Moc Approach For Open Cooling Water System 4c4a1o
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Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
MOC Approach for Open Cooling Water System Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
1
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Agenda • Mechanical – Cooling tower – Heat exchanger – Metallurgy
• Operation – pH – Cycle
• Chemical – Makeup water chemistry
SM
Essential Expertise for Water, Energy and Air
2
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
3
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
4
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Why cooling is important? • Cooling tower performance provide significant contribution to the plant performance and efficiency • Poor cooling tower performance could limit the plant production
SM
Essential Expertise for Water, Energy and Air
5
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Impact of Cooling Water Temperature
o
o
A 3 C (5.4 F) increase in approach temperature (on all stages) is equivalent to a 1% increase in energy consumption
SM
Essential Expertise for Water, Energy and Air
6
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Function of Cooling Towers • Remove heat from process operation
• Mostly by evaporation (80%) –partially by sensible heat loss (20%) • of hot water with cooler air
SM
Essential Expertise for Water, Energy and Air
7
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Process •
As ambient air is drawn past a flow of water, a small portion of the water evaporate. The energy released by water for evaporation reduces the remaining water temperature
•
Evaporation results in saturated air conditions and lowers the temperature of the water to a value close to wet bulb air temperature
SM
Essential Expertise for Water, Energy and Air
8
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Types of Cooling Towers
SM
Essential Expertise for Water, Energy and Air
9
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Crossflow Cooling Tower
SM
Essential Expertise for Water, Energy and Air
10
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Counterflow Cooling Tower
SM
Essential Expertise for Water, Energy and Air
11
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Fill •
Purposes of Tower Fills – Increases the water surface area for air – Increases time
•
Main Types of Fill – Splash Fill – Film Fill
Tower Fill
SM
Essential Expertise for Water, Energy and Air
12 12
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Fill Characteristics
SPLASH
FILM
EFFICIENCY
Medium
High
DURABILITY
Medium
Low/Medium
Low
High
FOULING
SM
Essential Expertise for Water, Energy and Air
13
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Problems with Film Fill • Easily fouled with microbio and solids • Hard to clean once fouled • Quick loss of efficiency
Tower Fill SM
Essential Expertise for Water, Energy and Air
14
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Factors Affecting Cooling Tower Performance • Wet bulb temperature • Dry bulb temperature • Plant (heat) load – Cooling water ∆T
• Cooling water flow – No of pump running
• Air flow – Fan (tip, angle, motor; etc)
• Cooling water distribution – Distribution system – Fill cleanliness
SM
Essential Expertise for Water, Energy and Air
15
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Wet Bulb Temperature Measurement
• A measurement of the lowest temperature that can be achieved by evaporative cooling of a water wetted ventilated surface.
Sling Psychrometer
SM
Essential Expertise for Water, Energy and Air
16
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
COLD WELL TEMPERATURE, OC
Liquid to Gas Ratio
TYPICAL L/G
37
PERFORMANCE CURVES
L/G = 2.0
35 33
L/G = 1.5 L/G < 1, TOWER OVERSIZED
31
L/G = 1.0
- TURN OFF FANS OR DOWNSIZE
29 L/G > 2.5, TOWER UNDERSIZED AND WILL NOT PROVIDE LOW
27
APPROACH TEMPERATURES
25 12
14
16
18
20
22
24
26
WET BULB TEMPERATURE, OC
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Essential Expertise for Water, Energy and Air
17
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Air Flow Issue Air Recycling (Incorrect Tip)
•
Air flow is a critical component to ensuring the proper heat rejection from a cooling system
•
Many cooling tower performance issues may well be airflow problems
ROTATION Air In-leakage From Fan Shaft
Fan Stall (Incorrect Pitch)
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Essential Expertise for Water, Energy and Air
18 18
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
What is the Correct Way to Evaluate Cooling Tower Performance ? 1) CW temperature range (∆T) 2) Cooling tower heat load •
M x x ∆T
3) CW supply temperature 4) Approach temperature 5) Evaporation rate SM
Essential Expertise for Water, Energy and Air
19
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Monitoring – Cooling Tower
GPSA Nomograph: (require ∆T& wet bulb temperatures) Performance Factor proportional to: •L/G ratio (L = CW flow, G = air flow both in kg/hr) •RR (or L) •1/(Fan Power)1/3 Performance Factor > design means performance deteriorated
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
21
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Why is This Important? • A critical component of the cooling system – Affect efficiency – Fouled exchangers also decrease throughput and capacity – Leaking exchangers can force unscheduled shutdown
