Note: Descriptions are shown in the official language in which they were submitted.
CA 02479289 2004-09-15
Method and Device for Regulating the Atmospheric Conditions
During a Spinning Process
The invention relates to a method and a device for controlling the room air
conditions
in a spinning process carried out in an open spinning area opposite the room,
whereby endless molded articles are extruded, in the spinning area, from a
spinning
mass containing cellulose, water and tertiary amine oxide, and the extruded
endless
molded articles are air-quenched with a gas phase in an air jet prior to the
immersion
into a precipitating bath, and wherein the spinning plant can be inspected and
maintained by operating staff in a staying area adjacent to the spinning area.
Endless molded articles from a spinning mass containing water, cellulose and
tertiary
amine oxide are substantially produced in the three process steps extruding,
drafting
and precipitating. N-methyl-morpholine-N-oxide (NMMNO) is used as tertiary
amine
oxide.
For the extrusion the heated spinning mass is passed through extrusion
openings of
the spinning plant and is extruded to form endless molded articles. An air gap
is
directly adjacent to the extrusion openings or, respectively, to the extrusion
or
spinning nozzles. In the air gap, a tensile force is applied to and drafts the
endless
molded articles. The thickness of the endless molded articles, e.g. the fiber
titer of
textile fibers, is adjusted by means of the tensile force. Moreover, under the
influence
of the tensile force, the molecules orientate themselves in the endless molded
articles thereby increasing the mechanical stability thereof. Subsequently,
the
endless molded articles are~immersed in a precipitating bath, in which the
solvent still
contained in the endless molded articles is precipitated. In industrial
practice the
spinning process takes place in a substantially closed room, mostly a hall, a
spinning
hall or the like.
The production of endless molded articles from a spinning mass containing
cellulose,
water and tertiary amine oxide involves on the one hand the problem that the
surface
adhesiveness or tackiness of the endless molded articles directly after the
extrusion
is very high. For rendering the fiber production process economical, extrusion
CA 02479289 2004-09-15
nozzles with a high spinning density, i.e. a high number of extrusion openings
per
surface unit have, on the other hand, to be used. This inevitably leads to a
small
spacing between the individual extrusion openings and the extruded endless
molded
articles in the air gap and, thus, to a negative influence on the thermal
balance in the
area of the extrusion and drafting zone. Thus, high temperatures are generated
that
may reduce the spinning or drafting viscosity of the extruded endless molded
articles
to such an extent that the fibers break.
For reducing the surface adhesiveness and the temperature of the endless
molded
articles in the air gap, some solutions have been proposed in the prior art.
Document US 4,246,221 describes the production of cellulose fibers and
filaments,
which are sprayed, in the air gap, with a nonsolvent such as water after the
extrusion
so as to reduce the adhesiveness of the filament surfaces.
As the spraying with a nonsolvent is relatively complicated, air quenching of
the
endless molded articles in the air gap with air or a gas mixture according to
the prior
art has generally been adopted.
In document WO 93119230 it was described for the first time that, for the
production
of cellulose fibers according to the NMMNO process, the filaments exiting the
nozzle
can be cooled with air or a gaseous medium directly after the exit, so as to
obtain a
higher productivity.
According to the teaching of WO 96121758 the spinning performance can be
improved and the fibrillation tendency can be reduced, if the air humidity in
two
portions of the air gap is adjusted at different levels.
In the two devices according to WO 95101470 and WO 95101473 an annular
spinning
nozzle is employed for the production of fibers, allowing the supply of the
cooling gas
stream to the filament bundles in a constantly laminar manner.
Document WO 96/17118 describes a method according to which conditioned air is
used for cooling the freshly spun filaments. In other words, air with a
relative air
CA 02479289 2004-09-15
humidity of up to 85% can be injected. DE 19717257 A1 describes an improvement
where air between 14 and 25°C is used for the air quenching.
Document WO 96/07777 describes a method for the production of cellulose
fibers,
whereby, for the production of fibrillation-reduced fibers, aliphatic alcohols
such as
methanol, ethanol, propanoi and butanol are introduced in a gaseous state for
air
quenching the extruded filaments.
All of the devices and processes according to the aforementioned prior art
documents commonly describe air-quenching at a very low velocity, so that the
quench air stream is substantially laminar. The laminar stream has the purpose
to
avoid too strong a mechanical load of the endless molded articles by the air
stream.
According to the devices described in documents WO 94128218 and WO 98/18983
the air jet is sucked off through a suction nozzle in the air gap on the
opposite side
for stabilizing the air-quenching direction.
As the cooling effects of these conventional air-quenching methods within the
air gap
are not sufficient to obtain high production rates of endless molded articles
by
simultaneously increasing the quality, which is due to the low air-quenching
velocities, a turbulent gaseous substance stream is directed at the endless
molded
articles in the air gap in accordance with the teaching of document DE 102 00
406
filed by the applicant, the entire contents of which are included by reference
in the
present specification. Such a turbulent cooling gas stream effects a more
efficient
cooling, and a better intermixture in the area of the endless molded articles,
as well
as a better thermal compensation. The type of air supply described in DE 102
00
406, preferably not directly after the filaments exit the nozzle and not
directly before
the immersion thereof in the precipitating bath, stabilizes the spinning
process. With
simultaneously high hole densities a sufficient drafting tension during the
extrusion
can be applied on one hand. On the other hand, the endless molded articles no
longer stick to each other in the air gap as soon as they touch each other,
which
could, otherwise, easily entail the tearing of individual endless molded
articles or
undrafted parts in the finished endless molded articles. If tearings occur,
the
extrusion process has to be stopped and restarted. Undrafted parts or
thickenings
result in a reduced fiber quality and increased waste.
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Due to the strong turbulent intermixture in such a turbulent cooling gas
stream,
however, solution substances and degradation products from the spinning
process
are entrained by the cooling gas stream to an increased extent, and are
transported
into the environment of the spinning plant.
