廚房油煙控制設備過濾特性與防制管理策略

Filtration Characteristics of Control Devices and Management Strategy of Cooking Oil Aerosol Emission

洪曉儀(Hsiao-Yi Hung)

指導教授 ： 陳志傑

國立臺灣大學/公共衛生學院/職業醫學與工業衛生研究所/碩士(2016年)

https://doi.org/10.6342/NTU201601136

摘要

近年來，大氣中細懸浮微粒(PM2.5)已成為各界所關注的重要環境議題，而根據空氣污染物排放清冊(Taiwan Emission Data System, TEDS)8.1版顯示，在臺北市中，住宿/餐飲業的PM2.5排放量約佔總量的37.5 %，因此，為了達成PM2.5減量的目的勢必先對烹煮油煙進行排放控制。目前不管是針對商用或家用的油煙/汙染控制設備(Air pollution control devices, APCDs)或抽油煙機中，並沒有一套管理其過濾效能的法規，因此，本研究的目的希冀能夠藉著實際實驗測試以及理論分析推估的方式，提供未來油煙/污染控制設備「過濾效率」規範的制訂參考以及檢測驗證的方法，進而提供環保單位施行政策，並且達到PM2.5減量的目的。

油煙控制設備的效能曲線應以微粒粒徑作為函數來呈現，本研究為得到油煙控制設備的最易穿透粒徑(收集效率最差的粒徑)，需進行微粒穿透率測試。由於油煙微粒之數目濃度以次微米粒徑以下微粒為主，因此作法以定量輸出鹽類微粒產生器(model 8118A-EN, TSI Inc., St. Paul, MN)與油類產生器(model 1081414R, TSI Inc., St. Paul, MN)產生次微米的挑戰氣膠分別作為實驗室和現場採樣的測試微粒，待微粒與空氣混和均勻後進入測試腔中，並利用風機調控測試流率。氣膠濃度、粒徑分布，以微粒電移動度掃瞄分徑器(SMPS, model 3936, TSI Inc.)進行採樣分析，而油煙控制設備上游(Upstream)與下游(Downstream)的微粒濃度相除即可得微粒穿透率。而不論是濾材式油煙控制設備及靜電式油煙控制設備皆有實驗室及現場測試的資料，此外，本研究亦評估市售濾油網的過濾效能，此測試方法除了上述儀器外，並搭配超音波霧化器(model 8700-120, Sonotek Inc., Highland, NY)產生微粒，接著，使微粒通過射源(Am-241)，中和微粒帶電分布，也利用氣動粒徑分徑儀(APS, model 3321, TSI Inc.)來量測0.7-5.0 μm的粒徑範圍。

汙染控制設備的初始過濾效率為一粒徑的函數，且在微粒呈波茲曼帶電平衡的情況下，不隨著液態或固態而有所不同。實驗結果顯示，在表面風速2 m/s下，一般市售濾油網僅能有效濾除(aerosol penetration < 10%)粒徑大於2.5 μm以上的油煙微粒，然而，靜電式油煙控制設備及濾材式油煙控制設備對於PM2.5的去除有很好的效果。實驗結果顯示，靜電式油煙控制設備的微粒穿透率隨著流率的上升而上升，而其最易穿透粒徑落在0.2-0.3 μm，此外，當微粒粒徑越小於0.02 μm時，由於越不容易使之帶有電荷，因此越不容易利用庫侖力的作用將其收集，不過，從「質量」的尺度而言，該部分微粒的排放貢獻有限。另一方面，流率不僅影響濾材式油煙控制設的微粒穿透率，其濾材上的帶電量也會對性能造成影響。而不論是實驗室測試或是現場採樣，帶電濾材的最易穿透粒徑一開始為50 nm左右，當濾材浸泡至異丙醇或負載油滴微粒時，纖維上的電荷會逐漸消失，於是濾材的最易穿透粒徑便逐漸回到機械式濾材200-400 nm的範圍。因此，在管制汙染控制設備的過濾性能上，其所提供的微粒粒徑範圍應從20 nm到700 nm才有足夠的代表性，且建議最易穿透粒徑的穿透率不得超過10%。若是要以「總穿透效率」來做為呈現的方式，則只要其測試微粒粒徑之CMD落在最易穿透粒徑附近，且GSD小於1.4，則不論利用總數目、總表面積、總質量所量測的穿透率結果誤差會小於5%。

