Zeeco "free-jet" technologies and application in industry

The increased knowledge of damage caused to our health and environment by pollution has led to state and federal legislation requiring very low NOx emissions for process heater and industrial boilers. This legislation has taken various forms, with California and Texas having the most stringent requirements in the United States. These requirements affect not only new installations, but also preexisting heaters. We will show in the next few pages how the Zeeco "Free-Jet" technology was developed and implemented to provide a cost effective solution to these requirements.

Z e e c o " F r e e - J e t " T e c h n o l o g i e s a n d A p p lic a ti o n in I n d u s t r y BY Scott Reed Vice President Zeeco Houston Office Rex Isaacs Director Burner Products Nigel Palfreeman Director Zeeco Europe AND Jesse Chambers Burner Applications Engineer Presented at the International Flame Research Foundation 16th Members Conference Combustion and Sustainability: New Technologies, New Fuels, New Challenges Hilton Boston Back Bay Hotel Boston, USA June 8-10, 2009 1.0 INTRODUCTION T he in c re ase d k n o w led g e o f d am ag e cau sed to o ur h ea lth and env iron m en t b y p o llu tio n has led to state and federal leg islatio n requ irin g v ery lo w N O x em issions for p ro cess h eater and industrial b oilers. T his legislation has taken various form s, w ith C alifo rn ia an d T exas h av in g the m ost stringent req uirem en ts in the U n ite d S tates. T hese requ irem ents affect n o t o n ly n ew installations, bu t also preex isting h eaters. W e w ill show in the n ex t few p ages h o w the Z eeco "F ree-Jet" te ch n o lo g y w as d ev e lo p e d and im p lem en te d to p ro vide a cost effectiv e solution to these req u irem en ts. 2.0 ISSUES CREATED T he issue o f low erin g N O x em issions has ex iste d for several years w ith ever decreasing levels needin g to b e achieved. T he b u rn er in d u stry o rig inally ad d ressed this n ee d w ith stag ed fuel for gas burners an d stag ed air for liq u id firing. T his stag ed style w as then m o d ifie d w ith the addition o f m ore tips, m ore com p lex tiles, and m o re co m p lex d iffuser p lates- an ything that w o u ld aid in the re d u c tio n o f em issio n levels. T his led to som e v e ry large, heavy, co m p lic ate d a n d h ard to m aintain b u rn ers. T he size issue, co u p led w ith the te n d en c y for the flam es in low N O x b u rn ers to b e longer th a n conv entional b u rn er flam e lengths, resu lted in com plications w h en p u t in n ew furnaces an d even g reater difficulties in retro fittin g equ ip m ent into existing heaters. T h e n ee d to m eet the n e w req uirem en ts saw several attem pts to shoeho rn these large, low em issions burn ers into old er heaters. W ith flanges cu t a n d tiles alm ost touching, flam e envelopes w o u ld m erge, n eg atin g any em issions red u ctio n g ain ed b y the n ew b urners. 3.0 DEVELOPMENT T he issues w ith th e lo w N O x b urners, su ch as w eigh t a n d com plexity, w ere th e leading causes for Z eeco to develop the "F ree-Jet" fam ily o f burners. T he old ideas o f add in g o n to staged fuel burners, m ak ing the b urn ers h eavier an d m ore com plex, w ere th ro w n out an d the design was started o n a clean slate. T he d esign p aram eters dictated: • that the b u rn er sh o u ld b e able to fit in the sam e cu to ut as a typical raw gas b urn er w ith a sim ilar fired duty; • the b urn er tile sh o u ld b e a p p ro x im ate ly th e sam e size an d w eigh t o f a typical raw gas bu rner; • the b urn er m ust be v ery sim p le to op erate a n d m aintain; • all o f th e above, w hile getting in d u stry lead in g N O x p erform ance. T he dev elo pm ent engineers focused o n the k e y p o in ts for em issions red u ctio n such as the red u ctio n o f the adiabatic flam e te m p era tu re an d the elim in ation o f ig n itio n gas in the b u rn er throat. It w as believ ed that these areas, if controlled, w o u ld g reatly red u c e th e N O x levels p ro d u ce d b y th e b urners. T he "F ree-Jet" cam e into b ein g as a desire to exp ose the m a x im u m am o un t o f fuel gas to the flue gas in sid e th e furn ace b efo re th e ig nitio n o f th e fuel gas. This m e th o d allow s the fuel gas to b e re c o n d itio n e d into a low er B tu fuel p rio r to com bustion, thus reducing the adiabatic flam e tem p eratu re across the entire flam e en v elo p e (Figure 1). T he use o f a u n iq u e tile desig n c o m b in ed w ith