Due to the high velocities of the cooling gas stream, a removal by suction -
as is
described in WO 94/28218 or WO 98/18983 - in the direct vicinity of the
endless
molded articles is no longer possible, as a strong suction effect would
otherwise be
exerted on the endless molded articles. Moreover, the turbulent cooling gas
stream
influences the room air conditions in the room in which the spinning process
takes
place, as it penetrates more easily through the endless molded articles deep
into the
spinning area or the staying area as a result of its high velocities.
In view of the aforementioned processes and devices comprising air-quenching
by
means of a gaseous substance stream, it is a basic problem that the
degradation
products transported by the gaseous substance stream are a burden to the room
air
conditions in the environment of the plant, thus entailing unfavorable working
conditions for the operating staff.
In view of the production of Rayon fibers it is known from the prior art, e.g,
from US
3,924,984 and US 4,477,951, to hermetically seal the spinning area and to suck
off
the degradation products released during the spinning process into the ambient
air
inside the sealed portion. The byproducts such as carbon disulfide and
hydrogen
sulfide are sucked out of the hermetically sealed spinning areas, as said
gases are
dangerous to health and must not be released into the work environment. Said
documents additionally disclose that the spinning points are subjected to
vapor for
adjusting the spinning ambient temperature and the humidity, as the room air
conditions are of great importance for the quality of the fibers.
Such insulated or sealed spinning areas are, however, disadvantageous in as
far as
the very unfavorable operating properties of such a plant are concerned: If
maintenance or repair works take place, a hermetic sealing of the spinning
area
under a kind of protection cover is problematical, as the operating staff
inspecting the
spinning plant and the spinning process from an inspection area located in the
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staying area cannot, or only with difficulties, notice malfunctions in the
spinning
process through said protection cover . Moreover, if maintenance works take
place in
the spinning area, it is complicated to remove the hermetic cover at first.
The
provision of a protection cover also negatively influences the exchange of
nozzles.
A solution for facilitating the maintenance and the inspection of a spinning
plant is
described in document DE 102 04 381 of the applicant, the entire contents of
which
are herewith incorporated by reference. The spinning plant according to DE 102
04
381 comprises spinning means, which are freely visible from an inspection area
being a part of a staying area for the operating staff, and which are, at the
same time,
accessible by the operating staff - essentially out of one posture - in a
maintenance
area located between the inspection area and the spinning plant, which
likewise
forms part of the staying area.
For obtaining, as a consequence, an efficient air-quenching on one hand, which
increases the quality of the spun endless molded articles, and, on the other
hand, an
easy inspection and maintenance performance of the spinning plant, it is
accordingly
necessary to keep the spinning area open with respect to the room, in which
the
spinning area is located or, respectively, in which the spinning process takes
place.
If the air-quenching in the air gap takes place at high flow rates, as are
commonly
required for the spinning of cellulose fibers, there is the problem that the
room air
conditions in both the spinning area and the staying area for the operating
staff
deteriorate. A deterioration of the room air conditions in the spinning area,
especially
an increase of humidity and temperature, may require stronger air-quenching
for
maintaining a constant spinning quality. This, on one hand, results in the
further
deterioration of the room air conditions or the atmospheric environment of the
room
in the maintenance area and, on the other hand, in an increased mechanical
stress
on the endless molded article, up to filament breakage.
The invention is, therefore, based on the object to provide a method and a
device
allowing the use of efficient air-quenching, with the simultaneous ergonomic
construction of the spinning plant, and the adjustment of the room air
conditions
necessary under the aspect of working technique.
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6
According to the invention this object for the above-mentioned method is
solved by
controlling the exhaust air from and the additional air to the room, taking
into account
the gaseous substance stream, such that predetermined room air conditions are
adjusted in the spinning area andlor maintenance area.
This solution is simple and differs from conventional air-conditioning plants
in that, for
the adjustment of the room air conditions, the gaseous substance stream is
explicitly
considered as a balancing quantity for controlling the room air conditions.
The air charged with the constituents formed during the spinning process will
in the
following be called process air, which comprises the vapors from the hot
spinning
mass and from the precipitating bath, the gaseous substance stream and heated
air
from the environment of the air gap.
An overall balancing of the air passage inside the room, in which the spinning
process takes place, as well an adjustment of the air conditions for the
process and
in the room, also in view of the conditions required by a favourite working
environment, do not appear to be known in the prior art.
Accordingly, the solution according to the invention allows to find a
compromise
between the air conditions in the spinning area, which are necessary for a
good fiber
quality, and the requirements relating to the room air conditions for the
operating
staff. For the fiber processing, specific air conditions have to be provided
and kept
constant over a longer period of time. Moreover, care must be taken that,
while
obtaining bearable climatic conditions at the working place, the air
conditions
required under the aspect of process engineering are not deteriorated, which,
again,
results in a poor product quality such as adhesiveness, thread breakings,
irregularities in the thickness and stability of the fibers and fiber tows in
the form of
filaments and staple fibers.
The worldwide use of spinning plants for processing solutions from cellulose
in
aqueous tertiary amine oxide, and the climatic conditions resulting therefrom,
which
differ according to the locations, have to be taken into account when making
concepts for spinning plants according to the amine oxide process. In the
tests
CA 02479289 2004-09-15
described below, room air conditions with additional air and exhaust air
streams were
simulated, and the spinning process was observed and the air volume withdrawn
from the spinning process was analyzed.
By adjusting predetermined room air conditions in the spinning area andlor the
maintenance area, the room air conditions can optimally be controlled in view
of the
process control and the well-being of the operating staff, despite the gaseous
substance stream from the spinning area, and the exhaust air can be supplied
to a
subsequent post-processing plant.
Another possibility for withdrawing air streams from the spinning machine and
the
spinning room to an exhaust air processing plant, for the adjustment of the
room air
conditions, is necessary, for instance, if spontaneous exothermal reactions of
the
mixture from cellulose and aqueous tertiary amine oxide occur, so that the
ambient
air not be contaminated by degradation products.
