Desalter vessels are a refinery’s first line of defence to reduce the amount of unwanted saltspresent in the feed inventory. Prior to crude oil en-tering a refinery processing stream it undergoesa water washing stage where the water used dur-ing this process is separated using Desalter ves-sels. In these vessels the oil and water mixtureseparate from each other using gravity and highvoltage coalescing plates. The water phase con-tains the washed salts as well as other sus-pended solids. Desalting and separation preventswater and salts from entering the crude unit fur-naces, distillation towers and other downstreamequipment. Salts, sediment, and other solids willfoul the process and can undergo chemicalchange to produce corrosive chemicals thatcause damage to process metallurgy. It is there-fore important to efficiently separate wastewaterfrom crude feedstock within the Desalter vessels.

Tracerco Tru-Scan™ technology provides you de-tailed data on where the oil/water interface level is,determines if there is a significant “rag” or emul-sion layer or detects how many solids are built upin the bottom of the Desalter. In addition to per-forming these applications our advanced tracerstudies are used to provide residence times of theoil and water phases and distribution within thevessel. Further to our scanning and tracer

technologies that can aid plant personnel in optimising your process, our award winning Tracerco Profiler™ HTX instrument provides accurate phase measurement including oil, emul-sion (rag), water and solids/sludge in real time.The installation of the Tracerco Profiler™ HTX caneliminate unplanned Desalter shutdowns, reducechemical usage, increase fluid throughput andprovide the capability to handle more challengingcrude blends.

Case study: Desalter distribution study

Recently a customer contacted Tracerco asking ifwe could provide an answer to his question: “Isthe liquid that is being introduced into my Desalterbeing evenly distributed via my distributor? Theysuspected the inlet distributor on their Desalter

may not be functioning prop-erly. A Tracerco Diagnostics™Distribution study was per-formed to help the customerdetermine what was actuallyhappening within their Desalter.

In this study, an organic tracerwas used to verify the oil distribution through the inletdistributor which was locatedin the middle of the vessel. (Figure 1) Sensitive detectorswere placed on the feed inlet

and oil outlet as well as various locations on theEast and West sides of the vessel to monitor forthe presence of the tracer and evaluate the qual-ity of distribution at the entrance and exit points.Each of the detectors should have equal area response if there is good distribution as illustratedin the example shown in Figure 2.

The results of the study are illustrated in Figure 3shown on page 2. The data indicated a much dif-ferent flow pattern when comparing the detectorson the North side of the vessel (red, green, black)as those on the South side (blue, pink, orange).On the South side of the vessel, the detector re-sponse curves were sharp with well-defined lead-ing and trailing edges. By comparison, thedetector response curves on the North side of thevessel showed very broad curves with leading

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Optimizing desalter performance is just one of Tracerco’s specialties we proudly provide. 1

Crude tower wash bed 3

Manage and control your turnaround costs to avoid possible surprises. 5

New Product Announcement: PED-ER and PED-ER+ 6

Inside this Issue…

insightVolume 8 Edition 2

– Detector placement illustration. Tracer was injected through the inlet distributor located in the middle of the Desalter.

– An example of the response from each detector in a distribution study directlyrelated to process flow close by its location. For a normally operating system, all of the de-tectors should detect similar amounts of tracer, producing similar responses. However,when tests show that some detectors have much larger responses than others, maldis-tribution is indicated.

Optimising Desalter Performance Is Just One of Tracerco’s Specialties We Proudly Provide.

(Continued on page 2)

2 www.tracerco.com tracerco@tracerco.com

and trailing edges spread out over a very long period of time. This was an indication that thefeed distribution was not properly distributing thefeed to both sides of the vessel. There appearedto be a much higher flow of feed to the South ascompared to the North. If the distribution wouldhave been even, then the North and South detectors would be expected to have shown uniform response curves.

Conclusion

Online investigations of desalters can identify the causes of poor performance. Once identified,the best course of action can be determined tocorrect the problem in the least amount of time.With a Tracerco Diagnostics™ Distribution studyyou can identify problems before they reach acritical point.

