Kitchen garbage pretreatment process and system with synergy of screw extrusion and biological enhancement

Abstract

A kitchen waste pretreatment process with cooperation of screw extrusion and biological enhancement comprises the following steps that 1, kitchen waste materials subjected to pre-sorting and impurity removal enter a first-stage screw extruder to be subjected to preliminary dehydration, the solid content of the dehydrated solid residue materials reaches a first target interval, and first-stage extrusion solid residues are obtained; step 2, conveying a primary extrusion solid residue material adjusted by the primary screw extruder into a temporary storage fermentation bin, and entering a fermentation wall breaking stage; 3, the materials subjected to fermentation and wall breaking enter a second-stage screw extruder to be subjected to deep dehydration, the solid content of the dehydrated solid slag materials is stabilized in a second target interval, and second-stage extrusion solid slag is obtained; and 4, conveying the second-stage extrusion solid residue material into a dry anaerobic fermentation tank, enabling the extrusion slurry obtained by extrusion in the first-stage screw extruder in the step 1 and the second-stage screw extruder in the step 3 to enter a three-phase centrifugal system, and recovering crude oil in the slurry. The solid content of the kitchen garbage can be efficiently increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of kitchen waste treatment equipment, and more particularly to a kitchen waste pretreatment process and system based on synergistic effect of spiral extrusion and biological reinforcement. BACKGROUND

[0002] Kitchen waste is the main component of urban organic waste, which is generated in daily life, catering services and unit catering activities, and has the characteristics of high water content and high organic matter content. It mainly includes leftover food, vegetable leaves, fruit peels, eggshells, bones, fats, and other perishable biomass waste. The significant feature of this kind of waste is that the water content is usually as high as 80% or more. Dry anaerobic fermentation technology is an efficient means to realize the reduction and resource utilization of kitchen waste. It has strict requirements for the solid content of the material entering the fermentation tank, which generally needs to be controlled within the range of 30-40%.

[0003] Currently, the traditional treatment scheme has obvious limitations in regulating the solid content of kitchen waste. Currently, the dry anaerobic fermentation tank for kitchen waste is generally not equipped with or only equipped with a single-stage extrusion dewatering. If a single-stage spiral extrusion process is used for pretreatment of kitchen waste, the dewatering effect is limited, and the solid content of the extruded material can only be increased to 25-30%, which cannot meet the optimal conditions for dry anaerobic fermentation. This not only leads to the generation of excessive biogas slurry in the fermentation system, increasing the difficulty of subsequent treatment, but also significantly reduces the solid content of the sludge in the fermentation tank, leading to the separation of impurities and other phenomena, affecting the economy and stability of the entire process.

[0004] In addition, some schemes add garden waste, wood chips and other auxiliary materials to adjust the solid content, which can achieve the goal to some extent, but increases the cost of materials and processing procedures, which is not conducive to the large-scale promotion of the process. At the same time, the unbroken plant cell walls in kitchen waste hinder the release of water, further reducing the efficiency of extrusion dewatering and exacerbating the problem of solid content regulation.

[0005] Therefore, how to optimize the pretreatment process to efficiently increase the solid content of kitchen waste and make it meet the requirements of dry anaerobic fermentation has become a key issue in promoting the development of kitchen waste resource utilization technology. The present application is thus produced. SUMMARY

[0006] The purpose of the present application is to provide a kitchen waste pretreatment process and system based on synergistic effect of spiral extrusion and biological reinforcement, which can efficiently increase the solid content of kitchen waste and meet the requirements of dry anaerobic fermentation.

[0007] In order to achieve the above purpose, the solution of the present application is: A kitchen waste pretreatment process based on synergistic effect of spiral extrusion and biological reinforcement comprises the following steps, Step 1: The pre-sorted and impurity-removed kitchen waste material enters a primary screw extruder for preliminary dewatering, and the dewatered solid residue material has a solid content rate in a first target interval, obtaining a primary extrusion solid residue; Step 2: The primary extrusion solid residue material adjusted by the primary screw extruder is transported to a temporary fermentation bin, and enters a fermentation and cell wall breaking stage; Step 3: The material completing the fermentation and cell wall breaking enters a secondary screw extruder, and the initial back pressure in the secondary screw extruder is greater than that in the primary screw extruder, for deep dewatering. The solid content rate of the dewatered solid residue material is stabilized in a second target interval, obtaining a secondary extrusion solid residue; Step 4: The secondary extrusion solid residue material is transported into a dry anaerobic fermentation tank, and the extrusion slurry obtained from the primary screw extruder in Step 1 and the secondary screw extruder in Step 3 enters a three-phase centrifugal system to recover the crude oil in the slurry.

