HEAT EXCHANGER TUBE INSERTS -

AN UPDATE WITH NEW APPLICATIONS IN CRUDE DISTILLATION UNIT

VACCUM APPLICATIO AND REBOILERS

By:

Francois Pouponnot, Petroval, France

e-mail: f.pouponnot@petroval.com

Artur W. Krueger, Senior Consultant, Petroval, Houston

e-mail: art.krueger@att.net

Presented at:

AIChE Spring Meeting

April 23 - 27, 2006

Disney’s Dolphin Hotel, Orlando, FL

ABSTRACT

Heat exchanger tube inserts have been used for many years as reliable means for heat transfer enhancement and fouling mitigation in petroleum refineries and chemical plants.

In this paper, we will present several new application examples for optimization of heat exchangers and related equipment, resulting in enhancement of the function of such equipment and improvement of on-line availability of the plant.

Usual insert applications in refining pre-heat trains continue to give good performances for fouling mitigation and heat transfer conservation. For the refiner, this improvement brings interesting energy savings but also longer run times with better overall performance of the pre-heat train. Tube inserts are largely used in CDU and VDU applications.

In some new applications such as reboilers (liquid and mixed phase flows), the observed efficiency was valuable because the shorter initial service times have been

expanded substantially (in some cases 4 to 6 times longer than the initial service time), and with higher efficiency levels achieved during this extended service time.

Some of these applications and results are described in this paper.

I. TUBE INSERT DESCRIPTIONS

a. SPIRELF

The Spirelf system falls within the category of "on-line mechanical cleaning devices". The principle is based on the insertion of flexible metal devices, in spiral form, into the tubes of "shell and tube type" heat exchangers. The devices are stretched over the length of each heat exchanger tube and are held in place by straight wires at each end (inlet and outlet).

Fig. 1a

Fig. 1b Fig 1c

OPERATING PRINCIPLE

After installation the insert stays under tension. Under the effect of the circulating flow, it enters into vibrations, radially and axially. The repeated contact between the loops of the devices and the inner tube wall has two effects:

• prevent the formation of deposits, • break the boundary layer in the tube side flow.

As a consequence, the mechanical effect of the SPIRELF system reduces fouling build-up inside heat exchanger tubes and the turbulent effect achieves an improvement of the heat transfer rate (the internal heat transfer coefficient is multiplied by 1.8). Overall the sum of these two effects results in a reduction of the apparent fouling factor by as much as three-quarters.

b. TURBOTAL

The Turbotal system falls within the category of "on-line mechanical cleaning devices". The main aim of Turbotal is the control of fouling in heat exchangers. The principle is based on the insertion of rotating metal devices, in rigid helicoidal form, into the tubes of "shell and tube type" heat exchangers.

Fig. 2a

Fig. 2b

HELICOIDAL DEVICE ROTATING BY THE FLUID FLOW

Fig.2 c

OPERATING PRINCIPLE

Turbotal is a system, which is held at the inlet of tubes by a fixing device allowing the mobile to rotate around its axis by means of the fluid flow.

This rotation causes a high turbulence in the flow and improves thus the internal heat transfer coefficient. As the boundary layer is continuously renewed, the wall temperature is lowered and fouling is slower. Combined with the mechanical effect of the rotation, TURBOTAL has a preventive effect against fouling with this two effects:

• prevent the formation of deposits, • break the boundary layer in the tube side flow.

The TURBOTAL is extremely versatile. The rotation speed can adapt itself according to the operating conditions. The TURBOTAL is able to cope with :

• flow rate variation • fluid properties variations (viscosity, density...) • accidental vaporization (caused for instance by massive water occurrence)

The fixing device of the coil is placed at the outside of the tube. The design of the coil itself is adapted for each case to the geometry of the tubes and the process conditions. As a consequence, the mechanical effect of the Turbotal system reduces fouling build-up inside heat exchanger tubes and the turbulent effect achieves an improvement of the heat transfer rate (the internal heat transfer coefficient is multiplied by 1.8). Overall the sum of these two effects results in a reduction of the apparent fouling factor by as much as three-quarters.

c. AREAS OF APPLICATION OF TURBOTAL AND SPIRELF

Due to the operation principle, Turbotal and Spirelf devices can be used in all multi-tubular heat exchangers with straight tubes, where deposits within the tubes are found.