The solution according to the invention eventually also allows the addition of
viscosity-modifying, slightly boiling liquids to the spinning mass, which
liquids
spontaneously evaporate during the extrusion, especially at extrusion and
processing
temperatures of approximately 100°C or more. Without the inventive
control of the
room air conditions in the spinning hall said vapors would escape into the
environment directly adjacent to the spinning plant, or into the working area,
e.g. in
the form of solvent vapor enriched with water, water vapor or with a cellulose
solvent
and the degradation products thereof, where they would negatively influence
the
climatic working conditions.
The room air conditions can especially be adjusted to predetermined values or
desired values (target values) of certain quantities of state. These
quantities of state
are preferably those that are most strongly influenced by the spinning
process. Such
quantities of state are, for instance, the contents of tertiary amine oxide
and/or other
degradation products of the spinning process in the room air, which the
gaseous
substance stream conveys out of the endless molded articles, or the humidity
or
temperature of the room air. Said quantities of state may be used individually
or in
CA 02479289 2004-09-15
optional combinations with each other as control quantities or actuating
variables for
controlling the room air conditions.
Thereby, the process quantities have to be adjusted and measured, such as the
exhaust air quantity in m3lh, the additional air quantity in m3lh, the exhaust
air
temperature in °C, the additional air temperature in °C, the
relative air humidity or the
humidity in the air in (kg water)I(kg dry air), and related to the operating
parameters
of the spinning machine. Additional measurements of the air composition in the
exhaust air, such as the contents of amines, other organic solvents and water
may
also take place, so as to control a possibly connected subsequent treatment
plant for
air in response to the process such that good spinning and room conditions, as
well
as a high recovery and precipitation degree of air ingredients are obtained.
According to an advantageous embodiment, one or more sensors may be provided
for this purpose in the spinning area and/or the maintenance area. These
sensors
detect the actual value of such a quantity of state representing the room air
conditions and forward the same to a controller. In the controller the actual
value can
then be compared with a predetermined desired value and, in correspondence
with
the deviation of the actually measured quantity of state from the desired
value, the
room air conditions can be tracked or controlled. Such a tracking of the room
air
conditions may, for example, be adjusted by controlling the volume flow rate
of the
exhaust air. Alternatively, or in addition to controlling the volume flow rate
of the
exhaust air, also the volume flow rate of the additional air supplied to the
room can
be tracked. Moreover, the temperature andlor the humidity of the additional
air can
be changed in correspondence with the deviation of the room air conditions
from the
desired value by heating devices andlor moisteners. If, for example, a
humidity
measured in the spinning area is too high, the additional air supplied to the
spinning
area may be dried to an increased extent.
The additional air may thereby consist of external air or, at least partially,
of purified
and circulated air.
For avoiding that too large a volume flow rate of the gaseous substance stream
enriched with the constituents from the spinning process escapes from the
spinning
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area into the maintenance area, where it burdens the room air conditions, the
exhaust air can, at least partially, directly be sucked out of the spinning
area by
means of a process air exhaustion. Preferably the entire, or at least the
major part, of
the process air is thereby sucked off, before it can reach the maintenance
area. For
this purpose, corresponding suction openings may be arranged in the spinning
area
itself, or in the direct proximity of the spinning area.
The exhaustion in the proximity of the air gap is, however, not unproblematic,
as a
sufficient distance of the suction openings from the endless molded articles
in the air
gap and from the surface of the precipitating bath is required, for not
loading the
filaments in the air gap by the exhaust stream too much on one hand, and for
keeping the precipitating bath surface as quiet as possible on the other hand.
This
embodiment has the advantage that, due to the direct exhaustion from the
spinning
area, the room air conditions in the spinning area can more directly be
controlled and
a larger exchange of air can be obtained.
According to another advantageous embodiment the exhaust air can, at least
partially, be sucked directly out of the maintenance area, so as allow the
direct
adjustment of the room air conditions also in this area by means of the
exhaust air
control.
For obtaining a temperature distribution in the room, in which the spinning
process
takes place, that is as constant as possible, and for avoiding the
accumulation of hot
room air in the proximity of the ceiling, it may be provided in accordance
with an
advantageous embodiment that the exhaust air is, at least partiaNy, sucked off
from
the portion of the room close to the ceiling.
For directly controlling the room air conditions in the staying area,
especially in the
maintenance area, part of the additional air may be supplied directly into or
adjacent
to the staying area.
In another advantageous embodiment the additional air stream is passed along
predetermined paths by positioning the exhaust air devices. Thus, especially a
flow in
the maintenance area and/or the spinning area can be obtained, by which the
CA 02479289 2004-09-15
to
operating staff is largely shielded against the affects of the gaseous
substance
stream and the process air. This shielding may, for instance, take place in
the form of
an air curtain, i.e. by a layer of air preferably streaming vertically along a
front of the
spinning plant.
In tests it has proved to be advantageous, if between 10 and 80 m3, preferably
between 10 and 30 m3, exhaust air per kg of endless molded articles produced
during the spinning process in the spinning area are sucked off in andlor in
the
proximity of the spinning area. The exhaust air sucked of at this point
primarily
contains process air.
According to another advantageous embodiment, between 3 and 50 m3 gaseous
substance per kg of endless molded articles produced during the spinning
process in
the spinning area can be blown into the air gap by the air-quenching device,
preferably at velocities of more than 30 m/s.
The room air conditions can particularly be improved by circulating 3 to 10
times the
volume of the room per hour.
The quantity of exhaust air sucked out of the room per hour may be 1.2 to 2.5
times
the gaseous substance stream from the air-quenching device.
According to another advantageous embodiment, which particularly also
constitutes
an invention independently of the inventive adjustment of predetermined room
air
conditions in the spinning area and/or the maintenance area, the exhaust air,
once
withdrawn from the room in which the spinning process takes place, can be
purified.
In accordance with an advantageous advanced development the exhaust air may,
for
this purpose, be fed to a purification step, in which the portion of the
portions deriving
from the spinning process in the exhaust air is reduced.
