1. UNIVERSITÀ DEGLI STUDI DI CATANIA DEPARTMENT OF INDUSTRIAL ENGINEERING MASTER-DEGREE IN CHEMICAL ENGINEERING FOR INDUSTRIAL SUSTAINABILITY
LUCA BARBAGALLO
MODELING GASIFICATION AND PYROLYSIS PROCESSES OF RESIDUAL BIOMASSES WITH CHEMCAD AND ASPEN PLUS
Relatore :
Prof. Francesco PATANIA
Prof. ANTONIO GAGLIANO
Correlatore: Ing. MARIA BRUNO
ACADEMIC YEAR
Good morning everyone my final work degree talks about the modeling gasification and pyrolysis processes of residual biomass with CHEMCAD and aspen

2. CHEMCAD and ASPEN PLUS Softwares
GOALS OF THE THESIS
The aim of the thesis is the Simulation of the Gasification and Pyrolysis processes of Biomass through:
CHEMCAD and ASPEN PLUS
Softwares
The implemented models were validated and calibrated through experimental data

3. the international political conflicts
INTRODUCTION
“The crude oil age” is not very far from the end, because of:
the international political conflicts
the increase of the demand and the price of the conventional fossil fuels
the need to minimize the environmental impacts
Today the crude oil age is not very far from the end………

4. the dependence by conventional fossil fuels;
INTRODUCTION
In this context, the production of energy from renewable sources is a very considerable resource for the future.
BIOMASSES and particularly RESIDUAL BIOMASSES from the agriculture and food factory, can be a very important source of energy.
From the residual biomasses it is possible to produce energy reducing:
the dependence by conventional fossil fuels;
the emission of carbon dioxide (and other pollutants) in the atmosphere;
the problem of the disposal of the residual biomasses.
Disposal of the residual biomass is the major issue due to management and costs of disposal itself

5. Biomass is all biologically-produced matter based on carbon, hydrogen, nitrogen and oxygen.
Several kinds of biomass have been identified in:
Ligno-cellulosic biomass: fiber sorghum, eucalyptus and black locust etc.;
Byproducts of tree crops: pruning of olive trees, citrus, fruit trees, almond and hazelnut;
Byproducts of the forestry: high forests and coppice;
Agro-industrial wastes: exhaust residues of olives from oil production, wood industry, etc.;
Municipal solid wastes: biomass derived from wet urban wastes, compost etc.
These biomass are very useful for the production of syngas and other heavy hydrocarbons as Bio-oil and Char, considered as raw materials in energy productions and other compounds like ammonia and methanol etc…

6. thermochemical PROCESSES of biomass
GASIFICATION
PYROLYSYS
Biomass reacts with oxygen at temperatures between ( ) °C, to form mainly hydrogen, carbon dioxide, carbon monoxide, methane, water and nitrogen.
Minor products are Char and Tar. O2 N2
Char
Tar
BIOMASS
CO2 N2
H2O
CH4
Biomass is involved in a thermal decomposition at temperatures between ( ) °C, in absence of air. The pyrolysis products are bio-oil, char and gas in percentages which are function of the operative conditions (slow, intermediate, fast pyrolysis).
BIOMASS °C
CH4
Bio-oil

7. thermochemical PROCESSES of biomass
TORREFACTION °C
The process occurs in the absence of oxygen, in atmospheric pressure and temperatures of the order of ( ) °C. Torrefaction products are pellets of the same biomass, CO, CO2 and traces of H2, lights hydrocarbons and water. CO
CO2,
trace of H2
CxHy
H2O
PELLETS

8. thermochemical PROCESSES of biomass
Biomass thermochemical conversion processes, pyrolysis/gasification, are very complex and the products yields, as well as their quality for the specific use to which they are addressed, are affected by a great number of parameters, especially process temperature, residence time and heating rate, biomass characteristics. The modeling of the processes has the aim to predict the yields and the quality of the process products as a function of the operative conditions and the biomass physic- chemical characteristics. Consequently, it could be very useful to the design and the management of the gasification and pyrolysis processes.

