PIC16 based blowdown controller for industrial boilers

Abstract

The general steam system consists of a boiler, piping and heat exchanger. The boiler generates steam, piping delivers steam from the boiler and returns condensate to the boiler and heat exchanger transfers heat to perform the work. The boiler is the heart of the steam system. The previous manual blowdown method consists of two cycles, viz. purge cycle and blowdown cycle. In purge cycle the operator periodically opens the blowdown valve to refresh the boiler water around the sensor before its impurity concentration is measured. In blowdown cycle, at the end of the purge duration the blowdown valve is closed and the impurity concentration is measured. If measured value is above the threshold value, water is blown down. However, this existing method requires continuous manual supervision and control actions. During this maneuver, timing constraints may arise which can affect the efficiency of boiler system. If the purge cycle is speeded up, the low concentration of impurities in water may lead to additional processing time for steam generation. On the other hand, if the purge cycle is delayed, the increased concentration of impurities in the boiler water will lead to adulterated steam. Such adulterated steam may cause damage to the relevant applications. In the proposed system, the above-mentioned drawbacks are overcome using a well-designed signal conditioning circuit and a micro-controller based control actions. This being a single step process eliminates the overhead of purge cycle and drawbacks due to the manual control of the blowdown valve. Thus the blowdown process becomes more precise and smooth. The proposed approach has attained the benefit of faster performance as compared to the existing blowdown controllers mitigating human errors. Further, the performance can be improved by combining temperature and conductivity sensors into a single module optimizing time and space. Also, data can be transmitted over a remote place for single or multiple boilers.