Odor adsorption type landfill covering system and preparation method

Abstract

The present invention provides an odor adsorption type landfill covering system and a preparation method. The odor adsorption type landfill covering system comprises a landfill sealing covering layer and at least one intermediate covering layer; the landfill sealing covering layer comprises six functional layers, from top to bottom: vegetation layer, drainage layer, geomembrane, gas collection layer under the membrane, odor adsorption layer I, gas collection layer I; the intermediate covering layer comprises three functional layers, from top to bottom, the upper gas collection layer of the intermediate covering layer, the odor adsorption layer II, and the lower gas collection layer. It can efficiently absorb H2S odor, improve the mechanical stability of the landfill garbage body, and solve the problem that the traditional soil covering layer cannot pass medium and heavy mechanical vehicles.

Description

Technical Field

[0001] The invention relates to the technical field of garbage landfill, in particular to an odor adsorption type garbage landfill covering system and a preparation method thereof. Background Art

[0002] In recent years, with the sustained and rapid development of my country's national economy and the acceleration of urbanization, urban garbage has increased dramatically. As of 2012, the amount of domestic garbage collected and transported in China's cities was about 171 million tons. In addition to a small amount of incineration, composting and recycling, more than 60% was disposed of by sanitary landfill. Domestic garbage contains a large amount of organic matter, which will release a large amount of odorous substances during the landfill process. Among various odorous substances, hydrogen sulfide (H2S) is the most typical and common.

[0003] The H2S odor in landfills mainly comes from the oxidation of sulfur-containing organic matter and the reduction of sulfate under anaerobic conditions. In the early stage of landfill, the organic sulfur-containing components in the garbage (such as sulfur-containing vitamins or proteins, etc.) decompose under the action of microorganisms to produce H2S and accumulate a large amount of sulfate; in the middle and late stages, anaerobic microorganisms (mainly sulfate-reducing bacteria) use various organic matter or hydrocarbons to reduce sulfate, forming H2S under alienation, which is also the main source of H2S in landfills.

[0004] H2S has an irritating and suffocating smell of rotten eggs. Exposure to H2S can cause various eye, respiratory and neurological diseases, and even shock and death, which is very harmful to the health of workers and surrounding residents. In recent years, odor pollution outbreaks have frequently occurred in municipal landfills in Beijing, Shanghai, Guangzhou, Shenzhen and other cities, which have had a huge impact on the quality of life of surrounding residents and caused serious social problems. Therefore, effectively dealing with H2S odor pollution in landfills, reducing its damage to the surrounding ecological environment, and protecting people's health have become an important part of the comprehensive management of landfills.

[0005] The pollution control of H2S odor in landfills can be achieved by inhibiting the generation of H2S at the source and reducing the emission of H2S at the end.

[0006] Generally speaking, the conventional approach to inhibiting the generation of H2S from the source is: (1) inhibiting the activity of microorganisms in the system, mainly by adding alkaline substances such as sodium hydroxide and calcium hydroxide to increase the pH value, or adding fungicides; (2) inhibiting the activity of sulfate-reducing bacteria, mainly by injecting oxygen, nitrates and other substances to increase the redox potential. However, in practice, this approach is not very effective.

[0007] The terminal control of H2S odor is mainly carried out through the purification of H2S in landfill gas and the optimization of the cover layer to reduce H2S emissions and other terminal control measures.

[0008] Among them, landfill gas purification is mainly achieved through the gas drainage and collection system in the landfill, which collects and centrally purifies the landfill gas generated during the garbage degradation process. However, these technologies have high initial investment and operating costs, and many landfills in China lack a complete landfill gas drainage and collection system. Therefore, their actual application in large landfill areas is often limited.

[0009] Currently, the most commonly used method for controlling H2S odor in landfills is to use a landfill cover to achieve in-situ control of the odor.

[0010] The material selection of the landfill cover is directly related to the effect of in-situ odor control. Although the traditional clay cover technology is relatively mature, it has the disadvantages of poor deodorization effect, large storage capacity, precious and difficult to obtain clay resources, expensive materials, and affecting the migration of biogas and leachate. The ideal landfill cover material should generally have the following physical properties: high specific surface area, high moisture retention capacity, high mechanical strength, low bulk density, high porosity, high buffering capacity, easy to obtain, low cost, low transportation cost, long service life, etc. However, no one has found an ideal material that meets these characteristics. Therefore, it is urgent to find a more suitable landfill cover material.

[0011] The landfill cover layer is divided into the intermediate cover layer and the closure cover layer.

[0012] The intermediate cover refers to the temporary covering of exposed garbage during landfill operations due to processes such as spreading, leveling and compacting, as well as the migration of the working surface. The main functions of the intermediate cover include: (1) preventing the garbage from being exposed to a large amount of rainwater for a long time and generating a large amount of leachate; (2) inhibiting the release of odor into the atmosphere; and (3) reducing mosquitoes and flies and improving the adverse visual environment.

[0013] Among them, the main functions of the capping layer are anti-seepage and air-tightness. Anti-seepage means preventing rainfall, surface runoff and groundwater from infiltrating into the garbage body, thereby reducing the production of leachate. Air-tightness means reducing the leakage of landfill gas, including reducing the leakage of odor, thereby reducing the impact of the landfill on the surrounding environment and residents' lives.

[0014] At present, geocomposite materials (such as HDPE membranes) and clay and other anti-seepage materials are mainly used for intermediate covering and site sealing.

[0015] As a covering material, the main problems of geocomposites are high construction quality requirements, high engineering costs, and easy failure due to puncture by hard and sharp garbage components. In addition, HDPE membrane cannot absorb or process H2S, so a large amount of gas often accumulates under the membrane, causing bulging, which affects the service life of the membrane.

[0016] The advantages of the soil middle cover layer are that it is widely available, low cost, and stable, but the soil cover layer also has disadvantages such as low strength, which will weaken the stability of the garbage body, occupy storage capacity, consume soil resources, affect construction, and poor economy. In order to solve the above problems, "CN201810659898-Landfill Middle Cover Layer and Preparation Method and Application thereof" proposes to use recycled aggregates to construct the middle cover layer, in order to achieve the purpose of improving the mechanical properties of the garbage body through the reinforcement effect of recycled aggregates, and provide a certain degree of anti-seepage and air-tightness function. Its air-tightness function is to reduce the amount of odor passing through the low permeability layer.

[0017] However, both soil cover layers and cover layers constructed with recycled aggregates have several serious defects: (1) These cover layers are not intended to absorb or treat H2S, but only provide a barrier to isolate and prevent spillover; (2) Since H2S is not absorbed or treated, it will accumulate under the low permeability layer, and the gas pressure will increase over time, eventually breaking through the intake pressure value of the low permeability layer, forming a through channel, and then losing the air-locking function. Summary of the invention

[0018] To solve the above problems, the present invention provides an odor adsorption type landfill covering system and preparation method, which can efficiently absorb H2S odor, improve the mechanical stability of landfill garbage body, and solve the problem that traditional soil covering layer cannot pass medium and heavy mechanical vehicles.

[0019] The objective of the present invention is achieved in the following manner: an odor adsorption type landfill covering system, comprising a landfill closure covering layer and at least one intermediate covering layer; the landfill closure covering layer comprises six functional layers, from top to bottom: vegetation layer, drainage layer, geomembrane, gas collection layer under the membrane, odor adsorption layer I, gas collection layer I; the intermediate covering layer comprises three functional layers, from top to bottom, an upper gas collection layer of the intermediate covering layer, an odor adsorption layer II, and a lower gas collection layer.

[0020] Both the odor adsorption layer I and the odor adsorption layer II are odor adsorption layers; the odor adsorption layer is a layer having an odor adsorption function.

[0021] The thickness of the odor adsorption layer I is 1.0-2.0m, and the thickness of the odor adsorption layer II is 0.4-0.8m; the raw material of the odor adsorption layer is recycled fine material, which is a mixture of recycled fine aggregate and recycled powder prepared from recycled construction waste. The proportion of concrete and mortar in the construction waste used to prepare the recycled fine aggregate and recycled powder is ≥95%, the strength of the waste concrete used to prepare the recycled fine material is not less than C30, and the pH value of the compacted recycled fine material is not less than 10; the particle size distribution curve of the odor adsorption layer is saddle-shaped. Specifically, according to soil mechanics standards, the particle size gradation curve characteristics of the recycled fine material must meet the following conditions: (a) the maximum particle size is ≤2mm; (b) the effective particle size d10 ≤0.005mm; (c) 1.2mm≤d 90 ≤1.8mm; (d) Unevenness coefficient C U ≥5; (e) Curvature coefficient C C Between 1 and 3, that is, 3 ≥ C C ≥1, compaction degree ≥95%, the permeability coefficient of the odor adsorption layer at the maximum dry density is 10 - 6 m / s—10 -8 m / s, air intake value 1kPa-10kPa, water absorption rate ≥10%, pore water saturation 60%-90%.

[0022] There are many types of concrete, among which cement concrete is the most widely used and common. The concrete described in the present invention specifically refers to cement concrete, that is, concrete prepared with various types of cement as cementitious materials. It must contain cement, and the general raw materials of cement contain silicate cement clinker, and silicate cement clinker contains calcium oxide, such as silicate cement, ordinary silicate cement, slag silicate cement, pozzolanic silicate cement, fly ash silicate cement, composite silicate cement, medium heat silicate cement, low heat slag silicate cement, fast hardening silicate cement, sulfate-resistant silicate cement, white silicate cement, road silicate cement, masonry cement, oil well cement, and gypsum slag cement.

[0023] The closure covering layer of the odor adsorption landfill covering system includes a vegetation layer including soil capable of cultivating vegetation, and the thickness of the vegetation layer meets the root system requirements of the planted vegetation, the thickness of the vegetation layer is ≥0.5m, and the compaction degree is ≥80%. The raw material of the drainage layer is recycled coarse aggregate prepared from construction waste buried in the landfill, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compacted relative density of ≥0.9. The geomembrane adopts a high-density polyethylene geomembrane or a linear low-density polyethylene geomembrane with a thickness of ≥1mm, and a non-woven geotextile is laid on the membrane. The specification of the non-woven geotextile is ≥300g / m 2 The raw material of the gas collection layer under the membrane is recycled coarse aggregate, with a thickness of 0.2-0.4m, a particle size of 2-10mm, and a compacted relative density of ≥0.9. The gas collection layer under the membrane is the odor adsorption layer I, and below the odor adsorption layer I is the gas collection layer I. The thickness of the gas collection layer I is 0.3-0.5m, and the raw material of the gas collection layer I is recycled coarse aggregate, with a particle size of 20-40mm, and a compacted relative density of ≥0.9.

[0024] The middle covering layer, the upper gas collecting layer and the lower gas collecting layer of the odor adsorption type landfill covering system are respectively constructed with recycled coarse aggregate, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compacted relative density of ≥0.9.

[0025] In the odor adsorption type landfill covering system, each functional layer is separated by a water-permeable and air-permeable insulating material layer to prevent the raw materials of each layer from mixing.

[0026] The original concrete strength of the materials of odor adsorption layer I and odor adsorption layer II is not less than C30. Except for the vegetation layer and geomembrane, other functional layers are prepared from recycled materials recovered from construction waste, and the original concrete strength of the recycled materials is not less than C10.

[0027] A gas collection layer under the membrane is provided with a gas collection layer exhaust device on the side, a gas collection layer I exhaust device on the side, and an upper gas collection layer exhaust device and a lower gas collection layer exhaust device on the sides, respectively.

