A method for estimation of recoverable heat from blowdown systems during steam generation

During the generation of steam, most water impurities are not evaporated with the steam and thus concentrate in the boiler water. The concentration of the impurities is usually regulated by the adjustment of the continuous blowdown valve, which controls the amount of water (and concentrated impurities) purged from the steam drum. Since a certain amount of continuous blowdown must be maintained for satisfactory boiler performance, a significant quantity of heat is removed from the boiler. It is necessary to provide a simple-to-use method to calculate the total amount of heat that is recoverable using this system. In the present work, a simple-to-use predictive tool, which is easier than existing approaches, less complicated with fewer computations and minimize the complex and time-consuming calculation steps, is formulated to arrive at an appropriate estimation of the percent of blowdown that is flashed to steam as a function of flash drum pressure and operating boiler drum pressure followed by the calculation of the amount of heat recoverable from the condensate. Since all of the heat in the flashed steam is recoverable, the total percent of heat recoverable from the flash tank and heat-exchanger system is calculated in the final step. Results show that the proposed predictive tool has a very good agreement with the reported data wherein the average absolute deviation percent was observed to be around 1.47%.