IMPROVING WOOD KILN BOILER RELIABILITY VIA A NEW WATER TREATMENT CONTROL TECHNOLOGY Authors: John D. Deines, David A. Grattan, PhD, Thomas S. Hughes, Brian V. Jenkins, John Ostberg, Benjamin D. Riley, Catherine J. Stetenfeld, Nalco Company Contributors: Ernie Lundquist, Steve Fuhriman, Ryan Lawrence and Robin Schernitzki, Boise Building Solutions, Manufacturing
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IMPROVING WOOD KILN BOILER RELIABILITY VIA A NEW WATER TREATMENT CONTROL TECHNOLOGY
Authors: John D. Deines, David A. Grattan, PhD, Thomas S. Hughes, Brian V. Jenkins, John Ostberg, Benjamin D. Riley, Catherine J. Stetenfeld, Nalco Company
Contributors: Ernie Lundquist, Steve Fuhriman, Ryan Lawrence and Robin Schernitzki, Boise Building Solutions, Manufacturing
Here’s what we’ll be covering this morning
• Purpose of the boiler in a wood products plant• Challenges associated with operating a boiler in a
wood products mill– Operational– Resources– Personnel work load
• Boiler chemical treatment, its application and evolution
• New developments in boiler feedwater scale and corrosion control
• Wood products plant application of the new technologies
• Outcome and benefits of the application
The boiler is crucial for wood products manufacturing
• Controls the drying process– Kiln coil heating– Steam humidification
• Optimum Moisture Content is Crucial– Higher end-use product value– Better material usability– Increased product strength– Lower shipping costs– Better insulating and finished material properties
• Drying too fast / too slow - both are bad
As much as 80% of a mill’s energy requirement can be for the drying process
Figure 1 Boiler scale greatly impedes heat transfer and reduces efficiency
There are two major water related challenges encountered in operating a boiler – scale and
corrosion
• Mineral Scale– Forms as a result of
dissolved minerals in the feedwater exceeding solubility
– Forms insulating material
– Impedes heat transfer
– Can result in equipment damage / boiler shutdown / loss of production
Corrosion is nature’s way of reclaiming refined metals…
• Corrosion– Two primary types
in boilers systems• Carbonic acid
(condensate)• Oxygen
– Reduce asset life• Pitting corrosion• General corrosion
– Cause iron deposits on boiler tubes (energy losses)
– Shutdown, production loss and safety issues
Over time, chemical treatment of boiler feedwater to prevent or reduce the impact of
these challenges has changed
For scale control, many advancements have taken place in chemistry over the last century
P r o g r a mD e v e l o p e d / u s e d A d v a n t a g e s D i s a d v a n t a g e s
C o a g u l a n t / S o d a A s h 1 9 0 0 - 1 9 5 0 R e d u c e d a n d e a s i e r t o r e m o v e s c a l e
S t i l l f o r m s s c a l e , p r o g r a m a d d s s o l i d s , i n c r e a s e s b l o w d o w n r e q u i r e m e n t s . S o d a a s h c a n r e s u l t i n i n c r e a s e d c o n d e n s a t e c o r r o s i o n
P h o s p h a t e 1 9 3 0 ' sR e d u c e d C a C O 3 s c a l eR e d u c e d s o l i d s a d d i t i o n S t i l l p o t e n t i a l f o r P O 4 s c a l e
C h e l a n t s E a r l y 1 9 6 0 ' s C o m p a r a t i v e l y l o w e r s o l i d s c o n t r i b u t i o nC o r r o s i o n p o t e n t i a l i f o v e r f e dP o t e n t i a l f o r M g S i O 3 s c a l e
P h o s p h o n a t e s L a t e 1 9 7 0 ' sC o u l d r e s u l t i n s c a l e i f f e e d w a t e r h a r d n e s s n o t v e r y w e l l c o n t r o l l e d
P o l y m e r o v e r l a y f o r p h o s p h a t e s o r c h e l a n t s L a t e 1 9 7 0 ' s
C o n d i t i o n e d s p e c i f i c t y p e s o f s u s p e n d e d s o l i d s - F e 3 O 4 , F e 2 O 3 , C a 3 ( P O 4 ) 2 , M g S i O 3 t o m a k e t h e m l e s s a d h e r e n t t o b o i l e r s u r f a c e s
S t i l l p o t e n t i a l f o r P O 4 s c a l eC o r r o s i o n p o t e n t i a l i f o v e r f e dP o t e n t i a l f o r M g S i O 4 s c a l e
P o l y m e r o n l y ( 1 s t g e n - p o l y a c r y l i c a c i d ) E a r l y 1 9 8 0 ' s