[0008] Further, in Step 1, a first microwave moisture meter is arranged at the material outlet of the primary screw extruder. The first microwave moisture meter monitors the solid content rate of the solid residue in real time and transmits the data to the PLC control system. If the detected value is lower than a preset threshold value, the PLC control system immediately feeds back to the primary screw extruder. The primary screw extruder automatically increases the back pressure of the extruder until the solid content rate is stabilized in the first target interval. If the detected value exceeds the first target interval, the back pressure of the primary screw extruder is reduced.

[0009] Further, in Step 1, the solid content rate of the pre-sorted and impurity-removed kitchen waste material is 20-24%, the preset initial back pressure of the primary screw extruder is 0.5-1.0 MPa, the solid content rate of the first target interval is 26-28%, and the preset threshold value is 25%.

[0010] Further, in Step 2, the stacking height of the primary extrusion solid residue material in the temporary fermentation bin is greater than 3.0 meters, and hot air and oxygen are introduced into the temporary fermentation bin. The oxygen concentration in the material stack of the temporary fermentation bin is maintained at 10-15%, and the fermentation and cell wall breaking process of the temporary fermentation bin lasts for 24 to 36 hours.

[0011] In Step 2, after the material is fermented and the cell wall is broken, part of the intracellular bound water in the material becomes free water and then becomes percolate exuding from the material stack. The percolate is discharged.

[0012] Further, in Step 3, the initial back pressure in the secondary screw extruder is 1.2-2.0 MPa.

[0013] Further, a second microwave moisture meter is arranged at the material outlet of the secondary screw extruder, the second microwave moisture meter monitors the solid content of the solid residue in real time and transmits the data to the PLC control system; if the solid content does not reach 32%-34% required by the fermentation tank, the PLC control system feeds back to the secondary screw extruder and the temporary storage fermentation bin, the secondary screw extruder increases the back pressure, and at the same time, the discharge amount per unit time of the temporary storage fermentation bin is reduced; if the solid content exceeds 35%, the back pressure of the secondary screw extruder is reduced and the discharge amount per unit time of the temporary storage fermentation bin is increased.

[0014] Further, in step 4, the solid residue material after secondary extrusion is conveyed into the dry anaerobic fermentation tank by a screw or a belt.

[0015] A system for the kitchen garbage pretreatment process of the above-mentioned screw extrusion and biological reinforcement synergy, the system comprises a primary screw extruder and a secondary screw extruder, a first microwave moisture meter is arranged at the material outlet of the primary screw extruder, and a second microwave moisture meter is arranged at the material outlet of the secondary screw extruder, and the primary screw extruder, the secondary screw extruder, the first microwave moisture meter and the second microwave moisture meter are electrically connected or communicatively connected to a PLC control system.

[0016] After the above scheme is adopted, since the moisture content of the kitchen garbage is relatively high, and the dry anaerobic fermentation tank has a requirement on the solid content of the material entering the tank, the present application controls the solid content of the material entering the tank through the two extrusion processes of the kitchen garbage primary screw extruder, the intermediate storage bin and the secondary screw extruder before entering the tank, the material is broken after the primary extrusion, and the material can be broken during the temporary storage in the storage bin, so that the material is more easily extruded in the secondary extrusion process, the screw extrusion and the biological reinforcement are synergized, the solid content is improved, and the problem that the kitchen garbage is directly extruded by the primary screw extruder and then enters the fermentation tank, the extrusion effect is general, and the solid content is not obviously improved is solved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The process flowchart of the present application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to further explain the technical scheme of the present application, the present application will be described in detail below through specific embodiments.

