JP2000017278A - Preparation of refuse solid fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for preparing a refuse solid fuel with a reduced content of chlorine by efficiently removing water soluble chlorides such as sodium chloride and sodium chlorate which cause the formation of hydrogen chloride, dioxin or the like. SOLUTION: Combustible waste is ground to a size of 30 mm or less, and the ground product is washed with water or dispersed into water having a temperature of 25 deg.C or higher for two minutes or more, dehydrated and then, dried to prepare a refuse solid fuel. In this instance, the dehydrated and dried, combustible ground product is further molded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing refuse solid fuel having a low chlorine content from combustible waste including kitchen waste and paper.

[0002]

2. Description of the Related Art Conventionally, combustible waste has been incinerated for the purpose of volume reduction, and incinerated ash generated by incineration has been disposed of by landfill. However, in recent years, it has been clarified that highly toxic dioxins are generated during waste incineration, which limits the operation of incineration facilities that emit large amounts of dioxins.
It has become mandatory to suppress the generation of dioxins by performing continuous operation while maintaining the incineration temperature at a high temperature of 850 ° C. or higher, and rapidly cooling the exhaust gas temperature to 300 ° C. or lower.

[0003] In order to stably operate the incinerator at such high temperatures as described above, it is necessary to continuously keep dust as homogeneous as possible. They vary widely and vary greatly depending on their transport and intermediate processing methods. Therefore, it is necessary to consider a wider area of garbage disposal including garbage transportation and disposal methods, which involves a very difficult problem.

[0004] Without depending on such a wide area of garbage disposal,
As a method for obtaining relatively homogeneous refuse fuel, refuse solid fuel conversion technology has attracted attention. This refuse solid fuel is obtained by using a combustible waste as a raw material, pulverizing the combustible waste to remove incombustible substances such as metal, and drying and molding. By such a treatment, the combustible waste is homogenized to become a solid fuel capable of stable combustion, and since a metal serving as a catalyst at the time of dioxin generation is removed, generation of dioxin is suppressed. Furthermore, since the lime-based additive added as required fixes the chlorine content during combustion, dioxin production can be further suppressed.

[0005] However, the conventional refuse solid fuel is effective in suppressing the generation of dioxins, but has a problem in that a sufficient effect of suppressing generation of corrosive gas such as hydrogen chloride cannot be obtained. Since corrosive gas such as hydrogen chloride corrodes not only incineration equipment but also exhaust gas dust collection equipment, it is necessary to suppress generation of dioxins and eliminate as much as possible. Therefore, various methods have been proposed for adding a desalting step to the refuse solid fuel production process to produce refuse solid fuel having a low chlorine content. However, both methods have problems such as high cost and difficulty in optimizing processing conditions. Therefore, there is a demand for a method of efficiently removing a chlorine source to produce a refuse solid fuel having a small amount of chlorine.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional refuse-to-fuel processing, and causes the generation of hydrogen chloride, dioxins, and the like when converting combustible waste into fuel. It is an object of the present invention to provide a method for producing a refuse solid fuel having a low chlorine content by efficiently removing water-soluble chlorides such as salt.

[0007]

That is, the present invention provides:
(1) A method for producing a refuse solid fuel, comprising crushing combustible waste to 30 mm or less, washing or dispersing the crushed material at a water temperature of 25 ° C. or more for 2 minutes or more, and then dehydrating and drying. About. The garbage fuel production method of the present invention comprises:
(2) A manufacturing method in which flammable waste is crushed to 20 mm or less, and then washed or dispersed in water at a water temperature of 30 ° C. or more for 3 minutes or more and a water amount ratio of 30 times or more, (3) Dewatered and dried flammable waste And (4) a method in which the combustible waste is already formed garbage solid fuel.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail with examples. The production method of the present invention reduces the amount of combustible waste to 30.
mm or less, preferably crushed to 20 mm or less, and the crushed product is at a water temperature of 25 ° C. or more, preferably 30 ° C. or more, for 2 minutes or more,
Preferably, the water-soluble chloride contained in the pulverized material is eluted and removed from water by washing or dispersing in water for at least 3 minutes, followed by dehydration and drying to produce a refuse solid fuel.

In the present invention, the term "combustible waste" refers to waste mainly composed of kitchen garbage, wood, paper or fiber, and is obtained by removing incombustibles and metals from kitchen garbage and paper. Therefore, it is waste generally called combustible waste.
The garbage may be separated and collected in advance as combustible garbage at the time of garbage collection, or may be obtained by separation processing after garbage collection.

