LU100035B1 - Shaft Furnace Plant With Full Recovery Pressure Equalizing System - Google Patents

Abstract

Shaft furnace plant comprises a shaft furnace with a charging device (12) arranged at the top of the shaft furnace (14), wherein the charging device comprises at least one hopper (20) for raw materials to be fed into the shaft furnace; a cleaning unit (36); and a pressure equalizing system comprising an evacuation piping (62) with an ejector (64), one end of the evacuation piping being connected to the hopper (20) and the other end to a gas collecting duct (52). The pressure equalizing system comprises a compressor (74) connected for receiving cleaned top gas from the cleaning unit, and compressing the gas. A high-pressure buffer reservoir (66) is arranged downstream of the compressor, for storing compressed gas fed from the compressor. The buffer reservoir (66) is fluidly connected to a driving side of the ejector (64) in such a way that compressed gas serves as motive fluid in the ejector.

Description

SHAFT FURNACE PLANT WITH FULL RECOVERY PRESSURE EQUALIZING SYSTEM

FIELD OF THE INVENTION

The present invention generally relates to the field of iron making and in particular to a shaft furnace plant. More specifically the invention relates to a shaft furnace plant comprising a top charging installation with full recovery pressure equalizing system.

BACKGROUND OF THE INVENTION

As it is well known in the art, a shaft furnace, such as the blast furnace, is a counter-current reactor designed to reduce and smelt iron with the maximum degree of thermal efficiency. The solid materials charged at the top descend through the stack gaining heat and losing mass; they leave the furnace in liquid form, the ore having been reduced from solid iron oxides to liquid iron. Simultaneously, air is blown into the furnace at high temperatures, burning with coke/carbon to form CO, which will remove the oxygen from the burden materials to form CO2. Consequently, on rising through the furnace the gases lose temperature and gain mass.

The charging of the blast furnace is conventionally carried out by means of a top charging installation, which serves the function of storing raw materials on the furnace top and distributing these materials batchwise into the furnace. The leading technology of top charging installations has been developed by the present Applicant Paul Wurth S.A. and is known as Bell Less Top®. Raw materials (charge / burden) are weighed in the stockhouse and delivered in a batch mode (via skip car or conveyor belt) to the furnace top charging installation, where they are stored in material hoppers. The material hoppers are lock-type hoppers with upper and lower seal valves, and a material flow control gate.

For distributing the charge material into the furnace, the top charging installation comprises a rotary charging device arranged at the furnace top, below the material hoppers. The rotary charging device comprises a stationary housing and a suspension rotor supporting a pivotable distribution chute, the suspension rotor being supported in the stationary housing so that it can rotate around the furnace axis. The suspension rotor and stationary housing form the main casing of the rotary charging device, in which mechanisms for driving the suspension rotor and pivoting the charge distributor are arranged.

The blast furnace is typically operated under pressure and process gas is extracted at the top of the furnace via gas uptakes, i.e., in the region of the top cone closing the blast furnace throat, and thus referred to as “top gas”.

Top gas is an important source of energy and can be used for various applications in the blast furnace plant and in the integrated steel plant. Before that, top gas must be cleaned in order to protect the life of the user facilities.

In fact, the treatment of top gas has been a constant concern for blast furnace designers and operators, following technological, economic and environmental goals. A top gas cleaning unit typically comprises two cleaning stages: a dry separation treatment is followed by wet scrubbing. At the exit of the cleaning unit, the gas has a residual dust content, which may e.g. be of less than 5 mg/m3. The cleaned top gas is then ready for use for other purposes in the blast furnace, discarded, or burnt.

It is in particular known to recover mechanical energy from the cleaned top gas in a top gas recovery turbine, known as TRT, downstream of the cleaning unit. The TRT is generally driven by the cleaned top gas in order to drive itself an electric generator, while the expanded top gas is returned to the plant network and may be burnt.

This kind of equipment allows treating most of the blast furnace top gas.