m ultiple gas tips w ith single firing ports h elp ed to elim inate th e ignition gas as u se d in co nv entional low N O x b urners, (Figure 2) w h ere a p ercentag e o f th e fuel gas is rap id ly m ix ed w ith the co m b u stio n air to create a stable flam e zon e (F igu re 3). T he "F ree-Jet" stabilization is b ased o n the control o f the available ox yg en in th e firebox. A s th e ox yg en con tent is reduced, the flam e front w ill m ov e u p th rou gh the stabilization points. T he flam e w ill u ltim a tely attach at the final stabilization p o in t w hen the oxy gen con ten t is ap proxim ately four to six p ercent, d ep ending o n th e fuel gas com p ositio n and other o perational param eters. T he co nd itio ned fuel gas an d the elim inatio n o f th e ignitio n gas results in a flam e that, und er the rig ht conditions, is alm ost transparent. T he flam e app earance an d the n e e d to b e able to safely operate the b u rner in furnaces w ith u n u su a lly lo w floor tem perature led to the installation o f th e aux iliary g as lances. T he au xiliary lance, w hile utilizing th e sam e co m po nents as a stan dard pilot, is con nected to the b u rn er fuel m a n ifo ld an d o perates as an additional gas tip (Figure 4). Figure 1. Reconditioning fuel gas F ig u r e 2. " F r e e -J e t" s ta b iliz a tio n Figure 3. Conventional stabilization F ig u r e 4 . " F r e e -J e t" b u r n e r a s s e m b ly This d esign co ncep t has allow ed us to create a b u rn er that is relatively sm all in size an d w hich m eets em issio n standards req u ired b y the industry. A m ajor ben efit o f the d esig n is that the gas flow follow s the air-stream w ith ou t any sw irling o r tangential spin. T his w ill keep the flam e d iam eter ju st slightly larger than th e o utside d iam eter o f the b u rn er tile. T he flam e diam eter, fuel used, ty p e o f heater, and op erational param eters are a few o f the variables that m u st b e considered w h en look in g at b u rn er-to -b urn er spacin g and the p rev en tion o f flam e interaction. T o solve the p ro b lem s o f b u rn er spacing, the "F re e-Jet" was m o d e led an d fired in a test furnace in a m ultip le b u rn er configuration. It w as d ecid ed that the heater co nfigu ration for this testing w o u ld b e a vertical cy lindrical h eater w ith a tigh t burnerto-bu rn er spacing. T he ability o f th e "F re e-Jet" to av o id flam e in teractio n in this v ery difficult con figu ration w o u ld instill confidence in the "F re e-Jet" w ith o th er less pro blem atic applications. T h e results o f this testing allow Z eeco to m eet string ent b u rn er spacing requirem ents w ith out flam e in teraction (Figure 5). Figure 5. Flame interaction 4.0 APPLICATION T he ultim ate test for any b u rn e r te ch n o lo g y is h o w w ell it p erform s in th e real w o rld aw ay from the co n tro lled en vironm ents o f the rese arch facility, an d o u t o f th e h an d s o f its designers. T h e real w o rld for a b urn er often m eans it w ill b e ex p o sed to the lim its or b e y o n d the d esig n ed fired duty, and it w ill b e ex p ected to p erfo rm w ith w hatev er fuel is provided, often in less than favo rable conditions. O ver th e n ex t few p ag es w e w ill share so m e results from applications, bo th retrofits and n ew heaters. T his d ata has b ee n p ro v id ed b y indep en dent th ird p arty testing or b y th e actual operating facility. I f a th ird p a rty w as involved, it w ill be n o te d in the data. 4.1 FCCU Raw oil charge heater This ex am p le show s the app licatio n o f E ig h t (8) "F ree-Jet" ro u n d flam e burners o n a very tight b u rn er circle in a vertical cylindrical furnace (F igu re 6). T he results o f the th ird p arty testing are sh o w n b elo w in T ab le 1. Figure 6. FCCU raw oil charge heater layout F C C U R aw O il C harge H eater T yp e o f H eater N atural D raft V .C . N u m b er o f B urners E ig h t (8) R etrofit R ad ian t Section H eig h t 13.1064m 43 F eet H eat R elease p er B urner ~ 2.1096 M W ~ 7.2 M M B tu/hr E xcess O xygen 3 .87% avg. NOx < 6.6363 ng/J CO < 0 .5 pp m v H eat D en sity 9 53.37 k W /m 2 < 0.0148 # /M M B tu 302,409 B tu/ft2 T a b le 1. T h ir d p a r ty d a ta F C C U r a w o il c h a r g e h e a te r 4.2 HCU RXN charge heater This ex am p le show s the app licatio n o f S ix (6) "F re e-Jet" burners in a tight b u rn er circle w ith the add ition o f a seven th "F re e-Jet" in stalled in th e center o f th e b u rn er circle (Figure 7). T he em issions and conditions as rec o