[0001] The present invention relates to a furnace containing a device for manoeuvring an
air-control mechanism, in a so-called "soda furnace", or soda pan for combustion of
waste liquor from pulp production, in which combustion air is supplied through a number
of air-supply ports in the furnace walls. The ports communicate with so-called "air
boxes", which are fed with air from outside. Each port is further provided with a
control member in order to determine the air volume passing through the port.
PRIOR ART AND PROBLEM
[0002] The aim of the equipment is to regulate the quantity of combustion air which is supplied
to the furnace and, by virtue of so-called "poking", to keep the ports free from the
coatings which are formed in the mouth of the ports.
[0003] The air quantity is regulated by a control member, often in the form of a control
sleeve, throttling the annular gap area which is formed between the inner sides of
the air port and the tip of the control sleeve. The gap area is changed by the axial
end position of the control sleeve being varied relative to the air port.
[0004] In soda furnaces, coatings are formed, during the combustion process, on the inner
sides of the furnace walls. The coatings threaten to block the air ports, with the
consequence of deteriorating combustion results. In order to remove such coatings,
so-called "poking" of the air ports is carried out, which is done by the control member
being moved past the set air-regulating position so that its end penetrates the air
port, whereupon the coatings which have formed are wiped off. The control sleeve is
often configured such that combustion air is allowed to flow internally through the
sleeve and into the furnace whenever the control sleeve is in the advanced poking
position, thereby enabling the sleeve to be cooled.
[0005] In previously known constructions, compressed-air driven pistons are used in order
to realize the principal axial displacement of the control member (control sleeve)
relative to the air-supply port. A difficult problem with such compressed-air systems
is that the pressure of the compressed-air network often varies due to condensation,
for example, or other causes. In the event of such undesirable falls in pressure,
for example if the pressure suddenly drops from 6 bar to 4 bar, it can happen that
the control sleeve, in the poking operation, is unable to get through the port, with
the consequence that it gets stuck and, despite air cooling, is burnt through.
[0006] It has simultaneously been shown that the poking motion of the compressed-air driven
control sleeve is not sufficiently powerful to remove particularly serious coatings
in a safe and reliable manner.
[0007] The control sleeve further needs to be able to be positionally adjusted within an
air-regulation zone so that the sleeve can be moved past the set air-regulating position,
whereupon its end penetrates the air port and is subsequently returned with great
accuracy to the set air-regulation position. This is particularly important in connection
with soda pans whenever it is wished to use the so-called ROTAFIRE\-method (see SE-9102546-0),
in which, by virtue of a specially regulated air supply, a rotation of the combustion
gases in the horizontal plane is created, so that the waste liquor injected into the
furnace chamber is slung by the gas rotation out towards the walls of the furnace,
whilst simultaneously undergoing drying and pyrolysis.
[0008] Where compressed-air cylinders are used for the displacement of the control sleeve,
an often complicated and expensive auxiliary system is required for the air-regulating
positional adjustment having the above-stated function. The problem with the prior
art is here, therefore, to get the control sleeve, without deviations, to resume its
set air-regulating position directly following completion of a poking motion.
[0009] Such auxiliary systems are usually controlled via a limit switch, which can operate
electrically, pneumatically or mechanically and is described, for example, in Swedish
patent specifications SE-379 846 and SE-462 440.
OBJECT OF THE INVENTION
[0010] The object of the present invention is to eliminate the above problems by producing
a device for manoeuvring an air-control mechanism in a furnace, which device is able,
at the desired force and in a safe and reliable manner, to perform a poking motion
in order to remove coatings which have been deposited in the said air ports, and at
the same time to completely obviate the need for complicated and expensive auxiliary
systems for positionally adjusting the control member (i.e. the control sleeve) for
air regulation and get it to resume the set position following completion of a poking
motion. The object is also, by virtue of a considerably simplified positional adjustment,
to facilitate the complicated controlling of the control sleeves 5 in connection with
use of the above-specified ROTAFIRE\-method.
