surface with various holes,
whereas these holes can be of various sizes, as demanded by the
method.
[0121] In other particularly preferred embodiments of the devices
of the present invention, said mold comprises a mold diameter of
about 520 to about 820 mm, a diameter of the mold holes of about
4.76 mm to about 19.05 mm ( 3/16'' to 3/4''), a width of the track
of the molds used of about 100 to about 220 mm, and a number of
holes in the molds used of about 860 to about 4600 holes.
[0122] In other particularly preferred embodiments of the devices
of the present invention, said compacting rollers having a diameter
ranging from about 140 mm to about 220 mm, an eccentric shaft, a
metal shield pressing, and a device with adjusting regulators.
[0123] In other particularly preferred embodiments of the devices
of the present invention said metal pressing shield of the
compacting roller has thickness ranging from about15 mm to about 40
mm and grooves about 2 to about 5 mm deep and about 2 to about 5 mm
wide, spaced about 8 to about 12 mm apart.
[0124] In embodiments of the devices according to the present
invention, said unit (e) comprises a variable-speed cleated or
similar type conveyor belt (13), a vibrating sifter (14), a cooler
(16) with a pleated conveyor belt with a perforated screen, and an
exhaust system with a cyclone (17).
[0125] In embodiments of the devices according to the present
invention, said unit (f) comprises a cleated or similar type
conveyor belt (18), big bag packing system (19) or silos (20).
[0126] In preferred embodiments of the devices according to the
present invention, said unit (d) and (e) are connected to unit (b)
via a cleated or similar type conveyor belt (15).
[0127] In preferred embodiments of the devices according to the
present invention, said units are integrated into one system.
[0128] In another preferred aspect thereof, the present invention
relates to pelletized combustible cellulosic fibrous material,
obtainable according to a method as above according to the present
invention.
[0129] Most preferred is a pelletized combustible cellulosic
fibrous material according to the present invention, wherein said
bagasse has an upper calorific content of about 4,500 to about
5,500 kcal/kg, a lower calorific content of about 3,500 to about
4,500 kcal/kg, a density of about 500 to about 600 kg dry
matter/m.sup.3, and a humidity of about 10% to about 15%. Further
preferred is a pelletized combustible cellulosic fibrous material
according to the present invention, wherein said pelletized
combustible cellulosic fibrous material is further blended with
coal. This will even further improve the combustion properties of
the inventive pellets.
[0130] In one embodiment of the present invention, the combustible
cellulosic fibrous material pellets obtained by the method
according to the present invention are used as renewable biomass to
generate energy.
[0131] In a further embodiment of the present invention, the
combustible cellulosic fibrous material pellets are used as biofuel
in the power generation sector.
[0132] In one embodiment of the present invention, the unprocessed
combustible cellulosic fibrous material pellets are blended with
coal.
[0133] In a further preferred embodiment of the present invention,
said pelletized combustible cellulosic fibrous material is selected
from pellets of at least one of paper mill sludge, wood chips,
paper fiber, cherry pits, olive pits, sugar-cane bagasse, sweet
sorghum bagasse, grass clippings, and fur trees, and combinations
thereof. Preferred is sugar-cane bagasse.
[0134] Another aspect of the present invention relates to the use
of combustible cellulosic fibrous material pellets according to the
present invention as a renewable biomass to generate energy and/or
as biofuel in the power generation sector.
[0135] Preferred is the use of a device according to the present
invention for producing a pelletized combustible cellulosic fibrous
material.
[0136] Further preferred is a use according to the present
invention, wherein said pelletized combustible cellulosic fibrous
material is selected from pellets of at least one of paper mill
sludge, wood chips, paper fiber, cherry pits, olive pits,
sugar-cane bagasse, sweet sorghum bagasse, grass clippings, and fur
trees and combinations thereof. Preferred is sugar-cane
bagasse.
[0137] It should be noted, that the term "about" in this
description means.+-.10%, if not indicated otherwise.
[0138] It should be understood that the features of the invention
as disclosed and described herein can be used not only in the
respective combination as indicated, but also in a singular fashion
without departing from the intended scope of the present invention.
For the purposes of the present invention, all references and
patents or patent applications as cited herein are incorporated by
reference in their entireties.
[0139] The invention will now be described in more detail by
reference to the following Figures, and the Examples. The following
examples are provided for illustrative purposes only and are not
intended to limit the invention.
[0140] FIG. 1 is a flow chart of the method for pelletizing
unprocessed sugar-cane bagasse. This flow chart shows each single
step of the converting from unprocessed sugar-cane bagasse into
unprocessed sugar-cane bagasse pellets to the storage of the final
product.
