The CANMET Hydrocyclone: An Innovative Technology for the ...

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The CANMET Hydrocyclone: An Innovative Technology for the ...

The CANMET Hydrocyclone: An Innovative Technology for theTreatment of Production FluidsKhalid A. Hashmi 1 and Hassan A. Hamza 1CANMET Energy Technology Centre – Devon, CanadaAbstractAs an oil field matures, water tends to become the dominant produced fluid. A large number ofproduction wells in the western Canada and the Gulf region are maturing, producing water cuts 90% orhigher. The treatment of these production streams and other oily effluents, including desalter effluents andslop oil, requires cost-effective, efficient, and environmentally friendly technologies capable of recoveringthe oil and turning out clean water suitable for reuse or disposal. In the past, treatment of these effluents(produced waters) was a relatively minor item in the design of production facilities. However, as a result ofincreased water production and more stringent environmental standards, it is now a costly component ofland-based and offshore production projects and an important environmental issue.Through research and extensive field testing at several Canadian oil company sites, Advanced SeparationTechnologies (AST) of the CANMET Energy Technology Centre–Devon has developed a newhydrocyclone that is specially suited for treating difficult-to-separate oily fluids, including production fluidsfrom aging wells, slop oil, and other oily effluents. The new CANMET hydrocyclone embodies a numberof unique design advances, including an adjustable overflow orifice and the capability to remove suspendedsolids in a separate stream. It also lends itself readily to on-line monitoring and control. The CANMEThydrocyclone was granted U.S. and international patent protection in early 1999.The new generation of hydrocyclones developed by AST offers an attractive alternative to conventionaltechnologies. The new design has already proved highly effective in treating heavy oil production fluidsand has demonstrated the potential to deliver significant cost savings when installed as a replacement forconventional treatment schemes. Under a collaborative program with Husky Energy, a CANMEThydrocyclone system was installed as a beta test site at the Husky Lloydminster oil refinery in January1999. The unit is currently processing about 500 m 3 /day of desalter effluent and its capacity may beexpanded to over 1000 m 3 /day.In this presentation, the main features of liquid-liquid hydrocyclones are discussed along with advances inhydrocyclone technology made by AST. The results of field testing of the CANMET hydrocyclone atwestern Canadian heavy oil operations are also presented, as well as the environmental and economicbenefits.INTRODUCTIONMeeting environmental regulations and maximizing economic gains in the recovery of oil from waste oilystreams (slop oil and produced waters) and maturing production wells having water cuts of 90% or higherpresents technological challenges for the oil industry in western Canada and the Middle East. Inconventional treatment systems, gravity-based oil separation equipment such as FWKO vessels, APIseparators, and settling tanks are used to separate the bulk of free oil, and filtration or dissolved-air flotationsystems are employed as polishers to remove residual oil down to less than 50 ppm, thus making the treatedwater suitable for disposal or reuse. Hydrocyclone technology offers an efficient and economicaltechnological solution to meet the challenges of high-water-cut production, and is also well-suited for thetreatment of other oily effluents and slop oil. In particular, the new CANMET hydrocyclone features thelatest advances specifically designed for these applications.Using a transportable CANMET hydrocyclone pilot test facility, the CANMET Energy TechnologyCentre–Devon (CETC–Devon) performed a number of successful field tests in cooperation with oilindustry clients. These field trials were focused on deoiling produced water and high-water-cut wellheadproduction fluids and the treatment of slop oil and oily wastes such as tank bottoms. The test results andThe Environment & Energy 2003 Conference 467


