Sugar Boiler Water Treatment Technologyjamaicasugar.org/SIRISection/JAST/JASTPapers/papers/Y2010/Boiler... · Sugar Boiler Water Treatment Technology 2010 Jamaica Association of Sugar

Confidential and proprietary to Garratt-Callahan Company

Sugar Boiler Water Treatment Technology

2010 Jamaica Association of Sugar Technologists(JAST)


Bagasse Boiler


Typical Firetube Boiler

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Confidential and proprietary to Garratt-Callahan Company4

Water-Tube Units– Water passes through (inside) tubes.– Used in power generation and industrial process steam.– Used for high pressure and high steam demand applications,

also used with low demand application too.– Best suited for large plants with steam turbines.– Very high and fast steaming rate, with low contained volume

of water.

Boiler Types


Water-Tube Units– Has large square feet of heating area.– Responds quickly to fluctuating steam loads.– Requires more care in water treatment, as tubes can get

plugged with scale, inhibiting circulation.– Has a steam drum and mud drum with interconnecting tubes.– Must be treated with preconditioned water. e.g. Softened.

Boiler Types


Water-Tube Unit Circulation

Boiler Types

Boiler Types

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Water-Tube Unit Types

Boiler Types

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Boiler Types

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Boiler System Overview

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Feed WaterTank or

Deaerator

Boiler

Ion Exchange

Makeup(Pretreatment)

BottomBlowdown

Steam

Condensate

FeedwaterPump

Load

SurfaceBlowdown


Condensate

• Condensate from the evaporators, pans and turbines supply in excess of 150% of the boiler feed water

• Condensate can be contaminated with sugar• Sugar contamination

– Drops the pH to acid levels under pressure.– Low pH feed water corrodes the tubes.– Corroded iron is laid down as scale on the tubes.– Sugar can caramelize and be laid down as carbon scale on the

tubes

Confidential and proprietary to Garratt-Callahan Company 12

Pre-Treatment Systems Sodium Cycle Cation Exchange

Strong AcidCation

ExchangerSodiumCycle

2HCO3

SO4

2Cl2NO3

CaMg2Na

CaMg2Na

SiO2

Influent

RegenerantNaCl

Regenerant Waste

CaCl2MgCl2NaCl

To Process

NaHCO Na2CO3Na2SO4

NaCl NaNO3SiO2

Make-up WaterSoftener

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Elution Study

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•Use a graduated cylinder and a Salometer

•Take samples every 5 minutes and plot curve.


Deaerating Heaters - Oxygen Removal .005 cc/L 7 pbb.


Dissolved oxygen:

– Can cause corrosive pitting attack on feed water/boiler surfaces.

– Usually caused by dissolved oxygen gas brought in by makeup water.

– Best removed with a deaerator (removes O2 down to 7 ppb).

– Oxygen scavengers are used to react with remaining amounts of oxygen.

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Deaerating Heaters

• Mechanical Deaeration– Spray Type– Tray Type– Atomizing Type


Deaerator

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Pressure vs. Temperature

• For every 1 # pressure there is a loss or gain of 3o F temperature

• 5 # pressure = 227o F • At 5 # pressure or 227o F the deaerator

removes O2 down to 7 ppb• Insure that you have gages to measure

both pressure and temperature


Deaerating Heaters

• Mechanical malfunction or flow control problems result in poor Oxygen removal.

• Causes of Improperly operating deaerators.– Inadequate venting.– Inadequate quantities of steam or steam pressure fluctuations.– Wide fluctuations in feed water flow.– Flow rates outside design specifications.– Malfunctioning spray nozzles, missing, plugged or broken.– Malfunctioning trays, missing, plugged or broken.

• Problems will almost always manifest as a broad temperature differential (>2°F; 1°C) between dome and storage section.


Oxygen Removal - Reducing Agents and Passivating Agents.

•Reducing Agents: Include a wide variety of oxygen scavengers and passivating agents, reducing agents are electron donors.

Oxygen scavengers react with dissolved oxygen directly.

Passivating agents react with iron and copper to form a protective oxide films even in the presence of up to 5 pbb dissolved oxygen.


Oxygen Removal / Passivation

Sodium Sulfite (or Bisulfite)Oxygen Scavenger:2SO3

= + O2 2SO4=

No Passivating PropertiesControl Range: Boiler Water

25-50 ppm <400 psig10-20 ppm 400-800 psig3-10 ppm 800-1250 psigNot Recommenced >1250 psig

Non-volatile, adds TDS, Can Poison Process catalysts.Not for use in attemperating water or standby in non-drainable superheaters.



