JP6261534B2 - Steel plate digestion tank repair method - Google Patents

Description

  The present invention relates to a method for repairing a steel plate digester that generates an digestion gas by anaerobic fermentation of organic waste such as sewage sludge and food waste.

  There are various conventional techniques related to digesters as described in Patent Documents 1 to 3. The prior art described in Patent Document 1 is a technique for efficiently removing deposits deposited on the bottom of a digestion tank to the outside of the tank. The prior art described in Patent Document 2 is a technique for improving the digestion efficiency of organic waste. Moreover, the prior art described in Patent Document 3 is a technique for stably performing anaerobic fermentation treatment of organic waste liquid and sludge having a high solid content concentration.

JP 2014-161813 A JP 2012-236126 A JP 2002-219485 A

  Here, in the digestion tank, there are a digestion tank made of concrete (made of prestressed concrete) and a digestion tank made of steel plate, and the inventors of the present invention pay attention to the digestion tank made of steel plate. The steel plate digestion tank can be reduced in weight compared to the concrete digestion tank, and the foundation work and temporary work can be reduced because the tank body is not buried in the ground. In addition, prestressed concrete cannot be drilled after its formation, but the steel sheet is excellent in workability, so it is easy to provide an inspection port and attach various measuring devices. Steel plate digesters have these advantages.

  Although the steel plate digestion tank has already been evaluated as having a useful life of 20 years or more by applying anticorrosion coating on the inner surface, it is not possible, but a hole is generated in the top plate part due to corrosion etc. It is useful to consider when you do.

  As a repair method when there is a hole in the top plate portion, for example, the following repair method can be considered. Since the digestion tank has a positive pressure due to digestion gas (combustible gas) generated inside, the anaerobic fermentation treatment is completely stopped and repaired from inside the tank. Specifically, after draining the internal sludge and digestion gas, build a temporary scaffold from the inside of the tank body, apply a pad to the hole in the top plate, and re-apply it to prevent the formation of another hole. Paint. However, in this method, the anaerobic fermentation process is completely stopped. Therefore, in a digestion tank without a spare machine, it takes a long time to start up the digestion tank again, which is a serious problem. Also, it is a difficult task to remove the sludge inside and to build a temporary scaffold.

  The present invention has been made in view of the above circumstances, and its purpose is to easily close a holed portion of a steel plate digester without completely stopping the anaerobic fermentation treatment, and to re-hole the hole. It is providing the repair method of the steel plate digestion tank which can suppress generation | occurrence | production of this.

  The present invention is a method of repairing a steel plate digestion tank in which organic waste is subjected to anaerobic fermentation treatment to generate digestion gas. The repair method includes a first step of closing a holed portion of the steel plate digestion tank with a repair material from the outside of the bath, and a second step of applying a fiber reinforced plastic lining on the repair material from the outside of the bath. It is characterized by.

  According to the present invention, since the holed portion of the steel plate digestion tank is repaired from the outside of the tank, it is not necessary to completely stop the anaerobic fermentation treatment, and repair work for closing the hole is easy. Further, the generation of holes again can be suppressed by the fiber reinforced plastic lining.

It is a sectional side view showing an example of a steel plate digestion tank. It is a sectional side view which shows the state which repaired the location with the hole of the top plate of the tank main body by the repair method which concerns on one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Structure of digester)
First, a steel plate digestion tank to be repaired will be described with reference to FIG. The steel plate digestion tank 100 includes a steel plate tank main body 1, a mechanical stirrer 2 (hereinafter referred to as "stirrer 2"), and the like.

  The tank body 1 is a tank for anaerobic fermentation treatment of sludge (sewage sludge, organic waste such as food waste). The sludge charged into the tank body 1 is heated by a heating device (not shown) and stirred by the stirrer 2. Digestion gas generated by anaerobic fermentation is allowed to exit from the top of the tank. In addition, illustration of the sludge injection | throwing-in means to the tank main body 1 and the digestion gas extraction means from the tank main body 1 is abbreviate | omitted. The digestion gas is a gas (biogas) of about 60% by volume of methane and about 40% by volume of carbon dioxide, and the pressure of the gas layer A inside the tank body 1 is 1 to 3 kPa. Since the digestion gas is a combustible gas, the inside of the tank body 1 is set to a positive pressure (a pressure higher than the external atmospheric pressure) so that the atmosphere does not enter the tank body 1.

  In this embodiment, although it is set as the vertical cylindrical tank main body 1, the shape of the tank main body 1 is not restricted to this.

  A stirrer 2 attached to the tank body 1 is for stirring the sludge charged into the tank body 1. The stirrer 2 includes an impeller 2a arranged in two stages, an electric motor 2b that rotates the impeller 2a, and the like. The impeller 2a is not limited to a two-stage arrangement, and may be a single stage or a plurality of stages.

  In the present embodiment, a mechanical stirrer that stirs sludge with the impeller 2a is used, but a draft tube type mechanical stirrer or a screw blade type mechanical stirrer may be used. Furthermore, a gas type stirring device may be used.

(Digestion tank repair method)
As described above, the steel plate digestion tank usually does not have holes, but the top plate 3 of the tank body 1 corrodes due to internal condensation during long-term use, and the top plate 3 has holes. The case where there was 3a was assumed. In addition, the part which always contacts the liquid layer part B of the side plate 4 of the tank body 1 is less likely to corrode than the top plate 3 and the side plate 4 part facing the air layer part A.

  Here, referring to FIG. 2, a method for repairing the top plate 3 when the top plate 3 has holes 3 a will be described as an example.

