SiC heat conduction material for cross-seasonal heat storage filling of soil source

Abstract

The invention discloses a SiC heat conduction material for cross-seasonal heat storage filling of a soil source, and relates to the cross technical field of new energy utilization and heat energy storage. The invention aims to provide a SiC heat-conducting material for cross-seasonal heat storage filling of a soil source, so as to solve the problems of high raw material cost, difficulty in large-scale application and the like in the preparation process of the SiC heat-conducting material. According to the technical key points, lignite is smashed, lignite powder is screened and then subjected to acid pickling, the acid-pickled solution is filtered to obtain impurity-removed lignite powder, hydrochloric acid remaining on the powder is washed away with flowing water, and finally the washed powder is dried; the method comprises the following steps: mixing lignite powder, rice hull powder and coal gangue powder, carrying out high-temperature carbonization reaction for 24-30 hours in a graphite crucible under the protection of argon at the reaction temperature of 1200-1300 DEG C, and cooling for 48-50 hours after the reaction is completed; and crushing the cooled reaction product to 4-5mm to serve as a raw material of the buried pipe backfill material. The adopted process raw materials are low in cost, and large-scale application can be achieved. The silicon carbide material suitable for improving the thermal conductivity of the cross-seasonal heat storage buried pipe backfill material is prepared in a low-cost mode, the raw materials are low-grade energy sources, the environmental protection requirement is met, and resource recycling is promoted.

Description

Technical Field

[0001] The present invention relates to the cross-technical field of new energy utilization and thermal energy storage, and in particular to a SiC thermal conductive material for soil source cross-seasonal heat storage filling. Background Art

[0002] Silicon carbide (SiC) is widely used in ceramics, electronic devices, and new energy heat storage due to its excellent thermal conductivity, high temperature stability, and chemical corrosion resistance. In the ground source heat pump system, the backfill material of the buried pipe is usually composed of cement, sand, etc., and its thermal conductivity is relatively low, which limits the improvement of heat exchange efficiency. Mixing silicon carbide with the backfill material can significantly improve the thermal conductivity of the backfill material, thereby enhancing the heat exchange capacity between the buried pipe and the surrounding soil, and thus improving the energy efficiency of the entire system. Due to the large amount of backfill material used in the buried pipe, the purity requirement for silicon carbide is relatively low, and the traditional silicon carbide production process usually relies on high-purity raw materials, resulting in high production costs, which limits its economic feasibility in large-scale applications. Low-grade energy (such as lignite, rice husks, and biomass) as a cheap and abundant raw material provides feasibility for the economic preparation of silicon carbide. By optimizing the processing process of low-grade energy, it is possible to produce low-cost, high-performance silicon carbide fillers suitable for buried pipe backfill materials.

[0003] The prior art also provides some information about the preparation process of silicon carbide. For example, the prior art with application number CN201510072827.8 discloses a method for preparing nano silicon carbide at low temperature using silicon-containing biomass as raw material and the prepared nano silicon carbide. The prior art method for preparing nano silicon carbide at low temperature using silicon-containing biomass as raw material comprises the following steps: washing the silicon-containing biomass, acid-boiling the biomass to remove inorganic salt ion impurities, repeatedly washing with distilled water, drying and grinding into powder, adding magnesium powder and ball-milling the mixture to mix evenly, and then putting it into a tubular furnace and keeping it warm at low temperature under an inert atmosphere to allow magnesium and carbon to fully react to generate MgC-2 and Mg-2C-3, and then keeping it warm at high temperature to allow magnesium carbide to reduce silicon dioxide to silicon carbide, and cooling to room temperature with the furnace, acid-washing the obtained product to remove silicon dioxide, magnesium oxide, silicon, etc., filtering and drying, and then air annealing to remove excess carbon to obtain nano silicon carbide. For example, the prior art with application number CN202411274593.0 discloses a preparation process for high-purity silicon carbide micropowder, which includes: mixing silicon powder and carbon powder in proportion; generating silicon carbide by mixing the raw materials in a heating chamber; cooling the silicon carbide; obtaining silicon carbide particles by preliminary grinding; purifying the silicon carbide particles; removing moisture from the silicon carbide particles by using a drying device and finely grinding them into silicon carbide micropowder; determining the production quality according to the purity of the silicon carbide micropowder; and determining the response method to improve the purity of silicon carbide according to the production quality.

[0004] The existing paper "Test and Analysis of Heat Transfer Characteristics of Silicon Carbide Energy Piles in Saturated Sand Foundation" proposes to study the heat transfer characteristics of silicon carbide energy piles by using standard test block tests and model tests. The pile body material mix ratio of silicon carbide energy piles is determined by testing the thermal conductivity and mechanical properties of pile foundation concrete test blocks; the heat transfer performance of silicon carbide energy piles in saturated sand foundations and the axial and radial temperature distribution and change law are analyzed by model tests of high-temperature heat release conditions of energy piles in saturated sand foundations. The results show that when the silicon carbide sand replacement rate reaches 16.0%, the thermal conductivity, compressive strength and flexural strength of the pile foundation concrete test block will increase by 64.1%, 19.9% ​​and 11.4% respectively, and the pile body material mix ratio of silicon carbide energy piles under this sand replacement rate is the best mix ratio. The highest temperature of silicon carbide energy piles appears in the middle of the pile body. Compared with ordinary energy piles, silicon carbide energy piles have higher pile body temperature, temperature growth rate and heat exchange power, showing better heat transfer performance. When the silicon carbide energy pile undergoes thermal cycling, the heat transfer efficiency between the pile and the soil decreases radially from the pile body to the outside; after the thermal cycle, the soil around the pile shows a heat accumulation phenomenon, and this phenomenon gradually increases as it approaches the pile body. The research results can provide an experimental basis for the design of silicon carbide energy piles and their application in saturated sand foundations.

[0005] The existing paper "Research on the Formulation of Cement Slurry System for Geothermal Well Cementing with "Water Retention and Heat Extraction" Based on Hybrid Weighted Method" points out that the heat exchange system of medium-deep "water retention and heat extraction" geothermal wells achieves the purpose of heat extraction by exchanging heat between the circulating working fluid flowing in the inner and outer casings and the cementing materials and formations. The heat transfer between the cementing material and the geothermal well casing is an important link in the downhole heat exchange system, and its thermal conductivity directly affects the downhole heat exchange efficiency of the geothermal well. Aiming at the problem of low thermal conductivity of existing geothermal well cementing cement, the author starts from the current cementing process, takes G-grade HSR oil well cement as the base material, selects carbon-based materials natural flake graphite (NG), cubic silicon carbide (β-SiC), inorganic thermal conductivity factor alumina (α-Al2O3) as cementing cement additives, selects thermal conductivity, compressive strength, fluidity, water-solid ratio four main control factors, through systematic experiments, orthogonal test and mixed weighted method (AHP-CRITIC), to determine the optimal mix ratio of high thermal conductivity cementing slurry system. The results show that under this mix ratio, the water-solid ratio is set to 0.45, the additives α-Al2O3, β-SiC and NG account for 3%, 1% and 8% of the cementing cement mass respectively, the average fluidity of the cementing slurry system is 17.7cm, and the thermal conductivity can reach 2.176W·(m·K)-1, which can be increased by 37.6% compared with the commonly used G-grade HSR cementing materials. The research results can provide technical reference for geothermal well cementing process optimization and thermal calculation.

[0006] However, in the existing technology, there is little research on the controllability of the purity of silicon carbide powder. In the silicon carbide preparation process, the controllability of its purity and production efficiency are crucial. No one has mentioned that SiC thermal conductive materials can be used for soil source cross-seasonal heat storage filling. In the existing SiC thermal conductive material preparation technology, the product or sample processing steps are cumbersome and the raw material cost is high, which limits its possibility of large-scale application. Summary of the invention

[0007] The technical problems to be solved by the present invention are:

[0008] The purpose of the present invention is to provide a SiC thermal conductive material for soil source inter-seasonal heat storage filling, so as to solve the problems of high raw material cost and difficulty in large-scale application in the preparation process of SiC thermal conductive material.

