Chemical Engineering Magazine feb 2015

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  • Team Industrial Services   
  • 76 Pages   
  • 12 Feb 2015
  • Page - 1 FUNDAMENTALS OF HIGH-SHEAR DISPERSERS • HEAT EXCHANGERS VOL. 122 NO. 2 FEBRUARY 2015 02• Fundamentals of High-Shear Dispersers February 2015page 40Heat Exchangers: Two-Part Feature ReportAdvances in 3-D PrintingFocus on Industrial HousekeepingFacts at Your Fingertips: Dimensionless NumbersValves for Extreme Service read more..

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    Downtime. A word often associated with high cost and low production. Team has been helping companies minimize downtime for over 40 years with our global online inspection, mechanical, and heat treating services. We’re here to help you repair, maintain, and ensure the integrity of your equipment to keep your facility up and operational. Team experts are available 24 hours a day, 7 days a week, 365 days a year. Call TEAM today: 1-800-662-8326 www.teamindustrialservices.comMinimizing Downtime. read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 20151February 2015 Volume 122 | no. 2 Cover Story40 Fundamentals of High-Shear DispersersSuccessful dispersion depends on a basic understanding of dispersion equipment and how dispersers should be used In the News7 Chementator Xylenes production method takes advantage of low-cost methanol feedstock; Electrode design increases efficiency of suspended-solids removal; Reduce maintenance of high-pressure pumps; A bio-based crosslinker for read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015258 Engineering Practice Flare Consolidation ConsiderationsConsolidating multiple flares can help mitigate emissions and maintenance62 Solids Processing Bulk Solids: Optimizing Screw Conveyors Despite their apparent simplicity, the complexity of these conveying systems demands proper design and an understanding of the underlying principles Equipment and Services29 Focus Industrial HousekeepingSafeguard industrial workwear and tools read more..

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    TRANSFER HEAT,NOT BLAME.In your line of work, you can’t afford downtime. You have to know that everything is doing its job so you can actually do yours. That’s why, at Eastman, we have you covered with a wide range of dependable Therminol heat transfer uids for some of the world’s most technical applications. And with our Total Lifecycle Care® Program, you can count on dedicated support throughout the system’s lifecycle. To learn more, go to or call 1-800-426-2463 in North read more..

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    CMYCMMYCYCMYK8x10.5 AD-PLASTO-1-22-2014.pdf 1 1/22/14 2:33 PMCircle 24 on p. 70 or go to read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 20155Editor s PageGood role models can greatly influence the path of a person’s career. While role models don’t always receive awards, re-cent announcements of award recipients describe a num-ber of professionals in chemistry and chemical engineering who have been singled out for their exceptional accomplishments. These women are indeed role models, and a source of inspiration to others in the chemical process industries (CPI).A read more..

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    ABCD“Join the ultra-high shear revolution.”When Ross introduced the first Ultra-High Shear Mixer, we revolutionized high speed, high shear mixing. Operating with tip speeds up to six times higher than conventional rotor/stator mixers, these mixers can produce sub-micron emulsions and dispersions faster than any conventional rotor/stator design. Today, in applications from foods to pharmaceuticals, coatings and adhesives, the results include smaller particle sizes, tighter particle size read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Chementator7Edited by:Gerald OndreyA new low-pressure process for mak-ing xylenes combines toluene with methanol to yield a xylenes prod-uct stream with the possibility of no benzene byproduct. Known as GT-TolAlk and developed by GTC Technology (Hous-ton;, the new process requires no hydrogen addition and produces only water as a byproduct. The first facility to use the process is cur-rently in the design phase, and read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 20158In hydraulic fracturing, high-pressure pumps force water bearing sand or ce-ramic proppants into a manifold, known as a missile, and subsequently into an oil or gas well. Exposure to the highly abrasive, proppant-filled fluids means the pumps re-quire frequent maintenance and have short-ened life spans. Energy Recovery Inc. (San Leandro, Calif.; has developed a missile that allows the abra-sive read more..

