TECHNICAL BOILER TRAINING

IntroductionWater is the raw material most used in nearly all industries.

US industry uses about 140 billion gallons per day.

Refinery Water Uses

Area

Per Cent

Boiler Make Up

Cooling Tower Make Up

Process Make Up

Desalter Make Up

Sanitary & Lab

30%

60%

1%

4%

4%

The Water MoleculeOxygen and hydrogen share electrons - this is called covalent bonding.

The bond angle is 105 degrees.

105 degHHO

The Hydrologic Cycle

FUNDAMENTALS OF AVAILABLE WATERSURFACE WATERLower in dissolved solidsHigher in suspended solidsQuality changes quickly with seasons and weatherGROUND WATERHigher in dissolved solidsLower in suspended solidsHigher in iron and manganeseLow in oxygen, may contain sulfide gasRelatively constant quality and temperature

Basic Water Chemistry

FOUR IMPORTANT CHEMICAL PROPERTIES OF WATER ARE:

1. Conductivity2. Hardness 3. Alkalinity 4. pH

CONDUCTIVITYA Measure of the Total Dissolved Solids (TDS) in the Water. Read in S/cm

Approximation:ppm TDS x 1,8 = S/cm

HARDNESSThe amount of Calcium and Magnesium ions in the waterTotal hardness and Ca-hardness

Read in ppm CaCO3

Water - the Universal SolventWater is a poor conductor of electricity.

As more ions dissolve, water becomes a better conductor.

Water - the Universal SolventThis phenomenon is used to indicate total dissolved solids.

ALKALINITYCarbonate or Bicarbonate Ions that Can Cause Scaling Problems together with Ca, Mg Ions.

Read in ppm CaCO3

Acid - Base ChemistryThe most common buffering system encountered in industrial plants is the carbonate buffering system.

pH

Acid - Base ChemistryThe actual distribution of carbonate speciesCO2HCO3-CO3=Carbonate Buffering System0102030405060708090 10000.81.62.43.244.85.66.47.288.89.610.411.21212.813.6pHMolar ratioCO2HCO3-CO3=

Acid - Base ChemistryExpressing hydrogen ion concentrations:

pH = negative log molar concentration of H+

pHH+ Conc.51.0 ppb60.1 ppb70.01 ppb80.001 ppb

Water - the Universal SolventExpressing the levels of dissolved solids:

per cent - used for concentrated solutionsppm - a weight relationshipppm as CaCO3 - an equivalent weight relationshipmg/l - same as g/ml - in dilute waters, same as ppm

FUNDAMENTALS OF WATERSPECIFIC HEATis the measure of how well a substance can absorb heat 1 Kcal/kgC

VAPORIZATION HEATEnergy to transform liquid to gaseous970 Kcal/kg at 100C

PretreatmentFiltrationSoftenerDealkalizerReverse OsmosesDemineralizer Dearator

PRETRATMENTSOFTENER

Softener - Ion Exchange ProcessIon Exchange ResinWater

Four Steps of Softener RegenerationBackwash

Brining Slow Rinse

Fast Rinse

Ca, MgNa, Na

Boiler tube failuredue to scaling andoverheating of tubemetal over critical temperature for steel

This leads to partialdestroyed boiler sectionsand even boiler explosion

Deaeration:Water Temperature is Increased So That CO2 and O2 Are Released from the WaterWater is Broken Into Small DropletsCO2 and O2 Are Removed By Venting

Solubility of Oxygen vs Temperature and Pressure

Oxygen CausesPitting Attack of metal due to Oxygen CorrosionIncreased Iron content in condensate/boilerIncreases TDS in boilerCorrosion CellDearator

Pitting by Oxygen Corrosion

Spray Deaerator

Tray Deaerator

Venting Requirements for Tray Deaerators

Types of Deaerating EquipmentOpen feedwater heaters0.5 to 1 ppm O2Vacuum degasifiers 0.29 to 0.43 ppm O2 2 to 10 ppm CO2Deaerators and deaerating heaters0.04 ppm O2 for heater0.007 ppm O2 for deaerators95% of free CO2

Major ProblemsCorrosion Scale

Boiler CorrosionTypes of CorrosionOxygen corrosionAlkalinity concentrationCaustic corrosionAcid corrosionChelant corrosionErosion/Corrosion

