JPH0426511A - Production of low-density porous particle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing low-density porous carbon particles that are highly effective mainly for soil improvement or water treatment.

[Conventional technology]

Slash-and-burn agriculture has been practiced since ancient times as a means of soil improvement to create an environment in which microorganisms useful for plants can easily grow. This is because the charcoal that remains after slash-and-burn cultivation has excellent water permeability and water retention that allows microorganisms to grow, and because it does not contain organic matter, brain-producing microorganisms and pathogenic microorganisms are not able to grow. This is because it has a variety of effects, such as preventing invasion and inhibiting the growth of mold due to its alkaline nature.

Conventionally, charcoal, sawdust charcoal, bark charcoal, coconut shell charcoal, straw charcoal, and rice husk smoked charcoal have been known as common carbon materials for the purpose of soil improvement.
It is thought to work by promoting the growth of symbiotic microorganisms such as VAill root fungi. Some believe that the presence of char increases the infection rate and spore formation of these fungi, increasing their ability to absorb phosphorus and other components, thereby promoting crop growth.

This type of soil conditioner has the following properties: ■Improves the air permeability and water permeability of the soil; ■Has an appropriate water retention capacity; ■Has a fertilizing capacity in the soil; ■Has a soil acid/alkali adjustment function. be,
■Items such as high retention of oxygen (air) in the soil are required, but if we translate this into the characteristics and properties of a carbon material, we can find low-density porous f with high porosity and specific surface area.
It is a granular material that does not easily break even though it has an illumination structure,
The ideal structure is one in which the internal skeleton is a soft porous structure and the outer shell is covered with a relatively hard carbon layer.

On the other hand, porous carbon particles are consumed in large quantities as activated carbon for water treatment. In this case, in addition to the physical action of separating the substances to be removed in the treated water, there is also a bioreactor-like action that utilizes the microorganisms grown in the tissue bore. Porous carbon grains used as a base material are also required to have the same characteristics and properties as the soil improvement material.

However, none of the conventional porous carbon material manufacturing techniques has been found that satisfies the above characteristics and properties.

That is, when sawdust, straw, etc. are carbonized at low temperatures, a soft porous structure can be formed, but this has the disadvantage that the skeleton easily collapses and the complex bores easily disappear. In this regard, carbonized rice husks and coconut husks are converted into relatively hard carbon bodies, but the problem is that the bores are too small to impart effective functional properties. In addition, tar,
A method is also known in which the material is molded using a binder such as a pinch and then carbonized, but this method has the problem of clogging the bore because the binder component is carbonized while remaining inside the skeleton.

In addition, there are examples of mineral-based soil improvement carbon materials such as coal and pitch coke being commercialized, but they appear to be hard types with a high porosity with an apparent specific gravity of 0.7 g/cc. Undesirable.

In order to solve the above problems, the present inventors first granulated plant-based powder with an aqueous solution of a binder component consisting of lignin, starch, or a mixture thereof, then dried it, and then fired the granulated product. We have developed and provided a method for producing low-density porous carbon grains that are carbonized (Japanese Patent Application No. 159925).

[The espionage that the invention attempts to solve]

In the prior art mentioned above, a mechanism is utilized in which the binder component migrates to the particle surface during the drying process by granulating using a binder substance that is not compatible with plant-based powder,
This method ultimately forms a hard shell-like carbon membrane around a soft porous skeleton, making it possible to form an ideal form for soil improvement and water treatment. However, when using this method, it is necessary to precisely adjust the binder, and if the concentration and amount of the binder aqueous solution fluctuates, the transfer to the grain surface during drying may not proceed uniformly, resulting in blockage of the bores or grain formation. It has the disadvantage of causing strength segregation.

The present invention seeks to eliminate the occurrence of such phenomena and aims to provide a method for producing low-density porous carbon grains that always have characteristics and properties suitable for soil improvement or water treatment using a bioreactor. be.

[Means to solve the problem]

In order to achieve the above object, the method for producing low-density porous carbon particles according to the present invention involves granulating plant-based powder using water as a granulation medium, drying it, and then converting it into liquid organic particles in a heated rotating drum. The structure is characterized in that the organic polymer substance is cured at the grain surface layer by rolling heating while spraying the polymer substance, and then the granules are fired and carbonized.

The plant-based powder serving as the base material of the present invention is obtained by pulverizing, for example, sawdust, thinned wood, bark, bulb chips, rice husks, straw, bamboo, etc., and a fine powder with a particle size of 200 μm or less is preferably used. If the particle size of the powder exceeds 200 μm, it becomes difficult to form particles and more dust is generated.

The plant-based powder is put into an agitation granulator together with water, which serves as a granulation medium, and is granulated by rotational motion.

As a granulator, a bottle-type one commonly used for wet granulation of carbon black is suitable for mass production.

At this time, if a natural water-soluble gum substance such as xanthan gum or guar gum is added to the water of the granulation medium in an amount of 3 parts by weight or less per 100 parts by weight of the plant-based powder, the grain structure will be tightened and the grain strength will be improved.

However, the addition of natural water-soluble gum substances in excess of the above-mentioned amount is undesirable because it leads to pore clogging.

The granules are subsequently dried. The drying treatment may be static drying, or may be carried out using a heated rotating drum in the post-process.

