asphaltene fluidised bed combustion - ffrcffrc.fi/liekkipaiva_2018/b4.pdf · • ecopetrol is the...
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24.10.2018 VTT – beyond the obvious 1
Asphaltene fluidisedbed combustion
Jaqueline Saavedra Rueda1
and Toni Pikkarainen2
1 Ecopetrol, 2 VTT
2
Background and motivation
• What is asphaltene?
• Why fluidized bed combustion?
Experimental work
• Test rig and fuels
• Test matrix
Results
• Burning times
• Sulphur release/capture
Summary
3
ECOPETROL & Business Group
4th Latin American Petroleum
40th world production
9000 employees
Ecopetrol & business group includes 19
companies: exploration, production, transportation,
refining, petrochemical, commercial, corporate…
• Ecopetrol is the largest company in Colombia and is an integrated company in the oil chain.
• In addition to Colombia, where it generates more than 60% of national production, it has a presence in exploration and production activities in Brazil, Peru and the United States (Gulf of Mexico).
• Ecopetrol has the largest refinery in Colombia, most of the pipeline and pipeline network in the country and is significantly increasing its participation in biofuels.
Owned by
Ministry of
Economic Affairs
and Employment
4
VTT – impact from excellence
Established in
1942
258M€Net turnover and
other operating
income (VTT Group
2017) 2,368
Total of personnel
(VTT Group
31.12.2017)
36%from abroad (VTT
Group 2017)
27%Doctorates and
Licentiates
(VTT Group
2017)
VTT Technical Research Centre of Finland Ltd is one of the leading research, development and innovation organizations in Europe. We help our customers and society to grow and renew through applied research. The business sector and the entire society get the best benefit from VTT when we solve challenges that require world-class know-how together and translate them into business opportunities.
OULU
KAJAANI
KUOPIO
TAMPERE
JYVÄSKYLÄ
ESPOO
SODANKYLÄ
OUTO-KUMPU
VIHTI
RAJAMÄKILAPPEEN-RANTA
5
Background and motivation
• What is asphaltene?
• Why fluidized bed combustion?
6
What is asphaltene?
The deasphalting process, developed by ECOPETROL SA, has as main objective the
processing of heavy and extra-heavy oil loads for the partial improvement of its transport
properties.
Main streams from the process are deasphalted crude oil (DAO) and a solid intermediate
stream, composed of asphaltenes and resins precipitated during the process.
The solids, composed mostly of asphaltenes,
correspond to the heaviest fraction of the crude oil
and once removed, they become an undesirable
product because they are classified as highly
contaminant.
7
Why fluidized bed combustion?
Ecopetrol was searching technological alternatives to utilize
asphaltenes as a fuel in generation of steam and/or electricity in
their oil production fields.
Advantages of circulating fluidized bed combustion technology:
• The widest fuel flexibility (with a single design)
• Sulphur capture in furnace (typically FGD not needed)
• Very low NOx levels due to low and uniform temperature level
• High combustion efficiency due to long residence time and high
mixing
The viability of fluidized bed combustion technology was evaluated
by bench scale testing carried out by VTT.
The bench and (on-going) pilot scale tests with techno-economic
assessment will give a valuable knowledge of the behavior of the
fuel and that information can be taken into account when designing
the boiler for a certain fuel, protects investment and minimizes
environmental impacts.
Source: Valmet
8
Experimental work
• Test rig and fuels
• Test matrix
24.10.2018 VTT – beyond the obvious 9
Bench scale BFB
24.10.2018 VTT – beyond the obvious 10
Fuels – asphaltene and petcoke
Both the fuels have low ash content, high sulphur content, quite high nitrogen content
and high heat value.
Asphaltene contains significantly more volatiles than petcoke whereareas fixed carbon
content of petcoke is higher.
Based on fuel analyses it can be expected that asphaltene is much reactive (shorter
combustion time) than petcoke and achieving of low SO2 and NO emissions would be
challenging for both the fuels.
