How a coal power station works?

Saturday, July 31, 2010

Boiler Tube Acoustic Steam Leak Detection Systems

Acoustic monitoring Instruments for Boiler tube leakage detection in Thermal Power Plants are cost effective hence must be installed immediately.

Acoustic Instruments may be used to detect early boiler tube leak to avoid secondary damage to pressure parts. Boiler acoustic tube leak detection system must be used as it prevents damage to costly boiler parts and it is very much cost effective. An increase in boiler availability of just one day will more than cover the cost of a leak detection system.

Traditional leak detection system such hearing hissing sound by ear or monitoring feed water flow or furnace vacuum is not much reliable because it can not detect small leak so damage to vital costly equipment of boiler may not be avoided. Writer noticed many instances where thermal power plants boiler allowed to run for long time due to confusion which caused permanent damage to many boiler tubes, refractory and boiler structures. Hence importance of acoustic monitoring leak detection systems sincerely felt.

Acoustic leak detection sensors detect high frequency emissions from site of leak and Sensitive piezoelectric sensors mounted to the structure transform these acoustic waves to electronic voltage signals, which are amplified, filtered, and processed to determine energy content.

Early detection by acoustic monitoring instruments results in substantial reduction of repair times and costs with a consequent increase in plant availability and profits. The early detection of a boiler tube leak will give financial savings which will easily exceed the initial capital cost of the detection system even at the very first event.

Finally, Acoustic monitoring instruments must be installed in boilers of thermal power plants. For more details go to

Acoustic monitoring international

p(330)305-1422f(330)494-9822-16707 harbour drive n.w cantou ohio 447

procon engineering

know more about boiler tube leakage, avoid clinker formation and furnace explosion

Tuesday, July 13, 2010

Boiler Furnace Explosion-Avoid it

To avoid furnace explosion you must ensure that ther must not be leakage of oil into boiler furnace and trip the boiler immdiately if flame disappears. Purging of boiler is necessary after every tip out.
There is one more precaution which is if at the start of ignitors or oil rows the flame is not established immediately then purge the furnace and relight again.

Clinker Formation in Boiler of Thermal Power Station is due to high Ash Content which have low fusion temperature below 1500 degree centrigrade

Clinker Formation in Boiler of Thermal Power Station is due to high Ash Content which have low fusion temperature below 1500 degree Centigrade and Minerals present in it. Due to poor Quality of Coal ash got fused and mineral content stick into Water Wall which is very difficult to remove often requires removal by pneumatic machines. This Clinker deposition may be stopped to some extent if sufficient water is sprayed into hopper and regular poking to remove deposition and using good quality of coal. Fusion temperature must be above 1500 degree Centigrade and soot blowing regularly at load by injecting steam by wall blowers. Over firing is also responsible hence firing must be properly adjusted by proper balance of primary and secondary air in boiler.

Accumulation of clinker may be checked if poking of hoppers done regularly and any negligence may start process of clinker deposition. If clinker is not removed immediately then same may choke hopper and often workers got burnt due to sudden fall of hot water which accumulated in hopper.

Once clinker formed into hopper than outage of unit is evident otherwise clinker may deposit in huge quantity which will be very difficult to remove because minerals content present in coal fused with ash deposit into water wall. Such hard Lumps of Clinkers requires pneumatic hammering which takes very much time resulting in forced closure of unit for weeks.

Although cause of clinker formation is poor coal quality and high mineral content in coal but accumulation in Water Wall is result of negligence by Workers and Engineers who do not poke hopper regularly and spray insufficient amount of water into hopper which may not flush fused slag to channels. Outage of clinker grinder and soot blower is also matter of concern may be termed as negligence.

Hence it is advised never blame to low coal quality, low GCV, low ash fusion temperature and high mineral content in coal. Instead of blaming to above factors try regular poking and provide sufficient water in hopper. Clinker Grinders must be made operational. Soot blowing must be done regularly by injecting steam. In India coal supplied to power plants is mostly of low quality which has high ash content so precaution is best solution here to avoid deposition and formation of clinkers in Boiler.

