JP3093147B2 - How to prevent smokeless combustion of cereal powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for preventing smokeless combustion of cereal powder.

[0002]

2. Description of the Related Art There are various factors in a powder fire occurring in a powder manufacturing process or the like, and the cause of ignition varies depending on the type of powder and the like, and it is difficult to specify the cause of the powder fire. Therefore, in order to prevent the occurrence of powder fire, the powder manufacturing process is constantly monitored manually, the air in the powder storage silo or the crusher is replaced with an inert gas, or the entire powder manufacturing process is Methods such as replacing air with an inert gas have been studied.

[0003]

However, it is not efficient to constantly monitor the process manually because many monitoring personnel are required, and it is not efficient in a powder storage silo, in a pulverizer, or in powder production. The method of replacing the air in the entire process with an inert gas has a problem that it is not economical because a large amount of the inert gas is required.

[0004] From such a viewpoint, in the case of the coal pulverizing step, the concentration of carbon monoxide and oxygen in the pulverizing apparatus is detected, and the inert gas is supplied to the pulverizing apparatus so that these concentrations become a certain value or less. Various methods have been proposed to reduce the amount of inert gas used by adopting a method such as supply of nitrogen (see, for example, Japanese Patent Publication No. 1-28613, Japanese Unexamined Patent Publication No.
29759, JP-A-6-246182, JP-A-7-
112140). On the other hand, in the case of cereal powder, effective measures for preventing fire are hardly taken at present.

[0005] An important point as a measure for preventing the occurrence of a powder fire is a measure against the powder concentration which causes a dust explosion, a measure against the ignition temperature of the powder, a measure against the electrostatic charging of the powder as the ignition energy of the powder, It is considered to be a measure against oxygen concentration that promotes combustion.

However, in the case of cereal powder, the concentration of the powder is sufficiently high in places where fires have conventionally occurred frequently in the cereal powder production process, and the concentration is not such that dust explosion is a problem. However, the above measures are not effective. Also, in the normal case where the cereal is pulverized at room temperature, the above measures are not effective because the cereal powder is not heated above the ignition temperature.

[0007] On the other hand, the amount of electrostatic charge on the powder in the grain powder production process is greatest when the grain powder is being conveyed by a conveyor, and particularly when the grain powder is conveyed by a screw conveyor, the static electricity is easily charged. Also, in the primary pulverized product in the grain powder manufacturing process, metal pieces and the like originally mixed in the grain raw material to be subjected to the pulverization may remain as they are, and the grain powder is conveyed during the transportation of the grain powder. It is conceivable that the charged electrostatic charge moves to a metal piece or the like, and the metal piece mixed during the transportation of the grain powder or the like approaches the metal casing or the like of the transport device and discharges, thereby igniting the grain powder. In addition, the burning method of ignited grain powder is smokeless combustion, in which the burning rate is considerably slower than the combustion with normal flame, and the packing density is such that an appropriate space is formed between the powders in order to spread the combustion. And sufficient oxygen contained in the space. Therefore, in order to prevent the ignition of the grain powder, the above measures are considered to be effective.

The inventors of the present invention have conducted intensive studies to find an effective method for preventing the fire of cereal powder, and as a result, the residence time of the cereal powder and the packing density of the cereal powder are low. Rather than examining fire prevention measures in the grain crusher, which is considered to be unlikely to occur, if there is a possibility of ignition due to electrostatic charge on the grain powder and a condition to continue burning of the ignited powder It was concluded that possible fire prevention measures in the transport equipment were important.

[0009] The present invention has been made based on the above-mentioned findings, and the use of the smallest possible amount of inert gas allows
It is an object of the present invention to provide a method for effectively preventing fire of grain powder.

[0010]

Means for Solving the Problems The grain powder of the present invention is
The smokeless combustion fire prevention method constantly monitors the concentration of carbon dioxide in the atmosphere in a transport device for transporting cereal powder that burns smokelessly by ignition, and controls the transport generated by burning the cereal powder. An inert gas other than carbon dioxide is supplied into the transfer device according to the concentration of carbon dioxide in the atmosphere in the transfer device.

