MXPA06004364A - A pipe segment for a transfer line for transporting hot particulate material - Google Patents

Abstract

The present invention relates to a pipe segment including an outer (2) and an inner pipe section (4), with the inner pipe section being positioned within the outer pipe section, and a support means (44, 14, 64) supporting the inner pipe section in relation to the outer pipe section so that the inner pipe section can expand axially relative to the outer pipe section in response to temperature changes in the material being transported in the pipe segment. Furthermore, the present invention refers to a transfer line for transporting hot particulate material, such as iron ore fines, in a carrier gas, including a plurality of these pipe segments and to a process for transporting hot particulate material in a carrier gas in a direct smelting plant for producing molten metal from a metalliferous feed material, in particular between a pretreatment unit and solid delivery means in the form of lances for injecting the material into a direct smelting vessel.

Description

A PIPELINE SEGMENT FOR A TRANSFER LINE FOR THE TRANSPORTATION OF MATERIAL HOT IN PARTICLES Field of the Invention The present invention relates to a pipe segment for transporting a hot particulate material, such as hot iron ore fines, in a carrier gas in a transfer line, to a transfer line for transporting hot particulate material which includes a plurality of such pipe segments, as well as a process for the transportation of hot particulate material in a conveyor gas in a direct casting plant to produce molten metal from a feedstock metal, in particular between a pre-treatment unit and means for distributing solids in the form of lances for the injection of the material into a direct casting vessel.

Background of the Invention An Australian provisional application in the name of the applicant and filed the same day as the present application describes a direct casting plant for the production of molten metal, such as molten iron, from metalliferous feedstock, such as fine iron ore, which includes: a) a pre-treatment unit for the pre-treatment of metalliferous feedstock and production of pre-treated feedstock having a temperature of at least 200 ° C; b) a direct casting container for melting metalliferous feed material pre-treated to molten metal, the container being adapted to contain a molten metal slag bath, the container includes a means of distributing solids to receive and subsequently supply material of metal feed pre-treated at a pressure above atmospheric pressure and at a temperature of at least 200 ° C inside the container; c) a hot feed material transfer apparatus for transferring pretreated metalliferous feed material from the pretreatment unit to the solids distribution means of the direct casting vessel, the transfer apparatus comprising: i) means for storing hot feed material for storing pre-treated metal feed material at at least 200 ° C and at a pressure above atmospheric pressure; ii) a hot feed material transfer line for transferring pre-treated metal feed material to at least 200 ° C under pressure to the solids distribution means of the direct casting vessel; iii) pressurizing means for supplying gas at a pressure above atmospheric pressure to the hot feed material storage means for pressurizing the storage means and to the hot feed material transfer line to act as a gas conveyor for transporting pre-treated metal feed material along the line to the solids distribution means. A commercial scale direct casting plant, of the type described in the Australian provisional application that is currently being constructed, will include a pretreatment unit that will pre-heat iron ore fines of 6-8 mm maximum size at a temperature of the order of the 680 ° C. The hot ore will be transported hot, that is, at temperatures of the order of 680 ° C, by means of the apparatus in transfer of hot feed material to the means of distribution of solids of the direct casting container and subsequently it is injected, suspended inside a carrier gas that has a velocity in the range of 70-120 m / s inside the container. The current design of the plant includes four means of distributing solids in the form of solid injection spears and two transfer lines to supply hot mineral fines to the spears., with a transfer line supplying hot mineral fines to a pair of lances. The plant is designed to process a significant amount of iron ore fines. Specifically, each transfer line is currently designed to transport 110-120 tph of hot ore fines to each pair of lances, with the hot ore fines being transported along the lines by nitrogen gas supplied at 20 ° C. at a speed of 3,100 Nm3 / hr. The direct casting plant described above presents important material handling issues for the hot feed material transfer apparatus. Specifically, the iron ore fines are abrasive and, therefore, the wear of the transfer lines is an important issue. In addition, although the direct casting plant is designed to work for long periods, typically more than 12 months, the temperature of the transfer lines will not remain constant during a season and, as a consequence, another important design issue for the lines Transfer is the accommodation of the thermal expansion while maintaining the integrity of the seal of the line. In addition, the pressure within the transfer lines will not remain constant for a season and can vary quite considerably, particularly in situations where deliberately sudden increases and decreases in internal pressures are used to clear blockages in the transfer lines. Consequently, the accommodation of internal pressure variations within the transfer lines, while maintaining the seal integrity of the line, is another important design issue for the transfer lines.

