JPS5815680B2 - Liquefied petroleum gas vaporization equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquefied petroleum gas vaporization apparatus that vaporizes liquefied petroleum gas such as propane, n-butane, i-butane, etc. by direct heating with an electric resistance heater.

As we enter the era of energy diversification, liquefied petroleum gas has come to play a widespread role as an energy source, partly due to the fact that liquefied petroleum gas can be stored and transported in a liquid state. ing.

Therefore, before liquefied petroleum gas can be used as a fuel, it must first be vaporized, and conventional vaporization devices include the following.

That is, it is an indirect heating method in which liquefied petroleum gas in a liquid state is heated and vaporized via a heating medium such as hot water or steam.

However, although this is good for large products with a vaporization capacity of several hundred to several thousand kilograms per hour, for small to medium capacity products, the efficiency is poor due to the intervening heating medium, which reduces the heat transfer area. It has the disadvantage that it must be large, is uneconomical, and cannot be miniaturized.

Other vaporizers include direct heating systems using electrical resistance heaters.

This involves immersing an electric resistance heater in liquefied petroleum gas and vaporizing it.

It is economical and can be miniaturized as a device with a small to medium vaporization capacity.

However, this direct heating method has safety risks.
Moreover, if the contact surface of the electric resistance heater with the liquefied petroleum gas becomes high temperature, excessive decomposition of the liquefied petroleum gas will occur.

For this reason, the above-mentioned indirect heating method is currently used even in products that require only a medium or lower vaporization capacity.

Therefore, there is a strong demand for miniaturization and high economic efficiency in vaporizers having medium or lower vaporization capacity.

The present invention has been made in view of the above points, and its first aspect is
The purpose of this is to provide a liquefied petroleum gas vaporization device that has a medium or lower vaporization capacity, is highly economical and safe, is highly efficient, and can be downsized. The object of the present invention is to provide a liquefied petroleum gas vaporization device that can achieve higher vaporization efficiency and more uniform vaporization, and can be made more compact.

The present invention will be explained in detail below based on illustrated embodiments.

In the figure, reference numeral 1 denotes a vertically long cylindrical outer cylinder with an inner cylinder 2 disposed therein, which is formed as a pressure vessel, and an inlet 5 through which liquefied petroleum gas is supplied and a drain valve 6 are provided at the lower end. A discharge port I equipped with a solenoid valve S is provided at the upper end.

The inner cylinder 2 is also cylindrical, and its outer diameter defines a cylindrical space 8 between the inner surface of the outer cylinder 1 and the flow path for liquefied petroleum gas and its vaporized gas.
is formed.

The inner cylinder 2 is arranged so that the upper end of the cylindrical space 8 is closed by fixing the flange 9 provided at the upper end to the flange 10 at the upper end of the outer cylinder 1. An electric resistance heater H (hereinafter referred to as heater H), which is a rod-shaped so-called sheath heater inserted from the upper end opening of 2, and a filler 3 hermetically filled in the remaining space are provided.

In the cylindrical space 8 between the outer cylinder 1 and the inner cylinder 2, a spiral heat dissipating fin 4 coaxial with the outer cylinder 1 and the inner cylinder 2 has its inner peripheral edge on the outer surface of the inner cylinder 2 and its outer peripheral edge on the outer surface. It is arranged in contact with the inner surface of the cylinder 1.

Here, the radiation fins 4 are arranged over substantially the entire length of the cylindrical space 8 in the vertical direction, and the pitch thereof is small at the bottom and becomes larger toward the top.

Of course, materials with good thermal conductivity are used for the radiation fins 4, the inner cylinder 2, and the filler 3, but the filler 3 is made of a solid material with good thermal conductivity, for example, a metal such as aluminum for the inner cylinder. Formed by casting into 2.

However, the heater H can be replaced from the heater terminal box 11 by covering the outer circumferential surface of the insulating material (sheath) with a tube made of a good thermal conductor or by making the heating element extractable from the insulating material.

