CN115650547B - Method for recycling and energy-utilizing excess sludge of urban sewage treatment plant - Google Patents
Method for recycling and energy-utilizing excess sludge of urban sewage treatment plant Download PDFInfo
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Abstract
The invention discloses a method for recycling and utilizing excess sludge of a town sewage treatment plant, which relies on a system for recycling and utilizing excess sludge constructed by interconnecting a plurality of units including a town sewage treatment plant, a sludge drying production line, a coal-fired power plant, a carbonization furnace, an autotrophic nitrogen treatment facility, a composite constructed wetland or a sponge city module, wherein the system for recycling and utilizing excess sludge comprises a sludge energy utilization method and a sludge recycling method. The invention can realize higher energy and resource utilization rate by means of the approaches of sludge electric vehicle transportation, waste heat steam circulation, dried sludge co-firing, porous filler preparation, aquatic plant carbon sink, waste filler phosphorus recovery and the like, and provides a systematic control scheme for various pollution discharge of high ammonia nitrogen wastewater, carbonized pyrolysis gas, aquatic plant harvesting residues and the like.
Description
Technical Field
The invention belongs to the technical field of sludge recycling, and particularly relates to a method for recycling and energy-saving excess sludge of a town sewage treatment plant.
Background
In recent years, a plurality of breakthroughs are made in the fields of key sludge treatment and treatment technology and complete equipment at home and abroad, and 4 main stream technical routes such as anaerobic digestion, land utilization, aerobic fermentation, land utilization, drying incineration, ash landfill or building material utilization, deep dehydration, sanitary landfill and the like are mostly adopted in combination with practical situations.
Researches show that the carbon emission intensity of the main flow technical route is followed from the aspects of energy consumption, drug consumption, emission of fugitive greenhouse gases, energy resource recovery convenience and the like in the sludge treatment process: anaerobic digestion, land utilization, aerobic fermentation, land utilization, drying incineration, ash landfill, deep dehydration and sanitary landfill. At present, sludge anaerobic digestion or aerobic composting facilities are not popular in domestic town sewage treatment plants. On the one hand, the reason is that the organic matter content in the domestic surplus sludge is low, and the sludge digestion effect and stability are difficult to reach the foreign application level (the reduction of more than 40 percent); on the other hand, the reason is that domestic sewage plants generally lack the operation management experience of related facilities, and greenhouse gases, organic residues and high-concentration wastewater generated during the operation management experience still need to be effectively managed and controlled for harmless treatment or resource utilization. The problems lead the popularization and application of the technical route to face huge investment pressure.
In order to solve the problem of low-carbon treatment and disposal of excess sludge of urban sewage treatment plants, centralized drying and incineration becomes a preferred technical route of a plurality of large and medium-sized cities in China, but a sludge recycling technical system matched with the centralized drying and incineration is not sound. The material flow and energy flow barriers still exist between the sludge reduction, stabilization, harmless and recycling treatment units, and the aims of energy conservation, consumption reduction and resource energy recovery are difficult to effectively cooperate. For example, the sludge drying process consumes a large amount of external energy and produces refractory high ammonia nitrogen organic wastewater, which puts high demands on matched energy and environmental protection infrastructure. For another example, sludge self-sustaining incineration generally requires that the organic matter content is higher than 40% -50%, and the actual sludge property in many areas is lower than the standard, so that the combustion improver is required to be additionally consumed, and the treatment cost and the carbon emission are increased. In addition, the recycling path (such as phosphorus recovery) of the incineration ash remains to be explored, and no obvious carbon compensation effect can be formed.
In view of this, the sludge treatment efficiency is enhanced, and the recycling and energy utilization are realized, so that the secondary pollution treatment, carbon emission reduction and technical economy are both considered, and the systematicness of the recycling and energy utilization of the excess sludge of the urban sewage treatment plant is further required to be improved. The method is used for opening up a material flow and energy flow barrier between sludge treatment and treatment, recycling and energy utilization, so that the cooperative reduction of sludge, wastewater and waste gas and energy recycling are realized, and the method becomes a key of the technical innovation of sludge treatment and treatment.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide a recycling and energy utilization method for excess sludge of an environment-friendly urban sewage treatment plant, which has higher treatment efficiency.
