Presented by Steve Connor January,...

Basic Deaerator Science Revealed

Presented by Steve ConnorJanuary, 2015

Component Selection &

Sizing

What is Deaeration?

Types & Operation When to Apply

Benefits Hydrological Cycle

What We Are Covering Today

2

Basic DeaeratorScience Revealed

The Hydrologic Cycle

3

Water the Universal Solvent

4

Dissolved Solids

Dissolved Gasses

Suspended Solids

CO2

CO2

Aluminum Chlorides

FluoridesNa2SO4

Mg(HCO3)2CaSO4MgSO4 MgCl2

O2

O2

O2O2

CarbonatesIronCO2

Calcium

SilicaSodium Magnesium

Manganese

Sulphates

5

Tolerances are Based on Pressure & Temperature

6

Feed Water Boiler WaterOxygen & CO2 SilicaIron & copper Total AlkalinityTotal Hardness Free OH AlkalinitypH Specific ConductanceNon-Volatile TOC(Total Organic Carbon)

Oily MatterASME Guidelines:

Broken down by feed water and boiler water, and then by firetube and watertube boilers.

Water Constituent Tolerance: 0-300 operating psig

Mechanical Chemical

7

Most Economical Long-Term Approach

Water Quality: Dissolved Gases

2 2

8

Today we’re concentrating on…

Oxygen CorrosionIron begins to dissolve when in contact with water.

Fe + 2H2O = Fe(OH)2 + 2H+

Iron + Water = Ferrous Hydroxide + Hydrogen


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Now add in dissolved O2

Process continues until 1 of 2 things occurs

1. No more dissolved O2

2. No more iron Fe

4Fe(OH)2 +O2 +H2O= 4Fe(OH)3Ferrous Hydroxide + Oxygen + Water = Ferric Hydroxide (RUST)


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Corroded Boiler Tubes

11

Firetube Watertube

Blisters

Holes

Courtesy:http://www.engineeringtoolbox.com/oxygen-steel-pipe-...

50 F

86 F

122 F

2 times more corrosive at 122oF than at 86oF


X

X

Carbon Dioxide – Friend or Foe?

2


13

Combines with Water to Create Carbonic Acid

CO2 + H2O = H2CO3

Creation of CO2 from Carbonates

Courtesy:http://www.spiraxsarco.com/resources/steam-engineering-tutorials/the-boiler-house/water-treatment-storage-and-blowdown-for-steam-boilers.asp


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15

CO2 gas combines with condensate forming carbonic acid; corroding pipes and heat transfer units.


Carbonic Acid attack

Carbon Dioxide AND Oxygen:

CO2

Carbon Dioxide together with Dissolved Oxygen is 40 percent more corrosive than if the two were acting alone.

O2


Dissolved Oxygen is 10 times more corrosive than CO2

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OK….what do we do?

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Solution to Manage These Gasses

Raise the Temperature!

2

Water Quality: Dissolved Gasses

CO2

18

19

10

0

2

4

6

8

21019017015013011090705030

Oxy

ge

n C

on

ten

t, p

pm

Temperature, Degree F.

Free Gases Are Insoluble At Saturation TemperatureWater Quality: Dissolved Gases

Manage pH @ approx. 11

CO2


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Reducing Surface Tension

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Mechanical Removal

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Deaeration Removes• Oxygen• Free Carbon Dioxide

Heat Agitate Liberate

• Spraying or filming – Reduce surface tension• Heating – Losing solubility• Mechanical – Agitation & scrubbing - Liberating• Releasing O2 & CO2 to atmosphere in gaseous form

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DA Methods: Operation

DA & Holding Hot Condensate

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Saturated Steam Table

Pressure (psig) 5 10 80 100

Saturation Temp 227.3 239.5 323.9 337.9

Volume (ft3/lb) 20.3 16.46 4.66 3.89

Sensible Heat (btu/lb) 195.5 207.9 294.4 308.9

Latent Heat (btu/lb) 960.5 952.5 891.9 880.7

Total Heat (btu/lb) 1156 1160.4 1186.3 1189.4

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Zero Condensate Returned800 HP Process Boiler• Evaporates 27,600#/HR• Incoming feedwater temperature is 50 Deg. F• DA operating at 5# (227 Deg. F)• 227 Deg. F – 50 Deg. F = 177 Btu/#• 27,600# X 177 = 4,885,200 Btu’s per hour• @ $0.50 per Therm (100,000)• 4,885,200/100,000 = 49 Therms/HR X $0.50 = $25.00/HR• $25.00 X 4000 = $100,000/Year in FW heating cost

XAll Condensate

Dumped!

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Return Some Condensate to Feed System

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800 HP Process Boiler• Incoming FW Temperature is 125 Deg. F• 227 Deg. F – 125 Deg. F = 102 Deg. F • 27,600 X 102 = 2,815,200/100,000 = 28 Therms/HR• 28 X $0.50 = $14.00/HR X 4000 HRs/YR = $56,000/YR

• Savings is $44,000 per year!

