MODELLING OF SULFUR DIOXIDE REMOVAL BY SEAWATER IN A FLUE GAS DESULFURIZATION TOWER

• Main Author: Shafiyya Ediansjah, Addina
• Format: Theses
• Language: Indonesia
• Subjects: Teknik saniter dan perkotaan; teknik perlindungan lingkungan
• Online Access: https://digilib.itb.ac.id/gdl/view/53590
• Institution: Institut Teknologi Bandung

Steam generated electricity plants produce various kinds of emission due to the burning of coal. The amount of SO2 emitted throughout the process depends on the used coal quality. Enactment of the Peraturan Menteri Negara Lingkungan Hidup Nomor 15 Tahun 2019 obligates these facilities to install an air pollution control device to manage the amount of emission going above the limit. Conventional technology such as wet scrubbers with the use of limestone poses another problem. Formed gypsum as a result of the process is categorized as hazardous in the second category according to Peraturan Pemerintah Republik Indonesia Nomor 101 Tahun 2014 which obligates further processing of the created byproduct. The control of SO2 by using seawater makes use of the alkalinity represented by CaCO3. The use of seawater reacts SO2 with HCO3- forming SO42- can be considered as a reasonable alternative. A model which corelates the equilibrium of the reaction with the salinity of the solution will be developed to predict the process of sulfur dioxide scrubbing inside a flue gas desulfurizer. A numerical model is generated to solve an existing problem with help of the corresponding data and theories needed to predict a specific phenomenon in the future. A SO2 absorption model in a packed tower by taking gaseous and liquid chemical reaction into consideration will be solved to predict the distribution of flow inside the absorption column. The proposed model has limiting factors of steady-state and adiabatic operation, negligence of gas and liquid flowrate fluctuation as well as heat transfer due to resistance and constant physical and thermal parameters. The reactions taking place at the time of scrubbing include the reaction of SO2 absorption in water in the thin film layer, reaction of SO2 forming bisulfite, dissociation of bisulfite to sulfite and the neutralization of bisulfite using seawater. The numerical model will be solved by using three key parameters which are reaction balance, mass balance as well as energy balance. Reaction balance parameter is limited by the Henry’s constant as a function of temperature will be solved by means of simple substitution. The concentration of the constituents HSO3-, H3O+, HSO4-, and SO32- will be solved by using the Newton-Rhapson method which generates a single function from four known functions. This method represents the tangential value of an initial guess of a certain root through a reference point. Mass balance as well as energy balance parameter will be solved with the Runge-Kutta method for ordinary differential equation. Runge-Kutta method is able to achieve solving accuracy similar to the use of Taylor without the need of finding the corresponding derivatives but rather the use of the increment function. Simulation using a gas and liquid flowrate of 1,691,277 m3/h and 68.912 m3/h resulted in a removal efficiency and pH of 30.46% and 4.19 coherent with corresponding references in field scale application. Simulation result by taking three main parameters (reaction, mass and energy balance) produced a removal efficiency trend matching main references whereas the increase in liquid flowrate led to an increase in removal efficiency. Calibration as well as validation was done by varying liquid flowrates as well as overall mass transfer coefficients with other parameters held constant. Calibration resulted in the liquid flowrate and overall mass transfer coefficient as the main factor in the process of SO2 removal within a flue gas desulfurizer.