GB2099969A - A dryer for particulate material - Google Patents

Abstract

A dryer for particulate material comprising a plurality of zones through which the material to be dried is carried sequentially by air through the zones to cause drying. The dimensions of the zones are arranged so that the velocity of the material passing into one zone is altered such that the material can be constrained to dwell in that zone and turbulate therein until it has dried sufficiently to be carried by the air into the next succeeding zone. <IMAGE>

Description

SPECIFICATION A dryer for particulate material The present invention relates to a dryer for particulate material such as powdered, granular, fibrous or loose material in general.

According to the present invention there is provided a dryer for particulate material comprising a plurality of zones through which the material to be dried is carried sequentially by air through the zones to cause drying, the dimensions of the zones being arranged so that the velocity of the material passing into one zone is altered such that the material can be constrained to dwell in that zone and turbulate therein until it has dried suffientiy to be carried by the air into the next succeeding zone.

Preferably, the zones are arranged in a column, the material travelling upwardly therethrough as it dries.

Preferably also, the final zone of the sequence is arranged to constrain the material therein until it is dry and can be carried by the air to a discharge region of the dryer.

Preferably also, vanes are located in the zones to prevent material turbulating therein from modulating or sticking together.

The present invention will now be described by way of example with reference to the accompanying drawing which shows in diagrammatic form a dryer according to the present invention.

A dryer according to the invention basically comprises three main regions, an inlet region 1 at the base of the dryer, a drying column 2 through which the material to be dried passes upwardly from the inlet region land a discharge region 3 where the material dried in the column 2 is collected and discharged and the air used to carry the material through the dryer is exhausted and can be recirculated.

The inlet region 1 comprises a fresh air intake 4, which is provided with a damper 5 and which leads into a heater 6 via a second damper 7. Both dampers 5 and 7 can be controlled by pneumatic cylinder or hydraulic ram or be manually operated. The heater 6 can be any suitable form of heater and powered by various fuels such as gas, oil or electricity or use steam to heat the incoming fresh air. This air is drawn into the dryer through the intake 4 and the heater 6 by a fan 8 which is located immediately downstream of the heater 6. The fan 8 discharges the heated air into pipework 9 at the base of the drying column 2 via an injector nozzle 10 located adjacent the fan 8. The flow of air into the pipework 9 is controlled by the damper 7.

The particulate material to be dried is introduced into the pipework 9 through a hopper 11. Alternatively, material can be supplied to the dryer by a screw, belt or pneumatic conveyor, or any other convenient means. If the material is supplied by a continuous centrifuge, however, to prevent the simultaneous supply of a large quantity of cold air a cyclone must be interposed between the centrifuge and the dryer.

The drying column 2 comprises a plurality of zones 12A, 12B, 12C and 12D which are arranged in a succession up the column 2. The zones 12 are arranged to have different cross-sectional areas so that the velocity of the air and thereby that of the material to be dried is altered as they pass upwardly along the column 2 from zone to zone 12. The zones 12 of the column 2 are, in fact, constructed for use with one particular material and for a predetermined range of air velocities. In use, each zone 12 is adapted to receive the particulate material carried by the air and owing to the cross-sectional area of the zone 12 reduce the velocity of the air carrying the material so that the wet particles thereof cannot move out of the zone 12 with the air flow.These wet particles are thereby retained within the zone 12 and turbulate therein until the particles have dried and reduced their weight sufficiently to be carried by the air into the next succeeding zone 12. Hence, the particles fly from one zone 12 to the next. The uppermost zone 12 of the column 2 is adapted so that the particles will turbulate until they have completely dried out before they can fly from the column 2 into the discharge region 3.

In orderto prevent the wet material passing up the column from taking up a modular form or from sticking together, vanes 13 can be located within the column 2 between the zones 12 to constrain the turbulating material to circulate therearound. The vanes 13 in successive zones 12 are inclined at opposed angles so that circulation takes place in opposite directions in any two adjacent zones 12.

This tends to prevent the wet particles from sticking together as they must change their direction of rotation on passing from one zone to the next which discourages modulation and breaks up clumps of particles.

The column 2 is connected at its top to the discharge region 3 of the dryer by U-shaped pipework 14. The now dry material issuing from the column into the pipework 14, is therefore forced to change direction so that it flies downwardly into the discharge region 3.

