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Twenty Years of Progress with T G ehydrationtA B S T R A C T

Dew-poin t depress ions a t t a inab le by g lyco l dehydra-t ion have been increased f rom about 40 F 2 0 y ea r s ag ot o a s h i g h a s 1 60 F today. The process of t r iethyleneglycol TE G ) dehydrat ion has come a long way in th i sper iod . I t i s s ti l l ha l f as cos t ly fo r th i s p rocess a s fo rdry c less ican t dehydrat ion . The many ref inements inrecen t years have a l lowed a much broader app l ica t ion .In 1 94 6 t h e f i r s t w o rk w as d o n e on s am p l es of T E G ,wi th major emphas i s p laced on i t s use in 1948 and1949, with the adv ent of gre at ly s implified and pack-aged wellhead g lyco l dehydrat ion un i t s . The nex t fewyears wi l l show cont inuous t rends toward the use ofglycol for very lo\v dew points .Dew-poin t depress ions tha t are a t t a inab le by g lyco ldehydrat ion have increased f rom about 40 F 20 yearsag o t o a s h i g h a s 1 6 0 F t o d ay . T w en t y y ea r s ag o v e ryfew g l y co l- ty p e d eh y d ra t o r s w ere i n u s e o n n a t u r a l -g a s s t r eam s . So m e g as w a s b e i n g d eh y d ra t ed i n d rydes iccan t un i t s u t i l i z ing ac t ivated bauxi tes . In mos tcases , however , water was no t removed f rom the gas .Hydrates were prevented in co ld weather by the in -jection of methanol.The f i r s t g lyco l - type dehydrators were cus tom-de-s igned and non-por tab le un i t s wi th fa i r ly e labora tereboi l ing and ref lux ing fac i l i t i es . The g lyco l in usea t t h a t t i m e w as p r i m ar i l y d i e th y l en e g l y co l, b u t i nsome cases ethylene glycol was used.In 1946 Prof . Lawren ce S. Reid , Un ivers i ty o f Okla-homa, began work on samples o f t r i e thy lene g lyco lw i t h s t ro n g s u p p o r t f ro m L es Po l d en n a n o f U n i o nCarb i d e Ch em i ca l s Co m p an y . D u r i n g t h e n ex t 5 o r 6years cons iderab le ef for t mas devoted to t ak ing l ab-o ra t o ry d a t a fo r t h e s y s t em t r i e t h y l en e g l y co l -w a t e r -n a t u r a l g as . P ro f . Re i d d i rec t ed s ev e ra l g r ad u a t e s t u -d en t s i n n u m ero u s i n v es t i g a t ~o n s , o m e o f w h i ch w e responsored by fel lowships provided by Black, Sival lsBryson , Inc . Pro f . Reid and J. A . Po r t e r r ep o r t ed s o m eof the ea r ly f ind ings In 1949.1 Pro f . Reid and Ma rkTournsend ma de addi t ional rep ort s in 195 1 an d 1953.2,3,4Major emphas i s was p laced on the use of t r i e thy leneglyco l in 1948 and 1949 wi th t he a dve nt of the gr eat lysimplified and packaged wel lhead glycol dehydrat ionuni t s . One of the f i r s t fo rmal repor t s o f such ins ta l l a-t io n s w as t h a t of L H. Peahl in 1950.0 Fig. 1 is a pic-tu re of one of th e 1949 model uni ts discussed by P eah l .A br ief v i sual compar i son of th e f i r s t TEG d eh y d ra -to r s wi th those fabr ica te d today wil l no t ind ica te a g re atch an g e . Fo r i n s t an ce , co m p are F i g . 2 a p ic ture o f arecen t s imi lar -s i zed un i t , wi th Fig . 1 Comparisons ofthe process f low d iagrams for the two un i t s would a l so

: Blnrk, Sivnlln R Urysnn, Inc.. Oklahoma City, Okla Since removedt Rhorles Cnrpnratinn.tpresenlerl t the s lrrins mcrting of the Mid-Continent DistrictAPT Division of l roduction. March 1967.=References are at the end of the paper.

