A co-treatment method for sewage plant sludge and blast furnace slag from steel plants

Abstract

The present invention relates to the technical field of sludge treatment, and particularly to a co-treatment method for sludge from sewage treatment plants and blast furnace slag from steel plants. It includes: S1. Calcining the sludge from the sewage treatment plant at 300-550 °C until the organic matter decomposes to obtain calcined sludge; S2. Grinding the calcined sludge obtained in step S1 together with blast furnace slag from the steel plant and an activator into ultrafine powder; S3. Granulating the ultrafine powder obtained in step S2 into spherical particles; S4. After the spherical particles in step S3 are frozen and cured to an appropriate age, an adsorption ball that can be directly placed in the sewage regulation pool of the sewage treatment plant is obtained; S5. The adsorption ball after adsorption in step S4 can be reused after being soaked in an EDTA-2Na solution. This method can not only co-dispose of the sludge from the sludge plant and the blast furnace slag from the steel plant, but also the entire disposal process is simple to operate, low-carbon and environmentally friendly. At the same time, the finished product can be used in the sewage treatment plant to adsorb heavy metals in sewage.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge treatment, and particularly to a method for co - treating sewage plant sludge and blast furnace slag from steel plants. Background Art

[0002] A large amount of sludge is generated during the treatment of urban domestic sewage. The sludge has a complex composition, and its main components include organic matter, fine particles, bacterial cells, etc. Direct landfill, incineration and other disposal methods of untreated sludge are likely to cause secondary pollution, posing a threat to the environmental ecology and public health. During the production process of steel plants, a large amount of blast furnace slag is generated. The slag mainly contains oxides such as calcium, silicon, and aluminum, as well as a small amount of sulfides. Due to the high alkalinity of blast furnace slag, landfill will cause serious damage to the soil ecology. Therefore, sludge and blast furnace slag must be properly treated by practical and effective engineering technologies.

[0003] In recent years, research has confirmed that preparing adsorption materials by modifying industrial residues and waste such as sludge and steel slag is an effective means of resource utilization. Due to the loose structure of sludge, which has abundant voids and a certain surface area; at the same time, blast furnace slag also has a certain adsorption capacity due to its high alkalinity, loose pores and large specific surface area, and both can serve as raw materials or auxiliary materials for preparing adsorption materials. This type of new adsorption material is expected to be used in the field of environmental pollution treatment to achieve pollution - free discharge and waste recycling during the sewage treatment process.

[0004] However, sludge has a high water content and a high organic matter content. Currently, the adsorption effect is mainly achieved by preparing sintered ceramsite, and the sintering temperature generally reaches above 1000°C, with high energy consumption and large pollution; although blast furnace slag also has a certain adsorption effect when used directly, its adsorption efficiency is low and the adsorption reuse rate is low.

[0005] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is the closest prior art. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for co - treating sewage plant sludge and blast furnace slag from steel plants. This method can not only co - dispose of sewage plant sludge and blast furnace slag from steel plants, but also the entire disposal process is simple to operate, low - carbon and environmentally friendly. At the same time, the finished product can be used in sewage plants to adsorb heavy metals in sewage quickly and can be recycled, which is beneficial to reducing the addition of chemicals, saving the subsequent transportation and treatment costs of sludge, and realizing the collaborative resource recycling of multiple solid wastes.

[0007] To achieve the above - mentioned purpose, the technical solution of the present invention is realized as follows. A method for co - treating sewage plant sludge and blast furnace slag from steel plants, the treatment method includes:

[0008] S1. Calcinate the sludge from the sewage treatment plant at 300 - 550 °C until the organic matter decomposes to obtain calcined sludge; the content of organic matter inside the sludge after calcination is not higher than 0.01%;

[0009] S2. Grind the calcined sludge obtained in step S1 together with the blast furnace slag from the steel plant and an activator into ultrafine powder; the median particle size of the ultrafine powder is 6 - 10 μm;

[0010] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles; the particle size distribution of the spherical particles is 2 mm - 15 mm;

[0011] S4. After the spherical particles in step S3 are frozen and cured to an appropriate age, an adsorption ball that can be directly placed in the sewage regulation tank of the sewage treatment plant is obtained;

[0012] S5. The adsorption ball after adsorption in step S4 can be reused after being soaked in an EDTA - 2Na solution.

