Integrated Automated System for Fuel Use Analysis and Equipment Diagnostics for Power Stations Units

摘要

Due to the past years experience, we have seen an influence on the coal purchase policies. The main reason for changing from the original design coal, apart from economic considerations, is to reduce NOx and SO2 emission by using a low sulfur content coal, coal-biomass co-firing in order to reduce greenhouse gases emission etc. Hence, the power generation plant was originally designed to operate on a particular coal, and due to high restriction in environmental requirements, emissions regulations, have led to modifications of the both coal type and firing mode, while the boilers must burn a different coal type and its blends. It may lead to boiler reliability degradation and as result to reducing of the power plant availability and increasing of operation and maintenance costs. In order to prevent a different faults in boiler operation and as a result a reliability reduction, special monitoring and diagnostic techniques are required for engineering analysis and utility production management. In this sense an on-line supervision system have been developed and implemented for 360-575 MW coal fired units. The aim of the system is to achieve more effective and reliable operation while reducing emissions. It is a valuable aid for: (1) operation staff and process engineers to survey the equipment and overall plant performance, (2) electricity production management in order to implement maintenance and operation strategies. The developed system provides on-line information regards furnace performance, including fireball location, furnace exit temperature increase that indicates the necessity of activate furnace sootblowers to control steam temperatures and prevent excessive accumulations of slag and heat surfaces tube overheating. The developed system indicates the superheater and reheater surfaces midwall metal temperature which provides timely information to assist engineering personnel to optimize mode of operation, to activate the optimal number of sootblowing of the corresponded surfaces, etc. The system includes also an on-line analysis of the erosion impact on the boiler backpass heat surfaces. By using the developed system we found a correlation between furnace fouling and NOx emission due to the effect of flame temperature on the rate of NOx formation. As a result optimized furnace operation mode and sootblowing practice is used to reduce the high cost of controlling NOx emission. The developed system allows finding the proper coal blends which provide a high boiler efficiency and reliability while minimizing NOx emissions.