JPS6049251B2 - Exhaust gas sampling probe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas sampling probe that inserts an exhaust gas sampling tube into a flue and supplies the exhaust gas led out through the exhaust gas sampling tube to an analyzer via a filter section. This relates to the exhaust gas sampling probe of the above type, which is equipped with a heat pipe whose heat receiving part is exposed to the flue gas, whose central part keeps the filter part warm above the dew point temperature, and whose heat radiating part at the other end projects outside the flue. .

This type of exhaust gas sampling probe is used to sample flue gas from thermal power plants, garbage incinerators, etc. and supply it to a gas analyzer.

Generally, exhaust gas contains a large amount of dust, water vapor, sulfuric acid mist, etc., and when the temperature drops below the dew point temperature in the filter section, condensed water is generated. When this condensed water interacts with dust and mist, it can clog the filter and cause corrosion of the components, so to prevent this, a heat pipe is used in the filter chamber to heat it using the heat of the flue gas itself.
A method has been proposed in which the sampling gas is maintained at a temperature above the dew point temperature. An exhaust gas sampling probe using a heat pipe will be described with reference to FIGS. 1 and 2. In FIGS. 1 and 2, the exhaust gas HG flowing through the furnace wall 1 enters the internal pipe 3 through the exhaust gas sampling pipe 2, and is filtered by the filter 4, resulting in purified sampling gas SG.
is supplied from a pipe 6 to an analyzer (not shown) via a flow path 5 formed at the rear end of the inner tube 3.

Note that an O-ring 9 seals between the filter 4 and the rear end of the internal tube 3, which is sealed with a lid 8 via a packing 7. On the other hand, a support flange 11 on the probe side is connected to a 7 flange 10 protruding outside the furnace wall 1 in order to support the entire probe inserted into the opening of the furnace wall 11. This support flange 11 and flange 10 are connected to the inner tube 3
It supports the outer protection tube 12 and the inner tube 3, which reduce heat radiation from the inner tube 3. Furthermore, in order to maintain the internal tube 3 at a temperature higher than the dew point temperature (110°C to 120°C) and to prevent exhaust gas from condensing in the filter chamber 4a that houses the internal filter 4, a A heat vibrator 13 whose central portion 13b is in close contact with each other and which extends in the axial direction is protected and provided within a protective tube 14, and a heat receiving portion 13a at one end of the heat vibrator 13 protrudes into the flue, and a heat dissipating portion 13c at the other end. are exposed from the protective tube 14 and protrude outward from the furnace wall 1. In this way, the heat receiving part 13a at one end of the heat vibe 13 is heated by the exhaust gas in the flue, which is usually 2000C to 400C, the filter chamber 4a is kept warm in the central part 13b, and the other end protrudes outside the flue. Excess heat is discarded in the heat dissipation section 13c of the filter chamber 4a, and the exhaust gas is heated to a temperature higher than the dew point temperature 1.
It is possible to keep the temperature at about 100C to 120C. If a normal heat vibrator is used as the heat vibrator 13 in the above probe, on the one hand, when the heat input is large, there is a problem that the sealing material becomes higher than the heat resistant temperature, and on the other hand, when the heat input is small, the filter part 4a
There was a problem where the temperature dropped below the dew point temperature.

The present invention was made with the aim of eliminating this drawback, and uses a variable conductance type heat vibrator filled with non-condensable gas at room temperature and atmospheric pressure as a heat vibrator used for heating the filter section. , the temperature of the filter section or sampling gas is higher than the dew point temperature,
It is characterized in that the temperature is maintained at a temperature lower than the heat resistance temperature of the sealing material.

Exhaust gas sampling probe of the present invention and its. The mechanical structure of the heat vibrator included therein may be the same as that shown in FIGS. 1 and 2 already described.

