Environment-friendly cement and preparation method thereof

Abstract

The invention discloses a preparation method of environment-friendly cement. The preparation method comprises the following steps: step 1, crushing and screening construction waste to obtain aggregate and powder; 2, the organic waste is subjected to pyrolysis treatment, and pyrolysis residues are obtained; 3, limestone, clay, the aggregate and powder in the step 1 and the pyrolysis residues in the step 2 are mixed, calcined and ground, and the environment-friendly cement is obtained. Wherein the construction waste is calculated according to the weight of the aggregate and the powder, the organic waste is calculated according to the weight of the pyrolysis residue, and the weight parts of the limestone, the clay, the construction waste and the organic waste are 35-45 parts, 5-10 parts, 45-55 parts and 6-18 parts respectively. Compared with the prior art, the cement has the advantages that the production cost is reduced by 15-30%, the heavy metal content of pyrolysis residues treated by the technical scheme is reduced by 40-70%, and the 28d strength of cement clinker is improved by 5-20% compared with that of common cement.

Description

Technical Field

[0001] The present invention belongs to the technical field of chemical industry, and in particular, relates to an environmentally friendly cement and a method for preparing the environmentally friendly cement. Background Art

[0002] As my country's urbanization process continues to intensify, the demand for cement remains high.

[0003] Cement is a powdery, hydraulic inorganic cementitious material. After adding water and stirring, it becomes a slurry, which can harden in the air or in water, and can firmly bind materials such as sand and stone together. Most of the raw materials for cement production come from stone, and the stone must be crushed, calcined, cooled and then ground before cement production. However, the existing production method has a huge demand for natural limestone, fly ash, etc., and natural gas or coal needs to be added during calcination.

[0004] CN107324675A discloses a cement production method, which changes the traditional batching method of cement manufacturing using limestone as raw material, uses lime as raw material, saves the process of limestone decomposing into lime in a rotary kiln, and increases the hourly output of rotary kiln clinker by 2-3 times. The method has the advantages of simple process, small equipment investment, low energy consumption, high output, and good comprehensive economic benefits. This method is particularly suitable for cement production in small rotary kilns of medium and small cement enterprises.

[0005] CN106927702A discloses a method for producing cement, which relates to the field of building materials. The method for producing cement is to collect waste bricks and tiles and waste ceramic products used for construction, wash and dry them, grind them, and then grind them into brick and tile powder and ceramic powder, and then use quicklime powder, gypsum powder, brick and tile powder, and ceramic powder to make cement. Using construction waste to make cement can save costs, turn waste into treasure, and protect the environment. Bricks and ceramics can provide sufficient calcium, silicon and other elements for cement, ensuring the quality of cement. This method only uses bricks and tiles and ceramic pieces in construction waste to make cement, and quicklime is still used as the main raw material. The cost reduction is not significant, and the quality of cement has not been improved.

[0006] Therefore, further research on the preparation method of environmentally friendly cement is needed in this field. Summary of the invention

[0007] The main purpose of the present invention is to provide an environmentally friendly cement and a preparation method thereof, so as to overcome the problems of high cement production cost, low strength, and difficulty in handling solid waste in the prior art.

[0008] In order to achieve the above object, the present invention provides a method for preparing environmentally friendly cement, comprising the following steps:

[0009] Step 1, crushing and screening the construction waste to obtain aggregates and powder;

[0010] Step 2, pyrolyzing the organic waste to obtain pyrolysis residue;

[0011] Step 3, mixing limestone, clay, aggregate and powder from step 1, and pyrolysis residue from step 2, calcining, and grinding to obtain environmentally friendly cement;

[0012] Among them, construction waste is measured by the weight of aggregate and powder, organic waste is measured by the weight of pyrolysis residue, and the weight proportions of limestone, clay, construction waste and organic waste are 35-45 weight parts, 5-10 weight parts, 45-55 weight parts and 6-18 weight parts respectively.

[0013] The method for preparing the environmentally friendly cement of the present invention, wherein the step 3 is: limestone, clay, the aggregate of step 1, and the pyrolysis residue of step 2 are evenly mixed, and then the powder of step 1 is added, mixed, calcined, and ground to obtain the environmentally friendly cement.