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    ACHEMA – Solutions from a single source for the chemical industryGet the answers to all of your questions from KSB, the only full-range supplier for pumps, valves and service. We look forward to welcoming you to ACHEMA 2015 from 15 to 19 June. Visit us at stand H14 in hall 8 to bene t from competent and comprehensive consultancy on all services throughout the entire life cycle of your equipment. Learn how we can optimise your life cycle costs, achieve maximum operating reliability and secure read more..

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    US H E R I NG I N TH E N E XT 1 00 YEAR S OF P RO CE S S I N NO VATIONSince 1915, The Chem Show is where producers of chemicals, pharmaceuticals, food and other processed products find the latest equipment and solutions for their operations. Join us in New York City as we embark on a new century of innovation in process technology.2015 CHEM SHOWNOV 17-19 / JAVITS CENTER / NYCEND O RS ED BYM E D IA PARTN E RB E C O M E A N E X H I B I TO R OR L EAR N MOR E:CH E M S HO W.C read more..

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    The research group of Keiichi Tomishige at Tohoku Uni-versity (Sendai,, in col-laboration with Daicel Corp. (Tokyo, both Japan;, has developed a catalytic reaction system that is highly efficient for syn-thesizing tetrahydrofuran (THF) — a widely used solvent and raw material for making polyether resin. The catalyst system consists of rhenium as the major active metal and palladium as a promoter, on a cerium oxide support. In laboratory trials, a read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201512of sugar) in a dioxane solvent at 140–180°C and H2 pressure of several tens of atmospheres. The catalytic reaction exhibited a turnover number velocity of 300 h–1, and turnover number of 10,000, which is one order of magnitude larger than alternative homogeneous catalyst systems that use rhenium catalysts reducing agents, which are more costly than H2. The Re/Pd catalyst is not only highly active, but it is easily recovered by read more..

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    A step closer to making CO by artificial photosynthesisResearchers at Toshiba Corp. (Tokyo, Japan; have developed an artificial photosynthesis system that uses solar energy to convert CO2 and water into CO with 1.5% efficiency — the highest efficiency achieved to date. The company believes the technology has the potential for utilizing CO2 to make CO — a precursor for methanol and other chemicals normally made from petroleum- or coal-based synthesis gas.Toshiba uses a gold read more..

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    Mechanical engineering students have been taught that true iso-thermal compression, while ideal from an energy-efficiency per-spective, is not achievable. However, a late 1800s’ technology, the Taylor Compres-sor has delivered isothermal compression in large industrial applications for nearly a century. The largest installation of the Tay-lor compressor powered multiple local min-ing operations in Canada for over 80 years, with no moving parts and no maintenance. It drew air and water down a read more..

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    e! What you see here is the essence of universality. Perfect for whenever you require a direct-acting 2/2-way solenoid valve. It’s the one valve you can use for each and every occasion. Built for both neutral and slightly aggressive media – powerful enough to work with dry gases or steam. Three design elements ensure you get maximum performance: its highest flow rates, its long service life and its top reliability. All of which come standard. And it’s no problem at all if your read more..

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    Your one-stop resourcefrom drop in spray lances to tank washing nozzlesRetractable Spray LancesMaxiPass® NozzlesHydroWhirl® Orbitor TF Spiral NozzlesAllow you to remove a nozzle for inspection or service without taking your process oflineThe ultimate in clog-resistance with the largest free passage in a full cone nozzleA versatile Clean-In-Place tank washing machine that combines high-impact cleaning with extended operating lifeProduce sprays composed of small droplets for quenching and read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201518and pulp-and-paper industries. The acquisition will enhance Sulzer’s of-fering of welding solutions.Indorama acquires Polyplex PET plant near IstanbulJanuary 8, 2015 — Indorama Ven-tures Public Co. (IVL; Bangkok, Thai-land; announced that its wholly owned subsidiary In-dorama Netherlands B.V. will acquire a 100% equity stake of Polyplex Tur-key, including a greenfield polyeth-ylene terephthalate (PET) plant read more..

