Study On Automatic Ammonia Injecting System Of Deionized Water

As large-capacity power plant units with high parameters are putting into operation in China, more and more strict demands for the quality control of water and vapor are put forward. The accurate and efficient regulation of water quality of boiler feed water plays an important role in the safe operation of thermal units, and is also an important approach to avoid equipment failures and accidents induced by the chemical causes. This paper chiefly studies on automatic ammonia injecting system of deionized water in order to make pH value quickly stabilized in a given target range. Some main works are presented as following:1. The technology of deionized water was introduced in this paper, and the significance of the automatic injecting ammonia system with pH value controll for the feed water in a high-parameter and large-capacity drum boiler was discussed. After analyzing the current situation and problems on pH value parameter control, the pH value is selected as the controlling parameter and the corresponding control targets are determined.2. The process mechanism and model of automatic injecting in deionized water was analyzed.3. PLC combined with the intelligent PID algorithm and frequency-converter was adopted to implement the automatic injecting control system design, debugging and applications.4. Aimed at these properties of the pH value control, including delay, nonlinear, time-varying characteristics and lack of the accurate mathematical model, advanced control algorithms were analyzed. The intelligent controller based on RBF neural network fuzzy PID was designed. The simulation results showed that the method had stronger robustness, good self-adaptive capacity, which may be uesed in these industrial processes with lack of accurate mathematical models, time-varying parameters, non-linearity and delay.