U.S. patent application number 12/124011 was filed with the patent office on 2009-11-26 for method for producing pressed products from fiber-containing raw materials.
This patent application is currently assigned to Buhler AG. Invention is credited to Matthias Franke, Markus Kratzer.
Application Number | 20090288792 12/124011 |
Document ID | / |
Family ID | 41341214 |
Filed Date | 2009-11-26 |
United States Patent
Application |
20090288792 |
Kind Code |
A1 |
Kratzer; Markus ; et
al. |
November 26, 2009 |
METHOD FOR PRODUCING PRESSED PRODUCTS FROM FIBER-CONTAINING RAW
MATERIALS
Abstract
A method produces pressed products from fiber-containing raw
materials such as wood, straw, peat or suchlike, which are also
referred to as secondary raw materials. In order to produce well
pressed products, fiber-containing raw materials are mixed with
water, vapor and, if need be, further additives while heating the
raw materials and additives, the mixture being held at high
temperature for a lengthy period of time before pressing.
Inventors: |
Kratzer; Markus;
(Kreuzlingen, CH) ; Franke; Matthias; (Reichenau,
DE) |
Correspondence
Address: |
MERCHANT & GOULD PC
P.O. BOX 2903
MINNEAPOLIS
MN
55402-0903
US
|
Assignee: |
Buhler AG
Uzwil
CH
|
Family ID: |
41341214 |
Appl. No.: |
12/124011 |
Filed: |
May 20, 2008 |
Current U.S.
Class: |
162/179 ;
162/100; 162/180; 162/415 |
Current CPC
Class: |
D21J 3/00 20130101 |
Class at
Publication: |
162/179 ;
162/100; 162/180; 162/415 |
International
Class: |
D21H 17/14 20060101
D21H017/14; D21H 17/23 20060101 D21H017/23; D21F 3/00 20060101
D21F003/00 |
Claims
1. A method for producing pressed products from fiber-containing
raw materials such as wood, straw, peat or the like in a pressing
or expander plant, the method comprising: mixing fiber-containing
raw materials with water, vapor and, if need be, further additives
while heating the raw materials and additives, wherein the mixture
is held at high pressure for a dwell period before pressing.
2. The method according to claim 1, wherein the mixture is held in
an intermediate container during the dwell period.
3. The method according to claim 1, wherein the conditioning
temperature comprises temperatures up to 200.degree. C.
4. The method according to claim 1, wherein the mixture is
preferably held at a temperature up to 150.degree. C.
5. The method according to claim 1, wherein fat and/or lignin are
additionally added to the raw materials.
6. The method according to claim 1, wherein the conditioning takes
place pressure-less or in the presence of excess pressure.
7. A device for producing pressed products from fiber-containing
raw materials such as wood, straw, peat or the like, the device
comprising: a pressing or expander plant performing a method
according to claim 1, wherein an intermediate container is disposed
downstream of a dwell-time unit following a mixer.
8. The device according to claim 7, wherein the intermediate
container is disposed upstream of a pellet mill or an expander.
9. The device according to claim 7, further comprising a double
screw disposed downstream of the intermediate container, wherein
screw flights of the double screw are mechanically coupled offset
by 180.degree. with respect to one another.
10. The device according to claim 7, wherein at least the
intermediate container is thermally insulated.
Description
BACKGROUND OF THE INVENTION
[0001] The invention relates to a method for producing pressed
products from fiber-containing raw materials such as wood, straw,
peat or suchlike, which are also referred to as secondary raw
materials.
[0002] The invention also relates to a device for performing such a
method.
[0003] Pellet mills or feed pellet mills or pellet presses have
been used in practice for many years in the feedstuff and foodstuff
industry and also in the non-food sector. Grainy, powdery and/or
pasty materials with the most varied moisture contents and
compositions are pressed.
