Energy and Power Engineering, 2013, 5, 287-290
doi:10.4236/epe.2013.54B056 Published Online July 2013 (
A Preliminary Research on a Plasma Spout-Fluid Bed
L. Tang1*, H. Huang2, X. Yang1, H. Hao1, K. Zhao1
1Department of Civil Engineering, Guangzhou University, Waihuanxi Road, Guangzhou, China
2Department of Environmental Engineering, Guangdong University of Technology, Waihuanxi Road, Guangzhou, China
Received February, 2013
A laboratory-scale plasma spout-fluid bed reactor with a 10 kW DC plasma torch was developed and tested using quartz
sand particle and rice hull. The preliminary experimental results including particle recirculation and attrition, bed tem-
perature distribution and stability, as well as biomass gasification system energy balance were presented in this paper.
Research results indicated that plasma spout-fluid bed reactor may be a technically feasible reactor for carbonaceous
organic material gasification.
Keywords: Thermal Plasma; Spout-fluid Bed; Gasification
1. Introduction
Thermal plasma pyrolysis/gasification is an innovation
technology for transforming high calorific waste streams
such as organic solid waste into a valuable synthesis gas
and a vitrified slag [1-3]. Up to now thermal plasma py-
rolysis/gasification technology was applied only to de-
stroy highly toxic compounds and to modify refractory
compound [4-5]. Thermal plasma pyrolysis/gasification
of solid waste for energy and chemical recycling are
seldom practiced for technical and economic reasons
Spout-fluid bed reactor is a combination of a fluidized
bed and spouted bed by combining the fluid flow of the
single central opening (spouted bed) with the auxiliary
fluid flow through the distributor plate (fluidized bed).
Spout-fluid bed reactors used for combustion or gasifica-
tion are reported to overcome the limitation of spouted
bed and fluidized bed by providing higher rate of mixing,
better solid fluid contact, even fluid flow distribution
resulting to the minimization of dead zones, better solid
fluid contact, improved mass and heat transfer character-
istics [8]. The basic principal of the plasma spout-fluid
bed reactor is essentially similar to that of a standard
spouted bed. The main difference, however, lies in the
fact that the spouting gas is substituted by a DC plasma
jet which discharges in the conical bottom of the reactor.
This has the main advantage that the radiation and con-
vection losses from the plasma are recuperated by the
solid charge of the reactor thus giving rise to substan-
tially higher energy efficiencies.
In this research, a DC plasma jet forms the spout
which provides heat for the process and this spout is sur-
rounded by a conventional fluidized bed. Plasma spouted
and spout-fluid beds have been reported [9], but very
little attention has been given ever since to the study of
its operating characteristics and the basic phenomena
involved. It is essential to this end, that the present study
has been conducted with the objective of obtaining basic
information about such phenomena as, spouting stability,
particle attrition and elutriation from the bed, tempera-
ture distribution and energy balance. The overall objec-
tive of this work was to assess the technical feasibility of
using a plasma spout-fluid bed to carry out a biomass
gasification to recover energy and resource.
2. Experimental
The experimental apparatus is shown schematically in
Figure 1. The rectifier, which provides DC power to the
plasma torch is rated at 10 kW. The plasma torch is of
the standard configuration with a conical tungsten cath-
ode and annular copper anode between which the plasma
forming gases pass. The torch current (and thus power)
and gas flow rates are controlled at the control panel. The
gasification reactor comprised a cylindrical column part
fitted to a conical base which coupled with the DC
plasma torch. The column has an inside diameter of 200
mm and a height of 500 mm, it is made of quartz for ob-
servational study conveniently. The total angle of the
cone is 6and the diameter of the plasma torch orifice
is 8 mm. A variable-speed screw feeder situated on the
top of the quartz tube ensured that the particles were fed
toward the cylindrical quartz reactor. A water bath is
Copyright © 2013 SciRes. EPE
1.nitrogen gas cylinder 2. flow valve 3. flow meter 4. plasma torch 5.6.
cooling water inlet 7. plasma gas inlet 8.9. cooling water outlet 10. cone 11.
fluid gas plenum chamber 12. cylinder 13. feed hopper 14. control system of
screw feeder 15. cyclone separator 16. filter 17.18. water scrubber 19. gas
sampling system 20. thermal couple 21. data acquisition system 23. plasma power source 24. pressure gage
Figure 1. Schematic of the plasma spout-fluid experimental
provided to filter the micron particles and cool the reac-
tor exhaust gases before they reach the sample bag or be
Two sources of N2 flow to the bed, the spouting gas is
provided by a DC plasma jet. Fluidizing N2 enter the
distributor which contains 300 holes (1 mm in diameter)
evenly distributed at the wall of the cone; the purpose of
the fluidizing gas is to provide gasifying agent such as
oxygen, water steam or air to the reactor, fluidifying the
reactant as well as cooling the reactor wall. The particle
used in our experiments is quartz sand with the mean
particle size of 200 μm and rice hull with the mean parti-
cle size of 350 μm.
