A high-value resource utilization system and method of waste concrete

Abstract

The application discloses a high-value resource utilization system and method of waste concrete, and the system comprises a preheating subsystem, a calcining subsystem, a cooling subsystem, a separating subsystem, a crushing subsystem, a dust collecting subsystem and a conveying subsystem. Waste concrete which is coarsely separated and pre-homogenized is mixed into cement raw materials to produce silicate cement clinker, and the test block after coarse crushing, screening, fine crushing and screening is directly stripped, and the separated powder can be used as a mixing material; the test block after stripping is preheated and calcined in a rotary kiln, the obtained material is cooled and stripped, and then sent into a V-type powder separator to separate coarse aggregates, and the fine aggregates and recycled waste concrete micro powder are separated through the powder separator and a dust collector. The application realizes the synergistic effect of pollution reduction and carbon reduction by combining with a cement production line, separates fine aggregates, coarse aggregates and hardened cement paste in the waste concrete, and realizes the high-value resource utilization of the waste in multiple ways according to the characteristics of each component.

Description

Technical Field

[0001] This invention relates to a system and method for utilizing solid waste materials, and more particularly to a system and method for the high-value resource utilization of waste concrete. Background Technology

[0002] Currently, construction waste disposal in many places still mainly relies on dumping and landfilling, with an overall resource utilization rate of less than 5%. Due to the complexity of the composition of waste concrete and the limitations of sand and gravel separation technology, the limited resource utilization is mainly concentrated on processing it into recycled aggregates.

[0003] There is limited research on the high-value resource utilization of waste concrete and its co-processing in cement production lines. In practical applications, there is currently no clear conclusion on the optimal reaction conditions for achieving complete and efficient separation of aggregates and hardened cement paste, and the development of corresponding engineering equipment is also limited. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a high-value resource utilization system for waste concrete that utilizes the advantages of co-processing waste in cement production lines to achieve continuous and stable deep resource utilization of waste concrete in construction waste.

[0005] The second objective of this invention is to provide a method for high-value resource utilization of waste concrete using the system described above.

[0006] Technical Solution: The high-value resource utilization system for waste concrete of this invention includes a crushing subsystem, a preheating subsystem, a calcination subsystem, a cooling subsystem, a separation subsystem, a dust collection subsystem, a conveying subsystem, and a cement production line system; the crushing subsystem includes a first jaw crusher, a first vibrating screen, a second jaw crusher, and a second vibrating screen connected in sequence; the separation subsystem includes a first ball mill, a second ball mill, a third vibrating screen, a V-type air classifier, an air classifier, and a cyclone separator; the outlet of the second vibrating screen is connected to the second ball mill and... The preheating subsystem has an inlet; the outlet of the second ball mill is connected to the third vibrating screen; the preheating subsystem is sequentially connected to the calcination subsystem, the cooling subsystem, and the first ball mill; the first ball mill is sequentially connected to the V-type classifier, the classifier, and the cyclone separator; the outlet of the cyclone separator is connected to the inlet of the dust collection subsystem; the conveying subsystem is connected to the dust collection subsystem, the cyclone separator, the V-type classifier, and the outlet of the classifier; the gas outlet of the grate cooler in the cement production line system is connected to the gas inlet of the V-type classifier and the preheating subsystem.

[0007] The method for high-value resource utilization of waste concrete using the above-described system includes the following steps:

[0008] (A) The waste concrete test blocks after coarse crushing, primary screening, fine crushing and secondary screening are stripped in the second ball mill, and the separated powder can be used as a mixture.

[0009] (B) Waste concrete test blocks, after coarse crushing, primary screening, fine crushing, and secondary screening, are preheated by a preheating subsystem. The heat source for the preheating subsystem is provided by the cement production line and the grate cooler in the middle and later stages of the cement production line. After preheating, the material is calcined in the calcination subsystem. After calcination, the material is cooled by the cooling subsystem, stripped by the first ball mill, and then sent to a V-type classifier to separate the coarse aggregate. The middle and later stages of the second grate cooler provide hot air to the V-type classifier.

[0010] (C) The material on the screen of the V-type air classifier is then separated by the air classifier and then by the dust collection subsystem to separate the fine aggregate and recycled waste concrete powder.