9. Gasification Thermodynamic EQUILIBRUM MODEL
The equilibrium model is based on the following global gasification reaction:
CHhOoNn + wH2O(liq) + a(O2 + 3,76N2) ↔ x1H2 + x2CO + x3CO2 + x4H2O(vap) + x5CH4 + x6N2
+ x6TAR+ x7Char
CHhOoNn is chemical formula of biomass;
w are moles of water in the biomass;
a are moles of the input air in the gasifier;
The reaction inside the gasifier takes place in conditions of thermodynamic equilibrium at pressure of 1 atm and the reactions proceed in an isothermal system;

10. Gasification THERMODyNAMIC EQUILIBRUM MODEL
The number of moles w of water, contained in the biomass, can be determined according to the humidity U: w = 𝑴𝑾𝒃𝒊𝒐 ∗ 𝑼% 𝑴𝑾𝒘𝒂𝒕𝒆𝒓∗(𝟏−𝑼%) Typically, in a gasifier, ERis (equivalent ratio) defined as: ER = 𝑨𝒓𝒆𝒂𝒍/𝑭 𝑨𝒔𝒕𝒐𝒊𝒄/𝑭 Where Arealand Astoichare expressed in Kg/h of air and F is the feed in Kg/h of input biomass. In function of the ER we can evaluate the moles equivalent of air a by the following expression: a= 𝟏+ 𝒉 𝟒 + 𝒏 𝟐 − 𝒐 𝟐 ∗𝑬𝑹 in which (1+h/4+n/2-o/2), corresponds to the stoichiometric amount of oxygen required for complete combustion of 1 mole of biomass. Finally the model is based on the choice of two intermediate reactions: Methanetion C + 2H2 ↔ CH4 Water gas shift CO + H2O ↔ CO2 + H2

11. CHhOoNn + ΔH(MJ) ↔ aH2 + bCO + cCO2 + dH2O(vap) + eCH4 + fCxHy + gChar
PYROLYSIS MODELS
Pyrolysis has been simulated both with a kinetic and an equilibrium model, based on the reactions of methanation and water gas shift.
The general reaction of pyrolysis is:
CHhOoNn + ΔH(MJ) ↔ aH2 + bCO + cCO2 + dH2O(vap) + eCH4 + fCxHy + gChar
ΔH (MJ) is the heat provided to biomass;
C + 2H2 ↔ CH4
CO + H2O ↔ CO2 + H2
The Kinetic model is based on the following expression of the kinetic rates of the methanation and water gas shift reactions
rm = km*CCH4 ; rwgs = kwgs*CH2*CCO2
where k is the kinetic constant rate of the Arrhenius expression
ki = Ai*exp[-Eai/RT]; i= 2

12. PYROLYSIS (equilibrium) MODEL
The equilibrium constants for the methanation and water-gas shift reactions in the equilibrium model are the following:
Ln (Km ) = Am + Bm/T
Ln (Kwgs) = Aw + Bw/T

13. Simulation of the Gasification and Pyrolysis processes
Rubber wood
In Aspen plus and Chemcad
Wood pellets
Process parameters: Biomass moisture content and Equivalent Ratio
Olive kernels
Olive pits
In Chemcad
Process parameters: Temperature
Olive Oil-Residues

14. modeling pellets gasification THROUGH aspen plus
Seven tests have been carried out considering different moisture content MC and ER
Input data:
Wood pellets (CH1,622O0,628 ) (Barrio et al, 2002)
MW = 23,67 [Kg/Kmol]
ER values were calibrated by using following equation:
ER = 0,008*MC% + 0,174

15. modeling pellets gasification THROUGH aspen plus
The Ryield block is fundamental to simulate the devolatilization of biomass in which the non-conventional components are converted into conventional components as H2, CO, CO2, CH4 and H2O. Temperature is set at 773 K.
The Mixer block allows to add air at the gases coming from Ryield
Pressure is set 1 atm.
The Rgibbs block allows to simulate the final step of gasification where the processes of methanation and WCS are developed. Temperature is set between ( ) K

16. Results for wood pellets gasification with aspen
The tests carried out through Aspen have been compared with experimental data (Barrio et al., 2002)
6,99%
14,9%
25,5%
27,5%
12,4%
11,7%
16,9%
0,15%
6,56%
1,33%
2,38%
7,34%
3,93%
6,93%
The model predictions are quite satisfactory, even if the H2 percentage in the producer gas is always overestimated by the model (16,55 %).
Anyway the overestimation of the H2 percentage is a typical behavior of the thermodynamic equilibrium models as confirmed by other literature studies.
The model predictions are very satisfactory in all the cases analyzed (different moisture content e equivalent ratio);
Indeed the average percentage error was (4,09 %)

