Sludge dewatering conditioner and method of use thereof in sludge dewatering

Abstract

The present application belongs to the field of sludge treatment, in particular to the field of municipal sludge treatment, more specifically to a sludge dewatering agent and a sludge dewatering method using the dewatering agent, wherein a homogeneous mixture prepared from ferric chloride hexahydrate and urea is used as a sludge dewatering conditioner, which not only has the advantage of cheap raw materials, but also has a simple preparation process and low preparation cost, meeting the needs of sludge treatment application and promotion. At the same time, the homogeneous mixture disclosed in the present application has no additional requirements for pH and temperature when applied in the sludge dewatering process, which makes this conditioner widely applicable. Compared with PAM and other conditioners, the homogeneous mixture disclosed in the present application is biodegradable and does not cause residual and secondary pollution, which is a new green and environmentally friendly conditioner with good development prospects.

Description

Technical Field

[0001] This invention belongs to the field of sludge treatment, particularly the field of urban sludge treatment, and more specifically to sludge dewatering agents and sludge dewatering methods using such dewatering agents. Background Technology

[0002] Sludge dewatering refers to the physical removal of water from sludge, and it plays a crucial role in sludge treatment. Firstly, dewatered sludge is significantly reduced in volume and weight, facilitating subsequent transportation and final disposal, thereby lowering transportation costs and reducing environmental pollution risks. Secondly, dewatering saves on sludge treatment and disposal costs, reduces the land resources occupied by sludge stockpiling, and also facilitates the resource utilization of sludge, such as producing organic fertilizer or building materials, thus promoting a circular economy.

[0003] Sludge conditioning is a pretreatment method for sludge, aiming to improve the efficiency of sludge thickening and dewatering, and to systematically improve sludge properties, thus laying the foundation for subsequent treatment processes. Currently, there are four existing conditioning methods: chemical conditioning, thermal treatment, freezing, and washing.

[0004] Chemical conditioning is the most commonly used sludge conditioning technology, which involves adding chemical reagents such as coagulants and flocculants to the sludge to achieve the purpose of conditioning the sludge. Coagulants cause fine sludge particles to aggregate into larger flocs, thus forming settling or filterable flocs, thereby achieving dewatering. Currently, the coagulants used in existing technologies include inorganic coagulants (the dosage is generally 7-20% of the dry solids weight of the sludge), polymeric coagulants (the dosage is generally less than 1% of the dry weight of the sludge), and microbial coagulants. Among them, polymeric coagulants PAC (polyaluminum chloride) and PAM (polyacrylamide) are widely used. However, these conditioning agents leave residues after treatment, which can have an impact on the environment, and their biodegradability is limited. In addition, in order to achieve the ideal dewatering effect, large amounts of dewatering agents are often required, which not only increases the cost of wastewater treatment but also causes various effects such as reagent toxicity. Summary of the Invention

[0005] The purpose of this invention is to provide a new dewatering conditioner that can replace the conditioners used in the prior art, thereby avoiding the problems of high toxicity and high cost, and providing a green and economical treatment solution for sludge dewatering.

[0006] To achieve the above-mentioned objective, this invention discloses a sludge dewatering conditioner, wherein the sludge dewatering conditioner is prepared by heating ferric chloride hexahydrate and urea in a water bath and stirring continuously until a reddish-brown homogeneous mixture is formed.

[0007] The molar ratio of ferric chloride hexahydrate to urea ranges from 0.8:1 to 2:1; preferably, the molar ratio of ferric chloride hexahydrate to urea is 1:1 or 2:1.

[0008] In a preferred embodiment, the water bath temperature is 60~80℃.

[0009] Furthermore, this invention discloses a method for applying the sludge dewatering conditioner obtained by the above method in sludge dewatering, wherein the dosage of the sludge dewatering conditioner is further limited to 0.2‰~10.0‰ (volume ratio) of the sludge volume. It should be noted that in specific sludge dewatering processes, there are subsequent operations such as plate and frame filter press, and these steps and methods can be referenced from existing technologies.

[0010] The sludge volume mentioned here refers to the total volume of sludge to be treated.

[0011] Preferably, the pH of the sludge dewatering system is maintained between 4 and 8.5, and more preferably between 6.61 and 8.5.

[0012] The above-mentioned sludge dewatering conditioner completes sludge dewatering under room temperature conditions, preferably with the system temperature maintained at 25~35℃.

