METHOD AND APPARATUS FOR SUPPLYING PRE-HEATED PARTICULATE MINERAL MATERIAL FOR MAKING A MINERAL MELT

Abstract

A method for supplying pre-heated particulate mineral material from a separating cyclone to a cyclone furnace inlet includes receiving the mineral material in a material receiving conduit from a bottom outlet of the separating cyclone. There is a first pressure in the receiving conduit. The mineral material is fluidised in the receiving conduit and flows upwards in an inclined elongated gas-lock valve from a lowermost section of the receiving conduit to an uppermost section of an outlet conduit. The mineral material is supplied from the outlet conduit to the inlet of the cyclone furnace, wherein there is a second pressure that is higher than the first pressure. A fluidisation unit in the gas-lock valve maintains the particulate mineral material in a fluidised state, such that the fluidised particulate mineral material flows due to gravity from the material receiving conduit, upwards through the gas-lock valve and to the outlet conduit.

Claims

1. (canceled)

2. A method for supplying pre-heated particulate mineral material from a separating cyclone to an inlet of a cyclone furnace, said method comprising: receiving the pre-heated particulate mineral material in a material receiving conduit from a bottom outlet of the separating cyclone, in which receiving conduit there is a first pressure P.sub.1; fluidising the pre-heated particulate mineral material in the receiving conduit; flowing the fluidised particulate mineral material upwards in an inclined elongated gas-lock valve from a lowermost section of the receiving conduit to an uppermost section of an outlet conduit; and supplying the particulate mineral material from the outlet conduit to the inlet of the cyclone furnace, wherein there is a second pressure P.sub.2, and where said second pressure P.sub.2 is higher than said first pressure P.sub.1; wherein a fluidisation unit in the gas-lock valve maintains the particulate mineral material in a fluidised state, such that the fluidised particulate mineral material flows due to gravity from 1) the material receiving conduit, 2) upwards through the gas-lock valve and 3) to the outlet conduit.

3. The method according to claim 2, wherein the material receiving conduit and the outlet conduit are arranged substantially vertically.

4. The method according to claim 2, wherein the fluidisation unit comprises a stirring element.

5. The method according to claim 4, wherein the stirring element comprises an axle extending longitudinally inside the gas lock valve, said axle being provided with radially extending elements.

6. The method according to claim 2, wherein one or more air inlets are provided in the material receiving conduit for fluidisation of the pre-heated particulate mineral material.

7. The method according to claim 2, wherein one or more air inlets are provided in the gas-lock valve for fluidisation of the particulate mineral material.

8. The method according to claim 2, wherein the fluidisation unit comprises a screw conveyor.

9. The method according to claim 2, wherein an inclination of the gas-lock valve is between 20 and 50 degrees relative to horizontal.

10. The method according to claim 2, wherein an amount of the preheated particulate material present is rising up in the material receiving conduit to a level which is at least above an outlet point where the fluidised particulate material flows into an uppermost section of the outlet conduit.

11. The method according to claim 2, wherein the bottom outlet of the separating cyclone is connected to a plurality of material receiving conduits via a material distributor.

12. A method for making a mineral melt, comprising the steps of: providing a cyclone furnace with an inlet; providing a separating cyclone with a bottom outlet; and supplying pre-heated particulate mineral material from the separating cyclone to the inlet of a cyclone furnace according to the method of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the following the invention is disclosed in further detail with reference to the accompanying drawings, in which:

[0015] FIG. 1 is a schematic diagram of an apparatus according to a preferred embodiment of the present invention, and

[0016] FIG. 2 is a schematic drawing of an apparatus for supplying pre-heated particulate mineral material according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] FIG. 1 shows a circulating combustion chamber 1 which comprises a cylindrical top section, a frustoconical bottom section and a cylindrical base section. Particulate fuel is introduced into the circulating combustion chamber from supply 2 and is preferably coal. Preheated mineral material is introduced into the circulating combustion chamber via a mineral material conduit 3. The coal and mineral material are introduced together with combustion air via an inlet conduit 4 and secondary air which is provided in compressed air supply 5 and is introduced through at least two tangential inlets such as a lance (not shown) into the circulating combustion chamber 1 to ensure thorough mixing of the coal 2 with the combustion air 6 and to sustain the circulating motion of the combustion gases and suspended material in the circulating combustion chamber 1. Secondary fuel, in this case natural gas may also be injected through supply (not shown) into the base section of the circulating combustion chamber 1.