TECHNICAL SOLUTION
[0011] The above object is achieved by the fact that the invention provides furnace with
a device for manoeuvring an air-control mechanism according to subsequent Patent claim
1.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The invention will be described below with the aid of an illustrative embodiment
and with reference to the following drawings, in which:
Fig. 1 shows a side view of an air-control mechanism according to the invention,
Fig. 2 shows a sectional view of a jack screw driven by an electric motor, according
to an embodiment of the invention,
Fig. 3 shows a diagrammatic horizontal section through a so-called "soda pan".
DESCRIPTION OF A PREFERRED EMBODIMENT
[0013] In Figure 1, the reference numeral 1 denotes in general terms an air-control mechanism
in a furnace such as, for example, a soda furnace. The walls 2 of the furnace are
constituted by parallel-running and welded-together water-cooled tubes, which, amongst
themselves, are either sealed tight or combined with the aid of intermediate fins
(not shown) in order to achieve a gastight wall. By bending apart two neighbouring
tubes, sufficient space is created for an air-supply port through which the furnace
is provided with combustion air in the desired quantity. A number of such air-supply
ports (hereinafter referred to as air ports) communicate with an air box 4 situated
on the outer side of the wall 2. The air box 4 is connected, in turn, to a feed pipe
(not shown), through which the air box 4 is provided with warmed air.
[0014] The wall 2 is further covered, on the outer side, with insulating material (not shown
in the figure).
[0015] The air boxes 4 are situated at different levels and along different walls of the
furnace. The air boxes 4 are further divided into sections, whereby each section supplies
a certain number of air ports 3 with combustion air. The same air box 4 is able, for
example, to supply two, four or more air ports 3.
[0016] Connected to each air port 3 there is a control member 5 in the form of a sleeve,
hereinafter referred to as the control sleeve 5. It should be noted, however, that
the control member 5 can also be differently configured. The control sleeve 5 can
be axially displaced forwards and backwards, in a known manner, for positional adjustment
relative to a frame piece 6 defining the air port 3. The cross-sectional area within
the frame piece 6 of the air port 3 increases in the direction from the wall 2, i.e.
to the right in Fig. 1. The quantity of air which is allowed to flow into the furnace
is regulated by the fact that the control sleeve 5, as a result of the above-described
axial displacement, varies the annular gap area 7 which is formed between the inner
sides of the frame piece 7 and the end 10 of the control sleeve 5. The axial displacement
here takes place in the directions of the double arrow 8. The control sleeve 5 is
additionally arranged to be moved past the set air-regulating position, so that its
end 10 penetrates the air port 3 in order to remove coatings which have been deposited
in the said air port. This process is given the name "poking" and is performed at
regular intervals in order to keep the air ports 3 free from coatings which threaten
to block the air ports 3 such that the desired quantity of combustion air is eventually
no longer able to be supplied to the furnace. The poking is therefore realized by
the control sleeve 5 executing a forward stroke to the dashed position 11 in the figure,
after which it is retracted back to the set air-regulating position which obtained
prior to the poking.
[0017] According to the invention, the control member 5 is connected to a mechanical jack
screw 13 for the realization of its axial motions both for air-regulating positional
adjustment and for the removal of coatings by poking. The jack screw 13 is here driven
by an electric motor 14, whose rotation speed, running time and direction of running
are controlled by a control unit 15 which is coupled to the electric motor 14 via
a cabling element 16, which is well protected against the dirty environment and the
high temperatures which obtain in the vicinity of the furnace.
[0018] The jack screw 13 will now be more closely described with reference partly to Fig.
1 and partly to Fig. 2, which shows a partially cut view of the gear housing 18 of
the jack screw 13, with connected electric motor 14.
[0019] The electric motor 14 here drives an axle 19 mounted in the gear housing 18 at two
mounting points 20, 21. A worm screw 23 is additionally configured integrated with
the axle 19. This worm screw 23 is engaged with a corresponding worm wheel 24, which
is engaged internally with a trapezoidally threaded spindle screw 25 directed perpendicular
to the axle 19. The spindle screw 25 can therefore be displaced axially (in a direction
perpendicular to the plane of the paper in Fig. 2), in known fashion, whenever the
worm screw 23 is rotated with the aid of the electric motor 14.
[0020] The jack screw 13 is connected via a fixture 27 to an axle 28, which, together with
a parallel guide rod 29, is connected to the control sleeve 5. The axle 28 runs within
a cylindrical holder 31, which is fixed to the air box 4 and supports the gear housing
18 of the jack screw 13.
