Process for producing concrete by recycling construction waste

Abstract

The invention provides a process for producing concrete by recycling construction wastes, which belongs to the technical field of concrete recycling and comprises the steps of primary crushing, primary screening, secondary crushing, secondary screening, aggregate modification and configuration. In the aggregate modification process, aggregate is separated from cement paste through high-temperature calcination, the purity of the aggregate is improved, meanwhile, a gas reducing agent is introduced into a calcining furnace, then the gas reducing agent reacts with rust in materials through the high temperature of calcination, elemental iron and carbon dioxide are generated, the carbon dioxide is directly discharged in the calcining process, and the elemental iron has magnetism, so that the carbon dioxide can be recycled. And subsequently, the iron remover is used for removing the reduced iron elementary substance, so that the aim of removing the iron rust in the material is fulfilled.

Description

Technical Field

[0001] The present invention belongs to the technical field of concrete recycling, and specifically refers to a process for recycling construction waste to produce concrete. Background Art

[0002] Recycled concrete from construction waste is a new type of concrete made by treating waste concrete in construction waste and mixing different grades of aggregates in proportion to partially or completely replace natural aggregates. It is a building material with broad application prospects and environmental protection significance. By reasonably utilizing the waste concrete in construction waste, not only can resource waste and environmental pollution be reduced, but also high-quality building materials can be provided for construction projects.

[0003] The production process of recycled concrete includes processes such as recycling, crushing, impurity removal, and grading of waste concrete blocks, and finally adding cement, water, etc. to prepare new concrete. However, during the construction process, usually when pouring concrete, steel bars are implanted inside the concrete to increase the strength of the concrete casting. Rust will be generated on the surface of the steel bars, which will cause non-magnetic rust (iron oxide) to adhere to the surface of the recycled construction waste and is difficult to remove. After re-preparing the concrete, the iron oxide will cause changes in the concrete performance and cannot meet the usage requirements. Summary of the Invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a process for recycling construction waste to produce concrete, which solves at least the above problems.

[0005] The technical solution adopted by the present invention is as follows: The present invention provides a process for recycling construction waste to produce concrete, including the following steps: S1: Material crushing, crushing the construction waste; S2: Material screening, conveying the material obtained in S1 to a horizontal screen for screening to obtain four grades of aggregates with particle sizes of 0 - 5.0 mm, 5.0 - 10.0 mm, 10.0 - 31.0 mm, and greater than 31.0 mm. The aggregates greater than 31.0 mm are returned to S1 for crushing; S3: Aggregate modification, calcining the aggregates with particle sizes of 5.0 - 10.0 mm and 10.0 - 31.0 mm in S4 to separate the aggregates from the cement slurry; S4: Configuration. Mix 500 - 600 parts of coarse aggregate with a particle size of 10.0 - 31.0 mm, 400 - 500 parts of fine aggregate with a particle size of 5.0 - 10.0 mm, 150 - 200 parts of cement, 60 - 180 parts of fly ash, 15 - 30 parts of silica fume, 30 - 40 parts of basalt - carbon fiber, 10 - 20 parts of water - reducing agent, 3 - 10 parts of air - entraining agent, and 180 - 250 parts of water by weight to obtain recycled concrete; Among them, in the step S3, introduce a gaseous reducing agent into the calciner, and make the content of the gaseous reducing agent in the air in the calciner greater than 95%, and the calcination temperature is 800 - 850 °C, and the calcination time is 1.0 - 3.0 h.

[0006] Furthermore, in the step S2, a negative - pressure air separator is provided, and the negative - pressure air separator is arranged above the horizontal screen in the step S2. While screening, remove the light substances in the raw materials by means of negative - pressure adsorption.

[0007] Furthermore, in the step S2, a specific gravity screen is provided, and the specific gravity screen is arranged at the output end of the horizontal screen, and the aggregates with particle sizes of 5.0 - 10.0 mm and 10.0 - 31.0 mm screened by the horizontal screen are respectively conveyed into the specific gravity screen for purification.

[0008] Furthermore, in the step S3, a three - stage iron remover is provided. After the aggregates in the step S3 are calcined and sufficiently cooled, they are conveyed by a conveyor belt to the three - stage iron remover to remove the iron reduced by the gaseous reducing agent during the calcination process.

