Electrostatic Precipitation Technologies for the Mitigation of Particulate Matter Emissions from Poultry Facilities.

摘要

Particulate matter (PM) emissions and air pollution have long been a great concern in animal feeding operations (AFOs), especially in poultry facilities, yet no viable solution currently exists. This research focused on the development of feasible electrostatic precipitation (ESP) technologies for mitigation of PM emissions from poultry facilities. Preliminary investigation was conducted using a commercially available ESP unit to assess the feasibility of using ESP technology for capturing poultry PM. Effects of operating parameters such as charger voltage, exhaust air velocity and PM concentration on performance of a two-stage plate ESP were examined. An empirical model for predicting ESP performance was also developed. To collect at least 90% of all particles, the operating conditions were 9 kV and 2.5 m/s. Power consumption of the ESP to collect 90% of the total particles is 90 watts/m2 of the ESP cross-sectional area. Results showed great promise, however the commercial ESP design was not optimized for removal of poultry PM. The ESP technology needs to be optimized to effectively capture poultry PM with lower power consumption. Effective PM mitigation equipment can be designed properly only if the properties of the PM emissions are well understood. The important characteristics of PM related to ESP performance include (a) concentration, (b) size distribution, (c) morphology, (d) particle density, (e) resistivity, and (f) elemental composition. PM was sampled from a poultry layer house in three consecutive seasons. The average concentration measured inside the barn was 17.5 ± 6.8 particles/cm 3 ranging from 5.8 to 31.9 particles/cm3 while the average mass concentration was 0.62 ± 0.26 mg/m3 with a range of 0.23 to 0.95 mg/m3. The average aerodynamic PM size was significantly smaller in winter (2.0 ± 0.2 µm) compared to the annual (2.5 ± 0.2 µm). The SEM photomicrographs revealed five basic PM morphologies namely: (a) flaky, (b) irregular, (c) spherical, (d) oblate spheroid, and (e) needle-like. Almost 78% of PM were irregular shaped particles. Using the above measured PM characteristics, a computer CFD model of the ESP process was developed and used to theoretically determine the effects of particle size, air velocity, charger voltage, and ESP geometry on PM collection efficiency. The CFD model was used to optimize an ESP design for capturing poultry PM and predicted the ESP performance with an accuracy of 98.7% (standard error of prediction 10%). The optimized ESP design was used to construct an ESP unit in the lab for evaluation of the CFD model and verification of the optimum ESP operating conditions: 13.6 KV, 1.7 m/s, and 0.047 watt/ [m3/h] power usage. The ESP unit collected 89.4 ± 7.3% of the total PM in the air stream during a continuous 6-hour lab test with inlet PM concentration of about 2 mg/m3. The same unit was tested at a commercial poultry farm. The performance of the ESP for collecting poultry dust was 81.8 ± 6.5% for the total PM during a continuous 10-day operation. This study confirmed that ESP is a very promising technology for mitigating poultry PM pollution.