Fig 1 arly day Packaged T G Dehydrator7ind ica te l i t t l e change. In sp i t e o f the smal l ou twardap p ea ran ce ch an g es , d eh y d ra t o r p e r fo rm an ces h av ebeen grea t ly improved . Fo r example , cons ider Fig . 3T h e cu rv e i n d i ca t ed w as f i r s t p u b l is h ed i n 1 95 2.6 A tt h a t t i m e t h e c u r v e i n d i c a t e d t h e m a x i m u m a b s o r b e rco n t ac t t em p era t u re a t w hi ch 7 Ib IMMscf water con ten tcou ld b e a t t a i n ed a t v a r i o u s ab s o rb e r p r e s s u re s. T h eb as i s fo r t h e cu rv e w as a 6 5 -F w a t e r d ew p o i n t d e -p re ss i on , t h e g rea t e s t t h a t co ul d b e re l ied u p o n a t t h a tt im e . T o d ay t h e s am e c u rv e a l m o s t ex ac t l y r ep re s en t st h e m a x i m u m a b s or b e r c o n t ac t t e m p e r a t u r e a t w h i ch1 4 Ib IMMscf water con ten t can be ob ta ined .Res idual w ate r con ten t s a s low a s 0 .165 IbIMMscfan d w a t e r d ew p o i n ts a s l o w as -50 F have been a t -t a in e d w i t h T E G . A t t h e s a m e t i m e t h e r e h a s b ee n l i t tl eincrease in g lyco l dehydrat ion cos t due to ref inementsthat have a l lowed increased capaci ty and decreasedut i l i ty costs .Unt i l about 1957 , g lyco l dehydrat ion was cons ideredin terms of 65 F dew po in t depress ions , 3 g a l / l b w a t e rc i rcu la t ion , and a 4 - t r ay contactor tower . T oda y specif icu n i t s a r e d es i-v ed fo r d ew p o i n t dep ress i on s f r o m 4 0to 160 F , fo r g lycol c i rcu la t ion ra te s o f f rom I g a l / l bof w a t e r t o a s m u c h a s 8 g a l l l b , a n d f o r t r a y s f r o m2 t o a s m a n y a s 1 6 .In i t i a l ly , regenera t ion t echniques provided fo r l eanglyco l so lu t ions of 95 to 96 percen t g lyco l . In r ea l i ty ,concent ra t ions as h i g h a s ab o u t 9 8.5 p e rcen t w ere i n i t -i a l ly a t t a ined , bu t ex i s t ing an aly t i ca l and f ie ld samp l ingtechniques d id no t a l low detec t ion un t i l about 1953 . Th erecen t development o f more sophis t i ca ted regenera t iont ech n i q u es an d m o re accu ra t e an a l y t i ca l m e t h o d s h av eal lowed cons i s ten t regenera t ion of t r i e thy lene g lyco l upt o a s h ig h as 99.98 percent glycol .

A n i m p o r t a n t s t e p i n t h e refinement of glycol de-

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T \ V E N T Y EARSO F P R O G R ES S ITH T E G D E H Y D R A T I O N 53

hy dr a t o r pe r f o r m a nc e ha s bee n i n m or e a c c ur a te l ye s t a b l i s h i ng e qu i l i b r i um w a t e r de w po i n t s i n t he TEG -w a t e r - ga s s ys te m . F i g . 4 i nd ic a t es t w o s e t s of da t a f o rt he s ys t e m i n 1966 f o r o n e c o n t a ct t e m p e r a t u r e . It i ss i gn i f i c a n t t o no t e t ha t no t h i ng ha s c ha nge d r e ga r d i ngt h e t r u e e q u i l i b r i u m b e t w e e n w a t e r a n d T E G . T h eon ly t h i n g t ha t ha s c ha nge d ha s bee n t he a c c ur a c y o fthe knowledge of the sys t em.

Fig. 2 High concentration DehydratorC ur ve B of Fig. 4 r e p r e s e n t s p r e d i c t e d pe r f o r m a nc e

ba s e d on e xpe r i m e n t a l da t a t a ke n by P r o f . M a r k Tow n-send and by W ise, Puck , and Fai ley.7 Scauzil loS ut i l izedac t iv i ty coef f i c i ent s f rom da ta t aken by Townsend andWise to predic t t he equi l ibr ium indica ted on C urve BCurv e of F ig . 4 represent s predic t ed per formancebased on the ext rapola t ion to inf in i t e number of t raysand to inf in i t e g lycol ra t es of ac tua l da ta t aken f romfield-size glycol units. This c ur ve r e p r e s e n t s r e fi ne m e n tof the sugges ted equi l ibr ium curve repor t ed by Loomerand Welch9 in 1961 . A l l o f t he da t a r e p r e s e n t e d byF i g . 4 a r e f o r 100 F c on t a c t t e m pe r a t u r e on l y .O n l y a t one ve r y e a r l y s t a ge i n t he de ve l opm e n t oft r ie t h y le n e g ly c ol a s a d e h y d r a t i n g a g e n t w a s t h e r e