[0028] A bottom anti-seepage lining is also provided below and on the sides of the lowest garbage body, so that the covering system involved in the present invention and the garbage body, as well as the bottom anti-seepage lining in the prior art, constitute "bottom anti-seepage lining-garbage body-middle covering layer (lower gas collection layer-odor adsorption layer II-upper gas collection layer)-garbage body-middle covering layer (lower gas collection layer-odor adsorption layer II-upper gas collection layer)-...-garbage body-sealing covering layer (gas collection layer I-odor adsorption layer I-sub-membrane gas collection layer-geomembrane-drainage layer-vegetation layer)". In this structure formed by the staggered superposition of the composite structure of "garbage-middle covering layer", the middle covering layer and the garbage body are in full contact, that is, the odor adsorption layer II of the middle covering layer is mixed in the garbage, and multi-level adsorption is achieved. On the one hand, the middle covering layer serves as a temporary odor adsorption during the landfill operation, and on the other hand, it can continue to adsorb odor as an intermediate layer of the garbage body after the site is sealed.

[0029] The odor adsorption type landfill cover system, as a landfill cover system, has its anti-seepage function realized by geomembrane, which can effectively prevent a large amount of rainwater from infiltrating into the garbage body to form leachate. Secondly, the geomembrane has an air-tight function, which can effectively prevent the odor from overflowing, reducing the impact of the landfill on the external environment and the degree of nuisance to residents.

[0030] The H2S odor adsorption function of the odor adsorption type landfill cover system is mainly achieved by a joint adsorption system composed of several intermediate cover layers and a sealing cover layer. The intermediate cover layers constructed during the landfilling provide layer-by-layer adsorption, and the sealing cover layer realizes the final adsorption. The odor adsorption in the intermediate cover layer is mainly achieved through the gas collection of the upper and lower gas collection layers and the adsorption reaction of the odor adsorption layer. The particles of the upper and lower gas collection layers are relatively large in size, and the landfill gas generated by the upper and lower garbage bodies can be collected, and a relatively high H2S partial gas pressure can be enriched and maintained in the upper and lower gas collection layers, so as to accelerate the chemical reaction between the recovered aggregate and the H2S gas in the odor adsorption layer II of the intermediate cover layer. Chemical reaction accelerates the adsorption of H2S; the adsorption of odor in the sealing cover layer is mainly achieved through the gas collection under the geomembrane, the gas collection layer I and the adsorption reaction of the odor adsorption layer I. The air-tight function of the geomembrane helps to maintain a higher air pressure and a higher concentration of H2S gas under the membrane, accelerating the adsorption of H2S; the particle size of the gas collection layer I is relatively large, which can enrich a large amount of gas; in addition, the gas collection layer under the membrane and the gas collection layer I are respectively equipped with exhaust devices to control the air pressure of the gas collection layer under the membrane and the gas collection layer I, especially the partial pressure of H2S gas, and then control the distribution of the partial pressure of H2S gas in the odor adsorption layer I with depth, so as to achieve the best odor adsorption effect.

[0031] The preparation method of the odor adsorption type landfill cover system comprises the following steps: (1) preparing materials according to the raw material requirements of each functional layer; before preparing the recycled aggregate and recycled powder, impurities such as wood, steel bars, and slag in the construction waste should be removed by pretreatment, leaving only waste concrete and mortar stone; (2) laying each functional layer according to the requirements of each layer.

[0032] The preparation method of the odor adsorption type landfill cover system comprises the following steps: (1) material preparation, the geomembrane needs to be purchased from outside and transported to the landfill, the soil material of the vegetation layer is obtained nearby, and a construction waste crushing station is set up to prepare recycled coarse aggregate, recycled fine aggregate and recycled powder; (2) water addition, mixing and curing, before constructing the closure cover layer and the intermediate cover layer respectively, the materials required for each functional layer are mixed with water to the optimal moisture content, and then sealed and cured to ensure uniform moisture; (3) intermediate cover layer laying: after a round of landfill operation is completed, it is cleaned, leveled and rolled, and then geotextile, lower gas collection layer, geotextile, odor adsorption layer II, geomembrane are laid in sequence. Before the next round of landfill operation, the geomembrane is uncovered and removed, and then the upper gas collection layer is laid on the odor adsorption layer II. After the upper gas collection layer is laid, the next round begins Landfill operation: After the next round of landfill operation is completed, the middle cover layer is re-laid. The laying method is as described above, and it is repeated until the landfill operation is completed to the predetermined landfill volume. Among them, the upper gas collection layer, the lower gas collection layer, the odor adsorption layer II, and the upper gas collection layer need to be laid in layers, and the thickness of a single layer should not exceed 10 cm; (4) Laying of the closure cover layer: After the landfill operation is completed, clean, level and roll, and then lay geotextile, gas collection layer I, geotextile, odor adsorption layer I, geotextile, sub-membrane gas collection layer, geomembrane, geotextile, drainage layer, geotextile, and vegetation layer in turn. Among them, gas collection layer I, odor adsorption layer I, sub-membrane gas collection layer, drainage layer, and vegetation layer need to be laid in layers, and the thickness of a single layer should not exceed 10 cm. Then the vegetation layer is greened and maintained. After the closure cover layer is laid, the entire cover system needs to be monitored and maintained.

[0033] Beneficial effects: The present invention provides an odor adsorption type landfill covering system and preparation method, which can control the theoretical adsorption capacity by controlling the material properties, particle size distribution, adsorption layer thickness, etc. of the odor adsorption layer, and control the contact area between the odor and the adsorption material, the moisture content of the odor adsorption layer, the odor flow rate, the odor flow rate, the odor flow time (i.e., the odor adsorption reaction time), etc. by controlling the compaction degree, the fine particle ratio, etc., thereby controlling the adsorption effect. And through the air-tightening, anti-seepage, and moisturizing effects of the geomembrane, the gas collection layer under the membrane and the gas collection layer I collect gas, especially the gas collection layer I collects gas, maintains a high concentration of odor, and maintains a humidity suitable for adsorption, thereby increasing the adsorption effect of the odor adsorption layer I. In addition, the vegetation layer and the drainage layer mainly play a drainage role to prevent the destruction of the lower layers by a large amount of water penetration. On the one hand, the intermediate covering layer plays a temporary odor adsorption role, and on the other hand, after the site is sealed, it can continue to adsorb odor as an intermediate interlayer of the garbage body. The covering system has the functions of anti-seepage and air-tightening as well as H2S odor absorption, and realizes the recycling of construction waste. High-strength recycled aggregates are used instead of low-strength soil to construct the middle covering layer, and the "weak interlayer" effect of the soil middle covering layer is improved into the "reinforcement" effect of the middle covering layer built with recycled aggregates, thereby improving the mechanical stability of the landfill waste body and solving the problem that the traditional soil middle covering layer is impassable for medium and heavy machinery vehicles. The construction is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the landfill covering system of the present invention.

[0035] Figure 2 It is a schematic diagram of the structure of the closure cover.

[0036] Figure 3 It is a schematic diagram of the structure of the intermediate covering layer.

[0037] Figure 4 It is the typical particle grading curve of each functional layer.

[0038] Figure 5 It is a schematic diagram of the adsorption principle of odor in the closure cover layer.

[0039] Figure 6 It is a schematic diagram of the adsorption principle of odor in the middle cover layer.

[0040] Figure 7 It is a schematic diagram of the principle of anti-seepage and air-tightness of the sealing cover layer.

[0041] Illustration: 1. Vegetation; 2. Vegetation layer; 3. Drainage layer; 4. Geomembrane; 5. Gas collection layer under the membrane; 6. Odor adsorption layer I; 7. Gas collection layer I; 8. Garbage body; 9. Water-permeable and breathable insulating material layer; 10. Upper gas collection layer; 11. Odor adsorption layer II; 12. Lower gas collection layer; 13 Air extraction device for the gas collection layer under the membrane; 14. Air extraction device for the gas collection layer I; 15. Air extraction device for the upper gas collection layer; 16. Air extraction device for the lower gas collection layer; 17 Anti-seepage lining layer; 18 Sealing cover layer; 19 Intermediate cover layer; 20 Rainfall; 21 Slope runoff; 22 Lateral drainage of the drainage layer.

[0042] Note: In this implementation, the drainage layer, air collection layer I, upper air collection layer, and lower air collection layer all use recycled coarse aggregate of the same particle size. Figure 4 In this embodiment, the odor adsorption layer I of the sealing cover layer and the odor adsorption layer II of the intermediate cover layer are made of the same material, so Figure 4 The particle size curves of the two overlap. DETAILED DESCRIPTION

[0043] The present invention will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. It is necessary to point out here that the schematic embodiments and descriptions of the present invention are only used to further explain the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical personnel skilled in the art can make some non-essential improvements and adjustments based on the contents of the present invention.

[0044] like Figure 1-Figure 7 As shown, an odor adsorption type landfill covering system consists of a landfill covering layer 18 and at least one intermediate covering layer 19; the landfill covering layer 18 includes six functional layers, from top to bottom: a vegetation layer 2, a drainage layer 3, a geomembrane 4, a gas collection layer under the membrane 5, an odor adsorption layer I6, and a gas collection layer I7; the intermediate covering layer 19 includes three functional layers, from top to bottom, an upper gas collection layer 10 of the intermediate covering layer, an odor adsorption layer II 11, and a lower gas collection layer 12.

[0045] In the odor adsorption type landfill covering system, each functional layer is separated by a water-permeable and air-permeable insulating material layer 9 to prevent the raw materials of each layer from mixing.

[0046] The original concrete strength of the materials of the odor adsorption layer I6 and the odor adsorption layer II11 is not less than C30. Except for the vegetation layer 2 and the geomembrane 4, the other layers use recycled aggregates recovered from construction waste, and the original concrete strength of the recycled aggregates is not less than C10.

[0047] A sub-membrane gas collection layer exhaust device 13 is provided on the side of the sub-membrane gas collection layer 5, a gas collection layer I exhaust device 14 is provided on the side of the gas collection layer I7, an upper gas collection layer exhaust device 15 and a lower gas collection layer exhaust device 16 are provided on the sides of the upper gas collection layer 10 and the lower gas collection layer 12 respectively.

[0048] In the odor adsorption type landfill cover system, the odor adsorption layer I6 and the odor adsorption layer II11 are both odor adsorption layers; the raw material of the odor adsorption layer is recycled fine material, which is prepared by mixing recycled fine aggregate and recycled powder prepared from recycled construction waste in a certain proportion, and the proportion of concrete and mortar in the construction waste for preparing the recycled fine aggregate and recycled powder is ≥95%, and the pH of the compacted recycled fine material layer is not less than 10; the particle size distribution curve of the odor adsorption layer presents a saddle shape. Specifically, according to soil mechanics standards, the particle size gradation curve characteristics of the recycled fine material must meet the following conditions: (a) the maximum particle size is ≤2mm; (b) the effective particle size d 10 ≤0.005mm; (c) 1.2mm≤d 90 ≤1.8mm; (d) Unevenness coefficient CU≥5; (e) Curvature coefficient C C Between 1 and 3, that is, 3 ≥ C C ≥1, compaction degree ≥95%, the permeability coefficient of the odor adsorption layer at the maximum dry density is 10 -6 m / s—10 - 8 m / s, air intake value 1kPa-10kPa, water absorption rate ≥10%, pore water saturation 60%-90%.

