A sludge-based light composite ceramsite preparation technique method

Abstract

The application discloses a sludge-based light composite ceramsite preparation technical method, which comprises the following steps: uniformly mixing dewatered sludge of a sewage plant with building waste powder, an expanding agent, an adjusting agent and a fluxing agent, adding a composite binder and adjusting the water content of the mixture, coating the outer surface of the prepared circular ceramsite embryo with a glaze layer material, naturally air-drying for 24-48 hours, sintering the dried ceramsite embryo at a temperature of 1030-1180 DEG C for 15-40 min, and naturally cooling to obtain the sludge-based light composite ceramsite. The application realizes the collaborative disposal and resource utilization of multiple solid wastes such as sewage plant sludge, iron-containing dust sludge and crop straw, the prepared light ceramsite has developed closed internal pores, low bulk density and high compressive strength, and can be widely applied in the fields of landscaping, thermal / heat insulation building materials and the like.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment, disposal and resource utilization technology, specifically relating to a method for preparing sludge-based lightweight composite ceramsite. Background Technology

[0002] With increasing national and societal emphasis on environmental protection, solid waste, as a misplaced resource, is receiving growing attention for its treatment, disposal, and resource utilization. Sludge, an organic solid waste generated during urban wastewater treatment, has a complex composition and often contains pathogenic microorganisms, parasite eggs, toxic and harmful heavy metals, and a large amount of recalcitrant substances. Improper treatment can easily cause secondary pollution. Currently, sludge resource utilization mainly includes co-incineration in cement kilns to recover heat energy, protein extraction or release of carbon sources from the sludge, production of building materials, preparation of RDF fuel, and land application after composting. Sludge utilization in building materials is an effective means of sludge reduction and resource utilization. The basic pathways for using sludge as a building material raw material can be divided into two categories based on different sludge pretreatment methods: one is direct use in building material manufacturing after sludge dewatering and drying; the other is use in building material manufacturing after sludge undergoes chemical composition transformation treatment, with incineration and melting being typical treatment methods. Currently, sludge utilization in building materials is considered a sustainable sludge disposal method and is rapidly developing in Japan and European and American countries and regions.

[0003] Existing patent CN108002859A discloses a process for producing lightweight porous ceramsite using sludge. The sludge is dried at temperatures above 100 °C, then sludge, kaolin, an expanding agent, and CaF2 are ground into a mixed powder, extruded and granulated to prepare ceramsite raw material, and preheated and baked at high temperature for an extended period, followed by calcination at 1300 °C for nearly 1 hour. This invention can produce high-quality ceramsite, but its process is relatively complex, the ceramsite firing time is long, and energy consumption is high. Patent CN112010668A discloses a sludge-based ceramsite preparation technology that requires no drying and no preheating. Dehydrated sludge and clay are mixed evenly according to a predetermined ratio to form ceramsite embryos, which are then air-dried under natural conditions and finally sintered in a high-temperature furnace. This invention simplifies the process and saves costs, but the amount of sludge disposed of during the preparation of ceramsite is very small, and clay accounts for more than 50% of the raw materials. Clay is a non-renewable resource, and the application of clay ceramsite has been banned by the state in recent years. How to develop new technologies for sludge-based ceramsite preparation that are adapted to local conditions and specific circumstances, can effectively dispose of large amounts of sewage sludge from wastewater treatment plants while significantly reducing the energy consumption of the ceramsite preparation process, urgently requires technological innovation and breakthroughs. Summary of the Invention

[0004] This invention provides a method for preparing sludge-based lightweight composite ceramsite. The method uses dewatered sludge from a wastewater treatment plant and powdered construction waste as the ceramsite matrix materials. An expanding agent, a regulating agent, a fluxing agent, and a composite binder are added sequentially to prepare the ceramsite embryo. The embryo is then coated with a glaze material, air-dried, and subjected to high-temperature sintering followed by natural cooling to obtain sludge-based lightweight composite ceramsite. The prepared ceramsite exhibits good porosity and a bulk density typically of 350–480 kg / m³. 3 With a compressive strength of 1.3~1.8 MPa, it is widely used in gardening, heat insulation / insulation, breathable drainage and building backfilling.

