JPS598198Y2 - Gas sampling device for 3 continuous measurements of NH↓ - Google Patents

Description

[Detailed explanation of the invention] This invention is applicable to coal-fired, heavy oil-fired boilers, cement kilns,
This relates to a gas sampling device used to continuously measure the NH3 concentration in a gas stream such as exhaust gas discharged from a glass melting furnace, etc. Especially when a large amount of dust is contained in the gas, the influence of dust may also be detected. It relates to gas collection that can be carried out continuously and effectively.

Methods for measuring NH3 concentration with instruments include the ion electrode method, solution conductivity method, infrared absorption method, chemiluminescence method after converting NH3 to NO, and microwave spectroscopy. Continuous measurement of accurate concentration is not possible due to the influence of coexisting gases such as , SOX, etc.

On the other hand, the chemiluminescence method uses a highly reliable instrument for NO measurement, and it is considered to be highly practical as there is almost no need to consider the effects of coexisting gases after converting NH3 to NO.

With this method, if the dust in the exhaust gas is not removed, various problems will occur in the sampling line and analyzer, so a primary filter is usually installed at the tip of the sampling line and a secondary filter is installed at the analyzer. If the value is high, the primary filter will need to be replaced more frequently.

In addition, conventional catalysts for converting NH3 to NO use granular products with a diameter of 2 to 4 mm, and when the dust concentration is low, there is no need to worry about dust clogging the catalyst layer.
If the dust concentration is high, it is only a matter of time before clogging occurs, so granular products cannot be used, and it is necessary to use a shape that is less affected by dust, such as a honeycomb shape or a pipe shape, which will not cause dust clogging.

The present invention improves the drawbacks of conventional NH3 analyzers that utilize chemiluminescence methods.

The present invention consists of widening the gas inlet into a conical shape and directing the inlet toward the downstream side of the gas flow so that gas sampling can be performed without sucking in dust as much as possible.
A feature of the catalyst is that it has a honeycomb-like or pipe-like shape with a catalyst surface parallel to the gas flow to prevent clogging due to dust.

That is, the present invention is a gas sampling device installed in a gas flow path for continuously measuring the NH3 concentration in a gas containing a large amount of dust. a sampling hole, an NH3 oxidation catalyst in the shape of a honeycomb or pipe having a catalytic surface parallel to the gas flow for converting NH3 into NO, provided inside the gas sampling device, and heating for heating the catalyst; This is a gas sampling device for continuous measurement of NH3, characterized by having a device.

Hereinafter, embodiments of the present invention will be described, focusing on the case where it is applied to flue gas.

FIG. 1 shows an embodiment of the present invention.

The gas inlet 1 faces the downstream side of the gas flow and expands into a conical shape, so that the sampling gas is sucked in as if it is being drawn into a vortex, and dust with large particle diameters is not introduced, and the gas is spread out in a conical shape. The rapid change in the gas flow rate in this area doubles the effect of sieving out dust with larger particle sizes, and the dust concentration introduced into this gas sampling device is reduced to 10% in the exhaust gas. The average particle size becomes smaller as the particle size increases.

Therefore, the primary filter, which was installed immediately after the gas inlet 1 in the sampling device before the present invention, is almost unnecessary in the present invention, and can be installed after the NH3 oxidation catalyst 3.

The primary filter 4 in the embodiment shown in FIG. 1 is installed as a safety measure in case of an emergency, and the rate of dust adhesion is reduced, and the frequency of its replacement is naturally reduced.

The NH3 oxidation catalyst 3 is a catalyst that converts NH3 to NO, and includes, for example, a catalyst in which oxides such as cobalt, copper, chromium, and manganese are supported on a porous refractory such as diatomaceous earth or silica alumina.

By heating this from 700℃ to 800℃,
% or more conversion efficiency.

Prior to this invention, the conventional catalyst shape was a granular product with a diameter of 2 to 4 mm, and the catalyst layer was clogged by dust and chemicals in exhaust gas, so the catalyst applied in this invention is a honeycomb shape that does not have the risk of dust clogging. A catalyst with a shape parallel to the gas flow, such as a shape or a pipe, is used.

Additionally, the area around the catalyst is heated with a heater 2 to raise the temperature to the level required for the oxidation reaction.

Since the catalyst 3 is installed in the flue 9, the heating temperature of the catalyst heating heater 2 only needs to be added to the exhaust gas temperature.
This point is also an advantage of installing the catalyst in the flue.

That is, when the gas to be measured has a high temperature, the amount of heat of the heating device can be saved by providing the gas sampling device of the present invention in the gas flow path.

Sampling gas is passed from gas inlet 1 to NH3 oxidation catalyst 3
, passes through a dust filter 4, and is led to a NOx analyzer via 5.

When using this sampling device with a NOx analyzer, the NOx concentration is calculated by calculating the difference between the NOx concentration in the gas in which NH3 in the exhaust gas is converted to NO in the catalyst layer and the gas that does not pass through the catalyst layer. Ru.

In this case, it is also possible to attach a gas sampling pipe to the NO detection line to this sampling device.

Although the gas inlet 1 of the gas sampling device in the embodiment of the present invention described above is oriented perpendicularly to the catalyst 3, it may be arranged in a straight line as shown in FIG. 2 of another embodiment of the present invention. In this case, it is necessary to insert the gas flow path into a curved pipe section so that it is not directly affected by the gas flow 10.

Further, it is generally desirable that the gas sampling device be constructed of a material that is resistant to corrosion against the exhaust gases of combustion devices such as boilers.

Particularly in the above-mentioned NH3 measurement for calculating the NOx concentration difference, the inside of the sampling tube led to the analyzer should be made of a material that does not convert NH3 into NO, such as quartz glass, stainless steel, or titanium.

The present invention is an effective means for continuously sampling and measuring the NH3 concentration in exhaust gas containing a large amount of dust using an analyzer, and is also highly applicable to denitrification equipment that uses NH3.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the principle of an embodiment of this invention, in which reference numeral 1 is a gas sampling hole, 2 is a heater for heating the catalyst, 3 is a honeycomb catalyst for converting NH3 into NO, and 4 5 indicates a dust filter, and the gas converted to NO is led to the measuring device through 5. Reference numeral 6 indicates a heater electric terminal, 7 indicates an insertion lid flange for the catalyst 3 and the dust filter 4, and 8 indicates a position fixing pin for the catalyst 3. The exhaust gas flows through the flue 9 in the direction of the arrow 10. FIG. 2 shows an embodiment of a structure in which the gas sampling hole and the catalyst 3 are arranged in a straight line, and shows an example in which the exhaust gas flue 9 is a curved pipe.

Claims (1)

[Scope of utility model registration request] In a gas sampling device installed in a gas flow path for continuously measuring the NH3 concentration in a gas containing a large amount of dust, a sampling hole provided with the expanding side facing the downstream side of the gas flow having a widening shape such as a conical shape, A honeycomb-shaped or pipe-shaped N catalyst with a catalytic surface parallel to the gas flow is installed inside the sampling device to convert NH3 into NO.
A gas sampling device for continuous measurement of NH3, comprising an H3 oxidation catalyst and a heating device for heating the catalyst.