JP2005297994A - Liquified natural gas tank lorry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the generation of a boiloff gas to enable the inexpensive construction of a liquified natural gas tank lorry and of a liquified natural gas loading equipment, and to reduce transportation costs by increasing the loadage of the tank lorry to improve economy. <P>SOLUTION: A liquified natural gas tank 3, which has a cross section of circular or elliptic shape, is carried on a traveling car body 2 having a cab 1. The gas tank 3 is composed of an wall of a heat insulating structure consisting of an inner tank 4 and an outer tank 5 formed on its outer periphery via a given gap, in which a heat insulating layer 6 made of a porous material, such as a urethane foam or a pearlite, is formed between the inner tank 4 and the outer tank 5. A low boiling point liquid tank 7, which is filled with a low boiling point liquid having a boiling point lower than that of the liquified natural gas, is so arranged in the center of the interior of the gas tank 3 that the liquid tank 7 penetrates the ceiling of the inner and outer tanks 4, 5. The low boiling point liquid is used to cool the liquified natural gas in the gas tank 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a liquefied natural gas tank lorry in which a liquefied natural gas tank having a heat insulating structure formed of a wall body having a heat insulating structure is mounted on a traveling vehicle body in order to accommodate and transport liquefied natural gas.

Conventionally, the liquefied natural gas tank lorry is configured by mounting a liquefied natural gas tank 03 on a traveling vehicle body 02 provided with a cab 01, as shown in the partially cutaway entire side view of FIG. The liquefied natural gas tank 03 is constituted by a wall body having a heat insulating structure including an inner tank 04 and an outer tank 05 arranged at a predetermined interval on the outer periphery thereof, and between the inner tank 04 and the outer tank 05. The space is evacuated and a high vacuum heat insulating layer 06 is formed on the outer peripheral portion of the inner tank 04 (see Patent Document 1).
JP-A-11-32433

  However, in the case of the above-described conventional example, since there is a large temperature difference between the outside and inside of both the inner tank 04 and the outer tank 05, it is necessary to configure the constituent material so as not to be affected by thermal expansion. is there.

  On the other hand, even when the high vacuum heat insulating layer 06 is formed on the outer peripheral portion of the inner tank 04, methane, which is a high boiling point component in the liquefied natural gas, is vaporized due to the influence of the outside air temperature, so-called boil-off gas is generated. However, due to the generation of the boil-off gas, the pressure in the liquefied natural gas tank becomes high, so that high pressure resistance is required.

  In order to eliminate the thermal expansion due to the temperature difference between the inside and outside, for example, it is conceivable to use a non-expandable material such as Invar steel. However, such a non-expandable material is expensive. In order to ensure pressure resistance, it has to be made quite thick and extremely expensive, and it has not been practical in cost to use a non-intumescent material for the production of a liquefied natural gas tank.

  Therefore, conventionally, materials such as SUS and carbon steel must be used to make the inner tank 04 and the outer tank 05 thick so as not to thermally expand, increasing the weight of the liquefied natural gas tank as a whole. In addition, there is a disadvantage that it is expensive.

  Further, since the weight of the liquefied natural gas tank lorry increases due to the increase in the weight of the liquefied natural gas tank, the load amount of the liquefied natural gas is reduced by the increase in the weight of the vehicle body. In addition, as a result of the generation of boil-off gas, the effective capacity of the liquefied natural gas with respect to the capacity of the liquefied natural gas tank is reduced to, for example, about 80 to 90%, and as a whole, the substantial load of liquefied natural gas is reduced. There was a drawback that the transportation cost per unit capacity of liquefied natural gas was expensive.

  Furthermore, when liquefied natural gas is loaded into the liquefied natural gas tank, it may be dangerous if it leaks into the atmosphere. Therefore, liquefied natural gas is gradually supplied into the liquefied natural gas tank, and the liquefied natural gas causes the liquefied natural gas tank to However, there are disadvantages that the cooling equipment is necessary in the loading equipment, the loading equipment is expensive, and the loading takes a long time.

  In addition, when liquefied natural gas is supplied to a liquefied natural gas satellite, there is a problem that due to the boil-off gas, the calorie fluctuation of the vaporized natural gas supplied to gas-using equipment such as a prime mover in the liquefied natural gas satellite has occurred. .

