JPS6241778B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a smoke and deodorization device for exhaust gas in an electric furnace for firing wax molds, and in particular, a device for eliminating smoke and deodorization for exhaust gas in a small electric furnace for dental technology. Related to deodorizing equipment.

(Background of the Invention and Prior Art) Generally, when baking plaster molds using wax in dental laboratories, etc., or producing precision castings using lost wax, the wax is melted and burned in the electric furnace. The process produces strong-smelling gas and soot. In particular, at the start of firing, the temperature inside the furnace is low and does not reach the ignition temperature, so the wax becomes evaporated and hydrocarbon gas and soot-like or tar-like partial decomposition products are generated, which are discharged from the furnace exhaust gas. Flows from the mouth. In this case, if the laboratory is small, the room will be filled with smoke with a strong odor, resulting in extremely poor environmental hygiene. Even when the exhaust gas from the exhaust port is led outside through a chimney, this exhaust gas has a strong odor, causing a pollution problem.

Accordingly, various devices have been developed to treat the exhaust gas from the exhaust port of the electric furnace to remove smoke and odor. A conventional device of this type is, for example, of the type shown in FIGS. The conventional device 10 shown in FIG. 1 attempts to burn and incinerate the exhaust gas flowing out from the exhaust port a of the electric furnace A by post-heating it with a heating wire 14 wound around a cylinder 12. Conventional devices have exposed heating wires, which are prone to deterioration due to wax decomposition products adhering to them, and therefore have defects that cause wires to break in a short period of time.Furthermore, the removal rate of smoke and odor, especially odor, is poor. Has low defects. The conventional device 10a shown in FIG. 2 is an improved version of the device 10 shown in FIG. 1 mainly for the purpose of increasing the deodorizing efficiency, and includes a heating wire 14a wound around a cylindrical body 12a.
The exhaust gas is first heated and decomposed by
- The treatment is performed through a catalyst layer 16a such as PD. Although this type of conventional device shows relatively good effects initially, the heating by the heating wire is limited to 300-500°C to maintain the activity of the catalyst.
For this reason, the combustion of soot and tar-like substances in the exhaust gas is insufficient, and as a result, the catalyst is contaminated and its activity is reduced, making it impossible to maintain the deodorizing effect over a long period of time. It is troublesome that it must be replaced within six months to one year, and since the heating wire is exposed, it has the defect that it is prone to premature disconnection, similar to the device shown in FIG.

(Object of the Invention) Therefore, the main object of the present invention is to capture and completely thermally decompose particles such as soot, tar, etc. contained in the exhaust gas flowing out from the electric furnace accompanying wax mold firing.
The object of the present invention is to provide a smoke and deodorizer with stable performance that prevents catalyst contamination.

Another object of the present invention is to provide a smoke and deodorizing device that is small and lightweight, robust, inexpensive, and has a high and stable smoke and deodorizing effect.

(Structure of the Invention) The present invention includes a conical dispersion and retention chamber disposed close to an exhaust port of an electric furnace, and a heater in which a heating wire is embedded, which is disposed above the dispersion and retention chamber and preheats exhaust gas in the dispersion and retention chamber. , a porous heat reflection plate disposed above the heater that captures particles and tar in the exhaust gas and decomposes them with the heat from the heater, and a porous heat reflection plate that guides the gas that has passed through the heat reflection plate. The present invention and the catalyst layer constitute a smoke and odor deodorizing device for exhaust gas in an electric furnace for firing wax molds, thereby achieving the above objects.

(Example) Next, one embodiment of the smoke eliminating and deodorizing device according to the present invention shown in FIGS. 3 to 5 of the accompanying drawings will be described.