[0009] The technical solution adopted by the present invention to solve the above technical problems is: a SiC thermal conductive material for soil source cross-seasonal heat storage filling, and the preparation process of the SiC thermal conductive material is as follows:

[0010] Step A: crushing lignite, and screening lignite powder with a particle size of 0.1 to 0.3 mm with a sieve, mixing the lignite powder with a hydrochloric acid solution with a mass percentage concentration of 30 to 40%, stirring for 1 to 3 minutes and then standing for 1.5 to 2 hours to remove carbonate mineral impurities in the lignite and retain silicate minerals; filtering the solution after acid washing to obtain the lignite powder after impurities are removed, washing the residual hydrochloric acid on the powder with running water, and finally drying the washed powder at a temperature of 100 to 120° C. for 1.5 to 2 hours;

[0011] Step B: crushing the rice husk and screening the rice husk powder with a particle size of 0.1 to 0.3 mm with a sieve for later use;

[0012] Step C: crushing the coal gangue, and screening the coal gangue powder with a particle size of 0.1 to 0.3 mm with a sieve for later use;

[0013] Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of (1.5-3):1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24-30 hours at a reaction temperature of 1200°C-1300°C. After the reaction is completed, the mixture is cooled for 48-50 hours; the cooled reaction product is crushed into 4mm-5mm and used as a raw material for the buried pipe backfill material.

[0014] The present invention has the following beneficial technical effects:

[0015] The technical concept of the present invention is: based on the alternative research of multiple raw materials, try other low-grade energy sources as raw materials, such as straw, waste plastics, wood chips, industrial waste residues, etc., to achieve raw material diversification. The feasibility and economy of alternative raw materials can further expand the production path of silicon carbide. Preparation process optimization: explore low-temperature processes to synthesize silicon carbide, reduce energy consumption and further reduce production costs. In addition to traditional solid-phase reactions, gas phase reaction methods (such as chemical vapor deposition) are used to prepare silicon carbide fillers, making the reaction conditions milder and reducing the impact on the environment.

[0016] The present invention crushes lignite to screen lignite powder and then performs pickling, filters the pickled solution to obtain the impurity-removed lignite powder, washes the residual hydrochloric acid on the powder with flowing water, and finally dries the washed powder; mixes lignite powder, rice husk powder, and coal gangue powder, and performs a high-temperature carbonization reaction in a graphite crucible under argon protection for 24 to 30 hours, the reaction temperature is 1200°C to 1300°C, and the reaction is cooled for 48 hours to 50 hours after completion; the cooled reaction product is crushed to 4mm to 5mm as a raw material for the backfill material of the buried pipe. The present invention improves the controllability of the purity of the preparation of silicon carbide micropowder by removing free carbon and pickling, improves the production efficiency, and is suitable for soil-source inter-seasonal heat storage filling. The present invention innovatively proposes a process for producing low-cost, high-performance silicon carbide fillers suitable for backfill materials of buried pipes based on low-grade energy as raw materials. The SiC thermal conductive material prepared by the process method is suitable for soil-source inter-seasonal heat storage filling. The process raw material cost adopted by the present invention is low and can be applied on a large scale. The present invention prepares a silicon carbide material suitable for improving the thermal conductivity of inter-seasonal heat storage buried pipe backfill materials in a low-cost manner. The raw materials are low-grade energy, meet environmental protection requirements, and promote resource recycling.