The combustible waste is pulverized in order to increase the efficiency of removing water-soluble chloride contained in the waste. Combustible waste may be difficult to pulverize because it contains a large amount of papers and fibers. It is preferable that they are once subjected to pressure molding and then pulverized. FIG. 1 shows the relationship between the degree of pulverization and the amount of chlorine eluted. As shown in FIG. 1, the smaller the particle size of the pulverized material, the larger the contact area between the pulverized material and water. It is easy to elute and has a high desalting effect. On the other hand, the smaller the particle size, the higher the pulverization cost. Therefore, it is preferable to determine the degree of pulverization in consideration of the desalting effect. As shown in FIG. 1, the amount of chlorine eluted gradually decreases as the particle size of the pulverized material increases from around 20 mm, and sharply decreases when it exceeds 30 mm. On the other hand, at 1 mm or less, there is not much change. Therefore, the degree of pulverization is appropriately from 30 mm to 1 mm in particle size, and preferably from 20 mm to 1 mm in particle size.

Next, water-soluble (water-soluble) chlorides such as sodium chloride and sodium chlorate contained in the ground material are eluted and removed by washing the ground material or dispersing it in water. FIG. 2 shows the relationship between the water treatment temperature and the chlorine elution amount. As shown in the figure, when the water temperature is lower than 20 ° C., the amount of chlorine eluted sharply decreases. 25 ° C to 90 ° C
In this case, the elution amount increases almost in proportion to the temperature rise, and under the processing conditions shown in the figure, about 45% or more of the contained chloride elutes at a water temperature of 30 ° C. or more. If the temperature exceeds 90 ° C., the heating cost increases. Therefore, the temperature of the treated water is more than 25 ° C,
30 ° C to 90 ° C is preferred.

According to FIG. 3 showing the relationship between the water treatment time and the chlorine elution amount, the chlorine elution amount is significantly reduced when the treatment time is less than 2 minutes, and is gradually saturated when the treatment time exceeds 3 minutes. When it is more than minutes, it hardly changes. Therefore, the water treatment time of the desalination treatment is suitably 2 minutes or more, and preferably 3 minutes to 15 minutes. The amount of water is 30 to 50 with respect to the weight of the pulverized material.
A factor of 2 is appropriate and stirring is preferred. In the treatment method, in addition to dispersing the pulverized material in water, the above-mentioned water temperature and processing time may be ensured, and the entire pulverized material may be uniformly washed in a shower using a sufficient amount of water.

After the above-mentioned water treatment, the pulverized material is recovered and dehydrated. The recovery and dehydration operations are not particularly limited. It is preferable to use a centrifuge, a filter press or the like. The cake obtained by dehydration preferably has a water content of about 70% by weight or less in consideration of the next drying step.

Next, the dehydrated cake is dried. As a drying means, mixing additives with exothermic reaction such as quicklime,
It is good to utilize the exothermic reaction. Further, drying may be performed using external heat of a boiler or the like. In the case of drying by external heat, before or after drying, lime powder such as quicklime or slaked lime, coal ash, cement, or gypsum are mixed, and drying efficiency is improved by using their water absorption. In both cases, the effect as a molding aid can be utilized.

After the above-mentioned drying, it is formed as required. The solid fuel of the present invention may be a powder or a compact. Molding is performed to make the shape suitable for transportation and combustion equipment,
In the case where the shape of the granular material during combustion is preferable, it is not necessary to mold. Rather, pulverize to the required particle size. In the case of molding, the amount of additives such as lime powder is adjusted according to the molding machine to be used, and molding is performed so as to obtain a desired shape, size, hardness and the like. As the molding machine, a known molding machine such as an extrusion molding machine or a roll press molding machine can be used.

In the above-mentioned production method, a solid fuel made into garbage by existing means can be used. That is, this is used as combustible waste and treated by the above method. For example, waste that is difficult to grind, such as a plastic bag or a string, is easily crushed by pressing once, and the desalting effect is improved by pulverization.

The refuse solid fuel of the present invention thus obtained has a low content of water-soluble chloride, so that the generation of hydrogen chloride is greatly suppressed, the field of application as a fuel is widened, and the amount of its use is increased. Can also be increased. Therefore,
It also contributes to solving the problem of garbage disposal, for which it is difficult to secure landfill sites.

[0018]

Next, the present invention will be specifically described by way of examples. The following is an exemplification and does not limit the scope of the present invention.

