I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US008480812B2
`
`c12) United States Patent
`Nath et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,480,812 B2
`Jul. 9, 2013
`
`(54) PROCESS FOR REMOVING
`HYDROCARBONS AND NOXIOUS GASSES
`FROM REACTORS AND MEDIA-PACKED
`EQUIPMENT
`
`(75)
`
`Inventors: Cody Nath, Houston, TX (US); Barry
`Baker, Odem, TX (US); Sean Sears,
`The Woodlands, TX (US)
`
`(73) Assignee: Refined Technologies, Inc., Spring, TX
`(US)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 517 days.
`
`(21) Appl. No.: 12/478,580
`
`(22) Filed:
`
`Jun.4,2009
`
`(65)
`
`(51)
`
`(52)
`
`(58)
`
`Prior Publication Data
`
`US 2010/0307536Al
`
`Dec. 9, 2010
`
`(2006.01)
`
`Int. Cl.
`BOBB 9/00
`U.S. Cl.
`USPC .................... 134/22.1; 134/22.14; 134/22.19;
`134/26; 134/30; 134/31; 134/36; 134/37;
`134/41
`
`Field of Classification Search
`USPC ................ 134/22.19, 22.1, 22.14, 31, 34, 37,
`134/26,28,29,30,36,41
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
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`12/1990 Watkins
`7/1991 Foutsitzis et al. ............. 208/138
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`6/1998 D'Muhala et al.
`1/2000 Hashimoto
`5/2000 Blomgren
`8/2001 Kawakami et al.
`9/2001 Furuta et al.
`3/2003 Gilmour et al.
`(Continued)
`OTHER PUBLICATIONS
`
`134/22.1
`
`Select File History in related U.S. Appl. No. 10/447,441, dated May
`28, 2003 through Mar. 8, 2005, 98 pages.
`Select File History in related U.S. Appl. No. 11/138,096, dated May
`26, 2003 through Jun. 28, 2006, 122 pages.
`
`(Continued)
`Primary Examiner - Saeed T Chaudhry
`(74) Attorney, Agent, or Firm - Lathrop & Gage LLP
`ABSTRACT
`(57)
`A process for quickly removing hydrocarbon contaminants
`and noxious gases in a safe and effective manner from cata(cid:173)
`lytic reactors, other media packed process vessels and asso(cid:173)
`ciated equipment in the vapor phase without using steam. The
`cleaning agent contains one or more solvents, such as terpe(cid:173)
`nes or other organic solvents. The cleaning agent is injected
`into contaminated equipment, along with a carrier gas, in the
`form of a cleaning vapor.
`20 Claims, 1 Drawing Sheet
`
`-B-----
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`1
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`I
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`ULI EXHIBIT 1009
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`US 8,480,812 B2
`Page 2
`
`U.S. PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`
`6,858,090 B2
`6,872,263 Bl
`6,893,509 B2
`6,936,112 B2 *
`6,972,274 Bl
`6,978,793 Bl
`7,198,103 B2
`2002/0139738 Al
`2004/0102351 Al
`2004/0238006 Al
`
`2/2005 Hebert
`3/2005 Jansen et al.
`5/2005 Sears et al.
`8/2005 Jansen et al.
`12/2005 Slikta et al.
`12/2005 Krueger
`4/2007 Campbell
`10/2002 Jujie et al.
`5/2004 Jansen et al.
`12/2004 Sears et al.
`
`134/19
`
`Select File History in related U.S. Appl. No. 11/278,168, dated Mar.
`31, 2006 through Jun. 26, 2007, 128 pages.
`Select File History in related U.S. Appl. No. 10/781,275, dated Feb.
`18, 2004 through Feb. 14, 2005, 82 pages.
`Select File History in related U.S. Appl. No. 10/304,370, dated Nov.
`26, 2002 through May 16, 2005, 144 pages.
`Examiner's Report dated Jan. 20, 2012 issued in related Canadian
`Patent Application No. 2674842, 5 pages.