[0021] An electric motor-driven jack screw 13, adjusted to realize the axial motion of the
control sleeve 5 according to the present invention, makes it significantly easier
to perform the air-regulating positional adjustment in the axial direction of the
control sleeve 5, compared with previously known solutions using compressed-air driven
cylinders and requiring expensive auxiliary systems for positionally adjusting the
control sleeve 5 for air-regulation and for getting it to resume the set position
following completion of the poking motion. In the case of the solution using a jack
screw according to the invention, no such auxiliary systems are required since the
position of the control sleeve 5 is clearly determined by the gear ratio of the jack
screw 13 and the rotation speed and running time of the motor and can therefore easily
be adjusted with the aid of the control unit 15.
[0022] In the poking operation, the control sleeve 5 according to the invention moves at
an axial speed of around 20 mm/s, which calls for a relatively high gear ratio of
the jack screw 13. A gear ratio of at least 1:5 and preferably 1:7 has here been found
to be suitable for the powerful removal of even seriously solidified coatings in the
air port 3.
[0023] The invention offers a host of major advantages over known solutions using compressed-air
driven systems. The solution according to the invention yields, for example, 2-3 times
greater compressive force than corresponding compressed-air driven systems, which
means significantly more reliable removal of the coatings in the air ports. The solution
further offers a compact equipment unit with few vulnerable mechanical parts and quiet
and powerful running.
[0024] The positional adjustment of the control sleeve 5, which positional adjustment is
easy to handle and reliable compared with known compressed-air systems, facilitates
in large measure the complicated and, relative to adjacent control members 5, related
positional adjustment which is required in applications in soda pans where it is wished
to use the so-called ROTAFIRE\-method, in which case, by virtue of a specially regulated
air supply, a rotation or vortex motion of the combustion gases is created in the
horizontal plane of the soda pan, so that the waste liquor injected into the furnace
chamber is slung by the said vortex motion out towards the walls 2 of the furnace,
whilst simultaneously undergoing drying and pyrolysis. This application is illustrated
in Fig. 3, which shows a horizontal section through a rectangular soda pan. It should
however be noted that the soda pan can also be polygonal, such as an octagon, for
example, whilst maintaining the function according to the invention. A plurality of
ports 3 having associated control members 5 (not shown) are situated along the furnace
walls 2, where the mutual axial position of the control members 5 is such that a vortex
motion in the horizontal plane of the soda pan is realized by means of the combustion
air supplied through the ports 3. More closely described, at least two of the furnace
walls 2 are provided with their own individual aggregate 9 having ports 3, disposed
alongside one another, with associated control members 5 (not shown), in which those
control members 5 which are located on a first side of the centreline 12 of the aggregate
have been positioned at a greater axial distance from their respective ports 3 than
those control members 5 which are located on the other side of the said centreline
12, in such a way that the supplied combustion air makes a positive contribution to
the said vortex motion. In the figure, the vortex motion is illustrated by the arrow
17 and the air currents which make a positive contribution to the vortex motion are
indicated by the arrows 22, which flow out in the axial direction of the air ports
3. The air flow through the air ports 3 can be regulated within wide limits by individual
positional adjustment of the control sleeve 5, whereupon the air flow from one aggregate
9, for example, in the figure the lowermost aggregate along the one longitudinal side
of the furnace, is preferably introduced through, in the figure, the right part of
the aggregate. By interaction with at least one further aggregate of air ports 3,
situated on one of the other walls 2 of the pan, the vortex motion 17 is thus created
in the manner described above. The rotational direction of the vortex motion can be
turned at regular intervals in order to reduce unilateral wearing of the components
of the hearth. This turning is realized by inverting the positional adjustments of
the control sleeves 5, such that those ports 3 which were previously adjusted for
low air flow are now instead adjusted for high air flow and vice versa. It can here
easily be seen that the particularly simple and reliable positional adjustment of
the control sleeves 5 according to the invention considerably facilitates the complicated
regulation of the mutual axial position of the control sleeves 5. The same regulation
using existing compressed-air driven systems requires expensive and difficult to manoeuvre
positioning systems for the compressed-air driven cylinders.
