Ecological environment-friendly water permeable brick based on biogas residue recycling and preparation method thereof
By adopting a quaternary composite system of biogas residue, calcium carbonate, glass powder and kaolin and a multi-stage temperature-controlled sintering method, the problem of unstable product performance in the construction of biogas residue was solved, realizing high-value utilization and long-term durability, and promoting the application of biogas residue in permeable bricks.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2026-01-14
- Publication Date
- 2026-04-14
AI Technical Summary
In the existing technology, the process of turning biogas residue into building materials has problems such as unstable product performance, lack of systematic optimization of raw material ratio, unclear impact mechanism of sintering process, and lack of assessment of long-term product durability, resulting in low efficiency of biogas residue resource utilization.
Eco-friendly permeable bricks were prepared by using a quaternary composite system based on biogas residue, calcium carbonate, glass powder and kaolin, combined with a multi-stage precise temperature control method of low-temperature pretreatment, rapid heating and high-temperature constant-temperature sintering.
This has enabled the high-proportion utilization of biogas residue, produced ecological permeable bricks with long-term durability and environmental safety, reduced material costs, and promoted the coordinated development of the construction industry and the environmental protection industry.
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Abstract
Description
Technical Field
[0001] This invention relates to a permeable brick and its preparation method. Background Technology
[0002] With the rapid urbanization and widespread adoption of wastewater treatment facilities in my country, the production of excess sludge has increased dramatically. Anaerobic digestion, as the mainstream technology for sludge stabilization and resource utilization, produces biogas but also a large amount of biogas residue (solid waste). Statistics show that approximately 0.4-0.6 tons of dry-basis biogas residue are generated for every ton of dry sludge treated. Currently, the main methods for disposing of biogas residue are land application (such as composting and garden substrate) and landfill, which suffer from low resource utilization efficiency, low product added value, potential risks of heavy metal and pathogen spread, and land resource consumption. How to achieve high-value utilization of biogas residue has become one of the key bottlenecks restricting the sustainable development of the sludge treatment and disposal industry.
[0003] On the other hand, with the deepening of the construction of "sponge cities" and "zero-waste cities," the market demand for eco-friendly building materials is growing rapidly. Permeable bricks, as the core paving material for sponge city construction, can effectively promote rainwater infiltration, alleviate urban flooding, replenish groundwater, and regulate the microclimate; while non-permeable environmentally friendly blocks can be used for wall filling, landscape construction, etc., replacing some clay bricks or concrete blocks. Traditional building material production consumes large amounts of natural resources such as clay and sand, resulting in high energy consumption and a heavy environmental burden. Therefore, utilizing industrial solid waste (such as fly ash, steel slag, and construction waste) to prepare eco-friendly building materials has become an important development direction. Biogas residue is rich in inorganic components such as silicon, aluminum, calcium, and iron, as well as some residual organic matter. Its chemical and mineral composition is somewhat similar to clay, theoretically possessing the potential to be used as a building material raw material.
[0004] However, the application of biogas residue in building materials is currently still in the laboratory or pilot-scale stage, facing several key technical bottlenecks: First, the loose and fragmented nature of biogas residue, coupled with its fluctuating composition, leads to unstable product performance; second, the proportions of raw materials (such as biogas residue, binder, flux, and foaming agent) lack systematic optimization guidelines; third, the impact mechanism of sintering processes (such as preheating temperature, final firing temperature, and holding time) on the microstructure and macroscopic properties of the product is not yet clear; and fourth, the long-term durability of the product (such as acid and alkali resistance, freeze-thaw resistance, and mechanical strength) lacks sufficient evaluation. Therefore, constructing a complete technical system encompassing raw material characteristic analysis, proportion optimization, process control, and performance evaluation is crucial for realizing the high-value utilization of biogas residue and promoting its industrialization. Summary of the Invention
[0005] In order to solve the problem of unstable performance of existing biogas residue building materials, this invention proposes an eco-friendly permeable brick based on biogas residue resource utilization and its preparation method.