In order to achieve the technical purpose and the technical effect, the invention is realized by the following technical scheme:
a method for recycling and energy utilization of excess sludge of urban sewage treatment plants depends on a system for recycling and energy utilization of excess sludge, which is constructed by interconnecting a plurality of units including urban sewage treatment plants, sludge drying production lines, coal-fired power plants, carbonization furnaces, autotrophic nitrogen removal treatment facilities, composite constructed wetlands or sponge city modules. The excess sludge recycling and energy utilization system comprises a sludge energy utilization path and a sludge recycling path. Wherein,
the specific method of the sludge energy utilization path comprises the following steps:
delivering surplus sludge generated after sewage treatment of the town sewage treatment plant to the sludge drying production line, drying the surplus sludge by the sludge drying production line, and delivering the dried sludge to the coal-fired power plant, wherein the coal-fired power plant mixes the dried sludge with coal to generate electricity, provides the generated electric energy for the sludge drying production line and the carbonization furnace to be used as energy sources, and simultaneously provides waste heat steam generated by power generation of the coal-fired power plant for the sludge drying production line to be used as a heat source;
the concrete method of the sludge recycling path comprises the following steps:
delivering surplus sludge generated after sewage treatment of the town sewage treatment plant to the sludge drying production line, and drying the surplus sludge by the sludge drying production line; after sludge is dried, the dried sludge is conveyed to the carbonization furnace, the carbonization furnace utilizes the dried sludge to prepare biochar, and then the biochar is further prepared into porous filler for construction of the composite constructed wetland or the sponge city module, so that plant growth is promoted to form ecological carbon sink; in addition, pyrolysis gas generated by the carbonization furnace during preparation of biochar is provided for the coal-fired power plant, and tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant; after sludge drying, conveying high ammonia nitrogen organic wastewater generated when the sludge drying production line dries sludge into the autotrophic nitrogen removal treatment facility, removing organic matters, ammonia nitrogen and total nitrogen in the wastewater by the autotrophic nitrogen removal treatment facility, and conveying treated effluent back to the town sewage treatment plant, wherein the residual wastewater sludge generated after the wastewater is treated by the autotrophic nitrogen removal treatment facility is used as a strain for sale;
meanwhile, tail water of the town sewage treatment plant is sent into the composite constructed wetland for deep purification, and the reclaimed water after deep purification is used for river ecological supplementing water or municipal water; intercepting and purifying the sponge city module by urban rainfall or agricultural non-point source sewage, wherein the intercepted and purified reclaimed water is used for river ecological supplementing water; plant residues generated by the town sewage treatment plant and the sponge city module are mixed with the dried sludge and then sent to the carbonization furnace for preparing biochar; the porous filler in the town sewage treatment plant and the sponge city module is transported to the coal-fired power plant for incineration power generation after several years of use.
Furthermore, in a set of excess sludge recycling and energy utilization system, a plurality of urban living sewage treatment plants can be arranged, or can be single, and are arranged close to the composite constructed wetland; the sludge drying production line, the coal-fired power plant and the carbonization furnace are respectively arranged close to the autotrophic nitrogen removal treatment facility.
Further, the sludge energy utilization path and the use proportion of the sludge resource utilization path are set according to actual requirements; when the number of the town sewage treatment plants is large and the output of the surplus sludge is large, the sludge recycling path and the sludge energy utilization path are simultaneously used, and the energy utilization and the recycling of the sludge are simultaneously carried out; when the number of town sewage treatment plants is small and the output of excess sludge is small, the sludge recycling path is preferentially used, and the recycling of sludge is preferentially carried out.
Furthermore, the urban sewage treatment plant is mainly used for treating sewage generated by daily life or commercial and religious activities of urban residents, and is not used for treating industrial wastewater containing toxic and harmful substances such as heavy metals; the surplus sludge generated by the urban sewage treatment plant mainly comprises redundant activated sludge generated by a secondary biochemical treatment system and a small amount of chemical sludge generated by a coagulating sedimentation process, the solid content of the surplus sludge is 10% -20% after the dehydration treatment in the urban sewage treatment plant, and the heavy metal content meets the B-level requirement of the agricultural sludge pollutant control standard (GB 4284-2018).
Furthermore, the town sewage treatment plant adopts electric transport vehicles to transport the surplus sludge to the sludge drying production line, and the electric transport vehicles are charged by charging stations around the sludge drying production line preferentially so as to reduce energy loss caused by power transmission.
Further, the sludge drying production line preferably adopts a 'thin layer evaporator+belt dryer' two-stage process, the thickness of a sludge layer is controlled to be 8-15 mm, waste heat steam of the coal-fired power plant is used as a heat source, the temperature of the waste heat steam is 180-200 ℃, the steam quantity required for drying each ton of residual sludge is 0.5-0.8T, the drying treatment time is 2-3 h, the solid content of the dried residual sludge is increased to 80% -90%, the heating value is not lower than 3000 kcal/kg (coal heating value measuring method GB/T213-2008), and the waste heat of the belt dryer can be recycled to the thin layer evaporator.
