In the oil and gas industries, highly flammable pressurized gas and liquid are normally contained and transported in cylindrical vessels. Blowdown is one of the common practices to reduce potential hazards by evacuating the fluid from the vessel in an emergency situation, such as an emergency shutdown or a control failure. However, the relatively rapid quasi-adiabatic expansion during the blowdown period leads to a significant temperature drop, and this temperature reduction can possibly reach below the ductile-brittle transition temperature. Moreover, blowdown can be a hazardous operation itself, especially for large pressure vessels, and the vessel tends to be fragile under even small stresses from the external environment.
Therefore, CEPI Lab. has been developing a new dynamic model to estimate the change of temperature and pressure during blowdown periods. The model considers heat transfer from the vessel wall to the discharged gas and its condensate, discharge rate at the exit orifice of the blowdown valve, and change of thermophysical properties during the blowdown period. For further delicate analysis, heat transfer from the vessel wall to the discharged gas for laminar and turbulent flows in the vessel was taken into consideration. CEPI Lab. is currently working on development of dynamic modeling for the design of flare networks, integrating it with the previously developed blowdown model.
[Figure 5] (a) Thermal stress after blowdown of a vessel (b) Estimation of temperature change during blowdown period
Against the background of increasing global concern about environment, the protection of environment has become a major issue and crucial factor in the future development of industrial processes. In practice, wastewater discharged from refinery or petrochemical plants contains very high concentration of organic pollutants and toxic compounds, and hence, an additional pretreatment system is necessary to treat such high strength wastewater. However, the conventional wastewater treatment processes, including biological and chemical treatments, are generally ineffective in removing non-degradable organic pollutants.
Therefore, CEPI Lab. collaborated with SK Innovation, Taegeuk IBA and KhaiEL companies to develop a new waste water treatment system by using an electro-oxidation method. This high-strength wastewater is generally produced from refineries during maintenance. The treatment of such wastewater via conventional biochemical processes is a challenging task owing to the high concentration of organic pollutants and an additional pretreatment system is required. In order to develop a new treatment system, we used Response Surface Methodology (RSM) with four parameters and three levels to design the experiments of new treatment system. The experiments were then carried out under various operating conditions with actual wastewater from a refinery. A number of design and operating variables such as dilution ratio, current density, reaction temperature, and reaction time were found to have significant influence on chemical oxygen demand (COD) removal efficiency. Lastly, we used a MATLAB optimization tool to find the optimum operation parameters. The results showed that the optimum COD removal was 70% with 3.3 payback periods for the installation of new treatment system.
[Figure 6] Direct and indirect oxidation processes
[Figure 7] (a) Experiment setting of electro oxidation system from (a) IBA company and (b) INHA University
Environmental regulation is annually becoming more strengthened over the discharge of industrial flue gas. Therefore, more capital investment for the facility of NOx removal system is required nowadays. For example, plants in the area of Pyeongtack and Incheon are classified to 1st-class discharge field in accordance with revised clean air conservation act since 2015. For the reason, CEPI has developed a new system to reduce NOx from the industrial flue gas.