Analysis of Coal
Coal Analysis techniques are specific analytical methods designed to measure the particular physical and chemical properties of coals.
There are two methods to analyze coal which are called proximate analysis and ultimate analysis.
Proximate analysis
he proximate analysis determines only the fixed carbon, volatile matter, moisture and ash percentages and it can be determined with a simple apparatus.
Ultimate analysis
The ultimate analysisdetermines all coal component elements, solid or gaseous and it needs properly equipped laboratory with skilled chemists.
It is useful in determining the quantity of air required for combustion and the volume and composition of the combustion gases.
These informations are required for the calculation of flame temperature and the flue duct design etc.
SGS has the equipment and the experience - backed by a global team of independent experts - to give you the results you need to ensure
- Compliance with international standards (ASTM, ISO, AS, D)
- Optimized plant operations
- Health and safety planning
- Contractual compliance
- Adherence to emission regulations
The analysis of coal determines the following aspects:
1. Measurement of moisture
The moisture content is being determine by placing a sample of powdered raw coal of size 200- micron in an uncovered crucible which is placed in the oven kept at 108 +2 °C along with the lid.
After that sample is cooled to room temperature and weighed again. The loss in weight represents moisture.
2. Measurement of volatile matter
A fresh sample of crushed coal is weighed, placed in a covered crucible, and heated in a furnace at 900 + 15 oC. After that sample is cooled and weighed.
Loss of weight represents moisture and volatile matter. The remainder is coke.
3. Measurement of carbon and ash
The cover from the crucible used in the last test (2) is removed and the crucible is heated over the Bunsen burner until all the carbon is burned.
The residue is weighed, which is the incombustible ash. The difference in weight from the previous weighing is the fixed carbon(FC).
In actual practice fixed carbon. The FC derived by subtracting from 100 the value of moisture, volatile matter and ash.
4. Proximate analysis
The proximate analysis indicates the percentage by weight of fixed carbon, volatiles, ash, and moisture content in coal.
The amounts of fixed carbon and volatile combustible matter directly contribute to the heating value of coal.
The fixed carbon acts as a main heat generator during burning.
The high volatile matter content indicates easy ignition of fuel and the ash content is important in the design of the furnace grate, combustion volume, pollution control equipment and ash handling systems of a furnace.
5. Fixed carbon
The fixed carbon gives a rough estimate of the heating value of coal. Fixed carbon is the solid fuel left in the furnace after volatile matter is distilled off.
It consists of maximum carbon but also contains some hydrogen, oxygen, sulphur and nitrogen not driven off with the gases.
6. Volatile matter
Volatile matter is an index of the gaseous fuels presence. The volatile matters are the methane, hydrocarbons, hydrogen, carbon monoxide and incombustible gases like carbon dioxide and nitrogen found in coal.
The typical range of volatile matter is 20 to 35%. It helps in setting the minimum limit on the furnace height and volume and easier ignition of coal.
7. Ash content
Ash is an impurity that will not burn. The typical range of ash is 5% to 40%.
The Ash Increases handling costs, affects combustion efficiency and boiler efficiency, reduces handling and burning capacity and may causes clinkering and slagging.
8. Moisture content
Moisture in coal must be transported, handled and stored. Since it replaces combustible matter, it decreases the heat content per kg of coal. The typical range is 0.5 to 10%.
The moisture aids radiation heat transfer, helps to a certain extent with binding fines and Increases heat loss, due to evaporation and superheating of vapour.
9. Sulphur content
The Sulphur content are typical range is 0.5 to 0.8% normally. It affects clinkering and slagging tendencies, limits exit flue gas temperature and corrodes chimney and other equipment such as air heaters and economizers.
properties of coal
Coal comes in four main types or ranks: lignite or brown coal, bituminous coal or black coal, anthracite and graphite.
Moisture
Moisture is an important property of coal, as all coals are mined wet. Groundwater and other extraneous moisture is known as adventitious moisture and is readily evaporated.
Surface moisture: water held on the surface of coal particles or macerals.
- Hydroscopic moisture: water held by capillary action within the microfractures of the coal
- Decomposition moisture: water held within the coal's decomposed organic compounds
Go to index page