Coal It Properties

8/8/2019 Coal It Properties

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What is Coal?

Coal is a readily combustible rock containing morethan 50 percent by weight of carbonaceous material,formed from compaction and in duration of variously

altered plant remains similar to those in peat.

Most coal is fossil peat. Peat is an unconsolidateddeposit of plant remains from a water-saturatedenvironment such as a bog or mire; structures of thevegetal matter can be seen, and, when dried, peat

burns freely.



Formation of Coal



COAL TYPE & ITCOAL TYPE & IT’’S PROPERTS PROPERT

Type/ Range UNITS LIGNITE BITUMINOUS ANTHR

Total Moisture % 40-50 5-10 0

Volatiles Matter % 40-50 10-40

Fixed Carbon % 10-30 30-50 60

Ash % 5-25 10-20 5

Calorific value Kcal/Kg 5000 6500 70

Chemical composition of ash

SiO2 % 40-60

Al2O3 % 15-40

Fe2O3 % 5-10CaO % 2-5



TYPE OF COAL

Peat Lignite

Bituminous anthracite



COAL & ITCOAL & IT’’S PROPERTIESS PROPERTIES

Fixed CarbonFixed Carbon-- solid fuel left after the Volatile Matter is driven solid fuel left after the Volatile Matter is driven

Part of the total carbon that does not volatilize at the temperunder non-oxidizing conditions.

Volatile matterVolatile matter--gases released when coal is heatedgases released when coal is heated

Compose mainly of light & heavy hydrocarbon and gas moleinto the capillary structure of the coal grinds. It exist because

reaction is never completed. Those coals with a high volatilecalled fatty coal & those with low volatiles content called leaThe volatile content affect mainly the flame pattern. Bituminoare easy burning but lead to shorter flame that shift the burnthe pre-cooling zone. They required less primary air and lessto be properly burned.



COAL & ITCOAL & IT’’S PROPERTIES PROPERTIEAsh Content-impurities consisting of Si ,Al , Fe and other inco

The ash is composed mainly of claylike minerals, formed by

tissues that originated the coal. One of the main agent of direattack on the bricks. The raw mix proportion takes into accouof ash from the fuel. So, to every fluctuation in the ash contecorresponds an immediate variation in LSF, SM, IM, thus chaburn ability, the clinker potential composition & the amount oin the burning zone. These change are followed by frequent

formation of coating, abnormal variation in clinker liter weighcontent obtained from hourly samples.

Moisture content

Free or Chemically bonded is an undesirable component like

it represent additional cost of transportation, drying & grindinUsually charcoal & lignite's are more hygroscopic than fatty c



COAL & ITCOAL & IT’’S PROPERTIES PROPERTIE

Moisture content … cont.

Moisture held within the coal itself is known as inherent moisanalyzed.Moisture may occur in four possible forms within coal:•Surface moisture : water held on the surface of coal particles•Hydroscopic moisture : water held by capillary action within tof the coal

•Decomposition moisture : water held within the coal's decomcompounds•Mineral moisture : water which comprises part of the crystal hydrous silicates such as clays

http://en.wikipedia.org/wiki/Capillary

http://en.wikipedia.org/wiki/Clay

http://en.wikipedia.org/wiki/Clay

http://en.wikipedia.org/wiki/Capillary



COAL ANALYSISCOAL ANALYSIS

• PROXIMATE ANALYSIS

• ULTIMATE ANALYSIA

• CALORIFIC VALUE



PROXIMATE ANALYSISPROXIMATE ANALYSIS

Moisture

Air dried Moisture (A) - Dried at room temperature until weight iInherent Moisture (R) - Loss of mass when heated to 110°C in aTotal Moisture = R * 100-A + A

100

Volatile Matter – ( sample base on air dried basis)

Loss of mass when heated at 950°C for 7 minutes.

Fixed Carbon = 100% - Moisture – VM – Ash

Ash – (Sample base on air dried basis)

Mass remaining after burning at 500°C up to 815°C for 21/2 ho



ULTIMATE ANALYSISULTIMATE ANALYSIS

The determination of the percentages of ca

hydrogen, nitrogen, sulfur, Chlorine and (b

difference) oxygen in the gaseous products

after the complete combustion of an organ

of a sample.

Carbon : Combusted and CO2 determined by I.R. spect

Hydrogen : Combusted and H2O determined by I.R. Sp

Nitrogen : Combusted, reduced to N2, determined by thconductivity

Sulfur : Combusted, SO2 detected by I.R. or H2SO4 by tit

Oxygen : determined by difference (or by neutron)




Empirical relationship to convert ‘proxim

analysis’ to ‘ultimate analysis’

• %C = 0.97C + 0.7(VM + 0.1A) - M(0.6 - 0.01M)

• %H2 = 0.036C + 0.086 (VM - 0.1A) - 0.0035M^2 (1 - 0.02M

• %N2 = 2.10 – 0.020 VM

Where

• C = % of fixed carbon

• A = % of ash

• VM = % of volatile matter

• M = %of moisture

Proximate analysis is on air-dried basis and ultimate analysis is




Typical Range for Coal (all types):

Carbon : 60 – 96%

Hydrogen : 2 – 6%

Nitrogen : 1 – 2%

Sulfur : 0.5 – 5%

Oxygen : 1 – 30%

Total Sulfur from raw coal ( air dried basis) was tested by XRF oAnalysis using Escheca mix & Barium chloride solution.



