Enhanced method and arrangement for gas regulation in mineral flotation

1. A method for controlling gas circulation in a mineral flotation process in a system comprising one or more flotation cell unit(s) with an apparatus comprising a gas recirculation loop comprising a recirculating compressor or blower for pressurising recirculating flotation gas flow, a flushing system comprising an expulsion line for connecting pressure side of the gas recirculation loop to atmosphere and a suction line comprising a water lock or means, other than a water lock, for restricting gas flow through the suction line and preventing back flow of unpurified gas to the atmosphere, for connecting suction side of the gas recirculation loop to the atmosphere, wherein the method comprises:

supplying flotation gas from the gas recirculation loop to each of the flotation cell units;

expulsing a part of the flotation gas from pressure side of the gas recirculation loop via the expulsion line to bypass flotation cells to outside of the gas recirculation loop;

allowing gas to be withdrawn into suction side of the gas recirculation loop through the suction line, thereby providing underpressure to the said suction side of the gas recirculation loop and the flotation cell unit(s); and

collecting flotation gas from the headspace(s) of the sealed flotation cell unit(s) and recirculating the collected flotation gas back to the flotation cell units via the gas recirculation loop.

2. The method as claimed in claim 1 , wherein the means, other than a water lock, for restricting the gas flow and preventing back flow of unpurified gas to the atmosphere comprises a gas restrictor and an interlock.

3. The method as claimed in claim 2 , wherein the interlock is provided as a gas scrubber comprising a bypass conduit for replacing the volume of gas forced through the gas scrubber and allowing gas to be withdrawn into suction side of the gas recirculation loop, whereby either by a sucking action of a high pressure venturi scrubber or by a blowing action caused by a blower or compressor positioned in connection of the gas scrubber, any expulsed unpurified flotation gas is forced to flow through the gas scrubber towards the atmosphere.

4. The method as claimed in claim 1 , further comprising controlling the amount of flotation gas by providing process gas to the gas recirculation loop to replace at least part of the flotation gas expulsed from the flushing system to the atmosphere.

5. The method as claimed in claim 1 , wherein process gas is introduced into the gas recirculation loop in the pressure side of the recirculating compressor.

6. The method as claimed in claim 1 , wherein gas, either in the atmosphere or present in the flushing line, is withdrawn into directly to the gas suction conduit.

7. The method as claimed in claim 1 , wherein gas, either in the atmosphere or present in the flushing line, is withdrawn into the suction side of the gas recirculation loop via any one of the flotation cell units.

8. An arrangement for circulation of gases in a mineral flotation process, comprising:

a gas recirculation loop comprising a recirculating compressor or blower for pressurising recirculating flotation gas flow and a gas feed manifold for providing the pressurized recirculating flotation gas into flotation cell units, means for providing process gas into the gas recirculation loop, and a gas suction conduit and optionally a sump suction conduit, for collecting flotation gas from the headspace(s) of the flotation cell unit(s), and optionally the headspace of a concentrate sump, respectively, and transferring it to the recirculating compressor or blower;

a flushing system comprising an expulsion line for connecting pressure side of the gas recirculation loop to atmosphere either directly or via a flushing line for allowing expulsion of a part of the flotation gas from the gas recirculation loop to bypass flotation cells to outside of the gas recirculation loop, and a suction line comprising a water lock, or means, other than a water lock, for restricting gas flow through the suction line and preventing back flow of unpurified gas to the atmosphere, for connecting the pressure side of the gas recirculation loop to the atmosphere either directly or through a flushing line and for allowing gas, present in the flushing line or from the atmosphere, to be withdrawn into the suction side of the gas recirculation loop through the suction line thereby providing underpressure to the pressure side of the gas recirculation loop and thus to the flotation cell unit(s);

a gas suction conduit, and optionally conduit, for collecting flotation gas from the headspace of the flotation cell units, and optionally the headspace of a concentrate sump, respectively, and transferring it to the recirculating compressor or blower.

9. An arrangement for circulation of gases in a mineral flotation process as claimed in claim 8 , comprising:

a gas recirculation loop comprising a recirculating compressor for pressurising recirculating flotation gas flow and a gas feed manifold for providing the pressurized recirculating flotation gas into flotation cell units, means for providing process gas into the gas recirculation loop, and a gas suction conduit and optionally a sump suction conduit, for collecting flotation gas from the headspace(s) of the flotation cell unit(s), and optionally the headspace of a concentrate sump, respectively, and transferring it to the recirculating compressor;

a flushing system comprising an expulsion line for connecting pressure side of the gas recirculation loop to atmosphere either directly or via a flushing line for allowing expulsion of a part of the flotation gas from the gas recirculation loop, and a suction line comprising a water lock for connecting the pressure side of the gas recirculation loop to the atmosphere either directly or through a flushing line and for allowing gas, present in the flushing line or from the atmosphere, to be withdrawn into the suction side of the gas recirculation loop through the suction line thereby providing underpressure to the pressure side of the gas recirculation loop and thus to the flotation cell unit(s);

a gas suction conduit, and optionally conduit, for collecting flotation gas from the headspace of the flotation cell units, and optionally the headspace of a concentrate sump, respectively, and transferring it to the recirculating compressor.

10. The arrangement as claimed in claim 8 , wherein the suction line connects to the first gas suction conduit via any one of the flotation cell units, preferably via the first flotation cell unit.

11. The arrangement as claimed in claim 8 , wherein the pressure side of the gas recirculation loop is connected directly to atmosphere.

12. The arrangement as claimed in claim 8 , wherein the pressure side of the gas recirculation loop is connected to atmosphere via a gas scrubber and a stack.

13. The arrangement as claimed in claim 8 , wherein the suction side of the gas recirculation loop is connected directly to the atmosphere.

14. The arrangement as claimed in claim 8 , wherein the suction side of the gas recirculation loop is connected to the atmosphere through a flushing line.

15. The arrangement as claimed in claim 14 , wherein the interlock is provided as a scrubber comprising a bypass conduit for replacing the volume of gas forced through the scrubber and allowing gas to be withdrawn into suction side of the gas recirculation loop, whereby either by a sucking action of a high pressure venturi scrubber or by a blowing action caused by a blower or compressor positioned in connection of the gas scrubber, any expulsed unpurified flotation gas is forced to flow through the scrubber towards the atmosphere.