JPS5858621B2 - Measuring method of sulfur dioxide gas concentration in gas - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously measuring the concentration of sulfur dioxide gas (802) in a gas coexisting with ammonia (NH3) and a large amount of water using an infrared gas analyzer etc. This invention relates to an ammonia decomposition catalyst for eliminating negative errors caused by the influence of ammonia and moisture, which are a problem in the production of ammonia.

This type of ammonia decomposition catalyst is generally desired to have the following performance.

(1) N)(3) Decomposition efficiency is high.

(Approximately 100 honors.

) (2) Do not affect SO3 concentration.

(Reaction absorption of SO3 by catalyst or oxidation reaction S
Decrease in SO2 concentration due to O2+%02→SO3.

)(3) Have excellent durability.

(4) The ammonia decomposer should be small and lightweight.

In various gases containing SO2, such as exhaust gas from heavy oil-fired boilers, ambient air, etc., SO2 in the gas! Conventionally, JIS-K was used as a method to continuously analyze concentration by instrumental analysis.
The infrared gas analysis method and solution conductivity method specified in O103 are known and widely used.

In particular, it is mandatory to measure the SO2 concentration in exhaust gas from heavy oil-fired boilers, etc., and it is important to perform highly accurate measurements.

On the other hand, NH
Although it is necessary to continuously measure SO2 in exhaust gas that coexists with NH3 and a large amount of water, it has been pointed out that the measured value of SO2 concentration varies greatly depending on the presence or absence of NH3 coexistence.

This is also true in the measurement of 802 concentration in the ambient air, and the negative error due to coexisting NH3 (the ambient air contains about several hundred ppb of NH3) is considered a problem.

In order to remove this difference (measurement error) or negative error, a technique for removing coexisting NH3 was published in
A method described in Japanese Patent No. 24492 is known.

This is a catalytic decomposition method in which a reactor filled with an ammonia combustion catalyst is installed in front of a continuous analyzer to burn off ammonia in the gas, and the gist of this method is as follows.

(1) Ammonia is the cause of negative errors in SO2 concentration measurements.

(2) As a NH3 decomposition catalyst (a) V2O3Mo03 (b) VxAyOzA=Cu, Zn, Sn, Pb, Ti
.

P, Cr, Fe, Co, Ni ←→ CrxAyOz A=Ni, Co, Zn
, Mo, W, SnP, Ti A=Sn, Sb, V, Co, Ag, Zn Ni, Ti, Mo, W A=S, P, As, Ge, Zr)■ Base metal oxide such as 205-WO3 A physical catalyst is used.

(3) The effective catalyst utilization temperature is 200 to 500°C. However, this method has the following disadvantages.

i) Base metal oxide catalysts tend to react and absorb SO2, giving a negative error to the SO2 concentration, and have the disadvantage that the NH3 decomposition reaction activity gradually decreases.

FIG. 1 is a graph showing the phenomenon in which a base metal oxide catalyst absorbs 802 in comparison with a Pd-Al2O3 catalyst.

As a base metal oxide catalyst, 10% by weight V2O5-5 weight ratio MoO3-A 1203, Pd-A 1203
2% by weight Pd-A 1203 was used as a catalyst.

These catalysts contain SO250ppm, CO215%
, 025%, N201 rice, and the rest N2 are brought into contact with each other for a predetermined time under the conditions of GH8V (space velocity) = 17.0001 and temperature 300°C, and the SO□ analyzer indication for the reaction time (minutes) is The values (ppm) were read and shown in FIG.

In FIG. 1, (I) shows a graph based on 2% by weight Pd-Al2O3, and (II) shows a graph based on 10% by weight V2O5-5% by weight M
Figure 2 shows a graph according to oO3-A 1203.

As is clear from Figure 1, the base metal oxide catalyst is SO
It can be seen that SO2 is easily absorbed by reaction, giving a negative error to the SO2 concentration.

il) When the catalyst is used at a temperature below 340°C, the coexisting sulfuric acid mist (it is said that the exhaust gas at the outlet of an ammonia catalytic reduction denitrification device contains a particularly large amount of sulfuric acid mist) condenses and accumulates on the catalyst. Gradually decreases the ammonia decomposition activity of.