Smoke eliminating and deodorizing device 2 according to the present invention shown in FIG.
0 is placed in an electric furnace A in the same manner as the conventional apparatus 10 shown in FIG. 1, and is used by being connected to its exhaust port a. This device 20 is equipped with a refractory body 22 made of ceramic or the like, and the body 22 has an opening or an exhaust gas inlet 221 for connecting to the above-mentioned exhaust port.
It has at the bottom. Gas flowing into the housing 22 from the inlet 221 is guided to a conical dispersion and retention chamber 222 which is a lower heating chamber. A heater 24 in which a heating wire (not shown), such as a Kanthal wire, is embedded is disposed above the dispersion and retention chamber 222, so that the gas flowing into the dispersion and retention chamber 222 moves radially through the dispersion and retention chamber. and the heater 24
heated evenly. The heater 24 is made of porous heat-resistant and food-resistant material, and is manufactured by, for example, using a porous ceramic fiber as a base material, sandwiching the heating wire in a sandwich shape, and firing the heated wire.
It has a planar shape as shown in FIG.
This heater 24 has a porous material as its base, but since the radiation pressure of the hot wire from the buried heating wire is applied, the gas in the dispersion and retention chamber does not pass through the porous base of the heater 24 and rise. 24
A notch 241 formed at the peripheral edge of the gas passage serves as a gas passage. The gas rising through this gas passage 241 flows into the upper heating chamber 223. This upper heating chamber 22
3 has a lower part composed of the heater 24, and an upper part composed of a porous heat reflecting plate 26 made of a heat-resistant material such as glass wool or ceramic wool. The heat reflecting plate 26 may have a planar shape as illustrated in FIG. The heat reflector 26 shown in FIG.
It is made of refractory material with a large number of pores 261 on the order of mm, and therefore has a certain ventilation resistance, but gas can permeate through it.
The gas flowing into the heating chamber 223 once remains in the heating chamber 223 and then rises further through the pores 261 of the heat reflecting plate 26. What should be kept in mind here is that
The first is that the lower surface of the heat reflecting plate 26 is heated by the radiant heat of the heater 24 and is in a red-hot state, and the second is that the heat reflecting plate 26 is in a tar-like state that may remain in the gas. It functions as a filter to trap undecomposed substances such as dirt and soot.

That is, due to the presence of the heat reflecting plate 26, the heating chamber 223
Since the temperature inside is 700 to 800°C, tar-like substances and soot remaining in the gas and captured by the heat reflecting plate 26 are ignited and decomposed and gasified, so that they do not accumulate. . In other words, the heat reflecting plate 26 functions as a self-cleaning filter by receiving the radiant heat from the heater 24.

The gas that has passed through the heat reflecting plate 26 no longer contains substances such as tar-like substances and soot, so the catalyst layer 2
Even if you lead it to 8, it won't turn it into a poison. The temperature of the gas that reaches the catalyst layer is 300 to 500°C, which is sufficient to activate a PT-PD type catalyst, for example. According to the device of the invention, the catalyst layer 28 is supported by a refractory casing 30.

The sleeve 30 and the sleeve 22 described above are fitted and housed in a cylinder 32 made of a metal material, for example, stainless steel, and a lid 34 having an opening at the top is attached to the cylinder 32. A cylindrical body 36 provided with a fan 361 is placed on this lid body.

One or more through holes (not shown) are bored in the upper part of the cylindrical body 32 along its periphery, and correspond to the peripheral wall of the lid body 34 so as to align with these through holes. A through hole 341 is bored. Reference numeral 38 designates an adapter that supports the catalyst layer 28 together with the sleeve 30, the upper part of which is configured as a cylindrical wall 381, and the through hole 341 of the lid 34 is connected to the cylindrical body. 32 through hole (not shown)
Even when the engine is fully opened in full synchronization with the
The gas that has passed through the catalyst layer can be effectively sucked by the fan 361.

Note that a through hole 341 is bored in the lid body 34 and the cylindrical body 3
Through-holes (not shown) corresponding to No. 2 are bored by adjusting the opening degree of these through-holes by rotating the lid body 34, thereby opening the gas inlet 221 of the device of the present invention. The purpose of this opening is to control the amount of exhaust gas introduced into the chamber, but it also serves as a cold air intake to cool the treated, still hot gas and complete its release. fan 361
serves to allow the gas to flow even when natural drafting of the gas is difficult due to resistance due to the heater 24, heat reflection plate 26, and catalyst layer 28 arranged in the device of the present invention.

