Hydrocarbon Processing - October 2021 - 46

Plant Safety and Environment
depends on the design of the probe and
the presence of internals.
The probe tip may be a thermocouple
for thermal profiling or a sintered metal
filter for gas sampling or pressure recording.
The thermocouple and pressure
readings are data logged for transfer to a
computer for analyses. A pre-pressured
gas sample cylinder, with inlet and outlet
valves, is filled with inert gas to very high
pressure and attached to the filter outlet
valve. The higher cylinder pressure is
used to clean the probe sample line and
filter. The sample cylinder is completely
de-pressurized and reopened to take fluid
bed gas and later analysed in the laboratory.
The movable probe is re-positioned
to obtain radial profiles. This technique
may require a short fluid bed shutdown to
mount the equipment on reactor nozzles.
The fixed-point detectors will require
a shutdown for installation of stationary
thermocouples or sintered metal filters at
various locations of interest inside the fluid
bed. Fixed-point detectors can provide
temperature, gas analysis and bed density
measurements. Density is obtained using
two paired pressure probes aligned axially
at suitable separation.
Commercial reactor diagnostic result.
A large-scale fluid bed operating < 500°C
and < 3 barg was analyzed using audio, a
movable probe and fixed-point detectors.
The overall reaction was (Eq. 2):
HYDRCARBON + O =
PRODUCT + CO + CO2
(2)
FIG. 2 provides the results of both audio
and movable probe analyses. The audio
data was qualitative and indicated the
loudest sound was in the northeast quadrant.
The movable probe data showed no
change in the temperature and chemistry
[carbon monoxide/carbon dioxide (CO/
CO2
rant of the reactor sampled.
Several
) ratio] within the southwest quadfixed-point
thermocouples
and
aligned paired sample filters were
installed at the same elevation during a
major shutdown. After steady-state operation,
the radial thermal profile was
mapped, as shown in FIG. 3. The radial
temperature profile indicated higher temperatures
in the northeast quadrant area
where the audio sound was the loudest.
The aligned, paired sample filters were
also used for composition, delta pressure
reading and bed density calculations. The
results are shown in FIG. 4.
The lower CO/CO2
and lower bed
density were in the northeast quadrant,
which is consistent with audio and temProbe
data set2
Probe,
% of
diameter
10%
25%
40%
Temp,
delta degree
of bed avg
+1
-1
+1
CO/CO2
1
0.97
1.02
FIG. 2. Audio and movable probe data.
,
fraction
of exit
Position,
#
#1
#2
#3
#4
#5
Reaction CO/CO2
fraction of exit
0.98
0.78
0.97
0.97
1.02
,
Bed density,
% mean value
103.1
68.6
100
96.9
109.4
FIG. 4. Gas samples and bed densities.
Takeaway. All techniques used yielded
the same conclusion.
STEPHEN JORDAN has more than
50 yr of experience for several large
international companies as a seniorlevel
engineering, design, projects,
commissioning, plant startup and
data analysis for 13 processes,
including coal gasification, fluid bed
Item
Center
20%
40%
TC-1
TC-2
Temp (+/-)
-1 to +1
-1 to +1
-1 to +1
+2 to +8
+1 to +6
FIG. 3. Temperature radial profiles.
46 OCTOBER 2021 | HydrocarbonProcessing.com
Material
#1
#1
#1
#2
#2
#2
Length,
meters
0.6
1.5
3
0.6
1.5
3
Reaction CO/CO2
fraction of exit
1
0.98
1.02
1.02
0.97
1.02
FIG. 5. Chemistry test on tubing material
and length.
BEHZAD JAZAYERI is a subject
matter expert with more than
40 yr of experience in process
engineering, technology
development, process scale-up,
and applications of fluidized beds
and gas-solid systems. He has
performed more than 50 techno-economic analyses
and has designed 30 pilot plant and first commercial
plants using fluids beds, 15 of which were built and
operated. His background includes bio-conversion,
coal gasification, chemical synthesis and polysilicon.
,
and solid processes, and chemical production. He has
managed or supported grassroot startups for several
domestic and international projects. He has extensive
experience with the operation of small- to large-scale
pilot plants, first commercial plants, as well as
laboratories, manufacturing, engineering, R&D, and
acting as an expert witness.
perature profiles. A simple test was conducted
to measure the effects of probe
tube length and tubing material of construction
on gas sample results. Two different
materials were used with three different
lengths inside the fluid bed. The
sample filters were tightly packed in a 15cm
circle located in the southeast quadrant.
The results are shown in FIG. 5.
The length and material of tubing
had no effect on sample tubing time exposure.
Since the reaction CO/CO2
is
expressed as a fraction of the fluid bed
exit gas CO/CO2
ratio, it was concluded
that the sintered metal filter was also not
changing the sample composition.
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