Nutrient recovery methods

Abstract

To provide a technique for efficiently recovering a nutrient salt from a used absorptive article.SOLUTION: A method for recovering a nutrient salt is a method for recovering a nutrient salt from a used absorptive article having a water-absorbing resin and a thermoplastic resin. The method for recovering the nutrient salt includes: a drying step of stirring and drying an object to be treated containing the absorptive article; a heating step of heating the object to be treated at a temperature which is equal to or higher than a softening point of the thermoplastic resin and lower than a thermal decomposition temperature of the water-absorbing resin; a granulation step of stirring the object to be treated and cooling the object to be treated to be lower than the softening point of the thermoplastic resin, and thereby obtaining a granule, after the heating step; and a recovery step of recovering the nutrient salt from the granule.SELECTED DRAWING: Figure 3

Claims

1. A method for recovering nutrients from used absorbent articles having a water-absorbent resin and a thermoplastic resin, A drying step in which the material to be treated, including the absorbent article, is stirred and dried. A heating step of heating the object to be treated at a temperature above the softening point of the thermoplastic resin and below the thermal decomposition temperature of the water-absorbing resin, After the heating step, the material to be treated is stirred and cooled to below the softening point of the thermoplastic resin to obtain granular material, The recovery step includes recovering the nutrients from the granular material by separating them based on the particle size of the granular material. Methods for recovering nutrients.

2. In the recovery step, the first granular material is recovered by separating the first granular material containing the nutrient salt and having a first particle size from the second granular material containing the water-absorbing resin and having a second particle size larger than the first particle size. A method for recovering nutrients according to claim 1.

3. The particle size distribution of the granular material has a first peak corresponding to the first particle size and a second peak corresponding to the second particle size. The method for recovering nutrients according to claim 2.

4. In the drying step, the absorbent article is crushed to expose the water-absorbing resin. A method for recovering nutrients according to claim 1 or 2.

5. In the heating step, a portion of the object to be treated is carbonized. A method for recovering nutrients according to claim 1 or 2.

6. The material to be treated contains cellulose. A method for recovering nutrients according to claim 1 or 2.

7. A method for producing a fertilizer containing nutrients from used absorbent articles having a water-absorbing resin and a thermoplastic resin, A drying step in which the material to be treated, including the absorbent article, is stirred and dried. A heating step of heating the object to be treated at a temperature above the softening point of the thermoplastic resin and below the thermal decomposition temperature of the water-absorbing resin, After the heating step, the material to be treated is stirred and cooled to below the softening point of the thermoplastic resin to obtain granular material, The recovery step includes recovering the nutrients from the granular material by separating them based on the particle size of the granular material. Fertilizer manufacturing method.

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