The Turbotal and Spirelf system applies:

• to all fluid up to 360°C-680°F, • in a liquid phase, • where flow velocities are between 2 and 6 ft/s (0.6 to 3.0 m/s) inclusive, • in pipes of an outside diameter between 1/2 and 2 inches inclusive • in tubes of length between 10 and 33 ft inclusive.

The first applications were in the refinery industry, particularly in atmospheric distillation preheat trains in which the fight against fouling is crucial. Nowadays Turbotal and Spirelf systems can also be applied to other industries, such as chemical and petrochemical applications.

d. FIXOTAL

Fig. 3a

Fig. 3b

Fig. 3c

FIXOTAL is a fixed device, which has been developed by TOTAL. Its function is primarily to increase the thermal efficiency of tubular heat exchangers and also to reduce the tubes fouling rate.

DESCRIPTION OF THE DEVICE

FIXOTAL consists of a wire coil, which is inserted inside every tube, with the wire in firm contact with the inside tube wall. Once in place, the device has no possibility of the slightest displacement (no vibration, no rotation, and no translation), the device can be easily removed if necessary.

The main effect of the wire is to create a turbulence effect, thus decreasing the boundary layer at the wall. The result is a significant increase of the tube side heat transfer coefficient, resulting in of a moderate increase of pressure drop through the tube. This has two major consequences :

• Increase of the thermal efficiency of the exchanger, due to an increase of the overall heat transfer coefficient. The extent of the gain depends on the split of the overall heat transfer resistance between the inside and the outside tube surface.

• Decrease temperature gradient between tube wall and bulk. This leads to a decrease of the tube side surface fouling rate, especially with fouling which is wall temperature dependant.The parameters influencing the heat transfer enhancement and the pressure drop have been investigated at pilot scale for one & two-phase flows.

To summarize, FIXOTAL is easy to install technology, which increases the thermal efficiency of tubular heat exchangers and also reduces their tube side fouling rate.

Its key advantages are :

• sustain of heat duty • reduction of fouling • debottlenecking aspect for existing undersized equipment

Fig. 4: U-tube equipped with Fixotal

II. APPLICATIONs OF TUBE INSERTS TO OIL REFINERIES

Spirelf, Turbotal and Fixotal are especially well adapted to the use in crude oil units, where the main fouling layer is composed by asphaltenes. In this application, the aim is primarily energy efficiency but also to improve maintenance management through extension of exchanger run times which at the same time results in improved throughput capacity.

Other units that can be equipped by Spirelf, Turbotal and Fixotal are desulphurisation units, hydrotreaters, with the condition of liquid phase tube side of the exchangers. Application on Naphtha, Kerosene, Gas Oil Light Crude Oil have been developed for several years successfully.

a. Main advantages of Spirelf, Turbotal and Fixotal

Spirelf, Turbotal and Fixotal installation and use do not require any modification of the heat exchanger.

Increased heat transfer rate :

• through higher flow turbulence (inner heat transfer coefficient -X 1.8) • reduction of fouling and coking in heat exchanger tubes • result : energy savings of up to US $ 500,000 per year, example : EEC

installation -23,800 barrels or 3 400 tons of oil equivalent/year. • Average cost/benefit ratio: 1 : 5

Reduction of maintenance work/ cost :

• decrease of exchanger cleaning through reduction of tube side fouling • extended run time through increase of cleaning intervals example: for unequipped exchangers = 6 month cleaning cycles, for equipped exchangers = 12-20 months cleaning cycles • extended tube life/reduced leakage due to reduction of under-layer corrosion • designed to avoid mechanical tube erosion.

De-bottlenecking improved throughput capacity :

• improved operating conditions at main column through equipment of pump around/reflux line exchangers

• in case of limited furnace capacity, increase of crude temperature possible by equipping exchangers directly

• before furnace (29 degr. F temperature increase documented compared to unequipped train)

• improved throughput capacity due to reduced need for exchanger cleaning (runtimes multiplied for equipped exchangers)

• better cooling of outgoing products to storage

b. Pressure drop

• Delta-P caused by Spirelf, Turbotal and Fixotal devices = between 1 and 3 psi or 0.1 and 0.2 bar per pass (depending on tube dimensions, crude type, flow velocity) Delta-P for two-pass exchanger = 3 psi or 0.2 bar (average value at 1 m/s flow velocity)

• Delta-P caused by fouling to be considered for comparison • Higher Delta-P resulting in increased flow turbulence (inner heat ~ transfer

coefficient X 1.8)

c. New cleaning frequencies

By experience : the cycle duration is generally multiplied by 2 sometimes by 3; which translates in avoidance of frequent cleaning operation. (depending on the tube diameter, the fouling degree...)

