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FOAM CHARACTERIZATION USING GLASS COKER
EXPERIMENTAL SET UP
Document by:Bharadwaj
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Abstract: A large number of industrial processes specially in the petroleum refinery
sector undergo problems with foaming which leads to fouling and decay of the process
equipments. Thus in certain cases in petroleum refineries, foaming leads to process
inefficiency and higher equipment maintenance cost. A very relevant aspect of current
petroleum refinery operations is the heating up of vacuum residue in a coke drum and the
subsequent generation of unwanted foam. This research paper describes the foam
produced by heating vacuum residue in a Glass Coker experimental set up in terms of
foam over temperature. The vacuum resids for analysis were obtained from Major U.S.
oil companies like Chevron, Shell, Petrobras, etc. Detailed plots are provided that
illustrate the variation of foam over temperature for different vacuum resids and with
different times during a Glass Coker run. The experimental results clearly lead to the fact
that foaming during a Glass Coker run is dependent on the residue (feedstock) properties
and run operating conditions.
Keywords: Glass Coker, foam over, foam, vacuum residue, experiments, petroleum
refinery
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Introduction
In oil/gas production, foaming is a serious issue and if left unattended, can lead to
unexpected process shutdowns. In literature [1], Callaghan et al. pointed out that the
foaming tendency of crude oil is directly proportional to the concentration of asphaltenes.
Kremer et al. [2] are very precise and point out that the vapor generation and the presence
of natural surfactants like asphaltenes and resins are crucial towards foam growth and
lead to enhanced foaming in delayed cokers. According to Guitian and Joseph [3], the
foam producing capability of a hydrocarbon mixture is dependent on the surfactant and
on the mixture components chosen to create the foam. Zaki et al. [4] point out that the
viscosity of the feedstock and asphaltene aggregation play an important role towards
foam growth. As per Joseph [5], the presence of surfactant is crucial for a gas-liquid
mixture to foam. As per Kouloheris [6], the amount of surfactant added to initiate
foaming has a very large effect in the generation of foam.
In the present study, a glass coker was constructed and testing was begun for the purpose
of visually observing and measuring foam formation under carefully controlled coking
conditions. The tests were performed in 2005 in the TUDCP Pilot Plant, Tulsa,
Oklahoma, U.S.A. The experimental setup for the glass coker is shown in Figure 1.
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Figure 1: Experimental setup
The setup comprised of three main components: the distilling flask, the temperature
control system and the heavy liquid collection system. A Pyrex brand 250 ml distilling
flask with side arm was used as the reactor. The heating mantle was a Glass-Col series
STM heating mantle that had an operating temperature range from ambient to 650C. The
temperature was monitored using a Digitrol temperature controller that had an
operating range of 0-750C. It is used to monitor temperatures at different locations in the
flask (0.5, 3.5, 6.5 inches from the bottom of the flask). The vapors are condensed in a
flask that is submerged in a water bath. The entire device was wrapped in a molded
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insulating blanket. The test device was surrounded by a blast shield and tests were
conducted in a vent hood.
The vacuum resids tested with the Glass Coker setup are shown in Table 1. The detailed
feedstock properties for the resids tested are also shown in the same table. The first 16
tests were conducted where a window was left in the insulation to observe the foaming
phenomena taking place. A second series of tests were conducted where the reactor was
totally insulated. The test matrix for the glass coker tests performed are depicted in Table
2 and Table 3 respectively.
Table 1: Feedstock properties of the vacuum resids tested
Property Equilon
Resid
(Shell)
Citgo
Resid
Chevron
Resid
Suncor
Resid
Marathon
Resid
Petrobras
Resid
API 0.5 4.6 5.7 2.9 10.3 6.5
Asphaltenes
wt %
39.2 34.2 17.6 25.2 12.1 24.3
Metal
content, Ni
(ppm)
142 110 193 125 38 63
Metal
content, V
(ppm)
739 703 148 330 57 69
Sulfur wt % 5.51 3.09 2.16 5.76 2.62 1.45
Sodium 8 8 8 30 7 23
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(ppm)
Table 2: Test matrix of selected glass coker tests with partial insulation
Run ID Resid tested Date tested
CIT 1 Citgo 06/01/2005
CIT 2 Citgo 11/01/2005
PETR 7 Petrobras 03/02/2005
CIT 9 Citgo 02/03/2005
SUNC 11 Suncor 11/03/2005
CHV 12 Chevron 17/03/2005
CHV 15 Chevron 25/03/2005
EQU 16 Equilon 29/03/2005
Table 3: Test matrix of selected glass coker tests with complete insulation
Run ID Resid tested Date tested
MARA 18 Marathon 05/04/2005
MARA 19 Marathon 08/04/2005
SUNC 20 Suncor 15/04/2005
Experimental Procedure
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The following operating procedure was followed for all the runs except MARA 19 and
SUNC 20 runs:
Before the resid is poured, 1 gm of boiling stones was added to the flask and then the
resid to be tested was poured into the flask (61gms). The flask was placed into the
heating mantle, was wrapped with insulation on the sides and the thermocouples were
inserted into it after closing the top with a stopper. The heating mantle was connected
with the temperature controller which was connected to a power source. The tubing was
connected with the side arm and was sent to a liquid collecting receiver placed inside a
stainless steel beaker containing cold water. The area around the flask and the mantle was
covered with the insulation jacket. The blast shield was then put in front of the distillation
flask. The first stage of heating was achieved by heating the resids to 600F with the
output clamped at 25%. The ramping during the second stage of heating from 600F to
850F was started after the stabilization of the bottom temperatures for each resid. Also
the ramping was done non-uniformly on an as-needed basis in order to reach 850F as
efficiently as possible. At the end of the run, the ramping was stopped and the power
settings were kept constant.
