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BBC One - Look East, 12/09/2012 - QR code The BBC has updated its cookie policy. We use cookies to ensure that we give you the best experience on our website. This includes cookies from third party social media websites if you visit a page which contains embedded content from social media. Such third party cookies may track your use of the BBC website. We and our partners also use cookies to ensure we show you advertising that is relevant to you. If you continue without changing your settings, we'll assume that you are happy to receive all cookies on the BBC website. However, you can change your cookie settings at any time. Continue Change settings Find out more ]]> Accessibility links Skip to content Accessibility Help BBC iD Notifications
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Recommendations for the Management of Strokelike Episodes in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Strokelike Episodes. - PubMed - NCBI
1 selected item: 26954033
JAMA Neurol. 2016 May 1;73(5):591-4. doi: 10.1001/jamaneurol.2015.5072.
Recommendations for the Management of Strokelike Episodes in Patients With Mitochondrial Encephalomyopathy, Lactic Acidosis, and Strokelike Episodes.
Koenig MK1, Emrick L2, Karaa A3, Korson M4, Scaglia F5, Parikh S6, Goldstein A7.
Departments of Pediatrics and Neurology, The University of Texas Medical School at Houston, Houston.
Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston.
Department of Genetics and Metabolism, Massachusetts General Hospital, Harvard Medical School, Boston.
Genetic Metabolic Center for Education, Salem, Massachusetts.
Department of Molecular and Human Genetics, Baylor College of Medicine and Texas Children's Hospital, Houston.
Center for Pediatric Neurology, Neurosciences Institute, Cleveland Clinic, Cleveland, Ohio.
Department of Pediatrics, Children's Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
Strokelike episodes are a cardinal feature of several mitochondrial syndromes, including mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (MELAS). Recent advances in the understanding of the pathophysiologic mechanisms of strokelike episodes in MELAS have led to improved treatment options.
Current understanding of the cause of strokelike episodes in MELAS and present recommendations to assist in the identification and treatment of patients with MELAS who present with stroke are presented. Mounting evidence points toward a benefit of the nitric oxide precursors, arginine, to both prevent and reduce the severity of strokes in patients with MELAS.
Although much information is still needed regarding the appropriate dosing and timing of arginine therapy in patients with MELAS, urgent administration of nitric oxide precursors in patients with MELAS ameliorates the clinical symptoms associated with strokelike episodes.
Nitric Oxide Deficiency Triggering Strokelike Episodes. [JAMA Neurol. 2016]
Nitric Oxide Deficiency Triggering Strokelike Episodes-Reply. [JAMA Neurol. 2016]
26954033
10.1001/jamaneurol.2015.5072
MELAS Syndrome/diagnosis*
MELAS Syndrome/therapy*
Encephalomyopathy - Genetic Alliance

type: global

value: This website is part of the United States National Library of Medicine , a branch of the National Institutes of Health . It is approved and funded by the government of the United States.


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Patent US6252370 - Electromagnetic alignment and scanning apparatus - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAn apparatus capable of high accuracy position and motion control utilizes one or more linear commutated motors to move a guideless stage in one long linear direction and small yaw rotation in a plane. A carrier/follower holding a single voice coil motor (VCM) is controlled to approximately follow the...http://www.google.com/patents/US6252370?utm_source=gb-gplus-sharePatent US6252370 - Electromagnetic alignment and scanning apparatusAdvanced Patent SearchPublication numberUS6252370 B1Publication typeGrantApplication numberUS 09/482,870Publication dateJun 26, 2001Filing dateJan 14, 2000Priority dateJun 27, 1994Fee statusPaidAlso published asUS6246204, US6255795, US6255796, US6323935, US6329780, US6693402, US6844695, US6844696, US6969966, US7012398, US7573225, US20020017890, US20030184253, US20030184254, US20050083006, US20050088133, US20050280390Publication number09482870, 482870, US 6252370 B1, US 6252370B1, US-B1-6252370, US6252370 B1, US6252370B1InventorsAkimitsu Ebihara, Thomas NovakOriginal AssigneeNikon CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (83), Non-Patent Citations (2), Referenced by (36), Classifications (28), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetElectromagnetic alignment and scanning apparatus
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3789285Mar 27, 1972Jan 29, 1974Handotai Kenkyu ShinkokaiPosition control system using magnetic forceUS3889164Jan 24, 1973Jun 10, 1975Handotai Kenkyu ShinkokaiPosition control system using magnetic forces for correcting the inclination of a controlled member including a torsional mountingUS3935486Aug 26, 1974Jan 27, 1976Citizen Watch Co., Ltd.Finely adjustable table assemblyUS4019109Apr 5, 1976Apr 19, 1977Hughes Aircraft CompanyAlignment system and method with micromovement stageUS4087729Apr 20, 1976May 2, 1978Nippon Telegraph & Telephone Public CorporationPosition finely adjusting apparatusUS4129291Jul 25, 1977Dec 12, 1978Hitachi, Ltd.Two-dimensional precision tableUS4234175Dec 18, 1978Nov 18, 1980Canon Kabushiki KaishaHigh precision positioning deviceUS4392642Dec 22, 1980Jul 12, 1983Anorad CorporationWorkpiece positioning table with air bearing padsUS4409860Apr 7, 1980Oct 18, 1983Hitachi, Ltd.Apparatus for precisely moving a tableUS4425508May 7, 1982Jan 10, 1984Gca CorporationElectron beam lithographic apparatusUS4443743Nov 13, 1981Apr 17, 1984Mcdonnell Douglas CorporationTwo axis actuatorUS4485339Jun 10, 1983Nov 27, 1984The Perkin-Elmer CorporationElectro-magnetic alignment deviceUS4492356Oct 26, 1982Jan 8, 1985Hitachi, Ltd.Precision parallel translation systemUS4504144Jul 6, 1982Mar 12, 1985The Perkin-Elmer CorporationSimple electromechanical tilt and focus deviceUS4506204Jun 10, 1983Mar 19, 1985The Perkin-Elmer CorporationElectro-magnetic apparatusUS4506205Jun 10, 1983Mar 19, 1985The Perkin-Elmer CorporationElectro-magnetic alignment apparatusUS4507597Jun 10, 1983Mar 26, 1985The Perkin-Elmer CorporationElectro-magnetic alignment assembliesUS4514858Mar 15, 1983Apr 30, 1985Micronix PartnersLithography systemUS4516253Apr 25, 1983May 7, 1985Micronix PartnersLithography systemUS4525659Sep 30, 1982Jun 25, 1985Telmec Co., Ltd.Positioning stage having a vibration suppressorUS4575942Oct 18, 1983Mar 18, 1986Hitachi, Ltd.Ultra-precision two-dimensional moving apparatusUS4615515Dec 14, 1984Oct 7, 1986Canon Kabushiki KaishaPrecise movement deviceUS4628238Jun 5, 1985Dec 9, 1986U.S. Philips CorporationPositioning device comprising pre-stressed contactless bearingsUS4630942Jan 18, 1985Dec 23, 1986Hitachi, Ltd.Guiding apparatusUS4641071Sep 25, 1985Feb 3, 1987Canon Kabushiki KaishaSystem for controlling drive of a wafer stageUS4648723Jul 18, 1985Mar 10, 1987Omron Tateisi Electronics Co.Static pressure air surface stageUS4648724Jul 18, 1985Mar 10, 1987Omron Tateisi Electronics Co.Static pressure air surface stageUS4653408Jul 30, 1985Mar 31, 1987Citizen Watch Co., Ltd.Table mechanism for controlling table attitudeUS4654571Sep 16, 1985Mar 31, 1987Hinds Walter ESingle plane orthogonally movable drive systemUS4667139Oct 30, 1985May 19, 1987Hitachi, Ltd.Table deviceUS4675891Jun 25, 1985Jun 23, 1987Thomson-CgrX-ray apparatus with focus position controlUS4676492Jul 1, 1985Jun 30, 1987Shamir Arye HShallow X-Y table positioning device having large travel capabilityUS4677651Dec 5, 1984Jun 30, 1987U.S. Philips CorporationRotary anode X-ray tube having a sliding bearingUS4684315Jan 31, 1986Aug 4, 1987Fujitsu LimitedFrictionless supporting apparatusUS4687980Jan 5, 1984Aug 18, 1987Eaton CorporationX-Y addressable workpiece positioner and mask aligner using sameUS4698575Jun 26, 1986Oct 6, 1987U.S. Philips CorporationPositioning deviceUS4708465Feb 27, 1987Nov 24, 1987Canon Kabushiki KaishaExposure apparatusUS4723086Oct 7, 1986Feb 2, 1988Micronix CorporationCoarse and fine motion positioning mechanismUS4742286Oct 29, 1985May 3, 1988Micro-Stage, Inc.Gas bearing X-Y-θ stage assemblyUS4744675Jan 16, 1987May 17, 1988Canon Kabushiki KaishaMoving mechanismUS4750721Oct 31, 1986Jun 14, 1988Dainippon Screen Mfg. 