CN113042676B

CN113042676B - Regeneration method of waste foundry sand and ceramsite sand prepared by method

Info

Publication number: CN113042676B
Application number: CN202110244858.2A
Authority: CN
Inventors: 孙贤洋; 包羽冲; 尹海军; 李元静; 马楠
Original assignee: Nanyang Renchuang Renewable Resources Co ltd
Current assignee: Nanyang Renchuang Renewable Resources Co ltd
Priority date: 2021-03-05
Filing date: 2021-03-05
Publication date: 2022-09-20
Anticipated expiration: 2041-03-05
Also published as: CN113042676A

Abstract

The invention provides a regeneration method of waste foundry sand, which comprises the steps of mixing and granulating the foundry fly ash and an auxiliary agent to obtain a ceramsite green body, and mixing the ceramsite green body with the waste foundry sand for thermal regeneration. The method can not only extract the heat value in the waste casting ash, but also consume the reclaimed sand to clean sewage, and obtain sintered ceramsite as a byproduct of heat value extraction. The regeneration method provided by the invention reduces the gas consumption in the thermal process, and can obtain sintered ceramsite, thereby realizing the resource utilization of casting wastes.

Description

Regeneration method of waste foundry sand and ceramsite sand prepared by method

Technical Field

The invention relates to the technical field of resource recovery, in particular to a regeneration method of waste foundry sand and ceramsite sand prepared by the method.

Background

China is the biggest casting producing country in the world, the total output of various castings is nearly 5000 ten thousand tons in 2020, and the method is far ahead of other countries. Among various casting modes, sand casting is widely used in the casting industry due to the advantages of simple process, convenient operation, low production cost and the like. In China and the world, castings produced by sand casting account for 70% -80% of the total production amount of the castings. However, the amount of waste ash generated in the sand casting process is also large, and if the waste ash is not disposed of, only stacking or deep burying treatment is performed, which not only wastes land resources but also causes serious environmental pollution. The casting yield of China can still continuously increase in the coming years, the generation amount of casting waste ash can also increase, and if the casting waste ash is not utilized, the damage to the environment is huge.

Therefore, how to utilize the waste foundry ash to create benefits for enterprises and reduce environmental pollution becomes an urgent problem to be solved. There are few methods related to the recycling of the calorific value of the waste foundry ash currently introduced at home and abroad, and other conventional similar schemes are as follows:

patent CN201811000053.8 discloses an artificial aggregate and a preparation method thereof, wherein the artificial aggregate comprises the following components in parts by weight: 500-1000 parts of casting waste ash, 50-100 parts of bentonite, 0-100 parts of fly ash and 0-5 parts of coal powder. The artificial aggregate has the advantages of low density, low water absorption, high strength and the like, and when the artificial aggregate is applied to the construction of large-span bridges and super high-rise buildings, the self weight of the structures can be reduced by 30-40%, the labor intensity can be reduced by about 20%, the material transportation amount can be reduced by 30-40%, the steel bar amount can be saved by about 10%, the construction cost can be comprehensively reduced by 10%, the self weight of the structure can be greatly reduced, and the foundation load can be reduced.

Patent CN201710572489.3 discloses a preparation method of light ceramsite, which is prepared from the following components in parts by weight: 95 parts of casting waste sand and waste ash, 3-7 parts of bauxite, 0.1-0.5 part of rubber powder and 0.1-0.3 part of polyvinyl alcohol, wherein the weight ratio of the casting waste sand to the waste ash is 8: 2-9: 1.

However, the above patent uses the casting waste ash as the raw material to produce the building aggregate and the ceramsite. The heat value in the waste casting ash is not extracted, so that the economic value of the waste casting ash is fully exerted. And the roasted ceramsite is not obtained, and the damage to the use environment caused by residual organic matters and the like can be caused.

