WO1999066083A1

WO1999066083A1 - The roasting of ores or ore concentrates in a gas suspension shaft furnace

Info

Publication number: WO1999066083A1
Application number: PCT/IB1999/001146
Authority: WO
Inventors: Alan Francis Newall
Original assignee: Alan Francis Newall
Priority date: 1998-06-19
Filing date: 1999-06-18
Publication date: 1999-12-23
Also published as: AU4159999A

Abstract

A process for treating ore or ore concentrate includes introducing particulate ore or ore concentrate and a carrier gas at a low elevation into a substantially vertically extending treatment zone such that the ore or ore concentrate particles are entrained in the carrier gas, thereby carrying the particles upwards through the treatment zone to a high elevation where they are removed from the treatment zone together with the carrier gas. The particles are roasted or treated at elevated temperature while they are moving upwards through the treatment zone.

Description

THE ROASTING OF ORES OR ORE CONCENTRATES IN A GAS

SUSPENSION SHAFT FURNACE

This invention relates to the treatment of ores or ore concentrates. More particularly, this invention relates to a process for treating ore or ore concentrate and to roasting apparatus suitable for roasting or treating ore or ore concentrate.

According to a first aspect of the invention, there is provided a process for treating ore or ore concentrate, the process including introducing particulate ore or ore concentrate and a carrier gas at a low elevation into a substantially vertically extending treatment zone such that the particles are entrained in the carrier gas, thereby carrying the particles upwards through the treatment zone to a high elevation where they are removed from the treatment zone together with the carrier gas; and roasting or treating the particles at elevated temperature while they are moving upwards through the treatment zone.

The metal may be a base metal . The ore or ore concentrate may include a mineral or metal selected from the group consisting of zinc, copper, nickel, iron, cobalt, a precious metal or mineral, and mixtures thereof. The ore or ore concentrate may be a mineral or metal bearing ore which includes sulphur, and the carrier gas may include oxygen. In principle, the ore or ore concentrate may be any particulate material resulting from the processing of ore, which reacts exothermically with the carrier gas to allow the roasting or reaction to proceed autogenously, even if an auxiliary fuel is to be added to the ore or ore concentrate. Treating the particles may thus include oxidising or reducing the particles.

The carrier gas may include a gas selected from the group consisting of air, nitrogen, sulphur dioxide, carbon dioxide, oxygen, carbon monoxide, hydrogen, chlorine, and mixtures thereof.

The roasting of metal sulphide-bearing ore or ore concentrate particles in the presence of oxygen is an autogenous, exothermal reaction which will proceed once the particles have reached a required initiation temperature. The process may include the step of controlling roasting conditions in the treatment zone by modifying the composition of the carrier gas. Thus, the temperature of the treatment zone may be controlled by controlling the partial pressure of the oxygen in the treatment zone. The partial pressure of the oxygen in the treatment zone may be controlled by introducing a gas selected from the group consisting of air, nitrogen, carbon dioxide, oxygen, and mixtures thereof at one or more selected elevations into the treatment zone. In one embodiment of the invention, nitrogen is added to the carrier gas, which is air, to decrease the concentration or partial pressure of oxygen . This is done where the process requires partial oxidation of the particles for use in a downstream process such as acid leaching . One such application for the process is the treatment of iron pyrites.

The carrier gas may be introduced into the treatment zone under pressure. Thus, the treatment zone may be maintained at a pressure of between 1 bar(g) and 30 bar(g) . Typically, the treatment zone is maintained at a pressure of between 3 bar(g) and 20 bar(g) .

The particles may be roasted or treated in the treatment zone for a period of between 1 s and 30s. However, it is to be appreciated that this period depends on the particular ore or ore concentrate, and may thus fall outside the range provided . The treatment zone may have a height of between 3m and 30m. Typically, the treatment zone has a height of between 3m and 20m.

