CN101251478A - A UV Differential Flue Gas Probe Based on Dual Optical Paths - Google Patents

Abstract

The invention relates to an ultraviolet differential flue gas probe suitable for on-line monitoring of flue gas, including a transmitting module and a receiving module, characterized in that the transmitting module and the receiving module are arranged at the same end, and the optical axes of the two modules are parallel to each other. A corner cube is fixed at the other end of the light path. The invention not only simplifies the optical path adjustment operation and reduces the adjustment difficulty, but also improves the measurement stability and prolongs the working life of the sensor.

Description

A UV Differential Flue Gas Probe Based on Dual Optical Paths

technical field

The invention relates to a probe suitable for on-line monitoring of flue gas, in particular to an ultraviolet differential flue gas probe.

Background technique

Sulfur dioxide (SO ₂ ) and nitrogen oxides (NO _x ) are the main gas pollutants in the atmospheric environment, and more and more attention has been paid to emission reduction and monitoring. In order to timely, accurately and systematically grasp the status of sewage discharge, continuous monitoring of emissions such as sulfur dioxide is required. At present, the commonly used continuous gas monitoring methods are mainly absorption spectroscopy and so on. The Lambert-Beer light absorption law is the most basic law for measuring the concentration of substances by absorption spectroscopy. It shows that when the incident light intensity is constant, the absorbance of the measured substance is proportional to the product of the concentration and thickness of the measured substance.

Absorption spectroscopy generally uses ultraviolet light sources to emit fixed-band beams, pass through a fixed-length measured gas measurement area, and finally receive the beams by the spectrometer, and use a computer to perform subsequent data processing with a certain algorithm to obtain flue gases of different components concentration.

The optical path of the widely used single-side insertion probe is shown in Figure 1. The composition structure is relatively simple. The light beam is emitted by the ultraviolet light source 1, passes through the collimating lens 2, enters the measured gas measurement area 7, and then enters the optical fiber through the focusing lens 3. 5. In practical application, this optical path installs the transmitting end 6 and receiving end 8 at both ends of the same probe, and the probe is provided with a measurement area, as long as the probe is inserted into the flue, the measurement can be started. Generally, the environment in the flue is relatively harsh. With the prolongation of the use time, the structural part of the optical path will be deformed due to factors such as high temperature and high humidity, and the light intensity received by the optical fiber 5 will decrease, which will seriously affect the measurement. Effect. At this time, it is necessary to adjust the position and attitude of the outgoing and receiving optical devices at the same time, but it is inconvenient to adjust the optical path on site, and the precision optical devices such as the optical fiber adapter 4 have been in the high-temperature smoke environment for a long time, and the service life is greatly reduced. The optical path design needs to be modified. .

Contents of the invention

The purpose of the present invention is to improve the optical path design of the existing flue gas measuring probe, overcome the above-mentioned shortcomings of the prior art, and provide a flue gas that can facilitate on-site optical path adjustment and improve measurement stability under the premise of completing the existing optical path functions. Online measuring probe. For this reason, the present invention adopts following technical scheme:

An ultraviolet differential flue gas probe based on dual optical paths, including a transmitting module and a receiving module, characterized in that the transmitting module and the receiving module are arranged at the same end, the optical axes of the two modules are parallel to each other, and an angle is fixed at the other end of the optical path corner prism.

As a preferred embodiment, the emission module of the ultraviolet differential flue gas probe based on dual optical paths of the present invention includes an ultraviolet light source, a parabolic reflector, and a collimating beam expander lens. The ultraviolet light source is placed on the focus of the parabolic reflector, and the parabolic reflector The reflected ultraviolet light is emitted through the collimating beam expander lens; the receiving module includes a focusing lens and a receiving fiber head, and the light beam reflected by the corner cube is received by the receiving fiber head after passing through the focusing lens.

The dual optical path design of the ultraviolet differential flue gas probe of the present invention changes the emitting and receiving devices of the measurement beam from the original opposite placement to the same placement, and folds the optical path through the corner cube, so that the optical path adjustment method is changed from double-ended adjustment. It is a single-ended adjustment, which can realize online adjustment and correction of the optical path. The invention not only simplifies the optical path adjustment operation and reduces the adjustment difficulty, but also improves the measurement stability and prolongs the working life of the sensor.

Description of drawings

FIG. 1 is a schematic diagram of an optical path of a single-side insertion probe in the prior art.

Fig. 2 is a schematic diagram of the optical path of the ultraviolet differential flue gas probe of the present invention.

Fig. 3 is a schematic diagram of the installation of the ultraviolet differential flue gas probe of the present invention.

Explanation of reference signs:

1 UV light source 2 Collimating lens 3 Focusing lens 4 Optical fiber receiving head

5 Optical fiber 6 Transmitter 7 Measuring area 8 Receiver

9 Parabolic reflector 10 Collimating beam expander lens 11 Corner prism 12 Transmitting and receiving end

13 reflective end 14 through the window

Detailed ways

The flue gas measurement optical path of the present invention adopts a one-time reflection design, introduces a corner cube 11 as a reflective device, places the emitting and receiving devices at the same end, and realizes long-term stable operation of the optical path through single-end adjustment. The specific design scheme is as follows:

(1) Optical path composition and arrangement

The optical path of the present invention is composed of ultraviolet light source 1, parabolic reflector 9, collimating beam expander lens 10, corner cube 11, focusing lens 3 and optical fiber receiving head 4, etc. The optical path is shown in Figure 2.