[0006] This invention relates to an eco-friendly permeable brick based on the resource utilization of biogas residue, which is made from dry biogas residue, calcium carbonate, glass powder and kaolin. The mass fraction of dry biogas residue is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the balance is kaolin.
[0007] The present invention provides a method for preparing eco-friendly permeable bricks based on biogas residue resource utilization, which includes the following steps:
[0008] Step 1: The wet biogas residue is dried, ground, and pre-treated to obtain dry biogas residue powder with a mass moisture content of less than 5%.
[0009] Step 2: Weigh the raw materials. The mass fraction of dry biogas residue in the raw materials is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the mass fraction of kaolin is the remainder. Dry mix and wet mix the weighed raw materials in sequence to obtain wet mixture.
[0010] The dry mixing and wet mixing processes are as follows: The raw materials are placed in a drum mixer and dry-mixed for 10-30 minutes to ensure uniform distribution of different components; then, water is added to the dry powder mixture under continuous stirring, and wet mixing continues for 8-12 minutes, with the amount of water added to the dry powder mixture being 12-15 wt.%.
[0011] Step 3: Fill the mold with the wet mixture obtained in Step 2, compact it, and then obtain the brick blank;
[0012] Step 4: After the brick blanks are naturally air-dried, they undergo low-temperature pretreatment and high-temperature constant-temperature sintering in sequence, and finally cool naturally to room temperature.
[0013] The process of the low-temperature pretreatment is as follows: the furnace temperature is raised to 400℃-500℃ and kept at this temperature for 20-30 minutes.
[0014] The high-temperature isothermal sintering process is as follows: the furnace temperature is raised to 1200℃-1300℃ at a rate of 15-20℃ / min; and the temperature is maintained at this level for 25-40 minutes.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0016] 1. This invention abandons the traditional raw material system mainly composed of fly ash and slag, and adopts a quaternary composite system of "biogas residue-kaolin-calcium carbonate-glass powder". Among them, the dry biogas residue content is stably increased to 25%-35%, realizing a high proportion of waste disposal.
[0017] 2. This invention proposes a multi-stage precise temperature control sintering method consisting of "low-temperature pretreatment + rapid heating + high-temperature isothermal sintering", which differs from the traditional one-step or simple two-stage sintering method and promotes densification sintering and stabilizes the pore structure.
[0018] 3. The permeable bricks prepared by this invention have undergone rigorous durability tests (acid and alkali resistance, permeability) and mechanical evaluations (strength, stiffness), demonstrating long-term durability and environmental safety: proving that the biogas residue bricks prepared under the optimized process of this invention have good environmental compatibility.
[0019] 4. This invention uses biogas residue as the base material for ecological permeable bricks, realizing the reduction, resource utilization, stabilization, and harmlessness of sludge, producing high-value green building materials, reducing material production costs, and promoting the coordinated development of the construction industry and the environmental protection industry. It has huge development prospects and application potential. Detailed Implementation
[0020] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.
[0021] Specific Implementation Method 1: This implementation method is based on the ecological and environmentally friendly permeable brick made from biogas residue resource utilization. It is prepared from dry biogas residue, calcium carbonate, glass powder and kaolin. The mass fraction of dry biogas residue is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the balance is kaolin.
[0022] 1. This implementation method abandons the traditional raw material system mainly based on fly ash and slag, and adopts a quaternary composite system of "biogas residue-kaolin-calcium carbonate-glass powder". Among them, the dry biogas residue content is stably increased to 25%-35%, realizing a high proportion of waste disposal.
[0023] 2. The permeable bricks prepared in this embodiment have undergone rigorous durability tests (acid and alkali resistance, permeability) and mechanical evaluations (strength, stiffness), demonstrating long-term durability and environmental safety: proving that the biogas residue bricks prepared under the optimized process of this embodiment have good environmental compatibility.
