JP2005226665A - Liquefied natural gas vaporizing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To vaporize liquefied natural gas so as to obtain fuel gas having no calorie fluctuation. <P>SOLUTION: Evaporation pipes 18 forming horizontal flow passages are vertically juxtaposed in a vessel 8 composing a vaporizor 2. The evaporation pipes 18 are connected to each other through the medium of a connection pipe 19 so as to form a vertical zigzag passage. Liquefied natural gas is supplied to one end side in a longitudinal direction of the evaporation pipe 18a disposed in the lowermost part of the system. A pump and a pressure compensated flow control valve are provided to the supply pipe. A calorie of fuel gas taken out of a termination of the evaporation pipe 18 is measured by a calorie meter. The supply amount of the liquefied natural gas is controlled so as to eliminate liquid-gas multi-phase flow at the most downstream part of the evaporation pipe 18a in the lowermost part by adjusting the discharge capacity of the pump and the opening of the pressure compensated flow control valve so as to maintain the measured calorie within the set range. By so doing, the calorie fluctuation of fuel gas supplied to a lean combustion type gas engine can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquefied natural gas vaporization system obtained by evaporating and vaporizing liquefied natural gas as a fuel gas supplied to a lean combustion gas engine.

  As a technology for vaporizing liquefied natural gas, conventionally, liquefied natural gas is accommodated in a container and vaporized by heat from the outside air, and liquid phase liquefied natural gas is taken out from the container and waste heat from the micro turbine is collected. There are some which are configured to vaporize (see Patent Document 1 and Patent Document 2).

In addition, a liquefied natural gas stored in a liquefied natural gas tank is supplied to the hot water vaporizer using a hot water vaporizer configured so that the piping of liquefied natural gas passes through warm water heated by exhaust heat from the gas turbine. However, some have been configured to vaporize liquefied natural gas by heating with warm water (see Patent Document 3).
JP 2002-71095 A (FIG. 1) Japanese Patent Laid-Open No. 2002-139198 (FIG. 1) Japanese Patent Laid-Open No. 2003-49718 (FIG. 1)

  However, in any of the above-described conventional examples, the composition ratio of the vaporized liquefied natural gas is different from the composition ratio of the liquid liquefied natural gas, and the composition ratio in the obtained gas phase liquefied natural gas varies. As the calorie fluctuates, the fluctuation rate per unit time of calorie exceeds the predetermined range, causing fluctuations in the output of the lean burn type gas engine or causing problems such as knocking, etc., the fuel gas of the lean burn type gas engine There was a disadvantage that could not be used as.

  Moreover, if it is going to suppress the above calorie fluctuation | variations, there existed a fault which requires a very big cushion tank, a site area becomes large, and initial cost becomes high.

  This invention is made | formed in view of such a situation, Comprising: The invention which concerns on Claim 1 enables vaporization of liquefied natural gas so that fuel gas without the fluctuation | variation of a calorie can be obtained. The invention according to claim 2 aims to make it possible to better suppress the calorie fluctuation of the obtained fuel gas, and the invention according to claim 4 makes hot water inexpensive. It aims to be able to obtain.

In order to achieve the above-described object, the invention according to claim 1
In a liquefied natural gas vaporization system obtained by evaporating and vaporizing liquefied natural gas, a fuel gas supplied to a lean combustion gas engine,
Evaporation pipes that form a horizontal flow path are arranged in a vertical direction in a container into which warm water that evaporates liquefied natural gas flows, and the connection pipes are connected so as to form a vertical zigzag path. And is configured to supply liquefied natural gas to one end side in the longitudinal direction of the lowermost evaporation pipe, and so that the gas-liquid mixed phase flow is eliminated at the most downstream portion of the lowermost evaporation pipe. It comprises control means for controlling.