The reason why the filler 3 is made of a solid material with good thermal conductivity is not only to achieve thermal integration of the heater H, inner cylinder 2, and radiation fins 4, but also to improve thermal response. This is to prevent corrosion of the heater H and damage to the heater H due to dry heating due to lack of liquid, as would be the case with liquids, and in particular, if the filler 3 is liquid, the heat distribution will be uniform by convection. Although it is difficult to prevent this from happening, the structure of the heat dissipating fins 4, which will be described later, equalizes the temperature of the vaporized gas of the liquefied petroleum gas, thereby eliminating overheating and excessive decomposition.

In the figure, ThL, ThM, and ThH are temperature sensing switches, respectively, and their temperature sensing elements are inserted into the upper part of the cylindrical space 8 from inside the control box 12 provided on the outer surface of the outer cylinder 1.

13 is a power cable, 14 is a heater H cable, 15
is the cable for solenoid valve S.

FIG. 4 shows an example of the control circuit of the above device,
The operation will be explained below based on this example circuit.

The temperature sensing switch ThL closes the contact when the temperature detected by the temperature sensing element exceeds tL- by 10α (t is the boiling point of liquefied petroleum gas under a predetermined pressure), and the temperature sensing switches ThM and ThH The temperature detected by the temperature sensing element is tM=t+β, respectively.

The contact is opened when tH=t+γ or more.

However, α and β<γ, and each value is determined depending on various conditions such as safety and environment.

However, by turning on the bush switch SWA, the relay RA
If energized, temperature sensing switch ThH and relay R
Relays R6 and RD are both energized through contact ral of A, and contacts rc2. The heater H is energized through the rdl, and this state is self-maintained by the contact rc1.

When the ambient temperature in the upper part of the cylindrical space 8 reaches tL, the temperature sensing switch ThL is turned on, and the contact rb1 of the relay RB and the normally closed contact ra2 . When contact rC3 of relay R is turned on, solenoid valve S opens and normal operation begins.

On the other hand, the liquefied petroleum gas guided from the inlet 5 to the cylindrical space 8 is heated by the heater H as shown by the heat conduction line T in FIG. It is vaporized while rising along the divided spiral flow path.

This vaporized gas is sent out from the outlet γ via the solenoid valve S.

Here, as mentioned above, the pitch of the heat dissipation fins 4 is increased as they go upward, and this is because the heat transfer surface is enlarged and a spiral flow path is formed to provide stirring to the liquefied petroleum gas. In addition to uniformizing the temperature distribution of the vaporized gas, the pitch of the radiation fins 4 is also important because the film heat transfer coefficient on the heat transfer surface is different between heating the liquefied petroleum gas to its boiling point and after vaporizing it. The thermal efficiency for vaporizing liquefied petroleum gas is extremely high, and the device can be made smaller.

When the upper temperature of the cylindrical space 8 reaches tM during the above operation,
Temperature sensing switch ThM is turned off, relay RD is deenergized, and contact rd1 is turned off, so that power to heater H is cut off.

When the temperature becomes about 5 degrees lower than M, power supply to the heater H is restarted.

And the temperature t at which a safety problem occurs due to some factor.
When the temperature rises to H, the temperature sensing switch ThH is turned off, and the deenergizing contacts rC2, rd1 . rC
3, the power supply to the heater H is cut off and the solenoid valve S is also closed for safety.

In this case, since the self-holding contact rcl of the relay Re is also turned off, the operation can be restarted by manually turning on the bushing switch SWA when the upper temperature of the cylindrical space 8 has fallen to 1M or less.

In addition, if the upper temperature of the cylindrical space 8 drops below tL, the temperature sensing switch ThL is turned off, and the relay RB is turned off.
Since the solenoid valve S is closed by turning off the contact rb1,
Liquefied petroleum gas is never delivered in a liquid state.

The same applies when the power is cut off, such as during a power outage.

With only manual operation of the bushing switch SWA, all other operations are electrically and automatically controlled, and it responds quickly to changes in load from no load to full load almost instantaneously, offering high safety. It is something.