The feature of the present invention is that while a normal heat vibrator only contains a working fluid, the heat vib of the present invention also contains an appropriate amount of non-condensable gas such as nitrogen gas! The effective area of the heat dissipation section is automatically changed depending on the magnitude of the heat input from the heating section. In other words, when the heat input is small (temperature is low), the vapor pressure of the working fluid is low, as shown in the water vapor pressure curve in Figure 3, and the interface between steam and gas moves in the direction of decreasing the effective heat radiation area. condensation area and the amount of heat dissipation. Conversely, when the heat input is large (high temperature), the vapor pressure of the working fluid is high, and the interface between steam and gas moves in a direction that increases the effective heat dissipation area. This increases the condensation area and increases the amount of heat dissipation, so even if the heat input fluctuates, the temperature of the object to be kept warm can be kept almost constant. A heat vibrator whose effective heat radiation area changes depending on the temperature is called a variable conductance type heat vibre to distinguish it from a normal heat vibrator whose heat radiation surface remains unchanged.An example of the heat vibrator of the present invention is Water as 17 and nitrogen gas as non-condensable gas 19 are sealed at room temperature and atmospheric pressure, and the non-condensable gas is converted into steam at 2k9/c!t (absolute pressure).

The same applies hereafter), and when the ratio of the vapor space to the non-condensable gas space becomes approximately 1:1, the non-condensable gas is configured to collect in almost the entire area of the heat dissipation section 13c. - At this time, when the exhaust gas temperature is low, the amount of heat received is small, but there is no heat radiation from the heat radiation part 13c, so if the filter part is provided at the position that becomes the steam space part, it is possible to always keep the temperature above the dew point temperature. In addition, when the exhaust gas temperature is high, the amount of heat received increases and the temperature at the bottom of the filter increases, but the vapor pressure increases and the non-condensable gas is further compressed, so the effective amount of heat radiation increases.This effective heat radiation In addition to the increase in area, the temperature difference with the surrounding air also increases, so the amount of heat dissipated increases, making it possible to maintain the filter section 4a below the heat-resistant temperature of the sealing material.Normally, the dew point temperature of the exhaust gas is determined by the temperature within the exhaust gas. The upper limit temperature is determined by the temperature of the sulfuric acid contained in the sulfuric acid, and the higher the sulfuric acid content, the higher the dew point temperature, but the upper limit is about 120C.

On the other hand, the heat resistance temperature of sealing materials such as Viton, silicone rubber, and Teflon is usually around 200°C. Water, which is a working fluid, boils at 100°C at 1k9/CTl (atmospheric pressure), and boils at a higher temperature when pressurized. For example, at 2 kg/CIL, it boils at 180°C at 1200C110.3k9/d, and at 200°C at about 15.9k9/Cd. Therefore, when the non-condensable gas is compressed to 2k9/d or more by steam, the heat is radiated at 120°C or more, and the heat radiation part 13c is designed to prevent the non-condensable gas from being compressed to more than 10k9/CTI (below 180°C). A radiation fin 13f that satisfies heat radiation conditions is provided outside the steam space.

By doing this, even if the heat input from the exhaust gas or the heat dissipation conditions in the heat dissipation section fluctuate, the temperature is always kept above the dew point temperature of the sampling gas and below the heat-resistant temperature of the sealing material, and the temperature range of the exhaust gas is wide. , for example 1500
It becomes possible to apply it in the range of C to 400C. Fourth
The figure shows the axial distribution of the surface temperatures A″, B″, and C″ of the heat vibrator for three types of exhaust gas temperatures A, B, and C (A>B>C).

Due to the difference in temperature, the position of the interface between steam and gas changes to X, Y, and Z.
It can be seen that the length of the effective heat dissipation section 13E changes accordingly. Figure 5 shows, as a specific example, the pressure of the non-condensable gas filled in at 0.5k9/Cd (curve 51), 1.0k9/CT
1 (curve 52) and 2.0 kg/CI (curve 53).

