Showing papers on "Process variable published in 1977"

Process measurement and control

Abstract: In the measurement of a variable process parameter and control of the process in response thereto, a transform of a process parameter measurement signal that can be described as the time derivative of a second order or higher lagged process parameter measurement signal is utilized to provide predictive capability. This transform is combined with the output of a PI controller to the input of which the process parameter measurement signal has been fed, thereby generating a process variable signal that either directly or after passing through another controller is utilized as a process control signal for controlling the process in response to the measured parameter. The system is particularly well adapted to control of a non-self-regulating process.

Mathematical model of the SL/RN direct reduction process

Abstract: A mathematical model has been developed to predict the operating behavior of an SL/RN direct reduction kiln from a knowledge of the main process variables. The model is based on steady state principles and is capable of quantitatively describing the different chemical reactions in the kiln such as reduction, Boudouard reaction, coal devolatilization, combustion in the freeboard together with the mass and heat flows. Results of the model, which are in the form of axial temperature profiles in the freeboard gas, solids bed and wall, and axial concentration profiles in the gas and solids, are in good agreement with measurements made on a 200 ton per day pilot plant at the Steel Company of Canada. The model has been used both to investigate the influence of process variables on the kiln performance and to elucidate operating features of the process. The model has shown that highly reactive coals such as subbituminous and lignite, and highly reducible pellets are most suitable for the SL/RN process. It has also demonstrated that the most important process variable from the standpoint of control is the air profile in the kiln; and consequently that heat transfer is the rate controlling step. The model has also been employed to examine scale-up of the SL/RN process by calculating the operating behavior of a large commercial kiln. It has shown that the large kiln should run cooler than the pilot-size unit so that accretion problems may be significantly reduced.

Operation and display system of process variable in dispersion type co ntroller

Abstract: PURPOSE:To smoothly change display, by increasing and decreasing the content of buffer, which takes in data that must be sent to a remote station, in a fixed inclination, based on process variable increasing and decreasing instruction from an operating panel while displaying the content of the buffer.

Dynamic Effects of the Dielectric Fluid in Electro-Discharge Machining

Abstract: From experimental investigations into the effects of variable dielectric flow rates through the working gap during electro-discharge machining, it has been found that machining characteristics can be greatly influenced by the rate of flow of the dielectric fluid. The purpose of this paper is to present results showing that the dielectric flow velocity has a more significant effect than has hitherto been realised. Using results in both qualitative and quantitative forms, it will be shown that the dielectric flow velocity has an effect on the wear ratio, the rate of erosion and surface geometry of the workpiece and must be taken into account as a process variable when considering other parameters.