[0017] Industrialization analysis of the present invention application: 1. Reduce production costs and improve market competitiveness: The present invention significantly reduces the raw material cost of silicon carbide production by using low-grade energy as raw materials. The production of traditional silicon carbide relies on high-purity raw materials, resulting in high costs, while low-grade energy is relatively cheap and abundant in resources. By optimizing the production process, the production cost can be greatly reduced, making the production of silicon carbide have obvious advantages in terms of economy. This cost advantage is crucial to the competitiveness of enterprises in the market, especially in large-scale application scenarios, where cost is a key factor in determining the popularity of products. 2. Improve the energy efficiency of ground source heat pump systems and increase market demand: Silicon carbide, as a high thermal conductivity material, can significantly improve the heat exchange efficiency of ground source heat pump systems. With the increase in global energy demand and the advancement of sustainable development goals, ground source heat pumps, as green and energy-saving energy systems, are increasingly favored by the market. Improving the thermal conductivity of backfill materials can not only optimize the overall energy efficiency of ground source heat pump systems, but also improve the long-term stability and economy of the system, which provides strong support for the sales and market share growth of ground source heat pump products. 3. Resource recycling and environmental protection advantages: The present invention uses low-grade energy, which not only reduces the dependence of traditional production methods on high-purity raw materials, but also effectively promotes the recovery and recycling of waste resources. This practice complies with environmental protection laws and regulations and the trend of sustainable development, and also helps to reduce the burden on the environment. By promoting this technology, enterprises can not only reduce production costs, but also improve their brand image and market recognition in the field of environmental protection.

[0018] The present invention uses low-grade energy as raw materials. If others use these specific raw materials without permission and produce silicon carbide fillers through similar processes, infringement evidence can be obtained through detailed investigation of their production process, raw material sources, product characteristics, etc. Evidence can be collected in the following ways: Procurement channel investigation, tracking the target company's raw material procurement records and supply chain links, and confirming whether the same or similar low-grade energy as the present invention is used. Product analysis, through experimental analysis of silicon carbide fillers produced by competitors, compare their performance indicators (such as thermal conductivity, chemical composition, etc.) to see if they are similar to the products of the present invention, especially when it comes to high-temperature carburization reactions, silicon carbide composition and physical properties after pickling treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention can be more deeply understood by referring to the description provided below in combination with the accompanying drawings. These drawings and the following detailed description together constitute an important part of this specification, which not only intuitively shows the technical framework and implementation process of the present invention, but also further explains the core principles of the present invention through specific preferred embodiments.

[0020] Figure 1 It is a flowchart of the preparation process of the present invention. DETAILED DESCRIPTION

[0021] The present invention relates to SiC thermal conductive materials for soil source cross-seasonal heat storage filling, focusing on solving the technical problems of target perception and recognition in backlit scenes, and realizing high-quality flight simulation display through multi-technical collaboration. The following describes the implementation method in detail from four aspects: system construction, image processing, target detection and recognition, and flight simulation display.

[0022] Regarding the key technical points of raw material selection and carbonization process, the present invention incorporates some experimental data, specific process parameters and key material selection into the technical embodiments, but some detailed operations involving existing ones can be slightly blurred to ensure the protection of core technologies. In order to avoid conflicts with other silicon carbide production patents, the present invention has paid close attention to patent documents related to existing silicon carbide production to ensure that the processes or raw material combinations used have not been described in detail in the prior art or have been patented.

[0023] like Figure 1 As shown, the preparation process of the SiC thermal conductive material for soil source inter-seasonal heat storage filling described in this embodiment is as follows:

[0024] Step A: crushing lignite, and screening lignite powder with a particle size of 0.1 to 0.3 mm with a sieve, mixing the lignite powder with a hydrochloric acid solution with a mass percentage concentration of 30 to 40%, stirring for 1 to 3 minutes and then standing for 1.5 to 2 hours to remove carbonate mineral impurities in the lignite and retain silicate minerals; filtering the solution after acid washing to obtain the lignite powder after impurities are removed, washing the residual hydrochloric acid on the powder with running water, and finally drying the washed powder at a temperature of 100 to 120° C. for 1.5 to 2 hours;

[0025] Step B: crushing the rice husk and screening the rice husk powder with a particle size of 0.1 to 0.3 mm with a sieve for later use;

[0026] Step C: crushing the coal gangue, and screening the coal gangue powder with a particle size of 0.1 to 0.3 mm with a sieve for later use;

[0027] Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of (1.5-3):1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24-30 hours at a reaction temperature of 1200°C-1300°C. After the reaction is completed, the mixture is cooled for 48-50 hours; the cooled reaction product is crushed into 4mm-5mm and used as a raw material for the buried pipe backfill material.