[0011] (D) Silicate cement clinker is produced by mixing coarsely sorted and pre-homogenized waste concrete into cement raw materials.

[0012] The proportion of the coarsely sorted and pre-homogenized waste concrete raw material is 5-15%, and the particle size is controlled to be ≤25mm.

[0013] The waste concrete test blocks after coarse crushing and primary screening have a size ≤150mm, while the test blocks after fine crushing and secondary screening have a size ≤50mm.

[0014] In step (A), coarse crushing is carried out in the first jaw crusher, primary screening is carried out in the first vibrating screen, fine crushing is carried out in the second jaw crusher, and secondary screening is carried out in the second vibrating screen.

[0015] The second ball mill uses high-carbon chromium bearing steel balls. Ball bearings with a diameter greater than 25.4 mm in the ball mill are removed and discarded. The amount of waste concrete test blocks is 1 / 6 to 1 / 3 of the effective volume of the ball mill cylinder. The peeling time is 5 to 15 minutes, and the cylinder rotation speed is 40 to 70 r / min.

[0016] Of this, 10-15% of the powder material stripped from the waste concrete, representing 10% of the total waste concrete mass, is directly used as cementitious admixture.

[0017] In step (B), the preheating temperature is 200-250°C, the preheating time is 20-40 minutes, and the heat source of the preheating subsystem is provided by the cooling subsystem and the middle and rear section of the grate cooler of the cement production line. The ratio of the provided hot air is 1:2 to 1:4.

[0018] In step (B), the calcination temperature of the calcination subsystem is 300–650°C, and the calcination time is 20–40 min.

[0019] Among them, the ball bearings of the first ball mill are ceramic zirconia balls. Ball bearings with a diameter greater than 25.4 are removed. The volume of construction waste occupies 1 / 6 to 1 / 3 of the effective volume of the cylinder. The stripping time is 5 to 15 minutes and the cylinder rotation speed is 40 to 70 r / min.

[0020] The ratio of hot air supplied from the middle and rear sections of the grate cooler in the cement production line to the V-type classifier and preheating subsystem is 1:2 to 1:4.

[0021] Beneficial effects: Compared with the prior art, the present invention achieves the following significant effects:

[0022] (1) Taking advantage of the co-processing of waste in cement production lines, and considering the high adhesion between hardened cement paste and aggregate in waste concrete, making separation difficult and making it hard to achieve classified resource utilization, fine aggregate (sand), coarse aggregate (stone), and hard cement paste in waste concrete are separated. Based on the characteristics of each component, multiple approaches are used to achieve high-value resource utilization of waste, realize high-value resource utilization of waste concrete combined with cement production lines, and use waste concrete as a substitute raw material for cement clinker production, cement admixture, recycled aggregate, etc., to achieve pollution reduction and carbon reduction synergistic efficiency, and help the cement industry develop in a green and low-carbon manner.

[0023] (2) To comprehensively control the treatment of waste concrete, establish an industrial-scale system for separating hardened cement mortar from coarse and fine aggregates, which has the characteristics of low investment and operating costs, strong production continuity, convenient management, energy saving and consumption reduction, and realize the continuous and stable operation of deep resource utilization of waste concrete. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0025] Figure 2 This is a photograph of the waste concrete from Example 1;

[0026] Figure 3 This is a photograph of the waste concrete from Example 2;

[0027] Figure 4 This is a photograph of the material after coarse crushing by the first jaw crusher in Example 2;

[0028] Figure 5 This is a photograph of the material undersize (≤50mm) after being crushed by the second jaw crusher in Example 2.

[0029] Figure 6 This is a photograph of the material after it was separated from the first ball mill.

[0030] Figure 7 This is a picture of the coarse aggregate separated by the V-type classifier in Example 3;

[0031] Figure 8 This is a photograph of the fine aggregate separated by the classifier in Example 3;

[0032] Figure 9 This is a photograph of the recycled waste concrete powder collected by the cyclone separator and dust collector in Example 3. Detailed Implementation

[0033] The present invention will now be described in further detail.

