FIELD OF THE INVENTION

The present invention relates to a sampling method for sampling dust with a sampling device from internal atmosphere of a metal production furnace (e.g. Flash Smelting Furnace) , a furnace for melting metals or from exit gas ducts of said furnaces. The present in ^¬ vention also relates to a sampling device to sample dust from internal atmosphere of a metal production furnace (e.g. Flash Smelting Furnace), a furnace for melting metals or from exit gas ducts of said furnac ^¬ es . BACKGROUND OF THE INVENTION

In prior art US 5,759,482 discloses a water cooled tubular sampling device that is insertable in a duct of a furnace to extract flue gas from the duct. The device comprises an outer tube comprising a closed lower end with a bottom 3 and a closed upper end having an outlet opening. An inner tube is arranged coax- ially inside the outer tube so that an annular gap is defined between the outer tube and the inner tube. Cooling fluid is arranged to flow in the gap. The in- ner tube comprises an outlet opening adjacent to its upper end for sucking gaseous substances out from the inner tube. The inlet opening via which the furnace gas and dust enter the inner tube is formed of the open lower end of the inner tube. The cooling of is indirect cooling because the transfer of the heat from the gas flowing inside the inner tube to the cooling fluid goes by conduction through the wall of the inner tube . The problem is that the indirect cooling is not very efficient, because the materials to be sampled tend to continue their reactions inside the sampling device and outside the furnace. Therefore, the condition of the reactions in the furnace cannot be reliably deter ^¬ mined from the taken samples.

An object of the present invention is to alleviate the problems described above and to introduce a solution that allows a sudden stop of reactions in the sampled gas and dust particles.

SUMMARY OF THE INVENTION

A first aspect of the present invention is a sampling method for sampling gas and dust with a sampling device from internal atmosphere of a metal production furnace (e.g. Flash Smelting Furnace), a furnace for melting metals or from exit gas ducts of said furnac ^¬ es. The method comprises sucking furnace gas and dust particles from the furnace atmosphere to the sampling device, cooling the sucked gas and dust particles with cooling fluid, and discharging gas and dust particles from the sampling device. In accordance with the in ^¬ vention cooling is implemented by directly spraying pressurized cooling fluid, e.g. water to the gas and dust particles to quench the dust particles by direct contact of cooling fluid to the dust particles and to scrub the furnace gas in the sampling device immedi ^¬ ately as furnace gas and dust particles enter the sam ^¬ pling device, and that the step of discharging the gas and dust particles is implemented by pumping out the slurry of cooling fluid and dust particles and sucking out the scrubbed gas and cooling fluid vapor.

A second aspect of the present invention is a sampling device to sample gas and dust from internal atmosphere of a furnace for producing metals, melting metals or from exit gas ducts of said furnaces. The sampling de ^¬ vice comprises an outer tube comprising a closed first lower end having a bottom, and a closed first upper end having a first outlet opening. The sampling device further comprises an inner tube arranged coaxial- ly inside the outer tube, so that an annular gap is defined between the outer tube and the inner tube. The inner tube comprises a closed second upper end, a se ^¬ cond outlet opening adjacent to the second upper end for sucking gaseous substances out from the inner tube, a second lower end, and an inlet opening for in- troducing furnace gas and dust particles into the in ^¬ ner tube. In accordance with the invention the second lower end of the inner tube is open and located at a distance from the bottom of the outer tube to provide flow path between the inner tube and the annular gap. The sampling device further comprises a spray nozzle arranged inside the inner tube to spray pressurized cooling fluid above the inlet opening to quench the hot dust particles by direct contact of cooling fluid to the dust particles as said dust particles together with the furnace gas enter via the inlet opening to the inner tube and to scrub the gas from said dust particles as the gas is sucked upwards to the second outlet opening. The slurry of cooling fluid and dust particles is collected on the bottom of the outer tube from which it can be discharged by pumping via the gap out from the first outlet opening. The slurry flowing in the gap cools the inner tube and the outer tube.

The advantage provided by the invention is that the reactions in the dust particles and gases can immedi ^¬ ately be stopped already in the sampling device at the moment they enter the sampling device by a sudden de ^¬ crease of temperature achieved by the direct cooling fluid spray. Furthermore, the invention allows sam- pling of such gases and dust which could react with each other. Because the reactions are stopped, in the analysis of the samples the furnace conditions can re- liably be observed. The sampling method and the sam ^¬ pling device of the invention are applicable for sam ^¬ pling gas and dust from e.g. a flash smelting furnace, an Ausmelt furnace, a roasting furnace, a sin- tering furnace and an electric arc furnace, a furnace for melting metals and/or from exit gas ducts of said furnaces .

In an embodiment of the invention, the sampling device comprises a sample receiver, a first pipeline connect ^¬ ed to the first outlet opening, and a first pump ar ^¬ ranged in the first pipeline for pumping the slurry of cooling fluid and dust particles to the sample receiv ^¬ er via a first exit branch of the first pipeline.

In an embodiment of the invention, the first pipeline comprises a drain forming a second exit branch of the first pipeline. The sampling device comprises a T- valve connected to the first pipeline or separate valves in each of the first and second exit branches of the first pipeline to guide the flow of slurry to the sample receiver and/or to the drain.