HydrazineOxygen Scavenger:N2H4 + O2 2H2O +N2

Passivating Properties:N2H4 + 6Fe2O3 4Fe3O4 + 2H2O + N2

Control Range: Boiler Water20-50 ppb Feedwater at economizer inlet.

Passivates iron and copper, Does not increase TDS, non-volatile, suspect carcinogen, and breaks down to ammonia.



Diethylhydroxylamine (DEHA)Oxygen Scavenger:4(C2H5)2NOH + 9 O2 8 CH3COOH+ 2N2 + 6H2OPassivating Properties:2(C2H5)2NOH + 27Fe2O3 18Fe3O4 + 4CH3COOH + 3H2O + NControl Range: Boiler Water

100-150 ppb Feedwater at economizer inlet.

Very similar to hydroquinone but: generates very little ammonia, volatile, and not as thermally stable. Volatizes with steam.



• Chemical Feed Considerations– Use stainless steel feed systems.– Use floating lids to minimize loss of products.– Use high purity, warm condensate or deaerated water

to prepare feed solutions. Never use cold water.– Limit agitation of the feed solution to 1-2 minutes– If there is no attemperation (control of superheated

steam temperature), any of the products may be fed to the deaerator storage section, just below the waterline.

– With attemperation, all sulfite products, are to be injected after attemperation takeoff.


Dissolved Oxygen Analyzer

The Series μAI-9060 Dissolved Oxygen System is a state-of-the-art microprocessor-based instrument package developed specifically for use in measuring low and high concentrations of dissolved oxygen in the power, desalination, and petrochemical industry.

•Disposable DO Sensor

•Automatic Calibration

•Auto Range Switching


Internal Boiler Water Treatments

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Internal Boiler Water Treatment Programs

• Carbonate Cycle• Phosphate-hydroxide• Coordinated pH-phosphate• Phosphate and polymer• Chelant Treatment and/or chelant polymer• All-polymer


• Chelant Treatment and/or chelant polymer– Chelant react with residual divalant metal ions

to form soluble complexes.– The complexes are removed through continues

blowdown.– Inconsistency in boiler water chemistry create an

imbalance:• Excessive chelant will result in attack on boiler

tubes. • The presents of dissolved oxygen will result in

greater deposition problems.



• All-polymer– Polymers maintain clean heat transfer surfaces in

several ways: scale inhibition, metal ion solubilization, crystal modification, and particulate dispersion.

– Polymer inhibit scale formation by disrupting the growth of deposits.

– Carboxylated polymers will form a soluble complex with feed water hardness.

– Polymers cannot be tested in process for residual, therefore inbalances in boiler water chemistry create dosing problems


Crystal Modification

Crystal Modification


• Phosphate and polymer– Phosphate precipitation.– Polymers disperse particles.– Polymers alter particle surface area and

surface charge to non scaling.– Can clean scaled boiler online.– Can be measured in process


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THE HIDDEN COSTS OF BOILER WATER TREATMENT

AN EVALUATION OF BOILERS IN THE LOUISIANA SUGAR INDUSTRY

James A. Cuddihy, Jr., Walter J. Simoneaux, Robert N. Falgout, and James S. Rauh


Do you have Boiler Problems?

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Facility:Date 3/17/2004

Boiler Clean Slightly Moderately Heavily Chipped Pit UnderTube Scaled Scaled Scaled Scaling Corrosion Scale

Corrosion

Boiler # Ctr Tube X Iron Oxide XDn Cmr X

Up Comr X XCtr Tube X XUp Comr X X

Dn Cmr X X

Boiler # Ctr Tube X XDn Cmr X XUp Cmr X X

Ctr Tube X XUp Cmr X XDn Cmr X X

Boiler # Ctr Tube XDn Cmr XUp Cmr X

Ctr Tube X XUp Cmr X X XDn Cmr X X

Boiler # Ctr Tube XDn Cmr X XUp Cmr X

Ctr Tube

Borescope Observation Form

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Borescope SummaryMill Clean Slightly Moderately Heavily Chipped Pit Under

Tube Scaled Scaled Scaled Scaling Corrosion Scale

8 Mills / 43 Boilers / 222 Tubes 1/32" 1/16"+ Corrosion

A 3 4 10 2 1 3

B 6 10 12 9 3 7 7

C 3 8 16 7 15

D 3 15 1 2 3

E 1 1 18 3 1 1

F 5 12 19 2 26 4

G 2 1 7 25 7 11 20

H 9 12 5 5 6 5

Total 24 51 55 92 24 54 58

Average 10.8% 23.0% 24.8% 41.4% 10.8% 24.3% 26.1%


Scale/Deposit Formation

• The primary reason for deposit and scale formation in steam generating systems is the fact that the solubility of many of the deposit forming salts decreases with an increase in temperature and concentrations. The water constituents usually responsible for these deposits are:

