Note: Descriptions are shown in the official language in which they were submitted.
1~32~5(~
The present invention is concerned with a process for the treatment
of substances in liqllid, semi-liquid or paste form, by another, more partic-
ularly, a gaseous phase. It applies, in particular, to the treatment of sub-
stances in liquid form, whether or not they contain solids in suspension, by
a gas at a high temperature.
This problem is well known~ for example, in connection with the
treatment of waste-water capable of being converted to substances dried by
oxidation.
Several solutions for this problem have already been suggested.
For example, French Patent 2 075 35~ suggests disposing of liquid
industrial wastes by transforming them into solid wastes by treating them
with a solution of silicate and a means for capturing the silicate. This is
obviously not a simple solution since it requires compounds not contained in
the waste water, involves several stages, and produces a compound which it is
desirable to remove. In this case, it becomes necessary to obtain solid
residues resistant to dilution with water, so that they may be incorporated
into certain types of ground formationsand may thus be recycled.
A totally different solution is proposed in French Patent
2 320 268. In this case the water, at a pH value of less than 7 and at tem-
peratures of between 20 and 200 C, is brought into contact with pure indus-
trial ox~-gen, at a pressure between normal and 20 bars, until the sulphur has
been converted into thiosulphates, and by then converting these thiosulphates
into sulphates, with industrial oxygen, at a pH of between 0 and 5, or between
0 and 8 for waste-waters containing only sulphates, at temperatures of be-
tween 20 and 200 C and at pressures of up to 20 bars~ possibly in the pres-
ence of catalysts.
It will be appreciated that this is also a lengthy operation having
several steps and involving physical and chemical treatments.
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More recently, in applicant's French Patent 2,406,610, it was proposed
to subject such waste-water to simultaneous atomizing and thermal oxidation and
then to separate, in a simple manner, the solid residues from the volatile
compounds.
In a practical application it has been proposed to use the process
according to FR 2,257,326 of bringing together substances present in different
phases, in which at least one phase is used to form an axially-symmetrical
vortex-sink flow, and at least one phase is introduced along the axis of symmetry
of the vortex-sink flow until, in the depression area of the said vortex-sink
flow, the quantity of movements of the volumetric elements of the vortex-sink
flow, in relation to the volumetric elements of the axial phase, are such that
the vortex-sink flow produces simultaneous disintegration, dispersion and take-
over of the axial phase, and possible treatment thereof by the vortex-sink flow.
The conditions of the treatment are, however, very demanding, since temperatures
of the order of 900 to 1200 C are required.
This entails the use of heads which can withstand such temperatures
and can resist the action of the products treated at these temperatures in an
oxidizing atmosphere, which is impossible with conventional spray heads.
It is for this reason that in applicant's French Patent 2,419,754, a
new device is proposed for carrying out the process according to FR 2,257,326,
that device comprising a unit producing a vortex-sink flow. The unit consists
of a body of revolution defining an annular space into which the gaseous phase
is introduced tangentially, limited by an axially-symmetrical distributing device
imparting axial symmetry, to the helicoidal flow thus produced, the flow from the
distributor being mechanically independent of the rigid unit of revolution. This
makes it possible to cool the unit satisfactorily, and the gaseous phase may be
raised to a very high temperature.
~nfortunately it is not always easy to produce such a device and it was
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found that excellent results could be obtained quite simply with the process
according to the invention.
The present invention provides a process for treating substances in a
first phase comprising a liquid, semiliquid, or paste phase, by a gaseous phase
wherein in a first reaction zone in a reaction chamber, a reaction is produced
between flows of fluids in an area remote from the chamber wall, by introducing
a first fluid, comprising a gas, in the form of a symmetrical helicoidal flow
which defines a symmetrical axial zone into which zone there is introduced
axially a second fluid comprising substance capable of reacting with the gas of
the helicoidal flow, said substance being brought to a temperature at which
reaction begins, the product of reaction of the helical flow and said substance
being passed from said reaction chamber to a treatment zone through a constricted
space in a vortex-sink flow; said first phase to be treated being introduced into
said treatment zone along the axis of revolution of the vortex-sink flow in such
a manner as to produce in said treatment zone simultaneously, disintegration,
dispersion and take-over of said first phase by the vortex-sink flow, the volume
throughput of the said vortex-sink flow at said constricted space being equal to
at least 100 times that of the volume of said first phase.
