Investigation of Fuel Chemistry and Bed Performance in a Fluidized Bed Black Liquor Steam Reformer

Abstract

EXECUTIVE SUMMARY (ABSTRACT)The University of Utah project "Investigation of Fuel Chemistry and Bed Performance in a Fluidized Bed Black Liquor Steam Reformer" (DOE award number DE-FC26-02NT41490) was developed in response to a solicitation for projects to provide technical support for black liquor and biomass gasification. The primary focus of the project is to provide support for a DOE-sponsored demonstration of MTCI's black liquor steam reforming technology at Georgia-Pacific's paper mill in Big Island, Virginia. A more overarching goal is to improve the understanding of phenomena that take place during low temperature black liquor gasification. This is achieved through five complementary technical tasks: (1) construction of a fluidized bed black liquor gasification test system, (2) investigation of bed performance, (3) evaluation of product gas quality, (4) black liquor conversion analysis and modeling and (5) computational modeling of the Big Island gasifier.Several experimental devices have been constructed under this program. The largest of these is a 10-inch diameter pressurized fluidized bed steam reformer having four bundles of 20 heaters and designed to simulate conditions within a full-scale reformer. This system is housed at the University of Utah's offcampus Industrial Combustion and Gasification Research Facility, and includes all necessary auxiliary equipment (steam generating boiler and feedwater conditioning system, steam superheater, syngas afterburner, flue gas cooler and computerized control system). A smaller nitrogen-fed fluidized bed system has been constructed at Brigham Young University for the purpose of studying bed agglomeration behavior and conditions that cause such agglomeration. An even smaller 2-inch nitrogen fluidized bed in the laboratories at the University of Utah allows investigation of mechanisms of particle growth, particularly coating and particle clustering by black liquor. Other experimental devices include a singledroplet reactor for study of liquor pyrolysis behavior and a Plexiglas cold flow model of the University of Utah steam reformer that allows visualization and measurement of gas and solid flow characteristics.Several computational models have been developed under this program. One developed at the University of Utah is a relatively simple, Microsoft Excel-based model that predicts gas velocities and compositions throughout the reactor and considers only the four major gas species: H 2 O, CO 2 , H 2 and CO. The value of this model lies in its simple interface and instantaneous updating when input parameters are changed. It is also easily configured to handle different reactor geometries and liquor properties. A more advanced model developed by Reaction Engineering International considers three phases within the bed (dense, bubble and wake) and takes backmixing of solids into account. Bubble hydrodynamics (size, velocity, splitting and coalescence) are also taken into consideration. The model calculates mass and energy balances of the system and uses drying and...