Method for preparing porous ceramic by mixing solid wastes

Abstract

The invention discloses a method for preparing porous ceramics by mixing solid wastes. The method comprises the following steps: (1) raw material pretreatment: dehydrating waste sludge; the waste heat preservation cotton is subjected to crushing treatment; (2) porous ceramic preparation: uniformly mixing the pretreated waste sludge, waste thermal insulation cotton and coal gasification slag to obtain a mixture; performing compression molding on the mixture to obtain a porous ceramic green body, sintering the porous ceramic green body at high temperature, and cooling to obtain the porous ceramic. According to the method, resource utilization of the waste sludge, the coal gasification slag and the waste heat preservation cotton is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource utilization, and in particular to a method for preparing porous ceramics by mixing solid wastes. Background Art

[0002] Porous ceramics, also known as porous functional ceramics, are new ceramic materials that form a large number of interconnected or closed pores in the material during the molding and sintering process. Because porous ceramics have a developed specific surface area and unique physical surface properties, they have selective permeability, energy absorption and pressure resistance to liquid and gas media; coupled with the unique high temperature resistance and corrosion resistance of ceramic materials themselves, porous ceramics are widely used in gas-liquid filtration, purification and separation, chemical catalytic carriers, advanced thermal insulation materials, and biological implant materials. The source of porous ceramics is natural minerals in nature. With the exploitation and utilization of resources, the original mineral content in nature is becoming less and less, and the cost of using natural minerals to prepare porous ceramics is also getting higher and higher. Therefore, researchers have conducted research on the use of industrial waste to prepare ceramic materials.

[0003] Coal gasification slag is a by-product of the coal gasification industry and a typical bulk solid waste. It is estimated that the annual output of coal gasification slag from the entrained flow gasifier in the coal gasification industry alone exceeds 60 million tons. The traditional method of treating coal gasification slag is landfill. The problems of this treatment method are: ① It occupies a large area, which reduces the available land area; ② Some coal gasification slag contains heavy metals, which will pollute the soil and water bodies and increase the cost of landfill. Therefore, it is necessary to seek a better method for treating coal gasification slag. Coal gasification slag is mainly composed of silicon oxide, aluminum oxide, residual carbon and some other metal oxides. Since the coal gasification fine slag in the coal gasification slag has a fine and loose structure, rich amorphous carbon, highly active siliceous components and rich pore structure, etc., it is very necessary to utilize the coal gasification slag as a resource.

[0004] Waste sludge is a waste that is prone to secondary pollution in traditional treatment and disposal processes. It generally refers to the sludge generated when urban sewage treatment plants treat sewage. The original urban sewage sludge treatment and disposal methods can no longer meet the development of society and people's needs. Therefore, the recycling and reuse of waste sludge has become a very important method for treating waste sludge because it can increase the utilization rate of waste sludge and reduce secondary pollution.

[0005] Waste insulation cotton is a common industrial solid waste, and its disposal and treatment is an important environmental issue. On the one hand, if these wastes are discarded directly without proper treatment, they will not only occupy a large amount of land resources, but may also cause pollution to the environment, such as releasing harmful gases and affecting the quality of soil and groundwater. On the other hand, waste insulation cotton contains reusable fibers or polymer components. Through reasonable recycling technology, it can be converted into renewable resources, realizing resource recycling, reducing the demand for new raw materials, and helping to build a sustainable circular economy system. Common methods for treating waste insulation cotton include physical methods (such as crushing, screening, and cleaning), chemical methods (such as dissolution and modification), and thermal methods (such as pyrolysis and incineration). Summary of the invention

[0006] The first object of the present invention is to provide a method for preparing porous ceramics by mixing solid wastes, so as to realize the resource utilization of waste sludge, coal gasification slag and waste insulation cotton.

[0007] A second object of the present invention is to provide porous ceramics prepared by the above method.

[0008] The purpose of the present invention is achieved through the following solutions.

[0009] A method for preparing porous ceramics by mixing solid wastes comprises the following steps:

[0010] (1) Raw material pretreatment: dehydrating the waste sludge; crushing the waste insulation cotton;

[0011] (2) Preparation of porous ceramics: pre-treated waste sludge, waste insulation cotton and coal gasification slag are mixed evenly to obtain a mixture; the mixture is pressed into a porous ceramic body, the porous ceramic body is sintered at a high temperature, and the porous ceramic is obtained after cooling.

[0012] Preferably, the dehydration treatment in step (1) is to expose the waste sludge to the sun and dry it to make its moisture content less than 5%.

[0013] Preferably, the particle size of the pretreated waste sludge, waste insulation cotton and coal gasification slag should be less than 0.1 mm.

[0014] As a specific implementation method, the pre-treated waste sludge, waste insulation cotton and coal gasification slag are sieved through a 200-mesh sieve to make their particle size meet the requirements; of course, other methods can also be used for particle size screening. The waste sludge and coal gasification slag can be sieved separately or mixed before sieving.

[0015] Preferably, the coal gasification slag is coal gasification fine slag, which contains a certain amount of residual carbon and amorphous aluminosilicate and is a good raw material for preparing porous ceramics.

[0016] As a specific implementation, in step (2), waste sludge, coal gasification slag, and waste insulation cotton are mixed in a mass ratio of 1-2:4-5:2-3.

[0017] As a specific implementation method, a magnetic stirrer is used to mix the pre-treated waste sludge, waste insulation cotton and coal gasification slag for 0.5 to 2 hours. Of course, other mixing methods can also be used, as long as the raw materials are mixed evenly.

[0018] As another specific implementation, when large-scale production is carried out, in order to accommodate a larger amount of raw material processing, in step (2), the pretreated waste sludge, waste insulation cotton and coal gasification slag are evenly mixed by ball milling, and the ball milling time is 30 minutes.

[0019] Preferably, in step (2), the pressure of the pressing molding is 15 to 20 MPa, and the pressure is maintained for 20 to 30 seconds.

[0020] Preferably, in step (2), the sintering temperature is 1000-1200° C. and the sintering time is 4 hours.

[0021] Preferably, in step (2), the sintering temperature is increased to 1000-1200° C. at a heating rate of 3-10° C. / min, maintained at a constant temperature for 4 hours, and then decreased to room temperature at a cooling rate of 2-6° C. / min.

[0022] The invention also provides a porous ceramic prepared by the method.

[0023] The porous ceramic has a water absorption rate of 50-70%, an apparent porosity of 60-65%, a compressive strength of 10-20 MPa, and an average pore size of 1.7-2 μm. In addition, the porous ceramic has almost no heavy metal residue due to high-temperature sintering.

[0024] Compared with the prior art, the present invention has the following beneficial effects.

[0025] The present invention adopts a waste-to-waste approach, using waste sludge, coal gasification slag and waste insulation cotton as raw materials to produce porous ceramics, thereby achieving resource utilization and high-value conversion of waste sludge, coal gasification slag and waste insulation cotton, promoting the development of a circular economy, and solving the problems of large-scale accumulation of solid waste, occupation of land resources and environmental pollution.

[0026] The present invention completely replaces the natural mineral raw materials in the traditional ceramic preparation through the efficient utilization of solid waste, which not only reduces the dependence on the raw materials for the traditional ceramic production, but also greatly improves the recycling rate of resources and reduces the production cost.

[0027] The present invention utilizes coal gasification slag as a basic raw material, waste sludge and waste thermal insulation cotton as pore formers and modifiers for each other, and obtains porous ceramics by optimizing the ratio and process flow, which not only ensures that the porous ceramics have a higher apparent porosity, but also improves its mechanical strength and toughness, thereby giving the product excellent water absorption, air permeability and filtration performance.

[0028] The porous ceramics prepared by the invention have high compressive strength, high water absorption rate and apparent porosity, and can be applied to water pollution control, air purification, sound insulation and heat insulation materials, etc. DETAILED DESCRIPTION

[0029] The present invention is further described below by means of specific examples.

[0030] The method for testing the performance of porous ceramic materials in the present invention is: using the "Test Method for Apparent Porosity and Bulk Density of Porous Ceramics" (GB / T 1966-1996) to measure the apparent porosity of porous ceramics, and using the "Test Method for Bending Strength of Ceramic Materials" (GB / T4741-1999) to test the bending strength; using a pore size distribution measuring instrument to measure the average pore size of porous ceramics.

[0031] In the following examples, the specific operations for pre-treating waste sludge, coal gasification slag and waste insulation cotton are:

[0032] The waste sludge is exposed to the sun and then placed in a constant temperature drying oven to dry it so that its moisture content is less than 5%, where the moisture content is expressed as a mass percentage;

[0033] Pass the dehydrated waste sludge and coal gasification slag through a 200-mesh sieve;

[0034] The waste insulation cotton is crushed and passed through a 200-mesh sieve.

[0035] Example 1

[0036] According to the weight ratio, 20 g of pretreated waste sludge, 50 g of coal gasification fine slag and 30 g of waste insulation cotton were weighed, stirred with a magnetic stirrer for 1 hour, and mixed evenly to obtain a mixture; the evenly mixed materials were pressed into a 50mm*50mm*10mm porous ceramic body with a hydraulic press, the molding pressure was 15 MPa, and the pressure was maintained for 20 seconds; then the porous ceramic body was placed in a muffle furnace, heated to 1000°C at a heating rate of 5°C / min, kept warm for 4 hours, and then cooled to room temperature at a cooling rate of 3°C / min, to finally obtain a porous ceramic.

[0037] The measurements showed that the prepared porous ceramic had a water absorption rate of 52.3%, an apparent porosity of 61%, a flexural strength of 10 MPa, and an average pore size of 1.7 μm.

