IE49618B1 - Apparatus for treating substances in different phases,such as the treatment of substances in liquid,semi-liquid or pasty form with another phase,in particular a gaseous phase - Google Patents

Abstract

1. Apparatus for treating substances in the form of a liquid, semi-liquid or pasty phase, with another phase, in particular a gaseous phase, comprising a combustion chamber (1) and a contacting chamber (2), said combustion chamber comprising a casing (3) which is closed in its upper portion by an end plate (4), an annular space (6) which is delimited internally by an internal perforated wall (7), a restricted passage (10), at least one conduit (8) for the tangential feed of a gaseous phase, and a means (5) for axial injection of the fuel through the end plate (4), characterized in that the casing (3) terminates at the downstream end with a convergent portion (9) in which an injection device (11) terminates substantially at the level of the restricted passage (10), on the axis of rotation of the combustion chamber (1), the contracting chamber (2) extending the combustion chamber (1) in a downstream direction on the same axis of rotational symmetry.

Description

The present invention relates to apparatus for treating substances in liquid, semi-liquid or pasty form with a substance in another phase, in particular a gaseous phase.

It applies in particular to apparatus for the treatment of materials in liquid form, which may or may not incorporate solid materials in suspension, with a gas at a high temperature.

This problem is conventional in the case, for example, of treating waste waters liable to lead to the formation of dry materials through oxidation.

Several different solutions have already been proposed· in order to resolve this problem.

Accordingly, in French Patent No. 2075354 it has been proposed to eliminate liquid industrial waste by transforming it into a solid state by treating it with a solution of silicate and a setting agent for said silicate.

It is apparent that this is not a simple solution since it resorts to compositions not included in the waste waters, involves several stages and leads to the formation of a composition which is itself advisable to eliminate thus making it necessary in the abovementioned case to obtain solid residues resistant to dilution in water In order to be able to introduce them into certain terrains and thus to gain further value from them. - 3 49618 A very different solution is disclosed in French Patent Publication FR-A-2320268 which comprises contacting the said waters at pH values higher than 7 and at temperatures between 20 and 200°C with pure industrial oxygen at a pressure between normal pressure and 20 bars until the sulphur is converted into thiosulphates, then transforming these thiosulphates into sulphates by the action of the oxygen at a pH of 0 to 5, or 0 to 8 for the waste waters containing only sulphates, at temperatures of between 20 and 200°C and at pressures of up to 20 bars, and optionally in the presence of catalysts.

It can be seen, therefore, that a solution of this kind is equally lengthy and has recourse to several operations involving physical and chemical treatments.

More recently in French Patent Publication 2406610 it was proposed to subject waste waters of this kind simultaneously to pulverisation and thermal oxidation treatment and then to separate in a simple manner the solid residues from the volatile compositions.

In practice, it has been proposed to carry out the process according to French Patent Publication FR-A2257326 of bringing into contact substances in different phases, in accordance with which at least one phase forms a vortex-well type flow having rotational axial symmetry and at least one phase is introduced along the rotational axis of symmetry of the said 9 6 18 vortex-well type flow (until it reaches the zone of depression of the said vortex-well type flow,) the momentum of the elements of volume of the vortex-well type flow in relation to the elements of volume of the axial phase being such that the said vortex-well type flow simultaneously causes the disintegration, dispersion and taking-up of the axial phase and. its optional treatment by the vortex-well type flow.

The apparatus claimed in this Patent comprises a unit consisting essentially of an outer casing, such as a cylindrical sheath, terminating in an end portion of convergent form, an inner perforated liner defining with the outer casing an annular space, at least one tangential inlet for the introduction of the gaseous phase into said annular space, said gaseous phase escaping via the perforations of the inner liner into the central space and leaving the head unit in the form of helicoidal trajectories. The axial phase is introduced via a conduit along the rotational axis of symmetry of the vortex-well type flow into the contact zone, which zone is formed by a space such as a biconical space of which the upstream part is of divergent form continuous with the converging end portion of the head unit.

When it is desired to carry out treatments at high temperature, a gaseous phase can be produced at the desired temperature. 9 618 - 5 This can be done by using apparatus according to French Patent Publication FR-A-2276086 which claims a generator for hot gas having a cold shell, in accordance with which a helicoidal flow with rotational symmetry is formed, the flame being confined in the central part of the apparatus.

The hot gases emerging from this generator may be introduced tangentially into the annular part of the head unit of the apparatus according to French Patent Publication FR-A-2257326.

But this association which involves the introduction of hot gas into an annular space and its flow in a confined passage results in a major disadvantage, since in order to meet treatment requirements it has been necessary to exceed temperatures of greater than about 800°C, even though one is able to produce gas at such a temperature.