know-how gained by CANMET staff led to the development of innovative hydrocyclone designs and flowsheet configurations to meet the requirements of the heavy oil industry in western Canada.The new CANMET hydrocyclone design has already proved highly effective in treating heavy oilproduction fluids in the Canadian provinces of Alberta and Saskatchewan. This success has led to theinstallation of commercial-scale multi-hydrocyclone systems at the Husky Energy refinery and upgrader inLloydminster, Alberta. Other operators are considering the installation of CANMET hydrocyclone systemsin their operations.HYDROCYCLONE ADVANTAGESLiquid-liquid hydrocyclone technology offers unique advantages over gravity-based separation methods.Hydrocyclones produce centrifugal forces more than 500 times the gravitational force, resulting in muchmore rapid separation than conventional methods.• Elegantly simple in design – Hydrocyclones are highly compact and portable compared to theequipment they replace (FWKO vessels, skim tanks, etc.). Residence time in hydrocyclones istypically about 2 seconds compared to hours in conventional treatment units. It is easy to relocate ahydrocyclone system, offering a much higher salvage value.• Simple to operate – The absence of moving parts ensures a minimum of maintenance and downtime.Wide fluctuations in feed rate can be handled without serious effects on efficiency or oil recovery.• Environmentally friendly – Hydrocyclone systems are energy efficient and generate no wastes. Theyreduce heating requirements and readily accommodate the recycling of heated fluids.THE CANMET HYDROCYCLONEENHANCED PERFORMANCEDesign advances in the CANMET hydrocyclone give superior performance compared to conventionaldesigns. Figure 1 shows a working model of an available commercial (conventional) hydrocyclone. Asoil/water separation occurs in the hydrocyclone, the lighter (dark-coloured) oil phase migrates towards thecentre of the vortex to form an oil core that exits the unit via an overflow orifice located at the centre of theupstream (left) end of the unit. As can be seen in Figure 1, the conventional design produces an oil corewith a corkscrew shape. This off-centred oil core hinders the removal of concentrated oil from the unit,regardless of orifice size.In contrast, the CANMET hydrocyclone, shown in Figure 2, produces a straight, symmetrical oil core thatreadily exits through the overflow orifice. For an added degree of operator control, the advanced CANMETdesign also features variable orifice size to ensure efficient oil removal and the desired overflow qualityover a range of feed properties.Schematic and component drawings of the CANMET hydrocyclone can be found in the patent documents(U.S. 5,858,237 and International PCT/CA98/00403). The following are unique features of the CANMEThydrocyclone:Multiple inlet ports. Unlike conventional hydrocyclones, which generally have one inlet port, theCANMET version has two, three, or four ports, evenly spaced around the involute. This produces a morestable vortex flow and oil core.Adjustable overflow orifice. Changing the diameter of the overflow orifice during operation adds anelement of performance control.Solids separation. An attachment can be installed at the downstream end of the hydrocyclone to removesolids that would otherwise report with the water stream.Heating jacket. Hot liquid or steam can be circulated around the hydrocyclone body to reduce oilviscosity and increase separation efficiency.The Environment & Energy 2003 Conference 468


ENIVIRONMENTAL ADVANTAGESReduced CO 2 emissions. Reduced heating requirements reduce CO 2 emissions.Example: For the treatment of 70% water cut production, each barrel of oil produced usingconventional gravity-based systems requires the consumption of approximately 100 standard cubicfeet (SCF) of natural gas to heat the wellhead production from ambient temperature to about 65 O C.This heating releases about 5.25 kg CO 2 to the atmosphere per barrel of treated oil. Usinghydrocyclones, the separation can be achieved at 40 O C; therefore, CO 2 emissions are reduced byan estimated 25%. For a typical 7500-bpd treatment facility, this would result in a reduction ofCO 2 emissions of nearly 10 tonnes per day.Reduced site degradation. Hydrocyclone systems have a much smaller footprint than conventionaltreatment trains and are less subject to accidental spills. For environmental and safety reasons,hydrocyclone installations include shutoffs that are automatically activated in the event of a leak or processupset. Inadvertent releases of process fluids or wash water are therefore no larger than a few litres, andthese are entirely recoverable since the hydrocyclone setup incorporates a drainage pan that drains to apumpable sump. In contrast, the potential spillage of tank volumes in conventional treatment schemesrequires large containment areas that still carry the risk of harmful seepage into surface and ground waters.Clean water. CANMET hydrocyclone systems are capable of producing oil-free water streams suitable forreuse or safe disposal, thus reducing the consumption of fresh water and the negative impacts of wastewaterdisposal.ECONOMIC ADVANTAGESJoint projects with oil industry clients demonstrated that, for the treatment of produced waters, and slop oil,and oily effluents from desalters, capital and operating costs are reduced as compared to conventionalseparators (FWKO vessels, skim tanks, etc.), which are bulky and require frequent maintenance.Capital costs. Hydrocyclone systems are relatively simple in design, require much less plant space thanthe equipment they replace, and are easily transportable.Example: For deoiling refinery desalter effluent, a CANMET hydrocyclone system with a capacityof 1000 m 3 /d and standard instrumentation, the construction cost would be approximately$300,000 CAD. This is about half the cost of a conventional separator installation of matchingcapacity. For systems with larger capacities, even greater cost savings per unit volume ofthroughput can be expected.Operating costs. Operating costs are reduced in several ways: Energy inputs are reduced, the absence ofmoving parts ensures a minimum of maintenance and downtime.Example: CANMET hydrocyclone system installed at a refinery for the treatment of 500 m 3 /d ofdesalter effluent:• Operating costs for servicing of water disposal wells were reduced by 50%.• Chemical costs were reduced by 30%.• Slop production was substantially reduced and nearly all of it was transformed intosaleable oil product.Prior to the installation of the CANMET hydrocyclone system, the total average operating cost forthe above items was approximately $300,000 CAD annually. As a result of the changeover, thiswas reduced to about $200,000.In high-water-cut oil production, the reduced operating costs associated with hydrocyclones effectivelyincrease total oil recovery by extending the economic lifetime of the production wells.The Environment & Energy 2003 Conference 469


