SIMULATION OF BIOMASS PARTIAL OXIDATION
V. Tukač
1
, J. Hanika
2
, V. Veselý
2
, J. Lederer
3
and D. Kovač
3
1
Institute of Chemical Technology Prague, Technická 5, 166 28, 6, Prague, Czech Republic
2
Institute of Chemical Process Fundamentals, Czech Academy of Sciences, v.v.i., 165 02, 6, Prague, Czech Republic
3
VUANCH, a.s., Revoluční 84, 400 01, Ústí n. Labem, Czech Republic
Keywords: Simulation, Biomass, Partial oxidation.
Abstract: Gasification of biomass by partial oxidation produces both syn-gas with high hydrogen content and explore
energy of renewable sources. The objective of this work was to develop computer models of pilot reactor
unit operated partial oxidation of rape meal/mineral oil suspension. The models were developed in process
simulator ASPEN Plus based both on Gibbs free energy minimization and reaction kinetic approach.
Alternative biomass characterizations were used: analogy with coal composition and representative
compounds of biopolymer structure. Flow characteristic of gasification reactor was tested by CFD method
in COMSOL Multiphysic. Simulated results were compared with pilot plant experiments with successful
agreement.
1 INTRODUCTION
Nowadays hydrogen demand caused by deep fuel
refining and the other sustainable processes leads to
utilization of new raw materials. Simultaneously,
extensive biodiesel production creates great amount
of biomass wastes transcendent over feeding
potential of farm animals. One of potentially useful
process of hydrogen production from renewable
natural sources seems to be partial oxidation (POX)
and gasification of biomass material like rape meal
from rape oil production and/or distillery slop
originated from bioethanol (Tukač, 2009).
The goal of this work was to develop simulation
models of pilot POX reactor working with mixture
of fuel oil and biomass.
2 EXPERIMENTAL
Experimental pilot plant unit was constructed in
UNIPETROL RPA Litvinov, consisted of water
steam generator, continuous suspension batcher,
gasification reactor equipped by co-annular feeding
jet burner and water quench and tubular heat
exchanger. Pilot POX reactor of I.D. 0.3 m and
overall length 2 m was equipped by 5 x 3 kW
electrical heating to reach temperature about 1200
°C. Suspension of dry biomass in mineral oil was
partially combusted in oxygen - water steam
atmosphere to produce carbon monoxide, dioxide
and hydrogen contained gaseous product.
3 PROCESS SIMULATION
Two different approaches were used to develop
mathematical models. First method consists in
formulation of steady state balancing models created
in process simulator Aspen Plus. Pseudo
homogeneous CSTR reactor model was used to fit
both reaction kinetics and chemical equilibrium on
experimental data. Chemical and phase equilibrium
was calculated by minimization of Gibbs function,
Peng-Robinson equation of state with Boston-
Mathias alpha function was used to describe real
behavior of gases. Another modelling employs CFD
capability of COMSOL Multiphysics (PDE solver
by finite element method) to find steady state gas
velocity, profiles inside of gasification reactor.
Complicated chemical composition was solved
by concept of representative chemical compounds
resulting in the same elemental composition as the
original raw material.
422
Tuka
ˇ
c V., Hanika J., Veselý V., Lederer J. and Kova
ˇ
c D..
SIMULATION OF BIOMASS PARTIAL OXIDATION.
DOI: 10.5220/0003617704220424
In Proceedings of 1st International Conference on Simulation and Modeling Methodologies, Technologies and Applications (SIMULTECH-2011), pages
422-424
ISBN: 978-989-8425-78-2
Copyright
c
2011 SCITEPRESS (Science and Technology Publications, Lda.)
Figure 1: Aspen Plus flowchart of basic part of pilot POX unit.
In the Fig. 1 simplified flowchart of main part of
pilot POX unit formulated in Aspen Plus is
presented. Simulation model incorporates biomass,
oil, water and oxygen input streams included water
quench of flue gas after reactor.
Models of apparatus incorporate heat exchangers
and phase separator. Two reaction models were
used: i) chemical and phase equilibrium calculated
by minimization of Gibbs function and ii) power law
formal kinetics for gasification.
In the following Tab. I simulated results of
chemical equilibrium for 10 % content of biomass in
mineral oil are presented. Adiabatic temperature rise
exceeds 800 K for both biomass tested, also
prospected products concentration is very promising.