[0009] Furthermore, the step S1 includes the following steps: S1.1: Primary crushing. Put the construction waste into a coarse crusher for primary coarse crushing; S1.2: Primary screening. Convey the material obtained in the step S1.1 to a heavy - duty relaxation screen to remove the soil on the surface of the material, and then convey it to an artificial picking table for sundry sorting; S1.3: Secondary crushing. Put the material obtained in the step S1.2 into a fine crusher for secondary fine crushing.

[0010] Furthermore, in the step S1.1, a bunker and a vibrating feeder are provided, and the vibrating feeder is arranged at the bottom discharge port of the bunker, and the bunker feeds the crusher in the step S1.1 at a uniform speed through the vibrating feeder.

[0011] Furthermore, in the step S1.1, a grate pre - screen is provided, and the grate pre - screen is arranged at the bottom of the vibrating feeder. While the vibrating feeder is feeding, the materials smaller than 100.0 MM can be pre - screened.

[0012] Furthermore, a primary iron remover is provided in S1.1, and the primary iron remover is arranged at the output end of the coarse crusher. The material output from the coarse crusher is conveyed to the primary iron remover through a conveyor belt, and iron is removed by the primary iron remover.

[0013] Furthermore, a secondary iron remover is provided in S1.3, and the secondary iron remover is arranged at the output end of the fine crusher. The material output from the fine crusher is conveyed to the secondary iron remover through a conveyor belt, and the secondary iron remover removes iron.

[0014] Furthermore, a positive pressure air separator is provided in S1.2, and the positive pressure air separator is arranged at the output end of the heavy-duty relaxation screen in S1.2, and adopts a positive pressure blowing method to remove light substances in the raw materials.

[0015] The beneficial effects achieved by the present invention using the above structure are as follows: High-temperature calcination is used to separate aggregates from cement slurry to improve the purity of aggregates. At the same time, a gas reducing agent is introduced into the calcining furnace, and the high temperature of calcination is used to make the gas reducing agent react with the rust (Fe2O3) in the material to generate iron element. Iron element is magnetic, and then an iron remover is used to remove the reduced iron element, thereby achieving the purpose of removing rust (Fe2O3) in the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a process flow chart for producing concrete by recycling construction waste, as proposed in an embodiment of the present invention.

[0017] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be understood that terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “top”, “bottom”, “inside” and “outside” indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0020] Example 1 As Figure 1 shown, an embodiment of the present invention provides a process for producing concrete using recycled construction waste, which includes the following steps:

[0021] S1: Material crushing; S1.1: Primary crushing, putting construction waste into a coarse crusher for primary coarse crushing.

[0022] In an alternative embodiment, the coarse crusher uses a jaw crusher, which has a large crushing ratio and can handle large pieces of construction waste.

[0023] Furthermore, in S1.1, a storage bin and a vibrating feeder are provided at the feeding port of the jaw crusher. The vibrating feeder is arranged at the bottom discharge port of the storage bin, and the vibrating feeder feeds the jaw crusher at a uniform speed to maintain the crushing efficiency of the jaw crusher and avoid the phenomena of material stacking or shortage in manual feeding.

[0024] Still further, in S1.1, a bar pre-screen is provided. The bar pre-screen is arranged at the bottom of the vibrating feeder. While the vibrating feeder is vibrating and feeding, by using the vibration of the vibrating feeder, materials smaller than 100.0 mm can pass through the bar pre-screen and be pre-screened, while materials larger than 100.0 mm are sent into the interior of the jaw crusher to improve the crushing efficiency of the jaw crusher. The materials crushed by the jaw crusher and the materials screened by the bar pre-screen are collected and transported.

[0025] Still further, in S1.1, a primary iron remover is provided. The primary iron remover is arranged at the output end of the coarse crusher. The materials crushed by the jaw crusher and the materials screened by the bar pre-screen are collected, and then transported to the primary iron remover by a conveyor belt. The primary iron remover removes the iron waste in the materials to improve the purity of the materials.

[0026] S1.2: Primary screening, transporting the materials obtained in S1.1 to a heavy-duty relaxation screen to remove the soil on the surface of the materials, and then transporting them to a manual picking table for sundry sorting.

[0027] Through the action of high acceleration, the heavy-duty relaxation screen thoroughly loosens and quickly separates the materials to be screened, thereby effectively removing the soil on the surface of the materials and improving the purity of the materials.

