Abstract: The invention relates to a method for the removal of mercury from gas containing sulphur dioxide and oxygen and from the sulphuric acid vapour contained in the gas. According to the method, the gas is washed with a water solution that contains selenium ions, whereby metallic selenium is formed in the presence of oxygen, which precipitates the mercury in the gas and vapour either as a selenide or in a chlorine-containing environment, as a dichloride of mercury and selenium. Gas washing occurs at a low temperature, below 50° C.

Abstract: This invention relates to a method for removing mercury from dilute sulphuric acid. According to the method sulphuric acid solution is scrubbed with an aqueous solution containing thiosulphate, which precipitates the mercury present in the sulphuric acid solution either as mercury sulphide or, in a chlorine-containing environment, as a mercury sulphide-mercury chloride double salt. The quantity of thiosulphate to be fed is adjusted so that it precipitates the mercury in the sulphuric acid solution, but still does not form elemental sulphur.

Abstract: The invention relates to a method and an apparatus for cooling a material to be removed from the grate of a fluidized bed furnace. Material at a high temperature is passed from the grate of the fluidized bed furnace into a fluidized bed cooler in charges of a given size by measuring the quantity of the material accumulating in the fluidized bed cooler. When the quantity of the material in the cooler has reached a predetermined limit value, the supply of material into the fluidized bed cooler is prevented. The charge is cooled in the fluidized bed cooler by fluidization air and via heat transfer into a cooling liquid circulation system and the temperature of the charge is measured. The charge is removed when the temperature of the charge has fallen to a predetermined limit value. The second end (5) of a supply conduit (3) is provided with a supply valve (15) actuated by a power means (16). A discharge conduit (14) is provided with a discharge valve (17) actuated by a second power means (18).

Abstract: This invention relates to a method for removing mercury from dilute sulphuric acid. According to the method sulphuric acid solution is scrubbed with an aqueous solution containing thiosulphate, which precipitates the mercury present in the sulphuric acid solution either as mercury sulphide or, in a chlorine-containing environment, as a mercury sulphide-mercury chloride double salt. The quantity of thiosulphate to be fed is adjusted so that it precipitates the mercury in the sulphuric acid solution, but still does not form elemental sulphur.

Abstract: The present invention relates to method, which helps to reduce and remove the build-up forming on the grate of a fluidized-bed furnace in the roasting of fine-grained material such as concentrate. The concentrate is fed into the roaster from the wall of the furnace, and oxygen-containing gas is fed via gas nozzles under the grate in the bottom of the furnace in order to fluidize the concentrate and oxidize it during fluidization. Below the concentrate feed point, or feed grate, the oxygen content of the gas to be fed is raised compared with the oxygen content of the gas fed elsewhere.

Abstract: This invention relates to a method for stabilizing a fluidized bed used in roasting by adjusting the oxygen content of the roasting gas in the bed. The fine-grained material for roasting is fed into the furnace above the fluidized bed and the roasting gas, which causes the fluidizing, is fed into the bottom of the furnace through a grate. In this method, the total amount of oxygen in the roasting gas to be fed and the average total oxygen requirement of the material to be roasted are calculated and the ratio between them regulated so that the oxygen coefficient in the bed is over 1.

Abstract: The present invention relates to an arrangement and method that help to reduce the build-up formed on the grate of a fluidized-bed furnace in the roasting of fine-grained material such as concentrate. The concentrate is fed into the roaster furnace from the wall of the furnace, and oxygen-containing gas is fed via gas jets under the grate in the bottom of the furnace in order to fluidize the concentrate and oxidize it during fluidization. Below the concentrate feed point, or feed grate, the oxygen content of the gas to be fed is raised compared with gas fed elsewhere using additional gas jets situated in the feed grate higher than the other jets. The extra jets of the feed grate are connected to their own gas distribution unit.

Abstract: The present invention relates to an arrangement and method that help to reduce the build-up formed on the grate of a fluidized-bed furnace in the roasting of fine-grained material such as concentrate. The concentrate is fed into the roaster furnace from the wall of the furnace, and oxygen-containing gas is fed via gas jets under the grate in the bottom of the furnace in order to fluidize the concentrate and oxidize it during fluidization. Below the concentrate feed point, or feed grate, the oxygen content of the gas to be fed is raised compared with gas fed elsewhere using additional gas jets situated in the feed grate higher than the other jets. The extra jets of the feed grate are connected to their own gas distribution unit.

Abstract: The invention relates to a method for the removal of mercury from gas containing sulphur dioxide and oxygen and from the sulphuric acid vapour contained in the gas. According to the method, the gas is washed with a water solution that contains selenium ions, whereby metallic selenium is formed in the presence of oxygen, which precipitates the mercury in the gas and vapour either as a selenide or in a chlorine-containing environment, as a dichloride of mercury and selenium. Gas washing occurs at a low temperature, below 50° C.

Abstract: The present invention relates to method, which helps to reduce and remove the build-up forming on the grate of a fluidized-bed furnace in the roasting of fine-grained material such as concentrate. The concentrate is fed into the roaster from the wall of the furnace, and oxygen-containing gas is fed via gas nozzles under the grate in the bottom of the furnace in order to fluidize the concentrate and oxidize it during fluidization. Below the concentrate feed point, or feed grate, the oxygen content of the gas to be fed is raised compared with the oxygen content of the gas fed elsewhere.

Abstract: This invention relates to a method for stabilizing a fluidized bed used in roasting by adjusting the oxygen content of the roasting gas in the bed. The fine-grained material for roasting is fed into the furnace above the fluidized bed and the roasting gas, which causes the fluidizing, is fed into the bottom of the furnace through a grate. In this method, the total amount of oxygen in the roasting gas to be fed and the average total oxygen requirement of the material to be roasted are calculated and the ratio between them regulated so that the oxygen coefficient in the bed is over 1.