ENVEA helps coal fired power plants to comply with new standards in India.

Coal combustion power plant | MIR 9000, PCME STACK 602, PicoFlow, WEX ™

India’s Ministry of Environment, Forest and Climate Change (MoEFCC) targeted significant reduction of particulate matter (PM), sulfur oxides (SOx) and nitrogen oxides (NOx) emissions from coal fired power plants. Other key stakeholders in this air pollution mitigation project are the Central Pollution Control Board (CPCB), the Ministry of Power (MoP), Central Electricity Authority (CEA), Government owned and India’s largest power producer NTPC Limited.

The most challenging piece of the government’s plan is retrofitting 440 power generation units, with a combined capacity of 166.5 Gigawatts (GW) with flue gas desulphurization (FGD) systems by December 2022 for plants near populous regions and the capital New Delhi, while utilities in less polluting areas have up to 2025 to comply or retire units. These plants represent about 54% of India’s installed power generation capacity and are all fueled by coal, which ranks them among the highest polluting industries in India.  Installing the FGD systems serves to greatly reduce their emissions to atmosphere, specifically sulfur oxides (SOx).

Introduced by the Indian Ministry of Environment, Forest and Climate Change (MoEFCC) in 2015, the power plant standards and pollution control equipment implementation have a target of December 2022 to achieve the targeted emission reductions.

Limit values trends in Indian Power Stations

As the largest emitter of SOx in the world, India accounts for approximately 15% of all anthropogenic emissions. Until the Indian Government’s 2015 order, there were no norms for the control of SOx emissions, demonstrating the importance of the FGD installation program.

Pollutant abatement control – technologies & solutions

Coal combustion is a dirty process, releasing a range of pollutants including sulfur dioxide, nitrogen oxides, carbon dioxide, volatile organic compounds, fly ash and a range of heavy metals. Neutralization/absorption of acidic pollutants, namely the NOx and SOx gases, prior to the fly ash filtration and treatment is essential to avoid damage to the filter media and excess of emissions. This operation is realized by the DeNOx (NOx reduction) and the FGD (SOx reduction) systems and is carried out by several techniques, including injecting a quantity of lime, limestone slurry, activated carbon or sodium bicarbonate, proportional to the pollutant concentrations.

To calculate and precisely adjust this pollutant reduction, on-line monitoring of HCl, NOx or SO2 (precursor of SO3 and sulfuric acid derivates) must be set on the process upstream of the abatement plant.  The advantage of flue gas Process monitoring with ENVEA’s MIR 9000 analyzer ensures that the pollutant abatement function is optimized, whilst reducing the overuse of valuable materials in the abatement process, in turn providing cost savings to the plant operator and minimizing pollutant releases.  Measuring additionally the water content would additionally allow the detection of a possible leak in the boiler.

The dust (fly ash) is captured and removed from the flue gas by electrostatic precipitators (ESP) or fabric bag filters (or sometimes both) located at the outlet of the furnace and before the final release point. To ensure that the dust filtration plant is operating at its maximum efficiency and ensuring optimum pollutant control, we can consider ENVEA’s range of filter performance monitoring systems.  For bag filters, we install our Electrodynamic sensors in the outlet of each filter compartment, to confirm where leaking filter bags are present, which greatly decreases maintenance time and costs by highlighting the bags that need to be changed.  For plants with ESP fitted, we can use the advantages of ENVEA’s unique, real-time data collection, via our “Pulse Log”, where precise variations in the emission profile during rapping (cleaning) of the ESP units is monitored.  Such precise data provides the plant teams with the benefit of being able to adjust the voltages applied to the ESP plates, providing cost saving and emission optimization outcomes.  The fly ash is periodically removed from the collection hoppers below the precipitators or bag filters.