[0049] The mechanism of using construction waste recycled aggregate as odor adsorption layer Ⅰ6 and odor adsorption layer Ⅱ11 is that there are unreacted quicklime (CaO) or slaked lime (Ca(OH)2) and other alkaline substances remaining in the construction waste, which react with the acidic substances (mainly H2S) in the odor to produce acid-base neutralization reaction. The chemical reaction equation is as follows:

[0050]

[0051] In order for the above chemical reaction to occur and develop, some environmental conditions are required, such as a large specific surface area to increase the reaction contact area, a humid environment, etc. In the present invention, the theoretical adsorption capacity is controlled by controlling the material properties of the odor adsorption layer I, the particle size distribution, the thickness of the adsorption layer, etc., and the contact area between the odor and the adsorption material, the moisture content of the odor adsorption layer I, the odor passing amount, the odor passing rate, the odor passing time (i.e., the odor adsorption reaction time), etc. are controlled by controlling the compaction degree, the fine particle ratio, etc., thereby controlling the adsorption effect.

[0052] The sealing cover layer 18 of the odor adsorption type landfill covering system is characterized in that: the outer cross-section of the sealing cover layer 18 is as follows: Figure 1If it is trapezoidal, it includes the plane and the inclined slope. If the outer cross-section is triangular, it only includes the inclined slope.

[0053] Among them, the soil of the vegetation layer 2 must meet the relevant requirements of the soil of the vegetation layer of the landfill, and the present invention does not impose additional restrictions. For example, the vegetation layer 2 is prepared by natural soil plus surface nutrient soil, or soil from the surrounding area of ​​the landfill can be used. The thickness should be determined according to the depth of the plant roots, and the thickness should not be less than 0.5m. The vegetation layer soil should be compacted in layers, and the compaction degree should not be less than 80%. The vegetation layer is preferably planted with turf with shallow roots, and the fertilization, irrigation, and tillage construction methods of the vegetation layer soil are determined according to the characteristics of the planted plants. The main function of the vegetation layer is to beautify the greening, prevent soil and water loss, and release the water that has infiltrated and stored in the vegetation layer into the atmospheric environment through surface evaporation and plant transpiration during non-rainfall time, so as to maintain the water balance of the closure cover layer. It should be noted that the main function of the vegetation layer in the present invention is as described above, and it does not bear the functions of anti-seepage, air-tightness, and odor adsorption. Therefore, the main considerations for parameter design of the vegetation layer are nearby materials, sufficient soil nutrients to support landfill vegetation growth, and low material costs.

[0054] Among them, the four functional layers of drainage layer 3, sub-membrane gas collection layer 5, odor adsorption layer Ⅰ6 and gas collection layer Ⅰ7 are all constructed of recycled materials prepared by recycling construction waste buried in landfills, preferably using discarded high-strength concrete. It is required that the strength of the original concrete of drainage layer 3, sub-membrane gas collection layer 5 and gas collection layer Ⅰ7 is not less than C10, and the strength of the original concrete of odor adsorption layer Ⅰ6 is not less than C30; and before preparing recycled aggregates from construction waste, impurities (including slag, steel bars, wood, glass, plastic, bricks, paper, fabrics, etc.) are removed, and only concrete and mortar blocks are retained, and the weight of concrete and mortar accounts for not less than 95%.

[0055] Among them, the drainage layer 3 is located below the vegetation layer 2, and is made of recycled coarse aggregate prepared by recycling construction waste buried in the landfill. The raw material of the drainage layer is recycled coarse aggregate prepared by recycling construction waste buried in the landfill, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compacted relative density ≥0.9. The main function of the drainage layer 3 is to drain the water that infiltrates into the drainage layer, and serve as a supporting layer for the vegetation layer 2, and together with the vegetation layer 2, it constitutes the upper protective layer of the geomembrane 4. Therefore, the main requirements for its parameter performance are that the mechanical strength is good enough to support the vegetation layer 2, the permeability is good so that the water that infiltrates the vegetation layer 2 and enters the drainage layer 3 is drained along the geomembrane 4 along the slope to avoid the accumulation of water on the geomembrane, and the material is convenient to obtain, the material cost is low, and the durability is good. The parameter design of the drainage layer needs to consider factors such as the local maximum rainfall, the maximum infiltration of the vegetation layer, the slope, the permeability coefficient of the drainage layer and the thickness of the drainage layer in order to meet the maximum drainage needs. In addition, since the strength of the aggregates recycled from construction waste far exceeds the mechanical properties of natural soil, it can meet the mechanical strength requirements of supporting the vegetation layer 2. On the other hand, the drainage layer 3 and the vegetation layer 2 together constitute the upper protective layer of the geomembrane 4 to prevent damage to the geomembrane.

[0056] Among them, the geomembrane 4 adopts high-density polyethylene (HDPE) geomembrane or linear low-density polyethylene (LLDPE) geomembrane, the thickness should not be less than 1mm, and non-woven geotextile should be laid on the membrane, and the specification of non-woven geotextile should not be less than 300g / ㎡. The performance indicators of the geomembrane should comply with the requirements of the current industry standards "High-density polyethylene geomembrane for landfill" CJ / T 234 and "Linear low-density polyethylene geomembrane for landfill" CJ / T 276. The functions of the geomembrane mainly include four aspects: anti-seepage, air-tightening, gas collection and moisture retention. First, the anti-seepage function as a covering layer is realized by the geomembrane, which can effectively prevent a large amount of rainwater from infiltrating into the garbage body 8 to form leachate. Secondly, the geomembrane has an air-tightening function, which can effectively prevent the overflow of odor and reduce the impact of the landfill on the external environment and the degree of nuisance. In addition, the geomembrane helps to collect H2S under the membrane. In the absence of vacuuming, the air-tight function of the geomembrane 4 helps maintain a higher air pressure and a higher concentration of H2S gas under the membrane, which can accelerate the chemical reaction between the recycled aggregate and the H2S gas in the odor adsorption layer, thereby accelerating the adsorption of H2S; in the case of vacuuming, it will also help enrich the H2S gas under the membrane, which has a favorable effect on odor adsorption. Finally, the geomembrane helps to keep the odor adsorption layer Ⅰ6 moist. The presence of the geomembrane can prevent the odor adsorption layer Ⅰ6 from evaporating and drying, which is conducive to maintaining the odor adsorption layer Ⅰ6 at a higher water content for a long time. The adsorption reaction of the compacted recycled fine aggregate with H2S will be accelerated in an environment with a higher water content, which can better adsorb odor.

[0057] The gas collection layer 5 under the membrane is made of recycled coarse aggregates made from construction wastes buried in landfills. The gas collection layer 5 under the membrane is constructed of recycled coarse aggregates with a thickness of 0.2-0.4m, a particle size of 2-10mm, and a compacted relative density of not less than 0.9. The gas collection layer 5 under the membrane is arranged between the geomembrane 4 and the odor adsorption layer Ⅰ6. The main purpose of the arrangement is to support and protect the geomembrane 4, to form a highly permeable gas collection layer under the geomembrane 4, to facilitate the collection of gases that break through the odor adsorption layer Ⅰ6, to maintain a relatively low relative air pressure under the membrane, and to avoid the geomembrane from bulging or even tearing due to the local accumulation of a large amount of gas. In addition, the sub-membrane gas collection layer 5 also needs to act as a protective layer for the geomembrane 4. Its functions include: (1) supporting. The geomembrane is a flexible material and must be laid on a reliable support layer so that the geomembrane is evenly stressed; (2) it is laid under the geomembrane to remove the accumulated water and air under the membrane to ensure the stability of the geomembrane 4; (3) it protects the geomembrane 4 and avoids contact between the geomembrane and the odor adsorption layer I6 so that it is not damaged by the lower layer.

[0058] Among them, the odor adsorption layer I6 uses recycled fine aggregate prepared by recycling construction waste and recycled powder, and its parameters are as follows:

[0059] (1) Material requirements: Recycled fine materials need to be quality controlled. Recycled fine materials prepared from discarded high-strength concrete are preferred. The strength of the original concrete is required to be no less than C30; the weight ratio of concrete and mortar is no less than 95%, of which cement stone (and cement paste hardening body) and mortar content is no less than 40%; the pH of the compacted recycled fine material layer is no less than 10. As the grade of the original concrete increases, the proportion of cement in the corresponding mix also increases, and the amount of alkaline substances such as quicklime (CaO) or slaked lime (Ca(OH)2) remaining in the original concrete will also increase, which is more conducive to improving its odor adsorption capacity.

[0060] (2) Layer thickness: 1.0m-2.0m. It should be noted that the thickness of the odor adsorption layer I depends on the thickness of the landfill operation and the type of landfilled garbage, as well as the adsorption characteristics of the adsorbent material in the odor adsorption layer I. When the thickness of the landfill operation increases and the content of sulfur-containing organic waste that can be degraded to produce H2S increases, it means that the H2S generated by the landfill garbage will also increase, and the thickness of the corresponding odor adsorption layer I will also increase.

[0061] (3) The particle size distribution curve is saddle-shaped, that is, the fine and coarse particles account for a large proportion, and the intermediate particles are relatively small. Specifically, according to soil mechanics standards, the particle size distribution curve characteristics of recycled fine materials must meet the following conditions: (a) the maximum particle size does not exceed 2 mm; (b) the effective particle size d 10 Not more than 0.005mm; (c) 1.2mm≤d 90≤1.8mm; (d) Unevenness coefficient CU≥5; (e) Curvature coefficient C C Between 1 and 3, that is, 3 ≥ C C ≥1. The purpose of designing this particle size distribution is that the particle size distribution curve of the odor adsorption layer Ⅰ6 obtained after compaction presents a saddle shape, among which the coarse particles have a higher shear strength, forming the skeleton of the odor adsorption layer Ⅰ6 obtained after compaction, and improving the mechanical properties of the odor adsorption layer Ⅰ6 obtained after compaction. Fine particles are filled in the skeleton pores constructed by the coarse particle aggregate to control the water holding capacity and air permeability coefficient of the odor adsorption layer Ⅰ6 obtained after compaction. A high proportion of fine particles can improve the water holding capacity of the odor adsorption layer Ⅰ6 obtained after compaction and reduce its air permeability coefficient.

[0062] (4) The compaction degree of the recycled fine material in the odor adsorption layer I is not less than 95%. Improving the compaction degree can improve its mechanical strength, compress the pore volume, and increase the water holding capacity; at the same thickness, increasing the compaction degree can use more recycled aggregates, which can increase the total amount of alkaline substances in the odor adsorption layer I and thus improve the adsorption capacity; on the other hand, it can also consume more construction waste and realize the recycling of construction waste.

[0063] (5) Requirements for the air permeability of the recycled fine material in the odor adsorption layer I: The air permeability coefficient of the compacted recycled aggregate in the odor adsorption layer I at the maximum dry density is 10 -6 m / s—10 -8 m / s, air intake value 1kPa-10kPa. The purpose of selecting the permeability parameters is to control the time for odor to pass through the odor adsorption layer I, thereby controlling the amount of odor passing through and extending the odor adsorption reaction time of odor in the odor adsorption layer I, thereby improving the odor adsorption effect.

[0064] (6) Water absorption requirement: The water absorption of the odor adsorption layer I material shall not be less than 10%. The water absorption of recycled aggregate depends on the pore volume and the hydrophilic properties of the material. Among them, the pores include the pores between the particles of the compacted odor adsorption layer I and the pores and cracks of the particles themselves. The pores between the particles depend on the shape, particle size and compaction degree of the particles. Generally speaking, the higher the cement stone (i.e. cement paste hardened body) and mortar content of the recycled fine aggregate, the greater the water absorption; the more microcracks in the fine aggregate, the greater the water absorption. The present invention requires that the proportion of concrete and mortar in the construction waste used to prepare the recycled fine aggregate is not less than 95%, and accordingly, the water absorption requirement for the prepared recycled fine aggregate is not less than 10%.

