JP7373324B2 - How to store and transport pellets - Google Patents

Description

The present invention relates to a method for storing and transporting pellets, and in particular, pellets that suppress fermentation and spontaneous combustion of pellets formed and dried from woody or herbaceous biomass, and improve storage and transport efficiency. Regarding storage and transportation methods.

In recent years, technology has been developed to effectively utilize resources called biomass instead of fossil fuels as fuel. In the following description, the term "pellet" includes both wood pellets and herbaceous pellets, unless otherwise specified. In addition, herbaceous and herbaceous species both refer to plant biomass other than trees, and when the term herbaceous is described below, it also includes herbaceous biomass.

Regarding the handling of such biomass, Patent Document 1 describes that biomass is not piled up outdoors, but is stored in a large storage container, and is attached to the biomass from vertically below the top surface of the biomass stored in the storage container. A technique has been proposed for blowing gas at a temperature higher than the growth limit temperature of microorganisms. As a result, it is possible to suppress the growth of microorganisms attached to biomass and reduce the moisture content in the biomass, thereby making it possible to suppress the generation of hydrogen by microorganisms, which in turn can lead to spontaneous ignition due to large storage of biomass. It is said that it is possible to suppress

Japanese Patent Application Publication No. 2014-118187

However, this technology requires a large, dedicated container to house the biomass, and special equipment to blow gas at a temperature above the growth limit of microorganisms. Furthermore, in order to transport biomass to consumption facilities, it is necessary to subdivide the biomass from storage containers into transportable amounts, which significantly increases storage and transportation costs and complicates the logistics system. There is a problem with becoming. Furthermore, if the number of times the container is handled increases, the amount of powdering increases and there is a risk of heat generation.

By reducing the number of times a container is handled, the present invention suppresses the risk of pellet pulverization and heat generation, increases pellet transportation efficiency, and enables pellet storage and transportation to be carried out easily and at low cost. The purpose is to provide a method for storing and transporting pellets.

The present inventors have made the following findings as a result of intensive study on the above-mentioned problem. That is, by storing the pellets in a covered container, it is possible to prevent an increase in water content due to rainfall, thereby suppressing fermentation and heat accumulation due to the accumulation of a large amount of pellets. In addition, by making the covered container a size that can be transported by a vehicle that can run on public roads, it is possible to suppress spontaneous heat generation of the pellets due to storing a large amount of pellets, and therefore, spontaneous combustion. Furthermore, by using the above-mentioned size for the covered container and limiting the bulk density of the pellets, it is possible to increase the filling rate of the pellets and to store and transport the pellets in the covered container, thereby reducing the number of times the pellets are handled. It is possible to reduce this and significantly improve pellet transport efficiency. Furthermore, by reducing the number of times of handling, it is possible to suppress powdering of the pellets and suppress heat generation due to oxidation.

The present invention has been made based on such knowledge.
That is, one aspect of the present invention is a method for storing and transporting pellets in which the pellets are stored and transported in bulk in a covered container, wherein the pellets are pellets obtained by drying and molding woody or herbaceous biomass. wherein the bulk density is 0.6 ton/m ³ to 0.8 ton/m ³ , the container has a maximum length of 17 to 21 feet, and the pellets are stored and stored in the container. When transportation is carried out and the pellets are accommodated in 60% or more of the capacity of the container, the total weight of the container is 29 tons or less, and the pellets are accommodated in 60% or more of the capacity of the container. To provide a method for storing and transporting pellets, characterized in that when storing and transporting the container by vehicle, the total weight of the vehicle is 44 tons or less.

In the method for storing and transporting pellets according to one aspect of the present invention configured as described above, it is preferable that the moisture content of the pellets is 15 wt% or less, and that the container is placed outdoors when storing the pellets. .

Moreover, it is preferable that the moisture content of the pellets is 10 wt% or less.

Furthermore, it is preferable that a hopper is provided above the container and supplies the pellets in bulk to the container, and the pellets are transported to a consumption area while being accommodated in the container.

Furthermore, it is preferable that the hopper is provided at a port and that the pellets unloaded from a ship are directly stored in the container.

Further, it is preferable that the hopper includes a cyclone that collects dust from the pellets.

According to the present invention, there is provided a method for storing and transporting pellets that suppresses heat generation, increases transport efficiency and handling efficiency of pellets, and makes it possible to store and transport pellets at low cost.