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    Looming NSPS Subpart Ja and other federal, state, and local regulations mean rethinking your entire flare system. Stay ahead of the curve – and the deadlines – by adding a ZEECO® Flare Gas Recovery System. Zeeco engineers flare gas recovery systems that are world-renowned for performance, reliability, and extra-long life. You’ll conserve fuel, operate more energy efficiently, and capture waste gases required to comply with EPA regulations. Zeeco puts more than 35 years of advanced read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Newsfront20The field of additive manufacturing (AM) — often referred to as three-di-mensional (3-D) printing — has seen explosive growth in the past three years, and seems poised to have a profound and lasting impact on manufacturing deci-sions across many industry sectors. Activity in the field has been largely motivated by the technology’s potential to lower manufactur-ing costs, and enable revolutionary designs for a wide read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201521 Y S INC. Custom Catalyst Milling / Grinding Calcining / Drying Solids or Liquid Mixing/Blending/Packaging ISO 9001:2008 Screening Vacuum Impregnating Metal Reclaim Pelletizing YS Inc. 4531 County Road 458 Collinsville, AL 35961 888-356-3343 TOLL MANUFACTURE SINCE 1982 Circle 31 on p. 70 or go to 22 on p. read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201522the ability to use more different types of materials in AM, but so far, the leading companies have not really pushed the envelope in terms of re-ally going after a wide range of new materials yet,” Wohlers remarks. “There’s going to be a lot of interest-ing activity in the area of expanding the materials, both in high-end per-formance materials to low-end, less expensive materials,” he predicts.UT’s Bourell says one of the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201523inspection services at Lloyd’s Reg-ister Energy. This is a major focus for Lloyd’s Register Energy, includ-ing participation on the British Stan-dards Institute Committee for addi-tive manufacturing, which is working towards generating a collection of ISO standards.“Consensus standards programs help provide a bridge between R&D work and commercialization,” remarks Pat Picariello, ASTM director of devel-opmental read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Newsfront24In the grand scheme of any chemical process, a valve might seem an after-thought. However, in reality, valves play as critical a role as any reactor, separator, mixer or other integral piece of equipment. For this reason, the reliability of valves is a major concern. No matter the application or valve style, processors require valves that can stand up to harsh chemicals and pro-cess environments, while reliably containing read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201525Groth. The valves protect low-pres-sure atmospheric storage tanks from excessive pressure and/or vacuum, but the all-polymer internal construc-tion enables them to operate in harsh chemical environments that would damage traditional metal and fiber-glass valves. The non-metallic pres-sure/vacuum relief valves are avail-able in polyvinylidene fluoride (PVDF), polypropylene (PP), high-density polyethylene (HDPE) and chlorinated read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201526full-bore with no flow restrictions, al-lowing processes with damaging flu-ids, such as lime or mineral slurries, to move without compromising per-formance. Because of the full-bore design, the valve itself becomes an integral part of the pipe and allows it to process the same fluids in the harshest of conditions.Similarly, Val-Matic (Elmhurst, Ill.; offers its Quadro-Sphere trunnion ball valves (Figure 2) for read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201527sions regulations and safety.”Improvements to typical stem-seal designs can often address these problems. “For example,” says Chau, “ITT offers a bellows assembly which removes all dynamic sealing surfaces and is hermetically sealed; thus deliv-ering a solution that inherently elimi-nates packing gland adjustment and stem packing leakage” (Figure 3).Jones agrees that seal design plays a major role in eliminating fu-gitive read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201528ally