On-line Monitoring System For SO2 Gas Processing Based On Multi-channel FTIR

Sulfur dioxide is one of the most important pollutants in industrial waste gas,direct air emissions will cause serious air pollution problems.In order to reduce air pollution,many industrial sites use sodium hydroxide solution to absorb sulfur dioxide in the exhaust gas and generate sodium sulfite for recycling.During this absorption process,the concentration of sodium hydroxide solution needs to be continuously monitored to avoid oversaturation.At present,the traditional manual sampling and laboratory chemical analysis methods are generally used.If multi-point measurement is to be performed,not only is the workload huge,the efficiency is low,there is secondary environmental pollution,and the measurement results have a large time lag.In order to solve these problems,this article takes a different approach and designs and develops an online multi-channel Fourier infrared spectroscopy analysis system,which can realize in-situ,real-time,continuous and efficient measurement of multiple measurement points.The main work of this paper is based on the construction of Fourier infrared spectrometer online monitoring system and the study of quantitative analysis methods.In the construction of the monitoring system,the main work is as follows:(1)The interferometer system of the Fourier infrared spectrometer designed with double solid angle mirror and coupled torsion pendulum is established and debugged,and the complex dynamic correction algorithm is eliminated Simple,compact structure,good seismic performance of the system,can better adapt to the industrial field application environment.(2)Designed and developed the corresponding host computer software,which can realize full-automatic cyclic acquisition of 8-channel spectral data,automatic quantitative analysis,continuous display of the result curve,one-key import and export of parameters,warning processing,remote communication and other Input and output functions.(3)In order to achieve high-speed and accurate communication between the host computer and the DCS,Beckhoff’s CX8090 embedded controller is used for design.Among them,ADS communication is used between the host computer and Twin CAT;two communication methods are designed between Twin CAT and DCS control system: the first is Modbus RTU communication,the second is analog + digital communication,and finally PLC programming is used to realize data communication.Through the actual test of the two communication methods,it is found that the data transmission can be completed accurately,reliably and quickly to meet the actual needs.In terms of quantitative analysis methods,for quantitative monitoring of sodium hydroxide,108 absorption spectra within 8 hours of the industrial site are collected in a gradient manner,and the results of synchronous sampling laboratory chemical quantitative measurements are used as standard values,and the partial least squares algorithm is used Modeling,study the impact of the first-order SG derivative,mean centralization,standardization and many other different spectral preprocessing methods on the prediction results.The experimental results show that the first-order SG derivative pretreatment method has the best effect on sodium hydroxide modeling;the first-order SG derivative + centralized pretreatment method has the best modeling effect on sodium sulfite,and the model prediction accuracy is higher.The experimental results prove that the multi-channel FTIR SO2 gas processing online monitoring system designed in this paper has the advantages of accurate quantitative analysis results and stable and reliable transmission results,and has good application prospects in industrial sites.