Development of a Condensable Particulate Matter Generator
Abstract No:
1656
Abstract Type:
Student Poster
Authors:
T LIN1, C Chen2, S HUANG2, C LIN2
Institutions:
1National Taiwan University, Taipei City, Taiwan, 2National Taiwan University, Taipei, Taiwan
Presenter:
TING-YU LIN
National Taiwan University
National Taiwan University
Faculty Advisor(s):
Chih-Chieh Chen
National Taiwan University
National Taiwan University
SHENG-HSIU HUANG
National Taiwan University
National Taiwan University
CHIH-WEI LIN
National Taiwan University
National Taiwan University
Description:
PM2.5 can be classified as filterable particulate matter (FPM) and condensable particulate matter (CPM). CPM is gaseous state at high temperature in stack after cooling it will form as particulate substance. Coal-fired power plants, industrial combustion and vehicle particle emissions are important contributors of CPM emissions. In the past, no country in the world has set limits on CPM emissions. Existing regulations only focus on FPM emissions. With the rapid development of FPM control technology, its emissions become extremely low. Some researchers found that CPM emission is higher than FPM by more than two times. In order to control CPM emission government should lay down a criterion and establish a accuracy sampling method. There are two CPM sampling methods from EPA such as dilution and condensation. Condensation method is generally thought to overestimate CPM emissions because of dissolved gases in stack. Dilution sampling have more accurately represent particulate concentrations from stack emissions because they better simulate the natural physicochemical processes of particulate formation in the atmosphere. To compared two methods measurement biases we designed a CPM generator to produce CPM with known composition, concentration and stability. With this CPM generator to evaluate the factors affecting CPM measurements and to improve the accuracy of the CPM methods.
Situation/Problem:
There are two CPM sampling methods from US EPA such as dilution and condensation. Many research found that dilution and condensation sampling measurement have different biases. Such as condensation method which may cause overestimate CPM emissions because of dissolved gases in stack. As for the dilution sampling system, according to EPA CTM-039, it required a large dilution chamber to well mixed with dilution air and sampling gas. After the sampling is completed, the entire surface of the dilution chamber must be rinsed with eluent, otherwise the deposition loss of the tube wall cannot be correctly evaluated, and the CPM concentration will be underestimated. Although dilution sampling was thought have more accurately represent CPM emissions because they are more simulate the natural physicochemical processes of particulate formation in the atmosphere but after sampling it also have to rinse the sampling train which may cause sample recovery problem. In order to compared two methods, we should have a controllable, stable CPM generating source. But general CPM amount in stack is unpredictable and unstable and its sampling amount may affect by flue gas temperature, humidity or material of the fuel in stack. Therefore, the aim of this study is design a CPM generator which can produce known composition, concentration and long-term stability CPM. Through this CPM generator to compare condensation and dilution CPM methods measurement amount and evaluate the factors affecting CPM measurements to improve the accuracy of the CPM methods.
Methods:
CPM uses IC automatic temperature control tin melting furnace to heat paraffin wax. Paraffin wax is solid at room temperature and begins to melt above approximately 37 °C and its boiling point is above 300 °C. Besides, paraffin wax has low vapor pressure (0.013kPa at 20°C) which can provide stable property of CPM. Heating paraffin wax is to produce paraffin vapor after cooling down vapor temperature by passing through a glass serum bottle to formed as paraffin wax particle simulating the CPM in stack. The glass serum bottle inside diameter is 8 cm which covered on the furnace as a condensation chamber of CPM and its dilution air is 4.8 L/min. There is a sampling hole on the bottle at a vertical height of 18 cm to provide enough space to condense paraffin wax vapor. Control CPM concentration by adjusting IC automatic temperature control tin melting furnace heating temperature (100-130°C) which can control the paraffin wax vapor amount.
Thermocouples are installed at the bottom of the tin furnace and sampling pipe entrance to represent the heating and sampling temperature, respectively. The instantaneous concentration and particle size of the CPM were analyzed by using an aerodynamic particle sizer, beta gauge, optical particle sizer and haz dust. OPS and haz dust mainly uses optical detection technology to detect particles which may cause light scattering polarization resulting in slight deviation of the measurements. In order to avoid this measurement bias, using 37 mm Teflon filters as the reference mass concentration. The sampling position of the particle mass is located behind the OPS optical cavity, so the OPS can be corrected by the mass concentration of the particles and both of filters and OPS sampling flow rate is 1 L/min. Due to this process, not only can correct the true value of CPM mass concentration but also can use direct reading instrument in the future to reduce the weighing time of the filters. After sampling, the CPM filters will put into weighing chamber for 24 hours to conditioning which control temperature and humidity at 20-30°C and 30-40%, respectively.
Method 202 mentions that after sampling the filters require conditioning for 24 hours. However, the actual CPM composition is complex and contains a certain proportion of volatile substances. In order to prove the characteristics of paraffin wax are stable and not easy volatile, after sampling the filters will move to weighing chamber to conditioning and every few days weighing the filters to evaluate the variability of paraffin wax weight.