Effect of pH on Boiler Corrosion

Effect of Scale on Heat Transfer

Effect of Scale on Tube Temperature

Scale ProblemsBoiler tube failure

Caused by reduced heat transfer and tube overheating

Under-deposit corrosion

Caused by high concentration of corrosive agents (usually NaOH)

Scale PreventionPrecipitation of hardness in the boilerReduce amount of hardness entering boilerKeep the hardness soluble

Treatment With Makeup SofteningRequirements for SuccessProper Operation and Maintenance of Make-up EquipmentChemical Conditioning for Residual Hardness

Process Objective To produce the required amount of Steam

To produce the required pressure Steam To produce the required purity Steam To produce Steam efficiently

How Is the Steam UsedHeat only Steam drives such as turbines Is process contamination a concern

The Generation of Steam Is Energy IntensiveNeed to minimize the amount of energy used Need to maximize efficiency of the boiler An understanding of how a boiler works and proper measurements can reduce energy usage.

Make-up WaterPrimary PretreatmentCondensateSteam HeaderBoilerDeaeratorChemical Feed SystemsFeedwaterBlowdownSecondary Pretreatment

Boiler:Produces SteamVariety of Shapes and SizesVariety of FuelsWide Range of Operating Pressures

Boiler CalculationsCalculations

Fire-Tube Boiler

Fire-Tube Boiler - Circulation

Water - Steam - Condensate System POTENTIAL PROBLEM

Why is CondensateNaturally Corrosive?Alkalinity in Boiler Breaks Down to CO2CO2 Leaves with SteamSteam Condenses with CO2 to Form Carbonic Acid

Why is Condensate corrosive?Alkalinity of BFW breaks down in Boiler Bicarbonate 2 NaHCO2 Na2 CO3 + CO2 + H2O Soda Na2 CO3 + H2O 2 NaOH + CO2 CO2 leaves with steam and reacts with condensed water droplets to Carbonic Acid CO2 + H2O H2 CO3 Carbonic acid Acid attack to metals low pH

% ConversionPressure (bar)Caustic

Typical Condensate CO2-Corrosion

Boiler Feedwater TreatmentINTERNAL TREATMENT

SCALE and DEPOSITS prevention

Phosphate Residual ProgramsBlend of Ortho- or Polyphosphate Chemically Remove Hardness from FeedwaterHelps Corrosion ProtectionPrecipitates Hardness and IronPO4-3 + Ca+2 Ca3(PO4)2 in combination with Organic Polymers Polymer Disperses Ca3(PO4)2 Sludge Keeps it from sticking to the Tubes

Chelant/Polymer ProgramsChemically Complexes HardnessPolymer Disperses IronContains EDTA or NTAKeeps Hardness from Forming Scale in BoilerImproves Boiler Cleanlinessif overfed aggressive to Metal surfaces!!!

(NTA3 + Ca+2 NTA Ca)Chelant maintains the Ions in a Soluble State thus:No Suspended Solides to Bake onto Boiler Tubes

Types of Sludge ConditionersSynthetic polymersTanninsLigninsStarches

Phosphate-Polymer ProgramsAdvantageCan provide much cleaner boilers than other conventional Phosphate programs DisadvantageRequires much stricter control of feedwater hardness and chemical program

Boiler Feedwater TreatmentOXYGENSCAVENGER andPASSIVATOR

Anorganic and Organic

SULFITE

Chemically reacts with oxygen (O2) to remove it from the boiler feedwaterReduces Corrosion PotentialDoes not form Magnetite no PassivationIncreases the TDS/conductivityFast reaction only if catalyzed

HYDRAZINEHYDRAZINE has long been the most applied Scavenger in Demi water systemsDoes not increase TDSPassivates Iron and Copper metallurgiesIs Slow reacting - does not protect sufficiantly: Condensate hot well and Preheaters Decomposes at high Temperature >340 oC, forming AmmoniaBad neutralization due to NH3 V/L distributionServe Cu corrosion in case of Oxygen inleakage Is Toxic and suspected Carcinogen (OSHA/NIOSH) at air levels attained in utilization areas