[0034] like Figure 1 As shown, 1 is the first jaw crusher, 2 is the first vibrating screen, 3 is the second jaw crusher, 4 is the second vibrating screen, 5 is the preheater, 6 is the first rotary kiln, 7 is the first grate cooler, 8 is the first ball mill, 9 is the V-type classifier, 10 is the classifier, 11 is the cyclone separator, 12 is the regulating valve, 13 is the dust collector, 14 is the fan, 15 is the chimney, 16 is the first chain conveyor, 17 is the second chain conveyor, 18 is the third chain conveyor, 19 is the fourth chain conveyor, 20 is the fifth chain conveyor, 21 is the second grate cooler, 22 is the second ball mill, 23 is the third vibrating screen, 30 is the raw material inlet, 31 is the first cyclone separator, 32 is the second cyclone separator, 33 is the third cyclone separator, 34 is the fourth cyclone separator, 35 is the fifth cyclone separator, 36 is the decomposition furnace, 37 is the second rotary kiln, and 301 is the flap valve. The present invention discloses a high-value resource utilization system for waste concrete, comprising a crushing subsystem, a preheating subsystem, a calcination subsystem, a cooling subsystem, a separation subsystem, a dust collection subsystem, a conveying subsystem, and a cement production line system. In this embodiment, the crushing subsystem includes a first jaw crusher, a first vibrating screen, a second jaw crusher, and a second vibrating screen connected in sequence; the preheating subsystem is a preheater; the calcination subsystem is a first rotary kiln; the cooling subsystem is a first grate cooler; the separation subsystem includes a first ball mill, a second ball mill, a third vibrating screen, a V-type classifier, a classifier, and a cyclone separator; the dust collection subsystem is a dust collector 13, specifically a bag dust collector; the conveying subsystem includes a first chain conveyor, a second chain conveyor, a third chain conveyor, a fourth chain conveyor, and a fifth chain conveyor; the cement production line system can use existing technology. In this embodiment, the cement production line system includes a first cyclone separator, a second cyclone separator, a third cyclone separator, a fourth cyclone separator, a fifth cyclone separator, a decomposition furnace, and a second rotary kiln. The discharge port of the first cyclone separator 31 is equipped with a flap valve 301, and its connection relationship is based on existing technology.

[0035] Specifically, the high-value resource utilization system for waste concrete in this embodiment includes a first jaw crusher 1, the discharge port of which is connected to the inlet of a first vibrating screen 2; the discharge port of the first vibrating screen 2 is connected to the inlet of a second jaw crusher 3; the discharge port of the second jaw crusher 3 is connected to the inlet of a second vibrating screen 4; the discharge port of the second vibrating screen 4 is connected to both the inlet of a second ball mill 22 and the inlet of a preheater 5; the discharge port of the second ball mill 22 is connected to the inlet of a third vibrating screen 23; the discharge port of the third vibrating screen 23 is connected to the inlet of the preheater; the discharge port of the preheater 5 is connected to the inlet of a first rotary kiln 6; the discharge port of the first rotary kiln 37 is connected to the inlet of a first grate cooler 7; the discharge port of the first grate cooler is connected to a first ball mill 8; and the discharge port of the first ball mill 8 is connected to the inlet of the first ball mill 6. The feed inlet of the V-type air classifier 9 is connected; the gas outlet of the middle and rear section of the second grate cooler 21 in the cement production line system is connected to two parallel paths, which are respectively connected to the gas inlet of the V-type air classifier 9 and the gas inlet of the preheater 8; the discharge outlet of the V-type air classifier 9 is connected to the air classifier 10, and the air classifier 10 is connected to the cyclone separator 11; the air outlet of the cyclone separator 11 is connected to the gas inlet of the dust collector 13 through the butterfly valve 12; the material outlet of the dust collector 13 is respectively connected to the feed inlets of the first chain conveyor 16 and the second chain conveyor 17; the feed inlet of the third chain conveyor 18 is connected to three parallel branches, which are respectively connected to the discharge outlets of the first chain conveyor 16, the second chain conveyor 17, and the cyclone separator 11; the discharge outlet of the V-type air classifier 9 is connected to the feed inlet of the fourth chain conveyor 19. The discharge outlet of the air classifier 10 is connected to the feed inlet of the fifth chain conveyor 35. In this embodiment of the invention, the bag dust collector, cyclone separator, flap valve, and other equipment are all existing devices, and their structures will not be described in detail. The flap valve may be a counterweight flap valve.