  This invention is made | formed in view of such a situation, The invention which concerns on Claim 1 suppresses generation | occurrence | production of boil-off gas, and it can comprise a liquefied natural gas tank truck and a liquefied natural gas shipping equipment inexpensively. The invention according to claim 2 aims to improve the durability of the liquefied natural gas tank by reducing the transportation cost by increasing the loading capacity and improving the economy. And

In order to achieve the above-described object, the invention according to claim 1
In a liquefied natural gas tank truck equipped with a liquefied natural gas tank formed of a heat insulating wall on the traveling vehicle body,
A low boiling point liquid tank filled with a low boiling point liquid having a boiling point lower than that of the liquefied natural gas is provided in the liquefied natural gas tank, and the liquefied natural gas can be cooled by the low boiling point liquid.

(Action / Effect)
According to the configuration of the liquefied natural gas tank lorry of the invention according to claim 1, the low boiling point liquid tank itself is used as a heat exchanger, and the low boiling point liquid tank is filled with the liquefied natural gas stored in the liquefied natural gas tank. It can be cooled by a boiling liquid.

  Therefore, it is possible to suppress the occurrence of boil-off gas due to the heat of the outside air, the pressure rise in the liquefied natural gas tank due to the boil-off gas is small, and the pressure resistance of the tank constituent material can be reduced, so that it is expensive without thermal expansion. Even if non-intumescent material is used, the thickness can be reduced, and the liquefied natural gas tank truck can be manufactured at low cost, thereby improving the economy.

  In addition, when the liquefied natural gas tank is shipped, the inside of the liquefied natural gas tank can be cooled in advance with a low boiling point liquid, so that it is not necessary to provide a facility for cooling the inside of the liquefied natural gas tank in the loading facility. On the other hand, it is possible to carry out loading quickly without any need for loading, and it is possible to reduce the transportation cost and improve the economic efficiency by making it possible to make the shipping equipment inexpensive and to efficiently transport the liquefied natural gas.

  In addition, the weight of the liquefied natural gas tank can be reduced, and the load of liquefied natural gas can be increased by the amount that can reduce the overall weight of the liquefied natural gas tank lorry. The effective capacity of the liquefied natural gas can be increased with respect to the capacity of the natural gas tank, and the substantial liquefied natural gas loading capacity can be increased to reduce the transportation cost per unit capacity of the liquefied natural gas, thereby improving the economy.

  And since generation | occurrence | production of the boil-off gas in a liquefied natural gas tank can be suppressed, the calorie fluctuation | variation of the vaporized natural gas supplied to gas use facilities, such as a motor | power_engine, in a liquefied natural gas satellite can be suppressed.

  In addition, since the low boiling point liquid tank is provided in the liquefied natural gas tank and the low boiling point liquid tank itself is configured as a heat exchanger, for example, a low boiling point liquid tank is provided outside and a heat exchanger is provided in the liquefied natural gas tank. When the low boiling point liquid is introduced from the low boiling point liquid tank to the heat exchanger in the liquefied natural gas tank, a high thermal insulation structure is required for the low boiling point liquid tank and the piping part introduced into the heat exchanger. Compared to the above, there is an advantage that a highly heat-insulating structure is unnecessary and the configuration can be simplified.

In order to achieve the above-described object, the invention according to claim 2
In the liquefied natural gas tank truck according to claim 1,
A first pressure gauge provided in the liquefied natural gas tank and measuring a gas phase pressure of the natural gas therein;
An exhaust pipe connected to a low boiling point liquid tank for discharging the vaporized low boiling point gas;
A pressure regulating valve that is provided in the exhaust pipe and adjusts the relief pressure of the low boiling point gas to adjust the evaporation pressure of the low boiling point liquid;
The gas phase pressure measured by the first pressure gauge is compared with a set pressure range, and when the measured gas phase pressure becomes larger than the set pressure range, the relief pressure of the pressure regulating valve is lowered, and Pressure control means for controlling the gas phase pressure of the natural gas by adjusting the pressure adjustment valve so as to increase the relief pressure of the pressure adjustment valve when the measured gas phase pressure becomes smaller than the set pressure range. Constitute.