[0005] The implementation steps of this invention are as follows:

[0006] (1) The dewatered sludge from the sewage treatment plant and the crushed construction waste are mixed as ceramic matrix material. An expansion agent, a regulator and a flux are added in sequence to achieve a good closed pore structure of the ceramic particles prepared under a lower temperature condition. A solid and liquid composite binder is added to adjust the moisture content of the material. The mixture is stirred and mixed evenly to prepare a round ceramic particle embryo with uniform texture.

[0007] (2) Coat the surface of the obtained ceramic pellet body with a glaze layer of 0.6~1.5 mm and air dry naturally for 24~48 hours;

[0008] (3) The dried ceramsite embryos are subjected to high-temperature sintering treatment and then naturally cooled to obtain sludge-based lightweight composite ceramsite.

[0009] Preferably, in step (1), the mass ratio of the dewatered sludge from the sewage treatment plant to the construction waste is 10:1~2, and the construction waste includes powdered waste bricks and mortar in a mass ratio of 8:3~5, wherein the particle size of the powdered waste bricks in the construction waste is 0.18~0.45 mm.

[0010] Preferably, in step (1), an expansion agent is added at 5% to 14% of the mass of the ceramic matrix material. The expansion agent is composed of two or more of iron-containing dust, Fe2O3, and red mud, and must contain Fe2O3 component, accounting for 20% to 35% of the mass of the expansion agent.

[0011] Preferably, in step (1), agricultural and forestry biomass waste is added as a regulator at 8% to 12% of the mass of the ceramic matrix material. The regulator includes sawdust, peanut shell powder, and corn cob powder, wherein sawdust accounts for 45% to 65% of the mass of the regulator.

[0012] Preferably, in step (1), a flux is added at 1.5% to 2.5% of the mass of the ceramic matrix material. The flux is composed of CaO and MgO in a mass ratio of 1:0.8 to 1.2.

[0013] Preferably, the composite binder in step (1) is composed of a solid binder and a liquid binder. The amount of solid binder added is 35% to 40% of the mass of the ceramic matrix material. The solid binder is composed of bentonite and coal gangue in a mass ratio of 10:2 to 4.

[0014] Preferably, the liquid binder is a polyacrylamide solution with a mother liquor concentration of 1.5~2.5 g / L, and 0.4~0.6 L of liquid binder mother liquor is added per 1 kg of ceramic matrix material.

[0015] Preferably, the glaze material in step (2) is composed of iron oxide, manganese oxide, calcium feldspar powder and bentonite, with mass fractions of 0~5%, 0~15%, 35~50%, and 40~55%, respectively.

[0016] Preferably, the moisture content of the ceramsite embryo is 64%~72%, and the moisture content of the air-dried ceramsite embryo is 12%~20%.

[0017] Preferably, the high-temperature sintering temperature of the ceramic pellet body in step (3) is 1030~1180 ℃, and the firing time is 15~40 min.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] (1) Expanded clay aggregates were prepared by using dewatered sludge from sewage treatment plants and solid waste from the construction industry and agricultural and forestry industries, realizing the synergistic treatment and resource utilization of multiple solid wastes. Among them, agricultural and forestry solid wastes can be used as fuel to provide heat energy and can also react with iron-based mixtures to cause the expanded clay aggregates to expand and generate internal closed micropores. Polyacrylamide liquid binder adjusts the moisture content of the expanded clay aggregate embryos, effectively improving the pelletizing performance of the expanded clay aggregate embryos and reducing the amount of bentonite used.

[0020] (2) No pretreatment of sludge is required during the preparation of ceramsite; the firing temperature of the ceramsite embryo is low and the firing time is short, which effectively reduces production energy consumption. The prepared ceramsite has highly developed closed micropores, low bulk density, light weight and high compressive strength. Attached Figure Description

[0021] Figure 1 This is a comparison diagram of the sludge-based ceramsite of the present invention and commercially available ceramsite. Detailed Implementation

[0022] The following specific implementation examples further illustrate the present invention, providing detailed implementation methods and operating procedures, but the scope of protection of the present invention is not limited to the content described.

[0023] Example 1

[0024] Wastewater sludge from the wastewater treatment plant, 0.3 mm powdered waste bricks, and mortar were mixed evenly at a mass ratio of 10:1:0.5. An expanding agent was added at 10% of the ceramic matrix material (unless otherwise specified, all ratios are by mass), with the expanding agent comprising red mud, iron-containing dust, and Fe2O3 in a mass ratio of 55%, 17%, and 28%, respectively. A modifier was added at 12% of the ceramic matrix material, with sawdust, peanut shell powder, and corn cob powder in a mass ratio of 60%, 25%, and 15%, respectively. A flux was added at 1.5% of the ceramic matrix material, with CaO and MgO in a mass ratio of 1:1. A solid binder was added at 40% of the ceramic matrix material, with bentonite and coal gangue in a mass ratio of 10:2. After the above solid materials were mixed evenly, a 1.5 g / L polyacrylamide liquid binder was added, at a concentration of 0.6 L per 1 kg of ceramic matrix material. The moisture content of the ceramic matrix mixture was adjusted to 66% to prepare round ceramic pellet blanks. Simultaneously, an enamel layer mixture was prepared by mixing iron oxide, manganese oxide, calcium feldspar powder, and bentonite in a mass ratio of 5%, 5%, 45%, and 45%, respectively. The enamel layer was then coated with a 1.2 mm layer using a disc feeder. After air-drying for 35 hours, the moisture content of the ceramic pellet blanks was reduced to 15%. The air-dried ceramic pellet blanks were then fired in a 1150 ℃ high-temperature furnace for 20 minutes, followed by natural cooling to obtain the finished ceramic pellets.

[0025] The bulk density of the obtained ceramsite is 375 kg / m³. 3 The compressive strength is 1.53 MPa, and the water absorption rate is 8.9%; the internal microporous structure of sludge-based ceramsite is similar to that of commercially available ceramsite. Figure 1 As shown.

[0026] Example 2

[0027] Wastewater sludge from a sewage treatment plant, powdered waste bricks, and mortar were mixed evenly at a mass ratio of 10:1.2:0.5. An expanding agent, a regulating agent, a fluxing agent, and a solid binder were added sequentially, with dosages of 8%, 12%, 1.5%, and 36% of the ceramic matrix material's mass, respectively. The expanding agent contained 70% iron-containing dust and 30% Fe2O3. The regulating agent contained 55%, 20%, and 25% sawdust, peanut shell powder, and corn cob powder, respectively. The fluxing agent had a CaO to MgO mass ratio of 1:0.8. The solid binder contained bentonite and coal gangue in a mass ratio of 10:3. After the solid materials were mixed evenly, a 2.0 g / L polyacrylamide liquid binder was added, with 0.5 L of liquid binder added per 1 kg of ceramic matrix material. The moisture content of the ceramic matrix mixture was adjusted to 70% to prepare round ceramic pellet blanks. A glaze layer mixture was prepared by mixing iron oxide, manganese oxide, calcium feldspar powder, and bentonite in a mass ratio of 0%, 15%, 35%, and 50%, respectively. The glaze layer material was then applied to the outer layer of the ceramic pellet blanks with a 0.9 mm thick coating using a disc feeder. The blanks were air-dried for 42 hours to reduce the moisture content to 18%. The air-dried ceramic pellet blanks were then placed in a 1060 ℃ high-temperature furnace and fired for 35 minutes, followed by natural cooling to obtain the finished ceramic pellets. All other conditions not mentioned were the same as in Example 1.

[0028] The bulk density of the obtained ceramsite is 360 kg / m³. 3 It has a compressive strength of 1.36 MPa and a water absorption rate of 17.3%.

