JPS59168096A - Wood fuel in pellets and its preparation - Google Patents

Abstract

PURPOSE:To prepare wood fuel in pellets having a high calorific value and excellent water and mildew resistance, by adding fatty oil or mineral oil to partly carbonized and crushed wood pieces and performing compression molding at 100 deg.C or higher. CONSTITUTION:Wood chips of wood waste obtained by pretreating thinned-out wood or wood waste is partly carbonized at 300-400 deg.C for about 30sec-2min in a heating oven and is crushed to a particle diameter of a few mm. by means of a hammer mill, etc. Fatty oil or mineral oil is added to the particles in an amount of 4-6% and the mixture pelletized under pressure at about 100 deg.C. The pellets consist of free carbon (17-35%), modified wood, fatty oil or mineral oil and a small amount of water and has a calorific value of 5,200-5,500kcal/kg.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to fuel pellets with a high calorific density made from Tochigi tree bark and other woody materials, and a method for producing the same, which has an even higher calorific density than conventional products.
The purpose of the present invention is to provide calorific pellets that are highly resistant to the infiltration of moisture due to atmospheric humidity and other factors during transportation, storage, etc., and that do not generate mold.

Conventionally, fuel pellets made from thinned wood, waste wood, and other wood materials include, for example, Okalight (trademark) from Otsuga, which is made from sawdust, Percoll from the United States, and Woodex Kugaro, which are made from water-phase chips. It is also well known for its trademarks. Since these known wood fuel pellets are compression-molded products of raw material wood, they naturally have a higher calorific density compared to the raw material, and are easy to handle and highly economical. 4000-4500 KCaJ
/Kg, has insufficient calorific value as an industrial fuel, is susceptible to moisture intrusion, and may disintegrate during the handling process.
There were major drawbacks such as the appearance of blue mold. In particular, industrial waste such as waste trunks, leaf petioles, fruit stalks, pulp fibers, etc., which are incinerated or abandoned, are discharged in large quantities from oil balm cultivated systematically and on a large scale in tropical regions after oil extraction. Even if you try to convert it into fuel, it is virtually impossible. In other words, in order to make pellets, it is necessary to crush the wood fibers finely using a hammer mill, etc., but oil palm fibers are strong and have a diameter of Q, 8 mm, and are covered with a hard film. This is because it cannot be crushed with a hammer mill, and the only way to crush it is with a specially constructed shredding machine, which is extremely inefficient.

This invention makes it possible to eliminate the above-mentioned drawbacks of conventional wood fuel pellets and the difficulty in selecting raw materials thereof, and the invention will be explained in detail below with reference to Examples.

That is, to produce the wood fuel pellets according to the present invention, wood such as forest thinning material including bark, waste water phase, wood chips, etc. is used as a raw material. Of course, strong fiber wood such as oil palm can be used. Wood chips and other pieces of wood that are of an appropriate size can be used as they are, but it is generally better to shred them to the size of what is called wood chips as a pretreatment. Next, such raw materials of appropriate size are heated for 30 minutes using a thermal furnace such as a continuous carbonization furnace.
Partial carbonization treatment is performed by holding at 0 to 400°G for a short time, for example, about 30 seconds to 2 minutes. In this case, the combustion of volatile matter in the wood and self-heating cause a considerable amount of water to evaporate, making the wood fiber brittle.
A considerable amount of free amorphous carbon is produced.

Next, if you charge the above-mentioned partially carbonized product into a crusher such as a hammer mill and crush it, the wood fibers are already brittle, so even if the raw material is a strong fibrous wood such as oil palm, for example. , it is easily crushed to a size of several mm.

Next, several percent of oil or mineral oil is added to the above-mentioned crushed material by an appropriate method such as spraying, and the material to which the oil has been added is compressed into pellets at 100° C. or higher.

In the conventional technology for producing wood fuel pellets, apart from the case where a binder is added for molding, the lignin contained in the wood itself is generally used as the cause of binding force during pelletization. What's more, the wood chips are treated with steam at the highest possible temperature. On the other hand, in the present invention, since the lignin in the wood has already been modified by the high temperature in the above-mentioned partial carbonization treatment, binding force cannot be expected from the viscosity of the lignin itself. However, pellets made by compression molding a material that has undergone the above-mentioned partial carbonization and crushing treatment and added oil at a temperature of 100°C or higher, compared to the pellets in which lignin is the cause of binding strength in the above-mentioned conventional technology, are It has a strength comparable to that of other materials.