• Also affect water treatment options – product selection and control limits
SM Water Distribution System
Essential Expertise for Water, Energy and Air
22 22
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger What We Need to Know ? • Type of heat exchangers • Hydraulic, mechanical and metallurgical • Mechanical stress to cooling water treatment • Performance monitoring
SM
Essential Expertise for Water, Energy and Air
23
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Type of Heat Exchangers There are several general types of heat exchangers: • Shell-and-tube
• Plate-and-frame
• Spiral flow
SM
Essential Expertise for Water, Energy and Air
24 24
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Shell and Tube Heat Exchanger (Water in Tube) • Most common heat exchanger type found in cooling water systems • Typically has adequate velocity – Throttle and spatial relationship could create problem
SM
Essential Expertise for Water, Energy and Air
25
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
A shell side heat exchanger offers challenges • Low velocity • High skin temperatures
SM
Essential Expertise for Water, Energy and Air
26
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanical “Stresses” Three main mechanical stress factors that impact the efficiency of heat transfer in heat exchanger are: 1)Cooling Water Velocity 2)Skin Temperature 3)Heat Flux
SM
Essential Expertise for Water, Energy and Air
27 27
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Water Velocity Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
> 1 m/s 0.6-1 m/s 0.3-0.6 m/s < 0.3 m/s
•
Scale and fouling deposition is more prone to occur at low velocity
•
Lower flow rate, lower turbulence that can lead to static thicker film of water at metal surfaces à reduces heat transfer
•
Lower velocity = higher skin temperature
SM
Essential Expertise for Water, Energy and Air
28 28
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Flux Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
< 7.5 kW/m2 7.5-25 kW/m2 25-40 kW/m2 > 40 kW/m2
• High heat flux will lead to high skin temperature • Typically v 3.15 – 15.8 kW/ M2 v 15.8 – 31.5 kW/ M2 v 31.5 – 63.1 kW/M2
: mild steel : alloy : copper or stainless steel
SM
Essential Expertise for Water, Energy and Air
29 29
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Skin Temperature Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
< 500C 50 - 600C 60 - 700C > 700C
• Reasons: – Corrosion rates ~double for each 10°C increase in metal temperature – Scaling tendencies become much more pronounced at high temperature – Film boiling may occur as skin temperature – Some treatment chemicals break down at high temperature
SM
Essential Expertise for Water, Energy and Air
30 30
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Other Important Mechanical Factors 1) Spatial Relationship 2) Metallurgy
SM
Essential Expertise for Water, Energy and Air
31 31
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Spatial Relationship and CW Distribution
108C
115C
146C
101J Coolers
128C
2nd
116C 1st
3rd
124C
101JC
2002JC
127C
Primary Cooling Water Header Secondary Cooling Water Header
Tertiary Cooling Water Header Cooling Water Return Header
SM
Essential Expertise for Water, Energy and Air
32
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Metallurgy – Copper alloys • High thermal conductivity • Sensitive to ammonia and oxidant • Need film forming inhibitor
– Titanium • Self ivating metal • Extremely brittle with very thin walls • Leaks common (especially during initial commissioning and startup) • ANY mechanical impingement can cause leaks
– Stainless Steel • Self ivating metal • Subject to chloride stress corrosion • Must ensure cooling water chloride level remains within limits • Under-deposit corrosion, MIC issues
Ammonia Grooving
Under Deposit Corrosion / MIC
Pitting / MIC SM
Essential Expertise for Water, Energy and Air
33
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Chloride and Stainless Steel
PLANT DATA Duty Area
3,286,000
Btu/hr 424 ft2 Btu/hr.ft2 91.2 .C 7750 Btu/hr.ft2 6.111 ft/s 91 F 100 F 637 F 300 F
U Heat Flux Velocity T CW in T CW Out Process In Process Out CALCULATIO N T Skin Max T Skin
106.34 F 41.3 C 146 F 62 C
SM
Essential Expertise for Water, Energy and Air
34
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Importance of Heat Exchanger Monitoring Ø Prevent the loss of cooling Ø Predict Onset of Problems Ø Potential Surprises - scaled exchanger Ø Loss of production
Ø Useful to troubleshoot problems Ø Methodology using appropriate data Ø Documentation
SM
Essential Expertise for Water, Energy and Air
35 35
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger Monitoring • Approach Temperature – Generally could represent HE performance – Approach = T Process Exit (air) – T Cooling Water Inlet (counter current)
• Others: C Factor, U Value, Fouling Factor; etc
SM
Essential Expertise for Water, Energy and Air
36
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
37
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Water Operation What We Need to Know ? • Basic mass balance calculation • Cycle management • Operational stress factor
SM
Essential Expertise for Water, Energy and Air
38
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Mass Balance Evaporation
Drift
Windage
