Fluidization Characteristic of Sewage Sludge Particles.
Applied Mechanics and Materials Vol 776 (2015) pp 294-299
© (2015) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.776.294
Submitted: 2015-02-19
Accepted: 2015-04-10
Fluidization Characteristic of Sewage Sludge Particles
I Nyoman Suprapta Winaya1, a, Rukmi Sari Hartati2,b, I Nyoman Gde Sujana1,c
1
Mechanical Engineering Department, Udayana University, Bali-Indonesia
2
Electrical Engineering Department, Udayana University, Bali-Indonesia
a
[email protected], [email protected], [email protected]
Keywords: fluidization, simulation, CFD, sewage sludge
Abstract: The main objective of this study is to determine the basic characteristics of fluidization
using sewage sludge particle as non-visual phenomena which can then be modeled physically and
numerically with the program of Computational Fluid Dynamic (CFD). CFD modeling using
Eulerian model incorporating the kinetic theory for solid particles was applied to the gas-solid flow
at various superficial velocities for different particle sizes. The transfer momentum was calculated
using Syamlal-O'Brien drag function and Eulerian multiphase model was used for analysis. TwoDimensional computational domains discretized using rectangular cells (Quad), made within the 20
iteration steps of 0,001s. The gas velocity is found to be the the most important factors that
influence the formation process of fluidization; by increasing the rate of fluidization the bed
expanse occurs higher as well the time of onset fluidization is shorter. The phenomenon can be
explained well by modeling and simulation.
Introduction
Fluidization is one of the contacting techniques through which fine solids are transformed into a
fluid using either gas or liquid. In fluidization a contact between the gas and solid particle occurs
appropriately because its wide range of contact surface. Better possibilities to simulate mixing of
gas and solids in fluidized beds are of interest for many researchers. One of the bed materials that
can be used in fluidized bed gasification technology is sewage sludge as fuel which is obtained from
wastewater treatment hospitality. In addition to the utilization of an alternative energy using sewage
sludge can also reduce the environment load because potentially to contaminate natural and source
disease if not treated properly. The waste water may also contain certain undesirable components,
including organic, inorganic and toxic substances, such as pathogenic microorganisms. Indonesia
especially Bali is one of the main tourist destination in the world in which the existing hotels with
qualified supporting facility is the obligation. To support the operations of hospitality, it is
necessary to provide the waste treatment process which can produce the energy for the hotel.
Computational Fluid Dynamic (CFD) offers an approach to predict the behavior of mixing
phenomena in fluidized bed reactor using any type of particles as the bed material. Simulations have
been developed in recent years, and CFD modeling is popularly used to simulate the hydrodynamic
of fluidization regimes [1]. The program could provide the flexibility to change the design
parameters without much cost, providing faster time of the trial, and also able to provide a detailed
information about the flow field especially in the area of measurement which is difficult or impossible
to obtain [2]. Armstrong and Luo developed a model approach Syamlal-O'Brien drag coefficient
which showed more local fluctuations on the basis of particle terminal velocity with slight sensitivity
to the microscopic scale [3]. Tasirin, et al. conducted an experimental study as well as modeling and
it was found for a higher in gas velocity the fluidization process could be improved [4].
Fluidization behavior involves three important phases namely: the particle-dominated,
predominantly gas and a mixture of both.
Applied Mechanics and Materials Vol. 776
295
Method
Simulation setup. The simulation process is in 2D model with mesh containing of 2,830
quadrilateral cells. Fig. 1 shows the messing and the boundary condition of the system. A solid-fluid
Eulerian model has been carried out applying in the bed material of sewage sludge. Solid particle
velocity was set at zero as minimum fluidization base, and gas velocity was assumed to have the
same value everywhere in the bed with air velocity variation of 0.05 to 0.15 m/s. Sewage sludge
properties as bed material with different particles diameter 0.5 mm, 0.6 mm, 0.7 mm which was
filled to the height of 10 cm. Momentum exchange coefficients were calculated by using the
Syamlal-O’Brien drag functions. The discretisation of the convective terms was carried out with the
second-order upwind scheme. A time step of 0,001s was used to ensure quick convergence with
7,000 iterations.
Pressure outlet
17 Interval count
walls (solid)
170 Interval count
Velocity inlet
17 Interval count
Fig. 1. Meshing and boundary conditions
Input and initial parameter simulation:
- Column diameter
= 5 cm
- Fluidization bed height
= 50 cm
- Initial static bed height
= 10 cm
- Total meshing
= 2,890 quadrilateral cells
- Superficial velocity
= 0.05 m/s, 0.10 m/s, 0.15 m/s
- Gravity force
= 9,81 m/s
- Time steps
= 0.001s
- Iterations
= 7,000
- Air as primary phase and sewage sludge particle with density 310,48 kg/m3 of as secondary
phase
Mathematical model. The interactions between gas and fluidized bed granular particles were used
Eulerian granular model. The model allows for the presence of two different phases in one control
volume of the grid by introducing the volume fraction variable as follows,
Gas phase:
∂
ϵ .ρ +∇. ϵg .ρg .
∂t g g
g
= 0 (1)
296
Recent Decisions in Technologies for Sustainable Development
Solids phase:
) + ∇. ( .
( .
) = 0 (2)
.
The conservation of momentum for the gas and solid phases are described as
Gas phase:
∂
. g .ρg . g +∇.
∂t
Solids phase:
∂
∂t
.
s .ρs . s
g .ρg . g
+∇.
s .ρs .
=-
=-
g .∇P+∇.τ̿g + ϵg .ρg .g –
s .∇P-∇P
Kgs .
+∇.τ̿s + ϵs .ρs .g – Kgs .
g- s
(3)
g- s
(4)
Drag coefficient model Syamlal-O’Brien based on the measurements of the terminal velocities of
particles in fluidized bed. These correlations give exchange coefficients in terms of the volume
fraction and relative Reynolds number as:
g
=
3
4
g g
,
,
where CD is drag coefficient:
= 0.63 +
4.8
−
(5)
(6)
(a)
Solid volume fraction
Solid volume fraction
Results and Discussion
Fig. 2a shows the sample of contour of solid volume fraction along the bed reactor at fluidization
velocity of 0.15 m/s at the time step of 0 to 7 s. It is observed the solid distribution continuously
flowed as the velocity has just started. The degradation of the red colour is found to change as the
solid fraction decreased mostly until the maximum bed height of 33cm as seen in Fig 2b. The
similar behavior is observed for different fluidization velocity in which the higher velocity resulted
in higher expansion of solid fraction distribution.
0s
1s
2s
3s
4s
5s 6s
7s
(b)
Bed height (m)
Fig. 2(a) Contour of solid volume fraction distribution at velocity of 0.15 m/s from 0 to 7s,
(b) Solid volume fraction along the bed height after 7s
Applied Mechanics and Materials Vol. 776
297
Contour of solid volume fraction. The contour of solid volume fraction during 7s of the 2D
simulation at velocity of 0.05 m/s and 0.15 m/s for particle diameter variation of 0.5mm, 0.6mm
and 0.7mm is shown in Fig. 3. At the lower velocity thick layers of dense suspension are observed
at all conditions. A small contour layer different are found for small variation of particle size as
noted as a, b and c.
a
v = 0,10 m/s
b
c
a
v = 0.15 m/s
b
c
Fig. 3. Contour of solid volume fraction at velocity (v) of 0.10 m/s and 0.15 m/s for particle
diameter of (a) 0,5mm, (b) 0,6mm, (c) 0,7mm
In Fig. 4, the average solid volume fraction during 7s is shown clearly higher at the higher velocity.
Clusters of particles are seen at higher elevations mostly at velocity of 0.15 m/s. A denser region is
shown close to the bed bottom. Solids are often collected in the vicinity of the wall.
0.5 mm
a
b
c
0.6 mm
a
b
c
0.7 mm
a
b
c
Fig. 4. Contour of solid volume fraction at particle size of 0.5, 0.6 and 0.7 mm for velocity of
(a) 0.05 m/s, (b) 0.10 m/s, (c) 0.15 m/s
Bubbling characteristic. The formation bubbling in fluidization phenomena is mostly dependent
on gas velocity and particle size employment. Simulation using sewage sludge as bed material with
solid density ( ) of 310,48 kg/m3 and gas density ( ) of 1,225 kg/m3 for particle size of 0.5 – 0.7
mm is classified using Geldart graphic [5].