`
`* cited by examiner
`
`Page 2 of 8
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`ULI EXHIBIT 1009
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`

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`U.S. Patent
`US. Patent
`
`Jul. 9, 2013
`
`US 8,480,812 B2
`US 8,480,812 B2
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`ULI EXHIBIT 1009
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`US 8,480,812 B2
`
`1
`PROCESS FOR REMOVING
`HYDROCARBONS AND NOXIOUS GASSES
`FROM REACTORS AND MEDIA-PACKED
`EQUIPMENT
`
`BACKGROUND
`
`This disclosure pertains to the operation and maintenance
`of chemical plants and refineries. More specifically, the
`present disclosure relates to the process for cleaning the inter(cid:173)
`nal surfaces of chemically contaminated reactors, packed
`beds, absorbent chambers, compressors, pipes, connectors
`and other equipment.
`Refineries and chemical plants must perform turnarounds
`on chemical processing units which utilize reactors and other
`vessels containing packed media. The purpose of these turn(cid:173)
`arounds is to replace catalysts or other media that have lost the
`ability to perform. Performance measures include catalyst
`activity, pressure drop, yields, molecular sieve selectivity, etc.
`When the turnarounds are being performed, the facility 20
`cannot upgrade refined products to higher value streams,
`resulting in irreversible loss of revenue to the refinery or
`chemical plant. Therefore, an incentive exists to minimize the
`duration of the outage and perform the change-out of the
`media as quickly and effectively as possible, while maintain(cid:173)
`ing a safe work environment.
`Moreover, new developments in environmental regulations
`and enforcement have led to more stringent emissions
`requirements. One of the major developments resulting from
`these regulations is the desire to minimize flaring from refin(cid:173)
`ing equipment. Many facilities have installed Flare Gas
`Recovery Units (FGRUs) to capture gases in the flare system
`and return them to the fuel gas system rather than flaring
`continuously. FGRU s typically consist of one or more liquid
`ring compressors capable of taking low pressure flare gas and
`pushing it into the fuel gas system or other medium pressure
`system. These new units are often mandated by Consent
`Decree agreements between refiners and the Environmental
`Protection Agency (EPA). As a result, there is significant
`environmental incentive to avoid flaring and to keep the gases
`within the constraints of the FGRUs when gases must be
`vented from the equipment. These constraints may include,
`for example, the following parameters.
`1) Flow Rate:
`The compressors are designed to capture a limited quantity
`of vapors in the flare system. If the compressors are over(cid:173)
`whelmed the gas will be flared.
`2) BTU Value:
`Nitrogen is frequently used to clear noxious chemicals
`from refining equipment. There is a limitation on how much
`nitrogen can be sent to the fuel gas system via the FGRU
`because the nitrogen, which has no heating value, dilutes the
`fuel gas system and causes the plant heaters to operate abnor(cid:173)
`mally. This can lead to further upsets, so the plant fuel gas
`BTU value is closely monitored.
`3) Temperature:
`Because the compressors are liquid ring compressors,
`there is a temperature limit which protects the compressors.
`Generally, temperatures above 170° F. are not allowed.
`The process vessels are generally at the heart of a hydro(cid:173)
`carbon processing facility but often cannot be isolated from
`adjacent supporting equipment. For example, a typical
`hydrotreating process unit in a petroleum refinery has a reac(cid:173)
`tor containing a metal catalyst, a hydrogen compressor, shell
`and tube heat exchangers, a heater, air cooled fin tube
`exchangers, piping and other miscellaneous pressure vessels.
`All equipment in the process circuit can be collectively
`
`5
`
`2
`referred to as the reactor circuit. When a turnaround occurs on
`such a unit, the entire reactor circuit must be cleaned together
`because the compressor and heat exchangers are used to
`circulate a gas used to cool down the reactor at a regulated
`rate.
`Under most circumstances, it may be desirable to ensure
`that the equipment in a reactor circuit are not exposed to water
`or steam due to concerns about technical items such as met(cid:173)
`allurgy, loss of catalyst activity and the destruction of expen-
`10 sive absorbent materials such as molecular sieves. Addition(cid:173)
`ally, there are practical concerns with respect to materials
`inside the equipment which may form clumps when soaked
`with water, making them difficult to remove. Moreover, in the
`case of reactors in hydrotreating units, the shutdown and cool
`15 down procedure requires that the hydrogen compressor in the
`system remain online, and because hydrogen compressors
`cannot pump steam, it must be cleaned without using steam or
`aqueous cleaners that are otherwise commonly used in the
`industry.