Makeup
Windage
Blowdown
Cycled Water Leaks SM
Essential Expertise for Water, Energy and Air
Loss 39 39
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Blowdown to Reduce Cycles
1000 ml 150 umhos
500 ml 150 umhos
500 ml 150 umhos
500 ml 100 umhos
Cycles = 125/100 = 1.25 Cycles
1000 ml 125 umhos
SM
Essential Expertise for Water, Energy and Air
40
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Blow Down and Cycle •
Blow down – portion of the water ejected or drained from a system to control solids in cooling water
•
Cycle – number of times that dissolved minerals in cooling water are allowed to concentrate. Cycle is controlled by blowdown
•
Cycle = Dissolved Solids Concentration in Cooling Water Dissolved Solids Concentration in M-Up
•
In general, the cycle of concentration allowed depends on both the level of solids in the make-up and the level of solids that can be tolerated in cooling water
SM
Essential Expertise for Water, Energy and Air
41
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Basic Cooling Tower Calculations
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Essential Expertise for Water, Energy and Air
42 42
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Holding Time Index (HTI) • HTI is indicate the time required to reduce the chemical added to the system to 50% of its original concentration • HTI = 0.693 x Holding Volume Blowdown Rate • It is important to select the right chemical program
SM
Essential Expertise for Water, Energy and Air
43
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Operational “Stresses” Variation of operational and control parameters cause stress in cooling water systems. The key examples of operational stresses as follows 1)Variation of cycle 2)Variation of pH 3)Variation of HTI
SM
Essential Expertise for Water, Energy and Air
44 44
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of Cycle Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
<20% 20-50% 50-80% > 80%
% Out of Spec Low High Total 17.7% 5.3% 23.0%
SM
Essential Expertise for Water, Energy and Air
45
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of pH Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
Control Parameter pH
Lower Spec 7.50
SM
Essential Expertise for Water, Energy and Air
Upper Spec 8.00
+ 0.1 + 0.2 + 0.4 + 0.6
Statistical Calculations LCL Mean UCL 7.16 7.72 8.28
STD 0.19
46
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of HTI Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
SM
Essential Expertise for Water, Energy and Air
< 40 hrs 40 - 100 hrs 100 - 200 hrs > 200 hrs
47
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cycle and pH – Operating Window
SM
Essential Expertise for Water, Energy and Air
48
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cycle Management
SM
Essential Expertise for Water, Energy and Air
49
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
50
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Main Problems in Cooling Water Operation Related to Water Treatment There are basically four inter-related problems in the operation of a cooling water system as depicted by the Cooling Water Treatment Triangle below. Each problem affects and is affected by the other problems.
SM
Essential Expertise for Water, Energy and Air
51
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Corrosion •
A natural process converting processed metals to their native states
•
Factors affecting: - Water chemistry - Physical environment (temperature, velocity, hydrodynamic) - Dissolved gases - Halogen or other oxidizers - Deposit
SM
Essential Expertise for Water, Energy and Air
52
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Scale •
A dense, adherent layer of minerals tightly bound to itself and to metal surface
•
Factors influences - pH - Minerals concentration (Ca, Mg, SiO2, Alkalinity;etc) - Temperature
SM
Essential Expertise for Water, Energy and Air
53
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Fouling •
Deposits that formed from material suspended in water (clay, silt, iron, manganese, microbiological)
•
Factors affecting – Suspended solids concentration – Hydraulic and flow velocity – Spatial relationship – Scale, corrosion and microbiological
SM
Essential Expertise for Water, Energy and Air
54
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Microbio Fouling •
The most prevalent problems in industrial cooling water systems
•
A good control of microbial growth is essential if we are to control the other water chemistry problems
•
Factors affecting: – Suspended solids – Contaminants (organics, ammonia, phosphate; etc) – Physical factor (velocity and hydrodynamic) – pH
SM
Essential Expertise for Water, Energy and Air
55
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
General Methods for Corrosion Inhibition •
Use Corrosion Resistant Materials
•
Apply Inert Barrier or Coating
•
Use Cathodic Protection
•
Adjustments to Water Chemistry
•
Application of Corrosion Inhibitors
SM
Essential Expertise for Water, Energy and Air
56
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Corrosion Inhibitors – Cathodic & Anodic Cathodic inhibition Prevents the transfer of electrons à prevent the reduction of oxygen.
Anodic inhibition prevents the dissolution of the base metal, iron.
•
Combinations of both anodic and cathodic inhibitors generally provide the best protection.