298
Recent Decisions in Technologies for Sustainable Development
Fig. 5. Particles size position of sewage sludge solid in Geldart particles classification graph
Fig. 5 shows the position of particle size of sewage sludge used for CFD simulation in the Geldart
graph. Considering the density and mean diameter particles, the sewage sludge is in group of A
(Aeratable) area in which the hydrodynamic behavior is specific. As the gas velocity is increased
above minimum fluidization, bubbles are formed at irregular form. The formation of the bubbles
can be tracked as the onset of fluidization is occurred as illustrated in Fig. 6, 7 and 8 for velocity of
0.15 m/s at particle size of 0.5, 0.6, and 0.7 mm respectively.
6s
7s
Fig. 6. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.5 mm
Fig. 6 to 8 are some example of the movement of bubble size during 7s in which bubble is
considered to play an important role of the fluidization. As the gas velocity is increased the bubble
rise is increased so that the added air flows into the bubble rather than into the dense bed. The
movement of the particles resulting from the gas that flows into the bed restrained by material
falling from the top so as to form bubbles. When a bubble reaches the top of the bed it breaks
through the surface above particles.
Applied Mechanics and Materials Vol. 776
299
5s
6s
7s
5s
6s
7s
Fig. 7. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.6 mm
Fig. 8. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.7 mm
Summary
From the 2D of CFD simulation, the contour of volume fraction of sewage sludge depends on gas
velocity and particle size employment. The gas velocity is important factor that influence the
fluidization forming as well as the bed expansion and characteristic of bubbling behavior. The
sewage sludge is considered in group of A (Aeratable) area in which the hydrodynamic behavior
such as bubbles are formed at irregular form. The formation of the bubbles can be tracked as the
onset of fluidization using the simulation.
Acknowledgement: This study was kindly supported by Directorate of Higher Education-The
Indonesia’s Ministry of Education and Culture through Hibah Desentralisasi Fundamental
2014 of Udayana University.
References
[1] Amit Kumar., 2008. CFD Modeling of Gas-Liquid-Solid Fluidized Bed. Department of
Chemical Engineering National Institute of Technology Rourkela-769008,Orissa.
[2] Armstrong L.M., Gu S. dan Luo K.H., 2010. Study of Wall-to-Bed Heat Transfer In a Bubling
Fluidized Bed Using the Kinetic Theory of Granular flow. International Journal of Heat and
Mass Transfer 53, 4949-4959.
[3] Tasirin S.M., Kamarudin S.K. dan Hweage A.M.A.,2008. Mixing Behavior of Binary Polymer
Particles in Bubbling Fluidized Bed. Journal of Physical Science, Vol. 19(1), 13–29.
[4] Kallio S., Gulden M., Hermason A., 2009. Experimental study and CFD Simulation of a 2D
Circulating Fluidized Bed. Proceedings of the 20th International Conference on Fluidized Bed
Combustion, pp. 818.
[5] Kunii, Lavenspiel, 2006. Fluidization Engineering Second edition, Copyright 1991 ButterworthHeinemann, a Division of Reed Publishing (USA) Inc.
Applied Mechanics and Materials Vol 776 (2015) pp 300-306
© (2015) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.776.300
Submitted: 2015-02-19
Accepted: 2015-04-10
Design of Fluidized Bed Co-Gasifier of Coal and Wastes Fuels
I Nyoman Suprapta Winaya1,a, Rukmi Sari Hartati2,b, I Putu Lokantara1,c,
I GAN Subawa3,d , I Made Agus Putrawan1,e
1
Mechanical Engineering Department - University of Udayana, Bali-Indonesia
2
Electrical Engineering Department - University of Udayana, Bali-Indonesia
3
PT Indonesia Power UBP Pesanggaran Bali-Indonesia
a
[email protected], [email protected], [email protected],
d
[email protected], [email protected]
Keywords: fluidized bed, co-gasifier, biomass, waste
Abstract. The solid waste produced from urban area is an urgent issue to be addressed. A fluidized
bed (FB) gasification technology has been widely applied and proven effective to convert waste
into clean energy and environmentally friendly. Co-gasification is a technique of mixing two or
more fuels that aims to improve calorific value of the gas production. A FB gasifier reactor is
designed using some previous experiments and available literature as well as from the internal
experience of the research group. The gasification reactor pilot plant scale using data input of waste
and biomass fuels has been fabricated with diameter of 0.7 m and a height of 1.5 m. The Tests
have been performed showing that the FB gasifier is very feasible to be developed.
