WO1993002330A1

WO1993002330A1 - Apparatus for drying sludge and similar materials

Info

Publication number: WO1993002330A1
Application number: PCT/DK1992/000233
Authority: WO
Inventors: Mikael Kau; Lars Christensen
Original assignee: Cimbria Unigrain Ltd AS
Current assignee: Cimbria Unigrain Ltd AS
Priority date: 1991-07-24
Filing date: 1992-07-24
Publication date: 1993-02-04
Anticipated expiration: 1994-01-24
Also published as: DK138991D0; AU2438592A; DK138991A

Abstract

In an apparatus for drying sludge and other materials of a porridge-like or paste-like consistency, said apparatus being of the kind comprising: (a) a rotating drum (1), open at both ends and adapted to be rotated about its at least roughly horizontal axis of symmetry, (b) substantially stationary means (2, 3) for introducing hot drying air into the apparatus, (c) supply means (12, 13) for introducing the material to be dried into the apparatus, and (d) separating means (4-6) for separating the material having been dried in the apparatus from the used drying air, the new feature consists in (e) such an arrangement, that the material to be dried is introduced directly onto the inside wall of the fire chamber of the apparatus, whereby the material and the drying air with a temperature of approximately 1000 °C are moved in co-current through the apparatus, so that the material is sterilized while at the same time being brought to give off water in the form of water vapour. With this arrangement, it is achieved partly that the material is sterilized and dried, partly that it is comminuted - especially by the use of scrapers (14) and stirring ribs (15) - so that a fine-grained dry product is produced.

Description

Apparatus for drying sludge and similar materials.

TECHNICAL FIELD

The present invention relates to an apparatus of the kind set forth in the preamble of claim 1.

BACKGROUND ART

When sewage is cleaned, e.g. in municipal sewage processing plants, two important waste products are produced. One of these waste products is in the form of gases from the putrefaction process, which, due to their large content of inter alia methane, can be utilized as fuel. The other waste product is sludge in the form of a porridge-like substance with a water content of more than 80%.

Removal of the sludge involves substantial problems with regard to transportation and/or the environment, inter alia because the sludge contains micro-flora and/or bacteria, possibly capable of spreading disease in humans, animals and/or plants, and because the sludge contains heavy metals, which are poisonous and for this reason should be prevented from entering any food chain.

DISCLOSURE OF THE INVENTION It is the object of the present invention to provide an apparatus of the kind referred to initially, with which the disadvantages referred to above may be avoided to a great extent, and this object is achieved with an apparatus, according to the present invention being constructed as indicated in the characterizing clause of claim 1.

With this arrangement, the quantity of sludge is reduced to about 1/5, and micro-flora and bacteria are killed, making it substantially less problematic to transport and deposit the sludge. It is also possible to burn the sludge, and in this case the quantity of ash produced will normally only amount to approximately 1/20 of the original amount of sludge.

With the embodiment set forth in claim 2, it is achieved, partly that the material to be dried and the air, with which it is to be dried, are introduced into and moved through the apparatus in the correct manner, partly that it is avoided to a great extent that the material turns into lumps or is "baked-on" to the walls of the apparatus.

Advantageous embodiments of the apparatus according to the present invention, the effects of which will be evident from the following detailed portion of the present specification, are set forth in claims 3-5.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed portion of the present specification, the present invention will be explained in more detail with reference to an exemplary embodiment of an apparatus according to the present invention, in part shown diagrammatically, whereas Figure 1 is a longitudinal sectional view of the apparatus, Figure 2 is a sectional view at the line II-II in

Figure 1, and Figure 3 is a sectional view at the linie III-III in Figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus comprises a rotating drum 1, into one end of which a fire chamber 2 protrudes through a small distance, while the other end of the drum 1 protrudes into a discharge chamber 4.

A burner 3 is placed in association with the stationary fire chamber 2, said burner being adapted to burn gas - e.g. the gas referred to above as coming from the putrefaction process of the sewage processing plants - or oil or other suitable fuel. The burner 3 heats the air in the fire chamber 2, said air possibly being introduced through the burner or together with its combustion gases.

