CN104482793A - Open rack vaporizer heat exchange tube capable of thermoelectrically recovering cold energy from LNG (Liquefied Natural Gas) - Google Patents

Abstract

The invention relates to an open-frame gasifier heat exchange tube capable of recovering cold energy of LNG by thermoelectricity. The pipe body is the gasification section of the open-frame gasifier, and the pipe body near the LNG outlet end is the heating section of the open-frame gasifier; it is characterized in that: the pipe body located in the gasification section There is an annular gap on the tube wall, and the thermoelectric material is filled in the annular gap. Corresponding to the position of the annular gap, an end cap for preventing leakage of the thermoelectric material is also provided on the tube wall of the tube body . The invention effectively adjusts the local thermal resistance of the heat exchange process by changing the structure of the heat exchange tube section with the largest heat transfer temperature difference of the heat exchange fluid inside and outside the tube, controls the growth of the ice layer on the surface of the heat exchanger, and at the same time, recycles the thermoelectric material into the LNG Part of the cold energy is converted into electrical energy. The invention can be widely used in the production process of heat exchange tubes.

Description

An open-frame gasifier heat exchange tube capable of thermoelectrically recovering LNG cold energy

technical field

The invention relates to an open-frame gasifier heat exchange tube, in particular to an open-frame gasifier heat exchange tube capable of thermoelectrically recovering LNG cold energy.

Background technique

In the LNG receiving station or gasification station, it is often necessary to heat the LNG to room temperature and the gas enters the urban transportation pipeline. The open rack vaporizer (ORV) is a gasifier that uses seawater as the heat source. It is used for large-scale base-load gasification devices. It can operate safely within the load range of 0% to 105%. Change to adjust the amount of vaporization. The basic unit of ORV is the heat exchange tube, which is composed of several heat exchange tubes in a plate-like arrangement, and the two ends are welded by gas collectors or liquid collectors to form a plate-shaped tube bundle, and then a gasifier is composed of several plate-shaped tube bundles. There is a seawater spraying device on the top of the device, and the seawater is sprayed on the outer surface of the plate-shaped tube bundle, and flows from top to bottom by gravity. LNG flows from bottom to top in the pipe, and in the process, seawater transfers heat to the LNG, heating it and gasifying it.

When the traditional ORV is running, the lower part of the plate-type tube bundle will freeze. Although the water film has a high heat transfer coefficient during the process of falling along the tube sheet, the thermal conductivity of the ice layer is much lower than that of aluminum, so it will Decrease the overall heat transfer performance of the gasifier. In order to improve the problem of icing outside the tube and improve the heat transfer performance of the gasifier, the SuperORV (Super Open Frame Gasifier) has improved the structure of the heat exchange tube on the basis of the traditional ORV. Double-layer heat exchange tube structure. The double-layer casing structure of SuperORV essentially sacrifices the compactness of the heat exchange structure, increases the heat transfer resistance, and reduces the local heat exchange temperature difference to achieve the purpose of ice layer control. During the gasification process of LNG, a large amount of cold energy will be released. During the operation of traditional ORV and SuperORV, this part of cold energy will be released directly, thus causing energy waste. In order to improve the problem of icing outside the tube and improve the heat transfer performance of the gasifier, it is necessary to improve and optimize the structure of the ORV heat exchange tube.

Contents of the invention

In view of the above problems, the object of the present invention is to provide a heat exchange tube for an open-frame gasifier that can not only improve the freezing problem outside the tube, but also recover the cold energy of LNG.

In order to achieve the above object, the present invention adopts the following technical solutions: an open-frame vaporizer heat exchange tube capable of thermoelectrically recovering LNG cold energy, which is characterized in that it includes a tube body, and the inside and outside of the tube wall of the tube body are arranged There are heat-enhancing structural fins, the tube near the LNG inlet is the gasification section of the open-frame gasifier, and the tube near the LNG outlet is the heating section of the open-frame gasifier; An annular gap is arranged on the tube wall of the gasification section, and the thermoelectric material is filled in the annular gap; corresponding to the position of the annular gap, an annular gap is arranged on the tube wall of the tube body for An end cap that prevents leakage of the thermoelectric material.

The thermoelectric material adopts bismuth telluride thermoelectric material with low thermal conductivity, and its length and thickness are set according to actual needs.

A turbulence element for enhancing heat exchange is also inserted in the tube body.

Because the present invention adopts the above technical scheme, it has the following advantages: 1. In the present invention, an annular gap is arranged on the tube wall of the gasification section of the heat exchange tube, and the thermoelectric material with low thermal conductivity is filled in the annular gap. Change the structure of the heat exchange tube section where the heat transfer temperature difference of the heat exchange fluid inside and outside the tube is the largest, and locally increase the heat transfer resistance, thereby inhibiting the growth of the ice layer on the surface of the open-frame gasifier. At the same time, while the heat exchange tube is heating the LNG, Thermoelectric materials recover part of the cold energy in LNG and convert it into electricity. 2. In the present invention, since the thermoelectric material with low thermal conductivity is arranged in the pipe section with higher heat transfer coefficient on the seawater side and the LNG side, the temperature difference on both sides of the thermoelectric material is relatively large, that is, the temperature gradient is relatively large, and the temperature of the thermoelectric material in this area is relatively large. The thermoelectric conversion efficiency is high, so the utilization rate of energy can be improved. 3. The present invention can intensify the turbulent flow intensity of the fluid in the tube and enhance the heat exchange because the turbulence element is inserted in the tube body. 4. Since the present invention utilizes recovered cold energy to generate electricity and drive some auxiliary machines, it can reduce power consumption and improve energy utilization. The invention can be widely used in the manufacturing process of the heat exchange tube of the open frame gasifier.

Description of drawings

Fig. 1 is a structural representation of the present invention, wherein, (a) is a front view, (b) is a bottom view, and (c) is a schematic sectional view along the A-A line in figure (b);

Fig. 2 is a schematic cross-sectional view of the gasification section of the present invention;

Fig. 3 is a schematic sectional view of the present invention, wherein (a) is a schematic sectional view of a gasification section, and (b) is a schematic sectional view of a heating section;

4 is a schematic diagram of the thickness distribution of the thermoelectric material in Example 1 of the present invention, wherein the abscissa represents the length of the heat exchange tube in m; the ordinate represents the thickness of the thermoelectric material in mm;

Figure 5 is a schematic diagram of the thickness of the ice layer along the length of the existing SuperORV heat exchange tube, wherein the abscissa indicates the length of the heat exchange tube in m; the ordinate indicates the thickness of the ice layer in mm;

6 is a schematic diagram of the distribution curve of thermoelectric conversion efficiency with tube length in Example 2 of the present invention, wherein the abscissa indicates the length of the heat exchange tube in m; the ordinate indicates the thermoelectric conversion efficiency in %;

Fig. 7 is a schematic diagram of the comparison of the experimental results of Example 2 of the present invention, wherein "●" indicates a heat exchange tube with a thermoelectric material, "▲" indicates a heat exchange tube without a thermoelectric material; the abscissa indicates the length of the heat exchange tube, The unit is m; the ordinate indicates the thickness of the ice layer, and the unit is mm.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

As shown in Figures 1 to 3, the open-frame gasifier heat exchange tube capable of thermoelectrically recovering LNG cold energy of the present invention is basically the same structure as the existing open-frame gasifier heat exchange tube, both including a tube body and a tube wall Both inside and outside are equipped with enhanced heat exchange structure fins, the tube body near the LNG inlet end is the gasification section of the open-frame gasifier, and the tube body near the LNG outlet end is the heating section of the open-frame gasifier; the difference of the present invention The location is: there is an annular gap on the tube wall of the gasification section, and the thermoelectric material 1 is filled in the annular gap; corresponding to the position of the annular gap, a tube wall is also provided to prevent the thermoelectric material 1 from leaking. The end cap 2.

In a preferred embodiment, the thermoelectric material 1 is used to recover part of the cold energy from the cold energy of LNG, and convert this part of cold energy into electrical energy. The thermoelectric material 1 can be a bismuth telluride thermoelectric material with low thermal conductivity, and its length And thickness can be set according to actual needs.

In a preferred embodiment, the height and thickness of the annular gap can be set according to actual needs.

In a preferred embodiment, a flow turbulence element for enhancing heat exchange can also be inserted in the tube body.

The use process of the open frame gasifier heat exchange tube capable of recovering LNG cold energy by thermoelectricity of the present invention will be described in detail below through specific embodiments;

Example 1:

1) The length of the heat exchange tube is set to 6m, the equivalent diameter inside the tube is 14mm, the finning ratio inside the tube is 3.0, the finning ratio outside the tube is 2.3, the outer diameter of the tube is 37mm, and the thickness of the tube is 8.5mm. There are spoiler elements, the length of the gasification section is 2.5m, the length of the heating section is 3.5m, the height of the annular gap is 3.2m, the thickness distribution of the annular gap gradually becomes thinner along the pipe body from the LNG inlet end, and the initial thickness is 4.5mm ; Bismuth telluride thermoelectric material is filled in the annular gap, and the distribution of its thickness changes along the tube body (as shown in Figure 4);

2) The temperature at the LNG inlet port is 113.15K, and the seawater inlet temperature is 284.95K;

3) LNG enters the gasification section of the heat exchange tube, and is heated and gasified by seawater in the gasification section. Since the gasification section is filled with bismuth telluride thermoelectric materials with low thermal conductivity, the heat transfer resistance is increased, so the ice layer can be controlled. The growth on the surface of the gasification section of the open-frame gasifier can reduce the thickness of the ice layer of the heat exchange tube, and can achieve the control level of SuperORV on the ice layer under the same conditions (as shown in Figure 5). At the same time, the bismuth telluride thermoelectric material can be recycled Part of the cold energy is converted into electrical energy. The heat exchange tube can output 0.48kW of electricity during operation. If an open-frame gasifier includes 720 heat exchange tubes, the open-frame gasifier can output 0.48kW of electricity during operation. Output 348.4kW power;

4) The LNG heated by the gasification section enters the heating section for further heating, transforms into normal temperature gas, and enters the transportation pipeline for transportation. The temperature at the LNG outlet is 281.5K.

Example 2:

1) The structure of this embodiment is basically the same as that of Embodiment 1, except that the length of the gasification section is 3m, the height of the annular gap is 3.0m, the thickness of the annular gap is 3.2mm, and the filling thickness in the annular gap is 3.2mm bismuth telluride thermoelectric material;

2) LNG enters the gasification section of the heat exchange tube, and is heated and gasified by seawater in the gasification section;

3) The LNG heated by the gasification section enters the heating section for further heating and is transformed into normal temperature gas. The LNG outlet of the heat exchange tube reaches 277.2K. A heat exchange tube of the present invention can also output 0.36kW power while it is running. If an open frame The open-frame gasifier includes 720 heat exchange tubes. During operation, the open-frame gasifier can also output 261.2kW of electricity, and its thermoelectric conversion efficiency decreases with the increase of the tube length and the decrease of the temperature difference (as shown in Figure 6 Shown), the average conversion efficiency is about 2.3%.

As shown in Figure 7, the comparison test between the heat exchange tube of this embodiment and the existing heat exchange tube shows that the maximum ice layer thickness of the present invention (heat exchange tube with thermoelectric material 1) is less than 4mm, while the existing heat exchange tube The maximum thickness of the ice layer of the heat pipe (the heat exchange tube without the thermoelectric material 1) reaches 7 mm. It can be seen that the present invention can effectively adjust the local thermal resistance of the heat exchange process and control the ice layer on the surface of the open-frame gasifier. grow.

The above-mentioned embodiments are only used to illustrate the present invention, wherein the structure, connection mode and manufacturing process of each component can be changed to some extent, and any equivalent transformation and improvement carried out on the basis of the technical solution of the present invention should not excluded from the protection scope of the present invention.

Claims (3)

1. one kind can be reclaimed the open-frame type gasifier heat exchanger tube of LNG cold energy by thermoelectricity, it is characterized in that: it includes body, enhanced heat exchange structure fin is provided with inside and outside the tube wall of described body, described body near the arrival end of LNG is the gasification section of described open-frame type gasifier, and the described body near the LNG port of export is the bringing-up section of described open-frame type gasifier; The body tube wall being positioned at described gasification section is provided with an annular gap, in described annular gap, fills thermoelectric material; The position of corresponding described annular gap, the tube wall of described body is also arranged an end cap for preventing described thermoelectric material from revealing.

2. a kind ofly as claimed in claim 1 can reclaim the open-frame type gasifier heat exchanger tube of LNG cold energy by thermoelectricity, it is characterized in that: described thermoelectric material adopts the bismuth telluride thermoelectric material of low thermal conductivity, and its length and thickness set according to actual needs.

3. a kind ofly as claimed in claim 1 or 2 can reclaim the open-frame type gasifier heat exchanger tube of LNG cold energy by thermoelectricity, it is characterized in that: also plug one in described body for the turbulent element of enhanced heat exchange.