Cleaning frequency before a tube inserts equipment

Service time of tube inserts or new cleaning frequency if chemical cleanings are not used

6 months (Turbotal, Spirelf and Fixotal) 1 year to 1 ,5 year 1 year (Turbotal, Spirelf and Fixotal) 2 years to 3 years 18 months (Spirelf and Fixotal) 3 years and more

d. Typical installations

• crude preheat train (with crude flow tube side) last exchangers before furnace, pumparound/reflux lines, product lines to storage

• Retrofit installation • New exchangers to be equipped to improve exchanger performance/extend

anticipated run time.

e. Possible alternative solution

In order to be able to run for longer time, there is possibility to perform some chemical cleaning on line with Spirelf and Fixotal in place. Tube inserts are used in order to keep high heat transfer efficiency and the chemical cleaning at regular period is a solution to recover the initial efficiency during an extended service time.

Fig. 6

Heat Exchanger Fouling Trend

50.060.070.080.090.0

100.0110.0120.0130.0140.0150.0160.0

SOR

+1

SOR

+21

SOR

+41

SOR

+61

SOR

+81

SOR

+101

SOR

+121

SOR

+141

SOR

+161

SOR

+181

SOR

+201

SOR

+221

SOR

+241

SOR

+261

SOR

+281

SOR

+301

SOR

+321

SOR

+341

U-V

alue

Solvent Cleaning Effect

Spirelf Effect Without Spirelf

With Spirelf

III. INDUSTRIAL RESULTS : THE TURBOTAL SYSTEM - EFFICIENCY COMPARISON IN A CRUDE UNIT

a. Unit description

In November 2003, Turbotal has been installed in CDU 1 heat exchangers 8ABEF. In order to evaluate the efficiency of the Turbotal in these heat exchangers, a comparison study has been performed between the 2 branches of the pre heat train (one equipped 8AB, one unequipped 8EF, see fig below).

Fig. 7

After 1 year operation, an evaluation based on refinery results is prepared. Working performance of equipped heat exchangers is still around 40% higher than the unequipped ones. The observed extra DP (average value around 0.6 bars) due to Turbotal is in line with the normal extra DP evolution. Based on these experimental results, the energy savings generated by a better preheat train efficiency are already paid back.

b. Heat exchanger characteristics (tube side) (Used for expected for study/real)

• Unit: Crude Distillation Unit (Pre heat train) • Tube number / bundle: 1 424 • Tube length: 6,100 mm • OD / BWG: ¾” / 14 • Product tube / shell side: Crude / Atmospheric residue • Flow velocity (tube side): 1.1 m/s • Tube insert: Turbotal • Replacement frequency: 2 years

The working conditions since the installation have been stabilized and generally match with the expected working conditions in tube side.

% U increase due to tube insert

0%10%20%30%40%50%60%70%80%90%

100%

11/11/2003 11/01/2004 11/03/2004 11/05/2004 11/07/2004 11/09/2004 11/11/2004

% increase U

% U increase Eq/Uneq-1

Fig. 8

Heater

E 8 E E 8 F

E 8 A E 8 B

Equipped heat exchangers

Explanation of the evolution:

• Fouling part of the new tubes under Turbotal control, • Fouling stabilization in equipped tubes and turbulent effect for heat transfer

compared with fouling accumulation situation in unequipped ones.

According to the flow sheet, the shell side product is atmospheric residue which is usually a fouling product which strongly influences the global duty of the heat exchanger and against tube insert cannot work. The equipped heat exchangers are now running with 50% improvement for the duty compared than without. The fouling in tube side would be a very substancial limitation of the global heat transfer in these heat exchangers.

The Delta T (Outlet – Inlet) evolution between both branches has been quite significativelly improved due to Turbotal:

Average value for the first year inlet outlet Delta T DT after 1 year Flow rate value in 8AB (°C, tube side) 203 242 39 37 Flow rate value in 8EF (°C, tube side) 212 242 30 27

Tube inserts installation in heat exchanger 8AB increased the average DT during the first year by 9°C. A conservation of 9°C is possibly observed at the furnace inlet by using tube insert during this period. The final monitored Delta T is still +10°C

c. Energy savings evaluation

The interest of Turbotal installation is both cleaning effect and turbulent effect in tube side by mechanical action. As it has been observed in this heat exchanger, it brings some better heat transfer performance which help to keep higher outlet temperature of the heat exchanger and when it is installed into the most strategic heat exchanger, this thermal improvement can bring some money savings due to energy savings among others.

