TECHNICAL BOILER TRAINING

Introduction u Water is the raw material most used in nearly all industries. u US industry uses about 140 billion gallons per day.

The Water Molecule Oxygen and hydrogen share electrons - this is called covalent bonding. The bond angle is 105 degrees. 105 deg H H O

The Hydrologic Cycle

FUNDAMENTALS OF AVAILABLE WATER SURFACE WATER Lower in dissolved solids Higher in suspended solids Quality changes quickly with seasons and weather GROUND WATER Higher in dissolved solids Lower in suspended solids Higher in iron and manganese Low in oxygen, may contain sulfide gas Relatively constant quality and temperature

Basic Water Chemistry

FOUR IMPORTANT CHEMICAL PROPERTIES OF WATER ARE: 1. Conductivity 2. Hardness 3. Alkalinity 4. pH

CONDUCTIVITY A Measure of the Total Dissolved Solids (TDS) in the Water. µS/cm Read in µS/cm Approximation: ppm TDS x 1,8 = µS/cm

HARDNESS The amount of Calcium and Magnesium ions in the water Total hardness and Ca-hardness ppm CaCO 3 Read in ppm CaCO 3

Water - the Universal Solvent uWater is a poor conductor of electricity. uAs more ions dissolve, water becomes a better conductor.

Water - the Universal Solvent This phenomenon is used to indicate total dissolved solids. Conductivity Total Dissolved Solids

ALKALINITY Carbonate or Bicarbonate Ions that Can Cause Scaling Problems together with Ca, Mg Ions. ppm CaCO 3 Read in ppm CaCO 3

Acid - Base Chemistry uThe most common buffering system encountered in industrial plants is the carbonate buffering system Free OH - and CO 3 = HCO 3 - becoming CO 3 = CO 2 becoming HCO 3 - FMA and CO 2 MPO pH

Acid - Base Chemistry The actual distribution of carbonate species CO 2 HCO 3 - CO 3 = Carbonate Buffering System pH Molar ratio CO 2 HCO 3 - CO 3 =

Acid - Base Chemistry Expressing hydrogen ion concentrations: pH = negative log molar concentration of H + pHH + Conc ppb 60.1 ppb ppb ppb

Water - the Universal Solvent Expressing the levels of dissolved solids: per cent - used for concentrated solutions ppm - a weight relationship ppm as CaCO 3 - an equivalent weight relationship mg/l - same as  g/ml - in dilute waters, same as ppm

FUNDAMENTALS OF WATER SPECIFIC HEATSPECIFIC HEAT is the measure of how well a substance can absorb heat 1 Kcal/kg°C VAPORIZATION HEATVAPORIZATION HEAT Energy to transform liquid to gaseous 970 Kcal/kg at 100°C

Pretreatment Filtration Softener Dealkalizer Reverse Osmoses Demineralizer Dearator

PRETRATMENT SOFTENER

Softener - Ion Exchange Process Ca Na Mg Ca Mg Ca Mg Na Regeneration with NaCl Softening Ion Exchange Resin Water

Four Steps of Softener Regeneration Backwash Brining Slow Rinse Fast Rinse

Ca, Mg Na, Na

Boiler tube failure due to scaling and overheating of tube metal over critical temperature for steel This leads to partial destroyed boiler sections and even boiler explosion

Deaeration: Water Temperature is Increased So That CO 2 and O 2 Are Released from the Water Water is Broken Into Small Droplets CO 2 and O 2 Are Removed By Venting

Solubility of Oxygen vs Temperature and Pressure

Oxygen Causes Pitting Attack of metal due to Oxygen Corrosion Increased Iron content in condensate/boiler Increases TDS in boiler Corrosion Cell Dearator

Pitting by Oxygen Corrosion

Spray Deaerator

Tray Deaerator

Venting Requirements for Tray Deaerators

Types of Deaerating Equipment Open feedwater heaters 0.5 to 1 ppm O 2 Vacuum degasifiers 0.29 to 0.43 ppm O 2 2 to 10 ppm CO 2 Deaerators and deaerating heaters 0.04 ppm O 2 for heater ppm O 2 for deaerators 95% of free CO 2

Major Problems Corrosion Scale

Boiler Corrosion Types of Corrosion Oxygen corrosion Alkalinity concentration Caustic corrosion Acid corrosion Chelant corrosion Erosion/Corrosion

Effect of pH on Boiler Corrosion

Effect of Scale on Heat Transfer

Effect of Scale on Tube Temperature

Scale Problems Boiler tube failure Caused by reduced heat transfer and tube overheating Under-deposit corrosion Caused by high concentration of corrosive agents (usually NaOH)

Scale Prevention Precipitation of hardness in the boiler Reduce amount of hardness entering boiler Keep the hardness soluble

Treatment With Makeup Softening Requirements for Success Proper Operation and Maintenance of Make-up Equipment Chemical 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 Used Heat only Steam drives such as turbines Is process contamination a concern

The Generation of Steam Is Energy Intensive Need 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 Water Primary Pretreatment Condensate Steam Header Boiler Deaerator Chemical Feed Systems Feedwater Blowdown Secondary Pretreatment

