On-line Monitoring Equipments of Dioxins and theirPrecursors for Incineration
PlantsMITSUHIRO OKADA*1
KENICHI YONEDA*1SHIGEKI MORII*2
TAKUMI SUZUKI*2
KATSUO SEKI*2

It usually takes a few weeks to analyze dioxins concentration in flue gas from MSW incinerators by official method.
In order to reduce the required time for analysis, we have developed an on-line measuring equipment for pentachlorodibenzofuran (P 5CDF) and a real-time measuring equipment for trichlorobenzene (T 3CB). The following results
were obtained from field tests carried out using these equipments. (1) The concentration of DXNs emitted can be
estimated and monitored by measuring the concentration of P5CDF contained in flue gas using a vacuum ultraviolet
ionization mass spectrometer (VUV analyzer) after automatic concentration of P5CDF. (2) Optimum operating conditions to reduce dioxins emission can be obtained by the T3CB measuring equipment which relates to dioxins' behavior inside furnaces real-timely, and (3) These equipments can be applied in adjusting operating conditions during thetrial operation of an incineration plant by monitoring them and for basic research and development.

ment for measuring trichlorobenzene (T3CB), which havebeen developed by MHI.

1. Introduction
Dioxin emissions (hereafter abbreviated as DXNs)
emitted from incineration plants have become an issueof major social concern. As a manufacturer of incineration plants, MHI has developed various means foradvancing the combustion control and flue gas treatment
of incinerators, and has achieved fruitful results in order to reduce DXNs(1),(2).
On the other hand, it is necessary to verify the effectiveness of these measures by analyzing DXN levels basedon official methods. However, a long time (several weeks)
is needed to analyze DXNs because the concentration of
DXNs is extremely small. Moreover, the DXNs must be
separated into various isomers and each isomer must be
quantitatively analyzed in order to assess the respective
toxicities of each type of DXNs present. This problem
has been a major barrier to verifying the effectiveness ofthe measurement of DXN levels. In addition, although
DXN precursors have been suggested as being more effective in controlling DXNs than the CO conventionallyused(3), they are said to be unsuitable as indices for controlling combustion because of the long time amount oftime required to analyze them like DXNs.
Therefore, the rapid measurement of DXNs and theirprecursors is very useful for the operation of incinerator
furnaces and flue gas treatment plants.
With the aim of finding suitable solutions to these
problems, this paper introduces a monitoring system consisting of an on-line equipment for measuring
pentachloro-dibenzofuran (P5CDF) and a real time equip-

2. Configuration of system
The monitoring system is shown in Fig. 1
1. This system is basically composed of both equipments describedabove. Table 1 shows the major specifications of thismonitoring system. The following paragraphs describe
the vacuum ultraviolet ionization mass spectrometer(hereafter abbreviated to VUV analyzer) used in common with both equipments, the on-line equipment forReal time equipment
for measuring T3CB
VUV
analyzer

Dusteliminating
equipment

Incinerator
furnace

Cooling
tower

Stack
Bag filter

Automatic
concentrating
equipment
VUV analyzer
On-line equipment
for measuring P5CDF

Fig. 1 Monitoring system
The system consists of an on-line equipment for measuring P5CDF anda real time equipment for measuring T3CB.

*1 Yokohama Dockyard & Machinery Works*2 Yokohama Research & Development Center, Technical Headquarters

1

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

Table 1 Specifications of system
Real time measuring
equipment for T3CB

On-line measuring
equipment for P5CDF

Substance measured

T3CB(Trichlorobenzene)

P5CDF(pentachloro- dibenzofuran)

Location where measured

Outlet of furnaceo(550 to 650 C)

Inlet of stack

Dust filtration

Concentrator

Items

Pre-treatment

80 to 240 ng/m3N
0.05 ng/m3N
Lowest limit of measurement (Depending on gas component) (Depending on gas component)
Measurement interval

20 seconds

2 to 6 hours(depending on installation)

Feeding flow rate or amount

100 cc/min

50 to 1 000 L(depending on installation)(mm)

W1 400 X L 3 000 X H 1 900(Measuring equipment)
W400 X L 400 X H 900(Dust filter)