[0141] FIG. 2 is a flow diagram of the method for pelletizing
unprocessed sugar-cane bagasse. This flow diagram shows each single
step of the converting from unprocessed sugar-cane bagasse into
unprocessed sugar-cane bagasse pellets to the storage of the final
product.
[0142] FIG. 3 is a flow diagram of the device for pelletizing
unprocessed sugar-cane bagasse. This flow diagram shows each unit
of the device for the production of unprocessed sugar-cane bagasse
pellets, comprising a continuous feeding unit (a), a cleaning unit
(b), a drying unit (c), a pelletization unit (d), a sorting and
drying unit (e), and a storing unit.
[0143] FIGS. 4A and 4B show one preferred example of a rotary
dryer, in form of a spinning tube dryer with a bundled tube
arrangement.
EXAMPLE
[0144] The method and the setup of the device as claimed in the
present application has been achieved through tests at our pilot
pelletization plant, using the following equipment:
[0145] One carbon steel grain hopper to receive and store raw
material, with 9 m.sup.3 capacity.
[0146] One screw transporter, with a 10-12 metric ton/hour
capacity, driven by a 5 hp at 1,750 rpm motor, to feed the
vibrating sifter.
[0147] One vibrating sifter, with a 10-12 metric ton/hour capacity,
driven by a 5 hp at 1,750 rpm motor, to separate the unprocessed
sugar-cane bagasse.
[0148] One screw transporter, with a 10-12 metric ton/hour
capacity, driven by a 5 hp at 1,750 rpm motor, to feed the
dryer.
[0149] One spinning tube dryer, with a 10-12 metric ton/hour
capacity, driven by a 7.5 hp at 1,750 rpm motor.
[0150] One hot-gas exhaust, with a 1,000 m.sup.3/hour capacity,
driven by a 25 hp at 1,750 rpm motor.
[0151] One cyclone to separate dust, with a 5 metric ton/hour
capacity.
[0152] One fan to insufflate hot air, with a 650 m.sup.3/hour
capacity, driven by a 7.5 hp at 1,750 rpm motor.
[0153] One steam radiator, with a 50,000 kcal/hour capacity.
[0154] One internal dryer screw transporter, with a 10-12 metric
ton/hour capacity, driven by a 0.75 hp at 1,750 rpm motor.
[0155] One dryer outlet screw transporter, with a 10-12 metric
ton/hour capacity, driven by a 5 hp at 1,750 rpm motor.
[0156] One pelletizer feeder screw transporter, with a 10-12 metric
ton/hour capacity, driven by a 5 hp at 1,750 rpm motor.
[0157] Three pelletizers, with a 1.5 metric ton/hour capacity each,
driven by 125 hp at 1,750 rpm motors.
[0158] One pelletizer, with a 5 metric ton/hour capacity, driven by
a 250 hp at 1,750 rpm motor.
[0159] Four pelletizer conditioners, with a 3 metric ton/hour
capacity each, driven by 5 hp at 1,750 rpm motors.
[0160] One pellet conveyor belt, with a 10-12 metric ton/hour
capacity, driven by a 5 hp at 1750 rpm motor.
[0161] One vibrating sifter, with a 2.5 metric ton/hour capacity,
driven by a 3 hp at 1,750 rpm motor.
[0162] One screw transporter for vibrating-sifter rejects, with a 1
metric ton/hour capacity, driven by a 0.75 hp at 1,750 rpm
motor.
[0163] Two pellet coolers, with a 2.5 metric ton/hour capacity,
driven by 1 hp at 1750 rpm motors.
[0164] Two cooler drivers with 3 hp at 1,750 rpm motors.
[0165] One pellet conveyor belt, with a 5 metric ton/hour capacity,
driven by a 3 hp at 1750 rpm motor.
[0166] One big bag loading system.
[0167] One set of carbon steel tubes used to feed steam to the
dryer and removed condensed matter which is send to the boiler
thermal air remover.
Working Example
[0168] With reference to FIG. 1 and the listing of material as
above, sugar-cane bagasse is first continuously fed into a feed box
(2), and loosened and flattened by a sprayer (3). The feed box can
hold a 15-minute supply in relation to the plant output capacity
and has a cleated type conveyor belt to transport the unprocessed
sugar-cane bagasse. Then, ferrous material and impurities of the
unprocessed sugar-cane bagasse are removed by an electromagnet (5)
with a minimum magnetic capacity of 1,500 gauss, and any other
impurities are removed by a di-stone (6) consisting of 5 to 8
perpendicular axes with star-shaped knives that counter rotate.
