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When Is Reverse Osmosis Right For Boiler Pre Treatment
- 1. W is R er Osmosis R forBoil Pre- hen ev se ight er T t reament
- 2. R Benefit O s • Reduced fuelcost t ough l erhea l /incr sed boil cycl s hr ow t oss ea er es • Reduced boil syst chemica teamentcost er em lr t s • Impr ed oper t &St m Pur y ov aion ea it • Reduced risk • Impr ed condensae corosion contol ov t r r • Reduced ext na t eamentcost pat al ifpr iousl usingcol orhotl er l r t s; ricul ry ev y d ime soft ening, ion excha a /orr gener bl DI nge nd e- a e • R e /r emov educe ha r a a ca ic chemicas zadous cid nd ust l • E ended ion excha r l xt nge esin ife
- 3. W tt considerw l ha o hen ookinga R forboil tO er pr r t et eament • Cycl ofconcent aion es rt • Size ofpl nt– st m pr ion a ea oduct • F Quait W ly - M ke- akainit Dissol ed miner lbr kdow a up l l y, v a ea n • % F ma up -% hotcondensae r ur W ke t et n • Pr e dea aororF t nk? essur er t Wa • F w t piping a pump constuct eed aer nd r ion • Is t e ause forR r ect(cool t erM her O ej ing ow U) • Chemica Pr a t l ogr m ypes -Sepaaes, alin- pow s, l r t l- ones, der iquids, et c.
- 4. Quest t hel you quaifyfea it of ions o p l sibil y r a demins w h R E epl cing it O/DI 1. Is t cust concer w h ha inga a ca ic? he omer ned it ndl cid nd ust 2. W tis t conduct it oft infl w t ? T highert dissol ed sol in t infl ha he iv y he uent aer he he v ids he uent w t , t gr t t pot ia benefit aer he eaer he ent l s. 3. Howmuch a a ca ic ae used a w tis t cost cid nd ust r nd ha he ? 4. W tis t costofpow ? ha he er 5. Ca t pl nteffect el use t R r ectw t ?Orw lt incr se in w t consumpt a n he a iv y he O ej aer il he ea aer ion nd w st v ume be a issue? a e ol n 6. Is t anewinst laion oris t cust consider r a his al t he omer ing epl cementoforr aing a exist enov t n ing deminer l syst aizer em?
- 5. A EG L S SM UIDE INE T bl 1 -Wt t Boil w h Super t /ur ae aerube er it heaerT bine AlPr es: F dissol ed oxygen < 7ppb (w h DA l essur W v it ) F aerpH: 8 -10 (0 90 psig)/pH8 -9.6(> 90 psig) eedw t .3 .0 - 0 .8 1 Boiler Feedwater Boiler Water Total Total Specific Drum Hardness Silica alkalinity Conductance Pressure Iron Copper ppm ppm ppm ( µmhos/cm) (psig) (ppm Fe) ( (ppm Cu) CaCO 3 )( SiO 2 )(CaCO 3 ) (Unneutralized) 0 to 300 0.100 0.050 0.300 150 350 3500 300 to 450 0.050 0.025 0.300 90 300 3000 451 to 600 0.030 0.020 0.200 40 250 2500 601 to 750 0.025 0.020 0.200 30 200 2000 751 to 900 0.020 0.015 0.100 20 150 1500 901 to 1,000 0.020 0.015 0.050 8 100 1000 1,001 to 1,500 0.010 0.010 0.000 2 - 150 1,501 to 2,000 0.010 0.010 0.000 1 - 100 Note: All limits are expressed “less than” the value specified (e.g., < 0.100 ppm)