[0025] One drawback with the previously known compressed-air driven systems is, as mentioned
above, that the pressure of the compressed-air network often varies. If the pressure
drops, the control sleeves then get stuck and can be burnt through. The electricity
network, on the other hand, has no such variations and the poking force can therefore
always be kept at the calculated level.
[0026] To sum up, the furnace with the device according to the invention offers considerably
improved poking capacity and an extremely reliable way of positionally adjusting the
control sleeve 5, and this, moreover, at lower cost compared with previously known
devices. The inventor has succeeded in overcoming a technical prejudice by showing
that electrically driven apparatus having suitable protection measures can be effectively
used even in a very dirty environment exhibiting a high ambient temperature.
[0027] The invention is not limited to the embodiment described above and illustrated in
the drawings, but can freely be varied within the scope of the following patent claims.
1. Furnace containing a device for manoevring an air control mechanism said furnace being
of the soda furnace type used for the combustion of waste liquor, provided with a
plurality of air-supply ports (3) in its walls (2), in which the said ports (3) communicate
with an air box (4) and in which each port (3) is provided with a control member (5)
which can be axially displaced forwards and backwards for positional adjustment relative
to the said port for the purpose of determining the volume of air passing through
the port, and in which the said control member (5) is additionally arranged to be
moved past the set air-regulating position, so that its end (10) during a so called
poking motion penetrates the port (3) in order to remove coatings which have been
deposited in the said port,
characterized in that the control member (5) is connected to a, by an electric motor (14) driven,
mechanical jack screw (13), with a gear ratio of at least 1:5, preferably 1:7, for
the realization of the control member's (5) axial motions both for air-regulating
positional adjustment and for the removal of in particular seriously solidified coatings.
2. Furnace containing a device for manoevring an air control mechanism according to Patent
Claim 1, characterized in that the axial position of the control member (5) is clearly determined by the gear
ratio of the jack screw (13) and the rotation speed and running time of the motor
(14).
3. Furnace containing a device for manoevring an air control mechanism according to Patent
Claim 1, characterized in that the mutual axial position of the control members (5) is such that a vortex motion
in the horizontal plane is realized by means of the combustion air supplied through
the ports (3).
4. Furnace containing a device for manoevring an air control mechanism according to Patent
Claim 3, in which at least two of the furnace walls (2) are provided with their own
individual aggregate (9) having ports (3), disposed alongside one another, with associated
control members (5), characterized in that those control members (5) which are located on a first side of the centreline
(12) of the aggregate have been positioned at a greater axial distance from their
respective ports (3) than those control members (5) which are located on the other
side of the said centreline (12), in such a way that the supplied combustion air realizes
the said vortex motion.
1. Ofen mit einer Vorrichtung zum Manövrieren eines Luftsteuermechanismus, wobei es sich
bei dem Ofen um einen Sodakessel handelt, der zur Verbrennung von Ablauge verwendet
wird, und er mit mehreren Luftzufuhröffnungen (3) in seinen Wänden (2) versehen ist,
wobei die Öffnungen (3) mit einem Luftkasten (4) in Verbindung stehen und wobei jede
Öffnung (3) mit einem Steuerglied (5) versehen ist, das zur Positionseinstellung bezüglich
der Öffnung zur Bestimmung des durch die Öffnung strömenden Luftvolumens axial nach
vorne und hinten verschoben werden kann, und wobei das Steuerglied (5) des weiteren
so angeordnet ist, daß es an der eingestellten Luftregulierposition vorbeibewegt werden
kann, so daß sein Ende (10) während einer sogenannten Stocherbewegung in die Öffnung
(3) eindringt, um Beschichtungen zu entfernen, die sich in der Öffnung abgesetzt haben,
dadurch gekennzeichnet, daß das Steuerglied (5) mit einer von einem Elektromotor
(14) angetriebenen mechanischen Hubspindel (13) mit einem Übersetzungsverhältnis von
mindestens 1:5, vorzugsweise 1:7, verbunden ist, uni die Axialbewegungen des Steuerglieds
(5) sowohl zur luftregulierenden Positionseinstellung als auch zur Entfernung insbesondere
von stark verfestigten Beschichtungen durchzuführen.
