A sludge forming agent and its application in sludge granulation

Abstract

This invention discloses a sludge forming agent and its application in sludge granulation. The sludge forming agent comprises, by mass percentage: 55%-70% phenolic resin, 15%-25% quicklime, and 10%-20% waste incinerator ash. This sludge forming agent is added to the sludge before thermal drying, and then the thermally dried sludge is granulated. Adding the sludge forming agent to the sludge before thermal drying not only significantly improves the efficiency of sludge thermal drying and the strength of the granulated sludge, but also significantly reduces fly ash generated by sludge co-firing during the incineration process in a grate incinerator, and reduces the frequency of coking on the furnace walls of grate-type waste incinerators caused by sludge co-firing.

Description

Technical Field

[0001] This invention relates to the field of sludge and municipal solid waste treatment, disposal and resource utilization technology, and in particular to a sludge forming agent and its application in sludge granulation. Background Technology

[0002] Currently, my country has over 4,000 urban wastewater treatment plants. As an inevitable byproduct of activated sludge treatment of domestic sewage, the annual output of sludge exceeds 60 million tons (calculated with a moisture content of 80%), creating immense pressure for treatment and disposal. Of this, nearly 20% of the sludge is incinerated. Sludge incineration includes two methods: separate drying and incineration, and co-incineration with waste. The former has a higher initial investment but better operational stability, making it suitable for large-scale sludge treatment, while the latter has lower operating and maintenance costs. Therefore, my country's Ministry of Housing and Urban-Rural Development recommends co-incineration of sludge with waste as the preferred incineration method.

[0003] In my country, grate incinerators are the primary type of waste incinerator. Current engineering practice shows that when sludge is co-fired in grate incinerators, the amount of fly ash increases dramatically, and frequent coking occurs at the bottom of the furnace. These phenomena not only significantly increase fly ash disposal costs but also lead to a marked increase in the frequency and duration of furnace maintenance. Consequently, this creates operational difficulties for incineration plants, hindering the widespread adoption of sludge co-firing technology in waste incinerators. To address these problems, sludge granulation has been used to reduce fly ash and coking frequency caused by sludge co-firing. However, due to the long drying time and high cost of granulation, this technology has not yet been widely adopted in practical engineering. Therefore, developing a sludge drying and granulation co-firing technology that can reduce the cost of sludge co-firing is of significant practical importance. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a sludge forming agent and its application that can improve the thermal drying rate of sludge and reduce coking during the co-incineration process. It is mainly used to control the increased fly ash generation and coking problems during the co-incineration of sludge and municipal solid waste. By adding the sludge forming agent and mixing it evenly, rapid drying can be achieved. After granulation, the purpose of controlling fly ash and coking during the co-incineration of sludge and municipal solid waste can be achieved.

[0005] To achieve the above objectives, the present invention provides a sludge forming agent comprising, by weight percentage: 55%-70% phenolic resin, 15%-25% quicklime, and 10%-20% waste incinerator ash.

[0006] Preferably, the phenolic resin is heat-cured at a temperature exceeding 100°C.

[0007] Preferably, the particle size of the ash residue from the waste incinerator is 1-3 mm.

[0008] The present invention also provides an application of a sludge forming agent in sludge granulation.

[0009] Furthermore, the application of the sludge forming agent in sludge granulation specifically includes the following steps:

[0010] S1. Add sludge forming agent to water-containing sludge;

[0011] S2. Stir the sludge treated in step S1 evenly and then perform thermal drying.

[0012] S3. Granulate the sludge after step S2 to form sludge granulation product.

[0013] Preferably, in step S1, the moisture content of the sludge is 75%-85% by mass percentage.

[0014] Preferably, in step S1, the sludge forming agent is in the form of a solid powder.

[0015] Preferably, in step S1, the amount of sludge forming agent added to the sludge is 4%-8% by mass percentage.

[0016] Preferably, in step S2, the temperature of the heat drying treatment is 100℃-300℃.

[0017] Preferably, in step S2, the heat drying treatment time is 1-3.5 hours.

[0018] Preferably, the moisture content of the sludge after thermal drying is 25%-35% by mass percentage.

[0019] This invention has at least the following technical effects:

[0020] 1. The sludge forming agent of the present invention is added to sludge before sludge thermal drying, which can not only significantly improve the sludge thermal drying efficiency (sludge drying rate can be increased by 25%-35%) and improve the strength of sludge granulation products (strength can reach 0.1-0.3 MPa), but also significantly reduce the fly ash generated by sludge co-firing in the waste incinerator during the incineration process of the sludge granulation product in the grate incinerator, and reduce the frequency of coking on the furnace wall of grate type waste incinerator caused by sludge co-firing.