[0013] Preferably, in step S1, the sludge from the sewage treatment plant is heated to 550 °C at a heating rate of 30 - 50 °C / min, calcined for 30 min, and then cooled to 300 °C at a cooling rate of 5 - 10 °C / min and calcined for 15 min, and the calcination atmosphere uses nitrogen as the carrier gas with an air flow rate of 80 - 150 ml / min.

[0014] Preferably, in step S2, the blast furnace slag from the steel plant is a mixture of blast furnace slag and blast furnace steel slag; the contents of CaO, Al2O3, and SiO2 in the blast furnace slag are not less than 80%.

[0015] Preferably, the mass ratio of the calcined sludge, blast furnace slag, and blast furnace steel slag is 1:3 - 7:1 - 2.

[0016] Preferably, the activator is NaOH or a composite agent of NaOH and Na2SiO3; and the mass ratio of the activator is 4 - 8% of the total mass of the calcined sludge and the blast furnace slag from the steel plant.

[0017] Preferably, the spherical particles in step S4 are frozen and then slowly melted in a low - temperature environment of 5 - 10 °C for 24 h.

[0018] Preferably, the appropriate age is determined according to the cylinder compressive strength of the spherical particles, and the cylinder compressive strength is not less than 4 MPa.

[0019] Preferably, the concentration of the EDTA - 2Na solution is 0.03 - 0.07 mol / L.

[0020] Preferably, the adsorption balls are used for adsorbing heavy metals in the sewage of sewage treatment plants, and the pH of the sewage used for the adsorption balls is 6-8; the temperature of the sewage used for the adsorption balls is 15-30 °C.

[0021] The beneficial effects of the present invention are embodied in:

[0022] (1) In the present invention, the sludge is calcined at a maximum temperature of 550 °C and continues to be calcined at a minimum temperature of 300 °C. Through such a calcination method, when the organic matter is calcined and volatilized, nano-scale connected pores will be formed in the sludge, and it also avoids the phenomenon that other components in the sludge will undergo pyrolysis when the temperature continues to rise, resulting in the loss of adsorption capacity after the pores are completely exposed. In addition, such a calcination temperature can effectively remove the organic matter in the sludge and eliminate the adverse effects of the organic matter on the strength and environmental safety during the subsequent application of the sludge.

[0023] (2) Based on the principle of crystal precipitation during the water freezing process, the present invention creates micron-scale pores in the spherical particles through freezing, and during the slow thawing process, water will react with the blast furnace slag under the excitation to undergo hydration reaction and be consumed, thereby providing support for the strength of the spherical particles. Through the dual synergistic reactions of physics and chemistry, the spherical particles can not only ensure that they are not easily broken during use, but also ensure the stability of their pores and are not easily cracked.

[0024] (3) By pyrolyzing and freezing the sludge, the present invention realizes the mutual matching of nano- and micro-scale pores, and uses the synergistic effects of physical adsorption and chemical replacement of the blast furnace slag to form spherical particles. The spherical particles produced by such a method not only improve the adsorption efficiency of the spherical particles, but also improve the adsorption capacity of the spherical particles, and have excellent effects on adsorbing heavy metals in sewage. Moreover, the hydration hardening of the blast furnace slag not only provides strength, but also solidifies the blast furnace slag and the sludge, exploring a new use for the recycling of sludge and blast furnace slag. Description of the Drawings

[0025] Figure 1 It is a schematic flow chart of the method of the present invention. Detailed Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Without conflict, the embodiments and features in the present application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0027] See Figure 1 As shown:

[0028] Example 1

[0029] A co - disposal method and its application for sewage treatment plant sludge and blast furnace slag of iron and steel plant, comprising the following steps:

[0030] S1. Heat the sewage treatment plant sludge to 550°C at a heating rate of 30°C / min, then calcine for 30 min, and then cool to 300°C at a cooling rate of 5°C / min and calcine for 15 min. Use nitrogen as the carrier gas for the calcination atmosphere, with a gas flow rate of 80 ml / min, until the organic matter is completely decomposed to obtain calcined sludge.

[0031] S2. Grind 1 part by mass of the calcined sludge, 7 parts by mass of blast furnace slag, 2 parts by mass of blast furnace steel slag, and 0.8 part by mass of NaOH into ultra - fine powder. The median particle size of the ultra - fine powder is 10 μm.