It is found that certain treatments necessitate temperatures in the region of 900 to 1200°C.

This involves contacting head units capable of withstanding similar temperatures and resisting the action of the products treated at these temperatures in an oxidizing medium, which is not so in the case of conventional atomising units.

This is why the Applicants' French Patent Publication No. 2419754 proposes a new device for carrying out the process according to French Patent Publication FR-A-2257326 comprising a unit for forming the vortex-well type flow which consists of a revolving element defining an annular space into which the gaseous phase is tangentially introduced, limited by a distributing element of axial symmetry giving the helicoidal flow thus formed an axial symmetry, the said distributing element being mechanically independent of the rigid revolving unit.

In this way the unit may be satisfactorily cooled and the gaseous phase may be raised to a very high temperature.

Unfortunately, it is not always easy to construct such a device and it has been found that excellent results could be obtained according to the process of the invention in a simple manner.

The present invention relates to apparatus for treating substances in the form of a liquid, semiliquid or paste with substances in a gaseous phase, comprising a combustion chamber and a contacting chamber, said combustion chamber comprising a casing which is closed in its upper portion by an end plate, an annular space which is delimited internally by an internal perforated wall, a restricted passage, at least one conduit for the tangential feed of the gaseous phase, and a means for axial injection of the fuel through the end plate, characterised in that the casing terminates at the 9618 - 7 downstream end with a convergent portion in which an injection device terminates substantially at the level of the restricted passage, on the axis of rotation of the combustion chamber, the contacting chamber extending the combustion chamber in a downstream direction on the same axis of rotational symmetry.

The gaseous phase is advantageously introduced at low pressure, less than one bar and preferably between 0.2 and 0.5 bar below the pressure prevailing downstream in the contacting chamber, the speed is generally between 10 and 100 m/sec and preferably between 30 and 60 m/sec.

The speed of injection of the substance reacting with the gaseous phase may reach speeds in the region of 100 to 150 m/sec.

According to the present invention the axial phase entering the combustion chamber consists of a hydrocarbon phase, for example fuel or any combustible material whatsoever which is injected into the inlet of said chamber along the axis of symmetry of the helicoidal current.

In order to achieve this one may employ a conventional pulverisation process, such as one operating under pressure or a rotating process, but one may also employ a process according to French Patent Publication FR-A-2257326 wherein droplets are formed by transferring the momentum by virtue of the vortex-well 9 618 - 8 type flow of high momentum.

The helcoidal phase consists therefore of a combustionsupporting gaseous phase, generally the ambient air, but of course this method of use is in no way limiting.

The substance to be treated is introduced in liquid, semi-liquid or pasty form axially at the end of the combustion zone. The speed of introduction is low, being in the region of 0.03 to 10 m/sec.

In this way the symmetrical vortex-well type flow disintegrates the liquid stream by transferring the momentum.

In this way it is possible to treat in a simple manner and at a high temperature liquid substances, since one avoids contacting the products with the walls and bringing these walls to the treatment temperature.

According to the present invention the gases at the exit of the combustion chamber may be brought without difficulty to a temperature between 900 and 1200°C which makes it possible, furthermore, to introduce the material to be treated at the ambient temperature.

Also, a particular application of the apparatus of the present invention concerns the treatment of waste waters.

It is known that in this last case it is advisable to simultaneously evaporate a large quantity of liquid and to carry out a thermal oxidation heat treatment and at the same time to separate the solid residues thus - 9 obtained from the volatile compounds.

The apparatus is applied in particular in the case of waste waters having a dry material content of up to 20 - 30%; certain of these dry materials are capable of oxidation as is the case with sulphides and polysulphides which are therefore eliminated in the form of sulphates. Advantageously, in this case the gases at the exit of the combustion chamber are brought to a temperature of between 900 and 1200°C and between 350 and 500°C in the contacting chamber.

It is still possible to cause cooling at the exit from the contacting chamber.

It is also possible to provide at the exit of the contacting chamber a rotating zone which is simply static.

In this way a dust-removing system is achieved.

In addition, this system may comprise injection means for a liquid and/or gaseous phase enabling a binding material to be introduced or a quenching effect to be achieved. One or several recycling operations may also be effected and the simultaneous introduction of several phases, particularly in the form of copulverisation.

Quite clearly the scope of the present invention is not limited to the problem of pollution caused by waste waters. 9 6 18 - 10 It is employed particularly each time a high temperature is required, i.e. notably: for the rapid evaporation of volatisable compositions and particularly for drying a product in susoension or in aqueous emulsion, or a concentration of solutions.