[0065] (7) Moisture content requirement: saturation 60%-90%. The present invention requires that the pore water saturation of the regenerated fine material is not less than 60%. This is because the H2S adsorption reaction is more suitable in a humid environment, and a higher moisture content can improve the efficiency of the adsorption reaction. However, in order to ensure the permeability of the odor adsorption layer I, the pore water saturation of the regenerated fine material layer cannot be 100%, otherwise the regenerated fine material layer is completely saturated and its permeability coefficient will become 0. Through research, the present invention proposes that the maximum saturation should not be higher than 90%. In order to ensure a saturation of 60%-90%, it is required that the compacted regenerated fine material of the odor adsorption layer I contains enough fine particles (especially clay particles, i.e. <0.002mm) to improve the water holding capacity of the odor adsorption layer I. In addition, the maintenance of the moisture content in the compacted recycled aggregate of the odor adsorption layer I requires processes such as mixing water to configure the optimal moisture content before laying the regenerated fine material and sprinkling water to the predetermined moisture content after laying.

[0066] Among them, the purpose of the particle size grading design of the odor adsorption layer I material is to increase the proportion of fine particles, thereby increasing the adsorbent material in the odor adsorption layer I material and improving the odor adsorption capacity; and to increase the total specific surface area of ​​the odor adsorption layer I material, thereby increasing the contact area with the odor and improving the odor adsorption efficiency and capacity; by increasing the proportion of fine particles, the water holding capacity of the odor adsorption layer I can be effectively enhanced, the permeability coefficient can be reduced, and the amount of odor passing through the odor adsorption layer I per unit time can be controlled and the odor passing time can be extended, thereby achieving the purpose of extending the odor adsorption reaction time of the odor in the odor adsorption layer I and improving the odor adsorption effect.

[0067] The function of the odor adsorption layer I is mainly to adsorb odor and provide a certain mechanical strength to improve the mechanical properties of the sealing cover layer; in addition, the odor adsorption layer I does not need to consider the anti-seepage and air-tightness function. In addition, the alkaline environment provided by the odor adsorption layer I can effectively inhibit the generation of odor. The odor adsorption layer I and the gas collection layer I of the sealing cover layer provided by the present invention use recycled aggregates from construction waste. According to literature reports, the pH value of compacted recycled aggregates is generally higher than 10, which exceeds the suitable pH environment of aerobic / anaerobic microorganisms for waste degradation, and can effectively inhibit the generation of H2S.

[0068] Among them, the gas collection layer I7 is constructed with recycled coarse aggregate, with a thickness of 0.3-0.5m, a particle size of 20-40mm, and a compacted relative density of not less than 0.9. The gas collection layer I7 is arranged between the odor adsorption layer I6 and the garbage body 8. Its main function is to be located between the odor adsorption layer I6 and the garbage body 8 to facilitate the collection of odor, and to control the intensity of the H2S gas partial pressure in the gas collection layer I through the gas collection layer I exhaust device 14, thereby controlling the partial pressure distribution of H2S gas in the closure covering layer. When the odor generated by the degradation of the garbage body 8 enters the closure covering layer, it is blocked by the geomembrane and enriched in the closure covering layer. The particle size of the gas collection layer I is large, the pore volume is high, and a large amount of gas can be enriched; and the gas collection layer I has a large permeability coefficient, and the odor can be quickly extracted and discharged when the gas is exhausted. The vertical distribution of the odor partial pressure in the covering layer can be controlled by the gas collection layer I exhaust device 14.

[0069] The intermediate covering layer 19 includes three functional layers, which are an upper gas collecting layer 10 of the intermediate covering layer, an odor adsorption layer II 11 , and a lower gas collecting layer 12 from top to bottom.

[0070] Among them, the three functional layers of the upper gas collection layer 10, the odor adsorption layer II 11, and the lower gas collection layer 12 are all constructed of recycled materials prepared by recycling construction waste buried in landfills, preferably using discarded high-strength concrete. It is required that the strength of the original concrete of the upper and lower gas collection layers is not less than C10, and the strength of the original concrete of the odor adsorption layer II material of the middle covering layer is not less than C30; and before preparing recycled aggregates from construction waste, impurities (including slag, steel bars, wood, glass, plastic, bricks, paper, fabrics, etc.) are removed, and only concrete and mortar blocks are retained, and the weight of concrete and mortar accounts for not less than 95%.

[0071] Among them, the upper gas collection layer of the intermediate covering layer is constructed with recycled coarse aggregate, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compacted relative density of not less than 0.9. The function of the upper gas collection layer of the intermediate covering layer is to separate the odor adsorption layer II of the intermediate covering layer from the garbage body 8 thereon to avoid direct contact between the two; a gas collection layer with high permeability is formed between the odor adsorption layer II of the intermediate covering layer and the garbage body 8 thereon, so that H2S gas can overflow downward from the garbage body 8 above the odor adsorption layer II and be enriched in the upper gas collection layer; under the control of the upper gas collection layer exhaust device 15, the partial gas pressure value of H2S gas in the upper gas collection layer is controlled, and then the partial gas pressure distribution of H2S gas in the odor adsorption layer II of the intermediate covering layer is controlled, thereby affecting the progress of the odor adsorption reaction.

[0072] Among them, the odor adsorption layer II of the middle covering layer is made of recycled fine material, which is a mixture of recycled fine aggregate and recycled powder prepared by recycling construction waste. Its thickness is 0.4-0.8m, and the other material performance parameters are the same as those of the odor adsorption layer of the closure covering layer. The odor adsorption layer II of the middle covering layer serves as a temporary odor adsorption when the middle covering layer is in place, and can continue to adsorb odor as an intermediate interlayer of the garbage body after the closure.

[0073] Among them, the lower gas collection layer of the middle covering layer is constructed with recycled coarse aggregate, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compacted relative density of not less than 0.9. The function of the lower gas collection layer of the middle covering layer is to separate the odor adsorption layer II of the middle covering layer from the garbage body below to avoid direct contact between the two; to form a gas collection layer with high permeability between the odor adsorption layer II of the middle covering layer and the garbage body below it, so that H2S gas can overflow upward from the garbage body below the odor adsorption layer II and be enriched in the lower gas collection layer; under the control of the lower gas collection layer exhaust device 16, the partial gas pressure value of H2S gas in the lower gas collection layer is controlled, and then the partial gas pressure distribution of H2S gas in the odor adsorption layer II of the middle covering layer is controlled, thereby affecting the progress of the odor adsorption reaction.

[0074] The covering system of the present invention and the garbage body and the bottom anti-seepage lining in the prior art constitute "bottom anti-seepage lining-garbage body-intermediate covering layer (odor adsorption layer II)-garbage body-intermediate covering layer-...-garbage body-sealing covering layer (odor adsorption layer I-geomembrane)", and the bottom anti-seepage lining is the anti-seepage cushion layer 17. In this structure formed by the staggered superposition of the composite structure of "garbage-intermediate covering layer", the intermediate covering layer and the garbage body are in full contact, that is, the odor adsorption layer II of the intermediate covering layer is mixed in the garbage, and multi-level adsorption is achieved. On the one hand, the intermediate covering layer serves as a temporary odor adsorption during the landfill operation, and on the other hand, it can continue to adsorb odor as an intermediate interlayer of the garbage body after the closure.

[0075] Among them, the water storage capacity of the odor adsorption layer of the sealing cover layer and the intermediate cover layer is mainly achieved through macropore accommodation, capillary pore absorption and fine aggregate particle absorption. The soil with a larger mass fraction of clay particles has more capillary content, more storage pores, a larger specific surface area, a stronger adsorption capacity, and a stronger water storage capacity. As shown in the soil-water characteristic curve, the soil volume moisture content in each water suction section decreases with the increase of clay mass fraction. In the medium and low water suction sections, the soil with a larger mass fraction of clay particles has more capillary content, a stronger capillary absorption capacity, and more water; in the high water suction section, the huge surface area and surface charge of clay particles make it have a strong ability to absorb water molecules, forming a thicker adsorption water layer or water film, and the pores between clay particles are extremely fine, forming a thicker adsorption water layer or water film, and the pores between clay particles are extremely fine, and it is possible to retain a certain amount of water outside the adsorption water film under the action of capillary force, and the soil with a larger mass fraction of clay particles has a stronger effect.

[0076] Since the particle sizes of the odor adsorption layer and the gas collection layer are quite different, in order to prevent the smaller particles from falling into the larger particles, a water-permeable and breathable insulating material layer is pre-laid to prevent mutual mixing. In addition, a geotextile may be laid between the gas collection layer and the garbage body to prevent mutual mixing. The gas collection layer of the present application is the sub-membrane gas collection layer, gas collection layer I, the upper gas collection layer or the lower gas collection layer, and the odor adsorption layer is the odor adsorption layer I or the odor adsorption layer II. A water-permeable and breathable insulating material layer may also be provided directly between the vegetation layer and the drainage layer, and the water-permeable and breathable insulating material layer is preferably a geotextile.

[0077] A water-permeable and air-permeable insulating material layer is provided between all adjacent functional layers.

[0078] The material used for the odor adsorption layer in this patent is a mixture of recycled fine aggregate and recycled powder prepared from construction waste, and its advantages include the following aspects:

[0079] (1) Large specific surface area. As mentioned above, increasing the specific surface area can increase the contact area between the compacted recycled aggregate and H2S gas in the odor adsorption layer, thereby increasing the chemical reaction between the compacted recycled aggregate and H2S gas and increasing odor adsorption. The particles of recycled fine materials recovered from construction waste are relatively fine, which can significantly increase the surface area. At the same time, the recycled recycled fine materials are also a typical porous material, and their pores mainly include primary pores and regenerated pores. Their pore volume is much larger than that of natural aggregates and soils with the same particle size grading. Among them, the primary pores are mainly the primary pores on the mortar surface caused by foaming and other reasons during the preparation of concrete, and the regenerated pores refer to the new cracks or pores generated during the crushing preparation of recycled aggregates. The increase in pores and cracks can greatly increase the specific surface area of ​​recycled aggregates, increase the contact area between the odor adsorption layer and H2S, and further improve the odor adsorption capacity.

[0080] (2) More fine particles and stronger adsorption capacity. The material with adsorption capacity in the recycled aggregate in the odor adsorption layer is mainly cement, and the sand and gravel in the original concrete have no adsorption capacity. The cement mortar content in the fine particles of the recycled aggregate is relatively high, so increasing the proportion of fine particles can effectively increase the odor adsorption capacity of the recycled aggregate.

[0081] (3) The small permeability coefficient can effectively control the amount and time of odor passing through the odor adsorption layer. By reducing the amount of odor passing between units and extending the time of passing, the adsorption effect can be improved.

[0082] (4) The alkaline environment provided by the odor adsorption layer can effectively inhibit the generation of odor. According to literature reports, the pH value of compacted recycled aggregates is generally higher than 9, which exceeds the suitable pH environment for aerobic / anaerobic microorganisms that degrade garbage, and can effectively inhibit the generation of H2S.

