Method for preparing building ceramic by classifying and preferably selecting coal gangue

Abstract

The invention provides a method for preparing architectural ceramics by classifying and preferably selecting coal gangue, and relates to the field of architectural ceramics preparation, and the method comprises the following steps: measuring the sulfur content and carbon content of the coal gangue, and determining the raw material category of the coal gangue, the raw material category being one of a common ceramic raw material, a high ignition loss ceramic raw material and an unqualified ceramic raw material; the coal gangue and ceramic powder are mixed to obtain a ceramic raw material, and the ceramic raw material is subjected to wet grinding, drying granulation, forming and firing to obtain the ceramic tile. According to the method disclosed by the invention, the coal gangue is classified according to the carbon content and the sulfur content, and then the ceramic product is prepared by adopting different sintering processes, so that efficient utilization of the coal gangue can be realized, and the ceramic product with high mechanical property is obtained.

Description

Technical Field

[0001] The present invention relates to the field of building ceramics preparation, and particularly to a method for classifying and preferentially preparing building ceramics from coal gangue. Background Art

[0002] Coal gangue, as a solid waste generated during coal mining and washing processes, has long been regarded as a source of environmental pollution due to problems such as occupying a large amount of land, emitting harmful gases and leachate. However, with the development of science and technology and the increasing awareness of environmental protection, the reuse of coal gangue has gradually become an important research direction, which not only helps to alleviate environmental pollution problems but also provides new resource ways for the production of building materials.

[0003] In the research on preparing building ceramics from coal gangue, researchers have successfully applied it to the production of traditional building decoration materials such as floor tiles and wall tiles through various process technologies, and have also expanded its application fields, such as sanitary wares, garden landscape materials, etc. These coal gangue ceramic products not only have good physical properties and chemical stability, showing excellent compressive strength, wear resistance and corrosion resistance, but also have relatively simple production processes and low costs, with significant market competitiveness.

[0004] However, although certain progress has been made in the research on preparing building ceramics from coal gangue, how to further improve the utilization efficiency of coal gangue, optimize the firing process, and improve the performance and quality of the produced ceramics to meet the needs of different fields and markets remains the focus and difficulty of current research. For example, how to maintain high performance of ceramics under high coal gangue doping levels; how to reduce energy consumption and improve product consistency and controllability through advanced sintering technologies; and how to develop new process flows, simplify production steps, and reduce production costs are all key directions for future research. Summary of the Invention

[0005] The present invention provides a method for classifying and preferentially preparing building ceramics from coal gangue to solve the technical problems in the prior art, such as low utilization efficiency of coal gangue, low doping amount during ceramic production, and low mechanical strength of ceramic products prepared from it.

[0006] To achieve the above-mentioned invention purposes, the technical solutions provided by the present invention are as follows:

[0007] A method for classifying and preferentially preparing building ceramics from coal gangue, comprising the following steps:

[0008] S1. Measure the sulfur content and carbon content of the coal gangue to determine the raw material category of the coal gangue, and the raw material category is one of ordinary ceramic raw materials, high-loss ceramic raw materials, and unqualified ceramic raw materials; the coal gangue is one or more of calcined coal gangue, low calorific value coal gangue, coal series kaolin coal gangue, and washed coal gangue.

[0009] S2. Mix the coal gangue with ceramic powder to obtain ceramic raw materials. The ceramic powder is a mixture of clay raw materials and feldspar raw materials. The clay raw materials are kaolin and bentonite, and the feldspar raw materials are potassium feldspar, calcium feldspar, and sodium feldspar. The ceramic raw materials are wet-ground, dried and granulated, formed, and fired to obtain ceramic tiles.

[0010] Preferably, in S1, the coal gangue is an ordinary ceramic raw material, and the mass percentage content of sulfur element in the ordinary ceramic raw material is less than 0.3% and the mass percentage content of carbon element is less than 0.5%.

[0011] More preferably, in S2, the incorporation amount of the coal gangue in the ceramic raw materials is 40 - 75 wt%.

[0012] More preferably, in S2, the thickness of the green body of the ceramic tile is 11 - 20 mm.

[0013] Preferably, in S1, the coal gangue is a high-loss ceramic raw material, and the mass percentage content of sulfur element in the high-loss ceramic raw material is 0.18 - 1.15% and the mass percentage content of carbon element is less than 2.5%.

[0014] More preferably, in S2, the incorporation amount of the coal gangue in the ceramic raw materials is 42 - 45 wt%.

[0015] Preferably, in S1, the coal gangue is an unqualified ceramic raw material, and the mass percentage content of sulfur element in the unqualified ceramic raw material is greater than 1.0% or the mass percentage content of carbon element is greater than 2.5%.

