Field of the invention Drying up-to fine powder of any alimentary, chemical, biological, liquid even sensible to the temperature, with solids in suspension or in solution, with any concentration of dry and with any viscosity (provided it is pumpable) securing low contact times and operating either under pressure or under vacuum, under low temperatures according to the requirements of the process to be performed.

The state of the technique Many types of dryers processing several products and operating according to several principles are known.

For products to be dried liquid, with any solid content, even in solution, with any viscosity (but pumpable), which cannot tolerate stated temperatures for lengths of time relatively long, which must be dried up-to powder, the sole typology of effective dryer since now known is the spray-dryer.

Nevertheless this type of dryer requires large room, considerable air deliveries, dust powder collection systems, odour knockdown systems meanwhile its energy yield is low.

Vice versa the dryer under this invention occupies small room, it requires a reduced investment, it doesn't needed air supply, it doesn't require considerable powder and odours

knockdown systems, it has an high energy yield, it can operate under vacuum and consequently under low temperatures and it offers the advantage of the possibility to be used even to preconcentrate the product to be dried, so reducing its quantity.

Description of the invention The machine of the invention is made of a cylinder with and heating jacket, in one or more sections, and an expansion head (machine body) ; a complex rotor, with stirrer-type spider motorization, with a fed product distribution system; a product to be dried feeding group ; a computerised power and control board. The components are described further on. Said machine can be incorporated into a common thin film evaporation plant of the types already known, either under pressure or under vacuum according to the requirements of the process to be performed. The geometry of the cylinder and of the rotor is such to allow to operate as thin film dryer, producing dried material in powder form, avoiding highly powerful motorizations and high stresses, and with contact times limited in a range not much over ten seconds. Said machine can operate even as a common high yield concentrator- evaporator allowing, if convenient, a preconcentration of the liquid to be dried, so reducing its quantity and increasing the capacity of the machine to produce dry material. The

whole of the plant in which the machine has to be incorporated is represented in Figure 1.

The machine body is a vertical cylinder with external jacket, fitted to an overstanding expansion head, which has an outlet opening and an overhead fitting for the rotor spider. The cylinder is placed vertically and it is open in the lower part to discharge the dried product. It can be fitted to a powder recovery tank. The expansion head has a side outlet for the discharge of the vapour produced during drying. Said outlet can be fitted to a condenser and suction equipment.

The whole is shown in Figure 2.

The rotor is made of: a motor group, a spider with seal, an hallow shaft, sleeves with vanes bearing rims, a product distribution system, a rotary fitting, a drain.

The rotor is shown in Figure 2. The motor group is of type and capacity suitable to the machine dimension. The spider is designed according to the requirements of the motor group and to the shaft length. The seal may be of ring, packing, mechanical type, etc. The shaft is designed according to the stresses it has to bear, it is hallow, it is connected at the top to a rotary fitting for the product feeding, it has a drain, at the bottom, for cleaning.

The sleeves with vanes bearing rims are fitted on the shaft, at predetermined distances, according to the vanes'length

and they subdivide the rotor into several sections. The whole is shown in Figure 3.

The rims can hold two or more vanes, where three vanes is the optimum number.

Consequently, even each secion of the rotor has two or more vanes, with an optimum of three.

The vanes are fixed to the rims by several ways, preferably by a pin, and they are specifically described further on.

The product distribution system can be of several types, as described further on and it is fed throughout the hallow shaft in correspondence with the several sections into which the rotor is subdivided by the sleeves with vanes bearing rims. The rotary fitting and the drain are common commercial devices.

The vanes are key devices of the machine under this invention. In fact their geometry is essential to utilise the centrifugal force caused by the rotation of the rotor: no scraping of the inner surface of the cylinder during the product distribution phase, a moderate scraping whenever the machine is exceptionally used as concentrator ; more or less heavy scraping whenever the machine is properly used as dryer and the cycle is in the dry product scraping phase.

Furthermore the vanes should not warp and they have to be light as much as possible to allow for low power requirements

during the rotor acceleration and deceleration phases.

Furthermore their geometry has to be such not'to slip out" from the contact with the inner surface of the cylinder as a consequence of the tear of their scraping part.

The vanes may have different shapes. The most convenient one is shown in Figure 4 characterised by a tube with a pin which performs as hinge, two bends which make their structure more rigid, a replaceable blade and an index mass.

Besides the type above described, named"scraping"vane, different vanes types may exist, with different functions.

One of these type is the"smearing"vane made of any material and even composite, with replaceable and even teflon coated "smearing"part, to reduce any encrusting possibility to a minimum. The"smearing"type vane is made of a pin at one side of which there is the"smearing"part of the vane and, on the other side, there is a mass.