The temperature distribution inside the bed is obtained
using 25 K-type thermocouples placed at different levels
in the bed. In addition, a K-type thermocouple is set
above the bed for measuring the gas outlet temperature.
The data are recorded by a data acquisition system. The
temperature image of the quartz reactor wall was ob-
tained using a thermal infrared imager (TH9100 wv,
NEC, Japan).
3. Results and Discussion
3.1. Particle Attrition
A special attention was given to the question of particle
attrition in the bed. Samples of the bed charge were taken
before and after plasma treatment and were subject to
particle size analysis. Results reveal a substantial change
in the quartz sand particle size distribution after only a
10 minutes treatment in the plasma at a power level of 10
kW. The influence of the operating parameters on the
attrition rate was not studied.
This could be attributed to attrition due to particle-
particle or particle-reactor internal face collision or sim-
ply thermal shock of the quartz sand as the particles are
exposed to the high plasma temperatures during their
short flight in the fountain region of the spout-fluid bed.
3.2. Temperature Distribution
It is interesting to examine the temperature profile which
results from the balance between the heat flux from the
plasma to the bed and, radiation and convective losses
from the reactor wall.
A typical variation of the bed temperature as a func-
tion of time is schemed on Figure 2. The temperature in
the bed increased rapidly with N2 plasma, then reach
plateau about 30s. Thus the temperature distribution after
30s would be considered as the steady temperature dis-
tribution. The temperature distribution in the reactor in-
volves the energy exchange between the plasma gas and
the entrained gas and solids from the spouted/fluidized
bed. Radiant energy transfer also occurs and probably
accounts for the major part of the heat transfer in a lateral
direction away from the plasma. The transfer of energy
from the plasma is an exceedingly complex process. In
addition to convective heat transfer and thermal radiation,
the energy transfer involves the mechanisms of Bremss-
trahlung radiation due to the interaction of atoms and
ions with free electrons, radiative recombination to ions
and electrons, and the reversion from excited metastable
states back to ground states. The extent of energy trans-
fer by any one of these mechanisms depends greatly on
the energy level and degree of ionization of the plasma,
and no attempt was made in this study to examine their
relative importance.
Typical temperature distributions obtained with opera-
tion condition of fluid gas 4 m3/h were shown in Figure
3. The map were plotted by interpolation on the basis of
25 thermocouple measurements. It may be note that, with
Figure 2. Typical variation of the bed temperature as a
function of time at z =300 mm (fluid gas 4 m3/h, quartz
sand 0 g and operation power 10 kW).
Copyright © 2013 SciRes. EPE
L. TANG ET AL. 289
the exception of the region in the region in the immediate
neighborhood of the fluid gas entrance, most of the re-
maining volume of the bed is at a reasonably uniform
temperature which can be attributed to some extent to the
high level of particle recirculation in the bed. Radial
temperature differences are large, ranging from 200 to
300, but axial temperature gradient are small; this ob-
servation indicates an efficient axial mixing due to the
plasma jet but a poor radial diffusivity inside the annu-
Thermal infrared imager images of quartz reactor wall
at fluid gas 4 m3/h were shown in Figure 4. As noted
earlier in this paper, one of the purposes of the fluid gas
is cooling the reactor wall so as to decrease the radiation
heat transfer between the reactor wall and surrounding.
Compare the experiments’ results, the level of the quartz
wall temperature decreased significantly after increase
the fluid gas.
3.3. Energy Balance
In order to evaluate the efficiency of the use of energy
for carbonaceous organic material pyrolysis/gasification
in the reactor, the amounts of energy required for reac-
tions, enthalpy of exit products and heat losses must be
Figure 3. Temperature distribution in the reactor at fluid
gas 4 m3/h (quartz sand 21.3 g and operation power 10 kW).
Figure 4. Thermal infrared imager image of quartz reactor
wall at fluid gas 4 m3/h (quartz sand 21.3 g and operation
power 10 kW).
determined. An energy balance on the reactor system
including the basic losses in the plasma due to energy
losses at the circuit is given as follows:
where is cone-column pyrolysis reactor mass in kg,
is the reactor specific heat in kJ·kg-1·K-1,
is the
temperature increase in K,
is the time interval of
observation in seconds, the three value are, respec-
tively, rates of power supply inputs, losses to circuit and
cooling water, and thermal loss, the enthalpy values are
heats of formation of reactants and products.
Complete energy balance were attempted for two ex-
periments, run 1 at input power 10 kW with fluid gas
flow rate 4 m3/h and run 2 at input power 10 kW without
fluid gas input, for the conditions of run 1 is the repre-
sentative condition of gasification experiments, while the
conditions of run 2 is the representative condition of py-
rolysis experiments. Because the high heating rate of
plasma, the reactor would be considered operating at
steady state and the energy storage term would be zero.