From another aspect, the invention provides apparatus for treating a
substance in a first phase comprising a liquid, semiliquid or paste phase com-
prising an external casing with a surface of revolution defining a reaction
chamber closed at one end and having a constricted outlet passage at the other
end, the said chamber also comprising a perforated internal wall defining, with
the said external casing, an annular space communicating with at least one
^ tangential inlet for a gaseous phase, said chamber also comprising means for the
axial in;ection of a substance through the closed end of the said casing for
reaction with said gaseous phase, said reaction chamber being extended beyond
:~ the constricted passage, by a treatment zone of increased cross section into
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which opens, substantially at the smallest cross section of the constricted
passage, a co~axial injection device for a substance to be treated.
It is desirable to introduce the gas at a pressure of less than 1 bar
(and preferably between 0,2 and 0,5 bar) above the pressure obtaining downstream
of the contact zone, the velocity being generally between 10 and 100 m/s, prefer-
ably between 30 and 60 m/s.
The injection velocity of the substance to be reacted with the gas may
be of the order of between 100 and 150 m/s.
In one embodiment the reaction zone is a combustion zone. The sub-
stance introduced axially into this reaction zone is then constituted by a
vapourizing phase, for example fuel or any combustible material injected
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into the inlet of the zone and along the axis of symmetry of the helicoidal
flow. This may be done by means of a conventional atomizing process such as
by pressure or rotation; or use may be made of the process according to
FR 2 257 326, wherein drops are ~ro~ed by transfer of part of the large rota-
tional energy of the vortex-sink flow. In this case, the helicoidal flow
consists of a gaseous phase generally burning with ambient air~ It is to be
understood, however, that this form of execution is in no way restrictive.
The substance to be treated is introduced in a ~et axially, in
liquid, semiliquid or paste form, at the end of the combustion zone, the
velocity of introduction being of the order of 0,03 to 10 m/s. In this way,
the symmetrical vortex-sink flow disintegrates the liquid ~et by transfer of
rotational energy. This pemits simple, high-temperature treatment of liquid
substances, since it inhibits contact between the products a~d the walls and
thus avoids raising the walls to the treatment temperature.
The gases at the outlet from the combustion zone may easily be
raised to a temperature of between 900 and 1200 C, so that it becomes pos-
sible to introduce the substance to be treated at ambient temperature.
One particular application of the present invention relates to the
treatment of waste-water. This is known to require evaporation of a large
quantity of liquid, oxidiæing heat-treatment, and separation of the solids
thus obtained from the volatile compounds.
The process is particularly applicable to waste-water containing
- up to between 20 and 30% of dry material, some of which, such as sulphides
and polysulphides, may be oxidized and eliminated in the form of sulphates.
It is desirable in this case to raise the gas at the outlet from the com-
bustion zone to a temperature of between 900 and 1200 C, the temperature in
the treatment zone being between 350 and 500 C. Cooling may be applied at
the outlet from the treatment zone.
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It is also possible to provide, at the outlet from the treatment zone,
a device producing a rotary flow which, in its simple form, is a stationary
device. Dust can be removed from this rotary flow.
This system may also comprise means for injecting a liquid and/or a
gaseous phase, making it possible to introduce a binder or to apply a quenching
action. It is also possible to provide one or more recycling stages and to intro-
duce a plurality of phases simultaneously, more particularly in the form of
co-atomization.
It is obvious that the present invention is not limited to the problem
of pollution caused by waste waters.
It is particularly applicable whenever high temperatures are required,
namely:
- for fast evaporation of volatile compounds and drying of products in suspension
or aqueous emulsion, or concentration of solutions. This is of particular
interest for concentrating mineral acids, such as phosphoric or sulphuric acids;
- for mixing operations and general impregnation of solids with liquids;
- for solidification of particles with conversion into small spheres, or surface
treatment of pellets, with possible change in the surface structure thereof;
- for carrying out reactions such as chlorination or oxidation within the homo-
geneous mixture produced.