OBJECTIVES AND SUMMARY OF THE INVENTION The present invention focuses on the transfer lines and, more particularly, on pipe segments for the construction of the transfer lines, for the transfer apparatus of the hot feed material of the direct casting plant described above. The present invention is not limited to this application and extends generally to transfer lines of hot particulate material and pipe segments for the construction of transfer lines. According to the present invention, a pipe segment is provided for the transportation of hot particulate material, such as hot iron ore fines, in a transport gas in a transfer line, pipe segment which includes: a) a outer pipe section b) an inner pipe section defining a passageway for a hot particulate material and a conveyor gas, the inner pipe section being positioned within the outer pipe section, and the inner pipe section being formed to Starting from or having an inner lining of an abrasion resistant material; and c) support means supporting the inner pipe section relative to the outer pipe section such that the inner pipe section can expand axially relative to the outer pipe section in response to temperature changes in the material which is being transported in the pipe segment, the support means including first support means located at one end of the pipe segment, the first support means including a support member that can receive an end of an inner pipe section of an adjacent pipe segment when the adjacent pipe segment is placed in use in an end-to-end relationship with said pipe segment and may allow axial expansion of that inner pipe section relative to the outer pipe section of said pipe section. adjacent pipe segment in response to temperature changes in the material that is being transported in said adjacent pipe segment. Preferably the support member encloses and extends axially from one end of the inner pipe section of said pipe segment and can receive and enclose the end of the inner pipe section of the adjacent pipe segment when said adjacent pipe segment it is placed in use in an end-to-end relationship with said pipe segment and may allow axial expansion of at least that inner pipe section while the ends remain enclosed within the support member. The above arrangement makes it possible for the inner pipe sections of said pipe segment and said adjacent pipe segment to be placed in an end-to-end relationship with openings between the ends of the inner pipe sections which may allow axial expansion of the pipe. one or both of the inner pipe sections relative to the outer pipe section or sections in response to the thermal expansion or contraction of the inner pipe section or sections and while maintaining an appropriate seal between the ends of the pipe sections inside. Preferably the support member forms a seal with the ends of the inner pipe sections of said pipe segment and said adjacent pipe segment. Preferably the support member includes a cylindrical surface that faces inward to contact the outer surfaces of the ends of the inner pipe sections of said pipe segment and said adjacent pipe segment. Preferably the support member is in the form of a handle having the cylindrical surface facing inwardly. In one embodiment the support member is directly attached only to the outer pipe section of said pipe segment, by means of which the inner pipe section can move axially relative to the support member and the outer pipe section in response to the thermal expansion or contraction of the inner pipe section. Preferably the first supporting means also support the inner pipe section relative to the outer pipe section so that the inner pipe section can expand radially relative to the outer pipe section.