(Action / Effect)
As a result of considering the conventional vaporization technique, liquid natural gas in a liquid phase is vaporized in a state where there is a depth from the liquid level in a container or pipe. Considering the degree of vaporization in that state, methane having a low specific gravity and a low boiling point was vaporized first in the components of liquefied natural gas, and then ethane having a higher specific gravity and higher boiling point than ethane was vaporized. Yes. Therefore, even if ethane at a deep position is vaporized, a distillation phenomenon occurs in which a part of the ethane is liquefied again due to a cooling action by the liquefied natural gas itself while floating in the liquid to the liquid level.

  In view of this, according to the configuration of the liquefied natural gas vaporization system of the invention according to claim 1, the liquefied natural gas is caused to flow in the horizontal direction in the lowermost evaporation pipe, and the most downstream portion of the lowermost evaporation pipe Thus, the gas-liquid mixed phase flow can be controlled to be eliminated, and the whole supplied liquefied natural gas can be vaporized without being influenced by distillation.

  Therefore, liquefied natural gas in the gas phase state having the same composition ratio as that of the liquefied natural gas supplied to the evaporation pipe can be obtained, and a fuel gas without caloric fluctuation can be obtained.

In order to achieve the above-described object, the invention according to claim 2
The liquefied natural gas vaporization system according to claim 1,
A liquefied natural gas supply pipe connected to the lowermost evaporation pipe is provided with a pump and a flow control valve, a calorimeter for measuring the calorie of the fuel gas taken out from the end of the evaporation pipe is provided, and measured by the calorimeter The control means is configured to control the supply amount of the liquefied natural gas by adjusting the pump or / and the flow rate adjusting valve so that the calories are maintained within the set range.

  As the calorimeter, a thermal conductivity type, a specific gravity type, or an ultrasonic type can be used. Further, these different types may be used in combination (claim 3).

(Action / Effect)
According to the configuration of the liquefied natural gas vaporization system of the invention according to claim 2, the calorie of the fuel gas taken out by vaporizing the liquefied natural gas is measured, and liquefied so that the calorie is maintained within the set range. The supply amount of natural gas can be controlled, and calorie fluctuation can be suppressed within a certain range.

  Therefore, the calorie fluctuation | variation of the fuel gas obtained can be suppressed more favorably.

In order to achieve the above-described object, the invention according to claim 4
In the liquefied natural gas vaporization system according to any one of claims 1, 2, and 3,
The cooling water of the lean combustion gas engine and / or the cooling water of the intercooler is used as the heat source of the hot water supplied into the container.

(Action / Effect)
According to the configuration of the liquefied natural gas vaporization system of the invention according to claim 4, the exhaust heat recovered in the cooling water of the lean combustion gas engine or the intercooler is used as a heat source for warm water for vaporizing the liquefied natural gas. Therefore, a dedicated heating facility for obtaining hot water can be dispensed with, and hot water can be obtained at a low cost, thereby improving economy.

  As is clear from the above description, according to the configuration of the liquefied natural gas vaporization system of the invention according to claim 1, the liquefied natural gas is allowed to flow horizontally in the lowermost evaporation pipe, and the lowermost evaporation pipe is Since the gas-liquid mixed phase flow is controlled to be eliminated at the most downstream location, and the entire supplied liquefied natural gas can be vaporized without the influence of distillation, the liquefied natural gas supplied to the evaporation pipe A gas phase liquefied natural gas having the same composition ratio can be obtained, and a fuel gas without caloric fluctuation can be obtained.

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

  FIG. 1 is a block diagram showing an embodiment of a liquefied natural gas vaporization system according to the present invention. A liquefied natural gas tank (indicated as an LNG tank in the drawing) 1 containing a liquefied natural gas and a vaporizer 2 are provided. It is connected via a liquefied natural gas supply pipe 5 having a variable discharge capacity type first pump 3 and a flow rate adjusting valve 4 interposed therebetween.