M a i n t a i n s h a r d n e s s i n s o l u b l e s t a t eR e d u c e s s o l i d s c o n t r i b u t i o n t o b o i l e r w a t e rR e d u c e d c o r r o s i o n p o t e n t i a l c o m p a r e d t o c h e l a n t p r o g r a m sD i s p e r s e s i r o n
C o u l d c o m p l e x w i t h b o i l e r m e t a l i f o v e r f e dH i g h h a r d n e s s c o u l d c a u s e p o l y m e r / h a r d n e s s c o m p l e x t o d e p o s i t
P o l y m e r o n l y ( 2 n d g e n - s u l f o n a t e d p o l y m e r ) 2 0 0 1
M a i n t a i n s h a r d n e s s i n a s o l u b l e s t a t e . L e s s c o r r o s i v e t h a n c h e l a n t . I n c r e a s e d t h e r m a l a n d o x y g e n s t a b i l i t yK e e p s s u s p e n d e d s o l i d s d i s p e r s e dD o e s n o t p r e c i p i t a t e o r f o r m p r e c i p i t a t e s R e d u c e s i r o n d e p o s i t i o n r a t e . C o u l d b e c o r r o s i v e i f g r e a t l y o v e r f e d
For control of oxygen corrosion in preboiler equipment, we have developed effective chemical oxygen scavengers …
Indirect Direct
Measuring ChemicalResiduals
► Dearator Inspections
► Monitoring DissolvedOxygen
► IronTesting
► ?
… but we have still lacked technology that could reliably monitor and control changes in that environment!
…however, the basic approach to controlling boiler water chemistry has always revolved around a “test and adjust” approach…
• Gather sample• Test• Adjust chemical feed• “Repeat as necessary”
Equipment damage / efficiency loss / production loss
(wasted chemical)USL
LSL
…and is still largely centered around testing the water after it is in the boiler
D E A E R A T O R
An event taking place
here….
…could take hours or days to
show up here!
By then, its far too late to detect or remedy
We’ll be talking about two new technologies:
• 3D TRASAR Technology for Boilers™– Measures and controls scale inhibitor
chemistry• Nalco Corrosion Stress Monitor™
– Measures and controls pre-boiler corrosion environment
• Real time, on-line control 24/7• Process visibility for these areas• Assurance of asset protection• Optimized chemical usage• Improved energy savings
Pre-boiler Corrosivity Desired control range: -400mV +/- 10 mV
Before automation 1/9-2/12/09
After initial automation
2/14 – 3/3/09
Comments Before automation 1/9-2/12/09
After initial automation
2/14 – 3/3/09
Comments
Average dosage
17.01 ppm 6.7 ppm Operating above the control range wastes treatment chemicals; operating below the
control range increases the risk of scale (wasted fuel), damage to the boiler
and production losses
Average reading
-366 mV -401 mV Values approaching zero (more positive) indicate a more corrosive environment. Excessively negative numbers may mean excessive oxygen scavenger use, leading to higher blowdown levels
Standard deviation
+/- 23 ppm + /- 2.4 ppm An 89.6% reduction in standard deviation
Standard deviation
+/- 71mV +/- 13 mV An 82% reduction in standard deviation
Outcome
Wet Chemistry Results…
As expected, wet chemistry control has gotten tighter as well.
Standard deviation has decreased by 49.2%
Another achievement was the reduction in water per volume of production
Some of the improvement highlights included
• Improvement in pre-boiler corrosion stress control– Before - 44% in desired range– After – 87.1%
• Scale control overfeed reduced from 73% to 15%– More improvement anticipated as next control protocol steps are
taken• Summary of improvements and ROI
– From the initial work since implementing the overall program – cycles have increased from 10 to 30
• Blowdown reduced by 69%• Water saved – 2.4 Million gallons
– Reduced wet testing– Extended equipment life– Improved efficiency– Greatly increased knowledge of system behavior– Enhanced process visibility– Reduced total operating cost
Summary
Key Take Aways…
• Asset Reliability and Efficiency is the Key in Steam Plant Operations
• Controlling Scale and Corrosion is the Key to Asset Reliability
• New Methods of Measurement and Control have “Changed the Game”
• Indirect Control to Direct Control• Reactive to Proactive• Greater Visibility with less Operations Time Requirement• Equals Greater Asset Reliability with lower Total Costs of