[0013] As mentioned earlier, conditioners have a significant impact on sludge dewatering. Factors such as the dosage of the conditioner, the pH conditions in the system, and the reaction temperature all have a crucial influence on sludge dewatering performance. This may be related to the floc structure in the sludge. Because these factors all affect the floc structure, and these factors are interconnected, exhibiting synergistic or inhibitory effects, in a comprehensive technical solution, we focus on the conditioner itself, the dosage of the conditioner, the system pH, and the temperature conditions required for dewatering. Of course, for practical applications, a treatment system that can adapt to different pH levels (i.e., without additional pH adjustment) and different system temperatures (i.e., without additional heating or cooling) is the preferred industrial solution. If the most basic dewatering requirements can be met under these conditions, we still consider it the preferred technical solution.

[0014] This invention uses a homogeneous mixture prepared from ferric chloride hexahydrate and urea as a sludge dewatering conditioner. It not only has the advantage of inexpensive raw materials, but also has a simple preparation process and low preparation cost, meeting the needs of sludge treatment application and promotion.

[0015] The homogeneous mixture disclosed in this invention can significantly improve the surface morphology of sludge and disrupt the sludge structure, promote the release of bound water, and facilitate water discharge, thereby significantly improving the sludge dewatering effect.

[0016] Furthermore, the homogeneous mixture disclosed in this invention does not have additional requirements for pH and temperature when applied in sludge dewatering processes, making this conditioner applicable to a wide range of scenarios. Specifically, experimental data shows that under room temperature conditions and in systems with pH 4–8.5, sludge treated with the conditioner disclosed in this invention can meet dewatering requirements, with significantly better results than traditional conditioner PAC and the use of ferric chloride hexahydrate and urea alone.

[0017] In addition, it is worth noting that, compared with conditioners such as PAM, the homogeneous mixture disclosed in this invention is biodegradable and is a new type of green and environmentally friendly conditioner with good development prospects. Attached Figure Description

[0018] Figure 1 Schematic diagrams of scanning electron microscopy (20 µm and 5 µm) of sludge from the blank control group, Examples 4-1, 4-10, and 4-12. Detailed Implementation

[0019] The present invention will be further described below with reference to specific embodiments, but it should be understood that the scope of protection of the present invention is not limited thereto.

[0020] Example 1

[0021] Ferric chloride hexahydrate and urea were mixed at a molar ratio of 2:1 and heated in a water bath (water bath temperature of 60~80℃) with constant stirring until a reddish-brown homogeneous mixture was formed, thus preparing conditioner A.

[0022] Example 2

[0023] Ferric chloride hexahydrate and urea were mixed in a molar ratio of 1:1 and heated in a water bath (water bath temperature of 60~80℃) with constant stirring until a reddish-brown homogeneous mixture was formed, thus preparing conditioner B.

[0024] Example 3

[0025] Ferric chloride hexahydrate and urea were mixed at a molar ratio of 0.8:1 and heated in a water bath (water bath temperature 60~80℃) with constant stirring until a reddish-brown homogeneous mixture was formed, thus preparing conditioner C.

[0026] Example 4

[0027] The conditioners obtained in Examples 1-3 were selected respectively, and the dewatering of sludge was investigated by measuring the capillary suction time (CST) of the residual sludge reactor, along with the dosage of the conditioners and the dewatering conditions of pH, temperature and other process conditions.

[0028] We constructed a blank control group to obtain CST (blank), and calculated the ratio of CST (test) to CST (blank) obtained under different process conditions to obtain CST (%), which was used as an indicator to measure the dewatering capacity under the process conditions. A CST (%) close to 100% indicates that the closer it is to the blank control group, the weaker the conditioning capacity. If CST (%) exceeds 100%, it indicates that the dewatering performance has deteriorated, which is not conducive to sludge dewatering.

[0029] Meanwhile, we performed electron microscopy on the sludge to observe the structural changes of the sludge after conditioning.

[0030] The specific experimental method is as follows:

[0031] Construction of blank control group: Only residual sludge was added to the residual sludge reactor, placed in a shaker, and shaken at 150 r / min and 10℃. After thorough mixing, CST was measured and used as the data of blank control group (CST).

