A device and method for anaerobic digestion of landfill leachate and kitchen waste

Abstract

The application discloses a kind of closed field leachate and kitchen garbage combined anaerobic digestion device and method, device includes sequentially and side by side and is connected and is arranged pretreatment bin, preliminary mixing bin and anaerobic digestion bin, preliminary mixing bin middle part is equipped with a for receiving the mixed component of solid kitchen garbage on the filter plate.S1, kitchen garbage pretreatment;S2, kitchen garbage humification treatment;S3, combined anaerobic digestion treatment;S4, gas collection.The application is by closed field leachate as inoculum, kitchen garbage is digestion material, carries out sequential batch combined anaerobic digestion treatment, so that closed field leachate has good inoculation function, under the condition that no any inoculum is added, combined anaerobic digestion system can quickly enter gas production peak period finally by kitchen garbage conversion formed humus is substantially completely degraded.

Description

Technical Field

[0001] This invention relates to the field of leachate anaerobic digestion technology, specifically to a device and method for the combined anaerobic digestion of landfill leachate and kitchen waste. Background Technology

[0002] Landfill closure leachate refers to the leachate produced after a municipal solid waste landfill ceases operation and is sealed off. Landfill closure leachate is weakly alkaline, has poor biodegradability, and low heavy metal content, generally requiring advanced treatment using membrane technology. As waste incineration has become the dominant method in economically developed regions, many coastal provinces and cities have achieved zero landfilling of raw waste. It is foreseeable that the proportion of landfill closure leachate in the annual landfill leachate production will increase significantly.

[0003] Food waste contains up to 75% carbohydrates, crude protein, and crude fat on a dry basis. Rich in various nutrients, it is an excellent raw material for anaerobic digestion. However, due to its high water content, easy decomposition, and tendency to breed bacteria and toxins, anaerobic digestion technology is often chosen to treat food waste and recover biogas. Municipal solid waste landfills are massive anaerobic bioreactors, rich in various anaerobic microorganisms that have undergone long-term domestication. Landfill leachate inevitably carries a rich anaerobic microbial community, including bacteria that can promote the putrefaction process and humic degradation of food waste.

[0004] Currently, there is very little research on the co-anaerobic digestion of leachate and food waste from landfill sites. The few existing studies indicate that co-anaerobic digestion of leachate and food waste helps enhance the stability of anaerobic digestion systems and improves biogas and methane production rates. However, research on the mechanism of action is scarce. Furthermore, the existing studies primarily focus on food waste with a small amount of leachate added, which significantly enhances the stability of the anaerobic digestion system and improves biogas production efficiency. However, few studies have explored devices or methods for digesting food waste using leachate as the main inoculum. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a device and method for the combined anaerobic digestion of landfill leachate and kitchen waste.

[0006] The technical solution of this invention is:

[0007] A combined anaerobic digestion device for landfill leachate and kitchen waste includes a pretreatment chamber, a preliminary mixing chamber, and an anaerobic digestion chamber arranged in parallel and connected in sequence.

[0008] The upper part of the pretreatment chamber is equipped with two grinding rollers for grinding food waste. The pretreatment chamber located below the grinding rollers is equipped with a filter plate that is inclined towards the primary mixing chamber. The lower part of the pretreatment chamber is a storage tank for temporarily storing liquid food waste.

[0009] The primary mixing chamber is equipped with a mixing component in the middle for receiving solid kitchen waste from the filter plate. The primary mixing chamber located below the mixing component is equipped with a liftable mixing tank. A guide chute is provided at the bottom of the primary mixing chamber on the side closest to the anaerobic digestion chamber.

[0010] The mixing assembly includes an annular shell and several mixing chambers located inside the shell. The outer walls on both sides of the shell are made of filter mesh, and the circular side walls of the shell are provided with several openings corresponding to the mixing chambers. Movable baffles are provided at the openings.

[0011] The anaerobic digestion chamber is equipped with a stirring rod, and the outer wall of the storage tank is equipped with a diversion pump, which is connected to the interior of the anaerobic digestion chamber through a diversion pipe.

[0012] Furthermore, the filter plate has an inclination angle of 25 to 35° with respect to the horizontal direction, and the filter plate is provided with filter holes.

[0013] Note: The inclined filter plate allows solid food waste to fall into the preliminary mixing chamber.

[0014] Furthermore, each side of the grinding roller is rotatably connected to the inner sidewall of the pretreatment chamber via a rotating shaft. A dual-axis motor is provided on the outer rear wall of the pretreatment chamber. The two output shafts of the dual-axis motor pass through the rear sidewall of the pretreatment chamber and are respectively connected to a rotating shaft on the rear side of the two grinding rollers.

[0015] Explanation: The grinding roller is rotated by a dual-axis motor to crush and grind kitchen waste, thereby improving the efficiency of subsequent composting treatment.

