Discusión de los resultados/ Objetivo general

An example case is described below showing how the emission factors and other variables

involved in the experiments were computed.

The experimental data was taken from the sensors and organized in a spreadsheet that has two

columns with date/time and the sensor readings. A graph was plotted with time on X-axis and

sensor readings on Y-axis. Looking at the graph, some of the fields in the Excel spreadsheet were

marked as special fields to indicate the start time, first peak, end peak, final time, and stop of the

experiments; they are described below:

Start time: Represents the time at which the experiment started

First peak: Represents the time where the steady-state condition begins

End peak: Represents the time where the steady-state condition ends

Final Time: Represents the time where the incense stick stops burning

Stop: Represents an additional time after the incense stick stops burning to allow the

pollutant concentration to fall to a initial level.

Note: The total time used in Eq (9) is the difference between start time and final time.

Detailed description for computing (PM2.5/PM10, number and mass) and CO EFs are described

below:

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5.1.3.1 Carbon monoxide EFs:

The following are the steps involved in computing the CO EFs and other variables for each

experiment:

•

First, the CO readings were downloaded from the CO sensor and saved in an Excel

spreadsheet

•

The sensor logs the CO values in parts per million (ppm) for every 10 seconds; these

values were converted to mass concentrations using the formula

𝐶_{𝑚𝑎𝑠𝑠}

=

1000𝐶𝑝𝑝𝑚𝑀𝑊𝑝

𝑉/𝑛

(10)

Where,

Cmass = mass concentration, μg/m3

Cppm = volume or molar concentration, ppm

MWp = molecular weight of pollutant gas, g/gmol

V/n = volume per mole of an ideal gas, value is 24.45 L/gmol at standard

temperature (25 oC) and standard pressure (1 atm)

•

After converting CO values to mass concentration, a graph is plotted with time on X-axis

and mass concentration readings on Y-axis as shown in Figure 8.

Figure 8: Carbon monoxide concentration vs time graph

0.00

5000.00

10000.00

15000.00

20000.00

25000.00

0

500

1000

1500

2000

2500

3000

C

O r

ea

d

in

gs,

µg

/m

3

Time, seconds

Carbon monoxide mass concentration vs time

end peak

first peak

25

•

From the graph, first peak, end peak, start time, and final time were noted

•

The average concentration was computed between the first and end peak as shown in

Figure 8.

•

With the calculated flow rate and the average concentration, the emission rate (E) was

calculated using Eq (4).

•

Using the emission rate (E) calculated in the previous step, the emission factor was

calculated using Eq (8) and Eq (9).

5.1.3.2 PM2.5 (mass) EFs:

The following are the steps involved in calculating the PM2.5 (mass)EFs and other variables for

each experiment:

•

First, the readings were downloaded from the Dylos particulate matter analyzer and saved

in an Excel spreadsheet

•

The sensor logs the values in two channels; small (0.5µ<particles<2.5µ) and large

(2.5µ<particles<10µ) in # particles per 0.01 cubic feet of air for every 1 minute; the small

(PM2.5) values were converted to mass concentrations using the formula recommended by

the manufacturer

PM2.5 mass concentration (µg/m3) = (# of particles per 0.01 cubic feet)/100

•

After converting values to mass concentration, a graph is plotted with time on X-axis and

mass concentration readings on Y-axis as shown in Figure 9.

26

Figure 9: PM2.5 mass concentration vs time graph

•

From the graph, first peak, end peak, start time, and final time were noted

•

The average concentration was computed between the first and end peak as shown in

Figure 9.

•

With the calculated flow rate and the average concentration, the emission rate (E) was

calculated using Eq (4).

•

Using the emission rate (E) calculated in the previous step, the emission factor was

calculated using Eq (8) and Eq (9).

5.1.3.3 PM2.5 (number) EFs:

The following are the steps involved in calculating the PM2.5 (number) EFs for each experiment:

•

First, the PM2.5 (small) readings were downloaded from the Dylos particulate matter

analyzer and saved in an Excel spreadsheet

•

The sensor logs the values in # PM2.5 particles per 0.01 cubic feet of air for every 1

minute; the values were converted to # particles per cubic meter.

•

After converting the values, a graph is plotted with time on X-axis and number

concentration readings on Y-axis.