  A carburetor 2 and a lean combustion gas engine (indicated as a gas engine in the drawing) 6 are connected via a fuel gas supply pipe 7 to supply the liquefied natural gas in the liquefied natural gas tank 1 to the vaporizer 2 and evaporate it. The vaporized liquefied natural gas obtained by vaporization is supplied to the lean combustion gas engine 6 as a fuel gas so that various driving devices (not shown) such as a generator can be driven.

  The vaporizer 2 includes a hot water inlet 9 on one end in the longitudinal direction of a container 8 that is horizontally long, and a hot water outlet 10 on the other end in the longitudinal direction. The hot water inlet 9 and the hot water outlet 10 are connected to the hot water circulation pump 11. The heat exchanger 12 is connected via a hot water circulation pipe 13 interposed.

  The heat exchanger 12 is introduced with a cooling water circulation pipe 15 provided with a discharge capacity variable type cooling water circulation pump 14 from the lean combustion gas engine 6, and engine cooling water after engine cooling, that is, a lean combustion type. The exhaust heat of the gas engine 6 is used as a heat source for vaporizing liquefied natural gas.

  A hot water temperature sensor 16 for measuring the temperature of the hot water discharged from the heat exchanger 12 is provided. The hot water temperature sensor 16 is connected to the hot water controller 17, and the hot water controller 17 is connected to the hot water circulation pump 14.

  The hot water controller 17 compares the temperature of the hot water measured by the hot water temperature sensor 16 with an upper limit set value (for example, 30.5 ° C.) and a lower limit set value (for example, 29.5 ° C.). When the temperature becomes higher than the upper limit set value, an increase signal is output to the hot water circulation pump 14 to increase the amount of hot water circulation. On the other hand, when the measured hot water temperature becomes lower than the lower limit set value, A decrease signal is output to reduce the hot water circulation rate, and the hot water temperature supplied to the vaporizer 2 is maintained at a set temperature (about 30 ° C.).

  In the container 8, as shown in the entire vertical sectional view of the vaporizer in FIG. 2, the evaporation pipes 18 forming the horizontal flow path are arranged in parallel in the vertical direction, and the zigzag path in the vertical direction is formed. Thus, the evaporation pipes 18 are connected to each other through the connection pipe 19. The evaporation pipe 18 and the connection pipe 19 may be integrally formed by bending a single pipe body.

  A plurality of the evaporation pipes 18 are arranged in parallel in the horizontal direction, the lowermost evaporation pipe 18a and the liquefied natural gas supply pipe 5 are connected via the inlet side header 20, and the uppermost evaporation pipe 18b and the fuel gas supply pipe 7 are connected. Are connected via an outlet-side header 21.

  A partition plate 22 is provided in the container 8 so that the lower passage and the upper passage are alternately formed at predetermined intervals in the longitudinal direction thereof, and the flow path of the hot water is formed in a zigzag shape in the horizontal direction. The heat of the warm water is sufficiently transmitted to the evaporation pipe 18.

  A calorimeter 23 for measuring the calorie of the fuel gas to be taken out is provided in the fuel gas supply pipe 7 at a place close to the connection with the uppermost evaporation pipe 18b, and a controller 24 as a control means is provided in the calorimeter 23. The controller 24 is connected to the pump 3 and the flow rate adjusting valve 4 while being connected.

  As shown in FIG. 1, the controller 24 compares the calorie of the fuel gas measured by the calorimeter 23 with the set lower limit value, and when the calorie of the measured fuel gas becomes lower than the set lower limit value, When the opening of the regulating valve 4 is reduced to reduce the supply amount of liquefied natural gas, and when the opening adjustment of the flow regulating valve 4 reaches the lower limit, the discharge capacity of the pump 3 is reduced and the lean combustion gas engine 6 is Control is performed so that the calorie of the supplied fuel gas does not become lower than the set lower limit value.

  On the other hand, when the calorie of the measured fuel gas is higher than the set upper limit value, if the discharge capacity of the pump 3 is smaller than the steady state, the discharge capacity of the pump 3 is increased and the discharge capacity of the pump 3 is steady. When in the state, the opening of the flow regulating valve 4 is opened, and control is performed so that the calorie of the fuel gas supplied to the lean combustion gas engine 6 does not become higher than the set upper limit value.