To comply with NOx emission limits the application of ammonia or derivatives of ammonia (e. g. urea) as a reduction agent has proved successful. The nitrogen oxides in the flue-gas basically consist of NO and NO2 and are reduced to N2 and water vapor by the reduction agent. Two processes are important for the removal of nitrogen from flue-gases: selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR). In both these systems, the flow rate and control of NH3 must be continuously adjusted and controlled to prevent excess NH3 emissions (slip), to avoid ducts corrosion increase catalyst lifetime and reduce environmental impact and cost of reagents. To optimize this process, it is essential to use a gas analysis system for simultaneous and continuous monitoring of NH3 and/or NOx.

ENVEA’s involvement with the Power generation industry over many years and all over the world, has led to the development of a unique range of process and pollution monitoring solutions, as well as approved (TÜV and MCERTS) technologies for in-stack measurement of gas, particulate, and flow rate. They allow to control in real time the efficiency of the FGD, DeNOx and ESP systems and to optimize the whole-plant’s efficiency through measurement & control, to reduce air pollution and facilitate legislative compliance. Furthermore, they help saving operational costs by reducing plant’s maintenance requirements and process downtime.

(click on the blue dots on the diagram to see the measurement solutions interactively)

Flow rate measurement for pulverized fuelAsh level detection at filter outletsFilter efficiency monitoringProcess gas monitoring (CO, O₂, NOx)Process gas monitoring (NOx, NH₃)Process gas monitoring (SO₂, O₂)Stack compliance measurement : NOx, SO₂, CO, CO₂, O₂, H₂O, NH₃, HCI, HF, Hg, TOC, PCDD/F, dust and flowProcess leakage detection : CO, CO₂, VOCs, SO₂, TRS, particles particles Electro-filter efficiency monitoring


Flow rate measurement for pulverized fuel


Ash level detection at filter outlets


Filter efficiency monitoring


Electro-filter efficiency monitoring


Process gas monitoring (CO, O₂, NOx)


Process gas monitoring (NOx, NH₃)


Process gas monitoring (SO₂, O₂)


Stack compliance measurement : NOx, SO₂, CO, CO₂, O₂, H₂O, NH₃, HCI, HF, Hg, TOC, PCDD/F, dust and flow

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Process leakage detection : CO, CO₂, VOCs, SO₂, TRS, particles particles

ENVEA’s solution for India’s power generation plants

  • For NOx abatement control (DeNOx), the use of the NDIR heated and extractive multi-gas analyzer MIR 9000H, offering the capability of measuring the NH3+H2O or NH3+NOx+H2O simultaneously is recommended. The same analyzer can measure additionally other parameters such as CO, CO2 and O2 if required by the process. If sole the monitoring of NH3 is to be made, the use of the Cross Stack TDL sensor LAS 300 XD-NH3 offers fast response, in situ measurements.
  • For the ESP dust removal efficiency control the use of the PCME Stack 602 DynamicOpacity monitor, installed before and after the ESP. We can also utilize an ENVEA Proscatter DM 170 backscatter sensor after the ESP for Process control, with the dual benefit of ensuring ESP control and ensuring that the bag filter is not overloaded.

For FGD performance control, the cold extractive NDIR-GFC analyzer MIR 9000 offers very high precision to measure online the SO2 or the SO2+O2.

An additional function of the FGD being the removal of the mercury eventually present in the flue-gas, this is achieved by injecting in the process an absorber/neutralizer. To avoid under-dosing or over-dosing of the absorber/neutralizer a precise control of its flowrate can be done with the use of a SolidFlow 2.0 or PicoFlow sensor.


  • Important savings on reagent consumption and related costs
  • Less reagent injected leads to a reduction of bottom ash quantity. Consequently, treatment costs of this solid outputs, most of time considered as hazardous, are significantly reduced.
  • Improved process robustness and reduced maintenance costs
  • Measuring the H2O content would avoid dampness of the reagent, which may lead to pasty deposits on the treatment filters.
  • Reduction of stack emissions and therefore compliance with regulatory ELV limits and air pollution reduction

Stack emission control

To ensure that standards are being met and the ELV are respected for all the parameters, plants that do implement the emissions reduction technology must install Continuous Emission Monitoring Systems (CEMS) in all the emission stacks.