v r s ugge s t i on t h a t t h e e qu i li b r ium w a t e r de w po i n t

BSORBER PRESSURE P SI G

Fig. 3 Dehydrator Performance in 1952 and 1966

.03

.02A F IEL O A T 0

.U -60 -90 -20 DEV POINT '20 F 40 60 80

Fig. 4 Equilibrium Dew Points for 100 F ContactPublished in 1966

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Fig. quilibrium Dew Points with VariousConcentrations of TEGwa s a func t lon of sys tem pressure Severa l exhaust ives tudies In the labora to ry and f ie ld opera t ions have fad edto Indica te any apprec iable e f fec t of press ure on dewpo in t s of w a te r I n t he TEG - wa te r sys t e m

Fig 5 r e p r e se n t s t he e c lu~ l ib r ium f o r t e m p e r a t u r er a nge s f r om 30 to 170 F As in t he c a se f o r C ur veo f F lg 4 the va lues were deve loped f rom ac tua l de -hydr a t ion un l t per f o r m a nc e da t a A l though som e da t awere take n a t wiclely vary ing tem pera tu res an d glycolconcentrations inost were collected In the glycol con-c e n t r at l on r a n ge f r om 99 to 09 95 pe r c e n t TE G a n d a tt e m pe r a tu r e s v a r y ln g f r om 60 F to 125 FF ig 6 1s a f low diag ram of tes t equipment used fo ra ve r y e xh a us t ive s tudy o f de w po in t de p re s sions ob

ta inab le wi th t r ie thylene g lycol The tes ts w ere con-duc ted 1~1 th u l l - sca le s ize equipment Th e tes t facilitiesl nc lude d p r ov i s ions f o r c i r c u l a t i ng up to 10 M M sc f /Do f g a s a t p r e ss u r e s u p t o 1 0 00 p si w i t h a s m u c h a s100 ps i press ure d rop In th e c losed g as sys tem Adcll-t i ona l s tud ie s a r e In p r og r e s s w i th u p to 20 c on ta c to rt r ay s an d a t a w ~ d e ang e of o pera t i ng condl tlonsR e f e r r ~ n go Fig 6 the t e s t g a s l e ave s t he r e c i rc u l a-t lon compressor passes through a hea te r where ~t ispr e he a te d a nd the n is contac ted wi th w at e r In a m ul t i -t r a y ve ssel T h e w a t e r e n t e r s t h e s a t u r a t i o n v e s s e l a t180 F o r h i g h e r T h e p r e h ea t ed g a s a n d w a t e r p r ov id ef o r t h e h e a t o f v a p o r iz a ti o n f o r t h e w a t e r t h a t 1s

v a p o r ~ z e d n t o t h e d r y -g a s s t r e am T h e w e t h o t g a ss t r e a m th e n i s c oo le d down to t h e p l a nne d ope r a t ingt e m p e r a t u r e C a r e i s t a k e n t o m a k e s u r e t h a t w a t e rcontinuously a c c uinn la t es i n t h e s e pa r a to r j u s t a he a dof the dehydration c on ta c to r i n o r de r t o a s su r e s a tu r a -t i on o f t he I n l e t ga s s t r e a m

Glyco l ha v lng c on s~ s t e n t oncentrations I n t h e r a n g ef r om 98 to 99 97 per c e n t w a s ob ta ine d f r om the r e -genera t ion sys tem Th e des iccant w as c i rculatecl overvarying num be r s of t r a y s In t h e c on ta c t ing towe rWa te r de w po ln t s we r e t a ke n be twe e n t r a ys a nd down-s t r e a m f r om t he un i t w i th bo th a n e l e c tr i ca l de w- po inta n a l y z e r a n d t h e U S B ur e a u of M ine s de w - po~ n tt e s t e r It 1s significant t o no te t ha t t he g lyc o l u t l l l z e dwa s typlca l of th a t in fielcl use ra t he r th an new c leang lyc ol S om e o f t he da t a we r e t a ke n wl th g lyc ol t ha tha d be en e xpose d to t e m pe r a tu r e s a s h igh a s 450 F f o rextended per lods of t lme in o rde r to reprod uce typica lfield conditions