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– Test results indicated a significantly slower flow in the North end of the Desalter indicating maldistribution.

Making Desalter vessels transparent to optimise crude processing...whatever the blend

Efficient separation requires the use of accurateand reliable interface control to manage its posi-tion and quality. An increasing number of refinershave successfully deployed the Tracerco Profiler™HTX for Desalter interface control. This device pro-vides an accurate measurement of the densitydistribution within a Desalter, offering continuoushigh resolution imaging and control of eachphase. This allows the most efficient operatingconditions to be maintained as well as monitoringthe effectiveness of chemical additive and mudwashing.

With repeatable, accurate and reliable real-timeprocess measurements, the Profiler™ HTX pro-vides operators with interface confidence. If the

interface can be controlled, it is feasible to raisethe interface level closer to the coalescing electrostatic grid system which in turn enhancesseparation of crude from water. By optimising separation to improve feedstock flexibility, upstream Desalter mixing can be increased tomaximize wash water contact, thus removingmore undesirable materials.

In a Desalter, the electrostatic grids prompt thecoalescence of the water molecules, whichcauses them to fall out of the oil, taking the solidswith them. Then the solids can be removed fromthe bottom of the vessel. Efficiency of thisprocess increases when the vessel can be operated within the ideal interface range.

In Figure 4 you can see from the screen shottaken from Profiler™ results, you are able to visualise the electrostatic grids and understand

how operations is able to maintain at the ideal position.

Solving the problem… long or short term

A Tracerco Diagnostics™ Distribution study isoften requested by our customers to detect mald-istribution issues in real-time, eliminating theguess work when trying to resolve process issues.

Installing our Tracerco Profiler™ HTX as a perma-nent solution will help visualise what is happeninginside your process and to gain the confidence toincrease fluid throughput and automatically control interface levels within the DCS system.

The Tracerco Profiler™ HTX can eliminate unplanned Desalter shutdowns, reduce chemicalusage, and provide the capability to handle morechallenging crude blends.

If you would like to learn more on all the productsand services Tracerco offers to help optimise yourDesalter contact a technical advisor in your area. – In this figure you can see from the screen shot from Profiler™ results, you are able to visualise the electrostatic grids

and understand how operations is able to maintain at the ideal position.

3 www.tracerco.com tracerco@tracerco.com

A Novel Approach

Marathon Petroleum Company LP’s (MPC)approach for operation of their vacuumtower wash bed is a novel approach. MPCregards the packing in the wash bed as aconsumable item. The goal - fully consumethe useful life of the packing by the end ofthe operating cycle to maximise operatingprofit by maximising HVGO yield. MPC usesTracerco’s ThruVision™ technology to rou-tinely monitor the wash bed density to helpmanage the wash bed useful life during theoperating cycle. The ThruVision™ technol-ogy provides a detailed density map at aspecific vertical elevation that can pinpointspecific areas of liquid maldistribution orsolids/liquid build-up.

Operation Challenge

The challenge was two-fold: first, what operat-ing variables could be manipulated to controlthe coking rate and second what could beused to monitor the coking rate in the packing?At the beginning of a cycle run a baseline Tru-Grid™ Scan and ThruVision™ scan weredone. Figure 5a shows the initial ThruVision™scan results.

Thereafter the scans were repeated on a peri-odic basis, approximately every three months.The vacuum tower wash bed was operatedvery aggressively during the first cycle - mini-mum wash oil to maximise HVGO yield. Thiswas purposely done to set parameters for ag-gressive operation. The first section of thegraph in Figure 6 shows the average wash beddensities calculated from the ThruVision™ scandata for Cycle 1. Figure 5b shows the ThruVision™ scan from the end of this cyclerun. Over the 2-year period there was a 40% in-crease in packing density due to coke build-upand/or excess liquid retention.