Place the ultraviolet light source 1 at the focal point of the parabolic reflector 9, and the light emitted by it irradiates on the parabolic reflector 9 to form a horizontal beam, which enters the measurement area 7 after collimation and beam expansion, and is measured by the gas to be measured. Selective absorption. The absorbed beam is reflected back by the corner cube 11 and finally enters the focusing lens 3 . The light beam is converged to the receiving head 4 by the focusing lens 3, and enters the spectrum analysis instrument through the optical fiber 5.

(2) Optical path characteristics

(1) Setting of measurement area 7: The entire optical path can be installed in the sensor structure as shown in Figure 3. The lower opening area is the measurement area 7. The beam emitting and receiving devices are located on one side of the sensor, and the optical axes are parallel to each other. , the other side is only fixed with the corner cube 11. The sensor is placed in the flue, and the output beam of the light source enters the measurement area 7 after being collimated and expanded, and then reflected back to the closed optical path channel inside the sensor through the corner cube prism 11, and finally received by the focusing lens 3 and converged to the optical fiber 5.

(2) Reflecting end 13 design: because the present invention adopts corner cube 11 as reflection device, and corner cube 11 itself has the characteristic that keeps incident and outgoing light parallel to each other, does not change light path direction, even if sensor takes place distortion, corner corner The prism 11 still reflects the light back according to the direction of the incident light. Therefore, in theory, as long as the optical axes of the transmitting and receiving devices are kept parallel to each other and the distance is constant, the optical path will not be disturbed.

(3) Device material: The optical device used in the optical path is made of uniform special material, which has high transmittance to the ultraviolet part, and minimizes the attenuation of the beam during propagation. In addition, the influence of non-linearity on the measurement caused by the different materials used in optical devices is also avoided.

(4) Adjustment method: During on-site use, the internal support structure of the sensor may be deformed due to high temperature and high humidity in the flue, which will cause the mutual position of each device in the optical path to move, causing some parallel beams to be displaced. If the device is blocked, the light intensity entering the receiving device will be seriously reduced, which will affect the measurement accuracy and accuracy. The present invention utilizes the characteristics of the corner cube prism 11, and only needs to adjust the parallelism and distance between the transmitting and receiving devices on the left to restore the optical path to the original state. For the optical path device that has been installed in the flue on site, there is no need to take the sensor out of the flue, and the adjustment is also in the same way, only need to adjust the attitude of the transmitting and receiving device in the transmitting and receiving end 12 outside the flue to restore the state of the optical path.

The specific structural design of the ultraviolet differential flue gas probe of the present invention is as follows:

(1) Sensor structure design

The beam emitting and receiving devices are respectively made into modular structures, wherein the emitting module mainly includes a light source, a parabolic reflector 9, and a collimating beam expander lens 10; the receiving module mainly includes a focusing lens 3 and an optical fiber receiving head 4. The positional relationship of the optical devices inside each module device is fixed, so that each device forms a rigid and stable connection with the module shell.

The transmitting and receiving end 12 of the sensor is respectively equipped with a lockable multi-degree-of-freedom adjustment mechanism for the transmitting and receiving modules, which can adjust the mutual attitude and distance of the two modules.

(2) Adjustment method

When the sensor is working in the flue, if the sensor structure is deformed due to environmental factors such as high temperature, the received light beam deviates from the focusing lens 3, and the received light intensity decreases, which affects the measurement. Then adjust the multi-degree-of-freedom adjustment mechanism of the transmitting and receiving end 12, judge the adjustment effect according to the light intensity collected by the spectrum receiving instrument, until the original positional relationship between the transmitting and receiving devices is restored, and the measurement can be carried out normally.

(3) Optical path auxiliary function design

Considering the actual environment of the work site, in order to prevent the dust in the flue from polluting the optical path and optical devices, clean air should be blown back to the connection between the sensor and the flue gas environment. At the same time, there are multiple optical devices inside the transmitting and receiving device, and the module should be designed with an airtight structure to ensure the cleanliness of the internal air.

As for the reflective end 13, it works in a high-dust, high-temperature and high-humidity environment for a long time, so it is extremely easy to be polluted. For this reason, in addition to being equipped with back blowing air and airtight design, other self-dust removal devices should be added to automatically remove the dust on the corner cube 11 on a regular basis to ensure that the light intensity attenuation at the reflection end 13 is minimal.

Claims (3)

1. the ultraviolet difference flue gas probe based on double light path comprises transmitter module and receiver module, it is characterized in that, described transmitter module and receiver module are arranged on same end, and the optical axis of two modules is parallel to each other, and is fixed with corner cube at the other end of light path.

2. the ultraviolet difference flue gas probe based on double light path according to claim 1, it is characterized in that, described transmitter module comprises ultraviolet source, parabolic mirror, collimator and extender lens, described ultraviolet source places on the focus of described parabolic mirror, and the ultraviolet light of described parabolic mirror reflects penetrates through the collimator and extender lens.

3. the ultraviolet difference flue gas probe based on double light path according to claim 1 and 2, it is characterized in that, described receiver module comprises that condenser lens, optical fiber receive head, receives by receiving optical fiber head after via condenser lens via described corner cube beam reflected.

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