Carbon Dioxide SourcesBreakdown of feedwater alkalinity2 HCO3- CO3= + H2O + CO2 Bicarbonate Carbonate Water Carbon DioxideCO3= + H2O 2OH- + CO 2Carbonate Water Hydroxide Carbon Dioxide

Air inleakage

pH Values of Solutions of Carbon Dioxide in Pure Water at Various Concentrations

Steam Traps

CONDENSATE TREATMENTNeutralizing and Filming Amines

Neutralizing AminesNeutralize Carbonic Acid to protect condensate systems from corrosive AttackMinimize Condensate Corrosion also in large condensate systems - Mixture! Different Vapor/Liquid distribution ratioKeep condensate pH between 8.5 and 9.0Reduce Iron levels in condensate return

Filming/Neutralizing AmineIncrease low condensate pHProtect when large amounts of Carbonic Acid are presentEffective between pH of 6.5 - 9.0Provide protection from Oxygen AttackHelp prevent Iron/Copper deposits in boiler system

Oxygen Corrosion in Condensate line

Filming AmineRepels condensate water droplets from surface and protects againstCO2 and O2

Optimum OperationWater & Fuel Cost

Water CostCity Water Cost: 1.00 L.E

Soft Water Cost: 1.25 L.E

Salt, water required for regeneration, resin replacement , depreciation

Fuel

Fuel Type: Natural gas (NG)

Calorific Value :8900-10700 Kcal/m3

Price: 0.18 L.E/m3

Cost of MM Kcal: 18 L.E

data

Energy Saving

Boiler Pressure12 Bar

Steam Production kilos/hr12000

Fuel TypeNatural gas

Fuel Cost L.E/M30.18

Make Up water TypeSoft Water

Water Cost L.E/M31.25

Concentartion Number (Nc)5101520

% Condensate Retrun45607590

Calculations

Nc = TDS of Boiler Blowdown/TDS of Feed water

Make up + Condensate Return = Feed (1)

Steam Production + Blowdown = Feed (2)

Feed = Steam Production X Nc/Nc-1 (3)

Blowdown = Steam Production X 1/Nc-1 (4)

B.D

Energy Saving due to Blowdown









Feed = Steam Production X Nc/Nc-1 (3)15000.0013333.3312857.1412631.58

Blowdown = Steam Production X 1/Nc-1 (4)3000.001333.33857.14631.58

Energy Losses Due to Blowdown2,550,000.001,133,333.33728,571.43536,842.11

kcal required for producing steam at 12 Bar850

L.E Cost for MM kcal18

Fuel losses due to B.D in 24 hours1101.60489.60314.74231.92

Water cost due to B/D per day90.0040.0025.7118.95

Total Losses L.E/day1191.60529.60340.46250.86

Cond.

Energy Saving due to Increasing Condensate Return










Condendate Return m3/hr5400.007200.009000.0010800.00

Make up water m3/hr6600.004800.003000.001200.00

Energy requied to rasise temp from 25 to 100 oC7549500036000022500090000

Energy Losses L.E/day213.84155.5297.2038.88

Make up water cost per day198.00144.0090.0036.00


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Sheet2

Calculations






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data

Energy Saving

Boiler Data









Calculations






B.D

Energy Saving due to Blowdown









Feed = Steam Production X Nc/Nc-1 (3)15000.0013333.3312857.1412631.58

Blowdown = Steam Production X 1/Nc-1 (4)3000.001333.33857.14631.58

Energy Losses Due to Blowdown2,550,000.001,133,333.33728,571.43536,842.11

kcal required for producing steam at 12 Bar850

L.E Cost for MM kcal18

Fuel losses due to B.D in 24 hours1101.60489.60314.74231.92

Water cost due to B/D per day90.0040.0025.7118.95


Cond.

Energy Saving due to Increasing Condensate Return










Condendate Return m3/hr5400.007200.009000.0010800.00

Make up water m3/hr6600.004800.003000.001200.00

Energy requied to rasise temp from 25 to 100 oC7549500036000022500090000

Energy Losses L.E/day213.84155.5297.2038.88

Make up water cost per day198.00144.0090.0036.00


Sheet4

Sheet2

Calculations






Sheet3

More SavingsWhere and Why

Thank You & Good Luck

Effect of Scale - Example

Documents

TECHNICAL BOILER TRAINING