Foundation structure of fused salt storage tank of photo-thermal power station and construction method of foundation structure

Abstract

The invention provides a foundation structure of a fused salt storage tank of a photo-thermal power station, which comprises a composite thermal insulation layer and a reinforced concrete retaining wall, the composite thermal insulation layer is arranged below a tank bottom plate of the fused salt storage tank, and the composite thermal insulation layer comprises a top cushion layer, ceramic fiber cloth and a ceramsite soil layer which are sequentially arranged downwards; an annular beam is arranged at the top of the composite heat preservation layer and composed of an annular steel plate and a heat-resisting concrete layer which are sequentially arranged below the tank bottom plate, a protective ring wall is arranged in the circumferential direction of the composite heat preservation layer, and a concrete foundation cushion layer with a built-in ventilation pipe and a built-in temperature measuring sleeve is arranged below the composite heat preservation layer. A circle of retaining wall is arranged on the periphery of the retainer wall, and the space between the retaining wall and the retainer wall is filled with compacted plain soil. The foundation structure reduces the leakage risk of molten salt.

Description

Technical Field

[0001] The present invention relates to the technical field of solar thermal project equipment, and in particular to a foundation structure of a molten salt storage tank in a solar thermal power station. Background Art

[0002] Solar thermal power generation is a solar concentrating thermal power generation technology. Solar radiation energy is focused to the absorber at the top of the absorption tower through mirror reflection. The molten salt or thermal oil heat storage medium absorbs heat and heats up. Then, water is heated in the heat exchange device to form high-temperature and high-pressure steam, which drives the steam turbine generator to operate and converts thermal energy into electrical energy. The solar thermal power generation project mainly includes four modules: the concentrating heat collection system, the heat storage and exchange system, the steam generation system, and the thermal system. Concentrating heat collection and heat storage and exchange technology are one of the key technologies for solar thermal power generation, and the working performance of the heat transfer medium directly affects the efficiency of the system. Commonly used heat transfer media in solar thermal power stations include water vapor, air, thermal oil and molten salt. Molten salt is the preferred heat transfer and storage medium for current solar thermal energy storage. Compared with thermal oil, molten salt has a series of advantages such as higher operating temperature, high thermal stability, and high specific heat capacity.

[0003] In the heat storage and exchange system, the cold and hot molten salt tanks store tens of thousands of tons of high-temperature molten salt. The medium working conditions are complex, and the construction quality is directly related to the safe operation of the power plant. Once a molten salt storage tank leaks, the power plant will be shut down and will cause huge losses and impacts. In addition to thermal insulation performance, the foundation of the molten salt storage tank also needs to take into account the functions of pressure resistance and load-bearing. The foundation of the molten salt storage tank of most existing solar thermal power stations is complex, and the huge diameter of the storage tank increases the difficulty of laying the thermal insulation material at the bottom of the tank. The materials of different layers are different, and due to the difference in expansion coefficients, mutual movement will be formed between different layers. The heavy tank body and the movement of the molten salt in the tank will cause gaps between different layers, resulting in weakened thermal insulation effect and bearing capacity. Therefore, it is difficult to ensure the uniformity of the temperature and thermal insulation effect of the bottom of the tank, especially the overall stiffness and settlement uniformity of the foundation, which in turn affects the safe operation of the heat storage tank. Summary of the invention

[0004] In order to reduce the risk of molten salt leakage due to foundation problems of molten salt storage tanks during the operation of a power plant, the present invention provides a foundation structure of a molten salt storage tank of a solar thermal power station.

[0005] In order to achieve the purpose of the present invention, the technical solution adopted by the present invention is:

[0006] A foundation structure of a molten salt storage tank in a solar thermal power station comprises a composite insulation layer and a reinforced concrete retaining wall, wherein the composite insulation layer is arranged below a tank bottom plate of the molten salt storage tank, the composite insulation layer comprises a top cushion layer, a ceramic fiber cloth and a ceramsite layer which are arranged in sequence downward, an annular beam is arranged on the top of the composite insulation layer, the annular beam comprises an annular steel plate and a heat-resistant concrete layer which are arranged in sequence below the tank bottom plate, a retaining ring wall is arranged circumferentially on the composite insulation layer, a concrete foundation cushion layer with a built-in ventilation pipe and a temperature measuring sleeve is arranged below the composite insulation layer, a circle of retaining walls is arranged on the periphery of the retaining ring wall, and compacted plain soil is filled between the retaining wall and the retaining ring wall; the top cushion layer comprises a fine sand cushion layer and a sand and gravel cushion layer from top to bottom, and a plurality of vertical ceramsite concrete partition walls are arranged in a tic-tac-toe pattern in the ceramsite layer.

