Note: Descriptions are shown in the official language in which they were submitted.
2182373
WO 95/21016 I P~ t 10
APPARATUS FOR MIXlNG A FIRST FLUID INTO A SECOND FLUID
TECHNICAL FELD
5 The present invention relates to an apparatus for mixing a first fluid into a second
fluid, which apparatus comprises:
- a housing having a flow chamber for the said second fluid,
- a flow restrictor member in the flow chamber, and
- means for introducing the said first fluid into at least one gap between the flow
restrictor member and those walls of the chamber facing towards the flow
restrictor member. The invention relates, in particular, to an apparatus for
mixing a fluid, preferably a gaseous fluid such as, for example, steam, ozone
or oxygen gas, into a cellulose pulp suspension.
15 PRIORART
The heating of liquids and ! , ' by means of direct steam can be difficult to
carry out for a large number of reasons. One is the difficulty of atomizing the steam
and ~ "p~ y keeping the suspension in such motion that a smooth and
continuous c.l~ L .. - :,., takes place, which requires, namely, that the steam is evenly
20 atomized in the liquid or g~rPn~ n This is especially difficult when a large quantity
of steam is supplied. When steam is added, it occurs, moreover, that the volume of
the steam bubbles can be so great that the convection of heat between the steam and
the liquid is insufficient for the desired continuous ç~-n~iPnC~rilm Because ofthis,
t, violent steam implosions arise, causing shocks and vibrations. These can
25 be so violent that mechanical damage is incurred, which is ~ the greater the
quantity of steam to be added.
In general, a number of ~ Uil C~ can be placed upon a steam mixer. The steam
should be added such that local surpluses do not occur during passage through the
30 mixer. The d~ adaL;ull or so-called fluidization must take place in such a way that
local pressure variations are minimized. Any implosions which occur because of steam
bubbles should take place in a section in which the cu..l~Jc~ ,..L~ or the construction
material cannot suffer damage resulting from the cavitation-like phPn~mPn~ The
mixer should have some form of in-built elasticity to enable it to absorb pressure and
35 shocks caused by possible IllUl~ ly di~Lull in the steam and pulp flows up to and through the mixer.
... . . . . ... ... .. ...... . . ... ., .. _ . . . . _
WO 95/21016 18 2 3 7 ~ 2
A large number of A~ ' in ~ for mixing a gaseous fluid into a pulp suspension are
known. The Swedish Patent No. 468 341 describes an apparatus for mixing a
suspension of a cellulose-containing fibre material and a fluid such as, for example,
gases in the form of ozone, oxygen and chlorine and liquids containing various active
5 substances, e g. chlorine dioxide. In its basic principle, this mixer comprises a fiunnel-
shaped part and, in this, a conical moving part. Between the funnel-shaped part and
the conical part there is formed an adjustable gap through which the pulp passes. In
the walls of the ~ ' ' . ' part there are located a number of openings for the
fluid which is to be mr~ed into the passing pulp. Draw~acks with this apparatus are
10 that it is relatively large, that its " , especially in existing pipe systems, is
~ ., ' 1, since the flow direction of the pulp alters in the mixer, requiring that the
pipe system to which the mixer is to be cormected has to be redirected, and that the
mixer requires some form of stand or base on which to be mounted.
l S Also common are mixer devices having a rotary part for mixing ffuid into the pulp. A
problem in these devices is that the rotation gives rise to large pressure variations,
which create local zones of very low pressure to which the steam makes its way,
resulting in implosions as described above. A fiurther problem is to distribute the
steam evenly in the pulp s.rsr especially when large quantities of steam are to
20 be supplied, as a result of which capacity problems can also arise.
BREF DISCLOSURE OF THE INVENTION
The object of the present invention is to remedy the said problems. There is therefore
proposed, according to the invention, a blending or mixer apparatus which does not
25 have any rotary parts, which does not presuppose that the said second fluid, which
can consist, for example, of a pulp suspension, does not require that the flow alters its
principal flow direction, thereby making the apparatus suitable for installation in
existing pipe systems, which is compact in its l,Ulla~ u..~;oll and which does not require
a stand or base for its mounting.