After the two-year period there was an oppor-tunity shutdown due to a problem unrelated tothe coking. Subsequent shutdown and inspec-tion showed the packing severely fouled withcoke and the packing was replaced. The nextcycle run was purposely operated with less ag-gressive operation, higher wash oil rates to re-tard the rate of coking. This cycle run alsolasted approximately two years. As seen fromthe second section of Figure 6, over the two-year cycle run the average packing density in-creased by a little more than 20%.

Data Analysis

Cycles 1 and 2 established boundaries for op-erating parameters between very aggressiveoperation and conservative operation. Severaloperating parameters were compared to theaverage packing density from the ThruVision™scans to correlate the best operating parame-ter with the rate of coking.

The third cycle run lasted almost six years. Thiscycle run can be divided into three segmentsdue to the operating demand placed on the re-finery. In late 2010, management decided tolengthen the cycle time beyond the original fiveyears. Therefore, the over-flash rate was dra-matically increased in order to retard the coking

Crude Vacuum Tower Wash Bed Optimisation

– (a) Baseline scan results of crude vacuum tower wash bed; (b) ThruVisionTM scan result at the end of Cycle 1.

– Cycle 1 wash bed densities when vacuum column operated aggressively. Cycle 2 wash bed densities when vacuumcolumn operated more conservatively.

(Continued on page 4)

On-line Distribution Analysis In Packed Beds,Piping And Fluidised Catalyst Systems

Tracerco’s ThruVision™ scan technology, similarto a CT scan, is a diagnostic technique that gen-erates a cross-sectional density profile of a reac-tor riser, distillation column, piping or otherequipment where knowledge of process flow dis-tribution is vital to performance. The ThruVision™

scan system is transportable and adaptable forscanning equipment while on-stream. This uniquescanning technique has been used by our cus-tomers to identify liquid maldistribution in packedbed columns, monitor the coking process in avacuum tower wash bed, investigate damage in amist eliminator pad, or generate a detailed cross-sectional density profile of a FCC Riser showing

catalyst flow distribution. It is often used to evalu-ate changes in design and operation of feed injection or lift steam nozzles. Scan results can determine if a nozzle is plugged or fouled.

Application of the ThruVision™ scan technologyhas provided a new “window” for observingphase distribution inside industrial process units inreal time at an economical cost.

4 www.tracerco.com tracerco@tracerco.com

rate at the expense of some HVGO yield. Thenin mid-2012, management advanced theplanned end of the cycle run. At that time, op-erations reduced the over-flash rate to increaseHVGO yield. Knowing the wash bed packingwas going to be replaced allowed operationsto tolerate an increased coking rate. However,to have a little cushion the decision was madeto not be as aggressive as was done duringCycle 1. Figure 7 shows the over-flash rate ver-sus the packing density during this entire 69-month cycle run.

ThruVision™ scans were used to monitor anddetermine the average wash bed packing den-sity through the cycle run. While the primarypurpose for doing a ThruVision™ scan is tostudy liquid distribution through a bed, the pri-mary use for this application was to track thebed density to monitor the bui ld-up of coke orthe retention of liquid in the packing due tocoke fouling.

Conclusion

Marathon Petroleum Company managescrude vacuum tower operating conditions tomaximise HVGO yield through a completecycle run. ThruVision™ technology provides adetailed density map yielding extensive cross-sectional coverage to monitor fouling/cokingin packed beds. The operating stratagem of

using Tracerco’s ThruVision™ technology toroutinely monitor the crude vacuum towerwash bed density for increases in density sig-nifying coke build-up and adjusting the columnoperating true over-flash rate is used to controlthe rate of coking, maximising profit fromHVGO yield and regarding the wash bed pack-ing as a consumable expense.

For a copy of the entire paper, email tracerco@tracerco.com and reference Crude

Vacuum Tower Wash Bed Article in the subjectline. Upon receipt of your request we will emailyou a pdf version of the full article.

If you would like to learn more on how ThruVision™ scans can help personnel gain amuch better understanding of the cokingprocess within the wash bed of a Vacuum column contact a Tracerco technical advisor.

– Trend of wash bed packing density versus true overflash over the 69 month run of Cycle 3.

