Draft Encyclopedia X April 2002 2.0 SUBPART X UNITS s/pdf... · Draft Encyclopedia X April 2002 ... munitions including 57-mm and 75-mm recoilless rifle shells, 75-mm howitzer and

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Draft Encyclopedia X April 2002

2.0 SUBPART X UNITS

This chapter provides basic descriptions of the moretypical units permitted as Subpart X units. Thechapter also discusses circumstances when it may beappropriate to permit proposed miscellaneous unitsas conventional hazardous waste management units.Examples of patented or trademark technologies arediscussed throughout this chapter. However, theAgency does not endorse the technology availablefrom any specific company.

2.1 TYPES OF UNITS INCLUDEDUNDER SUBPART X

2.1.1 Open Burning and Open DetonationUnits

Many waste propellants, explosives, andpyrotechnics (PEP), and munitions items are unsafeto treat by conventional methods of hazardous wastemanagement. Open burning and open detonation(OB/OD) remain the primary methods of treatmentfor these wastes. Currently, research is beingconducted to develop alternative methods oftreatment for PEP wastes. New technologies, suchas enclosed detonation chambers, are likely tobecome more widely available in the next severalyears. Some of these new technologies may qualifyfor permitting under Subpart X.

The unit descriptions provided here focus on militaryOB/OD units, because the majority of the units areoperated by the military. The design configurationsand operational standards discussed in this sectionwill, however, also be used at non-military facilities.

2.1.1.1 Open Burning: Physical and ProcessDescription

Open burning (OB) is used primarily to destroypropellants, and is generally conducted onengineered structures such as concrete pads, ormetal pans to avoid contact with the soil surface.Such structures may range in size from 3 to 5 feetwide by 5 to 20 feet long, and are 1 to 2 feet deep.OB pans should be made of a material sufficient to

View of burning pans on a secondarycontainment pad. Note that the pads do notappear to have berms around them.

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withstand the burning process, and should be ofsufficient depth and size to contain treatmentresidues. The pans may be elevated slightly abovethe ground to enhance cooling and to allowinspections for leaks. The pans should be coveredwhen they are not in use to prevent precipitationfrom entering them. Pans may be equipped withports for draining collected precipitation or cleaningsolutions. Collected precipitation should not bedischarged onto the ground unless the pan wasdecontaminated after its last use, or unless theprecipitation is sampled and analyzed anddetermined not to contain hazardous constituents. Ametal cage placed over the burn unit duringtreatment may be helpful to minimize the ejection ofresidues from the unit.

The ground beneath the trays or pans may besurrounded by berms to prevent runon and runofffrom the area; however, a well-designed andoperated burn pan may not require berms. Groundcover around and beneath the pans should beprepared for ease of recovery of ejected treatmentresidues and for prevention of fire hazards that suchresidues may pose. Maintenance of a packed soilsurface is the minimum preparation sufficient toaccomplish those goals.

To prevent propagation of an accidental detonationfrom one device to another, DoD regulations requirecontainment devices, trenches, and individual groundtreatment units be spaced at least 150 feet apart.Detailed design specifications for containmentdevices, whether trenches, pans or other types ofcontainment, should be included in the permitapplication.

Waste propellant to be treated is often contained inbags, which are placed directly into the unit. Thewaste may be primed (that is, an initiating device isplaced in the waste material) either electrically ornon-electrically with black powder squibs. Thewaste is then ignited and the established wait time isobserved. If explosives are treated, a wait time of atleast 12 hours typically is observed before siteworkers inspect the unit. A 24-hour wait timetypically is observed between OB events to allow

Closeup view of burning pans on concreteslab. Note the white covers in thebackground which can be rolled over thepans to prevent precipitation from enteringthem.

To view a video of an open burning operation,double click on the image above.

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the surface to cool. After the OB treatment,containment devices are cleaned of any residues.OB operations generally are restricted to daylighthours, and usually are not conducted duringinclement weather.

2.1.1.2 Open Detonation Unit: Physical andProcess Description

Open detonation (OD) is used primarily to treatmunition items. OD typically is conducted in pits ortrenches below ground to minimize the ejection oftreatment residue, although surface detonations areperformed under certain circumstances. Trenchesvary in size depending on the quantity of material tobe treated, and are usually 4 feet deep or greater,and can vary in size from 4 to 8 feet wide by 6 to 15feet long.

The maximum quantities to be treated are measuredby net explosive weight (NEW), which is the totalweight of explosives in the munition. The NEWdoes not include the weight of the explosive chargeused to initiate the detonation (donor charge).Military units often use Composition (C-4) (90percent RDX and 10 percent plasticizer, such aspolyisobutylene) as a donor charge for ODoperations. The quantity of donor charge used isusually equal to the NEW of the munitions to betreated.

Open detonation involves placement of wastes at thebottom of the pit, along with the donor charge. Thewaste and charge are then covered with soil to thetop of the pit. After detonation, any treatmentresidues should be removed to minimize the potentialfor releases of hazardous waste or hazardousconstituents to the environment. Surrounding soilsshould be maintained in a manner that minimizes thepotential for fire posed by dry vegetation or otherhazards.