`One previously disclosed method for preparing reactor
`circuits for safe work involves a "hot sweep," where the heater
`in the reactor loop is used to raise the hydrogen stream tem(cid:173)
`perature levels high enough to strip the heavy hydrocarbons
`from the catalyst as the hydrogen compressor circulates the
`25 gas. Following that step, the hydrogen is replaced with nitro(cid:173)
`gen by repetitively depressurizing the system to the flare
`system and pressuring it back up with nitrogen ( commonly
`called a "huff and puff'). At that point, the compressor is
`restarted, sending the nitrogen through the reactor circuit at
`30 the same time that the continuous injection and purge of
`nitrogen is occurring. The purge stream is sent to the flare
`system. The process gradually decreases the concentration of
`noxious gases in the circuit and cools down the reactor.
`Depending on the design of the compressor, nitrogen avail-
`35 ability and other considerations, the operator may use other
`gases instead of nitrogen, including purchased fuel gas
`(ethane and methane). These processes require enormous
`quantities of nitrogen, which is costly. The goal of the entire
`operation is to render the circuit safe for work (0% LEL, 0
`40 PPM H 2S and <100° F.). Depending on the size and state of
`the unit, the entire effort can take 3 or more days.
`In cases where the "huff and puff' and nitrogen purge steps
`are sent to a flare system with an FGRU, the constraints
`mentioned above will govern the flow rate and therefore will
`45 set the duration of the activity. In systems that include flare
`gas recovery, the FGRU becomes the limiting factor of all or
`most hydrotreater shutdowns.
`Another method known in the field for safely removing
`contaminated catalyst from a reactor is to perform a "wet
`50 dump." After the equipment is cooled down, the reactor is
`filled with water. The catalyst is subsequently dumped wet,
`effectively preventing fires and other hazards. Challenges to
`this method are time (system must be cooled down prior to
`introducing water), safe handling and disposal of hot water,
`55 increased amount of waste for disposal and difficulties
`involved in controlling a large system filled with hot catalyst
`and metal, mixed with cool water.
`Although it is possible in some cases to isolate a process
`vessel for cleaning and decontamination, it is not always
`60 practicable to use steam or aqueous solutions to clean the
`equipment. For instance, a compressor is typically not avail(cid:173)
`able for circulating gas through the process internals. One
`such example is an adsorbent chamber in the Parex™ Process
`(UOP technology). One method for removing noxious gases
`65 from such equipment is purging with an inert gas, most com(cid:173)
`monly nitrogen. A common method is to pressure a system
`with nitrogen up to a certain pressure, then vent it down to a
`
`Page 4 of 8
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`ULI EXHIBIT 1009
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`

`

`US 8,480,812 B2
`
`3
`low pressure. These steps may be repeated until the atmo(cid:173)
`sphere inside the system meets environmental and safety
`limits.
`In some cases, a continuous flow of nitrogen is introduced
`at one point in a system while the same amount is vented
`( either to the flare system or to the atmosphere) at another
`point. The nitrogen reduces contaminants in the vessel
`through dilution. Often the equipment is vented to the flare
`during the nitrogen purges; however, purging directly to the
`atmosphere is possible once environmental limits have been
`reached. At that point, the vessel is opened at several points to
`the atmosphere and air blowers are used to remove the nitro(cid:173)
`gen and the last traces of noxious gases. The end goal of all of
`the processes involving nitrogen or other gases is to render the
`equipment dry of free oil and the internal atmosphere free of
`noxious gases.
`In summary, most of these known methods are time-con(cid:173)
`suming and/or expensive to implement. Furthermore, any
`solution that requires further cleaning inside a confined space
`may introduce safety risk to the workers implementing the
`process.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`4
`molecular sieve or a desiccant. By way of example, a reactor
`circuit used in a refining hydrotreating process and associated
`equipment may be cleaned using the disclosed process. Asso(cid:173)
`ciated equipment may include, for example, a shell and tube
`5 exchanger, a fired heater, a distillation tower, or an intercon(cid:173)
`necting piping.
`The carrier gas may be nitrogen or other inert gases. Alter(cid:173)
`natively, the carrier gas may be a dry gas produced or used in
`a petroleum processing facility which has the chemical for-
`10 mula CnH2n+2 , wherein n is an integer greater than O but less
`than 6. Examples of such dry gas include ethane or methane
`( commonly referred to as "purchased fuel gas" or refinery
`fuel gas), Other suitable carrier gas may include suitable
`gases that are readily available within a refinery or petro-
`15 chemical plant, such as hydrogen used in a hydrotreating
`process.