This is particularly important in the case of the concentration of mineral acids such as phosphoric acid or sulphuric acid, - for mixing operations and in general for the impregnation of solids with liquids, for solidification of particles with transformation into small balls or treatment of grain surfaces with possible change in the superficial structure of the grains, for the possibility of carrying out in homogeneous mix reactions such as chlorination or oxidation reactions.

However, it is equally possible to treat thermosensitive materials, such as those with a protein base.

In this case the apparatus according to the invention enables operations to be carried out with a high temperature gradient, in other words under conditions permitting a good heat yield; while avoiding degradation of the treated materials such as occurs in the process described in the Applicants' French Patent Application No. 2396250. - 11 According to the possible characteristics of the invention the internal perforated wall is preferably perforated over a length dependent on the output of calories and the temperature of the gases.

This perforated wall has generally circular holes which, at least at the closed end of the apparatus, must have a narrow wall, i.e. the ratio of the diameter of the holes to the thickness of the wall must be greater than 5; the minimum thickness of the wall is determined only by mechanical requirements. There are at least 6 holes which are distributed over at least one circle, but preferably over several director circles of the cylindrical wall. The majority of the holes are disposed on the upstream side of the apparatus in order to encourage mixing of the substances to be contacted and correlatively to ensure that a fraction of these substances is preheated while protecting the internal walls from the thermal effects of the reaction. The total surface of the holes situated on the downstream side may be very small, even between 1/10 to 1/100 of the total surface of the holes.

If Dj designates the mean internal diameter of the external casing and D2 that of the perforated wall, then 1/2 (D^ - d2) is preferably between 1 and 10 cm according to the flow rate of the helicoidal current. The diameter D2 is determined as a function of the total emission of heat during the reaction and is preferably between 0.4 and 0.5/^/k mm, k being the number of kilocalories liberated per hour by this combustible material as it burns, or in general by the reaction caused.

Advantageously, D2 should not be less than 500mm when a viscous reagent is introduced into the rectilinear current, such a reagent being, for example, a heavy fuel which is preferably to be dispersed finely and homogenously.

There is no imperative dimension for the means of introducing the axial rectilinear flow of fuel. This means, which generally comprises a tube, at least on the exterior of the apparatus, should permit either a good liquid atomisation or a gas intake without an appreciable drop in pressure. This means may be embodied in several different ways. For example, when the combustible material is a liquid, one may advantageously use a device described in the aforementioned French Patent Publication 2257326 title A process for contacting substances in different phases (this does not mention the necessity for exerting pressure on the combustible material) or a simple tube, the outlet of which is in the shape of a truncated cone onto which there is welded on the exterior of the apparatus a conduit, through which the gas ensuring atomisation is introduced. The only - 13 additional precaution to be taken is to avoid the use of a device which would give a very divergent flow (an angle of more than 90°) when introducing a liquid.

The gaseous current subsequently caused to rotate is delivered through a tangential tubule, the conditions to be observed with regard to the cross-section of this tubule being laid down above all by construction requirements and the desire not to cause excessive pressure losses. As already mentioned above a pressure in the region of 0.2 bars is generally sufficient. The opening providing communication between this tubule and the annular jacket is preferably in the vicinity of the downstream end of this combustion chamber.

The ignition of the combustible material is ensured by a conventional device such as a spark-plug, wherein a spark jumps between the electrodes of said sparkplug. This spark-plug may be mounted on a retractable device comprising, for example, a metallic bellows assembly. The spark is produced in a zone where the combustible material and the fuel are in contact; then the ignition device may be withdrawn in order to lie flush with the perforated wall.

It clearly remains possible to ignite the mixture or to trigger the reaction with a flame.

Owing to the advantage of the low temperature of the walls it is possible to construct the apparatus in ordinary steel, the importance of using stainless steel 9 6 18 or other corrosion-resisting metals only becoming apparent when it is necessary to eliminate the presence of all oxide dusts.

The presence of the refractory element is of no use.

The combustible material may be a gas such as methane or propane, for example, or another light hydrocarbon; liquid residues to be destroyed by combustion with, possibly, tar or soot in suspension or a solid body at ambient termperature and melted before its injection, for example, sulphur. It is also possible to inject other bodies of very diverse kinds.

However, it is possible to use combustion chambers of a different type.

One can, in particular, use an annular toric space provided with a perforated shell or a removable mechanically independent distributor just as one may also use a cylindrical jacket and a truncated-coneshaped perforated shell with a downstream tangential inlet and perforations disposed upstream.

The contacting portion is identical to that described in the French Patent Publication FR-A-2257326 the only difference being that the vortex-well type movement used is that of the combustion chamber.

