Note: Descriptions are shown in the official language in which they were submitted.
~7~7~
BACKGROUND OF THE DISCLOSURE
_
1 Field of the Invention
__ _ _
This invention relates to a process for admixing
liquid components and to apparatus for carrying out
the admixing and is more particulaxly concerned with an
improved process and app~ratus for mixing liquid
components which enter into rapid chemical reaction
immediataly upon admixture.
2. escri~ on of the Prior Art
,: :
lQ Certain chemical reactions which are routinely
carried out on a commercial scale pos~ a very serious
problem because of the speed with which the reaction
takes place after the reactants are brought together.
The efficiency of mixing o such reactants is of
critical importance in carrying out the desired reaction.
Thu~, if the mixture o~ reactants lS not homogeneous
- when the reaction commences there will be variation,
rom site to site within the reaction mixture, of
the relative molar proportions of the reactants. Such
variation can lead to the formation of different products
at the different sites.
The reaction between phosgene and polyamines to
form polyisocyanates and the reaction between aniline and
formaldehyde, usually in the presence of hydrochloric
acid, to form methylene-bxidged polyphenyl polyamines,
are two such reactions. In both of these reactions the
initiation of reaction after admixture of the reactants
is almost instantaneous. Further, inefficient admixture
of the reactants can g~ive xise in both cases to the
formation of solid by-products which tend to separate as
:~7~
they are formed. Such deposition can, in certain circumstances, -
lead to clogging of apparatus and eventually to shutdown of the
reaction process.
Much attention has been paid in the prior art to the
particular problem of seeking to minimize the effects of solid
deposition in carrying out the above types of reactionO Thus,
the use has been reported of a rotary mixer with high shear mix
zone (U.S. patent 3,781,320 issued December 25, 1973 to Irwin),
of a high speed mixer (U.S. patent 3,188,337 issued June 8, 1965
to Gemassmer), and of a multi-staye rotary pump (U.S. patent ~-
3,947,4g4 issued March 30, 1976 to Mitrowsky et al). ~he latter
reference gives a lengthy analysis of the various prior art
methods which have been utilized for this type of reaction.
~,
One of the most successful devides hitherto employed in
the art for carrying out the above xeactions is that described
in U.S. patent 3~507,626 issued April 21, 1970 to Van Horn, and
:::.
~` the improvPment~thereof whi~h is described in British Patent
1,238,669 issued May 25, 1971. In the latter reference a device is
described by means of which the two streams of reactants are
caused to follow init~ially parallel annular paths one of which
ultimately flares ou~wardly and is united with the other, the
mixed fluids being carried rapidly downstream from the point
of mixing so that backmixing and deposition of by-pxoduct
solids at the site of mixing are both minimized. It has been
found, however, that even the use of this device gives rise
eventually to the buildup of layers of solid on the walls of
the mixing device adjacent the point o admixture of the two
reactant streams~ This leads to channeling of product in the
- mixing device and ultimately
. . ~
~:~37~6
requires that the device be taken out of service for
cleaning and repairs.
We have now found that the problems hitherto
encountered in the art in the efficient admixing of
highly reactive components can be minimized or eliminated
using the novel apparatus and process which are described
hexeinafter. Further, we have found that the increased
e~ficiency of mixing of the reactant~ which i5 achieved
by the process and apparatus herein described~ results
in production of end product of improved properties not
all of which appear to be a~tributable soleIy to the
more efficient mlxing of the starting reac~ants.
SUMMARY OF THE INVENTION
This invention comprises a method for intimately
mixing first and second liquid components which enter
into reaction one with another substantially immediately
after they are broughttogether which method comprises:
.
introduoin~ said first liquid component
under pressure in the form of a fan-shaped spray
into a substantially cylindrically shaped mixing
chamber ln a direction substantially along the
longitudinal axis of said mixing chamber;
simultaneously introducing said second
liquid component under pressure into the path
of said first li~uid component in said mixing
chamber, in a direction substantially ~erpen-
dicular to the direction of the spray of said `-
first component, in the orm of at least two
fan-shaped sprays; and
conducting the resulting mixture of said
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two liquid components from said mixing
chamber to a subsequent reaction zone.
