JP3641211B2 - Anti-corrosion of ballast tank and marine pollution prevention method by ballast water - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for preventing marine pollution caused by ballast water by preventing corrosion of a ballast tank in a ship and killing micro-organisms in the ballast tank.
[0002]
[Prior art]
At present, taking the case of a bulk cargo ship as an example, ballast water is loaded at the landing site of the luggage, and the cargo is loaded while discharging the ballast water at the loading area of the luggage.
Ballast water contains a large amount of micro-organisms that inhabit the sea near the landing site.
[0003]
Therefore, if ballast water is discharged at the loading area, a large amount of micro-organisms inhabiting other areas will be released to the surrounding sea area, which may destroy the environment of the ecosystem. For this reason, it is forced to change ballast water once on the sea while sailing.
[0004]
However, replacement of ballast water takes time, and if the procedure for draining ballast water is wrong, unexpected stress is generated in the hull, which may cause dangerous conditions such as damage to the hull. In addition, in order to save the trouble of replacing the ballast water, the ballast water may be replaced by supplying the ballast water to a full ballast tank and forcibly overflowing the air vent pipe. There is a risk that the pressure loss will increase due to blockage of the tank, and excessive pressure will be applied to the ballast tank, destroying the tank.
Furthermore, the polluted ballast water in the bay is discharged offshore, which pollutes the sea area and is not preferable from the viewpoint of environmental protection.
[0005]
[Problems to be solved by the invention]
This invention protects the ballast tank and kills micro-organisms in the ballast tank, thereby enabling the ballast water to be discharged at the loading base without changing the ballast water during the voyage, thereby reducing the transportation cost. The purpose is to protect the marine environment.
[0006]
[Means for Solving the Problems]
The present inventor disclosed in Japanese Patent Application Laid-Open No. Hei 6-182369 by injecting an inert gas into the water to be treated, reducing the dissolved oxygen concentration in the water to be treated, and The inventor can solve the above-mentioned problems by applying the invention to the anti-corrosion technology for ballast tanks using nitrogen gas disclosed in Japanese Patent Application Laid-Open No. 2000-103395, etc. It has become possible.
[0007]
Nitrogen gas is supplied into the ship's ballast tank to reduce the oxygen concentration in the ballast tank, thereby preventing corrosion of the ballast tank and killing micro-organisms in the ballast tank to prevent marine pollution from ballast water. It is characterized by doing.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
With reference to a block diagram shown in FIG. 1, an embodiment of a nitrogen gas supply method for anticorrosion and contamination prevention to a ballast tank according to the present invention will be described taking a crude oil tanker as an example.
The means for supplying anticorrosive nitrogen gas into each ballast tank 2, the means for supplying and draining ballast water in each ballast tank 2, and the oxygen concentration analysis gas line R installed in each ballast tank 2 are the same as known means. is there.
[0009]
In a crude oil tanker, the ballast tank is partitioned by a number of partition walls in the length direction of the tanker to form a number of sealed spaces. In the drawing, one ballast tank A is shown.
Nitrogen gas supplies liquid nitrogen from the liquid nitrogen tank 3 to the evaporator 4, vaporizes the nitrogen gas with the evaporator 4, and supplies it through the supply valve 6 in the middle of the supply pipe 5 to each ballast tank. Yes.
[0010]
Each ballast tank is provided with a discharge pipe 8 having a discharge valve 7 for nitrogen gas. The pressure in each ballast tank is detected by a pressure gauge 9 provided in each ballast tank 2 and supplied by a controller 10. 6. It is controlled to a set value by controlling the discharge valve 7.
Liquid nitrogen is produced by a known liquid nitrogen production apparatus 11 and supplied to the liquid nitrogen tank 3.
[0011]
The ballast water in each ballast tank 2 is poured and drained by a ballast water pump 12 through a valve 13. That is, when the crude oil in the coin oil tank 1 is unloaded by operating a cargo oil pump (not shown), the valve 13 is opened and seawater is injected into the ballast tank 2 by the ballast water pump 12. At this time, when the gas phase portion in the ballast tank is compressed and the pressure rises, the discharge valve 7 is opened by a command from the controller 10 to release the nitrogen in the gas phase portion into the atmosphere, and the pressure in the tank is adjusted to an appropriate pressure. keeping.
[0012]
Next, when the crude oil is loaded into the coin oil tank 1, the valve 13 is opened and the ballast water pump 12 discharges the ballast water to the outside. At this time, since the gas phase portion in the ballast tank 2 becomes negative pressure, the supply valve 6 is opened, and nitrogen gas is supplied from the supply pipe 5 into the ballast tank 2, and the pressure in the tank is maintained at an appropriate pressure.
During the voyage, the signal from the pressure gauge 9 is detected so that the nitrogen gas is filled at a constant pressure (about 0.05 to 0.1 atg) in consideration of the allowable pressure resistance in the ballast tank, and the supply valve 6 is detected by the controller 10. And the discharge valve 7 are controlled.
[0013]
