Development of Less-polluting incense: Characterization of Aerosol and GAS Emission from Buriing Incenses
Date Issued
2005
Date
2005
Author(s)
Yang, Tzu-Ting
DOI
zh-TW
Abstract
The characteristics of incense smoke have been examined in terms of aerosol size, shape, concentration, and chemical composition. However, very limited information is available on the effect of combustion condition, heating value and the chemical composition of incense material on the characteristics of aerosol emission from smoldering incense. The objectives were to characterize the gas and particulate emission from smoldering incense in various air flow rates and from the smoldering to the flame combustion of various incenses, to make less pollutant incense and to correct the indoor contamination caused by incense burning.
Various incense sticks with known heat value and elementary analysis. Air flow rates and various oxygen contents were regulated to vary the temperature on the surface of the smoldering tip in a test chamber. Real-time instruments were used to monitor carbon monoxide, carbon dioxide, TVOCs and particulates. To determine the mass concentration of the total particles 37mm filter cassette was used. Charcoal tube was used to sampling volatile organic compounds. Identifying and Quantifying Organic Compounds of Particulate Matter by GC-MS.
From burning various diameter incenses, the shape of each incense burning tip demonstrated a cone appearance. The length and average surface temperatures of the cones and the burning rates increased when the incense diameters also increased. The modal aerosol sizes of the two types of incenses were approximately 80 nm (with non-visible smoke) and 200 nm (with visible smoke), respectively. The aerosol number size distribution increased with increasing incense diameters. This possibly occurred since larger incense diameters produced more low volatile organic compounds by heterogeneous condensation, and the process of coagulation increased particles sizes. The total aerosol number (volume and mass) concentrations increased with the increasing incense diameters, but emission factors decreased. CO2, CO, TVOCs concentrations, and CO emission factors increased with the increasing incense diameters, but CO2 emission factors decreased at the same time. Furthermore, the combustion efficiency decreased when incense diameters increased, indicating that smoldering coarser incenses were more incomplete.
The burning-rate increases with increasing flow at 1~15 L/min, over 15 L/min high flow not only enhances the mass transfer of oxygen but also significantly increase the heat loss at the burning tip. The CO2, CO, TVOCs and the aerosol number (volume and mass) emission rates and emission factor increase along with increasing flow. The count (volume) median diameter decrease with increasing air flow because dilution effect coagulation of particles. Furthermore, the combustion efficiency in term of (CO2/(CO+CO2)) decreases with increasing flow.
The temperature of the smoldering incense increased (from 400 to 650℃) with the oxygen content increased, generating a transfer flame at over 650℃. The temperature was in the range from 800 to 1200℃ during flaming combustion. Smoldering incense burned more slowly than flaming incense. Under smoldering incense and as the oxygen contents increased, both the flammable gas emission rate and the surface temperature of the incense tip increased. When both the concentrations of flammable gases increased within the combustion limits and the temperature of the incense tip grew high enough to ignite this mixture of gases, the transition occurred from smoldering to flaming combustion. The emission factors of CO, TVOCs and PM (number) during flaming combustion were lower than during smoldering combustion.
The modal aerosol sizes of incense A, B and C were 200 (with visible smoke), 80 (with non-visible smoke) and 100 nm, respectively, at an oxygen content of 20 %. The varieties on the aerosol size were associated with incense materials. Smoldering and flaming incense produced the various aerosol size distributions under various oxygen contents. Those results were due to the various concentrations of low volatile vapors and initial concentrations of particles produced under various oxygen contents. By homogeneous condensations, these low volatile vapors formed new smaller particles. The particle sizes could also increase due to heterogeneous condensations of low volatile vapors on larger particles, and to coagulations of particles with each other. In addition the initial concentrations of particles were reduced due to coagulation. However, homogeneous condensation reactions increased particle concentrations. On the other hand, this study found that the partly particle phase organic compounds came from vaporized products of incense material having condensed on the surface of particles , and the gas phase organic compounds came from the vaporized products of incense materials that had been identified in the extracted liquid, and where others were known combustible products.
Smoldering incense produces many toxic organic compounds, which are potential pollutant sources in indoor environment. People should avoid burning incenses in their homes. If people must burn incenses in respect for their ancestors, the information in this work suggests that smoldering incense with low-volatility material, low air flow rates, fine diameter and at a minimal burning tip temperature may release heat to maintain combustion and produce the least amount of gas and particulate organic compounds. Flaming incense can be a good method to control toxic pollutant gases due to more complete combustion.
Subjects
拜香
悶燒
微粒
毒性有機化學物質
Incense
Smoldering combustion
Particle
Toxic organic compound
Type
thesis
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