Another portion of top gas that requires attention is the top gas contained in the material hoppers of the top charging installation. Indeed, the inside of the blast furnace is communicating with the surrounding atmosphere through the material hoppers, the pressure of which is increased or decreased in such a way that the materials may be charged to the blast furnace under the same pressure as the top pressure.

Still today, the most common way of equalizing the pressure in the material hoppers to charge the hoppers (i.e. decreasing the pressure) consists in releasing gas to the atmosphere through a depressurizing valve and duct connected to a gas outlet of the material hopper. Clearly, such release of CO, CO2 and dust containing top gas to the atmosphere causes serious environmental concerns.

To tackle this problem, blast furnace plants with pressure equalizing systems have been designed, to permit partial or full gas recovery from the hoppers.

In the conventional full recovery pressure equalizing systems, the top gas is extracted from each hopper through an evacuation piping with ejector, and returned to the gas network. The ejector is driven by semi-cleaned top gas branched off from the cleaning unit.

Full recovery is rarely implemented due to the following drawbacks. The system requires extra piping and is therefore quite costly compared to simple relief to atmosphere. Furthermore, the ejector has quite large footprint (up to 7 m) and is very noisy.

OBJECT OF THE INVENTION

The object of the present invention is to provide an improved pressure equalizing system for material hoppers of a top charging installation.

This object is achieved by a shaft furnace plant comprising a pressure equalizing system as claimed in claim 1.

SUMMARY OF THE INVENTION

According to the present invention, a shaft furnace plant comprises: a shaft furnace with a top charging device arranged above the shaft furnace, wherein the top charging device comprises at least one material hopper for temporary storage of burden material to be fed into the furnace; a cleaning unit, which is connected for receiving top gas from the shaft furnace and configured for removing dust from the top gas; a pressure equalizing system comprising an evacuation piping with an ejector, one end of the evacuation piping being connected to the hopper and the other end to a gas network, to which gas is returned (typically via gas collecting duct).

It shall be appreciated the pressure equalizing system comprises a compressor that is connected for receiving cleaned top gas released from the cleaning unit (typically branched off after), and compressing said gas. A high-pressure buffer reservoir is arranged downstream of the compressor, for storing compressed gas fed from said compressor. The buffer reservoir is fluidly connected to a driving side of the ejector in such a way that compressed gas from the buffer reservoir can be used as motive fluid in the ejector.

The pressure equalizing system according to the present invention is designed to produce compressed gas that is stored in the buffer reservoir. The buffer reservoir provides a source of high pressure gas that is advantageously used to drive the ejector of the pressure equalizing system. This allows reducing the size of the ejector, as compared to conventional pressure equalizing system where the ejector has a footprint of about 7m. In particular, it is estimated that with a buffer reservoir storing compressed gas at a pressure of about 8 bar, the size of the ejector can be decreased by 30%.

The pressure equalizing system is advantageously configured such that the buffer reservoir contains compressed gas at high pressure, preferably in the range of 6 to 12 bar, in particular about 8, 9 or 10 bar (absolute pressures).

In an embodiment, the compressor is mechanically coupled to a turbine, which is connected for receiving and being driven by shaft furnace top gas, preferably clean. Such compressor and turbine combination is advantageous as it uses the energy of blast furnace gas to compress the cleaned top gas that is stored in the buffer reservoir for driving the ejector.

The turbine and compressor are preferably connected by a common shaft for concerted rotation. A turbocharger device, or similar, may thus be used.

In embodiments, the evacuation piping comprises: a first section connecting a respective hopper to an inlet of the ejector; a second section connecting an outlet of the ejector to the gas collecting duct. The ejector further comprises a motive fluid inlet connected to receive high pressure compressed gas from the buffer reservoir.

The cleaning device may comprise a first cleaning stage and a second cleaning stage for sequentially cleaning the gas. In embodiments, the turbine and/or compressor is/are connected to receive gas exiting the second cleaning stage.

The plant may further comprise a TRT device arranged in said gas collecting duct, downstream of said cleaning unit, and said evacuation piping connected with said gas collecting duct downstream of said TRT device.