Precaution may stop clinker deposition and formation so remain vigilant.

Introduction and some facts about large thermal power station for efficient operation.

Boiler Turbo generator GT ESP ABT FSS De aerator Scanners Soot blowers Air heaters Economisers Super heaters Re heaters ID FD PA Fan BFP LPH HPH CW Pump

Introduction and some facts about large thermal power station for efficient operation.

Boiler is used for steam generation.

Ball Mill or Bowl mills are used for pulverisation of coal in powder form for efficient firing in boiler.

Raw Coal Feeders are used to supply coal to ball mills in controlled quantity.

PA Fan is used to transport and preheat pulverised coal to burners.

ID Fan is used to exhaust flue gases to chimney and create vacuum in Furnace.

Electrostatic Precipitators are used to separate ash particles from flue gases to control pollution. Here collecting electrode emitting electrode and rapping mechanism used.

FD Fan used to provide air to boiler for help in firing.

Steam produced in boiler is further superheated in Super heaters. There are lot super heaters such as platen, pendent, convection and final super heaters.

Boiler drum used for separation of steam from water and storage. Nowadays drum less once through boiler also used which operates at super critical temperature and Pressure.

Boiler circulation pump used for forced circulation of water in water wall because at high pressure natural circulation is not possible.

Soot Blowers used to remove soot from water wall, Super heater, Re heaters and Air Heaters by injecting steam into heating surfaces.

Ash slurry pumps are used to flush ash with water.

Boiler Feed Pump used to provide water to boiler Drum.

Deaerator used to separate dissolved air from Feed water.

In Turbine heat energy of steam is converted into mechanical energy.

ESV which is called emergency stop valve used to stop supply of steam to turbine when unit trips.

Re heaters used to reheat steam exhausted from HP turbine. After reheating up to 535 degree centigrade same steam is utilised in Intermediate Pressure Turbine.

Barring gear or shaft turning gear is used to rotate turbine rotor at 3.15 rpm when turbine is not running to check bending of rotor due to its own weight.

LP Heaters and HP Heaters are used to heat condensate and feed water supplied to boiler to increase efficiency by steam bled from turbine extraction.

Economiser is used to heat feed water by flue gages to increase efficiency. Heat of waste flue gas is utilised here.

Air Heaters uses heat of waste flue gases to preheat primary and secondary air. There are two types of air heaters tubular and rotary.

Condenser used to condense steam exhausted from turbine.

Condensate Pump are used to supply water to De aerator from condenser Hot well.

CW Pump used to cool steam exhausted from turbine into condensers.

Raw Water is circulated by cw pump into condenser tube hence leakage from condenser tubes must be checked to avoid mixing of raw water into Hot well.

Turbo generator converts mechanical energy into electrical energy.

H2 Gas used in generators used for cooling of generators.

Seal Oil system used to seal hydrogen gas from escape from generator.

Stator Water Cooling system provides demineralised water into hollow stator conductor of generator for its cooling.

Generating Transformer step up voltage for transmission.

Water Treatment Plant is used to produce demineralised water for steam generation. Cation anion and degasifier’s tower used to separate mineral and gases from water.PAC or alum used to separate mud and silica from water. Here minerals removed from water and ph value is maintained near 7 and silica value must less them 0.02 ppm

Coal Handling Plant supplies Coal to Boiler. Merry go round system or wagon tippler used to unload coal into hoppers. Coal is crushed in crusher to crush it in 25mm size. Magnetic separators used to separate metallic particles from coal.

ABCB, SF6, OCB, MOCB and VCB are circuit breakers used to make or break electricity contact at load.

Isolators are used to make or break contact at no loads.

ABT is availability based tariff system to maintain grid discipline.

Purging is done to clean furnace from combustible gases by running ID Fan and FD Fan at least 30% load for 5 minutes to avoid furnace explosion.