W1 400 X L 3 000 X H 1 900(Measuring equipment)
W1 200 X L 1 600 X H 1 800(Dust filter)(kg)

1 000 (VUV analyzer only)

1 300 (Including concentrator)

Outer dimensions

Mass

Ion detector
TOFMS

Microwave
Sample gas
Ion trap
Vacuumultraviolet lightDeflecting
electrodesTurbomolecular pump

Toxicity equivalency quantity (ng-TEQ/m3N)

Ionization chamber

Window

End cap electrodes

Fig. 2 Principle of VUV analyzer
After P5CDF or T3CB is selectively accumulated in an ion trap, either
substance can be quantitatively determined by TOFMS.

100
10
1
0.1
0.01
0.001
0.0001
0.01

0.1

1

10

100

1 000

Concentration of P5CDF (ng/m3

N)
Fig. 3 Correlation between P5CDF and toxicity equivalency
quantity (TEQ)
It can be seen from the graph that there is a strong correlation
between DXNs and P5CDF.

measuring P5CDF, and the real time equipment for measuring T3CB, respectively.
2.1 VUV analyzer
The principle of the VUV analyzer is shown in Fig. 2
2.
A gas sample introduced into the ion trap in the VUVanalyzer is irradiated with vacuum ultraviolet lightthrough a window in order to ionize an target substance(P 5CDF or T 3CB in this case). When an electrical voltage with a specified frequency is applied between theend cap electrodes of the ion trap, only one kind of ion
with a particular mass is selectively accumulated. After
that, the target ions are dissociated into fragments byapplying an electrical voltage with another specified frequency(4)(5). The target substance and any impurities canbe separated using this procedure. Finally, the target
substance can be quantitatively determined by supplying the ions dissociated into fragments to a time of flightmass spectrometer (TOFMS).
This VUV ionization method can measure a target
substance stably and to a high degree of sensitivity without being influenced by coexisting components, even insystems in which various components are mixed together

such as flue gas from an incinerator furnace.
2.2 On-line equipment for measuring P 5CDF
This equipment is installed downstream from the bag
filter (dust collector) in order to monitor the concentration of P5CDF in gas emitted into the atmosphere, so as
to contribute to the more effective operation of an incinerator or a flue gas treatment system. As shown in Fig. 1,
this equipment consists of the automatic concentrator
described later and a VUV analyzer.
It is very difficult to measure DXNs quickly, including
various congeners and isomers in trace amounts. In fact,
these components are analyzed in the present official
method through GC/MS method. In the newly developed
method described here, a particular congenrer that isclosely correlated with toxicity equivalency quantity is
chosen as an index, concentrated and then measured.
Fig. 3 shows relation between concentration of P5CDF
and the toxicity equivalency quantity of DXNs, which
Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

2

Sampling section
Flue gas
Condenser

Pressure
regulator
Nitrogen bomb
Solvent
reservoir

Primary
concentrating section

Solvent
supply system
Solvent trap

Suction pump
Sample gas
suction section

Drain trap

Impurity-removing
sectionHelium bomb

Waste solvent reservoir
Controller
Secondaryconcentrating section

VUV analyzer

Fig. 4 Automatic concentrator
The concentration and capillary-separationof P5CDF in a sample of gas are automatically performed and P5CDF is quantitatively
determined using the VUV analyzer.

Capillary column
Concentration of congeners of P5CDF(using the official method) (ng/m3N)100

