Abstract: Control of the temperature of an ammonia synthesis reactor is accomplished so as to reduce temperature oscillations throughout the reactor. This allows the ammonia synthesis reactor to be operated close to the lowest stable operating temperature which results in optimal reactor performance. The temperature of the effluent flowing from the ammonia synthesis reactor is monitored to detect the presence of thermal waves. The temperature of the effluent flowing from the synthesis reactor is utilized to generate a correction term which is utilized in temperature control for the ammonia synthesis reactor to stabilize the operation of the ammonia synthesis reactor.

Abstract: The rate of extrusion of an elongated article from a dynamic extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrusion rate to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The rate of introduction of polymer particles into the plasticization section of the extruder is automatically manipulated responsive to the control signal to maintain the extrusion rate at least substantially constant at the desired rate. The control signal can be adjusted to take into account variations in the temperature of the molten polymer entering the long land cooling die of the extruder.

Abstract: An override control system is provided in which the integral mode of the controllers not selected is forced to track the integral mode of the selected controller to prevent windup of the controllers not selected. Selection of the active controller is based only on the proportional mode for proportional-integral controllers. Selection of the active controller is based only on the proportional mode and the derivative mode for proportional-integral-derivative controllers.

Abstract: At least one radioactive source emitting at least two types of radiation is used with two detectors to measure properties of a material which are related to radiation attenuation by that material.

Abstract: Control of the inerts concentration level in the synthesis loop of an ammonia synthesis process is accomplished by using process measurements to provide a continuous estimation of the inerts concentration level in the synthesis loop. This estimation is utilized to provide feed forward control of the purge rate. A chromatographic analyzer is utilized to measure the actual inerts concentration level in the synthesis loop. The actual measured inerts concentration level is utilized to correct the estimation of the inerts concentration level at the sample times of the chromatographic analyzer to provide feedback control of the purge rate.

Abstract: The actual temperature of the extrudate issuing from a long land die extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrudate temperature to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The cooling fluid being circulated in heat exchange relationship with the extrudate in the long land die is manipulated responsive to the control signal to maintain the actual temperature of the extrudate substantially at the desired extrudate temperature. When the magnitude of the difference between the measurement signal and the setpoint signal exceeds a predetermined value, the rate of heat input to the plasticization section of the extruder and/or the rate of extrusion of the extrudate can be varied to reduce said difference to less than said predetermined value.

Abstract: The rate of extrusion of an elongated article from a dynamic extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrusion rate to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The rate of introduction of polymer particles into the plasticization section of the extruder is automatically manipulated responsive to the control signal to maintain the extrusion rate at least substantially constant at the desired rate. The control signal can be adjusted to take into account variations in the temperature of the molten polymer entering the long land cooling die of the extruder.

Abstract: The actual temperature of the extrudate issuing from a long land die extruder is measured and a measurement signal representative thereof is established. The measurement signal is then compared with a setpoint signal representing the desired extrudate temperature to produce a control signal which is responsive to the difference between the measurement signal and the setpoint signal. The cooling fluid being circulated in heat exchange relationship with the extrudate in the long land die is manipulated responsive to the control signal to maintain the actual temperature of the extrudate substantially at the desired extrudate temperature. When the magnitude of the difference between the measurement signal and the setpoint signal exceeds a predetermined value, the rate of heat input to the plasticization section of the extruder and/or the rate of extrusion of the extrudate can be varied to reduce said difference to less than said predetermined value.

Abstract: In a process control system, a control signal to the process is provided to a process model having a predictive element and a delay element adapted to reproduce as closely as possible the action of the measured process variable to the control signal. The variable input signal to the process controller, upon which generation of the process control signal is based, is generated by multiplying the signal from the predictive portion of the process model by a correction factor generated in response to the ratio of the actual process measurement signal to the delayed model output signal.