Environment-friendly municipal sludge comprehensive treatment and recovery process

Abstract

The invention belongs to the technical field of sludge treatment, and discloses an environment-friendly municipal sludge comprehensive treatment and recovery process which comprises the following steps: collecting water removed by primary dehydration into a sewage tank, filtering clarified water by a filtering device, and purifying the filtered water by a membrane device; conveying the sludge subjected to primary dehydration to a sludge heater for dehydration and drying by using conveying equipment; steam generated by the heater is condensed and recycled and then sent into a fractionating tower, organic liquid and water are separated out, and water is purified through a membrane device; the dewatered and dried sludge is fed into an incinerator to be combusted, and sludge slag is formed after the sludge is combusted; the sludge is fed into an incinerator for complete combustion, and furnace ash formed after combustion is used for manufacturing building materials or returning soil. Sludge can be completely treated after being treated by the process, sludge and sewage are efficiently recycled, water resources are saved, and underground water is protected; sludge is combusted as fuel, heat energy is recycled, and energy is saved.

Description

Technical Field

[0001] The invention belongs to the technical field of sludge treatment, and in particular relates to an environmentally friendly municipal sludge comprehensive treatment and recovery process. Background Art

[0002] Over the past 40 years, with the rapid development of China's economy and the accelerated urbanization process, the number of sewage treatment plants in the country has also increased dramatically. By the end of 2024, there will be 14,637 sewage treatment plants included in the emission source statistical survey in the country, with a sewage treatment capacity of 334.667 million tons / day, which produces a large amount of sludge. Due to the high cost and technical difficulty of sludge treatment, a large amount of sludge is piled up or landfilled, which will cause secondary pollution, such as air pollution, water pollution, etc., and there are serious environmental problems.

[0003] So far, there is no successful technology in China to completely treat municipal sludge. It is just landfill or storage. Even if it is treated, it is not thorough and causes environmental problems. Many professionals and companies have also conducted a lot of research work, but they all failed due to high treatment costs and immature technology. In summer, the stench is overwhelming and sewage seeps into the ground, causing serious pollution to the atmosphere and groundwater. Summary of the invention

[0004] In order to overcome the above technical problems, the present invention provides an environmentally friendly municipal sludge comprehensive treatment and recycling process.

[0005] The present invention adopts the following technical solutions: An environmentally friendly municipal sludge comprehensive treatment and recycling process, comprising: Primary Dehydration The water removed by primary dehydration is collected in a sewage pool, and a reagent is added for coagulation and clarification. The clarified water is filtered through a filter device, and the filtered water is purified through a membrane device. The filtered water is used to backwash the filter device, and the membrane device is backwashed with the water purified by the membrane. The wastewater generated by backwashing is collected in a sewage pool; Sludge drying The sludge that has undergone primary dehydration is transported to the sludge heater by a transmission device at a temperature of 180-220°C to dehydrate and dry the sludge; the waste heat of the sludge heater is led to the inlet end of the heater to heat the newly entered sludge; the steam generated by the heater is condensed and recovered and then sent to the distillation tower to separate the organic liquid and water, and the water is purified by the membrane device; Sludge incineration The dehydrated and dried sludge is sent to the incinerator for combustion at a combustion temperature of 800-1200°C. The fuel of the incinerator is biofuel and the above-mentioned organic liquid. The sludge is burned to form sludge; Combustion of sludge The sludge is sent to the incinerator for complete combustion at 800-1000℃ and a combustion time of 20-30 minutes. The combustion emits carbon monoxide. The heat generated by the incinerator is passed into the sludge heater. The ash formed after complete combustion is used to make building materials or return to soil.

[0006] Preferably, a composite coagulant is used in combination with an emulsifier to improve separation efficiency.

[0007] Preferably, the pH value of the sewage pool is monitored in real time, and the coagulation reaction is controlled within the pH range of 6.5-8.5 to optimize floc formation.

[0008] Preferably, a concentrated liquid treatment unit is added for the backwash water to avoid direct backflow and pollution of high-salinity wastewater.

[0009] Preferably, the membrane device uses ultrafiltration (UF) + reverse osmosis (RO) dual membrane combination technology to improve the water purification rate to the reuse standard.

[0010] Preferably, the waste heat recovery system is provided with a molten salt heat storage mechanism to balance heat load fluctuations.

[0011] Preferably, sludge incineration adopts two-stage combustion: the first stage is 800-1000℃ with biomass fuel as the main fuel to decompose organic matter, and the second stage is 1000-1200℃ with organic liquid fuel as the supplementary fuel to completely eliminate dioxins; the incinerator is equipped with an SNCR / SCR denitrification system + activated carbon injection device to control NOx and heavy metal emissions.

[0012] Preferably, a phosphate heavy metal curing agent is added to the furnace ash.

