CN115650547A - Method for recycling and energy utilization of excess sludge of urban sewage treatment plant - Google Patents
Method for recycling and energy utilization of 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 an excess sludge recycling and energy utilization system constructed by mutually connecting a plurality of units including the town sewage treatment plant, a sludge drying production line, a coal-fired power plant, a dry distillation type carbonization furnace, an autotrophic biological denitrification treatment facility and a composite artificial wetland or sponge city module, wherein the excess sludge recycling and energy utilization system comprises a sludge energy utilization method and a sludge recycling utilization method. The invention can realize higher energy and resource utilization rate by means of the ways of sludge electric vehicle transportation, waste heat steam circulation, dried sludge mixed combustion, porous filler preparation, aquatic plant carbon sink, waste filler phosphorus recovery and the like, and provides a systematic control scheme for various pollution discharges such as high ammonia nitrogen wastewater, carbonized pyrolysis gas, aquatic plant harvest residues and the like.
Description
Technical Field
The invention belongs to the technical field of sludge resource utilization, and particularly relates to a method for resource utilization and energy utilization of excess sludge of a municipal sewage plant.
Background
In recent years, a lot of breakthroughs are made in the fields of key technologies for sludge treatment and complete equipment at home and abroad, and 4 main technical routes such as anaerobic digestion and land utilization, aerobic fermentation and land utilization, drying incineration and ash landfill or building material utilization, deep dehydration and sanitary landfill and the like are mostly adopted in combination with practical situations in various places.
Researches show that the carbon emission intensity of a main technical route is in accordance with the following aspects of energy consumption and chemical consumption, dissipative greenhouse gas emission, energy resource recovery convenience and the like in the sludge treatment and disposal process by comprehensive consideration: the method comprises the steps of anaerobic digestion and land utilization, namely, aerobic fermentation and land utilization, namely, drying incineration and ash landfill, and further comprises deep dehydration and sanitary landfill. At present, sludge anaerobic digestion or aerobic composting facilities are not widely used in domestic town sewage treatment plants. On one hand, the organic matter content in domestic excess sludge is low, and the sludge digestion effect and the stability are difficult to reach the foreign application level (the reduction is more than 40 percent); on the other hand, domestic sewage plants generally lack the operation management experience of related facilities, and greenhouse gases, organic matter residues and high-concentration wastewater generated in the process still need to be effectively controlled and subjected to harmless treatment or resource utilization. The above problems make the popularization and application of such technical routes face huge investment pressure.
In order to solve the problem of low-carbon treatment and disposal of excess sludge in urban sewage treatment plants, centralized drying incineration has become a preferred technical route for a plurality of large and medium-sized cities in China, but a sludge recycling technical system matched with the centralized drying incineration is not sound. Material flow and energy flow barriers still exist among sludge reduction, stabilization, harmless and recycling treatment and treatment units, and the aims of energy conservation, consumption reduction and resource and energy recovery are difficult to effectively cooperate. For example, the sludge drying process needs to consume a large amount of external energy and generate high ammonia nitrogen organic wastewater which is difficult to treat, which puts high requirements on matching energy and environment-friendly infrastructure. For another example, self-sustaining incineration of sludge generally requires that the organic matter content is higher than 40-50%, the actual sludge properties in many regions are lower than the standard, combustion improver needs to be additionally consumed, and the treatment cost and carbon emission are increased. In addition, resource recycling paths (such as phosphorus recovery) of the incineration ash are still to be explored, and no obvious carbon compensation effect can be formed.
In view of this, the recycling and energy utilization of the excess sludge in the municipal sewage treatment plant are realized while enhancing the treatment efficiency of the sludge treatment, and the secondary pollution treatment, carbon emission reduction and technical economy are considered, so that the systematicness of the recycling and energy utilization of the excess sludge in the municipal sewage treatment plant needs to be further improved. How to get through material flow and energy flow barriers between sludge treatment and treatment, recycling and energy utilization, and further realize synergistic reduction of sludge, wastewater and waste gas and energy recycling becomes a key of sludge treatment and treatment technical innovation.
Disclosure of Invention
In order to solve the problems in the prior art, the invention aims to provide an environment-friendly method for recycling and energy utilization of excess sludge in a town sewage treatment plant, which has higher treatment efficiency.