Applications Note – ThruVision™

ThruVision™ of FCC Riser

ThruVision™ technique on piping to detect build-up.ThruVision™ scan simulated plugged nozzle.

5 www.tracerco.com tracerco@tracerco.com

A Tru-Scan™ or Tru-Grid™ Scan will assist in defin-ing and developing a turnaround critical path proj-ect scope at an early stage ensuring that yourturnaround meets your goals. The most commonuse of gamma scans is to give process engineersand operations an online tool that results in un-derstanding how a column is performing. Thisdata can be used in advance of a turnaround toidentify tray or packing damage and other processproblems without having to shut down the columnfor internal inspections. These results will fully pre-pare turnaround planners with the knowledge theyneed for critical path decisions that must be madeprior to a shutdown. At other times the results froma Tru-Scan™ or Tru-Grid™ Scan can either justifyan unscheduled shutdown or identify options thatwill enable a plant to continue operating until thenext scheduled shutdown.

Tower scans are used to evaluate the mechani-cal integrity and hydraulic performance of trayedcolumns by measuring froth levels on tray decks,liquid backup in downcomers, and clarity of liq-uid disengagement zones. Damaged or missingtrays or packing, plugged downcomers, feed is-

sues, and tray fouling are examples of problemswith columns that can be diagnosed with a Tracerco scan.

When damage is found, a turnaround coordinatorcan accurately define what trays and/or packingare needed, estimate the cost, and procure theneeded hardware weeks in advance of a sched-uled turnaround. Tru-Scan™ or Tru-Grid™ Scansperformed five to six weeks prior to a scheduledshutdown usually provides enough time to ordernew equipment without expediting charges and toschedule the required manpower. Should an upsetoccur after that point additional scanning could beperformed to identify if any new problems have de-veloped that would require a revision to a criticalpath item.

Case Study: Depropanizer Scan Data Determines Damaged Trays Was Not The Problem

A refiner requested that Tracerco perform scanson all of their towers within six processing unitsprior to an upcoming turnaround. A good illus-tration of how a Tru-Scan™ aided in their criticalpath decisions is from the results found in a Depropanizer column. The Depropanizer hadto be run with a high base liquid level in orderfor the column’s reboiler to operate properly.The base liquid level routinely covered the reboiler return nozzle.

The ∆P of the Depropanizer was higher than nor-mal. Operations suspected flooding, probably asa result of some tray damage to the lower traysdue to the high base liquid level. The scan resultsdid show the high base liquid level covering thereboiler return nozzle. As a result of the reboilerreturn vapor mixing with the base liquid there wasa lot of liquid entrainment below the bottom tray(Tray 1 in Figure 8). The bottom trays were flood-ing but had no apparent damage. These scan re-sults decided the course of action for the refineryduring the turnaround. Plans were made to mod-ify piping so the reboiler would operate correctlywith the proper base liquid level instead of pur-chasing trays when scan results indicted the ex-isting trays were not damaged.

The refinery turnaround planners utilized scandata results from all the columns prior to theirscheduled turnaround to order replacementequipment and help schedule the manpower re-quired for the turnaround. The data indicated me-chanical problems in three towers, process

problems in six tow-ers and no problemswere indicated in theeleven remaining tow-ers. Entry into theseeleven columns couldbe avoided if therewas no history of cor-rosion or other in-spection needed.

This information essentially set the turn-around plan and avoided potential surpriseson items that could have disrupted the original critical path. A chart of the results isshown in Figure 9.

Conclusion

Strategic use of Tracerco’s Pre-Turnaround scantechnology will enable you to identify equipmentthat does not need to be included in your turn-around project, evaluate the status of historicallyproblematic process equipment, and establish theequipment dictating the critical path. A unit man-ager can avoid shutting down a column basedupon the mere suspicion of tray damage, whenthe real problem may be related to process con-ditions. A turnaround coordinator can accuratelydefine, estimate, and procure trays, packing, andother hardware weeks in advance of the turn-around schedule. The largest payoff from usingPre-Turnaround gamma scans is when a unit man-ager can avoid shutting down a column altogether.

