Method for resource utilization of household garbage

Abstract

The invention relates to a method for resource utilization of household garbage, which comprises the following steps: fully and harmlessly treating kitchen wastes in the household garbage by using dry anaerobic fermentation, using the generated biogas for power generation, and using the waste heat for providing the heat demand in a plant; the method comprises the following steps: performing high-purity separation on high-value plastic components (mainly PE / PP) and other rubber and plastics and textiles by utilizing washing flotation, and performing hot melting granulation on the plastic components to produce high-value regenerated plastic particles; magnetic metal, inert inorganic components, fermentation residual organic components and residual combustible components in the household garbage are fully separated through mechanical sorting, and four types of products including the magnetic metal, nutrient soil, gravel and RDF (Refuse Derived Fuel) are respectively formed. According to the method, high-quality separation of high-value components / organic components / inert components / combustible components in the household garbage is realized through the process combination of mechanical separation, biological treatment and heat treatment, so that the aim of recycling and comprehensively utilizing all the components of the household garbage is fulfilled.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid waste resource treatment, and relates to a method for resource utilization of domestic waste, and in particular to a method for realizing resource utilization of all components of urban and rural domestic waste. Background Art

[0002] There has been a lot of exploration of methods for resource-based treatment of domestic waste for many years, including multi-stage screening + anaerobic fermentation stabilization of organic matter + inorganic brick / board making process, as well as rough crushing + drying + pyrolysis gasification reduction process, etc., among which there are many cases of actual construction projects. However, due to the complexity of domestic waste components, there are few cases that can be successfully operated, and many projects have environmental emission problems, process technology problems, downstream market absorption problems, economic problems, etc. Fundamentally, the core factors are the matching of product solutions with downstream markets, how to effectively separate the various components in domestic waste, and how to achieve lower operating costs and higher quality resource products.

[0003] According to the "Methods for Sampling and Analysis of Domestic Waste" (CJ / T313 2009), the physical composition of domestic waste is divided into 11 categories, including kitchen waste, paper, rubber and plastic, textile, wood and bamboo, ash and soil, bricks, tiles and ceramics, glass, metal, others, and mixed. In the time dimension, with the improvement of residents' living standards and changes in lifestyles, various components have also undergone phased changes. For example, with the changes in lifestyles such as express logistics and take-out catering, the rubber and plastic components in domestic waste, especially film plastic components, have increased significantly. The kitchen waste category has also shown an increasing trend in proportion overall, while ash and soil, bricks, tiles and ceramics have shown a decreasing trend. Among them, kitchen waste is the main source of odor components in domestic waste. In the field of domestic waste resource utilization technology, how to achieve the harmlessness of polluting components and how to achieve high-purity separation of various resource products are key factors in achieving overall resource utilization.

[0004] For domestic waste, in addition to incineration, anaerobic fermentation is a commonly used harmless and resource-based process technology. However, both wet anaerobic fermentation and dry anaerobic fermentation in the form of mechanical / pneumatic mixing have relatively high requirements for raw material particle size and impurity content. Wet anaerobic fermentation requires raw material pulping and material particle size <10mm. Dry anaerobic fermentation from different technical sources has slight differences in specific technical indicators, but usually requires impurity content <10% and material particle size <100mm. This means that for domestic waste with complex components, if the above process is used, the raw materials need to be pre-treated with complex mechanical sorting to meet the basic feed requirements for anaerobic fermentation. The common process is to use a combination of 2-3 levels of crushing + screening. This method requires a large amount of land and equipment investment. More importantly, crushing is not selective for materials. Textiles, rubber and plastics are also torn to varying degrees during the raw material crushing process, forming a large amount of fine textile fibers and broken plastic pieces. These debris are difficult to separate from organic matter. Ultimately, in addition to obtaining biogas that can be utilized as a resource, it is difficult to form resource products such as debris screened out in the mechanical sorting process and anaerobic fermentation residue. About 90% of the dry matter still needs to be transported for incineration or landfill, and the final dry basis resource utilization rate is less than 20%.