17. Results for wood pellets gasification with aspen
15,0%
33,5%
29,9%
29,3%
15,2%
10,5%
33,3%
0,73%
5,37%
4,51%
6,71%
1,61%
5,02%
6,21%
CH4 is underestimated if compared with experimental data.
Indeed the average percentage error was (23,81 %)
Lower heating values (MJ/Nm3) are slightly overestimated, but they show a very good agreement with experimental data.
Indeed the average percentage error was (4,31 %)

18. Modeling oil residues pyrolysis through chemcad
Four tests have been conducted with different process temperatures
Input data:
Oil-residues (CH1,366O0,675N0,02 ) (Uzun Et al, 2012)
MW = 24,22 [Kg/Kmol]
two models for pyrolysis were used :
Kinetic model
Equilibrium model.

19. Modeling oil residues pyrolysis through chemcad
The Pyrolyzer decomposes biomass at (400, 500, 550 and 700) °C in absence of oxygen.
It is set as PFR (plug flow reactor) in isothermal mode:
KREA (kinetic reactor)
REQUIL (equilibrium reactor).
Combustion of CH4 is used for generating the heat supplied for drying the biomass
The Dryer vaporizes
the water content of biomass
at 120 °C
Splitter separates:
Syngas from the top
Bio-oil (tar) from the central part
Char from the bottom

20. Results for oil residues pyrolysis with chemcad
Experimental data (Uzun et al., 2013), have been compared with those obtained from the simulations with equilibrium and kinetic models.
At the temperatures of 500 °C, that is the most suitable temperature for a pyrolysis process, the kinetic model is very reliable.
Average error, evaluated from kinetic and equilibrium model at 500 °C is (12,16 %).
At the temperatures of 500 and 550 °C, that are the most suitable temperatures for a pyrolysis process, the equilibrium model is very reliable.
Average error between 500 and 550 °C for equilibrium model is (24,6 %)

21. Results for oil-residues pyrolysis with chemcad
At the temperatures of 500 and 550 °C, that are the most suitable temperatures for a pyrolysis process, equilibrium model is sufficiently reliable.
Average error for equilibrium model at 500 and 550 °C is (3,5 %).
At the temperatures of 500 and 550 °C, that are the most suitable temperatures for a pyrolysis process, both the models are sufficiently reliable.

22. Results for oil-residues pyrolysis with chemcad
Char and Bio-oil have showed a very bad results respect to
literature references with kinetic model

23. Results for oil residues pyrolysis with chemcad
The results show that the char decreases when temperature increases from 400 up to 700 °C, in accordance with literature data.
This result is related with the char gasification when the temperature rises.

24. CONCLUSIONS
In this study we have implemented different models (equilibrium models or kinetic models) for modeling the gasification and pyrolysis processes.
The models proposed allows to predict of the chemical composition (H2, CO, CO2, CH4, C2H4, C2H6) and the lower heating value of the producer gas.
The validation and calibration of the processes were carried out through the comparison with experimental data that have allowed the refinements of the chosen process variables.
The comparison between simulated and experimental data shows a good agreement, both for the CHEMCAD and the ASPEN simulations.
- (16,55 % for H2, 4,09 % for CO and 23,81 % for CH4) (aspen-model).
- (12,16 % for H2, 24,6 % for CO and 3,5 % for CH4) (chemcad-model)
- Lower heating value (LHV) shows an average error of (4,31 %).
Considering the very high complexity of the pyrolysis and gasification processes, which are affected by a great number of parameters, it is possible to assert that the developed model gives quite reliable results.
The models implemented, could be very useful for the prediction of the gas composition with the aim to produce a syngas of high quality from a renewable resource.

25. I would like to thank my supervisor prof. : A
I would like to thank my supervisor prof.: A. Gagliano, the professor F. Patania and co-rapporteur engineer: M. Bruno

26. THANKS FOR YOUR ATTENTION\
THANKS FOR
YOUR
ATTENTION