[0083] (5) High water absorption and good water holding capacity. Studies have shown that in an environment with a high moisture content, the adsorption reaction between recycled fine aggregates and H2S will be accelerated, which can better absorb odor. Generally speaking, the moisture content of recycled recycled aggregates is 15 times that of natural aggregates, and the water absorption rate is 10.2 times that of natural aggregates. This is mainly because the recycled recycled aggregates have a large porosity. The pores in the recycled recycled aggregates include the pores between the particles and the pores inside the aggregate particles. Therefore, in the compacted recycled recycled aggregate layer, water can be stored in the pores between the aggregate particles and in the pores inside the particles. In addition, the cement mortar attached to the surface of the recycled aggregate has good hydrophilicity. According to the basic theory of unsaturated soil mechanics, the compacted recycled aggregate has good water holding capacity and can absorb and retain water more easily.

[0084] (6) High strength. The middle cover layer needs to have good mechanical properties so that it can form a reinforcement effect between different layers of garbage to improve the mechanical stability of the entire garbage body. According to literature reports, the mechanical strength of compacted recycled aggregate is much greater than that of natural soil or gravel with the same particle size distribution. Using recycled aggregate as the middle cover layer material can greatly improve the mechanical properties of the middle cover layer and further improve the stability of the garbage body.

[0085] (7) Low cost and easy to obtain. There are many technologies and materials for odor adsorption, but the cost is generally high and requires large-scale long-distance transportation, which results in low economic efficiency. Therefore, the odor adsorption layer should be made of low-cost and easy-to-obtain materials.

[0086] The working mechanism of the landfill covering system involved in the present invention is:

[0087] The core functions of the landfill covering system involved in the present invention include anti-seepage and air-tight functions, as well as the H2S odor adsorption function unique to the present invention.

[0088] Attached Figure 7 It is a schematic diagram of the anti-seepage and air-tightening principle of the present invention. The anti-seepage and air-tightening function is achieved by the geomembrane of the closure cover layer. The geomembrane has extremely low permeability and can effectively prevent a large amount of rainwater from infiltrating into the garbage body to form leachate. When it rains 20, on the one hand, most of the rainwater becomes slope runoff 21 and is drained down the slope; the remaining rainwater infiltrates into the vegetation layer 2. The rainwater entering the vegetation layer 2 is stored in the vegetation layer 2. When it exceeds the storage capacity of the vegetation layer 2, the infiltrated water enters the drainage layer 3 and is drained down the slope in the drainage layer along the surface of the geomembrane 4 (i.e., the drainage layer is drained laterally 22).

[0089] The geomembrane 4 has an air-tight function, which can effectively prevent the odor from escaping, reduce the impact of the landfill on the external environment and the degree of nuisance to residents.

[0090] Attached Figure 5 and 6 The schematic diagram of the odor adsorption principle of the present invention. The H2S odor adsorption function involved in the present invention is mainly achieved through the layer-by-layer adsorption of the intermediate covering layer 19 constructed during the landfilling, and the final adsorption of the sealing covering layer 18, that is, the combined adsorption system composed of several intermediate covering layers 19 and the final sealing covering layer 18 realizes odor adsorption together.

[0091] Among them, the principle of odor adsorption in the middle covering layer is that the odor adsorption in the middle covering layer 19 is mainly achieved through the gas collection of the upper gas collection layer 10 and the lower gas collection layer 12 and the adsorption reaction of the odor adsorption layer II 11. The particles of the upper and lower gas collection layers are larger in size, higher in pore volume, and larger in permeability coefficient, which can collect the landfill gas generated by the upper and lower garbage bodies, and enrich and maintain a higher H2S partial pressure in the upper and lower gas collection layers, that is, the upper and lower odor adsorption layers II of the middle covering layer are in an environment with a higher H2S partial pressure, which can accelerate the chemical reaction between the recycled aggregate and the H2S gas in the odor adsorption layer II of the middle covering layer, thereby accelerating the adsorption of H2S. In addition, the upper and lower gas collection layers are respectively equipped with exhaust devices for controlling the gas pressure of the upper and lower gas collection layers, especially the partial pressure of H2S gas, and then controlling the distribution of the partial pressure of H2S gas in the odor adsorption layer II with depth, so as to achieve the best odor adsorption effect.

[0092] As attached Figure 6 As shown, the present invention requires several intermediate covering layers, Figure 6 The middle cover layer with serial number N is used as an example. In the middle cover layer with serial number N, the depth of contact between the upper air collecting layer and the garbage body is D N0 The depth of contact between the upper gas collection layer and the odor adsorption layer Ⅱ11 is DN1 The depth of contact between the lower gas collection layer and the odor adsorption layer Ⅱ11 is D N2 , the depth of contact between the lower gas collecting layer and the garbage body is D N3 The partial pressure of H2S gas in the upper and lower gas collecting layers can be regarded as P N2 , the burial depth of the longitudinal middle thickness of the odor adsorption layer II is D NC , the burial depth is D NC The partial pressure of H2S gas at N1 . Odor adsorption layer Ⅱ11 from D NC To D N1 and D NC To D N2 The H2S gas pressure along the vertical direction increases with the depth from P N1 To P N2 The linear distribution of .

[0093] Generally, the H2S gas partial pressure P of the odor adsorption layer II of the intermediate cover layer is N1 The control value is between 0kPa and 2kPa, and the optimal control value is 0kPa. The partial pressure P of H2S gas in the upper and lower gas collecting layers of the intermediate covering layer N1 The control value is between 0kPa and 10kPa, ensuring that the H2S gas partial pressure P in the middle cover layer N1 and P N2 Under the condition that the standard is not exceeded, the partial pressure P of H2S gas in the middle cover layer should be appropriately increased. N1 and P N2 The value can effectively improve the efficiency and adsorption effect of the odor adsorption reaction. The partial pressure P of the H2S gas in the upper and lower gas collection layers is controlled by the upper gas collection layer exhaust device 15 and the lower gas collection layer exhaust device 16. N2 value, thereby controlling the distribution of the partial pressure of H2S gas in the odor adsorption layer II with depth, so as to achieve the best odor adsorption effect.

[0094] The covering system of the present invention, the garbage body, and the bottom anti-seepage lining in the prior art constitute "bottom anti-seepage lining-garbage body-intermediate covering layer-garbage body-intermediate covering layer-...-garbage body-sealing covering layer". In this structure formed by the staggered superposition of the composite structure of "garbage body-intermediate covering layer", the intermediate covering layer and the garbage body are in full contact, that is, the odor adsorption layer of the intermediate covering layer is mixed in the garbage, and multi-level adsorption is achieved. On the one hand, the intermediate covering layer serves as a temporary odor adsorption when serving as the intermediate covering layer, and on the other hand, it can continue to adsorb odor as the intermediate interlayer of the garbage body after the closure.

[0095] The principle of odor adsorption of the sealing cover layer 18 is that the odor adsorption in the sealing cover layer is mainly achieved through the gas collection layer 5 under the geomembrane, the gas collection layer I 7 and the adsorption reaction of the odor adsorption layer I 6. The air-tight function of the geomembrane 4 helps to maintain a higher air pressure and a higher concentration of H2S gas under the membrane, which can accelerate the chemical reaction between the recycled aggregate and the H2S gas in the odor adsorption layer I, and then accelerate the adsorption of H2S; the particle size of the gas collection layer I is larger, the pore volume is higher, and the permeability coefficient is larger, which can enrich a large amount of gas. In addition, the gas collection layer under the membrane and the gas collection layer I are respectively equipped with exhaust devices - the gas collection layer under the membrane exhaust device 13 and the gas collection layer I exhaust device 14, which are used to control the air pressure of the gas collection layer under the membrane and the gas collection layer I, especially the partial pressure of H2S gas, and then control the distribution of the partial pressure of H2S gas in the odor adsorption layer I with depth, so as to achieve the best odor adsorption effect.

[0096] As attached Figure 5 As shown, the partial pressures of H2S gas in the gas collection layer under the membrane and the gas collection layer I are P1 and P2 respectively, and the partial pressure of H2S gas in the odor adsorption layer I presents a linear distribution from P1 to P2 with depth. Usually, the control value of the partial pressure P1 of H2S gas in the gas collection layer under the membrane is between -1kPa and 1kPa, and the optimal control value is 0kPa. The control value of the partial pressure P1 of H2S gas in the gas collection layer I is between 0kPa and 10kPa. While ensuring that the partial pressure P1 of H2S gas in the gas collection layer under the membrane does not exceed the standard, appropriately increasing the partial pressure P1 value of H2S gas in the gas collection layer I can effectively improve the occurrence efficiency and adsorption effect of the odor adsorption reaction. The partial pressure P1 value of H2S gas in the gas collection layer is controlled by the exhaust device of the gas collection layer I. The partial gas pressure P2 of the H2S gas in the gas collection layer under the membrane is achieved by the combined action of the gas collection layer I and the exhaust device of the gas collection layer under the membrane, with the exhaust device of the gas collection layer I as the main one and the exhaust device of the gas collection layer under the membrane as the auxiliary one. It is preferred to use the exhaust device of the gas collection layer I.

[0097] The odor adsorption mechanism of the odor adsorption layer of the sealing cover layer and the intermediate cover layer of the present invention is that: the recycled aggregate of construction waste is used as the construction material of the odor adsorption layer, and the unreacted quicklime (CaO) or slaked lime (Ca(OH)2) and other alkaline substances remain in the construction waste, which react with the acidic substances (mainly H2S) in the odor to produce an acid-base neutralization reaction. The chemical reaction equation is as follows:

[0098]

[0099] In addition, the high-strength concrete crushing preparation, large thickness, high compaction, high proportion of fine particles, high proportion of concrete and mortar blocks, high water content and moisturizing function of the geomembrane of the odor adsorption layer can effectively increase the theoretical adsorption capacity of the odor adsorption layer and create a suitable environment for the adsorption reaction, thereby better improving the actual adsorption effect.

[0100] The method for manufacturing the covering system involved in the present invention is as follows:

[0101] (1) Material preparation: Geomembrane needs to be purchased from outside and transported to the landfill. The material performance requirements of the geomembrane must meet the requirements of relevant specifications, including GB / T 50290-2014 Technical Specification for Application of Geosynthetics, GB / T17642-2008 Technical Standard for Composite Geomembrane, etc. In addition, the performance of the geomembrane must also meet the requirements of relevant landfill specifications, such as GB50869-2013 Technical Specification for Sanitary Landfill Treatment of Municipal Waste, CJJ176-2012 Technical Specification for Geotechnical Engineering of Sanitary Landfill Sites of Municipal Waste, etc.

[0102] The soil material of the vegetation layer can be obtained nearby, and the material requirements of the vegetation soil must meet relevant specifications. The present invention does not make any special requirements.

[0103] The recycled aggregates required for the drainage layer, sub-membrane gas collection layer, odor adsorption layer I and gas collection layer I and the intermediate cover layer of the closure cover layer are preferably taken from the construction waste buried in the landfill site. The production and processing can refer to the production specifications of recycled aggregates for construction projects (such as GB / T25177-2010 Recycled coarse aggregate for concrete and DB894.1-Technical regulations for the application of recycled sand powder (Shanghai)), etc.) to facilitate large-scale industrial production and reduce process difficulty and production costs. Before the preparation of recycled aggregates, impurities such as wood, steel bars, and slag in the construction waste should be removed by pretreatment, leaving only waste concrete and mortar stone. Then, crushing, grinding, screening and other processes are carried out to prepare recycled coarse aggregates and recycled fine aggregates with corresponding predetermined particle size requirements. Micro powder (also called recycled powder) can be prepared by dust collection equipment, and the micro powder is mixed with recycled fine aggregate to obtain the materials required for the odor adsorption layer. The materials required for the closure cover layer and the intermediate cover layer need to meet the above requirements.