Boiler: Produces Steam Variety of Shapes and Sizes Variety of Fuels Wide Range of Operating Pressures

Boiler Calculations Calculations Nc Nc Number of Cycles = TDS Boilerwater TDS Feedwater t/h Feedwater (BFW) t/h Blowdown or BFW (t/h) Nc or Steam (t/h) Nc - 1 Blowdown Blowdown (t/h) = Blowdown in % BFW Blowdown in % BFW = TDS Feedwater TDS Boilerwater x 100 BFW BFW Boiler Feedwater (t/h) = Steam (t/h) x Nc Nc - 1

Fire-Tube Boiler

Fire-Tube Boiler - Circulation

PretreatmentSoftening Boiler Filter or Coagulation Surge Tank Returned Condensate Process Steam Turbine Steam Knockout Pot or Flash Tank Water Steam CO 2 Oxygen Ca ++ and Mg ++ Dearation Condensate tank & line Water - Steam - Condensate System POTENTIAL PROBLEM

Why is Condensate Naturally Corrosive? Alkalinity in Boiler Breaks Down to CO 2 CO 2 Leaves with Steam Steam Condenses with CO 2 to Form Carbonic Acid

Why is Condensate corrosive? Alkalinity of BFW breaks down in Boiler Bicarbonate 2 NaHCO 2 Na 2 CO 3 + CO 2 + H 2 O Soda Na 2 CO 3 + H 2 O 2 NaOH + CO 2 CO 2 leaves with steam and reacts with condensed water droplets to Carbonic Acid CO 2 + H 2 O H 2 CO 3 Carbonic acid Acid attack to metals low pH % Conversion Pressure (bar) Caustic

Typical Condensate CO 2 -Corrosion

Boiler Feedwater Treatment INTERNAL TREATMENT SCALE and DEPOSITS prevention

Phosphate Residual Programs Blend of Ortho- or Polyphosphate Chemically Remove Hardness from Feedwater Helps Corrosion Protection Precipitates Hardness and Iron PO Ca +2 Ca 3 (PO 4 ) 2 in combination with Organic Polymers Polymer Disperses Ca 3 (PO 4 ) 2 Sludge Keeps it from sticking to the Tubes

Chelant/Polymer Programs Chemically Complexes Hardness Polymer Disperses Iron Contains EDTA or NTA Keeps Hardness from Forming Scale in Boiler Improves Boiler Cleanliness if 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 Soluble Chelant Metal Complex Ion Chelant + Metal Ion

Types of Sludge Conditioners Synthetic polymers Tannins Lignins Starches

Phosphate-Polymer Programs Advantage Can provide much cleaner boilers than other conventional Phosphate programs Disadvantage Requires much stricter control of feedwater hardness and chemical program

Boiler Feedwater Treatment OXYGEN SCAVENGER and PASSIVATOR Anorganic and Organic

SULFITE Chemically reacts with oxygen (O 2 ) to remove it from the boiler feedwater Reduces Corrosion Potential Does not form Magnetite no Passivation Increases the TDS/conductivity Fast reaction only if catalyzed 2Na 2 SO 3 + O 2 2Na 2 SO 4

HYDRAZINE HYDRAZINE has long been the most applied Scavenger in Demi water systems Does not increase TDS Passivates Iron and Copper metallurgies Is Slow reacting - does not protect sufficiantly: Condensate hot well and Preheaters Decomposes at high Temperature >340 o C, forming Ammonia Bad neutralization due to NH3 V/L distribution Serve Cu corrosion in case of Oxygen inleakage Is Toxic and suspected Carcinogen (OSHA/NIOSH) at air levels attained in utilization areas

Blowdown flash tank Process Flash tank Low pressure steam Pre-Treatment DEAERATOR Condensate System

Carbon Dioxide Sources Breakdown of feedwater alkalinity 2 HCO 3 -  CO 3 = + H 2 O + CO 2 Bicarbonate Carbonate Water Carbon Dioxide CO 3 = + H 2 O  2OH - + CO 2 Carbonate Water Hydroxide Carbon Dioxide Air inleakage

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

Steam Traps

CONDENSATE TREATMENT Neutralizing and Filming Amines

Neutralizing Amines Neutralize Carbonic Acid to protect condensate systems from corrosive Attack Minimize Condensate Corrosion also in large condensate systems - Mixture! Different Vapor/Liquid distribution ratio Keep condensate pH between 8.5 and 9.0 Reduce Iron levels in condensate return

Filming/Neutralizing Amine Increase low condensate pH Protect when large amounts of Carbonic Acid are present Effective between pH of Provide protection from Oxygen Attack Help prevent Iron/Copper deposits in boiler system

Oxygen Corrosion in Condensate line

Filming Amine Repels condensate water droplets from surface and protects against CO 2 and O 2

Optimum Operation Water & Fuel Cost

Water Cost City 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 : Kcal/m 3 Price: 0.18 L.E/m 3 Cost of MM Kcal: 18 L.E

More Savings Where and Why

Thank You & Good Luck

Effect of Scale - Example