APPLICABILITY OF THE PROMULGATED FEDERAL "MACT" STANDARD FOR CHROMIUM EMISSIONS TO CURRENT AVAILABLE "ADD ON" CONTROL TECHNOLOGY

Transcription

1 APPLCABLTY OF THE PROMULGATED FEDERAL "MACT" STANDARD FOR CHROMUM EMSSONS TO CURRENT AVALABLE "ADD ON" CONTROL TECHNOLOGY BY ART BROOKS SALES MANAGER KCH SERVCES, NC.

2 NTRODUCTON The fnal rule for the control of emssons from hard and decoratve chromum. platng and chromum anodzng s now promulgated. The ntent of ths paper s to gve a general overvew of the standard as t apples to h e scrubber and mst elmnator technology and to explan the fundamental desgns of these technologes. t s not possble, n a paper of ths length, to nclude all the nformaton and requrements of ths standard. t s mperatve that the fnal rule be thoroughly studed and understood by : se who: must comply. and-clear communcaton wth ther gven admnstrator must be KCH SERVCES, NC 100 Wcsterly Hll Dr

3 ') HARD CHROMUM PLATNG Hard Chromum Platers have been spl., nto two source categores; Large platers and small platers. Large platers are those wth actual cumulatve rectfer capactes greater than 60 mllon ampere hours per year. Small platers are those wth actual cumulatve rectfer capacty of less than 60 mllon ampere hours a year. (1) "A gven faclty may determne ther sze by usng actual cumulatve rectfer capacty n leu of -::-.--x- maxmum potental rectfer capacty f non-resettable amp-hour.meters. are used on -1 affected tanks, and monthly records are kept of actual amp-hour.usage to-de that the usage has not been exceeded." b 8 The emsson lmtaton for all exstng and new hard chrome platng tanks at desgnated large facltes s mllgrams of total chromum per dry standard cubc - meter (mgldscm) of ventlaton ar (Table 1). The emsson for all new tanks at desgnated small facltes s also mg/dscm (Table 1). These emsson lmts are based on the use of a composte mesh pad control devce (CMP). The emsson lmtaton for all exstng tanks at desgnated small facltes s 0.03 mgldscm (Table 1). Ths emsson lmt s based on the use of a wet packed bed scrubber. Page 2 KCH SERVCES, NC 100 Westerly Hll Dr

4 Table 1. STANDARDS FOR CHROMUM ELECTROPLATNG AND CHROMUM ANODZNG TANKS BASED ON MACT ". 3 ".. "_"..-..._ "*..".._..-*"..--- *...* "..""*~"*." l*_.."~..*l.-.. """...".."."".-**..*_ *"-""-..**"-"-..."".**- TYPE OF TANK _".." _... EMSSON "...".. LMTATONS. "...,. "... *... t * SMALL LARGE, ""..._..""..._.. ". :......"..."..... HARD "----"-~-" ~ CHROMUM PLATNG TANKS : "-*"..*-".--" _. "... All edstna tanks [, mgldcsm mgldscm : (1.3 x 1 B5 grldscf) (6.6 x 10-6gddsCf)..._..."-.l "... " _ _.... "..".".."..." : All new tanks mddcsm mgldscm._.,t...,.~6.e-~~-~6.~ * "..-- -_...*.~6~6xlo-s-gr/dS~" "..--- DB4M.L:::....#... DECORATVE "..".._.._... *.... CHROMUM PLATNG TA...*...; _-... All new """...".."_...~"* and exstng..."... tanks..."... ~... ~. ^...!..."_...".." --..._" _ "..~... "...(......_.. "..."...* " All new and exstng tanks mqldscm2 (4.4 x 10-6 grldscf) n accordance wth (d)(2), owners or operators usng a fume suppressant contanng a wettng agent as a control technque can meet an altemate emsson lmtaton of 45 dynedm (3.1 x 10-3 ba).....,..,.. Page 2a KCH SERVCES, NC P.0. Box Westerly Hll Dr