FIG. 2 is a graph showing the phenomenon in which performance of a base metal oxide catalyst is degraded by sulfuric acid mist at low temperatures in comparison with a Pd-Al2O3 catalyst.

10% by weight V2O 55% by weight as base metal oxide catalyst
MoO3Al2O3 and 2% by weight Pd-A-1203 were used as a Pd-Al2O3 catalyst.

This square wax (this SO250ppm, 80320p
p.m.

CO2 15%, 0□5%, H2O1%, NH380pp
m, and the remaining N2 gas is GH8V=60.0
The S02 analyzer indicated value (
ppm) was read and shown in FIG.

In Figure 2, (1) shows a graph based on 2% by weight Pd-Al2O3, and (II) shows a graph based on 10% by weight V2055% by weight M
A graph according to oO3Al2O3 is shown.

From FIG. 2, it can be seen that in the case of a base metal oxide catalyst, the ammonia decomposition activity gradually decreases at a low temperature of 300° C. due to the influence of coexisting sulfuric acid mist.

The object of the present invention is to eliminate the drawbacks present in the above-mentioned known technology;
A highly practical N
An object of the present invention is to provide an H3 decomposition catalyst.

(1) High NH3 decomposition efficiency.

(It must be approximately 100%.

) (2) It should not affect SO2 concentration.

(Reaction absorption of SO2 by catalyst or oxidation reaction S02
Decrease in SO2 concentration by 10% 02-+803.

)(3) Have excellent durability.

(4) NI (3) The decomposer must be small and lightweight.

In order to achieve the above-mentioned object, according to the present invention, before continuously ff1lffi the concentration of sulfur dioxide gas in a gas coexisting with ammonia and a large amount of water, the gas is first passed through an ammonia decomposition catalyst to reduce the concentration of sulfur dioxide in the gas. In this method, a Pd-Al2O3 catalyst is used as the ammonia decomposition catalyst at a temperature of 340°C to 500°C and a GH8V (space velocity) of 60,000 to GH8V (space velocity). 150,0
It is characterized by being used under 00 conditions.

Hereinafter, the present invention will be explained in detail using the accompanying drawings.

FIG. 3 shows a flowchart of a performance testing apparatus for an ammonia decomposition catalyst used in the method of the present invention.

As shown in Figure 3, this device can prepare a test gas by mixing five types of gas to a desired concentration (excluding water in terms of tri-gas), and uses this test gas to test the performance of NH3 decomposition catalysts. It is possible to do this.

In FIG. 3, both SO2/N2 (SO□ standard gas with N2 balance) and NH3/N2 (NH3 standard gas with N2 balance) can be made to flow with N2 alone.

1 is a humidifier, and this humidifier 1 can change the moisture content of the test gas up to 20%.

2 is an SO2/S03 converter, converting a part of S02 to SO
3 to obtain a SO2+SO3 mixed gas.

3 is an NH3 decomposer filled with NH3 decomposition catalyst, 4 is N
5 and 5' are dehumidifiers, 6 and 6' are filters, 7 is an SO2 gas analyzer, and 8 is a NOx gas analyzer.

The NH3/N2x converter 4, the dehumidifier 5', the filter 6', and the NOx gas analyzer 8 together constitute an NH3 gas analyzer, and this series of systems is indicated by reference number 9.

In addition, bl, b2, b3, and b4 each indicate a bypass, and a three-way cock allows the flow path to be switched at the branch point.

Although not shown in the drawing, the humidifying gas flow path on the upstream side of the dehumidifiers 5 and 5' contains NH3 and SO due to moisture condensation.
The temperature is kept at 80 to 100°C to prevent absorption loss of x.

The zero points of SO2 gas analyzer 7 and NOx gas analyzer 8 are SO2/N2 gas inlet and NH3/N2, respectively.
It is adjusted by flowing N2 together with CO2p 02 and humidifying N2 from the gas inlet and introducing it into the SO2 gas analyzer 7 or the NOx gas analyzer 8 via bypasses b2 and b3.

