טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentCyjon Ronen
SubjectDeveloping Two-Chamber Reactor for Biomass Gasification
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Emeritus Yehoshua Dayan
Professor Leonid Mirkin
Full Thesis textFull thesis text - English Version


Abstract

Gasification of biomass is of great interest as part of the growing search for new sources of fuels for production of energy and feedstock, in the 21st century.

This project is focused on research of the two-chamber gasifier (2CG) for gasification of biomass, based on the Judd gasifier. In the 2CG, synthesis gas is produced during a chemical reaction of the biomass and steam entering to the gasifier.

The gasifier consists of two separated zones: one for gasification and one for combustion of ungasified biomass. The combustion process supply heat for the gasification process by recirculation of bed material between the two chambers. The gasifier is operated by maintaining a fluidized bed in the combustion chamber and a moving bed in the gasification chamber, and the recirculation of bed is enabled due to a small pressure drop caused by the different flow regimes.

The gasifier used in this project was designed and built in the technion. One gasifier was built for cold experiments and one for hot experiments (Fig. 1). The advantages of the two-chamber gasifier are high biomass conversion rate and syngas with high calorific value is obtained. The main disadvantage of the two-chamber gasifier is the relatively low solids circulation rate, which is limited to the pressure drop between the gasification and the combustion chambers.

The first goal of this project is to determine the working conditions for that gasifier. The steam and air flow rates are obtained using the stoichiometric ratio of each reaction, and the solids circulation rate inside the gasifier is obtained using balance of heat exchange rate for each chamber.

Then, the second goal of this project is reaching the steady state conditions as fast as possible.

Using a set of simplifying assumptions, a set of time dependent, differential equations is obtained. The set of equations is comprised of the energy and mass balances of each chamber, and provides the dynamic model of the gasifier.

The dynamic model is simulated for different air and steam flow rates inputs in order to determine the method for reaching the steady state conditions as fast as possible.

Finally, the third goal of this project is determining the steady state conditions.

Using the same assumption as in the dynamic model development and the dynamic model itself, the steady state model is obtained.

Simulations of the steady state model made while changing air and steam flow rates are used in order to define the gasifier working conditions.