2.1.2 Enclosed Treatment Units

In recent years, DoD has encouraged the use ofcontrolled thermal treatment units for the destructionof pyrotechnics, small arms ammunition and

View of open detonation.

Open detonation is usally conducted in anexcavated pit to minimize the ejection oftreatment residues, although surfacedetonations may be performed. Not the raincover in the background which can be rolledover the area.

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fireworks. Examples of enclosed thermal treatmentunits include the Donovan Blast Chamber, the BlastContainment Structure and the Hurd Burn Units.

2.1.2.1 Donovan Blast Chamber

The Donovan Blast Chamber is used to performcontrolled thermal treatment of PEP in a room-sizeblast chamber. The explosion chamber consists ofan elongated double-walled steel explosion chamberanchored by bolts to a reinforced concretefoundation. In the preferred design, the insidedimensions of the chamber are eight feet high, sixfeet wide and fifty feet long. The reinforcedconcrete foundation is preferably at least four feetthick. The chamber is equipped with a double-walled access door for charging batches ofexplosives and a double-walled vent door fordischarging the products of detonation. The double-walls of the chamber, access door and vent door arefilled with a granular shock-damping material such assilica sand and the floor of the chamber is coveredwith a shock-damping bed such as pea gravel.Within the chamber, plastic polymer film bagscontaining water are suspended from steel wiresover the explosive material. Detailed drawings anddesign specifications for the unit are available inUnited States Patent No. 5,613,453. Additionalinformation can also be found athttp://www.demil.net

Materials to be treated are placed in the unit throughthe access door and onto the granular bed. Thesuspended plastic bags contain an amount of waterthat approximates the weight of the explosive. Anelectrical blasting cap is attached to the igniter leadwires. The access and vent doors are interlockedwith the electrical igniter to block ignition unless bothdoors are positively shut. When the doors areopened after a detonation, a vent fan is activatedand the gaseous products of detonation are drawnthrough the vent door opening and discharged to ascrubber system or baghouse. The DonovanChamber can be utilized to safely detonate explosivecharges in a wide variety of sizes, ranging from twoto fifteen pounds NEW. A smaller transportableversion of the chamber called the T-10 can be used

To view a video of an open detonationoperation, double click on the image above.

Exterior view of the Donovan Blast Chamber.

http://www.demil.net

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to treat up to 10 pounds NEW per shot. Stacktests have been conducted at units located at theMassachusetts Military Reservation and Blue GrassArmy Depot. Performance data from these testswere outlined in Pollutant Emission Factors for aTransportable Detonation System for DestroyingUXO.

2.1.2.2 Blast Containment Structure

The Army Corps of Engineers, Engineering andSupport Center in Huntsville, Alabama hasdeveloped a blast containment structure which isdesigned to capture all significant blast pressures fora total NEW of up to six pounds of TNT. The unitis also designed to capture all fragments from casedmunitions including 57-mm and 75-mm recoillessrifle shells, 75-mm howitzer and 60-mm and 81-mmmortars. The container consists of a steel cylinder,six feet tall and three and one-half feet in diameter,with elliptical top and bottom caps. The top cap isremovable and is held in place by a hinged steel ring.The bottom cap is permanently welded to thecylinder but it features a four-inch diameter drainport for cleanout and several one-inch diameter ventholes. The entire container is mounted on a steelframed skid. The skid includes a working platform,made of fiberglass grating, and a hoist for removingthe top cap. All steel parts are cabled together in anelectrically continuous fashion and are grounded.

The container utilizes a multi-layer fragment capturesystem to capture debris. Ordnance and a boostercharge are placed in a sand-filled plastic cylinder.Just outside the sand layer, plastic bags filled withwater are used to absorb much of the heat of theexplosion and to reduce the blast pressures.Outside the sand layer is a steel cable mat shaped inthe form of the cylinder, with a top and bottom matto protect the end caps. The mat is similiar toblasting mats used at construction sites. A steelplate liner is located between the cable mat and theouter steel shell. The liner is made in easilyremovable segments. The sand and water arereplaced after each detonation. The cable mats areexpected to last for up to ten detonations beforebeing replaced. The liner plate may survive as many

Interior view of the floor of a DonovanBlast Chamber.

Schematic of Blast Containment Chamber.

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as 50 to 75 detonations before requiringreplacement. Additional information regarding thistreatment device is available at http://www.hnd.usace.army.mil/oew/tech/techindx.html

2.1.2.3 Hurd Burn Units

The unit consists of a quarter-inch thick steel,enclosed cylindrical box equipped with a hingeddoor on one end. The cylinder or barrel is mountedon a movable trailer which may be positioned on aconcrete pad when in operation. The fuel source forthe unit is a pair of propane tanks. Waste militarymunitions are placed onto screens in the barrel of theunits. The door to the unit is closed and the propanefuel source is turned on and adjusted through aregulator. The application of a flame ignites the unit.Air holes located on both sides of the unit provideoxygen for the burn. Air emissions escape throughthe vent at the top of the unit, the air holes on theside of the unit, and through cracks in the doorway.A maximum of 25 pounds NEW may be placed intoa single burn unit at any time. The maximumtreatment time is 20 minutes. Situating the unit on asteel reinforced concrete slab will provide additionalcontainment in the event of spillage of ash orkickout. However, the unit has no air pollutioncontrol features associated with it.