[0005] For example, CN103480633A discloses a domestic waste resource processing device, which includes a pretreatment chute, a feeding conveyor, a drum screen group, an air separation machine, a crusher, an eddy current separator, a cyclone dust collector, a double-layer vibrating screen, a hand-selected belt conveyor, a strong magnetic separator and a fermentation tank, and is intended to separate domestic waste into more than ten kinds of materials such as large garbage, ferrous metals, non-ferrous metals, plastics and foam materials, decomposable organic matter, non-decomposable organic matter, sandstone glass, mud, and landfill. However, the multi-stage screening method is not thorough in sorting various target objects. The process of breaking bags and multi-stage screening of domestic waste can only separate the main characteristic objects through characteristics such as particle size difference, magnetism, and density. However, since the domestic waste that is not thoroughly classified contains more kitchen waste, its separation characteristics are not obvious, which will result in the separated metals, plastics, and sandstone containing more kitchen waste, which greatly limits the resource utilization path of these target products. Summary of the invention

[0006] The purpose of the present invention is to provide a method for resource utilization of domestic waste. Through a combination of mechanical sorting, biological treatment and thermal treatment processes, high-value components / organic components / inert components / combustible components in domestic waste can be separated with high quality, thereby achieving the purpose of comprehensive resource utilization of all components of domestic waste.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] A method for recycling domestic waste, comprising the following steps:

[0009] S1. Breaking the bags of domestic garbage and screening them once to obtain a primary oversize and a primary undersize, wherein the primary oversize is subjected to air separation to obtain a primary light oversize and a primary heavy oversize;

[0010] S2, the primary screened material is loaded into a dry anaerobic fermentation unit for anaerobic fermentation treatment to produce biogas and stabilized biogas residue, wherein the biogas is used as a raw material to be supplied to a biogas purification power generation system for power generation;

[0011] S3. The heavy oversize material is loaded into the biological drying unit for aeration and supplementary heating, and is sent out as a derived fuel after reaching a predetermined moisture content;

[0012] S4, the light oversize material is washed and dehydrated to obtain a clean plastic mixture, which is then sent to a flotation device for buoyancy separation, wherein the overflow material is dehydrated to obtain clean plastic, which is further hot-melted, drawn, and pelletized to obtain recycled plastic particles, and the solid residue after the sediment is dehydrated is sent to the bio-drying unit;

[0013] S5. Dilute the sludge in S2 with water and perform secondary screening to obtain secondary oversize and secondary undersize, wherein the secondary oversize is subjected to air separation to obtain secondary light oversize which is sent to the flotation device, and the secondary heavy oversize is sent to the biodrying unit, and the secondary undersize is used as building material after sand removal and cleaning.

[0014] Furthermore, in S1, the domestic waste after bag breaking, before primary screening and during transportation is subjected to magnetic separation treatment to remove some magnetic metals contained therein.

[0015] Furthermore, in S1, the first screening process is: screening through a sieve aperture of 120-200 cm.

[0016] Furthermore, in S2, the temperature of the anaerobic fermentation treatment is 35-38°C, the time is 22 to 28 days, and the stacking height is 3 to 3.5 m.

[0017] Furthermore, in S3, in the biological drying unit, the material fed into the unit is first subjected to an aeration treatment for 6-8 days, and then the generator flue gas is cooled to 120-150°C by air distribution, and the hot flue gas is used for thermal drying until the moisture content reaches 20% or less.

[0018] Furthermore, in S4, the water in the water washing stage and the buoyancy separation stage is recycled in stages, wherein the solid content of the washing water used in the water washing stage is controlled to be less than 1%, and the solid content of the circulating water used in the buoyancy separation stage is controlled to be less than 0.6%.

[0019] Furthermore, in S4, the temperature of the hot melt is 180-220°C.

[0020] Furthermore, in S4, the hot melt having fluidity is extruded and screened through a 40-60 mesh screen to remove unmelted impurities including metals.

[0021] Furthermore, in S5, the biogas residue is diluted with water to a solid content of 12-18%.

[0022] Furthermore, in S5, the secondary screening process is a screening process using a 10-20 mm sieve.

[0023] The main innovative ideas and innovative points of the present invention are as follows:

[0024] 1. The process design idea takes high-value recycled plastic particles, organic nutrient soil, gravel, RDF, biomass energy (biogas), electricity and heat as the main product solutions.