These and other objects and advantages of the invention can be achieved by virtue of
the characteristics of the invention which are specified in the subsequent patent
claims. Further ~ a~ ;c~ and aspects and advantages of the invention can be
derived from the following description of a preferred . . . ,1 .c..l: .. 1
2182373
WO9S/21016 3 r~l. .t
BRIEF DESCRIPTION OF DRAWINGS
In the following description of a preferred ~IIIbU.' t, reference will be made to the
appended drawings, in which:
Fig. I is a partially cut-through end view of the apparatus according to the present
invention.
Fig. 2 is a side view in section taken along the line II-II in Figure 1.
Fig. 3 is a part view in section taken from Figure 2, showing the ~ '' of the
~lictrjhl~ti~n members, and
Fig. 4 is a p~ ,Liv~ view of a flow restrictor member forming part of the
apparatus.
Fig. 5 is a side view in section of an apparatus according to a modified c...~ - "
of the invention taken along the ,UI I ~-r ~' ~ section shown in Fig. 2,
Fig. 6 is a ~,, a~ iv~ view of a flow restrictor member included in an apparatusaccording to a modified ~;lllb~ ' of the invention, and5 Fig. 7 is a 1~ iv~ view of a flow restrictor member included in an apparatus
according to yet another ~" 1 ,~ l;, .... ,1 of the invention.
DE~SCRIPTION OF A PREFERRED EMBODlMLNT
The apparatus A comprises, according to the ~",1,-. 1; ,.. .,l, a main body I - hereinatter
20 referred to as the housing - which in turn exhibits a tubular or sleeve-shaped outer
wall 36, a first, plane end wall 37, a second end wall 38, which can also be plane but
which, according to the ~ I,u ' t, is inwardly conical, and between the said first
and second end walls a continuous elongated opening 39 - hereinafter referred to as
the flow chamber - which is limited to the sides by a pair of plane chamber walls ~, 10.
25 The shape of the flow chamber 39 will be described in greater detail below.
The flow chamber 39 divides the first, plane end wall into two circular-segment-shaped portions 37a and 37b and the second end wall 38 is also Cull~)ul~ ly
divided into two portions 38a and 38b, which can be described as conical segments or
30 plane, circular segments in the event ofthe end wall 38 being plane. Between the
outer wall 36 and the walls 5, 37a and 38a there is formed a first outer space 40a and
at the other side of the housing 1 there is l.;UI I ~-r ' ,,1~ formed a second outer
space 40b. Leading to these two first and second outer spaces 40a, 40b are supply
lines 41a, 41b for the fluid which has been referred to above as the first fluid and
35 which is to be mixed into the said second fluid. According to the r7,.1,o~;."~.,l the said
first fluid is intended to consist of steam, but can also, in other a~ nC of the
. _ . _ . _ . , . . .:, .. .. ... ... . . .. ....
~18237~
WO 95/21016 4 r~ o~l --
~ t ~`~
apparatus, consist of other gaseous fluids, e.g. oxygen, ozone, chlorine dioxide and/or
by a liquid.
The apparatus A is fastened, by means of the housing 1, between two pipelines 32,
33, which, according to the ~ o ' t, have the same diameter as the outer wall 365 of the housing 1. A different diameter is also, however, CU~ ;Vdblc The fastening can
be realized in a .,o.. . ~,...iullal manner by a flange joint. A pair of flanges on the housing
I are denûted by 34, 35. The apparatus A having the housing I is herein facing such
that the said second fluid flows firom the line 32 up through the flow chamber 39 and
onward up through the pipeline 33, the housing I facing with the plane, first end wall
10 37 towards the incoming pipeline 32 for the said second fluid and with the inwardly
conical, second end wall 38 facing towards the outgoing Ime 33.
At both ends of the flow chamber, the outer wall of the housing I is breached, thereby
forming lateral openings 43 and 44. Through these openings 43, 44, the flow chamber
lS 39 c.. " ,." ,. ~ with a pair of first and second cy1inder spaces 45 and 46
~,,.,~ c~,Li~ly~ disposed outside the housing 1. The associated first and second cylinders
27 and 28 are welded to the outer wall 36 of the housing I . In the cylinders 27, 28
there are located a first and a second piston 25 and 26, It~ ,Li~ . The said first
piston 25 is further connected by a piston rod 23 to a hydraulic piston 21 in a
20 hydraulic cylinder 20. A pair of supply lines for hydraulic oil have been denoted by
20a, 20b. Instead of hydraulic operation, pneumatic operation can also be envisaged.