watching manufacturers in these industries with a close eye.”He says as parts of its mandate to protect public health, the U.S. Envi-ronmental Protection Agency (EPA; Washington, D.C.) has issued a pro-tocol designed to detect and eliminate fugitive VOC leaks in a wide array of process equipment, including valves. “Method 21 currently allows for no more than 500 ppm [parts per mil-lion] leakage,” he says. In response, read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201529FocusSafeguard industrial workwear and tools with this rugged binThis company’s lockable industrial storage bin (photo) is available for gathering soiled workwear for laun-dering, used sorbent products (non-hazardous materials), maintenance tools and related industrial hygiene items. Its metal-free interior safe-guards the stored goods. Its one-piece, rotationally molded lid and door, made from 100% waterproof, ultraviolet read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201530against excessive marine growth — an essential step to allow for reliable operation and proper inspections. This company now operates a rental fleet to enable companies to use the FJCT. The product offering allows users to work with various inspection cameras, 3D modeling, lasers, tem-perature probes and cleaning tools, and to collect various types of infor-mation, data and images to guide subsea inspection and maintenance read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201531cars. The VentClean is now available in four model sizes to handle gas ca-pacities through 1,500 ft3/min. Two configurations are available to adapt to a variety of scrubbing liquid pref-erences. Type 1 is configured to use water on a once-through basis. Type 2 uses a special circulation pump that reduces water consumption, or allows for the use of chemical re-agents, such as sodium hydroxide on a recirculated batch basis. — read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201532related to robotic welding cells, material-handling operations, auto-mated assembly systems, palletizing and packaging machinery and oth-ers that require electronic safeguard-ing devices. — Rite-Hite Machine Guarding, Milwaukee, Wisc.www.ritehite.comMove drums without the need for a forkliftThe Pig Poly Deck with Pallet Jack Pockets (photo) is the latest product to join this company’s spill-contain-ment product offerings. Using read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015New Products33Molecular structure database now has 750,000 entriesOver 750,000 entries are now avail-able to the scientific community through the Cambridge Structural Da-tabase (CSD). This fully validated da-tabase, established in 1965, contains all small-molecule chemical structures ever published, and is an essential re-source to scientists around the world. Information derived from crystal struc-tures is vital to structural read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201534A new solenoid valve variant for high-pressure applicationsThis company’s Type 6027 solenoid valve (photo) is now available in a new, high-pressure version for pres-sures up to 250 bars. The new vari-ant of the type 6027 seals the valve seat with a ceramic ball seal. This seal is self-centering and provides reliable and longterm protection against leaks. The ball material (alu-minum oxide; Al2O3) is highly resilient against both read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201535AODD air-distribution system is now available in stainless steel The energy-efficient Pro-Flo Shift Air-Distribution System (ADS) is now avail-able in 316 stainless steel and poly-propylene plastic (photo) materials of construction, joining the original alumi-num and nickel-plated aluminum offer-ings. The introduction of the stainless-steel and plastic options allows the company’s air-operated, double-diaphragm (AODD) pumps to be read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201536Flow Measurement Extremely accurate measurements of liquids. Accuracy of rate ± 0,1%. Measurement range 1:150. Flow range from 0.1 to 7,500 l/min. No fl ow conditioning required. Valves and pipe elbows are allowed close to the fl owmeter. Electronic units that are coordinated to KRAL fl owmeters and their divers applications.Accuracy over a wide fl ow and viscosity range. One of the Most Precise read more..