[0028] Further, a positive-pressure air classifier is provided in S1.2. The positive-pressure air classifier is arranged at the output end of the heavy-duty relaxation screen in S1.2. The oversize material (aggregate) after screening by the heavy-duty relaxation screen is conveyed into the positive-pressure air classifier. A positive pressure is formed inside the positive-pressure air classifier, and the material enters the positive-pressure air classifier along the air flow direction. Inside the positive-pressure air classifier, the material is subjected to a strong air flow force and is sorted or separated under the action of a high-speed rotating separation wheel. Lighter substances such as light impurities or dust will be carried away by the air flow, while the heavier material will be discharged along the set path.

[0029] After the material is air-classified by the positive-pressure air classifier, it is conveyed to the manual picking table, and the sundries are sorted manually to remove large and difficult-to-remove-by-air-classification sundries, improving the purity of the material.

[0030] S1.3: Secondary crushing, putting the material obtained in S1.2 into a fine crusher for secondary fine crushing.

[0031] In an alternative embodiment, the fine crusher is a counterattack crusher. The counterattack crusher can flexibly adjust the discharge particle size by adjusting the rotor speed, the gap between the counterattack plate and the grinding chamber. Therefore, the material after primary crushing is subjected to secondary crushing to further reduce the particle size of the material, and by adjusting the discharge particle size of the counterattack crusher, the particle size of the crushed material meets the requirements.

[0032] Further, a secondary iron remover is provided in S1.3. The secondary iron remover is arranged at the output end of the fine crusher. The material output by the fine crusher is conveyed to the secondary iron remover by a conveyor belt, and the iron in the material is removed by the secondary iron remover to further reduce the iron content in the material.

[0033] S2: Material screening, conveying the material obtained in S1.3 to a horizontal screen for screening. The horizontal screen is provided with three levels of screen meshes, and the mesh number gradually increases from top to bottom. The material is first conveyed to the topmost screen mesh of the horizontal screen and then screened step by step downward. Four grades of aggregates with particle sizes of 0 - 5.0 mm, 5.0 - 10.0 mm, 10.0 - 31.0 mm, and greater than 31.0 mm can be obtained by screening with the three-level screen mesh. The aggregates greater than 31.0 mm are returned to the fine crusher in S1.3 for re-crushing. The aggregates of 0 - 5.0 mm are conveyed into a humidifying machine, humidified and mixed evenly, and then conveyed to the finished product warehouse for storage.

[0034] Further, a negative-pressure air classifier is provided in S2. The negative-pressure air classifier is arranged at the topmost screen mesh of the horizontal screen in S2. The material is first conveyed to the topmost screen mesh of the horizontal screen for screening. Under the vibration of the horizontal screen, the material is evenly dispersed on the screen mesh. At this time, the light substances in the raw material are removed by means of negative-pressure adsorption, further improving the purity of the material.

[0035] Furthermore, a specific gravity screen is provided in S2, and the specific gravity screen is arranged at the output end of the horizontal screen, and the aggregates with particle sizes of 5.0-10.0mm and 10.0-31.0mm screened by the horizontal screen are respectively transported to the specific gravity screen for purification.

[0036] The specific gravity screen uses the difference in the specific gravity of the material itself. Through the effect of air blowing on the vibrating screen surface, the materials with different specific gravities produce different movement trajectories, thereby realizing automatic classification. Specifically, the material with a higher specific gravity will pass through the sieve hole first, while the material with a lower specific gravity will be blocked by the screen. The specific gravity screen is used to remove the lightweight materials in the material and improve the purity of the material.

[0037] Furthermore, a cleaning device is provided in S2, and the cleaning device is arranged at the output end of the specific gravity screen. The aggregates with particle sizes of 5.0-10.0mm and 10.0-31.0mm output by the specific gravity screen are transported to the cleaning device for cleaning to improve the cleanliness of the material.

[0038] S3: Aggregate modification. Aggregates with particle sizes of 5.0-10.0mm and 10.0-31.0mm in S2 are calcined to separate the aggregates from the cement slurry. The separated cement is ground and then transported to the finished product warehouse. The dehydrated cement slurry has water activation properties after being fully ground and can be used to prepare recycled cementitious materials.

[0039] Furthermore, during the calcination process, a gas reducing agent is continuously introduced into the calcination furnace, and the content of the gas reducing agent in the air in the calcination furnace is always greater than 95%, and the calcination temperature is 800-850°C, and the calcination time is 1.0-3.0h. Under high temperature conditions, the gas reducing agent is used to reduce the rust (Fe2O3) in the material into single iron, which has magnetism.

[0040] A horizontal screen is also provided in S3. After the calcined material is fully cooled, it is transported to the horizontal screen to obtain materials with particle sizes of 0-5.0 mm (calcined and separated cement), 5.0-10.0 mm, and 10.0-31.0 mm.

[0041] Furthermore, a three-stage iron remover is provided in S3, and the screened materials are transported to the three-stage iron remover by conveyor belts to remove the iron element reduced by the gas reducing agent during the calcination process, and then transported to the silo for storage.

[0042] In a specific embodiment, the gaseous reducing agent is carbon monoxide (CO), and carbon monoxide (CO) and iron oxide (Fe2O3) generate iron and carbon dioxide (3CO+Fe2O3-2Fe+3CO2) under high temperature.

[0043] In this way, high-temperature calcination is used to separate the aggregate from the cement paste, improving the purity of the aggregate. At the same time, a gaseous reducing agent (CO) is introduced into the calcination furnace. Using the high temperature of the calcination, the gaseous reducing agent (CO) reacts with the rust (Fe2O3) in the material to form elemental iron and carbon dioxide (CO2). The carbon dioxide (CO2) is directly discharged during the calcination process, while the elemental iron is magnetic. Subsequently, a magnetic separator is used to remove the reduced elemental iron, thereby achieving the purpose of removing rust (Fe2O3) from the material.

[0044] S4: Preparation. 500 - 600 parts of coarse aggregate with a particle size of 10.0 - 31.0 mm, 400 - 500 parts of fine aggregate with a particle size of 5.0 - 10.0 mm, 150 - 200 parts of cement, 60 - 180 parts of fly ash, 15 - 30 parts of silica fume, 30 - 40 parts of basalt - carbon fiber, 10 - 20 parts of water - reducing agent, 3 - 10 parts of air - entraining agent, and 180 - 250 parts of water are weighed and mixed evenly to obtain recycled concrete.

[0045] The following are the performance verification data of the recycled concrete after removing rust, and a comparison is made with the performance of the recycled concrete without removing rust.

[0046]

[0047] Detailed steps of this embodiment: S1: Material crushing S1.1. The construction waste is put into the silo, and the vibrating feeder evenly feeds the material to the jaw crusher. While the vibrating feeder is vibrating and feeding, the vibration of the vibrating feeder enables the material smaller than 100.0 MM to pass through the grizzly pre - screen and be pre - screened out, while the material larger than 100.0 MM is fed into the interior of the jaw crusher. The crushed material of the crusher and the material screened out by the grizzly pre - screen are collected and transported. The crushed material of the jaw crusher and the material screened out by the grizzly pre - screen are collected, and then transported to the primary magnetic separator by a conveyor belt. The primary magnetic separator removes the iron waste in the material, improving the purity of the material. S1.2. The material obtained in S1.1 is transported to a heavy - duty relaxation screen to remove the soil on the surface of the material. The over - size material (aggregate) after screening by the heavy - duty relaxation screen is transported into a positive - pressure air - separator. A positive pressure is formed inside the positive - pressure air - separator. The material enters the positive - pressure air - separator along the air flow direction. Inside the positive - pressure air - separator, the material is subjected to a strong air flow force and is sorted or separated under the action of a high - speed rotating separating wheel. Lighter substances such as light impurities or dust will be carried away by the air flow, while the heavier material will be discharged along the set path. After the material is air - separated by the positive - pressure air - separator, it is transported to an artificial picking table, and manual sorting is carried out by workers to remove large and difficult - to - air - separate sundries, improving the purity of the material. S1.3, conveying the material obtained in S1.2 to the impact crusher for further crushing to reduce the particle size of the material, and adjusting the discharge particle size of the impact crusher so that the particle size of the crushed material meets the demand; The material output from the impact crusher is transported to the secondary iron remover through a conveyor belt, where the iron is removed to further reduce the iron content in the material. S2: Secondary screening S2.1, convey the material obtained in S1 to a horizontal screen for screening. The horizontal screen is provided with three-level screens, and the mesh size increases gradually from top to bottom. The material is first conveyed to the top screen of the horizontal screen, and then screened downward step by step. The three-level screen screening can obtain four-level aggregates with particle sizes of 0-5.0mm, 5.0-10.0mm, 10.0-31.0mm, and larger than 31.0mm. Aggregates larger than 31.0mm are returned to the fine crusher in S1.3 for re-crushing. Aggregates with a size of 0-5.0mm are conveyed to a humidifier, humidified and mixed by the humidifier, and then conveyed to a finished product warehouse for storage; S2.2, during screening, the material is first transported to the top screen of the horizontal screen for screening. Under the vibration of the horizontal screen, the material is evenly dispersed on the screen. At this time, a negative pressure air separator is used to remove light substances in the raw materials to further improve the purity of the material; S2.3, the aggregates with particle sizes of 5.0-10.0 mm and 10.0-31.0 mm sieved by the horizontal screen are respectively transported to the specific gravity screen for purification; S2.4, transport the aggregates with particle sizes of 5.0-10.0mm and 10.0-31.0mm output by the density screen to the cleaning equipment for cleaning to improve the cleanliness of the materials; S3: Aggregate modification S3.1, calcine the aggregates with particle sizes of 5.0-10.0mm and 10.0-31.0mm in S2 to separate the aggregates from the cement slurry, and continuously introduce a gas reducing agent (CO) into the calcining furnace, and make the content of the gas reducing agent in the air in the calcining furnace always greater than 95%, and the calcination temperature is 800-850℃, and the calcination time is 1.0-3.0h. Under high temperature, the gas reducing agent is used to reduce the rust (Fe2O3) in the material into iron element, and the iron element has magnetism; S3.2, after the aggregate is calcined in a gas reducing agent environment and fully cooled, it is transported to a horizontal screen for screening to obtain materials with particle sizes of 0-5.0 mm, 5.0-10.0 mm, and 10.0-31.0 mm; S3.3, the materials with particle sizes of 0-5.0mm, 5.0-10.0mm and 10.0-31.0mm output by the horizontal screen are transported to the third-stage iron remover by the conveyor belt to remove the iron element reduced by the gas reducing agent during the calcination process, thereby achieving the purpose of removing rust (Fe2O3) in the material; S3.4, transport the material with a particle size of 0-5.0mm (calcined and separated cement slurry) after iron removal to the grinder, and transport it to the finished product warehouse for storage after being fully ground; S3.5, transport the materials with particle sizes of 5.0-10.0mm and 10.0-31.0mm after iron removal to the finished product warehouse for storage; S4: Preparation: 500-600 parts of coarse aggregate with a particle size of 10.0-31.0 mm, 400-500 parts of fine aggregate with a particle size of 5.0-10.0 mm, 150-200 parts of cement, 60-180 parts of fly ash, 15-30 parts of silica fume, 30-40 parts of basalt-carbon fiber, 10-20 parts of water reducer, 3-10 parts of air entraining agent and 180-250 parts of water are mixed evenly to obtain recycled concrete.

[0048] Example 2 Compared with Example 1, the gas reducing agent in step S3.1 of this embodiment is replaced with ammonia (NH3), and other conditions are the same as those of Example 1.

[0049] Aggregates of 5.0-10.0 mm and 10.0-31.0 mm in S2 are calcined to separate the aggregates from the cement slurry. Meanwhile, a gas reducing agent (NH3) is continuously introduced into the calcining furnace, and the content of the gas reducing agent in the air in the calcining furnace is always greater than 95%. The calcination temperature is 800-850°C, and the calcination time is 1.0-3.0 h. Under high temperature conditions, the gas reducing agent is used to reduce the rust (Fe2O3) in the material into elemental iron, and nitrogen (N2) and water (H2O) are generated.

[0050] In this embodiment, the gas reducing agent (NH3) reduces rust (Fe2O3) into elemental iron under high temperature environment, and generates nitrogen (N2) and water (H2O) at the same time. The water (H2O) is evaporated at high temperature, and the nitrogen (N2) can be used as a protective gas during the reduction process.

[0051] In summary of the above embodiments: high-temperature calcination is used to separate the aggregate from the cement slurry to improve the purity of the aggregate. At the same time, a gas reducing agent is introduced into the calcination furnace. The high temperature of calcination is used to make the gas reducing agent react with the rust (Fe2O3) in the material to generate iron element. The iron element is magnetic. Subsequently, an iron remover is used to remove the reduced iron element, thereby achieving the purpose of removing the rust (Fe2O3) in the material.

[0052] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0053] The above describes the present invention and its embodiments. Such description is not restrictive. What is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Generally speaking, if those of ordinary skill in the art are inspired by it and, without departing from the gist of the present invention, design similar structural modes and embodiments to this technical solution without creative efforts, they shall fall within the protection scope of the present invention.

Claims

1. A process for producing concrete by recycling construction waste, characterized in that, It includes the following steps: S1: Material crushing, crushing construction waste; S2: Material screening, conveying the material obtained in S1 to a horizontal screen for screening to obtain four grades of aggregates with particle sizes of 0 - 5.0 mm, 5.0 - 10.0 mm, 10.0 - 31.0 mm, and greater than 31.0 mm. The aggregates greater than 31.0 mm are returned to S1 for crushing; S3: Aggregate modification, calcining the aggregates with particle sizes of 5.0 - 10.0 mm and 10.0 - 31.0 mm in S4 to separate the aggregates from the cement slurry; S4: Configuration, mixing 500 - 600 parts of coarse aggregates with a particle size of 10.0 - 31.0 mm, 400 - 500 parts of fine aggregates with a particle size of 5.0 - 10.0 mm, 150 - 200 parts of cement, 60 - 180 parts of fly ash, 15 - 30 parts of silica fume, 30 - 40 parts of basalt - carbon fiber, 10 - 20 parts of water - reducing agent, 3 - 10 parts of air - entraining agent, and 180 - 250 parts of water by weight to obtain recycled concrete; Among them, in S3, a gaseous reducing agent is introduced into the calcining furnace, and in the air in the calcining furnace, the content of the gaseous reducing agent is greater than 95%, and the calcining temperature is 800 - 850 °C, and the calcining time is 1.0 - 3.0 h.

2. The process for producing concrete by recycling construction waste according to claim 1, characterized in that: In S2, a negative - pressure air - separator is provided. The negative - pressure air - separator is arranged above the horizontal screen in S2. While screening, light substances in the raw materials are removed by means of negative - pressure adsorption.

3. The process for producing concrete by recycling construction waste according to claim 1, wherein: In S2, a specific gravity screen is provided. The specific gravity screen is arranged at the output end of the horizontal screen, and the aggregates with particle sizes of 5.0 - 10.0 mm and 10.0 - 31.0 mm screened by the horizontal screen are respectively conveyed into the specific gravity screen for purification.

4. The process for producing concrete by recycling construction waste according to claim 1, characterized in that: In S3, a three - stage iron remover is provided. After the aggregates in S3 are calcined and fully cooled, they are conveyed by a conveyor belt to the three - stage iron remover to remove the iron reduced by the gaseous reducing agent during the calcining process.

5. The process for producing concrete by recycling construction waste according to claim 1, characterized in that: S1 includes the following steps: S1.1: Primary crushing, putting construction waste into a coarse crusher for primary coarse crushing; S1.2: Primary screening, conveying the material obtained in S1.1 to a heavy - duty relaxation screen to remove the soil on the surface of the material, and then conveying it to an artificial picking table for sorting of sundries; S1.3: Secondary crushing, putting the material obtained in S1.2 into a fine crusher for secondary fine crushing.

6. The process for producing concrete by recycling construction waste according to claim 5, characterized in that: In S1.1, a bunker and a vibrating feeder are provided. The vibrating feeder is arranged at the bottom discharge port of the bunker, and the crusher in S1.1 is fed evenly through the vibrating feeder.

7. The process for producing concrete by recycling construction waste according to claim 6, characterized in that: In S1.1, a bar pre - screen is provided. The bar pre - screen is arranged at the bottom of the vibrating feeder. While the vibrating feeder is feeding, materials smaller than 100.0 MM can be pre - screened.

8. The process for producing concrete by recycling construction waste according to claim 5, characterized in that: In S1.1, a primary iron remover is provided. The primary iron remover is arranged at the output end of the coarse crusher. The material output by the coarse crusher is conveyed to the primary iron remover by a conveyor belt, and iron is removed by the primary iron remover.

9. The process for producing concrete by recycling construction waste according to claim 5, characterized in that: A secondary iron remover is provided in S1.3, and the secondary iron remover is arranged at the output end of the fine crusher. The materials output by the fine crusher are conveyed to the secondary iron remover through a conveyor belt, and iron is removed by the secondary iron remover.

10. The process for producing concrete by recycling construction waste according to claim 5, characterized in that: A positive pressure air separator is provided in S1.2, and the positive pressure air separator is arranged at the output end of the heavy-duty relaxation screen in S1.

2. The light substances in the raw materials are removed by means of positive pressure blowing.

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