Thermocouples are installed at the bottom of the tin furnace and sampling pipe entrance to represent the heating and sampling temperature, respectively. The instantaneous concentration and particle size of the CPM were analyzed by using an aerodynamic particle sizer, beta gauge, optical particle sizer and haz dust. OPS and haz dust mainly uses optical detection technology to detect particles which may cause light scattering polarization resulting in slight deviation of the measurements. In order to avoid this measurement bias, using 37 mm Teflon filters as the reference mass concentration. The sampling position of the particle mass is located behind the OPS optical cavity, so the OPS can be corrected by the mass concentration of the particles and both of filters and OPS sampling flow rate is 1 L/min. Due to this process, not only can correct the true value of CPM mass concentration but also can use direct reading instrument in the future to reduce the weighing time of the filters. After sampling, the CPM filters will put into weighing chamber for 24 hours to conditioning which control temperature and humidity at 20-30°C and 30-40%, respectively.
Method 202 mentions that after sampling the filters require conditioning for 24 hours. However, the actual CPM composition is complex and contains a certain proportion of volatile substances. In order to prove the characteristics of paraffin wax are stable and not easy volatile, after sampling the filters will move to weighing chamber to conditioning and every few days weighing the filters to evaluate the variability of paraffin wax weight.
Results / Conclusions:
In order to known the time required for the heating system to reach stability, using thermocouples and direct reading instruments to sampling the temperature and concentration of the system, respectively. The result shows that it takes approximately 20 minutes for the generator to be stabilized.
The relationship between heating temperature and mass concentration is a parabola. The mathematical relation between heating temperature and mass concentration is y=6×10⁻⁶exp(0.1056x). As the heating temperature increases, both the mass and the number concentration have a high peak in the large particle size. The main reason is that when the heating temperature is increased, the paraffin vapor will increase, too. The higher concentration of paraffin vapor in the condensation chamber the larger particle size it formed. In other words, the higher heating temperature the more CPM concentration the generator produced.
To reduce the weighing time of the filters, using OPS to sampling the concentration of the generator. But the optical detection technology may cause light scattering polarization resulting in slight deviation of the measurements. To avoid this situation, compared mass concentration of OPS, beta gauge, haz dust, aerodynamic particle sizer and filters. The result show that mass concentration of OPS, beta gauge, haz dust, aerodynamic particle sizer and filters can be estimated by the relationship of y=0.6231x, y=0.3643x, y=2.2267x, y=1.4747x.
Since CPM composition is complex and contains volatile substances which may cause bias when weighing the sampling filters. To prove the characteristics of paraffin wax are stable and not easy volatile, after sampling the filters will move to weighing chamber to conditioning and every few days weighing the filters to evaluate the variability of paraffin wax weight. The result shows that comparing with blank filter. After 22 days' condition, the CPM and blank filter weight variation is about 2.07, 1.45 μg which in keeping with the standard of constant weight of the filter (<0.5 mg).
In conclusions, this generator produces CPM with known composition, concentration and long-term stability. The system being stable required about 20 minutes and the material of CPM is not easy to volatile which can provide stable weight when weighing. Besides, with these mathematical relations above paragraphs not only can rapidly know how to produce controllable CPM concentration of this generator but also can know the real mass concentration without using filter sampling.
The relationship between heating temperature and mass concentration is a parabola. The mathematical relation between heating temperature and mass concentration is y=6×10⁻⁶exp(0.1056x). As the heating temperature increases, both the mass and the number concentration have a high peak in the large particle size. The main reason is that when the heating temperature is increased, the paraffin vapor will increase, too. The higher concentration of paraffin vapor in the condensation chamber the larger particle size it formed. In other words, the higher heating temperature the more CPM concentration the generator produced.
To reduce the weighing time of the filters, using OPS to sampling the concentration of the generator. But the optical detection technology may cause light scattering polarization resulting in slight deviation of the measurements. To avoid this situation, compared mass concentration of OPS, beta gauge, haz dust, aerodynamic particle sizer and filters. The result show that mass concentration of OPS, beta gauge, haz dust, aerodynamic particle sizer and filters can be estimated by the relationship of y=0.6231x, y=0.3643x, y=2.2267x, y=1.4747x.
Since CPM composition is complex and contains volatile substances which may cause bias when weighing the sampling filters. To prove the characteristics of paraffin wax are stable and not easy volatile, after sampling the filters will move to weighing chamber to conditioning and every few days weighing the filters to evaluate the variability of paraffin wax weight. The result shows that comparing with blank filter. After 22 days' condition, the CPM and blank filter weight variation is about 2.07, 1.45 μg which in keeping with the standard of constant weight of the filter (<0.5 mg).
In conclusions, this generator produces CPM with known composition, concentration and long-term stability. The system being stable required about 20 minutes and the material of CPM is not easy to volatile which can provide stable weight when weighing. Besides, with these mathematical relations above paragraphs not only can rapidly know how to produce controllable CPM concentration of this generator but also can know the real mass concentration without using filter sampling.
Primary Topic:
Aerosols
Secondary Topics:
Sampling and Analysis