have been obtained by MHI. As can be seen in this figure, there is a strong correlation between theconcentration of P5CDF and the toxicity equivalency quantity of DXNs. As a result, it is concluded that P5CDF canbe effective as a monitoring index substance for DXNs.
Since the concentrations of DXNs to be monitored are
as low as 0.01 to 0.1 ng-TEQ/m 3N, they are difficult tomeasure even with a VUV analyzer. Therefore, in the
newly developed on-line measuring equipment, the fluegas is concentrated before the P5CDF concentrations aremeasured using the VUV analyzer. Fig. 4 shows an overview of the automatic concentrating process.
The flue gas is cooled after all dust has been removed,
and is then fed to the primary concentrating section of
the equipment and P 5CDF is adsorbed with condensed
water to be primarily concentrated. After drying thewater adsorbed in the primary concentrating section,
P5CDF is then subjected to solvent-extraction under hightemperature and high pressure. After impurities havebeen removed from the solvent-extracted P 5CDF solution, the solvent is evaporated in the secondary
concentrating section. The concentrated P 5CDF sample(the entire amount) is separated in a capillary column
in gas chromatography, and finally fed into the VUVanalyzer to be quantitatively determined. In order toincrease the accuracy of the analysis, an internal standard substance is added for each measurement.
2.3 Real time equipment for measuring T3CB
It is known that incomplete combustion leading toformation of DXNs can be monitored by measuring theconcentrations of CO. However, it is suggested that theconcentration of DXN precursors has a better correlation with the combustion state than concentrations of
CO in the low concentration region(3). Basic data obtainedby MHI also supports this suggestion. Hence, the present

101: Demonstration furnace of MHI: Plant A: Plant B

0.1

0.01

0.1
1
10
100
Concentration of homologues of P5CDF(obtained with the newly developed method) (ng/m3N)

Fig. 5 Comparison of VUV measurement and official method
There is a good correlation between measurements obtained with
the VUV analyzer and the official method, thus confirming thepractical applicability of the VUV approach.

equipment can be used to monitor the DXNs formationin the furnace and to determine the operating condition
by measuring T 3 CB levels real-timely at the outlet of
furnace, because T 3CB is a good index of DXNs among
DXNs precursors.
The analysis procedure is as follows. The dust in theflue gas from the outlet of a furnace is at first removed
by filtration. The gas is then cooled to an appropriate
temperature, after which the VUV analyzer is used tomeasure the amount of T 3 CB present in real time foreach approximately 20 second interval.

3. Field test results
3.1 Result of P 5CDF measurement
The results of measurements carried out in the field
and results measured using the official method are shownin Fig. 5
5. The good correlation observed in the figure in
the concentration range from 0.05 to 10 ng-TEQ/m3N conMitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

3

Concentration of P5CDF (ng/m3N)5
4.5

Feed ofactivatedcarbon13.8 kg/h 6.1kg/h

9.8 kg/h

11.6 kg/h

4
3.5
3
2.5
2
1.5
1
0.5
0
4:00

8:00

12:00

16:00

20:00

0:00

4:00

8:00

12:00 16:00

Measurement time
Fig. 6 P5CDF concentration profile
The tendencies in the concentration of P5CDF can be determined by on-line measurement.

firms that measurement with a VUV analyzer is practically applicable.
In order to confirm the applicability of this method, aplant equipped with an electrostatic precipitator and aunit for supplying activated carbon powder into the fluegas for reducing DXNs was adopted as an example in
the field tests. Fig. 6 shows the results obtained by measuring concentrations of P 5 CDF when the amount ofactivated carbon powder was varied at the plant.
The tendency that the concentration of P 5 CDF decreases with increasing the amount of activated carbon
powder can be confirmed from Fig. 6. In addition, since
the optimum amount of activated carbon powder in thisplant can be determined with this equipment, the operating conditions of the flue gas treatment can also becontrolled using this equipment. Accordingly, it has been
proved that this equipment is also useful in reducing
the running costs of the plant.

The present frequency for taking measurements isonce per each two to six hours, depending on the concentration of P5CDF. These timings are considered to be very
effective for adjusting operating condition in an flue gas
treatment plant, bearing in mind the time needed forthe operation state to become stabilized after the condition has been changed. When the concentration of P5CDF
needs to be measured more frequently, the measuring
interval can be shortened by multiplying concentrator.
3.2 Result of T 3CB measurement
The effectiveness of the T 3CB-measuring equipment
was also investigated by the field tests using flue gas in
the same way as the measurement of P5CDF. Fig. 7 shows
the test results. It can be seen from this figure that there
is a very good correlation between the T3CB concentrations and the values analyzed by the official method.
Therefore, it was confirmed that the concentrations of
DXNs at the outlet of an incinerator furnace can be estimated by measuring the concentration of T3CB.
Fig. 8 shows the concentrations of T 3CB and CO obtained during continuous measurement with an intervalof twenty seconds. From this figure, the amount of T3CB
formed increases as the level of CO in the region where
the concentration of CO is high increases. Thus, it is conceivable that the combustion state inside a furnace canbe understood by this equipment and the optimum combustion condition can be found. The utilization of thisconcept is expected to be useful in ranges where concentrations of CO are low.
As described above, the ability to estimate theamount of DXN precursors continuously at the outletof a furnace is very useful. This method is not only applicable for predicting and better understanding themechanism of DXNs formation at the outlet of the furnace, but also possible to be utilized to a large extend
in the research of combustion behavior varying according to the variation of the combustion condition in a
furnace in the future.