  First, the supply of sludge to the tank body 1 is stopped for several days, for example, to suppress the generation of digestion gas (preparation step). Thereby, the pressure of the gas-layer part A in the tank main body 1 can be reduced, and discharge of the digestion gas from the hole 3a can be suppressed. Even if the supply of sludge to the tank body 1 is stopped for several days, the anaerobic fermentation process will not be completely stopped if the sludge exists in the tank body 1. In other words, when the supply of sludge to the tank body 1 is resumed, the normal operation state is immediately restored. Furthermore, even if the supply of sludge to the tank body 1 is stopped for several weeks, the anaerobic fermentation process will not be completely stopped if sludge is present in the tank body 1. However, in a digestion tank that does not have a spare machine, normally, the supply of sludge to the tank body 1 is stopped during the suspension period because the sludge digestion process that always occurs cannot be performed. The time required for the pressure drop of the gas layer part A in the tank body 1 is shortened by the time required for the first step and the second step described later).

  In addition, the supply of the sludge to the tank main body 1 is not stopped, but the supply amount of the sludge to the tank main body 1 is decreased as compared with the normal time, thereby reducing the pressure of the air layer portion A in the tank main body 1. Thus, the discharge of digestion gas from the holes 3a may be suppressed. If it does in this way, although the amount of processing falls, the digestion process of sludge can be continued.

  Furthermore, when there is little generation | occurrence | production of digestion gas (gas pressure is low), you may not stop supply of the sludge to the main body 1, or reduce supply amount.

  In addition, when reducing the pressure of the gas layer part A in the tank main body 1, the pressure is made not to become negative pressure (pressure lower than external atmospheric pressure). This is because when the negative pressure is reached, the atmosphere is sucked into the tank body 1 filled with the digestible gas, which is a combustible gas.

  The size of the hole 3a is not limited, but is assumed to be about 1 mm. Further, the hole 3a is not limited to a circular shape, and may be a hole like an elongated crack.

  Thereafter, the hole 3a is closed by sticking a water leakage repair tape 5 (an example of a repair tape, an example of a repair material) on the hole 3a from the outside of the tank (first step). Thereby, the hole 3a is closed and gas leakage from the hole 3a is prevented. At this time, if the hole 3a is completely closed with the water leakage repair tape 5 (when the gas leakage becomes zero), it will not be damaged, but a slight gas leakage is allowed. That is, as a result of closing the hole 3a with the water leakage repair tape 5, gas may slightly leak from the hole 3a. In the repairing method of the present invention, the holed area is closed with a repair material from the outside of the tank, and as a result of the holed area being blocked with the repair material, gas may leak slightly from the hole. In other words, closing the holed area with the repair material does not completely eliminate the gas leakage (although the gas leakage may be completely eliminated) but suppresses the gas leakage.

  In addition, by sticking the leak repair tape 5 on the hole 3a from the outside of the tank, the hole 3a is not blocked, but a putty material (an example of a repair material) such as a metal putty is filled in the hole 3a from the outside of the tank. The hole 3a may be closed. Furthermore, the gas leakage may be more completely suppressed by filling the putty material in the hole 3a and then sticking the leakage repair tape 5 thereon.

  Thereafter, an FRP lining 6 (fiber reinforced plastic lining) is applied to the water leakage repair tape 5 from the outside of the tank (second step). This completely suppresses (eliminates) gas leakage from the hole 3a.

  Note that the leakage repair tape and the metal putty are both known general repair materials, and are also known general techniques for FRP lining.

(Action / Effect)
In this invention, since the location where the hole of the steel-plate digestion tank was opened is repaired from the tank exterior, it is not necessary to stop anaerobic fermentation processing completely. In other words, since it is repaired without removing the internal sludge, the anaerobic fermentation process is not completely stopped. Moreover, since it is a repair work from the outside of the tank, the work of closing the hole is easy. Moreover, since corrosion prevention is performed by applying FRP lining, the generation of holes again can be suppressed.

  Here, as in the above-described embodiment, the supply of organic waste to the steel plate digestion tank is stopped before the holed portion of the steel plate digestion tank is closed with a repair material from the outside of the tank (first step). Or it is preferable to decrease. According to this configuration, it is possible to suppress the discharge of digestion gas from the open holes, so that the operation in the first step can be easily performed.

  As the repair material, it is preferable to use at least one of a leakage repair tape and a putty material. This is because the water leakage repair tape and putty material are easy to handle and are sufficient repair materials to temporarily suppress gas leakage.

(Modification)
In the above-described embodiment, an example in which the hole 3a in the top plate 3 of the tank body 1 is repaired has been shown. However, even when the side plate 4 of the tank body 1 has a hole, the repair method of the present invention can be applied.

1: Tank body 2: Stirrer 3: Top plate 3a: Hole 4: Side plate 5: Water leakage repair tape (Repair tape)
6: FRP lining 100: Steel plate digester

Claims (2)

A method for repairing a steel plate digestion tank that generates digestion gas by anaerobic fermentation of organic waste,
A first step of closing a holed hole in which the inner side of the steel plate digestion tank is an air layer part with a repair material from the outside of the tank;
A second step of applying a fiber reinforced plastic lining on the repair material from outside the tank;
Equipped with a,
Before performing the first step, by stopping or reducing the supply of organic waste to the steel plate digestion tank, the pressure of the gas layer part is reduced within a range that does not become negative pressure. And repair method of steel plate digestion tank. In the repair method of the steel plate digestion tank according to claim 1 ,
The repair material is a repair tape and putty material ,
The said 1st process WHEREIN: The said putty material is packed in the said hole from the tank exterior, and the said repair tape is stuck on it, The repair method of the digestive tank made from a steel plate characterized by the above-mentioned .

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