1. ENTRAINED FLOW GASIFICATION OF WOOD PYROLYSIS OIL
Muhamad Fazly Abdul Patah & Prof. Shusheng Pang
Department of Chemical and Process Engineering, University of Canterbury, Christchurch, New Zealand
ENTRAINED FLOW GASIFICATION OF WOOD PYROLYSIS OIL
BACKGROUND:
Densification of biomass into pyrolysis oil for gasification is gaining increasing interest. The major advantages of this approach include costs reduction for transportation and storage, easier feedstock handling as well as easier feeding of the bio-oil for pressurized gasification system.
In this project, woody biomass from local radiata pine trees is converted into pyrolysis oil where the oil is then sprayed into a high temperature entrained flow gasifier which was recently developed and commissioned at this university. The oil is atomized into fine droplets before going through series of conversion reactions to yield hydrogen and carbon monoxide rich gas product.
REACTOR DESIGN:
The construction material of the reactor is mainly 253MA stainless steel which is highly resistant to high temperature corrosion attack; including within oxygen-deficient environment.
The intended operation conditions of the reactor is at atmospheric pressure and maximum temperature of 1100oC.
The system is pre-heated to set operation temperature using LPG.
During gasification, gasifier temperature is solely controlled by the extent of pyrolysis oil combustion.
Fine pyrolysis oil droplets are generated by an external mix gas-assisted atomizer. This type of atomizer enables safe and independent control of pyrolysis oil and oxygen gas flow rates during gasification.
Figure 3: Syngas compositions at various ER (N2, He and H2O free)
PYROLYSIS OIL PROPERTIES:
Physical Properties: Elemental compositions:
Water Content: 15 – 40 wt% C = 27 – 42 wt%
Viscosity: 9 – oC H = ~ 8 wt%
pH: ~ O = 50 – 65 wt%
GASIFICATION SYSTEM: 4 7 2
CHALLENGES:
The main challenges in the operation of entrained flow gasification of pyrolysis oil are related to the large variations in pyrolysis oil properties; especially its viscosity and moisture content. Significant change in oil properties could deteriorate atomization performance and in many cases completely block/clog the oil feeding system. 5 6
DISCUSSIONS:
Gasification temperature is strongly influenced by flow rates of pyrolysis oil and oxygen gas. Nevertheless the effect of oil flow rate is found to be more dominant.
H2 and CO contents in the producer gas are the highest when the equivalent ratio is set to 0.3. At this condition CO2 yield is the lowest, suggesting an optimum condition for gasification.
H2 and CO yields are decreased when equivalent ratio is reduced below 0.3, potentially due to poor oil atomization at low oxygen flow rate. This suggests significant influence of spray characteristics on oil-to-gas conversion and the subsequent reactions pathways.
As the equivalent ratio increases to values greater than 0.3, oxidation reactions of gasification products become more significant thus causing progressive increase in CO2 on the expense of useful gaseous products such as H2, CO and CH4 gases. 1 8 3
RESULTS:
Figure 1: Influence of oxygen-oil equivalent ratio on gasifier average temperature at constant oil flow rate
Figure 2: Influence of oil flow rate and ER on gasifier temperature 9
1. Entrained flow reactor Syngas after-burner Atomizing gas (oxygen)
2. Atomizer and cooling jacket Oil filter and flow meter PLC and control panel
3. Gas burner PT and display Peristaltic pump
CONCLUSIONS:
There is a strong influence of pyrolysis oil and oxygen flow rates (hence the equivalent ratio) on the gasification temperature and atomization characteristics; which consequently affects the quality of syngas generated during gasification.
Research on this project is on-going and more gasification runs are planned in the future to investigate influence of different parameters on gasification products and performance.
ACKNOWLEDGEMENTS:
University of Canterbury, New Zealand
Ministry of Higher Education Malaysia