DXNs at outlet of furnace(using official method)(ng-TEQ/m3N)

100

10

1
: Plant A: Plant B

0.1
100

1 000

10 000T3CB (using newly developed method) (ng-m3N)
Fig. 7 Correlation between DXNs and T3CB
It can be seen that there is a good correlation between
DXNs and T3CB.

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

4

250

Concentration of CO (ppm)Concentration of CO
200

2 000
Concentration of T3CB
(average of ten measurements during a
20 second sampling interval)

150

1 500

100

1 000

50

500

0
11:42

Concentration of Precursors T3CB (ng/m3N)

2 500

0
12:12

12:42

13:12

13:42

14:12

14:42

15:12

15:42

Measuring time
Fig. 8 Trend in concentration of T3CB
It has been confirmed that the combustion state can be understood by measuring T3CB.

Moreover, by assessing DXNs levels, the T3CB-measuring equipment can also be applied to adjusting
combustion conditions in the trial operation of a furnace.

weeks to analyze, can be completed in several hours oreven in several dozens of seconds means that the very
effective information that had not been previously obtainable can be presented in a timely manner for the
more effective operation of incinerators and flue gas
treatment. It is certain that the technology introducedin this paper is also applicable to a wide range of fields
such as basic research and development other than theapplications reported here.
Part of this research was supported by the Ministryof the Environment through the scientific research grant
for waste treatment "Integration of DXNs Reduction
Technologies". The authors are grateful to Prof. Dr.
Masaru Tanaka, Okayama University, for his guidance
and many other related people.

4. Conclusion
The achievement described above can be summarized
as follows:(1) The concentration of DXNs emitted can be estimatedand monitored by measuring the concentration of
P 5CDF in flue gas using a VUV analyzer after automatically concentrating the flue gas.
(2) The conditions under which DXNs are formed insidea furnace can be grasped by measuring T 3CB levels,
thereby making it possible to determine the optimum
combustion conditions for controlling DXNs.
(3) During the trial operation of an incinerator furnace,
the on-line monitoring system could be used to adjust
operation by monitoring DXNs concentrations, so thatit can be effective in reducing running costs.
(4) The technology described above can be applied to thebasic research and development of incinerator furnaces.
At present, the measured values using the on-line
monitoring system cannot replace the values analyzed
by the official method. However, the fact that measurement of DXNs or their precursors, which requires several

References(1) Uoya et al., Reduction of Dioxins from Refuse Incinerator
Plant, Mitsubishi Juko Giho Vol.29 No.4 (1992) p.327(2) Uoya et al., Technology on Flue Gas Treatment of Fine Harmful Compounds from Municipal Incinerators, Mitsubishi
Heavy Industries Technical Review Vol.29 No.2 (1992) p.131(3) G. Sandstrom, 10th Int. Symp. on Dioxin, Vol.3 (1990) pp.151156(4) L. He, J. T. Wu, S. Parus and D. M. Lubman, Rapid Communications in Mass Spectrometry, 11, 1739 (1997)(5) Kuribayashi et al., Real-Time Detection System for TraceLevel Chlorinated Organic Compounds, Mitsubishi Juko Giho
Vol.38 No.5 (2001) p.262

Mitsuhiro Okada

Kenichi Yoneda

Shigeki Morii

Takumi Suzuki

Katsuo Seki

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol.40 No.5 (Oct. 2003)

5