The cylinder 2û consists in tbis case of a pneumatic cylinder and the lines 20a, 20b are
air lines.
25 In the flow chamber 39 there is disposed a flow restric,tor member 6, which extends
firom the first cylinder space 45, through the first lateral opening 43, onward through
the whole of the chamber 39 and, via the second lateral opening 44, into the second
cylinder space 46. At the same time as the flow restric;tor member 6 constitutes a
restrictor member in the flow chamber 6, it also constitutes a connecting element
30 between the two pistons 25 and 26, which are connected up to both ends of the flow
restrictor member 6.
The appearance of the integrated member, which consists of the flow restrictor
member 6, the said first and second pistons 25, 26, the piston rod 23 and the hydraulic
35 or pneumatic piston 21, is shown in Fig. 4. The 1. . ~ axis of the flow restrictor
member 6, also the centre a~is fûr the pistons 25 and 26, has been denoted by 24. This
WO 95/21016 ~ 1 8 2 3 7 3 P~ J - - IO~
s
is ~ d;~,ulal to the centre line 31 of the housing I, which ât the same time is the
prjncipal flow direction for the second fluid which is il allO~,v- ~ed through the pipelines
32 and 33 and into which the said first fluid is to be blended.
As can be seen flrom Figs. 1, 2 and 4, the flow restrictor member 6 has the general
shape of a six-sided polyhedron limited by a pair of side walls 7, 8, a bottom wall 48,
a top wall 49, a rear end wall 50, which is joined to the first piston 25, and a front end
wall 51, which is joined to the second piston 26. More specifically, the flow restrictor
member 6 is double wedge-shaped in that it is wedge-shaped both in its l--ngitll '
direction, i.e. in the direction ofthe axis 24, by virtue ofthe two side walls 7, 8
converging towards each other in a wedge shape, in the direction of the axis 24, from
the rear end wall 50 towards the front end wall 51, and in the transverse direction, by
virtue of the same end walls 7, 8 also converging towards each other in a wedge
shape, in the direction of the axis 31, from the top wall 49 towards the bottom wall 48
facing towards the inflowing second fluid.
The flow chamber 39 has a shape which is a~ uniform with the shape of
the flow restrictor member 6. When the flow restrictor member 6 is Oy i1ally
placed in the flow chamber 3 9, the side walls 7, 8 of the flow restrictor member,
however, form a small angle with the side walls 5 and 10, . ~O~ ,ly, of the chamber
39. There is thus formed between the said walls 5, 7 and 8, 10, ~ Liv~ly~ a gap 15
and 16, respectively, which widens somewhat in the flow direction. These two gaps
15, 16 constitute passages for the second fluid which is to pass from the pipeline 32,
through the apparatus A according to the invention, to the second line 3 3 . In
principle, the walls which define the gaps 15, 16 can be parallel in the position of
symmetry, but the small deviation from parallelism and hence the widening gap shape
is to be preferred.
The apparatus A further comprises means for introducing the said first fluid, which in
the envisaged application should be constituted by steam, into the gaps 15. 16. These
means comprise, on the one hand, the two outer spaces 40a and 40b and the supplylines 41a, 41b to these spaces and, on the other hand, holes 18 in the side walls 5 and
10 ofthe flow chambers 39. These holes 18 are distributed along the length oftheside walls 5, 10 and are preferably disposed closer to the inlet openings 11 and 1~,
l~ ,L;~.,IY~ ofthe two gaps 15 and 16 than their outlet openings 13 and 14,
respectively. The holes 18 can be configured, for example, as circular holes or as gaps
... . . . . .. ... .. . .... . .. .... . . ...
WO 95~21016 2 1 8 2 3 7 3 P~
or slots. The terrn "hol .shouid therefore not be given any restrictive meaning, but
should cover all thro~ openings, slots, etc., regardless of shape. In axial section, the
holes have a shape which widens from the outer spaces 40a, 40b to the gaps 15, 16.
This shape is particularly suitable where the second fluid, which flows up through the
5 gaps 15, 16, is a fibre-containing suspension. If the supply of the said second fluid -
the mix-in fluid - through the supply lines 41a, 41b were interrupted, whilst cellulose-
containing fibre material continues to flow through the apparatus A, then the holes 18
are blocked by the fibre material and do not penetrate into the outer spaces 40a, 40b.
