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A boiler is a device for generating steam, which consists of two principal parts: the furnace,

which provides heat, usually by burning a fuel, and the boiler proper, a device in which the heat

changes water into steam. The steam or hot fluid is then recirculated out of the boiler for use invarious processes in heating applications.

The water circuit of a water boiler can be summarized by the following pictures:

The boiler receives the feed water, which consists of varying proportion of recovered

condensed water (return water ) and fresh water, which has been purified in varying degrees

(make up water ). The make-up water is usually natural water either in its raw state, or

treated by some process before use. Feed-water composition therefore depends on the

quality of the make-up water and the amount of condensate returned to the boiler. The

steam, which escapes from the boiler, frequently contains liquid droplets and gases. The

water remaining in liquid form at the bottom of the boiler picks up all the foreign matter

from the water that was converted to steam. The impurities must be blown down by the

discharge of some of the water from the boiler to the drains. The permissible percentage of 

blown down at a plant is strictly limited by running costs and initial outlay. The tendency is

to reduce this percentage to a very small figure.

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Proper treatment of boiler feed water is an important part of operating and maintaining a boiler 

system. As steam is produced, dissolved solids become concentrated and form deposits inside the

 boiler. This leads to poor heat transfer and reduces the efficiency of the boiler. Dissolved gasses

such as oxygen and carbon dioxide will react with the metals in the boiler system and lead to

 boiler corrosion. In order to protect the boiler from these contaminants, they should be controlled

or removed, trough external or internal treatment. For more information check the  boiler water 

treatment web page.

In the following table you can find a list of the common boiler feed water contaminants,

their effect and their possible treatment.

Find extra information about the characteristics of boiler feed water .

IMPURITY RESULTING IN GOT RID OF BY COMMENTS

Soluble Gasses  

Hydrogen Sulphide (H2S)Water smells like rotteneggs: Tastes bad, and iscorrosive to most metals.

Aeration, Filtration, andChlorination.

Found mainly ingroundwater, and pollutestreams.

Carbon Dioxide (CO2) Corrosive, forms carbonicacid in condensate.

Deaeration, neutralizationwith alkalis.

Filming, neutralizing amiused to prevent condensline corrosion.

Oxygen (O2)Corrosion and pitting of boiler tubes.

Deaeration & chemicaltreatment with (SodiumSulphite or Hydrazine)

Pitting of boiler tubes, anturbine blades, failure ofsteam lines, and fittings

Suspended Solids  

Sediment & Turbidity Sludge and scale carryover. Clarification and filtration.Tolerance of approx. 5ppmax. for most applicatio10ppm for potable water

Organic Matter Carryover, foaming, deposits Clarification; filtration, and Found mostly in surface

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can clog piping, and causecorrosion.

chemical treatment

waters, caused by rottingvegetation, and farm runoffs. Organics break dowform organic acids. Resuin low of boiler feed-watpH, which then attacks btubes. Includes diatoms,molds, bacterial slimes,iron/manganese bacteria

Suspended particles colleon the surface of the watin the boiler and renderdifficult the liberation of steam bubbles rising to tsurface.. Foaming can als

be attributed to waterscontaining carbonates insolution in which a lightflocculent precipitate wilformed on the surface ofwater. It is usually tracean excess of sodiumcarbonate used in treatm

for some other difficultywhere animal or vegetaboil finds its way into theboiler.

Dissolved Colloidal Solids  

Oil & Grease Foaming, deposits in boiler Coagulation & filtrationEnters boiler withcondensate

Hardness, Calcium (Ca),

and Magnesium (Mg)

Scale deposits in boiler,inhibits heat transfer, andthermal efficiency. In severecases can lead to boiler tubeburn thru, and failure.

Softening, plus internaltreatment in boiler.

Forms are bicarbonates,sulphates, chlorides, andnitrates, in that order. Socalcium salts are reversisoluble. Magnesium reacwith carbonates to formcompounds of low solubi

Sodium, alkalinity, NaOH,NaHCO3, Na2CO3

Foaming, carbonates form

carbonic acid in steam,causes condensate returnline, and steam trapcorrosion, can causeembrittlement.

Deaeration of make-upwater and condensatereturn. Ion exchange;

deionization, acid treatmentof make-up water.

Sodium salts are found inmost waters. They are vesoluble, and cannot be

removed by chemicalprecipitation.

Sulphates (SO4)Hard scale if calcium ispresent

DeionizationTolerance limits are abou100-300ppm as CaCO3

Chlorides, (Cl)

Priming, i.e. uneven deliveryof steam from the boiler(belching), carryover of water in steam lowering

steam efficiency, can depositas salts on superheaters andturbine blades. Foaming if 

present in large amounts.