Disclosure of Invention

The invention aims to provide a regeneration method of casting waste sand, which is characterized in that casting dedusting ash and an auxiliary agent are mixed and then granulated to obtain a ceramsite green body, and the ceramsite green body is mixed with the casting waste sand and then subjected to thermal regeneration to extract a heat value in the casting waste ash. The regeneration method can obtain sintered ceramsite besides the regenerated sand.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the invention relates to a regeneration method of waste foundry sand, which comprises the following steps:

(1) mixing the casting dedusting ash, reclaimed sand reuse sewage and an auxiliary agent, and granulating to obtain a ceramsite green body;

preferably, 100 parts of casting dust removal ash, 8-15 parts of reclaimed sand reuse sewage and 0.1-0.5 part of auxiliary agent are mixed in parts by weight.

Preferably, the auxiliary agent is selected from at least one of sodium humate, polyvinyl alcohol (alcoholysis degree is 75-80%) and sodium carboxymethyl cellulose.

Preferably, in the auxiliary agent, the mass ratio of the sodium humate, the polyvinyl alcohol and the sodium carboxymethyl cellulose is (0-10): 1-10): 0-10.

Preferably, the particle size of the ceramsite green body is 0.5-2 cm.

(2) Mixing the ceramsite green body with casting waste sand, and then carrying out thermal regeneration;

preferably, the mass ratio of the foundry waste sand to the ceramsite green body is 100 (1-20).

Preferably, the roasting temperature of the thermal regeneration is 600-800 ℃, and the time is 2-5 h.

(3) After the thermal method regeneration is finished, screening the product by granularity to obtain regenerated sand and sintered ceramsite;

(4) and adding water into the reclaimed sand, stirring and cleaning, and performing water-sand separation after cleaning.

Preferably, the separated sewage can be returned to the step (1) to be used as the recycled sewage for granulation.

Preferably, the mass ratio of the reclaimed sand to the cleaning water is 1 (0.5-1).

The invention has the beneficial effects that:

the invention provides a regeneration method of waste foundry sand, which comprises the steps of mixing and granulating the foundry fly ash and an auxiliary agent to obtain a ceramsite green body, and mixing the ceramsite green body with the waste foundry sand for thermal regeneration. The method can not only extract the heat value in the waste foundry ash, but also consume reclaimed sand cleaning sewage, and obtain sintered ceramsite as a byproduct of heat value extraction. The regeneration method provided by the invention reduces the gas consumption in the thermal process, and can obtain sintered ceramsite, thereby realizing the resource utilization of casting wastes.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.

The embodiment of the invention relates to a regeneration method of waste foundry sand, which comprises the following steps:

wherein the casting dust removal ash is powdery solid waste generated in the casting production process. The catalyst mainly contains oxides of silicon, aluminum, calcium, magnesium and iron, a small amount of sodium, potassium and the like. If the metal pollutants in the dust are discarded as industrial waste, the activity of microorganisms in soil can be inhibited, and the ecological environment is damaged.

The results of analyzing the components of the waste ash from a certain foundry are shown in Table 1. The proportion of the visible coal dust residues is high, and the coal dust residues can be used as fuel to provide heat value in the waste sand regeneration process. The method does not need to carry out magnetic separation on the dust removal ash, and removes the metal powder in the dust removal ash. The reason is that after the casting dust removal ash is granulated and roasted, metal ions in the casting dust removal ash are sintered and locked in the ceramsite, and unpredictable influence on the environment cannot be generated in the using process.

TABLE 1 main components of casting fly ash

In one embodiment of the invention, 100 parts of casting dust removal ash, 8-15 parts of reclaimed sand reuse sewage and 0.1-0.5 part of auxiliary agent are mixed in parts by weight. Because the casting dust removal ash contains bentonite, the granulation can be carried out by utilizing the viscosity of the bentonite. When the mass percentage of the bentonite in the fly ash is lower than 20%, in order to improve the balling property or the cohesion, a certain amount of auxiliary agent can be added to assist in granulation, which is beneficial to keeping the integrity of the particle structure in the sintering process. Otherwise, the ceramsite green compact is not firmly condensed in the roasting furnace, the fly ash is rapidly separated, and the discrete ash content is mixed into the reclaimed sand and sintered on the surface of the reclaimed sand, so that the quality of the reclaimed sand is reduced, and the yield of the sintered ceramsite is reduced.

In one embodiment of the invention, the particle size of the ceramsite green body is 0.5-2 cm. If the particles are too large, the particles cannot be fully burnt through during roasting, so that the utilization rate of the heat value is reduced; if the particles are too small, the particles are easy to be mixed with sand grains and are not easy to be removed by a screen, so that the mud content and the acid consumption value of the reclaimed sand are improved, and the quality of the reclaimed sand is reduced.

The auxiliary agent is at least one selected from sodium humate, polyvinyl alcohol (alcoholysis degree is 75-80%) and sodium carboxymethyl cellulose. The sodium humate is nontoxic, odorless and corrosion-free, is very soluble in water, can increase the viscosity of a solution, has strong adsorption, exchange, complexation and chelation capabilities, can be used as a ceramic additive, and is beneficial to the stability of a ceramsite structure. The sodium carboxymethylcellulose is odorless, tasteless and hygroscopic, is easy to dissolve in water, is dissolved in water to increase the viscosity of the solution, can be used as an adhesive for ceramic industry, and is beneficial to the stability of a ceramsite structure. The polyvinyl alcohol is easy to dissolve in water, so that the solution viscosity is increased, and the effect of assisting in tackifying the solution is achieved. The mass ratio of the sodium humate, the polyvinyl alcohol and the sodium carboxymethyl cellulose is preferably (0-10) to (1-10) to (0-10).

(2) Mixing the ceramsite green body with casting waste sand, and then putting the mixture into a roasting furnace for thermal method regeneration;

if the casting dedusting ash is directly added in the process, the dedusting ash is easily pumped away by a dedusting system in the roasting process, the utilization rate of waste ash is reduced, the discharge amount of dust is increased, and sintered ceramsite cannot be obtained. Meanwhile, dust can be sintered on the surface of the reclaimed sand and is difficult to remove, so that the quality of the reclaimed sand is reduced.

In one embodiment of the invention, the mass ratio of the foundry waste sand to the ceramic particle green body is 100 (1-20). If the input amount of the ceramsite green body containing the casting dedusting ash is too small, the influence on the gas consumption is not obvious; if the input amount is too large, the excessive dust is adsorbed on the surface of the reclaimed sand and is difficult to remove after roasting, so that the quality of the reclaimed sand is reduced.

In one embodiment of the invention, the roasting temperature of the thermal regeneration is 600-. Within the temperature range, the ceramic green ceramic body can be formed to form a stable sintered ceramic product. If the roasting temperature is too low, the ceramic green body can not be ceramized; the temperature is too high, the heat value provided by the coal dust in the dust removal ash is limited, and the overall energy consumption is high. The optimum temperature obtained according to the float glass production process is 750 ℃.

(3) After the thermal method regeneration is finished, screening the granularity of the roasted product to obtain regenerated sand and sintered ceramsite; the particle size screening is preceded by a coarse screening step, wherein coarse particles with the particle size of more than 30 meshes (the particle size is 0.6mm) are screened out, the coarse particles are screened out after being cooled, and particles with the particle size of 0.6mm-0.5cm are screened out for standby.

(4) And (4) adding water into the reclaimed sand obtained in the step (3), stirring and cleaning, and performing water-sand separation after cleaning to obtain cleaned reclaimed sand and sewage.

In one embodiment of the invention, the cleaning serves to remove ash from the reclaimed sand surface. And (4) returning the separated sewage to the step (1) to be used as recycled sewage for granulation. Therefore, ash and water in the sewage can be utilized, the performance of the reclaimed sand is improved, the sewage treatment is avoided, and the cost is saved. The mass ratio of the reclaimed sand to the cleaning water is preferably 1 (0.5-1), preferably 1: 0.9.

The method comprises the steps of firstly granulating waste ash, putting the granulated waste ash and the casting waste sand into a roasting furnace for combustion, obtaining the casting waste sand and sintered ceramsite through a screening system after the combustion is finished, washing dust on the surface of sand grains from the casting waste sand through wet treatment, and drying to obtain a reclaimed sand product. The method can extract the heat value in the casting waste ash, reduce the fuel gas consumption in the thermal process, obtain sintered ceramsite and realize the resource utilization of casting wastes.

Example 1

(1) Selecting 100 parts by weight of casting dust removal ash, 10 parts by weight of reclaimed sand reuse sewage and 0.3 part by weight of auxiliary agent. The auxiliary agent contains 80% of sodium humate and 20% of polyvinyl alcohol. Firstly, uniformly mixing the auxiliary agent and the recycled sewage to obtain a mixed solution, and then pouring the casting dedusting ash and the mixed solution into a granulator in sequence for granulation to obtain a ceramsite green body with the particle size of 0.5-2 cm.

(2) Mixing the ceramsite green body with the casting waste sand, and then carrying out thermal regeneration in a roasting furnace. The mass ratio of the waste foundry sand to the ceramsite green body is 100: 10. The roasting temperature of the thermal regeneration is 750 ℃, and the time is 3 hours.

(4) and adding water into the reclaimed sand, and then stirring and cleaning, wherein the sand-water ratio is 1: 0.9. And after the cleaning is finished, carrying out water-sand separation to obtain the cleaned reclaimed sand. And (4) returning the separated sewage to the step (1) as recycled sewage for granulation.

The reaction conditions in examples 2 to 9 and comparative example were varied, and the specific settings are shown in Table 2. The other parameters of each example and comparative example were the same as those of example 1 except for the parameters shown in Table 2.

Table 2 example and comparative example set-up

Test example

Reclaimed sand performance test

The strength, the ignition loss acid consumption value and the mud content of the reclaimed sand obtained in part of the examples and the comparative examples are tested according to the standard of GB/T2684-. The results of the above measurements are shown in Table 3.

TABLE 3 reclaimed sand Properties

Wherein, the conventional reclaimed sand is the reclaimed sand obtained by adopting the hot method regeneration condition of the embodiment 1 and only carrying out hot method roasting on the waste foundry sand.

As can be seen from Table 3, the reclaimed sands obtained in examples 1 and 6 have similar properties to the virgin sands, and have lower ignition loss, acid loss value and mud content, and higher mechanical strength.

In the embodiment 5, the input amount of the ceramsite green body containing the casting dedusting ash is too small, so that the influence on the performance of the reclaimed sand is not obvious; in example 7, when the input amount of the raw ceramsite is too large, dust generated by friction between the ceramsite is attached to the surface of the reclaimed sand, and is difficult to remove after calcination, so that the quality of the reclaimed sand is reduced.

The roasting temperature of the embodiment 8 is too low, the roasting is incomplete, the surface impurities of the reclaimed sand are more, and the performance is poorer; the calcination temperature of example 9 is too high, which has no influence on the performance of reclaimed sand, but the heat value provided by the coal dust in the fly ash is limited, which causes high overall energy consumption.

Comparative example 1 only mixes and roasts casting dust ash and waste foundry sand, because do not carry out the granulation with the dust ash, more dust ash is sintered on the sand grain surface in the calcination process, follow-up through washing difficult to remove, lead to the regeneration sand performance to descend.

Comparative example 2 does not stir and clean the reclaimed sand, and a small amount of ash is also attached to the surface of the reclaimed sand, resulting in a decrease in performance. However, compared with comparative example 1, comparative example 2 has a smaller amount of adhering ash and has less influence on the performance, so that the reclaimed sand performance of comparative example 2 is better than that of comparative example 1.

Sintered ceramsite performance test

The ceramisites obtained in examples 1 to 9 were tested for their cylinder pressure strength, bulk density and water absorption according to GBT 17431.2-2010. The performance of the commercial sintered ceramsite is also according to GBT 17431.1-2010.

The results of the above measurements are shown in Table 4.

TABLE 4 sintered ceramsite Properties

As can be seen from Table 4, compared with the commercially available ceramsite, the ceramsite fired in the examples 1-4 of the present invention has stable properties, moderate barrel pressure strength and light weight, and is suitable for use as a waterproof pad for roofs and decorated kitchens and bathrooms. On the premise of meeting the requirements of strength and safety, the composite material can be used as an aggregate of prefabricated part products and ceramsite concrete in the fields of non-bearing walls, light plates and the like.

