JP2510041Y2 - Evaporator for low temperature fluid - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to an evaporator for low temperature fluid, and particularly to vaporize a liquid in a cryogenic state such as LPG using a high temperature heating medium.

[Prior art]

LNG (liquefied natural gas) whose main component is methane gas is used as the main gas in the city gas supply facility. Since the composition of this LNG varies widely depending on the place of origin, it is necessary to maintain a constant amount of heat during combustion. For this purpose, LPG (liquefied petroleum gas) vaporized gas is
The amount of heat is adjusted by mixing it with NG vaporized gas. Further, the amount of vaporized gas of LNG fluctuates according to the demand for city gas. Therefore, the LPG evaporator is also required to have load fluctuation followability that is about one-tenth of the amount of vaporized gas fluctuation. Conventionally, as a heat exchanger for vaporizing LPG, that is, an evaporator for a low temperature fluid, a triple-tube evaporator, a kettle evaporator, a multi-tube evaporator and the like can be mentioned. In these evaporators for low temperature fluids, the heating steam is used as a heating source to obtain economical efficiency and simplicity of the apparatus. On the other hand, in order to obtain accurate load followability using heated steam, the vaporized gas temperature should be superheated by 10 to 20 ° C above the boiling point so as not to mix mist in the vaporized gas at the outlet of the evaporator. is necessary. In order to meet these technical requirements, in each of the above-described low temperature fluid evaporators, the vaporized gas of LPG is sent to the superheater to reach a desired high temperature state and then merged with the city gas production line. .

[Problems to be solved by the device]

However, in the case of any evaporator for low temperature fluid, it becomes insufficient in terms of economical efficiency based on the need to attach a superheater, and the line to vaporization and superheat of LPG becomes long, The tendency that the load responsiveness deteriorates was inevitable. The present invention effectively solves these problems,
The objective is to simplify the structure, improve maintainability, suppress pressure fluctuations, and prevent bumping at low loads.

[Means for Solving the Problems]

As a means for solving such a problem, a plurality of heat transfer tubes are arranged in a vertical direction in a heat exchange section inside a container, and the lower part of the heat transfer tubes is attached in a state of penetrating the tube plate, At the position, the heated fluid inlet and the inlet plenum are arranged in connection with the lower opening of the heat transfer tube, and inside the heat exchange section, and near the tube plate, the sleeve-like heat transfer to the lower surface of the heat transfer tube. A configuration is adopted in which the suppressing member is covered and a fluid speed reducing member that suppresses runaway of the heated fluid is inserted inside the heat transfer tube.

[Action]

The fluid to be heated in the low temperature state is fed from the lower part into the heat transfer tube, and in the process of rising inside the heat transfer tube, it is heated by the heating fluid around it and led to the vaporized state, but near the inlet of the heat exchange part. In the fluid to be heated in, the temperature rise is moderated due to the heating being delayed by the heat transfer suppressing member, and the rapid vaporization phenomenon is prevented from occurring,
The fluid to be heated is gradually vaporized while passing through the heat transfer tube. When the fluid to be heated rises inside the heat transfer tube,
The fluid deceleration member prevents the heated fluid and the vaporized gas from abruptly moving upward, thereby suppressing runaway of the heated fluid and facilitating adjustment of the amount of vaporized gas generated according to the load. is there.