In order to achieve the technical purpose and achieve the technical effect, the invention is realized by the following technical scheme:
a method for recycling and utilizing excess sludge of a town sewage treatment plant relies on an excess sludge recycling and energy utilization system which is constructed by mutually connecting a plurality of units including the town sewage treatment plant, a sludge drying production line, a coal-fired power plant, a dry distillation type carbonization furnace, an autotrophic biological denitrification treatment facility and a composite artificial wetland or sponge city module. The excess sludge recycling and energy utilization system comprises a sludge energy utilization path and a sludge resource utilization path. Wherein,
the specific method of the sludge energy utilization path comprises the following steps:
conveying surplus sludge generated after sewage is treated by the urban sewage treatment plant to the sludge drying production line, drying the surplus sludge by the sludge drying production line, then conveying the dried sludge to the coal-fired power plant, mixing the dried sludge with fire coal by the coal-fired power plant to generate power, supplying the generated electric energy to the sludge drying production line and the dry distillation type carbonization furnace to be used as energy, and simultaneously supplying waste heat steam generated by power generation of the coal-fired power plant to the sludge drying production line to be used as a heat source;
the concrete method of the sludge resource utilization path comprises the following steps:
conveying excess sludge generated after sewage treatment by the urban sewage treatment plant to the sludge drying production line, and drying the excess sludge by the sludge drying production line; after the sludge is dried, conveying the dried sludge to a dry distillation type carbonization furnace, wherein the dry distillation type carbonization furnace utilizes the dried sludge to prepare biochar, and then the biochar is further prepared into porous filler which is used for constructing the composite artificial wetland or the sponge city module and promoting plant growth to form ecological carbon sink; in addition, pyrolysis gas generated by the carbonization furnace during the preparation of the biochar is supplied to the coal-fired power plant, and tail gas treatment is carried out by using pollution control measures matched with the coal-fired power plant; after sludge is dried, conveying high ammonia nitrogen organic wastewater generated when the sludge is dried by the sludge drying production line into the autotrophic biological denitrification treatment facility, removing organic matters, ammonia nitrogen and total nitrogen in the wastewater by the autotrophic biological denitrification treatment facility, and conveying treated effluent to the town sewage treatment plant, wherein residual sludge of the wastewater generated after the wastewater is treated by the autotrophic biological denitrification treatment facility is used as a strain sold to the outside;
meanwhile, tail water of the urban sewage treatment plant is sent into the composite artificial wetland for deep purification, and the regenerated water after deep purification is used as ecological supplementary water of a river channel or municipal water; the sponge city module is intercepted and purified by sewage such as urban rainfall or agricultural non-point source, and the intercepted and purified reclaimed water is used as ecological make-up water of a river channel; plant residues generated by the urban sewage treatment plant and the sponge city module are mixed with dried sludge and then are sent to the dry distillation type carbonization furnace for preparing biochar; the porous packing in the municipal sewage plant and the sponge city module is transported to the coal-fired power plant for incineration power generation after years of use.
Furthermore, in a set of excess sludge recycling and energy utilization system, a plurality of or a single urban domestic sewage treatment plant can be arranged near the composite artificial wetland; the sludge drying production line, the coal-fired power plant and the dry distillation type carbonization furnace are respectively arranged close to the autotroph denitrification treatment facility.
Further, the use proportion of the sludge recycling path and the sludge recycling path is set according to actual requirements; when the number of the urban sewage treatment plants is large and the output of the excess sludge is large, simultaneously using the sludge resource utilization path and the sludge energy utilization path to simultaneously carry out energy utilization and resource utilization of the sludge; and when the number of the urban sewage treatment plants is small and the output of the excess sludge is small, preferentially using the sludge resource utilization path and preferentially carrying out the resource utilization of the sludge.
Furthermore, the town sewage treatment plant is mainly used for treating sewage generated by daily life or commercial and cultural activities of town residents, and is not used for treating industrial wastewater containing toxic and harmful substances such as heavy metals; the excess sludge produced by the urban sewage treatment plant mainly comprises excess activated sludge produced by a secondary biochemical treatment system and a small amount of chemical sludge produced by a coagulating sedimentation process, after dehydration treatment in the urban sewage treatment plant, the solid content of the excess sludge is 10-20%, and the heavy metal content meets the B-grade requirement of the pollutant control standard in agricultural sludge (GB 4284-2018).
Further, the town sewage treatment plant adopts an electric transport vehicle to transport the residual sludge to the sludge drying production line, and the electric transport vehicle preferentially uses charging stations around the sludge drying production line for charging so as to reduce energy loss caused by electric power transmission.
Furthermore, the sludge drying production line preferably adopts a two-stage process of a thin-layer evaporator and a belt dryer, the thickness of the sludge layer is controlled within 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 to be consumed 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 determination method GB/T213-2008), and the waste heat of the belt dryer can be circularly used for the thin-layer evaporator.
