Heat Exchanger Operation and Maintenance Optimization for Increased Profitabilit

The occurrence of crude oil fouling in heat exchangers is a critical problem in the petroleum industry. It is the formation of impurities known as foulants that adhere to the surface of the heat exchanger which reduces its heat transfer capacity and increases the force required for the crude oil to flow in the heat exchanger thereby leading to higher costs to operate the equipment. These increases in operational costs lead to a reduction in the petroleum refinery profit margin which could be improved by optimizing the cleaning frequency (schedule) of the heat exchanger. This forms the basic aim of the praxis as a mathematical study of the heat exchanger cleaning frequency impact on the petroleum refinery operation profit is conducted.;A range of experimental studies have been performed by researchers to comprehend the fouling mechanism but they have not been able to understand the overall relationship between fouling, heat transfer, and pressure drop in detail. This praxis focuses on the study of the crude oil fouling in correlation with the operating conditions of the heat exchanger (i.e. bulk temperature and crude oil flow rate) via empirical models used to determine the fouling rate at varying heat exchanger bulk temperatures and consequently fulfil the overall aim of establishing a cost-effective heat exchanger operational plan.;The fouling rate of light crude oil was studied via experimental field data gathered from light crude oil tests in a highly pressurised crude oil system and compared to the fouling rate of heavy crude oil studied theoretically. A higher fouling rate of 1700 (m2K/KW)/hr was experienced in the heavy crude oil compared to the light crude oil fouling rate of 1430 (m 2K/KW)/hr which is due to the asphaltene and sulphur compounds in the heavy crude oil that drive higher fouling rates.;Pressure drop studies of both light and heavy crude oil fluids in the heat exchanger showed that increasing heat exchanger bulk temperature leads to a reduction of the fluid pressure drop due to the decrease in their viscosities. A significantly higher pressure drop of 32 bar was observed in heavy crude oil compared to the 0.14 bar pressure drop of light crude oil as a result of the higher viscosity of the heavy crude oil.;The study of the fouling resistance of the crude oil fluids showed an increase of the fluid's pressure drop as the crude oil fouling resistance increased as a result of the development of foulant material restricting the fluid flow in the heat exchanger. In addition, the study of the fouling rate impact on the crude oil heat transfer coefficient showed detrimental effects as increasing fouling rate led to a reduction of the fluid's heat transfer coefficient due to foulants formed that limit heat transfer from its resistive thermal layer. A higher heat transfer coefficient of 560 Wm-2K -1 was derived for the light crude oil compared to the heavy crude oil heat transfer coefficient of 99.5 Wm-2K-1 brought about from the asphaltene and sulphur composition of the heavy crude oil thereby reducing the overall heat transfer capacity between the fluid and the heat exchanger.;The results provided from the study set a basis for mitigation and control measures of crude oil fouling to be implemented in heat exchanger operations. They include the use of cleaning agents where cleaning of the heat exchanger should be performed tri-weekly to deliver optimal profitability of $4.8B annually compared to the annual cleaning schedule currently performed by refineries with a profit of $2.7B. Since crude oil production increases with increasing bulk temperature, tube inserts should be utilised whilst maintaining an optimum threshold (maximum) heat exchanger bulk temperature of 250°C in order to achieve minimal fouling in the heat exchanger and maximum petroleum production in the refinery.