Coal is sediment organic which the quality is hardly determined by some factor for example place there is of hollow, age and the many contamination. In its use machine design utilizing coal as component of burning must correspond to quality of the coal that machine utilized durable.
RECOGNITION of PUBLIC QUALITY OF COAL
Coal is generating raw material energy utilized for industry. Quality of from coal would of vital importance in determining equipments utilized. To determine quality of coal, some things which must be paid attention is : High heating value (kcal/kg), Total moisture (%), Inherent moisture (%), Volatile matter (%), Ash content (%), Sulfur content (%), Coal size (%), Hard grove grindability index (< 3mm, 40mm, 50mm), Fixed carbon (%), Phosphorus/chlorine (%), Ultimate analysis : (carbon, hydrogen, oxygen, nitrogen, sulfur, ash), ash fusion Einstein characteristic temperature.
a. High Heating Value (HHV)
High heating value hardly having an effect on to operation of equipment, like : pulverizes, coal pipe, wind box, burner. Excelsior high heating value hence coal stream every hour is increasingly low so that speed of coal feeder must be accommodated.
b. Moisture Content
Content moisture influences number of usages of the primary air, at coal with high moisture content will require primary air more to dry the coal at permanent mill exit temperature.
c. Volatile Matter
Volatile content matter influences perfection of combustion and flame intensity. perfection of Combustion determined by :
Fuel Ratio = Fixed Carbon / Volatile Matter
Excelsior fuel ratio hence carbon which is combustible not more and more.
d. Ash Content and Composition
Ash content will brought with combustion gas through combustion chamber and convection area in the form of fly ash or base ash. Around 20% in the form of elementary ash and 80% in the form of fly ash. Ash content excelsior and depends on the composition influencing level of defilement (fouling), abrasion and equipments corrosion passed by.
e. Sulfur Content
Sulfuric content had an effect on to level of cool side corrosion happened at element of air heater, especially if activity temperature lower than situation of sulfur dew, beside influential to dusty arrest effectiveness at equipments of electrostatic precipator.
f. Coal Size
Coal grain size limited at granule spread and harsh item. Softest item for measure and 3 mm, medium of harshest measure of 50 mm. softest item is limited dustiness and level of amenity controlled the flight of wind causing defiles area. Level of dustiness and amenity flies that there are still be determined also by content moisture coal.
g. Hard grove Grindability Index (HGI)
Capacities mill (pulverizes) designed at Hard grove grindability certain index, hence for lower HGI of the capacities lower than the measure value to yield the same fineness.
h. Ash Fusion Characteristic
Ash Fusion Characteristic will influence level of fouling, slagging and operation of blower.
PARAMETER QUALITY OF COAL
Quite a lot of parameter to determine quality of inter Alia coal :
1. Total moisture (%) ****)
2. Inherent moisture (%) ****)
3. Ash content (%) *
4. Volatile matter (%) *
5. Fixed carbon
6. Calorific value (kcal/kg) *
7. Total sulfur (%) ***)
8. Index hard grove *
9. Free expansion index ***)
10. Roga index ***)
11. Gray (Gy) king ***)
12. Diatometri ***)
13. Nitrogen ( %) **)
14. Phosphor *)
15. P2O5 *)
16. Plastometri ***)
*) Required the data for power station of steam power
**) Required the data for fuel
***) Required the data for industry coke metallurgy
Exploiting a certain coal type it is important to know a data set quality of coal needed to a certain need. This data obtained from result an examination analysis. From so much parameter quality of coal, usually only some just having a meaning in continuing an certain efficacy. But by having parameter complete data quality of coal from a certain reserve, would more seen all possibility that exploiting of the coal which can assist industry consumer.
MEANING OF QUALITY OF COAL AT THE EXPLOITING
At exploiting of coal it is important to know characters which will be pointed by the coal, good of character chemically, physical and mechanical. This characters will be able to be seen or concluded from data quality of coal result of the analysis and examination. From a number of data quality of the thereof can be taken the price of its mean, for example water content, chemical stuff other and dusty, but there is also cannot be taken the price of its mean but having to be seen price support and maximum, like at the price of hard grove index and ash melting point.
Some quality parameters which would hardly influences the exploiting is especially as component of burning is:
a. Water content
This distinguishable water content to free water content (free moisture), wafting water content (inherent moisture) and total water content (total moisture). This water content would many its(the influences at transportation, handling, grinder or at the combustion.
b. Ash content
Besides quality which will influence its handling, either as fly ash and also bottom ash but also the composition which will influence its exploiting as well as melting point which can generate fouling at pipes. In this case content Na2O in ash would hardly influences ash melting point. This ash can be yielded from wafting pollutant (inherent impurities) and also pollutant as result of the mining. Dusty composition properly is known carefully for possibility that the exploiting as component of building or ceramic and the operation to area problem which can be generated it.
c. Volatile Matter
Matter content flies very tightly of the bearing with the coal class, more and more matter content height flies more and more low its class. At coal firing, hence matter content flies high would more quickeningly is combustion of denseness carbon conversely matter flies more low hardened combustion process. Content ratio carbon is clinched to matter content to fly called as fuel ratio.
Fuel Ratio Various Coal Types :
1. Coal Type Coke Fuel Ratio 92
2. Coal Type Anthracite Fuel Ratio 24
3. Coal Type Semi of anthracite Fuel Ratio 86
Coal Type Bitumen
Ø Coal Type Low volatile Fuel Ratio 28
Ø Coal Type Volatile medium Fuel Ratio 19
Ø Coal Type High volatile Fuel Ratio 13
4. Coal Type Lignite Fuel Ratio 09
d. Caloric Value (Fuel Ratio)
The price of caloric value is quantifying from the price of heat combustion from coal former elements. The price of caloric value which can be reported is the price of gross calorific value and usually with water amount dried, medium of caloric value which really exploited at coal firing is net calorific value which is countable with the price of temperature latent and sensible influenced by total content from water and ash.
e. Hard grove Grindability Index (HGI)
Hard grove Grindability Index is guide about easy to difficult to of coal for grind. The Price Of Hard grove Grindability Index is obtained with formula :
HGI = 13,6 + 6,93 W
W is weight in gram from fairish soft coal 200 mesh. More and more height the price of HGI more and more the coal slack. A power station of steam power usually prepared to apply grinder capacities to a coal type with certain HGI.
f. Character Caking and Coking
Both the characters to pointed by free expansion value (free swelling index) and the price of dilatation, most off all gives image of character physical of mellowing of coal at its warm-up.
Price explained by result of the analysis and examination obtained from a number of samples by using certain procedures and in control. While practically its exploiting is very differing. For the reason need to be done watcher by coal consumer to result of combustion actually. Thereby will be obtained numbers which can be correlation to result of analysis and examination from coal sample.
Sources : Batubara and Gambut, Ir. Sukandarrumidi, MSc, Ph.D. Gajah Mada University Press
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