| Author: | Han, Shuwen |
| Title: | Investigation of emission characteristics and development of control techniques towards cooking oil fumes |
| Advisors: | Lee, Shun-cheng (CEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Cooking -- Environmental aspects Air -- Pollution Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxiv, 193 pages : color illustrations |
| Language: | English |
| Abstract: | Air pollution has emerged as one of the most critical environmental challenges worldwide, particularly in heavily populated urban areas where human activities are concentrated. Cooking oil fumes (COFs) are the exhaust emission gases produced from the mixture of cooking oils, raw food materials and condiments with complicated physical and chemical transformations including decomposition, oxidation, and polymerization in high temperature conditions from the cooking processes. In this study, the analysis results of the five different types of cooking methods, i.e., stir-frying, pan-frying, deep-frying, boiling and steaming from the in-lab cooking simulation kitchen revealed the PM2.5 concentration trend of stir-frying (381.66 μg/m3) > deep-frying (235.88 μg/m3) > pan-frying (146.87 μg/m3) > boiling (88.13 μg/m3) > steaming (38.58 μg/m3). OC was found to be the dominant component with the proportions of 39.3% - 49.3% and high OC/EC ratios were obtained in all these cooking sources. Carcinogenic PAHs were also detected in PM2.5 sampling which accounted for 29% to 49% of the total detected PAHs, indicating the existence of potential carcinogenic health risks. While the concentration trend of the total VOCs was observed as deep-frying (1166.2 μg/m3) > pan-frying (937.0 μg/m3) > stir-frying (897.3 μg/m3) > boiling (692.4 μg/m3) > steaming (133.4 μg/m3), indicating the oil-based cooking methods emitted higher concentrations of PM2.5 and VOCs than those from water-based cooking styles. A field study of the COFs from four common commercial restaurants including Chinese fast food (CFF), Western fast food (WFF), Cantonese cuisine (CAN) and Chongqing hot pot (CHP) were investigated, and the concentrations of PM2.5 in decreasing order were 269.85 μg/m3, 232.11 μg/m3, 199.95 μg/m3, and 85.69 μg/m3 for CAN, CFF, WFF, and CHP. The dominant cooking methods could be confirmed by the ratios of OC/EC and diagnostic analysis of PAHs. The VOC emission levels and composition profiles from the four restaurants were consistent with their major cooking methods with significant high VOC emissions of hexane, ethylene, and formaldehyde. Significant adverse environmental effects on the formation of O3 and secondary organic aerosols were revealed by the results of their high chemical reactivity, OFP, and SOAFP. The highest unit formation rates for ozone and SOA were obtained from CAN as 5.55 g OFP/g VOCs and WFF as 2.17 g SOAFP/ g VOCs. In addition, health risk assessment by inhalation exposure suggested that significant carcinogenic risks existed to kitchen staff in all the restaurants and to the customers of CHP in particular. Given the mitigation demands of the COFs due to their detrimental effects on environment and health, two promising control strategies by applying high gravity rotating packed bed scrubber and photocatalytic nanomaterial were investigated. The PM2.5 and TVOC removal efficiency of the scrubber could be as high as 86% and 74%, respectively, as suggested by the results from the field trails, and the LOH, OFP and SOAFP all exhibited superior improvement of 62.95%, 60.35%, and 61.05%, respectively. The successfully synthesized insulator-based STO/SCO nano-heterojunction was demonstrated to have degradation capabilities towards low-concentrated gaseous pollutants of NO and HCHO with removal efficiency of 44% and 40% respectively. And it could serve as a supplementary measure for degradation of excessive gaseous pollutants after scrubber. In summary, this thesis presents the characterization and evaluation of the COFs from various scenarios, which provides a comprehensive emission inventory in Hong Kong and Asian areas. Moreover, novel control strategies were developed based on the features of COFs with satisfactory purification performance and promising application potential. |
| Rights: | All rights reserved |
| Access: | open access |
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