Over 1 000 dew points were tak en in the in l t la l se r lesof run s Glycol concentra t ions were var ied f rom 98 to99 97 percent Press ures w ere var ied f rom 200 to 900ps i Te m p e r a tu r e s we r e va r i e d f rom 60 to 130 F Glycolcirculation r a t e s w e r e v a ri e d fr o m g a l t o 1 5 g a l ofg lyc o l pe r pound o f wa te r i n t he i n l e t ga s s t r e a mT h e d e w - p o ~ n tda t a we r e p lo t t e d a nd c o r r e l a t e d so

Fig 6 Flow Diagram of High Dew PointGlycol dehydrator Test Equipment

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WITH TEG DEHYDRATION 255

STF PRNG G S S FI GAL TEG

Fig. 7 Effect of Stripping Gas on TEGConcentration

th at th e effects of glycol concentrat ions glycol ci rcula-t ion ra t es con tac t t empe ra tu res con tac t p res su res andnumber o f con tac t t rays cou ld be predicted S m a l l r e -f inement s have been made a s a resu l t of ca refu l s tud iesmade on f i e ld opera t ing un i t s du r ing the pas t 8 y e a r sAl l g lyco l samples whethe r f ro m f ie ld un l t s o r f ro mthe l abora to ry f ie ld -s ize un i t a re ana lyzed fo r wa terc o n t e n t b y t h e K a r l F i s c h e r t i t r a t ~ o nmethod Com-par l son o f man y dup l i ca t e sa n~ p l es nd icates rep ro -ducibi l ity a s fol lowsTE G Glyco l Concen t ra t ion D~ffe rence e tweenRange Perce n t Dup l ica tes Perce n t

99 95 - 100 00 0 00599 50 - 99 95 0199 00 99 50 0 0298 00 99 00 0 04

The most effect ive refinement in the performance oft r iethylene glycol dehydration u n i t s h a s b ee n I n t h emethod of regeneration a s indicated In U S P a t e n t No3 105 74810 a ncl C a n a d ~ a n a t e n t N o 733 82011 ass lgnedto Black Sival ls Bryson Inc

In sum mary the new regenera t ion p r inc ip le invo lvesthe removal o f water f rom g lyco l by conventional r e -generat ion technlclues up to about 99 percent glycola n d t h e f u r t h e r purification b y g a s s t r i p p i n g T h e g a s -s t r ~ p p l n gechn ique cons i s ts o f p reh ea t ing a very smal lq u a n t i t y of n a t u r a l g a s a n d c o n t a c t ~ n g t counter-cur-r e n t l y w l t h 99 percen t t r l e thy lene g lyco l as ~t leavesthe rebo il e r and f lows to the s to ra ge t an k The smal lamo unt o f coun ter -cu r ren tly f lowlng na t u r a l g as re -duces the par t i a l p res su re o f water vapor in con tac tw l t h t h e p a r t ~ a l l y e g e n e ra t e d g l y co l t o a v e r y l o wq u a n t ~ t yThl s fo rces a sh i f t o f the equilibrium s o t h a ta d d i ti o n a l w a t e r v a p o r e n t e r s t h e v a p o r p h a s e a t e s se n -t i a l l y t h e s a m e t e m p e r a t u r e a n d r e s u l t s i n v e r y l o wresidual-water con ten t s Th l s techn ique IS par t i cu la r lyeffect ive when accomplished with counter-current con-tact lng techniques

Fig. rep resen t s the expec ted g lyco l concen t ra t ions

u n d e r v a r l o u s conditions of regene rat ion A s noted a400-5 r e b o l l e r t e m p e r a t u r e a t 1 200 f t elevation wlllresu l t i n abou t 99 p e r c e n t T E G

