GB2210152A

GB2210152A - Drying particulate material

Info

Publication number: GB2210152A
Application number: GB8722383A
Authority: GB
Inventors: Arthur Stanley Pittwood
Original assignee: FOXFIELD WALKDEN EQUIPMENT Ltd
Current assignee: FOXFIELD WALKDEN EQUIPMENT Ltd
Priority date: 1987-09-23
Filing date: 1987-09-23
Publication date: 1989-06-01
Anticipated expiration: 2007-09-23
Also published as: GB2210152B; GB8722383D0

Abstract

Drying apparatus comprises a rotary conveying drum having a perforated wall fast with an internal screw feed adapted on rotation of the drum to feed tumbling solid material generally in the direction of the inclined drum axis along at least one helical feed path while permitting liquid to drain through the wall. A stationary hollow tubular core is arranged coaxially within the drum so as to bound the feed path internally, an inlet for delivering wet material to one end of the drum conveyor, an outlet for removing solid material from the other end of the drum conveyor, and drying means arranged within said core for directing drying fluid outwardly across said feed path. Preferably the drying means is a high velocity air knife which blasts residual water through the drum wall as an atomised spray.

Description

DRYING APPARATUS This invention relates to drying apparatus.

It has been previously proposed to separate solids from suspension in liquid using a screen in the form of a rotary perforated drur.; fast wits an internal conveying screw for conveying the solid material out of suspension in the general direction of the upwardly inclined drum axis while permitting the liquid to drain thorough the drum. If dry material is required a further drying operation following the drum separator is necessary.

It is an object of the present invention to improve such screening apparatus by enabling it to dry the separated solid material.

Acccording to te present *nvent,o,l the is provided drying apparatus comprising a rotary conveying drum having a perforated wall fast with an internal screw feed adaP-eG OEX rotation of tiie drum to feed solid material generally in the direction of the preferably upwardly inclined drum axis along at least one helical feed path while permitting liquid to drain through the wall, a stationary hollow tubular core arranged coaxially within the drum so as to bound the feed path internally, an inlet for delivering wet material to one (preferably lower) end of the drum conveyor, an outlet for removing solid material from the other (preferably upper) end of the drum conveyor, and drying means arranged within said core for directing drying fluid outwardly across said feed path.

Preferably the drying mea;l comtLises ai least one air blower for blowing high velocity air through a narrow slot extending parallel to the axis of the drum adjacent an opening in the core wall.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic longitudinal section of one embodiment of drying apparatus according to the invention; Fig. 2 is a corresponding view of a second embodiment, and Figs. 3 and 4 are cross sections of Figs. 1 and 2 in the pianes lEI-III and IV-IV respectively.

Referring now to Fig. 1, the drying apparatus comprises a rotary conveying drum 1 of cylindrical shape with an upwardly inclined axis 2 about which the drum is rotated in use by means not shown. The drum wall 3 is perforated in known manner to permit drainagc of liquid ut prevent passbaye of soli6 material to be dried. The drum 1 is rotationally fast with a multi-start feed screw 4 for conveyina solid material from tfle lower (wet) end of the conveying drum to the upper (dry) end thereof.The conveying screw 4 is initiaily of reduclng pitch at the wet end of the drum and finally of increasing pitch at the dry end of the drum, the major extent thereof between the wet and dry ends being of close, uniform pitch. The drum 1 is supported on rollers 5, 6 in a casing C (Fig. 3).

At the wet end the drum 1 has a central opening through which extends an inlet pipe 7 for delivering solid particles with a relatively small amount of water into the vicinity of a solid feed cone 8. A hollow tubular stationary core 9 extends coaxially within the druir 1 from beyond tne dry enrj tnereof to near the inlet end of the drum. The core 9 has a solid cylindrical wall 10 closed at the lower end by a solid end wall 11. Accommodated within the core 9 is an air-blowing nozzle 12 of an air knife system for blowing high velocity air through a narrow slot extending lengthwise of the drum 3 in close proximity to a correspondingly dimensioned opening (not shown) in the cylindrical wall 10 of the core 9.The opening in the wall 10 is covered by > grid cr mech to prevent entry of material into the core 9. The nozzle 12 is connected by an air supply pipe 13 to a centrifugal fan or blower (not shown). Air knife systems are well known ano turtner information is contained in Technical Information Leaflet IND 48 published by The Electricity Council. As illustrated in Fig. 3 the air knife system may have two angularly spaced nozzles 12 but it is also possible to utilise one nozzle or to provide more than two nozzles.It will he noted that the cylindrical 11 1C of thc core 9 is in close proximity to the inner edges of the conveying screw 4 which thus defines with the bou:ldirlg wall provided by tnc drum wall 3 and the core wall 10 a number (corresponding to the number of screw starts) of helical feed paths 14 for the solid material.

The embodiment of Fig. 2 is of essentially the same construction save that the inlet, in this cast for solid particles with a large amount of water, is provided by an inlet pipe 15 extending coaxially through the core 9 and penetrating its end wall 11 to emerge in the vicinity of the solid feed cone 8 at the wet end of the drum 1. Features corresponding to those of Figs. 1 and 3 are given the same reference numerals in Figs. 2 and 4.

In operation, solid material is deliVL-Led .{J the wet end of the drum 1 by inlet pipes 7 or 15 and the drum 1 is rotated about its axis relative to the core 9. The solid material is fed into the feed paths 14 by the action -of the feed cone 8 and screw 4 and the majority of the water associated therewith is drained by gravity through the drum wall 3 before reaching the air nozzles 12, drainage being assisted by compaction owing to the reducing pitch of the feed screw 4. During the wultiple (the {the number cf which is determined by the pitch of the helical feed screw in the region of the air nozzles 12) of the solid material, the high velocity air knives issuing òm the nozzles 12 disperse tne residual water in the form of atomised water and vapour which is dispelled through the drum wall 3. Drying is assistea by tumbling of the solid particles in the feed paths 14.

Claims

1. Drying apparatus comprisin a rotary convQing drum having a perforated wall fast with an internal screw feed adapted on rotation of the drum to feed solid material generally in the direction of the inclined drum axis along at least one helical feed path while permitting liquid to drain through the wall, a stationary hollow tubular core arranged coaxially within the drum so as to bound the feed path internally, an inlet for delivering wet material to one end of te drum conveyor, an outlay Cor removing solid material from the other end of the drum conveyor, and drying means arranged within said core for directing drying fluid outwardly across said feed path.

2. Apparatus as claimed in claim 1, wherein the drum axis is upwardly inclined.

3. Apparatus as claimed in claim 1 or 2, wherein the inlet is at the lower end of the drum conveyor.

4. Apparatus as claimed in TT , wherein the inlet is provided Dy an open end of an inlet feed pipe extending through said core.

5. Apparatus as claimed in any one of the preceding claims, wherein the outlet is at the upper end of the drum conveyor.

6. Apparatus as claimed in any one of the preceding claims, wherein the drying means comprises at least one air blower for blowing high velocity air through a narrow slot extending parallel to the axis of the drum adjacent an opening in the core wall.

7. Drying apparatus, substantially as herein described with reference to the accompanying drawings.