GB2041183A

GB2041183A - Pneumatic particle transfer

Info

Publication number: GB2041183A
Application number: GB8000570A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-01-22
Filing date: 1980-01-08
Publication date: 1980-09-03
Also published as: GB2041183B

Abstract

Apparatus and method for disposing of waste material in which hot particles of refractory material are propelled upwardly, in a current of air, through a vertical duct 5 and are then allowed to shower downwardly from the upper end of the duct into the upper end of a surrounding hopper 7 which is conveniently of annular cross-section and into which the waste material is introduced. The waste material thus comes into contact with the hot particles and is heated by them before passing from the lower end of the hopper into the lower end of the duct to be burnt in the current of air. <IMAGE>

Description

SPECIFICATION Pneumatic particle transfer This invention relates to a method of and apparatus for pneumatically transferring hot particles of refractory material and entraining waste material with the particles so that the waste material is consumed during the particle transfer.

It is known that waste material can be consumed in a fluidised bed incinerator. In such incinerators the material is introduced into the fluidized bed of hot particles of refractory material and is consumed whilst it is in the bed.

The present invention relies on a different concept in that waste material is consumed whilst being pneumatically transferred along a duct along with hot particles of refractory material. The particles being displaced along the duct do not constitute a fluidised bed.

These particles are pneumatically blown or otherwise displaced along a duct and the waste material is consumed during its passage along the duct.

According to a first aspect of the present invention, in a method of disposing of waste material, hot particles of refractory material from adjacent the lower end of a hopper are displaced pneumatically upwardly along a substantially vertical duct and allowed to shower downwardly from the upper end of the duct into the hopper and waste material is introduced into the hopper into contact with the hot particles to be preheated thereby and the combustible content of the waste material is displaced with the refractory particles into the duct to be burnt therein.

By introducing the waste material into the hopper into contact with the hot particles, the waste material is preheated. There is insufficient oxygen present in the hopper to cause complete burning of the combustible content of the waste material but the waste material is heated and the combustible material pryolises.

The pyrolised material eventually enters the lower end of the duct where it comes into contact with a supply of oxygen causing the combustible content of the waste material to be burnt completely in the duct. The noncombustible content of the waste material, metal, stones and the like are not displaced up the duct by the air supply and are removed periodically from the lower end thereof.

According to a second aspect of the invention, apparatus for disposing of waste material comprises a substantially vertically disposed duct, means for passing air upwardly through the duct, and a hopper in communication with the upper and lower ends of the duct and means for introducing waste material into the hopper.

Gases of combustion both from the hopper and the duct flow out of a gas off-take located at the upper end of the duct.

In order that the invention may be more readily understood it will now be described, by way of example only, with reference to the accompanying drawing which is a sectional side elevation of apparatus for disposing of waste material in accordance with the invention.

Apparatus for disposing of waste material comprises an incinerator vessel 1 lined with refractory material 2. A vertical duct 5 is located within the vessel and plenum chambers 3 and 4 are located below the lower end of the duct. The outer wall 6 of the duct is separated from the wall of the vessel 1 to provide an annular hopper 7 surrounding the duct 5. The lower end of the hopper is in communication with the lower end of the duct and the upper end of the duct is in communication with the upper end of the hopper. A cylindrical guard 8 surrounds the upper end of the duct and defines a gas off-take 9. One or more feed tubes 10 extend through the wall of the vessel into the hopper intermediate its ends. Means (not shown) are provided for injecting liquid or gaseous fuel into the duct 5.

In use, particulate refractory material is contained in the hopper and air under pressure is supplied to the plenum chambers 3, 4. The air is blasted upwardly along the duct and it takes with it particulate refractory material entering the lower end of the duct from the annular hopper. The particulate material is heated in the duct and the particulate material spills over the top end of the duct downwardly back into the upper end of the hopper.

Waste material is introduced into the hopper through the feed tubes 10 and comes into contact with the hot particulate material. This hot material preheats the waste material and the combustible content of the material is pyrolised by the hot refractory material. Gases of pyrolysis leave the upper end of the hopper and pass through the curtain of refractory material falling into the hopper and leave the vessel through the gas off-take 9. The waste material eventually makes its way to the bottom of the hopper and enters into the lower end of the duct where it is blasted upwardly with the refractory material. The waste material thus comes into contact with a plentiful supply of air and the combustible content of the material is burnt in the duct 5. Ash and other particles from the burnt material flow over the upper end of the duct back into the hopper.The non-combustible content of the waste material, such as stones, glass, metal and the like, pass across the plenum chamber 3 into the plenum chamber 4 which is angled downwardly to direct these materials to an outlet 11 located at the base of the vessel.