The precipitated constituents, e.g. the recovered tertiary amine oxide, or the
degradation products formed in the thermal treatment during the production of
the
suspension solution in the spinning process, may be recirculated into the
spinning
process or may be removed. The purification step may particularly comprise a
drop
CA 02479289 2004-09-15
eliminator, a quencher andlor an aerosol separator, as well as a process step
in
which a substantially biological purification by means of a microbial
degradation of
degradation products of the spinning process takes place in biofilters.
Moreover, an
electrostatic filter with a purification upstream or downstream thereof may be
provided, in which the exhaust air is conducted through electrically charged
fixtures
such as netting wires. The aerosol separator is preferably arranged upstream
of an
acidic or alkaline washing stage so as to recover the useful materials N-
methyl-
morpholine-N-oxide (NMMNO), N-methyl-morpholine (NMM) and morpholine (M)
contained in the exhaust air, particularly in the withdrawn process air, and
to
recirculate them to the spinning process.
The device according to the invention may also be constructed as a retrofit
kit, with
which existing plants for the production of endless molded articles from a
spinning
mass containing water, cellulose and tertiary amine oxide may be retrofitted.
The invention will hereinafter be explained in more detail by means of working
examples with reference to the drawings, wherein
Fig. 1 shows an embodiment of a spinning process for the production of
endless molded articles from a spinning mass containing water,
cellulose and tertiary amine oxide in a schematic general survey;
Fig. 2 shows a perspective drawing of an embodiment of a spinning plant
comprising a spinning area and a staying area;
Fig. 3 shows a perspective drawing of the removal of exhaust air by suction
and the supply of additional air in a room comprising a spinning plant;
Fig. 4 shows a schematic general survey of the method for purifying the
exhaust air.
At first, a survey will be provided on the method for producing endless molded
articles from a spinning mass containing water, cellulose and tertiary amine
oxide,
with reference to fig. 1.
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12
In a reaction vessel 1 a spinning mass 2 is prepared, which contains
cellulose, water
and tertiary amine oxide, e.g. N-methyl-morpholine-N-oxide (NMMNO), as well
as, if
required, stabilizers for thermally stabilizing the cellulose and the solvent.
Such
stabilizers may, for example, be propyl gallate and media or mixtures thereof
with an
alkaline effect. If need be, further additives such as anorganic and organic
salts,
titanium oxide, barium sulfate, graphite, carboxymethylcelluloses,
polyethylene
glycots, chitin, chitosan, alginic acid, polysaccharides, colorants, chemicals
having
antibacterial effects, flame retardants containing phosphor, halogens or
nitrogen,
activated carbon, blacks or electrically conductive blacks, silicic acid as
well as
organic solvents such as low, medium and higher boiling alcohols, dimethyl
formamides, dimethyl acetamides, dimethyl sulfoxides as thinning agents etc.
may be
contained in the spinning mass.
The spinning mass 2 is transported via a pump 3 through a conduit system 4, in
which a pressure compensating container 5 can be arranged for compensating
pressure and volume flow rate deviations in the conduit system. Thus, an
extrusion
head 6 can be supplied with the spinning mass 2 continuously and constantly.
The
conduit system 4 is provided with temperature control devices (not shown), by
means
of which the temperature of the spinning mass 2 during the transport thereof
through
the conduit system 4 can exactly be controlled. An exact temperature control
is
necessary, as the chemical and mechanical properties of the spinning mass
strongly
depend on the temperature. For example, the viscosity of the spinning mass 2
drops
with increasing temperature and shear rate.
Moreover, burst protection devices (not shown) with bursting discs are
provided in
the conduit or line system 4 at regular intervals, which are necessary because
of the
tendency of the spinning mass to a spontaneous exothermal reaction. The burst
protection devices avoid damages in the conduit system 4 and in the pressure
compensating container 5 as well as of the subsequently connected extrusion
head
6, if such a spontaneous exothermal reaction takes place. If a reaction in the
spinning
mass takes place, the pressure in the conduit system 4 increases, which
results in
the bursting of the bursting discs and in the discharge of the bursting
pressure to the
environment.
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13
A spontaneous exothermal reaction in the spinning mass 2 can especially occur
when a certain temperature is exceeded, or as a result of aging of the
spinning mass
2, especially in areas with stagnant water. For avoiding such an aging of the
spinning
mass in areas of stagnant water, the conduit system is designed in a flow-
favorable
manner in the area flown through by the highly viscous spinning mass 2. In the
extrusion head 6 the spinning mass is distributed in a nozzle volume 7 to a
plurality
of extrusion channels 8 in the form of spinning capillaries arranged in
several rows,
which, in figure 1, extend perpendicularly to the plane of projection. Thus, a
plurality
of endless molded articles is simultaneously produced by one extrusion head 6,
whereby the endless molded articles exit the extrusion head substantially in
the form
of a plane curtain. Each spinning capillary 8 is, at least section-wise,
surrounded by a
heating device 9, by which the wall temperature of the spinning capillary is
controllable. The wall temperature of the spinning capillary 8 is
approximately 150°C,
the temperature of the spinning mass approximately 100°C. The heating
device 9
extends preferably up to the discharge opening 10 of the extrusion channel
positioned in the direction of flow S. Thus, the wall of the extrusion channel
8 is
heated up to the extrusion channel opening 10.
In the extrusion channel 8 the spinning mass is extruded and is subsequently
discharged into an air gap 12 in the form of a spinning filament 11. An air-
quenching
device 15 is arranged in the air gap 12, by which a gaseous substance stream
16 is
directed at the curtain of endless molded articles 11. The gaseous substance
stream
16 is turbulent and has a velocity of at least 30 mls. It is directed
downwardly with
respect to the horizontal line and clearly spaced away from the extrusion
head. Its
height in the direction, in which the endless molded articles are passed
through, is
less than 10 mm.
The extrusion head 6 and the elements described in the following form part of
a
spinning plant 14 standing in a room not illustrated in fig. 1, e.g, a factory
hall.