[0016] Furthermore, one end of the movable baffle is fixedly connected to one end of the opening via a spring shaft. The upper surface of the movable baffle is symmetrically provided with arc-shaped locking blocks on both sides. The locking blocks have locking grooves on their inner sides, and the two ends of the locking grooves pass through the two ends of the locking blocks. A first lifting motor is provided on one side of the top of the preliminary mixing chamber. A first lifting rod is provided at the output end below the first lifting motor. A first limiting block is provided at the end of the first lifting rod. The first limiting block extends into the inside of the locking groove and is slidably connected to the locking groove. The position of the first limiting block is located 5 to 10° behind the top of the mixing component. A reserved opening is provided between two adjacent movable baffles for the first limiting block to move out.

[0017] Explanation: The spring shaft enables the movable baffle to automatically reset after opening. Two lifting motors can control the automatic opening of each movable baffle at different positions, thereby achieving automated control during feeding and discharging.

[0018] Furthermore, a drive motor is provided on the inner wall of the preliminary mixing chamber near the anaerobic digestion chamber. The output shaft of the drive motor is provided with a first telescopic rod. The end of the first telescopic rod is fixedly connected to the middle of the side wall of the shell. The middle of the other side wall of the shell is fixedly connected to the side wall of the preliminary mixing chamber near the pretreatment chamber through a second telescopic rod. A second lifting motor is provided on the front side wall of the preliminary mixing chamber near the anaerobic digestion chamber. A second lifting rod is connected to the rear of the second lifting motor through a connecting rod. A second limiting block is provided at the top of the second lifting rod. After the second limiting block moves into the slot through the reserved opening, it is slidably connected to the slot.

[0019] Description: The mixing component is moved by a drive motor, which moves it to a suitable position according to the needs of feeding or discharging, and the two telescopic rods maintain stability during the movement.

[0020] Furthermore, the bottom of the mixing tank is raised and lowered by a hydraulic lift, the bottom of the stirring rod is rotated by a stirring motor, the top of the pretreatment chamber is provided with a feed inlet, the front side wall of the preliminary mixing chamber is provided with a feeding port, the rear side of the preliminary mixing chamber is provided with a first air outlet pipe, the top of the anaerobic digestion chamber is provided with a liquid inlet, the rear side of the anaerobic digestion chamber is provided with a second air outlet pipe, and a dripper is provided at the connection between the guide pipe and the interior of the anaerobic digestion chamber.

[0021] Note: The dripper can add liquid kitchen waste transported by the guide pipe into the anaerobic digestion chamber in the form of droplets.

[0022] This invention also provides a method for the co-anaerobic digestion of landfill leachate and food waste, based on the co-anaerobic digestion device for landfill leachate and food waste described in any one of the above-mentioned methods, comprising the following steps:

[0023] S1. Food waste pretreatment: The food waste to be treated is poured into the pretreatment chamber and ground by grinding rollers, and then filtered through a filter plate. After filtration, solid food waste and liquid food waste are obtained. The solid food waste flows into the preliminary mixing chamber through the filter plate, and the liquid food waste flows into the storage tank.

[0024] S2. Food waste composting treatment: Add the first batch of sealing leachate to the mixing tank, place the solid food waste in the mixing component, rotate the mixing component to make the solid food waste in each mixing chamber of the mixing component alternately mix with the first batch of sealing leachate in the mixing tank. The volume ratio of solid food waste to the first batch of sealing leachate is 1-2:1-2. Perform composting treatment for 3-7 days.

[0025] S3. Combined Anaerobic Digestion Treatment: Add the second batch of sealing leachate to the anaerobic digestion chamber, and mix it with the solid food waste that has undergone humification treatment. The amount of solid food waste added is 1.5 to 2.5% of the total volume of the second batch of sealing leachate. At the same time, gradually add liquid food waste from the storage tank to the anaerobic digestion chamber at a dripping rate of 0.04 to 0.06% of the total volume of the second batch of sealing leachate per hour, for a dripping time of 12 to 36 hours. Continuous anaerobic digestion treatment is carried out for 30 to 60 days, during which the temperature in the anaerobic digestion chamber is maintained at 35±2℃.

[0026] S4. Gas Collection: Collect the gases discharged from the preliminary mixing chamber and the anaerobic digestion chamber.

[0027] Furthermore, the particle size of the crushed solid kitchen waste in S1 is <2cm.

[0028] Explanation: By optimizing the particle size of the crushed solid waste, we can ensure its effectiveness in subsequent composting and anaerobic digestion.

[0029] Furthermore, the rotational speed of the mixing component in S2 is 50 to 100 rpm.

[0030] The beneficial effects of this invention are:

[0031] (1) The present invention provides a device and method for combined anaerobic digestion of landfill leachate and kitchen waste. By using landfill leachate as inoculum and kitchen waste as digestion material, a sequencing batch combined anaerobic digestion process is carried out, which enables the landfill leachate to have good inoculum function. Without adding any inoculum, the combined anaerobic digestion system can quickly enter the peak gas production period. According to the analysis of the organic carbon (DOC) measurement value and the relative fluorescence volume calculation value of each region, it can be seen that after one month of combined anaerobic digestion, the humic content in the digestion liquid can reach more than 20 times that of the original landfill leachate. Finally, the humic material formed by the conversion of kitchen waste is basically completely degraded.