FIG. 1 is a perspective view of a covered container used in an embodiment of the present invention. 2A is a diagram showing a method for storing and transporting pellets according to an embodiment of the present invention, FIG. 2A is a diagram showing a state in which pellets are put into a covered container, and FIG. FIG. 2C is a diagram illustrating a state in which containers are stored, and FIG. 2C is a diagram illustrating a state in which pellets are dispensed from a covered container at a consumption facility. Note that FIG. 2(b) is a front view (dispensing port) of the covered container.

Embodiments of the present invention will be described in detail below.
A method for storing and transporting pellets according to an embodiment of the present invention will be specifically described with reference to FIGS. 1 and 2.

Note that the pellets that are handled in the pellet storage and transportation method according to the present embodiment are generally those obtained by crushing, drying, and pulverizing wood or the like, and forming the pellets into pellets. Pellets include wood pellets formed from woody biomass and herbaceous pellets formed from herbaceous biomass. The raw materials for wood pellets are not limited to wood felled from forests, but also include leftover materials from woodworking plants, such as bark, sawdust, planer shavings, and scraps, as well as wood from thinned forests. Examples of raw materials for herbaceous pellets include empty fruit bunches (EFB), bagasse, straw, and rice husk produced as a result of producing palm oil from palm trees.

A method for storing and transporting pellets according to an embodiment of the present invention stores pellets in a covered container, and transports the pellets by a vehicle equipped with a covered container containing the pellets. Although various vehicles can be used, for example, a vehicle to which a trailer is connected can be mentioned. Covered containers are loaded onto trailers and transported by vehicles to storage locations and consumption locations.

By using a covered container to store pellets, it is possible to store, store, and transport the pellets in bulk, making it possible to differentiate the container from flexible containers used for grains and the like. Moreover, it can also be used for small-scale customers.

Furthermore, by using a covered container, it is possible to prevent moisture from entering from the outside (especially rainwater), and fermentation (especially anaerobic fermentation) using pellets with a high moisture content and heat generation can be suppressed.

Furthermore, if a large amount of pellets is stored in one large container for a long period of time, even if moisture is prevented from entering from the outside (especially rainwater), the moisture distribution within the container will increase, and in areas with unevenly distributed high moisture. , fermentation (especially anaerobic fermentation) may generate heat.

On the other hand, by housing the pellets in a container of a predetermined size, it is possible to avoid housing a large number of pellets in one room, thereby reducing the moisture distribution within the container and reducing the heat generated by fermentation. can be suppressed.

Furthermore, although pellets are often used as fuel, they have a lower calorific value than coal, making them suitable as fuel for small-scale facilities, and there is a large demand for them in small quantities. Therefore, it is advantageous to store and transport the pellets in a covered container as in the present invention.

As mentioned above, pellets are formed by crushing, drying, and pulverizing wood or herbaceous biomass into pellets. However, drying of crushed wood, etc. has a moisture content of more than 15 wt%. Since there is a possibility that the pellets may be fermented, it is desirable that the moisture content of the pellets after molding be 15% by weight or less, preferably 10% by weight or less. Thereby, fermentation and heat generation of the pellets during long-term storage and transportation can be suppressed, and spontaneous combustion of the pellets can be suppressed.
In addition, the document ``Survey on spontaneous flammability during pellet storage: Masayoshi Kimoto et al., Report from the Central Research Institute of Electric Power Industry: M08022'' states that when storing large quantities of pellets outdoors in piles, the following precautions should be taken: It has been reported that such problems occur.
(1) When the moisture concentration of the pellets increases, fermentation heat is generated by microorganisms, and the fermentation heat is stored in large quantities of stored pellets, which further progresses natural oxidation and generates heat, eventually causing the pellets to spontaneously ignite. leading to.
(2) According to basic experiments using four types of pellets, judging from the water activity value of the hygroscopic pellets, it was suggested that the pellets may be fermented with a water content exceeding 15 wt%. Furthermore, it was confirmed that heat generation due to natural oxidation occurs when the ambient temperature reaches about 65°C.

On the other hand, as in the present invention, by using a covered container to house the pellets, it is possible to prevent the inflow of moisture from the outside (especially rainwater) and maintain the moisture content of the pellets at the amount when the pellets are housed. Therefore, fermentation and heat generation of pellets can be suppressed.

The bulk density of the shaped pellets is preferably between 0.6 and 0.8 tons/m ³ . This is because even if a 20-foot container is fully loaded with pellets having such a bulk density, the weight is such that a vehicle carrying the pellets can run on public roads in Japan.