- 6. Impa offeedw t quait on boil oper t lefficiency ct aer l y er aiona F -o- ea efficiency uelt st m o F is 70– 8 % ofboil oper t cost uel 0 er aing s Fuel o Wt &Sew cost 3– 5% aer er s o But-F aerquait ha enormous eedw t ly s impa on boil efficiency ct er &fuelcosts Water & Sewer R ia it a a a a it el bil y nd v il bil y Energy Loss Versus o Industyst t ics – r aist Scale Thickness 7 T fa ur due t ube il es o 6 Energy Loss (%) 5 w t side mecha aer nisms 4 3 ae t l ding ca of r he ea use 2 1 0 unschedul Boil ed er 1/64 1/32 3/64 1/16 Scale Thickness (Inches) out ges a Iron & Silica High Iron Content "Normal" Scale
- 7. Impa offeedw t quait on boil oper t lefficiency ct aer l y er aiona St m pur y ea it o Steam purity is a direct function of boiler water dissolved solids content o Super t a t bine r ia it heaer nd ur el bil y o High- it pr pur y ocesses Semiconduct s or Phama icas r ceut l Caayt hydr r /chemica pr t l ic ocabon l ocesses F a bev a pr ood nd er ge ocessing/ er izaion st il t Comfor humidificaion t t M la r r st m st il t pr edica nd eseach ea er izaion ocesses
- 8. Boil feedw t quait consider t er aer l y aions Boil pr e a super t /ur st m er essur nd heaert bine ea pur yr ement gener lydefine it equir s al pr r t a feedw t quait et eament nd aer l y r ement equir s. In gener l– a > Soft orsingl pa R quait ma up < 600 psig ened e ss O- l y ke- > G al deminer l orR E ma up > 900 psi ener ly aized O/DI ke-
- 9. Resin Based Pretreatment Performance Typical Effluent Typical Boiler Syste Quality Operating m Pressure (psig) Softener 0.2-1.0 ppm hardness 0 to 600 (no TDS reduction) Dealkalizer 50 to 90% alkalinity 0 to 600 reduction (no TDS reduction) Standard two-bed <10 µmho 400 to 900 demineralizer <200 ppb silica Two-bed demineralizer with <5 µmho 900 to 1,200 counterflow regeneration <50 ppb silica Two-bed demineralizer with <0.1 µmho 1,200+ mixed bed polisher <10 ppb silica
- 10. Benefit fort Cust Conv sion fr Soft t R M keup s he omer er om ened o O a • Impr ed st m pur y&sa y ov ea it fet — Impr ed pur yofpr s/ ocesses cont ct byst m ov it oduct pr a ed ea — Reduced st m cont minaion ea a t — E nced r aor compl nce nha egul t y ia • Impr ed st m equipmentr ia it efficiency&l it ov ea el bil y, ongev y — Impr ed sa y-R ov fet educed cha ofcaa r fa ur nce t stophic il e — Impr ed t bine efficiency ov ur — Impr ed st m hea ta efficiency ov ea t r nsfer • Reduced t a costofoper t (mustquaifycaefuly) ot l aion l r l — Impr ed st m syst hea ta efficiency ov ea em t r nsfer — Impr ed boil t ma efficiency ov er her l — Reduced chemica teamentcost lr t s — Reduced regener ntcost a s
- 11. Quest t hel you quaifyfea it of ions o p l sibil y pur R conv sions fr Na suing O er om Z R w lgener lyr O il al educe ourov alboil chemica r enue byafa orof608 % . er l er l ev ct -0 Is cust l omer ooking t r o educe chemica? l Is t e asignifica oper t lorefficiencyissue t tca be sol ed byhigherpur yF ? her nt aiona ha n v it W Does t pl ntl ck bl dow hea r er equipment(oris itinoper bl he a a ow n t ecov y a e)? Is t e compet iv pr e orabid t tis compeling you t considerR a asol ion? her it e essur ha l o O s ut Ae curenta er ge cycl ofconcentaion < 10 r r va es rt ?