When steam or a different blend-in fluid is tumed on again through the lines 41a and
4 Ib into the spaces 40a and 40b, l ~,O~ , this fluid will blow away the fibre plugs
in the holes 18, so that these again become ready for use.
As a variant or improvement, the holes, slots or equivalent 18 can be disposed in
separate ~ ,g~ plates, which can be screw-fastened and can fill a larger
15 opening in the side walls 5, 10. By having access to a number of such ' _ ' ' ~
plates, which can be provided with a different number of holes I g or with holes 18 of
different shape, location, size etc., the user can acquire increased u~ n ~ U~ O to
adapt the inflow of the first fluid, in the present case steam, to other conditions. If, for
example, the production conditions should alter in the larger installation of which the
20 apparatus according to the invention constitutes a part, an ~ . . .1 " :~,, ..1,1~ plate can be
replaced so that a plate is obtained having holes matched to the altered production
conditions.
It is also in fact possible to supply the steam or other first fluid via the flow restrictor
25 member 6, in which case openings are cul~ ,,ld;..cly disposed in the side walls 7, 8
of the said flow restrictor member, preferably close to the inlet openings 11, 12 of the
gaps 15, 16.
Also fomling part of the equipment are pressure-detecting sensors, mounted upstream
30 and duwl~oLl ~l~ of the apparatus, and govemor devices (these parts not shown) for
controlling the piston 21 by influencing the flow in the lines 20a, 20b in order thereby
to control the 1110 ~ . ' of the wedge-shaped flow restrictor member 6, in the
l""L;~ direction ofthe flow restrictor member, Ll. ..,~ ely to the pnncipal flowdirection for the pulp suspension or equivalent other fluid through the apparatus A,
3 5 thereby enabling the width of the gaps 15, 16 and hence also the flow through the
apparatus to be regulated.
-
21~2373
WO 95/21016 7 T ~ S,'~ [ 104
In the follov~ing description of how the apparatus functions, it is presupposed that the
fluid which flows up through the pipelines 33, 34 and which in the patent claims and
in the preceding text is referred to as the second fluid is a suspension of cellulose fibre
pulp in water, and that the said first fluid, which is to be introduced into this
5 sl-cr~ncil-n, is steam.
The pressure-detecting sensors (not shown) and the said governor devices measure or
receive the ..,.,~U~ values of the pressures in the fibre pulp suspension upstream
and du . . I.~ ,dlll of the apparatus A in order to register a pressure differential. The
10 governor devices compare the registered pressure differential with a predefined
desired value, which is set in ~ upon prevailing production conditions such
as L~ lul ~, uu... Jt~ y, pulp type and capacity. This setting is preferably made
" "~.
15 The governor device activates the control cylinder 20 by regulating the pressure
and/or flow through the hydraulic lines 20a and 20b, so that the flow restrictormember 6 is shifted for~vards or backwards in the direction ofthe axis 24, i.e.
ly to the principal flow direction coinciding with the axis 31, in order to set
the gaps 15, 16 to the desired width.
If, for example, the pressure increases on the in~et side, i.e. in the pipeline 32, this is
registered by the said sensors and governor devices, so that the control cylinder 20 is
activated and moves the flow restrictor member 6 ~ to the principal flow
direction 31, so that the width of the gaps 15, 16 increases. The thereby increased
25 flow area makes it possible for the blockage to be dispersed and for a greater pulp
flow to be obtained until the pressure on the inlet side drops and the pressure
differential returns to normal. The control cylinder 20 is then re-activated, so that the
gap widths diminish, this continuing to be repeated until a stable state is achieved.
30 The flow restrictor member 6 is controlled in its axial movements by the pistons 25,
26 in the cy~inders 27, 28, so that the Ifm~i~llfl;nol axis 24 ofthe flow restrictor
member 6, the ll-n~jtl l~in~l axis of which at the same time constitutes the centre axis
for the pistons 25, 26, will always coincide with the plane of symmetry of the flow
chamber 39, this plane of symmetry coinciding with the principal flow direction 31 in
35 the apparatus A. The flow restrictor member 6 is nc~ h~ , able to wobble, by
small rotational IllUv~ about its centre axis 24, due to the fact that the bearing
.. . .. .. . ..... .. .. . .. ..
