The invention concerns a reactor which permits to per¬ form, together with chemical reactions, operations of size reduction of the solid materials in suspension.

Particularly, the invention concerns a reactor suited for the mentioned operations and named "TURBOPULPER" intend¬ ed particularly for treatments in the cellulose an /or paper pulp industries. This reactor presents an axial admission rotor with a radial delivery such as to create a turbolency inside the reactor itself. This reactor preferentially is under pressure and has a spheric shape and may be heated (fig. 1 and 2) .

The present invention concerns a reactor suited to perform chemical reactions and at the same time operations of size reduction of solid materials in suspension, such a reactor is particularly usable, but not exclusively, for example in the alkali-oxygen process for delignification. As known, generally the chemical reactions are acti¬ vated by a good mixing and by adequated temperatures. The reaction is still more active when conditions are created for a good "exchange of materials". Amongst these last conditions, there is the maximum possible exchange surface and interchange of the substances which must react along this surface. The general conditions summarized above are particularly difficult to attain in cases when the solid materials in suspension, interested in the reaction, are at high consistency in water or other liquid vehicles.

Particularly, these conditions must be reached in two separate equipments operating in the pulp industry and calle pulper and digester. The equipment referred to this inventio just summarizes both these operations carried out in this industry by the equipments mentioned above. These equipments generally are not in the conditions to completely satisfy all the requirements of the particular applications foreseen

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and to have at the same time the necessary flexibility to reach the optimum or nearest to optimum working conditions with the treated materials of different characteristics.

Therefore one of the aims of the present invention is to propose a new reactor for the applications foreseen, permitting under the mentioned conditions, to activate and speed up the chemical reactions, assuring that their effect should be distributed extremely homogeneously throughout the reacting mass. Particularly, one aim of the present invention is to propose a reactor, as mentioned above, which contemporane¬ ously presents the following advantages:

- capability to reduce the size of the particles of the solid matters in suspension to the desired level? - homogeneous distribution of chemicals throughout the mass, contemporaneously to the size reduction of the solid materials in suspension*

- complete recycling of the contents of the reactor inside its sphere so that the material passes at every cycle at least one inlet zone of the chemicals fed in continously,

- possibility of indirect heating that means, that the heating medium is not mixed with the suspension to be heated, and without the well known inconveniences deriv from the formation of deposits of the suspended materi on the hot surface and thus maintaining a high constan coefficient of heat exchange independently from the ty of suspension.

Essentially, following to the invention, all these and other aims are realized due to the fact that the reactor of the invention represents an essentially closed environment o treatment, where in the lower zone a rotor preferably with axial admission and radial delivery creats a turbolency with flows normally interesting the whole volume of the closed environment and at the same time, performs also the said siz reduction of the solid materials mixing them intimately with the suspending liquor. Always, following to the invention, t closed environment, as defined by the reactor, could advan-

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tageously be put under a higher than atmospheric pressure. The reactor is of an essentially spheric shape and is heate indirectly, for example by means of steam.

The presence of the mentioned rotor, operating as said before, permits to create a turbolent motion depending on the choice of the constructive and working characteristics of the rotor, to obtain the desired size reduction of the solid particles in suspension, optimizing the reaction conditions. The turbolence is furthermore cooperating to distribute homogeneously the chemicals, which are fed near the rotor, throughout the mass.

For some treatments, the best operative conditions are realized when the reactor is put under a pressure higher than the atmospheric one and is of an essentially spheric shape. This last configuration results of particula importance inasmuch permits to realize at the same time the following objectives:

- obtain the minimum possible ratio between the re¬ actor's surface- nd its useful volume, reducing the overall dimensions?

- reduce to the utmost possible the thickness of the resisting walls specially in the case when operating under pressure and consequent reduction of the weigh and cost of the equipment; - realize, downstreams of the turbolent motion phase, created near the rotor, guided uniform flows on the whole arch of 360 and on the different levels where the flows are developing,

- get indirect heating of the reactor for ex. by means of steam, without any danger of scaling by solid matters on the heated surfaces and hence maintaining a good heat exchange, coefficient, thanks to the turbolence and to the flows formed. These and other peculiarities and characteristics of the present invention will be, on the other hand, described more in details and referred to a preferred shape of realiz tion of the invention itself, illustrated in the enclosed

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drawings just for a simple examplification. In the drawings:

Fig. 1 shows a lateral view of a reactor as by the invention. Fig. 2 is a view of a partial section following to a plane passing through the vertical shaft of the reactor and illustrating the parts of the rotor. Fig. 3 a sectional view substantially along the line III - III of Fig. 2. Fig. 4 is a plan view of a possible alternative shape of the impeller of the equipment's rotor. Fig. 5 represents schematically the flow of the current inside the reactor. Fig. 6, 7 and 8 are schematic illustrations of the pos- sible modalities of utilizing the reactor as by the invention. Referring to the drawing and initially to Fig. 1, the reactor is essentially formed by a spheric body 10 which may have for example diameters up to 10 m. (500 cu.m of use- ful volume) supported by vertical rods 11.

In the lower part of the container 10 and outside of it, there is the shaft 12, coming out from the body of the container 10 through an adequate stuffing box controlling the rotation of the rotor. This shaft 12 may be driven through a control group 13 by means of a belt transmission, gear reducer or gearmotor; this last solution is preferred when a strong mechanical action is required for the size reduction of the suspended material requesting high power absorbtion with a power request up to 1000 kw.

The material to be treated is charged into the contain or reactor 10 through the charging opening 14 preferably arranged on the upper part, whilst the discharge is made through the outlet 15 connected to the bottom of the con- tainer. This procedure of feeding and discharging the mate¬ rial is used when the equipment operates in batch or is the first one of a series foreseen for continuous operating.

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5 However, in case of continuous operating or for special applications, the flow may be inverted by feeding through t connection 15 and discharging through the connection 14.

As said, the reactor is preferentially heated indirectl by means of a heating fluid, generally steam , which enters in 16 and goes out preferably as concensate, in 17, after having been put in contact with heat exchanging surfaces or elements as can be seen better in the following. Liquid or gaseous chemicals are let in through the corresponding conne tion union 18, whilst the gases produced by the reaction are discharged in 19, preferably under the control of a pressure regulator and analysis of samples of the discharged gases. Eventual safety and control devices, normally foreseen for pressurized vessels, as for ex. manometers and safety valves could be installed at the offtake 20.

The internal part of the reactor 10 in the zone of the turbolence formation is illustrated in details in figures 2, 3 and 4. They show how the shaft 12 enters inside the reacto through the stuffing box 21, this shaft bearing the rotor 22 and the rotating disc or ring 23 fixed to it which cooperate with the lower stationary disc 24 with a perforated zone 25 through which the material to be treated or the treated one are leaving or entering by way of the connection 15. The dis 24 and the eventual defibrating discs fixed to it are crosse by the duct 26 connected to the union 18 permitting the inle of liquid and/or gaseous reagents into the mixing and lamina zone 27 included between the discs 24 and 23. The gap of thi zone 27 or interspace between the static disc 24 and the ro tating disc 23 can be varied also with the machine working t better adjust it to the desired mechanical treatment to be performed. For the same reasons and depending on the materia treated, the surfaces of the discs 23 and 24 may assume diff rent constructive characteristics as for example, blades, stakes, abrasive surfaces or others. The rotor 22 and the defibrating disc 23 are built so as to realize an impeller of a helico-centrifugal pump with axial admission and radial delivery. Indeed in the central

part, the spokes 28 which bring the disc into rotation are so profiled as to constitute a section of a screw- for sus¬ pensions at higher consistencies and low speed of rotation (10-200 r.p.m.) -or a real propeller in case of suspensions 5 at lower consistencies and higher speed of rotation (200- 1500 r.p.m.) .

The centrifugal part of the pump obviously is formed by the surfaces of the rotating disc 23 and the correspon¬ ding channels between the already mentioned blades, stakes

10 or abrasive surfaces.

The rotor 22 with disc 23 may be substituted by an open agitator of the type shown with 29 in Fig. 4 specially when the treatment does not require an energetic action of defibration or disintegration.

15 The action of the impeller or helico-centrifugal pump now described, causes, in cooperation with proper baffles 30 a circulation of the treated mass of the type shown in Fig. 5, where it could clearly be seen, that the suspension, guided by the baffles 30 leaves radially the pumping group

20 and moves towards the top following the shape of. the spheric wall and then concentrates in correspondence of the superior pole from where if falls down forming a central column 31 sucked from the central part of the rotor.

This preceeding has shown to be of particular effi-

25 ciency to reach the desired aims and listed before. Further¬ more it was possible to heat indirectly the suspension durin the treatment by means of letting in the heating fluid throu suited connections 32 (Fig. 1 and 3) into the space defined by the baffles 30 between their surface and the wall of the zz 30 reactor's shell, space which consequently does not result to be in touch with the suspension during the treatment. The steam circulating inside the baffles 30 is discharged throug connections 33 (Fig. 1) and heats to the desired temperature the external surface 34 (Fig. 3) of said baffles, the number

35 and shape of which could vary depending upon the quantity of heat to be transmitted to the suspension. At the outside, t baffles are licked at high speed by the suspension pushed b

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the helico-centrifugal rotor, creating the conditions for a good heat exchange which is maintained during the opera¬ tion because scaling and deposits on the surface 34 are avoided. The heating fluid or steam condensate are recovered through a distribution ring 35 (Fig.. 11 and then passed through a heat source and again sent back in a closed cycle to the superior distribution ring 36.

The reactor now described and called "TURBOPULPER" can be used for batch operations as shown schematically in Fig. 6 or in continuόus ^~ operatiαns by putting in series two or more apparatus of the same type (Fig. 7) . The turbopulper could also be used for continuous operations, where a homo¬ geneous distribution of reagents and 0 ₂ is achieved, size reduction of the suspended material and heating to the re- action temperature is obtained, whilst the necessary reten¬ tion time for the complete development of the reaction is obtained in another static container 37 of an essentially conventional type, also this pressurized and of suited shape, in series with the turbopulper. If the appartus is used, as in the preferred case, to realize optimum conditions for a delignification treatment (cook) following the alkalioxygen process, it permits to overcome the mentioned difficulties of the known treatments, represented particularly by the indirect heating of a cellu- lose-fibres (from wood or short cycle vegetables, straw, etc) suspension in a liquid, achieving a progressive size reduc¬ tion of chips or fibre bundles from wood or annual plants with an increase of the total contact surface.

The apparatus performs also a perfect distribution and intimate mixing of the reagents with the fibres in suspen¬ sion. Moreover, in the case of the mentioned treatment, yields and activates the quantity of the oxygen required for the delignification of the fibrous material, overcoming the obstacle of the low solubility of oxygen in water and parti- cularly at the temperatures requested to obtain the deligni¬ fication (100-180°C) .

The capacity of the apparatus to distribute gas in

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liquid, creates a solution within the permitted limits of the equilibrium conditions and at the same time pro¬ duces an emulsion of gas in the liquid medium, thus giving rise to a continuous contact and replacement of 0 ₂ on the surface of the single fibres or bundles, which must be delignified.

As said before, the reaction is eased by a contempo¬ raneous mechanical defibration of the fibres. The reactions are speed up by the contemporaneous indirect heating. The turbopulper operates at consistencies of the fibre suspensions between 3 and 15% depending on the type of mate¬ rial in suspension and on the quantity of liquid necessary to contain the required quantity of 0 ₂ as a solution-emul¬ sion for the delignification. The quantity of 0 ₂ , in a liquid solution-emulsion, really active may reach 10% of the dry cellulosic fibres' contained in the reactor. The volume of the apparatus or of every single one in the case of operating in series, is chosen so as to realize reaction times which may vary between 30 minutes and 3 hours.

The heating medium (generally steam) has characte¬ ristics such as to permit the heating up to temperatures which may vary between 60 and 180°C. The turbopulper is tested for working pressures up to 20 bar. The pressure naturally depends from the performance required by the apparatus and is the equivalent of the partial gas (0 ₂ ) pressure plus that of the vapour at the corresponding working temperatures.

In the practice, the details accomplished for the realization could however be varied without giving rise for this to go out of the limits of the invention and hence of the dominion of the patent.