•
These combinations are called “synergistic” because the combination provides lower corrosion rates than either inhibitor could alone,
SM
Essential Expertise for Water, Energy and Air
57
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Saturation Index as a Tool for Scale Control
WATER CHEMISTRY
pH
TEMPERATURE
SYSTEM DESIGN
SATURATION INDEX
PROGRAM DESIGN
VARY CYCLE
VARY pH
VARY TEMPERATURE
SM
Essential Expertise for Water, Energy and Air
VARY CHEMISTRY
58
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Saturation Index Reference Chart Moderate High Stress Stress Calcite 6 80 140 Aragonite 7 80 140 Anhydrite 1.2 3 4 Gypsum 1.2 4 6 Tricalcium Phosphate 50 1000 1500 Hydoxyapetite Insufficent Data Insufficent Data Insufficent Data Flourite Insufficent Data Insufficent Data Insufficent Data Silica 1.1 1.2 1.5 Brucite 1.1 1.2 1.5 Magnesium Silicate 6 7 8 Iron Use of SI not indicative of iron fouling problems Mineral Scale
Mild Stress
SM
Essential Expertise for Water, Energy and Air
59
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Comparison Scale Inhibitors Capability
AMP
PSO
HEDP
PBTC
PAPEMP
2
5
3
1
1
CaCO3 SI
105
80
100
180
200+
CaSO4
734
483
130
257
574+
Cl2 Stab
2
5
3
5
3
Thermal Stability
3
5
2
5
4
Corrosion Inhibition
Note: 5 Best, 1 Worst
SM
Essential Expertise for Water, Energy and Air
60
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Nalco Chemical Programs for Scale and Corrosion PSO-Phosphate Stabilized Phosphate
pHreedom All organic
Alkaline Zinc
Under-saturated (corrosive)
Calcium Carbonate (Calcite)Saturation
Over-saturated (Scale)
High pH High Alkalinity Least environmental impact
Low pH Low Alkalinity High environmental impact
SM
Essential Expertise for Water, Energy and Air
61
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Function of Dispersant •
Prevent deposition commonly found minerals & inorganic particulates such as – – – –
•
Calcium phosphate Iron, Silt Zinc
Keep corrosion inhibitor “soluble” – To be able function the inhibitors must be dispersed in the water otherwise localized deposition will occur
SM
Essential Expertise for Water, Energy and Air
62
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Comparison Polymer Dispersant Condition
Conventional Dispersant Limit
High Stress Polymer Limit
Bulk Temperature, 0C
57
82
Velocity*, m/s
0.6
0.3
Holding Time Index*, hr
72
168
Calcium* (ppm)
750
1200
2
8
0.5
2
Iron (ppm) Aluminum (ppm)
Note * Depend of corrosion inhibitor program
SM
Essential Expertise for Water, Energy and Air
63
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanism of Chemical Scale & Fouling Inhibitors •
Scale Inhibitor Mechanisms – Treshold Inhibition & Crystal Modification – Sequestration – Scale conditioner (dispersant)
•
Fouling Inhibitor Mechanisms – Dispersant – Surfactants
Calcium Phosphate Crystal
SM
Essential Expertise for Water, Energy and Air
64
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanism of Chemical Scale & Fouling Inhibitors
SM
Essential Expertise for Water, Energy and Air
65
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Microbiological Control The goal is not to STERILIZE the system, but to MANAGE microbial fouling to a level that minimizes mechanical, operational, and chemical problems at an acceptable cost.
SM
Essential Expertise for Water, Energy and Air
66 66
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water •
Oxidizers (are usually the primary biocide) – Chemically oxidize organic components of the cell – Effective against nearly all microorganisms – Chlorine: as gas or bleach – Bromine: as NaBr or other bromine donors – Chlorine Dioxide
SM
Essential Expertise for Water, Energy and Air
67 67
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water Isothiazoline
DBNPA
•
Non-Oxidizing biocides – Organic compounds, react with cell components – Disrupt cell wall, metabolism, or reproduction
enyzm enyzm
– Effective to control specific organisms
amino
• Algae control
• Biofouling control Quat
• Pathogen control – Improved Bio-Control / BioManage practices
Glut
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Essential Expertise for Water, Energy and Air
68 68
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water •
Biodispersant & Bio-detergents –Disperse deposited particles –Improve the efficacy of biocides –Foaming could limit its application Before addition of biodetergent
After addition of biodetergent
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Essential Expertise for Water, Energy and Air
69 69
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Other Scale/Fouling Control Methods • Mechanical – – – –
Providing more cooling water flow HE modification Air rumbling, reverse flow and ball cleaning Install side stream filter
• Operational factor – Cycle management – pH control
SM
Essential Expertise for Water, Energy and Air
70
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Summary • ASU’s offers water treatment challenges – – – – – –
High skin temperatures Low flow Control capability Water chemistry Contamination Program limitations
• Understanding the MOC enables a complete understanding of the system stresses that need to be addressed
SM
Essential Expertise for Water, Energy and Air
71
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Summary • M – knowing the system • CT performance, H/E data, flows, temperatures, locations, etc. • Determine potential trouble spots. • Determine chemical program limitations.
• O – Operational variables • Control is very important for getting performance. Automation is best.
• C – Chemical variables • Scale and corrosion modeling with programs available. • Determine control limits.
SM
Essential Expertise for Water, Energy and Air
72
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Thank You!