(Smoking and deodorizing test) [] Equipment used (1) Electric furnace GC auto furnace (100V/860W)
(Manufactured by Shishi Dental Machinery Co., Ltd.) (2) Smoke and deodorizer of the type shown in Figure 3 (a) Dimensions Main body: 32 cylinder parts (diameter 162 x height 178 mm) Lid body 34: Diameter 162 x Height 65mm Fan part 361: Length 76 x Width 76 x Height 32mm (b) Heater power supply 100V/260W (c) Catalyst DASH-220 (2~4mm spherical catalyst 100ml) DASH-20MK4S (50 x 50 x (30mm honeycomb catalyst) (d) Fan power supply 100-115V/6W (3) Measuring equipment (a) Hydrocarbon meter (Model HCM manufactured by Shimadzu Corporation)
-IA-hydrogen flame ion type) (b) Recorder (model manufactured by Rika Denki Kogyo Co., Ltd.)
KA61) (c) CA thermocouple [] Preparation of test material Commercially available dental implant material (GC cristobalite) and water were kneaded at a weight ratio of 1:0.33.
4 commercially available dental waxes (GC Green Inlay Wax) in the ring (equivalent to 8g)
The ring that was buried for 3 hours was designated as a W (wet) ring, and the ring that was left for 1 to 2 days was designated as a D ring (dry) ring.

[] Firing method of test material and temperature and gas temperature measurement method Insert a pipe into the exhaust port of the electric furnace, connect the furnace exhaust port with the inlet of the smoke and deodorizer, and then insert the pipe into the electric furnace. The test material ring was fired by operating the The temperature inside the furnace was measured by recording the output of the furnace thermocouple on a recorder.

The concentration and temperature of the treated gas are determined by placing a cylindrical tube with an inner diameter of 75 mm and a height of 300 mm at the top of the smoke and deodorizing device.
A measurement point 20 mm above the exhaust port of the smoke and deodorizer was measured with a hydrocarbon meter and thermocouple, and recorded with a recorder.

[] Measurement results and discussion The measurement results are shown in Figures 6-10.

Among these figures, Figure 6 shows the case where a dry type ring is used as the test material and no catalyst is used in the smoke and deodorizing device, and Figures 7 and 8 show the case where dry type and wet type rings are used as the test material, respectively. This shows the case where a spherical type catalyst (DASH-220) is used.
On the other hand, Figures 9 and 10 show the case where dry and wet type rings were used as test materials and a honeycomb type ring (DASH-20MK4S) was used as a catalyst.

The maximum concentration of smoke and deodorization rate and treated exhaust gas is: without catalyst (corresponding to Figure 6): 69.6% (1600ppm), with spherical catalyst and dry ring (corresponding to Figure 7): 93.8% (150ppm), spherical catalyst, wet ring (corresponding to Figure 8): 98.9% (130ppm), honeycomb catalyst, dry ring (corresponding to Figure 9): 99.9% (not detected), honeycomb catalyst, In the case of wet ring (No. 10)
(equivalent to the figure): 99.9% (15 ppm or less), which means that the heater alone cannot achieve sufficient smoke and deodorizing effects, and that the initial effect is achieved by using the heater and catalyst treatment together.
It has been found that a honeycomb type catalyst is particularly effective.

[Brief explanation of the drawing]

Among the accompanying drawings, FIGS. 1 and 2 are partially cross-sectional views of a conventional smoke and deodorizer, FIG. 3 is a cutaway view of a smoke and deodorizer according to the present invention, and FIG. The figure is a plan view of a heater used in the smoke eliminating and deodorizing device according to the present invention, FIG. Figures 1 to 10 are graphs showing the relationship between the temperature and gas concentration inside the furnace and the temperature and concentration of the treated gas in test examples using the smoke and deodorizer according to the present invention, and Figure 6 is a graph showing the relationship between the temperature and gas concentration in the furnace and the temperature and concentration of the treated gas. Figures 7 and 8 are graphs when dry rings and wet rings are fired using a spherical catalyst, and Figures 9 and 10 are graphs when dry rings and wet rings are fired using a honeycomb catalyst. It is. Electric furnace...A (Fig. 1), Exhaust port...a, Exhaust gas deodorizing device...20, Dispersion and retention chamber...22
2. Heating wire...not shown, Heater...24, Heat reflecting plate...26, Catalyst layer...28.

Claims (1)

[Claims] 1. In an exhaust gas deodorizing device connected to the exhaust port of an electric furnace for firing wax molds, there is a conical dispersion and retention chamber located close to the exhaust port of the electric furnace, and a conical dispersion and retention chamber located above the dispersion and retention chamber. A heater with embedded electric heating wires that preheats the exhaust gas in the dispersion and retention chamber, and a porous heat source placed above the heater that captures particles and tar in the exhaust gas and decomposes them with the heat from the heater. 1. A device for eliminating smoke and deodorizing exhaust gas in an electric furnace for firing wax molds, comprising a reflector and a catalyst layer to which gas passing through the heat reflector is guided.