[0018] The coal 2 is combusted in the combustion gas 6, which is preferably oxygen-enriched air 5, in the circulating combustion chamber 1. The resultant melt 9 is collected in the base zone of the circulating combustion chamber 1 and exits the chamber via an outlet. The exhaust gases are fed through the flue 10 at the top of the circulating combustion chamber 1 to the first conduit 11 where they are used to heat the granular mineral materials about to be fed into the circulating combustion chamber 1. The exhaust gases are then led to a first pre-heater cyclone 12 where they are separated from the mineral materials which are at this point mixed together. The exhaust gases flow from the first pre-heater cyclone 12 to the second pre-heater cyclone 13 via a second conduit 14. Following the second pre-heater cyclone 13 the exhaust gases flow through conduit 15 to a dust cyclone 16 and into a further treatment 17 where indirect heat exchange with the combustion gas occurs to preheat the combustion gas. The exhaust gases are then treated to make them safe to pass to the atmosphere such as by filter (not shown).

[0019] The mineral materials are preheated prior to being added to the circulating combustion chamber 1. In detail, a first mineral material which is typically a raw stone material is supplied from supply 19 to second conduit 14 and undergoes initial preheating in second pre-heater cyclone 13. The first mineral material is then passed through first mineral material conduit 18 and introduced into first conduit 11 and subsequently passes to the first pre-heater cyclone 12. The second mineral material is provided from supply 20 to the first conduit 11 downstream of the first mineral material. The second mineral material is generally a processed mineral material typically bonded mineral fibres, such as recycled mineral fibres. To ensure that NOx reducing conditions are generated in the first pre-heater cyclone 12, nitrogenous materials such as ammonia can be added at position 21 into the first conduit 11 immediately before the first pre-heater cyclone 12. However, as the waste mineral wool supplied at 20 contains binder with nitrogenous content it may advantageously be obsolete to add ammonia to the conduit 11 as the ammonia contained in the recycled waste mineral wool is sufficient to ensure the NOx reducing conditions in the first pre-heater cyclone 12. Some of the first mineral materials may be carried up with the exhaust gases from the second pre-heater cyclone 13 through conduit 15. These are separated from the exhaust gases in dust cyclone 16 or in a filter and recycled back to join the preheated mineral materials via conduit 22.

[0020] The exhaust gases leave the circulating combustion chamber 1 via the flue 10. The exhaust gases enter the first conduit 11 and are quenched from a temperature of between 1500 and 1900° C., usually around 1650° C. to a temperature of between 1000 and 1500° C. normally around 1300° C. by quenching air. The first mineral material is introduced into the first conduit 11 via inlet downstream of the second mineral material which is introduced into the first conduit 11 via the conduit 20.

[0021] The chamber is generally a vertical rather than a horizontal furnace. It normally has a cylindrical top section into which the fuel, mineral material and combustion gas are injected, a frustoconical bottom section and a base section in which the melt can be collected. Alternatively the chamber can be wholly cylindrical. The base section is preferably an integral part of the chamber and can be simply the end part of the frustoconical bottom region or can be a cylindrical section at the end of the bottom region. Preferably, the diameter of the base section is not larger than the diameter of the top section in contrast to traditional systems which often employ a tank at the base of the chamber of enhanced volume.

[0022] The base section has an outlet for the mineral melt through which the melt passes as a stream 9. This stream 9 can then be subjected to fiberisation in any conventional manner, for instance using a cascade spinner or a spinning cup or any other conventional centrifugal fiberising process. Alternatively, the mineral melt can be used in other industrial processes.

[0023] The general motion of gases and suspended particulate material in the circulating combustion chamber is a cyclone motion. This is created by introduction of the combustion gas 6, as well as particulate fuel 2 and mineral material, at an appropriate angle to sustain the swirling motion. When used, the secondary combustion gas 5 is also preferably introduced in the same direction so as to sustain the circulating currents. The exhaust gases become separated from the mineral melt which is collected in the base of the chamber, and are passed to a heat exchange system, usually via a flue in the top of the circulating combustion chamber. The exhaust gases are then used to preheat the mineral material in a heat exchange system. The exhaust gases typically leave the circulating combustion chamber at a temperature of between 1300 and 1900° C., usually 1500 to 1750° C., such as around 1550 to 1650° C.

[0024] The heat exchange system preferably comprises at least one and preferably two or even three pre-heater cyclones 12, 13. The first and second mineral materials are typically added to a first conduit 11 which transports exhaust gases from the circulating combustion chamber 1 to the first pre-heater cyclone 12. In the first pre-heater cyclone 12, the exhaust gases are separated from the mineral material. The mineral material, which comprises the first and second mineral materials mixed, is passed through mixed mineral material conduits 3 to the inlets of the circulating combustion chamber 1 to be melted. In FIG. 1 two inlets 4 to the cyclone furnace are shown. There might be only a single inlet 4 or more than two inlets 4, such as three, four or more.