[0032] S3. Granulate the ultra - fine powder obtained in step S2 into spherical particles, and the particle size distribution of the spherical particles is 2 mm - 15 mm.

[0033] S4. Freeze the spherical particles obtained in step S3 and then place them in a low - temperature environment of 10°C to slowly melt for 24 h, and then cure for 27 d and directly place them in the sewage regulation pool of the sewage treatment plant for use.

[0034] S5. The spherical particles after adsorption in step S4 are soaked in an EDTA - 2Na solution with a concentration of 0.07 mol / L and reused.

[0035] Example 2

[0036] A co - disposal method and its application for sewage treatment plant sludge and blast furnace slag of iron and steel plant, comprising the following steps:

[0037] S1. Heat the sewage treatment plant sludge to 550°C at a heating rate of 50°C / min, then calcine for 30 min, and then cool to 300°C at a cooling rate of 10°C / min and calcine for 15 min. Use nitrogen as the carrier gas for the calcination atmosphere, with a gas flow rate of 150 ml / min, until the organic matter is completely decomposed to obtain calcined sludge.

[0038] S2. Grind 1 part by mass of the calcined sludge, 3 parts by mass of blast furnace slag, 1 part by mass of blast furnace steel slag, and 0.2 part by mass of NaOH into ultra - fine powder. The median particle size of the ultra - fine powder is 6 μm.

[0039] S3. Granulate the ultra - fine powder obtained in step S2 into spherical particles, and the particle size distribution of the spherical particles is 2 mm - 15 mm.

[0040] S4. Freeze the spherical particles obtained in step S3 and then slowly melt them in a low-temperature environment of 5 - 10°C for 24 h, and then cure for 27 d and directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0041] S5. Immerse the spherical particles after adsorption in step S4 in an EDTA-2Na solution with a concentration of 0.03 - 0.07 mol / L for reuse.

[0042] Example 3

[0043] A co-disposal method and its application for sewage treatment plant sludge and blast furnace slag from steel plants, comprising the following steps:

[0044] S1. Heat the sewage treatment plant sludge at a heating rate of 40°C / min to 550°C and then calcine for 30 min, and then cool at a cooling rate of 7°C / min to 300°C and calcine for 15 min. The calcination atmosphere uses nitrogen as the carrier gas with a gas flow rate of 120 ml / min until the organic matter is completely decomposed to obtain calcined sludge.

[0045] S2. Grind 1 part by mass of the calcined sludge, 6 parts by mass of blast furnace slag, 1.5 parts by mass of blast furnace steel slag, and 0.5 part by mass of NaOH into ultrafine powder. The median particle size of the ultrafine powder is 8 μm.

[0046] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles with a particle size distribution of 2 mm - 15 mm.

[0047] S4. Freeze the spherical particles obtained in step S3 and then slowly melt them in a low-temperature environment of 7°C for 24 h, and then cure for 27 d and directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0048] S5. Immerse the spherical particles after adsorption in step S4 in an EDTA-2Na solution with a concentration of 0.05 mol / L for reuse.

[0049] Example 4

[0050] A co-disposal method and its application for sewage treatment plant sludge and blast furnace slag from steel plants, comprising the following steps:

[0051] S1. Heat the sewage treatment plant sludge at a heating rate of 40°C / min to 550°C and then calcine for 30 min, and then cool at a cooling rate of 70°C / min to 300°C and calcine for 15 min. The calcination atmosphere uses nitrogen as the carrier gas with a gas flow rate of 120 ml / min until the organic matter is completely decomposed to obtain calcined sludge.

[0052] S2. Mix 1 part by mass of calcined sludge with 6 parts by mass of blast furnace slag, 1.5 parts by mass of blast furnace steel slag, 0.4 parts by mass of NaOH and Na2SiO3, and grind them together into ultrafine powder. The median particle size of the ultrafine powder is 8 μm.

[0053] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles. The particle size distribution of the spherical particles is 2 mm - 15 mm.

[0054] S4. Freeze the spherical particles obtained in step S3, then place them in a low-temperature environment of 7°C and slowly melt them for 24 h, and then cure for 27 d and directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0055] S5. The spherical particles after adsorption in step S4 are soaked in an EDTA-2Na solution with a concentration of 0.05 mol / L and reused.