[0104] (2) Add water, mix and cure. Before constructing the closure cover layer and the intermediate cover layer separately, the required materials need to be mixed with water to the optimal moisture content, and then sealed and cured to ensure uniform moisture. The optimal moisture content of each layer of material needs to be determined by experimental research in advance, and the determination method should comply with the requirements of relevant geotechnical test specifications (such as GBT 50123-2019 Geotechnical Test Method Standard). When configuring the optimal moisture content, ensure that the water is added evenly and fully stirred, and no large agglomerates occur. The materials should be cured in a closed and light-shielded environment, usually for 3-10 days.

[0105] (3) Laying of the intermediate covering layer: First, lay the bottom anti-seepage lining - the anti-seepage cushion layer 17 (performed according to the existing technology), and then fill the garbage. After the landfill operation is completed, the landfill is leveled and rolled, and then a layer of geotextile is laid. Then, the compacted coarse aggregate of the lower gas collection layer is laid on the geotextile, and the recycled coarse aggregate is laid in layers and fully compacted. The thickness of each layer should not be too thick (generally not more than 10cm), and the compaction degree must meet the requirements (relative density not less than 0.9). Then lay the geotextile. Then, lay the odor adsorption layer II on the geotextile. When laying, it needs to be laid in layers and fully compacted. The thickness of each layer should not exceed 10cm, and the compaction degree should not be less than 95%. When compacting in layers, pay attention to scraping the surface of the recycled fine aggregate layer after compaction in front, so that the front and back layers can fully contact and bond.

[0106] After the odor adsorption layer II is laid, it is necessary to manually sprinkle water or dry it in the sun so that its moisture content reaches the predetermined moisture content of the adsorption reaction.

[0107] The laying, welding, and maintenance of the geomembrane need to be carried out in accordance with relevant specifications (such as GB / T 50290-2014 Technical Specifications for Application of Geosynthetics), and the present invention does not make special requirements.

[0108] After the intermediate cover is laid, it needs to be monitored and maintained. In addition to the monitoring of anti-seepage and drainage, leachate, garbage degradation, garbage body settlement, etc. required for the traditional intermediate cover, it is also necessary to carry out the integrity and soundness of the geomembrane, the generation and distribution of landfill gas (especially H2S), and the operation of the odor adsorption function of the intermediate cover.

[0109] When the next round of landfill operation is carried out, it is only necessary to peel off the geomembrane, and then lay the geotextile first, and then lay the upper air collection layer on the geotextile, and the laying method is the same as the lower air collection layer, and then the garbage is landfilled. After the landfill operation, continue to lay the middle cover layer, and then carry out the next round of landfill operation until the predetermined landfill elevation is reached for sealing, and the sealing cover layer is laid.

[0110] (4) Laying of the cover layer: After the landfill operation is completed, the landfill should be cleaned, leveled and rolled. Pay attention to cleaning up sharp stones, tree roots and other debris, and clean up all debris to prevent the geomembrane from being punctured by debris. The base surface is not allowed to have local unevenness. The cleaned base surface should be compacted with a tamping hammer or tamping plate to make it dense and flat.

[0111] Then lay the geotextile first, and then lay the compacted coarse aggregate of the gas collection layer I on the geotextile. The recycled coarse aggregate is laid in layers and fully compacted. The thickness of each layer should not be too thick (generally not more than 10cm), and the compaction degree must meet the requirements (relative density not less than 0.9). Then lay the geotextile, and then lay the odor adsorption layer I on the geotextile. When laying, it needs to be laid in layers and fully compacted. The thickness of each layer should not exceed 10cm, and the compaction degree should not be less than 95%. When compacting in layers, pay attention to scraping the surface of the recycled fine aggregate layer after compaction in front, so that the front and back layers can fully contact and combine.

[0112] After the odor adsorption layer I is laid, it is necessary to manually sprinkle water or dry it in the sun so that its moisture content reaches the predetermined moisture content of the adsorption reaction.

[0113] Then lay the geotextile, and then lay the sub-membrane gas collection layer on the geotextile, that is, lay a thin layer of recycled coarse aggregate between the odor adsorption layer I and the geomembrane to prevent the geomembrane from bulging due to the accumulation of a large amount of gas locally. The laying method and requirements of the sub-membrane gas collection layer are the same as those of the gas collection layer I.

[0114] The laying, welding, and maintenance of the geomembrane need to be carried out in accordance with relevant specifications (such as GB / T 50290-2014 Technical Specifications for Application of Geosynthetics), and the present invention does not make special requirements.

[0115] Then lay the drainage layer, the laying steps and requirements of the drainage layer are the same as those of the air collection layer under the membrane. Then lay the geotextile on the drainage layer.

[0116] Then, the geotextile is laid, and then the vegetation layer is laid on the geotextile. The soil material of the vegetation layer is compacted in layers, and the hair needs to be scraped between the layers. Then, greening is planted on the vegetation layer. Fertilization, tillage construction, maintenance, irrigation, etc. of the vegetation are carried out in accordance with relevant specifications, and the present invention does not make special requirements.

[0117] After the closure cover is laid, it needs to be monitored and maintained. In addition to the monitoring of anti-seepage and drainage, leachate, garbage degradation, garbage body sedimentation, etc. required for traditional closure covers, it is also necessary to carry out the integrity and soundness of the geomembrane, the generation and distribution of landfill gas (especially H2S), and the operation of the odor adsorption function of the closure cover. In addition, vegetation maintenance is also required.

[0118] Among them, in the laying step, the geotextile laid between the functional layers is mainly used to prevent the large difference in particle size between the upper and lower layers from causing particle migration and the smaller particles from falling into the larger particles and mixing with each other. The geotextile is required to be water-permeable and air-permeable, and the strength meets the requirements. The present invention requires that the geotextile used meets the basic performance requirements of the geotextile conventionally used in landfills, and the present invention does not make special requirements.

[0119] In addition, compared with the operating characteristics of similar landfills, the operating characteristics of the landfill where the covering system involved in the present invention is located are "small amount and multiple times", that is, the thickness of a single landfill is reduced, and the total number of landfill operations is increased; in this way, the number of multiple composite structures of "garbage-intermediate covering layer-garbage" stacked up and down can be increased. Its design concept is to increase the number of intermediate covering layers in the garbage body as much as possible, and to increase the total contact area between the odor adsorption layer and the garbage body as much as possible, so as to improve the odor adsorption capacity and adsorption effect.

[0120] The thickness of a single landfill operation and the corresponding thickness of the intermediate cover layer, as well as the thickness of the closure cover layer, recommended by the present invention, all need to be calculated and demonstrated in order to match each other. Generally speaking, an increase in the thickness of a single landfill operation and an increase in the total amount of sulfur-containing organic matter in a single landfill garbage will inevitably lead to an increase in the theoretical amount of odor H2S generated in the garbage of a single landfill, which will inevitably lead to an increase in the thickness of the odor adsorption layer in the required intermediate cover layer. In addition, the thickness of the odor adsorption layer is also related to the adsorption capacity of the odor adsorption layer material. When the adsorption capacity of the odor adsorption layer material increases, the required adsorption layer thickness will also decrease accordingly. Therefore, the thickness design of the intermediate cover layer involved in the present invention is related to the total amount of H2S gas that can be generated by the garbage in a single landfill operation and the H2S adsorption capacity of the adsorption layer material. This design concept is very different from the design concept of the traditional intermediate cover layer.

[0121] Compared with the prior art, the present invention provides the following beneficial effects:

[0122] (1) The concept of "using garbage to absorb garbage odor" is proposed to achieve the recycling of construction waste, energy saving and emission reduction, and green environmental protection. The present invention creatively proposes to use construction waste buried in landfills to absorb the odor generated by landfill garbage, thus achieving the recycling of construction waste, energy saving and emission reduction, and green environmental protection.

[0123] (2) Provide a covering system for achieving odor control by means of H2S absorption treatment. The present invention provides a covering system for achieving odor absorption by means of adsorption, which includes a plurality of intermediate covering layers and a closure covering layer. The intermediate covering layer can be used as a temporary odor absorption after a single landfill operation is completed, and can also be used as an intermediate interlayer of the garbage body after closure to continue odor absorption.

[0124] (3) It can effectively inhibit the generation of H2S. The odor adsorption layer and gas collection layer of the covering system provided by the present invention are made of recycled aggregates from construction waste. According to literature reports, the pH value of compacted recycled aggregates is generally higher than 9, which exceeds the suitable pH environment for aerobic / anaerobic microorganisms that degrade waste, and can effectively inhibit the generation of H2S.

[0125] (4) Improve the permeability of the garbage body, improve the gas collection and extraction capacity, accelerate the degradation of the garbage body, and improve the odor adsorption effect. The intermediate covering layer in the covering system provided by the present invention contains upper and lower gas collection layers constructed of highly permeable recycled coarse aggregate. As the landfill operation proceeds, a layer of garbage is superimposed on an intermediate covering layer to form a composite structure with multiple gas collection layers with good permeability. This composite structure can greatly improve the permeability of the garbage body and enhance the gas collection and extraction capacity during the later maintenance process. In conjunction with engineering measures such as ventilation and exhaust, it can accelerate the degradation of the garbage body and accelerate the extraction capacity of methane (CH4) generated by the degradation of the garbage body. In addition, the improvement of the permeability of the garbage body is also conducive to the entry of H2S into the upper and lower gas collection layers and the odor adsorption layer II. In conjunction with engineering means, the air pressure of the gas collection layer can be controlled to maintain it at the pressure required for the optimal odor adsorption reaction, thereby promoting the adsorption effect of H2S gas. There is also a gas collection layer I in the sealing covering layer, which can also provide similar effects.

[0126] (5) Improve the moisture retention capacity of the covering layer, so that the garbage body and the odor adsorption layer in the covering system maintain appropriate humidity, thereby creating a suitable environment for the H2S adsorption reaction and accelerating the H2S adsorption reaction. The landfill covering layer in the covering system involved in the present invention uses a geomembrane for anti-seepage, airtightness and moisture retention. Under the action of the geomembrane, rainwater cannot penetrate into the landfill covering layer and the garbage body; at the same time, the moisture in the landfill covering layer and the garbage body will not evaporate into the air, thereby ensuring the stability of the moisture content in the landfill covering layer and the garbage body. In the actual working process, the moisture content of the landfill garbage will be pretreated before laying the geomembrane, and the coarse and fine recycled aggregates of the gas collection layer I and the odor adsorption layer I will also be pretreated to ensure that the moisture content of the garbage body and the gas collection layer I and the odor adsorption layer I reaches the predetermined value. This pretreatment method includes watering, stirring, drying, exposure to the sun, air drying, etc. For the closure cover treated by odor adsorption, the predetermined moisture content of the garbage, gas collection layer I and odor adsorption layer I depends on the progress of the odor adsorption reaction.

[0127] (6) Using construction waste from landfills to absorb H2S, local materials are used, and there is no need to transport a large amount of odor adsorption materials from outside, and the disadvantage of traditional odor adsorption materials and the constructed soil cover layer consuming the landfill storage capacity is avoided. The H2S absorption treatment method involved in the present invention does not require additional large-scale transportation of soil and odor adsorption materials from outside, and only requires local materials and recycling of construction waste buried in the landfill site. The geomembrane can be reused. After completing a landfill task, the intermediate cover layer is laid; before the next landfill is carried out, the geomembrane is uncovered and re-covered on the newly buried garbage body, and finally becomes the geomembrane in the sealing cover layer. Therefore, the covering system for odor adsorption treatment involved in the present invention does not require the transportation of a large amount of odor adsorption materials from outside; at the same time, it avoids the disadvantages of the traditional soil cover layer that requires a large amount of engineering materials to be transported from outside, and the disadvantages of the traditional soil cover layer being too thick, which seriously consumes the landfill storage capacity.

