Projeto e maximização de desempenho de um reator de gaseificação com sistema de craqueamento de alcatrão

Abstract

Aiming to meet global greenhouse gas emission reduction targets, solutions related to wasteto- energy recovery have gained prominence for enabling the monetization of an environmental liability. Among the available methods to achieve this purpose, the gasification process stands out due to the versatility of the generated synthesis gas (syngas), which can be applied in thermal and electrical power generation, as well as the production of hydrogen and other synthetic fuels. To carry out this process, the reactor must ensure a controlled atmosphere where the waste is thermally conditioned. Aiming to increase system efficiency, the design and the fluid dynamics and structural simulations were conducted using Siemens NX, Ansys Fluent, ANSYS Rocky, and MATLAB software. The objective was to design an optimized gasifier capable of mitigating condensable tar by increasing the filtration efficiency and the average gas residence time inside it. To this end, a computational study was performed through fluid dynamics simulations of high-temperature (800 °C) cyclones connected in series inside the reactor. For these simulations, several geometric alterations that dictate the behavior of these cyclones were tested, namely: pressure drop, filtration efficiency, and average residence time. These variables present a trade-off among themselves, which must be balanced to allow the formation of a clean syngas. Once the cyclone configuration was determined, a recirculation system for gas and filtered particles operating under the Venturi effect was added to its base. This mechanism considerably increased the filtration efficiency of the cyclones by scaling up their cut-off diameter, allowing them to capture nanometric particles, with the cyclone combination showing an overall efficiency of 100%. Furthermore, it extended the gas residence time inside the gasifier to 40.6 seconds, which, according to the scientific literature, contributes to mitigating condensable tar in the reactor. Additionally, a thermal study was conducted for modeling the outer shell, along with kinematic and structural simulations for developing an inspection door. Finally, a simulation of the behavior of the internal components subjected to a pressure of 0,2 bar and a temperature of 800 °C was carried out, identifying stress concentration points and displacements that could affect the structural integrity of the reactor.