[0025] The main difficulty in the resource utilization of domestic waste is that the general method of mechanical sorting cannot completely separate the various components, resulting in the sorted textiles, paper (or pulp), and gravel mixed with organic matter that has not been harmlessly treated, which will still release foul-smelling gases and may cause groundwater pollution if not properly disposed of; the sorted organic fertilizer will also contain a large proportion of glass, ceramics, ash, and broken textiles and plastics, which limits the use of organic fertilizers; in addition, in the process of traditional mechanical sorting, in order to improve the sorting efficiency, it is usually necessary to crush domestic waste to a particle size of 1-25cm, which will cause the plastic film in the garbage to be rubbed and torn into broken plastic pieces. These broken plastic pieces will be mixed with organic components and ash, making it difficult to separate them again, and a large amount of them will enter the organic fertilizer, greatly limiting the resource utilization of anaerobic fermentation sludge.

[0026] According to the component characteristics, application value and separation characteristics of domestic waste, domestic waste is separated with high purity according to high-value light film, organic component, inert heavy component and remaining combustible component. For organic components, biogas is produced by anaerobic fermentation for energy utilization. The viscosity of the remaining stabilized organic matter is reduced, and it is further separated and dehydrated to make nutrient soil; the heavy components are washed out by gravity sedimentation screening by circulating biogas slurry dilution to obtain a mixture of bricks, ceramics, glass and ash soil. After further washing and fermentation of residual organic matter, such inert components can be used as building aggregates or road cushions; textiles, paper fibers and low-density components in rubber and plastics (mainly mixed film components of PE and PP) are separated by positive pressure air separation and buoyancy separation. The plastic components can be further hot-melt granulated to form high-value recycled plastic granule products. The remaining mixture of textiles, paper, etc. is dried by the waste heat of biogas power generation generated by anaerobic fermentation, and then sent to downstream cement kilns and other heat-using units as derivative fuels for use as alternative fuels.

[0027] 2. The overall wet cleaning and sorting scheme is adopted, and the multi-stage cleaning water is recycled and utilized in cascade, which greatly reduces the amount of clean water and water treatment costs.

[0028] The washing and sorting of recycled plastics adopts hydraulic washing and flotation technology. The water replenishment of the flotation device adopts the membrane water produced by the sewage treatment unit. The suspended solids and broken plastic pieces washed out during the flotation process are reused after mechanical sorting and sedimentation, and discharged regularly; the flotation drainage is used in the water washing process of lightweight plastics to remove most of the dust and organic matter attached to the surface of the lightweight plastic film, and the washing water is reused for sludge washing. After the drainage of sludge washing is dehydrated and the inert organic components are separated, part of it is reused for anaerobic fermentation, and part of it enters the sewage treatment unit; after the sewage treatment unit completes the removal of nitrogen and phosphorus and the removal of suspended solids, part of the water is discharged into the municipal pipeline network, and part of the water is reused to the flotation device.

[0029] The previous sludge cleaning is not sensitive to suspended solids, COD, etc., so the flotation water can be reused for sludge cleaning without purification; the main factors affecting the flotation quality are suspended solids and COD, so the MBR membrane water produced by the sewage treatment unit is returned to the flotation, thereby realizing the circular cascade utilization of the cleaning water. Except for the process debugging stage, the system hardly needs to use additional clean water.

[0030] 3. Use buoyancy sorting and recycling to achieve high-value utilization of recycled plastics.

[0031] Domestic garbage contains various types of abandoned plastic products, including PE, PP, ABS, PET, PVC, etc. Among them, PE and PP are mainly sourced from packaging bags, fast food boxes, etc., which can be initially sorted at low cost by positive pressure air separation. The sorted plastic raw materials are further cleaned to remove dust and organic matter attached to the surface, and then separated by buoyancy separation to separate PE / PP film plastics with a density lower than water from other plastic components to obtain a pure PE / PP mixture. Components with a density greater than water, such as PVC and PET, sink to the bottom of the water. These components are mixed into RDF to provide heat and are no longer used for deep resource utilization. The physical and chemical properties of PE and PP are relatively similar, with a low melting point and a high melt flow index, and they have recycling value. The plastic granule products formed by hot-melt pelletizing of clean plastic raw materials have high economic value and a wide range of application scenarios.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The garage-style anaerobic fermentation process without mechanical stirring is selected, so the system has a very high tolerance for impurities and has no requirements for the impurity content and particle size of the materials. Therefore, the pretreatment stage only needs to break the bags to release the organic matter in the garbage bags, which greatly simplifies the mechanical sorting stage. On the one hand, it reduces the direct contact between operators and raw garbage, which is beneficial to occupational health and hygiene management. On the other hand, it also reduces the complexity of the system and avoids excessive crushing of textiles, rubber and plastics, greatly reducing the difficulty of subsequent sorting and resource utilization, making it possible to recycle various components, and the final dry basis resource utilization rate is >95%.

[0034] (2) There are many rubber and plastic components in domestic waste, among which PE, PP, PET, ABS, PVC, etc. are the main ones. In terms of form, packaging waste is the main one, accounting for more than 50%. This type of composition is mainly in the form of film, and its large surface area makes it easy to separate from other components by the wind separation method of the present invention. In addition, since the density of PE and PP is less than 1000kg / m 3 , PET, ABS, PVC> 1000kg / m 3, the distinct separation characteristics make it easy to separate the PE and PP mixture from other components by buoyancy sorting. At the same time, during the soaking process in water, the dust and organic residues attached to the surface of the film plastic can also be washed off to obtain relatively pure clean plastic. After dehydration, these clean plastics are hot-melted at 180-220℃ to form a certain fluidity without causing significant changes in their physical and chemical properties. After hot melting, the aluminum foil and other metals in the composite plastic are not melted, and then extruded and screened through a 40-60 mesh screen to obtain a product with a higher melt flow index, and then through wire drawing-granulation, a high-value recycled plastic granule product is formed, which can be used as raw materials for the manufacture of downstream products such as pallets and drain pipes. Through the above process, the resource utilization of high-value components in domestic waste is completed. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0039] In the following implementation manners or examples, unless otherwise specified, functional components or structures are conventional components or conventional structures used in the art to achieve corresponding functions.

[0040] In order to achieve high-quality separation of high-value components / organic components / inert components / combustible components in domestic waste, thereby achieving the purpose of comprehensive resource utilization of all components of domestic waste, the present invention provides a method for resource utilization of domestic waste. For specific steps, see Figure 1 As shown, the following steps are included:

[0041] S1. Breaking the bags of domestic garbage and screening them once to obtain a primary oversize and a primary undersize, wherein the primary oversize is subjected to air separation to obtain a primary light oversize and a primary heavy oversize;

[0042] S2, the primary screened material is loaded into a dry anaerobic fermentation unit for anaerobic fermentation treatment to produce biogas and stabilized biogas residue, wherein the biogas is used as a raw material to be supplied to a biogas purification power generation system for power generation;

[0043] S3. The heavy oversize material is loaded into the biological drying unit for aeration and supplementary heating, and is sent out as a derived fuel after reaching a predetermined moisture content;

[0044] S4, the light oversize material is washed and dehydrated to obtain a clean plastic mixture, which is then sent to a flotation device for buoyancy separation, wherein the overflow material is dehydrated to obtain clean plastic, which is further hot-melted, drawn, and pelletized to obtain recycled plastic particles, and the solid residue after the sediment is dehydrated is sent to the bio-drying unit;

[0045] S5. Dilute the sludge in S2 with water and perform secondary screening to obtain secondary oversize and secondary undersize, wherein the secondary oversize is subjected to air separation to obtain secondary light oversize which is sent to the flotation device, and the secondary heavy oversize is sent to the biodrying unit, and the secondary undersize is used as building material after sand removal and cleaning.

[0046] In some specific embodiments, in S1, the domestic waste after bag breaking and before primary screening and during transportation is further subjected to magnetic separation treatment to remove some magnetic metals contained therein.

[0047] In some specific embodiments, in S1, the first screening process is: screening through a sieve aperture of 120-200 cm.

[0048] In some specific embodiments, in S2, the temperature of the anaerobic fermentation treatment is 35-38°C, the time is 22 to 28 days, and the stacking height is 3 to 3.5 m.

[0049] In some specific embodiments, in S3, in the biological drying unit, the material fed in is first subjected to an aeration treatment for 6-8 days, and then the generator flue gas is cooled to 120-150°C by air distribution, and the hot flue gas is used for thermal drying until the moisture content reaches 20% or less.

[0050] In some specific embodiments, in S4, the water in the water washing stage and the buoyancy separation stage are recycled respectively, wherein the washing water used in the water washing stage is controlled to have a solid content of <1%, COD <8000 mg / L, and the circulating water used in the buoyancy separation stage has a solid content of <0.6%, COD <3000 mg / L.

[0051] In some specific embodiments, in S4, the temperature of the hot melt is 180-220°C.

[0052] In some specific embodiments, in S4, the hot melt having fluidity is further extruded and screened through a 40-60 mesh screen to remove unmelted impurities including metals.

[0053] In some specific embodiments, in S5, the biogas residue is diluted with water to a solid content of 12-18%.

[0054] In some specific embodiments, in S5, the secondary screening process is a screening process using a 10-20 mm sieve.

[0055] The above embodiments may be implemented individually or in any combination of two or more.

[0056] The above implementation is described in more detail below in conjunction with specific examples.

[0057] Embodiment 1:

[0058] The domestic waste directly obtained from a community is classified as follows: Figure 1 The process route shown is used for processing.

[0059] First, the incoming domestic waste is broken into bags by a bag breaker. The bag breaker basically does not play the role of material crushing. It only uses a bag breaker to open the bagged domestic waste in a targeted manner to release the organic matter in it to improve the efficiency of subsequent anaerobic fermentation. Subsequently, it is screened once by a drum screen with a mesh size of 120 to 200 mm. Components mainly composed of organic matter, ash, paper, glass and ceramics pass through the mesh and fall into the undersize phase (i.e., the primary undersize), accounting for about 60%-65% of the total amount of incoming domestic waste. The oversize phase (i.e., the primary oversize) is mainly composed of large items such as textiles, rubber and plastics. At the same time, a permanent magnetic iron remover is placed on the material conveyor belt sent to the drum screen to separate some magnetic metals, which are then recycled as scrap metals. After separation, the primary oversize is then subjected to positive pressure air separation by the 1# air separator, and the light and heavy phases of the air separation are collected separately. The light phase (i.e. the primary light oversize) is mainly composed of film plastics, some textiles, paper, etc., and the heavy phase (i.e. the primary heavy oversize) is mainly composed of large textiles. Through the above-mentioned mechanical rough separation, a total of four components are obtained, including drum screen undersize (mainly organic components, i.e. the primary undersize), air-selected light materials (mainly film plastics, i.e. the primary light oversize), air-selected heavy materials (mainly textiles, i.e. the primary heavy oversize), and scrap metals (mainly magnetic metals), with a mass ratio of about 60:10:30:0.5.

[0060] After rough sorting, the screened material is distributed to each dry anaerobic fermentation bin that constitutes the dry anaerobic fermentation unit through the fermentation bin distribution system. The number of fermentation bins is flexibly determined according to the processing scale. The screened material is left to stand in each fermentation bin for 25 days, and the stacking height is 3.5m. The biogas generated during the fermentation process is collected through pipelines to the storage cabinet and enters the biogas purification power generation system after desulfurization and dehydration. The generator generates electricity. The waste heat in the power generation process is used in the form of flue gas passing into the biological drying bin. After sufficient anaerobic fermentation, the residue (i.e., biogas residue) has most of the organic matter degraded and the remaining organic matter fully stabilized, thus completing the harmlessness and stabilization of domestic waste and the resource product in the form of biogas.

[0061] The air-selected light materials separated in the rough sorting stage are first sent to the plastic washing device for washing to wash away organic matter, textile debris and other impurities that are not fully fermented on the surface. The washed light materials are then sent to the washing and dehydration device for dehydration to obtain a clean plastic mixture. After washing to remove dust, paper and other debris, the clean plastic mixture enters the flotation device for buoyancy sorting. The flotation device is 30 meters long and adopts a structure similar to a horizontal flow sedimentation tank. PVC, remaining textile fibers, remaining dust, etc. are fully soaked in water and sink to the bottom of the water. They are fished out by the bottom scraper. The overflow material is mainly a PE and PP mixture with a high degree of cleanliness. After dehydration by the flotation dehydration device, clean plastic is obtained. The clean plastic is further hot-melted in the hot-melt impurity removal device. The hot-melt temperature is controlled at about 180-220°C. In this embodiment, it is preferably about 180°C. After passing through a 60-mesh screen to remove the unmelted metal debris on the surface of the composite plastic, it is then drawn and pelletized in a water ring pelletizing device to obtain recycled plastic particles. The water of the flotation device is recycled, and the solid content is controlled to be less than 0.6%. When it exceeds 0.6%, it is discharged regularly. The overall replacement cycle is about 5-7 days. The water after dehydration of the flotation discharge enters the circulating water purification device, and then is screened through a 30-mesh screen to remove plastic fragments, foam plastics and other debris torn during the dehydration process. It is then coagulated in a coagulation sedimentation tank to remove suspended solids in the circulating water, and then sent to the flotation circulating water pool as circulating water for reuse to extend the water replacement cycle. The flotation water circulation system uses the MBR membrane effluent of the sewage treatment system. Due to the membrane treatment, the MBR water is sufficient to meet the water quality requirements of the flotation system. The flotation drainage COD is ~3000mg / L, SS is ~5000-6000mg / L. This part of the drainage is reused in the washing section before flotation, that is, it is recycled to the plastic washing device through the washing circulating water tank. The washing section controls the solid content of the washing water to be less than 1%, and COD is less than 8000mg / L. The liquid phase after dehydration in the washing section is also screened through a 30-mesh screen and reused. After reaching the control index, it is reused to the circulating washing water tank and regularly discharged to the biomass separator for sludge dilution and cleaning, forming a low-medium-high concentration cascade water recycling system. The solid content of the solid residue screened out in the washing and flotation links is about 20%. These solid residues are mainly a mixture of textile broken fibers, broken plastics, foam plastics, pulp, etc. After being squeezed and dehydrated by a screw extruder to a solid content of about 50%, they are sent to the biological drying warehouse for drying, and finally used as a derivative fuel for energy.