[0007] The thermal conductivity of the gravel layer is high, while the thermal conductivity of the ceramsite layer is low. The gravel layer is composed of sand and gravel, and has a high bearing capacity. The gravel is embedded in the gravel layer to form a relatively stable skeleton structure. When the weight of the tank is applied to the foundation, the gravel layer can effectively support the load of the tank. There are many pores between the particles of the gravel layer, which allow water to pass smoothly. In areas with high groundwater levels or heavy rain, the gravel layer can be used as a drainage channel. When there is water accumulation around the tank foundation, the water will be quickly drained through the pores of the gravel layer, thereby avoiding the reduction of strength of the foundation soil due to excessive water content.

[0008] Setting a ceramsite layer in the tank foundation can effectively reduce the transfer of heat. The ceramsite layer can isolate the outside temperature. There are many tiny pores inside the ceramsite, which are filled with air, and air is a good heat-insulating medium. When heat tries to transfer through the ceramsite layer, it will be blocked by the air in these pores, which greatly reduces the efficiency of heat conduction. There is a certain elasticity and activity space between the particles of the ceramsite layer. When the tank is subjected to horizontal forces such as earthquakes or vibrates due to liquid shaking, the ceramsite layer can act as a buffer. The mutual collision and friction between ceramsite particles can consume part of the vibration energy, thereby reducing the vibration amplitude of the tank and improving the seismic performance of the tank.

[0009] The present invention adopts an annular steel plate on the upper layer of the annular beam because the surface of concrete is relatively rough, and the steel plate is conducive to increasing the contact area between the foundation and the bottom plate of the salt tank, which is more conducive to thermal expansion. Since the original ground elevation of the molten salt tank foundation is relatively low, a retaining wall is set outside the foundation structure, and the retaining wall and the retaining ring wall are compacted with plain soil. The outer side of the retaining wall is backfilled later to reduce the impact of the backfill soil on the salt tank foundation.

[0010] The retaining wall is made of reinforced concrete with a raft foundation, which enables the retaining wall and foundation to form a continuous structural system. This integrity can effectively resist uneven settlement. For example, on a soft soil foundation, a building may experience uneven settlement due to differences in the compressibility of the foundation soil. The retaining wall with a raft foundation can coordinate the deformation of each part and avoid cracking of the wall due to differences in foundation settlement. Compared with retaining walls on independent foundations or strip foundations, retaining walls with raft foundations can better maintain structural integrity under horizontal loads such as earthquakes.

[0011] Since the molten salt storage tank of the present invention has extremely high requirements for bearing capacity, the use of fine sand-sandstone cushion layer can meet higher bearing requirements. The fine sand-sandstone cushion layer combination can effectively disperse these loads into the foundation to ensure the stability of the tank foundation.

[0012] The sand and gravel cushion layer has high shear strength and can effectively resist shear deformation when subjected to horizontal forces (such as horizontal inertial forces generated by earthquakes or lateral pressure of foundation soil). The fine sand cushion layer can adjust its own shape to a certain extent and play an auxiliary supporting role for the sand and gravel cushion layer. When slight foundation deformation occurs, the fine sand cushion layer can adapt to the deformation by rearranging the particles while maintaining a cooperative working state with the sand and gravel cushion layer.

[0013] The gravel cushion layer provides the main load-bearing framework for the foundation. Its gravel particles support each other and can bear large vertical loads. The fine sand cushion layer can be filled between the gravel particles to make the load distribution more uniform. When the load of the building is transferred to the cushion layer, the gravel in the gravel cushion layer resists most of the pressure, while the fine sand plays a role in buffering and dispersing the pressure between the gravel particles to prevent local stress concentration.

