阅读说明：本技术 一种废弃混凝土回收再生的方法 (Method for recycling waste concrete ) 是由 徐中慧 蒋鑫 李宇 韩林沛 向应令 胡丹 于 2020-10-15 设计创作，主要内容包括：本发明公开了一种废弃混凝土回收再生的方法。该方法先利用水泥窑高温烟气对废弃混凝土进行预处理,再利用旋风分离器实现水泥石微粉与粗集料、细集料的分离。具体步骤如下：(1)将废弃混凝土从窑头送入回转窑,水泥窑高温烟气(未经处理)从窑尾送入回转窑；(2)将经回转窑预处理后的废弃混凝土送入对辊破碎机破碎；(3)通过筛分,将步骤(2)中的混凝土颗粒分为A组分(粒径≥5 mm的粗集料)和B组分(粒径<5 mm)；(4)将混凝土颗粒利用回转窑窑尾高温烟气喷吹送入旋风分离器中进一步破碎分离,实现细集料和水泥石微粉的分离回收。该方法可分别实现粗集料、细集料和水泥石微粉的分离回收,有效缓解废弃混凝土堆存对环境危害的压力。同时该方法减少了普通研磨筛分回收过程中造成的无活性集料与水泥石微粉的混合,提升了再生水泥石微粉的活性。(The invention discloses a method for recycling waste concrete. The method comprises the steps of pretreating waste concrete by using high-temperature flue gas of a cement kiln, and separating the fine cement powder from coarse aggregates and fine aggregates by using a cyclone separator. The method comprises the following specific steps: (1) feeding waste concrete into a rotary kiln from a kiln head, and feeding high-temperature flue gas (untreated) of the cement kiln into the rotary kiln from a kiln tail; (2) feeding the waste concrete pretreated by the rotary kiln into a double-roller crusher for crushing; (3) screening to separate the concrete particles in the step (2) into a component A (coarse aggregate with the particle size of more than or equal to 5 mm) and a component B (with the particle size of less than 5 mm); (4) and (3) blowing the concrete particles into a cyclone separator by using high-temperature flue gas at the tail of the rotary kiln to further crush and separate, thereby realizing the separation and recovery of fine aggregate and cement stone micro powder. The method can separate and recover coarse aggregate, fine aggregate and cement stone micro powder respectively, and effectively relieves the pressure of environmental hazard caused by stacking of waste concrete. Meanwhile, the method reduces the mixing of inactive aggregate and cement stone micro powder in the common grinding, screening and recycling process, and improves the activity of the regenerated cement stone micro powder.)

1. The invention discloses a method for recycling waste concrete, which is characterized by sequentially comprising the following steps:

(1) feeding waste concrete into a rotary kiln from a kiln head, feeding high-temperature flue gas (untreated) of the cement kiln into the rotary kiln from a kiln tail, and heating the waste concrete in the rotary kiln by using the high-temperature flue gas;

(2) feeding the waste concrete pretreated by the rotary kiln in the step (1) into a double-roll crusher for crushing;

(3) screening the concrete particles in the step (2) into a component A (coarse aggregate with the particle size of more than or equal to 5 mm) and a component B (with the particle size of less than 5 mm);

(4) and (4) sending the concrete particle component B in the step (3) into a cyclone separator, and separating and recovering the fine aggregate and the set cement by using high-temperature flue gas at the kiln tail of the rotary kiln for blowing.

2. The method for recycling waste concrete according to claim 1, wherein the waste concrete in the step (1) stays in the rotary kiln for 5 to 8 hours.

3. The method for recycling waste concrete according to claim 1, wherein the step (2) is performed by pressing a roller crusher, and the gap between two rollers of the roller crusher is 5 mm.

4. The method for recycling the waste concrete according to claim 1, wherein in the step (4), the bottom of the cyclone separator is connected with a high-temperature fan, the high-temperature flue gas of the rotary kiln is sent into the cyclone separator through the high-temperature fan, and the height-diameter ratio of the cyclone separator is more than 6: 1.

Technical Field

The invention relates to a method for recycling coarse aggregates, fine aggregates and cement stone micro powder in waste concrete, belonging to the technical field of green building materials.

Background

While the economy is rapidly developing, various industries are also developing rapidly, so that new construction, updating and dismantling of various buildings are accompanied. In the process, a large amount of construction waste, particularly waste concrete after the construction is dismantled, is generated. It occupies a large amount of land and may cause harm to the environment during stockpiling. The consumption of concrete by various engineering constructions is continuously increased, and the recycling of waste concrete draws wide attention of scholars at home and abroad. The waste concrete contains coarse aggregate and fine aggregate, and the fine aggregate is further crushed to obtain waste concrete micro powder.

The recovery process mainly comprises crushing, separating and screening. However, a general crushing process may crush coarse aggregates and fine aggregates at the same time, and thus cannot separate and separately recover the coarse aggregates and the fine aggregates. In chinese patent CN110125133A, brick and tile, metal, concrete and the like in the construction waste are subdivided and recovered respectively by using screening and crushing processes. The method has the advantages of complex screening procedure, long calcination time and high energy consumption, the calcination temperature has great influence on the activity of the waste concrete micro powder, and the calcination causes the increase of the cost.

The device in the Chinese patent CN103182339A integrates crushing, grinding, drying and grading, and has the advantages of high efficiency, low energy consumption, classified recovery, higher micro powder activity and the like. But the feeding granularity has certain requirements and the discharging granularity is larger. The fineness and activity of the micro powder obtained by crushing cannot be guaranteed, and the micro powder is not excited. In chinese patents CN107892497A and CN109704607A, waste concrete is crushed by mechanical crushing, and is subjected to multi-stage screening, and the activator is mixed with the micro powder, so that the micro powder can be practically used. Mechanical crushing may crush coarse and fine aggregates simultaneously, resulting in inefficient separation and separate utilization of the aggregates, and complicated sieving is inefficient.

In order to overcome the problems of high energy consumption, complex screening, low activity of micro powder and the like, the invention utilizes the high-temperature flue gas of the cement kiln to dehydrate and activate the waste concrete and can separate coarse aggregates, fine aggregates and set cement. The invention has the advantages of simplified equipment, low cost, simple process, realization of waste concrete activation and coarse and fine aggregate separation, and the like.

Disclosure of Invention

The invention provides a preparation method for regenerating waste concrete, which avoids the situation that the activity of recycled cement stone micro powder is lower due to the mixed grinding of aggregate and cement stone in the grinding process of the waste concrete. The specific invention content is as follows:

(1) the invention introduces the high-temperature flue gas of the cement kiln into the rotary kiln to heat the waste concrete. The high-temperature flue gas of the cement kiln is used as a heating mode, so that the cement stone, loose aggregate and cement stone are effectively activated, and the waste heat of the cement kiln is effectively utilized.

(2) The invention utilizes the roller crusher to extrude the activated waste concrete so as to further separate the aggregate and the set cement, and simultaneously reduces the probability of reducing the activity of the set cement micropowder caused by grinding the aggregate into fine powder in the common crushing process.

(3) The invention utilizes the high-temperature smoke ejected by the high-temperature fan to eject the component B of the concrete particles sent into the cyclone separator, and forms rotating airflow at the bottom of the cyclone separator; the height-diameter ratio of the cyclone separator is controlled to form a chimney effect to strengthen the rotating airflow, and the tornado-like ascending rotating airflow is formed in the cyclone separator; the strong rotating airflow throws the concrete particle B component onto the cylindrical wall of the cyclone separator, and the strong collision causes further crushing of the particles, thereby realizing further separation of fine aggregate and cement stone micropowder.

The invention has the beneficial effects that:

(1) according to the invention, the waste concrete is heated by using the high-temperature flue gas at the tail of the cement kiln, so that the economic benefit is improved.

(2) The method effectively separates the coarse aggregate, the fine aggregate and the cement stone micro powder of the waste concrete, improves the practical value of the waste concrete, and improves the activity of the cement stone micro powder.

(3) The method recycles and regenerates the waste concrete, avoids land occupation and environmental pollution caused in the process of piling up and storing the waste concrete, and is safe and environment-friendly.

Detailed Description

A method for recycling waste concrete comprises the following steps:

(1) feeding the waste concrete after impurity removal into a rotary kiln from a kiln head, feeding high-temperature flue gas (untreated) of a cement kiln into the rotary kiln from a kiln tail, heating the waste concrete for 5 hours by using the high-temperature flue gas of the cement kiln, taking out the waste concrete from the kiln tail, and naturally cooling the waste concrete;

(2) and (2) crushing the waste concrete in the step (1) by using a pair of roller crushers, wherein the gap between the pair of roller crushers is not more than 5 mm. And screening concrete particles produced by extrusion, and crushing the concrete particles with the size of more than 5 mm by using a roller crusher until the size of the concrete particles is less than 5 mm. The concrete particle sieve comprises a component A (coarse aggregate with the particle size of more than or equal to 5 mm) and a component B (with the particle size of less than 5 mm);

(3) removing magnetic substances in the concrete particles in the step (2) by using an electromagnetic disc respectively;

(4) feeding the concrete particle B component in the step (3) into a cyclone separator from one side of the bottom of the cyclone separator, and blowing high-temperature flue gas of a kiln head of the rotary kiln to the bottom of the cyclone separator by using a high-temperature fan; and recovering the fine aggregate obtained by separation from the bottom of the cyclone separator, and collecting the cement stone micro powder carried away by the upward cyclone by using a bag filter.

Finally, it is noted that the above-mentioned embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention as defined by the appended claims.