關鍵字

污染防制設備 ； 油煙機 ； 最易穿透粒徑 ； 收集效能

並列摘要

In recent years, the fine particulate matter (PM2.5) pollution has become a major environmental concern in Taiwan. According to the Taiwan Emission Data System, TEDS 8.1, more than 37.5 % of PM2.5 concentrations were contributed by emissions from both restaurants and accommodations in Taipei city. Therefore, efforts to reduce PM2.5 levels would be impeded if cooking oil emissions are not addressed. However, the use of air pollution control devices (APCDs) is not required in kitchen hood systems nowadays in Taiwan. Accordingly, the main purpose of this study was to develop a feasible filtration test method for evaluating the efficiency of APCDs in kitchen exhaust systems. The results might be helpful for environmental policy implementing and reducing the PM2.5 levels eventually.

To determine the particle penetration as a function of particle size in the range of 0.02~0.7 µm, a salt atomizer (model 8118A-EN, TSI Inc., St. Paul, MN) and an oil generator (model 1081414R, TSI Inc., St. Paul, MN) were used to generate polydisperse sub-micrometer-sized challenge aerosol particles for laboratory and field study, respectively. For laboratory tests, the generated particles were then passed through an aerosol neutralizer (25 mCi, Am241) to neutralize the aerosol particles to the Boltzmann charge equilibrium. Next, the neutralized aerosols were mixed with ambient air to obtain the desired flow rates. A scanning mobility particle sizer (SMPS, model 3936, TSI Inc.) was used to measure the aerosol concentrations and size distributions. Particle number concentration data, obtained upstream and downstream of an APCD, were used to assess the penetration of aerosol particles. In this work, filtration characteristics of filter media and electrostatic precipitators (ESPs) were measured both in the laboratory and field. Moreover, the efficiency curves of commercial grease filters were also evaluated. In this part of test, an aerodynamic particle sizer (APS, model 3321, TSI Inc.) incorporating with an ultrasonic atomizing nozzle (model 8700-120, Sonotek Inc., Highland, NY) was used to measure the aerosol penetration in the size range of 0.7~5 µm.

The APCD’s initial filtration efficiency is a function of the size of the particles, and is not dependent on whether they are solid or liquid. The results showed that the commercial grease filters were effective only at capturing particles with diameter larger than 2.5 µm at the face velocity of about 2 m/s. In contrast, ESPs and filter media tested in the present study were more effective in collecting PM2.5 particles. Experimental results showed that aerosol penetration through the ESP decreased with decreasing air flow rates. The most penetrating particle size (MPPS) of the ESP ranged from 0.2~0.3 µm. Although the collection efficiencies of ESPs decreased significantly for particles less than 20 nm due to the partial charge effect, those particles did not contribute significantly to emission based on mass. On the other hand, aerosol penetration through the filter media depended not only on air flow rates, but also on fiber charges. The data showed the tested filter media had an initial MPPS around 50 nm. When electrostatic charges are removed by dipping the filter in isopropanol or loading with oil particles, aerosol penetration increases substantially and the MPPS increases to 200~400 nm, which is the range expected for filters relying solely on mechanical collection mechanisms. The laboratory and the field tests both showed the same trend. In order to comprehensively regulate the emission of cooking oil aerosols, it is proposed that the aerosol penetration ranging from 20 to 700 nm is a required test for all APCDs, and aerosol penetration of the MPPS should not exceed 10%. Theoretical analysis results showed that using challenge aerosol with count median diameter (CMD) of MMPS and geometric standard deviation (GSD) less than 1.4, the worst efficiency of the ESP or filter could be obtained correctively within 5% error regardless of evaluating based on total number, surface, or mass.

並列關鍵字

air pollution control devices (APCDs) ； range hood ； most penetration size ； collection efficiency

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