In an embodiment of the invention, the sampling device comprises a second pipeline connected to the second outlet opening, and a blower arranged in the second pipeline for sucking out the cooling fluid vapor and gas . In an embodiment of the invention, the sampling device comprises a cooling fluid trap arranged before the blower in the second pipeline for extracting cooling fluid from the gas . In an embodiment of the invention, the sampling device comprises a third pipeline connected to the spray noz- zle, and a second pump to provide pressurized cooling fluid to the spray nozzle.

In an embodiment of the invention, the sampling device comprises a cooling fluid tank from which the second pump is arranged to pump cooling fluid via the third pipeline .

In an embodiment of the invention, the sampling device comprises a regulating valve arranged in the third pipeline to regulate cooling fluid flow to the spray nozzle .

It is to be understood that the aspects and embodi- ments of the invention described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the invention. A method and an apparatus which is an aspect of the invention may com- prise at least one of the embodiments of the invention described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to pro- vide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the de ^¬ scription help to explain the principles of the inven ^¬ tion. In the drawings:

Fig. 1 is a schematic section view of one embodiment of the sampling device of the invention.

Fig. 2 is a cross-section II-II from Fig. 1; and

Fig. 3 illustrates a schematic pipework in connection with the sampling device of Fig. 1. DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the embodi- ments of the present invention, examples of which are illustrated in the accompanying drawings.

Figure 1 shows a sampling device configured to sample gas and dust from internal atmosphere of a furnace F (see Fig. 3) .

The sampling device includes an outer tube 1 compris ^¬ ing a closed first lower end 2 having a bottom 3. The outer tube 1 further comprises a closed first upper end 4 having a first outlet opening 5. An inner tube 6 is arranged coaxially inside the outer tube 1, so that an annular gap 7 (see also Fig. 2) is defined between the outer tube 1 and the inner tube 6. As seen in Fig. 2 the cross-section of the inner tube 6 and outer tube 1 is circular.

Referring again to Fig. 1 the inner tube comprises a closed second upper end 8 and a second outlet opening 9. The second outlet opening 9 is adjacent to the se- cond upper end 8. Gaseous substances can be sucked out from the inner tube 6 via the second outlet opening 9. The inner tube 6 also has a second lower end 10.

An inlet opening 11 is arranged to introduce furnace gas and dust particles into the inner tube 6. The in ^¬ let opening 11 is located at a distance h from the bottom 3 of the outer tube 1. The inlet opening 11 ex ^¬ tends through the gap 7 and the wall of the outer tube 1 so that the opening is sealed by a seal member 25 to prevent leakage of the slurry of cooling fluid and dust particles out from the gap 7 and also to prevent furnace gases from entering into the gap 7. The second lower end 10 of the inner tube 6 is open and at a distance H from the bottom 3 of the outer tube 1 so that a flow path is provided between the in- ner tube 6 and the gap 7.

A spray nozzle 12 is arranged inside the inner tube 6 to spray pressurized cooling fluid above the inlet opening 11. The spray nozzle 12 is configured to spray the cooling fluid so that the cooling fluid spray hits the inner wall surface of the inner tube 6 just above the inlet opening 11. The furnace gas and dust parti ^¬ cles immediately come into contact with cooling fluid as they enter into the inner tube via the inlet open- ing 11. The hot dust particles are quenched by said direct contact to the cooling fluid. Also the gas is scrubbed from said particles by the cooling fluid spray as it is being suctioned upwards to the second outlet opening 9. The slurry of cooling fluid and dust particles collect on the bottom 3 of the outer tube 1 from which it is pumped via the gap 7 to the first outlet opening 5. The slurry flowing in the gap 7 towards the first outlet opening 5 cools the inner tube 6 and the outer tube 1.

The cooling fluid may be water or a suitable salt so ^¬ lution. In some cases the salt solution may be more inert (dissolves less gas and dust) than water.

Referring to Fig. 3 the sampling device comprises a first pipeline 14 connected to the first outlet open ^¬ ing 5 of the outer tube 1. A first pump 15 is arranged in the first pipeline 14 for pumping the slurry of cooling fluid and dust particles to a sample receiver 13. The first pipeline 14 also comprises a drain 16. Optimally, a T-valve 17 is connected to the first pipeline 14 to guide the flow of slurry to the sample receiver 13 and/or to the drain 16. The T-valve can be replaced with separate valves 17 , 17 (shown with dot ^¬ ted lines) in each exit branch 26 and 16 of the first pipeline . Further the sampling device comprises a second pipe ^¬ line 18 connected to the second outlet opening 9. A blower 19 is arranged in the second pipeline 18 for sucking out the cooling fluid vapor and gas. A cooling fluid trap 20 is arranged before the blower 19 in the second pipeline 18 for extracting cooling fluid from the gas .

The sampling device further comprises a third pipeline 21 connected to the spray nozzle 12. A second pump 22 provides pressurized cooling fluid to the spray nozzle 12. The third pipeline 21 may also be connected to a water distribution system (not shown) . Alternatively, a cooling fluid tank 23 may be arranged from which the second pump 22 pumps cooling fluid via the third pipe- line 21. A regulating valve 24 may be arranged in the third pipeline 21 to regulate cooling fluid flow to the spray nozzle 12.

While the present inventions have been described in connection with a number of exemplary embodiments, and implementations, the present inventions are not so limited, but rather cover various modifications, and equivalent arrangements, which fall within the purview of prospective claims.