22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Wooden waste processing with thermal plasma
A. Liavonchyk, V. Sauchyn and I. Khvedchyn
A.V. Luikov Heat and Mass Transfer Institute, Minsk, Belarus
Abstract: Investigation of plasma thermal wood waste gasification was carried out.
Thermodynamic calculation of high temperature gasification of wood waste in different
conditions was done. Results of calculation were checked experimentally with plasma
reactor
Keywords: plasma gasification, organic waste treatment, wood gasification
2. Experimental equipment
Experimental fasility is a reactor of 10 liters volume
designed in a form of ellipsoid. It is heated with an arc
DC plasma torch (power is 5-20 kW), nitrogen or air is
being used as a plasma forming gas. Material is supplied
with a feeder connected to the top part of the reactor.
3. Thermodynamic calculation
Preliminary thermodynamic calculation shows that
wooden material conversion into syn-gas (H 2 and
CO),CO 2 and H 2 O takes place. Depending on process
conditions some solid carbon in a form of soot can be
formed. According to results of calculation and data in the
literature [3,4] gas composition varies slightly in
temperature range of 1200-1700K ceteris paribus in air
(fig.1) and in nitrogen (fig.2) atmosphere. Reaction speed
grows with the temperature increase. Data [9, 10] was
used to estimate time of material conversion.
0.4
0.35
Mole fraction
0.3
0.25
H2
0.2
CO
0.15
CO2
0.1
C solid
0.05
0
1200
1400
1600
T, K
Fig. 1. Calculated composition of exhaust gases in air
atmosphere gasification with material moisture content of
10% and mass:gas=1:1 ratio.
0.4
0.35
0.3
Mole fraction
1. Introduction
During human life a significant and constantly growing
waste stream with a predominant organic part appears.
Problem of environmentally friendly and economic
method of the waste recycling is still not solved. One of
such methods is waste processing with thermal plasma [14], which means complicated organic substances
decomposition up to two and three atomic gases forming
in conditions of partial oxidizing and further its
utilization. Non-organic part of the wastes is melted into
homogeneous slag.
Investigation of organic material treatment was carried
out. Wood waste of various size was selected as a model
material. Air and nitrogen were selected as plasma
forming gas.
0.25
H2
0.2
CO
0.15
CO2
0.1
C solid
0.05
0
1200
1400
1600
T, K
Fig. 2. Calculated composition of exhaust gases in
nitrogen atmosphere gasification with material moisture
content of 10% and mass:gas=1:1 ratio.
4. Experiment results
Experiments of wooden material gasification sized from
2 to 30 mm and material:gas=3:1, 1,5:1 and 1:1 [6-8] ratio
were carried out. Moisture content when no additional
oxidizer is needed for full material gasification was
determined – 23%. Empirically obtained concentration of
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CO and H 2 at material moisture content of 10% and air
atmosphere are 10% less than calculated concentration.
Difference between experimental and theoretical
concentration of CO and H 2 in nitrogen atmosphere is
less than 5%. CO and CO 2 concentrations at moisture
content of 25% are correlated with theoretical data, H 2
concentration is two times less than calculated one. For
nitrogen atmosphere gasification CO and CO 2 content is
slightly different from calculated, hydrogen concentration
is also two times less than calculated one.
Fig. 3a, b shows the calculated (solid line) and the
experimentally obtained (dashed lines) concentration of
H 2 , CO and CO 2 in exhaust gases, nitrogen and air
respectively being used as the plasma forming gas for
gasification of wood of 10% humidity and a ratio of
material: gas = 1:1. Fig. 3 c, d shows the calculated (solid
line) and the experimentally obtained (dashed lines)
concentrations of H 2 , CO and CO 2 in exhaust
gases,nitrogen and air respectively being used as the
plasma forming gas forgasification of wood of 25%
humidity and a ratio of material: gas = 1:1.
Fig. 3. H 2 , CO, CO 2 concentrations in exhaust gases.
Difference between the experimental and calculated
data can be explained by the small residence time in the
reactor. This also leads to the formation of soot. Now this
problem is being solved with reactor form change to
increase material and forming gases residence tine in react
zone.
5. Conclusions
Gas with high concentration of H 2 and CO was
obtained in the experiments. Its calorific value is from 5,1
to 7 MJ/nm3 depending on the amount of the oxidant and
moisture content. Concentration of ballast gases (CO 2 ,
N 2 ) is significantly less comparing with classical air
gasification [5]. In this regard, the use of this technology
for processing wood or wastes of similar composition can
be considered as a stage of technology with syn-gas
application. Problem of small residence time in the
reactor is being solved with the reactor form change.
6. References:
[1]
Ducharme C. Technical and economic analysis
of Plasma-assisted Waste-to-Energy processes./ M.S.
Degree in Earth Resources Engineering Thesises.
Columbia University, 2010. – 79 p.
[2]
Young, G.C. Municipal Solid Waste to Energy
Conversion Processes. Economic, technical and
renewable comparisons / G.C. Young. – Hoboken, New
Jersey: John Wiley & Sons, 2010. – 384.
[3]
Hrabovsky, M. Pyrolysis of wood in arc plasma
for syngas production / M. Hrabovsky, M. Konrad, V.
Kopecky et al. // High Temperature Material Processes. –
2006. – Vol. 10, №4. – P. 557-570.
[4]
Hrabovsky M. Thermal Plasma Gasification of
Biomass// M. Hrabovsky// Progress in Biomass and
Bioenergy Production/ Edited by Dr. ShahidShaukat. –
InTech, 2011. – Ch.3. – P. 39-62
[5]
Plasma gasification of biomass in the case of
wooden outlets / A.N. Bratsev [et. al.]//TVT. - 2011. - T.
49, № 2. - S. 251–255.
[6]
Leonchik, A. I. Investigating processes of
gasification of wooden outlets in a plasma reactor in
oxygen-argon medium/ A.I. Leonchik, I.V. Hvedchin,
V.V. Savchin// Heat - and - Masstransfer-2012. – Minsk,
2013 - S. 183-187.
[7]
Leonchik, A.I. Comparing the process of
gasification of wood in a medium of air and nitrogen
2
P-III-9-20
plasma / A. I. Leonchik , V. V. Savchin , G. V.
Dolgolenko// Energy - and material-saving ecologically
clean technologies. Mat. 10 MNTK. – Minsk, 2014. – S.
81-88.
[8]
Gasification of wood in an electric arc plasma
reactor in atmosphere of air and nitrogen / A.I. Leonchik
[et. al.] // Ves. Nat. Acad. Science. Belarus. Ser. phys.tech. science. – 2014. – № 2. – S. 79-82.
[9]
Blinov, E.A. Fuels and theory of combustion.
Section - preparing and burning fuel: Educ.-method.
complex/ E.A. Blinov - SPb, Publ. SZTU, 2007 – 119с.
[10]
Modeling of Mass and Energy Transfer Between
Plasma and Material in Plasma Gasification Reactor / M.
Hlína [et al.] //CAPPSA 2007 Proc.: 3rd Intern. Congress
on Cold Atmospheric Pressure Plasmas Sources and
Applications. - Ghent, 2007. – P. 29-32
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