A NEW LASER FAST PYROLYSIS DEVICE
WITH IMAGING OF PARTICLES AND ON-LINE ANALYSIS OF VOLATILES
A. Dufour*a, S. Beckerb, H. Le Galla, M. Weberb, O. Dufauda, Y. Le Brecha, G. Mauviela, G. Parentb
b
a LRGP, CNRS, Université de Lorraine, ENSIC, Nancy, France
LEMTA, CNRS, Université de Lorraine, Vandoeuvre les Nancy, France
*anthony.dufour@univ-lorraine.fr
What is the real temperature of particles during their fast pyrolysis?
The real temperature of particles during their fast pyrolysis remains unknown due to the lack of real-time imaging of
the temperature during the reaction. Most of the fast pyrolysis micro-reactors present huge thermal lags of several
dozens of degrees [1,2]. Indeed the true heating rate and temperature of reacting particles can be different than the
heating rate and temperatures of the heating source [3,4]. Furthermore the temperature given by thin thermocouples
may not be accurate under fast conditions (thermal lag between the reacting particles and the thermocouple).
A novel device is under development at CNRS Nancy
The global concept of the set-up is based on 4 main features:
1) a well-controlled laser heating system combined with :
2) the imaging of the real temperature of particles;
3) the visual imaging of the shape of particles (bubbles, aerosols, etc.);
4) on-line analysis of volatiles by photoionisation mass spectrometry [5].
Filters on a
wheel
Mirror
Sampling
to PI-MS
Reactor in inox with various
windows in quartz (for visible
camera) & ZnSe (for pyrometry)
Particles
N2+ pyro
vapors
N2
Silica lamella
(20mm, 100µm)
ZnSe window
CO2 Laser
(180W, 10.2-10.8µm)
MCT
pyrometer
Control
of the
laser
Dichroic
beam
splitter
Beam
homogeniser
Mirror
The set-up is composed of:
- a high power (180W) CO2 laser emitting an IR light at 10.6µm;
- thin film (or particles) of solids/liquids are deposited over a silica
lamella (20mm, 100µm) absorbing the CO2 laser IR light;
- the laser heats the silica lamella and the temperature heating
program of this support is controlled by an advanced monitoring
system based on the analysis of lamella temperature with a MCT
pyrometer;
- the real-time temperature of particles undergoing pyrolysis is
measured by a multispectral IR camera (& pyrometer);
- the shape of particles (bubbles formation, aerosols ejection) is
analyzed by a fast visible camera;
- volatiles are sampled by a custom probe from the surface of
particles and are analyzed on-line by laser photoionisation mass
spectrometry (SPI and REMPI-MS) [5].
Preliminary results
500
Homogeneous heating of the lamella
Control of the lamella temperature
Good homogenity of heating on the surface
due to special laser beam homogeniser
Fast monitoring (response time of the
pyrometer: 30ms) with a custom FPGA
National Instrument system and custom
control interface of the laser (triggered
with the mass spectrometer).
Heating
time
Excellent
homogeneity
of temperature
on ~10mm
diameter of the
silica lamella
(total diam.
20mm)
Temperature of the lamella (°C)
Multispectral
pyrometer + camera
InSb (1.5-5µm)
Thermal imaging of
real temperature of
particles during
pyrolysis
On-line mass
spectrometry
Visible fast
imaging of
Material to be
the shape of
pyrolysed
particles
deposited over
a silica lamella
Heating by
CO2 laser
Set
temperature
Measured temperature
400
300
410
405
400
200
400
395
390
350
100
6
300
3.5
4
4.5
6.5
7
7.5
8
5
0
0
Snapshot of
the custom
interface for
controlling
the laser
2
4
6
Time (sec)
8
10
Good control of heating (up to 500K/s)
and good stability (5K variation at 400°C)
Future work
Visible image
(movie) of
lignin pyrolysis
Triggering all the signals (laser,
pyrometers, cameras, mass
spectrometer)
(1s to 400°C then
10sec. at 400°C)
Improving the resolution of images
Other analysis under-development
Temperature (°C)
References
[1]
[2]
[3]
[4]
[5]
Energy Fuels, 25 (1), 370-378, 2011.
Energy Fuels 23 (2), 993-1006, 2009.
JAAP, 113, 1-14, 2015.
Energies 3(4), 886-898, 2010.
Energy Fuels, 30 (3), 1555–1563