[0014] When building on a soft soil foundation, the foundation soil may experience a large settlement due to the upper load. The fine sand-sand-gravel cushion layer combination can buffer the impact of foundation settlement on the building foundation through its own compression and deformation. The fine sand-sand-gravel cushion layer can maintain the relative stability of the foundation during the foundation settlement process and reduce the uneven settlement of the building.

[0015] On the other hand, the fine sand cushion layer has finer particles and can fill the tiny gaps between the gravels in the sand and gravel cushion layer. Fine sand can be used as a "secondary filtration" material. On the basis of the rapid drainage of the sand and gravel cushion layer, it can further filter the discharged water, intercept the fine particles that may be carried in the water, and prevent the drainage system from being blocked.

[0016] The large pores formed by the gravel in the gravel cushion can quickly guide the water flow, while the fine sand cushion can improve the uniformity of drainage. For example, in areas with heavy rainfall, the groundwater level may rise rapidly. At this time, the gravel cushion first quickly guides a large amount of water to the drainage direction, while the fine sand cushion can ensure that the drainage speed at different locations is relatively consistent, avoiding excessive local water accumulation, thereby better keeping the foundation dry.

[0017] Ceramic fiber cloth is added between the ceramsite soil and the gravel cushion layer to play a role in heat insulation, which can effectively prevent the transfer of heat, reduce the loss or entry of heat, and thus play a good role in temperature control. The ceramsite concrete partition wall is arranged in a tic-tac-toe pattern in the ceramsite soil layer to facilitate compaction in different areas and ensure the foundation strength.

[0018] The distance between the retaining wall and the retaining wall of the present invention is 3500mm, and sufficient backfill volume is conducive to maintaining structural stability. A circle of water dispersion slope is arranged on the outer circumference of the retaining wall, and an expansion joint is arranged every 20m on the water dispersion slope. The expansion joint is arranged on the contact surface between the water dispersion slope and the retaining wall, and is filled with high temperature resistant sealing material.

[0019] The purpose of setting expansion joints on the water slope is to prevent possible uneven settlement, which may cause cracks on the water slope. After the salt tank melts the salt, the heat is transferred to the water slope to prevent the expansion joint sealing material of the water slope from being damaged, so high-temperature resistant sealing materials are selected for filling.

[0020] The heat-resistant concrete layer and the retaining wall of the present invention are both provided with a plurality of radial expansion joints, and the expansion joints of the heat-resistant concrete layer are filled with high-temperature resistant glass wool. Heat-resistant concrete expands and contracts after being heated, so radial expansion joints are provided and filled with glass wool to make heat transfer and heat conduction uniform. The retaining wall is at the end of the heat conduction of the salt tank and is less heated. The high-temperature resistant sealing material meets the heating requirements and the high-temperature resistant sealing material connects the concrete on both sides of the expansion joint, so that the concrete retaining wall is evenly heated.

[0021] The thickness ratio of the fine sand cushion layer and the gravel cushion layer of the present invention is 1:9; the sand and gravel are siliceous granular materials with a particle size not greater than 32 mm, and the total weight of particles with a particle size less than 0.1 mm does not exceed 1% of the total weight of all particles, and the sand equivalent value with a particle size below 4 mm is greater than 40.

[0022] The gravel cushion layer has a high bearing capacity due to its gravel content and can bear most of the weight of the tank. The gravels are embedded in each other in the cushion layer to form a stable skeleton structure. Although the fine sand cushion layer has a relatively weak bearing capacity, it can fill the gaps in the gravel cushion layer and play a role in auxiliary bearing. This 1:9 thickness ratio allows the two to work better together and evenly transfer the load of the tank to the foundation soil. The two can adapt to the changes in load from installation to use according to this ratio and grading, so that the foundation can maintain good bearing performance throughout the process.

[0023] The retaining ring wall of the present invention comprises a refractory brick layer and a steel outer wall from the inside to the outside. The steel outer wall is circumferentially provided with exhaust holes, and an exhaust pipe is installed on the exhaust hole. The exhaust pipe is in an upward L-shape, and the exhaust port is bent downward.