Preferably the first support means define a barrier to gas movement axially along the space between the inner and outer pipe sections of the pipe segments. In the event that conveyor gas escapes from the inner pipe sections of a transfer line into space, the gas flow axially along the space may result in buckling of the outer pipe sections of the pipe segments causing Hot spots on the surface of the outer pipe sections. Hot spots are an important safety issue and can have a substantial impact on the viability of a transfer line and replacement of damaged pipe segments is necessary. By providing each pipe segment with the barrier it is possible to confine the gas flow within each pipe segment for that pipeline segment only and thereby reduce the impact of the conveyor gas leak within the space between the sections of inner and outer pipe of the pipe segments. Preferably the first support means includes a frusto-conical barrier member having a larger diameter end and which is welded or otherwise connected to the outer pipe section of said pipe segment and a smaller diameter end. which is welded or otherwise attached to the support member. Preferably the frusto-conical barrier member is arranged so that the larger diameter end is located at the end of the outer pipe section and the smaller diameter end is located inwardly of the end of the inner pipe segment. In another embodiment, the support member is directly connected to both the outer pipe section and the inner pipe section, whereby the end of the inner pipe section (but not the rest of the inner pipe section) it is prevented from axial expansion relative to the outer pipe section at that end of the pipe segment. With this arrangement, the axial expansion in response to the thermal expansion or contraction of the inner pipe section is limited to the other end of the pipe segment. Preferably the support means includes second support means positioned at a location along the length of the pipe segment between the ends of the pipe segment and supporting the inner pipe section relative to the outer pipe section for expansion axial in relation to the outer pipe section. Preferably the second support means also support the inner pipe section relative to the outer pipe section such that the inner pipe section can expand radially relative to the outer pipe section. In one embodiment the second support means is welded or otherwise bonded to the outer pipe section and the inner pipe section.

In another embodiment the second support means are welded or otherwise attached to the outer pipe section only, by means of which the inner pipe section can move axially relative to the outer pipe section and the second pipe means. support. In another embodiment the second support means is welded or otherwise attached to the inner pipe section only by means of which the inner pipe section and the second supporting means can move axially relative to the outer pipe section . Preferably the second support means functions as a spring providing a resistance to radial expansion of the inner pipe section relative to the outer pipe section. More preferably the second support means are in the form of a plurality of rods, each of which is bent so as to function as a spring, which are arranged in spaced intervals around the circumference of the inner and outer pipe sections at a location along the length of the pipe segment. Preferably the inner pipe section (4) is made of a material resistant to wear and / or abrasion resistant, for example, cast iron, and does not comprise an inner and / or outer coating. More particularly, the abrasion-resistant material is a white cast iron.

Preferably the outer pipe section is formed from a steel. Preferably the pipe segment further includes thermal insulation in the space between the inner and outer pipe sections. Typically the particulate material consists of iron ore fines, for example, iron ore fines with a degree of reduction of between 0 and 100%, preferably a degree of reduction of between 8 and 95%. Typically the particulate material is at a temperature of between 200 and 850 ° C and preferably between 300 and 850 ° C. According to the present invention there is also provided a transfer line for the transport of hot particulate material, such as iron ore fines, in a carrier gas, transfer line which includes a plurality of the previously described pipe segments. , positioned in an end-to-end relationship with the ends of adjacent outer pipe sections welded or joined in some other manner and together, and the end of each of each pair of adjacent inner pipe sections extending into and engaging the other supporting member of the pairs of adjacent inner pipe sections. As indicated above, the transfer line of the present invention is particularly, though by no means exclusively, directed to the transport of hot iron ore fines between a pretreatment unit and solids distribution means that They are presented in the form of lances for the injection of hot mineral fines into a direct casting vessel in a direct casting plant. With this