On the other hand, if the bulk density of the pellets is less than 0.6 ton/ ^m3 , the calorific value per unit weight is small, so a large volume of pellets is required to be used as fuel, and therefore the number of containers required is This also increases transportation efficiency and handling efficiency.

On the other hand, if the bulk density of the pellets exceeds 0.8 ton/m ³ , if a 20-foot container is fully loaded with pellets, there is a risk that the weight of the vehicle carrying the pellets will exceed that required for driving on public roads in Japan.

Note that the dimensions of the pellets are not particularly limited, but are usually cylindrical with a diameter of 6 to 12 mm and a length of 3 to 70 mm.

FIG. 1 shows an example of a covered container that accommodates pellets. In FIG. 1, a covered container 1 has a rectangular parallelepiped shape, and a roof portion 2 thereof is provided with two hatches 3a and 3b that can be opened and closed. The covered container 1 can be loaded with pellets by opening the hatches 3a and 3b, and can accommodate and store the pellets inside by closing the hatches 3a and 3b. can. A door 4 is provided at the left end (one end surface in the longitudinal direction) of the covered container 1, and by opening the door 4, the pellets in the covered container 1 can be discharged to the outside. That is, the door 4 can function as a means for discharging pellets from the covered container 1. Note that the dispensing opening in the covered container 1 may be opened vertically or double-sided, or may have another dispensing shape.

The covered container 1 has a size that can be loaded onto a vehicle that can run on public roads, and its maximum length is 17 to 21 feet (about 5.18 to about 6.4 m). Container standards come in maximum lengths of 8 feet, 20 feet, and 40 feet, but 8 feet is too small to carry large amounts of pellets, and 40 feet requires special permission to transport by road. The present invention assumes that a covered container with a size of 20 feet (approximately 6.1 m) is used.

In the present invention, the weight of a covered container containing pellets in 60% or more of its capacity is 29 tons or less, and the total weight of a vehicle equipped with the covered container containing pellets in 60% or more of its capacity. is less than 44 tons. Note that the accommodating volume is the average height of pellets inside the covered container 1, and if the average pellet height is 60% of the internal height of the covered container 1, the accommodating volume is 60%.

The weight of a covered container that contains pellets in 60% or more of its storage capacity exceeds 29 tons, or the weight of a vehicle equipped with the covered container that contains pellets in 60% or more of its storage capacity exceeds 44 tons. Therefore, there is a risk that the weight will exceed the weight that can comply with domestic road-related laws and regulations. That is, with such a large weight, there will be a large number of traffic restricted sections, and the storage capacity of the container cannot be fully utilized, especially when the bulk density of the pellets is high.

Next, a method for storing and transporting pellets according to this embodiment will be specifically described. FIG. 2 is a schematic diagram showing a method for storing and transporting pellets by mounting the covered container 1 described above on a trailer 22 connected to a vehicle 21.

In FIG. 2A, a hopper 11 is placed in a port facility, and a cyclone 12 is attached to the hopper 11 to collect dust using centrifugal force. The number of cyclones provided in the hopper 11 can be appropriately set depending on the amount of pellets and convenience of handling, and may be one or two, or three or more. A vehicle 21 to which a trailer 22 carrying a covered container 1 is connected is parked below the hopper 11. In this case, the hatches 3a and 3b of the roof 2 of the covered container 1 are located directly below the outlet of the hopper 11.

To load pellets into the hopper 11, after the pellets are unloaded into the hopper 11 from a ship (not shown), the discharge port of the hopper 11 is opened, and the hatch 3a of the roof 2 of the covered container 1 is opened. This is done by loading the containers in bulk into the covered container 1 from 3b. Note that dust from wood and plant pellets has a complex shape and a large surface area, so it may clog bag filters. In addition, the dust accumulated on the filter cloth may become charged and cause a fire. Therefore, collection using a cyclone is suitable.

In this way, in this embodiment, pellets unloaded from a ship can be directly stored in the covered container 1, and thereafter, the pellets are stored in the covered container 1 throughout all the storage and transportation processes until they are discharged from the covered container 1 at the consumption site. 1, the handling process can be reduced, thereby reducing the amount of dust generated.

The pellets loaded into the covered container 1 loaded on the trailer 22 are transported to a storage location as shown in FIG. 2(b) by the traveling of the vehicle 21 connecting the trailer 22, and are unloaded there. Stored. Alternatively, as shown in FIG. 2(c), the product is directly transported to a consumption facility without being stored, and then discharged from the covered container 1 to the outside.