Introduction
The increased efforts of the need to reduce CO2 emission to prevent global warming from
power generation systems have led to an interest in biomass and wastes as fuel sources. As a
potentially energy renewable resource, biomass and wastes are gaining more attention worldwide.
The use of fluidized bed (FB) technology for waste and biomass fuels has expanded since the
twentieth century either for energy recovery or wastes disposal. This technology is well known for
its excellent gas-solid mixing and favorable emission characteristics. Pre-processing of
biomass/wastes feeds to acceptable particle size and moisture content, usually necessary for
conventional technologies, can then be minimized in fluidized bed operations, as long as it could be
conveniently fed into the bed. FB technology is usually indicated to be the best choice, or
sometimes the only choice, to convert alternative fuels to energy due to its fuel flexibility and the
possibility to achieve an efficient and clean operation. It is also found that a high recovery of heat
can be achieved, this is mainly due to the heat transfer coefficient in fluidized bed combustors is
much greater than that of conventional combustion systems.
Looking at the future potential of urban waste, the high energy content within the waste is very
urgent to utilize. Technology must find a feasible process which allows wastes to be converted as
energy in an environmental way. Fluidized bed gasification is a promising technology that can
convert energy from the low rank calorific solid fuel such as biomass and wastes into a combustible
gas whose composition and heating value are greatly dictated by the type of gasifying agents.
Because of the lower calorific values of waste fuels accompanied by flame stability problems, cogasification currently holds more appeal than any of the sole source technologies including more
advanced conversion options such as integrated gasification combined cycles. It is anticipated that
co-gasification of waste fuels with coal will reduce flame stability problems, as well as minimize
corrosion effects. The co-gasification of coal and wastes has the potential to reduce CO2 emissions
and the amount of pollutants as NOx and SOx. Co-gasification process has been widely studied
© (2015) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.776.294
Submitted: 2015-02-19
Accepted: 2015-04-10
Fluidization Characteristic of Sewage Sludge Particles
I Nyoman Suprapta Winaya1, a, Rukmi Sari Hartati2,b, I Nyoman Gde Sujana1,c
1
Mechanical Engineering Department, Udayana University, Bali-Indonesia
2
Electrical Engineering Department, Udayana University, Bali-Indonesia
a
[email protected], [email protected], [email protected]
Keywords: fluidization, simulation, CFD, sewage sludge
Abstract: The main objective of this study is to determine the basic characteristics of fluidization
using sewage sludge particle as non-visual phenomena which can then be modeled physically and
numerically with the program of Computational Fluid Dynamic (CFD). CFD modeling using
Eulerian model incorporating the kinetic theory for solid particles was applied to the gas-solid flow
at various superficial velocities for different particle sizes. The transfer momentum was calculated
using Syamlal-O'Brien drag function and Eulerian multiphase model was used for analysis. TwoDimensional computational domains discretized using rectangular cells (Quad), made within the 20
iteration steps of 0,001s. The gas velocity is found to be the the most important factors that
influence the formation process of fluidization; by increasing the rate of fluidization the bed
expanse occurs higher as well the time of onset fluidization is shorter. The phenomenon can be
explained well by modeling and simulation.
Introduction
Fluidization is one of the contacting techniques through which fine solids are transformed into a
fluid using either gas or liquid. In fluidization a contact between the gas and solid particle occurs
appropriately because its wide range of contact surface. Better possibilities to simulate mixing of
gas and solids in fluidized beds are of interest for many researchers. One of the bed materials that
can be used in fluidized bed gasification technology is sewage sludge as fuel which is obtained from
wastewater treatment hospitality. In addition to the utilization of an alternative energy using sewage
sludge can also reduce the environment load because potentially to contaminate natural and source
disease if not treated properly. The waste water may also contain certain undesirable components,
including organic, inorganic and toxic substances, such as pathogenic microorganisms. Indonesia
especially Bali is one of the main tourist destination in the world in which the existing hotels with
qualified supporting facility is the obligation. To support the operations of hospitality, it is
necessary to provide the waste treatment process which can produce the energy for the hotel.