[0024] The purpose of setting the exhaust pipe is to remove the gas generated by heat conduction in the ceramsite and insulation bricks. Since the height difference between the scattered water around the salt tank and the top of the steel outer wall is small, it is not suitable to set it to be inclined downward. Setting it with a "U" shape downward can effectively prevent rainwater from entering the salt tank foundation.

[0025] The thickness ratio of the base cushion layer, the composite thermal insulation layer and the top cushion layer of the present invention is 5:14:3; the slope from the center to the outside of the upper surface of the composite thermal insulation layer is 1.5%.

[0026] The thickness of the foundation cushion accounts for 5%, which mainly bears the weight of the tank and distributes it evenly on the foundation. The thicker cushion can effectively disperse the load and prevent the tank foundation from uneven settlement due to excessive local pressure.

[0027] The thickness of the composite insulation layer is 14, and the relatively thick insulation layer also plays a certain auxiliary role in load bearing. It is located above the foundation cushion layer. On the one hand, it can transfer part of the weight of the tank to the cushion layer. On the other hand, its own material structure and thickness can increase the overall stability of the foundation to a certain extent. Moreover, under the interaction between the insulation layer and the cushion layer, when the tank is subjected to lateral forces (such as wind force, horizontal forces generated by liquid sloshing), it can better resist these forces and maintain the stability of the foundation.

[0028] The top cushion layer is 3% thick and can be regarded as the "top reinforcement layer" of the entire foundation structure. It works together with the base cushion layer to better support the bottom of the tank. When the liquid distribution inside the tank changes or is subjected to dynamic loads (such as impact during the process of liquid entering and leaving the tank), the top cushion layer can balance these changes together with the base cushion layer to ensure the bearing capacity and stability of the foundation.

[0029] The main function of the composite insulation layer is heat preservation, and its thickness is the largest. The existence of the base cushion layer and the top cushion layer affects the insulation effect to a certain extent. The base cushion layer can prevent heat from being lost or transmitted through the foundation, and the top cushion layer can reduce the heat exchange between the bottom of the tank and the outside world. Together with the composite insulation layer, they construct a relatively closed insulation space. The setting of their thickness ratio makes the insulation performance optimal, avoiding the "thermal bridge" phenomenon caused by a certain layer being too thin, that is, a weak link where heat can easily pass through.

[0030] The slope of the upper surface of the composite insulation layer is to offset the deformation of the bottom plate caused by the foundation settlement after the tank is filled with the medium. When the load distribution of the tank is uneven, the inclined fine sand cushion can adjust the pressure on the foundation to a certain extent. In the area with less load near the edge of the tank, the sand cushion is appropriately tilted so that the load is transferred through the sand cushion and distributed more reasonably to the foundation soil. This can avoid excessive settlement of local foundation soil due to excessive pressure, thereby making the settlement of the entire tank more uniform and reducing the risk of tank tilting or damage due to uneven foundation.

[0031] On the other hand, the inclined fine sand cushion layer can use gravity to guide water flow. Water in the sand layer can be drained outward more quickly along the inclined direction, reducing water accumulation in the foundation soil, thereby reducing problems such as reduced strength of the foundation soil due to excessive water content.

[0032] At the same time, under the action of an earthquake, the inclined fine sand cushion can cause the building to have a certain displacement tendency in the horizontal direction. This displacement tendency can cause the earthquake energy to produce friction and dislocation between the particles of the sand cushion, thereby consuming part of the earthquake energy. It is similar to placing an object on an inclined plane. When an earthquake occurs, the movement of the object on the inclined plane and the relative sliding of the sand particles can have a shock-absorbing effect, which can reduce the damage to the building to a certain extent.

[0033] The construction method of the foundation structure of the molten salt storage tank of the solar thermal power station according to the present invention is characterized by comprising the following steps:

[0034] A. Foundation cushion construction

[0035] The foundation is excavated to the construction level of the foundation cushion, the ground is leveled and compacted, the retaining wall reinforcement and formwork are installed, and the temperature measuring sleeves and ventilation pipes in the foundation cushion are poured twice. The first layer of temperature measuring sleeves is poured first, and the ventilation pipes are constructed above the first layer of concrete to ensure the installation quality and improve the efficiency of pipeline welding. The steel embedded parts of the outer wall of the pre-embedded retaining ring wall and the second layer of cushion are poured with concrete;

[0036] B. Retaining wall construction

[0037] The steel outer wall of the retaining wall is welded and installed. After installation, earthwork is backfilled between the retaining wall and the steel outer wall. The partition wall formwork of ceramsite concrete is installed inside the retaining wall. After pouring, the refractory bricks on the inner side of the steel outer wall are laid.

