Big trouble for coal fired power plants?

Many new chimneys will spit acid and power plants will have to reduce capacity to prevent environmental disaster.
UPDATED ON NOV 25, 2020 06:19 PM IST

The Government of India is forcing coal fired power plants around the nation to fit “Flue Gas Desulphurisation Plants” (FGD) to strongly reduce their emissions of sulphur dioxide. This is very good news for the environment and for people’s health. There is a complication however: the chimneys of these coal fired power plants will be operating at very low temperatures and there is a risk of acid droplets being ejected out of these chimneys, both onto the power plant itself and onto surrounding communities, sometimes as far as several kilometres away.

This problem is called “spitting” and in order to avoid it, the chimneys have to operate with low flue gas velocities. In accordance with rules issued by the United States Electric Power Research Institute, now adopted by the Indian power industry, flue gas velocities may not surpass 18.3 m/s under any condition.

A number of projects are now under way and new chimneys have been designed, contracted and in some cases built for this “FGD Wet Stack” operation. The problem is, that in a number of power stations, contractors have tried to save cost by keeping chimneys too narrow. The flue gas velocity in these chimneys is 18.3 m/s during “Guarantee Operation”, but it will be clearly higher during “Design Operation”, reaching 20, 21 or even 22 m/s.

As a result, the owners of these stations must now choose between two bad options; they must either accept a high risk of acid spitting, or they must downgrade the capacity of their units to avoid operating at Design Capacity. One industry expert has commented, that he knows of four large power stations that would have to cut their joint capacity by more than 1,000 MW – and this is probably only the tip of the iceberg.

One US based design expert for FGD Wet Stacks has developed a special internal lining system for these chimneys that could allow chimneys to operate safely at higher velocities; this system is now being implemented at an NTPC power station in Bihar and it is hoped that this could be the solution for the problem. If not, there is a risk that thousands of MW of generating capacity could be lost nationwide.

Meanwhile, MoEF and CPCB have not formulated clear rules on the matter of Stack Liquid Discharge, so that power stations will have to deal with any “spitting problems” on their own, making sure that no damage or nuisance is experienced by its workers and especially surrounding communities.

Disclaimer: This is a company press release. No HT journalist was involved in the creation of this content.

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