Furthermore, the autotrophic nitrogen removal treatment facility preferentially adopts a combined process of an anaerobic expanded granular sludge bed and an integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor to treat high ammonia nitrogen organic wastewater generated in the sludge drying process; compared with the traditional activated sludge method, the combined process has the advantages of lower aeration energy consumption and lower sludge yield, and no need of setting internal reflux of sludge; wherein the anaerobic expanded granular sludge bed mainly removes organic matters in high ammonia nitrogen organic wastewater, creates low C/N ratio conditions for denitrification of the autotrophic organisms at the later stage, and feeds COD (chemical oxygen demand) Cr The load is controlled to be 3-5 kg (m) 3 D), purifying the generated biogas for preheating a production line; the integrated nitrosation/anaerobic ammoxidation granular sludge reactor can realize autotrophic removal of ammonia nitrogen and total nitrogen in high ammonia nitrogen organic wastewater, and the load of influent ammonia nitrogen is controlled to be 0.5-1.5 kg (m 3 D), the sludge age is 35-50 d, the particle size of the particles is 0.5-1.25 mm, anaerobic ammonia oxidizing bacteria in the particle sludge are mainly Candidatus Brocadia and Candidatus Kuenenia, and the relative abundance is 25% -50%; COD (chemical oxygen demand) of high ammonia nitrogen organic wastewater by adopting combined process of anaerobic expanded granular sludge bed and integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor of autotrophic nitrogen treatment facility Cr And ammonia nitrogen removal rate is greater than 80%, treated water is superior to wastewater quality standard of wastewater discharged into town (GB/T31962-2015), and the treated water is sent to a municipal wastewater treatment plant through a sewer.
Furthermore, the combined process of the anaerobic expanded granular sludge bed and the integrated nitrosation/anaerobic ammoxidation granular sludge reactor adopted by the autotrophic nitrogen removal treatment facility can be used for selling the high-added-value surplus sludge generated after the high-ammonia-nitrogen organic wastewater is treated as a strain to the outside so as to reduce the system operation cost.
Furthermore, the sludge drying production line directly mixes part of dried sludge or the dried sludge with plant residues, and then adds 2-10% of MgCl 2 As an activating agent, the activated sludge is sent to the carbonization furnace for rolling and heating for 1.5 to 3 hours at the temperature of 500 to 800 ℃ under the air-isolated condition to prepare sludge-based or mixed-based biochar, and about 1 ton of biochar is prepared per 10 tons of dried sludge (containing partial plant residues), and the specific surface area (BET) of the biochar is more than 50m 2 Per gram, the pH of the surface is 8.0-9.0, the density is 0.7-1.0 kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The pyrolysis gas generated in the early stage of carbonization contains a large amount of volatile matters and non-condensable gas, and is sent to a boiler of the coal-fired power plant, burned at 850-1000 ℃, and tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant, so that the ultra-clean emission standard is achieved; the biochar is made into porous filler by using a 3D printing technology and is used for constructing the composite constructed wetland or the sponge city module, so that plant growth in the composite constructed wetland or the sponge city module is promoted to form ecological carbon sink, and resource utilization is realized.
Further, after years of use, the porous filler is transported to the coal-fired power plant and the final disposal is completed by incineration power generation.
Further, the sludge drying production line fully mixes the other part of dried sludge with coal according to the mass ratio of 2% -10%, breaks the mixture into particles with the particle size of 120-200 meshes, and sends the particles into a boiler of the coal-fired power plant for combustion and power generation, so that the sludge energy utilization is realized; the boiler of the coal-fired power plant adopts a supercritical coal-fired unit, and the thermal efficiency reaches more than 40%; waste heat steam generated by a boiler of the coal-fired power plant is supplied to the sludge drying production line as a heat source, and electric energy generated by the coal-fired power plant is supplied to the sludge drying production line or the carbonization furnace as energy, so that energy circulation is realized.
Furthermore, the composite constructed wetland is generally composed of a subsurface flow wetland and a surface flow wetland and is mainly used for deeply purifying tail water of the urban sewage treatment plant, and water outlet of the composite constructed wetland is used for river ecological supplementing water or municipal water.
Further, the sponge city module is generally made of porous materials with high water permeability and is mainly used for intercepting and purifying surface source pollution of built-up areas such as urban rainfall, agricultural surface sources and the like, and the effluent of the sponge city module is used for ecological supplementing water of a river channel.
Furthermore, porous fillers prepared by 3D printing of sludge-based biochar are preferentially adopted in the composite constructed wetland and the sponge city module, then a soil layer is paved on the surface layer of the porous fillers, aquatic plants are planted in a configuration mode, and ecological carbon sinks can be formed while pollutants such as nitrogen, phosphorus and the like in water are effectively reduced.
Further, harvesting plants on the surface layer of the porous filler in autumn and winter each year, crushing the plants to 40-80 meshes, fully mixing plant residues with the dried sludge, and delivering the mixture to a carbonization furnace to prepare the mixed-base biochar.
Furthermore, after the porous filler in the urban sewage treatment plant and the sponge city module is used for a plurality of years, the porous filler can be transported to the coal-fired power plant for incineration power generation, so that the resource recycling is realized.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, the treatment of the excess sludge of the sewage plant is combined with the energy substance circulating unit, so that the existing facilities are not required to be modified in a large scale, and the construction investment cost can be effectively controlled; specifically, the invention can obviously improve the synergistic pollution reduction and carbon reduction efficiency of the whole sludge treatment process by combining the units such as a sludge drying production line, a coal-fired power plant, a carbonization furnace, an autotrophic nitrogen removal treatment facility, a composite constructed wetland or a sponge city module, and the like, the heavy metal in the sludge is converted into a stable residue state, the leachability and the biological effectiveness are greatly reduced, and the environmental risk is effectively controlled.