The invention also comprises apparatus adapted to
carry out the above process which apparatus comprises
S in combination:
a substantially cylindrically shaped
mixing chamber provided with exi.t means at
one end thereof and a plurality of inle-t
means at the other end thereof;
a first jet inlet means disposed
suhstantially symmetrically in the end of
the said mixing chambex remote from said exit
means and having the nozzle of said jet means
directed substantially along the longitudinal
axis of said mixing chamber;
at least two additional jet :inlet means
disposed in the slde walls of said mixing~
chamber at the end thereof remote from said
exlt means, the nozzles of said jets being
20 . directed towards the longitudinal axis of
said mixing chamber and in a plane at right
angles~to said axis;
means for introducing a first liquid
component under pressure through said first
jet inlet means;
means for introducing a second liquid
component under pressure simultaneously through ;each of said additional jet inlet means; and
means for conducting mixed liquid components
from said exi~ port to a subsequent reaction zone~
:~ _5_
~3~7~
BRIEF DESCRIPTION OE THE DRAWINGS ~ ~:
.
FIGURE 1 : is a pictorial representation, partly in
cross-section, of a side elevation of
one embodiment of an apparatus for inter-
mingling highly reactive components in
accordance with the invention.
FIGURE 2 : is a ~ross-sectional view taken along
the line A-A o~ the apparatus shown in
FIGURE 1.
FIGU~E 3 : is a perspecti~e vlew of a jet nozzle : .
employed in the embodiment of an .:~:
apparatus according to the invention. ~:
FI&URE 3A : is a plan view~o the top of the jet ,.
: - .
nozzle shown in FIGURE 3.
FIGURE 3B :: is a~plan view of an alternative embodi~
ment of ~a~top of a~jet nozzle for use~in
: the apparatus and~:method o:~ the lnvention. ~;
~ :FIGURE 4 : is a~pictorial~ representation of one ~ `
: : embodiment:~of the manner in which sprays ~ ;
: . :
.' 20 : o~ liquid components are brought together
in accordance:with the invention.
~ FIGUR~ 5 : is a~:pictorial represen~a~ion of another
`. : embodim~n~ o the manner in which sprays
of~liquld components are brought together
. - in accordance with the in~ention.
DETAILED ~ CRIPTION OF T~E INVENTION
. Re~erenoe is made: to FIGURE: l wherein there is shown
.. a side eIevation, partly in:cross-section, of one
-- embodiment of an apparatus in accordance with the invention
and to FIGURE 2 wherein there is shown a partial cross-sectional
. -6-
37~6
view taken along line A~A of FIGU~E 1. The embodiment
shown in FIGS. 1 and 2 is composed basically of a
hollow T-shap~d housing (2) having a hollow spool (4)
disposed in the crossbar section o the housing (2).
The spool (4) is provided with an annular passage (6)
; and with cylindrical channels (8), (10) and (12)
each of which communicateswith a mixing chamber (14)
formed by the inner walls o~ the spool (4). The mixing
chamber (14) has a bell shaped opening which leads to
an exit pipe ~20~ via lined pasaageway (18), said lining
being of material such as tungsten carbide which will
: withstand abrasion, corrosion and like forces to which
: it might be subjected by the particular reaction mixture
caused to pass therethrough.
Each of the cha~nels (8), (10) and (12) is adapted
to receive a fan jet~spray nozzle shown respectively as
~223, (24) and (26), the nozzle tips of which project
:
into the mixing chamber:(14). The precise extent to which
::, said nozzle tips project into the mixing chamber (14)
is limited by the provision of flanges (28), (30~ and (32)
on the outer ends o the baxrels of nozzles (22), (24)
and (26~ respectively, which flanges engage with corres-
ponding grooves provided in the outer ends of the
respect.lve channels (8), (10) and (12). The fan jet
:: 25 spray nozzle (22) and the channel (8) within which it :
is locate~ are aligned with their longi~udinal axes
disposed co-axialIy with the longitudinal axis of the
spool (4). The longitudinal axes of the fan jet spray
nozzles (24) and (26), and the respective channels (10)
and (12) in which they are housed, are aligned along a
`` ~137~7~i
CQmmon axis which is substantially perpendicular to
the longitudinal axis of the spool (4).
