JP2005145512A - Method and apparatus for storing refuse derived solid fuel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practical method capable of storing refused derived solid fuel with no danger of firing and explosion. <P>SOLUTION: Nitrogen separated from air by a pressure changing adsorption separation method is continuously introduced into a storage tank storing the refuse derived solid fuel. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a waste solidified fuel storage method and storage device. More specifically, the present invention relates to a waste solidified fuel storage method and storage device, characterized in that nitrogen separated from air by a pressure fluctuation adsorption separation method is introduced into a solidified fuel storage tank.

  Conventionally, a method and apparatus for producing and using a combustible waste that has been solidified for reuse as a fuel resource, that is, a solid waste fuel, is well known. Due to the need to reduce gas emissions, power generation using solid waste fuel is being implemented in various locations.

  For example, Non-Patent Document 1 describes a method for producing solid waste fuel and an outline of a power generation business. In this document, when waste is used as a solidified fuel for power generation, etc., non-combustible materials are sorted and removed from waste such as waste, pulverized, dried, mixed with lime, molded, and solidified fuel. It is described to do.

  Non-Patent Document 2 describes an interim report of a solid fuel power plant accident. This document describes an accident occurrence mechanism that is estimated as an overview of accidents caused by heat generation, ignition, etc. in a solid waste fuel storage tank. In addition, the temperature and gas concentration in the tank are measured to prevent fires and explosions in existing equipment, and sprinkler watering and inert gas sealing are included as fire extinguishing methods in the event of a fire. It is stated that there are facilities in preparation. Furthermore, Non-Patent Document 3 describes a heat generation problem of solid waste fuel in another facility.

Fukuyama City Environmental Homepage, “Summary of Fukuyama Recycling (RDF) Power Generation Project”, [online], [October 27, 2003 search], Internet <URL: http: // www. city. fukuyama. hiroshima. jp / kankyohozen / kankyo / top010417. html> Mie Prefecture Circulation System Promotion Team, “Garbage Solid Fuel Power Plant Accident Investigation Interim Report”, [online], September 16, 2003, [October 27, 2003 Search], Internet <URL: http: // / Www. eco. pref. mie. jp / kouhou / kyou / 200309161640401000 /> Sankei Shimbun Sankei Web article, “Garbage solid fuel is abnormally heated, and to the full export Ishikawa's power generation facility”, [online], October 16, 2003 [November 10, 2003 search], Internet <URL: http: // www. sankei. co. jp / news / 031016 / 1016sha093. htm>

  When waste solidified fuel is used for power generation or the like, it is necessary to carry out the produced solid waste fuel and store it in a storage tank until it is used. However, in recent years, in facilities that produce and use solid waste fuel, in order to prevent fires and explosions in storage tanks due to abnormal heating of solid waste fuel in storage tanks and accidents caused by spontaneous fires. Measures are urgently needed.

  Initially, less attention was given to the risk of heat generation and spontaneous ignition during storage of solid waste fuel. Of course, in solid waste fuel utilization facilities that are actually in operation, measures are taken against fires and explosions in storage tanks that store solid waste fuel. As described in Non-Patent Document 2, as a method of detecting signs of fire and explosion, temperature monitoring in the storage tank by a temperature sensor, measurement of carbon monoxide and methane concentration by a portable measuring instrument, etc. are adopted. As a fire extinguishing method in the event of a fire, sprinkler spraying and inert gas sealing are employed. However, as described in Non-Patent Document 3, even if a trouble such as a fire in a storage tank actually occurs, it cannot be said that these were sufficiently effective.

  When trying to detect and prevent signs of fire or explosion by measuring the temperature and gas concentration in the storage tank, it reaches a dangerous state from the results of regular measurements such as changes in temperature and gas concentration being relatively slow and constant. If the time is predictable, it is possible to take effective measures in advance. However, the temperature rise of solidified fuel in the storage tank is difficult to predict because it involves both microbial reactions and chemical oxidation reactions, and is moderate at low temperatures but accelerated rapidly when the temperature rises to some extent There are many. Moreover, it is generally difficult to predict the state of heat generation because it greatly fluctuates depending on the composition of raw material waste. Therefore, even when measuring temperature and gas concentration, countermeasures such as fire extinguishing are often not in time due to rapid temperature rise, and in order to prevent fires and explosions, there is always no risk of fire or explosion. It is necessary to take measures to keep it.