[0038] Here, the expanded clay concrete partition wall is poured first, followed by the refractory brick laying to ensure that the refractory bricks will not be damaged or contaminated during the pouring process.

[0039] C. Construction of composite insulation layer

[0040] The inside of the retaining wall is backfilled and compacted with expanded clay, and then the annular beam is installed. Ceramic fiber cloth is laid on top of the expanded clay, and finally the cushion layer is constructed.

[0041] Preferably, the expanded clay is laid in 4 layers, each of which is compacted, and the thickness of each of the lower 3 layers is twice the thickness of the uppermost layer. The maximum compacted thickness of each layer does not exceed 500 mm, thereby ensuring the density of the thermal insulation layer.

[0042] Preferably, C20 concrete containing an anti-sulfate preservative is added to the concrete of the foundation cushion layer, and a ceramic coating or an epoxy coating is added to the outer surface of the concrete.

[0043] Preferably, the heat-resistant concrete of the annular beam contains refractory aggregate and refractory fine material, and the mass ratio of the two is 3:1, the compressive strength is ≥19.1MPa, and the heat resistance temperature is ≥600°C; the refractory aggregate includes crushed clay bricks, clay clinker, alumina clinker and crushed high-alumina refractory bricks, etc.; the refractory fine material includes magnesia, crushed high-alumina bricks containing fly ash, crushed magnesia refractory bricks, magnesia and corundum sand.

[0044] The beneficial effects of the present invention are:

[0045] 1. The present invention uses multiple layers of cushions made of different materials. The fine sand-sandstone cushion combination can buffer the impact of foundation settlement on the building foundation through its own compression and deformation, maintain the relative stability of the foundation, reduce the uneven settlement of the building, and evenly distribute the weight of the storage tank to the foundation. It can also serve as a drainage channel to prevent the impact of rising groundwater on the foundation. The concrete cushion is mainly used to prevent the molten salt from penetrating downward after leakage. Its lower porosity can effectively block the penetration path of the molten salt; a retaining wall structure is set up, and the retaining wall adopts a reinforced concrete structure. When the molten salt leaks, it can limit the molten salt within a certain range to prevent it from flowing around, thereby reducing pollution and damage to the surrounding environment and other facilities.

[0046] 2. The concrete part of the foundation cushion of the present invention is made of concrete resistant to molten salt corrosion, and an anti-sulfate preservative is added to enhance the concrete's tolerance to molten salt. On the surface where the molten salt contacts the concrete, a ceramic coating or an epoxy coating is added as a protective coating to further enhance the protection against the molten salt. These coatings can form a barrier between the molten salt and the base material, preventing the molten salt from chemically reacting with the base material, thereby reducing the risk of leakage caused by corrosion.

[0047] 3. Install a temperature measuring tube inside the foundation cushion. Since the molten salt has a high temperature, when the molten salt leaks, it will cause the local temperature of the foundation to rise. By monitoring the temperature change, it can assist in judging whether the molten salt has leaked.

[0048] 4. The composite insulation layer is designed to be a slope, and the base surface forms a right cone shape. After the tank is filled with the medium, the deformation of the tank bottom plate is offset, the risk of cracks in the bottom plate weld is reduced, and thus the risk of molten salt leakage is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a partial schematic diagram of the basic structure of the molten salt storage tank of the solar thermal power station of the present invention.

[0050] Figure 2 This is a partial schematic diagram of the basic structure of the molten salt storage tank of the solar thermal power station of the present invention from another angle.

[0051] Figure 3 This is a schematic diagram of the structure of expanded clay concrete partition wall.

[0052] Figure 4 Schematic diagram of the structure of the concrete layer of the ring beam.

[0053] Figure 5 This is a partial schematic diagram of the basic structure of Example 5. DETAILED DESCRIPTION

[0054] In order to more clearly and in detail illustrate the technical solution of the present invention, the present invention is further described below through relevant embodiments. The following embodiments are only for specific explanation of the implementation method of the present invention, and do not limit the protection scope of the present invention.

