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NAVEED ANWARBSME01113020

NAVEED ZAFARBSME01113058

MUBASHIR AHSANBSME 01113088 A water containing vessel in which water is heated under pressureTransfer heat from a fuel source (oil, gas, coal) into steamThe steam or hot fluid circulates out of the boiler for use in various process or heating appliances.

What is a Boiler?Closed system: when 100% of the steam produced is returned to be reused.Examples of closed systems are close steam heating, hot water heating, and one-pipe systems.Open system: a system that does not return the condensate.

HOW DOES A BOILER WORKBURNERWATER SOURCEBRINEFUELBLOW DOWN SEPARATORVENTVENTEXHAUST GASSTEAM TO PROCESSSTACKDEAERATORPUMPSBOILERECO-NOMI-ZER

Super heater coils are used in a boiler to generate saturated steam. The super heater coils are specially used inBoilersof Power plant.We manufacture Super heater coils in various grades of Alloy steel T1, T9, T11, T22, T9 & T91 and in stain less steel tubes SS 304, SS310, SS316 and SS 347H with or without support & Header as per customers drawing.

SUPERHEATER COILS

Economizer coils are used in downstream of Boiler bank to preheat the feed water absorbing heat from hot exhaust gases. Economizers are always water tube typeECONOMISER COILS

These are tubes in the Boiler where water is evaporated to steam and are also called Steam Generating Tubes. These Tubes also form the Walls of the Boiler and are hence called Water Walls or Water Wall Panels. WATER WALL TUBES

Acheck valve,clack valve,non-return valveorone-way valveis avalvethat normally allows fluid(liquidorgas) to flow through it in only one direction.Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other forfluidto leave.Check valve

For pressure vessels and reaction vessels in M.S., Al, Cupronickel, etc., Tube Weld employs the latest techniques for expanding tube ends into tube sheets. High pressure tests are always carried out on these heat exchangers before they leave the factory. Brass, copper, M.S. and S.S. tube sheets are used.HEAT EXCHANGERS

Headersform an important part of all types of boilers. Steam from the generating tubes is collected in headers which are therefore always under pressure. This pressure may vary from 300 psi to 2000 psi.HEADERS

Fire Tube BoilerWater Tube BoilerPackaged BoilerStoker Fired BoilerPulverized Fuel BoilerWaste Heat Boiler

Types of boiler

Fire Tube BoilersThe combustion gases pass inside boiler tubes, and heat is transferred to water on the shell side.

Used for high steam demand and pressure requirements Capacity range of 4,500 120,000 kg/hour

Water Tube Boilers

Boiler water passes through the tubes while the exhaust gases remain in the shell side, passing over the tube surfaces.The features of water tube boilers are: Forced, induced and balanced draft provisions help to improve combustion efficiency.Less tolerance for water quality calls for water treatment plant.Higher thermal efficiency levels are possible . Packaged Boiler

Oil BurnerTo ChimneyComes in complete packageFeaturesHigh heat transferFaster evaporation Good convective heat transferGood combustion efficiencyHigh thermal efficiencyClassified based on number of passesa) Spreader stokersCoal is first burnt in suspension then in coal bedFlexibility to meet load fluctuationsFavored in many industrial applications

Stoke Fired Boilers5. Stoke Fired Boilersb) Chain-grate or traveling-grate stoker

Coal is burnt on moving steel grateCoal gate controls coal feeding rateUniform coal size for complete combustionPulverized Fuel Boiler

Pulverized coal powder blown with combustion air into boiler through burner nozzlesTemperature at 1300 -1700CBenefits: varying coal quality coal, quick response to load changes and high pre-heat air temperaturesWaste Heat Boiler

Used when waste heat available at medium/high tempAuxiliary fuel burners used if steam demand is more than the waste heat can generateUsed in heat recovery from exhaust gases from gas turbines and diesel engines.BoilerBoiler blow downBoiler feed water treatmentAssessment of a boiler

Causes of poor boiler performancePoor combustionHeat transfer surface foulingPoor operation and maintenanceDeteriorating fuel and water quality

Heat balance: identify heat lossesBoiler efficiency: determine deviation from best efficiency

Assessment of a Boiler

Heat BalanceBalancing total energy entering a boiler against the energy that leaves the boiler in different forms

Heat in SteamBOILERHeat loss due to dry flue gas Heat loss due to steam in fuel gas

Heat loss due to moisture in fuelHeat loss due to unburnts in residueHeat loss due to moisture in airHeat loss due to radiation & other unaccounted loss12.7 %8.1 %1.7 %0.3 %2.4 %1.0 %73.8 %100.0 % Fuel73.8 %Avoidable losses include:Stack gas losses (excess air, stack gas temperature)Losses by unburnt fuelBlow down lossesCondensate lossesConvection and radiation

Heat BalanceGoal: improve energy efficiency by reducing avoidable losses

Thermal efficiency: % of (heat) energy input that is effectively useful in the generated steam

Boiler Efficiency

26 UNEP 2006BOILER EFFICENCY CALCULATIONDIRECT METHOD:

2) INDIRECT METHOD:

The efficiency is the different between lossesand energy input

The energy gain of theworking fluid (water and steam) is compared with the energy content of the boiler fuel.Boiler Efficiency: Direct Method

Boiler efficiency () = Heat Input Heat Outputx 100 Q x (hg hf) Q x GCVx 100=hg -the enthalpy of saturated steam in kcal/kg of steam hf -the enthalpy of feed water in kcal/kg of water

gross calorific value of the fuel (GCV) in kcal/kg of fuel Boiler Efficiency: Indirect Method

Efficiency of boiler () = 100 (i+ii+iii+iv+v+vi)Principle losses:Dry flue gas Evaporation of water formed due to H2 in fuelEvaporation of moisture in fuel Moisture present in combustion air Unburnt fuel in ash Radiation and other unaccounted lossesControls total dissolved solids (TDS) in the water that is boiledBlows off water and replaces it with feed waterConductivity measured as indication of TDS levelsCalculation of quantity blow down required:2. Boiler Blow Down

Blow down (%) = Feed water TDS x % Make up waterMaximum Permissible TDS in Boiler waterBenefitsLower pretreatment costs Less make-up water consumption Reduced maintenance downtime Increased boiler life Lower consumption of treatment chemicals

Boiler Blow Down

Quality of steam depend on water treatment to control Steam purity Deposits CorrosionEfficient heat transfer only if boiler water is free from deposit-forming solids

3. Boiler Feed Water Treatment

Deposit controlTo avoid efficiency losses and reduced heat transferHardness salts of calcium and magnesiumAlkaline hardness: removed by boilingNon-alkaline: difficult to remove

Internal water treatmentChemicals added to boiler to prevent scaleDifferent chemicals for different water typesConditions: Feed water is low in hardness saltsLow pressure, high TDS content is toleratedSmall water quantities treatedInternal treatment alone not recommended

Boiler Feed Water Treatment

External water treatment:Removal of suspended/dissolved solids and dissolved gasesPre-treatment: sedimentation and settlingFirst treatment stage: removal of saltsProcessesIon exchangeDemineralizationDe-aerationReverse osmoses