Each o~ said spray jet nozzles (22~, (24) and (26)
is in sliding engagement with its respective housing
channels ~8), (10) and (12). The no~zles ~24) and (26)
axe held in place by contact between their outer ends
and the inner wall of the housing (2)o The nozzle (22) :: .
is held in place by a flange tip (34) having cylindrical
.~
passageway ~35) which, in turn, is held in place in
sealing engagement with the end of the crossbar section
o housing (2) by means of set screws (36) and (38)
. and O-ring (40)O The spool (4) is also thereby secured :~
in place in fluid tight engage~entwith the interior of
housing (2) by means of O-rings (51) and (51a), and by
the contact of flange (53~ with the corresponding flange
: on the interior of housing (2). Additiona~l means for
locking the nozzles~(22), (24) and (26) in place can ~:
be provided in the form of locking clips (not shown) and
the like, if desired.
The interior of feed pipe (42) communicates with
passageway (35) in spool (34) and permits one of the
two fluid components which are to be mixed to be fed to
fan jet spray nozzle (22). The second of the two liquid
components is fed`'through inlet port (52~ via a feed
~pipe (not shown) which can be attached in sealing engage-
ment at said inlet port using flange (54) and gasket surface
(56). Fluid fed through inIet port (52) passes to
i annular passage (6) and thence to fan je~ spray nozzles
(24) and (26).
FIGURE 3 is a perspec~ive drawing illustrating the
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7~6
configur~tion of a typical fan jet spray nozzlewhich can be employed in the embodiments shown in
FIGURES 1 and 2. The nozzle mouth (58) shown in
the jet nozzle in FIGURE 3 is elliptical in
cxoss-section as can be seen more readily in
FIGURE 3A which is a plan view of the top of the
jet nozæle shown in FIGURE 3. While this is the
preferred configuration for use in the process and
apparatus of the invention, it is also possible to
use other configurations. Illustratively, the
nozzle mouth of the je~ noz~le~can be circular
in cross-section and frusto-conical in overall
- configuration with the base of the frustum uppermost
as illustrated in the plan view of the top of the
jet nozzle shown in FIGURE 3B.
The~ three fan~et spray nozzles (22), (24) and
(26) can be identical in all respects or, in a
pre~erred embodiment discussed further below, the fan
iet spray nozzle~(22) is one whioh produces a smaller
spray pattern arc than the other two nozzles which
latter are preferably identical, i.e~ pro~uce identical
spray patterns.~
In carrying out the admixing of two highly
reactive fluid components using the illustrative
apparatus described~above with reference to FIGURES
l, 2 and 3, a first liquid component is fed under
pressure via feed pipe (42) and channel (35) to the
fan jet spray nozzle ~22). Advantageously, the
; pressure used lS of the order of 150 psi to 7Q0 psi
, 30 although the exact pressure employed in any given
_g _
~37~7~;
instance i5 not critical. The second fluid component
necessary for the xeaction is fed under pressure,
advantageously substantially equal to the pressure
employed for the first component, via feed inlet (52)
and annular passageway (6) to each of an jet ~pray :
nozzles (24) and (26).
The two s-~reams of said second component issuing
from said nozzles (24) and (26) into mixing chamber (14)
are preferably identical in shape and symmetrically
disposed one towards the othe.r so that the two streams
intersect in a plane coinciaent with the Longitudinal
axis of the mixing chamber (14). The stream of said
first fluid component issuing from fan jet spray nozzle
(22) into mixing chamber (14) intersects with the two
opposing streams of the second fluid component thereby
effecting highly efficient mixing of the two components
: under conditions of high turbulence~
The precisP position of th~ individual fan jet
spray nozzles and the design of the jets therein, the
size and.configur tion of the mixing chamber (14) and
tha spray patterns produced by the various nozzles, are
all actors which influence the efficiency of the mixing
of the two fluid c:mponents. The exact combination
of these factors which will give the most favorable
results for the mixing of a given pair of fluid components
is something which can be determined by a process of trial
and error~
In general r however, it is found preferable to employ
fan jet spray nozzles which produce a so called "flat"
spray, i.e. a spray which is elliptical in cross-section,
10- -
.