[0036] Another aspect of this invention provides a method for high-value resource utilization and carbon reduction technology of waste concrete. This method seeks to utilize cement production lines to co-process waste concrete, researches dedicated crushing and sorting technologies and equipment for waste concrete processing, effectively separates cement paste, coarse and fine aggregates from the waste concrete, forms a process scheme for waste concrete processing, and utilizes it as a substitute raw material for cement clinker production, cement admixture, recycled aggregate, etc.; thus forming a high-value resource utilization process route and technology for waste concrete. Specifically, it includes the following steps:

[0037] Waste concrete is fed into the first jaw crusher for coarse crushing. The material crushed by the first jaw crusher is then fed into the first vibrating screen for screening. Material with a particle size >150mm is returned to the first jaw crusher for further crushing, while material with a particle size ≤150mm is fed into the second jaw crusher for fine crushing. The material crushed by the second jaw crusher is then fed into the second vibrating screen for screening. Material with a particle size >50mm is returned to the second jaw crusher for further crushing, while material with a particle size ≤50mm is fed into a preheater for heating.

[0038] Waste concrete includes coarse aggregate, fine aggregate, and hardened cement paste. The hardened cement paste further includes hydration products of cement and other cementitious materials, unhydrated cement, and other cementitious materials. The amount of unhydrated cement can even reach more than 30% of the total cement content. This portion of unhydrated cement exists only as micro-aggregate in the concrete and does not exert its hydration activity.

[0039] After coarse and fine crushing, the waste concrete is made into block-shaped test blocks with a size of less than 50 mm. These waste concrete test blocks can be directly fed into the second ball mill 22 for stripping. After coarse and fine crushing, the macroscopic properties of the hardened cement paste change, especially the hardened cement paste covering the surface of the coarse aggregate, which is easier to strip. The second ball mill 22 uses high-carbon chromium bearing steel balls. Ball bearing balls with a diameter greater than 25.4 mm are removed from the ball mill. This process not only strips the hardened cement paste but also prevents some coarse aggregate from being crushed by the ball bearing balls and mixed into the powder. The waste concrete test blocks occupy 1 / 6 to 1 / 3 of the effective volume of the ball mill cylinder, and the stripping time is 5 to 15 minutes.

[0040] The waste concrete stripped from the second ball mill 22 enters the third vibrating screen 23 for separation. The oversize material is returned to the preheater, and the undersize material, namely the waste concrete powder stripped from the second ball mill, contains approximately 10-15%. 30% of the powder stripped from the second ball mill is added to silicate cement. A quantitative test of the compressive strength ratio of cement mortar is performed on the prepared samples. The activity index is tested according to the activity index test method for industrial waste residue in GB / T 1596-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures". The 3-day compressive strength is 23-25 ​​MPa, and the 28-day compressive strength is 36-38 MPa, corresponding to a 3-day activity of 65%-70% and a 28-day activity of 70%-75%. This indicates that the powder stripped from the second ball mill possesses a certain level of activity without calcination and can be directly used as a cement admixture. This is because waste concrete includes coarse aggregate, fine aggregate, and hardened cement paste. The hardened cement paste further includes hydration products of cement and other cementitious materials, unhydrated cement, and other cementitious materials. The amount of unhydrated cement can even reach more than 30% of the total cement content. This portion of unhydrated cement exists only as micro-aggregate in the concrete and does not exert its hydration activity.

[0041] The undersize material from the second vibrating screen 4 or the oversize material from the third vibrating screen 23 is fed into the preheater 5. The waste concrete test blocks undergo heat exchange within the preheater 5 at a preheating temperature of 200–250°C for 20–40 minutes. The heat source in the preheater 5 is provided by the rear section of the first grate cooler 7 and the second grate cooler 21, with a hot air ratio of 1:2 to 1:4. The preheated blocky waste concrete is then sent to the first rotary kiln 6 for calcination at a temperature of 300–650°C for 20–40 minutes. When hardened cement paste is exposed to a high-temperature environment, a series of physical and chemical transformations occur. Among these, the main components of the cement paste, CSH and Ca(OH)2, dehydrate at high temperatures, leading to a structural transformation of the cement paste. The calcined waste concrete material is fed into the first grate cooler 7 and cooled by extreme cooling. Due to the combined effects of high-temperature calcination and rapid cooling, the aggregate expands and the hardened cement paste shrinks, causing internal stress at the interface, which causes cracks in the interface area between the aggregate and the hardened cement paste, and the bonding in the cross-sectional area is relatively loose.

