JP2003284506A - Method for drying food dregs - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for drying food dregs by which valuable dried resources are obtained in a short time without causing scorches. <P>SOLUTION: The method for drying food dregs comprises repeating dry and moisturization of food dregs through subjecting the dregs to superheated steam heating until the food dregs have a limiting moisture content, and subjecting the dried and moisturized food dregs to high temperature air heating or indirect heating so as to dry them. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a drying treatment method for obtaining valuable drying resources from food dregs.

[0002]

2. Description of the Related Art It is known that food slag such as okara, juice slag, and shochu slag are dried and effectively used as feed for livestock. For example, JP-A-2000-189132 describes that a dried and sufficiently dried resource without charring can be obtained by heating and squeezing a pressed food slag with steam or hot water, and then heating and drying. Has been done.

[0003]

However, according to the treatment method described in the above publication, the moisture content of the food slag is significantly increased because the food slag is heated and moistened once with the purpose of releasing stress from the food slag. Therefore, in order to dry it, it is necessary to extend the drying time by the amount corresponding to the increase in the water content. Moreover, since the heating temperature cannot be raised because charring does not occur, a long drying process is required.

Therefore, the present invention provides a method for drying food slag that can obtain valuable drying resources by a short drying process without burning the food slag.

[0005]

Means for Solving the Problems The food slag drying treatment method of the present invention is to wet and dry the food slag by superheated steam heating, and then dry the wet and dried food slag by high temperature air heating or indirect heating. It is characterized by performing.

Wetting and drying by heating with superheated steam is
Repeat until the critical moisture content is reached. In addition, indirect heating can be used in combination for wetting and drying by heating with superheated steam and drying by heating with high temperature air.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The superheated steam used in the present invention is a heat-radiative gas, and heats and dries the food slag by convection and radiative heat transfer. The superheated steam is a condensable gas, and temporarily condenses on the surface of the food slag of the material to be dried at the initial stage of drying, and can rapidly heat and wet the inside.

[0008] Further, since superheated steam does not contain oxygen in the air stream, it is possible to dry the food slag without oxidizing it, and the superheated steam has a bactericidal action and sterilizes the bacteria in the food slag during drying. can do.

FIG. 1A is a graph showing the relationship between the water content and the temperature of the material to be dried, and FIG. 1B is a graph showing the relationship between the drying rate and the water content. In the present invention, wetting and drying by heating with superheated steam until reaching the limit water content is
As shown in Fig. 1, since the heat input is entirely consumed for drying during the constant rate drying period until the critical moisture content is reached, the temperature of the food dregs does not depend on the temperature of the heating medium, and the dynamic equilibrium temperature (approximately It is because the wet-bulb temperature of the heating medium) changes, and during the subsequent rate-decreasing drying, the temperature rises because part of the heat input is used to heat the food slag. If the temperature rises too much and charring occurs, the value as a drying resource decreases.

FIG. 2 is a diagram showing a system of the method for drying and processing food slag of the present invention. In FIG. 1, the first dryer 1
The food slag a is wetted and dried by the superheated steam c. The higher the temperature of superheated steam, the greater the effect.
It is set in the range of 00 ° C to 500 ° C according to the water content. The food dregs a dried by the first drier 1 in the second drier 2 is dried by the hot air d to become a dried product b. The temperature of the hot air may be 100 ° C or lower.

A known dryer can be used as the dryer. For example, a shaft provided with a plurality of stirring blades for conveying the food slag while stirring is arranged in the tube, and a jacket formed outside the tube and It is possible to use a dryer in which steam is flowed inside the shaft to indirectly heat the shaft. If the indirect heating is also used, the drying time can be shortened further.

[0012]

EXAMPLE FIG. 3 (a) is a graph showing the relationship between time and water content, and FIG. 3 (b) is a graph showing the relationship between time and the temperature of the material to be dried.

In the embodiment of the present invention, the first dryer was supplied with soybean curd having a water content of 80%, superheated steam of 300 ° C. was blown into it, and it was wet and heated with heated steam and steam for indirect heating at 100 ° C. After reaching the critical moisture content, it was heated and dried in the second dryer with high temperature air at 100 ° C and steam for indirect heating at 100 ° C.

As a comparative example, the first dryer has a water content of 80.
% Of okara was supplied, and steam for wetting at 100 ° C. was sprayed to wet, and then heated by hot air at 100 ° C. and steam for indirect heating at 100 ° C. to be dried.

In the present invention, as shown in FIG.
The water content of the superheated steam drastically decreased to the critical water content in a short time (see Fig. 3 (a)), and increased rapidly until the temperature of the dried product reached the critical water content and remained constant (Fig. 3 ( See b)). After reaching the critical moisture content, it was possible to dry to the final target moisture content in a short time by drying the hot air, and no charring was observed.

In comparison with the present invention, in the comparative example, in the high temperature air of 100 ° C., the decrease of the water content was slow to the limit water content (see FIG. 3 (a)), and it was low until the temperature of the dried product reached the water content limit. The temperature was changed (see FIG. 3 (b)). After reaching the critical moisture content, drying the hot air took a long time to dry to the final target moisture content.

As is clear from the graph shown in FIG. 3, the present invention was able to dry to the target water content in a shorter time than the comparative example.

[0018]

In the case of the prior art, after the food slag is moistened with steam or hot water, a long drying process is required to perform drying by high temperature air and indirect heating. By applying superheated steam heating to
A drying process can be performed in a short time. In addition, a high-quality and valuable dry resource free from charring, oxidization, and retained bacteria can be obtained.
Further, since the exhaust steam can be recycled and used, energy can be saved.

[Brief description of drawings]

FIG. 1A is a graph showing the relationship between water content and the temperature of a material to be dried, and FIG. 1B is a graph showing the relationship between drying rate and water content.

FIG. 2 is a diagram showing a system of a food dregs drying treatment method of the present invention.

FIG. 3 (a) is a graph showing the relationship between time and water content,
(B) is a graph which shows the relationship between time and a to-be-dried material temperature.

[Explanation of symbols]

1: First dryer 2: Second dryer a: food waste b: dried product c: Superheated steam d: hot air

Claims (5)

[Claims] 1. A method of drying food slag, which comprises heating and drying the food slag by heating with superheated steam, and then drying the wet and dried food slag by heating with high temperature air. 2. A food slag drying treatment method, which comprises moistening and drying a food slag by heating with superheated steam, and then drying the wet and dried food slag by indirect heating. 3. The food waste drying method according to claim 1 or 2, wherein the wetting and drying by heating with superheated steam is performed until the moisture content reaches a limit. 4. The method for drying food slag according to claim 1, wherein indirect heating is used in combination with said wetting and drying by heating with superheated steam. 5. The food waste drying method according to claim 1, 3 or 4, wherein indirect heating is used together with the drying by the high temperature air heating.