When a TRT is present, the compressor and turbine may be fed with clean top gas branched off from said gas collecting duct, upstream of the TRT device.

In embodiments, the charging device comprises a main casing with a stationary housing and a suspension rotor for a movable distribution chute, the suspension rotor being rotatably mounted with respect to the housing.

It will be noted that the high pressure gas stored in the buffer reservoir can be used in other user equipment, where desirable. For example, the buffer reservoir may be fluidly connected (additionally or alternatively) with a big blaster associated with a material gate of said the hopper, in order to feed said big blaster with compressed clean gas. This provides a convenient way of pressurizing big blasters.

In some embodiments, the plant may comprise a CO2 removal unit, downstream of the cleaning unit, for reducing the CO2 content in the cleaned top gas. The flow of C02 removed from the top gas can be forwarded to the compressor and then to the buffer reservoir.

The present invention has been particularly developed for blast furnaces, but can be used in any kind of shaft furnace with top charging installation requiring depressurization of the material hoppers.

According to another aspect of the invention, there is provided a method of operating a shaft furnace, the method comprising: providing a charging device having at least one material hopper, said material hopper comprising a hopper chamber, a material inlet aperture for feeding a burden into said hopper chamber, and a material discharge aperture for feeding a burden from said hopper chamber to said blast furnace; said material inlet aperture having an associated inlet seal valve for opening and closing said material inlet aperture and said material discharge aperture having an associated discharge seal valve for opening and closing said material discharge aperture; feeding a burden into said hopper chamber through said material inlet aperture, with the material inlet aperture open and the discharge seal valve closed; closing said inlet seal valve; pressurizing said hopper chamber by feeding pressurizing gas into said hopper chamber; and opening said material discharge valve and feeding said burden from said hopper chamber to said shaft furnace; closing said discharge seal valve; depressurizing said hoper chamber by communicating said hopper chamber with an evacuation piping comprising an ejector; and subjecting top gas recovered from said shaft furnace to a cleaning stage and subsequently compressing and storing the cleaned and pressurized top gas; wherein said depressurizing step comprises feeding at least a portion of said stored, cleaned and pressurized top gas to a driving side of said ejector to be used as motive fluid in said ejector.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will now be described, by way of example, with reference to the accompanying drawing, in which the unique Figure is a diagram of an embodiment of the present blast furnace plant.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS A schematic representation of the inventive blast furnace plant 10 is shown in the Figure. A top charging installation, generally indicated at 12, is placed above a blast furnace 14 (only the top region of which is shown). Conventionally, the top charging installation 12 rests on the top cone 16 that closes the throat 18 of the blast furnace proper. In the present embodiment, the top charging installation 12 is of the BELL LESS TOP® type, which is well known in the art and will only be briefly described. In an upper part of the top charging installation 12, raw materials, also referred to as burden or charge material, are placed in material hoppers 20, here a pair hoppers 20 in a so-called parallel configuration. The material hoppers 20 are generally lock-type hoppers each having a hopper chamber 22 therein for temporarily storing burden material. Conventionally, each material hopper 20 comprises a material inlet aperture and a material discharge aperture for receiving and discharging the burden. An inlet seal valve 24 is associated with the material inlet aperture for sealingly closing the latter. Similarly, a material flow control gate 26 and a discharge seal valve -in a common valve casing 28- are associated with the material discharge aperture for sealingly closing the latter.

Also shown in the figure, a receiving hopper 30 is located above material hoppers 20 and allows to selectively direct the raw material (arriving from a skip car, conveyor belt system or similar conveyor means - not shown) to a desired hopper chamber 22, via the material inlet aperture with the inlet seal valve 24 open.

