Recent developments in excess oxygen trim for boilers have resulted in more efficient and economic operation. Comparable developments have, however, not been applied to furnaces, although close control of combustion would be beneficial for both energy efficiency and product quality. One possible reason for the slower progress is the increased complexity of the automatic control system required for the dual control of furnace temperature and excess oxygen levels. Consideration of the probable control behaviour led to the need for a study of the dynamic behaviour of the furnace. This in turn led to the development of a mathematical model to predict the responses of various furnace temperatures to disturbances in air and/or fuel flow. The model is based on the balance of radiative heat transfer from the combustion gases to the walls and stock of the furnace and the conduction of heat within the walls and stock. The resulting non-linear equations are solved by computer to predict the required transient behaviour. Dynamic behaviour in a combustion gas control loop is likely to be dominated by the instrumentation characteristics and this was not included in the model. Tests on a slab reheating furnace at the Port Talbot works of the British Steel Corporation were used as part of a model validation exercise. Although much useful information was obtained these tests highlighted the difficulties in using operational plant for such experimental purposes and it was found that further model development is required to give an acceptable correlation between predicted and recorded results. Tests on combustion gas analysis equipment have indicated the dynamic behaviour likely to be met in this part of the control system and have also shown that non-linear effects, present in the current control system, are likely to be important in the design of the dual input/dual output temperature/excess oxygen control system.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638449 |
| Date | January 1987 |
| Creators | Peskett, S. C. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
Page generated in 0.0021 seconds