CN110229014A - A kind of lightweight aggregate and preparation method thereof being prepared using steel mill's sludge - Google Patents

Abstract

The invention discloses a kind of lightweight aggregates, aggregate is prepared using steel mill's sludge as raw material, composition of raw materials is 10~40% steel mill's sludge and 60~90% flyash, specific preparation method the following steps are included: steel mill's sludge after drying, smashing and grinding, sieving, the flyash that sieving is added presses certain weight ratio pelletizing after mixing, by the dry progress after a certain period of time of raw material ball and heat treatment, aggregate finished product is obtained after being finally sintered and cooled.The resulting lightweight aggregate of the present invention has the characteristics that small high intensity, density, good heat insulating, water absorption rate are low, there must be the lightweight aggregate of certain heat insulating ability merely with sludge and coal ash for manufacturing, raw material is solid waste, and realization is turned waste into wealth, it is energy saving and environmentally friendly, while reduction prepares the cost of aggregate.

Description

A kind of lightweight aggregate prepared from steel mill sludge and its preparation method

technical field

The invention relates to the field of reutilization of metallurgical solid waste, in particular to a light aggregate prepared by using steel mill sludge and a preparation method thereof.

Background technique

With the rapid development of social science and technology, the improvement of social productivity has accelerated the development of modernization, and at the same time, it has also brought ecological and environmental problems. In particular, the large-scale exploitation of natural resources in the industrial field has not only caused the reduction of non-renewable resources, but also caused the accumulation of a large amount of solid waste, occupying limited land resources and even causing secondary pollution. Therefore, it is of great practical significance to rationally utilize solid waste according to its characteristics.

Sludge from steel mills is a solid sediment treated by wastewater from steel mills and domestic sewage through reuse plants. Sludge is a typical solid waste in steel mills because of its wide source, complex composition, large output, and foul smell. and other characteristics, which bring great limitations to the processing method. From the perspective of main components, steel mill sludge belongs to inorganic sludge. For this kind of inorganic sludge, the conventional treatment methods are mainly stacking and landfilling. Stacking means abandoning wasteland without treatment, while landfilling is developed from traditional stacking. A disposal technology that has been developed is a treatment method that uses microbial activities to degrade and stabilize organic matter after compacted fill. In essence, these two treatment methods are only the reduction of sludge disposal, and have not made full use of its valuable components. In addition, the two methods may also cause secondary pollution to the environment. In contrast, the resource utilization of sludge makes full use of the valuable components of sludge, which meets environmental benefits and turns waste into treasure.

The composition of sludge is mainly composed of inorganic substances such as calcium, aluminum, iron, silicon and other elements. From the perspective of composition, it is similar to the raw materials of most building materials. The use of high-temperature sintering of sludge to prepare building materials can reduce heavy metals. Elements are solidified to avoid secondary pollution of the environment, so it can be applied to aggregates, cement clinker, etc. Among them, the use of sludge to prepare lightweight aggregate has a relatively broad prospect. Lightweight aggregate is an aggregate with a bulk density of less than or equal to 1200kg/m ³ , which is divided into fine light aggregate and coarse light aggregate according to different particle sizes. Lightweight aggregates with a particle size of less than 5mm are called fine lightweight aggregates, and lightweight aggregates with a particle size greater than 5mm are called coarse lightweight aggregates. According to different sources, they can be divided into artificial lightweight aggregates, natural lightweight aggregates, and industrial waste light aggregates. There are three types of materials. Generally, non-renewable resources such as clay and shale are used for artificial lightweight aggregates. However, large-scale mining of non-renewable resources to prepare aggregates is not in line with China's national conditions. Therefore, high-performance artificial lightweight aggregates are prepared using sludge-like components instead of non-renewable resources. Aggregate has become a technical problem to be solved urgently in the industry.

Although the patent CN100584794C discloses a method for preparing ceramsite lightweight aggregate from sludge, the method is applied to making steel sludge into lightweight aggregate, and the cylinder compressive strength of the resulting lightweight aggregate is less than 6.0. Does not meet the requirements of GB/T17431.2-1998. Therefore, those skilled in the art have reason to suspect that the method in the patent CN100584794C is not applicable to all sludges.

In this regard, those skilled in the art are committed to developing a lightweight aggregate made from steel mill sludge as a raw material. The lightweight aggregate has the characteristics of low density, high strength, low water absorption and good adhesion with cement.

