JPH0332445A - Method for removing smoke and malodorous gas from burnt mold - Google Patents

Abstract

PURPOSE:To quickly reduce smoke and malodorous gas generated from a mold just after burning by embedding the burnt mold adding thermosetting resin into heat resistant inorganic powder and bringing the burnt mold into contact with the inorganic powder for the necessary time. CONSTITUTION:The mold 3 after burning is high temp. and at the time of leaving the mold as it is, reaction is progressed with residual heat and the malodorous gas of ammonia, etc., and the smoke are generated. Therefore, the burnt mold 3 is required to be immediately cooled to restrain the generation of the malodorous gas and smoke. The burnt mold 3 is quickly cooled with heat transfer by contacting with the fluidized inorganic powder 5 or with gas supplied in order to fluidize the inorganic powder 5. By this method, temp. of the burnt mold 5 is quickly lowered and the hardening reaction is completed to eliminate the generation of malodorous gas and smoke. Further, the inorganic powder 5 is used as adsorbent of the malodorous gas or in the case of containing the moisture in flowing gas and the inorganic powder 5, the cooling is efficiently executed with the vaporizing heat thereof.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is a method for removing smoke from firing molds in which heat-resistant granules are bonded with a thermosetting resin binder, such as shell molds using shell mold sand. Regarding deodorizing methods. Firing molds are used as molds or cores for manufacturing exhaust manifolds, engine head covers, engine blocks, and the like. It is also used in many casting fields, such as gravity casting of aluminum and cast iron, low pressure casting of aluminum, and vacuum casting.

[Conventional technology] Exhaust manifolds, engine head covers, etc.
To manufacture products with complex shapes, molds or cores (hereinafter referred to as fired molds) are made by adding thermosetting phenolic resin as a binder to heat-resistant granules, such as silica sand, and firing the mixture. Widely used.

As a method for producing fired molds, a shell molding method using a shell mold sand made of silica sand coated with a phenolic resin binder is often used, and this shell mold sand is filled into a mold 2 having a desired shape (second ), the phenol resin is heated in the firing furnace 1 to harden it. The obtained fired molds 3 are usually taken out from the mold 2, sorted by type, arranged on a pallet P, and left to cool.

[Problem to be solved by the invention] However, in manufacturing the above-mentioned firing mold,
There is a problem in that a large amount of foul-smelling gas is generated during the curing reaction of phenolic resin, and deterioration of the working environment has become a bigger problem than in the past.

For this reason, various measures to prevent bad odors have been studied.For example, during the manufacturing process shown in FIG. Measures such as installing an exhaust duct 4 are being taken.

However, in the process of cooling the firing mold 3 taken out from the mold 2, there is a lot of manual work and a large space is required, so countermeasures against bad odors are insufficient. Measures have only been taken to prevent water from flowing in that direction. In particular, the firing mold 3 immediately after firing
The temperature is high, and the reaction proceeds with the residual heat, so foul-smelling gas and smoke are generated until the temperature reaches room temperature, which can spread into the factory and the factory grounds, potentially damaging the working environment.

In order to prevent the spread of bad odors, it is possible to place the mold after firing in a sealed container connected to an exhaust duct and leave it for a few minutes, and then arrange it on a pallet after the bad odor has ceased to occur. It takes time and has poor workability.

Therefore, an object of the present invention is to promptly reduce smoke and foul-smelling gas generated from a mold immediately after firing, without making large-scale equipment changes, and to improve the working environment.

[Means for Solving the Problems] The present inventors have conducted extensive studies in view of the above circumstances, and as a result, have
A fired mold obtained by adding a thermosetting resin as a binder to a heat-resistant granular material and firing it is buried in heat-resistant inorganic powder that is suspended and fluidized by flowing gas, and the fired mold and inorganic It has been found that smoke and odor removal from the firing mold can be easily achieved by contacting the powder with the powder for a predetermined period of time.

In the present invention, as the heat-resistant granules that serve as the base material constituting the firing mold, any material can be used as long as it is heat-resistant and does not decompose during high-temperature firing (usually at 250°C or higher).
Generally, silica sand is widely used from the point of view of economy and the like. Artificial ceramic powder etc. can also be used, but they are less economical.