Furthermore, the autotrophic biological denitrification 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, smaller sludge yield and no need of setting internal sludge reflux; wherein the anaerobic expanded granular sludge bed is mainly used for removing organic matters in the high-ammonia nitrogen organic wastewater and creating low C/N ratio strips for the denitrification of the autotrophs at the later stageMember, COD of inlet water Cr The load is controlled to be 3 to 5kg (m) 3 D), the biogas produced is purified and then used for preheating the production line; the integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor can realize autotrophic removal of ammonia nitrogen and total nitrogen in high ammonia nitrogen organic wastewater, and the ammonia nitrogen load of inflow water is controlled to be 0.5 to 1.5kg (m) 3 D), the sludge age is 35-50d, the particle size of the particles is 0.5-1.25 mm, anaerobic ammonium oxidation bacteria in the particle sludge mainly comprise Candidatus Brocadia and Candidatus Kuenenia, and the relative abundance is 25-50%; the combined process of 'anaerobic expanded granular sludge bed + integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor' adopted by the autotrophic biological denitrification treatment facility is used for treating COD (chemical oxygen demand) of high ammonia nitrogen organic wastewater Cr The removal rate of ammonia nitrogen is more than 80 percent, the treated effluent is superior to the water quality standard of sewage discharge to town sewers (GB/T31962-2015), and the treated effluent is sent to the town sewage treatment plant through a sewer.
Furthermore, the residual sludge with high added value 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 biological denitrification treatment facility can be used as a strain for sale, so that the system operation cost is reduced.
Further, the sludge drying production line adds 2 to 10 percent of MgCl directly or after mixing part of dried sludge with plant residues 2 Sending the biomass into the dry distillation type carbonization furnace as an activating agent, 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, wherein about 1 ton of biochar is prepared per 10 tons of dried sludge (containing part of plant residues), and the specific surface area (BET) of the biochar is more than 50m 2 The surface pH value is 8.0 to 9.0, and the density is 0.7 to 1.0 kg/m 3 (ii) a Pyrolysis gas generated in the earlier stage of carbonization contains a large amount of volatile components and non-condensable gas, is sent to a boiler of the coal-fired power plant, is burned at 850-1000 ℃, and is subjected to tail gas treatment by using pollution control measures matched with the coal-fired power plant, so that an ultra-clean emission standard is achieved; preparing biological carbon into porous filler by using a 3D printing technology, and using the porous filler for constructing the composite artificial wetland or the sponge city module to promote the composite artificial wetlandAnd plants in the wetland or the sponge city module grow to form ecological carbon sink, so that resource utilization is realized.
Further, after years of use, the porous filler is transported to the coal-fired power plant and is finally disposed of by incineration power generation.
Further, the sludge drying production line fully mixes the other part of dried sludge with the fire coal according to the mass ratio of 2-10%, the mixture is crushed into particles with the particle size of 120-200 meshes, and the particles are sent to a boiler of the coal-fired power plant for combustion and power generation, so that the energy utilization of the sludge is realized; the boiler of the coal-fired power plant adopts a supercritical coal-fired unit, and the heat efficiency reaches more than 40%; waste heat steam that coal fired power plant boiler produced supplies with sludge drying production line is as the heat source, the electric energy that coal fired power plant produced supplies with sludge drying production line or the dry distillation formula carbide furnace realizes the energy circulation as the energy.
Furthermore, the composite artificial wetland is generally composed of a subsurface flow wetland and a surface flow wetland and is mainly used for deep purification of tail water of the urban sewage treatment plant, and effluent of the composite artificial wetland is used for ecological supplementary water or municipal water of a river channel.
Furthermore, the sponge city module is usually made of a porous material with high water permeability and is mainly used for surface source pollution interception and purification of built areas such as urban rainfall, agricultural surface sources and the like, and the effluent of the sponge city module is used as ecological make-up water of riverways.
Furthermore, the composite artificial wetland and the sponge city module preferentially adopt the sludge-based biochar 3D printing prepared porous filler, then a soil layer is laid on the surface layer of the porous filler and aquatic plants are planted in the porous filler, and ecological carbon sink can be formed while pollutants such as nitrogen and phosphorus in water are effectively reduced.
Further, harvesting plants on the surface layer of the porous filler in autumn and winter every year, crushing the plants to 40-80 meshes, fully mixing plant residues with dried sludge, and sending the mixture to a dry distillation type carbonization furnace to prepare the mixed-base biochar.
Furthermore, after the porous fillers in the urban sewage treatment plant and the sponge city module are used for years, the porous fillers can be conveyed to the coal-fired power plant for incineration power generation, so that resource recycling is realized.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention combines the treatment and disposal of the excess sludge of the sewage plant with the energy substance circulating unit, does not need to carry out large-scale transformation on the existing facilities, and can effectively control the construction investment cost; particularly, the sludge drying production line, the coal-fired power plant, the dry distillation type carbonization furnace, the autotrophic biological denitrification treatment facility, the composite artificial wetland or sponge city module and other units are combined for use, so that the synergistic pollution reduction and carbon reduction effects of the whole flow of sludge treatment can be obviously improved, heavy metals in sludge are converted into stable residue states, the leachability and the biological effectiveness are greatly reduced, and the environmental risk is effectively controlled.