2. Ofen mit einer Vorrichtung zum Manövrieren eines Luftsteuermechanismus nach Anspruch
1, dadurch gekennzeichnet, daß die axiale Position des Steuerglieds (5) durch das
Übersetzungsverhältnis der Hubspindel (13) und der Drehzahl und Betriebszeit des Motors
(14) deutlich bestimmt wird.
3. Ofen mit einer Vorrichtung zum Manövrieren eines Luftsteuermechanismus nach Anspruch
1, dadurch gekennzeichnet, daß die gegenseitige axiale Position der Steuerglieder
(5) derart ist, daß eine Wirbelbewegung in der horizontalen Ebene mittels der durch
die Öffnungen (3) zugeführten Verbrennungsluft bewirkt wird.
4. Offen mit einer Vorrichtung zum Manövrieren eines Luftsteuermechanismus nach Anspruch
3, bei dem mindestens zwei der Offenwände (2) mit ihrem eigenen einzelnen Aggregat
(9) versehen sind, das nebeneinander angeordnete Öffnungen (3) mit zugeordneten Steuergliedern
(5) aufweist, dadurch gekennzeichnet, daß diese Steuerglieder (5), die sich auf einer
ersten Seite der Mittellinie (12) des Aggregats befinden, in einem größeren axialen
Abstand von ihren jeweiligen Öffnungen (3) positioniert wurden als jene Steuerglieder
(5), die sich auf der anderen Seite der Mittellinie (12) befinden, so daß die zugeführte
Verbrennungsluft die Wirbelbewegung bewirkt.
1. Fourneau contenant un dispositif pour manoeuvrer un mécanisme de régulation d'air,
ledit fourneau étant du type fourneau à soude utilisé pour la combustion de liqueur
usée, pourvu dans ses parois (2) d'une pluralité d'orifices (3) pour l'alimentation
d'air, dans lequel lesdits orifices (3) communiquent avec un caisson d'air (4) et
dans lequel chaque orifice (3) est pourvu d'un organe de régulation (5) qui peut être
déplacé axialement vers l'avant et vers l'arrière pour ajuster sa position par rapport
audit orifice afin de déterminer le volume d'air passant à travers l'orifice, et dans
lequel ledit organe de régulation (5) est disposé en outre de manière à être déplacé
au-delà de la position fixe de régulation d'air, de sorte que son extrémité (10),
au cours d'un mouvement dit de piquage, pénètre dans l'orifice (3) afin d'enlever
les revêtements qui se sont déposés dans ledit orifice,
caractérisé en ce que l'organe de régulation (5) est connecté à une vis de montée
mécanique (13) entraînée par un moteur électrique (14), avec un rapport d'engrenage
d'au moins 1:5, de préférence de 1:7, pour la réalisation des mouvements axiaux de
l'organe de régulation (5) à la fois pour ajuster sa position de régulation d'air
et pour enlever les revêtements en particulier fortement solidifiés.
2. Fourneau contenant un dispositif pour manoeuvrer un mécanisme de régulation d'air
selon la revendication 1, caractérisé en ce que la position axiale de l'organe de
régulation (5) est clairement définie par le rapport d'engrenage de la vis de montée
(13) et la vitesse de rotation et le temps de marche du moteur (14).
3. Fourneau contenant un dispositif pour manoeuvrer un mécanisme de régulation d'air
selon la revendication 1, caractérisé en ce que la position axiale respective des
organes de régulation (5) est telle qu'un mouvement de tourbillon dans le plan horizontal
soit réalisé au moyen de l'air de combustion alimenté par les orifices (3).
4. Fourneau contenant un dispositif pour manoeuvrer un mécanisme de régulation d'air
selon la revendication 3, dans lequel au moins deux des parois (2) du fourneau sont
pourvues de leur propre agrégat individuel (9) ayant des orifices (3) disposés l'un
à côté de l'autre, avec des organes de régulation (5) associés, caractérisé en ce
que les organes de régulation (5) qui sont situés d'un premier côté de l'axe central
(12) de l'agrégat ont été positionnés à une distance axiale de leurs orifices respectifs
(3) supérieure à celle des organes de régulation (5) qui sont situés de l'autre côté
dudit axe central (12), d'une manière telle que l'air de combustion fourni réalise
ledit mouvement de tourbillon.