Modelagem e simulação da perda de carga de um sistema de trocadores de calor em refino de petróleo

Abstract

Heat exchangers are widely used in industry in a variety of applications such as cooling, condensing, heating, and breaking down oil-water emulsions. It is common to use several of these devices in parallel to increase productivity. The expected effect is to have the same operating conditions at the output of the process. When a set of identical equipment presents different results, the causes that lead to these operational deviations must be investigated. The objective of this work is to carry out a study of a heat exchanger system in an oil refinery, more specifically the top condenser system of the fractionator in a catalytic cracking unit. The system consists of six heat exchangers, named with suffixes A to F and they operate in pairs. The last pair E/F operates with very different characteristics from the other two sets A/B and C/D. The methodology used in this work was to use modeling and simulation techniques to evaluate the system performance, based on energy balances, calculations of pressure drop in pipes and heat exchangers, sensitivity analysis studies, and construction of a fluid dynamic model. The results showed that energy balances and fluid dynamic model were not consistent with the analytical model – based on pressure drop calculations and sensitivity analysis. The results also revealed that the problem is in association with the high-pressure drop on the waterside, both in the exchanger tubes and in the distribution headers, mainly at the E/F set. To minimize this problem, it is concluded that the best solution would be to install orifice plates in sections A/B and C/D to equalize the pressure variation between the three pairs of heat exchangers, preceded by an installation of pressure and flow sensors at the inputs and outputs of each pair of equipment and real-time monitoring step of these variables.