GB1564404A

GB1564404A - Drying means

Info

Publication number: GB1564404A
Application number: GB5331175A
Authority: GB
Original assignee: Ferris A B; Ferris G K
Current assignee: Ferris A B; Ferris G K
Priority date: 1976-12-09
Filing date: 1976-12-09
Publication date: 1980-04-10

Description

(54) DRYING MEANS (71) We, GLENN KINGSLEY FERRIS, Australian citizen, of 80 Parthenia Street, Dolans Bay, New South Wales, 2229 Australia, and AUDREY BRENDA FERRIS, British citizen of the same address, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to drying means and more particularly to drying means for drying granular and/or shredded material wetted with an evaporable, combustible contaminant.

Following the introduction of stringent air pollution emission and doour levels difficulty has been experienced in the drying of granular and/or shredded materials, such as metal swarf, which have been wetted with combustible contaminants, such as cutting oils. The prior art proposals have either produced unduly high particulate emission levels due to combustion of the evaporate within the drying chamber or have been uneconomic compared with the present invention due to the plant complexity and necessity for extensive pollution control.

The present invention is designed to provide a viable alternative to the prior art proposals.

The present invention consists in drying means for drying granular and/or shredded material wetted with an evaporable, combustible contaminant, comprising: a rotatable drying drum having inlet and outlet means for the granular material; radiant heating means lying in juxtaposition with the drying drum and adapted to heat the granular material passing therethrough and to evaporate the combustible material therefrom, the radiant heating means deriving heat energy from an afterburner and conduit means arranged to conduct the combustible material evaporated from the granular material to the after-burner.

In a preferred embodiment of the invention the radiant heating means comprises a heating tube passing axially down the drying drum.

The after-burner, which is advantageously gas or oil fired, is preferably disposed in axial alignment with the heating tube adjacent the inlet end of the drying drum.

In a further preferred arrangement the evaporate is recycled from the outlet end of the drying drum to the after-burner by a fan.

The evaporate is preferably passed through a particle extractor such as a cyclone to remove dust particles from the evaporate stream. The evaporate preferably enters the after-burner in an eccentric manner specifically designed to bring about thorough mixing of the evaporate with the combustion gases in the afterburner.

The arrangement according to preferred embodiments of the present invention are particularly applicable to the drying of metal swarf, such as brass and aluminium swarf, which has been wetted with water soluble cutting oils. Large quantities of these material become available as scrap from the turning and machining of metals during manufacturing processes, however, the material cannot conveniently be resmelted without prior drying because of consequent pollution problems and melt losses. These materials can now be economically dried with the production of an oxide free, bright product without the production of unacceptable air pollution emission levels due to the thorough combustion of the evaporate in the after-burner.The economics of the process are enhanced by the recycling of the combustible evaporate to the after-burner such that the combustion of the evaporate contributes to the heating of the dryer.

Hereinafter given by way of example only is a preferred embodiment of the present invention which is described with reference to the accompanying drawings in which: Fig. 1 is a schematic side elevational view of drying means according to the present, and Fig. 2 is a schematic plan view of the drying means of Fig. 1.

The drying means 10 comprises a drying drum 11, a heating tube 12, an after-burner 13, and evaporate recycle means 14.

The drying drum 11 comprises an elongate cylinder 15 disposed to rotate about an axis which falls slightly from its inlet to its outlet ends. A pair of support rings 16 are disposed coaxially about the cylinder 15 and support it on rollers 17. The cylinder 15 is rotated by a motor 20 acting on a drive ring 22 disposed about the cylinder. Inlet means 18 ald outlet means 19 are provided to enable granular material to be introduced into the cylinder 15 and to be retrieved from it. If desired a helical flight (not shown) may be disposed about the inner surface to assist the movement of the granular material through the cylinder as it is rotated.

The heating tube 12 extends along the longitudinal axis of the cylinder 15 and projects from it at either end. The heating tube 12 is supported within the cylinder 15 by brackets (not shown) and rotates with it. The afterburner 13 which is preferably gas or oil fired, is disposed at the inlet end of the heating tube 12 while the outlet end of the heating tube is connected to a conventional exhaust stack 21.

The evaporate recycle means 14 comprises a recycle duct 23, a cyclone 24 and a circulating fan 25. The duct 23 is connected at its inlet end to the outlet means 19 and terminates at the after-burner 13 which it enters eccentrically in such a manner that thorough mixing of the evaporate and the combustion gasses of the after-burner is brought about.

In use the after-burner 13 is fired and the heating tube 12 heated to operating temperature. The after-burner is so designed that substantially complete combustion takes place within its confines to ensure that relatively clean gas is exhausted from the heating tube 12 through the exhaust stack 21.

Granular material to be dried is then admitted continuously to the cylinder 15. As the granular material passes down the cylinder 15 it is dried by the radiant heat emanating from the heating tube and the wetting contaminants evaporated from it. The granular material is discharged from the outlet means 19. In the case of metal swarf the slightly reducing atmosphere generated in the cylinder 15 due to the negative pressure engendered by the extraction of the evaporate from the cylinder 15 by the evaporate recycle means 14 reduces the oxidation of the metal swarf during the drying step and contributes to the production of an oxide free, bright, product which can be directly resmelted.

The evaporate passes from the cylinder 15, through the duct 23 to the cyclone 24 where dust particles are removed and thence, via the circulating fan 25 to the after-burner 13.

