GB2083189A

GB2083189A - Drying or toasting apparatus

Info

Publication number: GB2083189A
Application number: GB8121050A
Authority: GB
Original assignee: DOBSON PARK ENG
Current assignee: DOBSON PARK ENG
Priority date: 1980-08-23
Filing date: 1981-07-08
Publication date: 1982-03-17

Abstract

A hollow cylindrical drum 12 has a perforated cylindrical wall 40, which mounts in the drum interior a helical scroll 30. The drum is supported on an axial shaft 31 by arms 34 between the shaft and the scroll. The drum is rotated in a casing 11 to pass material such as particulate cereals along the drum from an inlet 28 to an outlet 29. The casing is partitioned 13, 14 into sections each of which has an air inlet 16, 17, 18 and an air outlet 21, 22, 23 for passing hot gas through the perforations in the drum. The wetted air is vented at 21 and the drier air from outlets 22,23 is recirculated. <IMAGE>

Description

SPECIFICATION Drying or toasting apparatus This invention relates to apparatus for drying or toasting friable particulate material such as cereal products.

Cereal products in friable particulate form are often dried or toasted by passing them through a heated, fluidised bed, or by passing them down a sloping, rotating hollow drum containing steamheated pipes or through which hot gases are passed.

Other methods are used including cascade drying. In all cases, there is a problem of some of the material being retained in the apparatus longer than other portions, so that drying or toasting is uneven.

Apparatus according to the present invention can be constructed to provide even drying and/or toasting.

The present invention provides drying and/or toasting apparatus, for friable particulate material, comprising a hollow cylindrical drum mounted for rotation about its cylinder axis, an inlet for particulate material at one axial end of the drum, an outlet for the material at the opposite axial end of the drum, a helical scroll extending along the interior wall of the drum, means for passing hot gases through the drum, and means for effecting rotation of the drum and the scroll.

Preferably, the hot gases are passed into the drum through the peripheral wall thereof. It is advantageous for the drum wall to be perforated both for passage of hot gases into the drum and for fines to be filtered out of the drum.

In one particular construction for use as toasting apparatus, the drum is rotatably mounted in a casing which is divided axially of the drum into segments, each segment having an independent inlet for hot gases. It is envisaged that the segment adjacent the inlet may have a vented outlet for moist gases and the outlet of the other segment or of each other segment may be connected in a circuit for recirculating the gases.

Reference is now made to the accompanying drawings, wherein: Figure 1 is a part-sectional view of a drum of toasting apparatus according to the invention; Figure2 is an end elevation of a casing of the apparatus, with the drum shown in dash lines; and Figure 3 is a side elevation of the casing perpendicular to the view of Figure 2.

The apparatus shown comprises a casing 11 (Figures 2 and 3) receiving a hollow, cylindrical drum 12. The casing is divided axially of the drum into segments by partitions 13, 14 (Figure 3). Each partition has a circular aperture (not shown) for receiving the drum periphery and each wall 1 lea 1 ib of the casing has an aperture for receiving a shaft 31 for the drum. Hot air is fed into the casing 11 below the drum 12 at a side 15 of the casing between said ends 1 la, 1 ib. The air is fed through three separate ports 16, 17, 18 into the three casing segments defined by the partitions 13, 14. Sealing strips 19, 20, which are in close proximity to the periphery of the drum, prevent the hot air from passing around the sides of the drum but need not be provided where shown in the drawings.The top of the casing has vents 21, 22, 23 for corresponding segments adjacent the opposite side 24 of the casing. The bottom part of the casing has sloping sides defining a hopper like construction 26. An opening at the bottom is closed by a removable plate 27.

At the end 11 a of the casing is provided a chute 28 for feeding material into the drum at an inlet end thereof. At the opposite end I ib of the casing is an outlet chute 29 for dried and toasted material spilling out of an outlet end of the drum.

As shown in Figure 1,the drum 12 is provided on its interior wall with a helical scroll 30 extending lengthwise of the drum and co-axially therewith. The scroll is carried by the axial shaft 31. Collars 32,33 are fixed on the shaft 31 and have radial arms 34 secured to the scroll 30 in positions so as not to impede passage of material through the drum. There is a space between the shaft and the scroll allowing free flow of hot gases radially of the drum. The drum has a multiplicity of perforations 40 over substantially its whole cylindrical surface for passage of hot air into the drum from the casing. The radial depth of the scroll is dependent on the desired bed depth of material passing through the drum. Drive means 36 is provided for rotating the drum and the scroll, at a desired speed, the drive means being connected with the shaft 31.

In use, the drum 12, is rotated, whilst moist material is fed through the chute 28 into the drum and hot air is fed into the casing through the ports 16,17, 18 from a heater 41. The material falls into the scroll 30 and passes along the interior of the drum, being propelled by the scroll 30, which rotates with the drum. The material is propelled by this action out of the drum to the chute 29. Hot air passes radially through the perforations 40 in the drum and hence through the material, whilst the material is moving along the drum. The movement of the scroll effects the turning of the particles of material to assit drying and toasting by the hot air. At the same time, fines pass through the perforations and collect in the hopper like construction 26.

The material is dried whilst passing through the first segment of the casing and the resultant moist air passes through the perforations to leave by the vent 21 of the segment for venting to atmosphere.

The material is toasted in the other segments and the air leaving the vents 22,23 is recirculated by being returned to the heater 41.

With this arrangement, all the material passing through the drum is retained in each segment for substantially the same period, so that the material is evenly dried and toasted.

It is envisaged that the drum may be rotated by external rollers, instead of by the spindle 31, thereby freeing the whole of the space within the scroll.

The fines collecting in the hopper-like construction 26 may pass onto conveying means for removing the fines continuously.

It is possible for the hot air to be passed axially into or out of the drum and hence radially out of or into the drum respectively especially where the apparatus is intended only for drying and where the partitions 16, 17, 18 are not provided.

Claims

1. Drying and/ortoasting apparatus, for friable particulate material, comprising a hollow cylindrical drum mounted for rotation about its cylinder axis, an inlet for particulate material at one axial end of the drum, an outletforthe material at the opposite axial end of the drum, a helical scroll extending along the interior wall of the drum, means for passing hot gases through the drum, and means for effecting rotation of the drm and the scroll.

2. Drying and/ortoasting apparatus according to Claim 1,wherein said means for passing hot gases through the drum includes radial openings in the cylindrical wall of the drum.

3. Drying and/or toasting apparatus according to Claim 2, wherein the drum has a multiplicity of perforations in its cylindrical wall for passing hot gases through the drum, and the drum is rotatably mounted in a casing having an inlet for hot gas below the drum.

4. Drying and/ortoasting apparatus according to Claim 3, wherein the casing has an outlet for gas located above the drum, so that gas passes out of the drum through said perforations.

5. Drying and/ortoasting apparatus according to Claims 3 or 4, wherein the casing is partitioned axially of the drum to define sections, each section having a respective hot gas inlet.

6. Drying and/or toasting apparatus according to Claim 5, wherein the segment adjacent said one axial end of the drum has a vent to atmosphere and the segment adjacent said opposite axial end has an outlet leading to recirculating means for recirculating the gas.

7. Drying and/or toasting apparatus according to any one of Claims 3 to 6, including means for receiving fires sieved from the material by said perforated cylindrical wall of the drum.

8. Drying and/ortoasting apparatus according to any preceding claim, wherein the scroll is secured by radial arms to a shaft which extends through the drum to define a space between the shaft and the scroll.

9. Drying and/or toasting apparatus constructed substantially as herein described with reference to the accompanying drawings.