2182373
WO 95/21016 8 1'~ 10-1 --
:
.
pistons 25, 26 are cylindrical. This means that if one of the gaps 15, 16 begins to be
blocked, the pressure in the other gap will increase and preferably in the region of the
outlet passages 13 or 14. This unbalanced pressure on the one or other ofthe side
walls 7 or 8 generates a torque which tums the restrictor member 6 about its centre
5 axis 24, thereby increasing the gap width where the gap is in the process of being
blocked. By increasing the gap width in the critical blockage region, the blockage or
"plugging" can be made to work loose. Above all, however, blockage of the gaps by
the mounting of the flow restrictor member 6 in the cylinders 27, 28 is avoided due to
the fact that the constant pressure variations which arise in the two gaps 15, 16
10 generate constant, small rotational movements of the flow restrictor member 26,
which inhibits blockage.
The pressure from the fluid flowing in the gaps 15, 16 acts upon the inner sides 29, 30
of the bearing pistons 25, 26 via the lateral openings 43, 44. The first piston 25, which
15 is placed closest to the control cylinder 20, has an inner surface 29 which is larger
than the surface 30 belonging to the other piston 27, which means that the pressure
from the flowing fluid endeavours to press the flow restrictor member 6 in the
direction of the control cylinder 20. This means that the control cylinder 20 operates
for the most part with a counter-pressure in order, so to speak, to resist the pressure
20 from the flowing medium. Where appropriate, a damping in the form of a pressure can
be imposed upon the other side of the control cylinder 20 so as to dampen the
from the flow restrictor member 6. A certain freedom of movement in the
"~ direction 24 of the flow restrictor member 6 is ~ , Lh~ desirable
since pressure variations in the said second fluid, which flows up through the
25 apparatus A, and the counter-pressure from the control cylmder 20 can generate
oscillating l.~ movements of the flow restrictor member 6, which also
counteract blockage or "plugging" of the gaps 15, 16. Where appropriate, the
apparatus A may also be provided with a vibrator, which is connected up to the
bearing piston 26 and acts in the 1~ direction of the flow restrictor member
30 6. . .
In order to control the flow of the said second fluid, i.e. the pulp suspension
according to the ~ I,od;ll.~ i, the narrower surface 48, facing towards the flowin~
medium, of the i. ~,It~ rr~ flow restnctor member 6 can be extended by a
35 projecting guiding body.
218~37
W0 95/21016 9 P~ 0~
Modified embodiments of the apparatus according to the invention will be described
below with reference to Figs. 5-7. In Figs. S and 6, details which have a directCU,lr~ in Figs. 1-4 have the same reference numbers with the addition of ',
and in Fig. 7 with the addition of s.
The apparatus A' comprises a main body or housing I ', with a first flat end wall 37'
and a second flat end wall 38' and between said first and second end walls 37', 38' a
flow chamber 39' with the same general forln as the flow chamber 39 in the previous
' The apparatus A' is mounted between the two pipelines 32' and 33' by
10 means of flange ~ analogous with the previous ~
In the flow chamber 39' there is disposed a flow restrictor member 6' which is
essentially formed as a six-sided polyhedron limited by a pair of side walls 7',8', a
curved bottom wall 48' and a curved upper wall 49'. Otherwise, the flow restrictor
15 member 6' may be designed in analogy with the flow restrictor member 6 in theprevious ~ ' However, it might be suitable to displace the centre axis 24' for
those pistons (cu,.,,."" " g to pistons 26, 27 in the previous e.lll,c ' t~ which
control the ...u . . of the flow restrictor member 6') closer to the bottom wall 48'
in order to center the flow restrictor member 6' under influence of the fluid flowing
20 through the flow chamber 39'.