[0021] 2. The phenolic resin in the sludge forming agent of this invention hardens under high temperature, acting as a binder and binder for sludge particles, increasing particle size and reducing coking in the incinerator during co-firing. Quicklime absorbs water and releases heat in wet sludge, thereby reducing sludge viscosity and increasing the thermal drying rate. The ash from waste incinerators contains abundant calcium, magnesium, iron, and silicon dioxide, which can act as aggregates and sludge loosening agents, further reducing sludge viscosity and increasing the thermal drying rate. Furthermore, the ash from waste incinerators has certain pozzolanic characteristics, reacting with quicklime during thermal drying and subsequent incineration to improve the strength of the granulated sludge product. In addition, the presence of silicon and other elements in the ash from waste incinerators increases the melting point of the sludge ash, effectively reducing coking caused by co-firing municipal solid waste. In addition, the addition of waste incinerator ash with a particle size of 1-3mm can create a large number of pores on the surface of the sludge granulation product during combustion, thereby achieving full combustion inside the sludge granulation product and improving resource utilization efficiency.

[0022] 3. The sludge forming agent provided by this invention is simple to prepare and low in cost. The entire sludge granulation process is simple and easy to implement, with significant effects, and will not cause secondary pollution. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0024] A sludge forming agent comprising, by weight percentage: 55%-70% phenolic resin, 15%-25% quicklime, and 10%-20% waste incinerator ash.

[0025] Phenolic resins harden when heated at high temperatures. In some embodiments, phenolic resins harden when heated to temperatures exceeding 100°C.

[0026] In some embodiments, the particle size of waste incinerator ash is 1-3 mm. If the particle size is too fine, it will affect the looseness of the sludge and have a poor effect on promoting sludge drying; if the particle size is too large, it will affect the granulation effect of the sludge product.

[0027] In some embodiments, the sludge forming agent comprises, by weight percentage: 65% phenolic resin, 15% quicklime, and 20% waste incinerator ash.

[0028] In some embodiments, the sludge forming agent comprises, by weight percentage: 55% phenolic resin, 25% quicklime, and 20% waste incinerator ash.

[0029] In some embodiments, the sludge forming agent comprises, by weight percentage: 70% phenolic resin, 20% quicklime, and 10% waste incinerator ash.

[0030] The application of a sludge forming agent in sludge granulation specifically includes the following steps:

[0031] S1. Add sludge forming agent to water-containing sludge;

[0032] S2. Stir the sludge after step S1 evenly and transport it to the sludge thermal drying equipment for thermal drying treatment.

[0033] S3. The sludge processed in step S2 is transported to a granulator for granulation to form sludge granulated products.

[0034] In some embodiments, in step S1, the moisture content of the sludge is 75%-85% by mass.

[0035] In some embodiments, in step S1, the sludge forming agent is in the form of a solid powder.

[0036] In some embodiments, in step S1, the amount of sludge forming agent added to the sludge is 4%-8% by mass percentage.

[0037] In some embodiments, the temperature of the heat drying process in step S2 is 100℃-300℃.

[0038] In some embodiments, the heat drying process in step S2 takes 1-3.5 hours.

[0039] In some embodiments, the moisture content of the sludge after thermal drying is 25-35% by mass.

[0040] Example 1

[0041] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 85%, was used. A sludge forming agent containing 65 wt% phenolic resin, 15 wt% quicklime, and 20 wt% incinerator ash (with an ash particle size of approximately 1 mm) was added. The sludge forming agent was added at a dosage of 6 wt% to the 85% moisture content sludge, and after thorough mixing, it was fed into a sludge paddle dryer for drying at 150℃ for 2.5 hours. After reducing the sludge moisture content to 25%, it was fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0042] Comparative Example 1

[0043] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 85% (the same sludge used in Example 1), was directly fed into a sludge paddle dryer for drying at 150°C. After reducing the moisture content to 25%, the sludge was fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0044] Compared to Comparative Example 1, the sludge in Example 1, when reduced to the same sludge moisture content, underwent a 32% shorter drying time in the paddle-type sludge dryer. Furthermore, the sludge granulation product from Example 1 achieved a strength of 0.3 MPa, while the sludge granulation product from Comparative Example 1 had a strength of less than 0.05 MPa. When the sludge granulation product from Example 1 was co-incinerated with municipal solid waste, the coking frequency caused by sludge co-incineration decreased by 93%, while the coking frequency caused by sludge co-incineration was only reduced by 68% when the sludge granulation product from Comparative Example 1 was co-incinerated with municipal solid waste.