Deionization

Priming, or the passage osteam from a boiler in"belches", is caused by tconcentration sodiumcarbonate, sodium sulphor sodium chloride in

solution. Sodium sulphatfound in many waters in

USA, and in waters whercalcium or magnesium isprecipitated with soda as

Iron (Fe) andManganese (Mn)

Deposits in boiler, in large

amounts can inhibit heattransfer.

Aeration, filtration, ionexchange.

Most common form is ferbicarbonate.

Silica (Si) Hard scale in boilers andcooling systems: turbine

blade deposits.

Deionization; lime sodaprocess, hot-lime-zeolite

treatment.

Silica combines with manelements to produce

silicates. Silicates form vtenacious deposits in boitubing. Very difficult to

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remove, often only byflourodic acids. Most critconsideration is volatilecarryover to turbinecomponents.

http://energyconcepts.tripod.com/energyconcepts/water_treatment.htm

 

Generating Electricity

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The principles of electricity generation were discovered by Michael Faraday in 1831. He found

that moving a bar magnet through a wire coil generated electricity. Modern generators are

more complex, but the difference is mainly one of scale.

Power stations range in size from single wind driven devices to major industrial sites, employing

many hundreds of staff, but what they are all doing is converting one kind of energy intoanother. Different stations use a variety of energy sources but they all generate electricity in the

same way.

Simplified to its essentials, a power station consists of just two major items. First, there is a

machine that generates electricity when its shaft is turned - the generator. Secondly, there is

some kind of engine to turn the shaft. The generated voltage can be up to 25,000 volts, which is

transformed to a higher voltage for transmission on the grid.

Generators need to turn fast and continuously, and the most efficient type of engine for this is the

turbine. In the United Kingdom, most power stations use steam-driven turbines.

In a power station generator, the equivalent of Faraday’s bar magnet is a powerful

electromagnet - a coil energised by direct current to produce a magnetic field. This is mountedon the central rotating shaft, and is called the rotor. Around the rotor is a series of coils called

the stator, in which the electrical voltage is generated by the rotating magnetic field. Both rotor 

and stator may weigh several hundred tonnes.

The rotor turns at 3000 revolutions per minute - 50 per second - to produce alternating current

with a frequency of 50 hertz (cycles per second). Modern generators typically produce 500megawatts of power, the largest generating up to 700 megawatts - enough to light seven million

100 watt bulbs!

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The Boiler 

The diagram below shows how coal is used to drive a turbine. Firstly the coal is pulverised into a

fine powder. Mixed with preheated air, the coal powder burns fiercely to heat water in the boiler 

tubes. The steam emerging at the top of the boiler is returned to the furnace to be superheated.

This increases its energy before it is piped to the high-pressure cylinder of the steam turbine.Superheated steam may be hot enough to make the steam pipe glow a dull red – over 560°C.

The hot gases leaving the boiler on their way to the chimney are used to preheat both the air 

needed for combustion and the condensed water returning to the boiler (in the economiser).

.

1. Coal is pulverised into dust2. Hot air blows coal dust into the furnace3. The dust burns like a gas and boils the water4. Superheated steam drives the turbines5. The generator produces electricity6. Steam is cooled and converted into water by the condenser7. The warm water is cooled by air blowing through the tower

8. Water is recirculated to maximise use

A modern boiler can burn over 260 tonnes an hour of pulverised coal. Transporting such

quantities is expensive; so many coal-fired power stations are built close to coalfields. Somecoastal stations have coal brought in by sea, but inland power stations generally have to be

supplied by train. These stations have their own loop line (‘merry-go-round’), where special

hopper wagons discharge their coal load on the move, into bunkers beneath the rails.

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For the same reasons, most oil-fired power stations are near oil refineries, or are located on the

coast or large estuaries. A typical 500 megawatt boiler can burn up to 2,750 tonnes of oil per day

 – over 115 tonnes per hour.

Power stations waste a lot of the energy in the fossil fuels they burn. The best convert only

about 38% of it into electricity. Most of the wasted energy is heat – in the flue gases, and in thewater used to condense the steam as it leaves the turbine cylinders. Combined heat and power

(CHP) units make use of this ‘waste’ heat to provide hot water for room heating. The electricitygenerated can be used locally or supplied to the National Grid. Although many CHP schemes are

currently being set up in Britain, the economics are not always favourable, mainly because we

have plenty of cheap natural gas for home and industrial heating. It may be worthwhile for certain users, such as small factories and schools, leisure centres, hospitals and office blocks.

CHP could become more important in the future, because it can help reduce the emission of 

carbon dioxide – a ‘greenhouse gas’ – into the atmosphere.