2. Compared with the current mainstream technical route of sludge treatment and disposal, 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-combustion, porous filler preparation, aquatic plant carbon sink, waste filler disposal and the like, and provides a systematic control scheme for discharging various pollutants such as high ammonia nitrogen wastewater, carbonized pyrolysis gas, aquatic plant harvest residues and the like;
firstly, compared with the traditional fuel oil vehicle, the invention adopts the electric vehicle to transport, which can effectively reduce the carbon emission in the dehydrated sludge transportation process, meanwhile, the sludge drying plant and the coal-fired power plant are arranged in a centralized way, the vehicle charging is carried out around the power plant, and the loss in the power transmission process can also be reduced;
secondly, the sludge drying production line adopts a two-stage process of a thin-layer evaporator and a belt dryer, and can obviously reduce the steam consumption of sludge drying by controlling the thickness of a sludge layer and energy recovery; the salt content of the high ammonia nitrogen organic wastewater generated by drying is lower than that of the traditional sludge digestive juice, the microbial inhibition effect is weaker, and the method is suitable for treating by using a combined process of an anaerobic expanded 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 disclosed by the invention not only can effectively remove indexes such as organic matters, ammonia nitrogen and total nitrogen in the wastewater, but also has lower energy and carbon source consumption in the treatment process, generates the excess sludge with high added value, and is beneficial to reducing the system operation cost;
thirdly, the dried sludge, the carbonized pyrolysis gas and the waste biochar filler are delivered to a boiler of a coal-fired power plant for incineration, so that the emission of atmospheric pollutants can be effectively reduced, and electric power is provided for sludge carbonization; the tail water purification wetland of the sewage plant and the sponge city module harvest aquatic plants in autumn and winter, can effectively avoid the loss of nutritive salt in plants to water, and prepares biochar by mixing with sludge, so that most nutritive salt is fixed, the biochar has higher slow-release fertility, and the problem of biomass waste disposal is also solved.
3. The invention can flexibly adjust the ratio of subsequent resource utilization and energy utilization 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 residues are used as one of raw materials for preparing the biochar, so that the porosity of the biochar in sludge 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 the raw material of the 3D printing porous filler, so that the urgent requirements of sewage plant tail water ecological purification and sponge city construction on various types of porous fillers can be met, the export problem of sludge resource products is effectively solved, and the biochar has good popularization and application prospects in upgrading and transformation of the domestic existing sludge treatment system.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is made with reference to the accompanying drawings. The detailed description of the present invention is 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 embodiment(s) of the invention and together with the description serve to explain the invention and do not constitute a limitation of the invention. In the drawings:
FIG. 1 is a schematic block diagram of a method for recycling and energy-recovering excess sludge from a plurality of municipal wastewater treatment plants according to embodiment 1 of the present invention;
FIG. 2 is a schematic block diagram of a resource utilization method of excess sludge from a single municipal wastewater treatment plant according to embodiment 2 of the invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments. The description set forth herein is intended to provide a further understanding of the invention and forms a part of this application and is to be construed as an exemplification of the invention and is not intended to limit the invention to the particular embodiments disclosed.
Example 1
9 urban sewage treatment plants are distributed in a certain area of the Taihu lake basin, a combined process of biochemical treatment and physicochemical/ecological advanced treatment is adopted, and the total treatment scale is about 75 ten thousand meters 3 (per) about 200 ten thousand meters of composite artificial wetland area for tail water purification 2 . The annual water content of dewatered sludge produced by urban sewage treatment plants is 80 percent (the solid content is 20 percent), the dewatered sludge is about 20.6 ten thousand tons, and the heavy metal content meets the B-grade requirement of pollutant control standard in agricultural sludge (GB 4284-2018). Except for a small amount of dewatered sludge which is treated by anaerobic digestion, other parts are subjected to resource utilization and energy utilization by adopting the method, and the method is shown in figure 1.
The dewatered sludge of the 9 urban sewage treatment plants is periodically transported to a sludge drying production line close to a large-scale coal-fired power plant by adopting an electric transport vehicle. The electric transportation vehicle preferentially uses charging stations around the sludge drying production line to charge so as to reduce energy loss caused by electric power transmission. A coal-fired power plant is provided with 2 supercritical coal-fired power generating sets with the grade of 60 ten thousand kilowatts, and the supercritical coal-fired power generating sets can be used for generating electricity by mixing and burning sludge. The number of the sludge drying production lines is 2, the drying capacity is 300 multiplied by 2 t/d, and the daily dry sludge is 133 t/d. The sludge drying adopts a two-stage process of a thin-layer evaporator and a belt dryer, the thickness of the sludge layer is controlled within 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, the steam consumption required by drying each ton of sludge is 0.5-0.8t, and 0.6 t is preferred in the embodiment. The drying process is 2 to 3 hours, 2.5 h is preferred in the embodiment, the dried sludge is granular, the solid content is increased to 80 to 90 percent, the specific value of the embodiment is about 85 percent, the calorific value is not lower than 3000 kcal/kg, and the embodiment is about 3100 kcal/kg. The belt dryer waste heat can be recycled to the thin layer evaporator.