[0013] Preferably, the content of polycyclic aromatic hydrocarbons (PAHs) in the ash is detected, and if it is >50 mg / kg, white rot fungi need to be added for bioremediation.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The sludge can be treated more completely by the process of the present invention, and the sludge and sewage can be efficiently recycled and utilized, thus saving water resources and protecting groundwater; the sludge residue is burned as fuel, and the heat energy is recycled and utilized, thus saving energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a brief schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0016] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. Unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are conventional methods in the art. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0017] Environmentally friendly municipal sludge comprehensive treatment and recycling process: Primary Dehydration Use centrifugal dehydration technology for primary dehydration. Collect the water removed by primary dehydration into the sewage pool. Add composite coagulant (such as polyaluminium chloride + polyacrylamide) and demulsifier for coagulation and clarification. Monitor the pH value of the sewage pool and control the coagulation reaction within the pH range of 6.5-8.5. The clarified water is filtered through a filter device, and the filtered water is purified through a membrane device. The membrane device uses ultrafiltration (UF) + reverse osmosis (RO) dual membrane combination technology to increase the water purification rate to the reuse standard; Use filtered water to backwash the filter device, and use membrane purified water to backwash the membrane device. The wastewater generated by backwashing is collected in the sewage pool, and the backwash wastewater is treated by the concentrate treatment unit (evaporation crystallization or advanced oxidation) to prevent high-salt wastewater from directly flowing back and polluting.

[0018] Sludge drying The sludge that has undergone primary dehydration is transported to the sludge heater by transmission equipment at a temperature of 180-220°C for dehydration and drying; the waste heat of the sludge heater is led to the inlet of the heater to heat the newly incoming sludge; the steam generated by the heater is condensed and recovered and then sent to the distillation tower to separate the organic liquid and water, and the water is purified by a membrane device.

[0019] Sludge incineration The dehydrated and dried sludge is sent to the incinerator for two-stage combustion: the first stage is 800-1000℃, mainly using biomass fuel to decompose organic matter, and the second stage is 1000-1200℃, using organic liquid fuel as a supplementary fuel to completely eliminate dioxins; the incinerator is equipped with an SNCR / SCR denitrification system + activated carbon injection device to control NOx and heavy metal emissions, and the sludge is burned to form sludge.

[0020] Combustion of sludge The sludge is sent to the incinerator for complete combustion at 800-1000℃ for 20-30 minutes. The combustion emits carbon monoxide. The heat generated by the incinerator is passed into the sludge heater. The waste heat recovery system is equipped with a molten salt heat storage mechanism to balance the heat load fluctuation. After complete combustion, add phosphate heavy metal solidifiers to the ash, and test the content of polycyclic aromatic hydrocarbons (PAHs) in the ash. If it is >50mg / kg, add white rot fungi for bioremediation; The ash after harmless treatment is used to make building materials or returned to the soil.

[0021] The process can achieve a sludge reduction rate of >95%, a resource utilization rate of >80%, and flue gas emissions meet the "Hazardous Waste Incineration Pollution Control Standards" (GB18484), reducing the overall treatment cost by about 15%-20%.

[0022] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the above embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An environmentally friendly municipal sludge comprehensive treatment and recovery process, characterized in that: include: Primary Dehydration The water removed by primary dehydration is collected in a sewage pool, and a reagent is added for coagulation and clarification. The clarified water is filtered through a filter device, and the filtered water is purified through a membrane device. The filtered water is used to backwash the filter device, and the membrane device is backwashed with the water purified by the membrane. The wastewater generated by backwashing is collected in a sewage pool; Sludge drying The sludge that has undergone primary dehydration is transported to the sludge heater by a transmission device at a temperature of 180-220°C to dehydrate and dry the sludge; the waste heat of the sludge heater is led to the inlet end of the heater to heat the newly entered sludge; the steam generated by the heater is condensed and recovered and then sent to the distillation tower to separate the organic liquid and water, and the water is purified by the membrane device; Sludge incineration The dehydrated and dried sludge is sent to the incinerator for combustion at a combustion temperature of 800-1200°C. The fuel of the incinerator is biofuel and the above-mentioned organic liquid. The sludge is burned to form sludge; Combustion of sludge The sludge is sent to the incinerator for complete combustion at 800-1000℃ and a combustion time of 20-30 minutes. The combustion emits carbon monoxide. The heat generated by the incinerator is passed into the sludge heater. The ash formed after complete combustion is used to make building materials or return to soil.

2. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: The composite coagulant and demulsifier are used together to improve the separation efficiency.

3. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: Monitor the pH value of the sewage pool in real time and control the coagulation reaction within the pH range of 6.5-8.5 to optimize floc formation.

4. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: A concentrated liquid treatment unit is added for backwash water to avoid direct backflow and pollution of high-salt wastewater.

5. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: The membrane device uses ultrafiltration (UF) + reverse osmosis (RO) dual membrane combination technology to improve the water purification rate to the reuse standard.

6. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: The waste heat recovery system is equipped with a molten salt heat storage mechanism to balance heat load fluctuations.

7. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: Sludge incineration adopts two-stage combustion: the first stage is 800-1000℃ with biomass fuel as the main fuel to decompose organic matter, and the second stage is 1000-1200℃ with organic liquid fuel as the supplementary fuel to completely eliminate dioxins; the incinerator is equipped with SNCR / SCR denitrification system + activated carbon injection device to control NOx and heavy metal emissions.

8. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: Phosphate heavy metal solidifying agent is added to the furnace ash.

9. An environmentally friendly municipal sludge comprehensive treatment and recovery process according to claim 1, characterized in that: The content of polycyclic aromatic hydrocarbons (PAHs) in the ash was tested. If it was >50 mg / kg, white rot fungi should be added for bioremediation.

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