In the method of the present invention, an inert gas supply port is provided at an upper portion of the grain powder conveying device, and at least one of the supply ports is provided near the grain powder supply port to the conveying device and in the grain powder conveying direction. On the other hand, it is preferable to provide an inert gas provided on the upstream side. In addition, the inert gas is supplied to the second and subsequent transporting devices from which the grain powder has been transported from the first transporting device connected to the grain powder classifying means, and from the second and subsequent transporting devices. By supplying all or a part of the discharged gas containing the inert gas to the first-stage transport device, it is possible to efficiently prevent fire of the grain powder.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the method of the present invention, as a conveying device for conveying grain powder, a belt conveyor, a bucket conveyor or the like which is an endless conveying device, a vibrating conveyor, a vibrating elevator or a rotary trough which is a vibrating trough conveying device. A screw conveyor, a tube conveyor, and the like, which are transfer devices, may be used. FIG. 1 shows a case of a screw conveyor as an example of a grain powder conveying device. The grain powder conveying device 1 shown in FIG.
The casing 2 is provided with a grain powder supply port 4 for supplying grain powder to the transport device 1, a grain powder outlet 5, and an inert gas supply port 6.

As the inert gas, nitrogen, carbon dioxide,
Examples include argon and helium, and nitrogen and carbon dioxide are preferred. The inert gas can be supplied from, for example, a liquefied nitrogen container or a nitrogen gas cylinder.
(Pressure fluctuation adsorption method), an inert gas can also be supplied from a membrane separation device or the like, and there is no particular limitation on a means for supplying the inert gas.

According to the method of the present invention, carbon dioxide
Conveyor generated by burning grain powder with concentration meter
In accordance with an increase in the concentration of carbon dioxide in
Activated gas should be supplied and the carbon dioxide concentration should be constant
Stop supplying the inert gas when it decreases below
It is to be. Non-dispersive as a carbon dioxide concentration meter
A densitometer such as an infrared type or an infrared absorption type is used.
In this method, inert gas other than carbon dioxide is used as inert gas
It is necessary to use gas. The burning of cereal powder
As mentioned above, because of the smokeless combustion with a slow burning rate,
Even if inert gas is supplied after the combustion of
The fire can be extinguished in a short time, and there is no fear that the combustion will spread.

When the transfer device 1 is a screw conveyor,
Since the grain powder is sent from the bottom of the casing 2 by the screw 3, if the inert gas supply port 6 is provided on the lower surface side of the casing 2, the grain powder is blown up to lower the transport efficiency. For this reason, when the transport device 1 is a screw conveyor, it is particularly preferable to provide the inert gas supply port 6 on the upper surface side of the housing 2. The inert gas supply port 6 may be provided at one place or at a plurality of places.
One is provided near the grain powder supply port 4 and on the upstream side with respect to the grain powder transport direction, and as shown in FIG. 2, the inert gas is added to the grain powder while the grain powder supplied from the supply port 4 falls. When supplied, the oxygen present between the grain powders can be efficiently replaced with an inert gas by using a smaller amount of the inert gas.

[0016]

In the above-described method of supplying an inert gas in accordance with an increase in the concentration of carbon dioxide in the transport device 1, the above method is used when the carbon dioxide concentration in the transport device 1 exceeds a certain value or when the carbon dioxide concentration rises rapidly. Supply an inert gas. When the supply of the inert gas is set to be started when the carbon dioxide concentration exceeds a certain value, the carbon dioxide concentration at which the supply of the inert gas is started is usually 0.1% by volume of the carbon dioxide concentration in the atmosphere. It is preferably 0.3%, which is a time when the composition in the atmosphere is increased by 0.02%, and is therefore preferably set to 0.05%. In addition, when the supply of the inert gas is set to be performed when a rapid rise in the carbon dioxide concentration is detected, the carbon dioxide concentration of 0.02% or more is set within the time that the cereal powder stays in the transport device 1. The time may be set to the time when the rise is detected, but is preferably set to 0.01% / 10 seconds or more in consideration of the response time of the detection device.