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"Step and Scan: A Systems Overview of a New Lithography Tool". The Perkin-Elmer Corporation, Connecticut Operations Sector, Norwalk, CT, SPIE, vol. 1088, Laser Microlithopgraphy II (1989), pp. 424-433.2Moriyama, et al., "Precision X-Y Stage with a Piezo-driven Fine-table," The Bulletin of The Japan Society Precision Engineering, vol. 22, No. 1, pp. 13-17, Mar. 1988.Referenced byCiting PatentFiling datePublication dateApplicantTitleUS6525803Dec 19, 2000Feb 25, 2003Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS6593997Nov 16, 2000Jul 15, 2003Nikon CorporationStage assembly including a reaction assemblyUS6603531Nov 16, 2000Aug 5, 2003Nikon CorporationStage assembly including a reaction assembly that is connected by actuatorsUS6693402Oct 16, 2001Feb 17, 2004Nikon CorporationElectromagnetic alignment and scanning apparatusUS6724466Mar 26, 2002Apr 20, 2004Nikon CorporationStage assembly including a damping assemblyUS6757053Nov 16, 2000Jun 29, 2004Nikon CorporationStage assembly including a reaction mass assemblyUS6844695Mar 27, 2003Jan 18, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS6844696Mar 27, 2003Jan 18, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS6924882Aug 28, 2003Aug 2, 2005Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS6969966Oct 28, 2004Nov 29, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS7012398Nov 15, 2004Mar 14, 2006Nikon CorporationElectromagnetic alignment and scanning apparatusUS7034920Dec 19, 2002Apr 25, 2006Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS7061577Mar 26, 2002Jun 13, 2006Nikon CorporationImage adjustor including damping assemblyUS7202937 *Feb 28, 2006Apr 10, 2007Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS7221433Jan 28, 2004May 22, 2007Nikon CorporationStage assembly including a reaction assembly having a connector assemblyUS7573225Aug 25, 2005Aug 11, 2009Nikon CorporationElectromagnetic alignment and scanning apparatusUS7852034Apr 6, 2005Dec 14, 2010Nikon CorporationDrive method of moving body, stage unit, and exposure apparatusUS7922159 *Apr 12, 2011F-Tool International AgClamping apparatus for positioning and fixing work piecesUS9152060Dec 31, 2008Oct 6, 2015Nikon CorporationStage device with two pairs of movable elements and two pairs of stators, exposure apparatus, and method of manufacturing devicesUS20030184253 *Mar 27, 2003Oct 2, 2003Nikon CorporationElectromagnetic alignment and scanning apparatusUS20030184254 *Mar 27, 2003Oct 2, 2003Nikon CorporationElectromagnetic alignment and scanning apparatusUS20030202167 *Jun 3, 2003Oct 30, 2003Mike BinnardStage assembly including a reaction assembly that is connected by actuatorsUS20030218732 *May 20, 2003Nov 27, 2003Watson Douglas C.Stage assembly including a reaction assemblyUS20040041994 *Aug 28, 2003Mar 4, 2004Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS20040252287 *Jun 11, 2003Dec 16, 2004Michael BinnardReaction frame assembly that functions as a reaction massUS20050083006 *Oct 28, 2004Apr 21, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS20050088133 *Nov 15, 2004Apr 28, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS20050206865 *Dec 19, 2002Sep 22, 2005Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS20050280390 *Aug 25, 2005Dec 22, 2005Nikon CorporationElectromagnetic alignment and scanning apparatusUS20060203216 *Feb 28, 2006Sep 14, 2006Asml Netherlands B.V.Balanced positioning system for use in lithographic apparatusUS20070210500 *Mar 12, 2007Sep 13, 2007F-Tool International AgClamping Apparatus for Positioning and Fixing Work PiecesUS20090122293 *Dec 31, 2008May 14, 2009Nikon CorporationStage device, exposure apparatus, and method of manufacturing devicesUS20110102761 *Sep 22, 2010May 5, 2011Nikon CorporationStage apparatus, exposure apparatus, and device fabricating methodEP1596423A1 *Jan 26, 2004Nov 16, 2005Nikon CorporationStage device, exposure device, and device manufacturing methodEP1596423A4 *Jan 26, 2004Apr 8, 2009Nippon Kogaku KkStage device, exposure device, and device manufacturing methodWO2011037275A1 *Sep 27, 2010Mar 31, 2011Nikon CorporationStage apparatus, exposure apparatus, and device fabricating method* Cited by examinerClassifications U.S. Classification318/649, 318/566, 414/936, 414/935International ClassificationG03F7/20, B64C17/06, G03B27/42, G03F9/00Cooperative ClassificationY10S414/135, Y10S414/136, G03F7/70766, G03F7/70725, G03F7/70716, G03F7/20, G03F7/70358, G03F7/709, G03F9/00, G03F7/70991, G03F7/70775European ClassificationG03F7/70N10, G03F7/70P16, G03F7/70N4, G03F7/70F28, G03F7/70N4B, G03F7/70P6F, G03F7/70N12, G03F7/20, G03F9/00Legal EventsDateCodeEventDescriptionNov 17, 2004FPAYFee paymentYear of fee payment: 4Nov 26, 2008FPAYFee paymentYear of fee payment: 8Oct 1, 2012FPAYFee 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Murder under a mystic moon (eBook, 2005) [WorldCat.org]
I thought you might be interested in this item at http://www.worldcat.org/oclc/742733618 Title: Murder under a mystic moon Author: Yasmine Galenorn Publisher: New York : Berkley Prime Crime, 2005. ISBN/ISSN: 9781101010471 1101010479 OCLC:742733618
Murder under a mystic moon.
(DLC) 2005575676
(OCoLC)57371267
9781101010471 1101010479
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schema:description "After psychic medium Emerald O'Brien literally stumbles across the body of her friend's best buddy, the police blame the death on a cougar attack. But Emerald senses something else wandering the forest--a killer of a more human kind. Includes a charm recipe."@en ;
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text: Fischer Tropsch ProcessUploaded by Nestor AquinoRating and Stats0.0 (0)Document ActionsDownloadShare or Embed DocumentEmbedView MoreCopyright: Attribution Non-Commercial (BY-NC)List price: $0.00Download as PDF, TXT or read online from ScribdFlag for inappropriate content111111 1111111111111111111111111111111111111111111111111111111111111US006716887B2 (12) United States Patent Newton et al. (10) Patent No.: (45) Date of Patent: US 6,716,887 B2 Apr. 6,2004 (54) FISCHER-TROPSCH PROCESS (51) Int. CI? C07C 27/00 (52) U.S. CI. 518/715; 518/700; 518/705 (58) Field of Search 518/700, 705, 518/715 (75) Inventors: David Newton, Farnham (GB); Barry Nay, Woking (GB) (73) Assignee: BP Exploration Operating Company Limited, London (GB) (56) References Cited ( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.c. 154(b) by 0 days. (21) Appl. No.: 10/297,253 (22) PCT Filed: May 23, 2001 (86) PCTNo.: PCT/GBOl/03329 U.S. PATENT DOCUMENTS 2,646,442 A 5,348,982 A 7/1953 Kendall 9/1994 Herbolzheimer et al. Primary Examiner-l. Parsa (74) Attorney, Agent, or Firm-Nixon & Vanderhye § 371 (c)(l), (2), (4) Date: May 8, 2003 (87) PCT Pub. No.: WOOI/94499 PCT Pub. Date: Dec. 13, 2001 (57) ABSTRACT (65) Prior Publication Data A process for the production of liquid hydrocarbon products by passing, at elevated temperature and pressure, synthesis gas and a fluidizing liquid through a fluidized catalytic bed within a reaction zone, characterized in that the fluidized catalytic bed is an aggregative fluidized catalytic bed comprising a particulate Fischer- Tropsch catalyst having a density of greater than 4,000 kg/m '. US 2003/0195264 A1 Oct. 16, 2003 (30) Foreign Application Priority Data Jun. 6, 2000 (GB) 0013793 24 Claims, 1 Drawing Sheet 17 u.s. Patent Apr. 6,2004 US 6,716,887 B2 24 23 27 19 17 US 6,716,887 B2 1 FISCHER-TROPSCH PROCESS This application is a 371 of PCT/GB01/02329 filed May 23,2001 The present invention relates to a process for the production of liquid hydrocarbons from a gaseous mixture comprising carbon monoxide and hydrogen (synthesis gas), in the presence of a Fischer- Tropsch catalyst. In particular, the present invention relates to the production of liquid hydrocarbons by contacting synthesis gas with a FischerTropsch catalyst in an aggregative fluidised bed. The production of hydrocarbons by contacting synthesis gas with a Fischer- Tropsch catalyst, typically a cobalt or iron catalyst, which may be either supported or unsupported, has been known for a considerable number of years. FischerTropsch processes have been operated commercially, for example, by Sasol Technology (Pty) Ltd in South Africa. Much of the early work on Fischer- Tropsch hydrocarbon synthesis was accomplished using fixed bed catalysts but in recent times attention has shifted to the use of liquid phase catalytic reactions largely because of the relative ease of removing the exothermic heat of reaction in such systems. Liquid phase Fischer-Tropsch processes typically employ a three-phase (liquid/gas/solid) slurry medium. In particular, use of fluidised beds in Fischer- Tropsch processes is known. In a fluidised bed, solid particles are transformed into a fluid-like state by the upward passage of a gas or liquid (fluidising fluid). When the velocity of the fluidising fluid reaches a critical velocity the drag force on the solid particles equals the buoyant weight of the bed. The bed is then supported by the fluidising fluid and possesses fluidlike properties such as flowing easily and maintaining a horizontal level when the bed is tilted. In addition, low density objects may be floated on the surface of the bed. This state is known as "fluidisation", and the critical superficial fluid velocity at which this occurs is termed the "minimum fluidisation velocity". When the fluidising fluid is a liquid (i.e. a liquid-solid system), an increase in the rate of flow of the liquid above the minimum fluidisation conditions, generally results in a progressive expansion of the bed, which gives rise to what is termed "particulate" or "homogeneous fluidisation". For large diameter fluidised beds, the expansion of a particulate fluidised bed can be approximated by the relationship: where V is the superficial liquid velocity, V t is the terminal fall velocity of the solid particles, E is the voidage of the solid particles, and n is the Richardson and Zaki exponent which is dependent upon the terminal Reynolds number, Ret and ranges from n=2.4 (Ret>500) to n=4.65 (Ret<0.2). The exponent n is also a function of the particle-to-bed diameter ratio, dID, as described by Yates in "Fundamentals of Fluidised-Bed Chemical Processes", Butterworths 1983, pages 14-15. This relationship can generally be ignored for 55 small particles in large diameter beds. Fischer-Tropsch processes which employ particulate fluidised beds in slurry bubble column reactors are described in, for example, V.S. Pat. Nos. 5,348,982; 5,157,054; 5,252, 613; 5,866,621; 5,811,468; and 5,382,748. Slurry bubble 60 column reactors operate by suspending catalytic particles in a liquid and feeding gas phase reactants into the bottom of the reactor through a gas distributor which produces small gas bubbles. As the gas bubbles rise through the reactor, the reactants are absorbed into the liquid and diffuse to the 65 catalyst where, depending on the catalytic system, they can be converted to both liquid and gaseous products. If gaseous 2 products are formed, they enter the gas bubbles and are collected at the top of the reactor. Liquid products are recovered by passing the slurry through a filter which separates the liquid from the catalytic solids. In slurry 5 bubble columns mixing is effected by the action of the rising gas bubbles. In V.S. Pat. No. 5,776,988, a Fischer- Tropsch process is operated by passing liquid and gas through the reactor in an ascending flow so as to expand a particulate fluidised 10 catalytic bed by at least 10% and up to 50% in relation to the height of the bed at rest and to place the catalyst in random movement in the liquid. By controlling the size and density of the catalytic particles, and the velocities of the gases and of the liquids, while taking into account the viscosity of the 15 liquid and the operating conditions, the catalytic bed expands to a controlled height. The size of the catalyst is typically of mean equivalent diameter of between 100 and 5000 ,um. A commercial scale plant operated according to the process of V.S. Pat. No. 5,776,988 would require a 20 catalytic bed of several meters in diameter and several meters deep. However, a limitation to particulate fluidisation, particuIarly when applied to Fischer-Tropsch processes, is the marked relationship between the liquid fluidising velocity 25 and the catalyst size and density. In order to avoid expansion of the bed out of the reaction vessel, a superficial liquid velocity must be employed below that of the terminal fall velocity, Vt, of the solid particles. To increase the "window" of operability of a commercial process, a larger catalyst 30 particle size can be used which increases the terminal fall velocity, V" and hence allows a higher superficial liquid velocity to be employed. Generally, in order to prevent segregation of the catalyst particles, a very narrow particle size distribution is employed (often referred to as monosized 35 catalyst particles). A different type of fluidisation behaviour is observed when the solid particles have a density which is considerably higher than that of the fluidising liquid. This type of fluidisation is called "aggregative" or "bubbling" fluidisation. The 40 fundamental reasons for the transition from particulate to aggregative fluidisation is not well understood but, without wishing to be bound by any theory, an important factor is the density ratio, pipt, where Ps is the density of the solid particles and Pt is the density of the fluidising fluid. If the 45 density ratio is high, aggregative behaviour is obtained; if the ratio is low, particulate fluidisation is observed. For particles having an average diameter in the range of 50 to 1000,um, fluidised with liquids having a density in the range of 700 to 1000 kg/m", the transition from particulate to 50 aggregative fluidisation occurs for solid particles having a density of greater than approximately 4000 kg/m '. Expansion of an aggregative fluidised bed does not follow the relationship: Instead, aggregative fluidised beds are characterised by the formation of particle free regions of fluidising liquid above the minimum fluidisation conditions. These particle free regions of fluidising liquid may be regarded as liquid "bubbles" or liquid "voids". Surprisingly, it has now been found that a Fischer- Tropsch process can be successfully operated using an aggregative fluidised catalytic bed. The present invention relates to a process for the production of liquid hydrocarbon products by passing, at elevated temperature and pressure, synthesis gas and a fluidising liquid through a fluidised catalytic bed within a reaction 3 US 6,716,887 B2 4 zone, characterised in that the fluidised catalytic bed is an aggregative fluidised catalytic bed comprising a particulate Fischer- Tropsch catalyst having a density of greater than 4,000 kg/m '. Advantages of employing an aggregative fluidised cata- 5 lytic bed include: 1. The process being less constrained by the size of the catalyst particles and by the liquid fluidising velocity. In particular, an aggregative fluidised bed can be operated using a wide catalyst size distribution and/or with a liquid 10 fluidising velocity above the terminal fall velocity, U" of the catalyst particles. 2. The presence of the "liquid bubbles" promote solid mixing within the fluidised bed. 3. The aggregative behaviour of the fluidised bed breaks up 15 bubbles of synthesis gas thereby increasing both the mass transfer rate and the effective utilisation of the catalyst. 4. The process can be operated with a smaller catalytic bed than is employed in a conventional particulate fluidised bed process. Suitably, the particulate Fischer- Tropsch catalyst is maintained in an aggregative fluidised state by the action of the flow of fluidising liquid through the reaction zone. Suitably, the rate of flow of fluidising liquid through the reaction zone is equal to or greater than the minimum fluidising velocity. 25 Suitably, the fluidising liquid comprises a hydrocarbon solvent. Preferably, the hydrocarbon solvent of the fluidising liquid may be one or more of the liquid hydrocarbon products which has an advantage that there is no requirement to separate the liquid hydrocarbon products from the 30 hydrocarbon solvent. Preferably, the hydrocarbon solvent of the fluidising liquid is a high boiling hydrocarbon solvent. By high boiling hydrocarbon solvent is meant a hydrocarbon solvent having a boiling point, at standard pressure, of greater than 280° C. Preferably, the liquid hydrocarbon products comprise a mixture of hydrocarbons having a chain length of greater than 5 carbon atoms. Suitably, the liquid hydrocarbon products comprise a mixture of hydrocarbons having chain lengths of from 5 to about 90 carbon atoms. Preferably, a 40 major amount, for example, greater than 60% by weight, of the hydrocarbons have chain lengths of from 5 to 30 carbon atoms. A low boiling solvent may also be introduced into the reaction zone. By low boiling solvent is meant a solvent having a boiling point, at standard pressure, in the range of from 30 to 280° c., preferably from 30 to 210° C. Preferably, the low boiling solvent is selected from the group consisting of aliphatic hydrocarbons having from 5 to 10 carbon atoms, alcohols (preferably, alcohols having from 1 to 4 carbon 50 atoms, in particular, methanol), and water. In order to simplify the process, it is preferred that the low boiling solvent is a low boiling liquid hydrocarbon product or mixtures thereof. Without wishing to be bound by any theory, it is believed that vaporisation of the low boiling solvent in the reaction zone aids and enhances the mixing of the synthesis gas (hereinafter referred to as "syngas"), fluidising liquid and the particulate catalyst thereby increasing conversion of syngas to liquid hydrocarbon products. Moreover, vaporisation of the low boiling solvent will remove some of the exothermic heat of reaction thereby allowing more control over the product selectivities and minimising the production of gaseous by-products, for example, methane. The aggregative fluidised bed may also be cooled within the reaction zone by means of a heat exchanger, for example, heat transfer tubes, positioned within the aggregative flui- dised bed, to assist in removing exothermic heat of reaction from the system. A further advantage of an aggregative fluidised bed is that the presence of the "liquid bubbles" improves heat transfer to the heat transfer tubes. In a first embodiment of the process of the present