The ratio of the volumetric flow rate of the carrier gas, expressed in Nm Is, to a cross-sectional area of the treatment zone, expressed in m , may be between 2: 1 and 36: 1 . Typically, the ratio is between 1 0: 1 and 20: 1 , e.g. about 1 2: 1 .

The particles may have a particle size between 0, 1μm and 6000μm. Typically, the particles have a particle size between 0, 1μm and 250μm.

The particles may be roasted at a temperature of between 600°C and 1 200 °C, e.g . about 1 000°C.

The treatment zone may be defined by a vertically extending vessel. It will be appreciated by a person skilled in the art that the carrier gas moves upwardly in the vessel at a velocity which is influenced, amongst other things, by the diameter of the vessel and the pressure differential across the vessel. The particles, which are entrained in the carrier gas, move upwards at a net velocity being the difference between the carrier gas velocity and the particle free settling velocity. The formation of a fluidised bed is thus to be avoided by ensuring that conditions in the treatment zone are such that the particles are entrained and carried through the treatment zone. The particle free settling velocity is influenced, amongst other things, by the density, and thus by the pressure, of the carrier gas in the treatment zone. The residence time of the particles in the treatment zone and the temperature of the treatment zone may thus be controlled by manipulating the pressure of the treatment zone.

The linear velocity of the carrier gas through the treatment zone may be between 0,2m/s and 1 0m/s. Typically, the linear velocity of the carrier gas is between 2m/s and 5m/s, e.g . about 3,5m/s. The process may include the step of dedusting product which leaves the treatment zone at pressure in small treatment units. Instead, the product may be released under pressure and treated in a low pressure device.

The process may include recovering energy from the carrier gas after it leaves the treatment zone. At least some of the recovered energy may be used to preheat the carrier gas prior to introducing it into the treatment zone.

Instead, or in addition, at least some of the recovered energy may be used to compress the carrier gas prior to introducing it into the treatment zone.

According to a second aspect of the invention, there is provided roasting or treating apparatus suitable for roasting or treating ore or ore concentrate, the apparatus including a vessel defining a treatment zone having a height and a horizontal cross- sectional area such that the ratio of the horizontal cross-sectional area to the height is at least 1 :6; and feed means for feeding particulate ore or ore concentrate and a carrier gas at a low elevation into the vessel, the vessel having an outlet for removing the carrier gas and particulate ore or ore concentrate at a high elevation from the vessel.

The feed means may include a carrier gas feed pipe opening out at a low elevation into the vessel, and particulate ore or ore concentrate supply means or storage means configured to feed particulate ore into the carrier gas feed pipe. Instead, the feed means may include a carrier gas feed pipe opening out at a low elevation into the vessel, and particulate ore or ore concentrate supply means or storage means configured to feed particulate ore or ore concentrate into the vessel at a low elevation, but above the opening of the carrier gas feed pipe.

The vessel may be a pressure vessel configured to operate at an internal pressure of between 1 bar(g) and 30 bar(g) . Typically, the vessel is configured to operate at an internal pressure of between 3 bar(g) and 20 bar(g), e.g about 1 5 bar(g) .

The vessel may have an internal refractory lining . The apparatus may include heating means for heating the refractory lining and/or the particulate ore or ore concentrate and the carrier gas fed into the vessel to a temperature of at least 600°C. The heating means may be in the form of a gas or fuel oil burner located at a bottom of the vessel.

The vessel may be cylindrical. The treatment zone may have a height of between 3m and 30m, and a diameter of between 0,2m and 2m. Typically, the treatment zone has a diameter of between 0,2m and 1 ,5m, and a height of between 3m and 20m, e.g a height of about 1 5m.

The vessel may include at least one gas inlet at an elevation above the elevation at which the feed means is configured to feed carrier gas into the vessel Typically, the vessel includes a plurality of vertically spaced gas inlets

The apparatus may include heat exchange means in flow communication with the outlet of the vessel and with the feed means, such that in use heat is transferred from the carrier gas exiting the vessel to the carrier gas being fed to the vessel.