In this particular case, energy savings can be calculated as follow:

Energy saving calculation:

Data: normal crude flow-rate : 800 metric t/hr - specific heat of crude : 0.65 kcal/kg.°C at 210°C - furnace yield : 0.85 - heating power of fuel : 9,700 kcal/kg 1°C higher at the furnace inlet corresponds to a daily savings of: 800,000 x 24 x 0.65= 1,500 kg of fuel saved per day per °C 0.85 x 9,700 (9 bbl of fuel oil saved per day per °C) Energy savings during one year of run : 3,285 bbl of fuel oil per year per °C Based on 20 Euro / bbl for fuel oil: Euro 65,700 savings per year per °C

With Turbotal, it has been calculated during the 6 first months of last run that an improvement of 9°C is a realistic improvement in these heat exchangers.

Euro 591,300 savings per year per 9°C

Global energy savings over 1 year : Euro 591 300 during the first year

This estimate is based on energy savings during one year. Then the 18 additional months would generate only purely energy savings. Usually Turbotal installation generates also production loss savings and maintenance savings (if in between shutdown can be avoided).

d. Conclusion in this CDU

Results of efficiency improvement and technical characteristics of this evaluation are quite positive because it is in line with the expected results:

• The heat transfer improvement (“U” value) was at start of run around + 50% with an average value during the 6 first months around + 30 % and a final stabilization at + 20%. During the second semester, the duty increased from 20 % up to 50%. The increased was especially visible during a stabilized period between end of August and November 2004.

• This improvement results into higher outlet temperature of +10°C for equipped branch. And the average improvement is around +9°C.

• Energy savings are then better then initially expected • Pay back time in less than 6 months.

IV. INDUSTRIAL RESULTS : SPIRELF IN CDU

Fig 9.

General working conditions for this heat exchangers are: • 800 tubes and 2 passes on tube side (for each bundle), • Flow rate: 249 t/h (Fluid velocity:1.2 m/s), • Desalted crude is flowing tube side and Top pump around is in shell side, • Straight tubes 6,096 mm / OD 19,05 mm / BWG 14. • Cleaning frequency of 1.5 years, when the hydraulic limit is reached. • 0.3 bar SOR and 1.8 bar EOR • Heat exchanger situated just after the desalter • Strong fouling deposit has been observed at the cleaning time. After Spirelf installation, the fouling factor had been reduced to the minimal value and kept under optimal value and optimized working conditions. Since it is installed, the fouling factor is stabilized to a low value and no excessive extra DP had been observed.

V. INDUSTRIAL RESULTS : THE TURBOTAL SYSTEM – INBETWEEN REMOVAL

Fouling Factor surveyExchangers T29&T30

0

10

20

30

40

50

60

70

0 40 80 120 160 200 240 280 320 360 400 440 480 520 560 600 640Duration in days

m2 .°C.h/kcal x 10 000

T29

T30

18 months run with Turbotal

Turbotal Removal

and cleaning

Fig. 10

After 18 months operation Turbotal had been removed because of production unexpected turnaround for a specific problem. The normal shutdown planned for 6 months later, the refinery decided not to install Turbotal for only 6 months but to go on without it during the final part of the run. The fouling factor increased dramatically without Turbotal where as it was under control during the period with Turbotal. At the shutdown, they reinstall the Turbotal in order to keep control with fouling factor. In this case the fouling factor evolution (slope) had been reduced by more than 3 time the one without tube inserts.

Since November 2002, this 2 heat exchangers are equipped with Spirelf with the idea to run and to perform some chemicals cleaning every years.

VI. INDUSTRIAL RESULTS : VDU APPLICATION - RELIABILITY ENHANCEMENTS WITH THE “FIXOTAL SYSTEM”

Heat exchanger characteristics

• Unit: Vacuum Distillation Unit (Pre heat train) • Position in the pre heat train: Before the furnace • Tube number / bundle: 1200 • Tube length: 6,100 mm • OD: 1” • Replacement frequency: 3 years (since 1998) • Product tube / shell side: Atmospheric residue / bottom reflux • Flow rate (tube side): 400 t/h

Installation problematics

Before installation, the heat exchanger was 6 passes with a strong problem of efficiency due to:

• Strong fouling even with high fluid velocity (around 2.2 m/s) • Short residence time (compared with the effective heat transfer coefficient

with fouling)

Observed results and production constraints:

• Poor heat transfer efficiency • High extra DP due to fouling • Cleaning frequency of 6 months • Furnace bottleneck because of lower inlet temperature

Decided modifications:

• Pass configuration modification: from 6 to 2 passes (Flow velocity from 2.2 to 0.8 m/s)

• Fixotal installation

Expected results:

• Reduction of pass number: increase of residence time and global heat transfer. Strong increase of the fouling is foreseen (X3).