  On the other hand, sprinklers used as a fire extinguishing method are effective as a temporary fire extinguishing method or an emergency heat removal method, but cannot always be carried out to prevent danger. The reason is that if solid waste fuel always contains an amount of water that can sufficiently prevent ignition, it will cause problems when used as fuel, and if the amount of included water is insufficient, ignition will occur. This is because not only can it not be sufficiently prevented, but also the reaction by microorganisms and the accompanying fever may be accelerated.

  On the other hand, there is no problem such as watering in the filling of the inert gas, so it is an effective measure if it can always be performed. However, in this case, a method for supplying an inert gas is a big problem in practical use. A typical example of the inert gas used is nitrogen, which is generally supplied from a cylinder or separated and stored as liquid nitrogen. According to these methods, the inert gas can be temporarily sealed in a small sealed tank, and it can be said that the method can be used practically when temporarily used.

  However, in the equipment for solidifying and utilizing a large amount of waste continuously, the storage tank for storing the solid waste fuel becomes huge, and the solid waste fuel inlet and discharge port of the storage tank are always or frequently used. Therefore, it is necessary to continuously supply a large amount of nitrogen in order to always maintain a nitrogen atmosphere. In order to supply such a large amount of nitrogen with a cylinder or liquefied nitrogen, it is necessary to install a large number of cylinders and a huge liquefied nitrogen facility corresponding to this, and costs, labor of loading cylinders and maintaining liquefaction equipment It is not realistic in terms of. For this reason, nitrogen is not always introduced to prevent fire during operation.

  Other countermeasures implemented for fire protection in general storage tanks include the use of a sealed / explosion-proof structure and cooling from the outside of the tank. However, if there is a sufficient amount of oxygen in the space in a large storage tank, heat generation can occur even if it is sealed, and in the case of a storage tank where solid waste fuel needs to be received and discharged at all times, It is difficult to seal itself. Further, when the volume of the storage tank is large, the waste solidified fuel having low thermal conductivity works as a heat insulating material, so that it is difficult to keep the temperature in the storage tank in a sufficiently safe range only by cooling from the outside.

  Accordingly, an object of the present invention is to provide a practical waste solidified fuel storage method and storage device that can store the solidified fuel without risk of fire and explosion in view of the above situation.

  The inventors of the present invention have intensively studied to achieve the above object, and it is preferable to introduce nitrogen as a method for preventing ignition without impairing the characteristics of the solid waste fuel. As a result of paying attention to the fact that the purity of the gas does not have to be ultra-high purity, it has been found that the above object can be achieved by introducing nitrogen separated from the air by the pressure fluctuation adsorption separation method into a storage tank for storing solid waste fuel. The present invention has been reached.

  That is, the present invention is a method for storing waste solidified fuel, characterized in that nitrogen separated from the air by a pressure fluctuation adsorption separation method is introduced into a storage tank for storing the solidified fuel. Another invention of the present invention is a waste solidified fuel storage device in which a pressure fluctuation adsorption separation device is connected to a storage tank for storing solid waste fuel via a nitrogen conduit.

  ADVANTAGE OF THE INVENTION According to this invention, the method and storage apparatus which can be practically employ | adopted as a production means and can store waste solidified fuel without the danger of a fire and an explosion can be provided.

  The purpose of introducing nitrogen into a storage tank for storing waste solidified fuel in the present invention is to reduce the oxygen concentration in the storage tank, and the solidified fuel generates heat due to reaction and chemical oxidation by microorganisms and further spontaneously ignites. It is to prevent. It is known that chemical oxidation including reaction and combustion by microorganisms is greatly suppressed when the oxygen concentration in the gas phase of the storage tank decreases. Therefore, what is necessary for this purpose is to reduce the oxygen concentration to a certain level, and it is not necessary to make the amount of oxygen in the storage tank extremely small.

  Furthermore, when nitrogen is continuously supplied to the storage tank and purged, the nitrogen released from the storage tank brings out heat, so that temperature rise due to heat accumulation is suppressed even when fermentation occurs in the storage tank and heat is generated. . Nitrogen is also used as an operating gas for a clogging blaster in a storage tank for storing solid waste fuel.

  A feature of the present invention is that nitrogen separated from air by the pressure fluctuation adsorption separation method is introduced into a storage tank for storing solid waste fuel. The pressure fluctuation adsorption separation method is a method for separating a target gas from a mixed gas by utilizing a difference in selectivity depending on the pressure of adsorption of a gas component to an adsorbent. When nitrogen is separated using raw material gas as air, raw material air is supplied under pressure to an adsorption tower filled with molecular sieve activated carbon as an adsorbent to selectively adsorb oxygen and separate nitrogen as a product. Is.