Examples 1 to 4 Combustible waste having the components shown in Table 1 was used.
kg by dry primary crushing using a twin-screw crusher.
Dry secondary pulverization using a rotary crusher combined with shearing
The crushed product having the particle size shown in Table 1 was obtained. These pulverized materials were put into water and stirred under the conditions shown in Table 2. After this water treatment,
The pulverized material was collected, dehydrated using a centrifuge, and the obtained cake was spread on a filter plate covered with a resin filter cloth and arranged.
After washing with 0 kg of water, the mixture was transferred to a compression press equipped with a filter cloth and dehydrated until the water content became 70% by weight. Further, this dehydrated cake was dried to a water content of 5% by weight with a sludge dryer to obtain about 6 kg of powdery refuse solid fuel. Table 2 summarizes the chlorine content and calorific value of these refuse solid fuels.

Example 5 The powdery solid fuel obtained in Example 1 was molded by using an extrusion molding machine, and was formed into a cylindrical solid waste fuel (diameter 15 mm, length 30 m).
m) was prepared. 10 kg of this cylindrical solid fuel was pulverized and water-treated according to the processing conditions shown in Table 2, dehydrated and dried to obtain about 6 kg of powdery solid waste fuel. Table 2 shows the chlorine content and the calorific value of this refuse solid fuel.

Example 6 The same combustible waste as in Example 1 (10 kg) was pulverized to a particle size of 50 mm or less by dry pulverization using a twin-screw crusher. The pulverized product was dried with a sludge dryer until the water content became 5% by weight. Next, the above-mentioned pulverized material was molded using an extruder to obtain about 6 kg of a cylindrical (15 mm in diameter, 30 mm in length) refuse solid fuel. 6 kg of this cylindrical solid fuel was pulverized to a particle size shown in Table 2 by primary dry pulverization using a twin-screw crusher and secondary dry pulverization using a rotary crusher combined with impact and shearing. This pulverized product was put into water and stirred under the conditions shown in Table 2. After this water treatment, the crushed material is collected,
The cake was dehydrated using a centrifugal separator, and the obtained cake was laid out on a filter plate covered with a resin filter cloth. It was dehydrated to 70% by weight. Further, this dewatered cake was dried with a sludge dryer to a water content of 5% by weight to obtain about 6 kg of powdery solid waste fuel. Table 2 summarizes the chlorine content and calorific value of these refuse solid fuels.

[0022] 30mm the particle size of Comparative Example grind process water temperature and 20 ° C., except that the processing time was 1 minute in the same manner as in Example 1-4, was ground and water treatment the combustible waste 10kg The powder was dehydrated and dried to obtain a powdery solid fuel. Further, this solid waste fuel was molded using an extruder to obtain about 6 kg of a cylindrical solid waste fuel (diameter 15 mm, length 30 mm). Table 2 shows the chlorine content and the calorific value of this refuse solid fuel.

[0023]

[Table 1]

[0024]

[Table 2]

As shown in Examples 1 to 6 in Table 2, the refuse solid fuel of the present invention, from which the water-soluble chloride was removed by optimizing the pulverized particle size and the water treatment conditions, was compared with the comparative example. Extremely low content and high calorific value.

[0026]

According to the method for producing refuse solid fuel of the present invention, water-soluble chloride can be easily removed from combustible waste,
A refuse solid fuel having a very low chlorine content and a high calorific value can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the particle size of the pulverized material and the chlorine elution amount.

FIG. 2 is a graph showing a relationship between a treatment water temperature and a chlorine elution amount.

FIG. 3 is a graph showing the relationship between treatment time and chlorine elution amount.

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazushi Izumi 2-4-2 Daisaku, Sakura-shi, Chiba F-term in Central Research Laboratory, Noda Co., Ltd. F-term (reference) 4H015 AA01 AA12 BA08 BA09 BA13 BB10 BB13

Claims (4)

[Claims] 1. A garbage solid fuel characterized in that flammable waste is crushed to 30 mm or less, and the crushed material is washed or dispersed in water at a water temperature of 25 ° C. or more for 2 minutes or more, and then dewatered and dried. Production method. 2. The method for producing refuse solid fuel according to claim 1, wherein the combustible waste is pulverized to a size of 20 mm or less, and then washed or dispersed in water at a water temperature of 30 ° C. or more for 3 minutes or more and a water amount ratio of 30 times or more. . 3. The method for producing a refuse solid fuel according to claim 1, wherein a dewatered and dried pulverized combustible waste is further formed. 4. The method for producing a refuse fuel according to claim 1, wherein the combustible waste is a previously formed refuse solid fuel.