Analysis Unit Asphaltene Petcoke
Moisture w-% a.r. 1.4 0.8
Ash (815ºC) w-% dry 0.7 0.3
Ash (550ºC) w-% dry 0.7 #N/A
Volatiles w-% dry 59.4 10.4
HHV MJ/kg dry 38.92 35.98
LHV MJ/kg dry 37.18 35.15
LHV MJ/kg a.r. 36.64 34.83
Carbon w-% dry 84.6 90
Hydrogen w-% dry 8.2 3.9
Nitrogen w-% dry 1.55 1.94
Sulphur w-% dry 4.57 3.06
Oxygen w-% dry 0.3 0.8
Chlorine w-% dry 0.041 #N/A
24.10.2018 VTT – beyond the obvious 11
Test matrix
Test matrix of batch feed tests included 8 tests:• with two fuels, asphaltene and petcoke (reference fuel)
• at two bed temperatures, 800ºC and 900ºC
• without and with limestone addition (limestone calcium to fuel sulphur ratio Ca/S=3.0 mol/mol)
Combustion air (100% prim. air) was diluted by N2 to contain 10 %-vol of O2
Each batch test was repeated 4 times to ensure repeatability.
12
Results
• Burning times
• Sulphur release/capture
13
Determination of time instants
Times for 50% and 90% combustion
(of carbon) and sulphur release
were determined based on O2
consumption and flue gas SO2
concentration
These t50% and t90% characterise the
fuel combustion reactivity and
sulphur release
Also total mass of released sulphur
was determined to evaluate sulphur
capture by limestone addition
0
0.2
0.4
0.6
0.8
1
0 30 60 90
mas
s/in
itia
l mas
s
Time (s)
Fuel
Sulphur
t50% t90%
14
Fuel and sulphur conversion
Asphaltene at 800ºC Asphaltene at 900ºC
Petcoke at 800ºC Petcoke at 900ºC
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
ma
ss/i
nit
ial m
ass
Time (s)
Fuel
Sulphur
0
0.2
0.4
0.6
0.8
1
0 20 40 60 80 100
ma
ss/i
nit
ial m
ass
Time (s)
Fuel
Sulphur
0
0.2
0.4
0.6
0.8
1
0 60 120 180 240 300 360
ma
ss/i
nit
ial m
ass
Time (s)
Fuel
Sulphur
0
0.2
0.4
0.6
0.8
1
0 60 120 180 240 300
ma
ss/i
nit
ial m
ass
Time (s)
Fuel
Sulphur
Much shorter conversion times for asphaltene than for petcoke
Two combustion stages can be distinguished: 1) rapid release and combustion of volatiles and
2) slower combustion of char
15
Combustion reactivity50% and 90% burning times
Asphaltene is much more reactive than petcoke
Increase in temperature increases the burning rate (decreases the reaction times)
for petcoke
The temperature has no practical effect on the reaction times for asphaltene
16
SO2 formation and capture
Sulphur capture was relatively poor by limestone for asphaltene and fair for petcoke.
At 800ºC no sulphur was captured with asphaltene and ~20% with petcoke.
At 900ºC a small share (~15%) of sulphur was captured by limestone with asphaltene and
relatively high share (~50%) with petcoke.
Released mass of sulphur per
mass fuel combusted (expressed
by columns to left y-axis) and
share of captured sulphur by
limestone (expressed by points to
right y-axis)
24.10.2018 VTT – beyond the obvious 17
Summary
18
Summary 1/2
The objective was to characterize asphaltene – a residue from oil refinery –
fluidized combustion and emission formation and compare them with
petcoke.
Circulating fluidized bed combustion technology was selected based on its
maturity, fuel flexibility, low emissions and high efficiency.
Chemical composition of asphaltene
was as expected: low ash and moisture
contents, and high volatiles and sulphur
contents.
• In contrast, petcoke have low volatile
content with otherwise quite similar
composition compared to asphaltene.
Source: Sumitomo SHI FW
19
Summary 2/2
Asphaltene was characterised as very reactive compared to petcoke. The
combustion time for asphaltene was some 4-times shorter than for petcoke.
• The short combustion time means rapid heat release and possible risk for
“hot spots” near the fuel/air feeding locations.
Sulphur capture by limestone was relatively poor for asphaltene and fair for
petcoke.
• Achieving a good in-furnace sulphur capture efficiency with asphaltene by
limestone will be challenging.
For asphaltene some softening and
sticky behaviour was observed even in
temperatures far below 100ºC.
• Fuel feeding system should be
carefully designed to avoid problems.
24.10.2018 VTT – beyond the obvious 20
Thank you!Questions!