In the case of the above pressure conditions, the temperature and pressure of the working fluid (water) at which the central part 13b has a uniform temperature are marked with black circles on the curve in Figure 3, and are associated with the numbers 51 to 53 in Figure 5. The temperatures are 100'Cll2O°C and 147C, respectively. This temperature corresponds to the temperature of the central portion 13b in FIG. Furthermore, these temperatures correspond to exhaust gas temperatures of 130° C., 1150° C., and 1170° C., respectively. In addition, T in Figure 5. is the ambient atmospheric temperature. The following can be said from Figure 5.

First, let's look at the case where a non-condensable gas is filled at 0.5k9/CIL. It is difficult to create a stable heat vibe under intermediate reduced pressure, and furthermore, when the exhaust gas temperature is high, it has the disadvantage that it exceeds the heat resistance temperature of the sealing material.

Next is the case where a non-condensable gas is filled with 2.0k9/Cd, but in this case, the entire central part can be kept above the dew point temperature only when the exhaust gas temperature is high, and when the exhaust gas temperature is low, In order to make the entire center area above the dew point temperature, it is necessary to increase the internal volume V2 of the heat dissipation section, which has the disadvantage that the probe becomes large. On the other hand, 1k9
When the non-condensable gas is sealed at /d (atmospheric pressure), it is easy to manufacture a stable and reliable heat vibrator because the non-condensable gas is sealed at atmospheric pressure. The maximum dew point temperature of the exhaust gas is around 120°C, and since heat is radiated only after the entire central region reaches 120°C, no dew condensation occurs. Furthermore, even when the amount of heat received is large, the volume change due to the temperature of the noncondensable gas is large, so it has various advantages such as being easy to maintain the temperature below the heat resistance temperature of the sealing material. As described above, according to the present invention, by using a variable conductance type heat vibrator in which non-condensable gas is sealed at room temperature and atmospheric pressure, exhaust gas temperature can be adjusted over a wide range, e.g.
400℃, the temperature at the center of the heat vibrator should be set from above the dew point temperature to below the heat-resistant temperature of the sealing material, e.g. 120-1
A versatile exhaust gas sampling probe that can be maintained at 80°C can be provided.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram showing the installation state of the exhaust gas sampling probe with heat vibrator, Fig. 2 is a longitudinal cross-sectional view showing details of the exhaust gas sampling probe with heat vibrator, Fig. 3 is a diagram showing the vapor pressure curve of water, FIG. 4 is a diagram showing the operating principle and temperature characteristics of the variable conductance type heat vibrator, and FIG. 5 is a diagram showing the temperature characteristics of the heat vibrator when the sealing pressure of non-condensable gas is changed. No. 2: Collection tube, 3: Internal tube, 4:
...filter, 4a...filter chamber, 13...
...heat vibrator, 13a...heating section, 13
b...Central part, 13c...Heat radiation part, 1
7... Working fluid, 19... Non-condensable gas.

Claims (1)

[Scope of Claims] 1. An exhaust gas sampling probe in which an exhaust gas sampling tube is inserted into the flue, and the exhaust gas led out through the exhaust gas sampling tube is supplied to an analyzer via a filter section, wherein one end of the heat receiving section is connected to the flue. In a heat pipe which is exposed to gas and keeps the filter part warm at the dew point temperature or higher at the center and whose heat dissipation part at the other end protrudes outside the flue, the heat pipe is used to heat the non-condensable gas at room temperature. An exhaust gas sampling probe characterized by using a variable conductance heat pipe sealed under atmospheric pressure. 2. In the exhaust gas sampling probe according to claim 1, water is sealed as a working fluid in the heat pipe, and the non-condensable gas is compressed by steam, so that the vapor space in the heat pipe and the non-condensable gas are compressed. An exhaust gas sampling probe characterized in that the non-condensable gas is configured to collect in almost the entire area of the heat radiation part when the volume ratio with the space part is approximately 1:1.