# Aspen tutorial : Gasification of biomass

These class will be given by Meire Ellen Ribeiro Domingos (meire.ribeirodomingos@epfl.ch).

## Overview

In this class you will learn how to model a gasification process in Aspen Plus. This model considered woody biomass as feedstock, using steam and air, at atmospheric pressure. 

Biomass gasification is a thermochemical conversion that decomposes biomass at elevated temperatures (>700°C) in presence of a gasification agent such as air, O_{2}, steam, CO_{2} or combination thereof. The gasification process is typically modeled as a series of interrelated drying, pyrolysis, reduction and combustion processes. The actual mass yields of volatiles, condensables, and solids in the pyrolysis reaction step, as well as the gaseous volumetric fractions of the hydrogen, carbon monoxide, carbon dioxide, methane produced in the reduction step strongly depend on the gasifier operating parameters, such as temperature, pressure, feed moisture and chemical composition, gasification agent, energy supply, among other hydraulic and structural characteristics.

In particular, a dual bed gasifier consists of two interconnected fluidized beds. The first bed is a bubbling fluidized bed, in which biomass is converted into syngas. The second bed is a fast fluidized combustion bed, which oxidizes the residual char with air or oxygen, thus providing the heating requirements of the the highly endothermic gasification reactions occurring in the first bed. The feed of biomass or other gasifying materials is supplied to the first gasifier bed with the help of a screw conveyor. The two fluidized beds are controlled separately, but they are interconnected via a non-mechanical valve, such as a loop seal valve, to ensure the circulation of the bed particles. A cyclone separator is employed to separate the heat-carrying material (e.g. sand with olivine) and the flue gases in the top of the combustion bed. The heat-carrying material is returned to the first gasifier, while the flue gases are sent to the heat recovery system. The product gas obtained from the gasifier is primarily composed of H2, CO, CO_{2}, CH_{4}, and small amounts of tar and other undesired components. The gaseous mixture continues to the purification units (e.g. water scrubber and ZnO guard bed) in order to remove the impurities and to upgrade the syngas quality.



## Questions

1)	Change the inlet mass flow of biomass to 500 t/h. What should be adjusted to converge the simulation?


*Answer 1:*


2) 	Modify the biomass proxanal and ultanal composition considering sugarcane as feedstock and give the new syngas composition.


*Answer 2:*
