Wastewater aeration in refining using Aspen Plus

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During the production process in refinery processing units, a certain amount of wastewater is generated, which contains acidic gases such as hydrogen sulfide, carbon dioxide, and ammonia. Therefore, this wastewater cannot be discharged directly into the sewage treatment plant; the refinery needs to carry out air stripping on it to ensure that the pollutant levels meet the required standards. This content involves a brief simulation of wastewater stripping using Aspen Plus. Modeling and analysis of wastewater aeration: 1. After selecting an appropriate design template, this design represents a highly non-ideal process; moreover, electrolyte reactions are involved in this design. Therefore, when defining the components, the corresponding electrolyte species such as NH4+, H+, OH-, HS-, S2–, etc., must be included. https://pic3.zhimg.com/v2-eea116ca53c650fdbb168afb5e0573aa_b.jpg2. The stripping process of acidic gases such as hydrogen sulfide, carbon dioxide, and ammonia is a highly non-ideal process; conventional thermodynamic equations do not yield accurate results for this process. Therefore, in Aspen Plus, the specialized ideal equation APISOUR can be used for simulation calculations. https://pic1.zhimg.com/v2-e1db08dbdf8dae00225c31d6058225f0_b.jpg After selecting appropriate physical properties, enter, confirm, and adjust the corresponding ionization equations in Chemistry->Global. https://pic2.zhimg.com/v2-2affae07f0d38a8112bbbe5920d261dd_b.jpg3. After the components and their physical properties have been determined, the unit operations are selected; corresponding models such as separators, heat exchangers, and distillation columns are chosen from the Model Palette to build the process model. https://pic2.zhimg.com/v2-c094c23a12f538fd9c05139e080e5339_b.jpg4. The design parameters for the distillation column are set: the number of theoretical plates is set to 26, a thermosyphon reboiler is selected, no condenser is used, and a strongly non-ideal liquid behavior is assumed to facilitate convergence during the iterative process. https://pic4.zhimg.com/v2-d2142f02d09dd0c767e1a94e07a955b7_b.jpg Set the feeding method and the position of the feeding plate, and define the side-stream extraction from the distillation tower as well. https://pic4.zhimg.com/v2-b105513e4771b0d1da044bed1817543b_b.jpg Set the pressure distribution for the entire tower in the pressure distribution settings. https://pic3.zhimg.com/v2-a6f46b2d967a753271646308ac49a9d6_b.jpg5. After performing simulation calculations, the hydraulics of the distillation column is designed and verified; by setting parameters such as the type of trays and the spacing between them, it is possible to carry out design analyses of the column’s hydraulic properties. https://pic4.zhimg.com/v2-f195b4963288779bcf81b019706eeddf_b.jpg https://pic1.zhimg.com/v2-5ccfe249ebfd56340e49d5d5b726c228_b.jpg After obtaining the design results, it is possible to conduct design verification by checking relevant parameters such as pressure drop and the maximum flooding factor. https://pic1.zhimg.com/v2-9b11efaab36ed3803fcf91adbd63e1f8_b.jpg https://pic4.zhimg.com/v2-17c73953139729748080e3cbff8628d7_b.jpg 6. By performing calculations, we obtain the corresponding values for the various components; more precise design parameters and models can be achieved through appropriate design specifications.