The eccentric introduction of the evaporate to the after-burner 13 is designed to ensure thorough mixing of the evaporate and the combustion gasses to bring about complete combustion of that part of the evaporate which is combustible. The evaporate is thus recycled from the cylinder 15 to the afterburner 13 and thence, via the heating tube 12 to the exhaust stack.

WHAT WE CLAIM IS:- 1. Drying means for drying granular and/ or shredded material wetted with an evaporable, combustible contaminant, comprising: a rotatable drying drum having inlet and outlet means for the granular material; radiant heating means lying in juxtaposition with the drying drum and adapted to heat the granular material passing therethrough and to evaporate the combustible material therefrom, the radiant heating means deriving heat energy from an after-burner and conduit means arranged to conduct the combustible material evaporated from the granular material to the after-burner.

2. Drying means as claimed in Claim 1 in which the radiant heating means comprises a heating tube passing axially down the drying drum.

3. Drying means as claimed in Claim 2 in which the after-burner is disposed in axial alignment with the heating tube adjacent the inlet end of the drying drum.

4. Drying means as claimed in any one of claims 1 to 3 in which the means to recycle the combustible material from the outlet end of the drying drum to the after-burner includes a fan.

5. Drying means as claimed in any one of claims 1 to 4 in which the means to recycle the combustible material includes a particle extractor such as a cyclone to remove dust particles from the recycled material.

6. Drying means as claimed in any one of claims 1 to 5 in which the means to recycle the combustible material is so arranged that the evaporate enters the after-burner in an eccentric manner specifically designed to bring about thorough mixing of the evaporate with the combustion gasses in the after-burner.

7. Drying means substantially as hereinbefore described with reference to the accompanying drawings.

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

Claims

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

coaxially about the cylinder 15 and support it on rollers 17. The cylinder 15 is rotated by a motor 20 acting on a drive ring 22 disposed about the cylinder. Inlet means 18 ald outlet means 19 are provided to enable granular material to be introduced into the cylinder 15 and to be retrieved from it. If desired a helical flight (not shown) may be disposed about the inner surface to assist the movement of the granular material through the cylinder as it is rotated.

The heating tube 12 extends along the longitudinal axis of the cylinder 15 and projects from it at either end. The heating tube 12 is supported within the cylinder 15 by brackets (not shown) and rotates with it. The afterburner 13 which is preferably gas or oil fired, is disposed at the inlet end of the heating tube

12 while the outlet end of the heating tube is connected to a conventional exhaust stack 21.

The evaporate recycle means 14 comprises a recycle duct 23, a cyclone 24 and a circulating fan 25. The duct 23 is connected at its inlet end to the outlet means 19 and terminates at the after-burner 13 which it enters eccentrically in such a manner that thorough mixing of the evaporate and the combustion gasses of the after-burner is brought about.

In use the after-burner 13 is fired and the heating tube 12 heated to operating temperature. The after-burner is so designed that substantially complete combustion takes place within its confines to ensure that relatively clean gas is exhausted from the heating tube 12 through the exhaust stack 21.

Granular material to be dried is then admitted continuously to the cylinder 15. As the granular material passes down the cylinder 15 it is dried by the radiant heat emanating from the heating tube and the wetting contaminants evaporated from it. The granular material is discharged from the outlet means 19. In the case of metal swarf the slightly reducing atmosphere generated in the cylinder

15 due to the negative pressure engendered by the extraction of the evaporate from the cylinder 15 by the evaporate recycle means 14 reduces the oxidation of the metal swarf during the drying step and contributes to the production of an oxide free, bright, product which can be directly resmelted.

The evaporate passes from the cylinder 15, through the duct 23 to the cyclone 24 where dust particles are removed and thence, via the circulating fan 25 to the after-burner 13.

The eccentric introduction of the evaporate to the after-burner 13 is designed to ensure thorough mixing of the evaporate and the combustion gasses to bring about complete combustion of that part of the evaporate which is combustible. The evaporate is thus recycled from the cylinder 15 to the afterburner 13 and thence, via the heating tube 12 to the exhaust stack.

WHAT WE CLAIM IS:- 1. Drying means for drying granular and/ or shredded material wetted with an evaporable, combustible contaminant, comprising: a rotatable drying drum having inlet and outlet means for the granular material; radiant heating means lying in juxtaposition with the drying drum and adapted to heat the granular material passing therethrough and to evaporate the combustible material therefrom, the radiant heating means deriving heat energy from an after-burner and conduit means arranged to conduct the combustible material evaporated from the granular material to the after-burner.
2. Drying means as claimed in Claim 1 in which the radiant heating means comprises a heating tube passing axially down the drying drum.
3. Drying means as claimed in Claim 2 in which the after-burner is disposed in axial alignment with the heating tube adjacent the inlet end of the drying drum.
4. Drying means as claimed in any one of claims 1 to 3 in which the means to recycle the combustible material from the outlet end of the drying drum to the after-burner includes a fan.
5. Drying means as claimed in any one of claims 1 to 4 in which the means to recycle the combustible material includes a particle extractor such as a cyclone to remove dust particles from the recycled material.
6. Drying means as claimed in any one of claims 1 to 5 in which the means to recycle the combustible material is so arranged that the evaporate enters the after-burner in an eccentric manner specifically designed to bring about thorough mixing of the evaporate with the combustion gasses in the after-burner.
7. Drying means substantially as hereinbefore described with reference to the accompanying drawings.