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    Flow Measurement Extremely accurate measurements of liquids. Accuracy of rate ± 0,1%. Measurement range 1:150. Flow range from 0.1 to 7,500 l/min. No fl ow conditioning required. Valves and pipe elbows are allowed close to the fl owmeter. Electronic units that are coordinated to KRAL fl owmeters and their divers applications.Accuracy over a wide fl ow and viscosity range. One of the Most Precise Flowmeters.www.kral.atwww.kral-usa.comKRAL AG, 6890 Lustenau, Austria, read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Facts At Your Fingertips38Dimensionless numbers refer to physical parameters that have no units of measurement. These numbers often appear in cal-culations used by process engineers. As long as consistent units are used, dimensionless numbers remain the same whether metric or other units are used in the equations. Here are some dimensionless numbers often used in chemical engineering fluid dy-namics calculations:Reynolds number (Re). read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Technology Profile39‘Green’ Ethylene ProductionBy Intratec Solutions With a global nominal ca-pacity of about 140 million ton/yr, ethylene is among the main petrochemicals produced worldwide, and is a key building block for the industry. Eth-ylene is produced mostly via steam-cracking of petroleum-based feed-stocks, such as naphtha. Ethylene is a raw material for the manufacture of polyethylene, polyvinyl chloride (PVC), ethylene read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201540High-shear mixers typically operate at high rotational speeds and are used for mixing applications that are best described as dispersion processes. They can be used in a variety of applications, such as to speed additions, wet powders, break lumps and provide pro-cess intensification. Many dispersion prob-lems are caused by incorrect use of equip-ment, when simple operational changes may give better results. While the inherent read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201541purpose of dispersion is rapid formation of a suitably uniform fluid. For processes involv-ing soluble solids, the equipment may be called a dissolver. With dispersed thicken-ers or emulsion formation, the fluid viscosity may increase.This lengthy description is needed be-cause different processes and applications can be accomplished with variations on similar equipment (see section on Types of High-Shear Dispersers). The open read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201542one or more baffles. Too much rotational flow and a surface vortex that draws air into the impeller can reduce dispersion and create unwanted air bubbles in the product. Flow through a stator eliminates much of the rota-tional flow from the discharge of rotor-stator mixers. Single or dual baffles may be adjust-able to control a surface vortex. In other dis-perser designs, off-center mounting or tanks with square cross-sections are read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201543form lumps. If the particles hydrate in the liquid, the particles must be sepa-rated and suspended quickly. If the solids are soluble, the rate of dissolution is determined primarily by equilibrium solubility and particle size. Fluid motion may enhance the exter-nal mass transfer around the particle, but concentration uniformity in the fluid provides the most effective driving force for dissolution.For insoluble solid particles, the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201544ary grid, are commonly called rotor-stator dispersers or even homogenizers. The dis-persion mechanisms with rotor-stator dis-persers are a complicated combination of primarily fluid shear with some mechanical shear. Any significant amount of mechani-cal shear will wear or damage the disperser head. The rotor of some dispersers looks like a typical bladed impeller. The stator may have either slots or holes, through which the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201545can be served by the same type of mixer. High-speed dispersers may be used simply to achieve rapid liquid addition and blend-ing. Dispersers are often used for a multi-step batch process that may involve both the addition of miscible liquids and disper-sion of solids for dissolving. The addition of miscible fluids with differing viscosities may require dispersion to effectively combine the fluids. The high power requirements of read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201546of mixing problems. Continued operation of the disperser may be sufficient to reduce some problems.TYPES OF HIGH-SHEAR DISPERSERSMost high-shear dispersers are top-mounted on cylindrical tanks. The tanks may be baf-fled, partially baffled, or unbaffled depending on the process and fluid viscosity. At low vis-cosity as an alternative to baffles or to im-prove vortex control, the disperser may be off-center mounted. The off-center read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201547to limit vortexing. Figure 8 shows a slotted rotor inside a slotted stator. The flow pattern is between the rotating slots and through the stationary slots.Unequal numbers of slots in the rotor and the stator allow flow through only a few slots at a time. The partial alignment of slots limits noise and vibration caused by flow pulsed through the slots.Some rotor-stator dispersers have an im-peller with blades rotating inside a read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Feature Report48IN BRIEFEVALUATION CRITERIATUBE-RUPTURE FLOW ESTIMATIONRELIEF-DEVICE SELECTIONRELIEF-DEVICE SIZINGEXAMPLESCLOSING THOUGHTSApplying dynamic simulation models to tube-rupture scenarios can help ensure more accurate sizing and hazard assessmentsTube rupture in heat exchangers is an extremely serious issue in the chemi-cal process industries (CPI; Figure 1). Heat-exchanger tube-rupture sce-narios can be