SM
Essential Expertise for Water, Energy and Air
73
MOC Approach for Open Cooling Water System Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
1
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Agenda • Mechanical – Cooling tower – Heat exchanger – Metallurgy
• Operation – pH – Cycle
• Chemical – Makeup water chemistry
SM
Essential Expertise for Water, Energy and Air
2
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
3
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
4
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Why cooling is important? • Cooling tower performance provide significant contribution to the plant performance and efficiency • Poor cooling tower performance could limit the plant production
SM
Essential Expertise for Water, Energy and Air
5
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Impact of Cooling Water Temperature
o
o
A 3 C (5.4 F) increase in approach temperature (on all stages) is equivalent to a 1% increase in energy consumption
SM
Essential Expertise for Water, Energy and Air
6
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Function of Cooling Towers • Remove heat from process operation
• Mostly by evaporation (80%) –partially by sensible heat loss (20%) • of hot water with cooler air
SM
Essential Expertise for Water, Energy and Air
7
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Process •
As ambient air is drawn past a flow of water, a small portion of the water evaporate. The energy released by water for evaporation reduces the remaining water temperature
•
Evaporation results in saturated air conditions and lowers the temperature of the water to a value close to wet bulb air temperature
SM
Essential Expertise for Water, Energy and Air
8
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Types of Cooling Towers
SM
Essential Expertise for Water, Energy and Air
9
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Crossflow Cooling Tower
SM
Essential Expertise for Water, Energy and Air
10
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Counterflow Cooling Tower
SM
Essential Expertise for Water, Energy and Air
11
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Fill •
Purposes of Tower Fills – Increases the water surface area for air – Increases time
•
Main Types of Fill – Splash Fill – Film Fill
Tower Fill
SM
Essential Expertise for Water, Energy and Air
12 12
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Fill Characteristics
SPLASH
FILM
EFFICIENCY
Medium
High
DURABILITY
Medium
Low/Medium
Low
High
FOULING
SM
Essential Expertise for Water, Energy and Air
13
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Problems with Film Fill • Easily fouled with microbio and solids • Hard to clean once fouled • Quick loss of efficiency
Tower Fill SM
Essential Expertise for Water, Energy and Air
14
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Factors Affecting Cooling Tower Performance • Wet bulb temperature • Dry bulb temperature • Plant (heat) load – Cooling water ∆T
• Cooling water flow – No of pump running
• Air flow – Fan (tip, angle, motor; etc)
• Cooling water distribution – Distribution system – Fill cleanliness
SM
Essential Expertise for Water, Energy and Air
15
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Wet Bulb Temperature Measurement
• A measurement of the lowest temperature that can be achieved by evaporative cooling of a water wetted ventilated surface.
Sling Psychrometer
SM
Essential Expertise for Water, Energy and Air
16
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
COLD WELL TEMPERATURE, OC
Liquid to Gas Ratio
TYPICAL L/G
37
PERFORMANCE CURVES
L/G = 2.0
35 33
L/G = 1.5 L/G < 1, TOWER OVERSIZED
31
L/G = 1.0
- TURN OFF FANS OR DOWNSIZE
29 L/G > 2.5, TOWER UNDERSIZED AND WILL NOT PROVIDE LOW
27
APPROACH TEMPERATURES
25 12
14
16
18
20
22
24
26
WET BULB TEMPERATURE, OC
SM
Essential Expertise for Water, Energy and Air
17
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Air Flow Issue Air Recycling (Incorrect Tip)
•
Air flow is a critical component to ensuring the proper heat rejection from a cooling system
•
Many cooling tower performance issues may well be airflow problems
ROTATION Air In-leakage From Fan Shaft
Fan Stall (Incorrect Pitch)
SM
Essential Expertise for Water, Energy and Air
18 18
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
What is the Correct Way to Evaluate Cooling Tower Performance ? 1) CW temperature range (∆T) 2) Cooling tower heat load •
M x x ∆T
3) CW supply temperature 4) Approach temperature 5) Evaporation rate SM
Essential Expertise for Water, Energy and Air
19
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Monitoring – Cooling Tower
GPSA Nomograph: (require ∆T& wet bulb temperatures) Performance Factor proportional to: •L/G ratio (L = CW flow, G = air flow both in kg/hr) •RR (or L) •1/(Fan Power)1/3 Performance Factor > design means performance deteriorated
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger Essential Expertise for Water, Energy and Air SM
SM
Essential Expertise for Water, Energy and Air
21
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Why is This Important? • A critical component of the cooling system – Affect efficiency – Fouled exchangers also decrease throughput and capacity – Leaking exchangers can force unscheduled shutdown
• Also affect water treatment options – product selection and control limits
