| Popis: |
In general, the first main step of petroleum refining consists in the distillation of the crude oil stream. In order to provide adequate fractionation, the crude stream must be fed in the atmospheric distillation column at about 380°C. Aiming to reduce energy consumption, heat from hot streams of side products and pumparounds is transferred to the crude stream in a heat integration scheme, called crude preheat train. The final heating of the crude stream is executed in a furnace. However, during the operation of the preheat train; the thermal effectiveness of the heat exchangers diminishes due to fouling and, as a consequence, fuel costs increases. The large volumes of crude oil processed and the scenario of crescent energy prices justify the importance of this problem for the oil companies. Seeking to provide a solution to reduce the impact of this problem, this paper presents the exploration of stream splitting in crude preheat trains composed by several parallel branches. In this case, each branch may present different fouling levels, which allows the exploration of different distributions of the stream flow rates along the system, through a proper optimization algorithm. This optimization algorithm searches the set of stream splitters related to the maximization of the final temperature of the crude preheat train. A mathematical model of the preheat train works coupled to the optimization method. An important focus of this paper is to explore the introduction of constraints in order to guarantee feasible operating solutions, i.e., the optimum solution must attend different operational aspects related to bounds on fluid flow velocities and heat exchanger capacities. The performance of the proposed approach is illustrated through a typical example of a petroleum refinery. |
