JPH11169900A - Treatment of hydrated cake - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the handling in a succeeding process by adding a water absorptive polymer into a wetted hydrated cake, mixing them and forming a granulated material having several millimeter major diameter. SOLUTION: In a process for producing molybdenum trioxide from an imported ore containing molybdenum, a large quantity of a molybdenum residue containing Fe(OH)3 , SiO2 and the like is generated. In the case of treating the hydrated cake containing molybdenum in this way, the dissolved residue containing molybdenum is dehydrated to obtain the dehydrated cake. Next, the adequate quantity of the water absorptive polymer is added into the cake and kneaded by a mixing means. The water absorptive polymer is a polymer having the ability to absorb and hold water several ten to several hundred times as much as the dead weight without being dissolved in water and a polymer having an ionic group fundamentally high in affinity to water. The hydrated cake is granulated by the addition of the water absorptive polymer to obtain the mobile granulated material having several millimeter major diameter and as a result, the treatment by the succeeding process is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of treating sludge-like slurry, and more particularly to a method of treating a wet cake obtained from this kind of slurry for easy handling such as transportation and storage. It is about.

[0002]

2. Description of the Related Art Slurry generated in various wastewater treatment processes, industrial waste, slurry generated in a sewage treatment plant and a human waste treatment plant, and the like are subjected to a constant moisture removal device such as a filter press, a belt press, and a centrifugal separator. Is removed and transferred to a subsequent processing step as a water-containing cake having a reduced water content. The same applies to slurry generated from boiler ash in refuse treatment plants, general waste, power plants, and the like.

However, since the above-mentioned wet cake is in a wet state, various problems occur in the subsequent processing steps. For example, even if only the process of transporting by a belt conveyor and throwing it into a hopper is taken up, problems such as adhesion to the belt conveyor during transport and solidification in the hopper to cause a shelf hanging phenomenon occur. For this reason, conventionally, prior to the transport of the wet cake, a process of applying pressure and vacuum dehydration to obtain a dehydrated cake, followed by drying and pulverizing was performed.

On the other hand, imported molybdenum ore is once dissolved to extract molybdenum, and the dissolved residue is dehydrated by a filter press or the like to form a wet cake. Although this moist cake contains 12 to 15% molybdenum, it is not used industrially conventionally because it has a large amount of water and is difficult to handle. It was only used.

[0005] As a treatment method for treating the above various wet cakes, a treatment method by adding a polymer flocculant and electrolysis tempering (see Japanese Patent Application Laid-Open No. 6-99200), and dehydration by a pressurized vacuum dehydrator. Subsequent pulverization method (JP-A-8-618)
No. 56), and a method of drying and pressing using low-carbonized particle size-adjusted pulverized coal (see Japanese Patent Application Laid-Open No. 8-1191982) has been proposed, but all of these steps are complicated and require pulverization. If it is necessary, there is a problem that dust measures must be taken.

[0006]

In recent years, efforts have been made not to generate waste in any field, but a large amount of slurry is still generated, and the treatment thereof is an important issue. Therefore, an object of the present invention is to provide a state in which the wet cake generated from the slurry is easily handled in a subsequent process.

[0007]

According to the present invention, there is provided a method for treating a water-containing cake, which comprises adding a water-absorbing polymer to a water-containing cake in a wet state and mixing the resulting mixture to obtain granules having a diameter of several millimeters. It is characterized by.

When the water-absorbing polymer is added to and kneaded with the water-containing cake which easily adheres to the belt or the like as described above, a relatively smooth and hardly adhered granular material is obtained, so that it is easy to handle in the subsequent processing steps. Become. The size of the granular material is preferably about 1 to 4 mm, and 2 to 3 mm
More preferably, However, it is not limited to these sizes.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described more specifically with reference to a method of treating a moist cake containing molybdenum as an example.