When producing grain powder, the grain powder pulverized in the pulverizer is classified into product powder and fine powder in a cyclone 7 as shown in FIG. 3, and the fine powder is removed by a bag filter. The product powder classified in the cyclone 7 is transferred to a product powder storage tank by a transfer device, or transferred to a step of filling the product powder. Generally, the product powder is transported to a storage tank and a filling step via a plurality of transport devices, but usually, a first-stage transport device 1a has a plurality of powder inlets connected to a plurality of cyclones 7, respectively. When the grain powder is supplied from each cyclone 7 into the transport device 1a, a large amount of air is also supplied into the transport device 1a at the same time. For this reason, a large amount of inert gas is required to replace oxygen in the first-stage transfer device 1a with an inert gas. On the other hand, the second-stage transport device 1b has only one inlet for receiving the grain powder from the previous-stage transport device. The oxygen concentration in the atmosphere in the first transfer device 1b can be lower than in the first transfer device 1a. Therefore, when an inert gas is supplied into the second-stage transfer device 1b to replace oxygen in the second-stage transfer device 1b with the inert gas,
The amount of inert gas used can be significantly reduced.
In the case where it is necessary to install the third and subsequent transfer devices due to problems such as the arrangement of transfer devices and equipment in the factory, and the residence time of the powder in the second transfer device cannot be secured for 1 minute or more. In this case, it is necessary to supply an inert gas also to the third and subsequent transfer devices so that the grain powder is exposed to an inert gas atmosphere for 1 minute or more.

In addition, all or a part of the gas containing the inert gas discharged from the second-stage transfer device 1b (if the inert gas is also supplied to the third- and subsequent-stage transfer devices, If necessary, all or a part of the gas containing the inert gas discharged from the third and subsequent transport devices) is supplied to the first transport device 1a. The oxygen concentration brought from the transfer device 1a to the transfer device 1b after the second stage can be greatly reduced, and the amount of inert gas used can be further reduced. In addition, all or a part of the gas containing the inert gas discharged from the third and subsequent transfer units is supplied to the powder separation unit of the cyclone 7 via the first-stage transfer unit 1a. It can be supplied directly to the powder separation section of the cyclone 7 from a transfer device after the eye, or can be discharged into the air. In the case where the inert gas is also supplied to the third and subsequent transfer devices, the inert gas may be supplied to the third and subsequent transfer devices via the second transfer device.
It may be supplied independently to the third and subsequent transfer devices.

In FIG. 3, reference numeral 8 denotes an inert gas supply facility, 9 denotes a gas flow meter, 10 denotes an oxygen concentration meter, 11 denotes a carbon dioxide concentration meter, and 12 denotes a filter. Reference numeral 13 denotes a control unit, 14 denotes a control valve, and 15 denotes a pressure reducing valve.

In the present invention, the conveying device 1 for supplying the inert gas is not necessarily a conveying device connected to the cereal crushing process, and the cereal powder is transferred from the storage tank storing the cereal powder to the powder filling process and the like. It may be a transfer device for transferring. Further, in the present invention, the above-described various devices are used as the transporting device 1. However, even if a screw conveyor in which static electricity is easily generated during transporting is used, according to the method of the present invention, the fire spread of the grain powder due to static electricity can be effectively prevented. Can be prevented.

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 A first-stage screw conveyor (a conveyor having a structure in which the periphery of a screw is surrounded by a housing; a total length of about 5 m) for collecting product powders carried out from six cyclones, and a product A second-stage screw conveyor for transporting the powder to the next step (similar to the first-stage screw conveyor, having a structure in which the periphery of the screw is surrounded by a housing. Total length is about 6)
m), and the product powder discharged from the cyclone was conveyed via a first-stage conveyor and a second-stage conveyor. 4 at the top of the housing of the second stage screw conveyor
Where an inert gas supply port is provided, one of which is provided upstream of the product powder supply direction to the second stage screw conveyor with respect to the product powder conveying direction, and the second stage screw is provided. Nitrogen gas is supplied from each inert gas supply port into the conveyor, and the nitrogen gas pressure in the conveyor is increased by 150.
mmAq (oxygen concentration: 5%), and the exhaust from the second stage conveyor was discharged to the atmosphere via the first stage conveyor.