Upon passing through the air gap 12, the curtain of endless molded articles
immerses into a precipitating bath 17, in which the solvent is precipitated
out of the
endless molded articles.
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i4
A deviation or deflector device 18 is arranged in the precipitating bath 17,
through
which the plane curtain is deviated in the direction of a bundling device 19.
The
bundling device bundles the individual endless molded articles 11 to
substantially
one point, and this fiber bundle is passed on to additional process steps (not
shown
in fig. 1 ).
The spinning plant may also comprise additional spinning locations, as is
schematically illustrated in fig. 1. Thus, an extrusion head 6 comprising
extrusion
openings distributed on an annular surface may be provided at another spinning
location, where the endless molded articles are immersed into the
precipitating bath
17 after they have passed through the air gap 12. In the precipitating bath
the
endless molded articles are guided into an annular gap between a spinning
funnel
and a displacer. A screen is arranged at the exit of the spinning funnel. The
deviation
device 18 is arranged outside the precipitating bath.
The spinning process illustrated in fig. 1 particularly affects the room air
conditions in
the spinning areas 20 shown in dotted lines in fig. 1. The room air, or
atmospheric,
conditions in this area are essentially characterized by the temperature
radiation of
the heated extrusion head 6 and the still hot endless molded articles 11, as
well as
by the constituents dissolved from the endless molded articles' 11 and the
precipitating bath 17 by the gaseous substance stream 16, and by the vapors of
the
hot spinning mass and the precipitating bath. The spinning area 20 comprises
the
area in which the spinning means 6, 12, 15, 16, 18 and 19 are arranged and the
air
climatic conditions are substantially influenced by the spinning process. The
spinning
means comprise the components of the spinning plant participating in the
extrusion
of the spinning mass up to the coagulation of the endless molded articles.
In fig. 2 the spinning plant 14 with its spinning area 20 is illustrated
schematically.
Fig. 2 moreover schematically shows operating staff 21 staying in a staying
area 22
for inspection and maintenance works on the spinning plant 21. The staying
area
extending along the spinning plant 14 with a distance of up to 1.5 - 3 m
comprises an
inspection area 23, in which the operating staff makes check patrols and can
inspect
and supervise the spinning process performed by the spinning plant 21. For
this
purpose, spinning means are freely visibly arranged in the spinning area 20
such that
CA 02479289 2004-09-15
they can at once be inspected by an operator making his check patrol. Thus,
the
operating staff immediately notices irregularities in the spinning area. In
particular,
the air gap 12 is positioned in the central vision area of an operator 21
walking or
standing upright in the inspection area 23.
Especially if the room, in which the spinning process takes place, is a
factory hall, the
staying area 22 and spinning area 20 are small in comparison with the room,
and
may cover less than half the volume of the room The room-climatic balancing
volume
thereby includes the staying area and the spinning area.
For carrying out maintenance works on the spinning means in the spinning area
20,
the person goes into a maintenance area 24 slightly elevated over the
inspection
area, which likewise forms part of the staying area 22. In the maintenance
area the
operating staff 21 can possibly access the entirety of spinning means without
having
to bend down. The entirety of spinning means is thereby located within the
reach of
the person standing in the maintenance area 21, so that the same can carry out
all
works in the spinning area 20 out of one posture.
The room air conditions in the staying area 22 and the spinning area 20 are
adjusted
to a desired or target value in view of at least one desired or target
quantity by a
device 25 for controlling the room air conditions. For this purpose the device
25
comprises exhaust air devices 26 through which exhaust air 27 is sucked out of
the
environment of the spinning plant 21. As is shown in fig. 2, an exhaust air
device 26
is also disposed in the proximity of the ceiling so as to suck off therefrom
hot air
accumulating in the upper portion of the room. Said exhaust air devices
primarily
suck off room air only slightly charged with process air.
Additional exhaust air devices take care that as little process air as
possible escapes
from the spinning area into the maintenance area and/or from the maintenance
area
into the remainder of the room.
Furthermore, exhaust air devices may be provided in or in the proximity of the
inspection area 23, which suck the air 29 out of the maintenance area 23.
Finally an
exhaust air device is provided, which is arranged in the spinning area 20 or
directly
CA 02479289 2004-09-15
16
adjacent thereto such that it sucks off the air 30 preferably only from the
spinning
area. In fig. 2, the exhaust air device 26 for the process air is integrated
in the portion
above the precipitating bath 17 of the spinning plant 14. For avoiding that an
air
current is generated by the exhaustion, which influences the spinning process,
the
exhaust air device is provided with a fluid mechanical device, not shown, by
means
of which the direction from which the air is sucked in out of the spinning
area can be
adjusted. An additional exhaust air device may be disposed above the
maintenance
area, as is illustrated by the dotted line.
The air sucked off by this exhaust air device is primarily the process air
with the
gaseous substance stream 16, and is enriched with constituents from the
spinning
process. Due to the heating of the extrusion head and the temperature of the
endless
molded articles said air, moreover, has a high temperature.
Another exhaust air system (not shown) may be arranged at the bursting
devices, so
as to immediately suck of the gases formed in an exothermal reaction and when
the
burst devices burst.
The room air conditioning device 25 moreover comprises an additional air
device 31,
through which additional air 32 can be fed to the room. The additional air 32
is
directed by the additional air device 37 such that only a few degradation
products
from the spinning process are contained in the staying area 22. The additional
air
may be fresh ambient air or circulated and purified air, or circulated and
purified
exhaust air is admixed to the ambient air.
The additional air device 31 interacts, especially in the spinning area 20,
with at least
one exhaust air device 26 such that the current 33 of additional air is
conducted in
predetermined directions. Thus, it can be assured that the operating staff 21
carrying
our maintenance works in the maintenance area 24 is supplied with sufficient
additional air and is protected against the room-climatic effects of the
spinning
process.
