Foam Characterization Using Glass Coker Experimental Set Up

8/3/2019 Foam Characterization Using Glass Coker Experimental Set Up

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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.

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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
http://www.engineeringpapers.blogspot.com/http://www.engineeringpapers.blogspot.com/

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Foam Characterization Using Glass Coker Experimental Set Up