JPS6048488A - Purifier for exhaust gas from high-temperature heating furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention particularly relates to an exhaust gas purification device for a high temperature heating furnace that discharges alkaline gas components.

Conventional configurations and their problems Heating furnaces include drying furnaces that volatilize substances with relatively low boiling points such as adsorbed moisture and various solvents from heated objects, and sintering furnaces and thermal decomposition furnaces that have relatively high internal temperatures. There is. Since most of the harmful gases discharged from the former drying furnace are hydrocarbons, these can be purified with an oxidation catalyst.

On the other hand, in the latter sintering furnace and cracking furnace, various cracked gases are generated in addition to low boiling point substances. The composition of these gases varies depending on the object to be heated, but generally includes hydrocarbons (HG), -carbon oxides (CO), and nitrogen oxides (NOx).

These include sulfur oxides (SOx) and ammonia (NH5), and may also include phosphorus oxide and proteins.

In particular, in the case of a heated object containing ammonia salt, ammonia gas is rapidly generated when the temperature exceeds 150°C. Among these gases, ammonia gas is converted to N by passing through an oxidation catalyst.
It may become Ox.

Conventionally, as a method of purifying ammonia generated from this type of high-temperature heating furnace, there is a method of passing water and absorbing ammonia into water, but since re-transpiration occurs, complete absorption and purification cannot be achieved. Activated carbon as an adsorbent for crushed solids is
It hardly adsorbs ammonia, and its adsorption capacity is low at high temperatures of 70 to 80°C, and desorption begins at temperatures above 100°C, and activated carbon burns at temperatures above 200°C.

Purpose of the Invention An object of the present invention is to eliminate the above-mentioned disadvantages and provide an apparatus that not only oxidizes and purifies gas, but also efficiently purifies alkaline gas components such as ammonia. .

Structure of the Invention The exhaust gas purification device of the present invention is characterized in that an oxidation catalyst is provided in the exhaust gas path of the high-temperature heating furnace.

DESCRIPTION OF THE EMBODIMENTS FIG. 1 shows the configuration of a high temperature heating furnace equipped with an exhaust gas purification device. Reference numeral 1 denotes a high-temperature heating furnace constructed of a heat insulating material and a metal exterior, and the furnace is provided with a heating source, a heater 2, and a shelf 3 on which objects to be heated are placed. 4 is a heated object housed in a container 5. Reference numeral 6 denotes an exhaust hole opened in the furnace.

7 is an alkaline component adsorption tank containing solid acid 8;
It is connected to a pipe 9 connected to an exhaust hole 6 of. A catalyst tank 10 is connected to the tank 7 by a pipe, and has an oxidation catalyst 11 and a heater 12 for heating the catalyst.

Next, the operation of this device will be explained. Gas generated by heating the object to be heated 4 is introduced into the tank 7 from the exhaust hole 6 through the pipe 9 by natural convection or forced air flow. Here, alkaline components such as NH5 in the gas are adsorbed by the solid acid 8. In addition, the solid acid is shown below.

AIH2P, 0.0 + 2NJ −) Al(NH5
)2PyO,Q When aluminum dihydrogen tripolyphosphate is heated, it changes as shown in the following formula.

AIH2P50jQ ・2H20 100~150℃ 11------→A12 H2P 30.0500~
550℃ 1111---→Al(PO3)i As is clear from the above, aluminum tripolyphosphate is stable at temperatures below 500℃, and unlike activated carbon and water, it can be used at high temperatures (500℃). It has the following characteristics.

The gas that has passed through the tank 7 as described above is NH.

Alkaline harmful gases such as gases are purified by adsorption chemical reactions, leaving only gases such as Hc and co.

These gases are oxidized and purified by the oxidation catalyst 11. The gas purified in this way is discharged to the outside.