Computational Fluid Dynamic (CFD) offers an approach to predict the behavior of mixing
phenomena in fluidized bed reactor using any type of particles as the bed material. Simulations have
been developed in recent years, and CFD modeling is popularly used to simulate the hydrodynamic
of fluidization regimes [1]. The program could provide the flexibility to change the design
parameters without much cost, providing faster time of the trial, and also able to provide a detailed
information about the flow field especially in the area of measurement which is difficult or impossible
to obtain [2]. Armstrong and Luo developed a model approach Syamlal-O'Brien drag coefficient
which showed more local fluctuations on the basis of particle terminal velocity with slight sensitivity
to the microscopic scale [3]. Tasirin, et al. conducted an experimental study as well as modeling and
it was found for a higher in gas velocity the fluidization process could be improved [4].
Fluidization behavior involves three important phases namely: the particle-dominated,
predominantly gas and a mixture of both.
Applied Mechanics and Materials Vol. 776
295
Method
Simulation setup. The simulation process is in 2D model with mesh containing of 2,830
quadrilateral cells. Fig. 1 shows the messing and the boundary condition of the system. A solid-fluid
Eulerian model has been carried out applying in the bed material of sewage sludge. Solid particle
velocity was set at zero as minimum fluidization base, and gas velocity was assumed to have the
same value everywhere in the bed with air velocity variation of 0.05 to 0.15 m/s. Sewage sludge
properties as bed material with different particles diameter 0.5 mm, 0.6 mm, 0.7 mm which was
filled to the height of 10 cm. Momentum exchange coefficients were calculated by using the
Syamlal-O’Brien drag functions. The discretisation of the convective terms was carried out with the
second-order upwind scheme. A time step of 0,001s was used to ensure quick convergence with
7,000 iterations.
Pressure outlet
17 Interval count
walls (solid)
170 Interval count
Velocity inlet
17 Interval count
Fig. 1. Meshing and boundary conditions
Input and initial parameter simulation:
- Column diameter
= 5 cm
- Fluidization bed height
= 50 cm
- Initial static bed height
= 10 cm
- Total meshing
= 2,890 quadrilateral cells
- Superficial velocity
= 0.05 m/s, 0.10 m/s, 0.15 m/s
- Gravity force
= 9,81 m/s
- Time steps
= 0.001s
- Iterations
= 7,000
- Air as primary phase and sewage sludge particle with density 310,48 kg/m3 of as secondary
phase
Mathematical model. The interactions between gas and fluidized bed granular particles were used
Eulerian granular model. The model allows for the presence of two different phases in one control
volume of the grid by introducing the volume fraction variable as follows,
Gas phase:
∂
ϵ .ρ +∇. ϵg .ρg .
∂t g g
g
= 0 (1)
296
Recent Decisions in Technologies for Sustainable Development
Solids phase:
) + ∇. ( .
( .
) = 0 (2)
.
The conservation of momentum for the gas and solid phases are described as
Gas phase:
∂
. g .ρg . g +∇.
∂t
Solids phase:
∂
∂t
.
s .ρs . s
g .ρg . g
+∇.
s .ρs .
=-
=-
g .∇P+∇.τ̿g + ϵg .ρg .g –
s .∇P-∇P
Kgs .
+∇.τ̿s + ϵs .ρs .g – Kgs .
g- s
(3)
g- s
(4)
Drag coefficient model Syamlal-O’Brien based on the measurements of the terminal velocities of
particles in fluidized bed. These correlations give exchange coefficients in terms of the volume
fraction and relative Reynolds number as:
g
=
3
4
g g
,
,
where CD is drag coefficient:
= 0.63 +
4.8
−
(5)
(6)
(a)
Solid volume fraction
Solid volume fraction
Results and Discussion
Fig. 2a shows the sample of contour of solid volume fraction along the bed reactor at fluidization
velocity of 0.15 m/s at the time step of 0 to 7 s. It is observed the solid distribution continuously
flowed as the velocity has just started. The degradation of the red colour is found to change as the
solid fraction decreased mostly until the maximum bed height of 33cm as seen in Fig 2b. The
similar behavior is observed for different fluidization velocity in which the higher velocity resulted
in higher expansion of solid fraction distribution.
0s
1s
2s
3s
4s
5s 6s
7s
(b)
Bed height (m)
Fig. 2(a) Contour of solid volume fraction distribution at velocity of 0.15 m/s from 0 to 7s,
(b) Solid volume fraction along the bed height after 7s
Applied Mechanics and Materials Vol. 776
297
Contour of solid volume fraction. The contour of solid volume fraction during 7s of the 2D
simulation at velocity of 0.05 m/s and 0.15 m/s for particle diameter variation of 0.5mm, 0.6mm
and 0.7mm is shown in Fig. 3. At the lower velocity thick layers of dense suspension are observed
at all conditions. A small contour layer different are found for small variation of particle size as
noted as a, b and c.
a
v = 0,10 m/s
b
c
a
v = 0.15 m/s
b
c
Fig. 3. Contour of solid volume fraction at velocity (v) of 0.10 m/s and 0.15 m/s for particle
diameter of (a) 0,5mm, (b) 0,6mm, (c) 0,7mm
In Fig. 4, the average solid volume fraction during 7s is shown clearly higher at the higher velocity.
Clusters of particles are seen at higher elevations mostly at velocity of 0.15 m/s. A denser region is
shown close to the bed bottom. Solids are often collected in the vicinity of the wall.
0.5 mm
a
b
c
0.6 mm
a
b
c
0.7 mm
a
b
c
Fig. 4. Contour of solid volume fraction at particle size of 0.5, 0.6 and 0.7 mm for velocity of
(a) 0.05 m/s, (b) 0.10 m/s, (c) 0.15 m/s
Bubbling characteristic. The formation bubbling in fluidization phenomena is mostly dependent
on gas velocity and particle size employment. Simulation using sewage sludge as bed material with
solid density ( ) of 310,48 kg/m3 and gas density ( ) of 1,225 kg/m3 for particle size of 0.5 – 0.7
mm is classified using Geldart graphic [5].
298
Recent Decisions in Technologies for Sustainable Development
Fig. 5. Particles size position of sewage sludge solid in Geldart particles classification graph
Fig. 5 shows the position of particle size of sewage sludge used for CFD simulation in the Geldart
graph. Considering the density and mean diameter particles, the sewage sludge is in group of A
(Aeratable) area in which the hydrodynamic behavior is specific. As the gas velocity is increased
above minimum fluidization, bubbles are formed at irregular form. The formation of the bubbles
can be tracked as the onset of fluidization is occurred as illustrated in Fig. 6, 7 and 8 for velocity of
0.15 m/s at particle size of 0.5, 0.6, and 0.7 mm respectively.
6s
7s
Fig. 6. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.5 mm
Fig. 6 to 8 are some example of the movement of bubble size during 7s in which bubble is
considered to play an important role of the fluidization. As the gas velocity is increased the bubble
rise is increased so that the added air flows into the bubble rather than into the dense bed. The
movement of the particles resulting from the gas that flows into the bed restrained by material
falling from the top so as to form bubbles. When a bubble reaches the top of the bed it breaks
through the surface above particles.
Applied Mechanics and Materials Vol. 776
299
5s
6s
7s
5s
6s
7s
Fig. 7. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.6 mm
Fig. 8. A contour of bubble rise movement at velocity of 0,15 m/s at diameter of 0.7 mm
Summary
From the 2D of CFD simulation, the contour of volume fraction of sewage sludge depends on gas
velocity and particle size employment. The gas velocity is important factor that influence the
fluidization forming as well as the bed expansion and characteristic of bubbling behavior. The
sewage sludge is considered in group of A (Aeratable) area in which the hydrodynamic behavior
such as bubbles are formed at irregular form. The formation of the bubbles can be tracked as the
onset of fluidization using the simulation.
Acknowledgement: This study was kindly supported by Directorate of Higher Education-The
Indonesia’s Ministry of Education and Culture through Hibah Desentralisasi Fundamental
2014 of Udayana University.
References
[1] Amit Kumar., 2008. CFD Modeling of Gas-Liquid-Solid Fluidized Bed. Department of
Chemical Engineering National Institute of Technology Rourkela-769008,Orissa.
