JPS5918599B2 - Liquefied gas vaporization method and device - Google Patents

Description

[Detailed description of the invention] The present invention relates to the vaporization of LPG.

Conventionally, various types of liquefied gas vaporization devices have been put into practical use.

For liquefied natural gas (LNG), the temperature of the heating medium is low (therefore, the problem of freezing the heating medium
There are very few examples of using an and-tube type heat exchanger.

On the other hand, there are many examples of liquefied petroleum gas (LPG) being vaporized at room temperature and high pressure using shell-and-tube heat exchangers, but there are few examples of direct vaporization of low-temperature LPG.

When vaporizing low-temperature liquefied gases, some methods are used for gases with relatively high liquid temperatures, such as butane, in the same manner as for LPG at room temperature and high pressure, but for gases with low temperatures of around -45°C, such as propane, For example, a method is used in which antifreeze is circulated as an intermediate heat medium for heating.

The disadvantage of this method is that it requires more heat exchangers than direct heating, which increases equipment costs.

Additionally, kettle-type heat exchangers that use alcohol as a heat medium are also used, but this type of heat exchanger also has a small capacity, and it is structurally impossible to convert it to a large capacity.
Rising equipment costs cannot be avoided.

Furthermore, in these indirect heat exchangers, when LPG is vaporized, LP
It also has the disadvantage that impurities in the G accumulate in the vaporizing pipe, lowering the heat transfer coefficient and causing various troubles.

Conventional vaporizers in the chemical industry only operate at a constant load, but in recent years LPG has come to be used in large quantities for power generation, and in power plants, LPG is operated at almost constant loads. Therefore, it has become necessary for vaporizers to respond to load fluctuations over a wide range.

The present invention provides a novel LPG vaporization method that overcomes the drawbacks and needs of these conventional methods, as well as an apparatus for use in the method.

In other words, when dispersing LPG into the vaporization chamber with vaporization as the first step, droplets of LPG are allowed to fall in the form of a liquid film on the top surface and inner wall surface of the tray, and then the top surface and outer wall surface of the baffle plate below are dropped. The heated gas and liquefied gas are caused to flow down in a liquid film and dispersed inside the vaporization chamber, causing direct contact between the heated gas and the liquefied gas, raising the temperature of the liquid, and storing it in the lower part of the vaporization chamber to bring the liquid temperature to around room temperature. In this method, the heated liquefied gas is heated and gasified by heat exchange formed by forming a thermosiphon-type circulation system between the vaporization chamber and the vaporization chamber.

The LPG supplied to the vaporization chamber is dispersed into as fine droplets as possible by a method such as atomization, and heated by direct contact with heated gas introduced into the vaporization chamber from a heat exchanger. While the unvaporized droplets flow further down, they are redispersed by a tray, baffle plate, etc., and are further heated by contact with the heated gas in the vaporization chamber.

The gas used for heat exchange is recovered from the gas recovery port at the top of the vaporization chamber.

The LPG is heated in this way, and when the liquid reaches the storage tank in the lower part of the vaporization chamber, it reaches a temperature close to room temperature.

The LPG that has flowed down to the storage tank is sent to a heat exchanger by thermosiphon action, where it is indirectly heated by a heating medium to become boiling liquid and heated gas, which are then introduced into the vaporization chamber again.

The gas introduced in this way is newly supplied to the LP.
As mentioned above, it is used to raise the temperature of G.

With LPG, the liquid sent to the heat exchanger is maintained at a temperature close to room temperature, so there is no need to use antifreeze as a heat medium (it has the advantage that hot water, steam, etc. can be used).

The amount of LPG heated in the heat exchanger is the newly supplied L
The flow rate is several times higher than the amount of PG, and since it is heated to a temperature above the boiling point (・), the temperature of the liquid stored in the lower part of the vaporization chamber is usually stable at a temperature close to the boiling temperature. It is maintained.

In addition, since the boiling temperature of LPG changes little with pressure changes, the liquid at the bottom of the reboiler easily generates gas when heated, and the bubbles help the liquid rise, so a thermosiphon heat exchanger can be used effectively. This allows a large heat transfer coefficient to be obtained, and as mentioned above, in an indirect heat exchanger using an intermediate heat medium, impurities in the LPG may accumulate in the LPG vaporization pipe and reduce the heat transfer coefficient. It is also possible to avoid problems that may cause trouble.

The present invention will be further described below with reference to embodiments shown in the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 shows an example of an embodiment of a vaporizer according to the present invention, and the LPG vaporizer consists of a drum 1 and a heat exchanger 2.

LPG is supplied from the inlet A into the vaporization chamber, that is, into the drum 1, and is sprayed into the drum 1 from the spray nozzle 3, becoming minute droplets and falling inside the drum 1.

At this time, the LPGO droplets are transferred to the upper surface of the tray 6 and the inner wall surface 8.
is caused to fall in the form of a liquid film, and then the upper surface of the baffle plate 7 and the outer wall surface 9 below it are caused to flow down in the form of a liquid film to be dispersed in the vaporization chamber.

On the other hand, the gas generated in the heat exchanger 2 rises from the bottom of the drum 1 and directly contacts heat exchange with the low temperature LPGO droplets.
The droplets are heated and some of the gas from the heat exchanger is condensed.

Most of the gas is released from gas outlet pipe B.

The LPG flowing down to the lower part of the drum 1 passes through the pipe 4 and enters the heat exchanger 2 due to the thermosiphon phenomenon, and a part thereof is gasified and returns to the drum 1 through the pipe 5 as a gas-liquid mixed phase.

The gas is used for heat exchange with the droplet-shaped low-temperature LPG while moving up the drum 1 as described above.