Calcium (Ca) Magnesium (Mg)Bicarbonate (HCO3) Iron (Fe)Sulfate (SO4) Carbonate (CO3)Silicate (SiO2) Phosphate (PO4)


Light Scale (1/32”)

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Light Scale (1/32”)


Calcium Phosphate Scale Typical 1/16” Deposit


Heavy Scaling


Heavily Scaled


Heavy Scale

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Heavy Scaling / Corrosion

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Chip Scale


Chip Scale

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Pit Corrosion

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Pit Corrosion


Pit Corrosion

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Scale & Corrosion


Under Deposit Corrosion

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EFFECTS OF DEPOSIT AND SCALE FORMATION

1. Heat transfer is retarded

• Boiler tube metal temperatures increase. The approximate softening temperature of boiler tube metal is about 900 0F. If heat retardation of boiler deposits causes this temperature to be reached, tube softening and rupture will occur.

• Even when deposit build-up may not be sufficient to cause tube failure, their insulating effect may still result in reduced boiler operation efficiency and energy wastage by allowing excessive heat to exit the boiler with the stack gas.


2. Deposits in boilers can reduce circulation through tubes.

• This encourages further deposit formation due to the reduction of the washing effect of circulating water on solids concentrating at heat transfer surfaces.

• Since deposits are poor conductors of heat, they retard heat transfer from combustion gases.


3. Deposits can also create differential corrosion cells beneath their surfaces (under scale corrosion).

• The result is localized corrosion or pitting. If such corrosion is severe, boiler metal can become thinned and weakened, resulting in ruptures due to internal boiler pressure.


Fuel Value of Bagasse

• 1 mt fresh bagasse fiber – (50% moisture)

• 2.2 barrels of fuel oil – (assuming 58% boiler efficiency)

• 13,200 cu ft of natural gas – (assuming 75% boiler efficiency)


Cost of Scale Formation Assumptions

• Mill grinds 10,000 TC/Day

• Bagasse = 33% of cane weight

• Fuel Prices– Fuel oil = $100.00 /barrel

• 1 ton of bagasse = 2.2 barrels of oil– Natural gas = $7.50 / mcf

• 1 ton bagasse = 13.2 mcf


What is the Cost of Scale?Mill grinding 10,000 tons cane per dayTons bagsse 3,300

Scale % Fuel Tons Bagasse Fuel Oil Natural GasThickness Wasted Wasted Cost Cost

($100 x 2.2 x bwt) ($7.50 x 13.2 x bwt)

1/32" 7% 231 $50,820 $22,8691/25" 9% 297 $65,340 $29,4031/20" 11% 363 $79,860 $35,9371/16" 13% 429 $94,380 $42,4711/11" 15% 495 $108,900 $49,0051/9" 16% 528 $116,160 $52,272


Additional Costs of Scale Formation

• Production Downtime• Mechanical Cleaning of Boilers• Acid Cleaning of Boilers• Tube Replacement• Increased Use of Boiler Water Chemicals


FIELD ANALYSIS Plant of: Date: November 19,2003AND Address:

SERVICE REPORT Attention: Copy To:

Midland Copy To:

SAMPLE FROM

pH P M OH Cl TH CaH

Fe Cu mmhos

SO3N2 H4

PO4 Mo O-P

NO2

Feedwater 12.4 60 64 20 0 .14 .02 280 2.5 0.0

Boiler #G 12.7 76 136 16 56 28 3.33 .07 2600 12.5 .10

Boiler #A 12.1 28 60 4 16 84 4.00 1.94 1200 5.0 7.9

Boiler #B12.6

80 124 36 40 92 4.10 2.25 2800 15.0 0.0

Boiler #C12.4

60 115 5 24 28 4.20 4.60 2300 12.5 0.0

Boiler #D11.8

20 28 12 16 20 3.56 4.63 660 5.0 0.6

Boiler #E11.9

24 40 8 8 68 3.06 .77 800 5.0 1.9

Boiler #F 12.5 64 76 52 16 80 4.21 2.34 2200 2.5 0.1

Control Range

9.511.5

700150300

0 0.10

.05

20003000

2040

2040

Field Analysis


Boiler Tube Scale Deposit Analyses

Constituent % Dry WeightTube #1 Tube #2

Calcium Phosphate 10.7 15.0Calcium Carbonate 5.0 0.0Iron Oxide 65.0 51.8Copper II Oxide 10.0 11.2Magnesium Hydroxide 5.8 7.2