[0055] Example 1

[0056] A foundation structure of a molten salt storage tank in a solar thermal power station comprises a composite insulation layer and a reinforced concrete retaining wall, wherein the composite insulation layer is arranged below a tank bottom plate of the molten salt storage tank, the composite insulation layer comprises a top cushion layer, a ceramic fiber cloth and a ceramsite layer which are arranged in sequence downward, an annular beam is arranged on the top of the composite insulation layer, the annular beam comprises an annular steel plate and a heat-resistant concrete layer which are arranged in sequence below the tank bottom plate, a retaining ring wall is arranged circumferentially on the composite insulation layer, a concrete foundation cushion layer with a built-in ventilation pipe and a temperature measuring sleeve is arranged below the composite insulation layer, a circle of retaining walls is arranged on the periphery of the retaining ring wall, and compacted plain soil is filled between the retaining wall and the retaining ring wall; the top cushion layer comprises a fine sand cushion layer and a sand and gravel cushion layer from top to bottom, and a plurality of vertical ceramsite concrete partition walls are arranged in a tic-tac-toe pattern in the ceramsite layer.

[0057] Example 2

[0058] This embodiment is based on embodiment 1:

[0059] The distance between the retaining wall and the retaining ring wall is 3500mm. A circle of water dispersion slope is arranged circumferentially on the outer side of the retaining ring wall. An expansion joint is arranged every 20m on the water dispersion slope. The expansion joint is arranged on the contact surface between the water dispersion slope and the retaining ring wall and is filled with high temperature resistant sealing material.

[0060] Example 3

[0061] This embodiment is based on embodiment 1:

[0062] The heat-resistant concrete layer and the retaining wall are both provided with a plurality of radial expansion joints, and the expansion joints of the heat-resistant concrete layer are filled with high-temperature resistant glass wool.

[0063] Example 4

[0064] This embodiment is based on embodiment 1:

[0065] The thickness ratio of the fine sand cushion layer to the gravel cushion layer is 1:9; the average particle size of the fine sand is less than 25 times the average particle size of expanded clay; the gravel is a siliceous granular material with a particle size not greater than 32 mm, and the total weight of particles with a particle size less than 0.1 mm does not exceed 1% of the total weight of all particles.

[0066] Example 5

[0067] This embodiment is based on embodiment 1:

[0068] The retaining ring wall comprises a refractory brick layer and a steel outer wall from the inside to the outside. The steel outer wall is circumferentially provided with exhaust holes, and an exhaust pipe is installed on the exhaust hole. The exhaust pipe is in an upward L-shape, and the exhaust port is bent downward.

[0069] Example 6

[0070] This embodiment is based on embodiment 1:

[0071] The thickness ratio of the base cushion layer, the composite thermal insulation layer and the top cushion layer is 5:14:3; the slope from the center to the outside of the upper surface of the composite thermal insulation layer is 1.5%.

[0072] Example 7

[0073] The construction method of the foundation structure of the molten salt storage tank of the solar thermal power station of the present invention comprises the following steps:

[0074] A. Foundation cushion construction

[0075] The foundation is excavated to the construction level of the foundation cushion, the ground is leveled and compacted, the retaining wall reinforcement and formwork are installed, and the temperature measuring sleeves and ventilation pipes in the foundation cushion are poured twice. The first layer of temperature measuring sleeves is poured first, and the ventilation pipes are constructed above the first layer of concrete. The steel embedded parts of the outer wall of the pre-buried retaining ring wall and the second layer of cushion are poured with concrete;

[0076] B. Retaining wall construction

[0077] The steel outer wall of the retaining wall is welded and installed. After installation, earthwork is backfilled between the retaining wall and the steel outer wall. The partition wall formwork of ceramsite concrete is installed inside the retaining wall. After pouring, the refractory bricks on the inner side of the steel outer wall are laid.

[0078] C. Construction of composite insulation layer

[0079] The inside of the retaining wall is backfilled and compacted with expanded clay, and then the annular beam is installed. Ceramic fiber cloth is laid on top of the expanded clay, and finally the cushion layer is constructed.