2.1.2.4 Confined Burn Facility

The U.S. Navy at Indian Head has designed aConfined Burn Facility (CBF) that uses a batch-feedchamber. Upon ignition of the wastes in thechamber, the hot gases that are generated arequenched with water and stored in a containmentreservoir for subsequent scrubbing and treatment ata slow continuous rate before discharge. The fiveburn chambers of the CBF are connected via ducts,equipped with scrubbing and quenching sprays, to acentral exhaust gas storage vessel. Each burnchamber can hold up to 1,200 pounds of explosivehazardous waste. All chambers are loaded at thebeginning of the shift. Each chamber is ignited oneat a time with 40 to 80 minutes between eachignition to allow processing of all gases. The designrequires no additional pre-treatment, and it can burn

View of Hurd Burn Unit. This is a moble unitwhich can be used for treating small quantitiesof PEP.

Schematic Diagram of Hurd’s Burn Unit.

http://www.hnd.usace.army.mil/oew/tech/techindx.html

http://www.hnd.usace.army.mil/oew/tech/techindx.html

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up to 6,000 pounds of energetics per shift. Itincludes redundant burn chambers of composite wallconstruction (inner wall is ablated during massdetonation to absorb shock waves, and it minimizesdamage to the chamber should a mass detonationoccur). It uses standard exhaust gas treatmenttechnology, and it uses burn pans similar to presentOB site operations.

2.1.3 Carbon and Catalyst RegenerationUnits

Carbon and catalyst regeneration units include bothcontrolled-flame and non-flame devices. Since1991, EPA has considered the regeneration orreactivation of spent carbon from a carbonabsorption system, used in the treatment of a listedhazardous waste or used to capture emissions froma listed hazardous waste, to be thermal treatmentunder the interim status provisions of RCRA. Thecarbon, which contains absorbed organics, isclassified as a hazardous waste under the “derived –from rule” (40 CFR §261.3 (c)(2)(i)). In thatprocess, organic contaminants are desorbed fromactivated carbon at temperatures as high as 1,800degrees (°) Fahrenheit (F). Carbon regenerationunits that use thermal treatment include rotary kilns,fluidized-bed regenerators, infrared furnaces ormultiple-hearth furnaces, all of which transfer heat tothe contaminated carbon. The most prevalentfurnace type is the multiple hearth furnace, followedclosely by rotary kilns. As an alternative, steam maybe used to desorb contaminants from the media indevices similar to tanks.

Catalyst regeneration processes can be similar tothose used for carbon regeneration. However, thetypes of catalyst to be regenerated, the types andconcentrations of contaminants to be desorbed, andthe conditions under which the desorption takesplace may alter the combustion chemistrysignificantly from that which is seen in carbonregeneration units.

Overview information regarding theConfined Burn Facility is available athttp://www.ih.navy.mil/environm.htm

Refer to August 8, 1991 Policy Memo andJanuary 5, 1998 Policy Memo regarding theregulatory status of Carbon RegenerationUnits.

http://www.ih.navy.mil/environm.htm

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Controlled-flame devices used for carbonregeneration are similar to those used for incinerationor for boilers and industrial furnaces (BIF).However, strict compliance with incinerator or BIFregulations may not be appropriate. Use of EPA’sincinerator and BIF destruction and removalefficiency (DRE) standard and carbon monoxideand total hydrocarbon monitoring in the off gasesmay be appropriate for such units. Following arebrief descriptions of some of the more commontypes of regeneration units.

A rotary kiln is an inclined rotating cylinder, linedwith refractory brick and internally fired. The spentcarbon is fed at the higher end of the kiln andmoves, driven by gravity, down the length of the kilnas the kiln rotates. A heated air stream passescountercurrent with the waste, volatilizing thecontaminants in the carbon. The exiting air streamcontains desorbed contaminants and any combustionproducts that may have formed within the kiln. Therotational speed of the kiln can be varied.Peripheral speeds of 0.5 meters/minute (m/min) to 2m/min are typical.

A fluidized-bed furnace is a cylindrical vertical vesselwith an air feed at the bottom of the unit. Influidized-bed units, the granular material (the bed) isfluidized by directing air upward through the bed.Fuel is charged directly into the fluidized-bed or intothe window box beneath the bed. The temperaturein the freeboard area above the bed can be higherthan that within the bed. Because of the airflowrequired to fluidize the carbon particles, fluidized-bed furnaces have a larger exhaust volume thanother types of regeneration furnaces with the samecarbon throughput rate.