[0019] Combined with Figure 1 the figure, the present application discloses a kitchen garbage pretreatment process of screw extrusion and biological reinforcement synergy, comprising the following steps, Step 1: the kitchen garbage material after pre-sorting and impurity removal enters a primary screw extruder for preliminary dehydration, and the solid content of the dehydrated solid residue material reaches a first target interval, and a primary extruded solid residue is obtained; Step 2: The first-stage extrusion solid residue material after adjustment by the first-stage screw extruder is transported to the temporary fermentation warehouse to enter the fermentation and cell wall breaking stage; Step 3: The material after completing the fermentation and cell wall breaking enters the second-stage screw extruder, and the initial back pressure pressure adopted in the second-stage screw extruder is greater than that in the first-stage screw extruder to perform deep dehydration, and the solid content rate of the dehydrated solid residue material is stabilized in the second target interval to obtain the second-stage extrusion solid residue. Step 4: The second-stage extrusion solid residue material is transported into the dry anaerobic fermentation tank, and the extrusion slurry obtained by the first-stage screw extruder in step 1 and the second-stage screw extruder in step 3 enters the three-phase centrifugal system to recover the crude oil in the slurry.

[0020] In step 1, the solid content rate of the kitchen waste material after pre-sorting and removing impurities is 20-24%, the preset initial back pressure pressure of the first-stage screw extruder is 0.5-1.0 MPa, and the first target interval can be customized by the user within a certain range. In this embodiment, the solid content rate of the first target interval can be set to 26-28%.

[0021] In step 1, the solid residue material generated by the first-stage screw extruder enters the online solid content rate detection area located at the material outlet. The first microwave moisture meter is arranged at the material outlet, which can monitor the solid content rate of the solid residue in real time and transmit the data to the PLC control system. The model of the microwave moisture meter can be Berthold LB 480, which has a penetration depth of 30 cm and can adapt to the unevenness of kitchen waste. The accuracy is ±0.5%. When the first microwave moisture meter detects, if the detection value is lower than the preset threshold value (which can be slightly lower than the solid content rate of the first target interval, such as 25%), the PLC control system immediately feeds back to the first-stage screw extruder, and the first-stage screw extruder automatically increases the back pressure pressure of the extruder (which can be adjusted by 0.1-0.3 MPa each time) until the solid content rate is stabilized in the first target interval. If the detection value is too high and exceeds the first target interval, the back pressure pressure of the first-stage screw extruder is appropriately reduced to avoid excessive extrusion leading to excessive equipment load, and also save energy consumption. For the adjustment of the back pressure pressure of the screw extruder, the hydraulic system can be used to implement the back pressure, and the PLC control system can adjust the back pressure by controlling the hydraulic system, and further control the screw rotation speed of the extruder by controlling the slow screw drive motor speed, so as to realize the adjustment of the solid content rate of the outlet material (or the extrusion strength).

[0022] In Step 2, the extrusion solid residue material adjusted by the first-stage extrusion is transported to the temporary storage fermentation bin to enter the fermentation and cell wall breaking stage. The stack height of the first-stage extrusion solid residue material in the temporary storage fermentation bin is greater than 3.0 meters, and appropriate hot air is introduced to accelerate the natural fermentation process and introduce oxygen to promote the reproduction and metabolism of natural microorganisms in the material. The ventilation volume can be controlled at 8.0-15 m³ / h (combined with the requirements of temperature rise and nutrition supply) to maintain the oxygen concentration in the material stack in the temporary storage fermentation bin at 10%-15%. The material in the bin is broken down by its own gravity and factors such as extrusion and collision, achieving the effect of breaking the cell walls. In addition, enzymes produced by microbial activity can decompose the cell walls of the material, destroying the cell structure of cellulose, pectin and other components in the kitchen waste, making it easier for the water in the cells to be squeezed out in the subsequent extrusion process, providing more favorable conditions for the second-stage extrusion process, and the spiral extrusion and biological reinforcement work together. The breaking process lasts for 24 to 36 hours. The leachate produced during the temporary fermentation process can be intercepted by most of the organic matter through layer-by-layer filtration of the high material, reducing the organic matter concentration of the leachate and reducing the sewage treatment load.