[0062] The solid content of the sludge obtained after anaerobic fermentation is about 35-40%. These solid sludges are transported by the sludge conveying system, diluted with recycled water from the washing section to a solid content of about 15%, and then screened by a 20mm sieve in the biomass separator. Most of the organic matter, ash, glass, ceramics, pulp and other components enter the undersize with the dilution water. The oversize part (i.e., the secondary oversize) is mainly textiles and plastic sheets screened in the pretreatment stage, which are further positively pressurized by the 2# air separator to improve the recovery rate of high-value plastics. The light matter has undergone anaerobic fermentation and has a low organic matter content, so it directly enters the aforementioned flotation device for buoyancy separation. The heavy matter is sent to the biological drying bin together with the solid sludge obtained from the aforementioned washing and flotation section for dehydration and drying to complete the resource utilization of the combustible components. After the undersize phase (i.e., the secondary undersize) is desanded by gravity in a spiral desanding machine, most of the heavy materials such as glass ceramics, ash and soil are removed. Since it is almost composed of various inorganic inert components, it is further washed and cleaned by a sand washer to remove the residual COD, and gravel can be used as building material aggregate, roadbed cushion, etc. The sand washing water used in the sand washing stage uses the condensed water from the flue gas treatment link of the biological drying warehouse in the thermal drying stage. The COD of this part of condensed water is relatively low, about 1000 mg / L, and the organic matter content in the sand and gravel components can be eluted to less than 0.5%, meeting the quality requirements of construction sand. The main component of the remaining liquid phase obtained after gravity desanding is soluble organic matter. This part of organic matter is processed in turn by a hydraulic screen, a plate and frame filter press and a mud cake crusher to obtain nutrient soil with a moisture content of about 50%, which can be used for garden flowers. The liquid phase produced in the plate and frame filter press is sent to the filtrate temporary storage box, part of which is reused in the water circulation system, and part of which is discharged after being treated in the sewage treatment system and meets the standards.

[0063] The components mainly composed of textiles, rubber, plastics, and pulp separated in the rough sorting stage, washing flotation, and other sections are sent to the sequential batch bio-drying bin (constituting the bio-drying unit) for drying. Aeration is first performed in the bio-drying bin to make full use of the organic heat attached to the screened material separated in the pretreatment stage. The organic matter in the screened material accounts for about 25% of the organic matter in the domestic waste, which can provide ~1700 kJ / kg of heat for the pile. This part of the treatment process lasts for about 7 days. After the material is fully deodorized, the aeration pipeline is switched to the flue gas pipeline, and the waste heat flue gas generated during the power generation process in the biogas purification power generation system is used for thermal drying. The material is dried to a moisture content of ~20%, and then further crushed and packaged (processed in the baler) to produce derivative fuel. After deodorization, inorganic component removal, and dehydration, the fully reduced derivative fuel is sent to the cement kiln for coordinated resource utilization.

[0064] In addition, the above-mentioned derivative fuels have completed dehydration and calorific value stabilization, and can be used for pyrolysis and incineration to produce steam to meet the heating needs of the entire site. The biogas produced in the anaerobic fermentation stage can also be purified into natural gas for further resource utilization.