A multiple hearth furnace typically consists of arefractory-lined vertical steel shell. Inside is a seriesof flat hearths that are supported by the walls of theshell. A rotating shaft runs vertically through thecenter of the hearth. Rabble arms attached to therotating shaft move the waste across each hearth.The hearths have holes, either in the center near the

Schematic of Fluidized-bed Furnace.

Schematic of Rotary Kiln.

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shaft or near the outside edge through which thewaste drops to the hearth below. Combustion airtravels countercurrent to the waste flow.

In an infrared furnace spent carbon is transportedthrough the horizontal furnace via a metal grate. Aseries of heating elements above the metal grate areelectrically heated to incandescence. The infraredradiation heats the carbon and a draft fan is used todraw air through the furnace and remove desorbedgases as they are released from the carbon.

These types of units may use a backflush of steam todesorb contaminants. The contaminated steam thenis condensed and transferred to a decanter. In thedecanter, a concentrated organic solvent phase isseparated from the water phase. The water phasecontains measurable concentrations of organiccontaminants and must be treated as hazardouswastes.

Some carbon regeneration tanks also may meet thedefinition of wastewater treatment unit under40 CFR §260.10. Such units are used to adsorbcontaminants from wastewaters. These units areexempt from permitting standards under RCRAwhen they are used to treat wastewater fordischarge under National Pollutant DischargeElimination System (NPDES) or publicly ownedtreatment works (POTW) standards.

2.1.4 Thermal Desorption Units

As outlined in a June 12, 1998 Policy Memo, theEPA regulations do not define “thermal desorber”,but the term generally applies to a unit which treatswastes thermally to extract contaminants (i.e.,volatile organics) from a matrix. A thermal desorberutilizing controlled flame combustion (e.g., equippedwith a directly fired desorption chamber and/or afired afterburner to destroy organics) would meetthe regulatory definition of an incinerator.Alternatively, a thermal desorber that did not usecontrolled flame combustion (e.g., equipped with anindirectly heated desorption chamber and thedesorbed organics were not “controlled”/destroyedwith an afterburner) would be classified as a

Schematic of Multiple Hearth CarbonRegeneration Unit.

Schematic of Infrared furnace.

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“miscellaneous unit”. Thermal desorption mayoxidize organics but in some cases merely volatilizesorganic compounds from the contaminated mediaand concentrates them in the desorber exhaust gasstream. Thermal desorption reduces the volume ofthe contaminated media, but the desorber exhaustgas stream typically still requires some form oftreatment.

A typical thermal desorption unit includes feedprocessing equipment, such as hoppers, sieves, orshredders. The feed material then is transferred intothe thermal treatment unit by such equipment asconveyor belts. The feed storage, preparation, andtransfer system may be unenclosed, posing risks ofreleases during those steps. Emission controls forthe ancillary equipment may be necessary to addresssignificant risks.

The thermal treatment unit itself may consist of arotary kiln, a fluidized-bed system, or a multiple-hearth system, as described above for regenerationunits. Typically, the waste feed travelscountercurrent to an air stream inside the desorber,where temperatures typically are between 400 and1,000°F. The contaminated air stream is directedthrough air pollution control devices, such asafterburners, venturi scrubbers, electrostaticprecipitators, or baghouses, before it is released intothe atmosphere.

2.1.5 Vitrification Units

The development of vitrification technology has beenpromoted by the large volume of low-level and highlevel radioactive waste requiring treatment at U.S.Department of Energy (DOE) sites. Much of thiswaste includes RCRA hazardous constituents and isregulated as mixed waste.

There are two general categories of vitrificationprocesses: those applied to site remediation (e.g.,contaminated soils) and those applicable totreatment of waste streams from uranium/plutoniumprocessing (e.g., tank wastes). Vitrificationprocesses used in the treatment of wastes aretypically conducted as ex-situ vitrification whereas

Additional Policy Memos regarding theapplicability of the Subpart X regulationsto Thermal Desorbers were issued onJuly 30, 1997, February 23, 1994,October 29, 1993 and May 18, 1988.

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treatment of contaminated soils is generallyconducted in-situ. A description of both ex-situ andin-situ vitrification processes follows.

2.1.5.1 Ex-Situ Vitrification

The ex-situ vitrification process is a thermaltreatment process that both oxidizes and vitrifieswastes. It can treat wastes in the form of solids oras slurries. Typically waste and fuel are mixed in apre-combustor before being transferred to acombustion chamber. Oxidation will take place inthe combustion chamber. After the waste has beenoxidized the ash is transferred to a vitrificationchamber where it is mixed with glass makingingredients to create glass materials. In somesystems, wastes treated this way are reportedlycapable of passing the toxicity characteristic leachingprocedure (TCLP).

