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), fabric bag filters or both. 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, installation of our Electrodynamic sensors in the main flue gas outlet and the outlet of each filter compartment can confirm where leaking filter bags are present and give an overall picture of filter perfroamnce and life, greatly decreasing maintenance time and costs by highlighting the bag rows that need to be changed.
For plants with an ESP fitted, a mix of ENVEA’s ProScatter technology (light scatter) and real-time data collection provides precise data to the plant operators to enable adjustment of the voltages applied to the ESP plates, providing cost saving and emission optimization.
For wet FGDs ENVEA can use its ProScatter Extractive technology, enabling wet flue gas emissions monitoring that complies to standards.
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.
A recent report from the International Institute for Sustainable Development (IISD) says India aims for all plants having FGDs by 2022. The report also states, “The provision of data from continuous emission monitoring system (CEMS) devices installed in the emission stacks of plants, to the electricity regulator and the broader public must be a first priority.”
ENVEA’s involvement with the Power generation industry over many years accross the world, has led to the development of a unique range of process and pollution monitoring solutions, as well as approved (TÜV/UBA, MCERTS and Ex) 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.