[0001] This invention relates to methods and apparatus for the introduction of fibrous material
into a substance or mixture. In particular but not exclusively, the invention relates
to such methods in which cellulose fibres, other organic fibres or mineral fibres
are provided in pelletised form for subsequent addition to mixture of ingredients.
[0002] Cellulose or mineral fibre are commonly used to modify the rheological properties
of liquid systems, including those based on cement and water, and those based on bitumen.
The fibres have a gelling or thickening effect on these systems which may include,
for example, a cement-based tile adhesive or a bituminous road surfacing compound.
Cellulose and mineral fibre usage has increased partly due to the demise of asbestos
fibre.
[0003] Cellulose fibre may be derived for example from recycled paper, timber, woodpulp,
or various other agri-materials such as straw, flax. Other organic fibres include,
for example, polyester, polythene and polypropylene. Mineral fibre is commonly made
from glass, basaltic rock or steel slag.
[0004] Fibre is normally supplied in compressed bales which may be from 1 Kg to 400 Kg in
weight. There are three main methods for adding fibre to the mixes. In one such method,
bales may be added direct to a mixer. Thus, in the case of hot bitumen mixes, the
whole bale (including polyethylene packaging) may be added, the plastic quickly dissolving
into the hot liquid bitumen. Alternatively, and particularly in the use of dry powder
mixes, the fibre is emptied from the packaging direct into the mixer, or perhaps via
a hopper and screw arrangement, possibly after a weighing operation to obtain the
exact quantity required for a batch. These methods are labour intensive and often
require an operative to work very close to mixing machinery, with environmental problems
of dust, fumes and noise.
[0005] In a further method, bales of fibre may be emptied into a pneumatic blowing machine
and dosed gravimetrically or volumetrically into the mixer along a pipe which may
be 25-150 mm in diameter for example. This method lends itself to the use of bigger
bales with consequent reductions in labour intensity, and also provides a solution
to the environmental problems. However, it still falls short of true bulk handling.
[0006] In another method, the fibre may be pelletised, or granulated possibly by the fibre
manufacturer, in a pelletising or granulating process in which small compressed pellets
or granules are formed by extrusion, pressing or other available method. Normally,
an additive is used which lubricates this process and acts as a binder. This additive
may be bitumen, wax, oil or other suitable materials. However it is also possible
to pelletise or granulate some fibres without any additives. The pellets or granules
lend themselves to true bulk handling. They can be delivered in bulk loads of up to
20 tonnes and blown into a silo in a similar method to that used for animal feed pellets
for example. From the silo, pellets or granules can be screwed, conveyed, dosed or
weighed as required in a fully automatic manner without labour costs. However, the
use of pellets or granules is very often not preferred because it is difficult to
achieve an effective dispersion of the fibre due to the work required in the mixer
to break up the hard-compressed pellets or granules into their constituent fibres.
[0007] Where pellets or granules are used, as a component of powder or liquid mixes, the
mixer is relied upon to achieve a fortuitous breakdown of the pellets or granules
into dispersed fibre by shear, attrition and abrasion effected by the other components
of the mix which may include stone aggregate for example, the mixer paddles themselves
and possibly by the elevated temperature of the mixture causing the binder material
if present to soften, or to diminish the binding effect. Dispersion of fibre in this
way is not what the mixer was designed to achieve and, therefore, it performs the
task usually inefficiently. The result can be longer mixing times with consequent
reduction in plant capacity and increased wear and tear and power consumption. Even
then, dispersion may be incomplete resulting in non-homogeneous mixes and inconsistent
thickening effect.
[0008] We have therefore designed an improved method for the addition and substantially
uniform dispersion of fibres in a mixture which overcomes or mitigates at least some
of the disadvantages of the above methods. In particular it provides a method in which
the fibrous material is initially rendered into compact pelletised or granulated form
for efficient storage, handling and transport and then returned to an open fluffy
state at the mixing station. This considerably improves storage, transport and handling
of the fibre as it is in a compact form which can be transported and handled in bulk
and which also can be metered automatically into a mixture using a screw conveyor
and the like.
