JPS6025177B2 - gas purification equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas purification device, particularly a device for purifying harmful gases contained in the atmosphere. This invention relates to an apparatus for purifying oxides N○x, sulfur dioxide S02, carbon monoxide, and ○, especially at room temperature.

Measures to reduce pollutants in the atmosphere are being strongly promoted, mainly focusing on measures to reduce their generation, but it is expected that the problem of localized high concentration pollution will still remain in the future.

These are workplaces where special work is carried out or in close proximity to pollution sources, and as long as there are people living there, it is desirable to achieve a level of harmful gas concentration in that environment. I can't wait. From this point of view, the need for air purification techniques is becoming more and more important. The related air purification technology is mainly S0
2, and techniques using activated carbon, alkali-impregnated filters, etc. have been utilized.

In addition, there is no technology available for removing NOx, and it has recently attracted attention due to the publication of medical and epidemiological data showing that NO is not harmless but rather highly harmful. There is.

The present inventors have discovered that a cured product obtained by hybrid molding of alkali chlorite, alkali, and cement material is excellent as a dry absorbent for NO at room temperature, and has already proposed this as a new NO removal technology.

Similarly, the present inventors have found that a cured product obtained by kneading and molding powdered activated carbon, alkali, and cement material has N
We discovered that it is an excellent dry absorbent for ○x at room temperature, and proposed this as an N02 removal technology. Both of these exhibit excellent S02 absorption ability, and by using them in combination, N*x and S02 can be almost completely removed. Next, it is highly necessary to remove CO, but it is extremely difficult to remove it at room temperature. A well-known family of hopcalite catalysts is manganese dioxide as the main ingredient and metal oxides such as copper, iron, cobalt, and silver added to it, but this catalyst is poisoned by moisture in the atmosphere and loses its ability quickly at room temperature. It has the disadvantage that it decreases. As a room-temperature type catalyst whose performance is rather improved due to the influence of moisture,
Catalysts supporting palladium and platinum group metals have been proposed in the past. For example, activated carbon is used as a carrier, and 0
．． For example, it supports 5% by weight of palladium.
However, these catalysts deteriorated significantly when put into practical use in the atmosphere, and reached the end of their lifespan after about 10 to 10 feeding hours, making them unusable. The present invention solves this problem and relates to a new device that can simultaneously purify CO and N*x at room temperature.

It is already known that in order to avoid the influence of catalyst poison, a filter for removing the poisonous substance is provided upstream of the catalyst to prevent the substance from coming into contact with the catalyst.

However, when operating a unique catalyst for a unique reaction, the mechanism of action of the catalyst used is completely unique, and therefore the mechanism by which the catalyst deteriorates is entirely unique to that reaction. It is unique to the catalyst.

It is necessary to fully understand the cause of the deterioration mechanism of the catalyst, such as poisoning of the catalyst, sintering, compound form, change in chemical composition, change in shape structure, etc. As for catalyst poisoning, without knowing what is poisoning the catalyst, we cannot say anything about which type of filter is effective. It was previously unknown why catalysts supported with noble metals such as palladium and platinum, as described above, deteriorate rapidly.

For example, when activated carbon is used as a mortar, it is possible that the activated carbon itself has a cocatalyst effect and that the activated carbon adsorbs various organic gases in the atmosphere, or that precious metals are , N02, and S02. Various measures have been attempted to prevent this, but although they have extended the lifespan to some extent, they have not been definitive measures, and the reason for the deterioration remains unknown. Ta. The present invention combines a catalyst layer supporting a platinum group metal catalyst such as platinum or palladium with a layer of a first nitrogen oxide removing agent made of a cured product containing an alkali chlorite and a cement material, and a layer of a first nitrogen oxide remover made of a cured product containing an alkali chlorite and a cement material. It has been discovered that by placing the second nitrogen oxide remover layer made of a hardened material containing cement on the downstream side, poisoning of the catalyst by NO can be prevented and harmful gases can be effectively removed. . Here, the first and second nitrogen oxide removers are made by thickening alkali chlorite or activated carbon with water and a hydraulic cement material such as alkali and alumina cement, bentonite, and calcined gypsum. These are molded and hardened into N○, N0 by the following reaction.
2. Has the function of removing S02. Since these nitrogen oxide removers absorb N○, N02, etc. as described below, they do not desorb harmful gases once absorbed. First, when sodium salt is used as the chlorite and calcium hydroxide is used as the alkali, the first nitrogen oxide remover absorbs N0 and N02 through the following reaction.

