**3.3 OSCC instrument developed for gas flow velocity measurement**

In order to measure gas flow velocity in stack, a gas flow velocity sensor was constructed based on the low frequency part of the double-path optical scintillation cross correlation. The schematic diagram of velocity and particle concentration measuring system is shown in Fig.11. Both processed LED light sources emit ideal Gauss spherical waves, the wavelength is 630 nm and the output power is 1 w. The receivers are silicon photoelectric diodes. The received signals will be magnified and filtered by low pass filter, then collected by a A/D card, and finally an industrial computer gets the data to process. Fig.12 shows the developed instruments. The left is the picture of instruments, and the right one is the picture installed on an industrial emission pipe for testing).

Fig. 11. The schematic diagram of velocity and particle concentration measuring system

Fig. 12. Developed instrument for online measurements of gas flow velocity.

The field testing measurement was carried out at a chemical factory in Weifang of Shandong province. It is a rectangular stack with the length of 2 m and the width of 0.55 m. The distance between transmitter and receiver is the length of the stack, and the distance between the two receivers is 0.35 m. The diameters of transmitter aperture and receiver aperture are both 30mm. (as shown in the right picture of Fig.12). The velocity of the stack gas flow is about 4 m/s calibrated with a commercial Pitot tube and the temperature is about 150ºC. The stack gas is produced from the burning of coal. Fig.13 is the received data

In order to measure gas flow velocity in stack, a gas flow velocity sensor was constructed based on the low frequency part of the double-path optical scintillation cross correlation. The schematic diagram of velocity and particle concentration measuring system is shown in Fig.11. Both processed LED light sources emit ideal Gauss spherical waves, the wavelength is 630 nm and the output power is 1 w. The receivers are silicon photoelectric diodes. The received signals will be magnified and filtered by low pass filter, then collected by a A/D card, and finally an industrial computer gets the data to process. Fig.12 shows the developed instruments. The left is the picture of instruments, and the right one is the picture

Fig. 11. The schematic diagram of velocity and particle concentration measuring system

The field testing measurement was carried out at a chemical factory in Weifang of Shandong province. It is a rectangular stack with the length of 2 m and the width of 0.55 m. The distance between transmitter and receiver is the length of the stack, and the distance between the two receivers is 0.35 m. The diameters of transmitter aperture and receiver aperture are both 30mm. (as shown in the right picture of Fig.12). The velocity of the stack gas flow is about 4 m/s calibrated with a commercial Pitot tube and the temperature is about 150ºC. The stack gas is produced from the burning of coal. Fig.13 is the received data

Fig. 12. Developed instrument for online measurements of gas flow velocity.

**3.3 OSCC instrument developed for gas flow velocity measurement** 

installed on an industrial emission pipe for testing).

plot from both receivers. Fig.14 shows that the power ratio of the optical scintillation spectrums in part of low frequency is -8/3.

Fig. 13. The received data signal from both receivers

Fig. 14. The low frequency part of optical scintillation spectrum.

The low frequency of optical scintillation caused by stack gas flow is relative to the particle concentration fluctuations at random, the scintillation caused by the fluctuations of particle concentration is analyzed. Fig.15 shows the continuous measurement results of gas flow velocity which shows good agreement comparing with Pitot tube point measurement results.

Real-Time In Situ Measurements

Optical path

chapter.

instrument.

of Industrial Hazardous Gas Concentrations and Their Emission Gross 83

Fig. 16. One of the testing circumstances for in situ on-line monitoring of industrial emissions.

Instruments room

Fig. 17. Another testing place for in situ on-line monitoring of industrial emissions.

Fig.18-21 are the industrial field testing results employing the instruments described in this

Fig. 18. The continually measurement results of industrial emitted HF and HCI with TDLAS

Fig. 15. Continuous measurement results of gas flow velocity with double-path OSCC sensor.

