Abstract
Corrosion and fouling has been a major menace to the operation, integrity and life expectancy of process equipment in the production line of refinery and petrochemical equipment. This research focuses on effective cooling water treatment technology by inhibitive and bio-remediative chemical injection to control fouling and minimizes corrosion in process equipment such as boiler, heat exchangers and heaters which form the livewire of a petrochemical plant. The research has been streamlined to consider Indorama Plc, formerly Eleme Petrochemical Plant network as a case study. Models for corrosion rate prediction and treatment level recommendation adopted uses a combination of laboratory, field and experiential data. The models provide tools for evaluating a cooling system under varying conditions to determine the impact of operating parameter changes (for example, acid feed, concentration ratio, pH) upon water corrosivity and corrosion inhibitor requirements. The study reviews the effectiveness and suitability of the existing chemical treatment program in place and measures it with performance indicators such as models, theories and empirical values such as Langelier saturation index (LSI), Ryznar stability index (RSI) to predict the tendency of corrossivity scaling of water, especially cooling water. Relevant data from daily analysis, routine checks, inspection and monitoring over a period of 1 year form the basis of the presented result and deductions. Corrosion coupons and relevant test instrument were employed for the research. Result obtained shows a good inhibitive treatment and consistent bio-activity control from effective chemical dosage given corrosion rate as low as 2 mpy on the average. The cycle of concentration that the cooling tower maintained had consistently been between 4 and 5. Calculated value of LSI and RSI on the average agrees with literature value for good treatment that enhances better performance. LSI and RSI values was obtained respectively to be, -0.1 to +0.1, and 0.4 giving credence to low corrosive and scaling tendencies that breeds fouling. Key words: Cooling, treatment, control, corrosion, fouling.
Highlights
The petrochemical plant unit carrying a cooling agent may suffer from internal corrosion, if there is water present in the system
Results include: monitoring and analyzing parameters from cooling water sample, monitoring of control parameters and performance of process equipments with special attention on boiler in olefins unit of the plant, and calculated values of models and performance indices used in predicting the efficiency of treatment program
The plot of zinc concentration versus time shows a great degree of compliance with standard treatment regime of 0.8 to 1.2 mg/L, zinc been a major harmful element to the environment, discharge must be minimal to the environment
Summary
The petrochemical plant unit carrying a cooling agent may suffer from internal corrosion, if there is water present in the system. In the cooling treatment unit the corrosivity will vary independence of factors such as the temperature, zinc concentration, ortho-phosphate concentration, calcium hardness (CaCO3), pH, turbidity, total iron, silica, cycles of concentration (based on silica) and Langeller saturation index, aerobic bacteria counts, bioscan counts, flow conditions, use of inhibiting chemicals etc. The corrosion allowance is based on assumption of the corrosivity during the production period. In order to maintain integrity, many cooling treatment plants are subject to intelligent cathodic protection/pig inspection at certain time intervals.
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