5 MESH PAD ELMNATOR The Mesh Pad Chrome Elmnator consstently outperformed the wet scrubber n emssons tests performed durng EPA Technology Study. The desgns of these devces have also mproved consderably over the duraton of the study. The most effectve chrome elmnator desgn consst of a vessel that ncorporates three or four mesh pads n, seres. The pads typcally consst of polypropylene monoflament woven or kntted nto the mesh confguraton. The best mesh pad confguratons utlze the largest monoflmants wth the * largest vod spaces as the frst stages, wth the followng stages utlzng ncrementally decreasng monoflament szes and vod spaces. Ths confguraton facltates removal of chromc acd mst n stages based on partcle sze. t also provdes protecton of the - hghest effcency stages, that are most prone to pluggage, by pre-control stages up front! Mesh pad elmnators work by the prncple of nertal mpacton (Le., Partcles. must.-be travelng wth suffcent velocty to mpact and adhere to surface of meda.) Ther effcences are determned to a specfc mst partcle sze. (Chromc acd emssons are lberated from the tank surface n mst form.) Mst partcles of varyng szes are collected by the specfc stages desgned tc c=!lect that part,c!e sze and through perodc washdown, the medums are flushed, and chrome s draned out of the unt to be sent to waste or to be used n the platng tank as make up.. kge 3 KCH SERVCES, NC 100 WCSterly Hll Dr

6 -1 A vessel desgn s crtcal to the capablty of the devce to meet the new standard. Due to the fact that hgh efcency mesh pads have hgh collecton effcences on mcroscopc partcle szes (some confguratons remove 99% at one mcron), they also create hgh pressure drops n nches of EO. f pads are not properly sealed nto the vessel wall, the pressure drop can cause the gas stream to follow the path of least resstance around the meda, creatng by pass, and causng excess emssons. Dran lnes must also be sealed, or trapped, to prohbt by pass through the unts dran manfold. Vessels must also ncorporate a well desgned washdown spray system to perodcally clean the medums and prevent pfuggage, or chromc acd buldup. The fnal rule requres that washdown of the (CMP) be conducted n accordance wth manufacturers recommendatons and be ncorporated nto. the faclty s operaton and mantenance Vessels must also be desgned wth accessble pressure taps to accommodate flexble tubng from a dfferental pressure gauge, enablng daly montorng and recordng of the devces pressure drop to be done, as s requred by the fnal rule. The dfferental pressure gauge should be easly accessble, whether located on the vessel - tself, or n a remote panel. The fnal rule states that CMP pressure drop must be montored and recorded daly and be mantaned to +/- one nch of water column from the ste-specfc pressure drop value establshed durng the successful, ntal performance test. (Montorng requrements summarzed n Table 3.) The vessel must also ncorporate accessble nspecton doors to allow quarterly nspectons of the meda as s requred by the rules work practce standards (summarzed on Table 3). KCH SERVCES, NC 100 Westerly Hll Dr Page 4

7 Control Technque 3 L mposte mesh pad P) system Packed-bed scrubber Table 2. Summary of Work Practce Standards Work practve standards 1. Vsually nspect devce to ensure there s proper dranage, no chromc acd buldup on the pads, and no evdence of chemcal attack on the structural ntegrty of the devce. 2. Vsually nspect back porton of the mesh pad closest to the fan to ensure there s no breakthrough of chromc acd mst. 3. Vsually nspect ductwork from tank or tanks to the control devce to ensure there are no leaks. 4. Perform washdown of the composte mesh-pads n lamordance wth manufacturers recommendatons. 11. Vsually nspect devce to ensure there s proper dranage, no chromc acd buldup on the packed beds, and no evdence of chemcal attack.on the structural ntegrty of the devce. 2. Vsually nspect back porton of the chevron blade mst elmnator to ensure that t s dry and there s no breakthrough of chromc acd mst. Frequency 1. llquarter 2. llquarter 3. llquarter 4. Per manufacturer 1. llquarter 2. llquarter PBSCMP system er-bed mst elmnator - Ar polluton control devce [(APCD) not lsted n rule 3. Same as number 3 above. 4. Add fresh makeup water to the rop of the packed bed.(see a,b 1. Same as for CMP system 2. Same as for CMP system 3. Same as for CMP system 4. Same as for CMP system 1. Vsually nspect fber-bed unt and preflterng devce to ensure there s proper dranage, no chromc acd buldup n the unts, and no evdence of chemcal attack on the structural ntegrty of the devces. 2.Vsually nspect ductwork from tank or tanks to the control devce to ensure there are no leaks. 3. Perform washdown of fber elements n accordance wth manufacturers recommendatons. To be proposed by the source for approval by the (Admnstrator. 3. llquarter 4. Whenever makeuo s added 1. llquarter 2. Uquarter 3. llquarter 4. Whenever makeup s added 1. llquarter 2. l/quarter 3. Per manufacturer To be proposed by thesource for approval by Admnstrator Ptot tube Stalag Backflush wth water, or remove from the duct and rnse wth fresh water. Replace n the duct and rotate 180 degrees to ensure that the same zero readng s obtaned. Check ptot tube ends for damage. Replace ptot tube f cracked or fatgued. Follow manufacturers recommendatons *l. llquarter