Furnace explosion may be checked by timely purging and adjusting firing properly using right quantity primary and secondary air and timely oil support and avoiding leakage of fuel oil in boiler. Furnace must be purged properly again if flame is not established during light up of boiler.

Flame scanners used to sense flame in boiler to detect flame failure to avoid boiler furnace explosion.

FSSS is furnace safeguards supervisory system to safeguard boiler.

Clinker formation which caused by more ash content having low fusion temperature and mineral in poor quality coal may be checked by proper poking and using more water for flushing and use of clinker grinder and regular soot blowing. Over firing which is also cause of clinker formation may be avoided by proper primary and secondary air ratio.

Acoustic Instruments used to detect early boiler tube leakage to avoid secondary damage to pressure parts, Refractory and structures of Boiler. Boiler must be immediately shut down in case of Boiler tube Leakage.

Detect Boiler Tube Leakage Early to avoid Secondary Damage

Super heater Water wall Economiser Tube Leakage may be detected by Acoustic Instruments to avoid secondary damage to Boiler

Detect Boiler Tube Leakage Early to avoid secondary Damage. Super heater Water Wall Economiser Tube Leakage may be detected by Acoustic Instruments to avoid secondary damage.BTL may damage boiler tubes, refractory, structure beams and choke Air heater tubes so it must be watched carefully.

There must be constant vigil on possibility of Boiler Tube Leakage because small negligence may result into heavy leakage to pressure parts of Boiler, its refractory’s and even to its Structure Beams etc. We must constantly watch furnace vacuum which must be maintained -10 to -20 mmwcl. If furnace vacuum is disturbed then we must physically inspect boiler for hissing sound of leakage of steam. Nowadays some Acoustic Instruments also available which may detect steam leakage from boiler tube. Feed water flow is another parameter which must be watched carefully to judge boiler tube leakage. Any increase of feed water flow and decreasing of de aerator level must be seriously examined.

There is several type of boiler tube leakage such as Super Heater Leakage, Water Wall Leakage and Economiser Tube Leakage, all type of boiler tube leakage are seriously dangerous for Boiler. In some cases I have seen that Economiser leakage not taken seriously and unit allowed running for some time which resulted into chocking of Air Heater Tube which resulted into pressurisation on Boiler Furnace.

Friday, July 9, 2010

Clinker Formation is due to Low GCV, Mineral Content in Coal

Clinker Formation is due to Low GCV, Mineral Content, high fused ash but accumulation in Water Wall may be checked by Poking and providing sufficient water into hopper and proper firing to avoid un burnt coal.

Cause of Clinker formation is high ash content, low GCV and high mineral content in coal but precaution is solution
In India Coal used in Power Plant is of often low quality which has high ash content and low GCV. Mineral content present in coal may increase this problem. In Water Wall ash is fused and stick on it. Presence of mineral content in coal may produce very hard lumps which are very difficult to remove. Such clinkers are removed by pneumatic hammer during shutdown of unit.

To avoid clinker formation we must use good quality of coal which has less ash, more GCV and less mineral content.

If the quality of coal is low then it is not possible to stop clinker formation but we can stop its accumulation in furnace to some extent by proper poking at ash hoppers and providing sufficient amount of water which may flush out fused slag. Precaution is key which may reduce down time of unit.

We must not blame coal quality for clinker formation but our vigilant attitude may stop its accumulation in Furnace.

Always keep watch on regular poking.

Provide sufficient amount of water in hopper which may flush out fused slag.

Firing in Boiler must be proper so there may not be UN burnt coal by using right proportion of primary and secondary air.

Fuel oil burners must be properly so there may not be un burnt oil in furnace. Fuel oil firing must be proper. Fuel oil must be properly atomized and steam must be properly charged into oil gun.

Above precaution may avoid chances of clinker formation and its deposition which may result into higher plant load factor.

For national interest we must check fuel firing to avoid un burnt fuel.