For MARA 19 and SUNC 20 runs, the same operating procedure was followed, the only
difference being that at 42 mins into the run, the ramping was started by gradually
increasing the power settings 3% every 5 mins.
Results & Discussion
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The bottom thermocouple temperature was recorded carefully versus time for the glass
coker runs. A foam over used to take place at a particular period of the runs with
extensive foaming. The bottom thermocouple temperature rose from 800F and exceeded
1000F within a couple of minutes. The side arm of the distillation flask was found to be
coated with resid. Table 4 and Table 5 provide the foam over data recorded for the
partially insulated and completely insulated glass coker runs.
Table 4: Observations for selected partially insulated runs
Run ID Foam over TB (F) First Foam over time
during a run (mins)
PETR 7 846 117
CIT 9 833 94
SUNC 11 833 80
CHV 15 854 88
EQU 16 825 78
Table 5: Observations for selected completely insulated runs
Run ID Foam over TB (F) First Foam over time
during a run (mins)
MARA 19 889 69
SUNC 20 864 70
855
860
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Figure 2: Foam over Temperature variations for different partially insulated glass coker
runs
Figure 2 and Figure 3 illustrate the variation of the foam over temperatures for different
resids versus time during the run when foam over took place the first time.
895
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Figure 3: Foam over Temperature variations for 2 different completely insulated glass
coker runs
Conclusions
For the partially insulated glass coker runs, the vacuum resids containing higher
concentration (wt%) of Asphaltenes (example-Equilon, Citgo resids), the foam over
temperatures are lower (820-840F) as well as the time taken to produce foam for the
first time (70-100 mins). So foam is readily and quickly produced from the tests using
vacuum resids with high content of Asphaltenes. For the completely insulated glass coker
runs, the foam over temperatures are significantly lower for the resids with greater wt%
of Asphaltenes (refer to Figure 3- Suncor vs Marathon resid). In general foaming
tendencies were found dictated by variation in feedstock property (wt% Asphaltenes) and
run operating conditions (total or partial insulation, non-uniform or uniform ramping for
heating the resid).
Nomenclature
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CIT- Citgo resid
PETR- Petrobras resid
SUNC- Suncor resid
CHV- Chevron resid
EQU- Equilon (Shell) resid
MARA- Marathon resid
Foam over TB- Bottom thermocouple temperature (F) at the foam over stage
Acknowledgements
I would like to thank The University Of Tulsa Delayed Coking Project Team, U.S.A. for
their generous support and help regarding the successful conduction of the experimental
work. I would also like to specially thank Dr. Keith Wisecarver and Dr. Volk (The
University Of Tulsa Delayed Coking Project Team, U.S.A.) for their active suggestions
during the pilot plant experimental work.
References
1. Callaghan et al., Identification of Crude Oil Components Responsible for
Foaming, SPE Journal, 25(2), pp. 171-175 (1985).
2. Kremer et al., Foam Control Methods in Delayed Cokers, Petroleum
Technology Quarterly, pp. 65-69 (2002).
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3. Guitian J., Joseph D., Foaminess Measurements Using A Shaker Bottle,
University of Minnesota (1996).
4. Zaki et al., Factors Contributing to Petroleum Foaming. 2. Synthetic Crude Oil
Systems,Energy Fuels, 16(3), pp. 711-717 (2002).
5. Joseph D.D., Understanding Foams and Foaming, Journal Of Fluids
Engineering, 119(3), pp. 497-498 (1997).
6. Kouloheris A.P., Foam-friend and foe, Chemical Engineering, 94(15), pp. 88-
97 (1987).
Document by:Bharadwaj
Visit my website
www.engineeringpapers.blogspot.comMore papers and Presentations available on above site
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