- 12. Technica consider t in conv sions fr NaZeol e t R er l aions er om it o ev se Osmosis M keup a • R per t cabon dioxide consider t &r ion st aegies O meae r aions educt r t — Corosiv yofR per t r it O meae — Al consider t loy aions — Pr r met ofpHa ust efered hods dj ment • Considerboil feed pump al er loys • Sel ion ofoxygen sca enger ect v • Int na t eamentpr a consider t er l r t ogr m aions • Condensae corosion discussion & pHcont olr nge t r r a
- 13. Zeol e Soft &Deakaizaion it ening l l t Advantages Limitations • Inexpensive – Ca a &operaing costs pit l t • No r ion in t a dissol ed sol (T educt ot l v ids DS) • Simpl t oper t e-o- ae • F quait ca l boil cycl W l y n imit er es • Dur bl ae • Notsuit bl forhigh- essur boil oper t (> 90 ae pr e er aion 0 psig) • Sa &inexpensiv fe e sodium chl ide r or egener nt a • No sil r ion ica educt • No akainit r ion w houtdeakaizer l l y educt it l l
- 14. R ba deminer l t esin- sed aizaion Advantages Limitations • R ion in aldissol ed sol educt l v ids • St ong a ca ic r ed for r cid/ ust equir • E bl high cycl oper t na es es aion regener t aion • Suit bl forhigh- essur boil s ae pr e er • Ca iccost high &v r bl ust s aia e • Ca t il t specificpur yneeds n a or o it • L ed a r l imit nion esin ife • E l sil r ect xcelent ica ej ion • Sil a sodium l ka ica nd ea ge • E l akainit CO2 r ect xcelent l l y/ ej ion • M npow int e a er ensiv • Oper t cost dir l aing s ecty pr t lt T oporiona o DS
- 15. R er Osmosis ev se Advantages Limitations • R ect ofaldissol ed sol ej ion l v ids • R aone notsuit bl forHPboil feedw t > 10 0 Ol ae er aer 0 • Oper t cost notdir l dependa on T aing s ecty nt DS psig w h t bine it ur • E bl high cycl boil oper t na es e er aion • Higherelectrica costs than resin-based systems (high- l • R es no chemica r equir l egener nt (a ca ic) a s cid/ ust pr e pumps) essur • Notl borint e a ensiv • G aes significa r ectstea ener t nt ej r m (t ly20– 3 % ofinputst ea ypical 0 r m) • V sail pa ings w h r ba syst er t e ir it esin- sed ems • Idea formobil a icaions l e ppl t • Does notr ectCO2 (g) ej
- 16. Pot ia membr ne sol ions forBoil syst ent l a ut er ems 1. R in fr ofexist deminer l s O ont ing aizer 2. R t r a ora O o epl ce ugmentsoft s ener 3. R E t r a r ba deminer l O/DI o epl ce esin- sed aizer -M bed quait ta ixed- l y r in 4. Ulr filr t in fr ofdemin. orR t r a ta taion ont O o epl ce ta iona filr t cl r t r dit l taion/ aificaion
- 17. Keyinputv r bl formodel &a l aia es ing naysis Economic Environmental TDSofinfluentwater R ion ofa ca ic inv or educt cid/ ust ent y Ca a equipmentcost (R pit l s O) Personnelsa y-chemica exposur fet l e Ca iccost ust s Wt scacit issues aer r y Eect ica pow r t l r l er aes Dischage/ miting issues r per t Infl w t cost uent aer s Sew a cost er ge s o V ume orV /DS- sis? ol olT ba o Can plant reuse RO reject? o Cr s orincent es forr edit iv euse T ca be a his n Regener ntneutaizaion cost a rl t s cr ica fa orbeca it l ct use Differ ia l borcost ent l a s dir sew a oft R ect er ge he O r ectstea ma be costy ej r m y l
- 18. Case 1 - Potential Benefits in the Addition of RO ahead of Demineralizer •Reduced a &ca ic r cid ust egener ntcost a s – 90– 95% r ion in r educt egener ntusa is t l a ge ypica •R educed oper t l bor aor a •R educed high T r DS egener ntneut aizaion dischage a rl t r • E ended ion excha r l xt nge esin ife – 4 – 50 ext 0 % ension in r l t l esin ife ypica – Geal r r ty educed r cycl &r egen. es educed ir or nic foul on/ ga ing • Impr ed feedw t &st m quait ov aer ea l y – Sodium &sil sl ge &br ks significa l r ica ippa ea nty educed
- 19. R Pr O eceding Deminer l aizer E mpl w h r aiv yinexpensiv w t a sew a xa e it el t el e aer nd er ge RO cost justified above approx. 200 ppm TDS RO to preceed Demin. $0.50/kgal raw water / $0.50/kgal waste 3 2.5 Demin. 2 RO $/kgal wdegas,neutr 1.5 Linear (wdegas,neutr) 1 0.5 0 Ca a a oper t pit l nd aing 100 312 473 costof TDS, ppm R incl O uded