According to the working example shown in fig. 2, the additional air device 31
blows
in additional air 32 from above between the person 21 and the frontage of the
CA 02479289 2004-09-15
spinning plant 14, and the exhaust air device 26 simultaneously sucks process
air out
of the spinning area 20 along the frontage of the spinning plant 14, shielded
by the
additional air 32. In addition, an optional exhaust air device 34 in the
bottom area of
the spinning plant 14 can suck off additional air out of the spinning area 20.
As is
outlined by the arrows in fig. 2, an air curtain is thereby formed between the
operator
in the maintenance area and the spinning area, especially in the air gap.
Alternatively, the additional air 32 may also be supplied as well or source
ventilation
(not shown) from below, e.g. from the bottom area or toe space of the spinning
plant,
or from the side.
The room air conditioning device 25 finally comprises at least one sensor 35,
by
means of which at least one quantity of state representative of the room air
conditions can be detected and forwarded to a controller 36 of the device 25.
The
quantities of state detected by the at least one sensor may differ in
dependence on
the position of the sensor. In the example shown in fig. 2, for example, a
sensor 35 is
provided in the inspection area 23, another sensor 35 is provided in the
maintenance
area 24 and a third sensor 35 is provided adjacent to the air gap 12 or in the
air gap
12 itself. The sensor in the proximity of the air gap 12 can, for instance,
detect the
contents of tertiary amine oxide or of other degradation products in the room
air. The
sensor 35 in the maintenance area can detect the humidity, and the sensor 35
in the
inspection area 23 can detect the temperature. Thus, each quantity critical
for the
room air conditions is detected respectively in each of said areas 20, 23 24,
so that
room air conditions being optimal in view of the separate relevant quantities
of state
can separately be generated in each area 20, 23, 24.
The controller 36 compares the actual values of the quantities of state
representative
of the room air conditions detected by the sensors 35 with desired values
stored in a
memory (not shown). Said desired values can be modified and monitored by an
inputloutput unit 37, e.g. a computer. The input/output unit 37 can also
detect the
current operating state of the device 25 and display the same for the
operating staff
21.
In case of deviations between the actual quantities of state detected by the
sensors
35 and the desired values, the controller 36 controls pumps 38 such that the
flow
CA 02479289 2004-09-15
18
rates 39 of additional or exhaust air are changed in combination with each
other or
individually such that the deviations from the desired values are reduced.
Also the
distribution of the volume flow rates of the exhaust air sucked off through
the
individual exhaust air devices can be modified via areas 22, 23, 24 by non-
illustrated
flap systems. Moreover, the blow-out direction of the additional air 32 can be
modified at some locations. In addition, the controller 36 controls additional
devices
39, such as heating devices and humidifiers or dehumidifiers, by means of
which
certain quantities of state of the additional air, such as humidity and
temperature, can
be changed and the deviations of the room air conditions from the desired
value can
be minimized in view of these quantities of state.
Fig. 3 shows a room 40 comprising the spinning plant 14 and the room air
conditioning device 25 in a perspective, easy to survey illustration. Room 40
is, for
instance, a hall or a similar room in a fabrication plant for endless molded
articles.
As can be seen from fig. 3, several spinning stations 41 can be arranged
parallel to
each other in the spinning plant 14, whereby at least one curtain of endless
molded
articles 11 is produced in each spinning station 41. Each spinning station 41
comprises an air-quenching device 15 associated therewith and a precipitating
bath
17. In room 40 also several rows of spinning positions 41 may be an-anged
successively. Each spinning position 41 may be associated with its own
spinning
area 20, which is equipped with sensors separated from the adjacent spinning
areas
and controlled to certain room air conditions.
The volume flow rate of the gaseous substance stream generated by the air-
quenching device 15 is, in each spinning station 41, between 10 and 500 m3/h,
depending on the dimensions of the individual spinning stations. In each
spinning
station heat between 0.5 and 4 KW has to be withdrawn from the spinning
process.
The surface of each spinning station is approximately 2 to 3 m2. The spinning
area 20
associated with each spinning station has a volume between 10 and 20 m3.
For clarity's sake, essential parts of the spinning plant 14, such as the
extrusion head
6 or the bundling device 19, have been omitted in fig. 3.
CA 02479289 2004-09-15
19
According to the example shown in fig. 3, the air-quenching devices 15 of
spinning
positions 41 are supplied with a gaseous substance stream 43 from a common
collective pipe 42.
According to the example shown in fig. 3, each spinning station or,
respectively, each
spinning area of a spinning station is associated with an exhaust air device
26, by
means of which the air 30, which primarily contains process air, is sucked out
of the
spinning area, and the air 29, which primarily contains larger portions of
room air and
only smaller portions of process air, is sucked out of the maintenance area
and is
forwarded to a collective pipe 44.
Furthermore, the hot air from the ceiling area of room 40 is sucked off in the
collective pipe 44 by means of exhaust air devices 26 provided close to the
ceiling.
The distribution of the volume flow rates between the exhaustion close to the
ceiling
and the exhaustion from the spinning area 20 or, respectively, the maintenance
area
22 is effected by hydraulic fixtures 45, such as flaps or throttles.
According to fig. 3, the additional air 31 is supplied in the maintenance area
24 above
the head level of the operating staff. Alternatively, the additional air can
also be
supplied from the bottom or the side. According to the working example shown
in fig.
3, the gaseous substance stream and the additional air come from different
sources.
The additional air supplied may, for example, be fresh air, the gaseous
substance
may be purified exhaust air. .
The exhaust air 45 conducted out of room 40 comprises, especially if it comes
from
the spinning area 20, a high concentration of constituents deriving from the
spinning
process. Said constituents are removed from the exhaust air by a purification
stage
as is, for example, shown in fig. 4.
Fig. 4 shows a schematic illustration of such a purification stage. In fig. 4,
the exhaust
air 45 is thereby exemplarily fed to the purification process from two
separate rooms
40.
CA 02479289 2004-09-15
The exhaust air 45 is at first fed to a washing system 46. The washing system
46
comprises a quencher 47 as well as at least one demister 48. The demister 48
is
supplied with washing media 50 via the dosing pumps 49. Such washing media may
be water, HCI, H2S04 or a solution containing NaOH.