The sludge or other material to be dried is introduced through a supply funnel 12, from where it is introduced into the fire chamber 2 by means of a worm 13 in such a manner, that the material hits the inside wall in the fire chamber 2.

Since the material to be dried and the air, with which it is to be dried, are introduced through the same end of the drum 1, the material and the drying air will move in co-current into and through the drum 1.

The drum 1 is kept in rotation by a motor 7 with associated gear drive means 8, and it rests on a number of bearing rollers 9.

The used drying air and the dry material leave the drum 1 in the discharge chamber 4, the, material leaving this chamber through an outlet chute 5, while the used drying air leaves through a chimney pipe 6, from where it may be conducted to a cleaning apparatus, e.g. a scrubber, and/or to a heat exchanger or other equipment, with which at least part of its heat content can be recuperated.

The apparatus also comprises a height-a justment mechanism 10, with which the inclination of the frame 11 of the apparatus and hence the inclination of the drum 1 can be adjusted in order to adjust the period of time, during which the material remains in the drum.

During operation, the burner 3, the supply means 12, 13 and the height-adjustment means 10 are adjusted in such a manner, that the drying air achieves a temperature of approximately 1000°C and that the time of residence is sufficiently long for killing micro-flora and bacteria in order to achieve a sterile product. Since the drying is carried out in co-current, i.e. that the material and the drying air are moved in the same direction, a very high efficiency is achieved, as the air leaving the apparatus is almost completely saturated with water vapour.

In order to avoid that the material to be dried burns in or adheres to the fire chamber 2, the apparatus comprises a number of scrapers 14, which are secured to the rotating drum 1 and hence continuously scrape the wall in the fire chamber 2. As will be evident from Figure 1, the scrapers 14 protrude into the fire chamber 2 beyond the location, at which the worm 13 debouches into the fire chamber, so that already at this location, the material will be subject to the action of the scrapers 14. Preferably, these scrapers 14 can be secured to diagrammatically shown stirring ribs 15 that are secured to the inside wall in the drum 1 and adapted to stir and/or convey the material present in the drum. The stirring ribs 15 ensure a continuous movement of the material in a uniform stream, and hence a uniform drying of the material.

Claims

C L A I M S

1. Apparatus for drying sludge and other materials of a porridge-like or paste-like consistency, said apparatus being of the kind comprising a) a rotating drum (1), open at both ends and adapted to be rotated about its at least roughly horizontal axis of symmetry, b) substantially stationary means (2, 3) for introducing hot drying air into the apparatus, c) supply means (12, 13) for introducing the material to be dried into the apparatus, and d) separating means (4-6) for separating the material having been dried in the apparatus from the used drying air, characterized by e) such an arrangement, that the material to be dried is introduced directly onto the inside wall of the fire chamber of the apparatus, whereby the material and the drying air with a temperature of approximately 1000°C are moved in co-current through the apparatus, so that the material is sterilized while at the same time being brought to give off water in the form of water vapour.

2. Apparatus to claim 1, characterized in a) that the means for introducing hot drying air in the apparatus comprise a^) a fire chamber (2), one end of which protrudes into one end of the drum (1) and the other end of which comprises a2) a burner (3) adapted to introduce hot gases of combustion and possibly additional air being heated by said gases of combustion into the fire chamber (2), and b) that the supply means (12, 13) for introducing the material to be dried into the apparatus are adapted to introduce the material into the fire chamber (2), preferably at a high-level location in same, and c) that scrapers (14) are secured to the end of the drum (1) facing the fire chamber (2), said scrapers protruding into the fire chamber (2) adjacent to its peripheral wall and beyond the location, at which the supply means (12, 13) for the material to be dried debouch into the fire chamber (2).

3. Apparatus according to claim 1 or 2, characterized in that the scrapers (14) are adapted to be adjusted relative to the fire chamber (2).

4. Apparatus according to any one or any of the claims 1-3 and comprising a number of stirring ribs (15) placed within the drum (1) and adapted to stir the material and/or convey the material through the drum, characterized in that the scrapers (14) are secured to the stirring ribs (15).

5. Apparatus according to any one or any of the claims 1-4, characterized by means (10) for adjusting the inclination of the drum (1).