  The adsorbent on which oxygen has been adsorbed is regenerated by desorbing oxygen by aeration and reducing pressure, and is used repeatedly. Although it is possible to use only one adsorption tower, it is inefficient because it is impossible to supply nitrogen while regenerating the adsorbent, and nitrogen is continuously supplied. In general, two adsorbing towers are used, and one adsorbs the adsorbent by desorption while the other produces nitrogen by adsorption. These are alternately adsorbed and desorbed by setting a timer to produce nitrogen, which is continuously supplied.

  According to the pressure fluctuation adsorption separation method, it is possible to produce high-purity nitrogen of 99.99% or more, but by slightly reducing the purity of the produced nitrogen, the amount of nitrogen that can be produced with the same equipment and power is greatly increased. The running cost required for the production of nitrogen can be greatly reduced. The pressure fluctuation adsorption separation method is advantageous in terms of the production cost of nitrogen, but is more advantageous when the purity of the produced nitrogen does not have to be so high. For example, in a small model, when 99.99% is reduced to 99.9%, or when 99.9% is reduced to 99%, the amount generated in the same apparatus is about 1.5 to 2 times. The medium size is about 1.2 to 1.5 times the same output, and 1.2 to 2 times the same equipment.

  Further, when nitrogen is produced and supplied by the pressure fluctuation adsorption separation method, a mixed gas having an oxygen concentration higher than that of air is generated when the adsorbent is regenerated. There is no problem even if this mixed gas is disposed in the air as it is, but due to the nature of the solid waste fuel and the combustion conditions, a high oxygen concentration gas was used when burning the solid waste fuel. This mixed gas can also be used if it is more advantageous.

  The material, size, or shape of the storage tank for storing the waste solidified fuel is not particularly limited as long as it does not interfere with the storage of the solidified fuel. As the shape of the storage tank, a concrete pit type, silo type (cylindrical tank type) or the like is preferably used. In particular, in the case of a facility that continuously processes a large amount of waste solidified fuel, a silo type storage tank having a waste solidified fuel inlet at the top and a discharge port at the bottom is preferable. Used.

  Nitrogen produced by the pressure fluctuation adsorption separation device is transported by a conduit to a storage tank for storing solid waste fuel. Depending on the structure and usage of the storage tank, nitrogen can be introduced into the storage tank by a method such as introducing the nitrogen outlet of the conduit into the storage tank only when the opening is opened without connecting the conduit to the storage tank. Usually, it is preferable to connect a nitrogen conduit to any part of the storage tank to introduce nitrogen into the storage tank.

  The connection position of the nitrogen conduit to the storage tank is appropriately determined in consideration of the structure of the storage tank. When the opening of the storage tank exists only on one side of the storage tank, a method may be adopted in which a nitrogen conduit is connected in the vicinity of the opening and the inflow of air into the storage tank is prevented by the nitrogen flow from the nitrogen conduit to the opening. When the storage tank is a silo type and there are openings in the upper and lower parts, it is preferable that the connection position of the nitrogen conduit is the middle part of the storage tank. The intermediate part here refers to a position of 10% to 80%, preferably a position of 20 to 60% from the bottom with respect to the height of the effective storage part of the storage tank. By using the nitrogen conduit as the storage tank intermediate part in this way, when nitrogen is released from the upper and lower openings, a nitrogen flow is generated from the storage tank intermediate part upward and downward. Since this nitrogen flow passes through the waste solidified fuel layer in the storage tank, there is an advantage that the entire storage tank is maintained in a good low oxygen state and heat removal effect by the nitrogen flow is also generated.

  The nitrogen conduit may be connected to one place of the storage tank or may be connected to a plurality of positions. When the storage tank is large, it is preferable to connect to a plurality of positions in order to obtain a good circulation state of nitrogen in the storage tank. It is preferable to connect nitrogen conduits to a plurality of locations in the height direction in that the nitrogen flow in the waste solidified fuel layer can be secured even if the storage amount varies. In the case where a plurality of places are installed in the height direction, some of them may be installed other than the middle part, such as connecting a conduit to the lower part of the storage tank so that the effect can be maintained even if the amount of fuel stored is reduced. A flow rate adjustment valve may be installed in each of the plurality of nitrogen conduits, and the nitrogen introduction state may be changed according to the storage state of the solid waste fuel. In order to prevent the nitrogen flow in the silo from being biased, it is more preferable to connect a plurality of nitrogen conduits in the circumferential direction of the storage tank.

