More specifically, my inventive concept directs itself to a cascade temperature control system, the objective of which resides in controlling the hydrogen-consuming processing of hydrocarbons. A corollary objective is directed toward a control system for preventing temperature run-away in a hydrocarbon conversion process in which hydrogen is consumed.
OBJECTS AND EMBODIMENTSĪn object of my invention is to provide a method for determining the location in an exothermic/endothermic reaction zone where the highest temperature occurs and which thus indicates the transition point where such reactions commence changing from exothermic to endothermic, and for controlling the temperature rise through such a reaction zone. The principal function of the present control system is to insure against deleterious temperature run-aways in hydrocarbon processes in which the reactions effected are primarily exothermic, while simultaneously considering the effect of endothermic reactions. As is well known in the appropriate art, unabated exothermic reactions can readily evolve into the natural consequence of a temperature run-away to the extent that catalyst damage (often irreparable), hardware damage and undesired side reactions take place. Specifically, the present control technique is particularly directed toward control of the temperature increase experienced through an exothermic catalytic reaction zone in which endothermic reactions are also taking place. In many such processes, the reactions being effected are both exothermic and endothermic, with the former generally predominating. Principally exothermic processes include hydrodesulfurization, hydrodenitrification, dealkylation, hydrotreating (olefin saturation), hydrocracking, etc., all of which have been previously categorized as hydroprocesses. a combination of hydrotreating followed by catalytic reforming.
The latter are prevalent in a multitude of hydrocarbon conversion processes widely utilized throughout the petroleum industry, and are often integrated in combination with an endothermic reaction process - e.g. dehydrogenation of naphthenes to aromatic hydrocarbons - are endothermic in nature, hydrogen-consuming reactions are primarily exothermic. Whereas hydrogen-producing reactions - e.g. Therefore, the present invention essentially involves a method for controlling the temperature rise through a catalytic reaction zone in which exothermic reactions predominate. My invention concept, as herein more fully described, encompasses a technique for determining the location, in an exothermic/endothermic catalytic hydrocarbon conversion process, where the highest temperature occurs and which thus indicates the transition point at which the reactions commence changing from exothermic to endothermic the technique is intended to prevent and alleviate so-called temperature run-away prevalent in such processes.
Enhanced control is afforded by selecting the higher of the outlet and highest intermediate temperatures, developing another representative signal and adjusting, or overriding the signal being transmitted to the charge stock bypass regulating means. The signal is transmitted to the inlet Temperature Recorder Controller to adjust the set point thereof, and the quantity of charge stock bypassing the feed heater is further regulated responsive thereto. The difference between the inlet and intermediate temperatures, and that between the intermediate and outlet temperatures are determined to produce two delta-T signals which are transmitted to a Double differential Temperature Recorder Controller (DdTRC) which develops a signal representing the difference between the two delta-T signals compared to a preset difference. The inlet temperature sensor co-acts with a Temperature Recorder Controller (TRC), having an adjustable set point (control point), to produce a representative signal which is transmitted to flow-regulating means which adjusts the quantity of charge stock bypassing the feed heater.
Control of temperature increases (delta-T) through a reaction zone, in which both exothermic and endothermic reactions are effected, is achieved by sensing the inlet temperature of the charge stock, a highest temperature from a plurality of intermediate loci within the reaction zone and the outlet temperature of the effluent from the reaction zone.
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