The dried granules are rolled and heated in a heated rotating drum while being sprayed with a liquid organic polymer substance. The organic polymeric substances used in this step are substances that are easily soluble in water or ordinary organic solvents, and that easily carbonize during firing and remain as a carbon layer, such as phenolic resins, furan resins,
Selected from epoxy resin, tar, pitch, lignin, starch, etc. The amount of the organic polymer substance to be sprayed is preferably set in the range of 5 to 100 parts by weight based on 100 parts by weight of the #ti material powder used as the base material, but if the amount is less than 5 parts by weight, it is easily It becomes difficult to impart grain strength that will not cause the grains to break, and if the amount exceeds 100 parts by weight, the outer carbon layer becomes thicker, increasing the bulk density, and the pores inside the grains become larger.
You won't be able to use it effectively.

The sprayed organic polymer material is immediately hardened at the grain surface layer through rolling heating in this step.

Then, the granules are fired and carbonized. Either the static carbonization method or the fluidized carbonization method can be applied to the calcination carbonization treatment, and there is no need to particularly strictly control the temperature increase rate. Temperature ranges are mainly used.

[For production]

According to the present invention, granules obtained by granulating plant-based powder with water or a water-based granulation medium are rolled and heated while spraying a liquid organic polymer substance, so that the organic polymer substance has a granular structure. Immediately hardens and fixes homogeneously on the surface layer of grains without penetrating inside. Since this grain structure is carbonized as it is during the calcination carbonization stage, the internal skeleton of the soft porous structure is coated with a hard carbon film, making it ideal for grains to not break easily while maintaining a low-density porous IR structure. It transforms into a physical property.

The unique characteristics and properties of List L make it extremely effective for soil improvement and water treatment. For example, when used for soil improvement purposes, the high specific surface area and porous skeletal structure help retain oxygen (air). It also supports the water retention function, supports microorganisms and fertilizers, and contributes to the W & adsorption of soil improvement active ingredients. Furthermore, since the grain surface forms a shell structure made of a relatively hard carbon film, it works to ensure fluidity, porosity (air permeability) when mixed into soil, and promote soil agglomeration.

〔Example〕

Examples of the present invention will be described below in comparison with comparative examples.

Examples I to 6 Wood flour prepared by adjusting the grain size of Japanese horse chestnut wood to various powder particle sizes was used as the base material. This wood flour was granulated using a bottle-type granulator using water or water to which 1 part by weight of guar gum was added per 100 parts by weight of wood flour as a granulation medium.

The granulated product was dried and placed in a heated rotating drum equipped with a spray nozzle, and heated by rolling while spraying an ethanolic solution of a phenolic resin or an aqueous solution of lignin as an organic polymer substance using nitrogen gas as a carrier. The conditions for this step were a temperature of 150° C., a rotation peripheral speed of 1 s/sec, and a closing speed of 1 s/sec.

Next, the granules after the spray treatment were transferred to a firing furnace maintained in a nitrogen gas atmosphere, and carbonized at a firing temperature of 800°C or 900°C to produce low-density porous carbon grains.

The conditions that were used in Table 1 are shown in correspondence with Example No.

Comparative Example Porous carbon grains were produced under the same conditions as in Example 1 by changing the granulation medium to a lignin aqueous solution (20 parts by weight of lignin component per 100 parts by weight of wood flour) (Patent Application No. 1-159)
(equivalent to the method of No. 925).

(Characteristic evaluation) Table 2 shows the particle size distribution (%) after granulation according to Example 1.5.6 and Comparative Example, and Table 3 shows various characteristics of low density porous carbon particles obtained according to Example and Comparative Example. are shown in comparison.

Table 2 From the results in Table 2, the particle size distribution of the granules shows that the particle size of wood flour is 20.
In Example 5, which included a portion exceeding 0 μm, the amount of dust tended to increase, and in Example 6, in which guar gum was added to the granulation water, the amount of dust tended to decrease.

In addition, from the results in Table 3, the low-density porous carbon grains according to the examples showed high porosity structure characteristics equivalent to those of the comparative examples, but in Example 4, the amount of spraying of the breeding polymer material was 100 parts by weight of wood flour. Since the amount exceeded 100 parts by weight, it was observed that the bulk density increased and the porous structure tended to decrease.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to efficiently produce low-density porous carbon grains that have high porosity and specific surface area and have grain strength that prevents them from easily breaking. These characteristics and properties are particularly ideal as a soil improvement material or a bioreactor for water treatment, and great effects can be expected for these applications.

July 10, 1990

Claims (1)

[Claims] 1. Plant-based powder is granulated using water as a granulation medium, dried, and then rolled and heated in a heated rotating drum while spraying a liquid organic polymer substance to form the organic material. A method for producing low-density porous carbon grains, which comprises curing a polymeric substance at the surface layer of the grains, and then firing and carbonizing the grains. 2. Add 3 parts per 100 parts by weight of vegetable powder to the water of the granulation medium.
2. The method for producing low-density porous carbon particles according to claim 1, wherein not more than parts by weight of natural water-soluble gum substances are added. 3. The amount of organic polymer substance to be sprayed is 100% plant-based powder.
The method for producing low-density porous carbon grains according to claim 1, wherein the amount is set in the range of 5 to 100 parts by weight.