【Example】

An embodiment of a cryogenic fluid evaporator according to the present invention will be described below with reference to FIGS. In each drawing, reference numeral 1 is an evaporator for low temperature fluid, 2 is a vertical container (shell), 3 is a heat exchange section, 4 is a heat transfer tube,
5 is a tube plate, 6 is a heated fluid inlet, 7 is a heated fluid outlet, 8 is a heated fluid inlet, 9 is a heated fluid outlet, 10 is an inlet plenum portion, 11 is an outlet plenum portion, 12 is a baffle plate, 13 is A support structure, 14 is a heat transfer suppressing member, 15 is a fluid deceleration member, 16 is a welded portion, and 17 is an exposed portion. Explaining these details, the evaporator for low temperature fluid 1 has a structure similar to a vertical shell-and-tube heat exchanger, and the container 2 is installed with its longitudinal direction aligned with the vertical direction. The heat exchange section 3 includes a plurality of heat transfer tubes 4 installed in the container 2, a tube plate 5 that penetrates both ends of the heat transfer tubes 4 and supports the heat transfer tubes 4 by welding portions 16. A baffle plate 12 which is arranged in the middle of the heat transfer tube 4 and forms a flow path from the heating fluid inlet 6 to the heating fluid outlet 7 as shown by the broken line in FIG. A heat transfer suppressing member 14 is arranged inside the heat transfer tube 4, and a fluid speed reducing member 15 is arranged inside the heat transfer tube 4 as described later. As shown in FIGS. 2 and 3, the heat transfer suppressing member 14 has a sleeve shape or the like that covers the lower surface of the heat transfer tube 4, and the heating fluid existing around the heat transfer tube 4 is It is intended to avoid direct contact with the lower surface. As shown in FIG. 1, the range of installation is from the position near the lower tube sheet 5 to at least the baffle plate 12 above it.
And a distance close to the upper surface of the lower tube sheet 5, and a space close to the upper surface of the lower tube sheet 5 to allow heat expansion and contraction of the heat transfer tube 4 and the heat transfer suppressing member 14 or the vicinity thereof. It is attached to the baffle plate 12 and is set so that the exposed portion 17 formed by this gap becomes small. As shown in FIG. 2, the fluid deceleration member 15 has, for example, a twisted plate shape, is inserted into the inside of the heat transfer tube 4, and imparts resistance by generating a spiral flow based on the shape, The fluid to be heated rising inside the heat transfer tube 4 is decelerated so that it cannot move rapidly.
It can be attached to important points on the inner wall of the. Then, when the evaporator 1 for low temperature fluid is in operation, as shown by each broken line arrow in FIG. 1, a heating fluid such as high temperature steam is sent from the heating fluid inlet 6 to the heat exchange section 3 and the baffle plate 12 Heat transfer tube 4 while flowing through the flow path divided by
Is heated and then discharged from the heating fluid outlet 7. Then, as shown by the solid arrows in FIG. 1, the low-temperature fluid such as LPG, that is, the heated fluid is sent from the heated fluid inlet 8 to the heat transfer tubes 4, whereby the heating fluid is heated in the heat exchange section 3. And the fluid to be heated are exchanged with each other, and the fluid to be heated is heated sequentially through the subcool zone, the boiling zone, and the superheat zone, so that the vaporized gas at the target temperature is obtained. In this case, the heated fluid is the inlet plenum 10
When it is fed into the heat transfer tube 4 from the inside, it is heated by contact with the lower tube wall of the heat transfer tube 4, and the temperature rises in the liquid state (temperature rise in the subcool region). The surface is covered with the heat transfer suppressing member 14, and the temperature rise is delayed due to the gradual temperature gradient in this portion and the decrease in heat transfer. Therefore, the film boiling state is prevented from being caused by the rapid vaporization of the fluid to be heated in the vicinity of the inlet of the heat exchange section 3, and the fluid deceleration member 15 has a twisted plate shape, so that the spiral flow is generated and the fluid to be heated is generated. Stirring of the heating fluid reduces uneven heating. Next, when the heated fluid reaches the vicinity of the central portion of the heat transfer tube 4 or the like, the total amount of heat supplied through the heat transfer tube 4 becomes large, so that the heated fluid has a boiling point (the boiling point of LPG is 12 to 13 kg /
It reaches a temperature of about 90 ° C at a pressure of about cm ² ) and becomes a nucleate boiling state (boiling region) to promote vaporization, but the temperature rise is suppressed. Further, when the fluid to be heated reaches the vicinity of the upper portion of the heat transfer tube 4 or the like, the total amount of heat supply is further increased, so that heating is performed in the supersaturated vapor state (superheat region), and vaporization of the target temperature is performed. Become gas and exit plenum
It is sent to the city gas production line via 11 and the heated fluid outlet 9. During heating and heat supply in these subcool area, boiling area, and superheat area, part of the heated fluid will move at high speed inside the heat transfer tube 4 due to expansion due to vaporization of the heated fluid. Even if such a phenomenon occurs, the presence of the fluid speed reduction member 15 causes a large resistance to the fluid to be heated, and when the fluid speed reduction member 15 has a twisted plate shape, the spiral By the stirring action based on the flow, the fluid to be heated is made uniform and runaway such as the phenomenon that the fluid to be heated is bumped is prevented. In particular, the occurrence of the bumping phenomenon due to the mixture of liquid and gas in the subcool region is caused by the fact that the surface of the heat transfer tube 4 is covered with the heat transfer suppressing member 14 and the heat transfer is small and the temperature rise is delayed. Since the fluid deceleration member 15 intervenes to generate resistance during movement, runaway of the heated fluid is suppressed.