The apparatus may include separation means downstream of the vessel outlet for separating particles from the carrier gas, and an expansion turbine downstream of the separation means for recovering energy from the carrier gas.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which Figure 1 shows a schematic representation of one embodiment of roasting apparatus in accordance with the invention, for use in a process for treating ore concentrate; and

Figure 2 shows a schematic representation of another embodiment of roasting apparatus in accordance with the invention, for use in a process for treating ore concentrate.

Referring to Figure 1 of the drawings, reference numeral 10 generally indicates roasting apparatus in accordance with the invention for treating or roasting ore concentrate. The roasting apparatus 1 0 includes a vertically extending pressure vessel 1 2 which defines a vertically extending treatment zone. The treatment zone has a height dimension as indicated by the arrow 1 4 of 30 metres.

The apparatus 1 0 includes feed means for feeding particulate ore concentrate and a carrier gas at a low elevation into the vessel 1 2. The feed means includes a carrier gas feed pipe 1 6 which opens out at a low elevation into the vessel 1 2, defining a carrier gas inlet 1 8. The carrier gas inlet 1 8 can also be used to drain solids from the vessel 1 2. A pressure regulator 20 is positioned in the carrier gas feed pipe 1 6, which leads from a carrier gas supply source generally indicated by reference numeral 22.

The vessel 1 2 has an outlet 24 at a high elevation.

The feed means also includes particulate ore concentrate storage means 26, which is connected by four feed pipes 28 to the vessel 1 2. The feed pipes 28 opens out into the vessel 1 2 at a low elevation, but above the carrier gas inlet 1 8.

An alternative feed arrangement is indicated by reference numeral

29. In this feed arrangement, the ore concentrate is fed into the carrier gas feed pipe 1 6 through an ejector or similar device. The carrier gas thus acts in this case as a pneumatic transport medium for the ore concentrate particles.

A conduit 30 leads from the outlet 24 to cyclones 32 which are arranged in series for removal of the ore concentrate particles from the carrier gas which emanates from the pressure vessel 1 2, and for reducing the pressure of the carrier gas. The carrier gas which emanates from the cyclones 32 are fed into a plant generally indicated by reference numeral 34, which, depending on the application, could be a conventional sulphuric acid plant, a custom-designed sulphuric acid plant which receives the carrier gas at a desired, elevated pressure, or an ore cleaning system.

In use, finely milled ore concentrate particles (75μm), in this case containing ZnS, are fed from the particulate ore concentrate storage means 26 via the feed pipes 28 into the vessel 1 2. The carrier gas, which is nitrogen enriched compressed air, flows under pressure (25 bar) from the carrier gas supply source 22 via the carrier gas feed pipe 1 6 into the vessel 1 2, and moves upwardly through the vessel 1 2, at a linear velocity which is higher than the free settling velocity of the ore concentrate particles in the carrier gas, thereby entraining the ore concentrate particles to form a carrier gas / ore concentrate particle mixture which is conveyed upwards through the vessel 1 2. The ore concentrate particles are roasted at a temperature of about 900°C in the treatment zone, before they are removed, together with the carrier gas, through the outlet 24. In the cyclones 32, the roasted ore concentrate particles are separated from the carrier gas, and the pressure of the carrier gas is reduced .

It will be appreciated that there are any number of variables which affect the efficiency of the roasting reaction inside the vessel 1 2. A vessel with a predetermined diameter and height can be designed for each ore-type. In designing a vessel which will optimise the roasting reaction, regard is firstly to be had to the specific ore which is to be treated . For ZnS, it is known that a suitable residence time, that is the time which the particles must remain in the treatment zone, defined by the vessel 1 2, to fully react is in the region of about 1 0 seconds. The velocity, V(net) at which the ore particles move upwardly in the vessel can be approximately determined by the formula

V(net) = V(g) - V(E) ( 1 )

with V(E) = the particle free settling velocity, which is influenced by the size of the particle and its specific gravity and which can be easily calculated by one skilled in the art; and

V(g) = the carrier gas velocity, that is the velocity at which the carrier gas moves upwardly in the vessel 1 2. The carrier gas velocity V(g) is influenced by the pressure at which the gas is introduced into the vessel 1 2, the pressure differential across the vessel 1 2, and the diameter of the vessel 1 2 and can be measured or calculated .

