WO1990001466A1

WO1990001466A1 - Method and device for melting meltable material

Info

Publication number: WO1990001466A1
Application number: PCT/SE1989/000429
Authority: WO
Inventors: Harry Ericsson
Original assignee: Harry Ericsson
Priority date: 1988-08-12
Filing date: 1989-08-10
Publication date: 1990-02-22
Also published as: SE8802890D0

Abstract

The invention relates to a method and apparatus for melting material, preferably glass. The material is pulverized and fed into a combustion chamber (1), together with combustion air and fuel, while being simultaneously subjected to the influence of low frequency sound waves. The sound waves have a sufficiently high intensity to cause the powder and the gas molecules to oscillate mutually in the combustion chamber (1), such as to increase the heat transfer coefficient.

Description

METHOD AND DEVICE FOR MELTING MELTABLE MATERIAL

The present invention relates to a method and apparatus for sintering or melting totally or partially meltable materials, such as mineral and/or metallic materials.

Known methods and apparatus intended for this purpose all have the drawback of being very inefficient. This applies both to those cases in which solid material is fed down into a molten-material container while sup¬ plying heat to the container, and also to those cases when a flame is directed onto the material to be melted down. In this latter case in particular, the efficiency of the process is extremely unsatisfactory when the solid material concerned is glass, which only absorbs a small part of the radiation from the flame. An efficiency in excess of 10% is very difficult to achieve, and consequently such methods and apparatus are not economically viable when applied to recycled glass and the melting down of disposable glass bottles. The efficiency achieved when melting down glass with the aid of these known methods and apparatus is often not higher than immediately above 2%.

The object of the present invention is to provide a method and an apparatus of the aforesaid kind which will produce efficiencies in the order of about 50%.

This object is achieved by the method according to the present invention, by pulverising the material and feeding the glass, together with combustion-air and fuel, into a combustion chamber while, at the same time, subjecting the material to low-frequency sound waves of sufficient intensity to set the powder and the gas molecules in mutual oscillatory motion in the combustion chamber, so as to increase the heat transfer coeffi¬ cient. By low-frequency sound waves is meant here sound waves which have a frequency of 10-100 Hz, preferably 10-20 Hz, so-called infrasonic frequencies.

The method according to the invention expands upon the increased thermal transmission coefficient which is attained when a particle oscillates in relation to the gas molecules present in a gas flow that has been sub¬ jected to high-intensity sound waves at the same time as combustion takes place around the material particles. This effect is particularly manifest when the particles comprise glass, which is a very poor absorber of thermal radiation.

The pulverized material is preferably heated in a flui¬ dized bed with aid of the waste gases deriving from the combustion chamber, and the combustion air is heated, advantageously in a heat exchanger by means of the gases deriving from the fluidized bed.

When the air of combustion is heated to 400°C and the pulverized material, for instance glass particles, is pre-heated to 600°C in the fluidized bed and said glass is heated to 1400^βC in the combustion chamber, the efficiency of the smelting process is as high as 72%. In order to ensure that the acoustic effect is sufficient, it is normally necessary to increase the air surplus, therewith lowering the efficiency to some extent. An efficiency of 50%, however, can be achieved without difficulty.

An apparatus for carrying out the inventive method is mainly characterized by an arrangement for pulverizing the meltable material, preferably glass, and feeding said material to a combustion chamber; a combustion-air delivery arrangement; an arrangement for feeding fuel to the combustion chamber; and an arrangement for genera- ting high-intensity sound waves and conducting said sound waves to the combustion chamber such as to cause the powder to oscillate in relation to the gas molecules therein.

The invention will now be described in more detail with reference to a preferred, exemplifying embodiment of an inventive apparatus and with reference to the accompany¬ ing drawing.

The single figure of the accompanying drawing illustra¬ tes apparatus for melting recycled glass and/or crushed glass, provided with a combustion chamber 1 which is connected to a furnace 3 by means of an inclined channel 2.

The combustion chamber 1 is provided with at least one nozzle device 4. Extending to the nozzle 4 is a fuel-oil delivery conduit 5, a conduit 6 for feeding pulverized glass G, and a combustion-air conduit 7. The glass to be melted down is pulverized to a particle size of 1 mm in a pulverizer 8 and is fed through a conduit 9 to a fluidized-bed container 10, and from there to a feed arrangement 11 connected to the feed conduit 6. Fluid- ization is effected in the container 10 with the aid of the waste gases deriving from the furnace 3, said gases being intended to pass through a conduit 12, extending from the furnace 3 to a gas cooler 13 connected to the bottom of the fluidized-bed container 10, and to pass up through the container 10 and its pulverized-glass content. The gases leave the container 10 through a conduit 14, through which said gases are conducted to an air pre-heater 15. The gases leave the pre-heater 15 through a conduit 16, which conducts the gases to a further gas cooler 17, by means of which the gases are cooled to a temperature as low as about 150°C. The waste gases can then passed to a fan device 18, through an outlet conduit 19.