Revised standards for coal-based thermal power plants,2015
Thermal Power Plants (units) installed before December 31, 2003
Particulate Matter 100 mg/Nm3
Sulphur dioxide (SO2) 600 mg/Nm3 (units smaller than 500 MW capacity)
200 mg/Nm3 (for units having capacity of 500 MW and above)
Nitrogen oxides (NOx) 600 mg/Nm3
Mercury (Hg) 0.03 mg/Nm3 (for units having capacity of 500 MW and above)
Thermal Power Plants (units) after January 1, 2004, up to December 31, 2016
Particulate Matter 50 mg/Nm3
Sulphur dioxide (SO2) 600 mg/Nm3 (units smaller than 500 MW capacity)
200 mg/Nm3 (for units having capacity of 500 MW and above)
Nitrogen oxides (NOx) 300 mg/Nm3
Mercury (Hg) 0.03 mg/Nm3
Thermal Power Plants (units) to be installed from January 1, 2017
Particulate Matter 30 mg/Nm3
Sulphur dioxide (SO2) 100 mg/Nm3
Nitrogen oxides (NOx) 100 mg/Nm3
Mercury (Hg) 0.03 mg/Nm3

Source: Ministry of Environment Forest and Climate Change, 2015

ENVEA’s QAL 1 certified and internationally approved CEMS technologies perfectly adapted for this specific application are:

  • For Gases SO2/NO/NO2/CO/CO2/O2 : the cold extractive multigas analyzer MIR 9000
  • For Particulate matter: the QAL 182 WS for wet FGD plants and QAL 991 for dry FGD plants
  • For Mercury: the SM-4
  • And the ProPitot™ Approved Flue Gas Velocity CEM StackFlow 200 for stack velocity, volumetric flow, and pollutant mass release calculations

Data acquisition is vital to the functionality of a Continuous Emissions Monitoring System (CEMS). As well as providing real time reports and data handling, the purpose of data acquisition and reporting software is to provide adherence to legislative compliance. It also ensures that the CEMS equipment is running at its fullest capabilities, eliminating the risk of excess emissions. The MCERTS certified WEX™ from ENVEA collects and processes environmental data for display, management and reporting purposes and has been designed to meet the requirements for Environmental and Continuous Emissions Monitoring reporting systems. It also provides trends and predictive data guaranteeing an optimized injection process of reagents. It ensures the availability of data from the continuous emission monitoring system (CEMS) devices installed in the emission stacks of plants, to the electricity regulator and the broader public.

ENVEA is currently working with most of the EPC’s operating in India such as: ISGEC, BHEL, GE (ALSTOM), MHPS, TATA Projects, THERMAX, etc. We provide supplying, installation, commissioning, and operation of complete monitoring solutions for the modernization of the Indian Coal fired Power Plants.

About ENVEA India (formerly known as Environnement SA India Pvt. Ltd):

ENVEA’s Indian subsidiary has been established in 2008 to strengthen the operations in India for the full benefit of valuable customers to provide advanced services, direct customer services and technical expertise, optimum cost-effective solutions, and direct access to local integrated AQMS and CEMS solutions, including data management.

With activities in India since the 1990’s, ENVEA India Pvt Ltd has delivered and installed hundreds of air pollution monitoring networks in the different States, perfectly addressing Indian Government supportive measures and regulations to curb air pollution. Furthermore, through its continuous stack emissions monitoring being installed in a huge number of industries across the territory such as: chemical & petrochemical industries, cement plants, metal & paper mills, etc., ENVEA assists their effort to come closer to compliance and meet pollution reduction goals. The subsidiary counts today over 250 employees, India being today the group’s third largest market.