BOILERS

TYPES OF BOILERS.

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• 1) WHAT IS BOILER?

-A BOILER IS A CLOSED VESSEL IN WHICH WATER OR OTHER FLUID IS HEATED.

• 2) TYPES OF METALS USED?

-BOILER IS USUALLY MADE OF STEEL, WROUGHT IRON, STAINLESS STEEL ETC.

-COPPER OR BRASS IS USED IN SMALLER SIZE BOILERS BECAUSE IT IS MORE EASILY FABRICATED. COPPER WAS USED FOR FIREBOXES PARTICULARLY FOR STEAM LOCOMOTIVES, BECAUSE OF ITS BETTER FORMABILITY AND HIGHER THERMAL CONDUCTIVITY

• WORKING PRINCIPLE OF BOILER?

-THE BASIC WORKING PRINCIPLE OF BOILER IS VERY VERY SIMPLE AND EASY TO UNDERSTAND. THE BOILER IS ESSENTIALLY A CLOSED VESSEL INSIDE WHICH WATER IS STORED. FUEL (GENERALLY COAL) IS BURNT IN A FURNACE AND HOT GASSES ARE PRODUCED. THESE HOT GASSES COME IN CONTACT WITH WATER VESSEL WHERE THE HEAT OF THESE HOT GASES TRANSFER TO THE WATER AND CONSEQUENTLY STEAM IS PRODUCED IN THE BOILER. THEN THIS STEAM IS PIPED TO THE TURBINE OF THERMAL POWER PLANT. THERE ARE MANY DIFFERENT TYPES OF BOILER UTILIZED FOR DIFFERENT PURPOSES LIKE RUNNING A PRODUCTION UNIT, SANITIZING SOME AREA, STERILIZING EQUIPMENT, TO WARM UP THE SURROUNDINGS ETC.

THERE ARE DIFFERENT TYPES OF BOILERS ARE PRESENT

• WATER TUBE BOILER AND

• FIRE TUBE BOILER.

-PRESENT THESE ARE THE MAIN TWO TYPES OF BOILERS ARE USED.

• PACKAGED BOILER

• FLUIDIZED BED COMBUSTION BOILER

• ATMOSPHERIC FLUIDIZED BED COMBUSTION BOILER

• PRESSURIZED FLUIDIZED BED COMBUSTION BOILER

• CIRCULATING FLUIDIZED BED COMBUSTION BOILER

• STOKER FIRED BOILER

• PULVERIZED FUEL BOILER

• WASTE HEAT BOILER AND THERMIC FLUID HEATER.

--LET US DISCUSS BRIEFLY ABOUT EACH BOILERS.

WATER TUBE BOILER

• IN WATER TUBE BOILER, BOILER FEED WATER FLOWS THROUGH THE TUBES AND ENTERS THE BOILER DRUM. THE CIRCULATED WATER IS HEATED BY THE COMBUSTION GASES AND CONVERTED INTO STEAM AT THE VAPOR SPACE IN THE DRUM.

• MOST MODERN WATER BOILER TUBE DESIGNS ARE WITHIN THE CAPACITY RANGE 4,500 – 120,000 KG/HOUR OF STEAM, AT VERY HIGH PRESSURES. MANY WATER TUBE BOILERS NOWADAYS ARE OF “PACKAGED” CONSTRUCTION IF OIL AND /OR GAS ARE TO BE USED AS FUEL. SOLID FUEL FIRED WATER TUBE DESIGNS ARE AVAILABLE BUT PACKAGED DESIGNS ARE LESS COMMON.

WORKING PRINCIPLE OF WATER TUBE BOILER

--THE WORKING PRINCIPLE OF WATER TUBE BOILER IS VERY INTERESTING AND SIMPLE.

-IT CONSISTS OF MAINLY TWO DRUMS, ONE IS UPPER DRUM CALLED STEAM DRUM OTHER IS LOWER DRUM CALLED MUD DRUM.

-THESE TWO DRUMS ARE CONNECTED WITH TWO TUBES NAMELY DOWN-COMER AND RISER TUBES.

