Utilization of various projectiles to mitigate fouling in tubular heat exchangers

Abstract

Projectiles of different shapes e.g. sponge balls can be propelled through the heat exchanger tubes by the flow to remove deposits. The frequency and duration of application depends on the severity of fouling and the strength of interaction between cleaning projectile and deposit. Optimum injection frequency and mitigation performance of projectiles are among key parameters that would greatly influence the efficiency of this technique. The "Clean-Ex" project which has been funded by the European Community endeavours to address some of these challenges. The principal objectives of this study were to i) calibrate and perform preliminary heat transfer experiments in a fouling rig that has already been designed for the project and to ii) carry out fouling experiments with or without projectiles (sponge balls) to determine their performance under various operating conditions. As for the first part, the test rig was calibrated and some parts were modified in order to improve its functionality to produce more reliable and accurate experimental data. The modifications were necessitated due to some technical problems that happened in the early stages of the experimentation. Furthermore, theoretical studies were carried out to calculate parameters such as pressure drop and convective heat transfer coefficient. In the second part of this study, Calcium sulphate was chosen as foulant due to its presence in many industrial application where fouling occurs. Different injection time intervals and flow velocities were studied in order to find the most effective injection frequency to mitigate fouling. Experimental results showed that once the deposit starts to form then subsequent injection of projectiles, here sponge balls, would not be effective to mitigate fouling. As the fouling experiments were carried out under accelerated fouling then the optimum frequency injection was found to be each injection in every two minutes.