It will further be appreciated that if the pressure of the carrier gas is increased, mass flow of carrier gas into the vessel is increased. In this process, the increased mass flow of carrier gas into the vessel is used to control the temperature inside the vessel, thereby substantially obviating the need for the addition of water to temper the roasting process as energy released by the roasting reaction will be used in heating up the additional mass of carrier gas.

In order to control the roasting reaction, even with an increased mass flow of carrier gas into the vessel, the composition of the carrier gas may be modified. In this example, the carrier gas comprises compressed air with nitrogen added to the air to decrease the concentration or partial pressure of oxygen in the vessel. The required reaction diameter for a given vessel can be determined if the following variables are known:

Typical conditions for roasting of ZnS, for an output of 25 000 kg/h, at 25 bar and 1 000 ° C:

Typical mass flow rate of compressed air = 47 000 kg/h.

Volumetric flow rate of compressed air through the vessel = 36306 Nm³/h. Actual volumetric flow rate of compressed air through the vessel = 6577m³/h.

Typical mass flow rate of diluent nitrogen = 8530 kg/h. Volumetric flow rate of nitrogen through the vessel = 6824 Nm^/h. Actual volumetric flow rate of nitrogen through the vessel = 1 223m³/h.

The total volumetric flow rate of compressed air and diluent nitrogen =

7800m³/h

The height of the vessel 1 2 = 30 m.

The required residence time = 1 0 seconds. The particle size of the ZnS particles = 75 μm.

The density of ZnS particles = 4000kg/m³

The free settling velocity as determined by formula ( 1 ) = ± 0.27 m/sec.

Required gas velocity for a 30 m reactor or vessel with a 1 0 second residence time = 3,27m/s. Thus, if Area = Flow / Velocity, then

Vessel diameter = (7800 m³/h / 3600 / 3.27 x 4//τ)⁰-⁵

91 8 mm.

Similarly, the required gas velocity for a 20 m reactor or vessel with a 1 0 second residence time = 2.27m/s. Thus, if Area = Flow / Velocity, then

Vessel diameter = (7800 Am³/h / 3600 / 2.27 x 4/t7)°- ⁵

1 1 02 mm. Referring to Figure 2 of the drawings, reference numeral 1 00 generally indicates another embodiment of roasting apparatus in accordance with the invention, for treating or roasting particulate ore concentrate. The roasting apparatus 1 00 includes a cylindrical vessel 1 02 defining a vertically extending treatment zone having a height of about 1 5m and a diameter of about 1 m. The apparatus 1 00 also includes feed means, generally indicated by reference numeral 1 04 for feeding particulate ore concentrate and a carrier gas at a low elevation into the vessel 102. The vessel 102 has an outlet 106 for removing the carrier gas and particulate ore concentrate at a high elevation from the vessel 1 02.

The feed means 1 04 includes a carrier gas feed pipe 108 opening out at a low elevation into the vessel 102, and particulate ore concentrate storage means 1 1 0. A screw conveyor 1 1 2 is provided to feed particulate ore concentrate from the particulate ore concentrate storage means 1 10 into the vessel 1 02 at a low elevation, but above the opening of the carrier gas feed pipe

108 into the vessel 1 02. An alternative feed arrangement for the particulate ore concentrate is shown in broken lines and identified by reference numeral 105. In this arrangement, the particulate ore concentrate is gravity fed directly into the carrier gas feed pipe 1 08.

A gas or fuel oil burner 1 14 extends into the vessel 1 02 through a bottom of the vessel 1 02, which has an internal refractory lining (not shown) .