The waste material need not necessarily be fed on to the top of the hopper but may be fed into the hopper at a position between its upper and lower ends.

The duct can be of any height chosen to provide the optimum residence time for combustion to take place. Since the particulate material in the duct is not fluidised, the particulate material is used as a heat sink and to entrain the waste material into the hopper.

The hot material also initiates and sustains a reasonable level of pyrolysis within the hopper.

The particulate material can be relatively small but within a wide size range so long as it can be pneumatically transported through the duct, but it does not have to meet any of the critical requirements as regards size, shape and density which apply to a fluidised bed.

The annular cross-section of the space between the upper end of the hopper and the upper end of the duct can be of any convenient cross-section.

The curtain of particles raining down into the upper end of the hopper effects final burnout of any material which has not been burnt in the duct.

Additional air jets can be introduced continuously into the duct either at the top of the duct or tangentially into the duct to impart a vortex or spin to the particles in the duct, or may be pulsed to agitate the material in the duct.

Tubes for providing heated water or steam may be located in the gas off-take.

Obviously, if the waste material is in very large pieces, some form of shredder is required to reduce it to reasonable sizes before introducing it into the hopper.

The duct and the cylindrical guard can be of refractory material, ceramic material or high alloy steel, and may conveniently be so designed as to form heat exchangers.

Instead of the apparatus having a central cylindrical duct and an annular outer hopper, it may alternatively comprise a central cylindrical hopper with a surrounding duct, which may be annular; in this case the gas take-off will be formed as a central "hood" and the plenum chamber will be in the form of an annulus surrounding the base of the hopper.

Claims

1. A method of disposing of waste material comprising the steps of (a) propelling hot particles of refractory material from the lower end of a hopper, upwardly through a substantially vertical duct, (b) allowing the said hot particles to shower downwardly from the upper end of the duct into the upper end of the hopper and (c) introducing the waste material into the hopper into contact with the hot particles so that the waste material is heated by the hot particles and the combustible content of the waste material is evolved and/or displaced with the refractory particles into the duct to be burnt therein.

2. A method as claimed in claim 1, in which the hot particles are propelled upwards pneumatically.

3. A method of disposing of waste material according to claim 2, in which the supply of oxygen in the hopper is limited so that the waste material is preheated but the combustible content is prevented from burning in the hopper and is pyrolised.

4. A method of disposing of waste material as claimed in any preceding claim, in which air jets are introduced into the duct to impart a vortex or spin to the particles.

5. A method of disposing of waste material as claimed in any preceding claim, further comprising passing hot gases from the top of the duct and the hopper through a heat-exchanger so as to provide transfer heat to a heat-exchange medium.

6. Apparatus for disposing of waste material comprising a substantially verticallydisposed duct having upper and lower ends, means for passing air upwardly through the duct, means for initiating combustion in the duct, a hopper having an upper and lower ends respectively in communication with the said upper and lower ends of the duct, and means for introducing waste material into the hopper.

7. Apparatus as claimed in claim 6, in which the duct is substantially cylindrical and the hopper is annular and surrounds the duct.

8. Apparatus as claimed in claim 6 or claim 7, in which the means for introducing waste material comprises at least one feed tube communicating with the hopper at a position intermediate its ends.

9. Apparatus as claimed in any one of claims 6 to 8, in which the said means for passing air upwardly through the duct comprises a plenum chamber positioned at the lower end of the duct.

1 0. Apparatus as claimed in claim 9, in which the said plenum chamber comprises a hollow annular body defining a central outlet for solid combustion products and incombustible waste, the upper surface of said body being formed with outlets for air and being inwardly angled to deflect said combustion products into said central outlet.

11. Apparatus as claimed in claim 10, comprising a further plenum chamber arranged beneath said central outlet and having a sloping upper surface, and also comprising an ash outlet below the level of said plenum chambers, whereby solid combustion products passing through said central outlet pass over said upper surfaces of said plenum chambers to be cooled by the said air and thereby preheat the air, and are deflected into said ash outlet.

1 2. Apparatus as claimed in any one of claims 7 to 11, further comprising an annular gas-take-off chamber surrounding the upper end of the hopper, and means connecting the hopper to the take-off chamber near the upper end of the hopper, whereby gases passing out of the top of the duct carry the refractory particles into the upper end of the hopper and then pass outwardly into said gas take-off chamber.

1 3. Apparatus as claimed in claim 12, further comprising heat exchange means connected to said take-off chamber.

1 4. A method of disposing of waste material substantially as herein described.

1 5. Apparatus for disposing of waste material substantially as herein described with reference to the accompanying drawing.