[0042] The material cooled by the first grate cooler 7 is fed into the first ball mill 8. To prevent the coarse aggregate from being crushed, the ball bearings of the first ball mill 8 are made of ceramic zirconia. The use of ceramic zirconia balls results in low power consumption. Simultaneously, after calcination and extreme cooling, new cracks are generated at the cross-sections of the cementitious material and the coarse and fine aggregates in the waste concrete, extending inwards and reducing bonding stress, making the hardened cement paste easier to peel off. Ball bearings with a diameter greater than 25.4 mm are removed. The volume of construction waste occupies 1 / 6 to 1 / 3 of the effective volume of the mill, and the peeling time is 5–15 minutes. The material peeled off by the first ball mill 8 is fed into the V-type classifier 9 to separate the coarse aggregate. The hot air supplied from the middle and rear section of the second grate cooler 21 to the V-type classifier 9 and preheater 5 is in a ratio of 1:2 to 1:4. The recycled coarse aggregate separated by the V-type air classifier is output by the fourth chain conveyor 19. The remaining material is carried by gas into the air classifier 10, where recycled fine aggregate is separated and output by the fifth chain conveyor 20. The remaining material is carried by gas into the cyclone separator 11 and the dust collector 13, respectively. The recycled waste concrete powder collected by the cyclone separator 11 and the dust collector 13 has cementitious properties. Using the recycled waste concrete powder as a cementing material, the prepared samples were subjected to a quantitative test of the compressive strength ratio of cement mortar. The activity index was tested according to the activity index test method for industrial waste in GB / T 1596-2005 "Test Method for Activity of Industrial Waste Residue Used in Cement Admixtures". The 3-day compressive strength was 24-28 MPa, and the 28-day compressive strength was 38-43 MPa, corresponding to a 3-day activity of 73%-85% and a 28-day activity of 74%-85%. The properties of the separated recycled coarse aggregate meet the requirements of Class II recycled coarse aggregate in GB / T 25177-2010 "Recycled Coarse Aggregate for Concrete"; the properties of the separated recycled fine aggregate meet the requirements of Class III in GB / T25176-2010 "Recycled Fine Aggregate for Concrete and Mortar".

[0043] Based on the chemical analysis results of waste concrete, it is mainly composed of calcium and silica materials, with low levels of harmful elements. This can effectively reduce the use of limestone, sandstone, and clay in the raw materials. Using crushed and ground waste concrete as a silica-alumina raw material for cement is a possible utilization approach. Further research is needed on the appropriate amount of waste concrete added and its impact on the burnability of the raw meal. Limited by the free calcium oxide content in cement clinker, when the original cement raw material has a fineness of 10% (i.e., residue on an 80μm sieve), if the waste concrete is primarily used for wall test blocks containing C30 or C20 concrete, and the raw meal ratio of the waste concrete test blocks is 5–15%, the free calcium content in the clinker is between 2.3% and 2.6%. The free calcium oxide analysis data shows that adding different proportions of waste concrete as raw meal results in normal burnability, indicating its potential as a raw meal component. Generally, the particle size of waste concrete entering the plant should be controlled to be ≤25mm. Due to the large fluctuations in the composition of waste concrete and bricks, pre-homogenization is required to reduce the fluctuations in composition. Considering factors such as chemical composition, flammability, clinker quality, and coal saving, controlling the appropriate particle size of waste concrete entering the plant and pre-homogenizing it can be used as cement raw material to produce qualified clinker and achieve a coal saving effect of 3-5%.

[0044] Example 1

[0045] Table 1 Chemical analysis results of waste concrete and its ingredients

[0046]

[0047] Taking a 5000t / d clinker production line as an example, such as Figure 2As shown, most of the waste concrete test blocks were from building walls, and the blocks maintained a good shape and were relatively hard. The chemical analysis results of the samples in Table 1 show that the waste concrete mainly consists of calcium and silica components, and its chemical composition meets the batching requirements, effectively reducing the amount of limestone, sandstone, and clay used in the raw materials. Waste concrete with a particle size ≤25mm is controlled before entering the plant. After pre-homogenization treatment, the waste concrete replaces part of the cement raw materials. The burnability test of the raw meal was conducted according to the national standard GB / T 26566-2011 "Test Method for Burnability of Cement Raw Meal". For this 5000t / d clinker production line, the free calcium content in the burnability test of the original raw meal with a fineness of 10% was 1.98%, and the free calcium content in the burnability test of the original raw meal with a fineness of 14% was 2.70%. The raw meal proportion of the waste concrete test blocks was 5-15%. The burnability test results of waste concrete as a cement raw material component are shown in Table 2. The free calcium content in the 14% fineness clinker was between 2.3% and 2.6%, slightly higher than that of the original raw meal, but within an acceptable range. Waste concrete can be used as a cement raw material to produce qualified clinker, achieving a 5% coal saving effect. For a 5000t / d clinker production line with a material consumption of 1.6, if waste concrete is added to the batching at 5-15%, the estimated waste concrete processing capacity is 400t / d to 1200t / d, or 120,000 tons / year to 360,000 tons / year. Using crushed and ground waste concrete as a cement silica-alumina raw material is a relatively simple utilization method, and the processing capacity of waste concrete is limited.

[0048] Table 2 shows the test results of the burnability of cement raw material components.

[0049]

[0050] Example 2

[0051] When the waste concrete processing capacity is 200,000 tons / year, the resulting waste concrete raw materials are as follows: Figure 3 As shown, the material is fed into the first jaw crusher 1 for coarse crushing. The material after coarse crushing is as follows: Figure 4 As shown, the material is fed into the first vibrating screen 2 for screening. Material with a particle size >150mm is returned to the first jaw crusher 1 for further crushing, while material with a particle size ≤150mm is fed into the second jaw crusher 3 for fine crushing. The finely crushed material is then fed into the second vibrating screen 4 for screening. Material with a particle size >50mm is returned to the second jaw crusher 3 for further crushing, while material with a particle size ≤50mm is fed into the second jaw crusher 4 for further crushing. Figure 5As shown, the material enters the second ball mill 22 for stripping. The second ball mill 22 uses high-carbon chromium bearing steel balls; ball bearings with a diameter greater than 25.4 mm are removed and discarded. The mill speed is 70 r / min. The waste concrete sample is filled to 1 / 5 of the effective volume of the mill cylinder, and the stripping time is 10 min. The stripped waste concrete enters the third vibrating screen 23 for separation, and the stripped powder content is approximately 10%. 30% of the powder is added to silicate cement, and a quantitative test of the cement mortar compressive strength ratio is performed on the prepared samples. The 3-day compressive strength is 25 MPa, and the 28-day compressive strength is 38 MPa, corresponding to a 3-day activity of 70% and a 28-day activity of 75%.

[0052] The undersize material from the second vibrating screen 4 or the oversize material from the third vibrating screen 23 is fed into the preheater 5. The preheating temperature is 200℃, and the preheating time is 25 minutes. The heat source in the preheater 5 is provided by the first grate cooler 7 and the middle and rear sections of the second grate cooler 21, with a hot air ratio of 1:4. The preheated blocky waste concrete is calcined in the first rotary kiln 6 at a temperature of 500℃ for 30 minutes. After calcination, the material is cooled by the first grate cooler 7 and then fed into the first ball mill 8. The ball bearings in the first ball mill 8 are ceramic balls. Ball bearings with a diameter greater than 25.4 mm are removed and discarded. The volume of construction waste occupies 1 / 5 of the effective volume of the cylinder, and the stripping time is 5 minutes. The material stripped by the first ball mill 8, such as... Figure 6 As shown, the coarse aggregate is separated by the V-type classifier 9. Hot air is supplied to the V-type classifier 9 and the preheater 5 from the middle and rear section of the second grate cooler 21 at a ratio of 1:4. The recycled coarse aggregate is output by the fourth chain conveyor 19, and the remaining material enters the classifier 10. After the fine aggregate is separated, it is output by the fifth chain conveyor 20.

[0053] The remaining materials are carried by gas into cyclone 11 and dust collector 13 respectively. The recycled waste concrete powder collected by cyclone 11 and dust collector 13 has cementitious properties. A quantitative test of the compressive strength ratio of cement mortar was conducted on the prepared samples. The 3-day compressive strength was 28 MPa, and the 28-day compressive strength was 43 MPa, corresponding to a 3-day activity of 85% and a 28-day activity of 85%. The properties of the separated recycled coarse aggregate meet the requirements of Class II recycled coarse aggregate in GB / T 25177-2010 "Recycled Coarse Aggregate for Concrete"; the properties of the separated recycled fine aggregate meet the Class III performance requirements in GB / T 25176-2010 "Recycled Fine Aggregate for Concrete and Mortar".

[0054] The effect of calcination temperature on the strength of cement mortar made from recycled micro powder is shown in Table 3.

[0055] Table 3

[0056]

[0057] Example 3

[0058] When the waste concrete processing capacity is 500,000 tons / year, the waste concrete is fed into the first jaw crusher 1 for coarse crushing. The coarsely crushed material is then fed into the first vibrating screen 2 for screening. Material with a particle size >150mm is returned to the first jaw crusher 1 for further crushing, while material with a particle size ≤150mm is fed into the second jaw crusher 3 for fine crushing. The finely crushed material is then fed into the second vibrating screen 4 for screening. Material with a particle size >50mm is returned to the second jaw crusher 3 for further crushing, while material with a particle size ≤50mm is fed into the second ball mill 22 for stripping. The ball bearings in the second ball mill 22 use stainless steel balls; ball bearings with a diameter greater than 25.4mm are removed and discarded. The mill rotation speed is 40 r / min. The waste concrete test blocks are loaded into the ball mill to occupy 1 / 4 of the effective volume of the mill cylinder, and the stripping time is 15 min. The stripped waste concrete is then fed into the third vibrating screen 23 for separation, with the stripped powder content being approximately 15%. 30% powder was added to silicate cement, and the prepared samples were subjected to a quantitative test of the compressive strength ratio of cement mortar. The cement mortar strength of the powder used in cement admixtures is shown in Table 4.

[0059] The undersize material from the second vibrating screen 4 or the oversize material from the third vibrating screen 23 is fed into the preheater 5. The preheating temperature is 250℃, and the preheating time is 30 minutes. The heat source in the preheater 5 is provided by the first grate cooler 7 and the middle and rear sections of the second grate cooler 21, with a hot air ratio of 1:3. The preheated blocky waste concrete is calcined in a rotary kiln at 650℃ for 30 minutes. After calcination, the material is cooled by the first grate cooler 7 and then fed into the first ball mill 8. The first ball mill 8 uses ceramic balls for ball bearings, and ball bearing balls with a diameter greater than 25.4 mm are removed and discarded. The volume of construction waste occupies 1 / 4 of the effective volume of the cylinder, and the stripping time is 10 minutes. The material stripped by the first ball mill 8 is fed into a V-type classifier 9 to separate coarse aggregate. The stripped coarse aggregate is as follows: Figure 7 The surface shown is smooth and has good integrity. Hot air is supplied from the rear section of the second grate cooler 21 to the V-type classifier 9 and preheater 5 at a ratio of 1:3. Recycled coarse aggregate is output by the fourth chain conveyor 19, while the remaining material enters the classifier 10. After the fine aggregate is separated, the fine aggregate is as follows... Figure 8 As shown, it is output by the fifth chain conveyor 20.

[0060] The remaining materials are carried by gas into cyclone separator 11 and dust collector 13 respectively. The recycled waste concrete powder collected by cyclone separator 11 and dust collector 13, such as... Figure 9As shown, the recycled waste concrete powder exhibits cementitious properties. A quantitative test of the compressive strength ratio of cement mortar was conducted on the prepared samples. The 3-day compressive strength was 24 MPa, and the 28-day compressive strength was 38 MPa, corresponding to a 3-day activity of 73% and a 28-day activity of 74%. The properties of the separated recycled coarse aggregate meet the requirements for Class II recycled coarse aggregate in GB / T 25177-2010 "Recycled Coarse Aggregate for Concrete"; the properties of the separated recycled fine aggregate meet the Class III performance requirements in GB / T 25176-2010 "Recycled Fine Aggregate for Concrete and Mortar".

[0061] Table 4

[0062]

Claims

1. A method for high-value resource utilization of waste concrete, characterized in that, Includes the following steps: (A) The waste concrete test blocks after coarse crushing, primary screening, fine crushing and secondary screening are stripped in the second ball mill (22), and the separated powder can be used directly as a mixture. (B) The waste concrete test blocks after coarse crushing, primary screening, fine crushing and secondary screening are preheated by the preheating subsystem. The heat source of the preheating subsystem is provided by the cooling subsystem and the middle and rear section of the second grate cooler of the cement production line. After preheating, it is calcined in the calcination subsystem. After calcination, the material is cooled by the cooling subsystem and stripped by the first ball mill (8). It is then sent to the V-type classifier (9) to separate the coarse aggregate. The middle and rear section of the second grate cooler provides hot air to the V-type classifier (9). (C) The material on the screen of the V-type classifier (9) is then classified by the classifier (10), and after dust collection by the dust collection subsystem, the fine aggregate and recycled waste concrete powder are separated. (D) To produce silicate cement clinker by adding coarsely sorted and pre-homogenized waste concrete into cement raw materials; The high-value resource utilization system for waste concrete used in the method includes a crushing subsystem, a preheating subsystem, a calcination subsystem, a cooling subsystem, a separation subsystem, a dust collection subsystem, a conveying subsystem, and a cement production line system. The crushing subsystem includes a first jaw crusher (1), a first vibrating screen (2), a second jaw crusher (3), and a second vibrating screen (4) connected in sequence. The separation subsystem includes a first ball mill (8), a second ball mill (22), a third vibrating screen (23), a V-type air classifier (9), an air classifier (10), and a cyclone separator (11). The outlet of the second vibrating screen (4) is connected to the second ball mill (22) and the preheating subsystem. The system inlet; the outlet of the second ball mill (22) is connected to the third vibrating screen (23); the preheating subsystem is connected in sequence to the calcination subsystem, the cooling subsystem, and the first ball mill (8); the first ball mill (8) is connected in sequence to the V-type classifier (9), the classifier (10), and the cyclone separator (11); the air outlet of the cyclone separator (11) is connected to the air inlet of the dust collection subsystem; the conveying subsystem is connected to the outlet of the dust collection subsystem, the cyclone separator (11), the V-type classifier (9), and the classifier (10), respectively; the gas outlet of the middle and rear section of the second grate cooler of the cement production line system is connected to the gas inlet of the V-type classifier (9) and the preheating subsystem, respectively.

2. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, Waste concrete raw meal, after coarse sorting and pre-homogenization, is used in the production of silicate cement clinker at a proportion of 5-15%, with a particle size controlled to ≤25mm.

3. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, Waste concrete used for producing silicate cement clinker has a test block size ≤150mm after coarse crushing and primary screening, and a test block size ≤50mm after fine crushing and secondary screening.

4. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, The second ball mill (22) uses high carbon chromium bearing steel balls. Ball bearings with a diameter greater than 25.4 mm in the ball mill are removed and discarded. The amount of waste concrete test blocks is 1 / 6 to 1 / 3 of the effective volume of the ball mill cylinder. The peeling time is 5 to 15 min and the cylinder speed is 40 to 70 r / min.

5. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, Powder, accounting for 10-15% of the total mass of waste concrete, is stripped from waste concrete and used directly as cementitious admixture.

6. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, In step (B), the preheating temperature is 200~250℃, the preheating time is 20~40min, and the heat source of the preheating subsystem is provided by the cooling subsystem and the middle and rear section of the second grate cooler of the cement production line. The ratio of the provided hot air is 1:2~1:

4.

7. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, In step (B), the calcination temperature of the calcination subsystem is 300~650℃, and the calcination time is 20~40min.

8. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, The ball bearings of the first ball mill (8) are ceramic zirconia balls. Ball bearings with a diameter greater than 25.4 are removed. The volume of construction waste occupies 1 / 6 to 1 / 3 of the effective volume of the cylinder. The peeling time is 5 to 15 minutes and the cylinder rotation speed is 40 to 70 r / min.

9. The method for high-value resource utilization of waste concrete according to claim 1, characterized in that, The ratio of hot air supplied from the middle and rear section of the second grate cooler of the cement production line to the V-type classifier (9) and the preheating subsystem is 1:2 to 1:4.

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