[0080] Example 8

[0081] This embodiment is based on Embodiment 7:

[0082] The expanded clay is laid in 4 layers, each of which is compacted, and the thickness of each of the lower 3 layers is twice the thickness of the uppermost layer, and the maximum compacted thickness of each layer does not exceed 500 mm.

[0083] Example 9

[0084] This embodiment is based on Embodiment 7:

[0085] C20 concrete with anti-sulfate preservative is added to the concrete of the foundation cushion, and ceramic coating or epoxy coating is added to the outer surface of the concrete.

[0086] The heat-resistant concrete of the annular beam contains refractory aggregate and refractory fine material, and the mass ratio of the two is 3:1, the compressive strength is ≥19.1MPa, and the heat-resistant temperature is ≥600℃; the refractory aggregate includes crushed clay bricks, clay clinker, alumina clinker and crushed high-alumina refractory bricks, etc.; the refractory fine material includes magnesia sand, crushed high-alumina bricks containing fly ash, crushed magnesia refractory bricks, magnesia sand and corundum sand.

[0087] Example 10

[0088] The construction method of the present invention is used to construct the foundation of the cold and hot molten salt tanks of the Jinghe solar thermal project. A reinforced concrete retaining wall is designed on the outside of the molten salt tank. The foundation cushion is a 500mm thick C20 concrete. The radius of the retaining wall of the hot molten salt tank is 20.111m, and the radius of the retaining wall of the cold molten salt tank is 19.8585m. The foundation height is 1700mm. The foundation includes a 40mm thick steel annular wall, a 300mm thick insulation brick, a heat-resistant concrete foundation, an annular steel plate, ceramsite, a sand and gravel cushion, a fine sand cushion, etc. The bottom elevation of the foundation cushion of the cold and hot molten salt tank is an absolute elevation of 451.00m. The temperature measuring sleeve and the air cooling ventilation duct are installed in the foundation cushion.

[0089] Layered compaction of expanded clay: The thickness of cold-tank expanded clay is 1.4m, which is compacted in 4 layers, with each of the lower 3 layers being 40cm thick and each of the upper layer being 20cm thick; The thickness of hot-tank expanded clay is 1.4m, which is compacted in 4 layers, with each of the lower 3 layers being 40cm thick and each of the upper layer being 20cm thick.

[0090] C20 concrete with anti-sulfate preservative is added to the concrete of the foundation cushion layer, and an epoxy coating is added to the outer surface of the concrete; the heat-resistant concrete of the annular beam contains refractory aggregate and refractory fine material, and the mass ratio of the two is 3:1, the compressive strength is ≥19.1MPa, and the heat-resistant temperature is ≥600℃.

[0091] By using this method, the construction process is optimized, the construction period is shortened, the construction quality of the foundation is guaranteed, there is no molten salt leakage problem, the material and energy consumption are reduced during the construction process, and environmental pollution is reduced. It has good social benefits and economic value for environmental protection and energy conservation and emission reduction.

[0092] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A foundation structure of a molten salt storage tank for a solar thermal power station, characterized in that: The invention relates to a retaining wall comprising a composite thermal insulation layer and reinforced concrete, wherein the composite thermal insulation layer is arranged below the tank bottom plate of the molten salt storage tank, wherein the composite thermal insulation layer comprises a top cushion layer, a ceramic fiber cloth and a ceramsite layer which are arranged downward in sequence, wherein an annular beam is arranged on the top of the composite thermal insulation layer, wherein the annular beam is composed of an annular steel plate and a heat-resistant concrete layer which are arranged in sequence below the tank bottom plate, wherein a retaining ring wall is arranged circumferentially on the composite thermal insulation layer, wherein a concrete foundation cushion layer with a built-in ventilation pipe and a temperature measuring sleeve is arranged below the composite thermal insulation layer, wherein a circle of the retaining wall is arranged on the periphery of the retaining ring wall, wherein compacted plain soil is filled between the retaining wall and the retaining ring wall; wherein the top cushion layer comprises a fine sand cushion layer and a sand and gravel cushion layer in sequence from top to bottom, wherein a plurality of vertical ceramsite concrete partition walls are arranged in a tic-tac-toe pattern in the ceramsite layer.