arrangement, preferably the iron ore fines are preheated to a temperature of 680 ° C in the pre-treatment unit, the carrier gas is at least substantially nitrogen and is supplied to the transfer line at an ambient temperature, and the operating conditions are controlled so that the hot iron ore fines are transported along the transfer line at a minimum speed of at least 19 m / s by the transporting gas, and are injected into the direct casting vessel with the carrier gas having a spear tip speed in the range of 70-120 m / s. Generally, the maximum size of iron ore fines falls within the range of 6 to 8 millimeters. Preferably at least 30% of the iron ore fines have a particle size of less than 0.5 mm, while the diameter d_50 falls between 0.8 and 1.0 mm with a wide particle size distribution. In this way, for example, 95% of the particles provide a particle size of less than 6.3 mm. The annular space that exists between the outer and inner pipe sections is typically insulated so that the temperature of the outer pipe is less than 100 ° C. Preferably the static pressure in both the inner and outer sections of the transfer line is substantially the same.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is described in more detail below, by way of example, with reference to the accompanying drawings and in which: Figure 1 illustrates a schematic diagram of the lower lowered hoppers, auger conveyors, transfer lines, and return lines that are part of a feed material transfer apparatus containing hot iron from a direct casting plant. Figure 2 is a cross section of an embodiment of a pipe segment according to the present invention. Figure 3 a is a cross-sectional and partially sectional view of a central section of the pipe segment shown in Figure 2 with the outer pipe section removed and illustrating in detail the second support members of the pipe segment. pipeline. Figure 3b is a pictorial representation of the second support means. Figures 4 to 6 are a sequence of 3 cross sections illustrating the flow paths of the conveyor gas escaping from the passage defined by the interior pipe sections at one end of a pipe segment and the annular space that exists between the inner and outer pipe sections and how the gas can return to the passageway at the other end of the inner pipe segment; and Figure 7 is a cross section and another embodiment of a pipe segment according to the invention and which consists of a modified form of the pipe segment shown in the other figures and includes a chamfered edge that can be included in a interior pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The following description is in the context of the transfer lines for transporting fines of hot iron ore between a pre-treatment unit and lances for the injection of the hot mineral fines into a container. direct casting in a direct function plant described in the Australian provisional application mentioned above. The main components of the direct casting plant are the following: a) a pre-treatment unit (not shown) in the form of a preheater to preheat iron ore fines, typically having a maximum size of 6-8 mm, typically at a temperature of the order of 680 ° C; b) a direct casting container 5 for melting pre-heated iron ore fines to molten iron; and c) a feed material transfer apparatus 7 containing hot iron (shown only partially in Figure 1) for storing pre-heated iron ore fines and transferring the fines under pressure to injection solids lances of the container direct casting The direct cast container 5 can be any suitable container for carrying out a direct casting process, such as the Hlsmelt process described above. Australian Provisional Application No. 2003901693 in the name of one of the applicants includes a description of the general construction of a Hlsmelt container and the description of the Australian provisional application is incorporated herein by reference. The vessel is also equipped with eight solids injection nozzles that extend downward and inward through the side walls for the injection of pre-heated iron ore fines, solid carbonaceous material, and fluxes entrained in a carrier gas. oxygen deficient within a molten bath in the container. The solids injection lances are in two groups of 4 lances, with the lances 27 in one group receiving fines of preheated hot iron ore and the lances (not shown) in the other group receiving coal and flux (via a injection system of carbonaceous / flux material, not shown) during a casting operation. The lances that are in the two groups are arranged alternately around the circumference of the container. The transfer apparatus 7 of the hot iron-containing feedstock referred to in item (c) above includes: a) a means of storing hot feedstock for storing pre-heated iron ore fines under pressure, illustrated in part in Figure 1 and which are identified generally by the numeral 61; b) a series of hot feed material transfer lines 11 for transferring pre-heated iron ore fines under pressure from the storage means 61 to the solids injection lances; c) a source of nitrogen gas 13 and