In this case, the covered container 1 is of a size that can be loaded onto a vehicle that can be driven on public roads, such as the vehicle 21 connected to the trailer 22, so unlike conventional large containers, the contained pellets can be divided into small pieces. The container can be transported by the vehicle 21 while being loaded onto the trailer 22 without having to be transferred to another small container. Therefore, pellet handling efficiency can be significantly improved.

As shown in FIG. 2(b), when the covered container 1 is transported to a storage location, stacked there, and stored, the covered container 1 has a size that can be loaded on a vehicle that can run on public roads. The amount of pellets accommodated is small, so even if stored for a long period of time, the amount of heat stored in the pellets will not increase significantly. In addition, by storing in the covered container 1, rainwater can be prevented from entering and the moisture content can be kept below a certain level even during long-term storage, so fermentation is suppressed.

Furthermore, since it is sufficient to simply store the covered container 1 containing the pellets as it is, no special storage equipment is required, and storage costs can be suppressed.
Generally, it is assumed that dedicated storage equipment is used to store bulk items, and even if they are stored in containers, they are required to be stored for as short a time as possible. On the other hand, pellets are desired to be stored outdoors for a long period of time, but in this embodiment, the covered container 1 directly serves as a dedicated storage facility, and it is possible to store the pellets outdoors for a long period of time, for example, for as long as three months.

In order to demonstrate the above effects, the following storage test was conducted.
[Storage test]
Pellets were stored in the covered container shown in FIG. 1, and tests were conducted to see how the physical properties and properties of the pellets changed during that time. Note that the pellets used in this test were wood pellets.
Domestic softwood pellets (diameter 6 mm, manufactured by Meiken Kogyo Co., Ltd.) were used as the wood pellets, and 20 tons of them were placed in a covered container 1 (length 6058 mm, width 2438 mm, height 2896 mm) shown in Figure 1. The covered container 1 was stored outdoors with the hatches 3a and 3b on the roof 2 closed.

The normal storage period for wood pellets is about two months, but in this test, the storage period was about five months (March to August), and the characteristics and properties of the softwood pellets were analyzed and measured for each number of days that elapsed during that period. The items to be analyzed and measured are moisture content, bulk density, mechanical strength (DU), pulverization rate, solid temperature, oxygen concentration inside the covered container, and rainfall amount. In addition, the bulk density was measured for both the coarse part and the dense part.
In addition, the presence or absence of dew condensation inside the covered container and the presence or absence of rainwater leaking into the covered container were also visually observed.
Among the analysis and measurement items, the details of mechanical strength (DU) and powdering rate are as follows.

[Mechanical strength DU]
It was calculated based on the following formula in accordance with the American Ministry of Agriculture and Industry standard AS AE S 269.4 and the German industrial standard DIN ENb 15210-1.
DU=(m1/m0)×100
In the formula, m0 is the weight of the sample before the rotation process, and m1 is the weight of the sample on the rack after the rotation process. A plate sieve with a circular hole diameter of 3.15 mm was used as the salmon.

[Powdering rate]
A sample A kg was sieved through a 3.35 mm sieve, the weight B kg on the sieve was measured, and the pulverization rate was calculated using the following formula.
Powdering rate (%) = (1-B/A) x 100

The results of the above measurements are shown in Table 1 below.
Furthermore, as a result of observing the inside of the covered container, no dew condensation or rainwater leakage was observed for any number of days that had passed.

The following can be seen from Table 1 above.
1. Although there was a cumulative rainfall of about 1,000 mm during the storage period of about 5 months, there was almost no change over time in any of the moisture content, bulk density, mechanical strength (DU), and pulverization rate. The numbers were within the margin of error.
2. All solid temperatures were within the normal temperature range, and no abnormally high temperatures were observed.
3. The oxygen concentration inside the covered container was at the same level as the atmosphere (21%), and there was no evidence that anaerobic fermentation had occurred.
As described above, the covered container 1 according to the present embodiment can be stored outdoors for a long period of about 5 months.

The transportation from Figure 2(a) to Figure 2(c) and from Figure 2(b) to Figure 2(c), that is, transportation to consumption facilities such as factories and power plants, takes a long time. Even if the pellets are transported from FIG. 2(a) to FIG. 2(b), the amount of pellets stored in the covered container 1 of a predetermined size is small, so the amount of heat accumulated during transport can be suppressed. Can be done. Moreover, since it is housed in the covered container 1, the moisture content can be kept below a certain level, and fermentation is suppressed.

