A method for anaerobic treatment of vegetable waste by liquid-solid separation

Abstract

The present invention discloses a method for anaerobic treatment of vegetable waste by liquid-solid separation. Step 1: The vegetable waste is separated into dry residue and filtrate through crushing and dehydration. Step 2: The dry residue is sent to a dry anaerobic treatment line; the filtrate is sent to an IC anaerobic treatment line. Step 3: The dry residue is processed by a pulper to obtain slurry, and the slurry, together with the recycled anaerobic discharge and the sedimented slurry at the bottom of the filtrate adjustment tank, is temperature-adjusted and formulated in the slurry adjustment tank; the adjusted slurry is sent to a dry anaerobic reactor for anaerobic fermentation, and a part of the product after fermentation, i.e., the anaerobic discharge, is recycled to the slurry adjustment tank. Step 4: The filtrate is passed through a basket strainer to remove colloidal, flocculent and floating impurities, and then the filtrate is cached and temperature-adjusted in the filtrate adjustment tank; the adjusted slurry is sent to an IC anaerobic reactor for anaerobic treatment. The present invention independently anaerobically treats the filtrate and dry residue after liquid-solid separation of vegetable waste, significantly reducing the volume and floor area of the anaerobic reactor, reducing the project investment and improving the anaerobic gas production efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste treatment and utilization, and particularly relates to a method for separating liquid from residue and anaerobically treating vegetable waste. Background Art

[0002] When vegetables are harvested, processed, transported, and sold, the old and damaged leaves are removed, generating vegetable waste, also known as tail vegetables. Vegetable waste comes in various types, including vegetable leaves, seedlings, stems, roots, fallen fruits, etc., with leaves and seedlings accounting for a relatively large proportion.

[0003] Vegetable waste has a relatively high water content, generally 80% - 95%. The water content of leaves and seedlings, which account for a relatively large proportion, is generally 90% - 95%. It has little dry matter, is prone to decay and deterioration. If randomly piled up or discarded, it is likely to produce malodorous gases and rotten liquid, breed mosquitoes and flies, spread bacteria, causing pollution to the fields, water bodies, and soil, and affecting environmental hygiene and human health. At the same time, vegetable waste contains abundant elements such as nitrogen, phosphorus, and potassium, as well as nutrient substances such as crude protein, crude fiber, and crude fat. It is a good raw material for biomass fermentation. It is mostly treated by anaerobic fermentation to produce biogas and aerobic composting. Some are also used for feed treatment. However, all these methods have drawbacks due to the high water content of vegetable waste. For example, the biogas production rate of anaerobic fermentation is low, the volume of anaerobic reactors is large, the occupied area is large, the output of biogas slurry is large, and additional high-solid auxiliary materials are required for aerobic composting and feed treatment.

[0004] The invention patent with the application number 201510424607.7 discloses a method for resource-efficient anaerobic fermentation of organic waste in intensive vegetable areas to produce biogas. By adding strains or feces and straw, the solid content of the material is adjusted to 8% - 12% for wet anaerobic fermentation. However, this method belongs to traditional wet anaerobic and still has the drawback of a large volume of anaerobic reaction equipment.

[0005] The invention patent with the application number 201611220575.X discloses a light and movable anaerobic dry fermentation system for vegetable waste and a method for anaerobic fermentation using this system. By adding high-solid straw to mix with vegetable waste for specific anaerobic dry fermentation, the biogas residue is directly composted without generating biogas slurry. However, this method is only suitable for vegetable waste with a water content lower than 88% and is only suitable for small-scale applications due to its mobility. Summary of the Invention

[0006] The present invention provides a method for separating liquid from residue and anaerobically treating vegetable waste to address the deficiencies of the prior art.

