Biomass Waste Incinerator

Description

This project investigates combustion inside an industrial biomass waste incinerator using ANSYS Fluent, with the goal of understanding how fluid flow, heat transfer, and chemical reactions interact to produce uniform combustion across the waste surface, a key factor in waste-to-energy efficiency. The geometry includes a trapezoidal waste pile, multiple air and fuel inlets, two exhaust gas outlets, and a cooling system, built in Design Modeler and meshed in ANSYS Meshing with 513,233 elements.

Methodology

The simulation runs steady-state with a pressure-based solver, using the Realizable k-epsilon model with standard wall functions to resolve the complex flow patterns inside the incinerator. The energy equation is enabled to capture the thermal behavior driving and resulting from combustion. Chemistry is represented through the Species Transport model, defining two primary reactions, CH4 + O2 and H2 + O2, with the eddy-dissipation model handling turbulence-chemistry interaction under the fast-chemistry assumption typical of industrial combustion. Since the waste itself continuously generates combustible gases as it burns, fixed source terms for CO and H2 mass fraction are applied directly at the rubbish surface boundary to represent this ongoing gas release.

Analysis

The results show a strong temperature gradient through the incinerator, rising from a 300 K inlet to an average zone temperature of 2619.4 K and an outlet chamber temperature of 4042.636 K, confirming substantial heat generation in the main combustion region. Velocity contours reveal complex internal flow patterns reaching up to 33.25 m/s, which govern how effectively air and fuel mix and how heat distributes through the chamber. Static temperature contours show peaks above 4000 K in the core combustion zone, with the waste surface itself showing higher temperatures near the fuel inlets and in areas of stronger air-fuel mixing. CH4 and CO2 mass fraction contours trace the reaction's progress directly, with CH4 concentrated near the fuel inlets and CO2 building up downstream in the post-combustion zones, while temperature-colored pathlines show recirculation zones forming as air and fuel streams interact, which enhances mixing and helps drive more complete combustion. Together these results indicate the current inlet layout achieves good overall combustion performance, though adjusting inlet positions and flow rates could further even out the temperature distribution across the waste surface, a change that would likely improve combustion efficiency and reduce emissions.