lines 15 of nitrogen gas for supplying nitrogen for pressurizing the storage means 61 and for transporting pre-heated iron ore fines along the transfer lines 11; and d) a return line 17 for returning the pre-heated iron ore fines to the pre-heater 3. The storage means 61 of the feed material transfer apparatus 7 containing hot iron are divided into two groups 9a and 9b, with one group being connected through a transfer line 11 to a pair of solids injection nozzles 27 and the other group being connected through another transfer line 11 to the other pair of solids injection nozzles 27. In use, fines of pre-heated iron ore are supplied through a worm conveyor 39 to the feed ends 45 of the transfer lines 11. Nitrogen gas under pressure and at room temperature is also fed at the inlet ends 45 of the transfer lines 11 from the nitrogen gas source via lines 47 and lifts and transports the pre-heated iron ore fines throughout of the transfer lines 11 to the injection lances 27 of solids. Each transfer line 11 branches into two sub-branches 1 la and 1 Ib in the region of the direct casting container 5 and the branching lines supply fines of pre-heated iron ore to a pair of injection spears 27 of solids that are opposed in a diametrical way. The return line 17 for each transfer line 11 extends from the return line 11 to the preheater 3. The return lines 17 include isolation valves A suitably located to control the flow of the pre-iron ore fines. -heated within the return lines 17. The hot material-containing transfer apparatus 7 also includes means for controlling the flow of pre-heated iron ore fines along the transfer lines 11 from the storage means 61 up to the injection spears 27 of solids. In any given situation, the actual flow rates of the nitrogen gas and the pre-heated iron ore fines that are supplied to the transfer lines 11 will be a function of a range of variables that include the particle size distribution of the mineral fines of iron, temperatures of nitrogen gas and iron ore fines, and target point velocities for injection spears 27 of solids. In a particular embodiment conceived by the applicants, the target collection speed is 19 m / s, the peak target speed of the transporting gas is in the range of 70-120 m / s and each group 9a and 9b of the storage means 61 supplies 123 tph of pre-heated iron ore fines (at 680 ° C) to the associated transfer line 11 and nitrogen gas 13 supplies 3100 Nm3 / hr of nitrogen gas at 20 ° C to the transfer line 11. The transfer lines 11 are constructed from a plurality of pipe segments shown in Figures 2 to 6 and placed in an end-to-end relationship. The end-to-end relationship of the pipe segments is illustrated in part in Figure 2. Specifically, the left side of the figure illustrates an end section of a pipe 22a shown only to a limited degree in the figure and that is coupled with the pipe segment 22 shown in detail in the figure. With reference to Figures 2 to 6, the pipe segment 22 includes: a) an outer pipe section 2 formed from steel, for example, formed from carbon steel SCK; b) an interior pipe section 4 defining a passage 6 for fines of hot iron ore and nitrogen transport gas, the interior pipe section 4 being positioned within the outer pipe section 2 and being formed from an iron white cast and abrasion resistant; c) means for supporting the inner pipe section 4 in relation to the outer pipe section; and d) thermal insulation in the annular space between the outer and inner pipe sections 2, 4. The inner and outer pipe sections (4, 2) are in a concentric relation with respect to each other. The support means has the double function of supporting the inner pipe section 4 relative to the outer pipe section 2 so that: a) the inner pipe section 4 can expand axially in response to temperature changes in the material that is being transported within section 4 of interior pipe; and b) the inner pipe section 4 may expand radially to changes in temperature or pressure within the interior pipe section 4. The support means are positioned at two locations along the length of the pipe segment. A location of the support means is at the left end of the pipe segment as seen in Figure 2. These first support means include a support member in the form of a handle 8 which is formed from the same material as the inner pipe section 4 and which fits around and welds to the left end (as seen in Figure 2) of the section 4 of interior pipe. The first support means also include a frusto-conical member 10 that is welded to the handle 8 and to the left end of the outer pipe section 2 and thereby attaches the handle 8 to the outer pipe section 2 and holds the handle 8 in relation to section 4 of interior pipe. The member 10 forms a barrier, that is, a septum, at that end of the pipe segment, which prevents gas flow along the length of the annular space that exists between the outer and inner pipe sections 2, 4. The handle 8 extends axially from the left side of the inner pipe section 4 and, in use, may receive one end of an inner pipe section 4a of an adjacent pipe segment 22a.