Magnetic Yes Yes


Hawaiian Sugar Mill

• Produces 60,000 tons raw sugar annually• Generates electric power for HELCO utility grid

BOILER PLANT - STARTUP 1972• Babcock & Wilcox - Sterling, two drum design• Operating Pressure 1200 psi• 825 oF Superheated Steam• Boiler Rating 375,000 lbs steam per hour• Operating Load 330,000 lbs steam per hour (average)• Turbine Generator - 23,800 kW• 160 psi Extraction Steam Used For Factory Operation• Condensate Return Averages 85%• Demineralized Makeup• Cochrane Deaerator


NEW DIRECTIONS IN BOILER WATER TREATMENT

• Phosphate Polymer Technology• combines internal phosphate treatment with the

latest in synthetic polymer technology• blends of polymers formulated to deal with specific

problems• enhanced thermal stability for high pressure boiler

performance• gives improved phosphate stability for hardness

control• disperses metal oxides and transports them

through the system• provides on-line removal of deposition - including

metal oxides


CHEMICAL TREATMENT PROGRAM RESULTS

• Tube failure in old section of arch tubes• Boiler inspected:

• one leak found in a waterwall tube• lesser amounts of loose deposit found in boiler• significant removal of old deposit on waterwall

tubes• new (replaced) arch tube sections deposit free


• Tube samples• Arch (Nose) tube and waterwall tube


• Sections cut from waterwall tube• A - “bracelet” distorted• B - “hot” side• C - “cold” side


• 1 inch length tube “bracelet”• Distorted to show extent of deposit

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Original deposit condition• Waterwall tube removed


• 8X magnification

• Original deposit on waterwall tube removed


• Deposit condition after 12 months on Polymer Program

• Adjacent waterwall tube removed• Significant removal of old deposit



• Diminished deposit on adjacent waterwall tube removed after 1 year


• New Arch tube installed

• No adhering deposits



• Clean arch tube after one year


Identifying Sugar Incursions

• Conductivity meters cannot measure sugar in boiler feed water– You measure the carryover solids (i.e.; ammonia,

non-sugars, organics)• Tracers and florescence light have not proved effective

at identifying sugar incursions at ppm.


Conductivity Meter Setup

1. Install automatic dump valve prior to feed water storage tank2. Place conductivity probe in condensate line prior to the dump

valve 1. False sugar positives will occur during stop and go

production as ammonia will buildup and set-off the alarm3. Set the conductivity valve set-point just above the background

reading4. When the conductivity meter sets off the alarm, the dump valve

should open automatically5. Factory personnel should test the water with Alpha-Naphthol

Test1. Find the point of contamination or if it was a false positive,

close the automatic valve.


Steam Treatment: Sugar Industry

Due to the ammonia carryover from the organics in the evaporators, the residual effect maintains a high enough pH so that amines are not normally needed for steam line treatment.

Chemical Feeding Methods and Feed Points

Feed WaterTank or

Deaerator

Boiler

BottomBlowdown

Steam

Condensate

FeedwaterPump

Load

SurfaceBlowdown

12

Economizer

3 3a

4

5

Treatment Feedpoint

Sulfite 1

Hydrazine 1

Sludge Conditioner 2

Chelant 3 or 3a

Phosphate 4

Neutralizing Amine 2,4,or 5(a)

Filming Amine 5 or 3a

(a) Must be diluted with condensate of feedwater.


Boiler Blowdown

• Surface blowdown– Removes dissolved solids, controls the

cycles of concentration.• Bottom blowdown

– Removes suspended solids, normally done once a shift for 5-10 seconds. Do not use to control cycles.


Anti-Foams

1. Counteracts the surfactant effect of High TDS, suspended solids, oil, or other organics.

2. May be more economical than increased blowdown or additional external treatment.

3. Frequently reduce fuel consumption by permitting lower blowdown rates while producing high quality steam.

4. Will only help with normal entrainment. Will not prevent volatile (Silica) carryover.


Anti-Foams

•Two types:

•Polyglycols

•Use in all boilers.

•Feed directly to boiler drum.

•Silicone

•Use in boilers with low operating pressure.

•Feed directly to boiler drum.

•Use in very small applications.

Sugar Boiler Water Treatment Technologyjamaicasugar.org/SIRISection/JAST/JASTPapers/papers/Y2010/Boiler... · Sugar Boiler Water Treatment Technology 2010 Jamaica Association of Sugar

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