• Fixotal installation: fouling mitigation and heat transfer increase by efficient turbulent effect at the tube wall.

Observed results :

• Efficient heat transfer coefficient during the run • Comparable service time • Chemical cleaning every 6 months to recover periodically the initial

performance.

Fouling factor evolution in VDU

0 15 30 45 60 75 90 105

120

135

150

165

180

195

210

225

Days

Rf (

m2.

K/W

)

Initial curve (6 passes configuration)Expected curve (2 passes without Fixotal)Observed curve (2 passes with Fixotal)

Fig. 11

Conclusion:

• Good thermal efficiency due to pass number reduction and Fixotal installation • Good fouling mitigation due to Fixotal. Comparable fouling evolution whereas

it should have been 3 times more severe and bring quite strong problem of the service time and production enhancement.

Chemical cleaning every 6 months in order to recover the initial efficiency but without removing Fixotal. A replacement is expected every 4years.

VII. INDUSTRIAL RESULTS : REBOILER APPLICATIONS

Generally reboilers are heated on shell side by steam, and the organic product flews tube side.

In terms of heat transfer, there is a big difference between the outside and the inner heat transfer coefficients, and this last one constitutes the main resistance for the heat transfer. This characteristic is even more pronounced in case of fouling coming from the organic product. Consequently, any increase of the inner coefficient (IHTC) translates to about the same improvement on the overall heat transfer coefficient (OHTC).

a. Action of the Spirelf System on vertical reboilers’ performance at start-up.

• Improvements to be expected from Spirelf System. • Spirelf devices have two actions, first a turbulent effect from the start-up of

the reboiler, then a combinated effect, turbulent and mechanical, giving a reduction of the fouling layer during the service time of the reboiler.

• From the start-up, through the increase of turbulence coming from the shape of the devices, there are different types of action on almost each region of the boiling tube.

• Apart from the annular flow region where there is not enough liquid phase, Spirelf increases the performance of the convective boiling:

• In the slug flow zone, due to its presence (as a packing), Spirelf reduces the formation of large size bubbles (reduction of the coalescence of small bubbles). It maintains a longer time the bubbly flow, more efficient than the slug (or plug) flow.

• In the bubbly flow region, without change of the number of nucleation sites (mainly depending on the metal surface), the increase of turbulence associated to the motion of the spring going into contact with the wall, reduces the residence time of the bubbles on the metal surface, giving a better efficiency for each site of nucleation.

• In the submerged area, at the lower part of the reboiler when this one is vertical, Spirelf reduces the “laminar layer” thickness on the surface of the tubes, increasing the convection coefficient (see description in fig. 12)

b. Special case of thermosiphon reboilers.

In the case of thermosiphon reboilers, the increase of vaporization due to Spirelf leads normally to increase also the flow rate of product (when flowing in the tubes), but at the same time, the inherent extra pressure drop introduced by the springs has as effect to reduce it.

At the start-up, the global effect of Spirelf on a thermosiphon reboiler can be translated by:

Less liquid but more % vaporization = same duty

In fact, we have always noticed that at the start-up, the performance of a thermosiphon reboiler was not affected by Spirelf. This result has been observed every time when such type of reboiler has been equipped with Spirelf devices.

c. Spirelf effect in service

Generally fouling grows on the tube surface, and a source of fouling on the organic product side, comes from the high temperature of the wall, heated by medium pressure steam (around 200° C – 400° F). After forming of the first layer of deposit on the wall, the tube surface becomes rough which makes for easier formation of new deposits on it. As at the same time, the wall temperature becomes higher due to the resistance of the fouling layer, organic compounds are transformed into coke. It is important, in order to prevent later severe fouling, to reduce the start-up the fouling formation from the beginning.

Without to take into account the mechanical effect of the Spirelf springs through their contact with the wall, the increase of turbulence itself reduces the “laminar layer” thickness, reducing the wall temperature and consequently fouling phenomena from the beginning.