Contents of the invention

In view of the above-mentioned defects in the prior art, the technical problem to be solved by the present invention is how to use steel mill sludge as a raw material to produce lightweight aggregate with low density, high strength, low water absorption and good adhesion with cement.

In order to achieve the above object, the present invention provides a kind of lightweight aggregate, the raw material of this lightweight aggregate includes industrial sludge and fly ash, according to weight ratio, industrial sludge accounts for 10%～40%, fly ash accounts for 60% to 90%, and the moisture content of industrial sludge is 45 to 55%.

Further, the industrial sludge comes from steel mills or power plants, and the components in the industrial sludge include CaCO ₃ 35-40%, SiO ₂ 5-10%, FeO 20-23%, Al ₂ O ₃ 8-12%, SiC 7-8%, ZnO 1-2%, MgO 3-5%, calculated by mass fraction.

Further, according to weight ratio, industrial sludge accounts for 20% and fly ash accounts for 80%.

Further, the lightweight aggregate is raw meal balls, and there are multiple closed holes inside the raw meal balls, and the diameter of the raw meal balls is 10-15mm.

Furthermore, the cylinder compressive strength of the lightweight aggregate is 8.0-9.6Mpa, the bulk density is 793kg/m ³ -987kg/m ³ , and the water absorption rate is 4.3%-20%.

The present invention also provides a kind of method for preparing lightweight aggregate, the raw material of lightweight aggregate comprises industrial sludge and fly ash, and method comprises the following steps:

(1) Dry industrial sludge with a moisture content of 45% to 55% at 100 to 110°C for 20 to 30 hours, and then grind the dried industrial sludge and fly ash separately and pass through a sieve below 200 mesh;

(2) Mix the sludge powder and fly ash powder obtained through the treatment in step (1) in a weight ratio, the sludge powder accounts for 10% to 40%, and the fly ash powder accounts for 60% to 90%, stirring to form mix;

(3) Take 2-4 kg of the mixed material in step (2) and pour it into the pelletizing machine, then spray water and feed alternately, and the pelletizing machine rotates 2330-2240 times in 70-75 minutes to obtain raw meal balls of 10-15 mm;

(4) Put the raw meal balls in step (3) into a drying oven, and dry them at 100-110°C for 60-90 minutes; in order to remove part of the moisture in the raw meal balls and prevent cracking of the balls during the roasting process;

(5) preheating the raw meal pellets obtained in step (4) at 300-500°C for 20-30 minutes to reduce the content of organic matter and carbon in the raw meal pellets before sintering;

(6) Calcining the preheated raw meal balls in step (5) at 1050-1200°C for 20-30 minutes, the raw meal balls are gradually vitrified, and the aggregates are formed after cooling.

Further, the average particle size of the sludge powder obtained in step (1) is 8-10 um, and the average particle size of the fly ash powder is 13-15 um.

Further, in step (5), the raw meal balls obtained in step (4) are heated to 300° C. at a heating rate of 10° C./min, and kept at 300° C. for 20 minutes.

Further, in step (6), the preheated green balls in step (5) are raised to 1050° C. at a heating rate of 5° C./min, and roasted at 1050° C. for 25 minutes.

Further, the industrial sludge comes from steel mills or power plants, and the components in the industrial sludge include CaCO ₃ 35-40%, SiO ₂ 5-10%, FeO 20-23%, Al ₂ O ₃ 8-12%, SiC 7-8%, ZnO 1-2%, MgO 3-5%, calculated by mass fraction.

technical effect

Compared with the prior art, the steel mill sludge of the present invention has the characteristics of high calcium and low silicon and aluminum. In addition, it also contains rich iron elements. CaCO ₃ and SiC can be used as better foaming components to ensure light weight Characteristics; SiO ₂ and Al ₂ O ₃ are used as ceramic components to provide aggregate skeleton and strength; metal oxides are used as flux components to reduce the glass transition temperature;

The phase components of aggregates with different raw material ratios were analyzed, and it was found that within the range of 10% to 40% of sludge and 60% to 90% of fly ash, aggregates have better strength. The aggregate outside the range is relatively brittle. According to the XRD spectrum, it can be found from the phase composition that the strength of the aggregate is mainly determined by the mullite phase;