Table 1: Simulated results of gasification of biomass in oil
suspension.
Variable 10 % rape
meal
10 %
distillery
slop
Adiabatic temperature
in reactor, °C
1038 1067
Hydrogen portion in
flue gases, % vol.
48.7 48.5
Carbon monoxide
portion in flue gases,
% vol
35.8 36.0
Molar ratio of carbon
monoxide/dioxide
8.08 8.44
Comparison of equilibrium simulation with
experiments with 5 % wt. biomass-oil suspension
gasification is shown in Fig. 2. Almost the same
hydrogen concentration verifies results of simulation
balance. On the other hand, lower experimental
concentration of carbon monoxide together with
higher value of carbon dioxide concentration implies
that presumptions of both ideal mixing in reactor
and/or complete chemical equilibrium are not
fulfilled. Also method to fit apparent equilibrium
temperature (
Bruggemann, 2010) corresponding to
experimental composition was treated. The resulting
temperature approach was found cca -500 °C and
both carbon oxide and methane concentration are
affected. In this case, it is possible to see in the Fig.
2. better agreement of that simulation with
experimental results.
Fitting of experiments by simple power law kinetic
of partial oxidation, water gas shift, steam reforming
and carbon monoxide oxidation the good agreement
was found with published data (Robinson, 2008).
Figure 2: Examples of 5 %wt. biomass in oil gasification
by oxygen – water atmosphere, mean experimental
temperature 1152 °C, apparent equilibrium temperature
672 °C.
SIMULATION OF BIOMASS PARTIAL OXIDATION
423
Hydrogen production depend both on oxygen
and water steam ratio to biomass and hydrocarbon
raw material mixture and also on flow characteristic
and internal mixing in the reactor. Distribution of
residence time of biomass particles in the reactor
affects results due to different rate of consecutive
reaction steps: pyrolysis, water gas shift and steam
reforming reactions. CFD modelling can help to
understand complex phenomena in the reactor. To
evaluate axial mixing in the reactor axial symmetric
cylindrical model in COMSOL multiphysics was
created. Fluid flow was described by Navier Stokes
equation and turbulence by k-ε model (
Cammarata,
2007). Resulting flow character is presented in Fig.
3, exhibiting vortexes in upper and bottom reactor
part and main stream in reactor axis. To choose
appropriate hydrodynamic model (
Bruggemann, 2010)
some RTD measurement should be necessary.
a)
b)
Figure 3: a) Velocity stream lines in longitudinal cross-
section of axial symmetric reactor model. Left edge – axis,
right border – wall.. b) Detail of jet nozzle vicinity.
4 CONCLUSIONS
Variant thermodynamic calculations of equilibrium
balances of biomass partial oxidation were made by
process simulator Aspen Plus. Prospective results
were found both for rape meal and distillery slops oil
suspension oxidation.
Comparison of equilibrium reactor model with
preliminary experiments shows good agreement, but
for existing deviations mixing structure in reactor is
suspected. The best results were acquired by model
with equilibrium temperature approach.
CFD results of 2D axial symmetric FEM model
invoke a need for experimental RTD identification
of axial mixing flow character.
ACKNOWLEDGEMENTS
Grant of Ministry of Industry and Commerce of CR
no. MPO 2A-2TP1/024 is gratefully acknowledged.
REFERENCES
Tukač, V., Hanika, J., Veselý, V., Lederer, J., Nečesaný, .,
F., 2009. Possibility of hydrogen production by partial
oxidation of waste biomass, CHEMagazín XIX (3)
8 – 9.
Robinson, P. J., Luyben, W. L., 2008. Simple dynamic
gasifier model that runs in Aspen Dynamics, Ind. Eng.
Chem. Res. 47 (20) 7784-7792.
Cammarata, G., Petrone, G., 2007, Radiating effect of
participating media in flameless industrial reactor, Int.
Jnl. of Multiphysics 1 (4), 393 – 406.
Bruggemann, P., Seifert, P., Meyer, B., Muller-Hagedorn,
M., 2010. Influence of temperatute and pressure on the
non-catalytic partial oxidation of natural gas, Chem.
Prod. Proc. Modelling, 5 (1), A1 1 – 24.
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Applications
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