[0023] Since the water in the material is divided into bound water and free water, the bound water mainly exists in the cells of animals, plants and microorganisms and cannot be removed by simple mechanical extrusion. For example, the water in the cells cannot be released, and the spiral extrusion dehydration efficiency cannot be improved. By performing fermentation and cell wall breaking in this step, the proportion of free water is greatly increased, and the dehydration resistance is significantly reduced, so that more water can be squeezed out. The solid content of the dehydrated material can be increased by 10%-20% or even more. In the prior art, even if the same equipment is used for continuous secondary extrusion, the effect of increasing the solid content of the material is not significant. In this step, a part of the bound water in the cells becomes free water after the material is fermented and the cell walls are broken. Some of these free water seeps out of the material stack as leachate, and the other part adheres to the material (relatively sticky oil adheres to the surface of the material). The leachate can be discharged, and the permeate does not enter the second-stage spiral.

[0024] In Step 3, the material that has completed fermentation and cell wall breaking enters the second-stage spiral extruder. This link uses a higher initial back pressure to perform deep dehydration. The initial back pressure in the second-stage spiral extruder is 1.2-2.0 MPa.

[0025] In step 3, a second microwave moisture meter is arranged at the material outlet of the secondary screw extruder, which can monitor the solid content of the solid residue in real time, perform secondary detection on the material, and transmit data feedback to the PLC control system. If the detected solid content does not reach the required solid content of 32%-34% in the fermentation tank, the PLC control system feeds back to the secondary screw extruder and the temporary storage fermentation bin, that is, the PLC control system will adjust two links: one is to increase the back pressure of the secondary screw extruder, and the other is to reduce the discharge amount per unit time of the temporary storage fermentation bin, that is, to reduce the processing capacity of the secondary screw extruder and prolong the residence time of the material in the screw extruder, thereby strengthening the dewatering effect through double adjustment. If the solid content exceeds 35%, the back pressure of the secondary screw extruder is reduced and the discharge amount per unit time of the temporary storage fermentation bin is increased to prevent the solid content of the material from being too high to affect the subsequent fermentation efficiency and the load tolerance of the running equipment.

[0026] In step 4, when the solid content of the material at the outlet of the secondary screw extruder is stabilized in the second target interval, the solid residue material of the secondary extrusion is conveyed into the dry anaerobic fermentation tank through a screw or a belt, and the whole process realizes full automatic adjustment without manual intervention. The extruded slurry obtained by two-stage screw extrusion enters a three-phase centrifugal system to recover the crude oil in the slurry, achieving economic utilization (the two-stage extrusion increases the slurry yield, and the increase in slurry yield also increases the amount of recovered crude oil). The whole system ensures the solid content of the material entering the fermentation tank, and reduces energy consumption through real-time feedback mechanism, thereby improving the stability and economy of the process operation.

[0027] The application also discloses a system of a kitchen waste pretreatment process which can be used for the above-mentioned screw extrusion and biological strengthening cooperation, the system comprising a primary screw extruder and a secondary screw extruder, a first microwave moisture meter arranged at the material outlet of the primary screw extruder, and a second microwave moisture meter arranged at the material outlet of the secondary screw extruder, wherein the primary screw extruder, the secondary screw extruder, the first microwave moisture meter and the second microwave moisture meter are electrically connected or communicatively connected to a PLC control system.

[0028] After adopting the above process, the application can have the following advantages: (1) The two-stage screw extrusion + storage bin wall breaking + online solid content detection cooperative mechanism can solve the problem of solid content increase of kitchen waste, and accurately control the final solid content, thereby providing sufficient conditions for stable operation of the dry anaerobic digestion tank; (2) After primary extrusion and preliminary dewatering, the material is naturally broken in the temporary storage fermentation bin through gravity and microbial action, so that water is more easily separated during secondary extrusion, thereby solving the technical difficulty of "hard extrusion and no water separation" in single-stage extrusion, and the wall breaking efficiency of secondary extrusion is significantly improved after wall breaking; (3) The kitchen garbage in the temporary storage fermentation bin can intercept the oil of the leachate due to the compact stacking of the material, so as to increase the oil content of the extrusion slurry of the secondary screw extrusion, increase the crude oil amount of the three-phase oil extraction of the extrusion slurry, and increase the economic benefits.