According tû the, l ' t, the two side walls S' and 10' of the flow chamber 39'
consist of a pair of double plates, namely an outer plate 5A', I OA' wbich is securely
welded to the end walls 37', 38', and an inner plate 5B', lOB' which is detachably
25 attached to the respective outer plate 5A', lOA' by means of bolts 60. Between on
one hand the two inner plates 5B' and IOB' and on the other hand the side walls 7'
and 8' of the flow restrictor member 6', a gap 15' and 16' ~ JC~ is provided in
the same manner as for the previous;
- 30 Accordmg to the rl 1 ~1 ~O~ 1, the sides of the walls 5B' and I OB' facing the gaps I S '
and 16', are provided with elongated recesses or grooves 61 in order to increase the
turbulence of the fluid flowing through the gaps 15', 16' and thereby further improve
the mr~ing of the second fluid which is to be mixed with said first fluid in the gaps 15',
16' . In the lower part of each inner side plate 5B ' I OB ', a series of holes 18 ' are
provided for ;IlLlud~l~,;llg the said first fluid into the gaps 15', 16'. Behind these holes,
an elongated opening 18A' is provided in the respective outer side wall 5A', lOA'.
WO 9~ 016 218 2 3 7 3 r~ h ~ c lo4
Outside the elongated Qpenings 1 8A', an outer space 40a' and 40b', . c ",~,~,Li~ , is
provided. Supply lineg i i a' and 4 Ib' are connected to these outer spaces 40a' and
40b', ~ iv~ , for said first fluid.
S In the preamble to this patent ~ ' ;"" is mentioned that t, violent
steam implosions may arise when steam is mixed into a fluid, causing chocks and
vibrations. In order to attenuate such chocks and to prevent or reduce any vibrations
of the flow restrictor member 6', the following provisions are made. Each of the two
side walls 7', 8' of member 6' is provided with a recess 62 on the side of the wall
facmg the gap 15' or 16'. The recesses 62 take up the major part of the said wall sides
and are covered by a tbin sheet 63 of stair~ess steel. The covered recesses 62 may be
filled with sand, lead or steel shots, rubber or any other chock dampening material in a
manner which may be known per se.
15 The operation of the apparatus shown m Fig. S ~UII ~ -r ~ to the above described
operation of the apparatus A according to the previous ~ lbOd;~ . Therefor,
reference is made to the previous description regarding the operation.
In tbe above description of the ~mho.' according to Fig. 5, it was mentioned that
20 the axis 24' preferably is displaced towards the firont end wall 48' of the flow
restrictor member 6' in order to counteract tilting of the fiow restrictor member 6' in
the flow chamber 39'. The rll,l,o.~;.,...,l according to Fig. 6 shows another way of
efficiently preventing such tilting. According to this ,, ' ' t, the two centre axis
24' and 24" of pistons 25' and 26', I~ ,ly, are parallel and displaced relative
each other. Preferably, they are displaced in such a way that the axis 24' and 24" are
in a vertical plane coinciding with the plane of symmetry of the flow restrictormember 6'.
In the ~;111' '' of Fig. 7, a guide pin 50, 51 is used on each of the pistons 25x and
26x, or optionally only on one of these in order to prevent tilting of the flow restrictor
member 6x. The guide pins 60, 61 are parallel with the piston axis and housed in the
respective cylinder house, not shown. "
The above-described apparatus A according to the invention exhibits a large number
35 of advantages over a~J~Jald~u~D according to the pnor art. It has a ~ub~all~ially
simpler design, is very compact and is simple to install in existing pipe systems. This
2182t.;~
WO95121016 11 PCI/SE9'..1DIO~
can be achieved by the fact that a pipe, in which the apparatus A is to be mounted,
oniy needs to be cut off in t~vo places in order to r ~ ' the apparatus, after
which the apparatus is suitably connected, e.g. by a flange joint, to the thus cut-off
pipe, with the pipelines 32 and 33 above ~UlI~ iillg to the cut-off parts of the
S pipe. No stand or base is needed to support the apparatus A which also facilitates
" ' A further advantage is that the principai flow, i.e. the flow ofthe pulp
suspension (the said second fluid), does not need to aiter its principai flow direction
through the apparatus A, which means that a high velocrty of the fluid through the
gaps 15, 16 can be 1, which means, in turn, that the added steam or other
10 first fluid is well distributed in the second fluid (pulp suspension), thereby aiso
reducing the risk of implosions. If such implosions should n~,v~ Lh~ ,, occur, they
will occur du....,~ l and wiil not therefore cause any serious problems. Anotheradvantage of the apparatus A is that, as a result of its design, inter alia its mounting, it
effectively inhibits blockage due to the fact that the flow restrictor member has a5 certain freedom of movement both in its Inn~ ' ' direction and about its
l axis.