Distribution

Electricity arrives in your area from the national supply network (the National grid) at 275,000 or 400,000 volts. It is reduced to 132,000 volts at a substation for distribution within each area of 

the country, travelling to further substations known as grid supply points. From these it is

distributed on overhead lines or underground cables at 33,000 volts - the primary distribution

networks - to the intermediate substations.

At the intermediate substations, electricity at 33,000 volts is reduced to 11,000 volts for 

secondary distribution. The secondary distribution networks then carry it at 11,000 volts to

individual towns, industrial areas and groups of villages.

Particularly heavy users such as manufacturing industries are supplied at 33,000 volts. Electrifiedrailways have their own substations which draw electricity direct from the grid supply point - the

latest overhead-line systems run at 25,000 volts.

At the final substations, transformers reduce the 11,000 volt supply to 230 volts for small scalecustomers such as homes and shops. A typical substation serves 200 to 300 houses. Larger users

such as farms take electricity at 415 volts.

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Pioneers of Electricity

Fantastic, the wind’s excellent. Look at that kite fly. I don’t like the look of those clouds though.

I think it might be going to rain. Just a few minutes more and I’ll have to pull the kite in and find

some shelter. It’s dangerous to fly a kite during a storm. Lightning might strike the kite and

the electricity would come down the string and through me as the quickest route to the ground, just like it would if you flew a kite too close to a power line. One of the people who first

discovered electricity did so by flying a kite in a storm. He was very lucky not to be hurt. Julie

knows quite a bit about the people who discovered electricity.

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 Ask Julie

Benjamin Franklin 1706-1790

Benjamin Franklin loved learning. He read and studied as much as he could. He was very

interested in the phenomenon of electricity and in 1749; he gave up editing and devoted himself to the study of science.

His spectacular, but very dangerous, experiment of flying a kite in a thunderstorm with a metal

key attached to the string proved that lightning had an electrical discharge. From these

experiments, he developed the first lightning conductor, which won him fame and recognitionfrom scientists around the world. Franklin introduced several electrical terms that are still in use

today including words such as battery, conductor, positive and negative charge, electric shock 

and electrician.

 James Watt 1736-1819

James Watt is an important figure in the history of electricity because he invented the modern

steam engine. The engineering principles that Watt perfected in his steam engine were very

important to the development of modern power stations which still use these principles inmodern steam turbines.

James Watt was such an important person in the history of electricity that his name was given to

the units measuring electric power.

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Luigi Galvani 1737-1798

Galvani is famous for using electricity to make a dead frogs leg jump. Galvani came up with

this amazing idea for an experiment after watching frogs legs which had been hung around aniron balcony at home. Galvani observed these legs moving (even though they weren’t attached to

a live frog) and realised that this happened even when there wasn’t an electric storm. He

concluded that an electrical charge was generated by the combination of the copper hooksholding the frogs legs and the iron balcony railing (which only goes to show what a dull night

life there must have been in Bologna during the 18th century).

Gavani went on to recreate this effect by creating an arc of electricity from a Leyden jar (a

rotating static electricity generator ) to a frog’s leg and making it jump.

These gruesome discoveries of Galvani’s led to the invention of the first battery by Volta.

Galvani also experimented on himself, connecting two pieces of metal to create a bimetallic arc.

By touching one end of the arc in his mouth, and the other end in the corner of his eye he saw a

 bright spark. (Do not try this at home!)

Count Alessandro Volta 1745-1827

Count Alessandro Guiseppe Antonio Anastasio Volta is most famous for his work on electric

current. His friend Galvani sent him copies of his papers on frogs legs and Volta queriedGalvani’s conclusion that the electric current he generated came from his living tissue rather than

the two metals. In 1794 Volta tested this theory using metals alone. An electric current was

 produced which obviously could not have come from living tissue. This discovery upset thefriendship and Galvani was still cross about Voltas experiments when he died.

In 1800 Volta constructed a device that would produce a large flow of electricity. Volta’s device

was the voltaic pile. The voltaic pile involved bowls of salt solution connected by strips (arc’s),

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of metal dipping from one bowl to the next – one end of the arc was copper and the other tin or 

zinc.

In further experiments, he managed to reduce the size of the battery by using small round discsof copper and zinc sandwiched by discs of cardboard moistened with a salt solution. This was

the first electric battery.

Volta played such an important part in the harnessing of electricity that his name was used as the

unit of electro motive force, ‘the Volt’.

André-Marie Ampère 1775-1836

André-Marie Ampère (January 22, 1775 - June 10, 1836) unravelled many of the mathematical

 principles of electromagnetism. The ampere unit measuring electric current was named in his

honour.