(Action / Effect)
According to the configuration of the liquefied natural gas tank lorry of the invention according to claim 2, when the gas phase pressure in the liquefied natural gas tank becomes larger than the set pressure range, the relief pressure of the pressure regulating valve is lowered, and the low boiling point liquid tank By reducing the internal vapor pressure, the boiling point of the low boiling point liquid is lowered to promote the cooling of the liquefied natural gas, and the pressure in the liquefied natural gas tank can be lowered.

  On the other hand, when the gas phase pressure in the liquefied natural gas tank becomes smaller than the set pressure range, the relief pressure of the pressure regulating valve is increased, and the vapor pressure in the low boiling point liquid tank is increased to reduce the boiling point of the low boiling point liquid. As a result, the cooling of the liquefied natural gas can be suppressed and the pressure in the liquefied natural gas tank can be increased.

  Therefore, since the pressure in the liquefied natural gas tank can be maintained within the set pressure range, it is possible to prevent the pressure in the liquefied natural gas tank from rising due to the influence of the external temperature and applying an excessive expansion pressure to the liquefied natural gas tank. The pressure in the liquefied natural gas tank is lowered by cooling too much with the low boiling point liquid, and it is possible to prevent the liquefied natural gas tank from being subjected to excessive contraction pressure, and it is possible to suppress fatigue associated with repeated expansion and contraction of the liquefied natural gas tank, The durability of the liquefied natural gas tank can be improved.

  According to the configuration of the liquefied natural gas tank lorry of the invention according to claim 1, the liquefied natural gas stored in the liquefied natural gas tank can be cooled by the low boiling point liquid filled in the low boiling point liquid tank.

  Therefore, it is possible to suppress the occurrence of boil-off gas due to the heat of the outside air, the pressure rise in the liquefied natural gas tank due to the boil-off gas is small, and the pressure resistance of the tank constituent material can be reduced, so that it is expensive without thermal expansion. Even if non-intumescent material is used, the thickness can be reduced, and the liquefied natural gas tank truck can be manufactured at low cost, thereby improving the economy.

  In addition, when the liquefied natural gas tank is shipped, the inside of the liquefied natural gas tank can be cooled in advance with a low boiling point liquid, so that it is not necessary to provide a facility for cooling the inside of the liquefied natural gas tank in the loading facility. On the other hand, it is possible to carry out loading quickly without any need for loading, and it is possible to reduce the transportation cost and improve the economic efficiency by making it possible to make the shipping equipment inexpensive and to efficiently transport the liquefied natural gas.

  In addition, the weight of the liquefied natural gas tank can be reduced, and the load of liquefied natural gas can be increased by the amount that can reduce the overall weight of the liquefied natural gas tank lorry. The effective capacity of the liquefied natural gas can be increased with respect to the capacity of the natural gas tank, and the substantial liquefied natural gas loading capacity can be increased to reduce the transportation cost per unit capacity of the liquefied natural gas, thereby improving the economy.

  And since generation | occurrence | production of the boil-off gas in a liquefied natural gas tank can be suppressed, the calorie fluctuation | variation of the vaporized natural gas supplied to gas use facilities, such as a motor | power_engine, in a liquefied natural gas satellite can be suppressed.

  In addition, since the low boiling point liquid tank is provided in the liquefied natural gas tank and the low boiling point liquid tank itself is configured as a heat exchanger, for example, a low boiling point liquid tank is provided outside and a heat exchanger is provided in the liquefied natural gas tank. When the low boiling point liquid is introduced from the low boiling point liquid tank to the heat exchanger in the liquefied natural gas tank, a high thermal insulation structure is required for the low boiling point liquid tank and the piping part introduced into the heat exchanger. Compared to the above, there is an advantage that a highly heat-insulating structure is unnecessary and the configuration can be simplified.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a partially cutaway entire side view showing a first embodiment of a liquefied natural gas tank lorry according to the present invention. A liquefied natural gas tank having a circular or elliptical cross section is provided on a traveling vehicle body 2 provided with a cab 1. 3 is configured.