A Blend of RawMakeup & Condensate125 Deg. F DA

Deaerator Applications

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• Boiler plants @ at 75 PSIG or higher

• Plants with no standby capacity

• Plants with critical loads

• Plants operating with 25% makeup or more

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7,000 – 280,000 pph

Types of DeaeratorsSpray Type

Spray cone

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Types of DeaeratorsSpray Head Design

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1,500 – 135,000 pph

Deaerating Column

Storage Tank

Packed Column TypeTypes of Deaerators

Packed Column DA

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Deaerating Column

Makeup Water In

Storage Tank

O2 & CO2 Vent

Corrosion Proof Rings

Steam In

Spray & Vent Condensing Section

Types of DeaeratorsTray Type

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30,000 – 1,200,000 PPH

40,000 PPH1,000,000 PPH

Tray DA

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Makeup/Condensate In

Spray Valve Assembly

Vent Condenser

Trays

Deaerated Water Downcomer

SteamInlet

High Temp. Returns

Advantages & Disadvantages

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Type Advantages DisadvantagesSpray • Head room

• Weight• Price• Capacity

• Mechanical components

• Critical adjustments to steam nozzle

• Limited HP returnsColumn • DA consistency

• Reliable• HP returns

• Head room• Weight• Limited capacity• Price

Tray • DA consistency• Reliable• HP returns• Highest capacity

• Head room• Weight• Price

Saturated Steam Table

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Pressure (psig) 5 10 80 100

Saturation Temp 227.3 239.5 323.9 337.9

Volume (ft3/lb) 20.3 16.46 4.66 3.89

Sensible Heat (btu/lb) 195.5 207.9 294.4 308.9Latent Heat

(btu/lb) 960.5 952.5 891.9 880.7

Total Heat (btu/lb) 1156 1160.4 1186.3 1189.4

High Pressure Receiver Tank

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• Takes high pressure condensate directly from the user

• No need to deaerate• Pump directly into

boiler• Feed the HPCR from

the DA

DA Component Selection & Sizing

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Spray Type

Spray Cone & Tank Assembly

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Formulas:• 200 HP X 34.5 = 6900#/HR• 6900/8.3 = 831 Gallons/HR• Tank storage: 10 minutes = 150 Gal.

Makeup Valve• Mechanical• Pneumatic• ElectronicSteam

H.P. Return

Vent

Exhaust OrFlash Steam

ToBoiler

Boiler FeedWater Pump

OverflowDrainer

Cold Make-UpWater

L.P. Condensate

Make-Up Valve

Check Valve

Formula:SQ Root of inlet press. – tank press. – nozzle press XCv = GPM

Example: (50# - 5# - 7#) = 6.1 X 12 = 73.2 GPMSQ Root

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Steam

H.P. Return

Vent

Exhaust OrFlash Steam

ToBoiler

Boiler FeedWater Pump

OverflowDrainer

Cold Make-UpWater

L.P. Condensate

Make-Up Valve

Check Valve

PRV

Selection Sequence:1. Maximum pumping rate of DA2. Estimate Average mix temperature of FW3. Determine amount of steam to heat FW to saturation4. Determine PRV size based on boiler operating

pressure

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Centrifugal Pumps

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Flexible Coupled Close Coupled

Vertical Multi-Stage

Flow:• BHP X Evaporation Rate = GPM• GPM X Safety Factor

- Continuous = 15%- Intermittent = 50%

TDH (In pounds or 2.31 feet of head )• Total Dynamic Head or…

Discharge Pressure Requirement for the pump to attain

• Specific gravity

NPSHR• Net Positive Suction Head Required• 2.31 Feet per pound

Formulation Example:Flow200 HP X 0.069 = 13.8 GalContinuous: X 15% = 16 GPMIntermittent: X 50% = 21 GPM

TDH DutyBoiler operating pressure + FW valve loss +Line loss = Total pressure loss X 2.31 = Total loss in Feet of Head/SG

<100# + 25# + 5# = 135 X 2.31 = 301 Feet of Head/0.95 = 317’>

NPSHRRead from the pump curve at the respective duty points

Centrifugal pumps

44

Vertical Multi-Stage

Centrifugal Pump Curve

100

200

300

400

500

20 40 60 80 100 120 140 160

10” Dia.

9” Dia.

8” Dia.

7”Dia.

6” Dia.

5” Dia.

3' 4' 5' 6' 7'8'

NPSHR

Hea

d in

Fee

t

Capacity in GPM

280

180

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Centrifugal Pump Curve

100

200

300

400

500

20 40 60 80 100 120 140 160

10” Dia.

9” Dia.

8” Dia.

7”Dia.

6” Dia.

5” Dia.

3' 4' 5' 6' 7'8'

NPSHR

Hea

d in

Fee

t

Capacity in GPM

X X

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Stand

47

Height depends on NPSHR for Pumps versus NPSHA

Safety Valve(s)

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Sizing considerations:1. Normally set at DA design pressure2. Must handle full output from PRV @ boiler’s safety valve setting

Summary

DA Benefits:- Hotter boiler feedwater saves fuel energy (10 Deg. F rise = 1%)- Saves on chemical costs- Reduces blow down; saves water, chemicals and sewer charges- Better protects the boiler and piping system; reduces downtime &

capital expense- Reduces thermal shock

MAJOR TAKE-A-WAYS- DA removes O2 & CO2

- O2 corrosion increases with temperature- CO2 is 40% more corrosive with O2 present- DA’s reduce water surface tension, heat, agitate & liberate gasses- Three types; Spray, Tray & Column- Return condensate as hot as possible- Spray is limited in the amount of high temp condensate it can handle- Changing duty points on a pump can cause cavitation.- Safety valves are the last line of defense!

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Contact Us

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Thomas LeunigProduct Manager-Packaged

Water [email protected]

Jesse SteffenSales Engineer-Packaged

Water [email protected]

Presented by Steve Connor January,...

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