Batch dryer control apparatus

Claim 2

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a wet bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, and wherein said second temperature sensing means includes a memory means arranged to record the temperature of said outlet drying gas during constant rate evaporation for determining the equilibrium temperature of the solid.

Claim 3

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a wet bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle.

Claim 4

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a wet bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle.

Claim 5

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a wet bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, and wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle, wherein said predetermined considerations are in the nature of an equation of the form Tf K (Ti) + (1-K) Ts where Tf represents said final outlet temperature, K represents said constant signal related to the desired value of moisture content, Ti represents said inlet temperature, and Ts represents said equilibrium temperature of the material.

Claim 6

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a wet bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, and wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle, wherein said predetermined considerations are in the nature of an equation of the form Tf K (Ti) + (1-K) Ts where Tf represents said final outlet temperature, K represents said constant signal related to the desired value of moisture content, Ti represents said inlet temperature, and Ts represents said equilibrium temperature of the material.

Claim 7

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a web bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle, wherein said predetermined considerations are in the nature of an equation of the form Tf K (Ti) + (1-K) Ts where Tf represents said final outlet temperature, K represents said constant signal related to the desired value of moisture content, Ti represents said inlet temperature, and Ts represents said equilibrium temperature of the material, and wherein said signal generator is manually adjustable and calibrated in terms of desired moisture content of the material.

Claim 8

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the equilibrium temperature during constant rate evaporation of the material, and computing means responsive to the outputs of said temperature sensing means for calculating the temperature of the outlet drying gas related to a particular moisture content of the material, wherein said second temperature sensing means includes a web bulb sensor whereby said sensor may also be used to detect the temperature of the outlet drying gas, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the drying cycle, wherein said predetermined considerations are in the nature of an equation of the form Tf K (Ti) + (1-K) Ts where Tf represents said final outlet temperature, K represents said constant signal related to the desired value of moisture content, Ti represents said inlet temperature, and Ts represents said equilibrium temperature of the material, and wherein said signal generator is manually adjustable and calibrated in terms of desired moisture content of the material.

Claim 9

For use with batch drying equipment including; a drying chamber for containing the material to be dried, an air inlet and outlet provided therewith in a manner allowing the air to flow into the chamber, contact the material and flow out therefrom, control apparatus comprising in combination; a first dry-bulb temperature sensing element located adjacent said air inlet for sensing the temperature of the air flowing into said chamber, a second dry-bulb temperature sensing element located adjacent said air outlet for sensing the temperature of the air flowing out of said chamber, memory means responsive to said second temperature element adapted to receive and store the temperature sensed during the constant rate evaporation phase of the drying cycle, control means adapted to receive as one input a control signal and terminate the drying cycle upon receipt of said control signal, computing means responsive to said first and second temperature elements and said memory means, operable to generate said control signal so as to maintain constant and equal to a predetermined value a ratio of temperature differences, said ratio being the ratio of the difference between the temperature of the outlet air at the end of the cycle and the temperature of the outlet air during constant rate evaporation and the difference between the temperature of the inlet air and the temperature of the outlet air during constant rate evaporation, whereby the moisture content of said material when the drying cycle is terminated is directly related to said predetermined value of said ratio, and whereby said drying cycle is controlled so as to repeatably and accurately dry the material to the desired moisture content, and whereby said desired moisture content is determined by the choice of said value for said ratio.

Claim 10

For use with batch drying equipment including; a drying chamber for containing the material to be dried, an air inlet and outlet provided therewith in a manner allowing the air to flow into the chamber, contact the material and flow out therefrom, control apparatus comprising in combination; a first dry-bulb temperature sensing element located adjacent said air inlet for sensing the temperature of the air flowing into said chamber, a second dry-bulb temperature sensing element located adjacent said air outlet for sensing the temperature of the air flowing out of said chamber, memory means responsive to said second temperature element adapted to receive and store the temperature sensed during the constant rate evaporation phase of the drying cycle, control means adapted to receive as one input a control signal and terminate the drying cycle upon receipt of said control signal, computing means responsive to said first and second temperature elements and said memory means, operable to generate said control signal so as to maintain constant and equal to a predetermined value a ratio of temperature differences, said ratio being the ratio of the difference between the temperature of the outlet air at the end of the cycle and the temperature of the outlet air during constant rate evaporation and the difference between the temperature of the inlet air and the temperature of the outlet air during constant rate evaporation, whereby the moisture content of said material when the drying cycle is terminated is directly related to said predetermined value of said ratio, and whereby said drying cycle is controlled so as to repeatably and accurately dry the material to the desired moisture content, and whereby said desired moisture content is determined by the choice of said value for said ratio.

Claim 11

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the temperature of the inlet drying gas and the equilibrium temperature of the material, and computing means responsive to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant indication representative of the moisture content of said material, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the dRying cycle.

Claim 12

For use with batch drying equipment including; a drying chamber for containing the material to be dried, and a drying gas inlet and outlet provided therewith in a manner allowing the drying gas to flow through the chamber, contact said material and outlet therefrom, control apparatus comprising in combination: a first temperature sensing means for determining the temperature of the inlet drying gas, a second temperature sensing means for determining the temperature of the inlet drying gas and the equilibrium temperature of the material, and computing means responsive to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant indication representative of the moisture content of said material, wherein said computing means comprises in combination; a signal generator for generating a constant signal related to the desired value of moisture content of said material, computing means responsive to said constant signal and to the outputs of said temperature sensing means operable according to predetermined considerations to provide a resultant temperature signal representative of a final outlet temperature, and comparator means responsive to said outlet temperature signal and said final outlet temperature signal for generating a control signal to terminate the dRying cycle.