[0128] (7) Use high-strength recycled aggregates to replace low-strength soil materials to construct the intermediate cover layer, and improve the "weak interlayer" effect of the soil intermediate cover layer into the "reinforcement" effect of the intermediate cover layer built with recycled aggregates, thereby improving the mechanical stability of the landfill garbage body. When the traditional cover layer is laid with soil materials, a large amount of silt and clay are often required, and the mechanical properties of such soil materials are poor. When the garbage contains several such intermediate cover layers, the intermediate cover layers are prone to form weak interlayers, which reduces the mechanical stability of the garbage body. In contrast, from a mechanical point of view, the shear strength of recycled coarse and fine aggregates of construction waste is higher and has a larger internal friction angle (or natural repose angle). When several intermediate cover layers built with construction waste are laid inside the landfill garbage body, it is equivalent to the "reinforcement" effect on the inside of the landfill garbage body, which can greatly improve the strength of the garbage body, thereby improving the stability of the landfill cover layer.

[0129] (8) More reasonable arrangement of the landfill garbage body shape and landfill construction process, increase the landfill storage capacity, and maximize the odor adsorption effect. The landfill garbage body is restricted by mechanical properties, and its height, slope, and single landfill layer thickness and other morphological parameters are restricted. The covering system of the present invention is constructed with high-strength recycled aggregates, and the implementation of the present invention makes the structure after the landfill is closed into "bottom anti-seepage lining-garbage-intermediate covering layer-garbage-intermediate covering layer-...-garbage-sealing covering layer". This garbage body formed by the staggered superposition of the composite structure of "garbage-intermediate covering layer" will play a mechanical reinforcement role due to the high mechanical strength of the intermediate covering layer, thereby improving the mechanical properties and mechanical stability of the garbage body. Therefore, the implementation of the present invention eliminates the above-mentioned restrictive factors, so that the shape of the landfill garbage body can be arranged more reasonably, the landfill garbage body can be higher, and the slope can be larger, thereby increasing the storage capacity of the landfill. On the other hand, by consuming the construction waste in the landfill, the storage capacity occupied by the construction waste can also be released, thereby increasing the storage capacity of the landfill from another angle. In addition, since there are no other limiting factors, the design concept of the landfill construction process of the garbage body will be mainly to maximize the odor adsorption, reasonably set the thickness of the single landfill layer and the thickness of the intermediate cover layer, and reasonably set the landfill operation process. The slope of the closure cover layer of the present invention can be 30°-60°, preferably 40°-50°.

[0130] (9) Consume a large amount of construction waste in landfills and release the storage capacity occupied by construction waste. In traditional landfills, construction waste occupies a large amount of storage capacity. The covering system involved in the present invention uses raw materials that are processed into recycled aggregates from landfill construction waste, and the recycled aggregates made from construction waste are used in the covering system. The excess recycled aggregates can also be exported for use in other civil engineering projects. In this way, construction waste can be effectively consumed and utilized, thereby releasing the storage capacity occupied by construction waste in landfills and improving the economic and social benefits of landfills.

[0131] (10) Solve the problem that the traditional soil middle cover layer cannot pass medium and heavy machinery and vehicles, and the construction is simple and efficient. Because the strength of the soil middle cover layer is too low, during the next stage of landfill, medium and heavy construction machinery cannot pass normally on the soil middle cover layer, causing further construction difficulties. The new middle cover layer constructed of recycled aggregates and recycled powder obtained from construction waste has high strength and can freely pass large machinery, making construction convenient.

[0132] (11) Convenient material acquisition, low cost, good durability, simple and low cost for later maintenance. The intermediate covering layer involved in the present invention is mainly made of construction waste in landfills, which avoids the need for traditional soil covering layers to transport a large amount of soil resources from outside and the high material and transportation costs. In addition, the material stability and durability of recycled aggregates are good, the intermediate covering layer has a stable structure, simple maintenance and low maintenance costs.

[0133] Below, the present invention provides an embodiment:

[0134] Specifically, in the present embodiment, the vegetation layer 2 is preferably made of local soil. In the present embodiment, the surrounding loess is selected, and the soil is rich in nutrients, which can meet the requirements of the relevant specifications for the vegetation soil in the landfill cover system. Therefore, no additional nutrients need to be added, and no requirements beyond the relevant specifications are imposed on it during the implementation of the present invention. The thickness of the vegetation layer is 0.5m, the compaction degree is 80%, and the selected vegetation 1 type is turf with shallow roots. The drainage layer 3 is constructed of recycled aggregates prepared by recycling construction waste buried in the landfill, with a thickness of 0.2m, a particle size of 20-40mm, and a compacted relative density of 0.9. The geomembrane 4 adopts a high-density polyethylene (HDPE) geomembrane with a thickness of 5mm. A non-woven geotextile with a specification of 300g / ㎡ should be laid on the membrane; a protective layer should be laid under the membrane, and the protective layer refers to the relevant standards for geomembrane construction technology. The performance indicators of the geomembrane meet the requirements of the current industry standards "High-density polyethylene geomembrane for landfill" CJ / T 234 and "Linear low-density polyethylene geomembrane for landfill" CJ / T 276. The sub-membrane gas collection layer 5 is constructed with recycled aggregates prepared from construction waste recycled from landfills, with a thickness of 0.2m, a particle size of 2-10mm, and a compacted relative density of 0.9. The raw material used in the odor adsorption layer I6 is recycled fine material, which is a mixture of recycled fine aggregates and recycled powder prepared from recycled construction waste, with a thickness of 1.2m, a compaction degree of 95%, a maximum particle size of 2mm, and an effective particle size d 10 =0.02mm, the air permeability coefficient of the compacted recycled aggregate of the odor adsorption layer at the maximum dry density is 10 -7 m / s—10 -8 m / s, air intake value 5kPa, water absorption rate 12%, pore water saturation 60%. The gas collection layer is constructed with recycled coarse aggregate, with a thickness of 0.3m, a particle size of 20-40mm, and a compacted relative density of 0.9.

[0135] The intermediate covering layer 19 includes three functional layers, which are the upper gas collection layer 10 of the intermediate covering layer, the odor adsorption layer II 11 of the intermediate covering layer, and the lower gas collection layer 12 from top to bottom. Among them, the upper gas collection layer 10 of the intermediate covering layer is constructed with recycled coarse aggregate, with a thickness of 0.2m, a particle size of 20-40mm, and a compacted relative density of 0.9. Among them, the odor adsorption layer II 11 of the intermediate covering layer is a mixture of recycled fine aggregate and recycled powder prepared by recycling construction waste, with a thickness of 0.4m, and the other material performance parameters are the same as the parameter requirements of the odor adsorption layer I of the sealing covering layer. Among them, the lower gas collection layer 12 of the intermediate covering layer is constructed with recycled coarse aggregate, with a thickness of 0.2m, a particle size of 20-40mm, and a compacted relative density of 0.9.

[0136] The particle size curves of the above layers except the geomembrane are shown in the attached figure. Figure 4 shown.

[0137] Among them, the recycled aggregate described in the above-mentioned functional layer material is preferably recycled aggregate prepared from discarded high-strength concrete, and the strength of the original concrete is required to be not less than C30; and before preparing the recycled aggregate from construction waste, impurities (including slag, steel bars, wood, glass, plastic, bricks, paper, fabric, etc.) are removed, and only concrete and mortar blocks are retained, and the weight proportion of concrete and mortar is not less than 95%, and the pH value of the prepared recycled material is not less than 10.

[0138] A water-permeable and air-permeable insulating material layer 9 is provided between the functional layers. The insulating material layer is preferably a geotextile, which should meet the requirements of relevant specifications. The purpose of setting the geotextile is that since the particle sizes of the sub-membrane gas collection layer 5, the odor adsorption layer I6 and the gas collection layer I7 are quite different, in order to prevent the smaller particles from falling into the larger particles, the geotextile 9 is laid in advance to prevent the mutual mixing. In addition, a geotextile may be laid between the gas collection layer and the garbage body to prevent mutual mixing.

[0139] It should be noted that in order to solve the problem that the strength of the traditional earthen cover layer is too low, large and medium-sized construction machinery cannot pass normally on the earthen cover layer during the next stage of landfill, causing further construction difficulties, the sub-membrane gas collection layer, odor adsorption layer and gas collection layer of this embodiment require a minimum bearing ratio (CBR) > 3% during the construction process to ensure sufficient strength to facilitate the passage of large and medium-sized machinery in the subsequent landfill process.

[0140] It should be noted that the particle grading shown in the above particle grading curve is not the only one and can be adjusted according to the characteristics and requirements of different landfills in specific application scenarios.

[0141] In this embodiment, the odor adsorption type landfill covering system is prepared by the following method:

[0142] (1) Prepare the ingredients.

[0143] Geomembrane needs to be purchased from outside and transported to the landfill, and the material performance requirements of the geomembrane must meet the relevant specifications.

[0144] The soil material for the vegetation layer can be obtained nearby, and the material requirements for the vegetation soil must meet relevant specifications.

[0145] The required recycled aggregates should be prepared from construction waste buried in landfills.

[0146] Establish a construction waste crushing station and prepare recycled coarse aggregate, recycled fine aggregate and recycled powder: Establish a construction waste crushing station in the landfill, and transport the construction waste to be landfilled in the landfill directly to the construction waste crushing station to prepare recycled aggregate. Before preparing the recycled aggregate, the impurities such as wood, steel bars, and slag in the construction waste should be removed through pretreatment, leaving only the discarded concrete and mortar stone. Then, the construction waste is prepared into recycled coarse aggregate, recycled fine aggregate and recycled powder through processes such as crushing, screening, removing impurities, grinding, drying and composite material selection. Recycled coarse aggregate and recycled fine aggregate with corresponding predetermined particle size requirements are prepared through crushing, grinding and screening processes. Micro powder (also called recycled powder) can be prepared through dust collection equipment, and the micro powder is mixed with recycled fine aggregate to obtain the recycled fine material required for the odor adsorption layer.

[0147] It should be noted that in the production process of recycled aggregate at home and abroad, recycled coarse aggregate and recycled fine aggregate can be prepared by crushing and grading, and fine powder (particle size can be less than 0.15mm) can be collected by dust collection equipment to prepare recycled powder. Since the recycled fine material of the odor adsorption layer in the present invention has requirements for its fine powder ratio, the recycled fine material required by the present invention can be prepared by mixing the recycled fine aggregate and the recycled powder in a certain ratio in the actual industrial production process (i.e., composite material selection).

[0148] The specific production and processing requirements of recycled materials can refer to or follow the production specifications for recycled aggregates in construction projects (such as GB / T25177-2010 Recycled coarse aggregate for concrete and DB894.1-Technical Specifications for the Application of Recycled Sand Powder (Shanghai)), so as to facilitate large-scale industrial production and reduce process difficulty and production costs.

[0149] It can be understood that the obtained recycled coarse aggregate, recycled fine aggregate and recycled powder can be used to construct the landfill cover system on the one hand, and can also be used for other civil engineering construction on the other hand; similarly, the raw materials for constructing the closure cover layer can also be obtained from other landfills or other places with construction waste crushing stations.

[0150] (2) Add water, mix and maintain.