If stripping g a s is in jected di rect ly in to the reboi lert h e r e s u l t s a r e a s I n d ic a te d b y t h e l o w e r c u r v e T h eupper curve of Fig 7 rep resen t s th e g lyco l concen tra -t lo n r e s u l t ~ n g r o m c o u n te r - c ur r e nt l y i n j e c t in g s t r i p -p i n g g a s a f t e r t h e m a j o r a m o u n t o f w a t e r v a p o r h a sbeen removed The d ra ma t i c difference r e s u l t s f r o mtwo ma jo r p r inc ip les One is t he p r inc ip le o f masst r a n s f e r b y c o u n t e r - c u r r e n t c o n t ac t o f t h e l ~ q u i d n dga s phases as compared to a s ing le co -cur ren t con tac to f the phases The second p r~ nc ip l e s t h e g r e a t e r d r iv -Ing fo rce resu l t lng f rom injection of stripping g a s a f t e rm o s t of t h e w a t e r is previously removed by the appl i -cation of hea t Th l s i s compared to the lower d r iv ingfo rce resu l t lng f rom in jec tlon o f s t r ip pm g ga s III t h es a m e a r e a w h e r e t h e b u lk o f t h e w a t e r IS releasedb y h e a t

The p r lnc lp le o f inj ec tlon of s t r ip p~ ng as in to ther e b o l l e r w a s a s t a n d a r d f e a t u r e o n a l l s t a n d a r d r e -g e n e r a t o r s furnished In 1950 by Black Sival lsBryson Inc The p rac t l ce w as d i scon t~nuec l In ear ly1951 because of lack of evidence of effective resu l t sThe l a t e r deve lopment of s t abi l ized Ka r l F i scher re -agent and the elect ronic detect ion of the analyt ical endpo ln t s p resen t ly a l low accura te measurement s o f smal lchang es In addi t ion th e development of elect ronicwa ter a na lyzers fo r g as a l lows accura te de tec tion of afew degrees change In dew po ln t s

Some of the f i rs t g lycol dehydrators bui l t u t i l izeclg lyco l-gas con tac to rs a s ~nc l i ca t ed n F ig 8 I n t h e s e

hS OUTLET

r G L Y O L OUTLETFig. 8 1950 Model Co Current Contactor

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GLYCOL INLET

1.,,I: ; ;

GAS INLET r ,

' * 1

GLYCOL COOLING COILS --GLYCOL COALESCER

GAS OUTLET

S P E C I A L G L lC O LCOALESCING PAD

GLYCOL OUTLET

a t m a x im u m un l t f low r a t e s , t he n too l i t t l e t u r bu le nc ewi ll p r e va l l a t l owe r g a s f low r a t e s .B y f a r t h e m o s t p o p u l a r t y p e o f c o n t a ct o r r e m a i n st h e b u b bl e- ca p T h e y g i v e v e r y h ~ g h n d p r e d i ct a b lepe r f o r m a nc e f o r a l l ga s a nd hqu ic l r a t e s a t r e a sona b lecos ts The y a r e less suscept ib le to loss of l iquid sea lu p o n s t a r t - u p a n d a t l ow t e m p e r a t u r e s

SUMRZ RYI n s u m m a r y , T E G d e h y d ra t io n h a s c om e a l o n g w a yin 20 ye a r s Toda y , it IS s t i l l ha l f a s c os t ly f o r g lyc o lde hydr a t ion a s f o r d ry - de si c c an t de hydr a t ion Them a ny r e f ine m e n ts i n r e c e n t y e a r s ha ve a l l owe d a m uc hb r o a d e r a pp l i ca t io n T h e n e s t f e w y e a r s w il l s h o wc on t inue d t r e nd s towa r d t he u se o f g lyco l f o r ve r y lowde w po in t s S om e g lyc o l dehyc l ra to rs a r e a l r e a dy in u sef o r de w po in t s a t -40 F a nd a s l ow a s 0 3 l b /M M sc fC a pa b i l i t i e s e x i s t f o r de s ign to e ve n lowe r wa te r c on -t e n t s a t m a n y no r m a l ope r a t ing c ondi ti ons .