NO+ is aC〆02 10th a (OH)2 1 Xa (N03) 20 is aC〆10 is 20 State 020 NaC So020 20 This nitrogen oxide remover has S02, day 2S due to the action of Alka IJ.
The main function is to oxidize NO to NQ with the oxidizing agent chlorite, and then absorb it with alkali.The oxidation rate of NO is extremely fast, but NO
The absorption rate of 2 is rather slow.

Therefore, although it is sufficient to remove NO, there are disadvantages such as the need to form a thick filling layer for NQ removal, that is, complete removal of NOx. As the alkali used here, hydroxides and oxides of alkali metals and alkali metals can be used.

Ca(OH)2 is most preferable as the alkali due to the stability of the head chlorate and other reasons, and as the cement material, calcined gypsum (calcium sulfate) CaS04.1/Group 20
is advantageous. Especially NaC〆02/Ca(OH)2/C
A composition with a S04.1/2LO ratio of around 4/3/3 by weight is excellent. Next, the second nitrogen oxide remover mainly absorbs and removes N02.

The main reaction is a reaction between N02 and alkali, but the reaction proceeds rapidly due to the NQ adsorption effect of activated carbon, which acts as a catalyst. The above-mentioned alkalis and cement materials can be used here, but K2C03 and Ca(OH) are used as alkalis from the viewpoint of reactivity and stability.
) 2 combination is effective.

The reaction in this case proceeds as follows via activated carbon. State Q+K2CQ+Xa(OH)2 →KN020Ca(N03)20KN020Ca(N0
2) Group 20 200C02 Also reacts with S02 as follows.

Male020K2C030Ca(OH)2 →K2S030CaS0310days 201C02 This nitrogen oxide remover is activated carbon/K2C03/Ca(OH)2/
CaS04・1/2 also has a weight ratio of 2/3/3/2.
Those with similar compositions are particularly good.

By using the first and second nitrogen oxide removers in combination, N0, N02, and S02 can be removed with high efficiency.

As is clear from the above reaction formula, it is preferable to arrange the second nitrogen oxide removing agent downstream of the first nitrogen oxide removing agent with respect to the gas stream to be purified. As a platinum group metal catalyst layer,
In combination with the layer of the nitrogen oxide remover mentioned above, even those using carbon or alumina as a carrier can maintain CO purification ability for a long period of time. The Cq purifying ability is excellent when the carrier is cured with .

The effects of the present invention will be explained below using examples. Figure 1 shows an outline of the equipment used to evaluate gas purification ability. 1, 2, 3
, 4 are gas cylinders of C○, N○, N02, and S02, respectively.

An air pump 5 takes in atmospheric air, humidifies it with a humidity control device 6, and sends it to a mixer 7.

The air mixed with various gases in the mixer 7 is introduced into the septic tank 9 through the three-way cock 8. A cylindrical tube on the inner diameter 18 side of the purified slag 9 is filled with a catalyst and the like, and is maintained at a constant temperature by a heater 10. The inlet gas concentration to the septic tank 9 is measured by directly introducing the gas into the analyzer 11 from the three-way cock 8, and the outlet gas concentration is measured by introducing the gas that has passed through the septic tank into the analyzer 11. Comparison of Cq purification ability using only the comparative example catalyst layer is shown.

Catalyst A with 0.5% by weight of palladium supported on activated carbon
, 0.5% by weight on activated alumina with a thin layer of silica
Catalyst B, which had platinum supported on it, and Catalyst C, which had 0.5% by weight of palladium and 0.1% by weight of platinum supported on a cured product made of activated carbon, potassium carbonate, and alumina cement, were used. The carrier for catalyst C was prepared by mixing activated carbon powder, potassium carbonate, and alumina cement in a weight ratio of 3:6:1, adding an equal volume mixture of water and ethanol to the mixture, kneading it, and molding it. It is hardened.