  In the figure, reference numeral 25 denotes a relief valve that returns liquefied natural gas to the upstream side of the pump 3 when the pressure on the downstream side of the pump 3 exceeds a set pressure. When the discharge capacity of 3 is increased, the pressure on the downstream side of the pump 3 can be prevented from becoming abnormally high.

  With the above configuration, the supply amount of liquefied natural gas to the vaporizer 2 is controlled based on the calorie of the fuel gas extracted from the vaporizer 2, that is, the gas-liquid mixed phase at the most downstream location of the lowermost evaporation pipe 18a. The flow is controlled so that there is no flow, the fuel gas is supplied to the lean combustion gas engine 6 while suppressing the fluctuation of calories by avoiding the distillation of methane during the evaporation process, and the engine output is stabilized by avoiding knocking. Can get.

  As the calorimeter 23, when a component other than the saturated hydrocarbon in the liquefied natural gas can be ignored, a specific gravity type, a thermal conductivity type, or an ultrasonic type may be used. On the other hand, when the nitrogen component cannot be ignored, an ultrasonic-thermal conductivity composite type may be used.

  According to the present invention, based on the relationship between the horizontal length of the lowermost evaporation pipe 18a and the temperature of hot water, the supply amount of liquefied natural gas that eliminates the gas-liquid mixed phase flow at the most downstream location of the lowermost evaporation pipe 18a And the control means may be configured to control the supply amount of the liquefied natural gas by adjusting the pump 3 and / or the flow rate adjusting valve 4 based on the hot water temperature.

  In the above embodiment, the cooling water of the lean combustion type gas engine 6 is used as the heat source of the hot water supplied into the container 8, but the cooling water of the intercooler of the lean combustion type gas engine 6 may be used. Separately, hot water obtained by heating means such as a boiler may be used.

It is a block diagram which shows the Example of the vaporization system of the liquefied natural gas which concerns on this invention. It is a whole longitudinal cross-sectional view of a vaporizer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 3 ... Pump 4 ... Flow control valve 5 ... Supply pipe 6 ... Lean combustion type gas engine 8 ... Container 18 ... Evaporation pipe 18a ... Lowermost evaporation pipe 19 ... Connection pipe 23 ... Calorimeter 24 ... Controller (control means)

Claims (4)

A liquefied natural gas vaporization system obtained by evaporating and vaporizing liquefied natural gas as a fuel gas to be supplied to a lean combustion gas engine,
Evaporation pipes that form a horizontal flow path are arranged in a vertical direction in a container into which warm water that evaporates liquefied natural gas flows, and the connection pipes are connected so as to form a vertical zigzag path. And is configured to supply liquefied natural gas to one end side in the longitudinal direction of the lowermost evaporation pipe, and so that the gas-liquid mixed phase flow is eliminated at the most downstream portion of the lowermost evaporation pipe. A liquefied natural gas vaporization system comprising a control means for controlling. The liquefied natural gas vaporization system according to claim 1,
A liquefied natural gas supply pipe connected to the lowermost evaporation pipe is provided with a pump and a flow control valve, a calorimeter for measuring the calorie of the fuel gas taken out from the end of the evaporation pipe is provided, and measured by the calorimeter A liquefied natural gas vaporization system in which control means is configured to control the supply amount of liquefied natural gas by adjusting the pump and / or the flow regulating valve so that calories are maintained within a set range. The liquefied natural gas vaporization system according to claim 2,
A liquefied natural gas vaporization system in which the calorimeter is selected from at least one of a thermal conductivity type, a specific gravity type, and an ultrasonic type. In the liquefied natural gas vaporization system according to any one of claims 1, 2, and 3,
A liquefied natural gas vaporization system that uses cooling water of a lean combustion gas engine and / or cooling water of an intercooler as a heat source of hot water supplied into a container.

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