The suitable range of the particle size of the heat-resistant granules varies depending on the type and shape of the mold, and is usually 35 to 270 mesh (420 mesh).
~53 μm> as appropriate. For example, when used as a core, it is preferable to use a mixture of 48 to 10 mesh (297 to 149 μm) as appropriate so that the gas generated inside can be easily removed.

A thermosetting resin such as a phenol resin is preferably used as the binder for binding the heat-resistant granules.

Specifically, a novolac type phenol resin to which a curing agent such as hexamethylenetetramine is added is used, and is cured by heating to firmly bond the heat-resistant granules.

The heat-resistant granules and the binder may be mixed when manufacturing the firing mold, but manufacturing is facilitated by using a commercially available shell mold sand in which the heat-resistant granules are coated with the binder in advance. . The blending ratio of the heat-resistant granules and the binder is changed as appropriate depending on the size of the product, the position of use, the casting method, etc.

When producing a firing mold, this shell mold sand is filled into a mold made to match the shape of the mold, and heated in a firing furnace. The firing temperature is such that the mold temperature is higher than the curing temperature of the binder, usually 250° C. or higher, and held for about 1 to 5 minutes to harden.

After firing, the fired mold is removed from the mold and immediately brought into contact with heat-resistant inorganic powder to remove smoke and odor.

Any inorganic powder may be used as long as it is heat resistant, does not change in quality due to heat, and can rapidly cool the mold by exchanging heat with the firing mold. For example, silica sand, which is the base material of the firing mold, has excellent thermal conductivity and is made of the same material, so even if fine powder adheres to the surface of the firing mold, it does not affect the subsequent process, which is preferable.

In addition to silica sand, porous materials such as Oya stone, Kanuma soil, pumice used for gardening, hydrated magnesium silicate clay minerals such as sepiolite (hereinafter referred to as hydrated clay minerals), zeolite, activated carbon, etc. are used. It's okay,
Because it is highly adsorbent, it acts as an adsorbent for malodorous components and enhances the deodorizing effect.

In particular, hydrous clay minerals are light and can be used with a relatively small amount of air, and they not only transfer heat through contact, but also absorb heat from the surrounding area through heat of evaporation when the attached water and crystallized water escape as steam. , enhance the cooling effect.

The particle size of the powder may be as long as it can easily float and flow by circulating gas, and in the case of silica sand, it is 6
No. sand (main particle size is 48-100 mesh; 297-14
9 μm), No. 7 sand (main particle size is 48 to 150 mesh:
297 to 105 μm) can be suitably used. In the case of porous materials, those having a particle size of 10 meshes (1.68 mm) or less, preferably 12 meshes (1.41 mm) or less, and containing 30% or more of particles with a particle size of 325 meshes (44 μm) or less are preferably used.

Note that metal powder may be used as the inorganic powder, and since it has excellent thermal conductivity, the cooling efficiency is high.

When removing smoke and deodorizing, as shown in FIG. By supplying gas 7 into 6, the inorganic powder 5 is made to float and flow. The firing mold 3 is buried in the inorganic powder 5 thus formed, and the two are brought into contact for a predetermined period of time.

The fluidized tank is large enough to accommodate the firing mold and its holder.
It is sufficient if there is sufficient room for the powder to flow.The larger the capacity, the better the smoke and deodorizing effect, but the lower the economical efficiency, so it is generally equivalent to the external dimensions including the firing mold or holder. It is preferable to have a volume that is 10 to 70 times that of the original.

The gas supplied into the fluidization tank may be any gas, but flammable or toxic gases are not preferred.From an economical perspective, air, especially compressed air, which is commonly used industrially, is suitable.

Also, the humidity in the gas is specified.

Although it is not necessary to do so, it is more effective to use air with a humidity of 5 to 70%, since the cooling effect is improved by the heat of evaporation when water evaporates.

Gas is supplied into the fluidized tank, for example, as shown in Figure 1.
This is done by providing a large number of small holes 8 in the bottom of the fluidization tank 6. small hole 8
The shape is such that the exit direction of the gas 7 can be adjusted so that the powder 5 floats evenly, and the powder 5 does not enter the small hole 8 when the gas 7 is not introduced. do. For example, it may be a countersunk machine screw with a cap that can be screwed down, or a valve type that floats up when gas passes through it and lowers when it stops, preventing powder from entering.