[0014] The method for preparing environmentally friendly cement of the present invention, wherein the construction waste is construction waste generated during the construction, reconstruction and expansion of buildings, containing bricks, concrete and a small amount of impurities; the organic waste includes at least one of domestic garbage, biomass, municipal sludge and waste tires.

[0015] The method for preparing environmentally friendly cement of the present invention, wherein the crushing and screening includes a crushing process and a screening process, the crushing process is performed at least once, the screening process is performed at least once, and the crushing process and the screening process are performed alternately.

[0016] The method for preparing environmentally friendly cement described in the present invention, wherein the crusher used for crushing treatment includes at least one of a jaw crusher, an impact crusher, and an impact crusher, and the screening treatment includes at least one of magnetic separation and screening, screening and soil removal, manual sorting, air separation, and powder selection.

[0017] In the method for preparing the environmentally friendly cement of the present invention, the particle size of the aggregate obtained by crushing and screening the construction waste is 5-31.5 mm, and the particle size of the powder is greater than 0 and less than 5 mm.

[0018] The method for preparing environmentally friendly cement described in the present invention, wherein the pyrolysis treatment is carried out in a fluidized bed pyrolysis furnace, a fixed bed pyrolysis furnace or a moving bed pyrolysis furnace, the temperature of the pyrolysis treatment is greater than or equal to 550° C., and the time of the pyrolysis treatment is 30-120 minutes.

[0019] In the method for preparing the environmentally friendly cement of the present invention, the carbon content of the pyrolysis residue is 25wt%-80wt%.

[0020] The method for preparing the environmentally friendly cement of the present invention, wherein in step 3, the calcination temperature is 1300-1500° C., and the particle size after grinding is less than 80 μm.

[0021] In order to achieve the above object, the present invention also provides environmentally friendly cement obtained by the above preparation method.

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention is to mix the recycled aggregate and pyrolysis residue produced by the treatment of organic waste such as construction waste and domestic waste with limestone and clay, and then calcine and grind them to produce environmentally friendly cement. The use of construction waste and pyrolysis residue can reduce the amount of raw material limestone used. Since the organic matter content in the pyrolysis residue is very high, the consumption of coal or natural gas can be reduced. In addition, the toxic and harmful substances in the pyrolysis residue are rendered harmless through cement solidification.

[0024] Compared with the cement made of limestone in the prior art, the cement of the present invention reduces production cost by 10-30%, reduces pollutant emission, and after calcination of pyrolysis residue, the heavy metal content in the product is reduced by 40-70% compared with the amount of heavy metals in the pyrolysis residue, and the 28d strength of cement clinker is increased by 5-20%. At the same time, the preparation method of the present invention comprehensively utilizes two kinds of waste, realizes waste into treasure, and protects the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a flow chart of the preparation of environmentally friendly cement in one embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical scheme of the present invention is described in detail below. The following implementation modes are implemented on the premise of the technical scheme of the present invention, and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following implementation modes. The structures or experimental methods of specific conditions are not specified in the following implementation modes, and generally conventional conditions are followed.

[0027] The present invention provides a method for preparing environmentally friendly cement, comprising the following steps:

[0028] Step 1, crushing and screening the construction waste to obtain aggregates and powder;

[0029] Step 2, pyrolyzing the organic waste to obtain pyrolysis residue;

[0030] Step 3, mixing limestone, clay, aggregate and powder from step 1, and pyrolysis residue from step 2, calcining, and grinding to obtain environmentally friendly cement;

[0031] Among them, construction waste is measured by the weight of aggregate and powder, organic waste is measured by the weight of pyrolysis residue, and the weight proportions of limestone, clay, construction waste and organic waste are 35-45 weight parts, 5-10 weight parts, 45-55 weight parts and 6-18 weight parts respectively.

[0032] The key point is that the present invention replaces limestone with construction waste and organic waste in a specific proportion, so that the strength of the produced environmentally friendly cement clinker is increased. In one embodiment, the weight parts of limestone, clay, construction waste and organic waste are 35-45 weight parts, 5-10 weight parts, 45-55 weight parts and 6-18 weight parts, respectively, based on 100 weight parts of environmentally friendly cement of the present invention.