When the operating load decreases, that is, the flow rate of LPG supplied into the drum 1 from the spray nozzle 3 installed at the top of the drum 1 decreases, the formula: % Formula % (1) (Here, F is the flow rate through the spray nozzle. Liquid flow rate; Δp indicates the differential pressure at the spray nozzle) The differential pressure Δp at the spray nozzle becomes smaller, which is expressed by the formula: % Formula % (2) (where d is the amount of sprayed droplets) From the relationship shown in (indicates the diameter), the diameter of the droplet is increased.

The surface of the sprayed droplets exchanges heat through direct contact with the gas rising in the drum 1 that is heated by the heat exchanger 2, but as the diameter of the droplets increases in this way, the liquid Since the surface area per unit weight of the material becomes smaller, the amount of heat exchanged becomes smaller.

In addition, when the amount of sprayed liquid is redispersed and heat exchanged on the tray and buckle, uneven flow tends to occur (this results in insufficient redispersion and heat exchange with the heated gas described above). It becomes even more inadequate.

When the operating load decreases in this way, it is expected that the temperature of the liquid flowing down to the lower part of the drum 1 will decrease.

However, the flow rate of the liquid heated by the heat exchanger 2 and returned to the drum 1 through the piping 5 depends on the liquid density at the bottom of the drum 1,
Average density of gas-liquid multiphase fluid in heat exchanger 2, piping 5
This is determined by the pressure loss in the heat exchanger 2, etc., so set these conditions in advance so that the amount of liquid that returns to the drum 1 is large enough to flow down from the spray nozzle 3 to the bottom of the drum 1. Even if the temperature of the flowing liquid decreases, since the amount thereof is small, the temperature of the liquid accumulated at the bottom of the drum 1 can be kept almost constant and not lower than 0°C.

Therefore, even if hot water or steam is used as the heating medium for the heat exchanger 2, the temperature of the LPG entering the heat exchanger 2 is 0° C. or higher, so there is no problem of freezing of the heated fluid.

What is important here is that a tray with an open inside and a baffle plate positioned below the tray are provided below the spray nozzle, thereby causing the LPGO droplets to descend once in the form of a liquid film on the top and inner wall surfaces of the tray. Then, the droplets are introduced onto a baffle plate located below the baffle plate, and then the droplets are caused to flow down in a liquid film along the upper surface and outer wall surface of the baffle plate.

In other words, from the relationships shown in equations (1) and (2) above, when the load is high, LPG is sprayed in the form of very small droplets, so the temperature increase is due to transmission by the heated gas at the point where it falls. Heat is dominant and the process is effective, but when the load is low, the droplets become large and sufficient heat transfer is not possible, so it is necessary to flow down the walls of the tray and baffle plate in the form of a liquid film to achieve even greater heat transfer. This is possible.

In other words, by employing such a tray, baffle plate, etc. in the present invention, stable operating conditions can be ensured over a wide range from low loads to high loads.

In other words, sufficiently stable operation can be achieved even with large load fluctuations.

Furthermore, the LPG droplets pass through trays, baffle plates, etc., and are flowed down in the form of a liquid film on the top and wall surfaces of the trays. Since the contact area can be made large, it has the advantage of significantly increasing the heat transfer effect due to heating.

Further, since the heated gas and the droplets are transferred in countercurrent flow and through direct contact, the heat transfer effect can be further improved.

FIG. 2 shows an example in which a horizontal thermosiphon heat exchanger is used, which can be used depending on the installation area or the size of the heat exchanger.

Part numbers in FIG. 2 that are the same as those in FIG. 1 indicate the same parts, and their functions and effects are the same as in FIG. 1, so their explanation will be omitted here.

However, in the heat exchanger 2 in Fig. 1, there is an L on the tube side.
PG, the heating medium is flowing to the shell side, while the second
In the heat exchanger 2 shown in the figure, on the contrary, a type is used in which the heat medium flows through the tube side and the LPG flows through the shell side.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of a vaporizer according to the present invention, and FIG. 2 is an explanatory diagram showing another embodiment. Explanation of the symbols of the main parts, 1... To Dora 2...
... Heat exchanger, 3 ... Spray nozzle, 4
... Piping, 5 ... Distribution V 6 ...
...Tray, 7...Baffle plate, 8...
... Inner wall surface of tray, 9 ... Outer wall surface of baffle plate, A ... Low temperature LPG inlet, B ...
...Gas outlet, C...Heating fluid inlet, D...
...Heating fluid outlet.

Claims (1)

[Claims] I In the method of vaporizing LPG, when dispersing LPG into the vaporization chamber, the LPGO droplets sprayed into the vaporization chamber are caused to fall in the form of a liquid film on the upper surface and wall surface of the tray, and then The top surface and outer wall surface of the baffle plate are made to flow down in the form of a liquid film, dispersed inside the vaporization chamber, and brought into direct contact with the heated vaporized gas introduced from the heat exchanger into the vaporization chamber in a countercurrent flow, thereby raising the temperature of the droplets. Most of the vaporized gas is recovered from the upper part of the vaporization chamber, and the droplets are stored in the lower part of the vaporization chamber to maintain the temperature around room temperature, forming a thermosiphon-type circulation with the heat exchanger. LP characterized by heating and gasification
How to vaporize G. 2. An LPG spray nozzle is provided in the LPG vaporization chamber, a tray with an open inner side and a baffle plate are positioned below the spray nozzle, a storage tank for unvaporized LPG is formed in the lower part of the vaporization chamber, and an LPG storage tank is formed in the upper part. There is an outlet for vaporized LPG on the side, an inlet for heated LPG gas from a heat exchanger forming a thermosiphon-type circulation system on the side, and an unvaporized LPG gas inlet connected to the heat exchanger at the bottom of the vaporization chamber. An LPG vaporization device having vaporization chambers each having an LPG discharge port.