`The disclosed processes may be used to remove organic
`contaminants and noxious gases from a system. Organic con(cid:173)
`taminants may include but are not limited to crude oil and its
`20 derivatives produced through the refining process, or hydro(cid:173)
`carbons. Noxious gases may include but are not limited to,
`hydrogen sulfide, benzene, carbon monoxide, and light end
`hydrocarbons which result in readings when testing an atmo-
`sphere for the Lower Explosive Limit ( commonly referred to
`as LEL's).
`In another aspect, the method of the present disclosure may
`include an additional step of circulating the carrier gas
`through the system using a compressor. In another aspect, the
`method may include a further step of bringing the vessel or
`30 system of equipment within the proper temperature range by
`either heating it or cooling it prior to the introduction of
`solvent.
`In another aspect, the disclosed method may be used on
`equipment which is operating, such as a hydrotreater under(cid:173)
`going a nitrogen cool-down. In another aspect, the disclosed
`method may be used on equipment which is taken out of
`service for cleaning. Example for such application may
`include, by way of example, isolated vessel such as a Parex
`adsorbent chamber.
`For equipment which is operating, the disclosed process
`may employ two potential delivery methods. In the first
`method, a solvent may be injected into a carrier gas. The
`mixture is in turn introduced into the equipment to clean its
`internal surfaces. Alternatively, in the second method, the
`actual process gas may be used as the carrier gas, utilizing the
`flow inside the process equipment to distribute the cleaning
`agents throughout the equipment to clean its internal surfaces.
`These two methods may have the advantage ofkeeping equip(cid:173)
`ment online during a cleaning operation.
`For equipment which will be taken out of service, the
`process may include following the standard shutdown proce(cid:173)
`dure, properly isolating the equipment to be cleaned, inject(cid:173)
`ing one or more solvents into a carrier gas, and introducing the
`carrier gas and solvent mixture into the equipment to clean its
`55 internal surfaces.
`The described process is particularly well suited to clean(cid:173)
`ing large surface areas such as reactors with contaminated
`catalyst beds. A relatively small amount of cleaning fluid is
`required as compared to other known methods. The equip(cid:173)
`ment used to introduce the cleaning agent may include a
`system of pumps, pipe fittings and, optionally, nozzles to
`vaporize and accurately control the volumetric ratios of
`chemical vapor and carrier gas. The injection rate and the
`volumetric or weight ratio between the solvent and the carrier
`65 gas depend on the nature of the equipment to be cleaned and
`may be adjusted accordingly. For instance, equipment with a
`larger enclosed volume generally requires a lower ratio of
`
`FIG. 1 illustrates the layout of equipment and the flow of 25
`media in a typical cleaning process.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`The disclosed embodiments introduce a non-aqueous
`cleaning agent or solvent that is not dependent upon water or
`steam as a carrier. The cleaning agent is carried into and
`through the equipment to be cleaned by a carrier gas that is
`free of water. The carrier gas volatilizes the solvent and deliv-
`ers it throughout the internal spaces and surface areas of the 35
`equipment to be cleaned, allowing the solvent to quickly
`dissolve organic residues from the vessel and carry away
`noxious gases.
`Furthermore, the present invention overcomes the con(cid:173)
`straints placed on refiners with FGRUs by expediting the 40
`procedure for freeing the equipment of noxious gases. By
`speeding up this process the refiner is able to reach environ(cid:173)
`mental and safety limits faster so that the equipment can be
`vented to atmosphere. The invention may allow the refiner to
`reach these limits before the equipment is cool enough for 45
`safe work, so the FGRU is no longer limiting the timeline of
`the event. Once these limits are reached, the equipment can
`continue cooling to atmosphere.
`In one embodiment, it is provided a method of cleaning
`contaminated equipment, the method may include the follow- 50
`ing steps:
`providing a carrier gas source which provides carrier gas
`such as nitrogen, purchased fuel gas, etc;
`providing a solvent source, preferably capable of supply(cid:173)
`ing a non-aqueous solvent;
`delivering the carrier gas and solvent from their respective
`sources to the system to be cleaned; and
`removing said contaminant out of the system as the carrier
`gas and solvent are delivered to or through the system,
`wherein substantial amount of said contaminant is dis- 60
`solved in said solvent in a vapor or liquid state as it is
`being removed from said system.