Span adjustment of the SO2 gas analyzer 7 is performed using S02. of the above-mentioned zero gases. Switch the /N2 gas inlet from N2 to SO2/N2 and use the same path as for zero point adjustment.

Further, the SO3 concentration generated in the S02/SO3 converter 2 is determined by subtracting the 8O2 concentration when passing through the S02/SO3 converter 2 from the SO2 concentration due to the bypass b2.

On the other hand, the NH3 concentration in the inlet gas of the NH3 decomposer 3 is SO
2/N2 gas inlet and NH3/N2 are introduced from the NH3/N2 gas inlet and bypass b2°b3.
N via b4) (determined by 3-gas analyzer 9).

By the above pre-operation, SO in the inlet gas of NH3 decomposer 3
2,803, the NH3 concentration can be determined.

Next, the performance test operation of the NH3 decomposition catalyst in the NH3 decomposer 3 will be described.

SO2/N2. CO2゜q gas flows through bypass b2, and N2 gas flows through humidifier 1 and bypass b2, and these are combined with NHa/N2 to form 5O2.
-NH3-N2002-CO! - Adjust the N2-based test gas.

This gas is then introduced into the NH3 decomposer 3, and further SO
S in the outlet gas of the NH3 decomposer 3 under various reaction conditions of the NH3 decomposition catalyst (catalyst layer temperature, GH8V) is
Measure the O2 or NH3 concentration and use the formula (1) shown below.
And (2), the SO2 residual rate and NH3 decomposition rate (both are preferably close to 100%) are determined.

The following tests were conducted using the performance test equipment and performance test operations as described above.

(4) Amplifying effect of coexisting water content on NH3 interference.

Using a 5O2-NH3-N20-02-CO2-N2 mixed gas, the amplification effect of coexisting water content on NH3 interference was tested, and the results are shown in the graph of FIG.

In this test, the gas composition (component ratio) of the mixed gas used was as follows.

802-=50 ppm NH3-80pp″′ 1. Iil C02=15 buns 02-5% Remaining N2 The water content was varied between 0 and 10 volumes.

From Figure 4, it is clear that N1 (3-
It can be seen that the indicated value of SO2 concentration decreases more significantly due to condensation of the 8O2-N20 mixture in the piping section.

That is, when moisture coexists in the mixed gas, NH3 interference is amplified, and the greater the amount of moisture, the more this interference is amplified.

■ NH3 interference effect of various catalysts.

The SO□-NH3-N20-o2-CO2-N2 mixed gas is passed through the NH3 decomposer 3 filled with the various catalysts shown below, and the effect of reducing the NH3 interference effect at this time is measured by the catalyst layer temperature (Q). The relationship with the SO2 residual rate is expressed in graphs as shown in FIGS. 5 to 8.

Catalyst used (a) 2% by weight Pt-Al2O3 catalyst (Figure 5) (
CI) 2wt% RuAl2O3 catalyst (Figure 6) (
C) 10% by weight V2O5-5% by weight M o 03AI
203 Catalyst (Fig. 7)) 2 Weight Pd-Al2O3 Catalyst (Fig. 8) These catalysts were prepared as follows.

(a) Preparation of the catalyst described in (A), O) and (2) above.

A soluble salt of a noble metal (H2PtCl4 ・6
N20. RuCl3・N20. The activated alumina support was impregnated in an aqueous solution containing PdCl2 for 2 hours at room temperature and then filtered, dried in a N2 stream at a temperature of 150°C for 5 hours, and then dried in a N2 stream at a temperature of 250°C for 3 hours. Prepared by reduction.

(b) Preparation of the catalyst described in (c) above: Heat an aqueous solution of vanadyl oxalate to a temperature of 85°C, impregnate it with an activated alumina carrier for 2 hours, and then filter it in a stream of air. 1
Dry for 5 hours at a temperature of 20 °C, then 450 °C in a stream of air.
Heated for 3 hours at a temperature of ℃, ■20510% by weight/Al2
A catalyst called O3 was obtained.

Next, this was impregnated in an aqueous ammonium molybdate solution at room temperature for 2 hours, and then filtered and soaked in an air stream at a temperature of 120°C for 5 hours.
It was dried for an hour and heated at a temperature of 400° C. for 3 hours.