[0033] A large amount of construction waste, domestic waste, biomass, municipal sludge, waste tires, etc. will be generated during the process of urban construction, renewal and people's production activities. Construction waste can be used to produce aggregates through crushing and screening processes. Organic waste such as domestic waste, biomass, municipal sludge, waste tires, etc. can produce pyrolysis residues through pyrolysis or pyrolysis gasification processes. At present, such aggregates or residues are generally disposed of by landfill, which not only wastes land but also causes waste of resources. In addition, there are a large number of toxic and harmful substances such as heavy metals in the pyrolysis residues, which have a serious impact on the environment.

[0034] The present invention prepares cement by treating aggregates and powder obtained from construction waste and residues produced by pyrolysis of organic waste in a specific ratio, which can not only improve the strength of cement clinker, but also reduce the production cost of cement. In addition, since the organic matter content in the pyrolysis residue of organic waste is very high, the consumption of energy such as coal or natural gas in the cement calcination process can be reduced, thereby reducing energy consumption.

[0035] In the present invention, the construction waste may be construction waste generated during the construction, reconstruction and expansion of buildings, and may contain bricks, concrete and a small amount of impurities.

[0036] The present invention carries out crushing and screening of construction waste, which may include crushing and screening of construction waste, the number of crushing is at least one, such as 2 times, 3 times, 4 times, etc., the number of screening is at least one, such as 2 times, 3 times, 4 times, etc., the crushing and screening can be performed alternately, but it is not limited that the crushing and screening must be performed strictly in a strict alternating order such as ABAB (A, for example, represents crushing, and B, for example, represents screening), and may also be in an order such as ABBAA. The crusher used for crushing includes at least one of a jaw crusher, an impact crusher, and an impact crusher, and the screening includes at least one of magnetic separation and screening, screening and soil removal, manual sorting, air separation, and powder selection.

[0037] In one embodiment, the construction waste is subjected to primary crushing, screening and soil removal, magnetic separation and screening, secondary crushing, and powder selection to obtain aggregate and powder. The powder selection itself does not produce fine powder, but rather selects particles with a certain particle size in the material in a timely manner. In another embodiment, in the present invention, the particle size of the aggregate is 5-31.5 mm, and the particle size of the powder is greater than 0 and less than 5 mm.

[0038] In another embodiment, Figure 1 As shown, the construction waste is crushed by a jaw crusher for primary crushing (for example, crushed to less than 150mm), magnetic separation to remove ferromagnetic materials (impurities affect the quality of cement and the operation of subsequent processing equipment), screening to remove soil (remove impurities, improve the purity of aggregates, and improve the quality of cement), manual sorting, wind separation (remove light materials), impact crusher crushing (production of powder), three-stage magnetic separation screening (three magnetic separations, three screenings), to obtain aggregates greater than 0 and less than 5mm, 5-10mm (excluding 10mm) and 10-31.5mm. Aggregates of 5-10mm and 10-31.5mm are crushed by an impact crusher, and then powdered together with aggregates greater than 0 and less than 5mm in a powder separator to obtain aggregates and powders.

[0039] In the present invention, step 2 is: subjecting the organic waste to pyrolysis treatment to obtain pyrolysis residue.

[0040] In the present invention, the organic waste can be domestic garbage, biomass, municipal sludge, waste tires, etc. Since the organic waste has a high organic content, using it to prepare cement can reduce the energy consumption in the cement calcination process.

[0041] In one embodiment, the pyrolysis of organic waste is carried out in a pyrolysis furnace, which can be a fluidized bed pyrolysis furnace, a fixed bed pyrolysis furnace, or a moving bed pyrolysis furnace. The temperature of the pyrolysis treatment is greater than or equal to 550°C, preferably above 850°C, and the time of the pyrolysis treatment is greater than or equal to 30 minutes, preferably 30-120 minutes. The heating method of the pyrolysis can be external heating or internal heating. In another embodiment, the carbon content of the pyrolysis residue produced by the pyrolysis is 20wt%-80wt%, preferably 25wt%-80wt%.

[0042] In another embodiment, Figure 1 As shown, the organic waste is firstly subjected to bag breaking, rolling screening, magnetic separation, and crushing treatment, and then pyrolyzed in a pyrolysis furnace to obtain pyrolysis residue. Among them, bag breaking is to break the outer packaging bag of the garbage.

[0043] In the present invention, step 3 is: mixing limestone, clay, aggregate and powder from step 1, and pyrolysis residue from step 2, calcining, and grinding to obtain environmentally friendly cement.

[0044] The present invention uses construction waste and organic waste to replace part of natural limestone, fly ash and other raw materials. The cement prepared by limestone, clay, construction waste and organic waste in a ratio of 35-45 weight parts: 5-10 weight parts: 45-55 weight parts: 6-18 weight parts can reduce production cost by 15-30%, and the 28d strength of cement clinker is increased by 5%-20%. Moreover, toxic and harmful substances in pyrolysis residues are rendered harmless through cement solidification, and the heavy metal content in the pyrolysis residues is reduced by 40-70%.

[0045] In one embodiment, the present invention first mixes limestone, clay, aggregates from step 1, and pyrolysis residues from step 2 uniformly, and then adds the powder from step 1, mixes, calcines, and grinds to obtain environmentally friendly cement. In this way, the raw materials can be mixed sufficiently and uniformly, the quality of cement is stable, and the material requirements for calcination are met.

[0046] In one embodiment, if Figure 1 As shown, calcination is carried out in a calcination kiln, and the calcination temperature is, for example, 1300-1500°C. After calcination, the cement clinker is cooled and then ground. The particle size after grinding is, for example, <80 μm. The environmentally friendly cement is obtained by bagging and sealing. The particle size after grinding can be adjusted as needed.

[0047] The environmentally friendly cement obtained by the method of the invention has low cost and high strength, and also recycles construction waste and organic waste, thereby avoiding the damage of waste to the environment and reducing the cost of waste treatment.

[0048] The present invention has been verified through experiments that if the weight ratio of limestone, clay, construction waste and organic waste does not meet 35-45 parts by weight: 5-10 parts by weight: 45-55 parts by weight: 6-18 parts by weight, even if cement is prepared from limestone, clay, construction waste and organic waste, the strength of the cement is the same as or 5-20% lower than that of ordinary cement in the prior art.

[0049] The technical solution of the present invention will be further described in detail below through specific examples. Among them, construction waste is measured by the weight of aggregates and powders, and organic waste is measured by the weight of pyrolysis residues. The following "%" refers to weight percentage unless otherwise specified.

[0050] Embodiment 1:

[0051] The process is divided into four steps: (1) crushing and screening construction waste to produce recycled aggregate (5-31.5 mm) and powder (greater than 0 and less than 5 mm); (2) crushing and screening domestic waste and then pyrolyzing it, controlling the furnace temperature to 850°C, the residence time to 45 minutes, and producing pyrolysis residue, the pyrolysis residue carbon content of 56wt%; (3) mixing limestone, clay, aggregate after treatment in step (1), and material after treatment in step (2), and then adding the powder after treatment in step (1), the weight ratio of limestone, clay, construction waste, and domestic waste is 39:7:46:8, and stirring evenly with a mixer; (4) calcining the mixture in step (3), the calcination temperature is about 1450°C, producing clinker and grinding to produce cement of suitable particle size, and bagging. After this treatment, compared with cement made of limestone and clay, the amount of limestone can be reduced by 54%, energy can be saved by 15.8%, and the production cost per ton can be saved by 5-10 yuan. After calcination, the heavy metal content of the pyrolysis residue decreased by 55.6%, and the 28-day strength of cement clinker increased by 13.4%.

[0052] Embodiment 2:

[0053] The process is divided into four steps: (1) crushing and screening construction waste to produce recycled aggregate and powder; (2) crushing and screening domestic waste and then pyrolyzing it, controlling the furnace temperature to 850°C, the residence time to 45 minutes, producing pyrolysis residue, the pyrolysis residue carbon content of 56wt%; (3) mixing limestone, clay, aggregate after treatment in step (1), and material after treatment in step (2), and then adding the powder after treatment in step (1), the weight ratio of limestone, clay, construction waste, and domestic waste is 44:6:40:10, and stirring evenly with a mixer; (4) calcining the mixture in step (3), the calcination temperature is about 1450°C, producing clinker and grinding to produce cement of suitable particle size, and bagging. After this treatment, compared with cement made of limestone and clay, the amount of limestone can be reduced by 50%, energy can be saved by 15.29%, and the production cost per ton can be saved by 5-8.5 yuan. After calcination, the heavy metal content in the pyrolysis residue decreased by 49.89%, and the 28-day strength of cement clinker increased by 15.6%.

[0054] Embodiment 3:

[0055] The process is divided into four steps: (1) crushing and screening construction waste to produce recycled aggregate and powder; (2) pyrolysis treatment of municipal sludge after pretreatment (water content is reduced to less than 60wt%), controlling the furnace temperature to 650℃, the residence time to 55min, and producing pyrolysis residue, the carbon content of the pyrolysis residue is 63wt%; (3) limestone, clay, aggregate after treatment in step (1), and material after treatment in step (2) are mixed, and then the powder after treatment in step (1) is added, the weight ratio of limestone, clay, construction waste, and municipal sludge is 35:5:52:8, and the mixture is stirred evenly by a mixer; (4) the mixture in step (3) is calcined at a calcination temperature of about 1450℃, clinker is produced, and the cement of suitable particle size is ground and bagged. After this treatment, compared with cement made of limestone and clay, the amount of limestone can be reduced by 42%, energy can be saved by 13.2%, and the production cost per ton can be saved by 6.2 yuan. After calcination, the heavy metal content in the pyrolysis residue decreased by 44.3%, and the 28-day strength of cement clinker increased by 12.4%.

[0056] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing environmentally friendly cement, characterized in that: The steps include: Step 1, crushing and screening the construction waste to obtain aggregates and powder; Step 2, pyrolyzing the organic waste to obtain pyrolysis residue; Step 3, mixing limestone, clay, aggregate and powder from step 1, and pyrolysis residue from step 2, calcining, and grinding to obtain environmentally friendly cement; Among them, construction waste is measured by the weight of aggregate and powder, organic waste is measured by the weight of pyrolysis residue, and the weight proportions of limestone, clay, construction waste and organic waste are 35-45 weight parts, 5-10 weight parts, 45-55 weight parts and 6-18 weight parts respectively.

2. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The step 3 is: mixing limestone, clay, the aggregate of step 1, and the pyrolysis residue of step 2 evenly, and then adding the powder of step 1, mixing, calcining, and grinding to obtain environmentally friendly cement.

3. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The construction waste is construction waste generated during the construction, reconstruction and expansion of buildings, containing bricks, concrete and a small amount of impurities; the organic waste includes at least one of domestic garbage, biomass, municipal sludge and waste tires.

4. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The crushing and screening includes a crushing process and a screening process. The crushing process is performed at least once, the screening process is performed at least once, and the crushing process and the screening process are performed alternately.

5. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The crushing machine used for the crushing process includes at least one of a jaw crusher, an impact crusher, and an impact crusher, and the screening process includes at least one of magnetic separation and screening, screening and soil removal, manual sorting, wind separation, and powder selection.

6. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The aggregate obtained by crushing and screening the construction waste has a particle size of 5-31.5 mm, and the powder has a particle size greater than 0 and less than 5 mm.

7. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The pyrolysis treatment is carried out in a fluidized bed pyrolysis furnace, a fixed bed pyrolysis furnace or a moving bed pyrolysis furnace, the temperature of the pyrolysis treatment is greater than or equal to 550° C., and the time of the pyrolysis treatment is 30-120 minutes.

8. The method for preparing environmentally friendly cement according to claim 1, characterized in that: The carbon content of the pyrolysis residue is 25wt%-80wt%.

9. The method for preparing environmentally friendly cement according to claim 1, characterized in that: In step 3, the calcination temperature is 1300-1500° C., and the particle size after grinding is less than 80 μm.

10. The environmentally friendly cement obtained by the preparation method according to any one of claims 1 to 9.

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