`For purpose of this disclosure, the term "substantial"
`means at least 50%. The process system to be cleaned may be
`a reactor, an absorbent chamber containing a molecular sieve,
`or a pressure vessel. Such a process system may contain a
`medium which may be a catalyst, a support material, a
`
`Page 5 of 8
`
`ULI EXHIBIT 1009
`
`

`

`US 8,480,812 B2
`
`5
`solvent to carrier gas. In one embodiment, the weight ratio
`between the solvent and the carrier gas is in the range of from
`about 0.1 to about 6.0, more preferably, from about 2 to about
`4. The equipment used to introduce the carrier gas may
`include a heater to bring the gas to the appropriate tempera(cid:173)
`ture prior to injecting the chemical solvent(s ). Preferably, the
`appropriate temperature is in the range from about 225° F. to
`about 400° F., more preferably from about 350° F. to about
`400° F. In another aspect, a vent to the flare system, atmo(cid:173)
`sphere or another piece of equipment is maintained through(cid:173)
`out the injection. Low points in the system are preferably kept
`dry and free of liquid (such as condensed solvents and dis(cid:173)
`solved organic contaminants) throughout the injection.
`In one embodiment, the solvent may be introduced into the
`carrier gas by joining or connecting the gas and solvent
`sources. In one aspect, the solvent may be introduced into an
`equipment that is idled or otherwise out of service. In another
`aspect, the solvent may be introduced into an equipment that
`is operating before, during and after the injection.
`Once the solvent has been administered, the vessel is 20
`allowed to dwell and cool, with carrier gas continually deliv(cid:173)
`ered until safety limits have been reached for the temperature
`which is typically about 100° F. Preferably, the vent and
`drains remain open during this process.
`The disclosed processes may be used to clean many pro- 25
`cess systems, such as reactor circuit and process vessel in a
`refinery or chemical plant which may be exposed to organic
`contaminants. These process systems may include, but are not
`limited to reactors, adsorbent chambers along with the aux(cid:173)
`iliary equipment associated with them such as shell and tube 30
`heat exchangers, piping, pressure vessels, fired heaters, dis(cid:173)
`tillation towers, and interconnecting piping. In one aspect, the
`adsorbent chamber suitable to be cleaned contains a molecu-
`lar sieve. In another aspect, the process system contains a
`media packed pressure vessel containing internal processing
`equipment or material, including but not limited to catalyst,
`support material, molecular sieve or desiccant. In another
`aspect, the process system contains associated equipment
`which may include some or all components of a reactor circuit
`in a refining hydrotreating process.
`Various solvents may be used for the present invention. The
`desired solvent may be directly added to the carrier gas.
`Suitable solvents may include any naturally occurring, syn(cid:173)
`thetic or processed organic solvents (i.e., aliphatic, paraffinic,
`isoparaffinic, aromatic, naphthenic, olefinic, dienes, terpenes,
`polymeric or halogenated), either as single compounds or
`multi-component materials. Some examples of the solvents
`include natural terpenes and their hydrogenated derivatives or
`any individual hydrocarbon or hydrocarbons or even a virgin
`untreated hydrocarbon having requisite characteristics, but 50
`usually it is a hydrocarbon fraction obtained as a product or
`by-product in a petroleum refining process. Furthermore, aro(cid:173)
`matic solvents (toluene, xylene, mixed xylenes ), virgin naph(cid:173)
`tha, terpenes and hexanes are solvents which might be
`obtained from other refining processes in the facility. In a
`preferred embodiment, the solvent source includes a non(cid:173)
`polar organic solvent. Combinations of solvents as described
`above might be used as well.
`In a preferred embodiment, the boiling point of the hydro(cid:173)
`carbon solvent(s) used is less than 450° C. (about 850° F.),
`and the solvents are hydrocarbons ranging from Cl to C50
`hydrocarbons. Solvent systems containing multiple com(cid:173)
`pounds as solvents may also be used, wherein the multiple
`compounds may have different boiling points. Generally, the
`solvents may be a distillate boiling range material that have a 65
`boiling range from about 165° C. to about350° C. (about330°
`F. to 650° F.). Within this range, the solvents may be either a
`
`6
`light or a heavy distillate. However, more volatile hydrocar(cid:173)
`bons may also be used. For example, hydrocarbons in the
`gasoline boiling range or even dry gas, may be used as well.