invention, a liquid stream containing entrained catalyst particles is withdrawn from the reaction zone and is passed to an external solid-liquid separator (for example, a filter, hydrocyclone or gravity separator) where the entrained catalyst particles are separated from the liquid stream thereby generating a substantially catalyst-free liquid stream (hereinafter "catalyst-free liquid stream"). Preferably, the separated catalyst particles are recycled from the external solid-liquid separator to the reaction zone as a concentrated slurry. The catalyst-free liquid stream is then passed from the external solid-liquid separator to a gas-liquid separator where a gaseous phase comprising unconverted syngas is separated from the catalyst-free liquid stream. Without wishing to be bound by any theory, the liquid 20 stream which is withdrawn from the reaction zone will contain entrained catalyst particles when (a) the liquid fluidizing velocity is substantially greater than the terminal fall velocity (U ,) of the largest catalyst particles in the bed and/or (b) the catalyst has a particle size distribution such that a proportion, preferably, a substantial proportion, of the catalyst particles have a U, below the liquid fluidizing velocity. Alternatively, in a second embodiment of the process of the present invention, the reaction zone may be provided with an internal solid-liquid separator (for example, a filter, hydrocyclone or gravity separator). Suitably, the internal solid-liquid separator is positioned in the upper part of the reaction zone. Preferably, the internal solid-liquid separator is in communication with a catalyst-free zone. Catalyst 35 particles are retained by the internal solid-liquid separator and catalyst-free liquid is passed, usually under pressure, from the internal solid-liquid separator to the catalyst-free zone. Preferably, the catalyst-free zone has a headspace above the level of the catalyst-free liquid. A gaseous phase comprising unconverted syngas separates from the catalystfree liquid and accumulates in the headspace of the catalyst- free zone so that the catalyst-free zone acts as a gas-liquid separator. A gaseous stream comprising unconverted syngas is withdrawn from the headspace of the catalyst-free zone 45 and a catalyst-free liquid stream is withdrawn from below the level of the catalyst-free liquid in the catalyst-free zone, for example, immediately after the solid-liquid separator. Suitably, the reaction zone and catalyst-free zone are zones within a Fischer-Tropsch reaction vessel. Where the aggregative fluidised bed is partially expanded there is no requirement for a solid-liquid separator since catalyst-free liquid will be present in the reaction zone above the surface of the partially expanded bed. Expansion of an aggregative fluidised bed can be controlled by adjusting one 55 or more of the following parameters: the liquid fluidising velocity, the rate of flow of gas through the aggregative fluidised bed, the catalyst particle size distribution and the density of the particulate catalyst. Thus, in a third embodiment of the process of the present 60 invention, a partially expanded aggregative fluidised bed (having catalyst-free liquid above the surface of the bed) is maintained in the reaction zone and a headspace is present in the reaction zone above the level of the catalyst-free liquid. A catalyst-free liquid stream is withdrawn from a 65 region of the reaction zone which is above the surface of the partially expanded bed and below the level of the catalystfree liquid. A gaseous phase comprising unconverted syngas 5 US 6,716,887 B2 6 separates from the catalyst-free liquid and accumulates in the headspace. Suitably, a gaseous stream comprising unconverted syngas is withdrawn from the headspace of the reaction zone. Alternatively, in a fourth embodiment of the process of the present invention, a partially expanded aggregative fiuidised bed (having catalyst-free liquid above the surface of the bed) is maintained in a reaction zone in the absence of a headspace. The reaction zone is in communication with a catalyst-free zone and catalyst-free liquid is passed, usually under pressure, from a region of the reaction zone which is above the surface of the partially expanded bed into the catalyst-free zone. Preferably, a headspace is present in the catalyst-free zone above the level of catalyst-free liquid. A gaseous phase comprising unconverted syngas separates from the catalyst-free liquid and accumulates in the headspace of the catalyst-free zone. Suitably, a gaseous stream comprising unconverted synthesis gas is withdrawn from the headspace and a catalyst-free liquid stream is withdrawn from below the level of catalyst-free liquid in the catalystfree zone. Preferably, at least a portion of the catalyst-free liquid stream (from the first, second or third embodiments of the present invention) is recycled to the reaction zone. Typically, the catalyst-free liquid stream is cooled, for example, by 25 being passed through a heat exchanger, before being recycled to the reaction zone. It is envisaged that the catalyst-free liquid stream will contain residual gases/ vapours (unconverted syngas, gaseous by-products, gaseous intermediate products, vaporised low boiling liquid hydro- 30 carbon products, vaporised water by-product and any vaporised low boiling solvent) in which case low boiling liquid hydrocarbon products, water by-product and any low boiling solvent may condense in the heat exchanger. Residual gases may be separated from the catalyst-free liquid stream (and 35 condensed liquid) in a gas-liquid separator, for example, a hydrocyclone. A gaseous stream from the gas-liquid separator may be recycled to the reaction zone and/or purged from the system. A liquid recycle stream is returned to the reaction zone (fiuidising liquid) from the gas-liquid separa- 40 tor via a liquid pump. Suitably, a product side stream is taken from the liquid recycle stream downstream of the liquid pump and is passed to a product purification stage (described below). A further advantage of the process of the present invention is that fiuidising liquid and not a suspension of 45 particulate catalyst particles in the fiuidising liquid is recycled to the reaction zone which reduces the duty on the liquid pump (size and power requirements). Preferably, at least a portion of the gaseous stream comprising unconverted syngas which is withdrawn: (i) from the headspace of the catalyst-free zone (second and fourth embodiments of the process of the present invention), (ii) from the headspace of the reaction zone (third embodiment of the process of the present invention), or (iii) from the external gas-liquid separator (first embodiment of the process of the present invention), is recycled to the reaction zone (hereinafter referred to as "gaseous recycle stream"). The gaseous recycle stream additionally comprises gas- 60 eous intermediate hydrocarbon products (gaseous products having 2 or 3 carbon atoms, in particular, ethane or propanes), vaporised low boiling liquid hydrocarbon products (e.g. pentanes, hexanes or hexenes), vaporised water by-product, and any vaporised low boiling solvent. The gaseous recycle stream is preferably cooled before being recycled to the reaction zone, for example, by passing the separated gaseous stream through a heat exchanger, to further assist in the removal of exothermic heat of reaction from the system. The gaseous recycle stream may be cooled to below its dew point to form a two phase mixture of gas 5 (syngas, methane by-product, intermediate gaseous hydrocarbons) and condensed liquid (water by-product, low boiling liquid hydrocarbon products and any low boiling solvent). The condensed liquid may be recycled to the reaction zone entrained in the gaseous recycle stream. 10 Alternatively, the condensed liquid may be separated from the gaseous recycle stream, for example, using a suitable gas-liquid separation means (e.g. a hydrocyclone, demister, gravity separator) and is recycled to the reaction zone, for example, using a nozzle. Preferably, excess water 15 by-product is removed from the separated condensed liquids using a suitable separation means (e.g. a decanter), before recycling the condensed liquids to the reaction zone. It is envisaged that the heat exchanger and gas-liquid separation means may be combined within a single vessel in order to 20 simplify recycling of the gaseous stream to the reaction zone. Fresh syngas may be fed to the gaseous recycle stream, either upstream or downstream of the heat exchanger. Where the syngas has not been pre-cooled, it is preferred that the syngas is fed to the gaseous recycle stream upstream of the heat exchanger. Preferably, the gaseous recycle stream is recycled to the reaction zone via a blower or compressor located downstream of the heat exchanger. Suitably, the gaseous recycle stream is fed to the reaction zone via a gas sparger. Preferably, a purge stream is taken from the gaseous recycle stream to prevent the accumulation of gaseous by-products, for example, methane, in the system. If desired, any gaseous intermediate products may be separated from the purge stream. Preferably, such gaseous intermediate products are recycled to the system where they may be converted to liquid hydrocarbon products. Preferably, the purge stream is taken downstream of the heat exchanger. Preferably, the ratio of hydrogen to carbon monoxide of the syngas used in the process of the present invention is in the range of from 1:1 to 3:1 by volume, typically 2:1 by volume. Impurities such as methane, carbon dioxide, nitrogen and water may be present in the syngas. The synthesis gas may be prepared using any of the processes known in the art including partial oxidation of hydrocarbons, steam reforming, and autothermal reforming. A discussion of these synthesis gas production technologies is provided in "Hydrocarbon Processing" V78, NA, 87-90, 92-93 (April 1999) and "Petrole et Techniques", N. 415, 50 86-93 (July-August 1998). It is also envisaged that the synthesis gas may be obtained by catalytic partial oxidation of hydrocarbons in a microstructured reactor as exemplified in "IMRET 3: Proceedings of the Third International Conference on Microreaction Technology", Editor W Ehrfeld, 55 Springer Verlag, 1999, pages 187-196. Alternatively, the synthesis gas may be obtained by short contact time catalytic partial oxidation of hydrocarbonaceous feedstocks as described in EP 0303438. Preferably, the synthesis gas is obtained via a "Compact Reformer" process as described in "Hydrocarbon Engineering", 2000, 5, (5), 67-69; "Hydrocarbon Processing", 79/9, 34 (September 2000); "Today's Refinery", 15/8, 9 (August 2000); WO 99/02254; and WO 200023689. The catalyst which is employed in the process of the 65 present invention may comprise any catalyst known to be active in Fischer- Tropsch synthesis which has a density of greater than 4,000 kg/m '. For example, Group VIII metals 7 US 6,716,887 B2 8 whether supported or unsupported are known FischerTropsch catalysts. Of these iron, cobalt and ruthenium are preferred, particularly iron and cobalt, most particularly cobalt. A preferred catalyst is supported on a support Preferred supports include cobalt metal and iron metal. Suitably, the catalyst is coated onto the support. Typically, the coating is from sub-micron to several microns thickness. The catalytic metal is present in catalytically active amounts in the coating usually about 1-100 wt %, the upper limit being attained in the case of iron based catalysts. Preferably, the amount of catalytic metal in the coating is about 2-40 wt %. Promoters may be added to the catalyst and are well known in the Fischer-Tropsch catalyst art. Promoters can include ruthenium (when it is not the primary catalyst metal), rhenium, hafnium, cerium, and zirconium, 15 and are usually present in amounts less than the primary catalytic metal (except for ruthenium which may be present in coequal amounts), but the promoter:metal ratio should be at least 1:10. Preferred promoters are rhenium and hafnium. A further advantage of the process of the present inven- 20 tion is that a wide size distribution of catalyst particle sizes can be employed compared with a conventional slurry process. Typically, the catalyst has a mean particle size in the range of from 20 to 1500 microns, preferably, 50 to 350 microns. Suitably, the liquid recycle stream is introduced at or near the bottom of the reaction zone. Suitably, gas (gaseous recycle stream and any fresh syngas) is sparged into the reaction zone through a sparger. Preferably, the sparger is positioned near the bottom of the reaction zone. 30 Preferably, the gas which is fed to the reaction zone comprises from 50 to 100% by volume of fresh syngas (make-up syngas). Preferably, the aggregative fiuidised bed has a diameter of less than 10 meters, for example, in the range of 0.5 to 8 35 meters and a height of less than 15 meters, for example, in the range of 1 to 10 meters. The present invention can be operated in batch or continuous mode, the latter is preferred. In a continuous process a product side stream is continu- 40 ously removed from the liquid recycle stream and is passed to a product separation stage. In the product separation stage, liquid medium and liquid hydrocarbon products are separated from any fines (any catalyst particles which are carried over from the internal or external solid-liquid 45 separator). The product separation stage comprises a suitable solid-liquid separation means. Examples of suitable liquid-solid separation means include hydrocyclones, filters, gravity separators and magnetic separators. Alternatively, the liquid medium and liquid hydrocarbon products may be 50 separated from the fines by distillation. Preferably, there are two or more product side stream withdrawal lines leading to dedicated solid-liquid separation means. This ensures continuous operation of the process by allowing one or more of the solid-liquid separation means to be taken off-line for 55 cleaning. The separated fines may be removed from the process or may be recycled from the solid-liquid separation means to the reaction zone. The separated liquid (liquid medium, liquid hydrocarbon products, any low boiling hydrocarbon solvent and any water by-product) is passed to 60 a product purification stage. As discussed above, the purification stage may be simplified by using a liquid hydrocarbon product as the liquid medium which eliminates the requirement to separate the liquid medium from the liquid hydrocarbon products. In the purification stage, any water 65 by-product is removed from the liquid hydrocarbon prod- ucts. In order to prevent the accumulation of water by-product in the system it is preferred that at least a portion of the water by-product is removed from the liquid recycle stream. This may be achieved by taking a side stream from the liquid 5 recycle stream. Water by-product is removed from the side stream (for example, using a decanter) before returning the side stream to the reaction zone. It is envisaged that removal of water by-product from the system can be incorporated into the product purification stage, by recycling a portion of 10 the separated liquids, from which water has been removed, back to the reaction zone. The process of the invention is preferably carried out at a temperature of 180-280° c., more preferably 190-240° C. The process of the invention is preferably carried out at a pressure of 5-50 bar, more preferably 15-35 bar, generally 20-30 bar. The liquid hydrocarbon products from the product puri- fication stage may be fed to a hydrocracking stage, for example, a catalytic hydrocracking stage which employs a catalyst comprising a metal selected from the group consisting of cobalt, molybdenum, nickel and tungsten sup- ported on a support material such as alumina, silica-alumina or a zeolite. Preferably, the catalyst comprises cobalt! molybdenum or nickel/molybdenum supported on alumina 25 or silica -alumina. Suitable hydro cracking catalysts include catalysts supplied by Akzo Nobel, Criterion, Chevron, or UOP. BRIEF DESCRIPTION OF DRAWING The invention will now be illustrated with the aid of a FIGURE. Reactor vessel (1) comprises a reaction zone (2) and a catalyst-free zone (3). An aggregative fiuidised catalytic bed (4) comprising a catalyst having a density of greater than 4,000 kg/m:' fills the whole of the reaction zone (1). A headspace (5) is present in the catalyst-free zone (3) above the level (6) of catalyst-free fiuidising liquid. The reaction zone (2) is maintained at a temperature of from 180 to 280° C. and at a pressure of from 5 to 50 bar. Cooling coils (7) are positioned within the aggregative fiuidised bed to assist in removal of exothermic heat of reaction. Syngas is sparged into the reaction zone (2) via a sparger (8). An internal hydrocyclone (9) is positioned in the upper part of the reaction zone to separate catalyst particles from the fiuidising liquid. Fluidising liquid is withdrawn after the internal hydrocyclone (9) via a line (10) and is passed through heat exchanger (11) which further assists in removing exothermic heat of reaction. The fiuidising liquid is passed from the heat exchanger (11) to a gas-liquid separator (12) via line (13) where residual gas is separated from the fiuidising liquid. A gaseous stream is withdrawn from the gas-liquid separator (12) via line (14). The gaseous stream may be recycled to the reaction zone and/or purged from the system (not shown). A liquid recycle stream, is also withdrawn from the gas-liquid separator (12) and is recycled to the reaction zone (2) via line (15), liquid pump (16) and line (17). A product side stream (18) may be taken from the liquid recycle stream downstream of liquid pump (16) and is passed to product separation and purification stages (not shown). A gaseous recycle stream comprising unconverted syngas, gaseous intermediate products, any vaporised low boiling solvent, any vaporised low boiling liquid hydrocarbon products and any vaporised