SM Water Distribution System
Essential Expertise for Water, Energy and Air
22 22
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger What We Need to Know ? • Type of heat exchangers • Hydraulic, mechanical and metallurgical • Mechanical stress to cooling water treatment • Performance monitoring
SM
Essential Expertise for Water, Energy and Air
23
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Type of Heat Exchangers There are several general types of heat exchangers: • Shell-and-tube
• Plate-and-frame
• Spiral flow
SM
Essential Expertise for Water, Energy and Air
24 24
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Shell and Tube Heat Exchanger (Water in Tube) • Most common heat exchanger type found in cooling water systems • Typically has adequate velocity – Throttle and spatial relationship could create problem
SM
Essential Expertise for Water, Energy and Air
25
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
A shell side heat exchanger offers challenges • Low velocity • High skin temperatures
SM
Essential Expertise for Water, Energy and Air
26
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanical “Stresses” Three main mechanical stress factors that impact the efficiency of heat transfer in heat exchanger are: 1)Cooling Water Velocity 2)Skin Temperature 3)Heat Flux
SM
Essential Expertise for Water, Energy and Air
27 27
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Water Velocity Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
> 1 m/s 0.6-1 m/s 0.3-0.6 m/s < 0.3 m/s
•
Scale and fouling deposition is more prone to occur at low velocity
•
Lower flow rate, lower turbulence that can lead to static thicker film of water at metal surfaces à reduces heat transfer
•
Lower velocity = higher skin temperature
SM
Essential Expertise for Water, Energy and Air
28 28
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Flux Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
< 7.5 kW/m2 7.5-25 kW/m2 25-40 kW/m2 > 40 kW/m2
• High heat flux will lead to high skin temperature • Typically v 3.15 – 15.8 kW/ M2 v 15.8 – 31.5 kW/ M2 v 31.5 – 63.1 kW/M2
: mild steel : alloy : copper or stainless steel
SM
Essential Expertise for Water, Energy and Air
29 29
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Skin Temperature Stress Range Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
< 500C 50 - 600C 60 - 700C > 700C
• Reasons: – Corrosion rates ~double for each 10°C increase in metal temperature – Scaling tendencies become much more pronounced at high temperature – Film boiling may occur as skin temperature – Some treatment chemicals break down at high temperature
SM
Essential Expertise for Water, Energy and Air
30 30
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Other Important Mechanical Factors 1) Spatial Relationship 2) Metallurgy
SM
Essential Expertise for Water, Energy and Air
31 31
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Spatial Relationship and CW Distribution
108C
115C
146C
101J Coolers
128C
2nd
116C 1st
3rd
124C
101JC
2002JC
127C
Primary Cooling Water Header Secondary Cooling Water Header
Tertiary Cooling Water Header Cooling Water Return Header
SM
Essential Expertise for Water, Energy and Air
32
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Metallurgy – Copper alloys • High thermal conductivity • Sensitive to ammonia and oxidant • Need film forming inhibitor
– Titanium • Self ivating metal • Extremely brittle with very thin walls • Leaks common (especially during initial commissioning and startup) • ANY mechanical impingement can cause leaks
– Stainless Steel • Self ivating metal • Subject to chloride stress corrosion • Must ensure cooling water chloride level remains within limits • Under-deposit corrosion, MIC issues
Ammonia Grooving
Under Deposit Corrosion / MIC
Pitting / MIC SM
Essential Expertise for Water, Energy and Air
33
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Chloride and Stainless Steel
PLANT DATA Duty Area
3,286,000
Btu/hr 424 ft2 Btu/hr.ft2 91.2 .C 7750 Btu/hr.ft2 6.111 ft/s 91 F 100 F 637 F 300 F
U Heat Flux Velocity T CW in T CW Out Process In Process Out CALCULATIO N T Skin Max T Skin
106.34 F 41.3 C 146 F 62 C
SM
Essential Expertise for Water, Energy and Air
34
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Importance of Heat Exchanger Monitoring Ø Prevent the loss of cooling Ø Predict Onset of Problems Ø Potential Surprises - scaled exchanger Ø Loss of production
Ø Useful to troubleshoot problems Ø Methodology using appropriate data Ø Documentation
SM
Essential Expertise for Water, Energy and Air
35 35
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Heat Exchanger Monitoring • Approach Temperature – Generally could represent HE performance – Approach = T Process Exit (air) – T Cooling Water Inlet (counter current)
• Others: C Factor, U Value, Fouling Factor; etc
SM
Essential Expertise for Water, Energy and Air
36
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
37
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Water Operation What We Need to Know ? • Basic mass balance calculation • Cycle management • Operational stress factor
SM
Essential Expertise for Water, Energy and Air
38
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cooling Tower Mass Balance Evaporation
Drift
Windage
Makeup
Windage
Blowdown
Cycled Water Leaks SM
Essential Expertise for Water, Energy and Air