`Several major advantages may be achieved using the pres-
`5 ently disclosed methods. The packed media in reactors and
`adsorbent chambers become spent over the course ofits oper(cid:173)
`ating life. For instance, catalyst may lose its catalytic activity,
`active sites may become plugged with contaminants and pres(cid:173)
`sure drop may increase. The cleaning methods of the prior art
`10 are all aimed at removing as much of the organic contami(cid:173)
`nants as possible to allow for safe removal of the spent media.
`However, these methods are often not effective at removing
`all of the contaminants to a point where the media may be
`15 removed from the reactor without subsequent safety issues.
`The powerful solvent strength and unique delivery method
`described in this disclosure allow for more efficient and effec(cid:173)
`tive removal of organic contaminants from catalyst and adsor-
`bent beds, therefore increasing the likelihood that the hazard(cid:173)
`ous contaminants will be completely removed prior to
`handling. Using previously disclosed method, equipment
`may test clear of noxious gases immediately after cleaning,
`but noxious gases may appear later during or after dumping
`because pockets of contamination may be exposed and
`release more contaminants. By contrast, because the pres(cid:173)
`ently disclosed process removes the contaminants more com-
`pletely than prior methods, it provides a safer process for
`disposition of the material without fear of fires or hazardous
`exposures to workers.
`Moreover, many previously disclosed methods depend on
`lengthy procedures of purging and venting using heat and
`dilution to remove contaminants from equipment. The
`present invention achieves the same results in a fraction of the
`time because of the use of the solvents. According to the
`35 present disclosure, it is possible to reduce the time required
`for rendering a particular piece of equipment safe for entry by
`several hours or even days. This reduction in cleaning time
`results in increased on-stream time for the affected unit, and
`thus helps recapturing revenue that would otherwise be lost if
`40 other methods of cleaning are used.
`Additionally, the decreased timeline required to render
`equipment free of organic contaminants and noxious gases
`may also lead to less manpower and materials used to achieve
`the goal. For instance, substantial cost savings may be real-
`45 ized by using less nitrogen, which usually has to be delivered
`via truck to the facility. Although the invention will utilize
`similar flow rates of nitrogen to the current art, less nitrogen
`will be needed for the present method because the present
`method can achieve the same results in less time.
`It is not uncommon that equipment may become fouled
`with organic contamination to the point where operating rates
`must be reduced to prevent catastrophic failure or a shutdown
`of the entire unit. One skilled in the art will be able to recog(cid:173)
`nize opportunities to apply the present invention in specific
`55 instances while the equipment is still operating to remove the
`organic contamination and return the equipment to a clean
`state. The benefit of this option for refiners and petrochemical
`plants is that they may be able to avoid or postpone total
`shutdowns and may be able to increase operating rates which
`60 would otherwise be constrained by the fouled equipment.
`
`EXAMPLES
`
`The following examples are provided to illustrate the
`present disclosure but not to limit the scope of the disclosure.
`Other applications of the disclosed process with or without
`modification will be apparent to one skilled in the art.
`
`Page 6 of 8
`
`ULI EXHIBIT 1009
`
`

`

`US 8,480,812 B2
`
`7
`Field tests have been conducted to prove the uniqueness
`and viability of the present invention. One example of the
`invention is described herein as described below and illus(cid:173)
`trated in FIG. 1. As illustrated in FIG. 1, a typical process
`system includes a feed drum (1), a slow roll compressor (2), 5
`a furnace (3), a reactor ( 4), heat exchangers (5), a compressor
`(6), a separator (7), a low point drain (8), an injection point
`(9), adjust fin fan exchanger (10), a sample point (11), and a
`trim cooler (12).
`In a typical chemical process system, such as a refinery, the 10
`starting material first enters a feed drum (1) which provides
`material feed surge capacity for the process. From the surge
`drum, process fluid is passed through a feed preheat
`exchanger (2) used to both heat the starting material stream
`before entering the furnace and partially cool reactor effluent. 15
`Before entering the reactor (4) the process fluid is passed
`through a furnace (3) where it is heated to an initial reaction
`temperature. Once in the reactor (4) the fluid reacts with a
`catalyst bed in the presence of high pressure hydrogen to
`generate the desired product(s) which then exit the reactor as 20
`a very hot effluent stream. This hot effluent stream is used to
`preheat the reactor feed at exchanger (2) and used to produce
`utility steam in reboil er (5). The hot effluent stream is further
`cooled in the fin fan exchanger (10) and trim cooler (12).
