| Summary: | 碩士 === 淡江大學 === 水資源及環境工程學系 === 90 === Air pollution problems such as smog, acid rain and the ozone depletion are all related to NOx pollutant. How to effectively and economically control NOx has become an important issue in air pollution control. Currently, SNCR or SCR are two major processes applied for flue gas De-NOx in industrial practice. Scrubbing absorption process however was seldom found in NOx control because of low solubility of NO in water. Since the solubility of NO2 in aqueous solution is higher than that of NO, a two-staged scrubbing system was proposed to convert NO to NO2 in the first stage and then to absorb NO2 in the sequent stage. The two-staged scrubber system was evaluated to be effectively and economically in NOx control. This study focuses on pilot test for the first stage by using NaClO(aq) to oxidize NO to NO2 under various operational parameters. The objective of the test is to get the optimal range for NOx scrubber design and operation parameters.
In this pilot scrubber study, the considered parameters are:
1.The influence of L/G ratio on NO conversion.
2.The influence of NaClO(aq) concentration on NO conversion.
3.The influence of pH value on NO conversion.
4.The influence of gas retention time on NO conversion.
5.The influence of gas velocity on NO conversion.
6.The influence of ORP value on NO conversion.
The pilot test validated that NaClO solution is an adequate oxidant for converting NO to NO2. The optimal range for scrubber parameters are 531.2 lbs/ft2-hr gas mass flow rate and 1000 lbs/ft2-hr liquid mass flow rate. With the parameters setting, 80% of NO conversion and 40% of NO2 generation can be achieved. When the ORP value was controlled within 1050 ~ 1100 which equivalent to pH value equals 5.5, the pilot scrubber system resulted in optimal NO conversion with 0.8 (w)% of NaClO as absorption solution. In the condition, the most HClO concentration, which is the key oxidant to convert NO into NO2, occurred in the solution. To complete the oxidation process, the 5.5 seconds of gas retention time or 0.65 m/s of gas velocity were found to be long enough for NO conversion. With current pilot test results to combine with NO2 absorbing test, the study can be extend to perform two-staged scrubber NOx absorption system test.
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