~37~6
such as illustrated in FIGURES 3 and 3A, and mo~t prefer- .
ably one in which the elliptical cross-section has a
longitudinal axis which is at least 1.5 times the shortest
axis. Further, it is found highly advantageous to select
fan jet spray no.zles with the appxopria~e jets to produce
flat sprays and to orient them in such a manner as to
produce an intersecting spray pa~ern such as that shown,
in highly idealized fashion, in the perspective drawing
shown in FIGURE 4. In this embodiment the ~lat spray
patterns issuing from fan jet spray nozzles (24) and
(26) are symmetrically disposed and have an elliptical
cross-section whose longitudinal axis, represented by the
common axis X-X at the plane of in~ersection o~ the two
streams, is perpendicular to the direction in which the
spray of the other component is issuing from the fan jet
spray nozzle (22). Further, the latter is a flat spray
pattern having an elliptical cross-section whose longitudinal
axis, represented by Y-Y at the point at which this spray
pattern intersects with the sprays from nozzles (24) and
(26), is perpendicular to the direction of the latter
two sprays. Finally, the confiyuration and location of
fan jet spray nozzle (22), relative to the configuration
and location o~ the other two nozzles, is so chosen that
the width of the spray-pattern of the spray issuing from
:: 25 nozzle (22) is significantly less than ~he width of the
spray pattern from the o~her two nozzles at the point
: at which the two patterns intersect.
FIGURE 5 illustrates another type of spray pattern
: which can be employed in which the flat~ spray pattern
issuiny from fan je~ spray noææle (22) has been rotated
37~7~
through an angle of substantially 90 from that shown
in the embodiment of ~IGURE 4 so that the longitudinal
axis Y-Y o~ the elliptical cross~section of said
spray pattern at the point of intersection with the other
two sprays is aligned in the same direction as the latter
sprays. In both of ~he embodiments shown in FIGURES 4
and 5 the spray patterns illustrated serve to ensure that
the fluid reactant component issuing as the spray ~rom
nozæle (22) is completely surrounded and enveloped
by the second fluid reactant issuing from spray nozzles
~24~ and (26). :
As will be obvious to one skilled in the art, the
particular combination of spray patterns shown in FIGURES
4 and 5 can be achieved in a number of ways. Illustratively~
one can use identical nozzles, all designed to give the
:'
;~ same elliptical spray pattern, in each of the three
positions but locating the nozzle (22) in a position such
that the distance through which~the spray from said nozzle
has to travel before it intersects with the spray from
the other two nozzles (24) and (26) is less than half
the distance between the latter two no2zles. Alternatively,
the three nozzles can be located substantially symmetrically
in the mixing chamber (14) so that the distance which the
spray from each nozzle has to travel before reaching the 25 point of intersection is substantially the same in all
cases. However, in order to achieve the desired result
in these circumstances, the fan jet spray nozzle (22)
is so chosen that the maximum angl~ described by the fan
spray pattern issulng therefrom is significantly less
than that described by ~he fan spray patterns issuing from
-12-
3~71~76
nozzles (24) and (26). Illustratively, in such an
embodiment the fan jet spray nozzle (22~ is so chosen ~'
that it produces a fan spray pattern which describes
an angle of about 45 while the fan spray pattern issuing
from nozzles (24) and (26) describes a maximum angle
of about 90.
While the above discussion and the various
embodiments illustrated in FIGURES 1, 2, 4 and 5 have
been limited to the use of only two fan jet spray
nozzles (24) and (26) to introduce the second liquid
component, it will be obvious that three or more
such nozzles could also be used, the only requirement
being that each such nozzle is disposed so that the
:
spray therefrom is projected in a direction towards the
central axis of the mixing chamber (14) and at right
angles to the direction of spray from the~nozzle (22).
The~bringing toqether of the two fluid components,
;~ using any of the various embodiments described above,
results in highly efficient mixing with very turbulent
conditions in the mixing chamber (14). In the particular
embodiments shawn in FIGURES 1 and 2 above the closed
end of the mixing chamber (14), i.e. the end which ~:
houses the three nozzles (22), (24~ and (26), is shown
as being hemispherical in configuration. This is a
very convenient configuration insofar as it ensures that
there are no "dead" spots in this location which might
lead to build up of deposited solids, etc. However, this
particular configur~tion is not critical to success `
and other configurations of this area of the mixing chamber
can be employed without de~racting from the overall
~L~ 3~
excellent mixing achieved by the process of the
invention.
The overall length of the mixing chamber (14) and
diameter thereof are not critlcal to success of the
method of the invention and the most appropriate dimensions
to be employed or achievins optimum mixing of any
particular combination of reactan~s can readily be
determined by a process of trial and error.