evaluated by read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201549Evaluation criteriaProcess-hazard analyses for shell-and-tube heat exchangers call for evaluation of tube-rupture scenarios if the difference in maximum allow-able working pressure (MAWP) be-tween the low-pressure (LP) and high-pressure (HP) sides is greater than that covered by the 10/13 (or 2/3 rule, as may be applicable). This is based on ASME Boiler and Pres-sure Vessel Code Section VIII, Div.1 [1], which requires a system to be read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201550in the case of incompressible-liquid-filled systems results in a waterham-mer-type effect that cannot be simu-lated with the dynamic simulation tools commonly used for analysis of these scenarios. Sometimes a rup-ture pin is also considered, allowing faster open times than rupture disks. Typical opening times for relief de-vices are 50–100 milliseconds (ms) for spring-loaded pressure safety valves (PSVs) and around 1–10 ms for read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201551on the LP side upon flowing across the tube rupture, resulting in its tem-perature dropping to –67°C immedi-ately after rupture, and subsequently increasing as the shellside pressure rises. While the fluid temperature in the shellside is estimated to drop to a minimum of –48°C near the rupture location, direct impingement of the rupture fluids on the intact adjacent tubes, shell and tubesheet is pos-sible. Conservative design read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201552Case 5: Liquid propane cooled by natural-gas condensate. A pro-pane-refrigerant-based natural-gas dewpointing plant uses natural-gas condensate to sub-cool liquid refrig-erant. Liquid propane at around 5–8 barg pressure is on the tubeside, and HP natural-gas condensate at 43 barg flows on the shellside of the exchanger, which is TEMA type AEL. The condensate state is two-phase, vapor-liquid in and out of the exchanger. Dynamic read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201553tected by the 10/13 rule Line sizing for the rupture disk’s •inlet and outlet should be based on the transient relief flows, with the criteria that the LP-side pres-sure rise is limited to the allowable design overpressureDynamic simulations allow evalu-•ations of suitable exchanger mini-mum metal design temperaturesDynamic evaluation of the heat-•exchanger tube-rupture scenario is often simplified by looking at the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Feature Report54IN BRIEFMAXIMIZING UCORRECT FLUID PLACEMENTMAXIMIZING EMTDMINIMIZING SHELLSIDE BYPASS Ensuring optimal performance of shell-and-tube heat exchangers requires knowledge of the controlling fluid, correct exchanger geometry and configuration, as well as proper fluid placementOptimizing the thermal design of a shell-and-tube heat exchanger re-quires minimizing the heat-transfer area for a given heat duty while remaining read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201555The tube velocity can be increased in the following ways: Increasing the number of tube passesi. Reducing the shell diameter and ii. increasing the tube length, thus reducing the number of tubes and the flow areaIncreasing the tube pitch while iii. keeping the same shell diameter and increasing the tube length, thus reducing the number of tubes and the flow area; however, it is to be noted that tube pitch is generally specified as read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201556the shellside crossflow velocity can be increased (as can be reduced) by lowering Di, B or r. Thus, the shell-side velocity can be increased in the following ways:Reducing shell inside diameteri. Reducing baffle spacingii. Lowering pitch ratio; however, tube iii. pitch is generally 1.25, 1.33 or 1.5 times the tube outside diameter, limiting the flexibility in lowering this parameterBased on the above discussions, the shellside read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201557of bypass behavior are as follows:Between the tube bundle and i. the shellBetween the baffles and the shellii. Through the tube-field pass-iii. partition lane, in the case of mul-tiple tube passes, when the pass-partition lane is parallel to shellside crossflowAnother type of bypass — through the baffle hole (between the tube and the baffle) — is not as harmful, as it does participate in heat transfer. The first type of bypass read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Engineering Practice58Many petroleum-refining and petrochemical fa-cilities have experienced tremendous growth in recent years in response to increas-ing demand for fuels and chemical precursors. Due to environmental regulations and economic consid-erations, it is frequently more de-sirable to increase the throughput on an existing facility rather than to build a new plant. As shown in Fig-ure 1, the total crude-oil processing read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201559is to install a flare-gas recovery unit (FGRU) for each flare system. The consolidation of multiple flare sys-tems into a single flare network could significantly reduce the cost of com-pliance as a single FGRU unit could be installed to service the entire facil-ity (or two FGRUs could be installed to improve availability). A simplified diagram of flare debottlenecking op-tions using this approach is shown in Figure 2. In addition, read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201560sizing parameters for the FGRU (es-pecially the compressor).2. Seal drums — To ensure that ex-cessive or insufficient pressure will not disrupt the liquid seal in the seal drum and result in unintended re-lease from a flare stack during nor-mal operations. Consideration must also be given to ensure that the seal-ing fluid does not freeze. 3. Liquid knockout — While most FGRU compressors can handle lim-ited liquid on the inlet, read more..

