JPS5817648B2 - Exhaust gas purification method for open combustion appliances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying exhaust gas from an open combustion appliance.

In recent years, air pollution caused by carbon oxide has become a problem.

The sources of carbon monoxide (hereinafter referred to as CO) are mobile sources such as automobiles and stationary sources such as large boilers.

The toxicity of carbon monoxide has long been widely known, but from the perspective of preventing air pollution, government efforts have been made to take measures against the source of carbon monoxide in the form of automobile exhaust gas regulations.
Although the level of general air pollution has been significantly reduced, on the contrary, from the perspective of indoor pollution,
The actual situation of some of them has been made public, and they are attracting attention as a problematic substance for indoor pollution.

CO easily binds to hemoguton pins in the blood, and when inhaled, it affects brain activities such as memory and learning, and when inhaled in large quantities, it causes toxic symptoms such as headaches, dizziness, and paralysis of the limbs, eventually leading to death. Arrive.

However, in open-type combustion equipment, there are limits to what can be done only by suppressed combustion technology; in particular, household gas and oil heating equipment generates CO of 0.3 to 0.51/hr, resulting in indoor The concentration far exceeds the environmental standard of ioppm.

Therefore, during combustion, it is necessary to open the window from time to time to exchange the air, but in winter, exhausting warm air outside is not desirable in terms of heating efficiency, and in order to maintain a good indoor air environment, it is necessary to It is desirable to use this method in combination with technology that purifies the CO indoors.

Furthermore, it is desired to establish purification technology for combustion appliances for hot water supply and cooking from the viewpoint of preventing indoor pollution.

'In order to remove CO generated from open combustion equipment, the present invention installs a blower above the combustion section when convection is insufficient, and provides a catalyst layer in the air flow path that oxidizes CO even at room temperature. This is a method of purifying exhaust gas air, and by adopting the present invention, CO released into the room can be significantly reduced.

A combustion device generates a large amount of CO during startup immediately after ignition.

This occurs due to incomplete combustion at startup, and decreases when combustion becomes stable.

For this reason, in open combustion devices, the generated CO is directly released into the room, and the room is contaminated with CO.

In order to prevent indoor air pollution, forced air supply and exhaust systems have been developed in recent years for oil and gas heating equipment that use outdoor air to perform combustion and exhaust the combustion exhaust gas outdoors, but this is why open stoves are cheaper. Removal of the still popular and emitted CO was desired.

Furthermore, in view of ease of use, performance, and technical difficulty, there has been a strong desire for small water heaters for water supply and burners for cooking utensils to be open-type and to remove the generated CO.

The only way to remove CO generated indoors is to convert it into harmless CO2 using a catalyst.

C0 oxidation catalysts include metal oxides such as fobucalide and noble metals such as platinum and palladium. Metal oxide catalysts exhibit sufficient activity even at room temperature, but have the disadvantage that they deteriorate quickly in the presence of water vapor.

A noble metal catalyst is a precious metal supported on a carrier with a high specific surface area such as alumina, silica, or activated carbon.The noble metal used is palladium, which is platinum, but it does not exhibit activity unless it is heated to a high temperature of 100°C or higher.

Therefore, since Co generated from combustion equipment contains water, it is necessary to remove water using a dehumidifier or the like when using a metal oxide catalyst.

In addition, when using a precious metal catalyst, it is necessary to heat it to over 100°C.Therefore, there are methods such as placing the catalyst near the combustion section or requiring other temperature raising equipment, but the above method does not require heating the catalyst. There were many practical limitations, such as technical difficulties as placing the fuel in the tank would affect combustion.

However, there is a strong desire to develop a technology that utilizes the heat generated by combustion, particularly at low temperatures around 70° C., to remove large amounts of CO, and the present invention provides a method for this purpose.

The heat and CO generated by the open combustion appliance rise to the top of the combustion section, then diffuse in the air and are distributed throughout the room.

Therefore, by installing a blower and a CO oxidation catalyst layer as necessary in the upper part of the combustion section where the temperature is around 40 to 100 degrees Celsius, the generated CO can be removed, without affecting combustion, and in actual When used, it has a small and compact structure and is fully effective even when installed at a position far away from the combustion section.

FIG. 1 shows an example of application of the present invention to a kerosene stove as an open combustion appliance.

Heat generated from a combustion part 2 of a kerosene stove 1 (open type combustion appliance) is reflected on reflectors 3 installed at the front and rear surfaces to warm indoor air.

On the other hand, the generated CO passes through the top plate 4 and is diffused into the room, so the CO collected by the blower 5 passes through the catalyst layer 6, is purified, and is discharged into the room from the blowout lower.

Since the catalyst is effective from room temperature to 100°C, the catalyst layer 7
A device 8 having an air blower 5 and a catalyst layer 7 inside is installed away from the combustion part so that the temperature reaches the temperature.

The blower 5 is optimally a sirocco fan, and its air volume is set to such an extent that hot air passes through the catalyst layer 6, so that the blowing air does not affect combustion.

The catalyst layer 6 is preferably one in which the catalyst is sandwiched between two sheets of non-woven fabric or a honeycomb type. In particular, the honeycomb type is optimal because it has low pressure loss and high activity.

The device 8 is of a type that is installed directly on top of the kerosene stove 1 or is attached to a wall.

FIG. 2 shows an example of application to a burner for cooking utensils as an open type combustion appliance.

CO generated from the combustion part 10 of the cooking utensil burner 9 is sucked into the duct 11 by a blower 12 provided inside the duct (air flow path) 11, converted into harmless CO2 by the catalyst layer 13, and exhausted into the room. .

The duct 11 is installed so that it does not get in the way when pots, pots, etc. heated by the combustion part 10 are taken in and out, but it is configured to sufficiently suck in air containing CO generated by combustion.

It seems appropriate for the blower 12 to be a cross fan.

For the catalyst layer 13, a layer in which a catalyst is sandwiched between two sheets of nonwoven fabric or a honeycomb layer is used.

The catalyst is a kneaded molded product of alkali, powdered activated carbon, and cement material, which supports one or more selected from platinum, rhodium, and ruthenium and palladium at the same time, or palladium alone.In particular, potassium carbonate is used as the alkali, and aluminum is used as the cement material. Those using acid lime and those supporting platinum and palladium at the same time were highly active.

Therefore, a kneaded and molded product of potassium carbonate, lime aluminate, and powdered activated carbon that simultaneously supports platinum and palladium is used.

The invention is also applicable to other open combustion appliances.

As an example, as a low-temperature CO oxidation catalyst, one or more selected from the group of platinum, rhodium, and ruthenium and palladium were simultaneously supported on a kneaded molded product of alkali, powdered activated carbon, and cement material, or palladium alone was supported.

The catalyst carrier must support the supported substance in a pure manner with fine particle size and uniform distribution over a wide range, and must also have a large specific surface area and high strength.

When a precious metal is supported on a carrier, the alkali is used to change the impregnating liquid PI- (in which noble metal chloride is dissolved) into an alkali, and the procedure must be optimized so that the noble metal is adsorbed onto the carrier in a fine and uniformly dispersed state. I measured it.

It is thought that the powdered activated carbon contributes to the pore physical properties of the carrier, such as increasing the specific surface area of the carrier.

It is believed that the cement material contributes to increasing the strength of the carrier and improving its heat resistance and abrasion resistance.

Examples of the alkali include potassium carbonate, potassium hydroxide, calcium hydroxide, sodium carbonate, etc., but potassium carbonate was the most suitable in terms of ease of use and performance.

Cement materials include portland cement, calcined gypsum, bentonite, and alumina cement whose main component is lime aluminate, but alumina cement was the most suitable in terms of performance.

The reason for this is thought to be the cocatalytic effect of ferric oxide and calcium oxide contained in alumina cement.

It is also presumed that alumina as a binder plays a role in forming a stable carrier.

Noble metals such as platinum, rhodium, ruthenium, and palladium were used as supporting materials.

Palladium, which is relatively inexpensive, becomes a highly active catalyst when used alone or in combination with other noble metal materials, and in particular, the combination of platinum and palladium exhibited a synergistic effect and achieved remarkable oxidation activity.

Next, the method for preparing the catalyst will be described.

Potassium carbonate is used as the alkali, and alumina cement is used as the cement material. Potassium carbonate has a particle size of 100 mesh, powdered activated carbon has a particle size of 300 mesh, and alumina cement has a composition of at least 45% alumina and ferric oxide. I used less than 10%.

The carrier was prepared by adding 0.5 part of sodium carboxymethyl cellulose (CMC) as a binder to 10 parts of potassium carbonate, 30 parts of powdered activated carbon, and 60 parts of lime aluminate in weight ratio, and kneading the mixture with water.

The kneaded material was thoroughly dried and then classified into 8 to 20 meshes to form a carrier.

After the carrier was sufficiently dried, it was immersed in a solution containing palladium and platinum to effect adsorption.

The amounts of palladium and platinum were adjusted so that 0.3 wt% of each was adsorbed on the carrier.

The adsorbed carrier was reduced with sodium borohydride, thoroughly dried, and heat-treated at 300° C. for 1 hour to obtain a catalyst.

The prepared catalyst was sandwiched between two polypropylene nonwoven fabrics to form a catalyst layer.

To determine the effectiveness of the present invention, an open kerosene stove was burned in a naturally ventilated 6-tatami room (volume: 29.6771''), and the indoor CO concentration was measured.

FIG. 3 shows the indoor CO concentration in case I without the present invention and in case II with the present invention, and the CO oxidation catalyst used here was the one explained in the above "Catalyst adjustment method".

Open type kerosene stove has a calorific value of 2200 to 2300 kc
The mixture was combusted at a L/hr, and the indoor concentration was analyzed using a non-dispersive infrared CO analyzer after sucking air from the center of the room.

(2) shows the case where the equipment having the configuration shown in Figure 1 is installed on the top plate of an open kerosene stove.

The catalyst layer was made by filling 100 g of catalyst in a uniform distribution between two sheets of polypropylene nonwoven fabric with a size of 300 x 100 mm at a layer height of 5 mm, and the temperature was 70 to 80°C.

A sirocco fan was used as the blower, and the amount of air blown was adjusted so that the air passed through the catalyst layer at a flow rate of 0.3 m/s.

The larger the airflow rate, catalyst packing density, and bed height, the higher the catalyst activity. As the height increases, the pressure loss increases, resulting in problems such as a decrease in air volume and a decrease in activity.

As a result of numerous tests regarding these factors, the above conditions were found to be optimal.

The temperature of the catalyst layer should be 100°C or less, preferably 70-80°C, since the limit temperature for use of polypropylene as a nonwoven fabric is 110 to 130°C, and it is desirable to use the catalyst at a temperature of 100°C or less. It is necessary to consider the position of the catalyst layer.

When the present invention is adopted, harmful gases, especially CO, generated indoors from open combustion appliances can be efficiently removed.

This is because the catalyst carrier is porous and supports the precious metal, which is a highly active substance, in a fine particle size and uniformly over a wide range, and it oxidizes CO with high activity at low temperatures and also eliminates the presence of water vapor. Since it works to improve activity, it is ideal as a catalyst for purifying combustion exhaust gas.

In terms of durability, differential thermal analysis shows that the catalyst decomposes with heat generation at 385°C, but is stable below that temperature range, and the inventors found that when the catalyst was left in a high-temperature atmosphere for a long time, it reached 300°C. It was confirmed that the activity did not decrease even after being left at 200°C for 1 month or 3 months at 200°C.

However, in practice, the catalyst is never placed under such conditions and is used in an atmosphere at a temperature of 70 to 80°C, so it is understood that it is sufficiently thermally stable.

On the other hand, regarding the effects of poisoning, NOx and H
Contains C etc.

During incomplete combustion, such as immediately after ignition, a large amount of CO is generated, but almost no NOx is generated.

On the other hand, during complete combustion, not much CO is produced, but NOx is relatively large.

However, most of the NOx in combustion is NO;
You don't have to think about 2.

Therefore, NOx poisoning occurs during stable combustion. Since this catalyst uses a noble metal as an active substance, it weakly adsorbs NO, but since it most easily reacts with CO, it is quickly desorbed and does not reduce the catalytic action.

In addition, although the carrier contains alkali and activated carbon, alkali and NO do not react with each other, powdered activated carbon does not adsorb NO, reduces NO2 to No in the presence of moisture, and has a small adsorption capacity for NO□, which can be desorbed. For some reason, there is almost no poisoning caused by NOx.

NOx can also be significantly reduced by improving combustion equipment.

SO2 hardly exists in the exhaust gas because the presence of S in the fuel component and H2S in the air is unlikely.

CO2 does not significantly affect the activity of the catalyst.

H2O helps activate the catalyst. Hydrocarbons are oxidized by a catalyst.

Through the use described above, this catalyst oxidizes CO with high performance without being affected by other component gases in exhaust gas.

The invention is equally applicable to other open combustion appliances, such as cooker burners.

The present invention eliminates carbon dioxide generated by combustion without improving the combustion part.
Since O is removed by installing a catalyst layer above the combustion section, it does not affect combustion.

Does not require large-scale equipment.

Not only does it have the advantage of not interfering with the installation of pots and kettles placed on top of the combustion section, but it also circulates within the campus, reducing the amount of CO and NOx generated, so it can be expected to be extremely effective.

[Brief explanation of drawings]

Figure 1 is a front view showing an example of application to a kerosene stove, Figure 2 is a side view showing an example of application to a cookware burner, and Figure 3 is a diagram showing changes in CO concentration when applied to a kerosene stove. It is.

Claims (1)

[Claims] 1 A catalyst layer supporting platinum and palladium is provided in the air flow path on a carrier obtained by kneading and molding alkali, powdered activated carbon, and cement material, and as the alkali, potassium carbonate,
A method for purifying exhaust gas from open combustion appliances using lime aluminate as a cement material.