| 摘要 |
1,255,541. Automatic control systems. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. March 10, 1969 [March 12, 1968], No.12381/69. Heading G3R. A method for the automatic control of a number of process variables by a digital computer in response to measured values of the variables is characterized by the provision of at least one alternative programme for use in the event of a disturbance in the operation of the process equipment or a part thereof. Change-over to the alternative programme may be automatic, and it may be designed to provide reduced normal product and/or a gradual termination of the process. The invention is described in relation to two alternative processes, a distillation system, Fig.1 (not shown) and a catalytic reforming process for hydrocarbons, Fig.2 (not shown). In the first of these pressure, fluid-flow and liquid level are measured at various points and if any of them are outside upper and lower limits the alternative programme is used to adjust e.g. the feed, condenser coolant flow, the flow in re-circulatory loops &c. until the variable is restored to within the limits. In certain cases a second and different correcting action is made if the first is insufficient. The system includes means for keeping the ratio between certain quantities constant so that corrective action is applied to both. The second system uses similar control arrangements of these same variables, and in addition the temperature in reactor vessels is kept constant by adjustment of heater fuel supply, and if the temperature drops below a minimum value the set point of a feed control system is lowered. The normal operation of these systems is not described in detail, and neither is the computer. |