Born in France Ampère started out being fascinated by mathematics. It was only in later life that

he became interested in first chemistry and the mathematics associated with physics and the new

field of electricity. In 1820 H.C Orsted published his discovery that a magnetic needle is

attracted or repelled by an electric current. Ampere was inspired and went on to develop amathematical theory to explain this phenomena and accurately predicted many more.

Michael Faraday 1791-1867

Michael Faraday is one of the most famous people associated with the discovery and harnessingof electromagnetic force.

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In 1831 Faraday demonstrated electro magnetic force to the Royal Institution in London. He

showed that an electro-motive force is set up in a wire when it is moved at right angles to a

magnetic field. If the wire is part of a closed circuit, an electric current is ‘induced’ inside it.

Faraday also worked out some of the ‘laws’ governing the production of electric current and

magnetic fields. He also invented a ‘magneto-electric machine’, a spinning disk between the poles of the magnet, which was in fact, a primitive dynamo.

Faraday was the first to establish a method for generating a constant current of electricity and paved the way for future power stations.

Faradays discovery of induced currents made possible the invention of the telephone, the

development of the telegraph, of electric lighting and the production of electricity for a thousand

and one uses of modern life.

Thomas Edison 1847-1931

Thomas Alva Edison was a prolific and successful inventor.

In 1889 he produced the ‘kinetograph’ which was the first motion picture camera, preceded by

the ‘kinetoscope’ the forerunner of the cinema. In 1912 he invented the kinetophone, whichlinked the invention of the film camera with that of the phonograph and made a talking picture

 possible.

By 1910 Edison had applied for over 1,300 patents mainly to do with electrical or mechanical

development. He persevered with his researches and patiently used his genius to become one of 

the most successful inventors the world has known.

Sir Charles Parsons 1854-1931

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Charles Parson is famous for designing the first turbine engines. These engines were the

 prototypes for the current turbine engines used to generate electricity.

After college Charles Parsons took an apprenticeship in engineering at Elswick Works of W.G.Armstrong in Newcastle upon Tyne. In 1884 Charles was made a junior partner and head of the

electrical section of Clarke, Chapman & Company, manufacturers of equipment for ships. Hetook out a patent for his new turbine engine in 1884 and immediately utilised the engine to drive

an electrical generator, which he also designed.

The Royal Navy used Parson’s turbine design on HMS Viper and HMS Cobra. And before long

the Admiralty designers recommended that all new Royal Navy vessels should have turbine

 power. In 1906 HMS Dreadnought was launched at Portsmouth, the first Royal Naval turbine

 powered battleship.

Sebastian Ziani de Ferranti 1864-1930

Sebastian Ziani de Ferranti, credited with building the first large scale electricity generation

and supply network , was born in Liverpool of Italian descent.

In 1886 Ferranti was appointed Engineer in Chief of the Grosvenor Gallery station. One of the problems he had inherited was that the transformers on consumers premises were connected to

the mains ‘in series’ – a lighting system that had worked well on railways. He replaced them

with others which he had designed to work ‘in parallel’ a system so successful that it is now useduniversally.

Ferranti improved the generation and supply of electricity so much that soon the station was

supplying premises in 100 miles of streets, from Regents Park to the Thames and from

Knightsbridge to the Law Courts at the boundary of the City of London. At a time when moststations were giving direct current supplies within a relatively small area.

What followed is a tribute not just to the engineering genius of Ferranti, but to the financial

courage and enterprise of those who were prepared to back his vision. On 26 August 1887 the

London Electric Supply Corporation – LESCo – was formed with an authorised capitol of £1million. With the money Ferranti built the first great power station, the prototype of the

 power stations that supply us with electricity today.

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INDUSTRIAL BOILER :

Series of SHL boiler is bulk industrial boiler, with dual boiler cylinders

and transverse arranged, natural cycling coal combustion water pipe boiler.

The transverse upper and lower boiler cylinders and water cooling pipe walls

together form silo type furnace, and together with convection pipe bundle and

collection chest to form the boiler body frame. At the rear part, there is

coal saver, air pre-heater; and if necessary, it is available to set up

super-heater inner furnace. The combustion equipment is scale grating, step

free timing control. Exit shop in bulk type for site assembly and

construction. The smog flow is a type of multi-backhaul.

DHL series of boilers are single boiler cylinder transverse horizontal water

pipe type bulk delivered boilers. The combustion equipment of the boiler is

scale type coal leak-free grating; the boiler is arranged in "Π" way, the

convection pipe bundles are arranged in the level flue; the steel pipes of

coal saver and air pre-heater are arranged at the tai part of the boiler. The

water cool furnace wall is of natural circulation, and the water in coal

saver and convection bundle pipes is of compelled flow. The boiler is bulk

delivered and generally assembled on site.