Cold air is delivered to the air pre-heater 15 through a conduit 20, which is connected to the outlet of a pulse generator 21, which is constructed so as to deliver an air stream in which high-intensity sound waves propa¬ gate. The sound waves have a frequency of between 10 and 100 Hz, but will preferably lie within the infrasonic frequency range and propagate with unappreciable damp¬ ing, via the conduits 20 and 7 and the air pre-heater connected thereto, and from there to the combustion chamber 1 and along the inclined channel 2 to the furnace 3.

The nozzle or nozzles 4 in the combustion chamber 1 generate a plurality of flames into which the pulverized glass is sprayed or injected. The glass particles and the gas molecules in the combustion chamber are caused to oscillate mutually by the sound waves, wherewith intensive heat exchange takes place between the hot gases and the glass particles, which rapidly melt, either completely or partially. The glass particles fall down into the opening of the channel 2 , and the molten glass G, which has been heated to a temperature of 1400°C, flows through the channel 2 , in contact with the waste gases, which have a temperature of about 1500°C, and are collected in the furnace 3. The glass G is subjected to the influence of the sound waves, during transportation of the glass through the channel 2. The molten glass may splash vigorously, at least at the entrance to the channel.

The heat content of the waste gases is recovered in a suitable manner, first in the gas cooler 13, where the temperature is lowered from 1500°C to 1200°C, and then in the fluidized bed, where the temperature, under the influence of the sound waves, is lowered to 600°C, this being the temperature to which the glass particles are preheated. The temperature of the waste gases is further lowered in the air pre-heater 15, at the same time as the combustion air is pre-heated to 400°C. The waste gases are cooled finally in the gas cooler 17, to a temperature of 150°C, as beforementioned.

The pulse generator 21 may, advantageously, be a valve- less displacement machine of the kind described in Swedish Patent Specification 8605104-2, at least in the case of large plants of the kind described here.

It will be understood that the invention is not restric¬ ted to the described method and illustrated apparatus but that modifications can be made within the scope of the inventive concept as defined in the following claims.

For example, the invention can be applied for melting, either completely or partially, other material than glass, for instance iron ore or metal scrap, e.g. for recovering aluminium from aluminium cans, or for sintering mineral materials, such as in the manufacture of cement.

Claims

1. A method of sintering or melting meltable material, either completely or partially, such as mineral and/or metallic material, characterized by pulverizing the material and feeding said pulverized material, together with combustion air and fuel, into a combustion chamber (1) while simultaneously subjecting the material to low- frequency sound waves of sufficiently high intensity to cause the powder and the gas molecules to oscillate mutually in the combustion chamber, such as to increase the heat transfer coefficient.

2. A method according to Claim 1, characterized by pre- heating the pulverized material in a fluidized bed (10) with the aid of waste gases deriving from the combustion chamber.

3. A method according to Claim 2, characterized by pre- heating the combustion air in a heat exchanger (15) with the aid of gases deriving from a fluidized bed.

4. Apparatus for carrying out the method according to Claim 1, characterized by an arrangement (8) for pul- verizing meltable material, preferably glass, and deli¬ vering said material to a combustion chamber (1) ; com¬ bustion-air supply means (21, 7,20); an arrangement (5) for delivering fuel to the combustion chamber; and an arrangement (21) for generating low-frequency sound waves of high intensity and leading these waves to the combustion chamber (1) such as to cause the powder to oscillate relative to the gas molecules in said combus¬ tion chamber.

5. Apparatus according to Claim 4, characterized by a channel (9,6) for conducting the pulverized material to the combustion chamber (l) through a container (10) in which the waste gases deriving from the combustion chamber are intended to pass in a manner such as to produce a fluidized bed therein.

6. Apparatus according to Claim 5, characterized by a heat-exchanger (15) in which the combustion air is intended to be pre-heated by the waste gases deriving from the fluidized-bed container (10).

7. Apparatus according to any one of Claims 4-6, charac¬ terized in that the arrangement for generating sound waves consists of a valveless displacement machine.