  In addition, the nitrogen conduit between the storage tank for storing solid waste fuel and the pressure fluctuation adsorption separation device includes a flow control valve, a distribution pipe for distributing the produced nitrogen to multiple conduits, It is preferable to install an atmospheric discharge pipe or the like used for inspection.

  When nitrogen is introduced, it is necessary to release the gas in the storage tank to the outside so that the inside does not become pressurized, but the method and place for releasing the gas also include the form of the storage tank and the reception of solid waste fuel, What is necessary is just to select suitably according to the payout method. A dedicated exhaust port may be provided for exhaustion. However, if the opening is provided so as to be released to the outside air, nitrogen is released from the opening.

  The introduction of nitrogen into the storage tank does not have to be continuous and constant, and may be performed by an appropriate method according to the apparatus and the operating conditions. When the storage tank can be closed or close to it, nitrogen sufficient to lower the oxygen concentration in the storage tank may be first introduced, and the introduction of nitrogen may be stopped during the sealing. In this case, when the apparatus is released when the solid waste fuel is taken in and out of the storage tank, a method of introducing nitrogen to prevent the intrusion of the outside air only while the apparatus is released may be employed.

  Nitrogen introduced into the storage tank is advantageous in that the higher the purity, the lower the oxygen concentration in the storage tank can be with a small amount of nitrogen. However, if the purity is too high, the equipment for producing nitrogen becomes large and the cost increases. On the other hand, if the purity of nitrogen is too low, it will be difficult to reduce the oxygen concentration in the storage tank to a safe range, and the oxygen concentration may increase due to air from the storage tank or air from the opening before the introduction of nitrogen. Will increase. Since it is said that ordinary fuel will not burn in a gas with an oxygen concentration of 11% or less, the purity of nitrogen introduced into the storage tank is high enough to achieve this oxygen concentration, in other words, oxygen in the introduced nitrogen. The amount is preferably sufficiently lower than 11%. Therefore, the purity of nitrogen introduced into the storage tank in the present invention is preferably 93% or more and 99.9% or less, more preferably 95% or more and 99.5% or less, and further preferably 97% or more and 99% or less.

  In addition, when the solidified fuel is received or discharged continuously or intermittently, nitrogen is continuously introduced when the storage tank has an opening opened to the outside air and is not sealed. It is preferable. The amount of nitrogen introduced may be appropriately determined according to the size of the storage tank, the size and opening / closing status of the opening, the purity of the nitrogen to be introduced, the level of safety required. Also in this case, the nitrogen introduction amount does not need to be constant, and may be varied according to the use state of the storage tank. For example, a method can be employed in which a thermometer is installed in the storage tank and the nitrogen introduction amount is increased or decreased according to the temperature condition, and a gas concentration meter is installed in the storage tank and the nitrogen introduction amount is increased or decreased depending on the gas concentration. In particular, a method of installing an oxygen concentration meter and controlling the amount of nitrogen introduced so that the oxygen concentration becomes a predetermined concentration or less is preferable. Alternatively, it is preferable to adopt a method of determining the amount of nitrogen introduced so that the nitrogen released from the opening has a constant flow rate, if possible, the discharge flow rate is 1 m / second or more at the opening, and the backflow of oxygen from the air can be prevented. . The pressure fluctuation adsorption separation method is an extremely suitable means for efficiently introducing nitrogen as described above.

  The solid waste fuel to be stored is usually a combustible waste from a home or the like as a raw material, which is crushed, sorted, dried and solidified into a solid fuel having a shape that is easy to use. In addition to ordinary household waste, combustible waste such as waste plastic can also be used as a raw material for solidifying fuel. If the shape of the solid waste fuel is too fine, it will cause problems such as scattering with the nitrogen stream and clogging each part of the device. Conversely, if it is too large, it will be difficult to transfer continuously. Usually, a cylindrical shape having a length of 50 to 100 mm and a diameter of 10 to 50 mm is preferably used. Further, the moisture content is preferably 10% or less, and if it is more than this, the amount of heat that can be effectively taken out when used as a fuel tends to decrease and heat generation due to microbial reaction tends to occur.