[0056] Comparative Example 1

[0057] A method for disposing of sludge in a sewage treatment plant and its application, including the following steps:

[0058] S1. Heat the sludge in the sewage treatment plant from room temperature to 550°C at a heating rate of 30 - 50°C / min, calcine for 30 min, then cool to 300°C at a cooling rate of 5 - 10°C / min and calcine for 15 min. The calcination atmosphere uses nitrogen as the carrier gas, and the gas flow rate is 80 - 150 ml / min until the organic matter is completely decomposed to obtain calcined sludge.

[0059] S2. Mix 7.5 parts by mass of calcined sludge with 0.4 parts by mass of NaOH and Na2SiO3, and grind them together into ultrafine powder. The median particle size of the ultrafine powder is 8 μm.

[0060] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles. The particle size distribution of the spherical particles is 2 mm - 15 mm.

[0061] S4. Cure the spherical particles obtained in step S3 for 28 d and directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0062] S5. The spherical particles after adsorption in step S4 are soaked in an EDTA-2Na solution with a concentration of 0.05 mol / L and reused.

[0063] Comparative Example 2

[0064] A method for disposing of blast furnace waste slag in an iron and steel plant and its application, including the following steps:

[0065] S1. Mix 6 parts by mass of blast furnace slag, 1.5 parts by mass of blast furnace steel slag, 0.4 parts by mass of NaOH and Na2SiO3, and grind them together into ultrafine powder. The median particle size of the ultrafine powder is 8 μm.

[0066] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles, and the particle size distribution of the spherical particles is 2 mm - 15 mm.

[0067] S4. After curing the spherical particles obtained in step S3 for 28 d, directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0068] S5. The spherical particles after adsorption in step S4 are soaked in an EDTA-2Na solution with a concentration of 0.05 mol / L and then reused.

[0069] Comparative Example 3

[0070] A co-disposal method and its application for sewage treatment plant sludge and blast furnace slag of steel plant, including the following steps:

[0071] S1. Heat the sewage treatment plant sludge at a heating rate of 30 °C / min to 550 °C, then calcine for 30 min, and then cool to 300 °C at a cooling rate of 5 °C / min and calcine for 15 min. The calcination atmosphere uses nitrogen as the carrier gas, and the gas flow rate is 80 ml / min until the organic matter is completely decomposed to obtain calcined sludge.

[0072] S2. Grind 1 part by mass of the calcined sludge, 7 parts by mass of blast furnace slag, 2 parts by mass of blast furnace steel slag, and 0.8 part by mass of NaOH into ultrafine powder, and the median particle size of the ultrafine powder is 10 um.

[0073] S3. Granulate the ultrafine powder obtained in step S2 into spherical particles, and the particle size distribution of the spherical particles is 2 mm - 15 mm.

[0074] S4. After curing the spherical particles obtained in step S3 for 28 d, directly place them in the sewage regulation tank of the sewage treatment plant for use.

[0075] S5. The spherical particles after adsorption in step S4 are soaked in an EDTA-2Na solution with a concentration of 0.07 mol / L and then reused.

[0076] At pH = 7 and room temperature of 25 °C, conduct an adsorption experiment on Cs + (400 mg / L) and Sr 2+ (400 mg / L), and test the contents of Cs + and Sr 2+ in the solution by ICP.

[0077] In the desorption experiment, at room temperature of 25 °C, dissolve 0.1 mol / L HCl and 0.5 mol / L NaCl in 100 mL of water, and then repeatedly wash the spherical particles with EDTA-2Na for 10 times.

[0078] In the adsorption test, the following formulas (1)-(3) were used to measure the adsorption rate + for Cs 2+ and Sr , adsorption capacity and adsorption retention rate after cyclic adsorption .

[0079] (1)

[0080] (2)

[0081] (3)

[0082] wherein, C i and C f respectively represent the initial concentration and equilibrium concentration of the solution, with the unit of mg / L; V is the volume of the solution, with the unit of L; m represents the mass of the adsorbent, with the unit of g.