2. Compared with the main flow technical route of the current sludge treatment, the invention can realize higher energy and resource utilization rate by means of the approaches of sludge electric vehicle transportation, waste heat steam circulation, dried sludge blending, porous filler preparation, aquatic plant carbon sink, waste filler treatment and the like, and provides a systematic control scheme for various pollution discharge such as high ammonia nitrogen wastewater, carbonized pyrolysis gas, aquatic plant harvesting residues and the like;
firstly, compared with the traditional fuel oil vehicle, the invention adopts electric vehicle transportation to effectively reduce carbon emission in the process of transporting dewatered sludge, meanwhile, a sludge drying plant and a coal-fired power plant are arranged in a concentrated way, vehicle charging is carried out at the periphery of the power plant, and the loss in the process of power transmission can be reduced;
secondly, the sludge drying production line adopts a 'thin layer evaporator+belt dryer' two-stage process, and the steam consumption of sludge drying can be obviously reduced by controlling the thickness of a sludge layer and energy recovery; the salt content in the high ammonia nitrogen organic wastewater generated by drying is lower than that in the traditional sludge digestion liquid, the inhibition effect on microorganisms is weaker, and the method is suitable for treatment by using a combined process of an anaerobic expansion granular sludge bed and an integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor; compared with the traditional activated sludge method based on the whole-course nitrification-denitrification reaction, the method can effectively remove the indexes such as organic matters, ammonia nitrogen, total nitrogen and the like in the wastewater, has lower energy and carbon source consumption in the treatment process, generates residual sludge with high added value, and is beneficial to reducing the system operation cost;
thirdly, the invention sends the dried sludge, carbonized pyrolysis gas and waste biochar filler to a boiler of a coal-fired power plant for incineration, thereby effectively reducing the emission of atmospheric pollutants and providing power for the carbonization of the sludge; the tail water purification wetland of the sewage plant and the sponge city module harvest aquatic plants in autumn and winter, so that the loss of nutrient salts in the plants to the water body can be effectively avoided, and most of nutrient salts are fixed by mixing the sludge to prepare biochar, so that the biomass waste disposal problem is solved.
3. The invention can flexibly adjust the subsequent recycling and energy utilization ratio according to the distribution condition of the sewage plant and the sludge yield, and has strong regulation and control flexibility; according to the invention, the plant harvesting residue is used as one of raw materials for preparing the biochar, so that the porosity of the sludge biochar can be effectively improved, the surface group composition is optimized, and the pollutant adsorption and microorganism fixation performances are enhanced; furthermore, the biochar is used as a raw material of the 3D printing porous filler, so that the urgent requirements of tail water ecological purification and sponge city construction of a sewage plant on various porous fillers can be met, the outlet problem of sludge recycling products is effectively solved, and the method has good popularization and application prospects in upgrading and reconstruction of the existing domestic sludge treatment and disposal system.
The foregoing description is only an overview of the technical solution of the present invention, and in order to make the technical means of the present invention more clearly understood, it can be implemented according to the content of the specification, and the following description is made with reference to the preferred embodiments of the present invention and with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail by the following examples and the accompanying drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic block diagram of a method for recycling and energy utilization of excess sludge in a plurality of town sewage treatment plants according to embodiment 1 of the present invention;
fig. 2 is a schematic block diagram of a method for recycling excess sludge of a single town sewage treatment plant according to embodiment 2 of the present invention.
Detailed Description
The invention will be described in detail below with reference to the drawings in combination with embodiments. The description herein is to be taken in a providing further understanding of the invention and is made a part of this application and the exemplary embodiments of the invention and their description are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Example 1
9 town sewage treatment plants are distributed in a certain area of the Taihu river basin, and a combined process of biochemical treatment and physical and chemical/ecological advanced treatment is adopted, so that the total treatment scale is about 75 ten thousand m 3 And/d, the area of the composite artificial wetland for tail water purification is about 200 ten thousand m 2 . Dehydrated sludge with annual output water content of 80 percent (solid content of 20 percent) in urban sewage treatment plants is about 20.6 ten thousand tons, and heavy metal content meets the B-level requirement of agricultural sludge pollutant control standard (GB 4284-2018). Except that a small amount of dehydrated sludge is treated by anaerobic digestion, other parts are recycled and energy-source-utilization by adopting the invention, and the method is shown in figure 1.