The handle 8 is formed so that the inner surface of the handle 8 comes into contact with the outer surfaces of the inner end section 4 of the pipe segment 22 and the inner pipe section 4a of the adjacent pipe segment and allows the sliding movement of the pipe. the inner pipe section 4a within the handle 8 in response to the thermal expansion / contraction of the inner pipe sections while maintaining a seal with the inner pipe sections 4, 4a. This is an effective way of an expansion board. The interior pipe section 4 at the right end of the pipe segment 22, as seen in Figure 2, extends beyond the outer pipe section 2 at that end and forms an end that can be extended in use to a position of successive pipe in an end-to-end relationship with the pipe segment 22 (see Figure 6). In this arrangement, the inner pipe section 4 at the right end of the pipe segment can expand axially to accommodate the thermal expansion or contraction of the inner pipe section 4 in the same manner as the section 4a of the inner end of the segment of pipe at the left end of Figure 2. The location of the other support means is halfway along the length of the pipe segment as seen in Figure 2. The second support means include a handle 44 and 3 stainless steel rods 14 which are welded to handle 44 and extend from there outwards. The support means also includes curved, slip pads 64, which are welded to the outer ends of the rods 14. As best seen in Figures 3a and 3b, the rods 14 are spaced equidistantly around the circumference of the handle 44. The handle 44 is fixed to the inner pipe section 4 by means of headless screws 46 (Figures 3a and 3b) or the like. The second support means are formed so that the slip and curved pads 64 come into contact with the inner surface of the outer pipe section 2 of the pipe segment. In this way, the inner pipe section 4 and the supporting means can move axially relative to the outer pipe section 2.

The second support means locate the inner pipe section 4 relative to the outer pipe section 2. This is important considering the length of the pipe segment and the objective of this mode of providing an arrangement in which the inner pipe section 4 can move axially and radially, relative to the outer pipe section 2. Regarding this last point, the rods 14 of the second support means are bent in a "V" shape and thus function as springs that can respond to changes in temperature or internal pressure in the interior pipe section 4 of the pipe segment 22 and provide a restoring force that resists radial expansion outwardly of the inner pipe section 4. The insulation in the annular space that lies between the inner and outer pipe sections 2,4 can be any suitable insulation. Figure 2 indicates that the insulation is in the form of a fiberboard insulation 36 along a significant portion of the length of the pipe segment. In addition, the embodiment of Figure 2 also includes a "wet package" insulation 38 adjacent the frusto-conical member 10. Figures 4 to 6 indicate that the insulation is in the form of a woven ceramic fiber mat 40 wrapped around the interior pipe sections 4, 4a and a calcium silicate insulation 42 that occupies the remainder of the annular space throughout of an important part of the length of the pipe segment. As is the case with the embodiment of Figure 2, the embodiment of Figures 4 to 6 also includes "wet package" insulation 46 adjacent to the frusto-conical member 10. Figures 4 to 6 illustrate the function of the bulkhead 10 of the first support means as a barrier to gas flow. The expansion joint defined by the handle 8 and the ends of the inner pipe sections 4 and 4a of the adjacent pipe segments 22 and 22a do not form a gas tight seal over the entire range of the operating pressure of the pipe line. transfer. As a consequence, there may be situations in which the conveyor gas that flows into the passageway 6 along the length of the transfer line escapes from the passageway 6 through the expansion joint and flows through the space-occupying insulation. annular between sections 2 and 4 of inner and outer pipe. As indicated above, said gas flow is undesirable. Figures 4 to 6 illustrate that the bulkheads 10 prevent the flow of gas in the annular space along the transfer line beyond the bulkheads 10 and finally the bulkheads 10 redirect the flow of gas back into the passageway 6. In this way, the seals 6 reduce the adverse impact of the gas leak. Figure 7 indicates a chamfered edge that can be included at least one end of the inner pipe section 4. The bevel 48 is preferably of the order of 30 ° (but may be of any other suitable angle) and may be located at one or both ends of the inner pipe. Where the bevel 48 is located only on one end of an inner pipe section 4, the section preferably is oriented so that the bevel 48 is located on the running side below the expansion joint. The chamfer 48 extends through the end face of the inner pipe from a point adjacent to the outer surface of the pipe to a point adjacent to the inner surface of the pipe. The adjacent point of the outer surface of the pipe is located adjacent to the terminal face and the point adjacent to the inner pipe surface is located internally of the pipe. In this form, the chamfer 48 forms part of the interior surface of the pipe that in use provides containment of the carrier gas and the fines. This location of the chamfer 48 allows any fines that may have accumulated in the expansion joint between adjacent sections of the inner pipeline to flow along the surface of the chamfer 48 with any subsequent expansion of the inner pipe sections. The bevel 48 helps prevent the accumulation of fines in an expansion joint by obstructing the relative movement of the interior pipes when they undergo expansion. Many modifications can be made to the embodiment of the present invention described above without departing from the spirit and scope of the invention.