From the outlet 1 06, a product line 1 1 6 leads to a heat exchanger

1 1 8, and from the heat exchanger 1 1 8 to a separation unit 1 20. A roasted ore concentrate line 1 22 emerges from the separation unit 1 20, as well as an acid plant feed line 1 24. A pressure regulator 1 26 is provided in the acid plant feed line 1 24.

The acid plant feed line 1 24 feeds into a sulphuric acid plant, generally indicated by reference numeral 1 28, from which a sulphuric acid product line 1 30 leads, as well as an offgas line 1 32. The offgas line 1 32 enters an expansion turbine 1 34, from where an offgas vent 1 36 leads to atmosphere.

The roasting apparatus 1 00 also includes a supply of compressed air 1 38, a supply of compressed oxygen 1 40 and a supply of compressed nitrogen 142. As will be appreciated, other gases such as chlorine or hydrogen, may be provided, depending on the reactions required. The supplies of compressed air, oxygen and nitrogen 138, 140, 142 may form part of a conventional air separation unit. As can be seen in Figure 2, the supplies of compressed air, oxygen and nitrogen 1 38, 1 40 and 142 are all connected to the carrier gas feed pipe 1 08, but also to six gas inlets 1 44, which enters the vessel

1 02 at vertically spaced positions.

In use, the carrier gas, in the form of compressed air at a pressure of 20 bar from the supply of compressed air 1 38, is fed via the carrier gas feed pipe 1 08, through the heat exchanger 1 1 8, into the bottom of the vessel 1 02. In the heat exchanger 1 1 8, hot carrier gas emanating from the vessel 1 02 via the product line 1 1 6 exchanges heat with the carrier gas in the carrier gas feed pipe 1 08, thereby preheating the carrier gas to a required temperature. However, in the majority of roasting, oxidation or reduction reactions for which the apparatus 1 0 can be used, it would be undesirable to preheat the carrier gas. A bypass 1 1 9 can then be employed.

Particulate metal or mineral bearing ore concentrate which requires roasting is fed from the particulate ore concentrate storage means 1 1 0 by means of the screw conveyor 1 1 2 into the vessel 1 02, where the ore concentrate particles are entrained and carried upwards through the vessel 1 02 as hereinbefore described . The roasting of sulphide bearing ore concentrate, and many other ore concentrates, are autogenous, exothermic processes. In order to initiate the roasting process, the burner 1 1 4 is used initially to heat the refractory lining of the vessel 102 and incoming carrier gas and particulate ore to a suitably high temperature to allow the roasting process to continue without any further energy input. Once the treatment zone is at a suitably high temperature to allow the roasting process to continue without further energy input, the burner 1 1 4 is switched off.

In the vessel 1 02, the ore concentrate particles are roasted whilst moving upwards through the vessel 102. A desired temperature in the treatment zone is maintained by increasing the pressure of the carrier gas and/or by adding air, oxygen or nitrogen into the vessel 1 02 by means of the gas inlets 144. The linear velocity of the carrier gas through the vessel 1 02 is manipulated by controlling the pressure differential across the vessel 102 by means of the pressure regulator 1 26. As will be appreciated, by means of injecting air, nitrogen or oxygen into the vessel 1 02 at different elevations, the reaction conditions inside the vessel 1 02 at different elevations can be manipulated .

From the vessel 1 02, the roasted ore concentrate particles and the carrier gas leave through the product line 1 1 6 and, if desired, exchanges heat with the carrier gas being fed to the vessel 1 02, in the heat exchanger 1 1 8 as hereinbefore described . The cooled particulate ore concentrate and carrier gas are fed into the separation unit 1 20, where roasted ore concentrate particles are separated from the carrier gas and discharged through the roasted ore concentrate product line 1 22. The carrier gas is fed along the acid plant feed line 1 24 into the sulphuric acid plant 1 28, where it is treated to produce sulphuric acid, which is discharged through the sulphuric acid product line 1 30. Offgas from the sulphuric acid plant 1 28 is fed by means of the offgas line 1 32 to an expansion turbine 1 34, where the pressure of the offgas is reduced to about atmospheric pressure, before the offgas is vented to atmosphere via the offgas vent 1 36. As will be appreciated, the energy recovered from the offgas by means of the expansion turbine 1 34 can be used to compress air for use as carrier gas, or for driving the compressor of an air separation unit.