  The liquefied natural gas tank 3 is constituted by a wall body having a heat insulating structure including an inner tank 4 and an outer tank 5 disposed at a predetermined interval on the outer periphery thereof, and between the inner tank 4 and the outer tank 5. A heat insulating layer 6 made of a porous material such as urethane foam or pearlite is formed.

  As each of the inner tank 4 and the outer tank 5, a non-expandable material having no thermal expansion such as Invar steel is used thinly (for example, about 1 to 2 mm).

  Further, a vacuum pump (not shown) is connected to the heat insulating layer 6, and the inside of the heat insulating layer 6 is evacuated to form a high vacuum heat insulating layer.

  At the center of the liquefied natural gas tank 3, there is provided a low boiling point liquid tank 7 which penetrates the ceiling portion of the inner tank 4 and the outer tank 5 and is filled with a low boiling point liquid having a boiling point lower than that of the liquefied natural gas. It has been. The low boiling point liquid tank 7 is made of an aluminum material having high thermal conductivity, and is configured so that the liquefied natural gas stored in and / or in the liquefied natural gas tank 3 can be cooled by the low boiling point liquid.

  Examples of the low boiling point liquid having a boiling point lower than the boiling point of liquefied natural gas to be filled in the low boiling point liquid tank 7 include liquefied nitrogen (boiling point at saturated pressure-195.8 ° C.), liquefied argon (boiling point at saturated pressure− 185 ° C.) can be used, but liquefied nitrogen is preferably used because of its availability. Examples of such low boiling point liquids include liquefied oxygen (boiling point at saturated pressure -183 ° C), liquefied air (boiling point at saturated pressure -194 ° C), and liquefied helium (boiling point at saturated pressure -269 ° C). However, liquefied oxygen and liquefied air are not suitable for use from the viewpoint of safety, and liquefied helium is expensive and cannot be used from the viewpoint of economy.

  The low-boiling point liquid tank 7 is connected to a first pipe 9 having a first relief valve 8 that opens at a set pressure (for example, 588 to 686 kPa), so that the pressure in the low-boiling point liquid tank 7 increases rapidly. In such a case, the vaporized nitrogen gas is released into the atmosphere, and the inside of the low boiling point liquid tank 7 is prevented from becoming abnormally high pressure.

  In addition, a second pipe 11 having a second relief valve 10 that opens at a set pressure (for example, 196 kPa) is connected to the upper space in the liquefied natural gas tank 3, which is abnormally caused by an external high temperature or the like. When the boil-off gas is generated and becomes a high pressure (for example, 196 kPa), the boil-off gas is allowed to escape to prevent the liquefied natural gas tank 3 from being damaged.

  The low boiling point liquid tank 7 is connected to a third pipe 13 having a pressure regulating valve 12 interposed. A pressure gauge 14 is provided in the upper space in the liquefied natural gas tank 3 to measure the gas phase pressure. The pressure gauge 14 is connected to a controller 15 as pressure control means, and the pressure adjustment valve 12 is connected to the controller 15.

  The controller 15 is provided with a comparison means. In the comparison means, the pressure measured by the pressure gauge 14 is compared with a set pressure range (for example, 9.8 to 98 kPa), and the measured pressure is higher than the upper limit value of the set pressure. When the pressure increases, the relief pressure of the pressure regulating valve 12 is lowered, and the vapor pressure in the low boiling point liquid tank 7 is lowered to lower the boiling point of the low boiling point liquid to promote the cooling of the liquefied natural gas. The pressure in the gas tank 3 is lowered.

  On the other hand, when the measured pressure becomes smaller than the lower limit value of the set pressure, the relief pressure of the pressure regulating valve 12 is increased, and the vapor pressure in the low boiling point liquid tank 7 is increased, thereby increasing the boiling point of the low boiling point liquid. Thus, the cooling of the liquefied natural gas is suppressed, and the pressure in the liquefied natural gas tank 3 is increased.

  With the above configuration, the pressure in the liquefied natural gas tank 3 can be maintained within the set pressure range.

  The capacity occupied in the liquefied natural gas tank 3 of the low boiling point liquid tank 7 is set to 2 to 10% of the capacity of the liquefied natural gas tank 3 (internal volume of the inner tank 4). This is because if it exceeds 10%, the load of liquefied natural gas decreases, while if it is less than 2%, the cooling effect decreases. Preferably it is 2 to 5%.

