Abstract: Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. Combustion of hydrogen sulfide is precisely controlled by the proposed system to maintain the hydrogen sulfide and sulfur dioxide concentrations in the tail gas at acceptable levels to minimize the environmental pollution.

Abstract: Control of a process for producing free sulfur from hydrogen sulfide is accomplished by manipulating the flow rate of a feed stream containing oxygen to a furnace in such a manner that a desired proportion of the hydrogen sulfide fed to the furnace is converted to sulfur dioxide. Combustion of hydrogen sulfide is precisely controlled by the proposed system to maintain the hydrogen sulfide and sulfur dioxide concentrations in the tail gas at acceptable levels to minimize the environmental pollution.

Abstract: In tuning a PID controller for a process in a feedback control system, a method is provided for bringing the system into symmetric self-excited oscillations for measuring the frequency and the amplitude of the oscillations, and tuning the controller in dependence on the measurements obtained. A control algorithm referred to as the modified relay feedback test is introduced into a system in series with a process to generate self-excited oscillations. Tuning includes the steps of selecting a desired gain margin or phase margin, generating oscillations with the algorithm parameter corresponding to a selected gain or phase margin, measurements of the amplitude and the frequency of these oscillations, and computing PID controller tuning parameters. Data and formulas are given for the computation of the specific parameter of the modified relay feedback test and for tuning the parameters of the PID controller. An apparatus for performing the method is disclosed.

Abstract: In tuning a PID controller for a process in a feedback control system, a method is provided for bringing the system into symmetric self-excited oscillations for measuring the frequency and the amplitude of the oscillations, and tuning the controller in dependence on the measurements obtained. A control algorithm (modified relay feedback test) is introduced into the system in series with the process to excite self-excited oscillations in the system. Data and formulas are given for the computation of the specific parameter of the modified relay feedback test and for tuning the parameters of the PID controller. An apparatus for performing the method is disclosed.

Abstract: In tuning a controller for a process in a feedback control system, a method is provided for bringing the system into asymmetric self-excited oscillations for measuring the frequency of the oscillations, average over the period value of the process output signal and average over the period control signal and tuning the controller in dependence of the measurements obtained. An element having a non-linear characteristic is introduced into the system in series with the process and set point signal is applied to excite asymmetric self-excited oscillations in the system. An algorithm and formulas are given for identification of the process model having the form of first order plus dead time transfer function. PI controller settings are given as a function of the dead time/time constant ratio. An apparatus for performing the method is disclosed.