[0028] More specifically, the preparation process of the SiC thermal conductive material for soil-source inter-seasonal heat storage filling described in this embodiment is as follows:

[0029] Step A: grind the lignite with a pulverizer, and screen the lignite powder with a particle size of 0.2 mm with a sieve, mix the lignite powder with a hydrochloric acid solution with a mass percentage concentration of 36%, stir for 1 minute and then stand for 2 hours to remove carbonate mineral impurities in the lignite and retain silicate minerals; filter the solution after acid washing to obtain the lignite powder after impurities are removed, wash the residual hydrochloric acid on the powder with running water, and finally dry the washed powder at 100° C. for 2 hours;

[0030] Step B: Crush the rice husks with a crusher, and use a sieve to screen the rice husk powder with a particle size of 0.2 mm for later use;

[0031] Step C: crushing the gangue with a crusher, and screening the gangue powder with a particle size of 0.2 mm with a sieve for later use;

[0032] Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of 2:1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24 hours at a reaction temperature of 1200°C. After the reaction is completed, the mixture is cooled for 48 hours. The cooled reaction product is crushed into 4 mm and filled into an underground pipe as a soil source inter-seasonal heat storage filling material.

[0033] Step B: Crush the rice husks with a crusher, and use a sieve to screen the rice husk powder with a particle size of less than 0.2 mm for later use;

[0034] Step C: crush the gangue with a crusher, and screen the gangue powder with a particle size of less than 0.2 mm with a sieve for later use;

[0035] Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of 2:1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24 hours at a reaction temperature of 1200°C. After the reaction is completed, the mixture is cooled for 48 hours; the cooled reaction product is crushed to 4 mm and used as a raw material for the buried pipe backfill material.

[0036] In step D, the powders obtained in steps A, B and C are mixed in a mass ratio of 2.5:1:1.

[0037] In step 4, under an argon atmosphere, the temperature is first increased to 500° C. to 600° C. at a heating rate of 20° C. / min to 30° C. / min, and then increased to 1200° C. at a heating rate of 5° C. / min to 10° C. / min.

[0038] The SiC thermal conductive material is obtained in block form and the desired particle size is obtained by grinding.

[0039] The thermal conductivity of SiC thermal conductive material reaches 150-180W / (m·K).

[0040] The prepared SiC thermal conductive material is mixed with cement (powder) in a mass ratio of 5:95 and used as backfill material for buried pipes for soil-source inter-seasonal heat storage in buried pipes. The prepared SiC thermal conductive material is used as a soil-source inter-seasonal heat storage filling raw material.

[0041] The present invention has been verified to completely solve the technical problems raised by the present invention and the technical effects recorded. The present invention improves the controllability of the purity of silicon carbide micropowder prepared by removing free carbon and pickling, improves production efficiency, and is suitable for soil-source inter-seasonal heat storage filling. The present invention innovatively proposes a process for producing low-cost, high-performance silicon carbide fillers suitable for buried pipe backfill materials based on low-grade energy as raw materials. The SiC thermal conductive material prepared by this process method is suitable for soil-source inter-seasonal heat storage filling. The process raw material cost adopted by the present invention is low and can be applied on a large scale. The present invention prepares silicon carbide materials suitable for improving the thermal conductivity of inter-seasonal heat storage buried pipe backfill materials in a low-cost manner. The raw materials are low-grade energy, meet environmental protection requirements, and promote resource recycling.

[0042] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments are contemplated within the scope of the invention thus described. The disclosure of the present invention is intended to be illustrative rather than restrictive of the scope of the invention, which is defined by the appended claims.