The burden material is charged into the blast furnace 14 by a rotatable and tiltable distribution chute 32. The distribution chute 32 is suspended to a suspension rotor to be pivotable about a horizontal axis, thereby allowing adjusting the angle of the chute. The suspension rotor is rotatable about a vertical axis, generally corresponding to the blast furnace central axis. The suspension rotor is surrounded by a stationary housing, in which it is rotationally supported by means of a slewing bearing. The suspension rotor and stationary housing form the main casing of the rotary charging device, in which mechanisms for driving the suspension rotor and pivoting the charge distributor are arranged. The stationary housing has a central channel with a feeding spout, guiding the charge material from the hopper region to the distribution chute 32. This part of the top charging installation with the casing hosting the suspension rotor for the distribution chute and corresponding gearings and drives is often referred to as chute transmission gearbox, and is generally designated 34 in the figure.

In operation, when burden material is fed into the hoppers 20, the material gate 26 and discharge seal valve 28 are in closed position, whereas the inlet seal valve 24 is open so as to allow inlet of the burden into the hopper chamber 22 of the material hopper 20. Once the desired amount of burden is in the hopper chamber 22, the inlet seal valve 24 is closed. Pressurizing means are operated in order to feed pressurizing gas into the hopper chamber 22 to pressurize the latter at a pressure no less than the operating pressure of the blast furnace. When the hopper chamber 22 is sufficiently pressurized, the material discharge valve 26 and the discharge seal valve 28 are opened and the burden is transferred to the interior of the blast furnace 14. The filling and pressurizing stages of hoppers, as well as the operation of the blast furnace itself are well known and will not be further described herein. Before the next filling of the material hopper 20, it will be necessary to decrease the pressure in the hopper chamber 22 by means of a pressure equalizing system, as disclosed further below.

High-temperature top gas is extracted from the blast furnace 14 through an offtake piping arrangement. This top gas is highly dust-laden and therefore is fed into a cleaning unit 36, which performs a two-stage cleaning. In the embodiment, the offtake piping arrangement comprises a set of offtake ducts 38 merging into a down comer line 40 that leads to a dust catcher 42 (or alternatively a cyclone). Dust catcher 42 is in turn connected by an intermediate duct 44 to a wet separator, which comprises a scrubber 48 and a demister 50. After the two cleaning steps, the gas has a residual dust content, which may e.g. be of less than 5 mg/m3. It may be noticed that cleaning of blast furnace top gas is conventional in the art and the cleaning device 36 may be designed according to conventional practice.

In the shown embodiment, the cleaned top gas is discharged from the cleaning unit 36 into a collecting duct 52, on which a TRT (top gas recovery turbine) device 54 is arranged, thus downstream of the cleaning unit 36. As it is known in the art, the TRT turbine 54 is generally driven by the cleaned top gas in order to drive itself an electric generator (not shown) mechanically coupled thereto, while the expanded top gas is returned to the plant network and may be burned. In the figure, clean gas exits cleaning unit 36 in collecting piping 52 connected to the TRT turbine 54, where it will drive the turbine and expand to lower pressure and temperature. Downstream of the TRT 54 the expanded gas may be returned to the plant gas network (indicated 55).

For an improved treatment of top gas, blast furnace plant 10 further comprises a pressure equalizing system, generally indicated at 60, associated with the material hoppers 20. The pressure equalizing system 60 includes an evacuation piping 62 with an ejector 64 that connects each hopper 20 to collecting piping 57 (downstream of TRT 54), which allows for full recovery of the gas contained in the material hoppers 20. The pressure equalizing system 60 is operated after a charging phase of the blast furnace, when the burden material has been discharged from the hopper chamber 22.

It shall be appreciated that the ejector 64 is driven by compressed and cleaned top gas stored in a buffer reservoir 66.

As can be seen in the figure, a part of the cleaned top gas is fed from collecting piping 52 through a first branch pipe 68 to the inlet side of a turbine 70, which is driven by the pressure of the cleaned top gas. The expanded gas exits the turbine 70 into a return pipe 72, by which it is returned to the collecting piping 52 downstream of the TRT 54, and hence to the gas network. Since the gas arriving at the network 55 still has a high content of combustible components, its energy content may be used to create heat by burning.