It is also possible, however, to treat heat-sensitive materials, for
example protein-base materials. In this case, the process according to the inven-
tion makes it possible to operate with a high temperature gradient, i.e. under
conditions producing satisfactory thermal efficiency, while avoiding degradation
of the materials treated, as in accordance with the process described in Canadian
Patent Application 306,609 filed in the Applicant's
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name.
The present invention may be reduced to practice with a hot-gas
generating device as described in FR 2276086, comprising an external casing
with a surface of revolution comprising a reaction chamber closed at one end
and having a restriction at the other end, the chamber enclosed by a per-
forated internal wall defining, with the external casing, an annular space
communicating with at least one tangential inlet conduit for a gaseous phase.
The chamber h&s means for axial in~ection of a part of the substances through
the closed end of the casing, the reaction chamber beine extended, beyond the
constricted passage, to a mixing chamber or treatment zone of larger cross
section into which, substantially at the location of the smallest cross sec-
tion of the constriction, opens a co-axial in~ection device for at least one
of the substances to be treated. The internal wall is preferably perforated
over a length which is dependent upon the calorific flow and temperature of
the gases. This perforated wall has generally circular holes and, at least
near the closed end of the unit, should be "thin-walled", i.e. the ratio hole-
diameter: wall-thickness should be greater than 5, the minimum thickness of
the wall being limited only by mechanical requirements. There are at least
six holes and they are arranged in at least one, preferably several, circular
rows in the cylindrical wall. Most of the holes are arranged at the upstream
end of the unit, in order to promote mixing of the substances to be brought
into contact and, correlatively, to ensure that the gas is preheated while
; the internal walls are protected from the heat of the reaction. The total
area of the holes located towards the downstream end may be very small, from
1/10 to 1/100 of the total area of the said holes.
If the aVerage inside diameter of the external casing is designated
D1 and D2 the inner diameter of the perforated wall, then 1 (Dl - D2) is
preferably between 1 and 10 cm depending upon the helicoidal flow. Diameter
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D2 is determined as a function of the total heat released by the reaction and is
preferably between OJ4 and 0,5 Vk mm, k being the number of kilocalories/hour
released by burning of the fuel or, in general, by the reaction induced.
It is desirable for D2 to be not less than 500 mm if a viscous reactant,
for example a heavy fuel, is introduced in the axial flow. The fuel is preferably
in the form of a fine, homogeneous dispersion.
There are no essential dimensions for the axial fuel input. This is
generally in the form of a tube, at least outside the unit, and must permit both
satisfactory atomization of the liquid and entry of the gas without appreciable
pressure drop. Thiæ may be achieved in many ways. For example, if the fuel is
a liquid, it is advantageous to use a device described in the Applicant's Canadian
patent 1,070,485 entitled: "Process for bringing into contact substances of
different phases" (this eliminates the need for pressurizing the fuel); or a
device in the form of a simple tube having a truncated-conical outlet to which is
welded, outside the unit, a conduit through which a gas effecting atomization is
supplied. The only additional precaution required is to avoid using any device
which would produce a highly divergent flow (at an angle of more than 90) when
the liquid is introduced.
The flow of gas, which ultimately forms the helicoidal flow, is through
a tangential line. The conditions to be met regarding the cross section of this
line are governed mainly by structural requirements, and the necessity of avoid-
ing excessive pressure drops, as already indicated above. A relative pressure of
0,2 bar is generally sufficient. The communicating aperture between this line
and the annular space is preferably at the downstream end of this reaction
chamber.
Ignition of the fuel is effected by a conventional device such as a
spark-plug with a spark jumping between the electrodes thereof.
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This spark-plug may be mounted on a retractable device comprising, for example,
a metal bellows. The spark is produced in a zone where the fuel and the gas or
oxidizing agent are in contact. The ignition means may then be withdrawn in
order to sweep over the perforated wall.
It is obviously possible to ignite the mixture, or initiate the
reaction, by means of a flame.
Because of the low temperatures imposed on the walls, the apparatus
may be made of ordinary steel. Stainless steel, or other corrosion-resistant
metals, need be used only if the presence of any rust must be avoided. There
is no need for any refractory material.