[0045] Example 2

[0046] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 75%, was used. A sludge forming agent containing 55 wt% phenolic resin, 25 wt% quicklime, and 20 wt% incinerator ash (with an ash particle size of approximately 2 mm) was added. The sludge forming agent was added at a rate of 4 wt% to the sludge with a moisture content of 75%, and after thorough mixing, the mixture was fed into a sludge paddle dryer for drying at 100℃ for 3.5 hours. After reducing the sludge moisture content to 35%, the mixture was fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0047] Comparative Example 2

[0048] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 75% (the same sludge used in Example 2), was directly fed into a sludge paddle dryer for drying at 100°C. After reducing the moisture content to 35%, the sludge was then fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0049] Compared to Comparative Example 2, the sludge in Example 2, when reduced to the same sludge moisture content, underwent a 25% shorter drying time in the paddle-type sludge dryer. Furthermore, the sludge granulation product from Example 2 achieved a strength of 0.1 MPa, while the sludge granulation product from Comparative Example 2 had a strength of less than 0.08 MPa. When the sludge granulation product from Example 2 was co-incinerated with municipal solid waste, the coking frequency caused by sludge co-incineration decreased by 90%, while the coking frequency caused by sludge co-incineration was only reduced by 72% when the sludge granulation product from Comparative Example 2 was co-incinerated with municipal solid waste.

[0050] Example 3

[0051] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 80%, was used. A sludge forming agent containing 70 wt% phenolic resin, 20 wt% quicklime, and 10 wt% incinerator ash (with an ash particle size of approximately 3 mm) was added. The sludge forming agent was added at a rate of 8 wt% to the 80% moisture content sludge, and after thorough mixing, the mixture was fed into a sludge paddle dryer for drying at 300℃ for 1 hour. After reducing the moisture content to 27%, the sludge was fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0052] Comparative Example 3

[0053] Dewatered sludge from a wastewater treatment plant in Shanghai, with a moisture content of 85% (the same sludge used in Example 3), was directly fed into a sludge paddle dryer for drying at 300°C. After reducing the moisture content to 27%, the sludge was fed into a granulator for granulation. The granulated sludge product was then mixed with municipal solid waste for co-incineration.

[0054] Compared to Comparative Example 3, the sludge in Example 3, when reduced to the same sludge moisture content, underwent a 35% shorter drying time in the paddle-type sludge dryer. Furthermore, the sludge granulation product in Example 3 achieved a strength of 0.2 MPa, while the sludge granulation product in Comparative Example 3 had a strength of less than 0.05 MPa. When the sludge granulation product from Example 3 was co-incinerated with municipal solid waste, the coking frequency caused by sludge co-incineration decreased by 93%, while the coking frequency caused by sludge co-incineration was only reduced by 62% when the sludge granulation product from Comparative Example 3 was co-incinerated with municipal solid waste.

[0055] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. 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 experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A sludge forming agent, characterized in that, The product is composed of the following raw materials by weight percentage: 55%-70% phenolic resin, 15%-25% quicklime and 10%-20% waste incinerator ash, wherein the particle size of the waste incinerator ash is 1-3mm and the phenolic resin is heat-cured at a temperature exceeding 100℃.

2. The application of the sludge forming agent according to claim 1 in sludge granulation, characterized in that, Includes the following steps: S1. Add sludge forming agent to water-containing sludge; S2. Stir the sludge treated in step S1 evenly and then perform thermal drying treatment at a temperature of 100℃-300℃. S3. Granulate the sludge after step S2 to form sludge granulation product.

3. The application of the sludge forming agent according to claim 2 in sludge granulation, characterized in that, In step S1, the moisture content of the sludge is 75%-85% by mass percentage.

4. The application of the sludge forming agent according to claim 2 in sludge granulation, characterized in that, In step S1, the sludge forming agent is in the form of a solid powder.

5. The application of the sludge forming agent according to claim 2 in sludge granulation, characterized in that, In step S1, the amount of sludge forming agent added to the sludge is 4%-8% by mass percentage.

6. The application of the sludge forming agent according to claim 2 in sludge granulation, characterized in that, In step S2, the heat drying process takes 1-3.5 hours.

7. The application of the sludge forming agent according to claim 2 in sludge granulation, characterized in that, The moisture content of the sludge after thermal drying is 25%-35% by mass percentage.