具有二階段喉部的濕壁型文氏洗滌器之研發

Abstract

傳統的文式洗滌器在處理次微米微粒時的壓損過高，且在長時間處理高濃度與高黏度微粒時會發生粉塵阻塞喉部的現象，使壓損提高，並增加操作成本。本研究開發一種具有二階段喉部的濕壁型高效率文氏洗滌器，目的在於避免粉塵之阻塞，並提昇高濃度細微粒的處理效率。本研究利用微粒在過飽和水蒸氣中異相核凝成長的原理來提高文式洗滌器的除塵效率。二段喉部的濕壁型文氏洗滌器設計，分成文氏外套管與文氏內套管兩部分，以便於製造及安裝。為避免產生粉塵堆積現象，此文式洗滌器於溢流水槽底部加裝兩導管來讓清洗文式外套管壁面之廢液流出至下方廢液儲存槽，洗滌後之乾淨空氣與洗滌廢液則由文式內套管一方排出，亦即廢氣中的粉塵洗滌與文式外套管面附著的粉塵洗滌分開。二階段喉部的濕壁型文氏洗滌器形狀簡單且容易製造，成本將較其他設備低廉。 本研究在實驗室完成避免文式洗滌器的粉塵阻塞的研究，並完成高效率、低壓損的設計參數及操作條件測試。 實驗室的研究發現二階喉部文氏洗滌器可在合理的壓損範圍內(10.7 inH2O)，微粒截取氣動直徑可低達130 nm，對於氣動粒徑大於300 nm之油酸微粒去除效率達到80 %以上。對於某石化工廠含有ABS微粒廢氣之微粒(MMAD:562 nm, σg=1.81)總質量去除效率也可達80 %以上。對於高溫製程的廢氣而言，處理1 CMM之廢氣一年的操作成本評估約為10.4萬元。因此本新型的二階段喉部文氏洗滌器，可在合理的操作成本範圍內，有效解決工廠製程所產生的細微粒及白煙問題。

In traditional venturi scrubbers, the gas pressure drop is too high when removing submicron particles. In addition, particles will be plugged in the venturi throat when particle concentration is high and particles are sticky, which results in high pressure drop and high running cost. In order to avoid the plugging of the venturi throat and improve the removal efficiency of fine particles, this research intends to develop a wetted wall 2-stage venturi scrubber. Heterogeneous growth of fine particles by using super-saturation of water vapor is employed to increase the removal efficiency of the venturi scrubber. The venturi tube of the present design is divided into inner and outer venturi tubes for ease of manufacturing and assembly. There are two connecting tubes that transport the cleaning fluid at the converging section into the liquid storage tank. The scrubbed clean gas will exit from the diverging section of the inner venturi, while the cleaning water for removing deposited particles on the outer venturi’s wall is discharged into the diverging section of the outer venturi to avoid high pressure drop. The current 2-stage venturi scrubber is simple and easy to make. Its cost is lower than other air pollution control devices.The experimental results showed that the cut-off diameter of wetted wall 2-stage venturi scrubber was 130 nm in aerodynamic diameter under a reasonable pressure drop of 10.7 in H2O. The collection efficiency for particles larger than 300 nm in aerodynamic diameter was higher than 80 % and 90 % for oil and salt particles, respectively. More than 80 % total mass removal efficiency was predicted for removing fine particles in the exhaust of an ABS plant (MMAD=562 nm, σg=1.81). To remove fine particles from a high temperature gas exhaust with a flow rate of 1 CMM, the theoretical running cost of this high efficiency venturi scrubber is predicted to be NT 104 thousands per year.