Furthermore, the operations of impregnation, drying, and decomposition of ammonium molybdate were repeated four times (total of five times), and finally v20510
Heavy weight.

A catalyst having 35% by weight of MoO/Al2O3 was obtained.

FIG. 5 is a graph showing the effect of reducing NH3 interference when this catalyst (a), that is, 2% by weight of Pt--Al2O3, is used as the ammonia decomposition catalyst.

This graph shows SO2 as a mixed gas: 50ppm e
CO2: 15%, 0□: 5%, NH3: Oppm
Or, it is expressed by determining the SO2 residual rate with respect to the catalyst layer temperature of 0 under the condition of GH8V = 60,000 using a gas with a composition of 80 ppm, 1% N2, and the remaining N2, and is expressed as "- 〇-” curve is NH
The value of sOppm is shown, and the curve of "-・-" is NH38
The value of 0 ppm is shown respectively.

Figure 6 shows the ammonia decomposition catalyst mentioned above (b), that is, 2 weight ratio Ru Al2O3, and Figure 7 shows the above mentioned (2).
C), that is, 10% by weight V2O5-5 weight rice cake MoO
3 AI □ 1 Figure 8 is the above), that is, 2 weight φ
It is a graph showing the NH3 interference reduction effect when Pd-Al2O3 is used, and is expressed in the same manner as in the above-mentioned FIG. 5.

Among the above-mentioned figures 5 to 8, in figures 5 to 7, NI
Although the J3 interference reduction effect is not very apparent, it is very clearly seen in Figure 8, and as a result, it can be seen that the Pd Al2O3 catalyst used in Figure 8 has the best performance as a catalyst for NH3 decomposition. .

In addition, in these graphs, the SO2 residual rate decreases on the high temperature side, but this is due to the reaction S02 + 3AO2 → SO
This is due to 3.

Not only does the S02 residual rate decrease at low temperatures, but also undecomposed NH3
This is due to an increase in

(C') Relationship between NH3 decomposition rate and 802 residual rate on Pd-Al□03 catalyst.

An example of the relationship between the N)13 decomposition rate and the SO2 residual rate on the Pd-Al2O3 catalyst is shown graphically in FIG.

This graph shows 2 wt% Pd-Al as an NH3 decomposition catalyst.
802:50 as a mixed gas using a 2O3 catalyst
ppm, CO2: 15% #02' 5% p
H20: 9%, NH3: 80 ppm remaining N2
Using a gas with a composition of GH8V=17,000, the catalyst layer temperature ('
This is expressed by determining the H3 decomposition rate.

In the figure, the curve r-EEhj represents the NH3 decomposition rate with respect to the catalyst layer temperature, and the curve "+" represents the SO2 decomposition rate with respect to the catalyst layer temperature.
Represents the survival rate.

From FIG. 9, it can be seen that the NH3 decomposition rate increases as the catalyst layer temperature increases and eventually reaches 100%, and the SO2 residual rate also increases as the NH3 decomposition rate increases.

Q)) Changes in the S02 residual rate depending on the SV characteristics and water concentration of the Pd-Al2O3 catalyst Figure 10 is a graph showing the test results on the influence of GH8V on the N)I3 interference reduction effect of the Pd-Al□03 catalyst. It is.

This graph shows 2 wt% Pd-A1 as an NH3 decomposition catalyst.
Using 203 catalyst, SO2 as mixed gas: 50 p
Using a gas with a composition of pm, CO2: 15, 02:5, N20: 9, NH3: 80ppm1 and the remainder N2, GH8V1'/, 000.60,000.100
, 000, the SO2 residual rate with respect to the catalyst layer temperature is shown.

Further, FIG. 11 is a graph showing test results regarding the influence of water concentration on the SO2 residual rate when using a Pd-Al□03 catalyst.

This graph uses 2% by weight PdA1゜03 catalyst as the NH3 decomposition catalyst, and SO2: 50ppm as the mixed gas.
, CO2: 15%, 02:5%, N20:1%4φ
or 9%, NH3: 80 ppm1 remaining N2
The SO2 residual rate with respect to the catalyst layer temperature is expressed under the condition of GI-(SV=60.000) using gases having the compositions (three types of gases with different moisture contents).