For palladium, a hydrochloric-acidic solution of palladium chloride is adsorbed onto a carrier, followed by reduction under heat with a formalin-alkaline solution.For platinum, a hexachloroplatinum solution is adsorbed onto a carrier and hydrogen is added. 300℃ inside
We used a method of reducing at a temperature of . 6 to 1 of each of the above catalysts
Fill the powder with a particle size of 0 mesh and heat it to a temperature of 3.
When air containing 100 cm of CO was aerated at a space velocity of 12,000 [hr-1] under a relative humidity of 60% and a relative humidity of 60%, the conversion rate of CO to CO2 was 35% for catalyst A and 35% for catalyst B.
was 42%, and C was 99%.

Next, when air containing S02 and N02 of IQ Cape's wind was continuously vented under the same conditions as above, catalysts A and B were
After 0 hours, the CO purification ability was completely lost. On the other hand, for C, the CO removal ability decreases by 5% even after 20 hours.
It was within In addition, when the air containing NO on the IQ side was continuously aerated under the same conditions as above, catalyst A reacted in about 1q hours.
In addition, B loses its ability to gradually remove Cq after about 10 feeding hours,
The Cq removal ability of C also decreased to about 10% after about 10 hours.

This means that for both palladium and platinum, N is higher than CO at low temperatures.
This is thought to be due to the strong adsorption of O, which caused primary poisoning due to adsorption of NO. 1 in order from the upstream side of the gas flow to the Example 1.
nitrogen oxide remover 12, second nitrogen oxide remover 1
3, and the catalyst 14 described above.

Note that the first nitrogen oxide remover contains sodium chlorite/
The mixture ratio of calcium hydroxide/calcium sulfate is 4:3:3 by weight, and the second nitrogen oxide remover is a mixture of activated carbon powder/potassium carbonate/calcium hydroxide/calcium sulfate. The cured products were used in a weight ratio of 2:3:3:2. These are kneaded with water and alcohol, extruded into a columnar shape with three ribs in diameter, and cured. A septic tank is equipped with a packed bed filled with 5 skins of each of the above three types, and air containing 10 ■ blood C○, 10 legs N○, IQ ■ N02, and 1 cucumber SQ is heated at a temperature of 35°C. , flow rate 1.0 so/min, space velocity 45000 at relative humidity 60%
Figures 2 to 4 show the time-dependent changes in the outlet concentration when aerated at [hr-1]. FIG. 2 shows the above catalyst A as the catalyst layer 14.
Figures 3 and 4 show the cases where catalysts B and C were used, respectively.

As is clear from the above results, according to the present invention, N○
, N02, and S02 almost completely, and the catalyst's original CO purification ability can be maintained without being affected by poisoning by these gases.

Harmful gases in the atmosphere are more likely to coexist than exist alone, and it is desirable that their removal and purification can be carried out at room temperature and in a dry process. According to the present invention, this ideal state can be achieved. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of the apparatus used for measuring the gas purification ability, and FIGS. 2 to 4 show a comparison of changes over time in the outlet gas concentration of Joirisho. Figure 3 [ Sphere diagram N Deployment scale moth

Claims (1)

[Scope of Claims] 1. A first nitrogen oxide removing agent layer made of an alkali chlorite, a cured product containing an alkali and a cement material, and a second nitrogen oxide layer made of a cured product containing activated carbon, an alkali and a cement material. A layer of an oxide removing agent and a catalyst layer formed by supporting a platinum group metal catalyst on a carrier made of a hardened material containing activated carbon, an alkali, and a cement material are provided in each gas flow path,
A gas purification device characterized in that the catalyst layer is disposed on the downstream side of the first and second nitrogen oxide removing agent layers. 2. The gas purification device according to claim 1, wherein the first nitrogen oxide removing agent layer is disposed upstream of the second nitrogen oxide removing agent layer. 3. The gas purification device according to claim 1 or 2, wherein the alkali is selected from the group consisting of potassium carbonate and calcium hydroxide. 4. The gas purification device according to any one of claims 1 to 3, wherein the cement material is calcium sulfate. 5. The gas purification device according to any one of claims 1 to 4, wherein the catalytic metal is selected from the group consisting of palladium and platinum.