The turbine 70 is mechanically coupled to a compressor 74 by a transmission unit 76. The transmission unit 76 may simply be a common shaft which connects the compressor 74 to the turbine 70; accordingly a conventional turbocharger may be used. However, the transmission 76 may be more complex, e.g. it may comprise a gear for creating different rotation speeds for the turbine 70 and the compressor 74.

The compressor 74 is fed with clean gas by a second branch pipe 78, which is branched off from collecting piping 52.

The gas is compressed and exits the compressor 74 via a pipe 80 leading to the buffer reservoir 66. The cleaned top gas compressed in compressor 74 is thus discharged and stored into the buffer reservoir 66, where it can be used for selected purposes. In this embodiment, the buffer reservoir 66 is a gas-tight and pressure resistant vessel, with an inlet 66.1 and an outlet 66.2, each with an associated, controllable seal valve. The buffer reservoir 66 may have a storage capacity of 10 to 30 m3. The buffer reservoir 66 is configured in such a way that it can contain a relatively high gas pressure of several bar, e.g. above 4 bar, in particular between 6 and 12 bar, and preferably about 8, 9 or 10 bar (absolute pressures).

By way of this configuration, the energy required for driving the compressor 74 is exclusively obtained from the pressure of the gas fed to the turbine 70, which pressure results from the energy of the top gas in the blast furnace 14. A given volume of compressed, cleaned top gas is available in the buffer reservoir 66, at relatively high pressure compared to regular blast furnace operating pressure. No external energy or external gas supply is required to compress the clean top gas to be stored in buffer reservoir 66.

In the shown embodiment, the volume of clean, pressurized gas stored in the buffer reservoir 66 is advantageously used to drive the ejector 64 installed in the evacuation piping 62 of the pressure equalizing system 60. Accordingly, buffer reservoir 66 is connected via pipe 82 to the drive side of the ejector 64. As it is known, such an ejector (also referred to as jet pump) uses the Venturi effect of a converging-diverging nozzle to convert the pressure energy of a motive fluid to velocity energy, which creates a low-pressure zone that draws in and entrains a suction fluid. In the present embodiment, the clean high-pressure gas stored in buffer reservoir 66 is used as motive fluid in the ejector 64. Hence, the ejector 64 can be advantageously used to draw gas out of the hopper chamber 22, thereby depressurizing the hopper chamber 22 down to atmospheric pressure. Any appropriate ejector technology may be used in the present system.

Referring to the figure, ejector 64 is connected in line with the evacuation piping 62. Ejector 64 has an inlet 64.1 in communication with a first section 62.1 of the evacuation piping connected to a gas outlet 83 in the wall of the hopper chamber 22. An ejector outlet 64.2 is connected to a second section 62.2 of evacuation piping 62 extending from ejector 64 to collecting piping 57. A depressurizing valve 84 is arranged in the first section 62.1 of the evacuation piping 62, in order to selectively open or close fluid communication between the respective hopper chamber and the ejector 64. For safety purposes, a relief valve 86 is arranged in a relief branch 62.3 of first section 62.1, upstream of valve 84.

As it will be clear to those skilled in the art, the present pressure equalizing system 60 is operated after discharging the hoppers and before a new filling phase. The hopper chamber 22 is normally empty and the pressure therein corresponds substantially to furnace pressure, e.g. between 1.5 and 2.5 bar. The inlet seal valve 24 and discharge seal valve 28 are closed. The pressure equalizing system 60 is operated by opening valve 84 and actuating ejector 64 by supplying compressed gas from the buffer reservoir 66. This pressure equalizing phase is performed until the pressure drops down to a given pressure, typically atmospheric pressure. Then the pressure equalizing phase can be stopped by closing off valve 84 and interrupting the flow of compressed gas from buffer 66 to ejector 64. After equalization phase, the inlet seal valve 24 can be opened for loading the hopper chamber with burden material.

