利用紅外光光譜建立即時微量煙霧監測系統及經濟型二氧化碳感測器之研製

On-line Trace Smoke Analysis Using Infra-red Active Monitoring System and Making of Economical Type CO2 Gas Sensor

劉光弘(Kuang-Hung Liu)

指導教授 ： 廖峻德

中原大學/工學院/醫學工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100245

摘要

本研究利用可調式長光徑管及傅立葉轉換紅外光譜儀建立即時監測煙霧成分的架構，並以此研究為基礎將其應用於經濟型CO2感測器之研製。基本實驗利用模擬燃燒室對Nylon 6，在N2環境下經熱烈解後所產生的氣體分析其組成。Nylon 6為燃燒物種，其中含有醯胺的結構，受熱後可能會產生有害氣體，如：CO、CO2、HCN、NH3。利用熱重分析儀對Nylon 6分析，得到其在N2與Air環境中，反應溫度範圍分別為377 ~ 500 oC與375.7 ~ 500 oC，He環境之反應溫度範圍則與N2環境中相近，故以此結果為模擬燃燒室之加溫參數，並設定ASTM相容之模擬燃燒室，使加熱功率為600瓦連接至1-16 m可調式光徑管加以分析。燃燒室內氣體環境比例使用多孔道質量流量控制器所調配(N2、O2、CO2)。燃燒前利用元素分析儀對Nylon 6內之C、H、O成份加以分析。得到其比例關係為 N：C：H = 11.66：61.30：9.80，經計算其熱值約為26.6 KJ g-1。Nylon 6燃燒於N2環境時，由氣相紅外光光譜分析得到其波數分別在2341 ~ 2360 cm-1、666 ~ 670 cm-1(CO2)、1670 cm-1(CO)、1654 cm-1、1557 cm-1(醯胺中-CO-及-CNH-)、930 cm-1(NH3)有吸收峰值。在利用質譜儀對特定分子量之氣體分析，分子量數包括17、27、28、43及44，確定其氣體組成成份有：分子量為17的NH3、27的HCN、28 的CO、43 的CONH及44 的CO2的產生。因此，模擬燃燒室產生氣相物質經紅外光光譜分析所得之結果為可靠且此線上煙霧監測系統之架構應為可行的設計。應用於感測氣氛中CO2濃度，利用小型化之氣室取代可調式光徑管，針對波長為4.3 μm的紅外光之強度，得到CO2濃度與處理後之電訊號關係為Y =26238.97128 - 103.32948 (X) ，相關係數為-0.99079。利用單晶片89C52為系統之CPU，將最後結果顯示於LCD，可監測濃度範圍為0 ~ 6000 ppm，可適用於公共空間平時之空氣品質調節或密閉空間內早期CO2異常增加的警示。

關鍵字

CO2感測器 ； 紅外光 ； FTIR ； 煙霧感測系統 ； 熱裂解 ； nylon 6

並列摘要

This work utilizes a variable path cell and Fourier-Transformed Infrared Spectroscopy (FTIR) to establish on-line IR-active smokes detection system; based upon the investigation, we apply its principal to make an economic type of CO2 sensor. In the fundamental study, nylon-6 forms pyrolysis under oxygen-free N2 environment. Nylon-6 is naturally flammable and is composed of CO-NH group; thermally decomposed by-products such as CO, CO2, and HCN are toxic to human being. Analytical result using Thermal Gravity Analyzer (TGA) demonstrates that under N2 or air environment, the reactive temperatures of nylon 6 occur in the range of 377-500oC or 375.7-500 oC; the reactive temperatures under He are similar to N2 environment. Taking TGA results as the references, practical experiments proceed in an ASTM-comparable reactive chamber using a power of 600 W in diverse heating rates and multi-channel mass flow controller to mix with different ratios of N2, O2 and CO2; subsequently, the smokes flow through a 1-16m variable path cell and are analyzed without delay. Analytical result using Mass Analyzer indicates that the ratio of N：C：H of nylon-6 is equal to 11.66：61.30：9.80, which corresponds to a heat value of 26.6 KJ.g-1. Survey for gaseous components designates the presences of IR-active absorbance in the range of 2341-2360 cm-1 and 666-670 cm-1 for CO2, 1670 cm-1 for CO, 1557 cm-1 for –CO- and –CNH-, and 930 cm-1 for NH3, respectively. Such released substances detected by Mass Spectroscopy present the molecular weight of 27 (HCN), 28 (CO), 43 (amide) and 44 (CO2), respectively. Using FTIR to detect the trace amount of smoke is thus feasible and potentially applicable for IR-active sensing devices to determine specific gaseous by-products. Applying this study to identify low CO2 concentration, we minimize the dimension of variable path cell and detect the intensity of IR wavelength around 4.3 mm. A correlation between CO2 concentrations (Y) and electrical signals (X) is calculated as: Y = 26,239 – 103X with a correlation coefficient of –0.99079. Data processing is recorded using CPU of 89C52 and is displayed on LCD; the detectable range is 0-6,000 ppm. This minimized device is applicable for air quality control in a public sector, or for early monitoring of irregular CO2 increase in a close environment.

並列關鍵字

FTIR ； Infrared ； CO2 sensor ； nylon 6 ； pyrolysis ； smokes detection system

參考文獻

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