In the first stage conveyor, the residence time of the product powder is the longest one due to the difference in cyclone position.
The operation of the second stage conveyor was performed such that the residence time of the product powder was 2 minutes. The maximum powder carrying capacity of this device is 300
During a load operation at a load of kg / hour, one of the connection ports of the first stage with the cyclone, which is closest to the conveyor outlet, is removed, and a simulated incense stick (length 20mm), ignited cotton (about 10m per side)
m) and ignited charcoal (a cube of about 10 mm on a side) were put into the product powder, and the state of fire spread was examined at the product powder outlet of the second stage conveyor. As a result, complete extinguishing was observed regardless of the type of fire added,
After that, it did not reignite even if left in the atmosphere.

[0025]

As described above, the method of the present invention utilizes the fact that the combustion of the cereal powder is smokeless combustion, monitors the carbon dioxide in the conveying device, and detects the concentration of carbon dioxide generated by the combustion of the cereal powder. location but or exceeds a predetermined value, the inert gas when the rapid increase was observed from the is supplied to the transfer device, the inside greater pulverizer capacity with an inert gas
Or replacing the entire powder manufacturing process with an inert gas
Uses much less inert gas than the law
Only a small amount of inert gas is used
It is possible to prevent fire of material powder .

In addition, an inert gas supply port for supplying an inert gas into the carrier is provided at an upper portion of the carrier, and at least one of the inert gas supply ports is provided near a grain powder supply port to the carrier. In addition, when the inert gas is supplied by being provided upstream with respect to the grain powder conveying direction, oxygen present between the grain powder can be effectively replaced with the inert gas to prevent fire. it can. Further, when the grain powder is transported from the first-stage transport device connected to the grain powder classification means sequentially through the second-stage or subsequent transport devices, the second-stage or as needed. The inert gas is also supplied to the third-stage and subsequent transfer devices, and all or a part of the gas containing the inert gas discharged from the second-stage or the second and subsequent transfer devices is removed from the third-stage transfer device. When the oxygen is supplied to the first-stage transport device, oxygen in the transport device can be effectively replaced with an inert gas, and an excellent effect of preventing fire of the grain powder is exhibited.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the method of the present invention, and is a partially cutaway schematic view of a transfer device.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 shows another embodiment of the present invention, and is a process schematic diagram of a grain powder production process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transport apparatus 1a 1st-stage transport apparatus 1b 2nd-stage transport apparatus 6 Inert gas supply port 7 Cyclone 9 Inert gas supply equipment 10 Oxygen concentration meter 11 Carbon dioxide concentration meter

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasushi Fukuda 2-690-133, Saiwai-cho, Saiwai-ku, Kawasaki-shi, Kanagawa (72) Inventor Kazunobu Shibuya 1-2-5-5 Izumi, Suginami-ku, Tokyo (56) References Special Kaihei 6-320024 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A62C 2/00-39/00 B02B 5/02 B02C 11/06

Claims (3)

(57) [Claims] 1. A method for carrying cereal powder that burns smokeless by ignition.
The concentration of carbon dioxide in the atmosphere in the transfer device for
Time and monitor the atmosphere in the conveyor caused by the combustion of the grain powder.
Depending on the concentration of carbon dioxide in the atmosphere,
Grains characterized by supplying an inert gas other than carbon
How to prevent smokeless burning of powder. 2. A method for supplying an inert gas into a carrier.
Is provided at the upper part of the transfer device, and
At least one of the grain powder supply ports to the conveyor
In the upstream direction with respect to the grain powder transport direction.
2. The grain according to claim 1, wherein an active gas is supplied.
Method of smokeless combustion fire of material powder. 3. A first stage connected to a means for classifying cereal powder.
From the second stage after the grain powder has been transported from the transport device
Supply the inert gas to the feeder and
Total gas including inert gas discharged from
Supplying a part or a part to the first-stage transfer device
Smokeless combustion of cereal powder according to claim 1 or 2,
Fire prevention method.