Claims

1. A SiC thermal conductive material for soil source inter-seasonal heat storage filling, characterized by: The preparation process of SiC thermal conductive material is as follows: Step A: crushing lignite, and screening lignite powder with a particle size of 0.1 to 0.3 mm with a sieve, mixing the lignite powder with a hydrochloric acid solution with a mass percentage concentration of 30 to 40%, stirring for 1 to 3 minutes and then standing for 1.5 to 2 hours to remove carbonate mineral impurities in the lignite and retain silicate minerals; filtering the solution after acid washing to obtain the lignite powder after impurities are removed, washing the residual hydrochloric acid on the powder with running water, and finally drying the washed powder at a temperature of 100 to 120° C. for 1.5 to 2 hours; Step B: crushing the rice husk and screening the rice husk powder with a particle size of 0.1 to 0.3 mm with a sieve for later use; Step C: crushing the coal gangue, and screening the coal gangue powder with a particle size of 0.1 to 0.3 mm with a sieve for later use; Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of (1.5-3):1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24-30 hours at a reaction temperature of 1200°C-1300°C. After the reaction is completed, the mixture is cooled for 48-50 hours; the cooled reaction product is crushed into 4mm-5mm and used as a raw material for the buried pipe backfill material.

2. The SiC thermal conductive material for soil source inter-seasonal heat storage filling according to claim 1 is characterized by: Step A: grind the lignite with a pulverizer, and screen the lignite powder with a particle size of 0.2 mm with a sieve, mix the lignite powder with a hydrochloric acid solution with a mass percentage concentration of 36%, stir for 1 minute and then stand for 2 hours to remove carbonate mineral impurities in the lignite and retain silicate minerals; filter the solution after acid washing to obtain the lignite powder after impurities are removed, wash the residual hydrochloric acid on the powder with running water, and finally dry the washed powder at 100° C. for 2 hours; Step B: Crush the rice husks with a crusher, and use a sieve to screen the rice husk powder with a particle size of 0.2 mm for later use; Step C: crushing the coal gangue with a crusher, and screening the coal gangue powder with a particle size of 0.2 mm with a sieve for later use; Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of 2:1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24 hours at a reaction temperature of 1200°C. After the reaction is completed, the mixture is cooled for 48 hours. The cooled reaction product is crushed into 4 mm and filled into an underground pipe as a soil source inter-seasonal heat storage filling material. Step B: Crush the rice husks with a crusher, and use a sieve to screen the rice husk powder with a particle size of less than 0.2 mm for later use; Step C: crush the gangue with a crusher, and screen the gangue powder with a particle size of less than 0.2 mm with a sieve for later use; Step D: The powders obtained in steps A, B and C are mixed in a mass ratio of 2:1:1, and subjected to a high-temperature carbonization reaction in a graphite crucible under argon protection for 24 hours at a reaction temperature of 1200°C. After the reaction is completed, the mixture is cooled for 48 hours; the cooled reaction product is crushed to 4 mm and used as a raw material for the buried pipe backfill material.

3. The SiC thermal conductive material for soil source inter-seasonal heat storage filling according to claim 1 is characterized by: In step D, the powders obtained in steps A, B and C are mixed in a mass ratio of 2.5:1:

1.

4. The SiC thermal conductive material for soil source inter-seasonal heat storage filling according to claim 2 is characterized by: In step 4, under an argon atmosphere, the temperature is first increased to 500° C. to 600° C. at a heating rate of 20° C. / min to 30° C. / min, and then increased to 1200° C. at a heating rate of 5° C. / min to 10° C. / min.

5. A SiC thermally conductive material for soil source inter-seasonal heat storage filling according to claim 1, 2, 3 or 4, characterized in that: The prepared SiC thermal conductive material is in block form and a desired particle size is obtained by grinding.

6. The SiC thermal conductive material for soil source inter-seasonal heat storage filling according to claim 5 is characterized by: The thermal conductivity of SiC thermal conductive material reaches 150-180W / (m·K).

7. An application of SiC thermal conductive material for soil source cross-seasonal heat storage filling, characterized in that: The prepared SiC thermal conductive material is mixed with cement (powder) in a mass ratio of 5:95 and used as backfill material for buried pipes for soil-source inter-seasonal heat storage in buried pipes. The prepared SiC thermal conductive material is used as a soil-source inter-seasonal heat storage filling raw material.

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