The momentum of the vortex-well type flow should be high in relation to that of the liquids, in a ratio of at least 100 and preferably of 1000 to 10,000 times.

The actual momentum of the gases is, therefore, under these conditions imposed in direction and intensity on the droplets of liquid isolated from one another in the region in which the two currents converge. The speed of the liquids is reduced, furthermore, close to the minimum speed permitting continuous flow. In these conditions, the flow rate of the gases may remain low enough to avoid the need for high pressures.

The ratio of the gas and liquid masses is clearly selected as a function of various factors, among them the temperature of these fluids and the final operation to be carried out, for example, vaporisation of the liquid, this ratio being at least two.

The speeds and consequently the momenta at the level of the restricted passage are calculated simply according to the inlet rates of the fluids and the cross-section of this passage, the pressures have little part to play. The axial current is considered rectilinear and as having a cross-section equal to that of the interior of its conduit, whether this emerges from the restricted passage or not.

The trajectories imposed by the gases form, at their exit from the restricted zone, one of the two families of generatrices of a nappe of a hyperboloid, or more precisely of a laminated pile of several hyperboloids. These generatrices pass a family of circles forming an annulus of small dimension situated downstream of the - 16 restricted passage of the helicoidal current before diverging. This annulus surrounds a depression zone, the effect of which is manifested on the one hand upstream on the liquid forming the rectilinear current and on the other hand downstream on the gases by causing a fraction of these fluids to be recycled. The liquid is fractionated into numerous small droplets, each being taken up by a certain volume of gas and subjected to a movement which creates a centrifugation effect, which enhances contact with the carrier gas and, where combustion takes place, ensures that the flame catches and is stable.

The ratio of the gas flow rate to that of the liquid flow rate may vary greatly, an increase in this ratio decreasing the dimensions of the droplets formed.

The process of contacting substances in different physical states may thus be applied with the aid of the described apparatus for different operations currently being carried out, in particular in the chemical and food industries.

In these operations the current subjected to the vortex movement is generally a gas or a vapour optionally transporting in suspension solids or liquids to be contactd with the substances introduced axially.

A pressure of several hundred grams per square centimetre (from 200 to 500 g/cm2) above the pressure prevailing in the portion of the apparatus disposed 9 6 18 downstream is sufficient to ensure that the device operates satisfactorily. The vortex movement generated by this current creates, as already indicated, a slight depression in its axial portion, such that a fluid flow can he produced in the internal tubule without any necessity to exert pressure on this fluid.

The contacting device may quite simply comprise a double-cone member.

The phase, or phases, to be treated is introduced at the level of the restricted portion advantageously at a distance from the circle of smaller cross-section comprised in the interval of more or less one radius in relation to the plane of this circle.

Advantageously, the external diameter of the injection device is at least equal to a quarter of the diameter of the restricted passage, and preferably equal to at least two-thirds of this diameter.

In order not to disturb the reaction taking place in the combustion chamber, the substance (or suhstances) to be treated is simply supplied through a tubule having an elbow bend but other devices may be used, such as an annular injector disposed substantially in the plane of the restricted passage.

Finally, cooling zones may be provided either at the level of the contacting chamber as in the Applicants' French Patent Publication 2419754 and according to - 18 4 9 6 18 which cooling takes place over the periphery of the zone where the phases are contacted or alternatively thermal treatment further downstream according to French Patent Publication 2396250 according to which at the exit of the flash treatment the product to be treated is subjected to a sudden temperature change, this treatment being applied in particular in the case of thermosensitive materials. In this case the gases at the exit of the combustion chamber are advantageously brought to a temperature between 200 and 700°C and the medium resulting at the exit of the contacting chamber is cooled down to a temperature between 20°C and 120°C. ilowever, the present invention will be more readily understood with reference to the accompanying drawings and examples given below by way of illustration and in no way to be considered as limiting.

Figure 1 illustrates apparatus according to the invention corresponding to a general case for treating a substance witl. a gaseous phase.

Figure 2 illustrates the specific case wherein a post-treatment device, in particular a dust-removing device, is disposed at the exit of the contacting chamber, and Figure 3 illustrates the specific case wherein a cooling device is provided.

The apparatus according to Figure 1 comprises a combustion chamber 1 and a contacting chamber 2.

Combustion chamber 1 has a casing 3 closed at its upper portion by an end plate 4 in which there is provided a space for locating a pulverising device 5. - 19 The combustion chamber has an annular space 6 internally limited by a cylindrical shell 7 perforated at its upstream portion.

A gaseous phase is introduced tangentially through a conduit 8 opening into the annular space 6.