[0032] (2) The anaerobic digestion device for combined closure leachate and kitchen waste of the present invention can realize the automatic collection and release of solid kitchen waste through the set mixing components, and the solid kitchen waste is alternately soaked in the closure leachate by rotation, thereby accelerating the decomposition process.

[0033] (3) The present invention optimizes the parameters in the anaerobic digestion process of the combined anaerobic digestion of the landfill leachate and the kitchen waste, especially limiting the amount and method of adding solid kitchen waste and liquid kitchen waste and landfill leachate, so as to ensure that the overall gas production process of anaerobic digestion remains stable, avoids the occurrence of a large amount of gas production in a short period of time, and has higher overall gas production efficiency and better treatment effect. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the overall structure of a combined anaerobic digestion device for landfill leachate and kitchen waste according to the present invention;

[0035] Figure 2 This is a top view of a combined anaerobic digestion device for leachate and kitchen waste of the present invention;

[0036] Figure 3 This is a schematic diagram of the internal structure of a combined anaerobic digestion device for landfill leachate and kitchen waste according to the present invention;

[0037] Figure 4 This is a schematic diagram of the mixing component structure of a combined anaerobic digestion device for landfill leachate and kitchen waste according to the present invention;

[0038] Figure 5 This is a side view of the mixing component of a combined anaerobic digestion device for leachate and kitchen waste of the present invention in the closed state;

[0039] Figure 6 This is a side view of the mixing component of a combined anaerobic digestion device for leachate and kitchen waste of the present invention with the upper movable baffle open;

[0040] Figure 7 This is a side view of the mixing component of a combined anaerobic digestion device for leachate and kitchen waste of the present invention with the lower movable baffle open;

[0041] Figure 8 This is the cumulative gas production curve (mL) of each anaerobic digester in Experiment Example 1 of this invention.

[0042] Among them, 1-pretreatment chamber, 11-grinding roller, 12-filter plate, 13-storage tank, 14-guide pump, 15-guide pipe, 16-rotating shaft, 17-dual-shaft motor, 18-feed inlet, 2-preliminary mixing chamber, 21-mixing tank, 22-guide trough, 23-drive motor, 24-first telescopic rod, 25-second telescopic rod, 26-hydraulic lift, 27-feeding port, 28-first vent pipe, 3-anaerobic digestion chamber, 31-mixing 32-Stirring motor, 33-Liquid inlet, 34-Second vent pipe, 35-Drip device, 4-Mixing assembly, 41-Housing, 42-Mixing chamber, 43-Opening, 44-Modible baffle, 45-Spring shaft, 46-Reserved opening, 5-Card block, 51-Card slot, 6-First lifting motor, 61-First lifting rod, 62-First limiting block, 7-Second lifting motor, 71-Connecting rod, 72-Second lifting rod, 73-Second limiting block. Detailed Implementation

[0043] Example 1

[0044] like Figure 1 As shown, a combined anaerobic digestion device for landfill leachate and kitchen waste includes a pretreatment chamber 1, a preliminary mixing chamber 2, and an anaerobic digestion chamber 3 arranged in parallel and connected in sequence.

[0045] like Figure 2 and Figure 3 As shown, the upper part of the pretreatment chamber 1 is equipped with two grinding rollers 11 for grinding food waste. Each side of the grinding roller 11 is rotatably connected to the inner wall of the pretreatment chamber 1 through a rotating shaft 16. The rear outer wall of the pretreatment chamber 1 is equipped with a dual-axis motor 17. The dual-axis motor 17 is a commercially available dual-axis motor. The two output shafts of the dual-axis motor 17 pass through the rear wall of the pretreatment chamber 1 and are respectively connected to a rotating shaft 16 on the rear side of the two grinding rollers 11. The pretreatment chamber 1 located below the grinding rollers 11 is equipped with a filter plate 12 that is inclined towards the preliminary mixing chamber 2. The inclination angle between the filter plate 12 and the horizontal direction is 30°. The filter plate 12 is equipped with filter holes. The lower part of the pretreatment chamber 1 is a storage tank 13 for temporarily storing liquid food waste.

[0046] like Figure 3 As shown, a mixing component 4 for receiving solid kitchen waste on the filter plate 12 is provided in the middle of the primary mixing chamber 2. A lifting mixing tank 21 is provided in the primary mixing chamber 2 below the mixing component 4. A guide trough 22 is provided at the bottom of the primary mixing chamber 2 on the side close to the anaerobic digestion chamber 3.