It will be appreciated that the availability of the source of high-pressure clean gas in buffer reservoir 66 permits to increase the pumping effect in the ejector 64, as compared to conventional pressure equalizing systems where the ejector is driven by low pressure semi-cleaned top gas (pressure in the range of 0.3 bar(g) to 2.4 bar(g)). Accordingly, it is possible to downsize the ejector to achieve the same efficiency as in conventional full recovery hopper equalizing systems. In particular, it is considered that with a buffer reservoir storing clean top gas at about 8 bar (absolute pressure), the size of the ejector can be reduced by about 30%. Also, as the ejector 64 is driven by clean gas instead of semi-clean gas in conventional plants, the gas flowing back to the network 55 is not polluted.

Since one material hopper is charged at a time, one ejector 61 is sufficient for a top charging installation with two or three material hoppers. The ejector will be operated in turn for the pressure equalization of each material hopper 20. Hence, each material hopper is connected by a respective first section of evacuation line 60. In the figure, the material hopper 20 on the left is connected to ejector 64 via a respective first piping section 62.T similar to section 62.1. First piping section 62.T is connected at one end to the gas outlet 83 of the hopper 20 and at the opposite end to the inlet side 64.1 of ejector 64. An on/off valve 84’ controls the flow towards the ejector 64. A relief valve 86’ is mounted on a branch pipe 62.3’.

As indicated above, the availability of clean, high pressure gas in the buffer reservoir 66 is advantageous in the blast furnace plant, as it can serve different purposes, in particular for driving the ejector as explained above.

Another possible use of the high pressure top gas is for pressurizing so-called “big blasters in the area of the material gates 26. A big blaster Is a pressurized cylinder typically containing a volume of 20 to 50 L of nitrogen gas at a pressure of up to 10 bar(g). The cylinder is closed by an on/off valve opening into a connecting end of a blasting duct, and having an opposite blasting end with a orifice for expelling nitrogen (possibly with nozzle). The blasting end of the blasting duct is positioned to blow away dust build-ip in the area of the material gate 26. This dust build up may occur due to condensation of blast furnace gas in combination with wet equalizing gas and dust particles from the burden material. Such dust build up may hinder the material gate from properly the closing the material discharge aperture.

It shall be appreciated that high pressure clean gas from the buffer reservoir 66 can be used to pressurize the big blaster. Dashed line 90 in the figure represents a pressurizing duct that connects the outlet of buffer reservoir to a big blaster 92 associated with material gate 26, in particular connected to a feed port of the big blaster.

In some embodiments, a C02 removal unit may be arranged downstream of the cleaning unit 36, for reducing the CO2 content in the cleaned top gas. The C02 removal unit may be a Pressure Swing Adsorption (PSA) installation or a Vacuum Pressure Swing Adsorption (VPSA) installation, as for example shown in US 6,478,841. PSA/VPSA installations produce a first stream of gas which is rich in CO and H2 and a second stream of gas rich in C02 and H20. The first stream of gas may be used as reduction gas and injected back into the blast furnace. The second stream of gas can be compressed and fed to the buffer reservoir, to serve as driving gas for the ejector 64.

In the figure, reference sign 96 designates such C02 removal unit arranged in the second branch pipe 78 upstream of the buffer reservoir 66. The second stream (with the removed C02) flows from the C02 removal unit 96 to the compressor via piping 78. The first stream is indicated by arrow 98 and can be reused in the furnace, as is known. The C02 removal unit 96 is optional and can be used to separate C02 from the cleaned top gas forwarded to the compressor 74 or to both the compressor 74 and turbine 70. The presence of a TRT 54 is not required. Also, one could use the C02 removal unit 96 in a configuration without the compressor-turbine arrangement shown in the figure, but where the gas discharged from the C02 removal unit is compressed by a compressor driven by a dedicated motor (electric or thermal) before being stored in the buffer reservoir.