2.1.5.2 In-Situ Vitrification

In-situ vitrification earth-melting technology wasdeveloped by Battelle Memorial Institute during the1980s for DOE and is now commercially availableas Geosafe Corporation’s GeoMeltTM technology.In-situ vitrification treats contaminated materialswhere they presently exist. This method is preferredwhen it is necessary to avoid the risks associatedwith excavation of the waste. The vitrificationprocess can simultaneously treat wastes with highconcentrations of both organic and inorganic (e.g.,heavy metal) contaminants. Organic constituents arethermally desorbed and then destroyed by thermaldecomposition (pyrolysis) within the oxygen-depleted media being treated. Nonvolatileinorganics (metals) are typically incorporated intothe melt and the resulting vitrified product. Suchincorporation occurs within the framework of theglassy product itself, as opposed to simpleencapsulation (being surrounded) by the glass. Alarge volume reduction (25-50% for soils) occursdue to elimination of void volume and vaporizablematerials during processing. This process worksbest with treatment zones that are >10 feet inthickness.

Schematic of high level waste melter used forex-situ vitrification.

In-situ vitrification hoods.

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Off-gas hoods are used to cover an area ofcontaminated soil. The process works by meltingsoil in place using electricity applied between pairsof graphite electrodes. The process employs jouleheating and typically operates in the range of 1,600to 2,000° Celsius (C) for most earthen materials. Ahighly conductive starter path is placed between theelectrodes to allow initiation of melting. Aselectricity flows through the starter path, the pathheats up and causes the surrounding media to melt.Once the media is molten, it too becomes electricallyconductive. Continued application of electricityresults in joule heating within the molten mediabetween the electrodes. After the melt is fullyestablished, the melt zone grows steadily downwardand outward through the contaminated volume.Successful melting is contingent upon the use ofadequate electrical conductivity. Additives includinglime, soda, ash, or pre-manufactured glass frit maybe used to improve performance.

A low vacuum can be pulled on the hood inoperation to capture emissions from the melt andsend them to the off-gas treatment system, whichmay include a quencher, scrubber, demister, heater,particulate filter, blower, and optional activatedcarbon or thermal oxidation units. The entire ISVsystem can be monitored from a process controlroom.

2.1.6 Rotary Metal Parts Treatment Unit

Rotary metal parts treatment (RMPT) is used in thedecontamination of empty projectile and mortarshells. The RMPT consists of a cylindrical structurerotating at a prescribed speed inside a cylindricalfurnace. The dimensions of the RMPT are 4 feet, 8-inches inner diameter by 15 feet, 7-inches in lengthwith design conditions of 15 psig/full vacuum at1,500 °F. The inside cylinder contains 15 cageswhich are evenly distributed around a 36-inchoutside diameter inner pipe, supported andstrengthened by baffles. Each cage is constructedwith three ½-inch diameter stainless steel rods,positioned at a 120-degree angle and parallel in theaxial direction. The size of the cages is dependanton the different munitions and mortars to be treated.

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The RMPT is heated by using external electricinduction coils and superheated steam as the carriergas.

Munitions that have been washed and drained aretransported by a conveyor system and loaded intothe cages on a unit feed basis. The furnace is heatedby induction power supplied from a radio frequencygenerator. The entire furnace wall area must beheated and maintained at a temperature of 1,250° F.The furnace shell must have a high emittance in orderto optimize performance. In addition, the shell mustalso have good chemical resistance to corrosion, inorder to resist the acid gases that are generatedduring operation. The total residence time for eachmunition ranges from 75 minutes for 105-mmprojectiles and 4.2-inch mortars to 105 minutes for155-mm projectiles. At the same time as amunition is loaded on the front end of the unit, atreated munition is discharged at the opposite end ofthe furnace. A vent gas reheater is installeddownstream of the RMPT to complete destructionof the agent. Downstream of the reheater, the ventstream is cooled and condensed in a quenchcondenser which is in contact with a recirculatedbrine stream. Noncondensable gases will be sent toa dedicated CATOX® offgas treatment system.

Internal parts removed from the 105-mm, 155-mmmunitions and 4.2-inch mortars are processed in asmaller Batch Metal Parts Treatment (BMPT) unit.The internal parts consist of burster wells, burstertubes, fuzes, nose cones, lifting lugs and plugs.Similiar to the RMPT, the BMPT consists of acylindrical furnace which uses external inductioncoils as the primary heat source and superheatedsteam as the carrier. The BMPT measures 4 feet,8-inches in diameter by 11 feet in length with designconditions of 15-psig/full vacuum at 1,500 ° F. Theinternal parts are removed from the main bodies ofthe projectiles or mortars and collected intorectangular boxes. These boxes are placed on arolling plane and fed into the furnace on a batchbasis.

Detailed process flow diagrams and designspecifications for the RMPT, the BMPT andthe associated ancillary equipment are inprovided in following document: RotaryMetals Parts Treatment.

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2.1.7 Shredder Units

Shredders typically are used to make waste moreamenable to subsequent treatment in other units,such as thermal desorbers, regeneration units, orincinerators, through reduction in size, and blending.Shredders may be regulated under Subpart X basedon the material managed. Refer to June 24, 1988Policy Memo. Drum shredders are found at anumber of facilities. If the unit is managing “RCRAempty” containers, then the unit is exempt fromRCRA Subtitle C regulations. (Refer to 40 CFR§261.7 for the definition of RCRA empty). Severaltypes of shredders are used, the major examples ofwhich are hammer mills, shear shredders, and augershredders.