[0047] like Figures 3-5As shown, the mixing component 4 includes an annular shell 41 and six mixing chambers 42 located inside the shell 41. The outer walls of the shell 41 are made of filter mesh. The circular side walls of the shell 41 are provided with six openings 43 corresponding to the mixing chambers 42. Movable baffles 44 are provided at the openings 43. One end of the movable baffle 44 is fixedly connected to one end of the opening 43 through a spring shaft 45. The upper surface of the movable baffle 44 is symmetrically provided with arc-shaped locking blocks 5 on both sides. The inner side of the locking block 5 is provided with a locking groove 51. The two ends of the locking groove 51 pass through the two ends of the locking block 5. A first lifting motor 6 is provided on one side of the top of the preliminary mixing chamber 2. A first lifting rod 61 is provided at the output end below the first lifting motor 6. A first limiting block 62 is provided at the end of the first lifting rod 61. The first limiting block 62 extends into the inside of the locking groove 51 and is slidably connected to the locking groove 51. The position of the first limiting block 62 is located 8° behind the top of the mixing component 4. A reserved opening 46 is provided between two adjacent movable baffles 44 for the first limiting block 62 to move out.

[0048] like Figures 3-5 As shown, a drive motor 23 is provided on the inner wall of the preliminary mixing chamber 2 near the anaerobic digestion chamber 3. The drive motor 23 is a motor assembly, including a commercially available electric push rod and a gear reduction motor. The output shaft of the drive motor 23 is provided with a first telescopic rod 24. The end of the first telescopic rod 24 is fixedly connected to the middle of the side wall of the housing 41. The middle of the other side wall of the housing 41 is fixedly connected to the side wall of the preliminary mixing chamber 2 near the pretreatment chamber 1 through a second telescopic rod 25. A second lifting motor 7 is provided on the front side wall of the preliminary mixing chamber 2 near the anaerobic digestion chamber 3. A second lifting rod 72 is connected to the rear side of the second lifting motor 7 through a connecting rod 71. A second limiting block 73 is provided at the top of the second lifting rod 72. After the second limiting block 73 moves into the slot 51 through the reserved opening 46, it is slidably connected to the slot 51.

[0049] The first lifting motor 6 and the second lifting motor 7 are both commercially available servo motors, which drive the first limit block 62 and the second limit block 73 to move up and down automatically.

[0050] like Figures 1-3 As shown, the anaerobic digestion chamber 3 is equipped with a stirring rod 31 inside, and a diversion pump 14 is installed on the outer wall of the storage tank 13. The diversion pump 14 is a commercially available product. The diversion pump 14 is connected to the inside of the anaerobic digestion chamber 3 through a diversion pipe 15. The bottom of the mixing tank 21 is controlled to rise and fall by a hydraulic lift 26. The bottom of the stirring rod 31 is controlled to rotate by a stirring motor 32. The pretreatment chamber 1 is equipped with a feed inlet 18 at the top. The preliminary mixing chamber 2 is equipped with a feeding port 27 on the front side wall. The preliminary mixing chamber 2 is equipped with a first air outlet 28 at the rear side. The anaerobic digestion chamber 3 is equipped with a liquid inlet 33 at the top. The anaerobic digestion chamber 3 is equipped with a second air outlet 34 at the rear side. A dripper 35 is installed at the connection between the diversion pipe 15 and the inside of the anaerobic digestion chamber 3.

[0051] Example 2

[0052] The difference between this embodiment and Embodiment 1 is that:

[0053] The angle of inclination of the filter plate 12 to the horizontal direction is 25°.

[0054] Example 3

[0055] The difference between this embodiment and Embodiment 1 is that:

[0056] The angle of inclination of the filter plate 12 to the horizontal direction is 35°.

[0057] Note: The tilt angle of the filter plate 12 can be selected according to the material of the kitchen waste to be processed. The larger the tilt angle, the faster the sliding speed, which is generally suitable for kitchen waste with a high solid content; conversely, the smaller the tilt angle, the slower the sliding speed, which is generally suitable for kitchen waste with a high liquid content.

[0058] Example 4

[0059] The difference between this embodiment and Embodiment 1 is that:

[0060] The first limiting block 62 is located 5° behind the top of the mixing component 4.

[0061] Example 5

[0062] The difference between this embodiment and Embodiment 1 is that:

[0063] The first limiting block 62 is located 10° behind the top of the mixing component 4.

[0064] Note: The position of the first limiting block 62 determines the position of the movable baffle 44. If the first limiting block 62 is located directly above the mixing component 4, the uppermost mixing chamber 42 will have already rotated past its apex when the movable baffle 44 is opened, which is not conducive to collection. Therefore, it needs to be offset by a certain angle so that the movable baffle 44 can be opened when it rotates to its apex.

[0065] Example 6

[0066] The difference between this embodiment and Embodiment 1 is that:

[0067] There are 8 mixing chambers in chamber 42.

[0068] Example 7

[0069] This embodiment provides a method for the combined anaerobic digestion of landfill leachate and food waste, based on the combined anaerobic digestion device for landfill leachate and food waste provided in Embodiment 1, including the following steps:

[0070] S1. Pre-treatment of kitchen waste: The kitchen waste to be treated is poured into the pre-treatment chamber 1 and ground by the grinding roller 11. Then it is filtered by the filter plate 12. After filtration, solid kitchen waste and liquid kitchen waste are obtained. The solid kitchen waste flows into the preliminary mixing chamber 2 through the filter plate 12, and the liquid kitchen waste flows into the storage tank 13. The particle size of the crushed solid kitchen waste is <2cm.