The applicant believes that the process of the invention, as illustrated, has several advantages, the first being that the temperature is controlled by pressure or addition of nitrogen or other diluent gas without additional moisture being introduced into the vessel which may adversely affect the process. Also, the process provides a means to reduce capital costs of pyrometallurgical equipment. The process has various applications and could be used on existing plants, especially where an existing oxygen plant and/or a nitrogen plant is in operation. Product is released from the vessel under pressure and can be used in applications where further treatment of the product is conducted at high pressure, such as in an acid plant, thereby resulting in a saving of costs. The applicant also believes that the process and apparatus, as illustrated, obviates the need for blending of minerals prior to roasting, as is often the case with conventional roasting processes and apparatus, in order to obtain a blend of sufficiently high grade.

The process and apparatus of the invention, as illustrated, provides the necessary residence time for roasting ore or ore concentrate, without the need for establishing and maintaining a fluidised bed .

It is expected that the process, as illustrated, will allow control over reaction conditions to limit the formation of undesirable roasting products, which can impede downstream ore or ore concentrate leaching processes.

Furthermore, due to smaller equipment, lower heat losses can be expected, which may be desirable in some roasting processes.

Claims

1 . A process for treating ore or ore concentrate, the process including introducing particulate ore or ore concentrate and a carrier gas at a low elevation into a substantially vertically extending treatment zone such that the ore or ore concentrate particles are entrained in the carrier gas, thereby carrying the particles upwards through the treatment zone to a high elevation where they are removed from the treatment zone together with the carrier gas; and roasting or treating the particles at elevated temperature while they are moving upwards through the treatment zone.

2. A process as claimed in claim 1 , in which the ore or ore concentrate includes a mineral or a metal selected from the group consisting of zinc, copper, nickel, iron, cobalt, a precious metal or mineral, and mixtures thereof.

3. A process as claimed in claim 1 , in which the ore or ore concentrate is a mineral or metal bearing ore or ore concentrate which includes sulphur, and in which process the carrier gas includes oxygen.

4. A process as claimed in claim 3, in which the temperature of the treatment zone is controlled by controlling the partial pressure of the oxygen in the treatment zone.

5. A process as claimed in claim 4, in which the partial pressure of the oxygen in the treatment zone is controlled by introducing a gas selected from the group consisting of air, nitrogen, carbon dioxide, oxygen, and mixtures thereof at one or more selected elevations into the treatment zone.

6. A process as claimed in claim 1 or claim 2, in which the carrier gas includes a gas selected from the group consisting of air, nitrogen, sulphur dioxide, carbon dioxide, oxygen, carbon monoxide, hydrogen, chlorine, and mixtures thereof.

7. A process as claimed in any one of the preceding claims, in which the treatment zone is maintained at a pressure of between 1 bar(g) and 30 bar(g) .

8. A process as claimed in claim 7, in which the treatment zone is maintained at a pressure of between 3 bar(g) and 20 bar(g) .

9. A process as claimed in any one of the preceding claims, in which the particles are roasted or treated in the treatment zone for a period of between 1 s and 30s.

1 0. A process as claimed in any one of the preceding claims, in which the treatment zone has a height of between 3m and 30m.

1 1 . A process as claimed in claim 1 0, in which the treatment zone has a height of between 3m and 20m.

1 2. A process as claimed in any one of the preceding claims, in which the particles have a particle size between 0, 1╬╝m and 6000╬╝m.

1 3. A process as claimed in claim 1 2, in which the particles have a particle size between 0, 1╬╝m and 250╬╝m.