[0083] Table 1 Adsorption performance of spherical particles for Cs + (Performance)

[0084]

[0085] Table 2 Adsorption performance of spherical particles for Sr 2+ (Performance)

[0086]

[0087] Since the adsorption of Cs + includes ion exchange in addition to physical adsorption, it has a better adsorption effect than Sr 2+ ; calcining the sludge at 550 °C does not cause the phase recombination of the sludge, so the adsorption effect of heavy metals in Comparative Example 1 is not obvious. The spherical particles of the present invention will form micron-sized pores during the natural thawing process after freezing, improving the physical adsorption effect. The spherical particles of Comparative Example 2 were directly cured without freezing, and the pore distribution was uneven and the sizes were different, resulting in poor physical adsorption effect. The spherical particles of Comparative Example 3 were not frozen, and both its adsorption capacity and the effect after repeated use were lower than those of the present invention.

[0088] As can be seen from the above, the present invention not only realizes the disposal of sewage treatment plant sludge and blast furnace slag of steel plants, but also has a significant effect on the adsorption of heavy metals in the sewage of sewage treatment plants, which is beneficial to the collaborative resource recycling of multi-source solid wastes.

[0089] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A co-treatment method for sewage plant sludge and blast furnace slag from steel plants, characterized in that, The described treatment method includes: S1. First, heat the sludge from the sewage treatment plant to 550 °C for calcination, and then cool it to 300 °C for calcination until the organic matter decomposes to obtain calcined sludge; the content of organic matter inside the sludge after calcination is not higher than 0.01%; S2. Grind the calcined sludge obtained from step S1 together with blast furnace slag from the steel plant and an activator into ultrafine powder; the median particle size of the ultrafine powder is 6 - 10 μm; the activator is NaOH or a composite of NaOH and Na2SiO3; and the mass ratio of the activator is 4 - 8% of the total mass of the calcined sludge and blast furnace slag from the steel plant; S3. Granulate the ultrafine powder obtained from step S2 into spherical particles; the particle size distribution of the spherical particles is 2 mm - 15 mm; S4. After the spherical particles in step S3 are frozen and cured to an appropriate age, an adsorption ball that can be directly placed in the sewage regulation tank of the sewage treatment plant for use is obtained; S5. The adsorption ball after adsorption in step S4 can be reused after being soaked in an EDTA - 2Na solution.

2. The co-treatment method of sewage plant sludge and blast furnace slag of steel plant according to claim 1, characterized in that, The spherical particles in step S4 are frozen and then slowly melted in a low - temperature environment of 5 - 10 °C for 24 h.

3. A co-treatment method for sewage plant sludge and blast furnace slag of steel plant according to claim 2, characterized in that The blast furnace slag from the steel plant in step S2 is a mixture of blast furnace slag and blast furnace steel slag; the contents of CaO, Al2O3, and SiO2 in the blast furnace slag are not less than 80%.

4. A co-treatment method for sewage plant sludge and blast furnace slag of steel plant according to claim 3, characterized in that, The mass ratio of the calcined sludge, blast furnace slag, and blast furnace steel slag is 1:3 - 7:1 - 2.

5. A co - treatment method for sewage plant sludge and blast furnace slag of steel plant according to claim 2 or 3 or 4, characterized in that, In step S1, the sludge from the sewage treatment plant is heated to 550 °C at a heating rate of 30 - 50 °C / min and calcined for 30 min, and then cooled to 300 °C at a cooling rate of 5 - 10 °C / min and calcined for 15 min, and the calcination atmosphere uses nitrogen as the carrier gas with a gas flow rate of 80 - 150 ml / min.

6. The co-treatment method of sewage plant sludge and blast furnace slag of steel plant according to claim 5, characterized in that, The appropriate age is determined according to the cylinder compressive strength of the spherical particles, and the cylinder compressive strength is not less than 4 MPa.

7. A co-treatment method for sewage plant sludge and blast furnace slag of steel plant according to claim 6, characterized in that The concentration of the EDTA - 2Na solution is 0.03 - 0.07 mol / L.

8. The co-treatment method of sewage plant sludge and blast furnace slag of steel plant according to claim 7, characterized in that, The adsorption ball is used for adsorbing metals in the sewage of the sewage treatment plant, the metals include Cs and / or Sr, and the pH of the sewage used by the adsorption ball is 6 - 8; the temperature of the sewage used by the adsorption ball is 15 - 30 °C.

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