The dewatered sludge of the 9 town sewage treatment plants is periodically conveyed to a sludge drying production line adjacent to a large-scale coal-fired power plant by adopting an electric transport vehicle. Electric transport vehicles are charged by charging stations around the sludge drying production line preferentially so as to reduce energy loss caused by power transmission. 2 supercritical coal-fired power generating units with the level of 60 kilowatts are built in the coal-fired power plant, and can be used for sludge mixed combustion power generation. The total number of sludge drying production lines is 2, the designed drying capacity is 300 multiplied by 2 t/d, and daily dry sludge is 133 t/d. The sludge drying adopts a 'thin layer evaporator+belt dryer' two-stage process, the thickness of a sludge layer is controlled to be 8-15 mm, 10 mm is preferred in the embodiment, waste heat steam (180-200 ℃) of a coal-fired power plant is used as a heat source, and the steam consumption required for drying each ton of sludge is 0.5-0.8 t, and 0.6 t is preferred in the embodiment. The drying process is carried out for 2-3 hours, preferably 2.5-h, the dried sludge is granular, the solid content is increased to 80-90%, the heating value is not less than 3000 kcal/kg, and the heating value is about 3100 kcal/kg. The belt dryer waste heat may be recycled to the thin layer evaporator.
The wastewater yield of the sludge drying process is about 400 and 400 m 3 /d，COD Cr The concentration of ammonia nitrogen and total nitrogen are 2500-3000 mg/L, 250-300 mg/L and 300-360 mg/L respectively. And 1 group of wastewater treatment facilities (autotrophic nitrogen removal treatment facilities) close to the matched construction of an anaerobic Expanded Granular Sludge Bed (EGSB) +integrated nitrosation/anaerobic ammonia oxidation (PN/A) granular sludge reactor. Wherein, EGSB inflow COD Cr The load is controlled to be 3-5 kg (m) 3 D), the preferred value of this example is 3.5 kg (m 3 D), the generated biogas is used for preheating a production line after carbon dioxide is removed; the influent ammonia nitrogen load of the PN/A granular sludge reactor is controlled at0.5~1.5kg·(m 3 D), the preferred value of this example is 0.8 kg (m 3 D) sludge age 35-50 d, in this embodiment about 40 d, particle size of 0.5-1.25 mm, anaerobic ammonia oxidizing bacteria in the granular sludge mainly Candidatus Brocadia and Candidatus Kuenenia, relative abundance between 25% -50%, and relative abundance between Candidatus Brocadia and Candidatus Kuenenia of this embodiment is preferably 34%; the combined process of the anaerobic expanded granular sludge bed and the integrated nitrosation/anaerobic ammoxidation granular sludge reactor adopted by the autotrophic nitrogen removal treatment facility can be used for selling the high-added-value surplus sludge generated after the high-ammonia-nitrogen organic wastewater is treated as a strain to the outside so as to reduce the system operation cost; combined process for COD Cr The removal rates of ammonia nitrogen and total nitrogen are respectively 80% -85%, 80% -90% and 80% -85%, and the COD of the effluent is the same as that of the waste water Cr The concentrations of ammonia nitrogen and total nitrogen are respectively lower than 450 mg/L, 35 mg/L and 70 mg/L, which are superior to grade A of wastewater discharge into urban sewer quality standard (GB/T31962-2015), and the wastewater is sent to urban sewage treatment plants through the sewer.
About 40% of dried sludge is directly added or mixed with the plant residues of the composite constructed wetland, and about 2-10% of MgCl is added 2 As activator, this example prefers 5% MgCl 2 As an activator, the mixture is sent to a double-cylinder carbonization furnace, and is rolled and heated for 1.5 to 3 hours at the temperature of 500 to 800 ℃ under the air-isolated condition to prepare sludge-based biochar or mixed-base biochar, the example is preferably rolled and heated for 2 h at the temperature of 700 ℃ under the air-isolated condition, the yield is about 5.5 t/d, and the specific surface area (BET) of the biochar is more than 50m 2 Per gram, the pH of the surface is 8.0-9.0, the density is 0.7-1.0 kg/m 3 . The pyrolysis gas generated in the earlier stage of sludge carbonization contains a large amount of volatile matters and non-condensable gas, the volatile matters and the non-condensable gas are sent to a boiler of a coal-fired power plant, the boiler is burnt at 850-1000 ℃, tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant, the ultra-clean emission standard is achieved, and the emission concentrations of smoke dust, sulfur dioxide and nitrogen oxides are respectively not higher than 10mg/m 3 、35mg/m 3 And 50mg/m 3 . By using a 3D printing technology, adding adhesives such as sodium silicate alginate and the like, preparing biochar into porous filler balls for updating the filler of the composite constructed wetland, and effectively promoting various plants such as reed, typha and allium giganteumAnd (3) growing the substances to form an ecological carbon sink, and using purified water as a river channel supplementing water source. The plants are harvested in autumn and winter each year, crushed to 40-80 meshes, and mixed with the desiccated sludge to be used as raw materials for preparing the biochar, so that the porosity of the biochar can be remarkably improved. After the porous filler is used for years, the final treatment can be realized by adopting incineration power generation, and the sludge recycling utilization can be realized.
The rest about 60% of the dried sludge is mixed with the coal according to the mass ratio of 5%, crushed into particles with the particle size of 120-200 meshes, sent into a boiler of a coal-fired power plant for combustion power generation, and used for providing steam and electric energy for a sludge drying production line and a carbonization furnace for carbonization, so that the sludge energy utilization is realized.