The casing 3 is terminated downstream by a convergent portion 9 having a restricted passage 10 wherein an injection device consisting of an elbow-bent conduit 11 is introduced along the rotational axis of the combustion chamber 1 with its outlet end substantially level with the minimum cross-section region of the restricted passage 10.

The contacting chamber 2 comprises a double-cone member, the upstream portion of which is of divergent shape and prolongs the convergent portion terminating the combustion chamber 1.

The apparatus according to Figure 2 has the same combustion chamber 1 and contacting chamber 2 as in Figure 1 but there is provided at the exit of the double-cone member 2 a dust-removing device 12 comprising a casing 13 wherein a reception cone 14 is disposed just below the double-cone member 2, and optionally a liquid supply means 15, said casing 13 in the form of a truncated cone being itself prolonged by a cylinder 16 which enables the rotating movement of the products to be retained and which leads the products to a centrifugal separator 17. - 20 The solid product emerges at 18 and the gas at 19.

The apparatus according to Figure 3 illustrates another embodiment, particularly adapted for use with thermosensitive materials.

This apparatus is similar to that shown in Figure 1 except that there is disposed at the exit of the double-cone member 2 a cooling system comprising a head with a perforated wall 21 and a tangential conduit 22, a tubule 23 and a cyclone 24.

Naturally, the present invention is not limited to the embodiments illustrated, in particular, it is possible to use contacting chambers 2 which are not biconical or which have an intermediate cylindrical portion.

The following example of use has been achieved with the aid of apparatus as illustrated in Figure 2.

Waste water containing 20¾ by weight of NaCl, 3 to 4% by weight of sodium sulphate and approximately 5% by weight of organic materials including polysulphates is treated.

The apparatus used has a combustion chamber 1 and an over-all height of 193 mm, 43 mm of which is the convergent portion.

The diameter of the casing 3 is 120 mm and that of the perforated shell 7 to 82 mm. The diameter of the restricted passage is 18 mm, the internal diameter of the conduit 11 at the level of the restricted passage - 21 is 12 mm, which therefore represents a ratio of 2/3 in relation to that of the diameter of the cross-section at 10, finally, the internal diameter of the cross-section of tube 11 is 4 mm.

The angle at the summit of the upper cone of the 5 double-cone member is 90°C.

The flow rate of the air feeding the combustion chamber through tube 8 is 60 Nm^/h, the pressure is 0.4 bar. The fuel injected at 5 is propane. In this example, the injection of propane is adjusted so as to obtain a temperature in the region of 1000°C at the level of the restricted passage and the supply of water to be treated is adjusted so that a temperature of around 500°C is maintained at the exit of the doublecone member.

The solid phase contains 3 kg of NaCl and 3 kg of sodium sulphate per 30 kg of water treated.

It is observed in particular that the gaseous phase has no fines and consists, apart from the combustion gases, substantially of water vapour only including traces of SO2· Thus, this example shows the importance of the present invention which makes it possible either to treat thermosensitive materials without degrading them and with a good thermal yield, or to effect treatment at high temperatures, for exanple, on polluting materials. - 22 However, as stated above, this example is not limiting. In particular, it is possible to use a similar device for the concentration of acids or the treatment of products such as gypsum. It is also possible to introduce during the course of an operation other products by co-pulverisation, a binding agent or to recycle certain products.

Claims (6)

1. Apparatus for treating substances in the form of a liquid, semi-liquid or paste with substances in a gaseous phase, comprising a combustion chamber and a contacting chamber, said combustion chamber comprising a casing which is closed in its upper portion by an end plate, an annular space which is delimited internally by an internal perforated wall, a restricted passage, at least one conduit for the tangential feed of the gaseous phase, and a means for axial injection of the fuel through the end plate, characterised in that the casing terminates at the downstream end with a convergent portion in which an injection device terminates substantially at the level of the restricted passage, on the axis of rotation of the combustion chamber, the contacting chamber extending the combustion chamber in a downstream direction on th same axis of rotational symmetry.

2. Apparatus according to claim 1 characterised in that the internal wall comprises a removable element.

3. Apparatus according to one of claims 1 and 2 characterised in that the annular space is toric.

4. Apparatus according to any one of claims 1 to 3 characterised in that the ratio of the outside diameter of the device for injecting the substance to be treated, to the inside diameter of the restricted - 24 passage, is at least 1/4 and advantageously 2/3.

5. Apparatus according to one of claims 1 to 4 characterised in that it has a cooling system, at the outlet from the combustion chamber. 5

6. Apparatus according to claim 1 for treating substances in the form of a liquid, semi-liquid or paste with substances in a gaseous phase, substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.