[0007] The technical solution of the present invention is: A method for separating liquid from residue and anaerobically treating vegetable waste, characterized by the following steps:

[0008] Step 1: Crush and dehydrate the vegetable waste to divide it into dry residue and filtrate;

[0009] Step 2: Feed the dry residues into the dry anaerobic treatment line; feed the filtrate into the IC anaerobic treatment line;

[0010] The dry anaerobic treatment line is connected in series by a pulping machine, a slurry regulating tank, a slurry feeding pump, and a dry anaerobic reactor in sequence;

[0011] The IC anaerobic treatment line is connected in series by a basket grille, a filtrate regulating tank, a filtrate feeding pump, and an IC anaerobic reactor in sequence;

[0012] Step 3: The dry residues are processed by the pulping machine to obtain slurry. The slurry, together with the recycled anaerobic discharge and the precipitated slurry at the bottom of the filtrate regulating tank, is temperature-adjusted and proportioned in the slurry regulating tank. The adjusted slurry is sent to the dry anaerobic reactor for anaerobic fermentation. The biogas generated anaerobically is processed and utilized. Part of the product after fermentation, i.e., the anaerobic discharge, is recycled to the slurry regulating tank, and the rest is used for composting treatment and utilization;

[0013] Step 4: The filtrate is passed through the basket grille to remove colloidal, flocculent, and floating foam impurities. Subsequently, the filtrate is buffered and temperature-adjusted in the filtrate regulating tank. The adjusted slurry is sent to the IC anaerobic reactor for anaerobic treatment. The biogas generated anaerobically is processed and utilized.

[0014] According to the embodiment of the present invention, the size of the vegetable residues after crushing in Step 1 is ≤1 cm, and the solid content of the dry residues after extrusion of the vegetable residues is 20% - 25%.

[0015] According to the embodiment of the present invention, the reflux ratio of the discharge of the dry anaerobic reactor to the slurry regulating tank in Step 3 is 10% - 50%. The solid content of the material after reflux and proportioning is 16% - 19%. The material is proportioned to 35°C by an external heat source, and the residence time of the material is 1 - 2 days.

[0016] According to the embodiment of the present invention, the filtrate in the filtrate regulating tank is proportioned to 35°C by an external heat source, the hydraulic retention time is 1 - 2 days, and the bottom sludge discharge pump regularly discharges the precipitated slurry into the slurry regulating tank.

[0017] According to the embodiment of the present invention, the reaction temperature of the dry anaerobic reactor is 35°C, and the residence time of the material is 20 - 25 days.

[0018] According to the embodiment of the present invention, the reaction temperature of the IC anaerobic reactor is 35°C, and the hydraulic retention time is 10 - 15 hours.

[0019] The beneficial effects of the present invention are as follows: (1) The filtrate and dry residue after separating the liquid and residue of vegetable waste are anaerobically treated independently, significantly reducing the volume and floor area of the anaerobic reactor, lowering the project investment, and improving the anaerobic gas production efficiency; (2) When the filtrate and dry residue after separating the liquid and residue of vegetable waste are anaerobically treated independently, the sum of the volumes and the sum of the floor areas of the corresponding dry anaerobic reactor and IC anaerobic reactor are respectively reduced by 40% - 67% and 10% - 28% compared with the traditional wet anaerobic reactor (CSTR), and the gas production increases by 25% - 70%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a process flow chart of a method for anaerobic treatment of vegetable waste by separating liquid and residue. DETAILED DESCRIPTION OF THE INVENTION

[0021] In order to better understand the above process method, the above process method will be described in detail below in combination with the drawings of the specification and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the process method of the present application, rather than limitations on the process method of the present application. Without conflict, the technical features in the embodiments of the present application and the embodiments can be combined with each other.

[0022] A method for anaerobic treatment of vegetable waste by separating liquid and residue, the steps of which include:

[0023] Step 1: The vegetable waste is divided into dry residue and filtrate after being crushed and dehydrated;

[0024] Step 2: The dry residue is sent to the dry anaerobic treatment line; the filtrate is sent to the IC anaerobic treatment line;

[0025] The dry anaerobic treatment line is connected in series by a pulping machine, a slurry regulating tank, a slurry feeding pump, and a dry anaerobic reactor in sequence;

[0026] The IC anaerobic treatment line is connected in series by a basket strainer, a filtrate regulating tank, a filtrate feeding pump, and an IC anaerobic reactor in sequence;