[0029] The above embodiments and drawings are not limited to the product shape and style of the present application, and any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the scope of the patent of the present application.

Claims

1. A pretreatment process for kitchen waste that combines spiral extrusion and biofortification, characterized in that: Includes the following steps, Step 1: The kitchen waste material after pre-sorting and impurity removal enters the first-stage screw extruder for preliminary dewatering, and the solid content of the dewatered solid residue material reaches the first target range to obtain the first-stage extruded solid residue; Step 2: The primary extruded solid residue material, after being adjusted by the primary screw extruder, is transported to the temporary fermentation chamber and enters the fermentation and cell wall breaking stage; Step 3: The fermented and cell-wall-breaking material is fed into a secondary screw extruder. The initial back pressure used in the secondary screw extruder is greater than that in the primary screw extruder to perform deep dehydration. The solid content of the dehydrated solid residue material is stabilized in the second target range to obtain the secondary extruded solid residue. Step 4: The secondary extruded solid material is conveyed into a dry anaerobic fermenter. The extruded slurry obtained from the primary screw extruder in Step 1 and the secondary screw extruder in Step 3 is fed into a three-phase centrifugal system to recover the crude oil in the slurry.

2. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhanced treatment as described in claim 1, characterized in that: In step 1, a first microwave moisture meter is installed at the material outlet of the first-stage screw extruder. The first microwave moisture meter monitors the solid content of the slag in real time and transmits the data to the PLC control system. If the detected value is lower than the preset threshold, the PLC control system immediately feeds back to the first-stage screw extruder. The first-stage screw extruder automatically increases the back pressure of the extruder until the solid content of the slag stabilizes within the first target range. If the detected value exceeds the first target range, the back pressure of the first-stage screw extruder is reduced.

3. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 2, characterized in that: In step 1, the solid content of the kitchen waste material after pre-sorting and impurity removal is 20-24%, the preset initial back pressure of the first-stage screw extruder is 0.5-1.0MPa, the solid content of the first target range is 26-28%, and the preset threshold is 25%.

4. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 1, characterized in that: In step 2, the height of the primary extruded solid slag material in the temporary fermentation chamber is greater than 3.0 meters, and hot air and oxygen are introduced into the temporary fermentation chamber. The oxygen concentration in the material pile in the temporary fermentation chamber is maintained between 10% and 15%, and the fermentation and cell wall breaking process in the temporary fermentation chamber lasts for 24 to 36 hours.

5. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 1, characterized in that: In step 2, after the material is fermented and its cell walls are broken, some of the bound water within the cells of the material becomes free water and then leachate seeps out of the material pile, and the leachate is discharged externally.

6. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 1, characterized in that: In step 3, the initial back pressure in the secondary screw extruder is 1.2-2.0 MPa.

7. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 1, characterized in that: The material outlet of the secondary screw extruder is equipped with a second microwave moisture meter, which monitors the solid content of the slag in real time and transmits the data to the PLC control system. If the solid content does not reach the 32%-34% requirement of the fermentation tank, the PLC control system feeds back to the secondary screw extruder and the temporary fermentation chamber. The secondary screw extruder increases the back pressure, while reducing the output per unit time of the temporary fermentation chamber. If the solid content exceeds 35%, the back pressure of the secondary screw extruder is reduced and the output per unit time of the temporary fermentation chamber is increased.

8. The pretreatment process for kitchen waste combining spiral extrusion and bio-enhancing as described in claim 1, characterized in that: In step 4, the secondary extruded solid slag material is conveyed into the dry anaerobic fermenter via a screw conveyor or belt conveyor.

9. A system for a pretreatment process of kitchen waste using a spiral extrusion and bio-enhanced synergistic method as described in any one of claims 1 to 8, characterized in that: The system includes a primary screw extruder and a secondary screw extruder. A first microwave moisture meter is installed at the material outlet of the primary screw extruder, and a second microwave moisture meter is installed at the material outlet of the secondary screw extruder. The primary screw extruder, the secondary screw extruder, the first microwave moisture meter, and the second microwave moisture meter are electrically or communicatively connected to the PLC control system.

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