Example 2
1 large town sewage treatment plants and coal-fired power plants are built in a centralized way in a certain area of the long triangle. The town sewage treatment plant adopts a combined process of biochemical treatment and physical and chemical advanced treatment, and the total treatment scale is about 20 ten thousand meters 3 And/d. Dehydrated sludge with annual output water content of 80 percent (solid content of 20 percent) in urban sewage treatment plants is about 2.8 ten thousand tons, and heavy metal content meets the B-level requirement of agricultural sludge pollutant control standard (GB 4284-2018). All the sludge is recycled and utilized by the invention, and the recycling and energy utilization are shown in figure 2.
And (3) the dewatered sludge of the town sewage treatment plant is periodically conveyed to a sludge drying production line by adopting an electric transport vehicle. Electric transport vehicles are charged by charging stations around the sludge drying production line preferentially so as to reduce energy loss caused by power transmission. 2 supercritical coal-fired power generating units with the level of 30 kilowatts are built in the coal-fired power plant, and can be used for sludge mixed combustion power generation. The total number of sludge drying production lines is 2, the designed drying capacity is 200 t/d, and daily dry sludge is about 40 t. The sludge drying adopts a 'thin layer evaporator+belt dryer' two-stage process, the thickness of a sludge layer is controlled to be 8-15 mm, 10 mm is preferred in the embodiment, waste heat steam (180-200 ℃) of a coal-fired power plant is used as a heat source, and the steam consumption required for drying each ton of sludge is 0.5-0.8 t, and 0.7 t is preferred in the embodiment. The drying process is carried out for 2-3 hours, preferably 2.5-h, the dried sludge is granular, the solid content is increased to about 80-90%, the heating value is not less than 3000 kcal/kg, and the heating value is about 3160 kcal/kg. The belt dryer waste heat may be recycled to the thin layer evaporator.
The wastewater yield of the sludge drying process is about 150 m 3 /d，COD Cr Ammonia nitrogen and total nitrogen concentrations were 2000 mg/L, 300 mg/L and 350 mg/L, respectively. And 1 group of wastewater treatment facilities (autotrophic nitrogen removal treatment facilities) close to the matched construction of an anaerobic Expanded Granular Sludge Bed (EGSB) +integrated nitrosation/anaerobic ammonia oxidation (PN/A) granular sludge reactor. Wherein, EGSB inflow COD Cr The load is controlled to be 3-5 kg (m) 3 D), the preferred value of this embodiment is 3.0 kg (m 3 D), purifying the generated biogas for preheating a production line; the load of ammonia nitrogen in inlet water of the PN/A granular sludge reactor is controlled to be 0.5-1.5 kg (m) 3 D), the preferred value of this example is 1.2 kg (m 3 D) sludge age 35-50 d, in this embodiment about 42 d, particle size of 0.5-1.25 mm, anaerobic ammonia oxidizing bacteria in the granular sludge mainly Candidatus Brocadia and Candidatus Kuenenia, relative abundance between 25% -50%, and in this embodiment, the relative abundance between anaerobic ammonia oxidizing bacteria Candidatus Brocadia and Candidatus Kuenenia is preferably 42%; the combined process of the anaerobic expanded granular sludge bed and the integrated nitrosation/anaerobic ammoxidation granular sludge reactor adopted by the autotrophic nitrogen removal treatment facility can be used for selling the high-added-value surplus sludge generated after the high-ammonia-nitrogen organic wastewater is treated as a strain to the outside so as to reduce the system operation cost; effluent COD of combined process Cr The concentrations of ammonia nitrogen and total nitrogen are respectively lower than 400 mg/L, 30 mg/L and 70 mg/L, which reach grade A of wastewater discharge into urban sewer quality standard (GB/T31962-2015), and the wastewater is sent to urban sewage treatment plants through the sewer.
