Abstract

A novel particle-based reactor network model (PRNM) was developed to predict the performance of a dry-feed, pressurized, single-stage, slagging entrained flow gasifier under various operational parameters. This model provides improved detail of particle conversion as a function of gasifier location, particle size, and fuel type not available in standard reactor network models. The model inputs were designed to allow changes in geometry, firing rate, stoichiometric ratio, fuel type, and inlet gas composition. Key performance metrics included the gas and refractory temperature profiles, axial gas compositions, and particle burnout. PRNM used a network of idealized reactors to specify the flow field within the gasifier. Particles were tracked using a Lagrangian approach and properties were calculated based on the gasifier environment. PRNM predictions compared well with CFD results for coal and woody biomass, and two coal-fired gasifiers from the literature. PRNM was used to explore the design space of a high-volatile bituminous coal and woody biomass and establish a preliminary gasifier design. The design space exploration evaluated the impact of geometry and operating conditions on gasifier performance. Fixed parameters included pressure (20atm), gasifier length (3.0m), carrier gas (CO2), burner diameter (0.03m), and restricting inlet gas compositions to O2, H2O, and CO2. Design variables included fuel type, gasifier inner diameter, stoichiometric ratio, CO2:F ratio, and added steam. A Latin Hypercube Sampling technique was used to efficiently explore the design space. Results of the preliminary design exploration for coal and wood found a gasifier length of 2.1m was sufficient to ensure particle burnout while meeting temperature constraints. The gasifier inner diameter did not impact model results, and a diameter of 0.3m was suggested. Stoichiometric ratio had the biggest impact on key outputs. For coal and wood, stoichiometric ratios ranging from 0.4-0.55 and 0.5-0.7, respectively, met the design constraints. Because coal required lower stoichiometric ratios to meet design constraints, coal produced higher CO and H2 syngas concentrations than woody biomass. CO2 and H2O concentrations acted as thermal diluents but had minor impacts on key parameters. The results were for a preliminary design space exploration. While they provided a good starting point, higher fidelity modeling, like CFD, along with engineering judgement should be used to establish the final design.

Degree

MS

College and Department

Ira A. Fulton College of Engineering; Mechanical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2024-08-07

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd13401

Keywords

entrained flow gasification, reactor network modeling, reacting particles, gasifier design

Language

english

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