2. The basic structure of the molten salt storage tank of a solar thermal power station according to claim 1 is characterized in that: The distance between the retaining wall and the retaining ring wall is 3500mm. A circle of water dispersion slope is arranged circumferentially on the outer side of the retaining ring wall. An expansion joint is arranged every 20m on the water dispersion slope. The expansion joint is arranged on the contact surface between the water dispersion slope and the retaining ring wall and is filled with high temperature resistant sealing material.

3. The basic structure of the molten salt storage tank of a solar thermal power station according to claim 1 is characterized in that: The heat-resistant concrete layer and the retaining wall are both provided with a plurality of radial expansion joints, and the expansion joints of the heat-resistant concrete layer are filled with high-temperature resistant glass wool.

4. The basic structure of the molten salt storage tank of a solar thermal power station according to claim 1, characterized in that: The thickness ratio of the fine sand cushion layer and the gravel cushion layer is 1:9; the sand and gravel are siliceous granular materials with a particle size not exceeding 32 mm, and the total weight of particles with a particle size less than 0.1 mm does not exceed 1% of the total weight of all particles, and the sand equivalent value with a particle size below 4 mm is greater than 40.

5. The basic structure of the molten salt storage tank of a solar thermal power station according to claim 1 is characterized in that: The retaining ring wall comprises a refractory brick layer and a steel outer wall from the inside to the outside. The steel outer wall is circumferentially provided with exhaust holes, and an exhaust pipe is installed on the exhaust hole. The exhaust pipe is in an upward L-shape, and the exhaust port is bent downward.

6. The basic structure of the molten salt storage tank of a solar thermal power station according to claim 1, characterized in that: The thickness ratio of the base cushion layer, the composite thermal insulation layer and the top cushion layer is 5:14:3; the slope from the center to the outside of the upper surface of the composite thermal insulation layer is 1.5%.

7. The construction method of the foundation structure of the molten salt storage tank of a CSP power station according to any one of claims 1 to 6, characterized in that: The following steps are involved: A. Foundation cushion construction The foundation is excavated to the construction level of the foundation cushion, the ground is leveled and compacted, the retaining wall reinforcement and formwork are installed, and the temperature measuring sleeves and ventilation pipes in the foundation cushion are poured twice. The first layer of temperature measuring sleeves is poured first, and the ventilation pipes are constructed above the first layer of concrete. The steel embedded parts of the outer wall of the pre-buried retaining ring wall and the second layer of cushion are poured with concrete; B. Retaining wall construction The steel outer wall of the retaining wall is welded and installed. After installation, earthwork is backfilled between the retaining wall and the steel outer wall. The partition wall formwork of ceramsite concrete is installed inside the retaining wall. After pouring, the refractory bricks on the inner side of the steel outer wall are laid. C. Construction of composite insulation layer Use expanded clay to backfill and compact the inside of the retaining wall, then install the annular beam, lay ceramic fiber cloth on top of the expanded clay, and finally construct the top cushion layer.

8. The construction method of the foundation structure of the molten salt storage tank of a solar thermal power station according to claim 7 is characterized in that: The expanded clay is laid in 4 layers, each of which is compacted, and the thickness of each of the lower 3 layers is twice the thickness of the uppermost layer, and the maximum compacted thickness of each layer does not exceed 500 mm.

9. The construction method of the foundation structure of the molten salt storage tank of a solar thermal power station according to claim 7, characterized in that: C20 concrete with anti-sulfate preservative is added to the concrete of the foundation cushion, and ceramic coating or epoxy coating is added to the outer surface of the concrete.

10. The construction method of the foundation structure of the molten salt storage tank of a solar thermal power station according to claim 7, characterized in that: The heat-resistant concrete of the annular beam contains refractory aggregate and refractory fine material, and the mass ratio of the two is 3:1, the compressive strength is ≥19.1MPa, and the heat-resistant temperature is ≥600℃; the refractory aggregate includes crushed clay bricks, clay clinker, alumina clinker and crushed high-alumina refractory bricks, etc.; the refractory fine material includes magnesia sand, crushed high-alumina bricks containing fly ash, crushed magnesia refractory bricks, magnesia sand and corundum sand.

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