[0024] 3. This implementation method uses biogas residue as the base material for ecological permeable bricks, realizing the reduction, resource utilization, stabilization, and harmlessness of sludge, producing high-value green building materials, reducing material production costs, and promoting the coordinated development of the construction industry and the environmental protection industry. It has huge development prospects and application potential.
[0025] Specific Implementation Method Two: This implementation method for preparing eco-friendly permeable bricks based on biogas residue resource utilization follows these steps:
[0026] Step 1: The wet biogas residue is dried, ground, and pre-treated to obtain dry biogas residue powder with a mass moisture content of less than 5%.
[0027] Step 2: Weigh the raw materials. The mass fraction of dry biogas residue in the raw materials is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the mass fraction of kaolin is the remainder. Dry mix and wet mix the weighed raw materials in sequence to obtain wet mixture.
[0028] The dry mixing and wet mixing processes are as follows: The raw materials are placed in a drum mixer and dry-mixed for 10-30 minutes to ensure uniform distribution of different components; then, water is added to the dry powder mixture under continuous stirring, and wet mixing continues for 8-12 minutes, with the amount of water added to the dry powder mixture being 12-15 wt.%.
[0029] Step 3: Fill the mold with the wet mixture obtained in Step 2, compact it, and then obtain the brick blank;
[0030] Step 4: After the brick blanks are naturally air-dried, they undergo low-temperature pretreatment and high-temperature constant-temperature sintering in sequence, and finally cool naturally to room temperature.
[0031] The process of the low-temperature pretreatment is as follows: the furnace temperature is raised to 400℃-500℃ and kept at this temperature for 20-30 minutes.
[0032] The high-temperature isothermal sintering process is as follows: the furnace temperature is raised to 1200℃-1300℃ at a rate of 15-20℃ / min; and the temperature is maintained at this level for 25-40 minutes.
[0033] 1. This implementation method abandons the traditional raw material system mainly based on fly ash and slag, and adopts a quaternary composite system of "biogas residue-kaolin-calcium carbonate-glass powder". Among them, the dry biogas residue content is stably increased to 25%-35%, realizing a high proportion of waste disposal.
[0034] 2. This implementation method proposes a multi-stage precise temperature control sintering method of "low temperature pretreatment + rapid heating + high temperature constant temperature sintering", which is different from the traditional one-step or simple two-stage sintering, and achieves densification sintering and stable pore structure.
[0035] 3. The permeable bricks prepared in this embodiment have undergone rigorous durability tests (acid and alkali resistance, permeability) and mechanical evaluations (strength, stiffness), demonstrating long-term durability and environmental safety: proving that the biogas residue bricks prepared under the optimized process of this embodiment have good environmental compatibility.
[0036] 4. This implementation method uses biogas residue as the base material for ecological permeable bricks, realizing the reduction, resource utilization, stabilization, and harmlessness of sludge, producing high-value green building materials, reducing material production costs, and promoting the coordinated development of the construction industry and the environmental protection industry. It has huge development prospects and application potential.
[0037] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the drying temperature in step one is 60℃-80℃, and the biogas residue is dried until the moisture content is 15wt.%.
[0038] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Two in that the drying temperature in step one is 80℃-100℃.
[0039] Specific Implementation Method 5: This implementation method differs from Specific Implementation Method 2 in that the particle size of the dry biogas residue powder mentioned in step one is <60 mesh.
[0040] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Two in that the calcium carbonate particle size range described in step two is <500 mesh.
[0041] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Two in that the glass powder particle size range in step two is <500 mesh.
[0042] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Two in that the kaolin particle size range described in step two is <60 mesh.
[0043] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method Two in that the low-temperature pretreatment process described in step four is as follows: the furnace temperature is raised to 500°C and maintained at that temperature for 20 minutes.
[0044] Specific Implementation Method 10: This implementation method differs from Specific Implementation Method 2 in that the high-temperature constant-temperature sintering process described in step four is as follows: the furnace temperature is raised to 1200℃ at a heating rate of 18℃ / min; and the temperature is maintained at this level for 25 minutes.
[0045] Example 1
[0046] This embodiment of the eco-friendly permeable brick based on biogas residue resource utilization is made from dry biogas residue, calcium carbonate, glass powder and kaolin; the mass fraction of dry biogas residue is 30%, the mass fraction of calcium carbonate is 5%, the mass fraction of glass powder is 5%, and the mass fraction of kaolin is the balance.
[0047] The preparation method of eco-friendly permeable bricks based on biogas residue resource utilization in this embodiment is carried out according to the following steps:
[0048] Step 1: The wet biogas residue is dried, ground, and pre-treated to obtain dry biogas residue powder with a mass moisture content of less than 5%.
[0049] The drying temperature is 80℃, and the biogas residue is dried until the moisture content is 15 wt.%.
[0050] The drying temperature is 80℃;
[0051] The particle size of the dried biogas residue powder is <60 mesh;
[0052] Because raw biogas residue typically has high moisture content, uneven composition, and contains lumps or impurities of a certain size, pretreatment is a crucial step to ensure the accuracy of subsequent batching and the uniformity of the product. First, the wet biogas residue is initially dried at 80℃ to dry the surface of large pieces, resulting in dry biogas residue with a moisture content of less than 15%. The dried biogas residue is then physically crushed using equipment such as a crusher / screw extruder / shear mill to break up large lumps and clumps, increasing the surface area and ensuring uniform particle size, thus guaranteeing uniformity in subsequent drying and carbonization processes. Subsequently, the ground biogas residue material is evenly spread on trays and placed in a constant-temperature forced-air drying oven for thorough drying at 80℃. This temperature is chosen to effectively remove free water and most of the bound water, while avoiding excessively high temperatures that could lead to premature decomposition or coking of organic components. The drying process continues until the material quality reaches a constant level, ultimately yielding dry biogas residue powder with a moisture content of less than 5%. This powder, with a particle size of less than 60 mesh, is then screened for use in the subsequent preparation of environmental protection materials.
[0053] Step 2: Weigh the raw materials. The raw materials contain 30% dry biogas residue, 5% calcium carbonate, 5% glass powder, and the remainder kaolin. Dry mix and wet mix the weighed raw materials in sequence to obtain a wet mixture.
[0054] The calcium carbonate particle size range is <500 mesh;
[0055] The glass powder has a particle size range of <500 mesh;
[0056] The kaolin particle size range is <60 mesh;
[0057] The dry mixing and wet mixing processes are as follows: the raw materials are placed in a drum mixer and dry-mixed for 10 minutes to ensure uniform distribution of different components; then, water is added to the dry powder mixture under continuous stirring, and wet mixing is continued for 10 minutes, wherein the amount of water added to the dry powder mixture is 13 wt.%.
[0058] Kaolin, as the main clay-based binder and source of silicon and aluminum in the raw materials, imparts plasticity to the green body and generates reinforcing phases such as mullite at high temperatures, forming the basis of structural strength. Calcium carbonate (CaCO3) decomposes at high temperatures, releasing carbon dioxide gas (CaCO3→CaO+CO2↑), and is a key foaming agent for forming internal pores in the material, achieving lightweight and functionality. Glass powder, as a flux, forms a liquid phase at high temperatures, lowering the eutectic temperature of the system, promoting sintering and bonding between particles, and simultaneously helping to encapsulate and stabilize the porous structure formed by the decomposition of calcium carbonate.
[0059] Step 3: Fill the mold with the wet mixture obtained in Step 2, compact it, and then obtain the brick blank;
[0060] In the wet mixing molding stage, the uniformly mixed wet mixture is filled into a pre-prepared mold. The wet mixture is filled and compacted into the mold cavity in stages by manual compaction or mechanical pressure to ensure that the edges and corners are full and there are no voids, and to obtain a flat surface. After the filling and compaction are completed, the green body is removed from the mold to obtain a wet brick green body with a specified shape and size.
[0061] Step 4: After the brick blanks are naturally air-dried, they undergo low-temperature pretreatment and high-temperature constant-temperature sintering in sequence, and finally cool naturally to room temperature.
[0062] The low-temperature pretreatment process is as follows: the furnace temperature is raised to 500°C and kept at that temperature for 20 minutes.
[0063] The high-temperature isothermal sintering process is as follows: the furnace temperature is raised to 1200℃ at a heating rate of 18℃ / min; and the temperature is maintained at this level for 25 minutes.
[0064] A multi-stage, precise temperature control method, involving low-temperature pretreatment, rapid heating, and high-temperature isothermal sintering, allows for segmented regulation of the pyrolysis process and optimization of material phase transformation and pore evolution. This is a key innovation for achieving high-performance products. The first stage is low-temperature pretreatment: the furnace temperature is raised to 500℃ and maintained at this temperature for 20 minutes. This stage aims to gently and thoroughly remove residual organic matter and water of crystallization from the green body, preventing cracking and blistering of the bricks due to rapid pyrolysis or vaporization in the subsequent high-temperature stage, thus ensuring the structural integrity of the green body before high-temperature sintering. The second stage, rapid heating and high-temperature isothermal sintering, involves raising the furnace temperature to the target sintering temperature of 1200℃ and maintaining it at this temperature for 25 minutes. During this stage, a series of synergistically optimized physicochemical changes occur. Kaolinite forms a highly stable mullite crystal phase through mullitization. Calcium carbonate (CaCO3) completely decomposes (CaCO3→CaO+CO2↑), and the released CO2 gas forms uniformly distributed micropores within the viscoplastic green body, laying the foundation for a permeable structure. Simultaneously, glass powder melts to form a low-temperature eutectic liquid phase. This liquid phase not only promotes sintering and diffusion bonding between particles but also effectively encapsulates and stabilizes the pores formed by the decomposition of calcium carbonate, preventing the pores from collapsing or merging at high temperatures, thereby achieving controllable pore structure. This embodiment effectively eliminates volatile components through low-temperature pretreatment, avoiding product defects caused by the explosive decomposition of organic matter in traditional one-step sintering. Then, rapid heating reduces the unstable region of the mesophase, combined with sufficient heat preservation at 1200℃, promoting full crystallization of mullite, rational distribution of the glass phase, and stable solidification of the pore structure, ultimately forming a composite functional structure with a ceramic phase as the framework and uniformly interconnected micropores. After sintering, the furnace is naturally cooled to room temperature to prevent microcracks in the brick due to thermal stress concentration, further ensuring the structural durability of the product.
[0065] Evaluation of the corrosion resistance of permeable bricks under various conditions:
[0066] Following the method described in Example 1, the mass fraction of biogas residue in the raw materials was varied to prepare the permeable bricks required for the experiment. To comprehensively examine the long-term service safety of the permeable bricks in real, complex environments, an environmental resistance evaluation was conducted, focusing on their chemical stability and durability under strong acid and strong alkali conditions. The evaluation results not only verified the reliable performance of the product under extreme conditions but also highlighted the breakthrough in environmental adaptability achieved by this invention through material design and process innovation.
[0067] Table 1
[0068]
[0069] Table 2
[0070]
[0071] The acid resistance of permeable bricks under various conditions is shown in Table 1, and the alkali resistance is shown in Table 2. At a firing temperature of 1200℃, the average mass loss rate after acid treatment was 17.50%, lower than the average mass loss rate (24.93%) at 1100℃. This indicates that high-temperature (1200℃) sintering significantly improves the acid resistance of ceramsite biogas residue. This is because high temperature makes the material structure denser, reducing acid penetration. At 1200℃, the ecological conversion material with 30% biogas residue as a reference showed the best acid resistance, with a loss rate of 6.46%, and an alkali resistance loss rate of 0.85%. This significant improvement in performance is mainly attributed to the densification and new phase formation brought about by high-temperature sintering. Higher temperatures promote the formation of the glassy phase and the melting-recrystallization process between particles, greatly reducing the porosity of the material and forming a denser microstructure. This dense structure effectively hinders the penetration and diffusion of acid and alkali solutions into the material, thereby reducing the degree of corrosion. Simultaneously, kaolin (mainly composed of Al₂O₃·2SiO₂·2H₂O) transforms into highly stable mullite (3Al₂O₃·2SiO₂) at high temperatures. Mullite is renowned for its excellent thermal stability and chemical inertness. 1200℃ is within the critical temperature range for the large-scale formation and growth of mullite crystals, while 1100℃ may not be sufficient to complete this full phase transformation. The material may contain more unreacted quartz or amorphous phases, which are more easily corroded in acidic or alkaline environments. Therefore, the material exhibits better acid and alkali resistance at 1200℃, and overall, the ecological bricks with a 30% biogas residue ratio show the best corrosion resistance.
Claims
1. An eco-friendly permeable brick based on biogas residue resource utilization, characterized in that: Eco-friendly permeable bricks based on biogas residue resource utilization are made from dry biogas residue, calcium carbonate, glass powder and kaolin; the mass fraction of dry biogas residue is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the mass fraction of kaolin is the balance.
2. The preparation method of eco-friendly permeable bricks based on biogas residue resource utilization as described in claim 1, characterized in that: The preparation method of eco-friendly permeable bricks based on biogas residue resource utilization is carried out according to the following steps: Step 1: The wet biogas residue is dried, ground, and pre-treated to obtain dry biogas residue powder with a mass moisture content of less than 5%. Step 2: Weigh the raw materials. The mass fraction of dry biogas residue in the raw materials is 25%-35%, the mass fraction of calcium carbonate is 3%-6%, the mass fraction of glass powder is 3%-6%, and the mass fraction of kaolin is the remainder. Dry mix and wet mix the weighed raw materials in sequence to obtain wet mixture. The dry mixing and wet mixing processes are as follows: The raw materials are placed in a drum mixer and dry-mixed for 10-30 minutes to ensure uniform distribution of different components; then, water is added to the dry powder mixture under continuous stirring, and wet mixing continues for 8-12 minutes, with the amount of water added to the dry powder mixture being 12-15 wt.%. Step 3: Fill the mold with the wet mixture obtained in Step 2, compact it, and then obtain the brick blank; Step 4: After the brick blanks are naturally air-dried, they undergo low-temperature pretreatment and high-temperature constant-temperature sintering in sequence, and finally cool naturally to room temperature. The process of the low-temperature pretreatment is as follows: the furnace temperature is raised to 400℃-500℃ and kept at this temperature for 20-30 minutes. The high-temperature isothermal sintering process is as follows: the furnace temperature is raised to 1200℃-1300℃ at a rate of 15-20℃ / min; and the temperature is maintained at this level for 25-40 minutes.
3. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The drying temperature in step one is 60℃-80℃, and the biogas residue is dried until the moisture content is 15wt.%.
4. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The drying temperature described in step one is 80℃-100℃.
5. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The particle size of the dry biogas residue powder mentioned in step one is <60 mesh.
6. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The calcium carbonate particle size range described in step two is <500 mesh.
7. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The glass powder in step two has a particle size range of <500 mesh.
8. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 2, characterized in that: The kaolin particle size range described in step two is <60 mesh.
9. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 1, characterized in that: The process of low-temperature pretreatment described in step four is as follows: raise the furnace temperature to 500°C and maintain it at that temperature for 20 minutes.
10. The method for preparing eco-friendly permeable bricks based on biogas residue resource utilization according to claim 1, characterized in that: The high-temperature isothermal sintering process described in step four is as follows: the furnace temperature is raised to 1200℃ at a rate of 18℃ / min; and the temperature is maintained at this level for 25 minutes.