Method and apparatus for rotary kiln control

Claim 2

A control system for rotary kiln apparatus including a kiln lining desirably maintained at a predetermined temperature and cooling apparatus including movable grate means adapted to receive materials from a discharge end of the kiln and a source of cooling air, said control system comprising means for indicating the kiln-lining temperature at the discharge end and means for indicating the heat transfer characteristics of discharged materials on the movable grate and control means responsive to said kiln-lining temperature measuring means and said characteristic indicating means and adapted for controlling said movable grate means so as to maintain the kiln-lining temperature at the predetermined value.

Claim 3

A control system as recited in claim 1 wherein said characteristic indicating means includes means operably coupled to said grate means for sensing the air pressure under said grate means.

Claim 4

A control system as recited in claim 2 wherein variable speed drive means are operably connected to said movable grate means, said control means including means responsive to said kiln-lining temperature means and the predetermined temperature value for determining the temperature difference and means coupled to said temperature difference means for generating a signal representing the desired grate means pressure as a function of the temperature difference and means responsive to said desired grate-pressure generating means and said grate-pressure sensing means for determining the pressure difference and means responsive to said pressure-difference generating means for producing a speed control signal, said variable speed drive means being responsive to the speed control signal

Claim 5

A control system as recited in claim 3 wherein said source of cooling air includes controllable means for transferring the cooling air through the grate and material on the grate, said control means additionally comprising means for measuring the cooling air temperature after the cooling air passes through the material and means responsive to said measurement of air temperature for controlling said source of cooling air.

Claim 6

A control system as recited in claim 4 wherein said source of cooling air cOmprises a fan and damper means for controlling air flow to the grate, said control means being responsive to said air temperature sensing means for generating a predetermined air temperature and means responsive to said air temperature sensing means and said predetermined temperature signal generating means for controlling said damper means.

Claim 9

A control method as recited in claim 6 wherein said analyzing the heat transfer characteristics includes the step of measuring the air pressure under the grate means caused by discharged materials, thereon,

Claim 10

A control method as recited in claim 7 wherein the grate means may be moved at variable speeds to thereby vary the amount of materials thereon, said control method including the additional steps of determining the difference between the measured kiln-lining temperature and the desired kiln-lining temperature and, in response thereto determining an undergrate-pressure setpoint and varying the movable grate speed so as to maintain the actual undergrate pressure equal to the undergrate-pressure setpoint.

Claim 11

A control method as recited in claim 8 wherein said cooling air source includes means for controlling cooling air flow through the grate means, said control method additionally comprising the steps of measuring the temperature of the air after it exits from the material and responding to said measurement for controlling the quantity of cooling air passing through the grate.

Claim 12

A control system as recited in claim 9 wherein said source of cooling air includes controllable damper means and a fan, the controllable damper means controlling the air flow through the material, said control method additionally comprising the step of determining a desired air temperature from measured air temperatures and, in response to a difference therebetween, controlling the damper positions to maintain the measured air temperature at the desired air temperature.