  Various methods can be adopted for the method of receiving waste solidified fuel into the storage tank and dispensing it from the storage tank depending on the solidification method of waste, the method of using solidified fuel, the amount handled, etc. As a preferred method for solidifying the solid waste and using it for power generation, etc., the waste solidified fuel transported from the waste solidified fuel production facility by a conveyor or the like is continuously fed from the inlet provided at the top of the silo storage tank. Or the method of receiving intermittently and paying out continuously or intermittently from the discharge opening provided in the lowest part of this storage tank is mentioned.

  In carrying out the method according to the present invention, it is necessary to take care not to cause accidents such as suffocation by the nitrogen discharged from the storage tank and from the storage tank, and the storage tank opening through which nitrogen is discharged during operation. It is preferable to implement countermeasures on the facility such as providing a manhole and a peep window with a width of 20 cm or less so that the worker cannot approach the door.

  An example of an embodiment of a method for storing solid waste fuel according to the present invention is shown in FIG. The solid waste fuel produced by the solid waste fuel production apparatus is sent to the receiving conveyor 2 by the conveyor 1, and sequentially from 2 to the storage tank 5 for storing the solid waste fuel by the packet elevator 3 and the input conveyor 4. Sent. The solid waste fuel stored in the storage tank 5 is put on a transport vehicle by a carry-out conveyor 6 and is transported to a power plant or the like. A pressure fluctuation adsorption separation device 7 is installed to prevent heat generation and ignition of the solid waste fuel storage facility. Nitrogen generated in 7 is constantly purged into the storage tank 5 through the conduit 8 and, if necessary, a blaster 10 to prevent clogging. Also used as a working gas.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
A silo-type storage tank having an outer shape with a diameter of 4.8 m and a height of 12 m was used as a storage tank for storing solid waste fuel. The internal storage capacity of the storage tank is 120 m ³ , a solid waste fuel receiving port having a diameter of 50 cm is provided at the upper portion, a discharging port having a diameter of 50 cm is provided at the lower portion, and the lower portion 6 m has a conical shape with the discharging port as a vertex.

Moreover, the product name "Kurasep RK-11" (a nitrogen production capacity of about 35 m ³ / hr having a purity of 99%) manufactured by Kuraray Chemical Co., Ltd. was used as the pressure fluctuation adsorption separation device. From the outlet of the pressure fluctuation adsorption separation apparatus, nitrogen is led out through a 40A pipe, and the height of the storage tank is circled through ring-shaped pipes provided in two middle parts of the silo side wall (6m and 9m from the lower part of the internal storage part). The 15 A installed at four locations at intervals of 90 ° in the circumferential direction and the ring piping were connected by a nitrogen conduit with a valve.

The storage apparatus of the solid waste fuel of this invention is shown.

Explanation of symbols

1 Waste Solidified Fuel Conveyor 2 Waste Solidified Fuel Receiving Conveyor 3 Bucket Elevator 4 Waste Solidified Fuel Input Conveyor 5 Solid Waste Fuel Storage Tank 6 Solid Waste Fuel Carrying Conveyor 7 Pressure Fluctuation Adsorption Separator 8 Nitrogen Conduit 9 Nitrogen atmospheric discharge pipe 10 Blaster 11 Blaster 12 Control valve 13 Control valve 14 Control valve 15 Control valve 16 Control valve 17 Control valve 18 Manhole 19 Transport vehicle 20 Waste solid fuel inlet 21 Waste solid fuel outlet

Claims (6)

  A method for storing solid waste fuel, comprising introducing nitrogen separated from air by a pressure fluctuation adsorption separation method into a storage tank for storing solid waste fuel.   The method for storing solid waste fuel according to claim 1, wherein the purity of the nitrogen is 95% or more and 99.5% or less. The waste solidified fuel storage method according to claim 1 or 2, wherein the nitrogen is continuously introduced into the storage tank.   A method for storing waste solidified fuel in which waste solidified fuel is received into and discharged from a storage tank continuously or intermittently, wherein nitrogen is continuously introduced into the storage tank, and waste The waste solidified fuel storage method according to claim 1, wherein the solidified fuel is discharged from a solid fuel receiving port and / or a discharge port.   A waste solidified fuel storage device in which a pressure fluctuation adsorption separation device is connected to a storage tank for storing solid waste fuel via a nitrogen conduit. 6. The storage tank for storing waste solidified fuel is a storage tank having a waste solidified fuel receiving inlet at an upper portion and a waste solidified fuel discharge port at a lower portion, and a nitrogen conduit is installed at a middle portion of the storage tank. The waste solidified fuel storage device described.

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