After the raw meal balls of the present invention are sintered and formed in an air atmosphere, there are many closed holes inside, thus ensuring the lightweight aggregate and thermal insulation properties;

The lightweight aggregate of the present invention has the characteristics of high strength, low density, good thermal insulation, and low water absorption, and uses solid waste from steel mills and thermal power plants as raw materials, which not only solves the whereabouts of waste, but also reduces the cost of preparing building materials. cost.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

Fig. 1 is a process flow diagram of utilizing high-calcium sludge to prepare lightweight aggregate in a preferred embodiment of the present invention;

Fig. 2 is the aggregate XRD collection of patterns of different raw material proportions of a preferred embodiment of the present invention;

Fig. 3 is a scanning electron microscope (SEM) photo of a lightweight aggregate section of a preferred embodiment of the present invention.

Detailed ways

The following describes several preferred embodiments of the present invention with reference to the accompanying drawings, so as to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned herein.

The experimental process of the present invention is as shown in Figure 1: dry the industrial sludge, grind the dried sludge and fly ash respectively after completion, pass through a 200-mesh sieve, mix the sludge powder and fly ash powder evenly, add water to make pellets to obtain raw meal balls, and then through drying, preheating, sintering, and cooling to obtain the final product.

As shown in Figures 2 and 3, the phase composition analysis was carried out for aggregates with different raw material ratios (F: W = fly ash: industrial sludge). The aggregates prepared purely from industrial sludge mainly contain three phases: SiO ₂ , Fe ₂ O ₃ , and Ca(Al ₂ SiO ₈ ). Aggregate prepared purely with fly ash mainly contains SiO ₂ , Fe ₂ O ₃ , Ca(Al ₂ SiO ₈ ), Al ₆ Si ₂ O ₁₃ . When the proportion of sludge is greater than 40%, the peak intensity of the mullite phase in the XRD of the aggregate is weak, which to some extent indicates that the mullite phase is less, while the peak of the anorthite phase is sharper, indicating crystallization good degree. By testing the properties of the aggregate within the range of 0% to 40% of sludge and 60% to 100% of fly ash, it is found that the aggregate within this range has a certain strength. However, the aggregate strength is low in the range of 40%-100% of the proportion of sludge and 0%-60% of the proportion of fly ash. Among them, the proportion of sludge is 20%, and the proportion of fly ash is 80%, which is the best. In summary, it can be concluded that the strength of the aggregate is mainly determined by the mullite phase from the perspective of phase composition.

Example 1

A method for preparing lightweight aggregate from pure high-calcium sludge, comprising the steps of:

a. Put the dewatered sludge with a moisture content of 47% into a drying box, dry it at 105°C for 24 hours, then pulverize and grind it into powder, and pass the obtained sludge powder through a 200-mesh sieve;

b. Take 3kg of sludge powder and pour it into the pelletizing machine, then spray water and feed alternately. After the pelletizing machine rotates 1760 times within 55 minutes, a raw pellet of 10-15mm is obtained, and the finished product volume is 1.1L;

c. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

d. Put the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1100°C at a heating rate of 5°C/min, and keep it warm 25min;

e. The fired aggregate is cooled to room temperature with the furnace.

By testing the performance of the prepared lightweight aggregate, the following main performance results are obtained. The obtained lightweight aggregate cylinder has a compressive strength of 1.9MPa, low strength, a bulk density of 547kg/m ³ , and a water absorption rate of 37%. It does not meet the national standard of lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Example 2

A method for preparing lightweight aggregate by utilizing high-calcium sludge accounting for 80% and fly ash accounting for 20%, comprising the following steps:

1. Put the dewatered sludge with a moisture content of 47% into a drying oven, dry it at 105°C for 24 hours, and then pulverize it to make powder, and pass the obtained sludge powder and fly ash through a 200-mesh sieve;

2. Mix according to the ratio of sludge weight ratio of 80% and fly ash weight ratio of 20%;

3. After mixing evenly, take 3kg of the mixture and pour it into the pelletizing machine, then spray water and feed alternately. The pelletizing machine rotates 2240 times within 70 minutes to get 10-15mm raw material balls, and the finished product volume is 1.8L;

4. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

5. Put the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1100°C at a heating rate of 5°C/min. 25min;

6. The fired aggregate is cooled to room temperature with the furnace.

By testing the performance of the prepared lightweight aggregate, the following main performance results were obtained. The cylinder compressive strength of the prepared lightweight aggregate was 2.1MPa, the strength was low, the bulk density was 558kg/m ³ , and the water absorption rate was 28%. It does not meet the national standard of lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Example 3

A method for preparing lightweight aggregate by utilizing high-calcium sludge accounting for 60% and fly ash accounting for 40%, comprising the following steps:

1. Put the dewatered sludge with a moisture content of 47% into a drying oven, dry it at 105°C for 24 hours, and then pulverize it to make powder, and pass the obtained sludge powder and fly ash through a 200-mesh sieve;

2. Mix according to the ratio of sludge weight ratio of 20% and fly ash weight ratio of 80%;

3. After mixing evenly, take 3kg of the mixed material and pour it into the pelletizing machine, then spray water and feed alternately. The pelletizing machine rotates 2464 times within 77 minutes to get 10-15mm raw material balls, and the finished product is 2.2L;

4. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

5. Put the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1100°C at a heating rate of 5°C/min. 25min;

6. The fired aggregate is cooled to room temperature with the furnace.

By testing the performance of the prepared lightweight aggregate, the following main performance results are obtained. The obtained lightweight aggregate cylinder has a compressive strength of 5.7MPa, higher strength, a bulk density of 605kg/m ³ , and a water absorption rate of 26%. It still does not meet the national standard of lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Example 4

A method for preparing lightweight aggregate by utilizing high-calcium sludge accounting for 20% and fly ash accounting for 80%, comprising the following steps:

1. Put the dewatered sludge with a moisture content of 47% into a drying oven, dry it at 105°C for 24 hours, and then pulverize it to make powder, and pass the obtained sludge powder and fly ash through a 200-mesh sieve;

2. Mix according to the ratio of sludge weight ratio of 20% and fly ash weight ratio of 80%;

3. After mixing evenly, take 3kg of the mixed material and pour it into the pelletizing machine, then spray water and feed alternately. The pelletizing machine rotates 2336 times within 73 minutes to obtain raw meal balls of 10-15mm, and the finished product volume is 2.5L;

4. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

5. Put the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1100°C at a heating rate of 5°C/min. 25min;

6. The fired aggregate is cooled to room temperature with the furnace.

By testing the performance of the prepared lightweight aggregate, the following main performance results are obtained. The obtained lightweight aggregate cylinder has a compressive strength of 8.3MPa, a high strength, a bulk density of 793kg/m ³ , and a water absorption rate of 20%. It complies with the national standard of lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Example 5

A method for preparing lightweight aggregate by utilizing high-calcium sludge accounting for 20% and fly ash accounting for 80%, comprising the following steps:

1. Put the dewatered sludge with a moisture content of 47% into a drying oven, dry it at 105°C for 24 hours, and then pulverize it to make powder, and pass the obtained sludge powder and fly ash through a 200-mesh sieve;

2. Mix according to the ratio of sludge weight ratio of 20% and fly ash weight ratio of 80%;

3. After mixing evenly, take 3kg of the mixed material and pour it into the pelletizing machine, then spray water and feed alternately. The pelletizing machine rotates 2336 times within 73 minutes to obtain raw meal balls of 10-15mm, and the finished product volume is 2.5L;

4. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

5. Place the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1050°C at a heating rate of 5°C/min. 25min;

6. The fired aggregate is cooled to room temperature with the furnace.

By testing the performance of the prepared lightweight aggregate, the following main performance results are obtained. The cylinder compressive strength of the prepared lightweight aggregate is 8.8MPa, which is high in strength, the bulk density is 852kg/m ³ , and the water absorption rate is 15%. , in line with the national standard for lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Example 6

A method for preparing lightweight aggregate by using high-calcium sludge accounting for 20% and fly ash accounting for 80%, comprising the following steps:

1. Put the dewatered sludge with a moisture content of 47% into a drying oven, dry it at 105°C for 24 hours, and then pulverize it to make powder, and pass the obtained sludge powder and fly ash through a 200-mesh sieve;

2. Mix according to the ratio of sludge weight ratio of 20% and fly ash weight ratio of 80%;

3. After mixing evenly, take 3kg of the mixed material and pour it into the pelletizing machine, then spray water and feed alternately. The pelletizing machine rotates 2336 times within 73 minutes to obtain raw meal balls of 10-15mm, and the finished product volume is 2.5L;