APPLICATIONS OF THE CANMET HYDROCYCLONETREATMENT OF DESALTER EFFLUENTRefinery desalters generate significant volumes of oily effluents. Depending on the upstream processes andthe initial feed, these effluents may contain significant amounts of oil (up to 10% by volume) and solids (upto 5%), especially during desand operations. High oil contents reduce the separating ability of the skimtanks and significantly lengthen the residence time of the fluid in the tank. Typical retention time of skimtanks ranges from a few hours to a day. Hence, it is highly desirable to utilize a separation technology thatis able to efficiently and effectively separate this effluent, reducing the retention time and hence reducingthe number of skim tanks required. With its low capital cost and virtually no maintenance costs, theCANMET hydrocyclone stands out as the best solution to this problem.A period of successful field testing was conducted at the Husky Energy Lloydminster refinery prior to theinstallation of the commercial CANMET hydocyclone system. The results obtained from the field testingwere very encouraging, as a stream of clean water containing ppm levels of oil and the bulk of the solids(mostly clean with the oil coating stripped off) was produced. From observations of the underflow samplescollected, the solids settled in less than 30 minutes in most cases. Hence, it was anticipated that theunderflow water could be separated in a significantly reduced period of time and would cause minimal orno problems when injected into disposal wells. As a result, a multi-hydrocyclone system with a capacity ofabout 1000 m3/d (shown in Figure 3) was constructed and installed at the Husky refinery. Figure 4 shows afront view of the open CANMET hydrocyclone vessel. The worker is installing a hydrocyclone unit.Excellent results were obtained after the installation of the multi-hydrocyclone system. Oil content analysesof feed, overflow, and underflow streams on various days are shown in Table 1. On some days, make-upwater was added to the effluent stream to meet the minimum processing capacity of the system. In anyevent, the multi-hydrocyclone unit can be set up for a lower processing capacity by replacing some of thehydrocyclone units with blanks. Figure 5 shows samples collected during normal desalter operation. Thefeed contained about 1% oil and 5.6% suspended solids. After the separation, the overflow contained about11% oil (with traces of solids remaining with the oil phase) and was free of settled solids. The underflowwas almost free of oil (on-site colour matching analysis showed oil concentration less than 100 ppm) andall of the solids reported with this stream. Figure 6 shows samples collected during the desanding phase ofoperation. This difficult-to-separate emulsion takes about 4–6 hours (and longer in some cases) to separatein a settling tank. The photograph was taken about 30 minutes after the three samples were collected. Noseparation could be observed in the feed sample. BS&W analysis showed that it contained about 7% oil and6% solids by volume. However, when this same feed was treated using the CANMET hydrocyclonesystem, it was separated into an oil-rich overflow containing about 35 vol% oil and traces of solids (about0.2%). Almost all of the solids in feed reported to the underflow stream with small amounts of residual oil.TREATMENT OF SLOP OILSlop oil is the fluid that is skimmed from deoiling skim tanks. It is a tight emulsion containing significantamounts of water, up to 90% by volume. Slop oil also contains “rag layer”, described by experienced oilfield workers as a solids-containing material found in the interphase region of the oil and water layers in askim tank. Rag layer is relatively viscous and is formed when residues from chemical injections in priorprocesses become attached to solids (fines), water, or oil droplets.A two-stage CANMET hydrocyclone system was set up at the client site to evaluate the performance of theCANMET hydrocyclone to treat slop oil produced during the processing of wellhead production. The testloop, designed and assembled by the AST hydrocyclone team, is shown schematically in Figure 7.The Environment & Energy 2003 Conference 470


Tests were conducted with and without conditioning of the slop oil feed to the hydrocyclone. Slop oilsamples were collected from bottom to the top of the slop tank; oil concentration varied from 15% to 40%by volume. Bench-scale testing (hot spin centrifuge from Alfa Laval was used) showed that these slopsamples, with oil concentrations higher than 15%, would be difficult to separate at temperatures of 50–70°C because of the high viscosity of the oil.Testing Without ConditioningInitial testing was conducted without conditioning the feed stream, at a process temperature of 70°C. Theoil concentration in the feed stream (to the first-stage) varied from 20% to 40% by volume. The operatingparameter settings (pressures and orifice size) predetermined as optimal for these test runs were: feedpressure (P F ) 700 kPa, overflow pressure (P O ) 300 kPa, and underflow pressure (P U ) 500 kPa (maintainingpressure differential ratio [PDR]* of 2, ), and a 2.5-mm overflow orifice.Results from these test runs, shown graphically in Figures 8 and 9 show the dependence of separationefficiency on feed temperature. In summary, for feed containing 15-20% oil at process temperatures from60°C to 75°C, maximum separation efficiency was 35% and oil recovery was 50%.Testing with ConditioningTo improve separation, the slop oil was conditioned by adding water and heating to around 90°C. Thislowered the oil concentration in the feed stream from the 30% range to 10-15%, and also reduced theviscosity. The hydrocyclone operating parameters were the same as for the tests without conditioning.As the graphs in Figure 8 and 9 show, the increase in temperature resulting from conditioning was a majorcontributor to improvements in separation efficiency and oil recovery.A series of tests were conducted at elevated temperatures (80-90°C); the results are given in Table 2. Withthe reduced oil viscosity, the water phase was able to migrate more easily through the oil phase towards theperimeter of the hydrocyclone, while oil droplets coalesced at the central core. As a result, higher oilconcentrations were achieved in the overflow stream. In most of the test runs, as Figure 10 shows, overflowoil concentrations of 65% to 75% were achieved, nearly five times the feed oil concentration. The resultssuggest that separation would be improved further by heating the feed to 95°C or by further reducing theviscosity of the slop oil by conditioning. A photograph of BS&W analysis of feed and product streamsfrom a test is shown in Figure 11SUMMARYIn extensive field testing the CANMET hydrocyclone has proved to be an effective and economicalternative for separating a variety of oily feeds into a concentrated oil stream and a clean water streamsuitable for reuse or disposal.Successful test programs have been conducted using refinery desalter effluent, slop oil, wellheadproduction, and other produced fluids.Compared to conventional treatment schemes, the CANMET hydrocyclone lowers capital and operatingcosts and reduces environmental impacts.* PDR = [P F – P O ] / [P F - P O ]The Environment & Energy 2003 Conference 471


Table 1 – Results from the treatment of desalter effluent at the Husky Energy refinerySampleOperationTempStreamsFlowRateOilContentWaterContentSolidsContentID Mode (C) (m3/d) (Volume %) (Volume %)(Volume%)Feed 377.9 3 96.25 0.75HLR –1 Normal 60 Overflow 16.7 10 89.95 0.05Underflow 358.4 ~0.O1 95.79 4.2Feed 420.4 1 93.40 5.6HLR –2 Normal 65 Overflow 18.7 11 88.95 0.05Underflow 399.9 ~0 95.30 4.2Feed 402.7 0.5 99.50 ~0HLR –3 Normal 66 Overflow 19.6 2 97.75 0.25Underflow 385.0 ~0 99.95 0.05Feed 369.6 1 98.75 0.25HLR –4 Normal 57 Overflow 19.4 3 97.00 ~0Underflow 346.0 ~0 99.50 0.5Feed 366.1 4 95.25 0.75HLR –5 Normal 55 Overflow 18.0 11 88.85 0.15Underflow 348.6 ~0.05 99.10 0.85Feed 388.8 1.8 94.20 4HLR -6 Normal 72 Overflow 18.9 28 68.80 3.2Underflow 365.2 ~0.05 98.75 1.2Feed 385.7 10 81.3 8.7HLR -7 Desand 67 Overflow 17.8 38.5 61.1 0.4Underflow 343.2 ~0.05 89.95 10Feed 406.4 7 87.00 6HLR -8 Desand 65 Overflow 23.0 35 64.8 0.2Underflow 382.3 ~0.05 94.15 5.8Feed 407.7 9 80.00 11HLR -8 Desand 72 Overflow 21.1 72 24.80 3.2Underflow 387.5 ~0.05 89.45 10.5The Environment & Energy 2003 Conference 472


