Increase the flexibility of steam boilers by optimisation of critical pressure component heating

The paper presents a new method for determining the optimum fluid temperature changes during heating cylindrical thick-walled components weakened by holes. An inverse heat conduction problem was solved to determine the temperature of the fluid so that the equivalent total stress due to pressure and thermal load at the edge of the hole at the point of concentration does not exceed the allowable stress. The stress concentration factor at the edge of the hole was determined using the Finite Element Method (FEM) to represent the actual shape of the junction between the element and the stub. Optimum temperature changes of the steam-water mixture in the boiler drum and live steam temperature in the outlet header of the final superheater during the boiler start-up were determined. Based on the optimum time temperature and pressure variations determined for all boiler pressure elements, it is possible to identify the critical element. The heating time for the critical element is the longest. The critical boiler element governs the process of boiler start-up. The flexibility of the boiler can be significantly improved using the proposed method as boiler start-up times can be shortened by approximately one-third compared to current practice.(c) 2022 Elsevier Ltd. All rights reserved.