rd e d b y a th ird p arty are sh o w n in T able 2. Figure 7. HCU RXN Charge heater burner layout H C U R X N C harge H eater T yp e o f H eater N atural D raft V .C . N u m b er o f B urners S ix+ O ne (6+1) R etrofit R ad ian t Section H eig h t 11.582 m 38 F eet H eat R elease p er B urner ~ 3.223 M W ~ 11 M M B tu /h r E xcess O xygen 6.8% avg. NOx < 10.04 ng/J CO < 1 .1 4 p p m v H eat D en sity 5 5 8 .6 1 9 k W /m 2 < 0.0 22 4 #/M M B tu 177,194 B tu/ft2 T a b le 2 . T h ir d p a r t y d a t a fo r H C U R X N c h a r g e h e a te r 4.3 Crucible style coker heater This ex am p le illustrates that th e "F re e-Jet" is w ell suited for fo rced draft an d p reh e ate d com b u stio n air applications. C o m puter m od eling w as u se d to pred ict the perfo rm an c e o f the sixty four (64) bu rners in this application an d p ro v e d to b e in ag reem ent w ith th e actual field results (Figure 8). T he data sh o w n in T ab le 3 w as su pplied b y p la n t p erson nel in this application. Figure 8. Crucible style model with "Free-Jets" C oker H eater T yp e o f H eater N u m b er o f B urners F o rc e d D raft C ruciform S ix ty four (64) R etrofit R ad ian t Section H eig h t 12.192 m 4 0 F eet H eat R elease p er B urner = 2.93 M W = 1 0 M M B tu /h r A ir P reheat T em perature 315.56°C 6 00°F NOx < 15.477 ng/J < 0.036 # /M M B tu T a b le 3 . D a t a fo r c o k e r h e a te r 4.4 Additional applications of "Free-Jet" burners T he follow ing tables sho w additional applications an d d ata ta k en b y th ird parties fo rw ard ed to Z eeco for ou r records. T he furnaces rep rese n te d are o f differen t co nfigurations an d sizes. P latfo rm er Stabilizer R eboiler T yp e o f H eater N atural D raft V .C . N u m b er o f B urners F o ur (4) R etrofit R ad ian t Section H eigh t 10.688 m 35 F eet H eat R elease p er B u rn er ~ 2.57 84 M W ~ 8.8 M M B tu/hr E xcess O xygen 5.7% avg. NOx < 7.35ng/J CO < 0.5 p p m v H eat D ensity 9 5 2 .6 3 6 k W /m 2 < 0.0171 #/M M B tu 3 0 2,1 76 B tu/ft2 Table 4. Third Party Data for Platformer Stabilizer Reboiler G D U H eater T yp e o f H eater F o rc e d D raft V .C . N u m b er o f B urners T w elv e (12) N ew Installation R ad ian t Section H eig h t 18.59 m 61 F eet H eat R elease p er B urn er ~ 3.809 M W ~ 13 M M B tu /h r A ir P reheat T em p erature 273.89 °C 525°F NOx < 6.406 ng/J < 0.014 9 # /M M B tu H eat D en sity 8 74.026 k W /m 2 277,241 B tu/ft2 Table 5. Third Party Data for GDU Heater F ield D ata E x am p le 1 T yp e o f H eater N atu ral D raft C abin B o tto m F ire d N u m b er o f B urners E ig h t (8) N ew In stallation H eat R elease p er B urn er 2.578 M W 8.8 M M B tu /hr F loo r T em perature 698 .89 °C 1290°F N O x (R efin ery F uel Gas) 9.8 ppm v T a b le 6 . F ie ld d a ta e x a m p le 1 F ield D ata E x am p le 2 T yp e o f H eater N atu ral D raft C abin B o tto m F ire d N u m b er o f B urners T w elv e (12) B urners p e r R o w x 's F o u r (4) H eat R elease p er B urner 2.271 M W 7.75 M M B tu /h r R ad ian t B ox T em p eratu re 1215.56°C 2 2 20 °F F loo r T em perature 1215.56°C 2 2 20 °F F u el Inform atio n C ontains 35-50% H 2 N O x (R efin ery F uel Gas) 28 p p m v Table 7. Field data example 2 F ield D ata E x am p le 3 T yp e o f H eater F o rc ed D raft V ertical C ylindrical N u m b er o f B urners T w elv e (12) B urners H eat R elease p er B urner 4.4 4 2 M W 15.06 M M B tu/hr R ad iant B ox T em p eratu re 800°C 1472°F A ir P reheat T em perature 260°C 500°F F u el Inform atio n C ontains 80% H 2 and 2 0% C 3 's N O x (R efin ery F uel Gas) 18 p p m v Table 8. Field data example 3 F ield D ata E x am p le 4 T yp e o f H eater N atural D raft V ertical C ylindrical N u m b er o f B urners F ou r (4) B urners H eat R elease p er B urner 3.516 M W 12 M M B tu/hr R ad ian t B ox T em p eratu re 843.33°C 1550°F F u el Inform atio n N O x (R efin ery F uel Gas) C ontains 15% H 2 10 p p m v T a b le 9 . F ie ld d a ta e x a m p le 4 5.0 CONCLUSION T he Z eeco G L S F -"F re e-Jet" fam ily o f burners has b e e n created to m eet the n eed s o f the industry an d d e sig n ed to w o rk in m ost applications. It has b ee n p ro d u ce d in flat flam e m odels and co m b in atio n designs for oil firing. T he flexibility o f this b u rn er design h as allow ed us to offer eq uipm ent for n o t o nly the refin in g an d p etro ch em ical industry, bu t also for oncethro ug h steam g en eratio n and industrial bo iler b u rn er applications. T he "F re e-Jet" has b een p ro ven th ro u g h m ultiple applications aro un d th e world.