[0016] More preferably, S2 is specifically: pre-burn the unqualified ceramic raw material and then mix it with ceramic powder to obtain ceramic raw materials, and the ceramic raw materials are wet-ground, dried and granulated, formed, and fired to obtain ceramic tiles.

[0017] More preferably, the ceramic tile is one of ceramic antique tiles, ceramic floor tiles, and ceramic exterior wall tiles.

[0018] More preferably, the pre-burning temperature is 800 °C and the time is 2 h.

[0019] The carbon-containing solid waste raw material gangue of the present invention has different calorific values and combustion properties due to different carbon and sulfur contents in the gangue, and its utilization methods and values show diverse characteristics; by classifying the gangue according to the carbon and sulfur contents, the efficient utilization of the gangue can be achieved.

[0020] For the ceramic raw materials with high loss on ignition, they contain a certain amount of volatile components sulfur oxide or / and carbon monoxide. In the process of preparing building ceramics, one or any combination of the following contents needs to be satisfied: ① The total ceramic sintering time is greater than 70 minutes; ② The two-fire process is adopted; ③ The ceramic tiles with a thickness of 6-11 mm are prepared and the roasting process is an oxidative combustion atmosphere.

[0021] The gangue is divided into three categories of gangue according to its sulfur content and carbon content, including ordinary ceramic raw materials: the mass percentage content of sulfur element is less than 0.3% and the mass percentage content of carbon element is less than 0.5%; high-loss-on-ignition ceramic raw materials: the mass percentage content of sulfur element is between 0.18-1.15% and the mass percentage content of carbon element is less than 0.5%, or the mass percentage content of sulfur element is less than 1.0% and the mass percentage content of carbon element is between 0.5-2.5%; and unqualified ceramic raw materials: the mass percentage content of sulfur element is greater than 1.0% or the mass percentage content of carbon element is greater than 2.5%. According to the different characteristics of these three categories of gangue, further adopting the above different dosages and related processes to prepare building ceramics can improve the production efficiency of preparing building ceramics with gangue.

[0022] The present invention has at least the following beneficial effects compared with the prior art:

[0023] 1) The present invention classifies and optimizes the gangue in advance according to the sulfur and carbon contents, improves the utilization efficiency of the gangue, efficiently and precisely processes the gangue, avoids the complex treatment of the gangue in the utilization process, and improves the utilization rate of the gangue;

[0024] 2) The present invention adopts different preparation processes for gangue with different carbon contents, further ensures the mechanical properties of the ceramic products, and lays a foundation for the large-scale application of gangue in the ceramic industry;

[0025] 3) The present invention classifies and optimizes according to the carbon content of the gangue, expands the gangue with high loss on ignition into ceramic raw materials, and adopts one or more measures such as extending the sintering time, increasing the oxygen content, and the two-fire process to ensure the application of the raw materials with high loss on ignition. Description of the Drawings

[0026] Figure 1 It is a physical picture of the ceramic tile prepared in Comparative Example 1;

[0027] Figure 2 It is a physical picture of the ceramic tile prepared in Comparative Example 2. Detailed Embodiments

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the accompanying drawings of the specification. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps: measuring the sulfur content and carbon content of calcined coal gangue. When the mass percentage of sulfur element in the calcined coal gangue raw material is 0.22% and the mass percentage of carbon element is 0.45%, it can be classified as a common ceramic raw material; mixing the coal gangue with kaolin and potassium feldspar (the mass ratio of kaolin to potassium feldspar is 1:1) to obtain a ceramic raw material, with the incorporation amount of coal gangue being 40 wt%. After wet grinding, drying granulation, and forming, the ceramic powder is pressed into a green brick blank with a thickness of 11 mm, and then sent to a drying kiln and a roller hearth firing kiln for firing. The maximum firing temperature in the kiln is 1185 °C, and the entire firing time in the kiln is 58 minutes; after firing, the average compressive strength of the ceramic brick is 35 MPa, and the water absorption rate < 1.0%. The performance of the ceramic brick finished product is qualified and meets the requirements specified in the national standard for ceramic bricks (GB / T 4100 - 2015).

[0031] Example 2

[0032] This embodiment provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0033] Measuring the sulfur content and carbon content of calcined coal gangue. When the mass percentage of sulfur element in the calcined coal gangue raw material is 0.25% and the mass percentage of carbon element is 0.25%, it can be classified as a common ceramic raw material; mixing the coal gangue with bentonite and anorthite (the mass ratio of bentonite to anorthite is 1:1) to obtain a ceramic raw material, with the incorporation amount of coal gangue being 75 wt%. After wet grinding, drying granulation, and forming, the ceramic powder is pressed into a green brick blank with a thickness of 19 mm, and then sent to a drying kiln and a roller hearth firing kiln for firing. The maximum firing temperature in the kiln is 1176 °C, and the entire firing time in the kiln is 68 minutes; after firing, the average compressive strength of the ceramic brick is 30 MPa, and the water absorption rate < 1.2%. The performance of the ceramic brick finished product is qualified and meets the requirements specified in the national standard for ceramic bricks (GB / T 4100 - 2015).

[0034] Example 3

[0035] This embodiment provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0036] Measure the sulfur content and carbon content of calcined coal gangue. The mass percentage of sulfur element in the calcined coal gangue raw material is 0.25% and the mass percentage of carbon element is 0.15%, which can be classified as ordinary ceramic raw materials. Mix the calcined coal gangue with kaolin and albite (the mass ratio of kaolin to albite is 1:1) to obtain ceramic raw materials. The incorporation amount of coal gangue in the ceramic raw materials is 55wt%. After wet grinding, drying granulation, and forming, the ceramic powder is pressed to form a green brick blank with a thickness of 20mm, and then sent to a drying kiln and a roller hearth firing kiln for firing. The maximum firing temperature in the kiln is 1170°C, and the total firing time in the kiln is 65 minutes. After firing, the average compressive strength of the ceramic brick is 27MPa, and the water absorption rate <1.5%. The performance of the ceramic brick finished product is qualified and meets the requirements specified in the national standard for ceramic tiles (GB / T4100-2015).

[0037] Example 4

[0038] This example provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0039] Measure the sulfur content and carbon content of low-calorie coal gangue. The mass percentage of sulfur element in the low-calorie coal gangue (also known as: white gangue) is 1.15% and the mass percentage of carbon element is 1.1%, which can be classified as high-loss ceramic raw materials for preparing ceramic floor tiles. Mix the low-calorie coal gangue with kaolin and albite (the mass ratio of kaolin to albite is 1:1) to obtain ceramic raw materials. The incorporation amount of coal gangue in the ceramic raw materials is 45wt%, and the ceramic sintering time is 75 minutes. The thickness of the ceramic brick blank is 12mm and the roasting process is an oxidative combustion atmosphere. The maximum firing temperature in the kiln is 1173°C. After firing, the average flexural strength of the finished brick blank is 28MPa, and the water absorption rate <2%. The performance of the ceramic brick is qualified and meets the requirements specified in the national standard for ceramic tiles (GB / T4100-2015).

[0040] Example 5

[0041] This example provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0042] After sorting the coal-series kaolin coal gangue, measure the sulfur content and carbon content of the coal gangue. The mass percentage of sulfur element is 0.18% and the mass percentage of carbon element is 2.1%. It can be classified as a high-loss-on-ignition ceramic raw material to prepare ceramic antique bricks. Mix the coal gangue with bentonite and albite (the mass ratio of bentonite to albite is 1:1) to obtain a ceramic raw material. The incorporation amount of coal gangue in the ceramic raw material is 42 wt%. The ceramic sintering time is 58 minutes. The thickness of the ceramic brick is 11 mm and the roasting process is an oxidative combustion atmosphere. The maximum temperature of the kiln firing is 1175 °C. The average compressive strength of the fired ceramic brick is 31 MPa. The performance of the ceramic brick finished product is qualified and meets the requirements specified in the national standard for ceramic tiles (GB / T 4100-2015).

[0043] Example 6

[0044] This example provides a method for classifying and preferably preparing building ceramics from coal gangue, including the following steps:

[0045] After sorting the coal-series kaolin coal gangue, measure the sulfur content and carbon content of the coal gangue. The mass percentage of sulfur element is 0.28% and the mass percentage of carbon element is 2.1%. It can be classified as a high-loss-on-ignition ceramic raw material to prepare ceramic antique bricks. Mix the coal gangue with bentonite and albite (the mass ratio of bentonite to albite is 1:1) to obtain a ceramic raw material. The incorporation amount of coal gangue in the ceramic raw material is 43 wt%. The ceramic sintering time is 65 minutes. The thickness of the ceramic brick is 11 mm and the roasting process is an oxidative combustion atmosphere. The maximum temperature of the kiln firing is 1155 °C. The average compressive strength of the fired ceramic brick is 28 MPa, and the water absorption rate is 2.8%. The performance of the ceramic brick finished product is qualified and meets the requirements specified in the national standard for ceramic tiles (GB / T 4100-2015).

[0046] Example 7

[0047] This example provides a method for classifying and preferably preparing building ceramics from coal gangue, including the following steps:

[0048] After washing and separating the coal gangue, measure the sulfur content and carbon content of the coal gangue. The mass percentage of sulfur element is 0.28% and the mass percentage of carbon element is 4.5%. It can be classified as unqualified ceramic raw material. Place it in a roasting furnace and roast it at 800 °C for 2 hours. After that, the carbon content is reduced to 0.3% and the sulfur content is reduced to 0.26%. Further, use it as a raw material to prepare ceramic antique bricks. The pre-roasted coal gangue is mixed with bentonite and albite (the mass ratio of bentonite to albite is 1:1) to obtain a new ceramic raw material. The incorporation amount of the pre-roasted coal gangue in the new ceramic raw material is 35 wt%. After forming the new ceramic raw material, sinter it. The sintering process is an oxidative combustion atmosphere. The highest temperature in the kiln is 1165 °C and the sintering time is 50 minutes. After firing, no bulging appears on the ceramic bricks. The average flexural strength of the fired finished brick blank is 30 MPa and the water absorption rate is <1.7%. The performance of the ceramic bricks is qualified and meets the requirements specified in the national standard for ceramic bricks (GB / T 4100-2015).

[0049] Comparative Example 1

[0050] This comparative example provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0051] After washing and separating the coal gangue, measure the sulfur content and carbon content of the coal gangue. The mass percentage of sulfur element is 0.28% and the mass percentage of carbon element is 4.5%. It can be classified as unqualified ceramic raw material. Use it to prepare ceramic antique bricks. The incorporation amount in the ceramic raw material is 35 wt%. The ceramic sintering time is 50 minutes. The thickness of the ceramic bricks is 11 mm and the roasting process is an oxidative combustion atmosphere. The highest temperature in the kiln is 1165 °C. After firing, bulging, partial cracks and black hearts appear on the ceramic bricks, as Figure 1 , which does not meet the requirements specified in the national standard for ceramic bricks (GB / T 4100-2015).

[0052] Comparative Example 2

[0053] This comparative example provides a method for classifying and preferentially preparing building ceramics from coal gangue, including the following steps:

[0054] Classify and preferentially select the calcined coal gangue raw material according to the carbon content to obtain coal gangue with a carbon content >5%. After crushing, mix it with kaolin raw material in a ratio of 1:2 and directly grind and granulate it to form ceramic powder. Press the ceramic powder to form a green brick blank with a thickness of 20 mm. The flexural strength of the green blank is 1.6 - 1.8 MPa. Then send it to a tunnel drying kiln and a tunnel firing kiln for firing. The highest temperature in the kiln is 1170 °C. After firing, the product performance does not meet the requirements specified in the national standard for sintered pavement bricks (GB / T 4100-2015), and there are problems such as cracking and black hearts in the brick body, as Figure 2 .

[0055] The above is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A method for preparing building ceramics by classifying and optimizing coal gangue, characterized in that: The following steps are involved: S1. Measure the sulfur content and carbon content of the gangue to determine the raw material category of the gangue, wherein the raw material category is one of ordinary ceramic raw materials, high ignition loss ceramic raw materials, and unqualified ceramic raw materials; the gangue is one or more of calcined gangue, low calorific value gangue, coal-based kaolin gangue, and washed gangue; S2. The coal gangue is mixed with ceramic powder to obtain ceramic raw materials, and the ceramic raw materials are wet-milled, dried and granulated, formed and fired to obtain ceramic tiles.

2. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 1, characterized in that: The coal gangue described in S1 is a common ceramic raw material, and the mass percentage of sulfur element in the common ceramic raw material is less than 0.3% and the mass percentage of carbon element is less than 0.5%.

3. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 2, characterized in that: The amount of coal gangue added to the ceramic raw material in S2 is 40-75wt%.

4. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 2, characterized in that: The green body of the ceramic tile in S2 has a thickness of 11-20 mm.

5. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 1, characterized in that: The coal gangue described in S1 is a high ignition loss ceramic raw material, and the mass percentage of sulfur element in the high ignition loss ceramic raw material is 0.18-1.15% and the mass percentage of carbon element is less than 2.5%.

6. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 5, characterized in that: The amount of coal gangue added to the ceramic raw material in S2 is 42-45wt%.

7. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 1, characterized in that: The coal gangue described in S1 is an unqualified ceramic raw material, and the mass percentage of sulfur element in the unqualified ceramic raw material is greater than 1.0% or the mass percentage of carbon element is greater than 2.5%.

8. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 7, characterized in that: S2 specifically comprises: pre-burning the unqualified ceramic raw material and mixing it with ceramic powder to obtain ceramic raw material, and wet-grinding, drying, granulating, molding and firing the ceramic raw material to obtain ceramic bricks.

9. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 7, characterized in that: The ceramic brick is a ceramic antique brick, a ceramic floor tile, or a ceramic exterior wall tile.

10. The method for preparing building ceramics by classifying and optimizing coal gangue according to claim 8, characterized in that: The pre-sintering temperature is 800° C. and the pre-sintering time is 2 hours.

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