- 20. R Pr O eceding Deminer l aizer E mpl w h mor expensiv w t a sew a xa e it e e aer nd er ge RO cost justified above approx. 400 ppm TDS RO value to precede demin, $1.50/kgal raw water, $2.00/kgal waste 5 4.5 4 RO 3.5 3 $/kgal 2.5 wdegas,neutr 2 Linear (wdegas,neutr) 1.5 1 Ca a a oper t pit l nd aing 0.5 costof 0 R incl O uded 100 312 473 TDS, ppm
- 21. Case 1 Summary - RO in front of Demineralizer Annual cost savings based on water production and savings per 1000 gallons $600,000 $500,000 Annual Savings $400,000 $0.50 $300,000 $0.75 $1.00 $200,000 $100,000 $0 100 250 500 1000 Flowrate GPM (24/7/365 basis)
- 22. Case 2 - Potential Benefits Conversion from Softened to RO make-up • Improved steam purity > Pr T bine ocess/ur • Improved condensate corrosion control > High- l l yw t s akainit aer • Minimizes operating and maintenance expenses > Boil w t side a st mside fa ur er aer nd ea il es • Maintains optimal thermal performance > Boil a st m hea ta efficiency er nd ea t r nsfer • Reduced chemical treatment costs > Highercycl oper t – l w st ge es aion ess a a > Low st m syst teamentr ement er ea em r t equir s
- 23. Typical Problems encountered in Softened water boiler systems St m pur yissues ea it ntr l co o Deposit Condensae Corosion t r nJoint ns io Expa e Failur
- 24. Al a fuela ook t nd w t sa ings w aer v hen incr sing boil ea er cycl not a es ing naur lcostof$8per ta decaher t m.
- 25. Pot ia E gyL V sus ent l ner oss er Wt side Scae T aer l hickness Ir &Sil on ica 7 High Ir Cont on ent 6 5 E gyL (%) 4 ner oss 3 "Nor l Scae ma" l 2 1 0 1/ 64 1/ 2 3 364 / 1/ 16 Scae T l hickness (Inches)
- 27. Sa ing Wt &E gy v aer ner is aBig W in E er Wy, in v y a a t cr t e use ofM a sol ions forBoil s ca hel you t ma it nd he eaiv embr ne ut er n p o ke ha a yourfa it ppen t cil y!
Editor's Notes
- Just as in the case of placing an RO ahead of a demineralizer system, things such as power costs, total dissolved solids limits in the water and the cost of regenerants become an issue. Again, dealing with the RO reject is an issue and must be thoroughly examined. Even if it becomes a waste stream, the RO reject is typically much better then the acid and caustic waste the plant currently deals with. Higher influent water conductivity will make the RO systems work harder to remove the dissolved solids but as long as the silt density index or SDI requirements for the RO can be met, then this combination is quite effective. Next slide please.
- This is just a rough summary or survey of what one would expect of the water quality out of various types of pretreatment equipment. Question the group on how well their equipment performs versus this profile.
- By providing better quality feedwater there is better quality steam being produced. This means control valves, processes that have direct steam contact, steam turbines used for electric generators, compressor or pump drives are less prone to failure. Superheaters remain free of boiler salts and maintain operating reliability. Steam expansion joints and steam headers do not suffer from caustic embrittlement that would lead to cracking of these stressed components. As the steam is pure, there are no concerns with contaminated product or product recalls or disposals. Even in systems that might experience mechanically induced steam purity problems, the fact that the water is more pure to start with means the resultant level of solids in the steam would be lessened when RO feedwater is used. Introducing less solids in the boiler means our internal treatment chemicals do not have to work as hard and are able to do a better job. This will greatly improve the reliability of the boiler. Next Slide Please.
