HANDLING OF COAL IN THERMAL POWER PLANT

Aim: To study about Out plant and Implant coal handling.Prepared by PATEL UTSAV AndAMIN DHRUV

HANDLING OF COAL IN THERMAL POWER PLANTOut-Plant HandlingIn-Plant Handling

IntroductionThermal power plant use fossil fuels, i.e.Solid fuel such as coalLiquid fuel such as oilGaseous fuel such as gas

The choice of fuels, their preparation and feeding, and their methods of firing deserve special attention for a power plant.

since our country is deficient in petroleum products, the main fuel use in steam power plant is coal.

Main target :To receive, process ,stored and feed coal.Bunkering of coal.Unloading of coal.Stacking of coal.

Constituents of coal:-Carbon:-42.9%Hydrogen:-2.96%Nitrogen:-0.91%Sulphur:-0.33%

The coal handling facility is the life line of a coal-fueled power plant.

Modern plants have high coal demands due to increase in sizes of turbine generator units.

Thus, coal handling facilities have to become more flexible, more reliable, and capable of handling larger quantities of coal in less time than ever before.

OUT-PLANT HANDLING OF COALDefine :- The transportation of coal from coal mines to power plant is known as out-plant coal handling.

Due to increase in power plant capacity the coal requirements per day are considerably large.

The mode of transporting coal from the mines to the power plant is determine by the location of the plant relative to the location of mines and also by the available practical methods of transportation such as i.e.

Sea or river (waterways)RailwaysHighways(roads)conveyors

TRANSPORTATION BY WATERWAYSIf the power plant is situated on the bank of river or near sea shore, it is often economical to transport coal in boats or barges.It is then unloaded mechanically by cranes or grab buckets.Then it is placed in storage yard or directly to the conveyor system to be carried to power plant.

TRANSPORTATION BY RAILIn India, the coal supply to power plants is mainly by railways.This mode of transport plays very important role for power plant which are located interior.A railway sliding line is taken into the power station and coal is delivered either in the storage yard or close to the point of consumption.The capacity of the railway siding should be equal to three days requirement of the plant.

TRANSPORTATION BY ROADThe transportation of coal by road is possible for small and medium size plant only due to traffic restrictions and transportation cost.

The great advantage of this system is that the coal can be carried directly into the power house up to the point of consumption.

TRANSPORTATION BY ROPEWAYSThe transportation of coal by ropeways is particularly used when the distance b/w the mine and power plant is less than 10 km.

This mode of transportation is very efficient.

It supplies the coal continuously and free from workers strike.

TRANSPORTATION BY PIPELINEThe power plants are far away from the coal mines and the existing railway facilities are not sufficient to cope with the increasing demands in the most of the countries.The transportation of coal by pipe line is considered most speedy and efficient method among all available.In this mode of coal transportation, coal slurries from remote mine are supplied to power plant by pipe line.

ADVANTAGES & DISADVANTAGES OF PIPELINE TRANSPORTATIONAdvantagesIt is unaffected by variation of climate & weather.Capable of transporting very large quantities of coal.Noise and dust problem is considerably reduced.Men power requirement is low.DisadvantagesIt requires high capital &operating cost.It requires large quantity of water as 1 kg of coal requires 1 kg of water.Power plant must be able to use coal with added surface moisture.

STORAGE OF COALPurpose of coal storage

To store the coal for a period of 30-90Days, therefore the plant is not require to be shut down due to failure of coal supply.

To permit choice of the date of purchase allowing the management to take advantage of seasonal market conditions in price of coal.

Storage of coal is primarily a matter of production against coal strikes, failure of transportation system & general coal shortages.It cost more as there is risk of spontaneous combustion, interest on capital cost of coal, possibility of loss & deterioration during storage, handling cost required by storage & reclamation, cost of area required & many others.10% of annual conception is sufficient in most of the cases, although the factors such as nearness coalfields, transportation facilities & weathering effects on coal must also be considered.

DEAD/OUTDOOR STORAGEIn this storage, the coal required at the power plant is stored in dead storage in the form piles lid directly on the ground.The coal stored has tendency to combine with oxygen of air & during this process call loss sum of its heating value and ignition quality.Due to oxidation the coal may ignite spontaneously.This can be avoided by storing coal in following ways

1)STOCKING THE COAL IN HEAPS OR PILESGenerally concrete floored area is used to prevent the flow of air from the bottom for stocking the coal.Coal is stored in the form of heaps or piles up to a height of 10-12 m directly on the concrete ground.During storage of coal in heaps the coal should be compacted in layer of 15-30 cm in thickness. It effectively prevents the air circulation in the interior of pile.

Second method of removing the heat of oxidation is the air is, allowed to move through the layers evenly so that air may remove the heat of reaction and avoid burning.

The sealing stored pile is desirable in order to avoid the oxidation of coal after packing an air tight layer of coal.

Asphalt, fine coal dust, & bituminous coating are the materials commonly used for these purpose.

2)UNDER WATER STORAGEThe possibility of slow oxidation and spontaneous combustion can be completely alimented by storing the coal under water.Following points should be kept in mind during selecting the site for storage and piling :Coal should be stored on solid ground free from water.The coal handling coast should be minimum.Fire fitting equipment must be available near the storage.The piles should be built up as far as possible compact.The coal storage area should be cleared of all foreign matter having a low ignition temp.

LIVE/ACTIVE STORAGELive coal storage implies the reclaiming and combustion of coal that has been stored for only a relatively short time, usually less than a weak.Coal from a live coal storage pile is usually supplied to combustion equipment without the use of mobile equipment.The coal is usually stored in the vertical cylinder bunkers or coal bins or silo. Coal from silo is transferred to the boiler greet.Live coal storage bunkers are normally constructed with a diamond shaped cross section storage area.The storage bunkers are made of steel or reinforced concrete to store the live coal.

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