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R S Sharma

Keeping pollution at bay

Modern power plants have tight checks, controls

Ever wondered as to why our waters are so transparently clean despite power plants working to full capacity?

By R S SHARMA

(MD- Bajaj Power & Ex-Chairman, NTPC)

During Covid 19 the river water quality improved, pollution vanished and ambient air quality improved for parameters like pm 2.5 , Nox (nitrogen oxides) and Sox (sulphur oxides) level improved to green level as per air quality index throughout the country and all also along the power plants . Water quality monitoring throughout the country by the various agencies reveal the water quality improvements of all rivers ,total suspended solids and bacterial count decreased , dissolved oxygen increased considerably making water fit for all the users .

This is in spite of the fact that during the entire period of Covid, power generation has been virtually to the same level as in 2019 except for period when there was total lockdown in the country, rather power demand in July 20 has risen by around 6-7 % as against same period in 2019 . This proves a point that it’s not the power stations which are polluting but the other industries particularly water contamination is of high level from other non power industries. Power plants of today’s time are fitted with the highest efficient ESPs (electrostatic precipitator - an effective method of particulate collection in power generation applications). As a matter of fact, most of new plants which have been set up post EA 2003 are fitted with such ESPs where spm (suspended particulate  matter) level is maintaining around 25-30 mg /nm3 only. New power plants are designed with zero liquid discharge and having mandatory provision of sewage treatment plants making use most of the water used in the power plants.

All the ambient data’s are directly connected to CPCB (Central Pollution Control Board) portal on real time basis including emissions from chimney across all the plants in the country .        

Power plants are running with higher COC level (cycle of concentration) resulting in water conservation and recycling . New power plants having lower heat rates are designed with a cycle efficiency of 39-40 % . Yes there are older plants too which either will require to be decommissioned or improved environmentally emissions from chimney if more and retrofitted to improve efficiency to reduce Co2 . Equally there is more of a case to work on those plants which are environmentally more sensitive . There must be more focus on these power plants improvement and other industries which are polluting more .

ECs of power plants provide mainly for spm from chimney , water consumption , water quality ,ash utilization and green belts . Model study is done in EIA (Environment Assessment Impact) study for the impact of flue gases from Chimney. Flue gas from chimney mostly consists of nitrogen oxide 68-72%, Co2 12%, So2 .05-07% and balance moisture, other gases oxygen . Model study for So2 dispersion shows concentration of So2 in ambient air within prescribed limits only and this is on this basis that EC is granted .

100% Ash utilization is much more critical concern and requires much more support from all the authorities. Enabling supports are equally as important as the promulgation of the regulation for 100% ash utilisation. This is going to be the one major issues in future.

Co2 is a green house gas . Hence the real concern from power plants should be to reduce Co2 . This was the precise reason that country has switched over to new plants based on supercritical technology. Co2 is a also useful gas and could be used for many applications like for power generation and converting it into hydrocarbons

Hence, it is imperative that more work should be done for Co2 to capture it from power plants and its use to a value added product .

NTPC NETRA  is working in big way for this . Other utilities must join in this endeavour. This will go a long way in reducing green house gases which are much harmful and increasing in the ambient air . Co2 has got a much wider use in converting it into liquid hydrocarbons if captured techno economically and made methanol which could for fuel for transport. There is need to focus on this by all the utilities by allocating some fund for this work .

Many pilot researches are in progress for use of supercritical Co2 for power generation at higher cycle efficiency than at present coal based thermal power plants .

FGDs (Flue-gas desulfurization – to remove sulphur oxides and dioxides) are highly capital intensive and shall be increasing the auxiliary power consumption by about 25-30% from present level thus increasing net heat rate and increase in variable cost apart from increase in fixed cost . Increase of auxiliary power by by 1.5% is too high . Fixed cost is increasing too with capital investment . These all will put a big question mark on affordability of power and capacity of Discoms to bear it .

Water consumption shall increase with FGD installation by about 0.3 M3 / MW . Can we afford this with scarce water resources in the country? There is increasing thrust to go for going to air cooled condensers to conserve water and here we are going consume more water . Water conservation and water saving shall require to be driven much more than electricity saving even. With all power plants going for FGD installation existing chimneys of 275 meter are going to become redundant and waste of capital invested. Can we afford it ?

Lining of chimney and absorber is very costly and increasing the cost of FGD .

These are the some fundamental questions which must be debted and sustainable answers shall require to be found out .

FGD requirements should be linked with the carrying capacity of Sox of the area. Study of this aspect should be carried out by IITs or other institutions.

FGD may be installed in those places where the concentration of Sox is more than permissible limit instead of in all the plants in a blanket way. Authorities will need to create data bank with stringent studies of Sox level carrying capacity around thermal power plants and there’s potential of increase. Only in such places the FGD should be installed.

Let’s remember the cost of FGD on on full commissioning may go to level where the impact of increase on cost may be too high to the tune of 30- 40-50 paise even depending upon the capital cost and lime stone quality . Let’s also understand that FGD with new plants under construction shall be much more economic as chimney heights will reduce , no need for booster fans etc and higher bargaining power for power plants as whole than a retrofit where some equipments are becoming redundant as pointed out above .

Authorities will need to see whether the scarce capital and costly capital should first go to control water parameters, reduction of green house gases , ash utilisation , and massive tree plantations etc OR reducing Sox which is much lower in concentration in ambient air and within limits except for some pockets where it may require to be installed .

I per say am not against installation of FGD but it should be based an environmental impact study around all plants and on the basis of techno-economic study by reputed institutes like IITs and experts who must examine the Sox impact around all power plants and based on this decision should be taken for the installation of FGD .

Disclaimer : These are the personal views of author .They don’t represent views of the organisation to which he is working or has worked .

 

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