When a high-temperature heating furnace is used, for example, to sinter a dental molding agent, ammonium phosphate salt is used as a binder in the molding agent, so it is decomposed together with the paraffin in the molding, and in addition to HC and Go, it is decomposed. Generates large amounts of ammonia gas.

2NH4MgP04・6H20→Mg2P2O7+13
H20→-2NH32NH4H2PO4→P2O5-1
-3H20+ 2NH5 In this way, the molding agent generates a large amount of ammonia gas, and the interior and exterior of the room are filled with the foul odor of ammonia gas.

In order to purify the exhaust gas of such a JJI thermal furnace, when the exhaust gas is introduced into water and ammonia is adsorbed to the water, the ammonia once dissolved in the water is re-evaporated. I cut it. By passing it through water, the gas temperature drops to water temperature, and must be heated with a heater before reaching the oxidation catalyst. This is because oxidation catalysts usually do not exhibit their effects unless heated to 200° C. or higher. On the other hand, the present invention uses a solid acid, which, unlike water, can be exchanged very easily! Ammonia is fixed by 1% sweet adsorption, so it does not evaporate again. Furthermore, since this solid acid can be used at a temperature of 500°C, the exhaust gas temperature does not drop as much as when water is used.

There is an effect that there is no need to use an auxiliary heater for heating the catalyst, or that the electric capacity thereof can be reduced.

Example 1 Ammonia gas of 100Q pHm was sealed in a sealed bag with a volume of 64 with 0.5 f/ aluminum dihydrogen tripolyphosphate granulated to a diameter of 1 to 2 mm, and changes in the ammonia gas in the bag during manufacturing were investigated. The results are shown in Figure 2a. On the other hand, as a comparative example, a similar test was conducted using Q.6 g of commercially available activated carbon granulated to a diameter of 2 to 3 mm, and the results are shown in Figure 2.

Commercially available activated carbon has an initial concentration of 11,000 PP.
Approximately 800 Pl'm per minute, 700 Pl'm per 80 minutes
However, with aluminum dihydrogen tripolyphosphate, it became approximately 3 o m in 60 minutes, and it became almost 0 in 60 minutes. Thus, aluminum dihydrogen tripolyphosphate is superior to commercially available activated carbon. The results are shown below.

Example 2 An experiment was conducted by filling the adsorbent tank 7 of the apparatus shown in FIG. 1 with 100 g of granulated aluminum dihydrogen tripolyphosphate having a diameter of 1 to 2 mm. The ammonia gas generated from furnace 1 is up to 10,0 OOI as shown in Figure 3? However, as shown in Figure 3B, the ammonia was almost completely purified by passing aluminum dihydrogen oxide, and 3 to 5 Pl'm of ammonia gas temporarily flowed. It wasn't too much.

At this time, the temperature of I.aluminum dihydrogen lipolyphosphate reached 350°C.

Effects of the Invention As described above, according to the present invention, it is possible not only to oxidize and purify high-temperature harmful gases generated from a high-temperature heating furnace, but also to efficiently adsorb and purify alkaline components such as ammonia.

[Brief explanation of drawings]

Figure 1 is a schematic vertical cross-sectional view of a high-temperature heating furnace equipped with an exhaust gas purification device according to an embodiment of the present invention, Figure 2 is a diagram showing changes over time in ammonia gas in the coexistence of various adsorbents, and Figure 3 is a diagram showing high-temperature heating. FIG. 3 is a diagram showing changes over time in the ammonia concentration in the exhaust gas of the furnace. 1... High temperature heating furnace, 6... Exhaust hole, 7... Alkali production adsorption tank, 1o... Catalyst tank.

Claims (1)

[Claims] High-temperature heating characterized in that an oxidation catalyst is provided in the exhaust gas path of the high-temperature heating furnace, and on the upstream side of the oxidation catalyst, an alkali gas component absorption section using a solid acid mainly composed of aluminum dihydrogen tripolyphosphate is provided. Furnace exhaust gas purification device.