- As I just said the inclusion of an RO can significantly reduce the chemical usage. For example in a plant producing 100,000 lbs per hour steam, with 70% condensate return going from 8 to 50 cycles, without any other changes, will reduce the boiler chemical volume from 40,000 to 15,000 lbs per year. If the inclusion of the RO would get the customer to realize better condensate quality without requiring more amine feed,especially if they are limited due to regulatory issues on the amount of chemical treatment they can supply, then you could be quite a hero at the account. This a powerful selling point This is what value added selling is all about. Increased condensate return means less makeup and better quality feedwater. RO water has less alkalinity so that condensate corrosion of steel and copper surfaces is minimized leading to cleaner boilers and better heat transfer. Think about adding that RO when the steam purity problems can not be solved by changes in system operation, chemical feeds or other means. The better quality water provided by the RO versus the softener could be just what the customer needs. Increased overall plant thermal efficiency is often achieved by increasing boiler cycles but only if the plant does not have blowdown heat recovery such as blowdown flash tanks and blowdown heat exchangers. When this equipment is installed and operating properly, there will be very little of the energy savings realized by operating the boiler at higher cycles. Be careful to consider this before even broaching the subject of RO with a customer or prospect when this is the major thrust you are using. If a competitor has not done their homework and proposes RO and the main point they are making is energy recovery, point out to your customer or prospect the fallacy of the argument when heat recovery equipment is in place. This will close down the competitive thrust into this account while gaining you instant credibility. Next Slide Please.
- In replacing a softener with an RO unit we must be conscious of the quality of the product water. RO permeate will be much lower in all species as the RO will remove >98% of all soluble species in the influent water. Gases will not be removed by the RO. The permeate will be acidic, typically pH 5-6, due to the presence of carbonic acid. For this reason piping resistant to corrosion will need to be installed. Such a change will maintain the purity of the permeate while maintaining the piping and pump network. Typically the change in metallurgy is to stainless steel or plastic. An alternative to metallurgy changes, would be to adjust the pH of the permeate using caustic or an amine. Both will protect the downstream piping but there are tradeoffs to consider. Adding caustic is cheap and effective but it will also affect the feedwater alkalinity, conductivity and boiler water pH. Adding amine will possibly be the better approach. Adding an amine will allow CO2 to be vented from the water in the deaerator and the amine will recycle. This will reduce the overall system demand for neutralizer. The amine in the feedwater will also not affect the boiler water chemistry. In a softened water system,the oxygen scavenger is often sulfite based. It is cheap, effective and the impact on cycles is typically not significant as they are already low. When we have gone to RO quality water the change to a sulfite replacement such as DEHA, hydroquinone, or one of the other organic scavengers maybe preferred. These products are effective, have limited effect on boiler water conductivity and will have benefits in the protection of the condensate as in the case of DEHA All polymer or other solubilizing internal treatment technology is now a real possibility with RO quality feedwater. Cleaner boilers, higher cycles, and easy testing are all benefits to be derived by changes to soluble versus the older precipitating programs. Next slide please.
- By installing an RO system ahead of the demineralizer we lower the consumption of acid and caustic due to the reduced number of regeneration cycles. This reduction in regenerant usage can be on the order of 90-95%. As the number of regenerations is reduced, so too is the operator time required to monitor or conduct the regeneration. In addition, where manual intervention by the operator is required such as checking of regenerant strengths, handling drums of acid and caustic or initiating steps in the regeneration sequence operator time is minimized. Other advantages are the worker exposure to chemicals is greatly reduced minimizing the potential for injury from chemical burns or physical injuries and the time and expense required to neutralize the waste stream is also vastly reduced. As we reduce the chemicals used in the demineralizer system, the amount of chemical discharge from regeneration is significantly reduced as well. This could be a major benefit where a customer is faced with a plant discharge limitation issue.The inclusion of the RO would make this a more environmentally friendly technology.This is even more of a benefit when we are looking at eliminating the need for acid and caustic entirely as is the case with RO-EDI. The presence of the RO will generally extend resin life by as much as 40-50%. Organic fouling of the anion resin will be greatly reduced as will iron fouling of the cation resin. Colloidal silica is also significantly reduced by using RO prior to a demineralizer. Next slide please.
- What are some of the typical problems encountered in a softened water boiler feedwater system? Lower operating cycles leading to higher fuel bills. Increased risk of steam purity problems due to lower quality feedwater. This low quality feedwater can not be concentrated too highly or carryover will take place leading to superheater, turbine or other critical system components being compromised. Additionally, the customer’s final product quality can be adversely affected leading to product recall, wastage, and negative publicity.. With lower quality feedwater the total alkalinity in the feedwater will be higher. This will lead to greater potential condensate corrosion levels. Higher condensate treatment cost and the potential for greater deposits in the boiler due to inadequate corrosion protection will also occur. Next slide please