Method of setting temperature of continuous heating furnace and method of controlling furnace temperature

Abstract

A space from a charging hole to a discharge hole of a continuous heating furnace is divided into zones. A furnace temperature is assumed for each zone and a plurality of furnace temperature patterns are set. A metallization rate α OUT at the discharge hole is calculated for each furnace temperature pattern, using the time functions of the metallization rate α and the carbon content rate β of a raw material calculated in advance using a test. The necessary amount of heat applied to the continuous heating furnace is calculated for the furnace temperature patterns in which the calculated metallization rate α OUT is greater than or equal to a target value. The furnace temperature pattern which realizes the minimum necessary amount of heat applied is set as the optimal furnace temperature pattern. A fuel supplied to a burner is controlled based on the optimal furnace temperature pattern.

1 . A method of setting the temperature of a continuous heating furnace which heats a raw material loaded on a moving hearth using a burner and performs a reduction treatment, comprising the steps of:
 calculating a time function α=f(t) of a metallization rate α and a time function β=g(t) of a carbon content rate β of the raw material, using a furnace temperature T of the continuous heating furnace and an initial carbon content rate β IN  of the raw material charged to the continuous heating furnace as parameters;   dividing a space from a charging hole to a discharge hole of the continuous heating furnace into first to m-th zones (m is a natural number), assuming a furnace temperature T i  (i=1, . . . , m) for each of the zones, and forming a plurality of furnace temperature patterns including the furnace temperature T 1  of the first zone to the furnace temperature T m  of the m-th zone;   calculating a metallization rate α 1   OUT  and a carbon content rate β 1   OUT  at the exit of the first zone, using the metallization rate α IN  of the raw material and the initial carbon content rate β IN  of the raw material when the raw material is charged as a metallization rate α 1   IN  and a carbon content rate β 1   IN  at an entrance to the first zone, and the time functions α=f(t) and β=g(t) at the furnace temperature T 1  of the first zone, and calculating a metallization rate αi OUT  and a carbon content rate βi OUT  at the exit of an i-th zone, using a metallization rate αi−1 OUT  and a carbon content rate βi−1 OUT  at the exit of an (i−1)-th zone (i=2, . . . , m) as a metallization rate αi IN  and a carbon content rate βi IN  at an entrance to the i-th zone, and the time functions α=f(t) and β=g(t) at the furnace temperature T i  of the i-th zone, thereby calculating the metallization rate α OUT  at the discharge hole for each of the furnace temperature patterns; and   calculating the necessary amounts of heat applied to the continuous heating furnace for the furnace temperature patterns in which the calculated metallization rate α OUT  is greater than or equal to a target value, and setting the furnace temperature pattern among the calculated necessary amounts of heat applied which realizes the minimum necessary amount of heat applied as an optimal furnace temperature pattern.   
     
     
         2 . The method of setting the temperature of the continuous heating furnace according to  claim 1 ,
 wherein a relational expression β=h(α) between the metallization rate α and the carbon content rate β of the raw material is calculated using the furnace temperature T of the continuous heating furnace and the initial carbon content rate β IN  of the raw material charged to the continuous heating furnace as the parameters,   when the furnace temperature T i-1  of the (i−1)-th zone is different from the furnace temperature T i  of the i-th zone, the relational expression β=h(α) at the furnace temperature T i  which satisfies the relationship between the metallization rate αi IN  and the carbon content rate βi IN  at the entrance to the i-th zone is selected,   the initial carbon content rate βi IN  of the relational expression β=h(α) is calculated,   the time functions α=f(t) and β=g(t) satisfying the calculated initial carbon content rate βi IN  and the furnace temperature T i  are selected, and   the metallization rate αi OUT  and the carbon content rate βi OUT  at the exit of the i-th zone are calculated.   
     
     
         3 . A method of controlling the temperature of a continuous heating furnace, comprising a step of:
 controlling a fuel supplied to a burner of the continuous heating furnace based on the optimal furnace temperature pattern obtained by the method of setting the temperature of the continuous heating furnace according to  claim 1 .   
     
     
         4 . A method of controlling the temperature of a continuous heating furnace, comprising a step of:
 controlling a fuel supplied to a burner of the continuous heating furnace based on the optimal furnace temperature pattern obtained by the method of setting the temperature of the continuous heating furnace according to  claim 2 .   
     
     
         5 . The method of controlling the temperature of the continuous heating furnace according to  claim 3 ,
 wherein the mass of a raw material charged to the continuous heating furnace is measured,   the position of the raw material in the continuous heating furnace is tracked, and   the fuel supplied to the burner which is close to the tracked position is corrected based on the mass of the raw material.