JPH0146196B2 - - Google Patents

Description

[Detailed description of the invention]

(b) Industrial application field The present invention collects fine powder containing a large amount of active bentonite from fine powder waste sand discharged from a dust collector attached to a sand processing device for green mold circulation molding sand, and The idea is to turn it back into foundry sand and reuse it. (b) Conventional technology Conventionally, although the waste sand discharged from this dust collector contains a large amount of active bentonite, it has not been possible to separate it, so the entire amount of waste sand has been treated as industrial waste. It is being disposed of in a landfill. (c) Problems to be solved by the invention However, this waste sand contained a mixture of fine powder parts of green foundry sand, that is, fine silica sand, carbonaceous substances, inert bentonite, activated bentonite, etc. It has become a state. Inert bentonite refers to bentonite that loses its function as a binder and becomes a mere fine powder due to the influence of heat when molten metal is poured into a mold. On the other hand, activated bentonite is bentonite that is not affected by heat and has the ability to act as a binding agent when molding molds. Therefore, if the inactive bentonite and active bentonite can be separated, the active bentonite can be returned to the green circulating molding sand and reused. (d) Means for Solving the Problem The present invention has been made in view of the above, and is made by stirring finely powdered waste sand discharged from a dust collector attached to a sand processing device for green circulating molding sand in water, and then The method is characterized by separating active and inactive bentonite by precipitation, collecting the upper suspension containing a large amount of active bentonite, and dehydrating and drying the suspension. (e) Effect Next, the effect will be explained with reference to FIG. Figure 1 is a conceptual diagram of waste sand particles. When we look at the fine powder waste sand microscopically, we see that around silica sand 1 with relatively large particle size, silica sand 2 with small particle size, carbonaceous substance 3, metallic substance 4, and inert bentonite 5. and activated bentonite 6 is attached. By stirring this waste sand in water, the particles are dispersed. This suspension is then allowed to settle gently. At this time, the precipitation rate differs depending on the particle size and specific gravity. In other words, silica sand with large grain size settles quickly,
Silica sand and carbonaceous substances with small particle sizes settle slowly. On the other hand, active bentonite has swelling properties in water, but inactive bentonite loses this property due to the influence of heat. This results in a difference in precipitation rate between active and inactive bentonite. Therefore, by collecting the suspension in the part where the precipitation rate is slow, it is possible to obtain a fine powder containing a large amount of active bentonite. Note that when the waste sand is stirred in water, by adding a dispersant, the dispersion of the waste sand particles is promoted, and as a result, the recovery efficiency of activated bentonite is further improved. (F) Example The following experiment was conducted to prove the phenomenon of the present invention. Example (1) 100 pieces of dry waste sand with the particle size distribution shown in Figure 2
g together with a dispersant into water adjusted to a total amount of 1000 c.c., and stirred for 2 minutes using a household mixer. The dispersant used was sodium pyrophosphate, and the amount added was 3 g, 0.6 g, and no additive. The stirred suspension was placed in a 1000 c.c. measuring cylinder shown in Figure 3, and allowed to settle gently for 30 minutes.
After 30 minutes, remove 200 m from the top of graduated cylinder A.
cc, 400c.c., 600c.c., 800c.c., and 900c.c. of the suspension were collected through conduit B with an inner diameter of 5 mm. Next, the collected suspension was thoroughly dried and used as a recovered fine powder for testing. Figure 4 shows the amount of recovered fine powder that could be collected. When the amount of dispersant added was 0.6 g, there was not much difference from the one without the addition, but when 3 g was added, the amount of collected fine powder increased for each suspension sample. In other words, the addition of the dispersant promoted the dispersion of the particles adhering to each other in the waste sand, increasing the number of particles that had a slow settling rate. Figure 5 is the X-ray diffraction diagram of waste sand, Figure 6 is the dispersant 3
This is an X-ray diffraction diagram of recovered fine powder collected up to 600 c.c. from the top of the measuring cylinder after adding Compared to waste sand, the recovered fine powder has a lower peak for quartz and a slightly higher peak for montmorillonite. This indicates that the precipitation treatment removed more silica sand from the waste sand than bentonite. Figure 7 shows the amount of methylene blue adsorbed by recovered fine powder, waste sand, and unused bentonite (virgin) under different recovery conditions. The amount of methylene blue adsorbed does not show much difference even when the amount of suspension collected is changed from 200 c.c. to 600 c.c., but it shows a decreasing tendency when it exceeds 600 c.c. If exceeded, it decreases rapidly.
Regarding the amount of dispersant added, at 0.6 g, no significant change was observed, but at 3 g, a clear difference occurred in the amount of methylene blue adsorbed. Next, FIG. 8 shows the relationship between the sedimentation time of the suspension and the amount of methylene blue adsorbed. From this figure, the efficient precipitation time was 30 to 60 minutes. In this example, sodium pyrophosphate was used as a dispersant, but other materials such as sodium hydroxide, water glass,
Sodium metaphosphate, sodium chloride, etc. have similar effects. Example 2 In order to further confirm the effects of the present invention described above, the following experiment was conducted. Experimental bentonite was prepared by mixing 50 g each of unused bentonite (active bentonite) and bentonite (inactive bentonite) which had been heated to 850° C. and then cooled. This experimental bentonite was subjected to the same treatment as described above, and the results were shown in the first
Table 2 shows the results. This experiment also confirmed that the amount of methylene blue adsorbed in the recovered fine powder collected from the top of the graduated cylinder was greater than the amount of methylene blue adsorbed in the fine powder collected from the precipitate remaining at the bottom. In other words, the separation phenomenon of active bentonite and inactive bentonite was confirmed in the treatment according to the present invention.

【table】

[Table] (g) Effects of the invention According to the present invention, fine powder containing a large amount of active bentonite can be recovered from the fine powder waste sand discharged from the dust collector attached to the sand processing device for green circulating molding sand. . That is, by treating the waste sand according to the present invention, it becomes possible to return the recovered fine powder to the green circulating molding sand and reuse it. Moreover, this method has great economic effects, such as reducing the total amount of waste sand that is disposed of in landfills as industrial waste and also leading to the saving of bentonite resources.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of waste sand particles, Figure 2 is a particle size distribution diagram of waste sand, Figure 3 is a diagram showing a 1000 c.c. graduated cylinder used as a sedimentation container for waste sand and the suspension collection method. Figure 4 is a diagram showing the amount of recovered fine powder collected when changing the amount of dispersant added and the amount of suspension collected. Figure 5 is an X-ray diffraction diagram of waste sand collected from the dust collector. Figure 6 shows the upper part of the suspension with 3g of dispersant added.
X-ray diffraction diagram of recovered fine powder collected from 600 c.c., Figure 7 is a diagram showing the methylene blue adsorption amount of recovered fine powder, unused bentonite and waste sand under different collection conditions, Figure 8 is the precipitation time required for precipitation treatment. FIG. 3 is a diagram showing the amount of methylene blue adsorbed by the recovered fine powder.

Claims (1)

[Claims] 1. Stir fine powder waste sand in water and gently settle it to separate active and inactive bentonite, collect the upper suspension containing a large amount of active bentonite, and collect the suspension. A method for recovering fine powder containing a large amount of active bentonite from fine powder waste sand discharged from a dust collector attached to a sand processing device for green circulating molding sand, which is characterized by dehydrating and drying sand. 2. Activated bentonite is extracted from the pulverized waste sand discharged from a dust collector attached to a sand processing device for green circulating molding sand according to claim 1, in which a dispersant is added when the pulverized waste sand is stirred in water. A method for collecting fine powder containing a large amount of water.