Claims (29)

1. Claims 1. A segment (22) of pipe for the transportation of hot particulate material, such as hot wick ore fines, in a conveyor gas in a transfer line, pipe segment (22) which includes: a) an outer pipe section (2) b) an inner pipe section (4) defining a passageway (6) for a particulate hot material and a conveyor gas, the inner pipe section (4) being positioned within the section (2) outer pipe, and the inner pipe section (4) being formed from or having an inner lining of an abrasion resistant material; and c) support means supporting the inner pipe section (4) in relation to the outer pipe section (2) such that the inner pipe section (4) can expand axially relative to the section (2) of outer pipe in response to temperature changes in the material being transported in the pipe segment (22), the support means including first support means located at one end of the pipe segment (22), the first means of support including a support member that can receive an end of an inner pipe section (4a) of an adjacent pipe segment (22a) when the adjacent pipe segment (22a) is placed in use in an end-to-end relationship with said pipe segment (22) and may allow axial expansion of that inner pipe section (4a) relative to the outer pipe section of said adjacent pipe segment (22a) in response to temperature changes in the material being transported in said adjacent pipe segment (22a). A pipe segment according to claim 1, characterized in that the support member encloses and extends axially from one end of the section (4) of the inner pipe of said pipe segment (22) and can receive and cramming the end of the inner pipe section (4a) of the adjacent pipe segment (22a) when said adjacent pipe segment (22a) is placed in use in an end-to-end relationship with said pipe segment (22) and it can allow axial expansion of at least that inner pipe section (4) as long as the ends remain enclosed within the support member. A pipe segment according to claim 1 or 2, characterized in that the support member forms a seal with the ends of the pipe sections (4 and 4a) inside said pipe segment (22) and the aforementioned one. segment (22a) of adjacent pipe. A pipe segment according to any of the preceding claims, characterized in that the support member includes a cylindrical surface that faces inward to contact the outer surfaces of the ends of the sections (4, 4a ) of inner pipe of said pipe segment (22) and said segment (22a) of adjacent pipe. A pipe segment according to any of the preceding claims, characterized in that the support member is in the form of a handle (8) having the cylindrical surface facing inwardly. A pipe segment according to any of the preceding claims, characterized in that the support member is directly and only connected to the outer pipe section (2) of said pipe segment (22). 7. A pipe segment according to any of claims 1 to 5, characterized in that the support member is directly connected to both the outer pipe section (2) and the inner pipe section (4), so that the end of the inner pipe section (4), but not the remainder of the inner pipe section (4), is prevented from axial expansion relative to the outer pipe section at that end of the pipe segment (22). 8. A pipe segment according to any of the preceding claims, characterized in that the first support means also support the inner pipe section (4) in relation to the outer pipe section (2). A pipe segment according to any of the preceding claims, characterized in that the first support means define a barrier to gas movement axially along the space between the inner and outer pipe sections (4, 2). ) of the pipe segment (22). 10. A pipe segment according to claim 9, characterized in that the first support means includes a frusto-conical barrier member (10) having an end with a larger diameter and which is welded or otherwise attached to the outer pipe section (2) of said pipe segment (22) and a smaller diameter end that is welded or otherwise attached to the support member. A pipe segment according to claim 9, characterized in that the frusto-conical barrier member (10) is arranged so that the larger diameter end is located at the end of the pipe section (2) outer and the smaller diameter end is located inward of the end of the inner pipe segment (4). A pipe segment according to any