4. Put the raw meal balls in a drying oven and dry them at 105°C for 1 hour;

5. Put the dried raw meal balls in a muffle furnace, raise the temperature to 300°C at a heating rate of 10°C/min, keep it at 300°C for 20 minutes, and raise it to 1200°C at a heating rate of 5°C/min. 25min;

6. The fired aggregate is cooled to room temperature with the furnace.

Through testing the performance of the prepared lightweight aggregate, the following main performance results are obtained. The cylinder compressive strength of the prepared lightweight aggregate is 9.6MPa, which is very high in strength, the bulk density is 987kg/m ³ , and the water absorption rate is 4.3%. , in line with the national standard for lightweight aggregate "GB/T 17431.1-2010 Lightweight aggregate test method".

Preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (10)

1. a method for preparing lightweight aggregate, is characterized in that, the raw material of described lightweight aggregate comprises industrial sludge and fly ash, and described method comprises the steps: (1) Dry industrial sludge with a moisture content of 45% to 55% at 100 to 110°C for 20 to 30 hours, and then grind the dried industrial sludge and fly ash separately and pass through a sieve below 200 mesh; (2) Mix the sludge powder and fly ash powder obtained through step (1) by weight ratio, the sludge powder accounts for 10% to 40%, and the fly ash powder accounts for 60% to 90% %, stirring to form a mixture; (3) Take 2-4 kg of the mixed material in step (2) and pour it into the pelletizing machine, then spray water and feed alternately, and the pelletizing machine rotates 2330-2240 times in 70-75 minutes to obtain raw meal balls of 10-15 mm; (4) Put the raw meal balls in step (3) into a drying oven, and dry at 100-110°C for 60-90 minutes; (5) Preheat the raw pellets obtained in step (4) at 300-500°C for 20-30 minutes; (6) Calcining the raw meal balls preheated in step (5) at 1050-1200° C. for 20-30 minutes, the raw meal balls are gradually vitrified, and the aggregate is obtained after cooling. 2. The method according to claim 1, wherein the average particle size of the sludge powder obtained in step (1) is 8-10 um, and the average particle size of the fly ash powder is 13-15 um. 3. The method according to claim 1, wherein, in step (5), the raw pellets obtained in step (4) are heated to 300° C. at a heating rate of 10° C./min, and kept at 300° C. for 20 minutes. 4. The method according to claim 1, wherein in step (6), the raw balls preheated in step (5) are raised to 1050° C. at a heating rate of 5° C./min, and roasted at 1050° C. for 25 minutes. 5. The method according to claim 1, wherein said industrial sludge originates from steel mills or power plants, and the components in said industrial sludge include CaCO 35-40%, SiO ₂ 5-10%, FeO ₂₀ ～23%, Al ₂ O ₃ 8～12%, SiC 7～8%, ZnO 1～2%, MgO 3～5%, calculated by mass fraction. 6. A lightweight aggregate, characterized in that the raw materials of the lightweight aggregate include industrial sludge and fly ash, and according to the weight ratio, the industrial sludge accounts for 10% to 40%, and the fly ash The proportion is 60%-90%, and the water content of the industrial sludge is 45-55%. 7. The lightweight aggregate as claimed in claim 6, wherein the industrial sludge comes from a steel mill or a power plant, and the components in the industrial sludge include CaCO 35-40 _{%, SiO 2 5-10} %, FeO 20-23%, Al ₂ O ₃ 8-12%, SiC 7-8%, ZnO 1-2%, MgO 3-5%, calculated by mass fraction. 8. The lightweight aggregate according to claim 7, wherein, according to the weight ratio, the industrial sludge accounts for 20% and the fly ash accounts for 80%. 9. The lightweight aggregate as claimed in claim 6, wherein the lightweight aggregate is a raw meal ball, and there are a plurality of closed holes inside the raw meal ball, and the diameter of the raw meal ball is 10-15mm . 10. The lightweight aggregate according to claim 6, wherein the cylinder compressive strength of the lightweight aggregate is 8.0-9.6Mpa, the bulk density is 793-987kg/ ^m3 , and the water absorption is 4.3%-20%.