Claims (15)

1. A furnace installation comprising: a shaft furnace (14) with a loading device (12) arranged at the top of the shaft furnace, wherein the loading device comprises at least one hopper (20) for raw materials intended to be fed into the shaft furnace; a cleaning unit (36), which is connected to receive a top gas from the tank furnace and configured to remove dust from the top gas; a pressure equalization system comprising an evacuation line (62) with an ejector (64), one end of the evacuation line being connected to the hopper and the other end to a line (52) for collecting gas; characterized in that said pressure equalization system comprises: a compressor (74) connected to receive a cleaned blast gas from the cleaning unit, and compressing said gas; a high pressure buffer tank (66) downstream of said compressor for storing compressed gas supplied from said compressor; and wherein said buffer tank (66) is in fluid connection with a driving side of said ejector such that the compressed gas from the buffer tank can be used as a motor fluid in said ejector. 2. A furnace installation according to claim 1, wherein said high pressure buffer tank (66) contains the high pressure compressed gas, preferably in the range 6 to 12 bar, more preferably 7 to 11 bar, particularly about 8 bars. 3. A furnace installation according to claim 1 or 2, wherein said compressor (74) is mechanically coupled to a turbine (70), which is connected to receive and be driven by a furnace gas, preferably clean. 4. A furnace installation according to claim 3, wherein said turbine and said compressor are connected by a common shaft (76) for a concerted rotation. 5. A furnace installation as claimed in any one of the preceding claims, wherein said drain line (62) comprises: a first section (62.1) connecting a respective hopper (20) to an inlet (64.1) of said ejector; a second section (62.2) connecting an outlet (64.2) of said ejector to said gas collection line; and wherein said ejector (64) further comprises a motor fluid inlet connected to receive a high pressure compressed gas from said buffer tank (66). The furnace installation according to any one of the preceding claims, wherein the cleaning device (36) comprises a first cleaning stage and a second cleaning stage for sequentially cleaning the gas. 7. A furnace installation according to claim 6 according to claim 3 or 4, wherein the turbine and / or the compressor are / are connected (s) to receive a gas leaving the second cleaning stage. 8. A furnace installation as claimed in any one of the preceding claims, comprising a TRT device (54) downstream of the cleaning unit. 9. A furnace installation according to claim 8, wherein the TRT device is arranged in said gas collection pipe (54) downstream of said cleaning unit, and said evacuation pipe connects with said gas line. gas collection downstream of said TRT device. 10. A furnace installation according to claim 9 according to claim 3, wherein said compressor and said turbine are supplied with clean clean gas stitched on said gas collection pipe, upstream of said TRT device. Tank furnace installation according to one of the preceding claims, in which the loading device (12) comprises a main casing with a stationary housing and a rotor in suspension for a movable distribution duct (32), said rotor in suspension being rotatably mounted relative to the housing. 12. A furnace installation according to any one of the preceding claims, wherein said buffer tank (66) is further fluidly connected to a compressed air gun (92) associated with a material valve of said material hopper, to supply said compressed air gun with a clean compressed gas. 13. A tank furnace installation as claimed in any one of the preceding claims comprising a CO 2 removal unit (96) downstream of the cleaning unit for reducing the CO 2 content in the cleaned top gas. 14. A furnace installation according to any one of the preceding claims, wherein said furnace is a blast furnace. A method of operating a furnace charging apparatus, said method comprising: providing a loading device having at least one material hopper, said material hopper comprising a hopper chamber, an opening material inlet for feeding a load into said hopper chamber, and a material discharge opening for feeding a load from said hopper chamber to said blast furnace; said material inlet opening having an associated inlet seal valve for opening and closing said material inlet opening and said material discharge opening having an associated discharge seal valve for opening and closing said opening material discharge; feeding a load into said hopper chamber through said material inlet opening, with the open material inlet opening and the closed discharge seal valve; closing said inlet sealing valve; pressurizing said hopper chamber by feeding pressurized gas into said hopper chamber; and opening said material discharge valve and feeding said load from said hopper chamber to said furnace; closing said discharge sealing valve; depressurizing said hopper chamber by placing said hopper chamber in communication with an exhaust pipe including an ejector; characterized by subjecting a top gas recovered from said tank oven to a cleaning stage and then compressing and storing cleaned and compressed top gas; wherein said depressurizing step comprises feeding at least a portion of said top gas stored, cleaned and compressed to a driving side of said ejector for use as a motor fluid in said ejector.