The contact time, that is, the time required for the firing mold to cool down and stop emitting smoke or bad odors, varies depending on the type of powder used. Effects can be seen with contact for 5 seconds or more per 10m. In addition, the effect of hydrous clay minerals is seen when they are in contact for 1 second or more per 10 parts of the thickness of the fired mold, but in order to further reduce the diffusion of foul-smelling gases, the contact time should be about 5 to 10 seconds. It is preferable. Thereby, the ammonia gas concentration can be reduced to about 115 to 1/7, for example.

[Function] The mold is at a high temperature immediately after firing, and if it is left as is, the reaction will proceed due to the residual heat and generate foul-smelling gas such as ammonia and smoke. The present invention attempts to suppress the generation of foul-smelling gas and smoke by immediately cooling the firing mold. The gas supplied for this purpose cools down rapidly. As a result, the temperature of the firing mold decreases rapidly; for example, in the case of silica sand and hydrous clay minerals, the surface temperature decreases from 180 to 190 degrees Celsius by 40 to 50 degrees Celsius to below about 140 degrees Celsius after 15 seconds of contact. When the process is complete, there will be no more foul-smelling gas or smoke. Furthermore, if the inorganic powder acts as an adsorbent for the malodorous gases generated, or if water is contained in the circulating gas or inorganic powder, the heat of evaporation will make cooling more effective and in a shorter time. Smoke and odor are removed.

[Examples] Hereinafter, the present invention will be explained in detail by examples, but the present invention is not limited by these examples unless the gist thereof is exceeded.

Example 1 Outer diameter 80 m, inner diameter 605 m*, height 137 m5, wall surface Further, the above baking and deodorizing steps were performed continuously at 5 minute intervals with contact with the powder for 15 seconds, and good results were obtained. was obtained, and it was found that there was no problem with continuous use. However, when using hydrous clay minerals, the temperature near the center of the powder in which the fired mold is buried tends to rise, so a slatted plate is installed in the fluidized bath.
The powder was moved back and forth from time to time in the lateral direction to ensure uniform temperature. Since this temperature rise is extremely slow, gas may be introduced from the side of the fluidized tank at the top, center, and bottom of the suspended inorganic powder, and may be introduced intermittently in a direction perpendicular to the air, or a propeller-like agitator may be placed at the top of the fluidized inorganic powder. You can also stir the powder. Although fine powder adhered to the surface of the firing mold, it did not affect the casting process.

Example 2 Inner diameter 80III! 11. A mold with a bottom having a height of 90 mm and a draft angle of 2° was heated to 300° C., and shell mold sand having the same composition as in Example 1 was filled into the mold. Approximately 1
After holding for a minute, the mold was reversed and the unfired shell mold sand was taken out to obtain a cup-shaped fired mold with a thickness of approximately 8 to 9 mm.

Next, this fired mold was placed in a fluidized bath and powdered water-containing clay mineral (main particle size 12-325 mesh (particle size 1
, 41 + ma to 44 μm > containing 30% of 325 mesh or less. 9 The air flow rate was IOJ/min. The air flow rate was IOJ/min.

When the mold was fired and the smoke and odor removed were performed continuously at intervals of about 5 minutes, good results were obtained as in Example 1, and a remarkable effect of reducing smoke and bad odor was observed.

[Effects of the Invention] As explained above, according to the present invention, the firing mold can be easily and quickly de-smoked and deodorized, and the working environment can be significantly improved.

Moreover, since there is no need to reduce work efficiency or make major equipment changes, it is highly economical and has extremely great industrial value.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the smoke and deodorization process of a firing mold according to the present invention, Fig. 2 is a diagram showing a conventional manufacturing process of a firing mold, and Fig. 3 is a diagram showing a manufacturing process of a conventional firing mold.
4 and 4 are characteristic diagrams showing relative odor intensity changes and ammonia concentration changes in Examples of the present invention, respectively. ■...Bacining furnace 2...Mold 3...Firing mold 5...Inorganic powder 6...Fluidized tank Fig. 1 Figure 2 Figure 3 Contact time (seconds) Figure 4 Contact time (seconds)

Claims (1)

[Claims] A fired mold obtained by adding a thermosetting resin as a binder to a heat-resistant granular material and firing it is buried in heat-resistant inorganic powder that is suspended and fluidized by flowing gas, and then a fired mold is created. 1. A method for removing smoke and deodorizing a fired mold, which method comprises contacting an inorganic powder with an inorganic powder for a predetermined period of time.