Moreover, fresh water is supplied to the demister via a conduit 51. Part of
the
washing media can circulate inside the demister via conduits 52 and can be
reused.
Another part of the liquid accumulated in the demister 48 is fed to a waste
line 53.
The discharged portion is supplemented with the fresh water.
The washed exhaust air is sucked out of the upper part of the demister of the
washing system 46 via a fan 54.
The exhaust air is finally supplied to a chimney 57, where it flows into the
ambient air
in the form of pure gas. The precipitate from the chimney is likewise supplied
to the
waste line. Alternatively, the purified exhaust air can also be admixed to the
additional air fed to room 40.
The exhaust air can be supplied to an aerosol separator 55 provided upstream
of the
washing system, allowing the recovery of the useful materials such as N-methyl-
morpholine-N-oxide (NMMNO), N-methyl-morpholine (NMM) and morpholine (M)
contained in the exhaust air, as well as of other reaction products, prior to
a possible
acidic or alkaline washing. An electrostatic filter may thereby be provided,
in which
the exhaust air passes an electrically charged filter system. Upstream andlor
downstream of the electrostatic filter the exhaust air may be washed.
The aerosol separator is likewise supplied with fresh water via a conduit 56.
The
waste water from the aerosol separator 55 is likewise fed to the waste line
53.
The exhaust air washing plant may, as is illustrated, be provided with
additional
washing devices in multiple stages, or only with parts of the illustrated
washing
device. A ventilator can be positioned upstream, inside or downstream of the
washing plant.
CA 02479289 2004-09-15
21
In addition to the components shown in fig. 4, the purification stage may also
comprise a microbial purification, during which a microbial degradation of
constituents in the exhaust air out of the spinning process takes place by
means of
bio~ltration.
In the hereinafter described examples, the air conditions in the spinning area
or,
respectively, in the room in which the spinning process takes place were
influenced
by varying the process conditions, and the effects on the spinning process and
the
operability of the spinning plant were analyzed.
An NMMNO spinning mass consisting of 13% pulp of the MoDo type having a
medium DP of 680.76% and 11 % water was fed to the spinning machine at
different
spinning solution temperatures.
By means of a rectangular spinneret the spinning solution was extruded into an
air
gap in the form of a filament and precipitated in an NMMNO-containing
precipitating
bath. The endless molded articles exiting the spinning nozzle in the form of a
filament
were subjected to an air stream by means of different air-quenching devices.
The height of the air gap in the direction in which the endless molded
articles are
passed through was between 15 and 25 mm.
In all cases a Lyocell fiber having a fiber fineness of approximately 1.4 dtex
was
produced. The devices employed therefor are, for example, described in DE 100
19
660 A1 and DE 100 37 923 A1, both of which documents are entirely incorporated
in
the disclosure of this application.
In the tests for exactly balancing the air volumes the plant was sealed, so
that the
subsequently described production density expressed in fiber production per
room
surface [kg/h per m2] could be illustrated.
In the following examples, the volume and the temperature of the process air,
the
process exhaust air and the room air was varied and measured.
CA 02479289 2004-09-15
22
The air volume currents were determined by means of a propeller-type volume
flow
rate meter of the company Testoterm. For determining the air temperatures a
resistance thermometer was employed.
The temperature of the additional room air was uniformly approximately
25°C.
The exhausting devices used in examples 2 to 8 were adjusted by varying the
exhaustion geometry such that the secondary air factor, which is the
dimensionless
relation of process exhaust air volume to additional process air volume, i.e.
the gas
stream volume from the air-quenching device, corresponded to the values
mentioned
in the examples. A secondary air factor of 0 thereby designates an open system
where no process air exhaustion takes place. A secondary air factor of 1
designates
a closed, shielded system, in which exactly the air from the air-quenching
device is
sucked off, and a secondary air factor >1 designates a partially open system,
in
which the process exhaustion additionally exhausts room air at the exhaust
edges.
Finally, the odor burden in the maintenance area, the spinning behavior and
the
accessibility and operability of the plant by a person standing in the
maintenance
area were assessed subjectively. In view of the odor burden it was likewise
taken into
account if a visible smoke development, which typically is an indication of
high
temperatures, occurred in the spinning area. This resulted in a worse
evaluation.
For the better comparability all values and data were related to 1 kg/h of
produced
fiber.
Exam~ie 1:
The air-quenching device had an air gap width of 8 mm, by which a laminar
quench
air current with a moderate quench air velocity, but large volume flow rate
(28 m3 air
per kg product) was generated.
The spinning process was carried out without an own exhaust air device for
process
air.
CA 02479289 2004-09-15
23
The discharged heated process air escaped unimpededly into the spinning or,
respectively, operating area. In the operating area a temperature of nearly
40°C was
adopted at the head level of an operator positioned in the maintenance area.
Moreover, a relatively strong odor burden and white smoke could be observed.
The room exhaust air volume was adjusted to approximately 48 m3lkg by means of
an exhaust air ventilator controlled by a frequency converter, which
corresponds to a
ventilation number (change of the air volume in the room per hour) of
approximately
7.
The air was withdrawn at a temperature of approximately 30°C.
The spinning behavior was good. Due to the absence of an exhausting device in
the
spinning area also a good operability from the maintenance area and a good
visibility
from the inspection area were provided.
Example 2:
In example 2, an exhausting device extending over the entire air gap height
and
nozzle width was arranged in the spinning nozzle area as illustrated in fig.
2. Apart
therefrom, the conditions remained unchanged. Said exhausting device effected
a
nearly complete shielding of the spinning area against the operating area.
By this arrangement the process air was blown to the filaments by means of the
air-
quenching device and simultaneously sucked through the yarn sheet by means of
the
exhausting device.
The secondary air factor of the exhausting device was in this case 1, as the
additional process air volume and the process exhaust air volume were adjusted
to
the same value.