water by-product may be withdrawn from the headspace (5) through line (19). By means of a heat exchanger (20), the gaseous recycle stream may be cooled to 9 US 6,716,887 B2 10 a temperature at which liquid condenses out. The condensed liquid (typically comprising low boiling hydrocarbon products, water by-product and any low boiling solvent) may be separated from the gaseous recycle stream in a gas-liquid separator (21). The condensed liquid may be withdrawn from the gas-liquid separator (21) via line (22) and may subsequently be recycled to the reaction zone (2), optionally after having removed water by-product (not shown). The gaseous recycle stream from the gas-liquid separator (21) is recycled to the reaction zone (2) via line (23), compressor/blower (24) and lines (25) and (26). A purge stream may be taken from the gaseous recycle stream via line (27) to prevent the build up of gaseous by-products (e.g. methane) in the reaction zone (2). Fresh syngas may be introduced to the sparger (S) via line (2S). We claim: 1. A process for the production of liquid hydrocarbon products by passing, at elevated temperature and pressure, synthesis gas and a fiuidising liquid through a fiuidised catalytic bed within a reaction zone, characterised in that the fiuidised catalytic bed is an aggregative fiuidised catalytic bed comprising a particulate Fischer-Tropsch catalyst having a density of greater than 4,000 kg/m '. 2. A process as claimed in claim 1 wherein the liquid fiuidising velocity is greater than the terminal fall velocity of the particulate Fischer- Tropsch catalyst and a liquid stream comprising fiuidising liquid and liquid hydrocarbon products is withdrawn from the reaction zone together with entrained catalyst particles and is passed to an external solid-liquid separator wherein the entrained catalyst particles are separated from a catalyst free-liquid stream. 3. A process as claimed in claim 2 wherein the separated catalyst particles are recycled from the external solid-liquid separator to the reaction zone as a concentrated slurry. 4. A process as claimed in claim 2 wherein the catalyst- 35 free liquid stream is passed to a gas-liquid separator wherein a gaseous stream comprising unconverted synthesis gas is separated from the catalyst-free liquid stream. 5. A process as claimed in claim 1 wherein the reaction zone is provided with an internal solid-liquid separator for 40 separating catalyst-free liquid from the aggregative fiuidised bed. 6. A process as claimed in claim 5 wherein the catalystfree liquid is passed to a catalyst-free zone. 7. A process as claimed in claim 6 wherein the catalyst- 45 free zone has a headspace above the level of the catalyst-free liquid and a gaseous phase comprising unconverted synthe- sis gas separates from the catalyst-free liquid and accumulates in the headspace. S. A process as claimed in claim 7 wherein a gaseous 50 stream comprising unconverted synthesis gas is withdrawn from the headspace of the catalyst free zone and a catalystfree liquid stream comprising fiuidising liquid and liquid hydrocarbon products is withdrawn from below the level of the catalyst free liquid in the catalyst free zone. 9. A process as claimed in claim 1 wherein a partially expanded aggregative fiuidised bed is maintained within the reaction zone having a catalyst free-liquid region above the surface of the partially expanded bed. 10. A process as claimed in claim 9 wherein a headspace is present in the reaction zone above the level of the catalyst-free liquid and a gaseous phase comprising unconverted synthesis gas separates from the catalyst-free liquid 5 and accumulates in the headspace. 11. A process as claimed in claim 10 wherein a catalystfree liquid stream comprising fiuidising liquid and liquid hydrocarbon products is withdrawn from a region of the reaction zone which is above the surface of the partially 10 expanded bed and below the level of the catalyst free liquid and a gaseous stream comprising unconverted synthesis gas is withdrawn from the headspace of the reaction zone. 12. A process as claimed in claim 9 wherein the partially expanded aggregative fiuidised bed is maintained in the 15 reaction zone in the absence of a headspace. 13. A process as claimed in claim 12 wherein the reaction zone is in communication with a catalyst free zone and catalyst-free liquid is withdrawn from a region of the reaction zone which is above the surface of the partially 20 expanded bed and is passed into the catalyst free zone. 14. A process as claimed in claim 13 wherein the catalyst free zone has a headspace above the level of the catalyst-free liquid and a gaseous phase comprising unconverted synthesis gas separates from the catalyst-free liquid and accumu- 25 lates in the headspace. 15. A process as claimed in claim 14 wherein a gaseous stream comprising unconverted synthesis gas is withdrawn from the headspace of the catalyst-free zone and a catalystfree liquid stream comprising fiuidising liquid and liquid 30 hydrocarbon products is withdrawn from below the level of the catalyst free liquid in the catalyst free zone. 16. A process as claimed in claim 1 wherein the fiuidising liquid is a high boiling hydrocarbon solvent having a boiling point, at standard pressure, of greater than 2800 C. 17. A process as claimed in claim 1 wherein a low boiling solvent having a boiling point, at standard pressure, in the range of from 30 to 2800 C. is introduced into the reaction zone. IS. A process as claimed in claim 1 wherein the aggregative fiuidised bed is cooled within the reaction zone by means of heat transfer tubes positioned within the aggregative fiuidised bed. 19. A process as claimed in claim 4 wherein at least a portion of the gaseous stream comprising unconverted synthesis gas is recycled to the reaction zone. 20. A process as claimed in claim 19 wherein the gaseous stream is cooled before being recycled to the reaction zone. 21. A process as claimed in claim 2 wherein at least a portion of the catalyst-free liquid stream is recycled to the reaction zone. 22. A process as claimed in claim 21 wherein the catalystfree liquid stream is cooled before being recycled to the reaction zone. 23. A process as claimed in claim 1 wherein the catalyst 55 comprises iron or cobalt supported on a support. 24. A process as claimed in claim 23 wherein the support is cobalt metal or iron metal. * * * * * Recommended DocumentsDocuments Similar To Fischer Tropsch ProcessSkip carouselFischer Tropsch ProcessesFischerTropschFischer-Tropsch Synthesis- Overview of Reactor-BH DavisApplication of Fischer-Tropsch Synthesis in Biomass to Liquid ConversionFischer-Tropsch (FT) ProcessMore From Nestor AquinoSkip carouselMethanolExperience GermanyHacia Una Energia Escasa, Importada y CaraMicropower, The Next Electrical ErasMicropower, The Next Electrical Eraset205.pdfIndustria Petroquimica.pdfIndustria Petroquimica.pdfIndustria Petroquimica.pdfIndices de Riesgo- Dow- Mond..pdfperdidas-petroleoList API StandardsList API StandardsGNL57764012-LUBRICACION (1)Fischer Tropsch Processbiodiesel24_congress_REFINING_CHINAJara Empresa de Termocuplas

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WHEN asked how it feels to blow out a knee, an athlete is likely to recall the sudden, sickening snap, not unlike the sound of celery breaking in two, or the dizzying blast of pain. But when Jesse Cohen talks about tearing the anterior cruciate ligament of his right knee during football practice at Cornell in 1976 -- an injury that ended his college athletic career on the spot -- what he remembers is the sense of loss.''That injury changed my life forever,'' he said last month during a visit to his orthopedist, Elliott Hershman. Since then, Mr. Cohen, a 43-year-old real-estate executive and father of two from Summit, N.J., has undergone three operations to fix his right knee: an anterior cruciate ligament reconstruction, which left twin scars that resemble jagged railroad tracks, and two procedures to scrape out bits of bone and cartilage eaten away by arthritis.Mr. Cohen loved baseball and basketball, as well as football. All are now out of the question, and although he recently started skiing, he does that with great caution. ''The way I look at it,'' he says, ''an injury is something you bring with you. It means you can't do certain things. You get used to it.''Yet when the pain spikes, as it has in recent weeks, Mr. Cohen visits Dr. Hershman, a knee specialist at Lenox Hill Hospital in Manhattan, an institution that specializes in sports medicine, among other fields. Dr. Hershman is also the team orthopedist for the New York Jets, whose signed portraits adorn his office; in his 14 years with the team, he has repaired tears, ruptures and fractures in the likes of Vinny Testaverde, Wayne Chrebet and Keyshawn Johnson. During football season, he is likely to be found at the 30-yard line at Giants Stadium, or aboard the Jets' chartered plane -- where the players' sprained joints, just like some travelers' feet, tend to swell in flight.