-WATER IN THE LOWER DRUM AND IN THE RISER CONNECTED TO IT, IS HEATED AND STEAM IS PRODUCED IN THEM WHICH COMES TO THE UPPER DRUMS NATURALLY.

- IN THE UPPER DRUM THE STEAM IS SEPARATED FROM WATER NATURALLY AND STORED ABOVE THE WATER SURFACE.

TYPES OF WATER TUBE BOILER

THERE ARE MANY TYPES OF WATER TUBE BOILERS, SUCH AS

• 1) HORIZONTAL STRAIGHT TUBE BOILER

• 2) BENT TUBE BOILER.

• 3) CYCLONE FIRED BOILER.

1)HORIZONTAL STRAIGHT OR LONGITUDINAL OR BABCOCK TUBE BOILER.

-HORIZONTAL STRAIGHT TUBE BOILER AGAIN CAN BE SUB-DIVIDED INTO TWO DIFFERENT TYPES, SUCH AS

1. LONGITUDINAL DRUM BOILER

2. CROSS DRUM BOILER.

LONGITUDINAL DRUM BOILER

- ORIGINAL THIS TYPE OF WATER-TUBE BOILER IS OPERATED ON THE THERMO-SIPHON PRINCIPLE.

THE PRINCIPLE OF THE THERMO-SYPHON SYSTEM IS THAT COLD WATER HAS A HIGHER SPECIFIC DENSITY THAN WARM WATER, AND SO BEING HEAVIER WILL SINK DOWN. THEREFORE, THE COLLECTOR IS ALWAYS MOUNTED BELOW THE WATER STORAGE TANK, SO THAT COLD WATER FROM THE TANK REACHES THE COLLECTOR VIA A DESCENDING WATER PIPE. IF THE COLLECTOR HEATS UP THE WATER, THE WATER RISES AGAIN AND REACHES THE TANK THROUGH AN ASCENDING WATER PIPE AT THE UPPER END OF THE COLLECTOR

CROSS DRUM BOILER.

-THE WORKING PRINCIPLE OF CROSS DRUM BOILER IS SAME AS LONGITUDINAL DRUM BOILER .

• 1) THE FEED WATER IS FED TO THE CROSS DRUM THROUGH FEED WATER INLET.

• 2) THEN THIS WATER COMES DOWN THROUGH THE DOWN-COMER PIPE AND ENTERS INTO INCLINED WATER TUBE PLACED IN HOT CHAMBER.

• 3) HERE, THE WATER BECOMES HOT AND STEAM IS PRODUCED IN THE WATER WHICH COMES INTO STEAM CHAMBER.

• 4) HERE IN THE STEAM DRUM STEAM IS SEPARATED FROM WATER IN NATURAL WAY.

BEND TUBE BOILER

BENT TUBE BOILER ALSO CAN BE SUB-DIVIDED INTO FOUR DIFFERENT TYPES, SUCH AS

1. TWO DRUM BENT TUBE BOILER.

2. THREE DRUM BENT TUBE BOILER.

3. LOW HEAD THREE DRUM BENT TUBE BOILER.

4. FOUR DRUM BENT TUBE BOILER.

BEND TUBE BOILER

• BEND TUBE BOILER IS THE DEVELOPED VERSION OF WATER TUBE BOILER. THE WORKING PRINCIPLE OF BEND TUBE BOILER IS MORE OR LESS SAME AS OTHER WATER TUBE BOILERS, BUT IT UTILIZES FOUR DRUMS.

• WORKING PRINCIPLE OF BENT TUBE THE FEED WATER FIRST ENTERS INTO RIGHT MOST UPPER DRUM. DUE TO MORE DENSITY THIS WATER COMES DOWN IN THE LOWER WATER DRUM. THE WATER WITHIN THAT WATER DRUM AND THE CONNECTING PIPES TO THE OTHER TWO UPPER DRUMS, ARE HEATED UP AND CONSEQUENTLY STEAM BUBBLES ARE PRODUCED. THIS IS THE MOST BASIC WORKING PRINCIPLE OF BENT TUBE BOILER .