The supply valve 6 and the discharge valve 7 are controlled so that the oxygen concentration in the gas phase portion in the ballast tank 2 is 2% or less from the viewpoint of anticorrosion and prevention of marine pollution caused by ballast water discharge. That is, when oxygen dissolved in seawater in the ballast tank is released into the gas phase and the oxygen concentration in the gas phase increases to 2% or more, the discharge valve 7 is opened to open the ballast tank 2. When the gas is released to the outside of the tank and the pressure in the ballast tank is lowered, the supply valve 6 is opened, and nitrogen gas produced by evaporation and evaporation in the evaporator 4 is supplied into the ballast tank 2 to reduce the oxygen concentration. .
[0014]
In order to measure the oxygen concentration, an oxygen concentration analysis gas line R is installed in each ballast tank 2 and is performed by a known zirconia oxygen analyzer 14. In addition, if the analysis gas contains a large amount of water, the zirconia oxygen analyzer causes a poor insulation of the sensor part and a large measurement error. Therefore, the drain separator 15 and the silica gel moisture absorber 16 are included in the oxygen concentration analysis gas line. To dehydrate the analysis gas. Reference numeral 17 denotes a drain separator drain valve.
[0015]
When the pressure and oxygen concentration in the ballast tank are within a predetermined range, the supply valve 6 is closed, so that the liquid nitrogen tank 3 is evaporated due to heat intrusion or the like, so that the liquid nitrogen evaporates. Therefore, when the relief valve 18 is provided and the pressure exceeds the specified pressure, the nitrogen gas is discharged into the atmosphere, or the nitrogen gas is supplied into each ballast tank 2 through the pipe line 19 to consume the nitrogen gas. Saving.
[0016]
In FIG. 1, the means for filling the ballast tank with nitrogen gas is such that both the front end of the nitrogen gas supply pipe 5 from the evaporator 4 and the front end of the pipe 19 are opened and bubbled into the ballast water of the ballast tank. Although one of them can be opened in the ballast tank cavity and the other is opened in the ballast water for bubbling, both can be opened in the ballast tank cavity. It is most preferable to adopt the illustrated example from the viewpoint of reducing dissolved oxygen.
[0017]
In the experimental results, a remarkable anticorrosive effect has been confirmed if the oxygen concentration in the gas phase part of the ballast tank is constantly kept below 2%. On the other hand, experimental results have confirmed that marine micro-organisms can be killed in 2 to 3 days if the oxygen concentration in the gas phase part of the ballast tank is kept constant at 2% or less.
Figure 2 is when the experiment and when nitrogen gas was blown thereinto at a rate of 0.3 Nm ³ / hr in sea water of 1000 m ^3, the oxygen concentration in the ballast tank vapor phase when blown at a rate of 4 Nm ³ / hr Is the measured value.
[0018]
When seawater in the ocean is filled in the ballast tank, the dissolved oxygen concentration immediately after is usually about 10 ppm. If the oxygen concentration in the gas phase portion of the ballast tank is kept at 2% in this state, the dissolved oxygen concentration is reduced to about 1 ppm. It can be easily estimated that a large amount of nitrogen gas should be supplied to reduce the dissolved oxygen in the ballast water in a short time, but the apparatus becomes expensive.
On the other hand, if the supply amount of nitrogen gas is reduced, the cost of the apparatus can be reduced, but it takes time to reduce the oxygen concentration.
[0019]
When the amount of nitrogen gas blown per 1000 m ^{3 of} ballast water is 0.3 Nm ³ / hr, on a voyage of about 30 days, keep the oxygen concentration in the gas phase of the ballast tank at 2% or less for the last few days of the voyage. Is possible.
Therefore, when the number of voyage days is long, it is not necessary to reduce the oxygen concentration in a short time, and therefore it can be sufficiently implemented with an inexpensive device.
[0020]
【The invention's effect】
According to the present invention, at the same time as the anti-corrosion of the ballast tank, the micro-organisms in the ballast tank are killed with nitrogen gas, and marine pollution due to the discharge of ballast water can be prevented.
Therefore, since the ballast water supplied at the landing site can be discharged at the loading place, it is not necessary to replace the ballast water during the voyage as in the past. There is no fear of transport and the transportation cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an embodiment of a method for supplying nitrogen gas to a ballast tank according to the present invention.
[Fig. 2] Experimental measurement values representing changes in oxygen concentration in the ballast tank due to nitrogen blowing amount [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Coal oil tank 2 Ballast tank 3 Liquid nitrogen tank 4 Evaporator 5 Supply pipe 6 Supply valve 7 Discharge valve 8 Discharge pipe 9 Pressure gauge 10 Controller 11 Liquid nitrogen production apparatus 12 Ballast water pump 13 Valve 14 Zirconia type oxygen analyzer 15 Drain separator 16 Silica gel moisture absorber 17 Cold trap 18 Relief valve 19 Pipe line

Claims (2)

Nitrogen gas is supplied into the ballast tank so that the oxygen concentration in the gas phase in the ballast tank of the ship is 2% or less, and the oxygen concentration in the ballast tank is reduced to prevent corrosion of the ballast tank. At the same time, a method of preventing marine pollution from ballast water by killing micro-organisms in the ballast tank. The supply amount of nitrogen gas is 0.3 to ⁴ Nm ³ / hr per 1000 m ³ of ballast water, and the anti-corrosion of the ballast tank according to claim 1 is performed, and the micro-organisms in the ballast tank are killed to ballast the ballast tank. A method of preventing marine pollution from water.

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