#### **3.4 Online monitoring of industrial emission gross**

The aim of the project we have carried out during the past few years is to develop a novel system to realize in site real-time monitoring the industrial emission gross. The idea is through on-line measurements of the targeted gas concentrations and gas flow velocity within a stack before emitted to air and plus with help of the theoretical path-weighted function built based on the configuration of stack cross section to gain *in situ* monitoring of industrial emission gross. Although most works including development of theoretical model and instrument constructions have been fulfilled. However, nowadays it is very hard for us to find a standard commercial instrument to certify the accuracy of our measurements and calculation. Obviously there are still lots of works needed to be further carried out. Here we still use the traditional method to calculate the emission gross presented in the section 4, i.e.,

$$F = M \times p \times \left(\mathbf{S} \times \boldsymbol{\upsilon} \times \mathbf{C}\right) / RT \tag{36}$$

Where F is the emission gross, M is the molecular weight, S is the cross section of the stack at the measurement path, C and *ν* are the measured gas concentration and mean gas flow velocity, respectively.

#### **4. Experimental results and discussions**

In order to demonstrate the developed instruments, a number of preliminary field trials have been carried out at few sites under different industrial field circumstances as shown in Fig.16 and Fig.17.

Fig. 15. Continuous measurement results of gas flow velocity with double-path OSCC

The aim of the project we have carried out during the past few years is to develop a novel system to realize in site real-time monitoring the industrial emission gross. The idea is through on-line measurements of the targeted gas concentrations and gas flow velocity within a stack before emitted to air and plus with help of the theoretical path-weighted function built based on the configuration of stack cross section to gain *in situ* monitoring of industrial emission gross. Although most works including development of theoretical model and instrument constructions have been fulfilled. However, nowadays it is very hard for us to find a standard commercial instrument to certify the accuracy of our measurements and calculation. Obviously there are still lots of works needed to be further carried out. Here we still use the traditional method to calculate the emission gross

Where F is the emission gross, M is the molecular weight, S is the cross section of the stack at the measurement path, C and *ν* are the measured gas concentration and mean gas flow

In order to demonstrate the developed instruments, a number of preliminary field trials have been carried out at few sites under different industrial field circumstances as shown in

*F M p S v C RT* ( )/ (36)

**3.4 Online monitoring of industrial emission gross** 

presented in the section 4, i.e.,

**4. Experimental results and discussions** 

velocity, respectively.

Fig.16 and Fig.17.

sensor.

Fig. 16. One of the testing circumstances for in situ on-line monitoring of industrial emissions.

Fig. 17. Another testing place for in situ on-line monitoring of industrial emissions.

Fig.18-21 are the industrial field testing results employing the instruments described in this chapter.

Fig. 18. The continually measurement results of industrial emitted HF and HCI with TDLAS instrument.

Real-Time In Situ Measurements

**5. Conclusions** 

**6. Acknowledgement** 

Vol.10, pp53-70.

**7. References** 

of Industrial Hazardous Gas Concentrations and Their Emission Gross 85

In conclusion, based on TDLAS, PTR-MS and OSCC techniques we have developed a system to monitor a number of industrial hazard gas emissions. However, it should point out here, the measurement results for on-line monitoring the gross of industrial emissions reported here are still in the early stage. Many further works need to be done and will be published in the future. For instance, we have developed a new complex theory based on path-weighted function and the averaged gas flow velocity to calculate the total emissions with the help of gas concentration measurements, however since nowadays there are no any instruments available to certify the measurement accuracy. Therefore in this chapter the

The authors acknowledge the financial support from the National High-tech Research and

Andrews, L.C.; Phillips, R.L & Hopen, C.Y. (2000). Aperture averaging of optical

Blake, R.S.; Whyte, C.; Hughes, C.O.; Ellis, A.M. & Monks, P.S. (2004). Demonstration of

trace volatile organic compounds. *Analytical Chemistry*, Vol.*76*, pp3841-3845.

scintillations: power fluctuations and the temporal spectrum,*Wave Random Media*,

proton-transfer reaction time-of-flight mass spectrometry for real-time analysis of

Fig. 21. The measurement results of daily emission gross for VOCs.

common method for calculation of total emissions is still used.

Development Program of China (Grant No. 2007AA06Z420).

Fig. 19. The total mass scans of VOCs inside the stack measured with PTR-MS

Fig. 20. On-line monitoring results of the VOCs emission rate measured with PTR-MS

Fig. 21. The measurement results of daily emission gross for VOCs.