[0071] S2. Food waste composting treatment: Add the first batch of sealing leachate to the mixing tank 21, place the solid food waste in the mixing component 4, rotate the mixing component 4 at a speed of 70 rpm, so that the solid food waste in each mixing chamber 42 inside the mixing component 4 is alternately mixed with the first batch of sealing leachate inside the mixing tank 21, and the volume ratio of solid food waste to the first batch of sealing leachate is 1:1, and carry out composting treatment for 5 days;

[0072] S3. Combined Anaerobic Digestion Treatment: The second batch of sealing leachate is added to the anaerobic digestion chamber 3, and the solid kitchen waste that has undergone humification treatment is mixed in for combined anaerobic digestion treatment. The amount of solid kitchen waste added is 2% of the total volume of the second batch of sealing leachate. At the same time, liquid kitchen waste from the storage tank 13 is gradually added to the anaerobic digestion chamber 3 at a dripping rate of 0.05% of the total volume of the second batch of sealing leachate per hour for 24 hours. The anaerobic digestion treatment is carried out continuously for 50 days, during which the temperature in the anaerobic digestion chamber 3 is maintained at 35℃.

[0073] S4. Gas collection: Collect the gas discharged from the preliminary mixing chamber 2 and the anaerobic digestion chamber 3.

[0074] Example 8

[0075] The difference between this embodiment and embodiment 7 is that:

[0076] S2. Food waste composting treatment: Add the first batch of sealing leachate to the mixing tank 21, place the solid food waste in the mixing component 4, rotate the mixing component 4 at a speed of 100 rpm, so that the solid food waste in each mixing chamber 42 inside the mixing component 4 is alternately mixed with the first batch of sealing leachate inside the mixing tank 21. The volume ratio of solid food waste to the first batch of sealing leachate is 2:1, and composting treatment is carried out for 3 days.

[0077] Example 9

[0078] The difference between this embodiment and embodiment 7 is that:

[0079] S2. Food waste composting treatment: Add the first batch of sealing leachate to the mixing tank 21, place the solid food waste in the mixing component 4, rotate the mixing component 4 at a speed of 50 rpm, so that the solid food waste in each mixing chamber 42 inside the mixing component 4 is alternately mixed with the first batch of sealing leachate inside the mixing tank 21. The volume ratio of solid food waste to the first batch of sealing leachate is 1:2, and composting treatment is carried out for 7 days.

[0080] Note: Increasing the rotation speed of mixing component 4 can appropriately shorten the total processing time.

[0081] Example 10

[0082] The difference between this embodiment and embodiment 7 is that:

[0083] S3. Combined Anaerobic Digestion Treatment: The second batch of sealing leachate is added to the anaerobic digestion chamber 3, and the solid kitchen waste that has undergone humification treatment is mixed in for combined anaerobic digestion treatment. The amount of solid kitchen waste added is 2.5% of the total volume of the second batch of sealing leachate. At the same time, liquid kitchen waste from the storage tank 13 is gradually added to the anaerobic digestion chamber 3 at a dripping rate of 0.04% of the total volume of the second batch of sealing leachate per hour, and the dripping time is 36 hours. The anaerobic digestion treatment is carried out continuously for 60 days, during which the temperature in the anaerobic digestion chamber 3 is maintained at 35℃.

[0084] Example 11

[0085] The difference between this embodiment and embodiment 7 is that:

[0086] S3. Combined Anaerobic Digestion Treatment: The second batch of sealing leachate is added to the anaerobic digestion chamber 3, and the solid kitchen waste that has undergone humification treatment is mixed in for combined anaerobic digestion treatment. The amount of solid kitchen waste added is 1.5% of the total volume of the second batch of sealing leachate. At the same time, liquid kitchen waste from the storage tank 13 is gradually added to the anaerobic digestion chamber 3 at a dripping rate of 0.06% of the total volume of the second batch of sealing leachate per hour, and the dripping time is 12 hours. The anaerobic digestion treatment is carried out continuously for 30 days, during which the temperature in the anaerobic digestion chamber 3 is maintained at 37℃.

[0087] Note: When the amount of solid food waste added is small, the amount and speed of liquid food waste added should be increased appropriately, and the temperature should be increased appropriately to shorten the processing time.

[0088] Working principle of the hybrid component 4: The working principle of the hybrid component 4 of the present invention will be further explained in detail below with reference to the method of the present invention.