A hammer mill is a type of shredder that reduces thesize of the waste by impaction and that works bestwith friable materials. The mill can handle a widerange of solids but must be matched well with thewaste to prevent problems related to excessiveequipment wear and jamming. Stringy or stickymaterials also can jam the mechanism. Shear andauger shredders use low-speed knives or counter-rotating augers to shred solid materials, such asdrums.

A mechanical feed system, typically consisting of afeed hopper and some type of conveyance system,should be available to avoid the need for plantpersonnel to be near the opening of the hopperduring operation. To prevent flying debris and tominimize emissions, the feed system should beenclosed. The shredder also must be designed tocontain dusts and mists of toxic materials, as well as,in the case of hammer mills, particulate matterescaping the unit at high velocity. Dust and fumescan be controlled by drawing them into an airpollution control device associated with theshredder. In some cases, flame-suppression devicesmay be necessary to prevent explosion and fire inthe feed hopper and the shredder.

Schematic of HammerMill Shredder.

Schematic of Shear Shredder.

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2.1.8 Filter Press Units

Filter presses are used to separate solids from fluidsunder pressure. The most basic type of filter pressis the plate-and-frame press. As shown in theschematic to the right, the unit consists of alternatingsolid plates and hollow frames that are situated onparallel support bars. The filter medium is placedagainst each side of the solid plates, the surfaces ofwhich are slotted or grooved. The entire collectionof plates and frames is pressed together using ascrew or hydraulic ram assembly, which shouldachieve essentially a fluid-tight closure. The filtermedium between the plates and frames acts as agasket. This schematic also shows the flow pathwithin a plate-and-frame press. Although the figureshows filtrate exiting through a closed system, otherdesigns discharge filtrate through cocks located atthe base of each plate into open collection trays. Aclosed discharge system is essential to prevent toxicor volatile air emissions.

Filter presses often drip and leak. Emptying andcleaning of a filter press may include disassembly ofthe press and scraping of the filter cloth by hand.For such units, secondary containment (e.g., asrequired for tanks under 40 CFR §264.193) may beappropriate to minimize the potential for harm posedby releases that may occur during operation andmaintenance of the units.

2.1.9 Drum Crushers

Drum crusher units that are eligible to be permittedunder Subpart X, handle containers of hazardouswastes. Typically, a can or drum crusher handlesone container at a time. The container’s lid may beremoved before it is placed in the crusher, or the lidcan be left in place if an opening, such as abunghole, is present. Some units are designed to cutoff the top of the drum to allow easier access to theinterior. After the container is conveyed into the unitand opened, the interior of the container may besprayed with an appropriate solvent to mobilizehazardous waste residues.

Schematic of Filter Press.

A Policy Memo concerning the applicabilityof Subpart X to Drum Crushers was issuedon May 21, 1991.

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Within the unit, a perforated plate is clamped on thetop of the container, and then the container is flippedover and crushed with a hydraulic ram. Thehydraulic ram may be electric or pneumaticpowered. The rinse solvent and residues are forcedout of the container and down through theperforations. The solvent and rinsate drain from thebottom of the can crusher unit into a collection tank.The crushed container, which typically isapproximately one-inch thick, is then conveyed outof the unit. The hazardous waste that drains into thecollection tank may be thick and difficult to mobilize.The collection tank may have ancillary equipment forsuch processes as agitation, grinding, or addition offluid to enhance removal of the hazardous waste.

The drum crusher unit should be enclosed, so that anitrogen or carbon dioxide blanket can be appliedduring crushing to minimize the risk of explosion.The unit also should be equipped with a flame-arrester vent that is connected to appropriateemission control equipment. Secondary containmentmay be necessary for the entire unit.

2.1.10 Drum Washer

Commercial drum washing systems are availablefrom several manufacturers. These units areregulated as Subpart X units if the units are handlingnon-RCRA empty drums. The definition of RCRA-empty container is provided in 40 CFR §261.7.Drum washers may be fully automated with severalstations to flush, rinse, purge, and siphon both polyand steel drums. In general, a drum washing systemprovides enclosed containment to capture the liquidsolvent used to clean the interior and exterior of adrum. The solvent may be applied by a high-pressure spray wand or automated rotating brushes.The cleaning solvent may be as simple as high-pressure water, although it is common to use acommercial chemical solvent. Recovered solventcarries drum bottoms and may be recycled througha closed-loop solvent recovery system associatedwith the drum washer. The drum washer may alsoinclude an exhaust fan and air pollution controlequipment (e.g., fume scrubber) to capture volatileorganics and particulates evolved during drum

Schematic of Drum Crusher.

Schematic of Drum Washer.

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cleaning. In addition to drum washers, systems arealso available to clean smaller containers such astotes and pails. Examples of drum washing units areshown in the column to the right.

