The Development Of An Intelligent Intergrated EDI Module Suitable For Pure Water And Ultre-Pure Water

Reverse Osmosis technique(RO)and continuous electric deionization technique(EDI)as two efficient water treatment techniques are the commonly used pure water and ultra-pure water preparation methods in laboratory,industrial and other high purity water application fields.Due to poor water quality in some environments and large changes in inlet pressure,the water quality,water yield and life of EDI equipment will be greatly affected.Therefore,how to improve RO membrane and EDI equipment to improve water quality stability and reduce the difficulty and cost of use has become an urgent problem to be solved at the present stage.In order to improve the operating life and stability of EDI equipment,this paper develops the intelligent integrated EDI module suitable for pure water ultra-pure water.The main research contents are as follows:1)System structure design.As the pre-processing of EDI,RO technology can reduce the ion load in EDI module and extend the service life of EDI module.Therefore,in order to further maintain the stability of EDI water production and reduce the occurrence of scale phenomenon,so as to extend the life of EDI and bring higher economic benefits,In this paper,a new "double membrane and double pump" double stage reverse osmosis process is designed for its pre-treatment process "reverse osmosis".This process can improve the inlet water quality of EDI device,prolong the service life of EDI device,and avoid the scaling problem caused by high intake salt content.At the same time,this process maintains the stability of RO water yield.So as to ensure EDI water production meet production requirements.At the same time,aiming at the problem of low integration of existing EDI devices,this paper designs a small integrated EDI module for laboratory.This module integrates all kinds of sensors,power sources and actuators required by EDI module operation,which can realize the acquisition and control of important parameters in EDI process.2)System hardware design.The hardware circuit with embedded STM32F4 series processor as the control core,integrated display,measurement,control,communication and other related functions.In order to solve the problem of low measurement accuracy caused by polarization effect and capacitance effect in solution conductivity measurement,a high-precision conductivity acquisition circuit driven by bipolar square wave was designed,and the measurement error was less than 2% in the range after calibration.At the same time,based on the requirements of water generation resistivity control and influent flow control,the adjustable constant current source circuit based on DAC and the speed regulating circuit of booster pump based on PWM are designed.3)System software design.The system architecture is designed based on μcos-II operating system,including key acquisition,Modbus-RTU communication,information acquisition and alarm,resistivity and pressure control.Aiming at the problem that the RO water yield is greatly affected by pressure and further leads to the instability of EDI water yield,PID control method is adopted to precisely control the pressure on both sides of the two-stage RO film,so as to ensure that the RO water yield can meet the demand of EDI device.Aiming at the problem that EDI module cannot adjust the working current and make it adjust automatically with the inlet water quality,flow rate and resin aging to maintain the stability of water quality,a fuzzy controller is designed to introduce the EDI process in the original open-loop state into closed-loop control,so as to realize the accurate and rapid control of water production resistivity.4)Build a test platform to verify the above design.According to the main function points,the test platform was built and tested respectively for two-stage reverse osmosis pressure control,electrical conductivity measurement accuracy,electrical conductivity control of water production and power consumption.The experiment proves that the function effect of the intelligent integrated EDI module designed in this paper can meet the expectation,and verifies the feasibility of the hardware and software design.Finally,the electromagnetic compatibility and constant humidity and heat experiments were carried out to verify the stability of PCB design.