Due to the above-mentioned reasons, the cause of the binding strength of the fuel pellets of this invention cannot be determined from the lignin itself in the wood, but it is believed that the crushing before forming into pellets contains a large amount of amorphous carbon in the free station part. Considering that wood fibers are denatured by high temperatures during partial carbonization treatment, and the denatured hexarose is exposed due to the destruction of cell membranes, it is important to consider that wood fibers are denatured by high temperatures during partial carbonization, and that the denatured hexarose is exposed due to the destruction of cell membranes. It is thought that the high temperature oil that has penetrated is the main cause of the binding strength. In addition, denatured lignin may also be one of the causes of binding. In addition, if the crushed material that has undergone the above-mentioned partial carbonization treatment is molded without adding oil, the molded product will be extremely brittle regardless of the molding temperature, and even if oil is added, the molded product will be extremely fragile. The fact that similarly brittle pellets are obtained even when the molding temperature is below 100°C supports the above assumption regarding the cause of the cohesiveness of the pellets according to the present invention.

In any case, in this invention, it is necessary to maintain the molding temperature at 100°C or higher, so it is natural to maintain the temperature of the molding die at a high temperature. It is also very effective to raise the temperature to near the flash point, or to add oil at room temperature, heat treat it, and then charge it into a molding die. Incidentally, the fact that the addition of the above-mentioned oils contributes to an increase in the calorific value of the pellets is also a great advantage of the method of this invention.

Furthermore, as mentioned above, in the conventional technology for producing wood fuel pellets, it was necessary to treat the material to be treated with high-pressure steam before molding. The composition of the product is determined by the fact that not only is there no need for high-temperature steam generation equipment such as a high-pressure boiler, but there is also no need to consider the increase in moisture due to contamination during steam treatment. It is extremely convenient to do so. Furthermore, in pellet molding, since oils are added to the processed material, the dies are highly lubricated, and therefore the die has less wear and has a long equipment life, which is a great advantage. As shown in the test results described later, the fuel pellets according to the present invention, unlike conventional products, have remarkable water resistance and at the same time have properties that prevent the growth of mold. It is thought that such favorable properties are due to the fact that the composition contains a large amount of free carbon and a small amount of oil.

There are various well-known means for pelletizing powder by compression molding, and in carrying out this invention, 100°C
Any means can be used as long as the above molding temperature is maintained.

Listed below are the test results of the fuel pellets produced according to the invention described above. However, for pelletization, Swiss company Pühler Plathers (Buhler B)
A Cupex pellet mill manufactured by Rothers was used. This pellet making machine has a molding pressure of 10,000-20,000 Kg/cm at 120-160°C.
It is.

Dimensions 6mmφX25mm Specific gravity 1.4-1.8 Calorific value 5200-5500 KCal/J Moisture 8
~12% Oil content 4-6% Free M carbon 17-35% Yield based on raw materials 65-78% Water resistance No disintegration and mold resistance after being left in room temperature water for 100 hours Stored indoors in summer and outdoors with a roof for 3 months, mold does not form In other words, the wood fuel pellets according to the present invention are composed of the following compression-molded composition.

This composition contains 17 to 35% of free carbon generated by heating wood and 4 to 6% of fat or mineral oil.
%, and a residual substance containing heat-modified wood and water excluding the free carbon, and 5200-55
It has a calorific value of 00 Kcal/Kg.

Thus, according to the present invention, it is not only possible to provide wood fuel pellets that have a much higher calorific value than those produced by the conventional technology and have strong water resistance and mold resistance, but also allows the production of wood fuel pellets that The smoothness of molding and the long life of the molding die are ensured. Furthermore, since high-pressure steam treatment as in conventional production technology is not required, the production equipment is economical, and there is less troublesome work to adjust the water content due to contamination with steam. Furthermore, according to this invention, it is easy to use almost worthless and strong fibrous wood such as oil balm waste as a raw material.
The ability to supply large quantities of inexpensive industrial fuel pellets is extremely effective in contributing to industrial development.

Claims (2)

[Claims] (1) Composed of the following compression-molded composition, which contains 17 to 3 free ra carbons produced by heating wood.
5%, fat or mineral oil 4 to 6%, and the remaining substance containing wood heating substances excluding the free carbon and water, and 5200-5500 KC, al/Kg
wood fuel pellets with a calorific value of (2) Add 4 to 6% fat or mineral oil to crushed wood chips that have partially carbonized by holding at 300 to 400°G for a short time, and compression mold them into pellets at 100°C or higher. A method for producing wood fuel pellets, characterized by: