| Electrostatic precipitator (ESP) was wildly used in flue gas treatment systems. Thecollection efficiency on particulate matter, especially on fine particles, was relativelylower. It was urgent to improve the performance of ESP on fine particles. Wet ESPshowed good performance on fine particles. This paper studied the enhancementmechanism and process of water on particle removal in wet ESP.First, the thermophoresis, vapor and water film ESPs were set up. The effects ofthermophoresis, vapor, and water film on the performance of ESP were experimentallystudied separately. The results showed that thermophoresis could promote the collectionefficiency of particles and the improvement was about3%~5%. Thermophoresis wasmore effective for small particles (diameter less than0.2μm) than large particles(diamter larger than1μm). Water vapor significantly improved the removal of smallparticles and the improvement was about20%. But it had a slight effect on largeparticles. Water film greatly improved the collection efficiency of small particles andthe enhancement was about30%~50%. Meanwhile, it also improved the removal oflarge particles and the improvement was about8%.Next, the effects of humidity on negative ion mobility and negative coronainception electric field were studied. The effects of humidity and temperature on thenegative ion mobility were experimentally studied. A formula was proposed for theeffects of humidity and temperature on the negative ion mobility. The calculated valueswere in good agreement with the experimental results. The influence of humidity onnegative corona inception electric filed was calculated based on the streamer theory.The negative corona inception electric filed decreased with the increase of humidity. Acorrection function to Peek formula was suggested for the effect of humidity. Theeffects of humidity on corona current and corona electric field were studied andcompared with the experimental results.Next, a pilot-scale ESP system was set up. The effects of operating parameters onthe performance of ESP were studied. The results showed that the collection efficiencydecreased with the increase of gas velocity. The total collection efficiency greatlyincreased with water injection and the improvement was about8.7%. The collectionefficiency gradually improved as the operating voltage increased. The efficiency improvement with water injection increased approximately linearly with the increase ofoperating voltage. The removal efficiency slightly increased as the gas temperatureincreased. The efficiency enhancement with water injection increased approximatelylinearly with the increase of gas temperature. The collection efficiency slightlyimproved with the increase of relative humidity. The efficiency greatly improved withwater injection. But the improvement decreased as the relative humidity increased. Theamount of water injection had little effect on particle removal efficiency. The collectionefficiency was not affected when wastewater was used instead of clear water.Last, a numerical simulation platform for the multiphysical processes in wet ESPwas set up. The effects of structural parameters on the performance of wet ESP werestudied. The results showed that the collection efficiency increased with the increase ofcorona wire spacing. The efficiency improvement became slight when the wire spacingwas larger than the plate spacing. The collection efficiency greatly improved as thenumber of corona wire increased when the wire spacing was constant. But the averageefficiency of a single wire decreased. As the corona wire diameter decreased, thecollection efficiency significantly improved and the change of collection efficiency dueto operating voltage fluctuations decreased. With the increase of plate spacing, thecollection efficiency greatly decreased. But the change of collection efficiency due tooperating voltage fluctuations decreased. |
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