Control for Incense Smoke Pollutant(2/2)
Date Issued
2005-07-31
Date
2005-07-31
Author(s)
林嘉明
DOI
932320B002051
Abstract
To develop a less polluting incense, this study characterized the gaseous and particulate
emission from burning four types of Chinese incenses (A, B, C, D) with different heat values
(3936-5060 Kcal/Kg), chemical compositions (carbon content 45-65% and volatile component
20-80%) at the controlled atmospheric conditions (air flow rate and oxygen content of air). The
experimental trials were conducted in a test chamber where air flow rate (1-20 L/min) as well as
oxygen content (20-45%) was regulated to keep incense smoldering up to burst of flame burning .
The direct reading instruments were employed to measure the surface temperature at tip of a
burning incense, characteristics of particulates (number concentration, volume concentration and
size distribution), and concentrations of CO2, CO and total volatile compounds (TVOCs),
respectively. The 37 mm quatz filter in a three pieces holder for sampling total particulates and
the activated charcoal tube for sampling gaseous volatile organic compounds were applied to
collect incense smoke for GC/MS analysis. The combustion rate (g/hr) and combustion efficiency
(=[CO2/(CO+CO2)]) of an incense, and the emission rates (mg/hr or particle number /hr) as well
as the emission factors (mg/g incense consumed or particle number /g incense consumed) for
gaseous and particulate pollutants were calculated.
The so-called “less smoke incense” had greater amount of carbon, less volatile component and
greater heat value in comparison to the “smoke incense”. The incense with greater heat value
required less oxygen content to shift it from smoldering state to flame burning state. The
temperatures at tip of a burning incense during smoldering ranged from 400 ℃to 650 ℃.The
incense soon shifted to flame burning at temperature beyond 650 ℃.At atmosphere with fixed air
flow rate and oxygen content, the smoldering incense with greater heat value had relatively high
surface temperature at burning tip and the incense with greater diameter did as well. The surface
temperature also raised with the increase of oxygen content and air flow rate, respectively.
However, the cooling effect due to high flow rate beyond 15 L/min tended to keep the
temperature around 210 ℃.The burning rate of an incense and the emission rates as well as
emission factors for particulate, CO2, CO and TVOCs increase with the increase of the surface
temperature at burning tip. The linear regression was fitted well for the rate or the factor versus
the inversely temperature in Kelvin. In comparison with the “smoke incenses” (types A, C and E),
the “less smoke incense”(types B and D) with greater carbon content, greater heat value but less
volatile component had relatively greater emission rates and emission factors of CO2 and CO ,
less emission of TVOCs, less particulate concentration and smaller size of particulate. Within a
group of incenses prepared by the identical raw materials, burning the coarse incense yielded
greater number concentration of submicron particulates. The number concentration increased but
the size of particulates decreased as the air flow rate increased from 1L/min up to 15 L/min.
GC/MS analysis identified 25, 19 and 84 species of chemicals in the solvent extracts of
incenses A, B and C, respectively. Most chemicals such as alkanes, alkenes, alcohols, aldehydes, ketones, esters and phenols are likely attributed to the vegetarian raw materials of an incense
while a few of chemicals like musk found in the extract of the Incense C may be from animal
source. Plasticizers such as diethyl phthalate and bis(2-ethylhexyl)phathalate were also found in
the extracts of the incenses. Particulate–bound chemicals found in incense smoke mainly were
heat decomposed organic compounds although parts of the particulate-bound chemicals with low
volatility were identical to the chemicals found in the extract of the incenses. The
particulate-bound chemical species with greater carbon number increased along with the increase
of oxygen content during smoldering of incenses but soon decreased as the incenses turned to
flame burning. On contrary, the particulate-bound chemicals with less carbon number decreased
with the increase of oxygen content in the supply air. The similar trends happened in gaseous
phase of incense smoke. We concluded that the incense with low carbon content and less volatile
component burning in atmosphere with low air flow rate yields less amount of pollutants in terms
of TVOCs, particulates and particulate-bound chemicals.
Subjects
Incense
Smoldering combustion
Submicron particle
Particulate-bound
chemicals
chemicals
Publisher
臺北市：國立臺灣大學公共衛生學院環境衛生研究所
Type
report
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