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    If interested in posting a job, please contactDIANE BURLESON | Direct: 512-337-7890 | dburleson@accessintel.comLooking for that dream job in the chemical process industries?Don’t let the competition score that perfect position you deserve. Let Chemploy work for you. job center focuses exclusively on jobs in the CPI. Post your resume and cover letters at today!Receive job alerts that will notify you by email of new jobs posted that read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 2015Solids Processing62Screw conveyors play a major role in a wide variety of in-dustrial operations that in-volve the handling of bulk solids. While their use is generally limited to relatively short conveying distances, their versatility in being able to provide reliable operation for conveying over a wide range of el-evation angles from the horizontal to the vertical is well established. De-spite their apparent simplicity, their mode read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201563be of heavy cross section to resist the torsional, wind-up deformation imposed by the conveying action. The need to limit the fill ratios of U-shaped trough conveyors is neces-sary to prevent “throwback” and a loss in conveying efficiency.This article provides an overview of key performance and design as-pects of enclosed screw conveyors.Enclosed screw conveyorsReferring to the enclosed screw con-veyor shown in Figure 1, the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201564Q = QtV• (1)Where:Qt = 60 ND3• (2)=4(1 + 2CD)2(DCD)2 pDtSD • (3)Effect of conveyor diameter — Corresponding speeds. Corre-sponding speeds are given by a non-dimensional, specific speed number, NS, which is defined by Equation (4):NS =2Rog=N2D1789• (4)It follows from Equation (4) that screw conveyors of large diameter attain their maximum output at lower speeds compared to conveyors of smaller diameter read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201565with radius describes the vortex mo-tion in the screw and is expressed by Equation (8):•VT rn= CV (8)In Equation (8), Cv is the vortex constant, and n is the vortex index. It has been shown by Roberts [2, 3] that n ≈ 0, that is, the velocity component VT is approximately constant and, in fact, does not vary with the increase in radius from Ri at the shaft to Ro at the outer pe-riphery. This is because the choking action in the read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201566tive motion will be governed by in-ternal friction and not by surface or boundary friction.It should be noted that the surface friction angles for cohesive bulk sol-ids decrease with an increase in nor-mal pressure. It is important that the surface friction angles be measured and that the appropriate friction angles corresponding to the pres-sures generated at the screw and casing surfaces be used in the con-veyor design.Force read more..

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    CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM FEBRUARY 201567high enough for the fill ratio F < 1.In multiple-conveyor installations where transfers are employed, it is most important that blockages be avoided. As an illustration, the transfer from a horizontal to a verti-cal screw conveyor as depicted in Figure 12 is considered. Two design conditions need to be considered. First, the discharge Q1 from the horizontal conveyor will be cyclical at a frequency related to the con-veyor read more..

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    Order your copy today by visiting store.chemengonline.comThis guidebook contains how-to engineering articles formerly published in Chemical Engineering. The articles in Volume 2 provide practical engineering recommendations for process operators faced with the challenge of treating inlet water for process use, and treating industrial wastewater to make it suitable for discharge or reuse.There is a focus on the importance of closed-loop or zero-discharge plant design, as well as the selection, read more..

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