2.1.11 Mercury Bulb Crushers

Fluorescent lamps are widely used in businesses, asthey provide an energy-efficient source of lighting.The commercial and industrial sectors dominateusage of fluorescent lamps, accounting for over 90percent of total usage. Fluorescent lights aredesigned so that approximately half of them willoperate after 20,000 hours of operation. Wherethese lamps are being used on a small scale, they aregenerally replaced as they burn out, one at a time.However, in large companies and industries, thismethod is not practicable, and, therefore, grouprelamping is done on a regular basis. Typically,group relamping is performed at 15,000 hours, or75 percent of the lamp’s rated life. This translates toreplacement every two years for continuousoperations, and every three to five years fornoncontinuous operations, which are much morecommon. Approximately 20 percent of all lampsare currently replaced annually. Group relampingoperations generate large quantities of lamps to bedisposed of at a single time.

A typical fluorescent lamp is composed of a sealedglass tube filled with argon gas at a low pressure(2.5 Torr), as well as a low partial pressure ofmercury vapor, thus the tube is a partial vacuum.The inside of the tube is coated with a powdercomposed of various phosphor compounds.Tungsten coils, coated with an electron emittingsubstance, form electrodes at either end of the tube.When a voltage is applied, electrons pass from oneelectrode to the other. These electrons pass throughthe tube, striking argon atoms, which in turn emitmore electrons. The electrons strike mercury vaporatoms and energize the mercury vapor, causing it toemit ultraviolet radiation. As this ultraviolet lightstrikes the phosphor coating on the tube, it causesthe phosphor to fluoresce, thereby producing visiblelight. The most commonly used fluorescent lamp isthe 40-watt, 4-foot long tube, although smaller,

View of interior Drum Washer.

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larger and differently shaped lamps are also used.The amount of mercury in fluorescent lamps variesconsiderably with manufacturer, and typically rangesfrom 27 to 41 mg of mercury per lamp. Manyfluorescent, high-pressure sodium, mercury vaporand metal halide lamps exhibit the toxicitycharacteristic for mercury. In addition, some high-density discharge (HID) and incandescent lampsmay contain lead solder at levels which exceed thetoxicity characteristic regulatory level for lead.Fluorescent light fixtures may also contain hazardousconstituents in their ballasts (i.e., polychlorinatedbiphenyls (PCBs) and diethylhexyl phthalate(DEPH)).

Historically, spent hazardous waste lamps wereplaced in landfills. On July 6, 1999 EPA addedspent hazardous waste lamps to the list of federaluniversal wastes (64 FR 36466) in order toencourage recycling of these wastes. The UniversalWaste Rule is codified in 40 CFR §273. TheUniversal Waste Rule for spent lamps becameeffective at the federal level on January 6, 2000.However, the rule is not effective in states that areauthorized for the base RCRA program until thestate chooses to adopt it. Some states may chooseto not adopt the universal waste regulations butrather to regulate units which treat hazardous wastelamps under a Subpart X permit.

The simplest of crushers is essentially a single unit,with a crusher mounted on top of a barrel, usually a55-gallon drum. This system is used in manyindustrial facilities to crush their fluorescent lamps asa means to reduce the solid waste volume beforedisposing the material in a landfill. In this version,light lamps are hand-fed to a feeder chute of variablelength and diameter. This chute is not necessarilylonger than the lamps being fed into it. The lampspass to the crushing unit, typically consisting ofmotor-driven blades, which implode and crush thelamps. From here, the crushed powder drops intothe barrel below the crusher. There are no airpollution controls on the device. The crushed lampsare collected in drums until they are full, and then thefull drums are transported to one of several facilities.The crushed material may then be separated into

View of a barrel-mounted crusher utilizing anegative air exhaust system.

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glass, metal, and powder components. Typically,the untreated powder is then deposited in a landfill.This is currently the most common method ofdisposing these lamps. Alternatively, the barrelsmay be transported to a mercury recovery facility,which will separate the mercury-containing phosphorpowder from the crushed glass and aluminumendcaps, and recycle all the materials.

A more sophisticated version of this barrel-mountedcrusher utilizes a negative air exhaust system to drawthe crushed debris and prevent it from reemergingthrough the feeder tube. The drawn air is thenpassed through a High Efficiency Particulate Air(HEPA) filter to remove particulate matter from theexhausted airflow. The crushed material is thendisposed in one of the manners discussed above.