The wastewater yield of the sludge drying process is about 400 m 3 /d，COD Cr The concentration of the ammonia nitrogen and the total nitrogen is 2500 to 3000 mg/L, 250 to 300 mg/L and 300 to 360 mg/L respectively. A wastewater treatment facility (autotrophic denitrification treatment facility) 1 group of anaerobic Expanded Granular Sludge Bed (EGSB) + integrated nitrosation/anaerobic ammonia oxidation (PN/A) granular sludge reactor is constructed near the matched facility. Wherein, EGSB influent COD Cr The load is controlled to be 3 to 5kg (m) 3 D), this embodiment is preferably 3.5 kg (m) 3 D) the biogas produced is used for preheating the production line after carbon dioxide removal; controlling the inflow ammonia nitrogen load of the PN/A granular sludge reactor to be 0.5 to 1.5kg (m) 3 D), this embodiment is preferably 0.8 kg (m) 3 D), the sludge age is 35-50 d, the sludge age is about 40 d in the embodiment, the particle size is 0.5-1.25 mm, the anaerobic ammonium oxidation bacteria in the granular sludge are mainly Candidatus Brocadia and Candidatus Kuenenia, the relative abundance is 25% -50%, and the relative abundance of the anaerobic ammonium oxidation bacteria Candidatus Brocadia and Candidatus Kuenenia in the embodiment is preferably 34%; the combined process of 'anaerobic expanded granular sludge bed + integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor' adopted by the autotrophic biological denitrification treatment facility can be used for selling high-value-added excess sludge generated after the high-ammonia-nitrogen organic wastewater is treated as strains 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 effluent COD Cr The concentration of ammonia nitrogen and the total nitrogen are respectively lower than 450 mg/L, 35 mg/L and 70 mg/L, which are superior to the A-level water quality standard of sewage discharge to town sewers (GB/T31962-2015), and the sewage is delivered to a town sewage treatment plant through a sewer.
About 40 percent of the dried sludge is directly added with MgCl of about 2 to 10 percent after being mixed with the plant residues of the compound artificial wetland or after being mixed with the plant residues of the compound artificial wetland 2 As the activator, 5% is preferable in this exampleMgCl of 2 As an activating agent, the active agent is sent to a double-barrel dry distillation type carbonization furnace, and is rolled and heated for 1.5 to 3 hours under the conditions of 500 to 800 ℃ and air isolation to prepare sludge-based biochar or mixed-based biochar, in the embodiment, the active agent is preferably rolled and heated for 2 h under the conditions of 700 ℃ and air isolation, the yield is about 5.5 t/d, and the specific surface area (BET) of the biochar is more than 50m 2 The surface pH value is 8.0 to 9.0, and the density is 0.7 to 1.0 kg/m 3 . Pyrolysis gas generated in the earlier stage of sludge carbonization contains a large amount of volatile components and non-condensable gas, is sent to a boiler of a coal-fired power plant, is burnt at 850-1000 ℃, and is subjected to tail gas treatment by using pollution control measures matched with the coal-fired power plant to reach an ultra-clean emission standard, wherein the emission concentrations of smoke dust, sulfur dioxide and nitrogen oxide are respectively not higher than 10mg/m 3 、35mg/m 3 And 50mg/m 3 . By using a 3D printing technology, adding a binder such as sodium diatomate and the like, preparing biochar into porous filler balls, using the porous filler balls for filler renewal of a composite artificial wetland, effectively promoting the growth of various plants such as reed, cattail, allium mongolicum and the like, forming an ecological carbon sink, and using purified water as a riverway water supply source. Harvesting plants in autumn and winter every year, crushing the plants to 40 to 80 meshes, mixing the crushed plants with the dried sludge to be used as a raw material for preparing the biochar, and obviously improving the porosity of the biochar. After the porous filler is used for years, final disposal can be realized by adopting incineration power generation, and resource utilization of sludge is realized.
Mixing the residual 60% of the dried sludge with the fire coal according to the mass ratio of 5%, crushing the mixture into particles with the particle size of 120-200 meshes, sending the particles into a boiler of a coal-fired power plant for combustion and power generation, providing steam and electric energy for a sludge drying production line and a dry distillation type carbonization furnace, and realizing energy utilization of the sludge.
Example 2
In a certain area of the long triangle, 1 large-scale town sewage treatment plant and 1 coal-fired power plant are centrally built. The town sewage treatment plant adopts a combined process of biochemical treatment and physicochemical advanced treatment, and the total treatment scale is about 20 ten thousand meters 3 And d. The annual water content of dewatered sludge produced by urban sewage treatment plants is 80 percent (the solid content is 20 percent), the dewatered sludge is about 2.8 ten thousand tons, and the heavy metal content meets the B-grade requirement of pollutant control standard in agricultural sludge (GB 4284-2018). All the sludge is recycled and energy-utilized by adopting the inventionAs shown in fig. 2.
And (4) adopting an electric transport vehicle to transport the dewatered sludge of the urban sewage treatment plant to a sludge drying production line regularly. The electric transportation vehicle preferentially uses charging stations around the sludge drying production line to charge so as to reduce energy loss caused by electric power transmission. A coal-fired power plant is provided with 2 supercritical coal-fired power generating sets with the grade of 30 ten thousand kilowatts, and the supercritical coal-fired power generating sets can be used for generating electricity by mixing and burning sludge. The number of the sludge drying production lines is 2, the design drying capacity is 200 t/d, and the daily produced dry sludge is about 40 t. The sludge drying adopts a two-stage process of a thin-layer evaporator and a belt dryer, the thickness of the sludge layer is controlled within 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, the steam consumption required by drying each ton of sludge is 0.5-0.8t, and 0.7 t is preferred in the embodiment. The drying process is 2 to 3 hours long, preferably 2.5 h is adopted in the embodiment, the dried sludge is granular, the solid content is increased to about 80 to 90 percent, specifically about 85 percent in the embodiment, the heat productivity is not lower than 3000 kcal/kg, and about 3160 kcal/kg in the embodiment. The belt dryer waste heat can be recycled to the thin layer evaporator.
The wastewater yield of the sludge drying process is about 150 m 3 /d，COD Cr The concentration of ammonia nitrogen and the total nitrogen are 2000 mg/L, 300 mg/L and 350 mg/L respectively. A wastewater treatment facility (autotrophic denitrification treatment facility) 1 group of anaerobic Expanded Granular Sludge Bed (EGSB) + integrated nitrosation/anaerobic ammonia oxidation (PN/A) granular sludge reactor is constructed near the matched facility. Wherein, EGSB influent COD Cr The load is controlled to be 3 to 5kg (m) 3 D), this embodiment is preferably 3.0 kg (m) 3 D), the biogas produced is purified and then used for preheating the production line; controlling the inflow ammonia nitrogen load of the PN/A granular sludge reactor to be 0.5 to 1.5kg (m) 3 D), this embodiment is preferably 1.2 kg (m) 3 D), the sludge age is 35 to 50d, the sludge age is about 42 d in the embodiment, the particle size is 0.5 to 1.25 mm, the anaerobic ammonium oxidation bacteria in the granular sludge are mainly Candidatus Brocadia and Candidatus Kuenenia, the relative abundance is 25 to 50 percent, and the relative abundance of the anaerobic ammonium oxidation bacteria Candidatus Brocadia and Candidatus Kuenenia in the embodiment is preferably 42 percent; anaerobic expanded granular sludge adopted by autotrophic biological denitrification treatment facilityThe bed and integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor combined process can be used for treating the high-ammonia nitrogen organic wastewater to generate high-value-added excess sludge which can be used as strains for external sale so as to reduce the system operation cost; effluent COD of combined process Cr The concentration of ammonia nitrogen and the total nitrogen are respectively lower than 400 mg/L, 30 mg/L and 70 mg/L, reach the A-grade of the Water quality Standard for wastewater discharge into urban sewerage (GB/T31962-2015), and are delivered to an urban wastewater treatment plant through a sewer.
Adding MgCl with the content of about 2-10% directly or after mixing the dried sludge with plant residues of sponge city modules 2 As an activator, 10% MgCl is preferred in this example 2 As an activating agent, the biomass is sent to a double-drum dry distillation type carbonization furnace, and is rolled and heated for 1.5 to 3 hours under the conditions of 500 to 800 ℃ and air isolation to prepare the sludge-based or mixed-based biochar, the biomass is preferably rolled and heated for 2 h under the conditions of 700 ℃ and air isolation in the embodiment, the yield is about 4.5 t/d, and the specific surface area (BET) of the biochar>50 m 2 The surface pH value is 8.0 to 9.0, and the density is 0.7 to 1.0 kg/m 3 . Pyrolysis gas generated in the earlier stage of sludge carbonization contains a large amount of volatile components and non-condensable gas, is sent to a boiler of a coal-fired power plant, is burnt at 850-1000 ℃, is subjected to tail gas treatment by using pollution control measures matched with the coal-fired power plant, achieves ultra-clean emission standards, and has the emission concentrations of smoke dust, sulfur dioxide and nitrogen oxide of not higher than 10mg/m 3 、35mg/m 3 And 50mg/m 3 . And (3) adding a binding agent such as sodium diatomate and the like by using a 3D printing technology, and preparing the biochar into porous filler for updating the sponge city module. The porous filling material of the sponge city module is planted with various plants such as reed, calamus, canna and the like, and the purified water is used as a riverway water supply source. The plants are harvested in autumn and winter every year, and the plants and the dried sludge are jointly used for preparing the mixed-base biochar, so that resource utilization is realized.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement 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 utilization of excess sludge of a town sewage treatment plant is characterized by comprising the following steps: the method relies on a surplus sludge recycling and energy utilization system which is constructed by mutually connecting a plurality of units including a town sewage treatment plant, a sludge drying production line, a coal-fired power plant, a dry distillation type carbonization furnace, an autotrophic biological denitrification treatment facility and a composite artificial wetland or sponge city module; the excess sludge recycling and energy utilization system comprises a sludge energy utilization path and a sludge resource utilization path, wherein,