of the preceding claims, characterized in that the support means includes second support means placed at a location along the length of the pipe segment (22) between the ends of the segment. (22) of pipe and support the inner pipe section (4) in relation to the outer pipe section (4) for axial expansion relative to the outer pipe section (2). A pipe segment according to claim 12, characterized in that the second support means also support the inner pipe section (4) in relation to the outer pipe section (2) in such a way that the section (4) ) of the inner pipe may expand radially relative to the outer pipe section (2). A pipe segment according to claim 12 or 13, characterized in that the second support means are welded or otherwise connected to the outer pipe section (2) and the inner pipe section (4). A pipe segment according to claim 12 or 13, characterized in that the second support means are welded or otherwise bonded to the outer pipe section (2) only. 16. A pipe segment according to claim 12 or 13, characterized in that the second support means are welded or otherwise connected to the inner pipe section (4) only. 17. A pipe segment according to claims 12 to 16, characterized in that the second support means functions as a spring providing a resistance to radial expansion of the inner pipe section relative to the outer pipe section. A pipe segment according to claims 12 to 17, characterized in that the second support means is in the form of a plurality of rods (14), each of which is bent so that it functions as a spring, which are arranged in spaced intervals around the circumference of the sections (4, 2) of inner and outer pipe at a location along the length of the pipe segment (22). A pipe segment according to any of the preceding claims, characterized in that the abrasion resistant material of the inner pipe section (4) is a cast iron. A pipe segment according to claim 19, characterized in that the inner pipe section (4) is made of a material resistant to abrasion and / or wear resistant, for example, cast iron. 21. A pipe segment according to any of the preceding claims, characterized in that the outer pipe section (2) is formed from a steel. 22. A pipe segment according to any of the preceding claims, characterized in that the pipe segment (22) also includes thermal insulation (36, 38, 42, 46) in the space between the sections (4, 2). ) of inner and outer pipe. 23. A transfer line for the transport of hot particulate material, such as iron ore fines, in a carrier gas, transfer line which includes a plurality of pipe segments (22) according to any of claims 1 to 22. 24. A transfer line in accordance with claim 23, characterized in that the pipe segments (22) are placed in an end-to-end relationship with the ends of adjacent outer pipe sections (22a) welded or joined in some other way and together, and the end of each of each pair of adjacent inner pipe sections (4, 4a) extending into and engaging the other supporting member of the pairs of sections (4, 4a) of adjacent inner pipe. 25. A process for the transportation of hot particulate material in a conveyor gas in a direct casting plant to produce molten metal from a metalliferous feedstock, in particular between a pre-treatment unit and means of distributing solids in the form of lances for injecting the material into a direct casting container, characterized in that the material is transported on at least one transfer line according to claim 23 or 24. 26. A process according to claim 25 , characterized in that the particulate material consists of iron ore fines with a degree of reduction of between 0 and 100%, preferably a degree of reduction of between 8 and 95%. 27. A process according to claim 25 or 26, characterized in that the particulate material is at a temperature between 200 and 850 ° C and preferably between 300 and 850 ° C. 28. A process according to any of claims 25 to 27, characterized in that the carrier gas is at least substantially nitrogen. 29. A process according to any of claims 25 to 28, characterized in that the hot iron ore fines are transported along the transfer line at a minimum speed of at least 19 m / s by the transporting gas. , and are injected into the direct casting vessel with the carrier gas having a spear tip speed in the range of 70-120 m / s.