| OCR Text |
Show Typically, two approaches have been used for optimal tuning of the process. First, the global stoichiometry can be controlled by performing an oxygen concentration measurement in the stack. This approach introduces long response times to the control strategy because of the process volume and the measurement location (stack) relative to the source (burner). In addition, the global nature of the measurement does not identify individual burners that may be problematic. The second method uses flow control from flow meter information. In this case errors can be introduced because of changes in fuel and/or oxidant properties, e.g., flow, temperature, composition, and pressure. After combustion is optimized for a furnace; the duration that the process can maintain these optimal conditions is time dependent due to process variables drifting over time. For these reasons it is important to have alternative and secondary means to monitor and control as accurately as possible key process parameters such as, stoichiometry and firing rate for each burner. To address these issues the Air Liquide Research Centers have developed optical sensors integrated into an oxy-fiiel burner. The information obtained from the sensors can then be used for stoichiometry and firing rate monitoring and control of the burners performance. The concept offers a number of advantages such as, fast response time, point-of-use monitoring, and safety monitoring. In the following w e present the sensor concept and results obtained in a 2 MMBtu/hr pilot furnace and an industrial glass melting furnace. O. BURNER MONITORING CONCEPT The light emission observed from a flame is one of the most characteristic features that can provide information on the chemical and physical processes taking place during the combustion of fuel. Monitoring the flame radiation can be easily performed in well controlled environments typically found in laboratories. However, implementing flame light emission monitoring on industrial burners is difficult in practice for a number of reasons. First optical access requires positioning of viewports at strategic location for collecting the flame light emission. Second, the excessive heat from the process is troublesome for measuring equipment, necessitating external 3 |