3) CYCLONE FIRED BOILER.

• A CYCLONE FURNACE IS A TYPE OF COAL COMBUSTOR COMMONLY USED IN LARGE INDUSTRIAL BOILERS.

-CYCLONE FURNACES WERE ORIGINALLY DESIGNED TO TAKE ADVANTAGE OF FOUR THINGS

A. LOWER FUEL PREPARATION TIME AND COSTS

B. SMALLER MORE COMPACT FURNACES

C. LESS FLY ASH AND CONVECTIVE PASS SLAGGING

D. FLEXIBILITY IN FUEL TYPES

ADVANTAGES OF WATER TUBE BOILER

-THERE ARE MANY ADVANTAGES OF WATER TUBE BOILER. THESE TYPES OF BOILER ARE ESSENTIALLY USED IN LARGE THERMAL POWER PLANT.

1) LARGER HEATING SURFACE CAN BE ACHIEVED BY USING MORE NUMBERS OF WATER TUBES.

2) DUE TO CONVECTIONAL FLOW, MOVEMENT OF WATER IS MUCH FASTER THAN THAT OF FIRE TUBE BOILER, HENCE RATE OF HEAT TRANSFER IS HIGH WHICH RESULTS INTO HIGHER EFFICIENCY.

3) VERY HIGH PRESSURE IN ORDER OF 140 KG/CM2 CAN BE OBTAINED SMOOTHLY.

DISADVANTAGES OF WATER TUBE BOILER

1) THE MAIN DISADVANTAGE OF WATER TUBE BOILER IS NOT COMPACT IN CONSTRUCTION.

2) THE COST IS NOT CHEAP.

3) DIFFICULTY FOR TRANSPORTATION AND CONSTRUCTION.

FIRE TUBE BOILER

FIRE TUBE BOILER

• IN FIRE TUBE BOILER, HOT GASES PASS THROUGH THE TUBES AND BOILER FEED WATER IN THE SHELL SIDE IS CONVERTED INTO STEAM. FIRE TUBE BOILERS ARE GENERALLY USED FOR RELATIVELY SMALL STEAM CAPACITIES AND LOW TO MEDIUM STEAM PRESSURES.

• AS A GUIDELINE, FIRE TUBE BOILERS ARE COMPETITIVE FOR STEAM RATES UP TO 12,000 KG/HOUR AND PRESSURES UP TO 18 KG/CM2.

• FIRE TUBE BOILERS ARE AVAILABLE FOR OPERATION WITH OIL, GAS OR SOLID FUELS. FOR ECONOMIC REASONS, MOST FIRE TUBE BOILERS ARE NOWADAYS OF “PACKAGED” CONSTRUCTION FOR ALL FUELS.

WORKING PRINCIPLE OF FIRE TUBE BOILER.

• IN FIRE TUBE BOILER, THE FUEL IS BURNT INSIDE A FURNACE.

• THE HOT GASES PRODUCED IN THE FURNACE THEN PASSES THROUGH THE FIRE TUBES. THE FIRE TUBES ARE IMMERSED IN WATER INSIDE THE MAIN VESSEL OF THE BOILER.

• THE HEAT ENERGY OF THE GASSES IS TRANSFERRED TO THE WATER SURROUNDS THEM.

• AS A RESULT STEAM IS GENERATED IN THE WATER AND NATURALLY COMES UP AND IS STORED UPON THE WATER IN THE SAME VESSEL OF FIRE TUBE BOILER.

• THIS STEAM IS THEN TAKEN OUT FROM THE STEAM OUTLET FOR UTILIZING FOR REQUIRED PURPOSE. THE WATER IS FED INTO THE BOILER THROUGH THE FEED WATER INLET.

TYPES OF FIRE TUBE BOILER

• THERE ARE TWO TYPES OF FIRE TUBE BOILER

• EXTERNAL FURNACE AND

• INTERNAL FURNACE TYPE.