[0009] The process also includes the novel step of refibreising the pellets or granules
prior to addition to the mixture. Thus the method as a whole includes the innovative
feature of temporarily reducing a fibrous material to a compact pelletised or granular
state for storage, transport, handling and metering and thereafter returning it to
an open-textured state prior to mixing.
[0010] In one aspect, this invention provides a method of producing a substantially uniform
dispersion of fibrous material in a mixture, which comprises:
providing a supply of pellets or granules of compacted fibrous material;
refibreising said pellets or granules to cause at least some of said pellets or granules
to expand to a relatively open-textured fibrous material; and
introducing said refibreised fibrous material into said mixture and mixing it therewith.
[0011] In another aspect, this invention provides a method of producing a substantially
uniform dispersion of fibrous material in a mixture at a mixing station which comprises:
pelletising or granulating at a pelletising or granulating station a fibrous base
material by at least one of compaction and possibly binding of the fibres of the fibrous
base material;
transporting said pelletised or granular base material to a remote refibreising station;
refibreising said pelletised or granular base material to recover a relatively open-textured
fibrous material; and
introducing and mixing said refibreised fibrous material into said mixture.
[0012] In each aspect, said fibrous material preferably comprises cellulose or other organic
or mineral fibres or a mixture thereof. Cellulose fibre may be derived from e.g. recycled
paper, timber, woodpulp or various other agri-materials such as flax or straw. Organic
fibres may be of polyethylene, polyester, or polypropylene. Mineral fibres may be
derived from glass, basaltic rock or steel slag.
[0013] Preferably, said refibreising is performed by means of one or more of grinding hammer-milling,
disc-refining, pulverising and air impaction or other means of attrition. The preferred
objective is to separate the fibres by mechanical means without causing unnecessary
damage to the fibres themselves. The opening and re-fibreising of the material may
continue after addition to the mixture, by the mixing action applied thereto.
[0014] Said mixture may comprise a wide range of different materials, but this method has
been designed with particular reference to the addition of fibrous material into a
liquid-based system to improve its rheological properties, for example those based
on cement and water (e.g. a cement-based tile adhesive) and those based on bitumen
(e.g. road-surfacing compounds).
[0015] In another aspect, there is provided apparatus for the introduction of a generally
open-textured fibrous material into a mixture, said apparatus comprising:-
storage means adapted to store in use a supply of pelletised or granulated fibrous
material;
a fibreising means adapted to expand said pelletised or granular material to a generally
open-textured form;
means for delivering in use said pelletised or granular fibrous material from said
storage means to said fibreising means;
means for conveying said expanded open-textured fibrous material from said fibreising
means, and introducing it into said mixture.
[0016] In yet a further aspect, this invention provides a method for the transport and metering
of a fibrous additive material into a mixture, which method comprises reducing said
fibrous additive material from an open-textured form into compact pelletised or granular
form, transporting said pelletised or granular fibrous additive material to a mixing
station, returning said fibrous material from said compact pelletised or granular
form to an open-textured form, and thereafter adding said open-textured material to
said mixture.
[0017] Whilst the invention has been described above, it extends to any inventive combination
of features set out above or in the following description.
[0018] The invention may be performed in various ways, and an embodiment thereof will now
be described by way of example only, reference being made to the accompanying drawing,
which is a schematic view of a refibreising and mixing station for use in an embodiment
of the invention.
[0019] The described embodiment implements a storage handling and metering system for fibrous
materials. In this system fibrous material is initially rendered into compact pelletised
or granulated form using generally conventional techniques, so that the material may
be handled and transported relatively easily. Thereafter the pellets or granules are
passed to a fibreising means which breaks down the pellets or granules so as to regenerate
the open, 'fluffy' fibrous matrix from which the pellets or granules were made. This
fibrous matrix can then be passed to a mixer where it is readily dispersed in either
the liquid or powder mixture without the need for excessive mixing.
[0020] The fibreiser consists of a system for inputting the pellets or granules, a method
of 'opening' them to reconstitute the raw fibre, and an output system to discharge
the fibre. The method used to open the fibre can employ one of many available techniques
including grinding, hammer-milling, disc refining, pulverising and air impaction.
Different types of pellet or granules may be best handled by different of these various
techniques and each application would need to be considered on its merits. The throughput
of the fibreiser can be controlled by air conveying, gravity, centrifugal forces or
by a combination of methods.