REFERENCESI P o r t e r , J. A a n d R e id , S P r e s e n t e d a t A I M Emeet ing, Sa i l Antonio , Texas , Oc tober 1949ZPol itz lner , I , T ownsend, F M , a n d R e id , L S

Fig. 9 1966 Model Co Current Contactor P r e s e n t e d a t A I M E m e e t in g , S t L o u is , M o , 1 95 1.aTownsend, F M Va por- L ic luid Equ i l i b r ium D a ta f o rc a se s t he r e m ova l o f wa te r va por r e su l t e d f r om c o -c u r r e n t c on ta c t o f g lyc o l i n a p ipe in t e r na l t o sm a l l -d l a m e te r s e pa r a t ion ve s se l s The y r e su l t e d in a bou t40 F de w po in t de p r e s sions whe n r e l~ o l l e r e m pe r a tu r e sw e r e k e p t a t 3 90 F These contac tors were abandonedin 1951 because of h t t le e f fec tive contac t be tween t heg as and l iquid Never the less , some co-cur rent contac-t o r s a r e s t i ll b ei n g u se d t h a t a r e n o m o re e f f e c t ~ v e h a nthose a ba ndone d ye a r s a go

D u r l n g t h e p a s t 5 y e a r s t h e r e h a s b e en a t r e n d b a c ktowa r d the c o - c u r r e n t c on ta c to r i n som e spe c i a l c a se sN o t e t h a t it is v e r y l n ~ p o r t a n t h a t e ff ec ti ve c o n t ac tbe twe en g a s a nd l i qu id be a t t a ine d a t a l l ga s fl ow r a t e sI n o r de r t o ob ta in s a t i s f a c to r y r e su l t s w i th c o - cu r re n tc on ta c to r s Th i s is of ten accompl ished in uni ts a s indi -c a te d i n F i g 9The use o f c o - c u r r e n t t ype c on ta c to r s r e qu i r es m uc hm or e g lyc o l t ha n eff ic ient cou nte r - cur re nt type Thi sr e s u l t s p ri m a r i l y f r o m t h e f a c t t h a t t h e b e s t p e r f o n n -ance wi l l a l low near equi l ibr ium wi th the d i lu ted g lycol

r a t h e r t h a n w i t h t h e w a t er - le a n g l yc ol I n o r d e r t oa ppr oa c h th i s e qu i l i b r ium , ve r y tu r bu le n t ga s - l i qu idc on ta c t o r e x t r e m e su r f a c e a r e a i s r e qu i re d As a r u l e ,it is necessa ry to u t i l ize a much more sophisticatedm i s t ( a n d f o g ) e x t r a c t o r t h a n f o r o t h e r t y p e s of c o n-t a c to r . I f t he m or e e ff ic ie nt m i s t e x t r a c to r is not needed

D E G a n d T E G - W a t e r - N a t u r a l G a s S y s t e m , G a s C o n -di t ionlng Conference , May 1953ownsend, F M E q u i ll b rl u m W a t e r C o n t e n t s o fNa tu r a l G a s De hydr a t e d by Aclue ous D ie thy le ne a ndTr i e thy le ne G lyco l S o lu t ions a t Va r ious Te m p e r a tu r e sa nd P r e s su r e s , P h D d i s se r t at i on , Un ive r s i t y o f Ok la -holria, 1955.S P e a h l, L H I ns t a l la t i on , Ope r a t ion , a nd P e r f o r m -a nc e of a S k id -m oun te d Ga s De hydr a t ion P la n t , OilGus J 92, Ju ly 13 (1950)6Canlpbel1, John M and Laurence , Law ton L Glycol

Dehydration P a r t 111 of De hydr a t ion o f Na tu r a l Ga san d Hydroc arbon Liquids , Pe t r . Ref iner , 3 [ll] 109(1952).W i s e , H , P u ck , T T , a n d Fa il ey , C F J P I y sCl~enz zstrg, 4, 734 (1950)sS ca uzi ll o , F r a n k R Equ i l i b r ium R a t io s of Wa te r i nthe W a te r -Tr i e thy le ne G lyc ol - Na tu r a l Ga s S ys t e m , J.P e t r T e c h , J u l y ( 1 9 6 1) .gLoomer, J a nd We lc h , J W S om e C r i t i c a l As -pe c ts o f De s ign ing f o r H lgh De w P o in t De pr e s sion w i thGlycols , Gas Condi t ioning Conference , Univers i ty ofOklahoma, March 19611 U S. P a t e n t No 3 105 748 a s s igne d to B la c k ,S iva l ls Bryson , Inc.1 l C a n a d z a n P a t e n t No 733 820 a s s igne d to B la c k ,S iva l ls Bryson, Inc .