Azione 4 Sediment plasma treatment

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Azione 4
Action 1
Action 3
Sediment plasma
treatment
Action 4
Action 5
Action 2
Ing. Emanuele Ghedini
Action 6
Action 7
Action 8
Università di Bologna,
Dipartimento di Ingegneria delle
costruzioni meccaniche nucleari
aeronautiche e di mettallurgia
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Azione 4: Sediment plasma
treatment
Action 1
Action 3
 Documentation
demonstrating
the
efficiency of a further innovative technique
(plasma torch) to treat the finest fraction of
sediment (size between 20 and 75 μ).
Action 4
Action 5
Action 2
Expected results:
Action 6
Action 7
Action 8
 A technical report demonstrating the
efficiency of the extraction of silicon from
sediment.
 Vitrified sediment sample for each of the
sediment type (pollution level) in different
operating conditions, using graphite crucible
and in-flight plasma treatment
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RESEARCH GROUP FOR
INDUSTRIAL APPLICATION
OF PLASMAS:
Prof. Vittorio Colombo
Ing. Emanuele Ghedini - Researcher
Ing. Alessia Concetti – PhD Student
Ing. Paolo Sanibondi – PhD Student
Ing. Matteo Gherardi – PhD Student
Ing. Marco Boselli – Post Doc
Ing. Brais Vazquez Iglesias – Post Doc
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 THERMAL PLASMAS PHYSICS AND MODELING
 CALCULATION OF TRANSPORT PROPERTIES OF
THERMAL PLASMAS (Ar, H2, O2, N2, CO2, ...)
 PLASMA SOURCES DESIGN AND CHARACTERIZATION
 DC ARC PLASMA CUTTING, WELDING
 DC PLASMA SPRAYING MODELING
 RF PLASMA TREATMENT OF MATERIAL
(SPHEROIDIZATION, NANOPARTICLE PRODUCTION, ...)
 RF PLASMA TREATMENT OF WASTE (FLY AND BOTTOM
ASH, FLUORESCENCE LAMP GLASS)
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PLASMA APPLICATIONS
• Plasma spraying
• Welding
• Surface coating
• Waste destruction
• Plasma cutting
• Metallurgy
• Powder spheroidization
• Nanoparticle production
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Enthalpy
IONIZATION
PLASMA
4th STATE OF MATTER
VAPOR
LIQUID
THERMAL PLASMAS:
T = 5’000 – 30’000 K
p = 100 kPa
SOLID
Tm
Tb
Temperature
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PLASMA IS A GAS HEATED
UP TO ATOM IONIZATION
ELECTRON DENSITY
MAKES PLASMA AN
ELECTRICAL CONDUCTIVE
MEDIUM
DUE TO HIGH
TEMPERATURES (OVER
12’000 K) EVERY
MOLECULAR SPECIES IS
DISSOCIATED
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PLASMA TORCHES
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PLASMA SILICON PRODUCTION
Silicon (Si) production is done using the reaction of pure silica (SiO2) with carbon (C) in
an electric plasma arc furnace with graphite electrodes.
At temperatures over 2000 °C the carbon reduces the silica to silicon according to the
reactions:
SiO2 + C → Si + CO2 SiO2 + 2 C → Si + 2 CO
WELL ESTABLISHED
TECHNOLOGY!
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THE MOST INNOVATIVE ASPECT IS THE
USE OF A PLASMA TORCH TO TEST:
Extraction process for obtain metallurgic
grade Silicon (Si) from contaminated
sediment
Separation of metals
SEDIMENT +
CARBON
Destruction of hydrocarbons
(~20% Si + pollutants)
Treatment of the finest sediment
component, that is usually characterized
by a pollutant content higher than sandy
fractions.
SEDIMENT
(~20% Si + pollutants)
VITRIFIED SLAG
SiO2 + C → Si + CO2
Advantages:
 avoid treatment phase;
 silicon of metallurgic grade for commercial use.
Advantages:
 could be re-used as secondary raw material in
engineering works.
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EXAMPLE OF INDUSTRIAL SCALE 2 MW PLASMA REACTOR WITH A DC ARC (Tetronics)
THE COST FOR A 500 kW PROTOTYPE
FOR SEDIMENT TREATMENT WOULD BE
VERY HIGH FOR A RESEARCH PROJECT.
PLASMA TREATMENT WILL BE DONE
AT LAB-SCALE USING UNIBO-DIEM
PLASMA TORCH.
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RF PLASMA TORCH AT THE UNIVERSITY OF BOLOGNA – DIEM
TEKNA PL-35 TORCH
POWER: 35 kW
GAS: Ar, N2, Air, O2, H2
Powder injection from 10 m to 150 m
diameter
Vacuum reaction chamber for controlled
atmosphere treatments
Graphite substrate and
deposition experiments.
holder
for
LAB SCALE TREATMENT:
- high flexibility
- relatively low costs
- small quantities of sediment needed for
each test
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SEDIMENT + CARBON
Ar + H2
SILICON
EXTRACTION
SEDIMENT
FROM
CRITICAL ASPECTS:
PLASMA TORCH
(T ≈10,000 K)
CO2
(from the reduction
of SiO2)
+ VOLATILIZED
POLLUTANTS
HYDROCARBO
N AND
COMPLEX
MOLECULES
PYROLISIS
MOLTEN BATH
(~2,000 K)
SLAG
METALLIC PHASE
GRAPHITE
CRUCIBLE
 Purity of the Si metallic phase
(metallurgical grade si is 98 % pure)
 % of Si that can be extracted by the
sediment
 Carbon must not exceed SiO2 in order
to avoid SiC formation
 Volatile metals (Cd, Pb, Hg) will be
vaporized and must be collected from
the exhaust gas
 In order to vitrify the slag some SiO2 is
needed and will not be available for
silicon extraction
 Estimation of the operating costs of a
full scale process
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SEDIMENT
VITRIFICATION OF SEDIMENT
Ar + H2
CRITICAL ASPECTS:
 Vitrification depends on the SiO2
content
 Volatile metals (Cd, Pb, Hg) will be
vaporized and must be collected from
the exhaust gas
 Vitrified slag can be reused as
construction material
 It could not be economically feasible
PLASMA TORCH
(T ≈10,000 K)
HYDROCARBO
N AND
COMPLEX
MOLECULES
PYROLISIS
VOLATILIZED
POLLUTANTS
MOLTEN BATH
(~2,000 K)
VITRIFIED SLAG
GRAPHITE
CRUCIBLE
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PREVIOUS UNIBO RESEARCH ACTIVITY ON PLASMA TREATMENTS
Laboratorio ENVIREN
Regione Emilia-Romagna - Misura 4
“Sviluppo di rete”
Azione A – Laboratori di ricerca e
trasferimento tecnologico
Bando del 26/11/2007 (DGR n,1853/2007)
VITRIFICATION OF INCINERATOR BOTTOMASH AND FLY-ASH .
THIS ACTIVITY SHOWED THE FEASIBILITY OF
LAB-SCALE
PLASMA
TREATMENT
TO
REPRODUCE THE FULL SCALE INDUSTRIAL
PROCESS.
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ANALYSIS OF VITRIFIED BOTTOM-ASH AND FLY-ASH SLAG
Fe BALL WITH Ne AND Cu.
EVIDENCE OF SEPARATION BETWEEN
VITRIFIED MATERIAL AND METALS.
Leechability of vitrified slag is below limits
BOTTOM-ASH + GLASS
BOTTOM-ASH
FLY-ASH + GLASS