The spinning behavior in this example was worse than in example 1. The air
passage
seems to be negatively influenced by the effect exerted by the exhaustion on
the
quench air stream.
CA 02479289 2004-09-15
24
The arrangement of the exhausting device directly upstream of the filaments
prevented any vision to the filaments during the operation, which implied a
strong
restriction of the operability. For routine inspection purposes during the
operation it
was necessary at each time to remove the exhaustion. This handling always
included
the risk of producing spinning errors.
A slight smoke development occurred in the lateral portions of the nozzles,
due to the
incompletely entrained process exhaust air, which created a slight odor burden
in the
operating area.
In the operating area a temperature of approximately 30°C was adopted
at head
level.
Example 3:
Example 3 was conducted analogously to example 2. However, instead of a
laminar
quench air stream with a moderate quench air velocity, a turbulent quench air
stream
with a high velocity was passed through the yarn sheet. Said air-quenching
device
consisted of single-row multi-channel nozzles of the Lechler Whisperblast
type. The
air volumes (additional process air and process exhaust air) of approximately
10.7
m3/kg were essentially smaller than in the preceding examples.
In this example, tvo, the spinning behavior was negatively influenced by the
presence of the exhausting device. In these examples, too, white smoke with an
accompanying odor burden occurred in the marginal portions of the exhaustion.
Due
to the clearly smaller quantities of process air the burden was, however,
slightly
smaller than in example 2.
Examples 4 to 6:
In examples 4 to fi the air-quenching device of examples 1 and 2 (laminar
quench air
stream with moderate quench air velocity, but large volume flow rate) was
employed.
CA 02479289 2004-09-15
In contrast to examples 1 and 2, an exhausting device was used in these
examples,
allowing, due to its geometric design, the exhaustion also of room air in
addition to
the process air, and additionally also the possibility to see the filaments.
The
geometric arrangement of the exhausting device was varied in these three
examples
such that the secondary air factor, the relation between additional process
air volume
and process exhaust air volume, ranged between 1.7 and 2. Moreover, different
spinning solution temperatures were tested, and process air volumes of 28 to
45
m3/kg were applied (depending on the spinning temperature).
In all these examples, the temperature in the direct spinning area was adopted
at a
value of approximately 30°C. There was no odor burden and no white
smoke plumes.
The operability, without an influence on the spinning process or on the
ability to see
the filaments during the operation, was provided due to the described
geometric
arrangement. The spinning behavior turned out to be good.
Examples 7 and 8:
In examples 7 and 8 the air-quenching device of example 3 (turbulent quench
air
stream with high velocity by using single-row multiple channel nozzles of the
Lechler
Whisperblast type) was employed. The additional process air volume ranged
between 8.5 and 10.5 m3/kg, i.e. it was substantially smaller than in the
preceding
examples.
The exhausting device was constructed analogously to examples 4 to 6.
The secondary air factor of the exhausting device, the relation between
additional
process air volume and process exhaust air volume, ranged between 2 and 2.5.
In said two examples, the temperature in the direct spinning area was adopted
at a
value of approximately 30°C. There was no odor burden and no white
smoke plumes.
The operability, without an influence on the spinning process or on the
ability to see
the filaments during the operation, was provided due to the described
geometric
arrangement.
CA 02479289 2004-09-15
26
The spinning behavior in examples 7 and 8 turned out to be very good. Even an
increase in the production density (kg/h product per m2 spinning hail surface)
did not
entail any negative effects.
Summarizing, it can be noted in connection with the performed tests that the
performances of examples 7 and 8 are preferable in comparison with the other
variants as far as the air conditions in the spinning area, the spinning
performance,
the operability and the fiber quality are concerned.
Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Ex.7 Ex.8
Production density2.3 2.3 2.3 2.3 2.3 2.3 2.3 3.3 kg/hm'
(kg/h
product per mZ
spinning
hall surface
spec. room volume 3.4 3.4 3.4 3.4 3.4 3.4 3.4 2.5 m' per
(m'
er k lh fiber roduction k /h
Room thermal load 231.5231.5231,5231.5231.5231.5231.5165.3W per
from
drives, thermal kg/h
radiation,
etc.
Process air volume28.4 28.4 10.7 28.4 33.8 44.4 8.9 10.2 m'/kg
per
k roduct
Spinning solution 95 95 95 95 110 125 95 105 C
tem-
erature on nozzle
**
Room tem erature 25 25 25 25 25 25 25 25 C
Additional air 17 21 23 18 20 21 26 24 C
tempera-
ture - air uenchin
Secondary air factor0.0 1.0 1.0 2.2 1.9 1.7 2.5 2.0
pro-
cess exhaustion
(ratio
exhausted volume
I
additional rocess
air
Room air exhausted- 28.4 10.7 62.6 64.2 75.6 22.2 20.3 m'/kg
by
process exhaustion
- for
exhaust air urification
Air temperature ---- 33.3 55.8 29.6 30.1 29.6 46.0 47.0 C
prior to
exhaust air urification
Room exhaust air 48.3 23.1 23.1 0.6 4.3 3.6 4.0 2.2 m'Ikg
(room
exhaustion via
roof on
ceilin
Exhaust air temperature30.4 31.0 31.0 29.0 29.0 29.0 33.0 33.0 C
to environment
Ventilation number5.8 6.7 6.7 10.1 10.1 10.1 5.0 5.0
in
room (change of
air
volume er hour
Temperature difference7.0 6.0 6.0 4.0 4.0 4.0 8.0 8.0 C
additional room
air /
room exhaust air
CA 02479289 2004-09-15
27
Air temperature 35-4025-3025-3025-3025-3025-3025-3025-30
in the
direct o eratin
area
Odor burden in yes smallsome no no no no no
the direct
o eratin area
Spinning behavior good bad averagood good good very very
a ood ood
Accessibility, good bad bad good good good good good
operability
*) 0 .... Open
System, 1....
Closed System,
>1.... Partially
Opened System
**) At spinning
solution temperature
110C or, respectively,
125C the cellulose
concentration was
increased to 13.5%.