Loss 39 39
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Blowdown to Reduce Cycles
1000 ml 150 umhos
500 ml 150 umhos
500 ml 150 umhos
500 ml 100 umhos
Cycles = 125/100 = 1.25 Cycles
1000 ml 125 umhos
SM
Essential Expertise for Water, Energy and Air
40
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Blow Down and Cycle •
Blow down – portion of the water ejected or drained from a system to control solids in cooling water
•
Cycle – number of times that dissolved minerals in cooling water are allowed to concentrate. Cycle is controlled by blowdown
•
Cycle = Dissolved Solids Concentration in Cooling Water Dissolved Solids Concentration in M-Up
•
In general, the cycle of concentration allowed depends on both the level of solids in the make-up and the level of solids that can be tolerated in cooling water
SM
Essential Expertise for Water, Energy and Air
41
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Basic Cooling Tower Calculations
SM
Essential Expertise for Water, Energy and Air
42 42
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Holding Time Index (HTI) • HTI is indicate the time required to reduce the chemical added to the system to 50% of its original concentration • HTI = 0.693 x Holding Volume Blowdown Rate • It is important to select the right chemical program
SM
Essential Expertise for Water, Energy and Air
43
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Operational “Stresses” Variation of operational and control parameters cause stress in cooling water systems. The key examples of operational stresses as follows 1)Variation of cycle 2)Variation of pH 3)Variation of HTI
SM
Essential Expertise for Water, Energy and Air
44 44
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of Cycle Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
<20% 20-50% 50-80% > 80%
% Out of Spec Low High Total 17.7% 5.3% 23.0%
SM
Essential Expertise for Water, Energy and Air
45
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of pH Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
Control Parameter pH
Lower Spec 7.50
SM
Essential Expertise for Water, Energy and Air
Upper Spec 8.00
+ 0.1 + 0.2 + 0.4 + 0.6
Statistical Calculations LCL Mean UCL 7.16 7.72 8.28
STD 0.19
46
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Variation of HTI Mild Stress Moderate Stress High Stress Severe Stress
Minimal effect of reliability Needs to be considered Will typically be a problem Typically a problem
SM
Essential Expertise for Water, Energy and Air
< 40 hrs 40 - 100 hrs 100 - 200 hrs > 200 hrs
47
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cycle and pH – Operating Window
SM
Essential Expertise for Water, Energy and Air
48
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Cycle Management
SM
Essential Expertise for Water, Energy and Air
49
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
SM
Essential Expertise for Water, Energy and Air
50
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Main Problems in Cooling Water Operation Related to Water Treatment There are basically four inter-related problems in the operation of a cooling water system as depicted by the Cooling Water Treatment Triangle below. Each problem affects and is affected by the other problems.
SM
Essential Expertise for Water, Energy and Air
51
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Corrosion •
A natural process converting processed metals to their native states
•
Factors affecting: - Water chemistry - Physical environment (temperature, velocity, hydrodynamic) - Dissolved gases - Halogen or other oxidizers - Deposit
SM
Essential Expertise for Water, Energy and Air
52
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Scale •
A dense, adherent layer of minerals tightly bound to itself and to metal surface
•
Factors influences - pH - Minerals concentration (Ca, Mg, SiO2, Alkalinity;etc) - Temperature
SM
Essential Expertise for Water, Energy and Air
53
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Fouling •
Deposits that formed from material suspended in water (clay, silt, iron, manganese, microbiological)
•
Factors affecting – Suspended solids concentration – Hydraulic and flow velocity – Spatial relationship – Scale, corrosion and microbiological
SM
Essential Expertise for Water, Energy and Air
54
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Microbio Fouling •
The most prevalent problems in industrial cooling water systems
•
A good control of microbial growth is essential if we are to control the other water chemistry problems
•
Factors affecting: – Suspended solids – Contaminants (organics, ammonia, phosphate; etc) – Physical factor (velocity and hydrodynamic) – pH
SM
Essential Expertise for Water, Energy and Air
55
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
General Methods for Corrosion Inhibition •
Use Corrosion Resistant Materials
•
Apply Inert Barrier or Coating
•
Use Cathodic Protection
•
Adjustments to Water Chemistry
•
Application of Corrosion Inhibitors
SM
Essential Expertise for Water, Energy and Air
56
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Corrosion Inhibitors – Cathodic & Anodic Cathodic inhibition Prevents the transfer of electrons à prevent the reduction of oxygen.
Anodic inhibition prevents the dissolution of the base metal, iron.
•
Combinations of both anodic and cathodic inhibitors generally provide the best protection.
