CN101561369A - Gas production pipe for eliminating flue negative pressure - Google Patents

Abstract

The invention relates to a gas production pipe for eliminating flue negative pressure, in particular to a pipe leading flue negative pressure stressed by two ends of a smoke sampling extraction pump to be always in a counteract state.

Description

The gas production pipe of eliminating flue negative pressure

Affiliated technical field

The present invention relates to flue gas sampler, smoke dust sampling instrument, flue gas analyzer or the fixed-contamination source emission fume continuous monitoring system of environmental monitoring field stationary pollution source flue gas sampling, smoke dust sampling, especially a kind of gas production pipe of eliminating flue negative pressure.

Background technology

At present, the flue gas sampler of Shi Yonging, smoke dust sampling instrument, flue gas analyzer or fixed-contamination source emission fume continuous monitoring system (following it is combined is called " tester ") all will extract flue gas from the gaging hole of fume emission pipeline (being called for short " flue ") in the industry.Under a lot of situations, flue adopts the induced draft fan smoke evacuation, causes the negative pressure at induced draft fan front end gaging hole place.The gas production pipe of existing tester all is to bleed in flue, is discharged to outside the flue through behind the test component.As shown in Figure 1.Aspiration pump in the tester also will overcome negative pressure " back suction power " F to pump, thereby cause the gas production flow less than calibrational capacity except will overcoming original pipe resistance.If test component (as electrochemical sensor) to the flow velocity sensitivity, will bring measuring error.

The basic functional principle of galvanochemistry class flue gas analyzer is: extract flue gas from flue, each electrochemical sensor of at the uniform velocity flowing through by the sampling rifle.Sensor is converted to the concentration of the gas with various composition experienced the electric signal of corresponding size.With sulphuric dioxide is example:

Sulfur dioxide in flue gas (SO ₂) diffuse through the sensor permeable membrane, enter electrolytic tank, deciding that oxidation reaction takes place on the current potential working electrode:

SO ₂+2H ₂O＝SO ₄ ^-2+4H ⁺+2e

Produce limiting diffusion current i thus, within the specific limits, its size of current is directly proportional with sulfur dioxide concentration, that is:

$i=\frac{\mathrm{ZFSD}}{\mathrm{\δ}}C$

Under the regulation condition of work, electron transfer number Z, Faraday constant F, diffusion area S, diffusion coefficient D and thickness of diffusion layer δ are constant, so sulfur dioxide concentration C can be measured by limiting current i.

Limiting current i is amplified, after the analog to digital conversion, delivers one-chip computer and handle.

What need indicate is: the electron transfer number Z and the flow velocity V of the sensor of flowing through are " positive correlation " relation, so the size of limiting current, also are " positive correlation " with flow velocity V.The HJ/T 57-2000 of State Environmental Protection Administration standard lay special stress on: " variation of gas production flow velocity directly influences the test reading of instrument ".

Concerning a certain tester, flow velocity is directly proportional with flow.

In the laboratory, the calibrating gas of concentration known C is pumped to sensor by a certain flow Q1, record output current I1, be calculated as follows out scale-up factor k and be stored in the instrument.

k＝C/I1

Detecting on-the-spotly, the flue gas of unknown concentration is being pumped to sensor by the flow Q2 that equates in the laboratory, recording output current I2.Flue gas concentration then

x＝k×I2

What result if flow Q2＜Q1 can cause?

Laboratory experiment: to one bottle of SO ₂Gas carries out concentration and detects, manual change's gas production flow, and the instrument indicating value changes as following table:

0.67	0.6	0.55	0.5	0.45	0.4	0.35	0.3	0.25	0.2	0.15	0.1
												2837	2771	2677	2603	2523	2354	2256	2168	2031	1876	1665	1481

Above data are plotted coordinate curve as shown in Figure 2.