The bushing switch SWB is for emergency stop, and operation of this bushing switch SWB cuts off all circuits and stops the operation.

As described above, in the present invention, a cylindrical space in which radiation fins are arranged is provided between the inner cylinder and the outer cylinder in which the heater is housed, and liquefied petroleum gas is supplied to this cylindrical space from the lower end. The vaporized gas is sent out from the upper end of the shaped space, and the inner cylinder is filled with a filler made of a solid material with good thermal conductivity, so the heater and the heat radiation surface are thermally integrated. It has extremely good thermal conductivity, small temperature differences between parts of the heat dissipation surface, high vaporization efficiency of liquefied petroleum gas, can be made compact, and can be directly heated without using a heating medium. Even though the heater is used for heating, there is no safety risk because the heater is covered with a filler material, and there is no risk of excessive decomposition.Furthermore, there is no risk of damage to the heater, and it is small and high-rise. It is highly efficient and safe.

In particular, in the combined invention, since the heat dissipation fins are spirally shaped to form a spiral flow path in the cylindrical space, it is possible to further promote uniformity of temperature distribution of the liquefied petroleum gas and its vaporized gas flowing along this flow path. In this respect, it is possible to prevent some overheating and excessive decomposition, and since the pitch of the spiral heat dissipation fins is continuously variable, it is possible to increase the temperature, vaporize, and further expand the liquefied petroleum gas. It is possible to deal with the heat distribution in the cylindrical space required for phenomena such as pressure rise due to heat exchange, and almost all of the heat radiation energy of the heater can be used efficiently, resulting in extremely low energy loss and high heat resistance. This makes it possible to achieve further miniaturization with efficiency.

In addition, when making the pinch of the radiation fins continuously variable, it is not only necessary to increase the pitch upward as shown in the example shown, but also to increase the pitch to infinity in a part of the cylindrical space where liquefied petroleum vaporizes. In other words, it may be arranged along the axial direction of the cylindrical space, and the pitch may be made smaller above this so as to form a spiral.

[Brief explanation of drawings]

Fig. 1 is a cutaway perspective view of one embodiment of the present invention, Fig. 2 is a fracture pressure surface view of the same, Fig. 3 is a heat conduction diagram of the same, and Fig. 4 is a circuit diagram showing an example of the control circuit of the above. . 1 is an outer cylinder, 2 is an inner cylinder, 3 is a filler, 4 is a radiation fin, 5
1 indicates an inlet, T indicates an outlet, 8 indicates a cylindrical space, and H indicates an electric resistance heater.

Claims (1)

[Scope of Claims] 1. An inner cylinder in which an electric resistance heater is installed, and an outer cylinder surrounding the inner cylinder, forming a cylindrical space between which the lower end communicates with the inlet and the upper end communicates with the outlet, A radiation fin thermally connected to the inner cylinder is arranged in the cylindrical space that is the flow path for liquefied petroleum gas and its vaporized gas, and a gap between the electric resistance heater and the inner peripheral surface of the inner cylinder is arranged inside the inner cylinder. A vaporizing device for liquefied petroleum gas, characterized in that the liquefied petroleum gas vaporizer is formed by sealingly filling a filler made of a heat-conducting solid. 2. The liquefied petroleum gas vaporization device according to claim 1, wherein the density of the radiation fins is changed according to the required heat distribution within the cylindrical space. 3. A cylindrical space is formed between the inner cylinder in which the electric resistance heater is installed and the outer cylinder surrounding the inner cylinder, the lower end of which communicates with the inlet and the upper end of which communicates with the outlet. A spiral heat dissipation fin that is thermally connected to the inner cylinder is placed inside the cylindrical space that is the flow path for the vaporized gas, dividing the cylindrical space into a spiral flow path, and the pitch of the heat dissipation fin is continuously variable. 1. A liquefied petroleum gas vaporization device, characterized in that the inner cylinder is sealed with a filler made of a thermally conductive solid that fills the gap between an electric resistance heater and the inner peripheral surface of the inner cylinder.