The fluid mixture resulting from the bringing
together of the two liquid components in the above
manner passes in a continuous manner under pressure
from the mixing chamber ~14) via the exlt pipe ~0~
to a further reaction zone (not shown) wherein the mixture
is subjected to further treatment in accordance wlth
procedures conventional in the art for whatever particulax
reaction is being carried out. The exit~(16) from th
mixing chamber (14) is shown, in the particular embodiments
illustrated in ~IGU~ES 1 and 2, as having a flared
bell-Like configuration. This is not a critical feature
of the mixing process and apparatus of the invention
but is merely a convenient manner of accomplishing a
smooth~passage of miYed reactants from the mixing chamber
(14) to the ~xit~pipe (20) which, in the particular
embodLment shown, has a greater internal diameter than
the mixing chamber itself. The particular configuration
shown for exit section (16) ensures that there are no
restrictions~pockets and the like which can lead to
- buildup of deposits or create "dead" spots, i.e.
accumulations of mixed reactants which are bypassed by
; 30 the main stre~m of mixed reactants.
. .
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~L~37~76
Similarly the use of the special liner (18),
which is shown in the paxticular embodiments illustrated
in FIGURES 1 and 2, is an optional feature intended to
ensure longer life of the apparatus~ i.e. to protect
against corrosion and abrasive forces and the like,
and is not a critical eature of the method and
apparatus of the invention.
The method of the in~ention can be applied to
achieve mixing of any of a wide variety of reactants
which are known to undergo rapid reaction lmmediately
after they are;brought together and which, therefore,
require highly efficient and rapid mixing in order to
ensure a homogeneous reaction mixture and, hence, a
;~ homogeneous reactlon product. Illustrative of such
- 15 reactions are that which involve the reaction between
polyami~es and phosgene (both components being employed
as solutions in an inert solvent such as chloroben~ene~
.
; to produce the corresponding isocyanates and the reaction
between aniline (as an aqueous solution containing
hydrochloric acid) and aqueous formaldehyde to produce
a mixture o methylene~bridged polyphenyl po}yamines. `~``
Both of these reactions are wPll-recognized in the art
as capable of producing unwanted by-products so~e of
:
which are solid in nature. The formation o~ these
solid by-products nas caused considerable problems in
carrying out the reactions in question because of rapid
.
buildup of deposits of the solids in the apparatus
hitherto employed to bring the reactants together. In
many instances the buildup of solids occurs so rapidly
that it is necessary to shut down the process to effect
--1 5~
3~7~ 1
cleaning of the apparatus at frequent intervals. Such ~`
requiremen~s are clearly highly undesirable particularly
in pxocesses which are required to be run on a continuous
basis.
The use of the method and apparatus of this invention
has been found to obviate the difficulties hitherto
involved in reactions of the above type and has enabled
the reactions in question to be carried out continuously
over prolonged periods with no significant buildup of
solid deposits. Furthex, it is found that the reaction
products achieved by use of the method and apparatus of
the invention are characterized by a markedly improved
uniformity of composition and a markedly lower proportion
of undesirable by-products than products produced in
accordance with prior procedures.
The process of reactlng polyamines with phosgene
to produce polylsocyanates and the process of reacting
:-~ aniline with formaldehyde (generally in the presence of
: aqueous hydrochloric acid incorporated in the aniline :
stream~ to produce methylene bridged polyphenyl polyamines
are both characterized by the fact that one reactant, ~ ;
namely phosgene in the first case and aniline in the second
case, is generally present in. excess of the stoichiometric
amount required for the reaction. In all such cases the
reactant which is to be employed in excess is the reactant
which is fed to the two nozzles (24)and ~26) in the
~ embodiments shown in FIGURE5 1 and 2 and the other reactant
is the one fed to the nozzle (22).
It is to be understood that, while tha method and
~: 30 apparatus of the invention have been described above by
-16-
-` ` il3 ~0~76
reference to certain particular embodiments thereof,
it is to be clearly understood that these embodiments
have been given for purposes of illustration only and
are not intended to be limiting. The scope of the
S invantion i5 bounded only by the scope o the claims
which are set out hereafter.
.
.
'' ' . :' '
:. . - .
~ 17