•
These combinations are called “synergistic” because the combination provides lower corrosion rates than either inhibitor could alone,
SM
Essential Expertise for Water, Energy and Air
57
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Saturation Index as a Tool for Scale Control
WATER CHEMISTRY
pH
TEMPERATURE
SYSTEM DESIGN
SATURATION INDEX
PROGRAM DESIGN
VARY CYCLE
VARY pH
VARY TEMPERATURE
SM
Essential Expertise for Water, Energy and Air
VARY CHEMISTRY
58
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Saturation Index Reference Chart Moderate High Stress Stress Calcite 6 80 140 Aragonite 7 80 140 Anhydrite 1.2 3 4 Gypsum 1.2 4 6 Tricalcium Phosphate 50 1000 1500 Hydoxyapetite Insufficent Data Insufficent Data Insufficent Data Flourite Insufficent Data Insufficent Data Insufficent Data Silica 1.1 1.2 1.5 Brucite 1.1 1.2 1.5 Magnesium Silicate 6 7 8 Iron Use of SI not indicative of iron fouling problems Mineral Scale
Mild Stress
SM
Essential Expertise for Water, Energy and Air
59
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Comparison Scale Inhibitors Capability
AMP
PSO
HEDP
PBTC
PAPEMP
2
5
3
1
1
CaCO3 SI
105
80
100
180
200+
CaSO4
734
483
130
257
574+
Cl2 Stab
2
5
3
5
3
Thermal Stability
3
5
2
5
4
Corrosion Inhibition
Note: 5 Best, 1 Worst
SM
Essential Expertise for Water, Energy and Air
60
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Nalco Chemical Programs for Scale and Corrosion PSO-Phosphate Stabilized Phosphate
pHreedom All organic
Alkaline Zinc
Under-saturated (corrosive)
Calcium Carbonate (Calcite)Saturation
Over-saturated (Scale)
High pH High Alkalinity Least environmental impact
Low pH Low Alkalinity High environmental impact
SM
Essential Expertise for Water, Energy and Air
61
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Function of Dispersant •
Prevent deposition commonly found minerals & inorganic particulates such as – – – –
•
Calcium phosphate Iron, Silt Zinc
Keep corrosion inhibitor “soluble” – To be able function the inhibitors must be dispersed in the water otherwise localized deposition will occur
SM
Essential Expertise for Water, Energy and Air
62
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Performance Comparison Polymer Dispersant Condition
Conventional Dispersant Limit
High Stress Polymer Limit
Bulk Temperature, 0C
57
82
Velocity*, m/s
0.6
0.3
Holding Time Index*, hr
72
168
Calcium* (ppm)
750
1200
2
8
0.5
2
Iron (ppm) Aluminum (ppm)
Note * Depend of corrosion inhibitor program
SM
Essential Expertise for Water, Energy and Air
63
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanism of Chemical Scale & Fouling Inhibitors •
Scale Inhibitor Mechanisms – Treshold Inhibition & Crystal Modification – Sequestration – Scale conditioner (dispersant)
•
Fouling Inhibitor Mechanisms – Dispersant – Surfactants
Calcium Phosphate Crystal
SM
Essential Expertise for Water, Energy and Air
64
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Mechanism of Chemical Scale & Fouling Inhibitors
SM
Essential Expertise for Water, Energy and Air
65
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Microbiological Control The goal is not to STERILIZE the system, but to MANAGE microbial fouling to a level that minimizes mechanical, operational, and chemical problems at an acceptable cost.
SM
Essential Expertise for Water, Energy and Air
66 66
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water •
Oxidizers (are usually the primary biocide) – Chemically oxidize organic components of the cell – Effective against nearly all microorganisms – Chlorine: as gas or bleach – Bromine: as NaBr or other bromine donors – Chlorine Dioxide
SM
Essential Expertise for Water, Energy and Air
67 67
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water Isothiazoline
DBNPA
•
Non-Oxidizing biocides – Organic compounds, react with cell components – Disrupt cell wall, metabolism, or reproduction
enyzm enyzm
– Effective to control specific organisms
amino
• Algae control
• Biofouling control Quat
• Pathogen control – Improved Bio-Control / BioManage practices
Glut
SM
Essential Expertise for Water, Energy and Air
68 68
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Bio-Control Practices in Recirculating Cooling Water •
Biodispersant & Bio-detergents –Disperse deposited particles –Improve the efficacy of biocides –Foaming could limit its application Before addition of biodetergent
After addition of biodetergent
SM
Essential Expertise for Water, Energy and Air
69 69
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Other Scale/Fouling Control Methods • Mechanical – – – –
Providing more cooling water flow HE modification Air rumbling, reverse flow and ball cleaning Install side stream filter
• Operational factor – Cycle management – pH control
SM
Essential Expertise for Water, Energy and Air
70
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Summary • ASU’s offers water treatment challenges – – – – – –
High skin temperatures Low flow Control capability Water chemistry Contamination Program limitations
• Understanding the MOC enables a complete understanding of the system stresses that need to be addressed
SM
Essential Expertise for Water, Energy and Air
71
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Summary • M – knowing the system • CT performance, H/E data, flows, temperatures, locations, etc. • Determine potential trouble spots. • Determine chemical program limitations.
• O – Operational variables • Control is very important for getting performance. Automation is best.
• C – Chemical variables • Scale and corrosion modeling with programs available. • Determine control limits.
SM
Essential Expertise for Water, Energy and Air
72
Obtained from EDMS, Approved Electronic Copy. [Printed 08 Jul . 2011]
Thank You!
SM
Essential Expertise for Water, Energy and Air
73
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