[Other Embodiments]

The following configuration can be adopted instead of the above-described embodiment. (A) The heat transfer suppressing member 14 is made of a material suitable for reducing the heat transfer coefficient outside the heat transfer tube 4, such as stainless steel or a coating layer. (B) The heat transfer suppressing member 14 has a shape other than a right cylinder, for example, a corrugated pipe shape. (C) The fluid deceleration member 15 has a shape other than the twist plate, for example, a metal mesh shape or a coil spring.

[Effect of device]

As described above, the evaporator for low temperature fluid according to the present invention has the following excellent effects. (1) Since it is a vertical shell-and-tube type, the structure is simplified and the improvement of economy and maintenance can be achieved, and the whole line is short and the residence time of the fluid to be heated is shortened. Therefore, the load responsiveness is excellent. (2) A heat transfer suppressing member is provided on the lower surface of the heat transfer tube,
And since the fluid speed reduction member is inserted inside the heat transfer tube,
Adjusting the amount of vaporized gas generated according to the load by allowing fluctuations from low load to 100% load by reducing the heat exchange amount near the heated fluid inlet and suppressing vaporization in the liquid region Can be done easily. (3) Due to the above, the occurrence of abnormal fluid movement and pressure fluctuation in the entire area of the heat transfer tube is suppressed, and the heat transfer coefficient of the heat exchange section is increased in combination with the addition of the stirring action of the fluid deceleration member, By smoothly vaporizing the cryogenic liquid and heating it to the required temperature, it is not necessary to attach a super heater as in the conventional example, and the size can be reduced. In addition, even if the fluid to be heated inside the heat transfer tube is rapidly heated due to a large temperature difference between the upper and lower positions of the tube sheet, the heat exchange amount and the heat transfer tube near the tube sheet are suppressed due to the above. With the support of, the thermal influence of the heat transfer tube near the tube sheet can be reduced.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of an evaporator for cryogenic fluid according to the present invention. FIG. 2 is an enlarged view of a chain line II portion in FIG. FIG. 3 is a view taken along the line III-III in FIG.

[Explanation of symbols]

 1 ... Evaporator for low temperature fluid 2 ... Vessel (shell) 3 ... Heat exchange section 4 ... Heat transfer tube 5 ... Tube plate 6 ... Heating fluid inlet 7 ... Heating fluid outlet 8 ... Heated fluid inlet 9 ... Heated fluid outlet 10 ... Inlet plenum 11 ... Outlet plenum 12 ... Baffle plate 13 ... Support structure 14 ... Heat transfer suppressing member 15 ... Fluid moderator 16 ... Welding portion 17 ... … Exposed part.

Claims (1)

(57) [Scope of utility model registration request] 1. A plurality of heat transfer tubes (4) are arranged in a vertical direction in a heat exchange section (3) inside a container (2), and a lower part of the heat transfer tubes penetrates a tube plate (5). Mounted in a state, the heated fluid inlet (8) and the inlet plenum (10) are arranged below the tube sheet in a connected state with the lower opening of the heat transfer tube, inside the heat exchange section and near the tube sheet. The lower surface of the heat transfer tube at the position is covered with a sleeve-shaped heat transfer suppressing member (14), and a fluid deceleration member (15) for suppressing runaway of the fluid to be heated is inserted inside the heat transfer tube. An evaporator for a low temperature fluid, which is characterized in that: