Method and arrangement for feeding fine-grained matter to a concentrate burner or a matte burner of a suspension smelting furnace and controlling means and computer program product

A method for feeding fine-grained matter to a concentrate burner or a matte burner of a suspension smelting furnace, wherein the method comprises

• a dosing step for feeding fine-grained matter from a dosing bin to a screw conveyor that is in communication with the concentrate burner or the matte burner of the suspension smelting furnace,
• continuously measuring the mass of the fine-grained matter that is fed from the dosing bin to the screw conveyor by means of a loss-in-weight means and calculating a mass flow rate by using the continuously measured mass of the fine-grained matter that is fed from the dosing bin to the screw conveyor,
• continuously adjusting the speed of the screw conveyor based on the mass flow rate, and
• determining the mass of the fine-grained matter in the dosing bin and performing a filling step for filling fine-grained matter into the dosing bin from a filling bin located at a level above the dosing bin, if the weight of the fine-grained matter in the dosing bin goes below a refill low level, wherein the filling step includes opening a filling valve between the dosing bin and the filling bin to let fine-grained matter in the filling bin to flow into the dosing bin, and subsequently closing the filling valve when the weight of the fine-grained matter in the dosing bin goes above a pre-set high-limit,
• characterized by the following steps:
• (i) calculating after closing the filling valve in a number of subsequent filling steps a feed rate difference between a process value for the actual feed rate and a predetermined set point for the feed rate by subtracting the predetermined set point for the feed rate from the process value for the actual feed rate,
• (ii) adding together the calculated feed rate differences obtained in step (i) to obtain a sum of the calculated feed rate differences,
• (iii) calculating of a ramp parameter by using at least one coefficient in a form of the number of calculated feed rate differences summed together in step (ii) and by dividing the sum of the calculated feed rate differences obtained in step (ii) with the coefficient to obtain the ramp parameter, and
• (iv) adjusting the speed of the screw conveyor during the filling step subsequent to the last filling step used for the calculation in step (i) by using the ramp parameter obtained in step (iii);
• further characterized
• by if when calculating for a number of subsequent dosing steps a feed rate difference in step (i) the calculated feed rate difference changes from positive to negative or from negative to positive when compared to a previously calculated feed rate difference, in step (ii) only the calculated feed rate differences of the number of subsequent dosing steps calculated prior said changing of the calculated feed rate difference from positive to negative or from negative to positive when compared to the previously calculated feed rate difference are summed together to obtain said sum of the calculated feed rate differences.