BIOMASS GASIFICATION WITH A FAST INTERNAL CIRCULATING FLUIDIZED BED - PARAMETRIC STUDY BASED ON A OD-MODEL USING THE EXPERIMENTAL DESIGN APPROACH

摘要

The present work deals with biomass gasification using the FICFB process (Fast Internal Circulating Fluidized bed). In order to optimize the FICFB gasifier operation for the use of syngas to produce bioSNG (Substitute Natural Gas) through a downstream methanation process, a 0D-model of the gasifier has been developed before the beginning of the GAYA project, and implemented so has to get a functional software. This software has been used to achieve a sensitivity study on the gasification equipment. The purpose of this study is to determine which operating parameters of the gasification unit are significant in the design and operation of the reactor and how its behavior is impacted by a variation of these parameters, using the 0D-model. Experimental design methodology was chosen for this sensibility study. It is a mathematical tool to help the experimenter to get the best knowledge of a process by running the minimum number of experiments. In this type of approach, the process is seen as a black box with outputs called responses or objectives. In the present case, the responses are, for instance, the gasification equipment energy efficiency or the syngas flow rate. The responses may vary under the effect of factors, or variables. In our case, these might be biomass moisture content, fluidization steam flow rate or biomass capacity. The study went through different levels: screening to identify the parameters having a significant effect on the responses, and a quantitative study to express the responses using a mathematical expression functions of the different parameters. The study pointed out that some parameters have strong effects on the operation of the gasification equipment. Biomass moisture content has to be minimized in order to maximize syngas production, and thus bioSNG production. In addition to biomass moisture content, energy efficiency is impacted by combustion air temperature and biomass LHV. They tend to increase the efficiency when they are set at their highest values. An optimization study is then carried out. The objective of this study is to determine the values of each parameter that minimize or maximize one or several responses. As the purpose of the biomass gasification is to produce bioSNG, we choose to optimize the syngas production.