`Finally, the effluent reaches the separator drum (7) where it is 25
`depressured and passed on for further refinery processing. A
`gaseous steam is drawn from the top of the separator drum (7).
`A continuous process loop is formed as the recycle compres(cid:173)
`sor (6) circulates the gaseous stream which joins the initial
`feed stream at the preheat exchanger (2). The purpose of the 30
`recycle compressor is to move a high volume of hydrogen
`across the reactor catalyst bed.
`In cases where systems to be cleaned include additional
`equipment, or fewer equipment, for instance, if the individual
`reactor is the only equipment that needs to be cleaned, the 35
`disclosed process may be adapted by one of skill in the art.
`The procedure outlined below contains steps that may be
`taken in a typical cleaning procedure. These steps may be
`modified according to the specific situation as may be deter(cid:173)
`mined by one of ordinary skill in the art.
`
`40
`
`PROCEDURE
`
`8
`iron of the reactor gives up heat. Normally the unit will cool
`at a rate of 50 F to 100 F/hour.
`Step 4: Isolation of the Reactor Circuit from Fractionator
`and Feed Drum (1).
`The reactor circuit is isolated from the fractionator and
`feed drum by inserting flange blinds or closing valves at the
`outlet of the feed surge druni pumps and at vent/drain (8).
`Step 5: Slow Roll Compressor (6).
`The compressor (6) is started and allowed to operate at an
`idle speed that is significantly slower than that used for unit
`processing operation. In this step, a slow operating speed
`allows the compressor to pass vapor from the inlet to the
`outlet-necessary for establishing a complete circuit-with
`no damage to the compressor while the system is depressured.
`Step 6: Depressurizing the System.
`The system including furnace (3), reactor (4), heat
`exchangers (5) and (10), compressor (6) and separator (7) is
`depressurized and the atmosphere is allowed to change to
`95% nitrogen.
`More specifically, during this step, the hot hydrogen is
`purged from the system using nitrogen so that when com(cid:173)
`plete, nitrogen constitutes at least 95% of the circuit's internal
`atmosphere. This may be accomplished using a process com(cid:173)
`monly known as "huff and puff' in the industry. More spe(cid:173)
`cifically, hydrogen is vented from the circuit to achieve atmo-
`spheric pressure, the circuit is then repressurized by the
`introduction of nitrogen. The nitrogen is then allowed to vent
`so that the circuit returns to atmospheric pressure. This pro(cid:173)
`cedure may be divided into at least 3 sub-steps (a)-(c):
`(a) Allowing residual hydrogen to escape to the flare or
`other gas processing system through vent and drain (8)
`so that the residual system pressure falls below 10 psig;
`(b) Increasing the system pressure as high as practical by
`injecting nitrogen gas through injection point (9); and
`( c) Repeating steps (a) and (b) so that a grab sample of the
`gas exiting the vent point (8) measures at least 95%
`nitrogen when tested using gas chromatography (GC).
`Alternatively, the same procedure has been used to backfill
`the circuit with natural gas in lieu of nitrogen. Natural gas is
`readily available in the refinery and may be processed by the
`refinery after being used in cleaning. Nitrogen and natural gas
`work equally well as a transport system for the cleaning
`process.
`Step 7: Bringing Compressor (6) Up to Max Speed.
`With the circuit filled with 95% nitrogen (or natural gas),
`the compressor is sped up to maximum operating speed. With
`the compressor operating at full speed, a gas circulation loop
`50 is established from the compressor (6) through exchanger (2)
`and furnace (3), into reactor (4) and back to the compressor
`(6) through exchangers (5, 10 and 12) and separator (7). The
`circulation loop helps move the cleaning chemistry to all parts
`of the circuit in subsequent steps.
`Step 8: Cooling Down.
`Adjust fin fan exchanger (10) to maintain outlet tempera(cid:173)
`ture as warm as possible without reaching high compressor
`discharge limit.
`The cleaning process is most eff