Table 2 – Results from slop oil testing with conditioning of feedSlop OilTest #Temp Oil Content (vol%) Flow rate(L/min)OilRecoverySeparationEfficiency( o C) Feed U/F O/F Q F Q U (%) (%)SOT - 1 88 15 0.15 65 21.5 18 99.2 58.8SOT - 2 90 5 0.03 53 26. 24 99.4 50.5SOT - 3 88 5 0.20 43 30. 27 96.4 40.0SOT - 4 83 13 2 74 31 28 86.1 70.1SOT - 5 85 18 6 64 33 31 68.7 56.1SOT - 6 87 19 8 74 28 25 62.4 67.9SOT - 7 89 12 10 68 30 27 25.0 63.6SOT - 8 81 12 6 60 34 29 57.4 54.5SOT - 9 85 18 8 60 36 30 63.0 51.2SOT - 10 91 10 1 74 31 27 91.3 71.1SOT - 11 88 12 10 68 34 29 28.9 63.6SOT - 12 88 14 8 76 31 26 52.1 72.1SOT - 13 84 8 4 66 33 30 54.5 63.0SOT - 14 84 9 4 70 36 32 60.5 67.0Oil recovery and separation efficiency were calculated as follows:Oil recovery = 1 – [K U·Q U / K F·Q F ]Separation efficiency for concentrating oil = 1 – [(1-K O )/(1-K F )] whereK U = oil concentration (vol%) in underflowK F = oil concentration (vol%) in feedK O = oil concentration (vol%) in overflowQ U = volumetric flow rate in underflowQ F = volumetric flow rate in feedFigure 1 – Reverse flow pattern in conventional hydrocycloneThe Environment & Energy 2003 Conference 473


Figure 2 – Reverse flow pattern in the CANMET hydrocycloneFigure 3 – The CANMET multi-hydrocyclone systemThe Environment & Energy 2003 Conference 474


Figure 4 – Opened from front view of the CANMET hydrocyclone unitFigure 5 – Photograph of samples from the desaltersThe Environment & Energy 2003 Conference 475


Figure 6 – Photographs of samples from the desaltersSlop OilTankT-20325-50% OilFIHot WaterfromTank T-30110-15% OilOil Conc.MeterIn-line MixerOil-rich Stream(~65% oil)Hydrocyclone1st-StageTankT-202B~5% Oil~20% OilHydrocyclone2nd-StageClean water(ppm level oil)Figure 7 – Test loop for slop oil hydrocyclone testingThe Environment & Energy 2003 Conference 476


807060Separation Efficiency (%)5040302010060 65 70 75 80 85 90 95Feed Temperature (C)Without Conditioning With ConditioningFigure 8 – Separation efficiencies at different feed temperatures100908070Oil Recovery (% )605040302010060 65 70 75 80 85 90 95Feed Temperature (C)Without ConditioningWith ConditioningFigure 9 – Oil recovery at different feed temperaturesThe Environment & Energy 2003 Conference 477


Oil Concentration (%)8070605040302010U/FFeedO/F032a 1 36a 2 37a 3 38a 4 39a 5 39b 6 40a 7 41a 8 42b 9 43a 10 44a 11 44b 12 45a 13 46a 14 46b 15Test Identity (SOT)Figure 10 – Oil concentration in feed, U/F, and O/F streamsFigure 11– BS&W analysis of feed (10% oil), first-stage overflow (74% oil), and second-stage underflow(150 ppm oil)The Environment & Energy 2003 Conference 478

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