[0065] In general, the main goal of the present invention is to achieve high-quality separation of high-value components / organic components / inert components / combustible components in domestic waste through a combination of mechanical sorting, biological treatment, and thermal treatment processes, thereby achieving the purpose of comprehensive resource utilization of all components of domestic waste. By using dry anaerobic fermentation, the kitchen waste in domestic waste is fully harmlessly treated, the generated biogas is used for power generation, and the waste heat is used to provide heat demand in the factory; by using water washing flotation, high-value plastic components (mainly PE / PP) are separated from other rubber, plastic, and textile products with high purity, and the plastic components are then hot-melt granulated to produce high-value recycled plastic particles; by using mechanical sorting, the magnetic metals, inert inorganic components, fermentation residual organic components, and remaining combustible components in domestic waste are fully separated to form four types of products: magnetic metals, nutrient soil, gravel, and refuse-derived fuel (RDF); in addition, waste-derived fuel is used as a raw material for pyrolysis and gasification to form steam products; by combining the above technical means, the resource utilization of all components of domestic waste is achieved, and the overall resource utilization rate can reach more than 95%.

[0066] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for resource utilization of domestic waste, characterized in that: The following steps are involved: S1. Breaking the bags of domestic garbage and screening them once to obtain a primary oversize and a primary undersize, wherein the primary oversize is subjected to air separation to obtain a primary light oversize and a primary heavy oversize; S2, the primary screened material is loaded into a dry anaerobic fermentation unit for anaerobic fermentation treatment to produce biogas and stabilized biogas residue, wherein the biogas is used as a raw material to be supplied to a biogas purification power generation system for power generation; S3. The heavy oversize material is loaded into the bio-drying unit for aeration and ventilation and supplemented with heating by the flue gas generated by the biogas purification power generation system. After reaching the predetermined moisture content, it is sent out as a derivative fuel; S4, the light oversize material is washed and dehydrated to obtain a clean plastic mixture, which is then sent to a flotation device for buoyancy separation, wherein the overflow material is dehydrated to obtain clean plastic, which is further hot-melted, drawn, and pelletized to obtain recycled plastic particles, and the solid residue after the sediment is dehydrated is sent to the bio-drying unit; S5. Dilute the sludge produced in S2 with water and perform secondary screening to obtain secondary oversize and secondary undersize, wherein the secondary oversize is subjected to air separation to obtain secondary light oversize and is sent to the flotation device, and the secondary heavy oversize is sent to the bio-drying unit, and the secondary undersize is used as building material after sand removal and cleaning.

2. A method for recycling domestic waste according to claim 1, characterized in that: In S1, the domestic waste after bag breaking, before primary screening and during transportation is also subjected to magnetic separation treatment to remove some magnetic metals contained therein.

3. A method for recycling domestic waste according to claim 1, characterized in that: In S1, the first screening process is: screening through a sieve hole of 120-200 cm.

4. The method for recycling domestic waste according to claim 1, characterized in that: In S2, the temperature of anaerobic fermentation treatment is 35-38°C, the time is 22 to 28 days, and the stacking height is 3 to 3.5 m.

5. The method for recycling domestic waste according to claim 1, characterized in that: In S3, in the biological drying unit, the material fed into the unit is first subjected to an aeration treatment for 6-8 days, and then the flue gas generated by the biogas purification power generation system is cooled to 120-150°C by air distribution, and the hot flue gas is used for thermal drying until the moisture content reaches 20% or less.

6. The method for recycling domestic waste according to claim 1, characterized in that: In S4, the water in the water washing stage and the buoyancy separation stage is recycled in stages, wherein the solid content of the washing water used in the water washing stage is controlled to be less than 1%, and the solid content of the circulating water used in the buoyancy separation stage is controlled to be less than 0.6%.

7. The method for recycling domestic waste according to claim 1, characterized in that: In S4, the hot melt temperature is 180-220°C to avoid degradation and carbonization of the plastic components.

8. A method for recycling domestic waste according to claim 1 or 7, characterized in that: In S4, the hot melt having fluidity is further extruded and screened through a 40-60 mesh screen to remove unmelted impurities including metals.

9. The method for recycling domestic waste according to claim 1, characterized in that: In S5, the biogas residue is diluted with water to a solid content of 12-18%.

10. The method for recycling domestic waste according to claim 1, characterized in that: In S5, the secondary screening process is a screening process using a 10-20 mm sieve.

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