The fuel may be a gas such as methane or propane or some other light
hydrocarbon liquid residue which has to be burnt off, possibly having tars or
soot in suspension, or a body which is solid at ambient temperature and is melted
prior to injection, for example sulphur. Other substances of widely varying
kinds may also be in;ected.
Combustion chambers of different shapes may be used. More particularly,
it is possible to use an annular toroidal space equipped with a perforated basket
or a mechanically-independent detachable distributor. It is also possible to
use a cylindrical envelope and a perforated truncated-conical basket with a
tangential inlet downstream and perforations located upstream.
. The treatment zone or mixing chamber is in accordance with that
described in Canadian 1,070,485, except that the vortex-sink movement used is
that of the reaction chamber.
The throughput volume of the vortex-sink flow must be large in relation
to that of the liquid, the ratio being at least 100, and preferably between
1000 and 10,000 times. Under these conditions, the movement for the gases is
imposed, in direction and intensity, upon the liquid droplets
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isolated from each other in the æone where the flows converge. The velocity
of the liquids is furthermore red.uced to close to the minimum permitting
continuous flow. Under these conditions, the velocity of the gases ma~J
remain low enough not to re~uire high pressures.
The ratio between the masses of gas and li~uid is obviously select-
ed as a function of various factors such as the temperature of these fluids
and of the final operation to be carried out, for example vapourization of the
liquid, the said ratio being at least 2.
The velocities, and therefore the volumes, at the location of the
constricted passage are easily calculated from the inlet flows of the fluids
and the cross section of the passage. Pressures have little effect. The
axial flow is considered as rectilinear,the cross section thereof being equal
to that of the interior of its conduit, whether or not this emerges from the
constricted passage.
The paths imposed by the gases form, as they emerge from the con-
stricted zone, one of the two families of generatrices from a hyperboloid to
a nappe or, to be more precise, of a laminated stack of a plurality of
hyperboloids. These generatrices pass a family of circles forming a not very
wide ring located downstream of the constricted helicoidal passage prior to
diverging. This ring surrounds a depression zone, the effect of which man-
ifests itself, on the one hand, upstream on the liquid constituting the
rectilinear flow and, on the other hand, downstream on the gases, causing
aome of these fluids to recirculate. The liquid is broken down into a multi-
tude of droplets, each being taken over by a volume of gas and subjected to
a movement which creates a centrifuging effect. This improves the con-tact
with the gas and, where combustion takes place, ensures retention and stabil-
ity of the flame.
The ratio between the flows of gases and liquids may vary within
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wide limits, any increase in this ratio reducing the dimensions of the droplets
formed.
The process of bringing into contact substances in different physical
states may also be applied, in the device described, to various known operations,
especially in the chemical and foodstuffs industries. In these operations, the
flow subjected to the vortex movement is generally a gas or vapour, possibly
carrying in suspension solids or liquids to be brought into contact with sub-
stances introduced axially. A pressure of a few hundred grams per square centi-
meter (between 200 and 500 g/cm2) above the pressure obtaining in the downstream
part of the apparatus is sufficient to ensure satisfactory operation of the
device. The vortex movement generated by this flow, produces, as already indi-
cated, a slight depression in the axial part, such as may be produced by a flow
of fluid in the internal piping, without any need to apply pressure to this
fluid.
The mixing device may be simply a double cone. The phase, or phases,
to be treated may then be introduced at the location of the constriction, prefer-
ably at a distance from the minimum cross section of more or less one radius in
relation to the plane of the circle.
It is desirable for the outside diameter of the inlet line to be at
least equal to 1/4 of the diameter of this circle, preferably at least 2/3 of
this diameter.
With a view to avoiding disturbance of the reaction occurring in the
first chamber, the substance to be treated is introduced simply through a line
having an elbow, but other means may be used, for instance an annular injector
located substantially in the plane of the constriction.
Finally, cooling zones may be provided, either in the treatment zone
(as in Applicant's French Patent 2,422,435) in which cooling is applied to the
periphery of the phase-contacting zone or further downstream (as in Canadian
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113~'Z850
Application 306,609), according to which, at the outlet from the "flash" treat-
ment, the product to be treated is subjected to an abrupt temperature change, a
treatment which is applied particularly in the case of heat-sensitive materials).