[0089] During S2, the mixing tank 21 is first lowered to the bottom using the hydraulic lift 26. Then, the drive motor is turned on to move the entire mixing assembly 4 above the mixing tank 21. The first telescopic rod 24 and the second telescopic rod 25 keep the mixing assembly 4 stable during movement. The first limiting block 62 enters the slot 51 of the locking block 5 through the reserved opening 46. The drive motor 23 is turned on to rotate the mixing assembly 4. Whenever the movable baffle 44 rotates to the position of the first limiting block 62, the first lifting motor 6 also drives the first lifting rod 61 and the first limiting block 62 to move up and down. When rising, the first limiting block 62 pulls the slot 51 to open the movable baffle 44. At this time, the corresponding opening 43 opens and the mixing chamber 42 is located below the filter plate 12. Solid kitchen waste slides down the filter plate 12 and enters the mixing chamber 42. Here, we can allow some solid kitchen waste to spill out, or add a control valve to cooperate with opening and closing.

[0090] After all the solid food waste is introduced in sequence, each mixing chamber 42 contains a portion of solid food waste. Then, the mixing tank 21 is raised by the hydraulic lift 26 so that a portion of the leachate in the mixing tank 21 covers the bottom 1 / 3 of the mixing component 4. As the mixing component 4 rotates, the leachate assists in the decomposition of the solid food waste. Of course, the mixing tank 21 can also be raised immediately during the above transfer process so that the transfer and auxiliary treatment are carried out simultaneously.

[0091] Before proceeding to S3 after completing S2, the mixing tank 21 needs to be lowered to the bottom using the hydraulic lift 26. Then, the drive motor is turned on to move the entire mixing component 4 above the guide chute 22, so that the second limiting block 73 enters the slot 51 of the card block 5 through the reserved opening 46. Then, the mixing component 4 is rotated. The working principle of the second limiting block 73 is the same as that of the first limiting block 62. Material is discharged when each movable baffle 44 is opened in sequence.

[0092] Experimental Example

[0093] To verify the feasibility of the method of the present invention, we conducted a series of experiments. First, we need to verify whether the leachate from the landfill has a promoting effect on the anaerobic digestion of kitchen waste.

[0094] The leachate used in the experiment was taken from a landfill that had been closed for 10 years. The food waste was taken from a university student canteen; after removing impurities, it was pulped and refrigerated for later use. The main characteristic parameters of the anaerobic digestion feedstock are shown in Table 1.

[0095] Table 1 Characteristic parameters of anaerobic digestion feedstock

[0096]

[0097] Experimental protocol

[0098] The anaerobic digestion unit uses a sequencing batch reactor (SBR). The total mass of the digestible feedstock and digestate added to the reactor is 1500g. The anaerobic digestion experiment consists of four reactors, numbered EL0, EL1, EL2, and EL3 according to the initial food waste loading rate. Table 2 shows the initial loading rate, the amount of food waste added, and the amount of leachate added.

[0099] Table 2 Experimental Design

[0100]

[0101] The anaerobic digestion experiment was conducted at a mesophilic temperature (35℃), with a temperature error not exceeding 1℃. After the anaerobic digestion experiment began, the amount of gas produced during the digestion process was recorded daily, and the methane concentration of the biogas was measured according to specific conditions; parameters such as pH, NH3-N, and VFA of the digestate were measured periodically.

[0102] The experiment was conducted in two phases. Phase 1 involved the decomposition of kitchen waste, lasting one month (days 1-31). On day 31, after the completion of Phase 1, the first three-dimensional fluorescence spectroscopy sampling and analysis was performed. Phase 2 lasted four months (days 32-152), after which a second three-dimensional fluorescence spectroscopy sampling and analysis was performed. Sample numbers are shown in Table 2.

[0103] Analytical methods

[0104] A certain amount of leachate and anaerobic digestion slurry were taken separately, filtered first with qualitative filter paper, and then filtered through a 0.45 μm filter membrane. The organic matter in the filtrate was the DOM (domestic organic matter). The DOC of each sample was determined using the direct measurement method (NPOC) with a German multi N / C 2100DOC analyzer. Then, according to the different DOC contents, pure water was added to dilute the DOC contents of the samples to the same level, and three-dimensional fluorescence spectroscopy analysis was performed.

[0105] The various fluorescent substances contained in DOM will exhibit different reactions under certain excitation wavelengths, displaying fluorescence peaks at different positions in the three-dimensional fluorescence spectrum. Using the three-dimensional fluorescence region integration method, various organic compounds in DOM can be quantitatively analyzed. This analytical method has been widely applied to the analysis of dissolved organic pollutants in various substances.

[0106] Table 3. Classification and regional division of characteristic fluorescence peaks in leachate

[0107]

[0108] As shown in Table 3, the fluorescence spectrum was divided into five regions using the fluorescence spectroscopy region integration method: tyrosine-based proteins (region I), tryptophan-based proteins (region II), fulvic acid (region III), soluble microbial byproducts (region IV), and humic acid (region V). Then, the components of the soluble organic matter were quantitatively analyzed using the fluorescence spectroscopy region integration method.