[0021] The fibreiser is placed at a convenient point in the line between the storage hopper
or silo for the pellets or granules, and the mixer to which they are to be added.
Feed to the fibreiser can be by gravity, screw or belt conveyor or by pneumatic blowing
for example, and the discharge into the mixer can equally employ one or more of these
methods.
[0022] Referring now to the Figure, this shows a schematic arrangement for a typical process
for making a mixture including dispersed fibre in accordance with this invention.
The process shown is that which might be used for the production of road asphalt although
the invention could equally be applied to other mixtures which include a liquid component
or to dry powder mixes.
[0023] Fibre pellets or granules 1 previously produced by extrusion, pressing etc. with
or without a binder as required are delivered by a bulk vehicle 2 and blown pneumatically
via a pipe 3 into a storage silo 4. A screw conveyor 5 conveys the pellets as required.
The pellets then fall by gravity through a fibreiser 6 into a mixer 9.
[0024] The fibreiser may employ one or more of the actions described above, thereby partially
or fully opening the fibre pellets or granules to at least partially return them to
an open matrix form whereby substantially uniform distribution of the constituent
fibres throughout the mixture is assured. At the same time, different grade aggregates
which are stored in the hoppers 7 are weighed into the weigh hopper 8 which also discharges
into the mixer 9. Hot liquid bitumen is added and, on completion of mixing, the batch
is dropped into a discharge chute 10, and travels along a conveyor 11 into a storage
hopper 12, where it is held until it is required to be loaded into a lorry 13 for
transport to the road construction site.
1. A method of producing a substantially uniform dispersion of fibrous material in a
substance, which comprises:
providing a supply of pellets or granules of compacted fibrous material;
refibreising said pellets or granules to cause at least some of said pellets or granules
to expand to a relatively open-textured fibrous material; and
introducing said refibreised fibrous material into said substance and mixing it therewith.
2. A method of producing a substantially uniform dispersion of fibrous material in a
substance at a mixing station which comprises:
pelletising or granulating at a pelletising or granulating station a fibrous base
material by at least compaction of the fibres of the fibrous base material;
transporting said pelletised or granular base material to a remote refibreising station;
refibreising said pelletised or granular base material to recover a relatively open-textured
fibrous material; and
introducing and mixing said refibreised fibrous material into said substance.
3. A method according to Claim 2, wherein said pelletising or granulating step includes
binding of the fibres of the fibrous material.
4. A method according to any preceding Claim, wherein said fibrous material comprises
cellulose, other organic fibre, or mineral fibres or a mixture thereof.
5. A method according to Claim 4, wherein said cellulose fibres are derived from one
or more of recycled paper, timber, wood pulp, flax or straw.
6. A method according to Claim 4, wherein said mineral fibres are derived from one or
more of glass, basaltic rock or steel slag.
7. A method according to any preceding Claim, wherein said refibreising is performed
by means of one or more of grinding, hammer-milling, disc-refining, pulverising and
air impaction.
8. A method according to any preceding Claim, wherein said substance is liquid-based.
9. A method according to any preceding Claim, wherein said substance comprises a mixture
of cement and water.
10. A method according to Claim 8, wherein said substance comprises bitumen-based material.
11. Apparatus for the introduction of a generally open-textured fibrous material into
a substance, said apparatus comprising:-
storage means adapted to store in use a supply of pelletised or granulated fibrous
material;
a fibreising means adapted to expand said pelletised or granular material to a generally
open-textured form;
means for delivering in use said pelletised or granular fibrous material from said
storage means to said fibreising means;
means for conveying said expanded open-textured fibrous material from said fibreising
means, and introducing it into said substance.
12. A method for the transport and metering of a fibrous additive material into a substance,
which method comprises reducing said fibrous additive material from an open-textured
form into compact pelletised or granular form, transporting said pelletised or granular
fibrous additive material to a mixing station, returning said fibrous material from
said compact pelletised or granular form to an open-textured form, and thereafter
adding said open-textured material to said substance.
13. A method substantially as hereinbefore described with reference to the accompanying
drawing.
14. Apparatus substantially as hereinbefore described with reference to, and as illustrated
in, the accompanying drawing.