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Ash Disposal in Power Plants From the Ashes: How to Deal With Ashes in Power Plants?

| Author/ Editor: H Ramakrishna* / Dominik Stephan

Transportation and disposal of ash in thermal power station burning high sulphur coal — Coal is the primary fuel for a thermal power plant. Few power plants burn imported coal and pet coke which contains higher quantity of sulfur. While burning this type of fuel, lime will be injected to absorb the sulfur dioxide liberated while burning the coal in order to reduce the quantity of sulfur dioxide emitted in to the atmosphere along with the flue gas. The ash generated contains Calcium sulfate and unburnt CaO.

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A substantial part of India’s coal is being imported from Indonesia and other countries to bridge the gap between the domestic demand and supply. The imported coal has higher calorific value but also a higher content of sulfur. While burning, more than 95 % of this sulfur gets converted into sulfur dioxide. As per the recent amendment to the Indian environment protection act, emission norms for power stations have become more stringent.

The latest regulation has considerably reduced the allowable emission of sulfur dioxide. In order to meet these figures, power stations have to be able to absorb sulfur dioxide from flue gas. Sulfur dioxide is acidic, therefore the sorbent slurries or other materials used to remove the sulfur dioxide from the flue gases are alkaline like lime. There are different methods of controlling sulfur in the pipestack. The most common are the following: