A buried LNG storage tank heat tracing system and method

Abstract

The application relates to a buried LNG storage tank heat tracing system and method, which comprises a tank bottom fluid heat tracing system, a temperature acquisition module, a pressure acquisition module, a flow acquisition module, a heat tracing module and a working medium pump module, the temperature acquisition module and the heat tracing module are installed in a bearing platform of an LNG storage tank, the pressure acquisition module and the flow acquisition module are installed at a total inlet and a total outlet of fluid entering the heat tracing module, and the working medium pump is installed at the total inlet of the heat tracing module to provide pressure for fluid heat exchange; a tank wall electric heat tracing system, which comprises a temperature acquisition module and an electric heat tracing module, the temperature acquisition module and the electric heat tracing module are in the form of heat tracing bands and are laid in a concrete outer tank wall of the LNG storage tank; and a control system which is electrically connected with the tank bottom fluid heat tracing system and the tank wall electric heat tracing system respectively.

Description

TECHNICAL FIELD

[0001] The application relates to a buried LNG storage tank heat tracing system and method, and belongs to the technical field of liquefied natural gas storage tanks. BACKGROUND

[0002] Due to the strict site selection requirement of the overhead storage tank area, in order to meet the construction demand of the LNG storage tank in a poor geological condition area, a ground-mounted, semi-underground or underground storage tank is used to make up for the deficiency of the overhead storage tank construction.

[0003] Since the tank body is directly in contact with the soil and there is no air circulation, the influence of the low temperature of the liquid in the storage tank on the foundation cannot be compensated. Therefore, in order to prevent the soil under the tank bottom from freezing, a heating system needs to be arranged at the tank bottom to ensure the consistency and continuity of the temperature in the protection zone, and the boiling of the LNG in the tank cannot cause the economic efficiency of the LNG storage tank to be reduced.

[0004] There are three main heating methods in the current chemical field, namely fluid heat tracing, skin effect electric heating and resistance electric heat tracing. The fluid heat tracing method involves many devices and has a complex structure, and the temperature is difficult to control, but it has certain economic advantages for chemical projects that can easily obtain low-cost heat sources or heat media (such as projects that have waste heat sources in the plant area or are close to power plants and thus can provide a large amount of cheap steam source due to the need for a large amount of cooling water for process circulation); the skin effect electric heat tracing method has a general local heat tracing effect, and there is a risk of corrosion caused by leakage voltage, and it also needs to meet the welding requirements, so it is difficult to be laid in the pile cap structure and is not suitable for LNG storage tank heat tracing systems with high temperature control accuracy and position requirements. SUMMARY

[0005] In view of the above technical problems, the application provides a buried LNG storage tank heat tracing system and method, which can provide heat tracing for the buried LNG storage tank, can monitor and compensate the cold leakage of the storage tank in real time, can ensure the consistency and continuity of the temperature of the compensated area, and can avoid excessive compensation to cause the evaporation of the LNG in the tank and reduce the economic efficiency of the storage tank.

[0006] To achieve the above object, the application adopts the following technical scheme:

[0007] A buried LNG storage tank heat tracing system, comprising:

[0008] A tank bottom fluid heat tracing system, comprising a temperature acquisition module, a pressure acquisition module, a flow acquisition module, a heat tracing module and a working medium pump module, the temperature acquisition module and the heat tracing module are installed in a pile cap of an LNG storage tank, the pressure acquisition module and the flow acquisition module are installed at a total inlet and a total outlet of fluid entering the heat tracing module, and the working medium pump is installed at the total inlet of the heat tracing module to provide pressure for fluid heat exchange;

[0009] The tank wall electric heat tracing system comprises a temperature acquisition module and an electric heat tracing module, and the temperature acquisition module and the electric heat tracing module are arranged in the form of a heat tracing belt in the concrete outer tank wall of the LNG storage tank.

[0010] A control system is electrically connected with the tank bottom fluid heat tracing system and the tank wall electric heat tracing system respectively.

[0011] Preferably, the heat tracing module comprises a plurality of heating pipes arranged in the bearing platform and a heating medium arranged in the heating pipes.

[0012] Preferably, the plurality of heating pipes are arranged in the bearing platform in parallel at intervals.

[0013] Preferably, the plurality of heating pipes are arranged in the bearing platform in a grid pattern in a crisscross manner.

[0014] The second aspect of the present application provides a heat tracing calculation method of the buried LNG storage tank heat tracing system, comprising the following steps:

[0015] Acquiring information required for heat tracing calculation of the LNG storage tank;

[0016] According to the classification of the LNG storage tank structure and the heat tracing area division, the BOG evaporation amount of the LNG storage tank is calculated, and the heat exchange amount requirement of the required heat tracing area, i.e., the heat flux of the tank bottom and the tank wall, is determined.

[0017] After obtaining the heat flux of the tank wall, the fluid heat tracing medium, the pipeline, and the pipe diameter are calculated, and after obtaining the optimal coupling scheme, the tank bottom fluid heat tracing design is performed.

[0018] After obtaining the heat flux of the tank wall, the electric heat tracing belt selection, the power density, and the arrangement method are determined, and after obtaining the optimal coupling scheme, the tank wall electric heat tracing design is performed.

[0019] Preferably, the information required for heat tracing calculation of the LNG storage tank comprises basic parameters, storage tank design data, and basic data of the LNG storage tank, the basic parameters comprise environmental temperature, humidity, altitude, and power supply voltage grade, the storage tank design data comprises an LNG storage tank design specification, a storage tank BOG evaporation rate calculation report, a storage tank overall structure diagram, and a storage tank electrical system description, and the basic data comprises the material quality, thickness, and thermal conductivity of each cold insulation material of the storage tank.

[0020] Preferably, the heat flux of the tank bottom = the heat leakage rate of the tank bottom center area + the heat leakage rate of the tank bottom A area + the heat leakage rate of the tank bottom B area.

[0021] The heat tracing calculation method, preferably: the heat flux calculation formula of the tank bottom is as follows:

[0022]

[0023] In the formula, Q 底 represents the heat flux of the tank bottom; Q b represents the heat leakage rate of the center area of the tank bottom; Q bA represents the heat leakage rate of the A area of the tank bottom; Q bB represents the heat leakage rate of the B area of the tank bottom; A b represents the heat exchange area of the center area of the tank bottom; A bA represents the heat exchange area of the A area of the tank bottom; A bB represents the heat exchange area of the B area of the tank bottom; T a represents the temperature of the tank bottom; T LNG represents the temperature of LNG; λ represents the thermal conductivity of the cold insulation material of the cold insulation layer; t represents the thickness of the cold insulation material of the cold insulation layer; i is each layer of the heat preservation material at the center position of the tank bottom; j is each layer of the heat preservation material in the A area of the tank bottom; and k is each layer of the heat preservation material in the B area of the tank bottom.

[0024] The heat tracing calculation method, preferably, the heating fluid flow is calculated as follows:

[0025]

[0026]

[0027] Wherein, Q represents the heat flux of the process, because it is in a state of thermal equilibrium, the heat exchange efficiency is calculated as 75%, Q represents the effective heat exchange area of the heat exchange pipe; represents the average temperature of the tank wall bottom; represents the fluid inlet temperature; represents the fluid outlet temperature; represents the specific heat of the fluid; represents the total heat transfer coefficient of the heat fluid to the storage tank; represents the heat flux lost in the heat tracing process; represents the mass flow rate of the fluid.

[0028] The present application has the following advantages due to the above technical scheme:

[0029] 1. The buried LNG storage tank heat tracing system and method provided by the present application can perform systematic calculation and arrangement on the heat tracing of the buried storage tank, specifically analyze the heat flux demand, perform heat tracing calculation, and obtain the optimal heat tracing scheme according to the calculation results through coupling of each input condition, so as to ensure the safe and stable operation of the LNG storage tank.

[0030] 2、The heating calculation method and system provided by the application are more complex than the relative sitting tank heating system, and can provide a theoretical reference for the heating of the semi-underground tank, and are also applicable to the heating of the above-ground LNG tank, and fill the blank of the semi-underground LNG tank heating.

[0031] 3、The fluid heating and the electric heating are coupled in the application, the diversity of the heating method is improved, the surrounding waste heat source can be effectively utilized, the economy of the tank heating is improved, and the operation and maintenance cost is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 A schematic diagram of the fluid heating in the buried LNG tank heating system provided by an embodiment of the application is shown in the figure.

[0033] Figure 2 A fluid heat exchange model schematic diagram of the buried LNG tank heating system provided by the embodiment of the application is shown in the figure.

[0034] Figure 3 A general structure schematic diagram of the buried LNG tank containing the heating system provided by the embodiment of the application is shown in the figure.

[0035] The various marks in the figure are as follows:

[0036] 1-LNG tank; 2-heating pipe; 3-heating medium; 4-concrete; 5-soil; 6-inner tank wall plate; 7-prestressed concrete outer wall; 8-raft; 9-concrete gasket; 10-radial heating pipe; 11-circumferential heating pipe; 12-tank wall outer wall inner annular heating belt. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the application more clear, the technical scheme in the application is described clearly and completely below, obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the person skilled in the art without creative labor are within the protection scope of the application.

[0038] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the ordinary meaning as understood by a person having ordinary skill in the art to which the present application pertains. The terms "first", "second", "third", "fourth" and similar words used in the present application do not indicate any order, number or importance, but are only used to distinguish different components. The terms "include" or "contain" and similar words mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0039] For ease of description, spatial relative terms can be used in the description to describe the relationship of one element or feature to another element or feature as shown in the drawings, such as "inner", "outer", "inside", "outside", "below", "above", etc. Such spatial relative terms are intended to include different orientations of the device in use or operation in addition to the orientation depicted in the drawings.

[0040] There are three main heating methods currently used in the chemical industry, namely fluid heat tracing, skin effect electric heating and resistance electric heat tracing. The fluid heat tracing method involves many devices and complex structure, and the temperature is difficult to control, but it has certain economic advantages for chemical projects that can easily obtain low-cost heat sources or heat media (such as having waste heat sources in the plant itself, or being close to a power plant and requiring a large amount of cooling water for process circulation, thus providing a large amount of cheap steam source); the skin effect electric heat tracing method has general local heat tracing effect, and there is a risk of corrosion due to leakage voltage, and it also needs to meet the welding requirements, which is difficult to lay in the pile cap structure, and is not suitable for LNG storage tank heat tracing systems with high temperature control accuracy and location requirements.

[0041] Based on the above problems, the present application provides a buried LNG storage tank heat tracing system and method, which can provide heat tracing for the buried LNG storage tank, can monitor and compensate the cold leakage of the storage tank in real time, and can avoid overcompensation to cause the evaporation of LNG in the tank and reduce the economy of the storage tank while ensuring the temperature consistency and continuity of the compensated area.

[0042] As shown in Figure 1 , Figure 2 The buried LNG storage tank heat tracing system provided by the present application comprises:

[0043] The tank bottom fluid heat tracing system comprises a temperature acquisition module, a pressure acquisition module, a flow acquisition module, a heat tracing module and a working medium pump module, the temperature acquisition module and the heat tracing module are installed in the bearing platform of the LNG storage tank 1, the pressure acquisition module and the flow acquisition module are installed at the total inlet and the total outlet of the fluid entering the heat tracing module, and the working medium pump is installed at the total inlet of the heat tracing module to provide pressure for fluid heat exchange; the tank wall electric heat tracing system comprises a temperature acquisition module and an electric heat tracing module, and the temperature acquisition module and the electric heat tracing module are in the form of heat tracing bands and are laid in the concrete outer tank wall of the LNG storage tank 1; and the control system is electrically connected with the tank bottom fluid heat tracing system and the tank wall electric heat tracing system respectively.

[0044] Further, the heat tracing module comprises a plurality of heating pipes 2 laid in the bearing platform and a heating medium 3 in the heating pipes 2.

[0045] In some specific preferred examples, the plurality of heating pipes 2 are arranged in parallel at intervals in the bearing platform, and more preferably, the plurality of heating pipes 2 are arranged in a grid pattern by interlacing the longitude and latitude.

[0046] The second aspect of the present application also provides a heat tracing calculation method of the buried LNG storage tank heat tracing system, comprising the following steps: acquiring information required for heat tracing calculation of the LNG storage tank 1; calculating the BOG evaporation amount of the LNG storage tank 1 according to the classification of the structure form of the LNG storage tank 1 and the heat tracing region division, and determining the heat exchange amount requirement of the required heat tracing region, i.e. the heat flux of the tank bottom and the tank wall; after obtaining the heat flux of the tank wall, calculating the fluid heat tracing medium, the pipeline and the pipe diameter respectively, obtaining the optimal coupling scheme, and then performing the tank bottom fluid heat tracing design; after obtaining the heat flux of the tank wall, determining the electric heat tracing band selection, the power density and the arrangement method respectively, obtaining the optimal coupling scheme, and then performing the tank wall electric heat tracing design.

[0047] Specifically, the information required for heat tracing calculation of the LNG storage tank 1 comprises basic parameters of the LNG storage tank 1, storage tank design data and basic data, the basic parameters comprise environmental temperature, humidity, altitude, power supply voltage level, the storage tank design data comprises the LNG storage tank design specification, the storage tank BOG evaporation rate calculation report, the storage tank overall structure diagram and the storage tank electrical system description, and the basic data comprises the material quality, thickness and thermal conductivity coefficient of each cold insulation material of the storage tank.

[0048] Further, in the design of the tank bottom fluid heat tracing system, the heat tracing calculation is divided into five regions: fluid type, working medium pump, pipeline, (including pipeline, pipe material, valve and support) and fluid heater.

[0049] To prevent the low temperature LNG from leaking cold and causing the soil to freeze in winter to affect the structure foundation of the storage tank, the design temperature of the tank bottom of the LNG storage tank 1 should not be lower than 5℃, in which the cold fluid LNG is conducted and convected through the inner tank and the outer wall concrete of the cold insulation layer of the storage tank; the hot fluid (water) medium is conducted and convected through the concrete layer of the pile cap, the cold insulation layer of the outer tank, and the inner tank to the tank, and is conducted and convected through the concrete layer of the pile cap to the soil layer; in addition, the heat transfer process also exists heat dissipation to the surrounding environment, causing a certain heat loss. For the convenience of design calculation, the above heat exchange model is simplified as follows (as shown in Figure 2

[0050] 1) The heat exchange pipe of the fluid is considered to be made of stainless steel and has a small wall thickness, and the thermal resistance of the steel part is smaller than that of the cold insulation material, so the influence of the heat exchange pipe is ignored in the calculation.

[0051] 2) The heat dissipation Q5 changes greatly under different environmental temperatures, and the fluid heat tracing demand of the project is considered only in winter working condition, so for safety, the extreme environmental temperature -13.2℃ is selected as the basis for heat dissipation calculation.

[0052] 3) The initial soil temperature of the project is assumed to be uniform and constant, and the soil temperature T3 in winter is 5℃.

[0053] 4) Considering the pipe laying workability of the tank bottom, the effective contact area of the heat exchange model is 70% of the bottom area.

[0054] 5) Because the heat transfer of the fluid medium is bidirectional, the LNG also has a stepwise transfer when leaking cold, and the equivalent heat transfer process is a three-layer heat conduction structure in which the LNG leaks cold to the heat exchange medium, and the heat exchange medium transfers heat to the soil.

[0055] 6) The design purpose of the project is to prevent frozen soil, and it is assumed that Q2=Q4, and the soil temperature remains unchanged in the heat transfer process, and the external LNG leakage is supplemented by the heat of the heat exchange medium.

[0056] 7) In order to avoid abnormal evaporation of the LNG in the tank and the occurrence of frozen soil, the tank bottom interface temperature T2 is controlled at 5℃.

[0057] 8) It is assumed that under the stable heat tracing working condition, the heat is in a balanced state, and the contact surface temperature of the heating medium with the tank bottom is uniform and stable.

[0058] The thermal conductivity of the heat insulation material is the highest value under the environmental conditions.

[0059] The technical solutions of the present application will be described in detail below in combination with specific examples.

[0060] In this example, circulating hot water is used as the heating and insulation medium for analysis, and the principles of other medium schemes can be referred to simultaneously, and the heat transfer characteristics are accurate for specific media. In addition to the electric heating technology, the heating system of the semi-underground storage tank of the LNG project is analyzed according to the overall structure diagram of the storage tank​Figure 3 The heat exchange model is decomposed, and the cold insulation material and corresponding heat exchange area parameters used in the calculation are shown in the following table.

[0061] Table 1 Cold insulation material performance parameter table

[0062]

[0063] Table 2 Heat exchange area parameter table of each region

[0064]

[0065] The heat flux calculation formula of the tank bottom is as follows:

[0066]

[0067] Wherein, Q 底 represents the heat flux of the tank bottom, W; Q b represents the heat leakage rate of the center area of the tank bottom, W; Q bA represents the heat leakage rate of the A area of the tank bottom, W; Q bB represents the heat leakage rate of the B area of the tank bottom, W; A b represents the heat exchange area of the center area of the tank bottom, m 2 ; A bA represents the heat exchange area of the A area of the tank bottom, m 2 ; A bB represents the heat exchange area of the B area of the tank bottom, m 2 ; T a represents the temperature of the tank bottom, ℃, taking the control temperature 5 ℃; T LNG represents the temperature of LNG, -165 ℃; λ represents the thermal conductivity of the cold insulation material of the cold insulation layer, W / (m•k); t represents the thickness of the cold insulation material of the cold insulation layer, m; i is the center position of each layer of the tank bottom insulation material; j is each layer of the tank bottom insulation material in the A area; k is each layer of the tank bottom insulation material in the B area.

[0068] According to the calculation, the heat flux of the tank bottom is as shown in Table 3:

[0069] Table 3 Heat flux of the tank bottom

[0070]

[0071] The heating fluid flow is calculated as follows:

[0072] Taking 40 ℃ hot water as an example, the required heating fluid flow is calculated. The heat exchange process involves hot fluid.

[0073]

[0074]

[0075] Wherein, Q represents the heat flux of the process, since it is in thermal equilibrium, the heat exchange efficiency is calculated at 75%. represents the effective heat exchange area of the heat exchange pipe, m 2 ; Ta represents the average temperature of the tank wall bottom, 5°C; t1 represents the fluid inlet temperature, 40°C; t2 represents the fluid outlet temperature, 10°C temperature difference, t2 is 30°C; C represents the specific heat of the fluid; represents the heat flux lost in the heat tracing process; represents the mass flow rate of the fluid; Ka represents the total heat transfer coefficient of the hot fluid to the tank, W / (m 2 ·k), Ka can be calculated by the following formula:

[0076]

[0077] Wherein, R represents the pipe fouling thermal resistance, considering the influence of scale and other factors on heat transfer, the water for boiler is 0.00026(m 2 ·k) / W; represents the surface heat transfer coefficient from the outermost layer of the heating pipe to the outside of the tank.

[0078] According to the forced turbulent heat exchange correlation formula Dittus-Boelter formula:

[0079]

[0080] Wherein, Nu is the Nusselt number, , is the surface heat transfer coefficient from the outermost layer of the heating pipe to the outside of the tank; is the pipe diameter; Pr is the Prandtl number, , is the roughness coefficient; is the constant-pressure specific heat; Re is the Reynolds number, , is the fluid density; v is the kinematic viscosity.

[0081] Using hot water fluid, the initial fluid pressure characteristics and the initial value of the heating pipe diameter need to be set, the heat exchange area requirement is calculated, whether the heating pipe quantity arrangement requirement can be met under the tank bottom area is determined, and the pipe pressure drop is estimated according to the heating pipe condition compared with the preset initial pressure, and the appropriate heating pipe diameter and quantity corresponding to the fluid temperature are selected by continuous trial calculation to meet the heating demand of the project.

[0082] If heat conducting oil is used for heating, the following heat exchange series formula is used for calculation, and the other iterative design calculation process is the same as that of water medium.

[0083]

[0084]

[0085]

[0086] wherein, is the surface heat transfer coefficient from the outermost layer of the heating pipe to the outside of the storage tank; is the convection coefficient; is the Grashof number; is the inner diameter of the pipe; is the acceleration of gravity; is the volumetric expansion coefficient; t is the temperature difference;

[0087] In the design of the electrically heated tank wall system, the electrically heated heat exchange capacity and the safety factor are calculated as follows:

[0088] In order to prevent the low-temperature LNG from leaking cold and causing the soil to freeze in winter to affect the structure foundation of the storage tank, the design temperature of the LNG storage tank wall should not be lower than 5°C, and the electrically heated pipe in this design transfers heat to the soil layer through the concrete layer of the outer wall of the storage tank. In addition, there is also heat dissipation to the surrounding environment in this heat transfer process, causing a certain heat loss.

[0089] (1) Power density of the heating cable:

[0090] Under the condition of 5°C and 220V, considering a 5% voltage drop of the power supply line (according to GB50052-2011, the voltage loss at the power receiving end of the electrical equipment should not be greater than 5%).

[0091] (2) Total length of the heating cable;

[0092] (3) Capacity Qh of the heating system:

[0093] The calculation formula of the capacity Qh of the heating system is as follows: Qh=Ph×Lh, wherein Ph is the power density of the electrically heated pipe, and Lh is the length of the electrically heated pipe.

[0094] (4) Safety factor Sf:

[0095] The calculation formula of the safety factor Sf is as follows: Sf=Qh / Q.

[0096] (5) Duty cycle Dc:

[0097] The duty cycle defines the working time of the heating system in one cycle, and the duty cycle of the system is calculated using the electrically heated cable arranged in the center with a smaller safety factor.

[0098] Dc=100 / Sf, wherein Sf is the safety factor.

[0099] It should be pointed out finally that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit the same; and although the present application has been described in detail with reference to the foregoing embodiments, it should be appreciated by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features thereof can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for calculating the heat tracing of a buried LNG storage tank heat tracing system, the buried LNG storage tank heat tracing system comprising: The tank bottom fluid heat tracing system includes a temperature acquisition module, a pressure acquisition module, a flow acquisition module, a heat tracing module, and a working fluid pump module. The temperature acquisition module and the heat tracing module are installed in the slab of the LNG storage tank (1). The pressure acquisition module and the flow acquisition module are installed at the total inlet and total outlet of the fluid entering the heat tracing module. The working fluid pump is installed at the total inlet of the heat tracing module to provide pressure for fluid heat exchange. The tank wall electric heat tracing system includes a temperature acquisition module and an electric heat tracing module, wherein the temperature acquisition module and the electric heat tracing module are laid in the form of heat tracing cables inside the concrete outer tank wall of the LNG storage tank (1); The control system is electrically connected to the tank bottom fluid heating system and the tank wall electric heating system, respectively. Its features include the following steps: Collect the information required for heat tracing calculation of the LNG storage tank (1); Based on the classification of the structural form of the LNG storage tank (1) and the division of the heat tracing area, the BOG evaporation of the LNG storage tank (1) is calculated, and the required heat exchange demand of the heat tracing area is determined, namely: the heat flux of the tank bottom and the tank wall. After obtaining the heat flux at the bottom of the tank, the fluid heating medium, pipeline, and pipe diameter are calculated respectively. After obtaining the optimal coupling scheme, the fluid heating design at the bottom of the tank is carried out. After obtaining the heat flux of the tank wall, the selection, power density, and arrangement method of the electric heating cable are determined. After obtaining the optimal coupling scheme, the electric heating design of the tank wall is carried out. Heat flux at the bottom of the tank = heat leakage rate in the central region of the bottom of the tank + heat leakage rate in region A of the bottom of the tank + heat leakage rate in region B of the bottom of the tank; The formula for calculating the heat flux at the bottom of the tank is as follows: In the formula, Q 底 Q represents the heat flux at the bottom of the tank; b Q represents the heat loss rate in the central region of the tank bottom; bA Q represents the heat leakage rate in region A at the bottom of the tank; bB Indicates the heat leakage rate in region B at the bottom of the tank; A b Indicates the heat exchange area of ​​the central region at the bottom of the tank; A bA Indicates the heat exchange area of ​​region A at the bottom of the tank; A bB T represents the heat exchange area of ​​region B at the bottom of the tank; a Indicates the temperature at the bottom of the tank; T LNG λ represents the temperature of LNG; λ represents the thermal conductivity of the insulation material in the cold insulation layer; t represents the thickness of the insulation material in the cold insulation layer; i represents the insulation material in each layer at the center of the tank bottom; j represents the insulation material in each layer in area A of the tank bottom; k represents the insulation material in each layer in area B of the tank bottom.

2. The heat tracing calculation method according to claim 1, characterized in that: The information required for the heat tracing calculation of the LNG storage tank (1) includes the basic parameters of the LNG storage tank (1), the tank design data, and the basic data. The basic parameters include: ambient temperature, humidity, altitude, and power supply voltage level. The tank design data includes: LNG storage tank design specifications, tank BOG evaporation rate calculation report, overall tank structure diagram, and tank electrical system description. The basic data includes: material, thickness, and thermal conductivity of each insulation material of the tank.

3. The heat tracing calculation method according to claim 1, characterized in that, The heating fluid flow rate is calculated as follows: Where Q represents the heat flux of this process, and since it is in thermal equilibrium, the heat exchange efficiency is calculated as 75%. This indicates the effective heat exchange area of ​​the heat exchange tube; This indicates the average temperature at the bottom of the tank wall; Indicates the fluid inlet temperature; Indicates the fluid outlet temperature; Indicates the specific heat of a fluid; This represents the overall heat transfer coefficient of the hot fluid to the storage tank; This indicates the heat flux lost during the heat tracing process; This indicates the fluid mass flow rate.

4. The heat tracing calculation method according to claim 1, characterized in that, The heat tracing module includes several heating pipes (2) laid in the foundation and a heating medium (3) located in the heating pipes (2).

5. The heat tracing calculation method according to claim 4, characterized in that, Several heating tubes (2) are arranged in parallel at intervals within the support.

6. The heat tracing calculation method according to claim 4, characterized in that, Several heating tubes (2) are arranged in a grid pattern within the support.

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