The"smearing"vane, on the side where the mass is fixed, is connected by a pretensioned spring to the rotor shaft and it is such made that, whenever the rotor rotates at low velocity, the vane slips on the inner cylinder wall and, whenever the speed is higher it detaches: that is, it operates exactly in an opposite way versus of the"scraping" vane.

The combination on the same rotor of"smearing"vanes with

"scarping"vanes allows to perform the best drying cycle.

The cylinder/rotor/section/vanes geometry. In Figure 5 there are shown: rç inner cylinder circumference radius ; rm vanes masses baricentral radius; r, vanes hinges radius ; ruz vanes'slipping out"radius; I rotor section high ; a angle between rc and vane dip.

The geometry of the machine of the object of the invention is such that: rm = (0.5-0.9) rc ; ra = (0.2-0.7) rc ; = [ (1, 01- 1,20) rc]-ra ; I = 300-900 mm ; rc = (0. 2-1) I a = 20°-70° To make sure that the vanes do not scrape the product at the lower rotor velocity, the same might be equipped with a polling back spring fixed to the shaft of the rotor and to the vane, of such a force to be capable to contrast the centrifugal force caused by the vane mass whenever the rotor rotates at the minimum velocity, but not whenever it rotates at the maximum velocity.

The product feeding is made throughout the hallow shaft of the rotor. The distribution is made by nozzles fixed on the same shaft, placed in correspondence with each rotor section.

The nozzles are preferably of flat jet, self cleaning, with angle such that, according to the cylinder section geometry, their jet invests nearly completely the length of the

cylinder generatrix included within the section toward which the nozzles are oriented, leaving a small lower part free which performs as"security"to product potential flow down.

The best performance is obtained by using self-closing self cleaning-nozzles, which prevent the clogging and the product drying inside the nozzles. By the rotation of the rotor the product is consequently distributed uniformly on the inner surface of the cylinder. The device is shown in Figure 6.

Whenever self-closing, self-cleaning nozzles are used the residual pressure inside the same nozzles is released by an electrically operated valve placed on the feeding pipe or placed on the head of the rotary fitting, allowing the product to flow, because of the initial pressure to be discharged, into a recovery tank.

An alternative to this distribution system is that one made by equalizers and distribution pipes. The equalizer is a manifold with an inlet and one or more outlets, which are connected either to another equalizer or to distribution pipes. It is made in such way to cause the product to go to all the outlets in the equalizer. An example is shown in Figure 7. In order to operate properly, inside the equalizer there should be a breackwave, of any type, to force the product to fill completely the lower part of the equalizer

before it flows out to the distribution pipes. By the rotor rotation the pipes distribute the product on an inner cylinder wall circumference and the product flows down on the inner cylinder surface, and it dries.

The equalizers and pipes distribution system is less effective then the nozzles system, because it does not secure a uniform distribution and therefore it causes some crust percentage. Furthermore it is more difficult to be managed and it is subject to incrustations and cloggings as a consequence of the inside pipes product drying.

One more alternative to the nozzles and to the equalizer and pipes distribution system is a direct distribution, obtained by pipes directly connected to the rotor shaft, each of them having and overflow at the same high as shown in Figure 8.

It works like as the preceding alternative but without an equalizer, Independently from the product distribution system, the product feeding is always pulsanting and associated to a cyclic rotor running, meanwhile the same rotates at a choosen minimum velocity such that the vanes don't scrap the product during its distribution and during the subsequent drying time, until the drying is completed and, only at that time, thanks to the increase of the angular velocity of the rotor, they start scraping.

A fundamental characteristic of the present invention is the cyclic running of the machine. The cycle is composed of: a feeding and on the inner cylinder wall product distribution phase as short as possible, an on the inner cylinder wall product drying phase, and a dried product scraping and gravity powder falling to the equipment bottom phase. The operating cycle is controlled by the power and control board.

Examples of operating cycles are shown in Figure 9.

To alternate vanes scraping phases to non scraping phases, the variation of the centrifugal force (and therefore of the pressure of the vanes blades on the cylinder surface) caused by the variation of the angular velocity of the rotor is utilised.

The product feeding group is such to secure high deliveries for very short lengths of time, so allowing for a delivery regime as much as possible"'nothinq-maximum-nothinq". This can be achieved by different ways, amoung which the most reliable one is made of a pump, an autoclave-tank (of small volume), a high flow ultra quick shutter valve. A flow metering controller device, of magnetic type, allows for the most convenient machine use.

The power and control board includes a programmable inverter, a PLC (or a set of timers), an amperometer, a flow controller, and other possible instruments. The power and control board secures the machine cyclic running.