While he can treat anything from a dislocated elbow to a broken neck, Dr. Hershman has a thing for the knee. ''You have this great interplay between bones and all the soft tissues that hold them in place,'' he says. ''It's a puzzle. You have to put it back together to make it work.'' Continue reading the main story
(The same may not be true of women's athletics, where experts are calling the prevalence of ruptured ligaments in college basketball an epidemic.)Another byproduct of sports journalism is the high expectations of patients. Paul Feinstein, who snapped an anterior cruciate ligament while skiing in Vermont last year, came to Lenox Hill partly because of Dr. Hershman's link with the Jets. The doctor told him he could forgo an operation if he planned to live a sedentary life, but Mr. Feinstein replied: ''That's not me. I want to be good as new, without restrictions.'' He had a goal: to run the annual marathon organized by New York Road Runners, the nonprofit organization in which he is chief financial officer.So one morning in May 2000, he slipped into a blue gown and was wheeled into one of the 17 operating rooms on the hospital's 10th floor. An anesthesiologist administered an epidural to block sensation in Mr. Feinstein's legs and a sedative to steady his nerves. As classical music emanated from Dr. Hershman's boombox, the surgeon began carving a half-inch-wide strip of tendon from the top of Mr. Feinstein's kneecap, then anchored it, using titanium screws, where the ligament had once crossed from the tip of the thigh bone to the tibia below. The 90-minute procedure cost about $7,000 and was covered by the patient's insurance.Mr. Feinstein left the hospital on crutches that afternoon and started physical therapy at 6:30 the next morning. By July, he was running on a rubberized track at a school near his house. He decided not to try the marathon, but by winter he was ready for skiing. ''I really worked that rehab,'' he says, ''and I'm fine now. Good as new.''G UNG-HO athletes are nothing new to Dr. Hershman. ''They can be tremendously motivated patients,'' he says. A green light starts to flash over his shoulder, indicating that a patient is waiting for him.The patient, Andy Cohen, 24, is wearing hospital-issue paper shorts that reveal a black-and-blue upper left leg. Dr. Hershman takes a brief history. ''I play basketball and baseball,'' says Mr. Cohen (no relation to Jesse Cohen), an analyst at Goldman, Sachs. ''I was a big Rollerblader,'' he adds. ''Until last Sunday.''He was flying down Lexington Avenue on his skates, he says, when a taxi door opened in his path, crashing him into the curb. ''That's what we call an urban sports injury,'' says Dr. Hershman, carefully poking his patient's swollen knee.The anterior cruciate ligament seems fine. So do the ligaments that stabilize the knee along the sides. There could be a rip in the meniscus, or more likely, an infusion of blood from the bruised thigh. Only an M.R.I. will tell, says Dr. Hershman.''We've got to get you back to baseball, basketball and Rollerblading,'' he tells his patient. Continue reading the main story

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Patent US6807466 - System and method for steering a multi-wheel drive vehicle - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA system and method of controlling a multi-wheel drive vehicle is provided. The invention is preferably applicable to the steering of such a vehicle and determines the individual velocities for each wheel drive. In this regard, the invention includes two general steps. The first step includes determining...http://www.google.com/patents/US6807466?utm_source=gb-gplus-sharePatent US6807466 - System and method for steering a multi-wheel drive vehicleAdvanced Patent SearchPublication numberUS6807466 B2Publication typeGrantApplication numberUS 10/279,606Publication dateOct 19, 2004Filing dateOct 24, 2002Priority dateFeb 1, 2001Fee statusPaidAlso published asCA2432510A1, EP1360104A2, US6526336, US7191042, US20020147539, US20030055539, US20040186633, WO2002060742A2, WO2002060742A3Publication number10279606, 279606, US 6807466 B2, US 6807466B2, US-B2-6807466, US6807466 B2, US6807466B2InventorsThomas StrothmannOriginal AssigneeInvacare CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (24), Referenced by (1), Classifications (16), Legal Events (5) External Links: USPTO, USPTO Assignment, EspacenetSystem and method for steering a multi-wheel drive vehicle
US 6807466 B2Abstract
(a) determining a turning reference and a vehicle velocity; (b) determining a reference distance from the turning reference based on the following relationship: S R={square root over (a 2+H 2)}
where SR is the reference distance, a is the turning reference, and H is a wheel base dimension of the vehicle;
(c) determining a wheel drive distance from the turning reference for each wheel drive of the multi-wheel drive vehicle; (d) determining a velocity for each wheel drive based on the vehicle velocity, wheel drive distance, and reference distance; and (e) outputting the determined velocity for each wheel drive to each wheel drive. 2. The method of claim 1 wherein step (a) comprises reading the position output of a user manipulable control device.
6. The method of claim 1 further comprising the step of determining a steering angle for at least one wheel drive.
7. The method of claim 6 further comprising the step of outputting the determined steering angle to the at least one wheel drive.
8. A system for controlling a multi-wheel drive vehicle comprising the steps of:
(a) an input device; (b) a controller in circuit communication with the input device; (c) at least two wheel drives in circuit communication with the controller; and (d) logic for: (1) determining a turning reference and a vehicle velocity from the input device; (2) determining a reference distance from the turning reference based on the following relationship: S R={square root over (a 2−H 2)}
where SR is a reference distance, a is the turning reference, and H is a wheel base dimension of the vehicle;
(3) determining a wheel drive distance from the turning reference for each wheel drive of the multi-wheel drive vehicle; (4) determining a velocity for each wheel drive based on the vehicle velocity, wheel drive distance, and reference distance; and (5) outputting the determined velocity for each wheel drive to each wheel drive. 9. The system of claim 8 wherein the input device comprises a user manipulable input device.
10. The method of claim 8 wherein the input device comprises a steering servo-mechanism.
11. The system of claim 9 wherein the user manipulable input device comprises a joystick input device.
12. The system of claim 8 wherein the logic determining a turning reference and a vehicle velocity from the input device comprises logic for determining the turning reference based on the following relationship:
13. The method of claim 8 further comprising logic for determining a steering angle for at least one wheel drive.
14. The method of claim 13 comprising logic for outputting the determined steering angle to the at least one wheel drive.
15. A system for controlling a multi-wheel drive vehicle comprising the steps of:
(a) means for inputting at least one control signal; (b) a controller means in circuit communication with the means for inputting a plurality of control signals; (c) at least two wheel drive means in circuit communication with the controller means; (d) means for determining a turning reference and a vehicle velocity from the input device; (e) means for determining a reference distance from the turning reference based on the following relationship: S R={square root over (a 2−H 2)}
(f) means for determining a wheel drive distance from the turning reference for each wheel drive of the multi-wheel drive vehicle; (g) means for determining a velocity for each wheel drive based on the vehicle velocity, wheel drive distance, and reference distance; and (h) means for outputting the determined velocity for each wheel drive to each wheel drive. 16. The system of claim 15 wherein the means for inputting at least one control signal comprises a user manipulable means.
17. The system of claim 16 wherein the user manipulable means comprises a joystick device.
18. A The method of claim 15 wherein the means for inputting at one control signal comprises a steering servo-mechanism.
19. The system of claim 15 wherein the means for determining a turning reference and a vehicle velocity from the means for inputting comprises means for determining the turning reference based on the following relationship:
20. The method of claim 15 further comprising the logic for determining a steering angle for at least one wheel drive.
21. The method of claim 15 further comprising logic for outputing the determined steering angle to the at least one wheel drive.
22. A method of driving a multiple wheel drive vehicle comprising the steps of:
(a) reading an angle value associated with a steering position; (b) determining a velocity for at least one wheel drive based on the angle value, a vehicle reference point's velocity and location from a predetermined origin, and at least one wheel drive base dimension; the location from a predetermined origin being related to the formula S R={square root over (a2−H2)}
wherein SR is a function of the location from the predetermined origin, a is a function of an angle value, and H is a function of at least one wheel drive base dimension; and (c) outputting the determined velocity to the at least one wheel drive. 23. A system for driving a multi-wheel drive vehicle comprising:
(a) means for inputting at least one control signal; (b) a controller means in circuit communication with the means for inputting a plurality of control signals; (c) at least one wheel drive means in circuit communication with the controller means; (d) means for determining a velocity for the at least one wheel drive means based on the at least one control signal, a vehicle reference point's velocity and location from a predetermined origin, and at least one wheel drive base dimension; the location from a predetermined origin being related to the formula S R={square root over (a2−H2)}
wherein SR is a function of the location from the predetermined origin, a is a function of an angle value, and H is a function of the at least one wheel drive base dimension; and (e) output means conveying the determined velocity to the at least one wheel drive.
This application is a continuation of application Ser. No. 09/773,793, filed Feb. 1, 2001, now U.S. Pat. No. 6,526,336, and titled �System and Method for Steering a Multi-Wheel Drive Vehicle.�
Illustrated in, FIG. 1 is a block diagram of a system 100 of the present invention. System 100 has a controller 102, logic 104, input device 106, and wheel drives 108, 110, 112, and 114. Controller 102 is any computer-based controller suitable for controlling a vehicle. In this regard, controller 102 generally has a processor, memory, and input/output components (not shown). Controller 102 can also have electric motor drive circuitry associated therewith (not shown).