The discharge region 3 is principally made up of a sleeve filter box 15 which comprises a cavity or chamber 16 defined by filter walls 17. The air entering the box 15 from the pipework 14 passes through the filter walls 17 into an outer chamber 18 leaving the dry particulate material to collect within the cavity 16. At the lower end of the cavity 16 is an air lock arrangement 19 with a valve 20 which can be opened to discharge the material from the cavity 16 when desired. If the material is to be discharged into, for example, a hopper or on to a conveyor, then the air lock arrangement 19 can be operated so that the valve 20 is opened at timed intervals to ensure that the air within the cavity 16 is not continually lost and is recirculated.Alternatively, if the material is to be packaged into impermeable bags or bins which can be fitted to the lower end of the cavity 16, then the air lock arrangement 19 is not required as the impermeable nature of the bag or bin attached to the filter box 15 itself prevents the air from the cavity 16 being lost.

The air which passes into the chamber 16 is discharged in one or two ways. Part of the air is evacuated directly to atmosphere by means of a fan 21 via a damper 22 which closes off a passageway 23 housing the fan 21. The rest of the air is recirculated into the dryer via a duct 24 which is connected into the inlet region 1 upstream of the air control damper 7 but downstream of the damper 5 in the intake 4. It will be appreciated that, when an air lock arrangemenu is provided, to ensure that the heated airwhich has passed through the column 2 does pass into the chamber 15 to be discharged or evacuated and not short circuit directly to atmosphere, the valve 20 cannot be left continually open and must only be opened for short periods to discharge material into the air-lock arrangement 19.

It will be appreciated that the dryer of the invention is adapted for use with many different forms of particulate material such as powdered, granular, fibrous or loose material generally. If the material is abrasive in nature, for example sand, then the interior of the dryer as a whole, apart from the filter box 14, can be lived with a material such as cast basalt. As is described above, the size of column 2 and the quantity of air drawn into the dryer as controlled by the fan 6 and damper 7 according to the particular material to be dried. It is envisaged that the damper 7 will normally occupy a position which is less than fully open except when it is desired to scavenge and clean the dryer when the damper 7 would be fully opened.

CLAIMS (filed 6April 1982) 1. A dryer for particulate material comprising a plurality of zones through which the material to be dried is carried sequentially by air through the zones to cause drying, the dimensions of the zones being arranged so that the velocity of the material passing into one zone is altered such that the material can be constrained to dwell in that zone and turbulate therein until it has dried sufficiently to be carried by the air into the next succeeding zone.

2. A dryer according to claim 1, wherein the zones are arranged in a column, the material travelling upwardly therethrough as it dries.

3. A dryer according to claim 1 or 2, wherein the final zone of the sequence is arranged to constrain the material therein until it is dry and can be carried by the air to a discharge region of the dryer.

4. A dryer according to claim 1,2 and 3, wherein vanes are located in the zones to prevent material turbulating therein from modulating or sticking together.

5. A dryer substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. housing the fan 21. The rest of the air is recirculated into the dryer via a duct 24 which is connected into the inlet region 1 upstream of the air control damper 7 but downstream of the damper 5 in the intake 4. It will be appreciated that, when an air lock arrangemenu is provided, to ensure that the heated airwhich has passed through the column 2 does pass into the chamber 15 to be discharged or evacuated and not short circuit directly to atmosphere, the valve 20 cannot be left continually open and must only be opened for short periods to discharge material into the air-lock arrangement 19. It will be appreciated that the dryer of the invention is adapted for use with many different forms of particulate material such as powdered, granular, fibrous or loose material generally. If the material is abrasive in nature, for example sand, then the interior of the dryer as a whole, apart from the filter box 14, can be lived with a material such as cast basalt. As is described above, the size of column 2 and the quantity of air drawn into the dryer as controlled by the fan 6 and damper 7 according to the particular material to be dried. It is envisaged that the damper 7 will normally occupy a position which is less than fully open except when it is desired to scavenge and clean the dryer when the damper 7 would be fully opened. CLAIMS (filed 6April 1982)

1. A dryer for particulate material comprising a plurality of zones through which the material to be dried is carried sequentially by air through the zones to cause drying, the dimensions of the zones being arranged so that the velocity of the material passing into one zone is altered such that the material can be constrained to dwell in that zone and turbulate therein until it has dried sufficiently to be carried by the air into the next succeeding zone.

2. A dryer according to claim 1, wherein the zones are arranged in a column, the material travelling upwardly therethrough as it dries.

3. A dryer according to claim 1 or 2, wherein the final zone of the sequence is arranged to constrain the material therein until it is dry and can be carried by the air to a discharge region of the dryer.

4. A dryer according to claim 1,2 and 3, wherein vanes are located in the zones to prevent material turbulating therein from modulating or sticking together.

5. A dryer substantially as hereinbefore described with reference to the accompanying drawing.