[0027] Step 3: The dry residue is processed by the pulping machine to obtain slurry, and the slurry, together with the recycled anaerobic discharge and the slurry precipitated at the bottom of the filtrate regulating tank, is temperature-adjusted and formulated in the slurry regulating tank; the adjusted slurry is sent to the dry anaerobic reactor for anaerobic fermentation, and the biogas generated anaerobically is processed and utilized. A part of the product after fermentation, that is, the anaerobic discharge, is recycled to the slurry regulating tank, and the rest is used for composting treatment and utilization;

[0028] Step 4: The filtrate is passed through the basket strainer to remove colloidal, flocculent, and floating impurities, and then the filtrate is cached and temperature-adjusted in the filtrate regulating tank; the adjusted slurry is sent to the IC anaerobic reactor for anaerobic treatment, and the biogas generated anaerobically is processed and utilized.

[0029] The effluent of the IC anaerobic reactor is subjected to other treatments and utilization.

[0030] The vegetable waste is in a state without impurities after cleaning, and the solid content is 3% - 12%.

[0031] After the vegetable waste is crushed, the size of the vegetable residue is ≤ 1 cm. The solid content of the dry residue after extrusion of the vegetable residue is 20% - 25%, and the dry residue becomes slurry-like after pulping.

[0032] The reflux ratio of the anaerobic discharge to the slurry adjustment tank is 10% - 50%. The solid content of the material after reflux blending is 16% - 19%. The material is adjusted to 35°C by an external heat source, and the residence time of the material is 1 - 2 days.

[0033] The filtrate in the filtrate adjustment tank is adjusted to 35°C by an external heat source, and the hydraulic residence time is 1 - 2 days. The sludge discharge pump at the bottom regularly discharges the precipitated slurry into the slurry adjustment tank.

[0034] The reaction temperature of the dry anaerobic reactor is 35°C, and the residence time of the material is 20 - 25 days.

[0035] The reaction temperature of the IC anaerobic reactor is 35°C, and the hydraulic residence time is 10 - 15 hours.

[0036] A system for anaerobic treatment of vegetable waste with liquid-solid separation includes a dry anaerobic treatment line and an IC anaerobic treatment line. In the dry anaerobic treatment line, a crusher, the dry residue outlet of a dehydrator, a pulper, a slurry adjustment tank, a slurry feed pump, and a dry anaerobic reactor are connected in series in sequence. In the IC anaerobic treatment line, the filtrate outlet of the dehydrator, a basket strainer, a filtrate adjustment tank, a filtrate feed pump, and an IC anaerobic reactor are connected in series in sequence.

[0037] The crusher is a double-shaft crusher.

[0038] The dehydrator is a screw extrusion dehydrator.

[0039] The form of the mesh holes of the basket strainer is round steel rectangular holes, and the mesh size is 0.3 cm * 0.3 cm. There is also a grid plate on the upper layer of the basket strainer, and the void size of the grid plate is 0.5 cm * 0.5 cm.

[0040] The basket strainer can intercept and remove potential colloidal, flocculent, and floating impurities.

[0041] Vertical agitators are installed in the centers of both the slurry adjustment tank and the filtrate adjustment tank, and a sludge discharge pump is installed at the bottom of the filtrate adjustment tank.

[0042] The sludge discharge pump regularly discharges the precipitated slurry that may be generated at the bottom.

[0043] The dry anaerobic reactor is a plug-flow steel-concrete structure reactor, and the reactor is equipped with general accessories such as a stirrer, a heating hot water coil, a heat preservation layer, and a positive and negative pressure protector.

[0044] The IC anaerobic reactor is a general-purpose IC reactor.