From the above-mentioned FIGS. 10 and 11, it is clear that Pd-A120
3 catalyst G) (SV = 17,000 ~ 100,00
It can be seen that by using the 0 temperature within the range of 290 to 470°C, a high SO2 residual rate of 95 or more can be obtained even for exhaust gas with a high moisture content and containing a high concentration of NH3 compared to SO2.

The catalyst can be used outside this range, but when 803 (sulfuric acid mist) is present in a high concentration in the gas, it is preferable to use it at GH8V=60.000 or higher and at a temperature of 340°C or higher.

However, unless the loading of the frying catalyst is done with care, which greatly exceeds GH8V2100,000, the performance will deteriorate due to gas blow-through or the catalyst activity will decrease at high temperatures, so the upper limit of GH8V is considered to be around 150,000. It will be done.

Furthermore, if the catalyst temperature is set too high, the catalyst deteriorates due to the high temperature, and the S02 residual rate decreases due to an increase in the SO2→SO3 reaction, so the upper limit of the catalyst temperature is about 500°C.

Summarizing the above test results (1) to 0, the gist of the present invention is as follows.

Nu used in SO2 gas analyzer is P as a decomposition catalyst.
d-Al2O3 catalyst is optimal.

Since the present invention employs this catalyst, (1) there is no negative error with respect to the SO2 indication value or deterioration of NH3 decomposition activity due to absorption of SOx;

(2) High NHa decomposition activity and at the same time the reaction SO2
+3A 02→SO3 has a small negative error with respect to the SO2 indicated value.

(3) A wide range of usage conditions (temperature, GH8V) can be selected even for gases containing high concentrations of NI (3) and moisture, and the NH3 decomposer can be made smaller and lighter.

etc., all the performances required for an NH3 decomposition catalyst are satisfied.

Moreover, the catalyst is heated at a temperature of 340°C to 500°C and a G
When used under conditions of H8V 60,000 to 150,000, even if sulfuric acid mist exists in the gas, it will not be affected by this.

[Brief explanation of drawings]

Figure 1 shows a graph showing the So2 absorption curve by a base metal catalyst, Figure 2 shows a graph showing the deterioration of catalyst performance due to sulfuric acid mist at low temperatures, and Figure 3 shows a graph showing the deterioration of catalyst performance due to sulfuric acid mist at low temperatures.
(Figure 4 shows the flow sheet of the performance test device for the 3 decomposition catalyst, Figure 4 shows the graph showing the effect of the amount of coexistence water on the interference of NH3, Figures 5 to 8 show the N of various catalysts)-I
3 shows a graph showing the interference reduction effect, and Figure 9 shows Pd
- A graph showing the relationship between the NI (3 decomposition rate and the SO2 residual rate on the Pd-Al
A graph showing the influence of GH8V on the NH3 interference reduction effect of the 2O3 catalyst is shown in Fig. 11.
A graph showing the influence of water concentration on the S02 residual rate for the three catalysts is shown. 1... Humidifier, 2... SO2/SO3
Converter, 3...NH3 decomposer, 4...
NHa/NOx converter, 5゜5'...dehumidifier,
6, 6'... Filter, 7... SO2
Gas analyzer, 8...NOx gas analyzer, 9...
...NH3 gas analyzer, bl, b2, b3
, b4...Binogus O

Claims (1)

[Claims] 1. Before continuously measuring the concentration of sulfur dioxide gas in a gas containing ammonia and a large amount of water, the gas is first passed through an ammonia decomposition catalyst to decompose the ammonia content in the gas, and then the ammonia content in the gas is decomposed. In the method of measuring sulfur dioxide gas concentration, a Pd-Al2O3 catalyst is selected as the ammonia decomposition catalyst, and this catalyst is heated at a temperature of 3
40℃~500℃ and space velocity 60,000~15
For measuring sulfur dioxide gas concentration in gas, which is characterized by being used under conditions of 0,000