Design And Research Of Online Measuring And Controlling System For Vegetable Hypochloric Acid Disinfection Solution

At present,hypochloric acid disinfection method is most widely used in the processing of fresh-cut vegetables.But excess chlorine residues may lead to the formation of carcinogenic,teratogenic,mutagenic substances.The addition of disinfectant is mostly done manually.The lack of automated equipment for online measuring and controlling of hypochlorous acid disinfectant is restricting the processing efficiency and disinfection quality and safety of fresh-cut vegetables.In order to solve this problem,an online measuring and controlling system for hypochloric acid disinfectant was designed.The pH adjusting method is used to produce hypochloric acid.The system can produce hypochloric acid disinfectant on-site,measure and automaticly control its free chlorine concentration and pH value online.Control algorithms were designed and studied.A mathematical model for the change of free chlorine concentration was established.An expert PID control algorithm for free chlorine concentration control was proposed.A mathematical model for the change of pH value was established.A compound control algorithm for pH value was proposed.The control process was simulated using Matlab.The simulation results showed that control performance is good.A prototype device of online measuring and controlling system for hypochloric acid disinfectant was designed and produced.For the funtions of human-machine interaction,automatic controlling,and data collection,a PLC and a touch screen were used as the main controller.The divice consists of key components such as free chlorine sensor,pH sensor,temperature sensor and metering pumps.An online test was conducted.The system was applied to a fresh-cut vegetable production line.The measuring error for free chlorine concentration was less than 5%.The measuring error for pH value was less than 0.1.The test results showed that in free chlorine concentration control the adjustment range is 30?200 mg/L,setting time is less than 300s,steady-state error is less than 5%.And in pH value control the adjustment range is 5.5?7.0,setting time is less than 300s,steady-state error is less than 0.2.