[0029] Example 3

[0030] Wastewater sludge from a sewage treatment plant, powdered waste bricks, and mortar were mixed evenly at a mass ratio of 10:1.2:0.6. An expanding agent, a regulating agent, a fluxing agent, and a solid binder were added sequentially, with dosages of 7%, 12%, 1.9%, and 40% of the ceramic matrix material's mass, respectively. The expanding agent contained 65% red mud and 35% Fe2O3. The regulating agent contained 50%, 15%, and 35% sawdust, peanut shell powder, and corn cob powder, respectively. The fluxing agent contained CaO and MgO in a mass ratio of 1:1.2. The solid binder contained bentonite and coal gangue in a mass ratio of 10:4. After the solid materials were mixed evenly, a 2.5 g / L polyacrylamide liquid binder was added, with 0.4 L of liquid binder added per 1 kg of ceramic matrix material. The moisture content of the ceramic matrix mixture was adjusted to 65% to prepare round ceramic pellet blanks. A glaze layer mixture was prepared by mixing iron oxide, manganese oxide, calcium feldspar powder, and bentonite in a mass ratio of 5%, 0%, 50%, and 45%, respectively. The glaze layer material was then applied to the outer layer of the ceramic pellet blanks by a disc feeder to a depth of 1.5 mm. The blanks were air-dried for 28 hours to reduce the moisture content to 15%. The air-dried ceramic pellet blanks were then fired in a 1120 °C furnace for 25 min, followed by natural cooling to obtain the finished ceramic pellets. All other conditions not mentioned were the same as in Example 1.

[0031] The bulk density of the obtained ceramsite is 450 kg / m³. 3 It has a compressive strength of 1.72 MPa and a water absorption rate of 12.5%.

Claims

1. A method for preparing sludge-based lightweight composite ceramsite, characterized in that, Includes the following steps: (1) The wastewater sludge from the sewage treatment plant is mixed with construction waste and used as the ceramic matrix material. An expansion agent, a regulator, a flux, and a composite binder are added in sequence to adjust the moisture content of the mixture. The mixture is stirred and mixed evenly to prepare a round ceramic pellet body. The mass ratio of the wastewater sludge to the construction waste is 10:1~2. The construction waste includes powdered waste bricks and mortar in a mass ratio of 8:3~5. The particle size of the powdered waste bricks in the construction waste is 0.18~0.45 mm. The composite binder is composed of a solid binder and a liquid binder. The amount of solid binder added is 35%~40% of the mass of the ceramic matrix material. The solid binder is composed of bentonite and coal gangue in a mass ratio of 10:2~4. The liquid binder is a polyacrylamide solution with a mother liquor concentration of 1.5~2.5 g / L. 0.4~0.6 L of liquid binder mother liquor is added for every 1 kg of ceramic matrix material. (2) Coat the surface of the obtained ceramic pellet body with a glaze layer of 0.6~1.5 mm and air dry naturally for 24~48 hours; the glaze layer material is composed of iron oxide, manganese oxide, calcium feldspar powder and bentonite, with mass fractions of 0~5%, 0~15%, 35~50%, and 40~55%, respectively; (3) The dried ceramsite blanks are sintered at high temperature and then cooled naturally to obtain sludge-based lightweight composite ceramsite. The high temperature sintering temperature of the ceramsite blanks is 1030~1180 ℃ and the firing time is 15~40 min.

2. The method for preparing sludge-based lightweight composite ceramsite according to claim 1, characterized in that... Step (1) Add an expanding agent at 5% to 14% of the mass of the ceramic matrix material. The expanding agent is composed of two or more of iron-containing dust, Fe2O3, and red mud, and must contain Fe2O3 component, accounting for 20% to 35% of the mass of the expanding agent.

3. The method for preparing sludge-based lightweight composite ceramsite according to claim 1, characterized in that... Step (1) Add agricultural and forestry biomass waste as a regulator at 8% to 12% of the mass of the ceramic matrix material. The regulator includes sawdust, peanut shell powder and corn cob powder, wherein sawdust accounts for 45% to 65% of the mass of the regulator.

4. The method for preparing sludge-based lightweight composite ceramsite according to claim 1, characterized in that... Step (1) Add flux at 1.5% to 2.5% of the mass of the ceramic matrix material. The flux is composed of CaO and MgO in a mass ratio of 1:0.8 to 1.

2.

5. The method for preparing sludge-based lightweight composite ceramsite according to claim 1, characterized in that... The moisture content of the ceramsite green body is 64%~72%, and the moisture content of the air-dried ceramsite green body is 12%~20%.

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