EXTERNAL FURNACE FIRE TUBE BOILER.

--THERE ARE MAINLY THREE TYPES OF EXTERNAL FURNACE FIRE TUBE BOILER.

• 1) HORIZONTAL RETURN TUBULAR FIRE TUBE BOILER.

• 2) SHORT FIRE BOX FIRE TUBE BOILER.

• 3) COMPACT FIRE TUBE BOILER.

HORIZONTAL RETURN FIRE TUBE BOILER

• HORIZONTAL RETURN FIRE TUBE BOILER IS MOST SUITABLE FOR LOW CAPACITY THERMAL POWER PLANT.

• THE MAIN CONSTRUCTIONAL FEATURES OF THIS BOILER ARE ONE BIG SIZE STEAM DRUM WHICH LIES HORIZONTALLY UPON SUPPORTING STRUCTURES. THERE ARE NUMBERS OF FIRE TUBES COME FROM FURNACE AND ALSO ALIGNED HORIZONTALLY INSIDE THE DRUM. WHEN THE DRUM IS FILLED WITH WATER THESE TUBES ARE SUBMERGED IN WATER.

• THE HOT GASSES IN THE TUBES UNDER WATER TRANSFER HEAT TO THE WATER VIA THE TUBE WALLS. DUE TO THIS HEAT ENERGY STEAM BUBBLES ARE CREATED AND COME UPON THE WATER SURFACE. AS THE AMOUNT OF STEAM IS INCREASED IN THAT CLOSED DRUM, STEAM PRESSURE INSIDE THE DRUM INCREASES WHICH INCREASE SIGNIFICANTLY THE BOILING TEMPERATURE OF THE WATER AND HENCE RATE OF PRODUCTION OF STEAM IS REDUCED. IN THIS WAY A FIRE TUBE BOILER CONTROLS ITS OWN PRESSURE.

INTERNAL FURNACE FIRE TUBE BOILER

-THERE ARE ALSO TWO TYPES OF INTERNAL FURNACE FIRE TUBE BOILER

• 1) HORIZONTAL TUBULAR.

• 2) VERTICAL TUBULAR FIRE TUBE BOILER.

ADVANTAGES OF FIRE TUBE BOILER

• 1) COMPACT IN CONSTRUCTION.

• 2) FLUCTUATION OF STEAM DEMAND CAN BE MET EASILY.

• 3) CHEAPER THAN WATER TUBE BOILER.

DISADVANTAGES OF FIRE TUBE BOILER

• 1) DUE TO LARGE WATER THE REQUIRED STEAM PRESSURE RISING TIME QUITE HIGH.

• 2) OUTPUT STEAM PRESSURE CANNOT BE VERY HIGH SINCE THE WATER AND STEAM ARE KEPT IN SAME VESSEL.

• 3) THE STEAM RECEIVED FROM FIRE TUBE BOILER IS NOT VERY DRY.

• 4) IN A FIRE TUBE BOILER, THE STEAM DRUM IS ALWAYS UNDER PRESSURE, SO THERE MAY BE A CHANCE OF HUGE EXPLOSION WHICH RESULTING TO SEVERE ACCIDENT.

• PRESENT THESE TWO BOILERS ARE MAINLY WE ARE USING FOR THE STEAM BOILERS.

• BOILER IS AN ESSENTIAL PART OF THERMAL POWER PLANT.

• THE PERCENTAGE OF TOTAL HEAT EXPORTED BY OUTLET STEAM IN THE TOTAL HEAT SUPPLIED BY THE FUEL(COAL) IS CALLED STEAM BOILER EFFICIENCY.

• A TYPICAL EFFICIENCY OF STEAM BOILER IS 80% TO 88%.

• ACTUALLY THERE ARE SOME LOSSES OCCUR LIKE INCOMPLETE COMBUSTION, RADIATING LOSS OCCURS FROM STEAM BOILER SURROUNDING WALL, DEFECTIVE COMBUSTION GAS ETC.

CONCLUSION

THANKS FOR WATCHING

T.MAHENDRA REDDY

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