Hence one can see that, and electrochemical sensor output signal and gas production flow are " positive correlation " relation.When tester timing signal under no negative pressure state, inner aspiration pump only need overcome the pipeline internal resistance; And in the on-the-spot detection of negative pressure, aspiration pump should overcome the pipeline internal resistance, also will overcome " the back suction power " of negative pressure, and the gas production flow is inevitable less than calibrational capacity.Negative pressure is high more, and the gas production flow is more little.When serious, gas production flow=0 (take out and hold one's breath).

At high negative pressure, many instrument producers have both at home and abroad increased the power of aspiration pump, are called " anti-negative pressure ".Can this measure prove effective? by above analysis as can be known: high-power air pump, even can also extract gas out at the high negative pressure flue, but the gas production flow is necessarily low under the no negative pressure condition than timing signal.And as long as the gas production flow reduces, it is necessarily on the low side to detect indicating value.

Summary of the invention

In order to overcome the shortcoming of existing tester, the invention provides the gas production pipe of a kind of " clearing up negative pressure ", increased muffler and and air collecting pipe all place the interior same place of flue, allow negative pressure cancel each other at entrance and exit, suffered " the back suction power " in aspiration pump two ends that is in communicating pipe is cancelled each other, thereby guarantee " gas production flow=calibrational capacity ".

Technical scheme

As shown in Figure 3.Compare with the gas production pipe of traditional tester, apparatus of the present invention have increased muffler, and air collecting pipe and muffler same place in flue all.

The invention has the beneficial effects as follows that flue negative pressure is in " counteracting " state all the time at air collecting pipe inlet and muffler outlet, the aspiration pump in the tester no longer bears unidirectional " back suction power ".With the same at the laboratory timing signal, mainly be to overcome the pipeline internal resistance, this has just guaranteed " gas production flow=calibrational capacity " effectively, and the test indicating value is not reduced.This is not " the anti-negative pressure " said usually, but thoroughly " has cleared up " negative pressure!

And when flue existed malleation or flue static pressure fluid, also because the reason of " clearing up ", it is higher or unstable that the tester indicating value also is unlikely to.

Description of drawings

Fig. 1 is a traditional tester gas production pipe synoptic diagram

Fig. 2 is that fluctuations in discharge influences the experimental data coordinate curve to the tester indicating value

Fig. 3 is the negative pressure gas production pipe synoptic diagram of clearing up of the present invention

In Fig. 1 and Fig. 3:

1.---smoke inlet;

2.---air collecting pipe;

3.---aspiration pump;

4.---sensor module;

5.---muffler;

6.---exhanst gas outlet.

The present invention is further described below in conjunction with drawings and Examples.

Embodiment

According to Fig. 3,5. muffler is synthesized on the sampling rifle (for example inner and outer pipes be nested " two-tube " structure) insert the flue gaging hole or fixingly lay or be connected between flue gaging hole and the tester exhausr port temporarily.6. 1. flue negative pressure produce " back suction power " F with exhanst gas outlet simultaneously to smoke inlet.In the communicating pipe that 5. 2. air collecting pipe form with muffler, these 2 masterpieces be used for aspiration pump 3. two ends and cancel each other.After 3. aspiration pump starts, only need overcome tester in the same pipe resistance of laboratory timing signal, guaranteed " gas production flow=calibrational capacity " effectively, avoided the measurement indicating value that causes because of negative pressure on the low side.

The present invention cooperates practical 7 years with my utility model patent ZL02272211.4 " integrated flue gas analyser ", prove that this is to prevent that flue negative pressure from causing resulting structure or even unique resulting structure of tester oligodactyly.

Claims (2)

1. gas production pipe, it is characterized in that: the air collecting pipe and the muffler at aspiration pump two ends all place in the flue.

2. gas production pipe according to claim 1 is characterized in that: muffler synthesizes on the sampling rifle or fixes and lay or be connected between flue gaging hole and the tester exhausr port temporarily.

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