[0169] Then, the unprocessed sugar-cane bagasse is dried in a
spinning tube dryer (8) using a system of bundled tubes conveying
saturated steam at 9 kgf/cm.sup.2, at a temperature of about
175.degree. C. inside the tube, providing indirect contact with the
product in the tube's external wall (i.e. the steam inside the
pipes dry without contact with the bagasse, whilst the steam flow
heating the internal surface of the pipes and bagasse has contact
with the external surface of the pipes). This results in a
temperature of about 138.degree. C. The spinning tube dryer is
fitted with deflectors positioned at about 45.degree. attached to
the tube bundles. The unprocessed sugar-cane bagasse is then cooled
down to approximately room temperature.
[0170] The unprocessed sugar-cane bagasse now remains inside the
spinning tube dryer for 12 minutes, at 4 rpm using approx. 2 to 3
metric tons of steam per hour. After leaving the tubular bundles,
the bagasse is insufflated with hot air by a duct coming from a
heat radiator (9) fed by saturated steam (VS). This operation heats
the gases in counter flow with the bagasse, thus helping the drying
method and preventing any accumulation of solid residues (powder)
inside the dryer. The hot and humid gases are removed on the
opposite side of the entrance of the dryer by a duct with forced
exhaust (10), and sent to a cyclone, or similar equipment, where
the solid particles (powder) are separated and sent to be burned by
the boiler.
[0171] The now dried sugar-cane bagasse with a humidity varying
between 13 to 20% is then taken to the pelletizers by a cleated
type conveyor belt and fed continuously to the pelletizer by spouts
to the conditioner of the pelletizer (12). The spouts are sloping
spouts with adjustable gates and magnetic plates that withhold any
ferrous impurities that have not been collected before to prevent
any damage to the pelletizer.
[0172] The conditioner of the pelletizer (12), which is a spinning
cylindral metal box with 450 mm diameter, is fitted with wings and
now loosens the bagasse and feeds it to the pelletizer. The machine
is driven by a 5 hp motor. In this conditioner, the bagasse
receives an injection of saturated steam (VS) which helps
pelletization and adjusts humidity.
[0173] Then, the sugar-cane bagasse enters the pelletizer's
pressing system which is driven by a motor of 125 hp at about 1750
rpm. Said pelletizer's pressing system has a mold rotating at about
360 rpm and two pressing rollers and regulators, whereas the
pelletizer comprises a cast-steel, holding the primary shafts, the
hollow mold shafts, the compacting rollers and the motor itself,
whereas the main shaft fixes the two compacting rollers and the
scrapers. The mold is fixed at the hollow rotating shaft, driven by
gears and an electric motor with power varying from 100 hp to 400
hp, at 220 rpm to 420 rpm, depending on the type of raw material
the pelletizer is processing. Furthermore, the mold comprises a
mold diameter of 650 mm, with a diameter of the mold holes of about
9.53 mm (3/8''). and a width of the track of the molds of 125 mm,
and a number of holes in the molds used of 890.
[0174] The compacting rollers have a diameter of 125 mm, an
eccentric shaft, a metal shield pressing, and a device with
adjusting regulators. The adjusting regulators enable greater
roller pressure on the mold and thus increase the pressure on the
unprocessed sugar-cane bagasse, which ensures more consisting
compacting of the pellets and consequently greater density. The
metal pressing shield of the compacting roller has thickness of 30
mm and grooves 3 mm deep and 3 mm wide, spaced 10 mm apart. In
contact with the unprocessed sugar-cane bagasse, these grooves
ensure better traction and improve pressing against the mold.
[0175] Then, the sugar-cane bagasse pellets are removed from the
pelletizers by a variable-speed cleated type conveyor belt and
subsequently sorted by size by a vibrating sifter. Any material
rejected at the sifter, together with any excess dried sugar-cane
bagasse from the feeding conveyor belt (11) is returned back to the
feed box to be reused in the process.
[0176] The sugar-cane bagasse pellets are then cooled down to room
temperature of approx. 30.degree. C. After the pellets are sorted
they are transported by a cleated conveyor belt cooler (16) having
a perforated screen and an exhaust system featuring a powder
retention cyclone device (17). This removes any solid material,
which goes back to the pelletization method. Above the system,
there is an exhaust system that aspires all solid particles (dust)
from the air and cools the pellets to room temperature, i.e.
approx. 30.degree. C.
[0177] The final sugar-cane bagasse pellets, having a humidity
ranging from about 9 to about 13% and a density between about 0.55
to about 0.60 g/cm.sup.3 are taken to a storage system by a
conveyor belt (18). The final sugar-cane bagasse pellets are then
suitably stored in big bags before further transport thereof.
* * * * *