Design And Implementation Of Wide Range CEMS Sample Handing System

As a key technology of continuous emission monitoring system, sample handling system technology had received a wide attention at home and abroad.However, in practical application,the sample handing system technology currently in use showed a highly targeted, narrow the scope of application and many other limitations. Toa large extent, it cannot meet the requirements such as different fuels, different combustion ways, different dust content, different flue gas humidity, temperature and other conditions of emission monitoring system.Based on the above limitations, key technical problemsof wide range sample handling systemapplied to CEMS were analyzed systematically in this article, which will coordinate the relationship among the gas sample conditions, environmental conditions and application conditions. The important effect factors during the design process of handling sample system, such as sampling probe, the influence of moisture, pipeline leaks, the adsorption and the changing of environmental conditions. Importantfactors such as sampling probe, water effects, pipe leaks, adsorption effects, and the impact of changes in environmental conditions were analyzed beyond the design process of sample handling system. Moreover, themethods to reduce or eliminate the errors were given in this paper.Based on the above theoretical analysis, a completely design solution of wide range sample handling system was given. The main design includes sampling probe, transmission pipeline, sample processing unit and other accessories. Among them, the sampling probe system as the core and key set of sample handling system, determines the success of later analysis to a large extent. Theallowable length of the probe was designed and calculated to avoidpossible breakage caused by resonance. Inaddition, the structure of probe filter was completely designed, andPLC program control technology was used to achieve the automatic back purge of probe filter.For the sample pretreatment unit, three-level filtration design technology was designed to achieve the sample gas dust removal,whichis using ceramic filters at the probe, the SiC high efficiency filter in the middle, membrane filterbefore the sample gas into the analytical instrument. In addition, Nafion tube dehumidifying desiccant technology and modular filtration technology were used to solve the sample dehumidification problem.Finally,the effect of the sample handling systemhas been proved by experiments. Commonvolatile organic compounds such as benzene and hexane were used in the experiments. After the sample handling system, the loss rate of the sample is within 2%. Testof quantitative repeatability showed RSD=0.2766%,linear correlation coefficient R2>0.999. The effects of different humidity on the three systems were compared and analyzed using cold-dry extraction, hot-wet extraction and dilution-extractive. Theresults show thatto dry flue gas, linear correlation coefficient R2 of the three tested systems were about 0.999. The results of the simulation wet flue gas show that the effect of moisture on SO2 is significantly greater than NO, which is more significant in low concentrations.Comparing the results of three sets of systems, it can be seen that hot wet extraction systems are more sensitive to moisture content, the dilution-extractive methoddisplays a superior anti-jamming performance for moisture under the precise control the dilution ratio.