  2 is a partially cutaway entire side view showing a second embodiment of a liquefied natural gas tank lorry according to the present invention, and FIG. 3 is a cross-sectional view (a cross-sectional view taken along the line XX in FIG. 2), which is different from the first embodiment. Is as follows.

  That is, the liquefied natural gas tank 3 is configured in a quadrangular cross-sectional shape. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  According to the second embodiment, by utilizing the fact that the liquefied natural gas in the liquefied natural gas tank 3 can be cooled by the low boiling point liquid in the low boiling point liquid tank 7 and the pressure rise caused by the generation of boil-off gas can be suppressed. The internal volume can be increased, and the load of liquefied natural gas can be increased.

  In detail, in order to avoid concentration of pressure, the cross-sectional shape of the liquefied natural gas tank 3 is circular or elliptical. However, since the pressure can be reduced, even if pressure is concentrated in the corner as a quadrangle, This is because the pressure is low enough to withstand.

  FIG. 4 is an overall side view showing Embodiment 3 of the liquefied natural gas tank lorry according to the present invention. The differences from Embodiment 1 are as follows.

  That is, the liquefied natural gas tank 3 has a quadrangular cross-sectional shape, and further, on the lower side, a tank protruding portion 21 is provided so as to enter between the left and right frames of the traveling vehicle body 2 to further increase the internal volume of the liquefied natural gas tank 3. The liquefied natural gas loading capacity can be further increased. Other configurations are the same as those of the first embodiment, and the same reference numerals are given and description thereof is omitted.

  In the above embodiment, the low-boiling point liquid tank 7 is provided near the center of the liquefied natural gas tank 3 so that the area in contact with the liquefied natural gas can be increased as much as possible. In other words, the low boiling point liquid tank 7 may be provided in the liquefied natural gas tank 3 so as to be in contact with the inner peripheral surface of the liquefied natural gas tank 4.

  The present invention is not limited to the liquefied natural gas tank lorry for road driving as in the above-described embodiments, but can also be applied to a container type liquefied natural gas tank lorry transported by railroad or a transport ship.

It is a partial notch whole side view which shows Example 1 of the liquefied natural gas tank lorry which concerns on this invention. It is a partial notch whole side view which shows Example 2 of the liquefied natural gas tank lorry concerning this invention. FIG. 3 is a sectional view taken along line XX in FIG. 2. It is a whole side view which shows Example 3 of the liquefied natural gas tank lorry concerning this invention. It is a partial notch whole side view which shows the liquefied natural gas tank lorry of a prior art example.

Explanation of symbols

2 ... traveling vehicle body 3 ... liquefied natural gas tank 7 ... low boiling point liquid tank 12 ... pressure regulating valve 14 ... pressure gauge 15 ... controller (pressure control means)

Claims (2)

In a liquefied natural gas tank truck equipped with a liquefied natural gas tank formed of a heat insulating wall on the traveling vehicle body,
The liquefied natural gas tank is provided with a low boiling point liquid tank filled with a low boiling point liquid having a boiling point lower than that of the liquefied natural gas, and the liquefied natural gas can be cooled by the low boiling point liquid. Natural gas tank truck. In the liquefied natural gas tank truck according to claim 1,
A first pressure gauge provided in the liquefied natural gas tank and measuring a gas phase pressure of the natural gas therein;
An exhaust pipe connected to a low boiling point liquid tank for discharging the vaporized low boiling point gas;
A pressure regulating valve that is provided in the exhaust pipe and adjusts the relief pressure of the low boiling point gas to adjust the evaporation pressure of the low boiling point liquid;
The gas phase pressure measured by the first pressure gauge is compared with a set pressure range, and when the measured gas phase pressure becomes larger than the set pressure range, the relief pressure of the pressure regulating valve is lowered, and Pressure control means for controlling the gas phase pressure of the natural gas by adjusting the pressure regulating valve so as to increase the relief pressure of the pressure regulating valve when the measured gas phase pressure becomes smaller than a set pressure range;
Liquefied natural gas tank truck.

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