Method and system for controlling a selected zone in a fuel fired furnace

A furnace having a heating zone in an entrant end, an exit end and means for moving work through said zone from said entrant end to and through said exit end;

• burner means at said exit end of said zone for propelling a flame from said exit end torward said entrant end;
• means for controlling the firing rate of said burner means in direct proportion to temperature of said work at said exit end;
• and automatic means for controlling the length of said propelled flame in accordance with a relationship between said firing rate and the temperature of said work adjacent said entrant end of said zone.

A method of heating a selected zone in a fuel fired furnace having means for moving work through said selected zone from an entrant end to and through the exit end of said zone at a variable production rate, said furnace further having a fuel fired burner means including at least one fuel fired burner at said exit end of said zone and control means for varying the length of said selected zone which is directly fired by a flame or flames from said fuel fired burner means between a first length with said direct fired portion of said zone being adjacent said exit end only and a second length with said direct fired portion of said zone being generally from said exit end of said zone to a position substantially spaced from said exit end in a direction toward said entrant end of said zone, said method comprising measuring temperature in said zone adjacent said entrant end as a function of the production rate of work through said zone, determining whether said measured entrant temperature is above or below a set point temperature and inversely adjusting said length of said direct fired portion in accordance with a preselected relationship.

A method of heating a selected zone in a fuel fired furnace having means for moving work through said zone from an entrant end to and through an exit end, said furnace having first adjustable means for controlling the firing rate in said zone and second adjustable means for varying the portion of said zone which is directly fired between a first condition with said direct fired portion of said zone being adjacent said exit end and a second condition with said direct fired portion of said zone being generally from said exit end to a position generally adjacent said entrant end, said method comprising the steps of:

• (a) controlling said first adjustable means in accordance wtih a selected temperature in said zone;
• and,
• (b) simultaneously controlling said second adjustable means in accordance with the actual heating of said selected zone as sensed at least by the firing rate of said first adjustable means.

A system for controlling the heating of a selected zone in a fuel fired furnace having means for moving work through said selected zone in a given direction from an entrant end to and through an exit end of said zone at a variable production rate, said furnace further having first means for controlling the heating rate in said zone and second means for controlling the temperature profile in said zone and in a direction parallel to said given direction between a first short profile with the point of maximum energy liberation adjacent said exit end and a second long profile with said point of maximum energy liberation spaced from said exit end, said system comprising:

• means for controlling said heating rate by said first means in accordance with the exit temperature of said selected zone and adjacent to said exit end of said zone;
• means for establishing a desired set point temperature at said entrant end of said zone corresponding to said heating rate as controlled by said exit temperature;
• and, means for inversely adjusting said temperature profile by said second means in response to deviation of the actual temperature at the entrant end of said zone from said set point temperature until said heating rate and temperature profile reach an equilibrium condition.

A method of heating a selected elongated zone in a multizone reheating furnace in response to parameters in the selected zone, said zone accepting work moving from an entrant end to an exit end at a variable throughput, said method comprising:

• sensing a temperature in the zone controlled by the current throughput rate in said zone;
• and, changing the heating profile between said entrant end and said exit end to change the effective length of said zone as a function of said current throughput rate.

A system of heating a selected elongated zone in a multizone reheating furnace in response to parameters in the selected zone, said zone accepting work moving from an entrant end to an exit end at a variable throughput, said system comprising:

• means for sensing a temperature in the zone controlled by the current throughput rate in said zone;
• and, means for changing the heating profile between said entrant end and said exit end to change the effective length of said zone as a function of said current throughput rate.