In this case it is desirable to bring the gas at the outlet from the reaction
zone to a temperature of between 200 and 700 C, ~he resulting medium being sub-
jected, at the outlet from the treatment zone, to a cooling action at a tempera-
ture of between 20 and 120C.
The invention will be more easily understood in conjunction with the
following diagrams and examples, which are given by way of illustration, but are
in no way restrictive.
In the accompanying drawings:
Figure 1 shows a device according to the invention suitable for general
treatment of a substance by a gaseous phase.
Figure 2 shows a more special case in which an after-treatment device,
more particularly for removing dust, is arranged at the outlet from the contact-
ing zone.
Figure 3 illustrates the special case in which a cooling device is
provided.
The device according to Figure 1 comprises a combustion chamber 1 and
a mixing chamber 2. Chamber 1 consists of a casing 3 closed at the upper end
by an end plate 4 having a space to accommodate an atomizing device 5. The
combustion chamber has an annular space 6 defined internally by a cylinder 7,
the upstream portion of which is perforated. A gaseous phase is introduced
tangentially through a line 8 opening into annular space 6.
Casing 3 terminates downstream in a convergent section 9 producing a
constricted passage 10. A bent pipe 11 opens into this passage, substantially
at the location of the constriction, in the axis of rotation of
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chamber 1.
Mixing chamber 2 is in the form of a double cone, the divergent
upstream part of which extends from the convergent end of chamber 1 at the
passage 10.
The device according to Figure 2 has the same combustion chamber 1
and mixing chamber 2 as in Figure 1, but the outlet from double cone 2 is
provided with a dust-removing device 12 comprising a casing 13 in which a
receiving cone 14 is arranged just below the double cone chamber 2 and may
include a liquid inlet 15. Truncated cone casing 13 is itself extended ~y
a cylinder 16 which allows the rotary movement to be maintained, and which
passes the products to a centrifugal separator 17. The solid product emerges
at 18 and the gas at 19.
The device according to Figure 3 is an embodiment which is par-
ticularly suitable for heat-sensitive materials. This device resembles that
shown in Figure 1, except that, arranged at the outlet from double cone
chamber 2 is a cooling system comprising a head having a perforated wall 21,
a tangential conduit 22, a line 23 and a cyclone 24.
It is to be understood that the present invention is not restricted
to the embodiments illustrated. For example, the mixing chambers need not be
double cones, or they may have an intermediate cylindrical section.
The following example relates to a device in accordance with Figure
2.
The waste-water to be treated contains 20% by weight of NaCl,
between 3 and 4% of sodium sulphate, and about 5% of organic substances con-
taining polysulphides.
The device used has a combustion chamber 1 having an overall height
of 193 mm the convergent section having a height of 43 mm. The casing 3 is
120 mm in diameter, and perforated cylinder 7 82 m~ in diameter. The con-
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stricted passage 10 is 18 mm in diameter and the outside diameter of conduit
11, at the location of the constricted passage, is 12 mm, representing a 2/3
ratio in relation to the diameter o~ passage 10. Finally, the inside diame-
ter of the cross section of tube 11 is L~ mm.
The angle at the apex of the upper cone of the cha~ber 2 is 90 .
The flow of air to the combustion chamber through tube 8 is 60
Nm3/h at a pressure of 0,4 bar. The fuel injected at 5 is propane.
In this example, the propane in~ection is ad~usted to provide a
temperature of about 1000C at the constricted passage and at the inlet of
the water to be treated, so that a temperature of the order of 500 C is
maintained at the outlet from the double cone.
For every 30 kg of water treated, the solid phase contains 3 kg of
NaCl and 3 kg of sodium sulphate.
It should be noted that the gaseous phase contains no fines and
consists, apart from combustion gases, mainly of water vapour with only
traces of S02.
This example illustrates the importance of the present invention,
which makes it possible either to treat heat-sensitive materials without
degrading them and with satisfactory thermal efficiency, or to carry out
high-temperature treatments of polluting substances, for example.