CALORIFIC VALUE (HEATING VACALORIFIC VALUE (HEATING VA

Heating or Calorific Value is the amount of heat released

mass fuel is burned (Btu/Ib or Kcal/kg)Tested by Bomb Calorimeter and sample on air dried ba

Hardness test

Using hardgrove equipment & the results know as

HGI ( hardgrove grindability Index), higher the figure much eIf the lower the figure very hard to grind ( HGI range 30-60).



Bomb Calorimeter

Thermometer

Insulation Jacket

Bucket

Stirrer

Bomb

Water

Heats of Combustion as determined in an oxygen bomb calorimeter aremeasured by the substitution procedure in which the heat obtained from thesample is compared with the heat obtained from the combustion of a similar

amount of benzoic acid or other standardizing material whose calorific value isknown. These measurements are obtained by burning a representative sample ina high-pressure oxygen atmosphere within a metal pressure vessel or “bomb”.The energy released by this combustion is absorbed within the calorimeter andthe resulting temperature change within the absorbing medium is noted. Theheat of combustion of the sample is then calculated by multiplying thetemperature rise in the calorimeter by a previously determined energy equivalentor heat.

Standardization

Before a material with an unknown heat of combustion can be tested in a bombcalorimeter, the energy equivalent or heat capacity of the calorimeter mustfirst be determined. This energy equivalent is determined empirically at regularintervals by burning a sample of a standard material with a known heat of combustion under controlled and reproducible operating conditions.

Benzoic acid is used exclusively as a reference material for fuel calorimetry

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because it burns completely in oxygen; it is not hygroscopic and is readilyavailable in very pure form.

The amount of heat introduced by the reference sample is determined bymultiplying the heat of combustion of the standard material by the weight of the

sample burned. Then, by dividing this value by the temperature rise produce inthe rest, we obtain a resultant energy equivalent for the particular calorimeter.

For example:Weight of known sample, w : 1.651 gramsHeat of combustion of known sampler, H : 6318 cal/gRise in temperature, t : 3.047ºCEnergy equivalent, W : ???? cal/ºC

W = (w * H)/ t = (1.651 * 6318)/ 3.047= 2416 cal/ºC

Thus, energy equivalent for this calorimeter is 2416 cal/ºC.

The fuel test

After the energy equivalent has been determined, the calorimeter is ready fortesting duel samples. Samples of known weight are burned and the resultanttemperature rise is measured and recorded. The amount of heat obtained fromeach sample is then determined by multiplying the observed temperature rise bythe energy equivalent of the calorimeter. Then, by dividing this value by the

weight of the sample we obtain the calorific value (heat of combustion) of thesample in a unit weight basis.

For example:Weight of fuel sample, w : 0.9936 gramsHeat of combustion of fuel sampler, H : ???? cal/gRise in temperature, t : 3.234ºCEnergy equivalent, W : 2416 cal/ºC

H = (t * W)/ w = (3.234 * 2416)/ 0.9936= 7863 cal/g

Thus, heat of combustion for the fuel is 7863 cal/g.

For simplicity, corrections for acids and fuse have been omitted.

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Coal influence upon the clinker & Coal influence upon the clinker & The coal affect clinker quality & coating stability in three different ways1. Through the ash- will lower the LSF, higher SM & IM of clinker if th

raw mix not compensated with the ash % & chemistry

2. Through the atmosphere in the burning zone-If the O2 content in bzone is lower, large CO volume may arises as a consequence of icombustion, flame temperature will decrease & increasing the Frecontent. ( The Transition zone moves toward the burning zone andcalcinated materials reach the burning zone), after sometime the coff due to thermal shocks. The clinker C3A content is increased a

happen flash/quick setting in finish cement.In a reducing atmosphere, it will lead to formation of the ring at theZone. Clinker produced under reducing condition leads to lower 28The coating stability is also affected through basic brick reduction.

3. Through the flame pattern/displacement - depends on several factosimultaneously. The fluctuation in ash , moisture contents, coal

fineness and heating value continuously displace the flame duringkiln operation. Chemical reaction take a certain time for completioarea. If the reaction time is higher than clinker residence time, the cthe best characteristic- this call hard burning clinker.

The most serious situation arises when the flame length is increaseclinker cooling zone moved towards the burning zone. This mean sclinker cooling zone rate & reduce the clinker reactivity.









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Coal It Properties