This reduction of fouling is illustrated hereafter in one industrial case, where a direct comparison of performance has been made between two identical parallel reboilers.

Single phase liquid

Bubbly flow

Slug flow

Annular flow

Fig. 12

d. Unit description: Spirelf Effect for increased efficiency in duty and service time for thermosiphon reboiler

This is an application of Spirelf in a vertical reboiler, where strong fouling situation was a bottleneck issue for the chemical plant. This unit dealing with fluoric compound required a monthly water injection in order to clean them and to come back to normal situation.

The initial working conditions were:

• Natural thermosiphon • 1 heat exchanger of 80 tubes and 1 pass on tube side, • Flow rate: between 15 and 30 t/h, • Boiling organic is flowing tube side, • Straight tubes 1,500 mm / OD 27.45 mm / internal diameter 21.4 mm.

Solution description

Due to the low velocity in single liquid phase, the implementation of Spirelf in this reboiler was proposed in order to generate a turbulent effect in this part of the tubes. This effect was expected to increase the convection coefficient of the liquid and accelerate the gas formation.

Due to higher turbulence and reduction of boundary layer thickness because of Spirelf, the fouling reduction was estimated around 50% reduction.

Service time with Spirelf is usually doubled (theoretical expectation). As normal Spirelf life time is about few years, if fouling mitigation is strongly effective it can last around 5 times or more the initial service time.

Observed results

Initial evaluation after the first installation in February 2004 after 3 months installation the Spirelf was still in service and the 6 months service time without water cleaning was expected at the time of the evaluation. Observed results are a strong mitigation of the fouling deposition. Observed U value in equipped situation is now stabilised at higher U value than the expected stabilisation (around 200). As additional result, it is more than twice higher than the stabilisation without Spirelf.

Thermosiphon Reboiler, Spirelf effect

050

100150200250300350400450500

0 20 40 60 80 100days

U v

alue

2003 (Without Spirelf)

2004 (With Spirelf)Cleaning by water injection

Fig. 13

There are 4 reboilers in the unit, and 2 of them were in bottleneck situation because of fouling. After this test, the chemical plant decided to equip both critical reboilers in order to be able to run 1 year with water injection every month.

List of Publications

The Petroval Tube Inserts Systems: “SPIRELF®, TURBOTAL, and FIXOTAL

have been described in the following publications:

Petroles et Techniques n°295, Janvier fevrier 1983 Chem. Eng. Progress, September 1991,"Heat Transfer Heads into 21st Century" ASME 1995, National Heat transfer Conference, 7 August 1995, "Field of

application of double enhanced tubes in shell and tube and air cooled heat exchangers", Hydrocarbon Processing, February 1998, "Revamping Crude Units" AIChE, March 8-12, 1998, "New Heat Integration Techniques for Boosting

Profitability", AIChE, March 14-18, 1999, "A Practical Approach to Fouling Mitigation in

Refineries: Spirelf System". ESDU Doc. 000 16,2000, “Heat exchanger fouling in crude oil distillation units”, Proceedings, August 2000, 2nd Intl. Conference on Petroleum and Gas

Phase/Fouling, Copenhagen, UEF Heat Exchanger Fouling Conference, 2001, Davos (Switzerland) Publico, 2001, Heat Exchanger Fouling Mitigation and Cleaning Technologies, Ed.

H.Mueller-Steinhagen. AIChE Spring Meeting, March 2002 ARTC 5th Annual Meeting, April 2002, Session on Refining and Petrochemical

Technology, Bangkok ARTC Reliability Conference, November 2002 Singapore (SK Corp. Korea) HDT Haus der Technik Heat Exchanger and Cleaning Seminar, Sept. 2003 Bad

Duerkheim (Germ.) ARTC 7th Annual Meeting/Reliability Conference, April 2004 Singapore (Thai

Caprolactam/Petroval) AIChE National Meeting, April 2004, New Orleans (Shell/SGS, Argonne, Petroval ) HOD Intl. Conference on Heavy Organic Depositions, Nov. 2004, Los Cabos

(Mexico) NPRA National Petrochemical and Refiners Assoc. Technical Q&A sessions: 1996,

1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 ECI Conference on Heat Exchanger Fouling and Cleaning, Bad Irsee, Germany,

2005 SGS, Shell Amsterdam Conference on Heat Exhanger Fouling and Cleaning, 2005