The dried sludge is directly mixed with plant residues of the sponge city modules or is added with about 2 to 10 percent of MgCl 2 As activator, 10% MgCl is preferred in this example 2 As an activator, the mixture is sent to a double-cylinder carbonization furnace, and is rolled and heated for 1.5 to 3 hours at the temperature of 500 to 800 ℃ under the air-isolated condition to prepare sludge-based or mixed-base biochar, and the example is preferably rolled and heated for 2 h at the temperature of 700 ℃ under the air-isolated condition, the yield is about 4.5 t/d, and the specific surface area (BET) of the biochar is the same as that of the sludge-based or mixed-base biochar>50 m 2 Per gram, the pH of the surface is 8.0-9.0, the density is 0.7-1.0 kg/m 3 . The pyrolysis gas generated in the earlier stage of carbonizing sludge contains a large amount of volatile matters and non-condensable gas, the volatile matters and the non-condensable gas are sent to a boiler of a coal-fired power plant, the boiler is burnt at 850-1000 ℃, and tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant, so that the ultra-clean emission standard is achieved, and the emission concentrations of smoke dust, sulfur dioxide and nitrogen oxides are respectively not higher than 10mg/m 3 、35mg/m 3 And 50mg/m 3 . And 3D printing technology is used, an adhesive such as sodium silicate alginate is added, and the biochar is made into porous filler for updating the sponge city module. The porous filler of the sponge city module is planted with reed, calamus, canna and other plants, and purified water is used as a river channel supplementing water source. The plants are harvested in autumn and winter each year, and the mixed base biochar is prepared together with the desiccated sludge, so that the resource utilization is realized.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for recycling and energy-utilizing excess sludge of urban sewage treatment plants is characterized in that: the method relies on a residual sludge recycling and energy utilization system constructed by interconnecting a plurality of units including town sewage treatment plants, sludge drying production lines, coal-fired power plants, carbonization furnaces, autotrophic biological denitrification treatment facilities, composite constructed wetlands or sponge city modules; the excess sludge recycling and energy utilization system comprises a sludge energy utilization path and a sludge recycling path, wherein,
the specific method of the sludge energy utilization path comprises the following steps:
delivering surplus sludge generated after sewage treatment of the town sewage treatment plant to the sludge drying production line, drying the surplus sludge by the sludge drying production line, and delivering the dried sludge to the coal-fired power plant, wherein the coal-fired power plant mixes the dried sludge with coal to generate electricity, provides the generated electric energy for the sludge drying production line and the carbonization furnace to be used as energy sources, and simultaneously provides waste heat steam generated by power generation of the coal-fired power plant for the sludge drying production line to be used as a heat source;
the concrete method of the sludge recycling path comprises the following steps:
delivering surplus sludge generated after sewage treatment of the town sewage treatment plant to the sludge drying production line, and drying the surplus sludge by the sludge drying production line; after sludge is dried, the dried sludge is conveyed to the carbonization furnace, the carbonization furnace utilizes the dried sludge to prepare biochar, and then the biochar is further prepared into porous filler for construction of the composite constructed wetland or the sponge city module, so that plant growth is promoted to form ecological carbon sink; in addition, pyrolysis gas generated by the carbonization furnace during preparation of biochar is provided for the coal-fired power plant, and tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant; after sludge drying, conveying high ammonia nitrogen organic wastewater generated when the sludge drying production line dries sludge into the autotrophic nitrogen removal treatment facility, removing organic matters, ammonia nitrogen and total nitrogen in the wastewater by the autotrophic nitrogen removal treatment facility, and conveying treated effluent back to the town sewage treatment plant, wherein the residual wastewater sludge generated after the wastewater is treated by the autotrophic nitrogen removal treatment facility is used as a strain for sale;
meanwhile, tail water of the town sewage treatment plant is sent into the composite constructed wetland for deep purification, and the reclaimed water after deep purification is used for river ecological supplementing water or municipal water; the urban precipitation or agricultural non-point source sewage is trapped and purified by the sponge urban module, and the trapped and purified reclaimed water is used for river ecological supplementing water; plant residues generated by the town sewage treatment plant and the sponge city module are mixed with the dried sludge and then sent to the carbonization furnace for preparing biochar; the porous filler in the town sewage treatment plant and the sponge city module is transported to the coal-fired power plant for incineration power generation after several years of use.
2. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: in a set of excess sludge recycling and energy utilization system, the matched number of the urban domestic sewage treatment plants is multiple or single, and the urban domestic sewage treatment plants are arranged close to the composite constructed wetland; the sludge drying production line, the coal-fired power plant and the carbonization furnace are respectively arranged close to the autotrophic nitrogen removal treatment facility.
3. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1 or 2, characterized in that: the utilization ratio of the sludge energy utilization path and the sludge recycling path is set according to the actual surplus sludge yield, and the sludge recycling path is preferentially utilized in comparison with the sludge energy utilization path.
4. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the surplus sludge produced by the urban sewage treatment plant comprises redundant activated sludge produced by a secondary biochemical treatment system and a small amount of chemical sludge from a coagulating sedimentation process, the solid content of the surplus sludge is 10% -20% after the dehydration treatment in the urban sewage treatment plant, and the heavy metal content meets the B-level requirement of GB 4284-2018; the town sewage treatment plant adopts electric transport vehicles to transport surplus sludge to the sludge drying production line, and the electric transport vehicles are charged by charging stations around the sludge drying production line preferentially so as to reduce energy loss caused by power transmission.
5. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the sludge drying production line adopts a two-stage process of a thin layer evaporator and a belt dryer, the thickness of a sludge layer is controlled to be 8-15 mm, waste heat steam of the coal-fired power plant is used as a heat source, the temperature of the waste heat steam is 180-200 ℃, the steam quantity required for drying each ton of residual sludge is 0.5-0.8 t, the drying treatment time is 2-3 h, the solid content of the dried residual sludge is increased to 80% -90%, the heating value is not lower than 3000 kcal/kg, and the waste heat of the belt dryer can be recycled to the thin layer evaporator.
6. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the autotrophic nitrogen removal treatment facility adopts a combined process of an anaerobic expanded granular sludge bed and an integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor to treat high ammonia nitrogen organic wastewater generated in a sludge drying process; wherein,
the anaerobic expanded granular sludge bed mainly removes organic matters in high ammonia nitrogen organic wastewater, creates low C/N ratio conditions for denitrification of the autotrophic organisms at the later stage, and feeds COD (chemical oxygen demand) Cr The load is controlled to be 3-5 kg (m) 3 D), purifying the generated biogas for preheating a production line;
the integrated nitrosation/anaerobic ammoxidation granular sludge reactor realizes autotrophic removal of ammonia nitrogen and total nitrogen in high ammonia nitrogen organic wastewater, and the load of influent ammonia nitrogen is controlled to be 0.5-1.5 kg (m) 3 D), the sludge age is 35-50 d, the particle size of the particles is 0.5-1.25 mm, anaerobic ammonia oxidizing bacteria in the particle sludge are mainly Candidatus Brocadia and Candidatus Kuenenia, and the relative abundance is 25% -50%;
COD (chemical oxygen demand) of high ammonia nitrogen organic wastewater by adopting combined process of anaerobic expanded granular sludge bed and integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor of autotrophic nitrogen treatment facility Cr The ammonia nitrogen removal rate is more than 80%, the treated effluent is superior to GB/T31962-2015, and the treated effluent is sent to the town sewage treatment plant through a sewer;
in addition, the high added value surplus sludge generated after the high ammonia nitrogen organic wastewater is treated by the combined process of the anaerobic expanded granular sludge bed and the integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor adopted by the autotrophic nitrogen treatment facility can be used as a strain for external sale.
7. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the sludge drying production line is used for adding 2-10% of MgCl after mixing part of dried sludge directly or with plant residues 2 As an activating agent, the activated agent is sent to the carbonization furnace for rolling and heating for 1.5 to 3 hours at the temperature of 500 to 800 ℃ under the condition of air isolation to prepare sludge-based or mixed-based biochar, and 1 ton of biochar is prepared from 10 tons of dried sludge or the mixture of the dried sludge and plant residues, wherein the specific surface area of the biochar is more than 50m 2 Per gram, the pH of the surface is 8.0-9.0, the density is 0.7-1.0 kg/m 3 ；
The pyrolysis gas generated in the early stage of carbonization contains a large amount of volatile matters and non-condensable gas, and is sent to a boiler of the coal-fired power plant, burned at 850-1000 ℃, and tail gas treatment is carried out by utilizing pollution control measures matched with the coal-fired power plant, so that the ultra-clean emission standard is achieved;
the prepared sludge-based or mixed-based biochar is prepared into porous filler by adopting a 3D printing technology and is used for constructing the composite constructed wetland or the sponge city module so as to promote plant growth in the composite constructed wetland or the sponge city module to form ecological carbon sink;
after several years of use, the porous filler is transported to the coal-fired power plant and the final disposal is completed by incineration power generation.
8. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the sludge drying production line is characterized in that part of dried sludge is fully mixed with coal according to the mass ratio of 2% -10%, crushed into particles with the particle size of 120-200 meshes, and sent to a boiler of a coal-fired power plant for combustion and power generation, so that sludge energy utilization is realized; the boiler of the coal-fired power plant adopts a supercritical coal-fired unit, and the thermal efficiency reaches more than 40%; waste heat steam generated by a boiler of the coal-fired power plant is supplied to the sludge drying production line as a heat source, and electric energy generated by the coal-fired power plant is supplied to the sludge drying production line or the carbonization furnace as energy.
9. The method for recycling and utilizing energy of excess sludge of urban sewage treatment plants according to claim 1, which is characterized in that: the composite constructed wetland consists of a subsurface flow wetland and a surface flow wetland and is used for deeply purifying tail water of the urban sewage treatment plant, and the effluent after deep purification is used for river ecological makeup water or municipal water; the sponge city module is made of porous materials with high water permeability and is used for intercepting and purifying non-point source polluted water in a built-up area, and the intercepted and purified water is used for ecologically supplementing water in a river channel.
10. The method for recycling and utilizing energy of excess sludge of town sewage treatment plants according to claim 9, wherein the method comprises the following steps: porous fillers prepared by 3D printing of sludge-based biochar are preferentially adopted in the composite constructed wetland and the sponge city module, then a soil layer is paved on the surface layer of the porous material, aquatic plants are planted in a configuration mode, and ecological carbon sinks are formed while nitrogen and phosphorus pollutants in water are effectively reduced; harvesting plants on the porous filler in autumn and winter each year, crushing the plants to 40-80 meshes, fully mixing the crushed plants with the dried sludge, and delivering the mixture to a carbonization furnace to prepare the mixed-base biochar.
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| EP2692701A1 (en) * | 2012-07-31 | 2014-02-05 | Gabriel Marius Rus | Process and plant for wastewater treatment and energy generation |
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| EP2692701A1 (en) * | 2012-07-31 | 2014-02-05 | Gabriel Marius Rus | Process and plant for wastewater treatment and energy generation |
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