•

Then, the same steps were used as discussed in calculating PM2.5 mass emission factors

0.00

100.00

200.00

300.00

400.00

500.00

600.00

0

10

20

30

40

50

60

PM

2.5

(µ

g

/m

3

)

Time, minutes

PM_2.5mass concentration vs time

27

5.1.3.4 PM10 (mass) EFs:

The following are the steps involved in calculating the PM10 (mass) EFs for each experiment:

•

First, the readings were downloaded from the Dylos particulate matter analyzer and saved

in an Excel spreadsheet

•

The sensor logs the values in two channels; small (0.5µ<particles<2.5µ) and large

(2.5µ<particles<10µ) in # particles per 0.01 cubic feet of air for every 1 minute; the PM10

(small + large) values were converted to mass concentrations using the formula

recommended by the manufacturer

PM10 mass concentration (µg/m3_{) = small/100 + large/3}

•

Then, the same steps were used as discussed in calculating PM2.5 mass emission factors

5.1.3.5 PM10 (number) EFs:

The following are the steps involved in calculating the PM10 (number) EFs for each experiment:

•

First, the readings were downloaded from the Dylos particulate matter analyzer and saved

in an Excel spreadsheet

•

The sensor logs the values in two channels; small (0.5µ<particles<2.5µ) and large

(2.5µ<particles<10µ) in # particles per 0.01 cubic feet of air for every 1 minute; the PM10

number concentration was calculated by adding the small and large channels. The values

were converted to # particles per cubic meter.

•

After converting the values, a graph is plotted with time on X-axis and number

concentration readings on Y-axis.

28

5.2 Experimental Design

Experiments were conducted in four different cases (scenarios) to estimate the emission factors

accurately. Table 1 shows the various cases used in this research.

Table 1: Experimental design

Case1

One incense stick with one fan

Case2

Two incense sticks with one fan

Case3

One incense stick with two fans

Case4

Two incense sticks with two fans

Several test runs were performed for each case to test the repeatability of the results; all the

experiments for each case were conducted at the University of New Orleans in the months of

March, June, and July in the test chamber designed for the research. Dylos particulate matter

analyzer and industrial scientific carbon monoxide sensors were used to log the PM2.5, PM10, and

CO readings while conducting experiments. The PM2.5 (mass and number), PM10 (mass and

number), and carbon monoxide emission factors for each case were computed and reported in the

results section.

29

5.3 Experimental Procedure

All the experiments involved in this research were conducted at the University of New Orleans.

The following procedure was followed for each experiment performed.

•

Initial weight of the incense stick (before burning) was measured using a weighing

balance

•

The whole box was cleared with ambient air, so the initial concentration is approximately

zero, and the fans were turned on

•

The particulate matter and carbon monoxide sensors were initiated to log the readings

•

Then, incense stick was lighted and left in the chamber, and the top of the box was closed

to keep it air-tight. The start time of the experiment was noted

•

The experiment was performed until the incense stick stopped burning. The final time of

the experiment was noted

•

The instruments were kept running until the pollutant concentration came to initial level

(this usually takes around 5 minutes)

•

The total time of the experiment was noted

•

The final weight (small stick left after burning) of the incense was measured

•

The data was downloaded from the sensors and then analyzed to compute the results

Several experiments were conducted with a time gap of 30 minutes between each experiment.

This was to ensure the pollutant concentrations inside the chamber come to the initial levels.

30

5.4 Materials

5.4.1 Test Chamber

The test chamber required for this research is designed as per the EPA Method 1 guidelines. The

setup with all the dimensions is shown in Figure 10. It is made of acrylic glass to see the smoke

from the incense burning visually. The box was fabricated in such a way that all the openings

were sealed to make it an airtight box. It has openings on one side to allow ambient air to enter

as shown in Figure 10. It has a lid on the top that can be opened to setup the incense stick, a cup

holder and a container as shown in Figure 11.

A fan was installed to draw the air through the rectangular duct as shown in Figure 11. The fan

was fixed to a plate that can slide down as shown in Figure 11. Sensors were placed inside the

chamber to record the pollutant readings. An incense stick in a cup holder was placed in a

container with water; this was to ensure that the soot generated from incense burning does not

affect the particulate matter readings. The actual laboratory setup of the test chamber is shown in

Figure 12, 13.

Figure 10: Isometric view of the test chamber. A. Incense stick, B. Cup holder, C. Container, D. Fan, E.

CO sensor, F. Dylos Sensor

31

Figure 11: Isometric view showing the initial setup

32

Figure 13: Test chamber used in this research (Isometric view)

5.4.2 Dylos Monitor

The Dylos DC 1700 particulate matter analyzer was used in the experiments as shown in Figure

14. It is a real-time analyzer that can be used for both ambient and indoor environments. It has an

LCD screen that displays the number of particles in real-time; the left number represents the

number of particles that are >0.5 microns and <2.5 microns in size, and the right number

represents the number of particles that are >2.5 microns and <10 microns in size. It works on the

principle of laser-based particle counter; it has an internal battery that runs for 6 hours of

continuous operation. It has a real-time clock that stamps the date and time of each reading. Data

can be logged in varying time intervals ranging from one minute to one hour. It has an internal

memory that can store up to 10,000 data points, and the data can be downloaded by connecting

the instrument to PC or laptop through RS 232 cable provided by the manufacturer [22]_.

33

Figure 14: Dylos particulate matter analyzer

The manufactured recommended formulas were used for converting the number concentration to

mass concentration.

PM2.5 mass concentration (µg/m3_{) = (# of particles per 0.01 cubic feet on the left channel)/100}

PM10 mass concentration (µg/m3_{) = (# of particles per 0.01 cubic feet on the right channel)/3}

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