[2] Armstrong L.M., Gu S. dan Luo K.H., 2010. Study of Wall-to-Bed Heat Transfer In a Bubling
Fluidized Bed Using the Kinetic Theory of Granular flow. International Journal of Heat and
Mass Transfer 53, 4949-4959.
[3] Tasirin S.M., Kamarudin S.K. dan Hweage A.M.A.,2008. Mixing Behavior of Binary Polymer
Particles in Bubbling Fluidized Bed. Journal of Physical Science, Vol. 19(1), 13–29.
[4] Kallio S., Gulden M., Hermason A., 2009. Experimental study and CFD Simulation of a 2D
Circulating Fluidized Bed. Proceedings of the 20th International Conference on Fluidized Bed
Combustion, pp. 818.
[5] Kunii, Lavenspiel, 2006. Fluidization Engineering Second edition, Copyright 1991 ButterworthHeinemann, a Division of Reed Publishing (USA) Inc.
Applied Mechanics and Materials Vol 776 (2015) pp 300-306
© (2015) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMM.776.300
Submitted: 2015-02-19
Accepted: 2015-04-10
Design of Fluidized Bed Co-Gasifier of Coal and Wastes Fuels
I Nyoman Suprapta Winaya1,a, Rukmi Sari Hartati2,b, I Putu Lokantara1,c,
I GAN Subawa3,d , I Made Agus Putrawan1,e
1
Mechanical Engineering Department - University of Udayana, Bali-Indonesia
2
Electrical Engineering Department - University of Udayana, Bali-Indonesia
3
PT Indonesia Power UBP Pesanggaran Bali-Indonesia
a
[email protected], [email protected], [email protected],
d
[email protected], [email protected]
Keywords: fluidized bed, co-gasifier, biomass, waste
Abstract. The solid waste produced from urban area is an urgent issue to be addressed. A fluidized
bed (FB) gasification technology has been widely applied and proven effective to convert waste
into clean energy and environmentally friendly. Co-gasification is a technique of mixing two or
more fuels that aims to improve calorific value of the gas production. A FB gasifier reactor is
designed using some previous experiments and available literature as well as from the internal
experience of the research group. The gasification reactor pilot plant scale using data input of waste
and biomass fuels has been fabricated with diameter of 0.7 m and a height of 1.5 m. The Tests
have been performed showing that the FB gasifier is very feasible to be developed.
Introduction
The increased efforts of the need to reduce CO2 emission to prevent global warming from
power generation systems have led to an interest in biomass and wastes as fuel sources. As a
potentially energy renewable resource, biomass and wastes are gaining more attention worldwide.
The use of fluidized bed (FB) technology for waste and biomass fuels has expanded since the
twentieth century either for energy recovery or wastes disposal. This technology is well known for
its excellent gas-solid mixing and favorable emission characteristics. Pre-processing of
biomass/wastes feeds to acceptable particle size and moisture content, usually necessary for
conventional technologies, can then be minimized in fluidized bed operations, as long as it could be
conveniently fed into the bed. FB technology is usually indicated to be the best choice, or
sometimes the only choice, to convert alternative fuels to energy due to its fuel flexibility and the
possibility to achieve an efficient and clean operation. It is also found that a high recovery of heat
can be achieved, this is mainly due to the heat transfer coefficient in fluidized bed combustors is
much greater than that of conventional combustion systems.
Looking at the future potential of urban waste, the high energy content within the waste is very
urgent to utilize. Technology must find a feasible process which allows wastes to be converted as
energy in an environmental way. Fluidized bed gasification is a promising technology that can
convert energy from the low rank calorific solid fuel such as biomass and wastes into a combustible
gas whose composition and heating value are greatly dictated by the type of gasifying agents.
Because of the lower calorific values of waste fuels accompanied by flame stability problems, cogasification currently holds more appeal than any of the sole source technologies including more
advanced conversion options such as integrated gasification combined cycles. It is anticipated that
co-gasification of waste fuels with coal will reduce flame stability problems, as well as minimize
corrosion effects. The co-gasification of coal and wastes has the potential to reduce CO2 emissions
and the amount of pollutants as NOx and SOx. Co-gasification process has been widely studied