Research And Development Of Key Technologies In The Ammonia Nitrogen On-line Monitoring Device

Ammonia nitrogen content is one of the most important control indicators of water pollutant after the COD.With the aggravation of water pollution and the increasingly attention of environmental protection,water quality monitoring,especially on-line monitoring,early warning and control,has become the focus of attention.According to the status quo of online monitoring,research to development a new type of ammonia nitrogen on-line monitoring device,focus on some key technologies existing in the system,such as accurate sampling,solid MgO substitution,efficient distillation and titration end point determination,put forward the corresponding technical solutions,and verify the effectiveness of the proposed method,provides an important reference for the development and improvement of the comprehensive performance of ammonia nitrogen on-line monitoring device.The main work of this paper are as follows:(1)The existing ammonia nitrogen monitor products were investigated and analyzed,analyse principles,advantages and disadvantages of different ammonia nitrogen monitors are analyzed.(2)According to the manual operation and analyse principle of distillation neutralization titration method,designed the key technology solutions of the ammonia nitrogen on-line monitoring device,and build the experimental system,complete calculation and processing of the equipment which needs to be customized and measurement and control instruments are selected.(3)The method of automatic overflow sampling is developed,and the sampling equipment for the ammonia nitrogen monitor is designed and processed.The experimental results show that the overflow sampling device can control the error introduced in the sampling interval well within 0.5%.(4)According to the pretreatment demand of the samples,developed a electric heating,small amount,speedy distillation device,realized power adjustable and distilling rate controllable.On the basis of the developed device,developed a method which is using Na2HPO4-NaOH instead of solid MgO to maintain the solution in a weak alkaline pH during distillation,in view of the inevitable problem which high concentration ammonia was ran out of the equipment as entrainment by the air initially in the equipment and hard to completely absorbed,designed a subsection heating method,which uses small power to heat in the initial stage of distillation,and the other time is heated with the maximum power,so as to realize fast and efficient distillation.The experimental results show that the error introduced by the distillation process is less than 10% in low concentration(less than 2.0mg/L)analyze condition,less than 1.5% in high concentration(more than 2.0mg/L)analyze condition,the performance of the on-line monitor can be improved.(5)The automatic method of titration was studied to take place of the indicator in original method.Reference to the principle of feedback control and expert control,designed the method of rapid titration,and simulated in the software named MATLAB,results show that the selected method realized the rapid titration,and the error of titration far less than manual titration.