Another model design consists of a hand fedapparatus with two feeder chutes. One chute is 5feet long, to accommodate 4 foot lamps, and theother tube is 9 feet, in order to accommodate 6 to 8foot lamps. Each chute is placed at an angle, andhas a 9-inch by 12 inch opening, which canaccommodate several lamps at a time. The lampsare delivered down this angled tube onto a motordriven blade made of heavy gauge hardened steelrotating at 2700 rotations per minute. The rotatingblades implode and crush the lamps as they arrive.The crushing unit has an operating capacity of 62.5lamps per minute. A vacuum system collects airfrom beneath the crusher, preventing mercury-ladenair from exiting through the feed tube. Materialcollected in the vacuum system first passes through acyclone separator. This removes glass particles,which drop into the drum. Air from the cycloneseparator contains phosphor powder and somemercury vapor. After passing through the cyclone,the air is pulled through to a baghouse, where fabricfilters trap particulate matter in the air stream. Every45 seconds, these fabric filters are cleaned with areverse pulse of air. The air leaving the baghouse istypically composed only of air and mercury vapor.This air and mercury vapor mixture continuesthrough several more particulate matter and HEPAfilters, to ensure that all particulates have been

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removed. From here, the exhaust is delivered totwo 250-pound activated carbon beds, which trapthe mercury vapor.

The entire process is vacuum-sealed and monitoredcontinuously for leaks and to ensure that air in thecontainment area is in compliance with OSHAregulations. Effectively, the only time where levels ofmercury in the workplace may approach the OSHAlimit of 0.05 mg/m3, is when lamps have beendropped and broken.

A third design is a completely enclosed system thatfeeds fluorescent lamps in one end to a crusher,passes the exhaust through an extensive filteringsystem, and delivers the powder to a thermalreduction unit (TRU), which recovers the mercuryfrom the phosphor powder. Thus, this systemcarries out the entire mercury recycling process,from the crushing of fluorescent light lamps to theretorting and reclamation of mercury from phosphorpowder.

Lamps are hand-fed into feeder tubes of differentlengths, depending upon the size of the lamps beingprocessed. The lamps are fed to the crusher, whichimplodes and crushes the lamps into small fragments.The operating capacity of the unit is 60 lampscrushed per minute. As with the second design, theentire process is conducted under negative airflow.The crushed debris is exhausted first to a cyclone,where the larger particles, such as crushed glass andaluminum endcaps, are separated out. At this point,much of the phosphor powder drops out into acyclone hopper. From this collection hopper, thephosphor powder, containing mercury, is transferredto the TRU via an enclosed auger conveyer. Afterthe cyclone, the airflow proceeds to a baghouse,where fabric filters continue to remove particulatematter from the airstream. The fabric filters arecleaned with a reverse pulse mechanism, and thepowder that drops out here is also routed to thecyclone hopper. The air stream leaving thebaghouse proceeds to a HEPA filter, and then to apotassium iodide-impregnated carbon filter. Thisremoves the mercury vapor, by precipitating it in theform of mercuric iodide.

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2.1.12 Underground Mines, Caves, andGeologic Repositories

Placement of hazardous waste in subterraneanfeatures, such as mines, caves, and salt domes, isregulated under 40 CFR Part 264 Subpart X andconstitutes land disposal. Hazardous waste placedin these units must be treated before disposal, incompliance with treatment standards promulgatedunder the land disposal restrictions (LDR), 40 CFR§268, unless the owner or operator demonstratesthat there will be no migration of hazardousconstituents from the unit, in accordance with 40CFR §268.6.

The design considerations for these units are similarto those for landfills. Because of the depth ofgeologic repositories, it may be extremely difficult toimplement groundwater monitoring. The stability ofthe underground formation also is an importantconsideration.

At cave and mining sites, infiltration of water shouldbe evaluated carefully. The presence of caves ingeologic formations indicates the presence of waterwithin the formation at some time. The permitapplicant must demonstrate that ground water is notexpected to discharge into the unit for at least thetime period of operation of the unit. Thatrequirement can be met by demonstrating that thereare no nearby aquifers above the level of the unit, orthat aquitards exist above the repository level.Should the applicant be unable to demonstrate thatcondition, some form of infiltration control must beprovided (a requirement similar in concept to that forleachate control for landfills).

2.1.13 Biological and Chemical TreatmentUnits

A permit writer may receive a permit application fora biological or chemical treatment unit that theapplicant is attempting to permit under Subpart X.Many of these types of units may be moreappropriately permitted under either the tank or landtreatment unit regulations, or should incorporatesuch standards as part of the Subpart X permit.

Schematic of geologic repository at YuccaMountain.

1. Canisters of waste, sealed in special casks,are shipped to the site by truck.

2. Shipping casks are removed, and the innertube with the waste is placed inmultilayered storage container.

3. An automated system sends storagecontainers underground to the tunnels.

4. Containers are stored along the tunnels, ontheir side.

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2.1.14 References

Additional information regarding these unitsdescribed above can be found in the followingdocuments:

EPA. 1992. Alternative Control Document.Carbon Reactivation Processes. EPA 453/R-92-019. December.

U.S. Patent Office. 1997. Patent No. 5613,453.Donovan Chamber.

EPA. 1994. Evaluation of Mercury Emissionsfrom Fluorescent Lamp Crushing. EPA 453/R-94-018. U.S. EPA Control Technology Center.February.

Documents

Draft Encyclopedia X April 2002 2.0 SUBPART X UNITS s/pdf... · Draft Encyclopedia X April 2002 ... munitions including 57-mm and 75-mm recoilless rifle shells, 75-mm howitzer and