[0109] Results and Analysis

[0110] Cumulative gas production: Table 4 and Figure 1 The figure shows the cumulative gas production of each anaerobic digester at different time points. Although no specific inoculum was added, the three combined anaerobic digesters quickly entered a gas-producing state after the experiment began due to the abundance of various functional microorganisms in the sealing leachate.

[0111] When leachate was anaerobically digested alone, only 2055 mL of gas was produced on day 32. With an initial loading rate of 1%, the anaerobic digester began producing gas on day 1, reaching 15930 mL, or 95% of the total gas production. The reactor with an initial loading rate of 2% produced 20730 mL of gas on day 1, accounting for 90% of the total gas production.

[0112] Reactor EL3, with an initial loading rate of 3%, produced 23,500 mL of methanogens within the first 7 days of the experiment, accounting for 44% of the total gas production. Subsequently, due to the excessively rapid hydrolysis and acidification, the growth and reproduction of methanogens were inhibited, and the system ceased gas production. After nearly three months of recovery, a second peak in gas production began on day 96, producing approximately 20,000 mL of gas within a week, accounting for about 38% of the total gas production.

[0113] Table 4. Gas production (mL) of each anaerobic digester at different time periods.

[0114]

[0115] Experimental results show that when the food waste load rate is ≤2%, the experimental system can achieve efficient degradation of food waste and basically complete the gas production process within 24 hours; when the load rate is ≥3%, the reactor enters an intermittent gas production state, and the experimental system becomes unstable.

[0116] Currently, to improve the gas production rate per unit volume of anaerobic digester reactors, researchers typically increase the solids content. However, increasing the solids content accelerates system acidification and can even lead to system collapse. Therefore, increasing the gas production rate of food waste under low solids content conditions, thereby improving the gas production rate per unit volume of the anaerobic digester reactor, may be a more stable and effective method. We can also see that the gas emission time points in the above experiments are concentrated in a certain period (day 1 and days 8-18). To achieve industrial-scale production, the timing and method of mixing the leachate and food waste should be optimized. Based on this, we further researched and derived the method of this invention.

[0117] Under the same experimental conditions, the gas production rate was optimized at different time periods by using the method of the present invention. Taking Example 1 as an example, the gas production rate after processing S1 to S4 is as follows:

[0118] The first day's output was 159 mL, the second to seventh days' output was 1345 mL, the eighth to eleventh days' output was 28235 mL, the thirteenth to thirtieth days' output was 7754 mL, and the thirtieth to thirteenth days' output was 121 mL, with a total gas production of 37614 mL. The gas production process was relatively stable and controllable, and the efficiency was greatly improved. Therefore, after one month of combined anaerobic digestion, the humic content in the digestate could reach more than 20 times that of the original leachate from the sealed site. In the end, the humic material formed by the conversion of kitchen waste was basically completely degraded.

Claims

1. A combined anaerobic digestion device for landfill leachate and kitchen waste, characterized in that, It includes a pretreatment chamber (1), a preliminary mixing chamber (2), and an anaerobic digestion chamber (3) arranged in parallel and connected. The upper part of the pretreatment chamber (1) is provided with two grinding rollers (11) for grinding kitchen waste. The pretreatment chamber (1) located below the grinding rollers (11) is provided with a filter plate (12) that is inclined to one side of the preliminary mixing chamber (2). The lower part of the pretreatment chamber (1) is a storage tank (13) for temporarily storing liquid kitchen waste. The primary mixing chamber (2) is provided with a mixing component (4) in the middle for receiving solid kitchen waste on the filter plate (12). The primary mixing chamber (2) located below the mixing component (4) is provided with a lifting mixing tank (21) for receiving the first batch of leachate added. Correspondingly, a guide chute (22) is provided at the bottom of the primary mixing chamber (2) near the anaerobic digestion chamber (3). The mixing component (4) includes an annular shell (41) and several mixing chambers (42) located inside the shell (41). The outer walls on both sides of the shell (41) are made of filter mesh. Several openings (43) corresponding to the mixing chambers (42) are provided on the circular sidewalls of the shell (41). Movable baffles (44) are provided at the openings (43). The solid kitchen waste in each mixing chamber (42) inside the mixing component (4) is alternately mixed with the first batch of leachate from the mixing tank (21). The anaerobic digestion chamber (3) is used to receive the second batch of sealing leachate. It is equipped with a stirring rod (31) inside. A diversion pump (14) is provided on the outer wall of the storage tank (13). The diversion pump (14) is connected to the inside of the anaerobic digestion chamber (3) through a diversion pipe (15).

2. The anaerobic digestion device for combined leachate and kitchen waste according to claim 1, characterized in that, The angle between the filter plate (12) and the horizontal direction is 25~35°, and the filter plate (12) is provided with filter holes.

3. The anaerobic digestion device for combined leachate and kitchen waste according to claim 1, characterized in that, The grinding roller (11) is rotatably connected to the inner wall of the pretreatment chamber (1) on both sides by a rotating shaft (16). A dual-axis motor (17) is provided on the outer rear wall of the pretreatment chamber (1). The two output shafts of the dual-axis motor (17) pass through the rear wall of the pretreatment chamber (1) and are respectively connected to a rotating shaft (16) on the rear side of the two grinding rollers (11).