[0045] Example: The vegetable waste with a solid content rate of 6% and a quantity of 100 t / d after collection and impurity removal is successively processed by a crusher and a dehydrator to obtain filtrate and dry residue. The dry residue has a solid content rate of 20%. The dry residue is processed by a pulper to obtain slurry. The slurry, together with the recycled anaerobic discharge (recycle ratio 10%) and the precipitated slurry at the bottom of the filtrate adjustment tank, is temperature-adjusted and formulated in the slurry adjustment tank to 35°C and a solid content rate of 19%. The adjusted slurry is sent to the dry anaerobic reactor for anaerobic fermentation for 22 days. Part of the product after fermentation, i.e., the anaerobic discharge, is recycled to the slurry adjustment tank, and the rest is used for composting treatment and utilization. The filtrate obtained by the dehydrator is passed through a basket grille to remove potential colloidal, flocculent, and floating foam impurities. Subsequently, the filtrate is cached and temperature-adjusted to 35°C in the filtrate adjustment tank. The adjusted slurry is sent to the IC anaerobic reactor for anaerobic treatment for 10 hours. The effluent from the IC anaerobic reactor is subjected to other treatments and utilization. The biogas generated by the dry anaerobic reactor and the IC anaerobic reactor is collected and then processed and utilized.

[0046] The sum of the volumes and the sum of the floor areas of the dry anaerobic reactor and the IC anaerobic reactor are respectively 47.5% and 10.6% less than those of the traditional wet anaerobic reactor (CSTR), and the gas production increases by 70%.

[0047] Finally, it should be noted that the above specific embodiments are only used to illustrate the process method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the examples, those of ordinary skill in the art should understand that the process method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the process method of the present invention, and all of them should be covered by the scope of the claims of the present invention.

Claims

1. A method for anaerobic treatment of vegetable waste by liquid-solid separation Its characteristic steps include: Step 1: The vegetable waste is separated into dry residue and filtrate through crushing and dehydration; Step 2: The dry residue is sent to a dry anaerobic treatment line; the filtrate is sent to an IC anaerobic treatment line; The dry anaerobic treatment line is successively connected in series by a pulping machine, a slurry adjustment tank, a slurry feed pump, and a dry anaerobic reactor; The IC anaerobic treatment line is successively connected in series by a basket grille, a filtrate adjustment tank, a filtrate feed pump, and an IC anaerobic reactor; Step 3: The dry residue is processed by a pulping machine to obtain slurry. The slurry, together with the recycled anaerobic discharge and the sediment slurry at the bottom of the filtrate adjustment tank, is temperature-adjusted and formulated in the slurry adjustment tank; the adjusted slurry is sent to the dry anaerobic reactor for anaerobic fermentation. The biogas generated anaerobically is processed and utilized. Part of the product after fermentation, i.e., the anaerobic discharge, is recycled to the slurry adjustment tank, and the remainder is used for composting treatment and utilization; the reflux ratio of the discharge from the dry anaerobic reactor to the slurry adjustment tank is 10% - 50%, and the solid content of the material after reflux and formulation is 16% - 19%; Step 4: The filtrate is passed through a basket grille to remove colloidal, flocculent, and floating foam impurities, and then the filtrate is cached and temperature-adjusted in the filtrate adjustment tank; The adjusted slurry is sent to the IC anaerobic reactor for anaerobic treatment, and the biogas generated anaerobically is processed and utilized.

2. The method for anaerobic treatment of vegetable waste by liquid-solid separation according to claim 1, characterized in that in Step 1, the size of the vegetable residue after crushing the vegetable waste is ≤ 1 cm, and the solid content of the dry residue after extrusion of the vegetable residue is 20% - 25%.

3. The method for anaerobic treatment of vegetable waste by liquid-solid separation according to claim 1, characterized in that in Step 3, the material is adjusted to 35°C by an external heat source, and the residence time of the material is 1 - 2 days.

4. The method for anaerobic treatment of vegetable waste by liquid-solid separation according to claim 1, characterized in that the filtrate adjustment tank adjusts the filtrate to 35°C by an external heat source, the hydraulic residence time is 1 - 2 days, and the bottom sludge discharge pump regularly discharges the sediment slurry into the slurry adjustment tank.

5. The method for anaerobic treatment of vegetable waste by liquid-solid separation according to claim 1, characterized in that the reaction temperature of the dry anaerobic reactor is 35°C, and the residence time of the material is 20 - 25 days.

6. The method for anaerobic treatment of vegetable waste by liquid-solid separation according to claim 1, characterized in that the reaction temperature of the IC anaerobic reactor is 35°C, and the hydraulic residence time is 10 - 15 hours.

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