After the covered container 1 is transported to a pellet consumption facility, as shown in FIG. 2(c), the pellets are discharged from the covered container 1 to the interior of the consumption facility, where they are stored in a pile. The pellets are removed from the covered container 1 by opening the door 4 of the covered container 1 shown in FIG. That is, by driving the trailer 21 and lifting the side end of the covered container 1, the covered container 1 is tilted diagonally, and the pellets housed inside are swept out by its own weight from the left opening where the door 4 is opened. They are taken out, piled up, and stored away. According to the tests conducted by the present inventors, the pellets were removed smoothly and completed in about 15 minutes.

Since the pile storage is carried out indoors, there is no increase in moisture content due to rainwater intrusion, and since the amount of pellets stored in piles is not that large and the period of pile storage is short, there is no rise in temperature due to heat accumulation. Furthermore, no hydrogen gas is generated. Therefore, spontaneous combustion of the pellets does not occur. In addition, it may be stored for a certain period of time while being accommodated in the covered container 1 outdoors of the consumption facility.

The pellets stored in piles inside a consumption facility are then consumed as fuel, but may be subjected to low-temperature carbonization treatment before being used as fuel. Low-temperature carbonization treatment is a technique in which carbonization is performed at a lower temperature of about 200 to 400°C, unlike conventional carbonization treatment at temperatures of 600°C or higher. This increases the calorific value and increases the added value as a fuel.

According to the method for storing and transporting pellets according to the embodiment of the present invention described above, a predetermined amount of pellets having a predetermined bulk density are stored in a covered container of a predetermined size and then stored and transported. can be maintained below a predetermined value, and spontaneous combustion of pellets can be suppressed. Furthermore, since the method is to store and transport the product while it is housed in a covered container, transportation efficiency and handling efficiency can be improved.

Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the range described in the embodiments described above. Various changes or improvements can be made to each of the above embodiments.

For example, in the embodiment described above, the covered container 1 was described as having two hatches 3a and 3b on the roof 2, but the container is not limited to this, and can accommodate and store pellets, and Various types of containers can be used as long as they have a size that can be loaded onto a vehicle that can run on them.

Further, in the above-described embodiment, the vehicle on which the covered container 1 is loaded is described as a vehicle to which a trailer is connected, but the vehicle is not limited to this, and is capable of transporting a covered container and can run on public roads. As long as it is a vehicle, it is possible to employ various vehicles.

1...Covered container 2...Roof part 3a, 3b...Hatch 4...Door 11...Hopper 12...Cyclone 21...Vehicle 22...Trailer

Claims (5)

A pellet storage and transportation method in which pellets are stored and transported in bulk in a covered container, the method comprising:
The pellets are pellets made by drying and molding woody or herbaceous biomass, and have a bulk density of 0.6 ton/m ³ to 0.8 ton/m ³ ,
The container has a maximum length of 20 feet and has a hatch in the roof;
The pellets are stored and transported in the container,
When the pellets are accommodated in 60% or more of the capacity of the container, the total weight of the container is 29 tons or less, and the pellets are accommodated in 60% or more of the capacity of the container. When transported by vehicle, the total weight of the vehicle is 44 tons or less,
The moisture content of the pellet is 15 wt% or less,
When storing the pellets, the container is placed outdoors;
20 tons of wood pellets were placed in the container, stored outdoors with the roof hatch closed, and after 148 days, the sample A kg was sieved through a 3.35 mm sieve and the weight B kg on the sieve was measured. A method for storing and transporting pellets, characterized in that the powdering rate calculated by the formula (pulverizing rate (%) = (1-B/A) x 100) is 4.0% or less. In the method for storing and transporting pellets according to claim 1,
A method for storing and transporting pellets, characterized in that the moisture content of the pellets is 10 wt% or less. In the method for storing and transporting pellets according to claim 1 or 2,
a hopper provided above the container for supplying the pellets in bulk to the container;
A method for storing and transporting pellets , characterized in that the pellets are transported to a consumption area while being accommodated in the container . In the method for storing and transporting pellets according to claim 3 ,
A method for storing and transporting pellets, wherein the hopper is provided at a port, and the pellets unloaded from a ship are directly stored in the container . In the method for storing and transporting pellets according to claim 3 or 4,
A method for storing and transporting pellets , wherein the hopper includes a cyclone that collects dust from the pellets .

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