Manage and Control Your Turnaround Costs to AvoidPossible Surprises.

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Tracercowww.tracerco.com

– Tru-Scan™ results decided the course of action forthe refinery during their turnaround. Modifications to the towerwere made instead of preparing to replace damaged trayswhich scan results found were not necessary.

Summary of ProblemsCrude UnitAtmospheric Tower All trays in placeVacuum Tower LVGO distributor plugged or damaged HVGO draw tray leaking or wash oil distributor damage

Crude UnitMain Fractionator Trays 21 and 22 damaged, all other internals in place

Alky UnitIsostripper High reflux rate or subcooled reflux causing flooding on top four trays, lower accumulator tray leakingDepropanizer Severe liquid entrainment throughout the tower, no indications of mechanical damageAcid stipper No problems indicatedAcid regenerator No problems indicated

Unsat Gas PlantIsobutune Absorber Flooding Present on top 32 trays

Amine Absorber No problems indicatedDebutanizer No problems indicated

Delayed Coking UnitCoker Fractionator No problems indicated

Sat Gas PlantStripper No problems indicatedAmine Absorber No problems indicatedDebutanizer Severe flooding throughout the towerDepropanizer Dryer High reflux rate or subcooled reflux flooding top three trays, Tray 10 heavily loaded - possible downcomer restrictionSponge Oil Absorber No problems indicatedMain Absorber All trays in place

Naptha Splitter No problems indicated

Depropanizer No Tray Damage. High base liquid level covering the reboiler return inlet.

– Turnaround planners utilised scan data results fromall the columns scanned prior to the scheduled turnaround toorder replacement equipment and schedule the manpower required.

Tracerco has added to its award-winningrange of radiation monitors with two new Personal Electronic Dosimeters (PEDs) – the PED-ER and PED-ER+. With an extendeddose rate range of up to 1 Sv/h (100 R/h), an energy range of 48 Kev to 3 MeV, and alight, compact, robust and reliable design, thePED-ER and PED-ER+ provide the ultimateradiation monitoring, measurement and management solution for those working inchallenging environments.

As per our existing PEDs (the PED-IS, PEDBlue and PED+), the PED-ER has been de-signed to keep things simple. With one buttonoperation and an easy to follow menu system,the device can be easily operated with notraining needed. Audio and visual alarms witha vibration function, also ensure that person-nel are immediately notified if a set dose rateis reached or exceeded.

The PED-ER+ has the same unique featuresas the PED-ER in terms of portability, an IP67rating and the ability to provide immediatedata on an intuitive, large clear display, how-ever it also boasts a number of additional fea-tures. Most notably, the PED-ER+ can beused as both a Personal Dosimeter and ahandheld dose rate survey meter, ensuringthat the safety of both the worker, and thosepersonnel that are in the area of the event isnever compromised. Pop-up message alarms(when dose limits are reached), to the user,also allow personnel to organise, plan and respond to radiation more efficiently.

The PED-ER+ comes complete with Blue-tooth technology, meaning live dose rates canbe transmitted to an Android device located ina safe area. This allows the management andmonitoring of situations to be undertaken inreal time, away from a potentially hazardousevent. The addition of GPS tracking also pro-vides location data alongside dose data, giv-ing a map of potential radiation hazards whendata is downloaded.

Graham Barker, Senior Commercial Managernoted “The capability to act quickly and safelyto incidents in dangerous and hazardous en-vironments is extremely important for indus-trial Non-Destructive Testing (NDT) workers,

the emergency services and first responseteams (CBRNe). The development and launchof the PED-ER and PED-ER+ will ensure thatupon entry into both known (for example thoseworking in the Industrial NDT market) and unknown (for example first responders) scenarios, that personnel are equipped withthe correct radiation monitoring equipment toensure any radiological hazard is detectedand any exposure to radiation is monitoredcarefully”.

To request more information on our Tracercorange of personal radiation monitors email usat radiation.monitors@tracerco.com.

New Product Announcement: PED-ER and PED-ER+

tracerco@tracerco.com www.tracerco.com

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