[0004] They comprise pressing moulds and strippers in order to
produce cubes or pellets in the desired size. Such a pellet mill is
disclosed for example in EP-A-371519. The material to be pressed
passes from a feed hopper into a conveying and metering apparatus
and from there into a mixer. Both apparatuses are disposed at the
upper side of the housing of the actual press, whereby the outlet
of the mixer conveys into a bent feed box (and into a mould cover),
which is disposed thereunder but is not rigidly connected to the
mixer. The material passes from the mould cover into the pressing
mould.
[0005] One pressing mould is fixedly connected to a rotating press
moulding holder. A pulley carrier with a roller bar fixed thereto
is also disposed fixedly. Two rollers are disposed adjustably by
means of a piston-cylinder unit, so that different gaps and
pressing pressures can be adjusted on the mould die.
[0006] Another pelletising press is shown by EP-B-489046, wherein
the mould and at least one press roller can be driven at variable
speeds and as a function of the gap height.
[0007] Various solutions are known for fixing the moulds in a
pellet mill. The initially mentioned fixed arrangement, which
involves simply screwing down the mould, is cost-effective, but
necessitates a time-consuming mould replacement. Also known,
however, are solutions for a rapid replacement, e.g. according to
U.S. Pat. No. 4,979,887, wherein for example the individual
clamping segments are actuated by short-stroke hydraulic cylinders
at the periphery of a wear ring. The hydraulic cylinders are
connected to an external hydraulic pump for the mould
replacement.
[0008] According to DE-OS 2108326, it is also known, for the
purpose of better assembly, to hold the clamping segments by means
of spring elements in the position that clamps the die, adjusting
means being provided which release the clamping segments against
the action of the spring. As a result of the spring tensioning
forces being overcome, the die is intended to be easily released
from the column or can be fixed again. Hydraulic winches are used
as the adjusting means. A similar solution is shown by DE-OS
2756647, wherein a conical ring is used for fixing the die.
[0009] Mixing units are known for example from EP-B-231764 and
EP-B-610789. Here, a metering device is incorporated upstream of
such a mixer and a pressing mould or an expander is in turn fed
from the mixer. The mixing unit is provided with a heating jacket
and contains a rotating shaft, which is fitted with mixing and
conveying elements.
[0010] Such units are either tailor-made for use in pressing or
expander plant or can be used solely in isolation, since the
adaptation cost is high.
[0011] Pressing and expander plant are used primarily for the
production of foodstuff or feedstuff, although the production of
pellets from wood or waste from grinding grain, for example from
wheat bran, is however also known. DE-A-10205105 discloses a method
for producing pellets from wood, wherein wood material with a
pre-adjusted moisture content is pressed in a pelletising press,
material with higher moisture content being pre-pelletised with the
generation of heat and moisture subsequently being conveyed away.
It is known from DE-A-10010414 to mix wood fibers or suchlike with
up to 50 wt. % of a thermosetting resin and to extrude the
mixture.
SUMMARY OF THE INVENTION
[0012] The problem underlying the invention is to develop a method
for producing pressed products from fiber-containing raw materials,
which for example enables the production of pellets from wood,
straw, peat or paper, plastic mixtures, or any kind of secondary
raw materials which can be pelletised for energy production.
[0013] The method is characterised by a lengthy dwell time
(long-time conditioning) at high temperature after the mixing-in of
water, vapour and possibly other additives. The dwell period is
prior to the pressing.
[0014] Long-time conditioning is understood to mean the process
time or dwell time lying above the normal mixing time, possibly
with two mixers incorporated one after the other, each mixer
approx. 15-20 seconds. There is also an additional dwell time in a
buffer depot.
[0015] The conditioning temperature can amount to up to 200.degree.
C., a range up to 150.degree. C. being preferred.
[0016] The conditioning can also take place under excess pressure
(high-pressure conditioning). In order to be able to reach dwell
times up to several hours, the dwell containers/maturing containers
are preferably insulated.
[0017] Further additives are for example fat or lignin.