In the process of producing molybdenum trioxide from imported ore containing molybdenum, Fe (OH) ₃ , SiO ₂
A large amount of molybdenum residue including the above is generated. This residue was conventionally sold as fertilizer, but since it is not used as fertilizer at present, its treatment is a problem. Since the molybdenum residue contains about 30 to 35% of water, it is difficult to handle, and it is difficult to recover the molybdenum contained therein, but the present invention makes it possible.

FIG. 1 is a flowchart showing the processing steps. First, a water-containing cake obtained by dehydrating the dissolved residue containing molybdenum with a filter press or the like is a starting material,
This cake contains about 30 to 35% water (% by weight, the same applies hereinafter), about 12 to 15% molybdenum, and about 4.27% sodium, for example. An appropriate amount (for example, about 2%) of a water-absorbing polymer (highly water-absorbing polymer) is added to the cake, and kneaded by a known mixing means such as a kneader.

A water-absorbing polymer is a polymer that has the ability to absorb and retain water tens to hundreds of times its own weight without being dissolved in water. Basically, it is a polymer having an ionic group having a high affinity for water, and has a cross-linked structure with bonds between polymer molecules. Among them, a crosslinked product of a sodium acrylate polymer having a sodium carboxylate group is widely known.

By the addition of the water-absorbing polymer, the water-containing cake is granulated to give a free-flowing granular material having an outer diameter of several mm. This is not because water is removed, but because a large amount of water contained in the water-containing cake is retained by the water-absorbing polymer, and apparent water content is reduced. The amount of the polymer to be added may be an optimum amount depending on the type of the polymer, but is usually several% (% by weight). If the addition amount is small, it becomes blocky and it is difficult to obtain a granular material having desired properties, and if the addition amount of the polymer is too large, the particle size of the granular material becomes too fine.

The obtained molybdenum-containing granular material is easy to handle with ease, and hardly adheres to a conveyor, a container, or the like, so that the treatment in the following steps can be easily performed. For example, in the case of a granular product obtained from the above-mentioned molybdenum-containing water-containing cake, the granular product is sent to the following step in order to recover the molybdenum contained therein. First, sodium carbonate is added to the granules and mixed. After baking this in a kiln at 800 to 900 ° C. for 5 to 10 hours, the solution obtained by leaching with warm water is acid-precipitated with hydrochloric acid. As a result, molybdic acid precipitates and is collected. The recovery is usually 95% or more.

(Example) A water-containing cake containing 3% (by weight, the same applies hereinafter) of molybdenum and 30% of water was coated with a water-absorbing polymer of sodium polyacrylate (Aqualic CAK4, manufactured by Nippon Shokubai Kagaku Co., Ltd.). And kneaded in a kneader. After 20 minutes, the water-containing cake had a spherical shape of about 3 mm, and the particles did not stick to each other. The particles granulated by the above method were not sticky even when touched with a finger, and did not adhere to the inner surface of the belt conveyor or the hopper.

When molybdenum was recovered using the granular material as a raw material, it was easy to handle in the treatment step and could be recovered in high yield. Although the above water-absorbing polymer contains sodium, alkali leaching is performed in a subsequent step, so that there is no problem even if the amount is large. Further, since the water-absorbing polymer completely burns at 350 ° C., it did not remain in the final product, and there was no problem.

[0017]

As described above, according to the present invention,
Since the water-containing cake which is easily adhered to each other and easily adheres to a container or the like can be changed to a granular material which is not easily adhered to the cake, the subsequent processing is extremely easy. In the above embodiment, the recovery of molybdenum has been described as an example, but the same effect can be obtained for other wet cakes generated from industrial wastes and the like.

[Brief description of the drawings]

FIG. 1 is a flowchart showing processing steps.

Claims (2)

[Claims] 1. A method for treating a wet cake, comprising adding and mixing a water-absorbing polymer to a wet cake in a wet state to obtain granules having a diameter of several millimeters. 2. The method for treating a water-containing cake according to claim 1, wherein the water-containing cake is a water-containing cake containing molybdenum.