[0038] Example 2

[0039] According to the weight ratio, 20 g of pretreated waste sludge, 40 g of coal gasification fine slag and 30 g of waste insulation cotton were weighed, stirred with a magnetic stirrer for 1 hour, and mixed evenly to obtain a mixture; the evenly mixed materials were pressed into a 50mm*50mm*10mm porous ceramic body with a hydraulic press, the molding pressure was 15 MPa, and the pressure was maintained for 30 seconds; then the porous ceramic body was placed in a muffle furnace, heated to 1200°C at a heating rate of 9°C / min, kept warm for 4 hours, and then cooled to room temperature at a cooling rate of 6°C / min, to finally obtain a porous ceramic.

[0040] The measurements showed that the prepared porous ceramic had a water absorption rate of 65%, an apparent porosity of 60.7%, a compressive strength of 12 MPa, and an average pore size of 1.7 μm.

[0041] Example 3

[0042] 1.5 kg of pretreated waste sludge, 5 kg of coal gasification fine slag and 3 kg of waste insulation cotton were weighed according to the weight ratio, ball-milled for 30 minutes, and mixed evenly to obtain a mixture; the evenly mixed materials were pressed into a plurality of 50 mm*50 mm*10 mm porous ceramic bodies using a hydraulic press, the molding pressure was 20 MPa, and the pressure was maintained for 20 seconds; then the porous ceramic bodies were placed in a muffle furnace, heated to 1200°C at a heating rate of 3°C / min, kept warm for 4 hours, and then cooled to room temperature at a cooling rate of 4°C / min, to finally obtain porous ceramics.

[0043] The measurements showed that the prepared porous ceramic had a water absorption rate of 70%, an apparent porosity of 62.5%, a compressive strength of 15 MPa, and an average pore size of 1.8 μm.

[0044] Example 4

[0045] According to the weight ratio, 20 kg of pretreated waste sludge, 40 kg of coal gasification fine slag and 20 kg of waste insulation cotton were weighed, ball-milled for 30 minutes, and mixed evenly to obtain a mixture; the evenly mixed materials were pressed into a plurality of 50 mm*50 mm*10 mm porous ceramic bodies by a hydraulic press, the molding pressure was 20 MPa, and the pressure was maintained for 20 seconds; then the porous ceramic bodies were placed in a muffle furnace, heated to 1000°C at a heating rate of 5°C / min, kept warm for 4 hours, and then cooled to room temperature at a cooling rate of 4°C / min, to finally obtain porous ceramics.

[0046] The measurements showed that the prepared porous ceramics had a water absorption rate of 69%, an apparent porosity of 64.2%, a compressive strength of 15 MPa, and an average pore size of 1.7 μm.

[0047] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be noted that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing porous ceramics by mixing solid wastes, characterized in that: The following steps are involved: (1) Raw material pretreatment: dehydration of waste sludge; Crushing the waste insulation cotton; (2) Preparation of porous ceramics: pre-treated waste sludge, waste insulation cotton and coal gasification slag are mixed evenly to obtain a mixture; the mixture is pressed into a porous ceramic body, the porous ceramic body is sintered at a high temperature, and the porous ceramic is obtained after cooling.

2. The method for preparing porous ceramics by mixing solid wastes according to claim 1, characterized in that: The dehydration treatment is to expose the waste sludge to the sun and dry it to make its moisture content less than 5%.

3. The method for preparing porous ceramics by mixing solid wastes according to claim 2, characterized in that: The pretreated waste sludge, waste insulation cotton and coal gasification slag are sieved through a 200-mesh sieve.

4. The method for preparing porous ceramics by mixing solid wastes according to claim 3, characterized in that: The coal gasification slag is coal gasification fine slag.

5. The method for preparing porous ceramics by mixing solid wastes according to claim 4, characterized in that: In step (2), waste sludge, coal gasification slag and waste insulation cotton are mixed in a mass ratio of 1-2:4-5:2-3.

6. The method for preparing porous ceramics by mixing solid wastes according to claim 5, characterized in that: In step (2), the pressure of the pressing molding is 15 to 20 MPa, and the pressure is maintained for 20 to 30 seconds.

7. The method for preparing porous ceramics by mixing solid wastes according to claim 6, characterized in that: In step (2), the sintering temperature is 1000-1200° C. and the sintering time is 4 h; The sintering temperature is specifically raised to 1000-1200° C. at a heating rate of 3-10° C. / min, kept constant for 4 hours, and then dropped to room temperature at a cooling rate of 2-6° C. / min.

8. The method for preparing porous ceramics by mixing solid wastes according to claim 7, characterized in that: The pretreated waste sludge, waste insulation cotton and coal gasification slag are mixed with a magnetic stirrer and stirred for 0.5 to 2 hours.

9. The method for preparing porous ceramics by mixing solid wastes according to claim 7, characterized in that: The pretreated waste sludge, waste insulation cotton and coal gasification slag are evenly mixed by ball milling, and the ball milling time is 30 minutes.