Adaptation of the OP-650k boilers in power units No. 1, No. 2, No. 3, No. 4, No. 5 and No. 6 at Tauron Generation, plc. – Electric Power Plant Jaworzno III to reduce emission of nitrogen oxides (NOx).

From 2010 to 2015 the Division of Automation together with the Division of Boilers is involved in upgrade of OP-650k boilers at Tauron Generation, plc. – Electric Power Plant Jaworzno III. The upgrade is aimed to mitigate emission of nitrogen oxides.

The scope of jobs assigned to the Division of Automation includes:

• Development of the engineering documentation for the scope of Automation and Control,
• Extension of the Procontrol system with an additional system cabinet,
• Delivery, installation and commissioning of pneumatic cylinders along with positioning devices for gate valves on air ducts,
• Delivery, installation and commissioning of electric driven actuators for gate valves on air ducts,
• Delivery, installation and commissioning of electric driven actuators on pipelines leading to all-day reservoirs of water and urea,
• Delivery, installation, calibration and commissioning of pressure, level and differential pressure converters along with installation of sensing lines,
• Delivery, installation and commissioning of sensors and temperature converters,
• Delivery, calibration, installation, calibration and commissioning of the measuring system for oxygen content in flue gas downstream the economizer (ECO),
• Delivery, installation and commissioning of flame scanner for ignition burners,
• Engineering, installation and commissioning of the air system for Automatic and Control,
• Disassembling, inspection and reinstallation of propane and mazout lances along with actuators,
• Commissioning of burners,
• Engineering, delivery, installation, calibration and commissioning of the system for measurements and analyses of flue gas composition,
• Installation and commissioning of the electric system,
• Cold and hot start up.

Lowering of content of nitrogen oxides in flue gas is achieved by means of two methods – the primary and secondary ones. The primary one consists in redeployment of the system for air supply to boilers to decrease combustion temperature below the boundary threshold when nitrogen oxides no longer are formed. For the secondary method a special system for injection of urea into the combustion chamber is applied. Urea undergoes a chemical reaction inside the boiler, which leads to mitigation of NO_x emission.

The key factor for the first method is the possibility to adjust amount of air supplied to the boiler according to current working parameters of the boiler. For that purpose dedicated gate valves with electric and pneumatic actuators have been instead in ducts of the primary, secondary and tertiary air.

The secondary methods needs, as the most important thing, appropriate control of injection nozzles. Urea must not be injected into boiler regions with excessively high temperature since it will be evaporated therein and the reaction of nitrogen reduction fails to not occur. To prevent such inappropriate operation the boiler is provided with an acoustic system for measurements of temperature that scans distribution of temperature on the cross-section of the combustion chamber and uses the measurement results to actuate necessary injection nozzles.

After commissioning and optimization of the system operation the emission of nitrogen oxides was achieved below 180 mg /Nm³.