[0032] Comparative Experiment Example 1: Add an equal amount of residual sludge to the residual sludge reactor as the blank control group, and add PAC at a volume ratio of 2.5‰. Place the reactor in a shaker and shake at 150 r / min and 10℃. After thorough mixing, measure the CST and calculate the ratio of CST (blank) to the blank control group. Record it as CST (%) - control, CST (%) - control = 80.15.

[0033] Comparative Experiment Example 2: Add the same amount of residual sludge as the blank control group to the residual sludge reactor, and weigh it according to the required mass and add ferric chloride hexahydrate separately. Place it in a shaker, shake at 150 r / min and 10℃, mix thoroughly, and then measure its CST. Calculate its CST ratio with the blank control group (blank), and record it as CST (%) - control. CST (%) - control = 78.64.

[0034] Comparative Experiment Example 3: Add the same amount of residual sludge as the blank control group to the residual sludge reactor, weigh out the same mass as required for the configuration, add urea separately, place in a shaker, shake at 150 r / min and 10℃, mix thoroughly, detect its CST, and calculate its CST ratio with the blank control group (blank), recorded as CST (%) - control, CST (%) - control = 152.17.

[0035] Examples 4-1 to 4-12

[0036] Add an equal amount of residual sludge to the residual sludge reactor as the blank control group. Add the conditioner prepared in Examples 1 to 3 according to the conditions listed in Table 1. Place the mixture into the residual sludge reactor and shake at 150 r / min. At the same time, adjust the system according to the dosage, system temperature and pH listed in Table 1. Keep the dosage, pH and temperature of the system under these conditions. After thorough mixing, measure the CST and calculate the CST (blank) ratio with the blank control group. Record them as CST (%) - Example (4-1) to CST (%) - Example (4-12).

[0037] The specific conditions and results are as follows:

[0038] Table 1:

[0039]

[0040] The sludge dewatering effect is mainly evaluated by the conditioner's concentration-to-sludge ratio (CST), which is related to the conditioner's composition and dosage. Under different experimental conditions, the combined effect of these two factors, after reaching equilibrium, results in different dewatering effects, specifically manifested in the different final CST values.

[0041] Meanwhile, as shown in Table 1, the conditioner disclosed in this invention can produce good sludge conditioning and dewatering effects at dosages ranging from 0.2‰ to 10.0‰. This wide dosage range helps reduce the complexity and precision requirements of the operation. Furthermore, even with the same conditioner and dosage, temperature and pH still have a further impact on the dewatering effect.

[0042] This dehydration system requires no special heating or cooling environment; it achieves good dehydration results at room temperature and still meets dehydration requirements without pH adjustment. Therefore, it has better adaptability and a wider range of applications. Furthermore, when the pH value in the reactor is varied from 6.61 to 8.5 without adjustment and the dosage is 2.5‰, the CST value at each reaction temperature shows a significant difference compared to the CST (blank), with the highest ratio reaching 30.64%. This further demonstrates that the conditioner has excellent dehydration conditioning effects over a broad pH range and at ambient temperatures. This significantly reduces the need for acid and alkali reagents and avoids the special requirements and corrosion damage that acid and alkali reagents impose on equipment.

[0043] Combination Figure 1 The electron microscope images shown show that, compared to the sludge structure in the blank control group, the sludge structure after conditioning in Examples 4-1, 4-10, and 4-12 has formed pores.

[0044] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A sludge dewatering conditioner, characterized in that: The sludge dewatering conditioner is prepared by heating ferric chloride hexahydrate and urea in a water bath and stirring continuously until a reddish-brown homogeneous mixture is formed; wherein the water bath temperature is 60~80℃; and the molar ratio of ferric chloride hexahydrate to urea is 2:

1.

2. The method of applying the sludge dewatering conditioner according to claim 1 in sludge dewatering, characterized in that: The dosage of sludge dewatering conditioner is 0.2‰ to 10.0‰ of the sludge volume (by volume).

3. The application method according to claim 2, characterized in that: The pH of the dehydration system is between 4 and 8.

5.

4. The application method according to claim 2, characterized in that: The pH of the dehydration system is 6.61~8.

5.

5. The application method according to claim 2, characterized in that: The sludge dewatering conditioner completes sludge dewatering under room temperature conditions.

6. The application method according to claim 2, characterized in that: The temperature of the dehydration system is maintained at 25℃~35℃.

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