Design And Research Of Intelligent Seawater Concentration Devices Based On PLC

Seawater salinity is the main factor of ocean observation and marine hydrology study.Researchers use marine instruments to measure seawater salinity based on the relative method mostly,which relies on a standard substance currently.Chinese first grade standard seawater and series standard seawater are standard substance of the salinity value.Because of the lower salinity of natural seawater,the primary process of making natural seawater into standard seawater is to concentrate seawater.A intelligent seawater concentration device based on PLC is designed according to the requirements of the relevant departments in this thesis.On account of many disadvantages in other seawater concentration devices such as seawater pollution,destruction of seawater composition,impatience corrosion,short-lived,and low degree of automation,the direction of the research and design goal are determined to solve these shortcomings.The device must achieve seawater cryoconcentration and the temperature of seawater must below 40? according to the request.The seawater is heated by exchanging heat between pipes and seawater to avoid the seawater pollution and destruction in the process of heating.In order to accelerate the speed of seawater concentration,the refrigeration system is introduced to cool the cover and form the temperature field in the seawater tank.To ensure a constant low temperature in the glass lid,the frequency inverter technology is proposed.The heat,which comes from compressor refrigeration,can heat seawater,so as to save power and make full use of energy.With the evaporation of water,salinity value of seawater is getting high.Once the salinity reaches the set value,the device will stop running automatically.Siemens S7-200 SMART series PLC is the main control unit in the control system,and the analog IO modules are extended.The temperature of the tank cover and seawater are controlled precisely by applying Fuzzy PID control strategy and frequency control technology.Human machine interface is applied in the device,and it makes the operation more convenient and enhances the observability of parameters.