Method of producing pulverized coal

Method of producing pulverized coal, comprising:

• providing a drying gas heated to a predefined temperature in a hot gas generator;
• feeding the heated drying gas into a pulverizer;
• introducing raw coal into the pulverizer, the pulverizer grinding the raw coal into pulverized coal;
• collecting a mixture of drying gas and pulverized coal from the pulverizer and feeding the mixture to a filter, the filter separating the dried pulverized coal from the drying gas;
• collecting the dried pulverized coal for further use and feeding the drying gas from the filter to an exhaust line;
• collecting the drying gas exiting said filter and feeding part of said collected drying gas to a recirculation line for feeding recirculation drying gas to said hot gas generator
• wherein
• said step of providing said drying gas comprises feeding a variable flow rate of hot stove waste gas to said hot gas generator through a hot stove waste gas line so as to maximize the amount of hot stove waste gas used as drying gas;
• a pressure of said drying gas at a pulverizer gas inlet is controlled by regulating a flow rate of said hot stove waste gas through said hot stove waste gas line;
• and
• wherein
• the method comprises a hot stove waste gas operation mode and a first intermediate operating mode and the method switches from said hot stove waste gas operating mode to said first intermediate operating mode if said hot stove waste gas has a concentration of a predetermined component above a first concentration threshold and/or if said hot stove waste gas has a temperature below a first temperature threshold,
• wherein in the hot stove waste gas operating mode:
• said recirculation line is shut-off;
• such that no recirculation drying gas is fed to said hot gas generator;
• said hot stove waste gas line is open, such that only hot stove waste gas is fed at a variable flow rate to said hot gas generator;
• said pressure of said drying gas at said pulverizer gas inlet is controlled by a flow rate of said drying gas in said exhaust line and by regulating said flow rate of said hot stove waste gas through said hot stove waste gas line, and
• in the first intermediate operating mode:
• said recirculation line is open, such that recirculation drying gas is fed at a variable flow rate to said hot gas generator;
• said hot stove waste gas line is open, such that hot stove waste gas is fed at a variable flow rate to said hot gas generator;
• and
• said pressure of said drying gas at said pulverizer gas inlet is controlled by setting a flow rate of said drying gas in said exhaust line and by regulating said flow rate of said hot stove waste gas through said hot stove waste gas line.