[0018] The device comprises an intermediate container disposed
downstream of a mixer, in which intermediate container the mixed
preliminary product dwells for a lengthy period at high
temperature, so that mixed-in additives can penetrate sufficiently
into the raw material in order to guarantee good pressing.
[0019] In addition, a pulsating product input into a press or an
expander can be avoided by means of the intermediate container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The invention is described in greater detail below in an
example of embodiment with the aid of a drawing.
[0021] FIG. 1 shows a pelletising plant in a schematic
representation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] A pressing plant comprises a mixer 2, a dwell-time unit 3
(long-time conditioning), which are disposed above one another.
Mixer 2 and dwell-time unit 3 each comprise identical front plates
5 and 6 respectively.
[0023] The conveying of the product takes place via suitable
product supply opening 7 and product discharge opening 8. The
transfer of the product into intermediate container 4 takes place
via product discharge opening 8 of dwell-time unit 3 and from said
intermediate container via a double screw 9 into a pellet mill
1.
[0024] The mill is fed with product to be pressed in a
pulsation-minimised manner from intermediate container 4 by means
of double screw 9, the screw flights whereof are mechanically
coupled offset by 180.degree. with respect to one another. A
defined offset is essential in order to minimise the pulsing. The
coupling can take place by means of a chain, gearing, belt etc.
[0025] Mixer 2 comprises a high-speed rotor for the intensive
product mixing with vapour, gases and/or liquids. Dwell-time unit
3, on the other hand, is provided with a slow-running rotor. In
dwell-time unit 3, the heated, mixed product is already held at a
defined temperature for a preset time.
[0026] In mixer (2), the mixture is heated by means of vapour or
other energy carrier up to 125.degree. C. Furthermore, water for
achieving the optimum pelletising water content and other additives
for optimising the pelletising process are added in mixer 2.
[0027] An intermediate container 4 (a buffer depot) is disposed
downstream of dwell-time unit 3. After the product in mixer 2 has
been brought to temperature and the optimum water content, the
product dwells for a defined dwell time in dwell-time unit 3, the
conditioning temperature being held during the previously defined
dwell time. This is achieved by means of insulation or external
heating mats on dwell-time unit 3. First In-First Out applies.
[0028] Intermediate container 4 extends the dwell time and
counteracts pulsating feeding of the mill, i.e. compensates for the
latter.
[0029] The walls of intermediate container 4 and, if need be,
dwell-time unit 3 are insulated or provided with external heating
mats.
[0030] Mixer 3 and dwell-time unit 4 comprise tightly sealable
openings in the respective jacket. Jackets and transfer openings as
well as face plates 5, 6 can if necessary be fully lined with
heating mats and insulating means. The inner surfaces of the
jackets, including the product transfer openings (7 and 8), are
preferably completely smooth.
[0031] Mixer 2 and dwell-time unit 3 contain rotors with work
elements. These are designed screw-shaped (solid screw) in
dwell-time unit 3 and paddle-shaped in mixer 2.
[0032] All the components are preferably compatible and
combinable.
[0033] Dwell-time unit 3 has lower speeds of the rotor than mixer
2, so that the capacity of the individual units can be matched for
a continuous operation.
[0034] After leaving pellet mill 1, the pellets are cooled in a
cooler and then fed in the usual way to further stations.
[0035] Advantages of such long-time conditioning are: [0036]
steady, optimised pelletising process [0037] high throughput [0038]
low energy expenditure per tonne of pellets [0039] longer service
lives of machine parts and wearing parts [0040] better pelletising
capacity for products difficult to pelletise
REFERENCE NUMBERS
[0041] 1. pellet mill/press
[0042] 2. mixer
[0043] 3. dwell-time unit
[0044] 4. intermediate container
[0045] 5. face plate
[0046] 6. face plate
[0047] 7. product supply opening
[0048] 8. product discharge opening
[0049] 9. double screw
* * * * *