A turning reference point �P� exists that is a turning reference distance �a� from point �O�. Turning reference point �P� defines a point about which the vehicle desires to turn. A third point �R� exists laterally between wheel drives 112 and 114 and spatially defines the vehicle's velocity reference point. The steering servo-mechanism 116 is mechanically coupled to the rear wheels. The steering servo-mechanism 116 is typically a geared motor, which drives a lever and a position feedback potentiometer. The feedback potentiometer defines an angular position in terms of an angle β, as shown. The angle β is used to determine the turning reference distance a between turning reference point �P� and point �O�, as shown in FIG. 2. This determination is made via Equation (1):
P=−H R�cot(β)=H R�cot(−β) Eq. (2) Having defined the turning reference distance a and the wheel base positions, reference is now made to FIG. 3. FIG. 3 illustrates distances S from turning reference point �P� to each wheel drive and the velocities V of each wheel drive. In this regard, logic 104 employs either of two approaches to determine the individual wheel drive velocities. The first approach utilizes a two step analysis wherein the first step is to determine, from turning reference point �P�, the distance of each of the wheel drives and the vehicle's velocity reference point �R�. Once these distances are known, the individual wheel drive velocities can be determined based on the known velocity at the vehicle's velocity reference point �R� and the wheel drive's distance from turning reference point �P�. The second approach utilizes the steering servo-mechanism's 116 angular positions β and the vehicle's wheel drive base dimensions.
Referring now to FIG. 3, the present discussion will now focus on the first approach described above. In this regard, distance SFL is the distance between wheel drive 108 and turning reference point �P.� Similarly distances SFR, SBL, and SBR represent the distances between wheel drives 110, 112, and 114, respectively, and turning reference point �P.� Distance SR represents the distance between vehicle's velocity reference point �R� and turning reference point �P.� So defined, these distances can be determined according to Equations (3)-(7): S FL = a - w 2 Eq.��(3) S FR = a + w 2 Eq.��(4) S BL={square root over ((a−W BL)2 +H BL 2)} Eq. (5)
S BR={square root over ((a+W BR)2 +H BR 2)} Eq. (6) S R ={square root over (a2 +H R 2)} Eq. (7) Once all of the wheel drive distances S from turning reference point �P� have been determined, the vehicle's velocity VR and the individual velocities VBL, VBR, VFL, and VFR, for wheel drives, 112, 114, 108, 110, respectively, can be determined. In this regard, velocities VR, and VBL and VBR for wheel drives 112 and 114 can be determined from Equations (8)-(10):
V R=�(x,y) Eq. (8) V
Eq.��(10)
In Equation (8), the vehicle's velocity VR is a function �(x,y) of the output signals of input device 106. In this regard, The �x� coordinate provides data for determining a turning vector's magnitude and direction and the �y� coordinate provides data relevant to both the vehicle's velocity vector magnitude and direction and the turning vector magnitude and direction. Typically, the function �(x,y) also provides for, among other things, limitations on the vehicle's top velocity, rate of acceleration, and/or rate of deceleration, for safety and proper operation of the vehicle. The exact parameters of function �(x,y) are generally determined based on a particular wheelchair's design. Also, the vehicle's turning vector information is typically a function g(x,y) of both the �x� and �y� coordinate data. In this regard, the �y� coordinate (or velocity data) is typically used to reduce the magnitude of the turning vector at higher vehicle velocities for purposes of safety (e.g., to prevent the vehicle from flipping or rolling over.) Once again, the exact parameters of g(x,y) are determined based on a particular wheelchair's design. Additionally, the velocity function �(x,y) and turning function g(x,y) may be implemented using the polar output information (r,θ). Hence, the velocity function would be in the form of �(r,θ) and the turning function would be in the form of g(r,θ), where the parameters of each function are determined based on a wheelchair's particular design. Moreover, the turning function g(x,y) or g(r,θ) can itself be modified by a function m(g(x,y)) to account for the difference between the turning function's angular output result and the servo-mechanism's actual angular position. Such differences arise, for example, because the servo-mechanism requires a finite time between changes in angular positioning and because the actual servo-mechanism angular position may be slightly different from that determined via the output of input device 106. Once the reference velocity VR is determined, it is stored in the memory of controller 102 for use in determining the individual wheel drive velocities.
The equations for determining velocities VFL, and VFR for wheel drives 108 and 110, respectively, are dependent on angle β and can be shown to be defined by Equations (11)-(14): V FL = S FL S R � V R for   0 ≥ β ≥ - π Eq.��(11) V FR = S FR S R � V R for   0 ≥ β ≥ - π Eq.��(12) V FL = - S FL S R � V R for   0 ≤ β ≤ π Eq.��(13) V FR = - S FR S R � V R for   0 ≤ β ≤ π Eq.��(14) Generally, Equations (9)-(14) determine each wheel drive's velocity V by ratioing each wheel drive distance S with the vehicle's velocity reference point distance SR and then applying that ratio to the vehicle velocity VR designated at the vehicle velocity reference point �R�. Hence, by determining the individual wheel drive distances, the individual wheel drive velocities can be determined therefrom.
Still referring to FIG. 3, the second approach described above utilizes the steering servo-mechanism's 116 angular position β and the vehicle's wheel drive base dimensions to determine each individual wheel drive velocity. In this regard, wheel drive velocities VBL, VBR, VFL, and VFR can be defined by the following Equations (15)-(18) derived from FIG. 3: V BL = V R � [ H R � cos  ( - β ) - W B 2 � sin  ( - β ) ] 2 + [ H B � sin   ( - β ) ] 2 H R Eq.��(15) V BR = V R � [ H R � cos  ( - β ) + W B 2 � sin  ( - β ) ] 2 + [ H B � sin   ( - β ) ] 2 H R Eq.��(16) V FL = V R � [ cos  ( - β ) - W F 2 � H R � sin  ( - β ) ] Eq.��(17) V FR = V R � [ cos  ( - β ) + W F 2 � H R � sin  ( - β ) ] Eq.��(18) In Equations (15)-(18), wheel drive base dimensions WB=WBL+WBR and WF=WFL+WFR and reference dimension HB=HBL=HBR and VR is determined via Eq. (8). (See, for example, FIG. 3 showing the aforementioned dimensions and angle). Additional drive wheels that are connected to a steering servo-mechanism would follow the general form of Equations (15) and (16) such as, for example, in the case of a six-wheel drive vehicle that has four steerable wheel drives. Equations (15)-(18) are similar to Equations (9)-(14) except that Equations (15)-(18) incorporate the steering servo-mechanism's 116 angular position β and, therefore, simplify the determination of VFL and VFR. Hence, the individual wheel drive velocities can be determined based on the steering servo-mechanism's 116 angular position β and the wheel base dimensions of the vehicle.
P=(XP,0) Wheel drive 108=(XFL,0) Wheel drive 110=(XFR,0)
R=(XR,YR) Wheel drive 112=(XBL,YBL) Wheel drive 114=(XBR,YBR)
The steering angle for wheel drive 112 can then be determined via Equations (19)-(22): V BL Y = ( X R - X BL ) � V RX Y R + V RY Eq.��(19) V BL X = Y BL � V RX Y R Eq.��(20) ∠   V BL → = arctan  ( V BL y V BL x ) for   V BL x ≥ 0 Eq.��(21) ∠   V BL → = arc   tan  ( V BL y V BL x ) + π for   V BL x < 0 Eq.��(22) wherein VRX=VR sin β and VRY=VR cos β. Equations (19) and (20) determine the �x� and �y� components of velocity VBL for wheel drive 112. Equations (21) and (22) determine the angle based on the sign of VBLX. The velocity VBL can be determined via Equation (23):
V BL={square root over ((V BLx)2+(V BLy)2)} Eq.(23) The velocities and steering angles for wheel drives 108, 110, and 114 can be similarly determined. Once the velocities and steering angles have been determined for all of the wheel drives, they can be output to each wheel drive to effect movement of the vehicle.
Illustrated in FIG. 4 is a flowchart 400 representation of the above-described logic employing Equations (1) and (8)-(14). The logic starts in step 402 where the logic reads the angular position β of steering servo-mechanism 1116. The logic next advances to step 404 where the reference distance a, individual wheel drive distances S, and vehicle velocity reference point distance SR are determined via equations (1) and (3)-(7), respectively. After step 404, the logic, advances to step 406 where the velocities for each wheel drive are determined based on each wheel drive's distance S, the vehicle velocity reference point distance SR, the overall vehicle velocity VR, and angle β. (See, for example, FIG. 3 and Equations (8)-(14)). After all of the wheel drive velocities have been determined, they are output in step 408 to the wheel drives. After step 408, the logic loops back to step 402 and the logic repeats. It should also be noted that an additional step can be included for individually steerable wheel-drives that includes outputting the steering angle for each wheel drive to the individual wheel drive for effecting movement of the vehicle.
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