1 4. A process as claimed in any one of the preceding claims, in which the particles are roasted or treated at a temperature of between 600┬░C and 1 200 ┬░C.

1 5. A process as claimed in any one of the preceding claims, in which the residence time of the particles in the treatment zone and the temperature of the treatment zone are controlled by manipulating the pressure of the treatment zone.

1 6. A process as claimed in any one of the preceding claims, in which the linear velocity of the carrier gas through the treatment zone is between 0,2m/s and 1 0m/s.

1 7. A process as claimed in any one of the preceding claims, in which the ratio of the volumetric flow rate of the carrier gas, expressed in Nm^/s, to a cross-sectional area of the treatment zone, expressed in m is between 2: 1 and 36: 1 .

1 8. A process as claimed in any one of the preceding claims, in which energy is recovered from the carrier gas after it leaves the treatment zone.

1 9. A process as claimed in claim 1 8, in which at least some of the recovered energy is used to compress the carrier gas prior to introducing it into the treatment zone.

20. Roasting or treating apparatus suitable for roasting or treating ore or ore concentrate, the apparatus including a vessel defining a treatment zone having a height and a horizontal cross- sectional area such that the ratio of the horizontal cross-sectional area to the height is at least 1 :6; and feed means for feeding particulate ore or ore concentrate and a carrier gas at a low elevation into the vessel, the vessel having an outlet for removing the carrier gas and particulate ore or ore concentrate at a high elevation from the vessel.

21 . Apparatus as claimed in claim 20, in which the feed means includes a carrier gas feed pipe opening out at a low elevation into the vessel, and particulate ore or ore concentrate storage means configured to feed particulate ore or ore concentrate into the carrier gas feed pipe.

22. Apparatus as claimed in claim 20, in which the feed means includes a carrier gas feed pipe opening out at a low elevation into the vessel, and particulate ore or ore concentrate storage means configured to feed particulate ore or ore concentrate into the vessel at a low elevation, but above the opening of the carrier gas feed pipe.

23. Apparatus as claimed in any one of claims 20 to 22 inclusive, in which the vessel is a pressure vessel configured to operate at an internal pressure of between 1 bar(g) and 30 bar(g) .

24. Apparatus as claimed in claim 23, in which the vessel is configured to operate at an internal pressure of between 3 bar(g) and 20 bar(g) .

25. Apparatus as claimed in any one of claims 20 to 24 inclusive, in which the vessel has an internal refractory lining, the apparatus further including heating means for heating the refractory lining and/or the particulate ore or ore concentrate and the carrier gas fed into the vessel to a temperature of at least 600┬░C.

26. Apparatus as claimed in any one of claims 20 to 25 inclusive, in which the vessel is cylindrical and the treatment zone has a height of between 3m and 30m.

27. Apparatus as claimed in any one of claims 20 to 25 inclusive, in which the vessel is cylindrical, with a diameter of between 0,2m and 2m.

28. Apparatus as claimed in any one of claims 20 to 27 inclusive, in which the vessel includes at least one gas inlet at an elevation above the elevation at which the feed means is configured to feed carrier gas into the vessel.

29. Apparatus as claimed in claim 28, in which the vessel includes a plurality of vertically spaced gas inlets.

30. Apparatus as claimed in any one of claims 20 to 29 inclusive, which includes heat exchange means in flow communication with the outlet of the vessel and with the feed means, such that in use heat is transferred from the carrier gas exiting the vessel to the carrier gas being fed to the vessel.

31 . Apparatus as claimed in any one of claims 20 to 30 inclusive, which includes separation means downstream of the vessel outlet for separating particles from the carrier gas, and an expansion turbine downstream of the separation means for recovering energy from the carrier gas.

32. A process as claimed in claim 1 , substantially as herein described and illustrated .

33. Apparatus as claimed in claim 20, substantially as herein described and illustrated .

34. A new process, or new apparatus, substantially as herein described.