The rate of delivery of electrical energy to the system
input was 10kW. By measure the cooling water inlet
and outlet temperature and calculated the thermal loss
taking by the cooling water, the value of lossescircuit in
these two conditions had nearly the same value of 1.678
kW. lossesradiant from the reactor is calculated by the
reactor surface temperature and the environmental tem-
perature. The reactor surface temperatures were esti-
mated using the thermal infrared imager images.
For this is the preliminary experiment using the reac-
tor, the fluid gas used in the reaction is nitrogen, while if
using gasifying agent such as oxygen, water steam or air
as the fluid gas, the content of the combustible gas in the
product gas would increase due to the chemical reactions
between the carbon and oxygen. Secondly, the flow rate
of the gasifying agent (fluid gas) should adjust according
to the feedback rate, and the fluid gas may be a bit more
than that is needed. It is likely that future research in
both fluid gas ingredient and flow rate will continue to
improve the energy transfer efficiency of plasma spout–
fluid systems.
In pyrolysis condition, the magnitude of the numbers
about 36% show that a large percentage of the total en-
ergy delivered into the system is lost to circumstances,
while the thermal loss was about 33% of total energy in
gasification condition. The thermal losses of this labora-
tory reactor were still high, and the amount of energy
used by the feedstock was small. This could be attributed
to two reasons: 1) this laboratory reactor was a small
scale apparatus having a large ratio of surface area/reac-
tor volume; 2) in order to observe the plasma, transparent
quartz tube was used for the reactor wall, which had in-
Copyright © 2013 SciRes. EPE
Copyright © 2013 SciRes. EPE
creased the radiant heat loss. An industrialized scale sys-
tem would allow a much higher proportion of the energy
to be utilized. Then the ability to reduce the losses
through the circuit and deliver more energy to the treat-
ment of the feedstock is critical for economic feasibility
of the technology.
4. Conclusions
The plasma spout-fluid bed reactor offers interesting
characteristics as an efficient gas solid contactor which
could find wide applications in the area of pyroly-
sis/gasification of solid carbonaceous material such as
biomass and organic solid waste. Experimental data and
an analysis of spout-fluid ability and thermal efficiency
of a plasma spout-fluid bed reactor have been presented
in this paper; over the range of experimental conditions
investigated: the bed temperature distribution and stabil-
ity are proper for biomass gasification and fluid gas
would decrease the convective and radiant heat losses
efficiently. Special attention should be given to the im-
portant question of particle attrition and the excessive
elutriation of fine particles from the reactor which could
represent an important problem.
5. Acknowledgements
We thank the support from the National Natural Science
Foundation of China (51078092), “Yangcheng scholar”
project of Education Bureau of Guangzhou (10A039G)
and Guangzhou city-belonged university research project
of Education Bureau of Guangzhou (10A020).
[1] P. G. Rutberg, “Some Plasma Environmental Technolo-
gies Developed in Russia,” Plasma Sources Sci. Technol.,
Vol. 11, No. 3A, 2002, pp. A159-A165.
[2] Z. Zhao, et al., “Biomass Pyrolysis in an Ar-
gon/Hydrogen Plasma Reactor,” Chemical Engineering
Technology, Vol. 24, No. 5, 2001, pp. 197-199.
[3] T. Inaba and T. Iwao, “Treatment of Waste by Dc Arc
Discharge Plasma,” IEEE Transactions on Dielectrics &
Electrical Insulation, Vol. 7, No. 5, 2000, pp. 684-692.
[4] K. Koutaro, et al., “Melting Municipal Solid Waste In-
cineration Residue by Plasma Melting Furnace With a
Graphite Electrode,” Thin Solid Films, Vol. 386, No. 2,
2001, pp. 183-188. doi:10.1016/S0040-6090(00)01640-0
[5] K.Seok-Wan, et al., “100 kW Steam Plasma Process for
Treatment of PCBs (Polychlorinated Biphenyls) Waste,”
Vacuum, Vol. 70, No. 1, 2003, pp. 59-66.
[6] B. G. Ivan and I. M. Boris, “Some General Conclusions
from the Results of Studies on Solid Fuel Steam Plasma
Gasification,” Fuel, Vol. 71, No. 8, 1992, pp. 895-901.
[7] K. E. Sherick and J. E. Findiey, “Energy and Costs
Scoping Study for Plasma Pyrolysis Thermal Processing
System,” Energy Citations Database,G-WTD-9993,1992.
[8] P. Suwannakuta, “A Study on Biomass Gasification in
Spout-Fluid Bed,” Master thesis No. ET-02-22, Asian In-
stitute of Technology, Bangkok, Thailand, 2002.
[9] R. J. Munz and O. S. Mersereau, “A Plasma Spout-fluid
Bed for the Recovery of Vanadium from Vanadium Ore,”
Chemical Engineering ScienceVol. 45, No. 8, 1990, pp.