| Abstract Title: | Quantum Cascade Lasers for In-situ Measurements |
| Session Choice: | Monitoring Techniques: Combustion gases |
| Presenter Name: | Dr Anish Bekal |
| Co-authors: | Dr S K Karthick Kumar Mr Yashwant Rajshirke Mr Chayan Mitra Mr Dattatreya Kuvalekar |
| Company/Organisation: | Forbes Marshall Pvt Ltd |
| Country: | India |
Abstract Information :
With the tightened emission regulations for thermal power plants Selective catalytic reactors are being installed in Indian power plants to reduce NOx levels along with FGD for reduction of SOx. Selective catalytic reactors used require precise control of NH3 injected into the system so that excess ammonia does not form ammonium bisulphate which would clog the preheater. Typically two NO sensors are required one before the SCR (500 pmm) and one after the SCR outlet (< 100 ppm) to facilitate feedforward control and feed back control of NH3 Injection. NH3 sensor also would be needed at the outlet to measure the NH3 slip which is of the order of 2 - 5 ppm. Typically measurement of these gases at the outlet are done through extractive systems or close-coupled systems. These systems do not give a true representation of the gas concentrations inside the duct due to reduction in temperature during sample extraction and hence resulting in change of chemical composition and hence the concentration and also, typical extraction points are very near to the walls of the SCR which may not give the true representation of composition in the center of the SCR. Best form of measurement for effective control is to use an in-situ analyser which can measure the gas concentration in its native environment. The design of such an analyser requires laser based Gas spectroscopy methods. The recent developments in Quantum Cascade Technology (QCT) has made it possible to build such analyzers. QCT based Spectroscopy system is effective in countering most of the challenges encountered and provide accurate and reliable measurement. In this paper we will be demonstrating the QCT based spectroscopy analyser which is capable of countering interference effects of moisture and other gases, also power variations caused by vibrations, optical mirror degradation, and heavy dust concentrations.
