Method and arrangement for removing solid particles and tar component from carbon monoxide gas

1. A method for removing solid particles and tar component from carbon monoxide gas which contains solid particles and volatile tar components, in which method

carbon monoxide gas is conducted from a ferroalloy smelting furnace to a gas scrubber,

the carbon monoxide gas is scrubbed in the gas scrubber by a liquid medium for removing part of the solid particles,

the carbon monoxide gas is conducted from the gas scrubber to a blower,

the flow rate of the carbon monoxide gas is increased by the blower, and

the carbon monoxide gas is conducted to a particulate filter,

by means of the particulate filter, the remaining solid particles are essentially filtered from the carbon monoxide gas, characterized in that prior to conducting the carbon monoxide gas to the particulate filter, said gas is conducted to a particle feeder, where finely divided adsorbent particles comprising coke dust are fed to the carbon monoxide gas for adhering the tar component on the surface of the adsorbent particles, and the carbon monoxide gas flow containing adsorbent particles is conducted to the particulate filter, so that the tar component adhered to the adsorbent particles is discharged in the particulate filter; where the carbon monoxide gas flow rate is accelerated and the adsorbent particles are mixed in the carbon monoxide gas with an accelerated flow rate; characterized in that in the particle feeder, the flow rate of the carbon monoxide gas is accelerated by a venturi pipe, and the adsorbent particles are mixed in the carbon monoxide gas in the venturi pipe by means of a feed pipe opening into the venturi pipe.

2. A method according to claim 1 , characterized in that 80-90% of the coke dust has a grain size not larger than 0.075 mm.

3. A method according to claim 1 , characterized in that the carbon monoxide gas flow rate is accelerated and the adsorbent particles are mixed in the carbon monoxide gas with an accelerated flow rate.

4. A method according to claim 1 , characterized in that for a uniform mixing of the adsorbent particles, the flow rate of the carbon monoxide gas is accelerated to the rate of roughly 25-29 m/s.

5. An arrangement for removing solid particles and tar component from carbon monoxide gas which contains solid particles and a volatile tar component, said arrangement including

a gas scrubber, which is arranged to receive carbon monoxide gas from a smelting furnace ( 1 ) for scrubbing the carbon monoxide gas by a liquid medium in order to remove part of the solid particles,

a blower, which is arranged to increase the flow rate of the carbon monoxide gas, and

a particulate filter, which is arranged to remove solid particles from carbon monoxide gas, characterized in that the arrangement includes a particle feeder, which is arranged in the flowing direction prior to the particulate filter for feeding in the carbon monoxide gas finely divided adsorbent particles comprising coke dust adsorbing the tar component; characterized in that the particle feeder includes a venturi pipe for accelerating the carbon monoxide gas flow rate, and a feed pipe, which opens into the venturi pipe for feeding adsorbent particles to the carbon monoxide gas flow with an accelerated flow rate.

6. A method according to claim 5 , characterized in that 80-90% of the coke dust has a grain size not larger than 0.075 mm.

7. An arrangement according to claim 5 , characterized in that the flow rate of the carbon monoxide gas in the venturi pipe is roughly 25-29 m/s.

8. An arrangement according to claim 5 , characterized in that the particle feeder includes a gas-tight tank for storing adsorbent particles; a gas duct, through which oxygen-free inert gas, such as nitrogen or carbon dioxide, can be fed to the tank in order to create an inert gas atmosphere inside the tank; and a shut-off feeder for feeding a continuous adsorbent flow from the tank to the feed pipe.

9. An arrangement according to claim 5 , characterized in that the particulate filter includes:

a filtering chamber, inside which there is provided a filter element, through which the carbon monoxide gas can be conducted, and on the surface of which filter element the solid particles remain;

cleaning nozzles provided inside the chamber for directing the inert gas blasting to the filter element for removing solid matter from the filter surface;

washing nozzles for feeding washing liquid to the chamber in order to slurry the solid matter removed from the filter to slurry; and

a discharge chamber for collecting the slurry; and—a discharge channel for removing the slurry from the discharge chamber.

10. A method of cleaning carbon monoxide gas created by smelting ferrochromium in the presence of incompletely coked coke as a reductant, the method comprising:

scrubbing carbon monoxide gas employing a liquid medium for removing solid particles from the carbon monoxide gas,

adding finely divided adsorbent particles comprising coke dust to the carbon monoxide gas for adhering tar present in the carbon monoxide gas to the surface of the adsorbent particles, and

subsequently removing adsorbent particles from the carbon monoxide gas, whereby tar adhering to the adsorbent particles is removed from the carbon monoxide gas,

and wherein the method comprises, after the scrubbing step and before the step of removing adsorbent particles from the carbon monoxide gas, increasing the flow rate of the carbon monoxide gas.

11. A ferrochromium smelting process comprising:

supplying incompletely coked coke as a reductant to a ferrochromium smelting furnace,

removing carbon monoxide gas from the furnace, and

cleaning the carbon monoxide gas by a method according to claim 10 ,

wherein the step of supplying incompletely coked coke as a reductant to the ferrochromium smelting process comprises receiving a supply of incompletely coked coke, separating particles of coke dust from the received supply of incompletely coked coke, and supplying coke that remains after separation of the particles of coke dust to the ferrochromium smelting furnace,

and the step of adding particles comprising coke dust to the carbon monoxide gas comprises adding the particles of coke dust separated from the received supply of incompletely coked coke to the carbon monoxide gas.