In example 5, because the addition amount of the green ceramsite is small, the ceramsite is not sufficiently rubbed with each other in the roasting process, so that more loose ash is left on the surface of the ceramsite, and the strength of the ceramsite after sintering is low.

Compared with example 5, the strength of examples 6 and 7 is slightly enhanced because the green ceramsite is added in a large amount and rubbed with each other, the loose layer on the surface is ground off, the density of the rest part is high, the overall strength is improved, but part of dropped ash is sintered on the surface of reclaimed sand, and the quality is slightly reduced.

In example 8, the calcination temperature was too low, resulting in insufficient burning of the ceramsite and lower strength. The strength of the ceramsite in example 9 is high, but the calcination temperature is too high, the heat value in the ceramsite green body is limited, the fuel gas consumption is too large, and the cost is increased.

Energy consumption testing

For the processes of example 1 (adding the ceramsite green compact when performing thermal method regeneration on the foundry waste sand) and conventional thermal method regeneration (only performing thermal method regeneration on the foundry waste sand at the same roasting temperature without adding the ceramsite green compact), the same equipment and treatment capacity (the treatment capacity of the regenerated sand is 3t per hour, and the continuous production is performed for 24 hours per day) are adopted, and the gas consumption (natural gas) data of the thermal method regeneration within 7 days are respectively counted. The results are shown in Table 5.

TABLE 5 comparison of thermal regeneration energy consumption

Time	Gas consumption (m) for conventional thermal regeneration ³ )	Example 1 gas consumption (m) of thermal regeneration ³ )
			1d	1420	703
2d	1453	687
			3d	1448	720
4d	1395	694
			5d	1435	688
6d	1421	712
			7d	1444	701
In total	10016	4905

As can be seen from Table 5, the gas consumption for thermal regeneration is significantly reduced after the ceramsite green compact is added. When 8-9% of ceramsite green bodies are added, the total gas consumption of 7d is reduced by 5111m ³ . Compared with the conventional thermal regeneration without adding the ceramsite green compact, the method saves the gas consumption by about 51 percent. According to 3-5 yuan/m ³ The gas price calculation of (2) is 26d per month, the production is 11 months per year, and about 62.6-104.4 ten thousand yuan can be saved per year on average, thus having better economic benefit.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. The regeneration method of the foundry waste sand is characterized by comprising the following steps of:

(1) mixing 100 parts of casting dedusting ash, 8-15 parts of reclaimed sand reuse sewage and 0.1-0.5 part of auxiliary agent by weight, and granulating to obtain a ceramsite green body;

(2) mixing the ceramsite green body with casting waste sand, and then carrying out thermal regeneration, wherein the mass ratio of the casting waste sand to the ceramsite green body is 100 (1-20);

(4) adding water into the reclaimed sand, stirring and cleaning, and performing water-sand separation after cleaning;

in the step (1), the auxiliary agent is at least one selected from sodium humate, polyvinyl alcohol and sodium carboxymethyl cellulose.

2. The method as claimed in claim 1, wherein the mass ratio of sodium humate, polyvinyl alcohol and sodium carboxymethyl cellulose in the auxiliary agent is (0-10): (1-10): (0-10).

3. The method according to claim 1, wherein in the step (1), the particle size of the green ceramsite is 0.5-2 cm.

4. The method as claimed in claim 1, wherein in step (2), the calcination temperature of the thermal regeneration is 600-800 ℃ and the time is 2-5 h.

5. The method of claim 4, wherein in step (2), the calcination temperature of the thermal regeneration is 750 ℃ and the time is 3 h.

6. The method according to claim 1, wherein in step (4), the separated sewage is returned to step (1) to be pelletized as recycled sewage.

7. The method according to claim 1, wherein in the step (4), the mass ratio of the reclaimed sand to the cleaning water is 1 (0.5-1).