4. The anaerobic digestion device for combined leachate and kitchen waste according to claim 1, characterized in that, One end of the movable baffle (44) is fixedly connected to one end of the opening (43) via a spring shaft (45). The upper surface of the movable baffle (44) is symmetrically provided with arc-shaped locking blocks (5) on both sides. The locking blocks (5) are provided with a locking groove (51) on the inner side. The two ends of the locking groove (51) pass through the two ends of the locking blocks (5). The top side of the preliminary mixing chamber (2) is provided with a first lifting motor (6). The output end of the first lifting motor (6) is provided with a first lifting rod (61). The end of the first lifting rod (61) is provided with a first limiting block (62). The first limiting block (62) extends into the inside of the locking groove (51) and is slidably connected to the locking groove (51). The position of the first limiting block (62) is located 5~10° behind the top of the mixing component (4). There is a reserved opening (46) between two adjacent movable baffles (44) for moving the first limiting block (62) out.

5. The anaerobic digestion device for combined leachate and kitchen waste according to claim 4, characterized in that, A drive motor (23) is provided on the inner wall of the preliminary mixing chamber (2) near the anaerobic digestion chamber (3). The output shaft of the drive motor (23) is provided with a first telescopic rod (24). The end of the first telescopic rod (24) is fixedly connected to the middle of the side wall of the shell (41). The middle of the other side wall of the shell (41) is fixedly connected to the side wall of the preliminary mixing chamber (2) near the pretreatment chamber (1) through a second telescopic rod (25). A second lifting motor (7) is provided on the front side wall of the preliminary mixing chamber (2) near the anaerobic digestion chamber (3). A second lifting rod (72) is connected to the rear side of the second lifting motor (7) through a connecting rod (71). A second limiting block (73) is provided at the top of the second lifting rod (72). After the second limiting block (73) moves into the slot (51) through the reserved opening (46), it is slidably connected to the slot (51).

6. The anaerobic digestion device for combined leachate and kitchen waste according to claim 1, characterized in that, The bottom of the mixing tank (21) is controlled to rise and fall by a hydraulic lift (26), and the bottom of the stirring rod (31) is controlled to rotate by a stirring motor (32). The top of the pretreatment chamber (1) is provided with a feed inlet (18), the front side wall of the preliminary mixing chamber (2) is provided with a feeding port (27), the rear side of the preliminary mixing chamber (2) is provided with a first air outlet pipe (28), the top of the anaerobic digestion chamber (3) is provided with a liquid inlet (33), the rear side of the anaerobic digestion chamber (3) is provided with a second air outlet pipe (34), and the connection between the guide pipe (15) and the interior of the anaerobic digestion chamber (3) is provided with a dripper (35).

7. A method for the combined anaerobic digestion of landfill leachate and food waste, based on the combined anaerobic digestion device for landfill leachate and food waste as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1. Pre-treatment of kitchen waste: The kitchen waste to be treated is poured into the pre-treatment chamber (1) and ground by the grinding roller (11). Then it is filtered by the filter plate (12). After filtration, solid kitchen waste and liquid kitchen waste are obtained. The solid kitchen waste flows into the preliminary mixing chamber (2) through the filter plate (12), and the liquid kitchen waste flows into the storage tank (13). S2. Food waste composting treatment: Add the first batch of sealing leachate to the mixing tank (21), place the solid food waste in the mixing component (4), rotate the mixing component (4) so ​​that the solid food waste in each mixing chamber (42) inside the mixing component (4) is alternately mixed with the first batch of sealing leachate inside the mixing tank (21). The volume ratio of solid food waste to the first batch of sealing leachate is 1~2:1~2. Perform composting treatment for 3~7 days. S3, Combined anaerobic digestion treatment: Add the second batch of sealing leachate to the anaerobic digestion chamber (3) and mix it with the solid kitchen waste that has been decomposed for combined anaerobic digestion treatment. The amount of solid kitchen waste added is 1.5~2.5% of the total volume of the second batch of sealing leachate. At the same time, gradually add liquid kitchen waste from the storage tank (13) to the anaerobic digestion chamber (3). The dripping rate is 0.04~0.06% of the total volume of the second batch of sealing leachate per hour. The dripping time is 12~36h. Continuous anaerobic digestion treatment for 30~60 days, during which the temperature in the anaerobic digestion chamber (3) is maintained at 35±2℃. S4. Gas collection: Collect the gas discharged from the preliminary mixing chamber (2) and the anaerobic digestion chamber (3).

8. The method for combined anaerobic digestion of landfill leachate and kitchen waste according to claim 7, characterized in that, The particle size of the crushed solid kitchen waste in S1 is <2cm.

9. The method for combined anaerobic digestion of landfill leachate and kitchen waste according to claim 7, characterized in that, The rotational speed of the mixing component (4) in S2 is 50~100 rpm.

Images