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9 '"1 EPA's technology study concluded that the overall removal effcency of CMP systems was drectly correlated to the unts nlet loadng of chromum. Hgher removal effcences were acheved n systems where nlet loadng of chromum was consdered hgh (ex. 10 mllgrams per ampere hr). Lower removal effcences resulted when nlet loadngs were lower. Ths could have been due to mst partcle sze beng smaller, wth lower nlet loadng. However, most all source tests that am aware of, show the outlet concentraton fom four stage CMP devces to be less than the requred mg/dscm. n many cases test have shown emsson rates to be ten tmes lower and n a small number of cases, even one hundred tmes lower. -)... PACKED BED SCRUBBERS Wet packed scrubbers are currently beng used to control chromum emssons at many platng facltes across the US. Most of these packed bed scrubber desgns consst of, a vessel capable of slowng the ar stream down to 500 feet per mnute or below, a. depth of random packng of one-three feet, a spray chamber and recrculaton system to contnuously saturate the pack, and a chevron blade mst elmnator to remove entraned scrubbng soluton. As was prevously stted, EPA based the emsson lm~ton of 0.03 mgklscm, fgr exstng tanks at small platng facltes, on the wet packed bed scrubber. Typcally wet L),*-a- scrubbers are most effectve scrubbng gaseous vapors (HCL, HF, NH3, etc.). However, wth short packed beds, (as are typcally n use for chromum emsson control) these KCH SERVCES, NC 100 Westerly Hll Dr Page 5

10 , scrubbers functon more on the prncple of mechancal mpngement of the mst, rather 7 that gas absorbtons that many wet scrubbers are desgned for. Chromum mst wll come n contact wth the ntal spray, saturatng the partcles, and then wll mpnge on the surface of the random packng meda. The contnuous recrculaton system wll then wash the mpnged chromum to the bottom of the scrubber. Perhaps EPA s ratonale for the contnued use of the wet scrubber for small platng facltes was to mnmze ther economc burden n complyng wth the standard. However, the fnal rule does requre an ntal source test, specfc operatng condton, as well as montorng and good work practces to ensure that the wet scrubber consstently meets the 0.03 mg/dscm emsson lmtaton..._ ) The fnal rule requres the ncorporaton of a spray chamber over the packed bed and the use of fresh water added to the top of the packed bed whenever makeup addtons occur. Some wet scrubbers tested by EPA dd not ncorporate fresh water addtons at the top of the unt, and consequently dd not acheve the emsson level of 0.03 mg/dscm. - The fnal rule also requres montorng of the velocty pressure (gas velocty) at the nlet of the scrubber and also pressure drop across the unt. (Table 3) Ar velocty gauges and dfferental pressure gauges, as was prevously dscussed, are utlzed for ths purpose. To be n complance wth the standard velocty pressure must be mantaned to wthn +/- 10% and the pressure drop mantaned to wthn +/- 1 nch of water column, accordng to the parameters that were establshed durng the ntal complance test. Page 6 KCn SERVCES, NC 100 Westerly Hll Dr

11 3 The requrement that sources must montor the chromum concentraton n scrubber water has been elmnated. Although the emsson lmtatons for decoratve chromum and chromc acd anodzng of 0.01 mgldscm, are based on fume suppressants' and the mantenance of bath surface tenson at 45 dynes per centmeter. The rule also allows for the use of an add on control devce. The chrome mst elmnator (CMP system) has demonstrated the capablty to control emssons from decoratve chrome platng and chromc acd anodzng to an emsson level of and below mgldscm. Specfc technology for chromum emsson control s not mandatory n the fnal rule. How the emsson lmts are compled wth are between the affected source and the admnstrator; t s mperatve that the fnal rule be thoroughly read and understood by those who must comply, to gan knowledge of the requrements of operaton and mantenance, work practce standards, montorng, record keepng, and reportng. KCH SERVCES, NC p.0. Box Westerly hll Or Page 7