the specific method of the sludge energy utilization path comprises the following steps:
conveying excess sludge generated after sewage treatment by the urban sewage treatment plant to the sludge drying production line, drying the excess sludge by the sludge drying production line, then conveying the dried sludge to the coal-fired power plant, mixing the dried sludge with fire coal by the coal-fired power plant to generate power, supplying the generated electric energy to the sludge drying production line and the dry distillation type carbonization furnace to be used as energy, and simultaneously supplying waste heat steam generated by power generation of the coal-fired power plant to the sludge drying production line to be used as a heat source;
the concrete method of the sludge resource utilization path comprises the following steps:
conveying excess sludge generated after sewage treatment by the urban sewage treatment plant to the sludge drying production line, and drying the excess sludge by the sludge drying production line; after the sludge is dried, conveying the dried sludge to a dry distillation type carbonization furnace, wherein the dry distillation type carbonization furnace utilizes the dried sludge to prepare biochar, and then the biochar is further prepared into porous filler which is used for constructing the composite artificial wetland or the sponge city module and promoting plant growth to form ecological carbon sink; in addition, pyrolysis gas generated when the carbonization furnace is used for preparing the biochar is provided for the coal-fired power plant, and tail gas treatment is carried out by using pollution control measures matched with the coal-fired power plant; after sludge is dried, conveying high ammonia nitrogen organic wastewater generated when the sludge is dried by the sludge drying production line into the autotrophic biological denitrification treatment facility, removing organic matters, ammonia nitrogen and total nitrogen in the wastewater by the autotrophic biological denitrification treatment facility, and conveying treated effluent to the town sewage treatment plant, wherein residual sludge of the wastewater generated after the wastewater is treated by the autotrophic biological denitrification treatment facility is used as a strain sold to the outside;
meanwhile, tail water of the urban sewage treatment plant is sent into the composite artificial wetland for deep purification, and the regenerated water after deep purification is used as ecological supplementary water of a river channel or municipal water; the sponge city module is intercepted and purified by sewage such as urban rainfall or agricultural non-point source, and the intercepted and purified reclaimed water is used as ecological make-up water of a river channel; plant residues generated by the urban sewage treatment plant and the sponge city module are mixed with dried sludge and then are sent to the dry distillation type carbonization furnace for preparing biochar; the porous packing in the municipal sewage plant and the sponge city module is transported to the coal-fired power plant for incineration power generation after years of use.
2. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: in a set of excess sludge recycling and energy utilization system, the number of the urban domestic sewage treatment plants is multiple or single, and the excess sludge recycling and energy utilization system is arranged close to the composite artificial wetland; the sludge drying production line, the coal-fired power plant and the dry distillation type carbonization furnace are respectively arranged close to the autotroph denitrification treatment facility.
3. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1 or 2, wherein: the utilization ratio of the sludge energy utilization path and the sludge resource utilization path is set according to the actual excess sludge yield, and the sludge resource utilization path is preferentially used over the sludge energy utilization path.
4. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: the excess sludge generated by the urban sewage treatment plant comprises excess activated sludge generated by a secondary biochemical treatment system and a small amount of chemical sludge generated from a coagulating sedimentation process, after dehydration treatment in the urban sewage treatment plant, the solid content of the excess sludge is 10-20%, and the heavy metal content meets the B-grade requirement of the pollutant control standard in agricultural sludge; and the town sewage treatment plant adopts an electric transport vehicle to transport the residual sludge to the sludge drying production line, and the electric transport vehicle preferentially uses charging stations around the sludge drying production line for charging so as to reduce energy loss caused by electric power transmission.
5. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: 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 a coal-fired power plant is used as a heat source, the temperature of the waste heat steam is 180-200 ℃, the steam quantity required to be consumed for drying per ton of excess sludge is 0.5-0.8t, the drying treatment time is 2-3 h, the solid content of the dried excess sludge is increased to 80-90%, the heat productivity is not lower than 3000 kcal/kg, and the waste heat of the belt dryer can be recycled for the thin-layer evaporator.
6. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: the autotrophic biological denitrification 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 the high-ammonia nitrogen organic wastewater, creates a low C/N ratio condition for the denitrification of autotrophs at the later stage, and feeds water with COD Cr The load is controlled to be 3 to 5kg (m) 3 D), the biogas produced is purified and then used for preheating the production line;
the integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor realizes autotrophic removal of ammonia nitrogen and total nitrogen in high ammonia nitrogen organic wastewater, and the ammonia nitrogen load of inflow water is controlled to be 0.5 to 1.5kg (m) 3 D), the sludge age is 35-50 d, the particle size of the particles is 0.5-1.25 mm, anaerobic ammonium oxidation bacteria in the particle sludge mainly comprise Candidatus Brocadia and Candidatus Kuenenia, and the relative abundance is 25-50%;
the combined process of 'anaerobic expanded granular sludge bed + integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor' adopted by the autotrophic biological denitrification treatment facility is used for treating COD (chemical oxygen demand) of high ammonia nitrogen organic wastewater Cr The removal rate of ammonia nitrogen is more than 80 percent, the treated effluent is superior to the water quality standard of sewage discharged into town sewers, and the effluent is sent to the town sewage treatment plant through the sewer;
in addition, the combined process of the anaerobic expanded granular sludge bed and the integrated nitrosation/anaerobic ammonia oxidation granular sludge reactor adopted by the autotrophic biological denitrification treatment facility can be used for treating the high-ammonia nitrogen organic wastewater to generate high-value-added excess sludge which can be used as a strain for external sale.
7. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: the sludge drying production line adds 2-10% of MgCl directly or after mixing part of dried sludge with plant residues 2 As an activating agent, sending the biological carbon into the dry distillation type carbonization furnace, rolling and heating for 1.5 to 3 hours at 500 to 800 ℃ under the condition of air isolation to prepare sludge-based or mixed-based biochar, wherein 1 ton of biochar is prepared per 10 tons of dried sludge or the mixture of the dried sludge and plant residues, and the specific surface area of the biochar is more than 50m 2 The surface pH value is 8.0 to 9.0, and the density is 0.7 to 1.0 kg/m 3 ；
Pyrolysis gas generated in the early stage of carbonization contains a large amount of volatile components and non-condensable gas, is sent to a boiler of the coal-fired power plant, is burned at 850-1000 ℃, and is subjected to tail gas treatment by using pollution control measures matched with the coal-fired power plant to reach an ultra-clean emission standard;
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 artificial wetland or the sponge city module so as to promote plants in the composite artificial wetland or the sponge city module to grow to form ecological carbon sink;
after the porous filler is used for years, the porous filler is conveyed to the coal-fired power plant and is subjected to incineration power generation to finish final disposal.
8. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 1, wherein: the sludge drying production line fully mixes part of dried sludge with fire coal according to the mass ratio of 2-10%, the mixture is crushed into particles with the particle size of 120-200 meshes, and the particles are sent to a boiler of a coal-fired power plant for combustion and power generation, so that the energy utilization of the sludge is realized; the boiler of the coal-fired power plant adopts a supercritical coal-fired unit, and the heat efficiency reaches more than 40%; waste heat steam generated by the 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 dry distillation type carbonization furnace as energy.
9. The method for recycling and reusing the excess sludge of the town sewage treatment plant according to claim 1, wherein the method comprises the following steps: the composite artificial wetland consists of an undercurrent wetland and a surface current wetland and is used for deeply purifying tail water of the urban sewage treatment plant, and effluent after deep purification is used for river channel ecological supplementary water or municipal water; the sponge city module is made of porous materials with high water permeability and is used for intercepting and purifying surface source polluted water in a built area, and the intercepted and purified effluent is used for ecological replenishing water in a river channel.
10. The method for recycling and energy-recovering excess sludge from town sewage treatment plants according to claim 9, wherein: the composite artificial wetland and the sponge city module preferentially adopt sludge-based biochar 3D printing prepared porous fillers, then a soil layer is laid on the surface layer of the porous material, and aquatic plants are planted in the soil layer, so that ecological carbon sink is formed while pollutants such as nitrogen and phosphorus in water are effectively reduced; harvesting plants on the porous filler in autumn and winter every year, crushing the plants to 40-80 meshes, fully mixing the plants with the dried sludge, and sending the mixture to a dry distillation type carbonization furnace to prepare the mixed base biochar.
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| CN102285740A (en) * | 2010-06-21 | 2011-12-21 | 天津科技大学 | Non-waste treatment method for garbage leachate |
| EP2692701A1 (en) * | 2012-07-31 | 2014-02-05 | Gabriel Marius Rus | Process and plant for wastewater treatment and energy generation |
| CN112851029A (en) * | 2021-01-19 | 2021-05-28 | 苏州科技大学 | Water pollution purification and resource utilization system and application thereof |
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| CN102285740A (en) * | 2010-06-21 | 2011-12-21 | 天津科技大学 | Non-waste treatment method for garbage leachate |
| EP2692701A1 (en) * | 2012-07-31 | 2014-02-05 | Gabriel Marius Rus | Process and plant for wastewater treatment and energy generation |
| CN112851029A (en) * | 2021-01-19 | 2021-05-28 | 苏州科技大学 | Water pollution purification and resource utilization system and application thereof |
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