[0025] The pressure P.sub.1 of the bottom outlet of the first pre-heater cyclone 12 is much lower than the pressure P.sub.2 at the inlet to the combustion chamber 1. This pressure difference gives problems with regard to the dosing of the pre-heated particulate mineral material as the pressure difference will stimulate a “back-flow” in the outlet conduit 3 if no means are taken to avoid this. However, as shown in FIG. 2, this problem is addressed by providing a gas-lock valve 7 in the conduit 3. If the cyclone furnace has more than one inlet 4 there will be provided a gas-lock valve 7 for each conduit 3 and a material distributor will be arranged between the bottom outlet of the separating cyclone 12 and the gas-lock valves 7. The or each gas-lock valve 7 comprises a material receiving conduit 3a adapted for receiving the pre-heated particulate mineral material 100 from the bottom outlet of the separating cyclone 12, wherein there is the first pressure P.sub.1. The apparatus further comprises an outlet conduit 3b supplying the particulate mineral material 100 to the inlet 4 of the cyclone furnace 1, wherein there is the second pressure P.sub.2. The particulate mineral material 100 is fluidised and flows due to gravity from the material receiving conduit 3a to the outlet conduit 3b through a gas-lock valve 7, which comprises an elongated housing 71 providing an inclined particulate material flow passage between the receiving conduit 3a and the outlet conduit 3b. As can be seen in FIG. 2, both the receiving conduit 3a and the outlet conduit 3b are substantially vertically oriented. The fluidised particulate material flow is flowing due to gravitational pressure provided by the material that is supplied from the bottom of the separating cyclone to the receiving conduit 3a and the inclination of the elongated housing 71 therefore is directing the material flow upwards in the gas-lock valve 7. Hereby, the constant presence of particulate material in the gas-lock valve 7 prevents a back-flow as the two pressures P.sub.1 and P.sub.2 at either ends are prevented from equalising each other.

[0026] The elongated housing 71 is preferably provided with stirring means, such as a screw conveyor 72, also sometimes referred to as a worm conveyor. The screw conveyor 72 is driven by an electric motor or similarly suitable drive means 73. The screw conveyor 72 is not provided to transport the material, but to stir the particulate material in the elongated housing 71 to keep the particulate material in a fluidised state.

[0027] One or more air inlets 31 are preferably provided in the wall of the material conduit 3a of the gas-lock valve 7 to keep the particulate mineral material 100 in a fluidised state.

[0028] The elongated housing 71 is inclined upwards from said material receiving conduit 3a at a lowermost section of the housing 71 to said outlet conduit 3b at an uppermost section of the housing 71, so that the fluidised particulate mineral material 100 flows due to gravity from the material receiving conduit 3a into the housing 71 at the lowermost section thereof and from the housing 71 into the outlet conduit 3b at the uppermost section of the upwardly inclined housing 71. The gravitational flow of the material 100 is due to the column of fluidised mineral material which is built up in the receiving conduit 3a which is higher than the level d.sub.2 between the mineral material entry point and the mineral material exit point in the inclined elongated housing 71.

[0029] The inclination of the elongated housing 71 may be in the order of 20-50 degrees, such as 30 degrees, relative to the horizontal. The elongated housing 71 has a diameter d.sub.1 and the amount of fluidised material present is at least an amount rising up in the first conduit 3a to a level d.sub.2 which is at least above the outlet point where the particulate material flows out of the elongated housing 71 and into the outlet second conduit 3b. This level d.sub.2 is preferably at least similar to the diameter d.sub.1 of the elongated housing 71, as indicated in FIG. 2, which ensures stability of the gas-lock valve 7 even if there are some pressure pulsation at the either end thereof. This means that the elongated housing 71 is filled with material between the inlet at the lowermost end of the housing 71 and the outlet at the uppermost end of the housing 71 so that no back flow of gas can occur as the particulate material then prevents the gas at the higher pressure P.sub.2 at the outlet from entering into the housing 71 and escape to the material receiving conduit 3a where the low pressure P.sub.1 is present.

[0030] Above, the invention is described with reference to a preferred embodiment. It is realised that other variants, dimension relationships and other embodiments may be provided without departing from the scope of the invention as defined in the accompanying claims. For instance, by the invention it is realised that the gas-lock valve would work even if the height d.sub.2 in the receiving conduit 3a is low, but practice has shown that it is advantageous that this height d.sub.2 should at least correspond to d.sub.1. The reason is that there occasionally may occur some pressure pulsation in the system and if the level in the receiving conduit 3a is too low there is a risk that a back-pressure may blow the elongated housing of the gas-lock valve empty.