[0151] Before constructing the enclosure cover layer and the intermediate cover layer, add water to the materials required for each functional layer and mix them to the optimal moisture content, and then close and cure them to ensure uniform moisture content. When configuring the optimal moisture content, ensure that the water is added evenly and stirred fully without large agglomerations. The materials should be cured in a closed and light-shielded environment, usually for 3-10 days.

[0152] (3) Laying of the intermediate covering layer.

[0153] First, the bottom impermeable lining - the impermeable cushion layer 17 is laid (according to the existing technology), and then the garbage is landfilled. After the landfill operation is completed, the landfill is cleaned, leveled and rolled. Pay attention to cleaning up sharp stones, tree roots and other debris, and all debris must be cleaned up. The base surface is not allowed to have local unevenness. The cleaned base surface must be compacted with a rammer or rammer board to make it dense and flat to form a garbage body 8.

[0154] Then lay geotextile on the compacted and leveled garbage.

[0155] Then lay the compacted coarse aggregate of the lower air collection layer on the geotextile, and lay the recycled coarse aggregate in layers and compact it fully. The thickness of each layer should not be too thick (10cm here), and the compaction degree must meet the requirements.

[0156] Then the geotextile is laid. The geotextile meets the basic performance requirements of geotextiles commonly used in landfills, and the laying process should also comply with relevant specifications (such as GB / T 50290-2014 Technical Specifications for Application of Geosynthetics).

[0157] Then lay the odor adsorption layer II on the geotextile. It needs to be laid in layers and fully compacted. The thickness of each layer is 10cm and the compaction degree meets the requirements. When compacting in layers, pay attention to scraping the surface of the recycled fine material layer after the previous compaction so that the front and back layers can fully contact and combine.

[0158] After the odor adsorption layer II is laid, it is necessary to manually sprinkle water or dry the odor adsorption layer so that its moisture content reaches the predetermined moisture content of the adsorption reaction.

[0159] The laying, welding, and maintenance of the geomembrane need to be carried out in accordance with relevant specifications (such as GB / T 50290-2014 Technical Specifications for Application of Geosynthetics), and the present invention does not make special requirements.

[0160] After the middle cover layer is laid, it needs to be monitored and maintained. When the next round of landfill operations is carried out, it is only necessary to peel off the geomembrane, and then lay the geotextile, and lay the upper gas collection layer on the geotextile. The laying method and requirements of the upper gas collection layer are the same as those of the lower gas collection layer. Then lay the geotextile and landfill the garbage on the geotextile. After the landfill operation, continue to lay the middle cover layer, and then carry out the next round of landfill operations until the predetermined landfill elevation is reached for sealing, and the sealing cover layer is laid. The geomembrane continues to be used as the geomembrane of the sealing cover layer.

[0161] (4) Laying of the closure cover layer.

[0162] After the landfill operation is completed, the landfill site should be cleaned, leveled and compacted. Pay attention to cleaning up sharp stones, tree roots and other debris, and all debris should be cleaned up. No local unevenness is allowed on the base surface. The cleaned base surface should be compacted with a rammer or rammer board to make it dense and flat.

[0163] Then lay geotextile on the compacted and leveled garbage.

[0164] Then lay the compacted coarse aggregate of the air collection layer I on the geotextile, and lay the recycled coarse aggregate in layers and compact it fully. The thickness of each layer should not be too thick, which is 10cm, and the compaction degree must meet the requirements.

[0165] Then the geotextile is laid. The geotextile meets the basic performance requirements of geotextiles commonly used in landfills, and the laying process should also comply with relevant specifications (such as GB / T 50290-2014 Technical Specifications for Application of Geosynthetics).

[0166] Then lay the odor adsorption layer I on the geotextile. It needs to be laid in layers and fully compacted. The thickness of each layer is 10cm and the compaction degree meets the requirements. When compacting in layers, pay attention to scraping the surface of the recycled fine material layer after the previous compaction so that the front and back layers can fully contact and combine.

[0167] After the odor adsorption layer I is laid, it is necessary to manually sprinkle water or dry it in the sun so that its moisture content reaches the predetermined moisture content of the adsorption reaction.

[0168] Then lay the geotextile, and lay the sub-membrane gas collection layer on the geotextile, that is, lay a thin layer of recycled coarse aggregate between the odor adsorption layer I and the geomembrane to prevent the geomembrane from bulging due to the accumulation of a large amount of gas locally. The laying method and requirements of the sub-membrane gas collection layer are the same as those of the gas collection layer I.

[0169] Then, geotextile is laid, and geomembrane is laid on the geotextile. The laying, welding, and maintenance of the geomembrane need to be carried out in accordance with relevant specifications, and the present invention does not make special requirements.

[0170] Then lay the geotextile, and then lay the drainage layer on the geotextile. The laying steps and requirements of the drainage layer are the same as those of the air collection layer under the membrane. Then lay the geotextile on the drainage layer.

[0171] Then the vegetation layer is laid. The soil material of the vegetation layer is compacted in layers, and the layers need to be scraped. Then greening is planted on the vegetation layer. Fertilization, tillage construction, maintenance, irrigation, etc. of the vegetation are carried out in accordance with relevant specifications, and the present invention does not make special requirements.

[0172] After the closure cover is laid, it needs to be monitored and maintained. In addition to the monitoring of anti-seepage and drainage, leachate, garbage degradation, garbage body sedimentation, etc. required for traditional closure covers, it is also necessary to carry out the integrity and soundness of the geomembrane, the generation and distribution of landfill gas (especially H2S), and the operation of the odor adsorption function of the closure cover. In addition, vegetation maintenance is also required.

[0173] The technical solutions provided by the embodiments of the present invention are introduced in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, according to the embodiments of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for preparing an odor adsorption type landfill covering system, the odor adsorption type landfill covering system comprising an uppermost landfill covering layer and at least one intermediate covering layer; characterized in that: The enclosure covering layer includes six functional layers, which are, from top to bottom: vegetation layer, drainage layer, geomembrane, gas collection layer under the membrane, odor adsorption layer I, and gas collection layer I; the intermediate covering layer includes three functional layers, which are, from top to bottom, the upper gas collection layer of the intermediate covering layer, the odor adsorption layer II, and the lower gas collection layer; the covering system and the garbage body form a structure of "garbage body-intermediate covering layer-...-garbage body-enclosure covering layer", and there is at least one "garbage body-intermediate covering layer" composite structure in the structure that is staggered and superimposed; Odor adsorption layer I and odor adsorption layer II are both odor adsorption layers; the thickness of odor adsorption layer I is 1.0-2.0m, and the thickness of odor adsorption layer II is 0.4-0.8m; the raw material of the odor adsorption layer is recycled fine material, and the recycled fine material is mixed with recycled fine aggregate and recycled powder prepared from recycled construction waste. The proportion of concrete and mortar in the construction waste for preparing recycled fine aggregate and recycled powder is ≥95%, and the pH of compacted recycled fine material is not less than 10; the particle size distribution curve of the odor adsorption layer is saddle-shaped. Specifically, according to soil mechanics standards, the particle size gradation curve characteristics of the recycled fine material must meet the following conditions: a) the maximum particle size ≤2mm; b) the effective particle size d 10 ≤0.005mm; c)1.2mm≤d 90 ≤1.8mm; d) Unevenness coefficient CU≥5; e) Curvature coefficient C C Between 1 and 3, that is, 3 ≥ C C ≥1, compaction degree ≥95%, the permeability coefficient of the odor adsorption layer at the maximum dry density is 10 -6 m / s—10 -8 m / s, air intake value 1kPa-10kPa, water absorption ≥10%, pore water saturation 60%-90%; The method for preparing an odor adsorption type landfill covering system comprises the following steps: 1) Prepare materials according to the requirements of each functional layer; transport the geomembrane to the landfill, take the soil material of the vegetation layer nearby, and prepare recycled coarse aggregate, recycled fine aggregate and recycled powder; before preparing recycled aggregate and recycled powder, impurities such as wood, steel bars, and slag in the construction waste should be removed through pretreatment, leaving only waste concrete and mortar stone; 2) Add water, mix and maintain. Before constructing the closure cover layer and the intermediate cover layer respectively, add water to the materials required for each functional layer and mix them to the optimal moisture content, and then close and maintain them to ensure uniform moisture content. 3) Laying of the intermediate cover layer: After one round of landfill operation is completed, clean, level and roll, and then lay geotextile, lower gas collection layer, geotextile, odor adsorption layer II, geomembrane in sequence. Before the next round of landfill operation, remove the geomembrane, and then lay the upper gas collection layer on the odor adsorption layer II. After the upper gas collection layer is laid, start the next round of landfill operation. After the next round of landfill operation is completed, re-lay the intermediate cover layer. The laying method is as follows: The above steps are repeated until the landfill operation is completed to the predetermined landfill volume, among which the upper gas collection layer, lower gas collection layer, odor adsorption layer II and upper gas collection layer need to be laid in layers, and the thickness of a single layer should not exceed 10 cm; 4) Laying of the sealing cover layer: After the landfill operation is completed, clean, level and roll the land, and then lay geotextile, gas collection layer I, geotextile, odor adsorption layer I, geotextile, gas collection layer under membrane, geomembrane, geotextile, drainage layer, geotextile and vegetation layer in turn, among which the gas collection layer I, odor adsorption layer I, gas collection layer under membrane, drainage layer and vegetation layer need to be laid in layers, and the thickness of a single layer should not exceed 10 cm, and then the vegetation layer should be greened and maintained.

2. The method for preparing the odor adsorption type landfill covering system according to claim 1, characterized in that: The vegetation layer includes soil that can cultivate vegetation, and the thickness of the vegetation layer meets the root system requirements of the planted vegetation. The thickness of the vegetation layer is ≥0.5m, and the compaction degree is ≥80%; the raw material of the drainage layer is recycled coarse aggregate prepared from construction waste, with a thickness of 0.2-0.4m, a particle size of 20-40mm, and a compaction relative density of ≥0.9; the geomembrane uses high-density polyethylene geomembrane or linear low-density polyethylene geomembrane, with a thickness of ≥1mm, and non-woven geotextile is laid on the membrane. The specification of non-woven geotextile is ≥300g / m 2 ; The raw material of the gas collection layer under the membrane is recycled coarse aggregate, with a thickness of 0.2-0.4m, a particle size of 2-10mm, and a compacted relative density ≥0.9; the thickness of the gas collection layer I is 0.3-0.5m, and the raw material of the gas collection layer I is recycled coarse aggregate, with a particle size of 20-40mm, and a compacted relative density ≥0.

9.

3. The method for preparing the odor adsorption type landfill covering system according to claim 1, characterized in that: The upper air collection layer and the lower air collection layer are constructed with recycled coarse aggregate, with thickness of 0.2-0.4m, particle size of 20-40mm and compacted relative density ≥0.

9.

4. The method for preparing the odor adsorption type landfill covering system according to claim 1, characterized in that: A water-permeable and air-permeable insulating material layer is provided between each functional layer to prevent the raw materials of each layer from mixing.

5. The method for preparing the odor adsorption type landfill covering system according to claim 1, characterized in that: The original concrete strength of the materials of odor adsorption layer I and odor adsorption layer II is not less than C30. Except for the vegetation layer and geomembrane, other functional layers use recycled aggregates recovered from construction waste, and the original concrete strength of the recycled aggregates is not less than C10.

6. The method for preparing the odor adsorption type landfill covering system according to claim 1, characterized in that: A gas collection layer under the membrane is provided with a gas collection layer exhaust device on the side, a gas collection layer I exhaust device on the side, and an upper gas collection layer exhaust device and a lower gas collection layer exhaust device on the sides, respectively.

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